diff --git a/doc/draft/draft-ietf-dnsop-dnssec-operational-practices-01.txt b/doc/draft/draft-ietf-dnsop-dnssec-operational-practices-01.txt deleted file mode 100644 index 04815175fd..0000000000 --- a/doc/draft/draft-ietf-dnsop-dnssec-operational-practices-01.txt +++ /dev/null @@ -1,1344 +0,0 @@ - -DNSOP O. Kolkman -Internet-Draft RIPE NCC -Expires: August 30, 2004 R. Gieben - NLnet Labs - March 2004 - - - DNSSEC Operational Practices - draft-ietf-dnsop-dnssec-operational-practices-01.txt - -Status of this Memo - - This document is an Internet-Draft and is in full conformance with - all provisions of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that other - groups may also distribute working documents as Internet-Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at http:// - www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on August 30, 2004. - -Copyright Notice - - Copyright (C) The Internet Society (2004). All Rights Reserved. - -Abstract - - This document describes a set of practices for operating a DNSSEC - aware environment. The target audience is zone administrators - deploying DNSSEC that need a guide to help them chose appropriate - values for DNSSEC parameters. It also discusses operational matters - such as key rollovers, KSK and ZSK considerations and related - matters. - - - - - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 1] - -Internet-Draft DNSSEC Operational Practices March 2004 - - -Table of Contents - - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 1.1 The Use of the Term 'key' . . . . . . . . . . . . . . . . 3 - 1.2 Keeping the Chain of Trust Intact . . . . . . . . . . . . 3 - 2. Time in DNSSEC . . . . . . . . . . . . . . . . . . . . . . . . 4 - 2.1 Time Definitions . . . . . . . . . . . . . . . . . . . . . 4 - 2.2 Time Considerations . . . . . . . . . . . . . . . . . . . 5 - 3. Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 3.1 Motivations for the KSK and ZSK Functions . . . . . . . . 7 - 3.2 Key Security Considerations . . . . . . . . . . . . . . . 8 - 3.2.1 Key Validity Period . . . . . . . . . . . . . . . . . 8 - 3.2.2 Key Algorithm . . . . . . . . . . . . . . . . . . . . 8 - 3.2.3 Key Sizes . . . . . . . . . . . . . . . . . . . . . . 8 - 3.3 Key Rollovers . . . . . . . . . . . . . . . . . . . . . . 9 - 3.3.1 Zone-signing Key Rollovers . . . . . . . . . . . . . . 10 - 3.3.2 Key-signing Key Rollovers . . . . . . . . . . . . . . 13 - 4. Planning for Emergency Key Rollover . . . . . . . . . . . . . 14 - 4.1 KSK Compromise . . . . . . . . . . . . . . . . . . . . . . 15 - 4.2 ZSK Compromise . . . . . . . . . . . . . . . . . . . . . . 15 - 4.3 Compromises of Keys Anchored in Resolvers . . . . . . . . 16 - 5. Parental Policies . . . . . . . . . . . . . . . . . . . . . . 16 - 5.1 Initial Key Exchanges and Parental Policies - Considerations . . . . . . . . . . . . . . . . . . . . . . 16 - 5.2 Storing Keys So Hashes Can Be Regenerated . . . . . . . . 16 - 5.3 Security Lameness Checks . . . . . . . . . . . . . . . . . 17 - 5.4 DS Signature Validity Period . . . . . . . . . . . . . . . 17 - 6. Security Considerations . . . . . . . . . . . . . . . . . . . 17 - 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 - 8.1 Normative References . . . . . . . . . . . . . . . . . . . . 18 - 8.2 Informative References . . . . . . . . . . . . . . . . . . . 18 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 19 - A. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 19 - B. Zone-signing Key Rollover Howto . . . . . . . . . . . . . . . 20 - C. Typographic Conventions . . . . . . . . . . . . . . . . . . . 20 - D. Document Details and Changes . . . . . . . . . . . . . . . . . 22 - D.1 draft-ietf-dnsop-dnssec-operational-practices-00 . . . . . 22 - D.2 draft-ietf-dnsop-dnssec-operational-practices-01 . . . . . 22 - Intellectual Property and Copyright Statements . . . . . . . . 23 - - - - - - - - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 2] - -Internet-Draft DNSSEC Operational Practices March 2004 - - -1. Introduction - - During workshops and early operational deployment tests, operators - and system administrators gained experience about operating DNSSEC - aware DNS services. This document translates these experiences into - a set of practices for zone administrators. At the time of writing, - there exists very little experience with DNSSEC in production - environments, this document should therefore explicitly not be seen - as represented 'Best Current Practices'. - - The procedures herein are focused on the maintenance of signed zones - (i.e. signing and publishing zones on authoritative servers). It is - intended that maintenance of zones such as resigning or key rollovers - be transparent to any verifying clients on the Internet. - - The structure of this document is as follows: It begins with - discussing some of the considerations with respect to timing - parameters of DNS in relation to DNSSEC (Section 2). Aspects of key - management such as key rollover schemes are described in Section 3. - Emergency rollover considerations are addressed in Section 4. The - typographic conventions used in this document are explained in - Appendix C. - - Since this is a document with operational suggestions and there are - no protocol specifications, the RFC2119 [5] language does not apply. - -1.1 The Use of the Term 'key' - - It is assumed that the reader is familiar with the concept of - asymmetric keys on which DNSSEC is based (Public Key Cryptography - [Ref to Schneider?]). Therefore, this document will use the term - 'key' rather loosely. Where it is written that 'a key is used to sign - data' it is assumed that the reader understands that it is the - private part of the key-pair that is used for signing. It is also - assumed that the reader understands that the public part of the - key-pair is published in the DNSKEY resource record and that it is - used in key-exchanges. - -1.2 Keeping the Chain of Trust Intact - - Maintaining a valid chain of trust is important because broken chains - of trust will result in data being marked as bogus, which may cause - entire (sub)domains to become invisible to verifying clients. The - administrators of secured zones have to realise that their zone is, - to their clients, part of a chain of trust. - - As mentioned in the introduction, the procedures herein are intended - to ensure maintenance of zones, such as resigning or key rollovers, - - - -Kolkman & Gieben Expires August 30, 2004 [Page 3] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - be transparent to the verifying clients on the Internet. - Administrators of secured zones will have to keep in mind that data - published on an authoritative primary server will not be immediately - seen by verifying clients; it may take some time for the data to be - transfered to other secondary authoritative nameservers, during which - period clients may be fetching data from caching non-authoritative - servers. For the verifying clients it is important that data from - secured zones can be used to build chains of trust regardless of - whether the data came directly from an authoritative server, a - caching nameserver or some middle box. Only by carefully using the - available timing parameters can a zone administrator assure that the - data necessary for verification can be obtained. - - The responsibility for maintaining the chain of trust is shared by - administrators of secured zones in the chain of trust. This is most - obvious in the case of a 'key compromise' when a trade off between - maintaining a valid chain of trust and the fact that the key has been - stolen, must be made. - - The zone administrator will have to make a tradeoff between keeping - the chain of trust intact -thereby allowing for attacks with the - compromised key- or to deliberately break the chain of trust thereby - making secured subdomains invisible to security aware resolvers. Also - see Section 4. - -2. Time in DNSSEC - - Without DNSSEC all times in DNS are relative. The SOA's refresh, - retry and expiration timers are counters that are used to determine - the time elapsed after a slave server syncronised (or tried to - syncronise) with a master server. The Time to Live (TTL) value and - the SOA minimum TTL parameter [6] are used to determine how long a - forwarder should cache data after it has been fetched from an - authoritative server. DNSSEC introduces the notion of an absolute - time in the DNS. Signatures in DNSSEC have an expiration date after - which the signature is marked as invalid and the signed data is to be - considered bogus. - -2.1 Time Definitions - - In this document we will be using a number of time related terms. - Within the context of this document the following definitions apply: - o "Signature validity period" - The period that a signature is valid. It starts at the time - specified in the signature inception field of the RRSIG RR and - ends at the time specified in the expiration field of the RRSIG - RR. - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 4] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - o "Signature publication period" - Time after which a signature (made with a specific key) is - replaced with a new signature (made with the same key). This - replacement takes place by publishing the relevant RRSIG in the - master zone file. If a signature is published at time T0 and a - new signature is published at time T1, the signature - publication period is T1 - T0. - If all signatures are refreshed at zone (re)signing then the - signature publication period is equal signature validity - period. - o "Maximum/Minimum Zone TTL" - The maximum or minimum value of all the TTLs in a zone. - -2.2 Time Considerations - - Because of the expiration of signatures, one should consider the - following. - o The Maximum Zone TTL of your zone data should be a fraction of - your signature validity period. - If the TTL would be of similar order as the signature validity - period, then all RRsets fetched during the validity period - would be cached until the signature expiration time. As a - result query load on authoritative servers would peak at - signature expiration time. - To avoid query load peaks we suggest the TTL on all the RRs in - your zone to be at least a few times smaller than your - signature validity period. - o The signature publication period should be at least one maximum - TTL smaller than the signature validity period. - Resigning a zone shortly before the end of the signature - validity period may cause simultaneous expiration of data from - caches. This in turn may lead to peaks in the load on - authoritative servers. - o The Minimum zone TTL should be long enough to both fetch and - verify all the RRs in the authentication chain. - 1. During validation, some data may expire before the - validation is complete. The validator should be able to keep - all data, until is completed. This applies to all RRs needed - to complete the chain of trust: DSs, DNSKEYs, RRSIGs, and - the final answers i.e. the RR that is returned for the - initial query. - 2. Frequent verification causes load on recursive - nameservers. Data at delegation points, DSs, DNSKEYs and - RRSIGs benefit from caching. The TTL on those should be - relatively long. - - - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 5] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - We have seen events where data needed for verification of an - authentication chain had expired from caches. - We suggest the TTL on DNSKEY and DSs to be between ten minutes - and one hour. We recommend zone administrators to chose TTLs - longer than half a minute. - [Editor's Note: this observation could be implementation - specific. We are not sure if we should leave this item] - o Slave servers will need to be able to fetch newly signed zones - well before the data expires from your zone. - 'Better no answers than bad answers.' - If a properly implemented slave server is not able to contact a - master server for an extended period the data will at some - point expire and the slave server will not hand out any data. - If the server serves a DNSSEC zone than it may well happen that - the signatures expire well before the SOA expiration timer - counts down to zero. It is not possible to completely prevent - this from happening by tweaking the SOA parameters. However, - the effects can be minimized where the SOA expiration time is - equal or smaller than the signature validity period. - The consequence of an authoritative server not being able to - update a zone, whilst that zone includes expired signaturs, is - that non-secure resolvers will continue to be able to resolve - data served by the particular slave servers. Security aware - resolvers will experience problems. - We suggest the SOA expiration timer being approximately one - third or one fourth of the signature validity period. It will - allow problems with transfers from the master server to be - noticed before the actual signature time out. - We suggest that operators of nameservers with slave zones - develop 'watch dogs' to spot upcoming signature expirations in - slave zones, and take appropriate action. - When determining the value for the expiration parameter one has - to take the following into account: What are the chances that - all my secondary zones expire; How quickly can I reach an - administrator and load a valid zone? All these arguments are - not DNSSEC specific. - -3. Keys - - In the DNSSEC protocol there is only one type of key, the zone key. - With this key, the data in a zone is signed. - - To make zone re-signing and key rollovers procedures easier to - implement, it is possible to use one or more keys as Key Signing Keys - (KSK) these keys will only sign the apex DNSKEY RRs in a zone. Other - keys can be used to sign all the RRsets in a zone and are referred to - as Zone Signing Keys (ZSK). In this document we assume that KSKs are - the subset of keys that are used for key exchanges with the parents - - - -Kolkman & Gieben Expires August 30, 2004 [Page 6] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - and potentially for configuration as trusted anchors - the so called - Secure Entry Point keys (SEP). In this document we assume a - one-to-one mapping between KSK and SEP keys and we assume the SEP - flag [4] to be set on KSKs. - -3.1 Motivations for the KSK and ZSK Functions - - Differentiating between the KSK to ZSK functions has several - advantages: - - o Making the KSK stronger (i.e. using more bits in the key material) - has little operational impact since it is only used to sign a - small fraction of the zone data. - o As the KSK is only used to sign a keyset, which is most probably - updated less frequently than other data in the zone, it can be - stored separately from (and thus in a safer location than) the - ZSK. - o A KSK can be used for longer periods. - o No parent/child interaction is required when ZSKs are updated. - - The KSK is used less than ZSK, once a keyset is signed with the KSK - all the keys in the keyset can be used as ZSK. If a ZSK is - compromised, it can be simply dropped from the keyset. The new keyset - is then resigned with the KSK. - - Given the assumption that for KSKs the SEP flag is set, the KSK can - be distinguished from a ZSK by examining the flag field in the DNSKEY - RR. If the flag field is an odd number it is a KSK if it is an even - number it is a ZSK e.g. a value of 256 and a key signing key has 257. - - The zone-signing key can be used to sign all the data in a zone on a - regular basis. When a zone-signing key is to be rolled, no - interaction with the parent is needed. This allows for relatively - short "Signature Validity Periods". That is, Signature Validity - Periods of the order of days. - - The key-signing key is only to be used to sign the Key RR set from - the zone apex. If a key-signing key is to be rolled over, there will - be interactions with parties other than the zone administrator such - as the registry of the parent zone or administrators of verifying - resolvers that have the particular key configured as trusted entry - points. Hence, the "Key Usage Time" of these keys can and should be - made much longer. Although, given a long enough key, the "Key Usage - Time" can be on the order of years we suggest to plan for a "Key - Usage Time" of the order of a few months so that a key rollover - remains an operational routine. - - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 7] - -Internet-Draft DNSSEC Operational Practices March 2004 - - -3.2 Key Security Considerations - - Keys in DNSSEC have a number of parameters which should all be chosen - with care, the most important once are: size, algorithm and the key - validity period (its lifetime). - -3.2.1 Key Validity Period - - RFC2541 [2] describes a number of considerations with respect to the - security of keys. The document deals with the generation, lifetime, - size and storage of private keys. - - In Section 3 of RFC2541 [2] there are some suggestions for a key - validity period: 13 months for long-lived keys and 36 days for - transaction keys but suggestions for key sizes are not made. - - If we say long-lived keys are key-signing keys and transactions keys - are zone-signing keys, these recommendations will lead to rollovers - occurring frequently enough to become part of 'operational habits'; - the procedure does not have to be reinvented every time a key is - replaced. - -3.2.2 Key Algorithm - - We recommend you choose RSA/SHA-1 as the preferred algorithm for the - key. RSA has been developed in an open and transparent manner. As the - patent on RSA expired in 2001, its use is now also free. The current - known attacks on RSA can be defeated by making your key longer. As - the MD5 hashing algorithm is showing (theoretical) cracks, we - recommend the usage of SHA1. - -3.2.3 Key Sizes - - When choosing key sizes, zone administrators will need to take into - account how long a key will be used and how much data will be signed - during the key publication period. It is hard to give precise - recommendations but Lenstra and Verheul [9] supplied the following - table with lower bound estimates for cryptographic key sizes. Their - recommendations are based on a set of explicitly formulated parameter - settings, combined with existing data points about cryptosystems. For - details we refer to the original paper. - - [Editor's Note: DSA???] - - - - - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 8] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - Year RSA Key Sizes Elliptic Curve Key Size - 2000 952 132 - 2001 990 135 - 2002 1028 139 - 2003 1068 140 - 2004 1108 143 - - 2005 1149 147 - 2006 1191 148 - 2007 1235 152 - 2008 1279 155 - 2009 1323 157 - - - 2010 1369 160 - 2011 1416 163 - 2012 1464 165 - 2013 1513 168 - 2014 1562 172 - - 2015 1613 173 - 2016 1664 177 - 2017 1717 180 - 2018 1771 181 - 2019 1825 185 - - - 2020 1881 188 - 2021 1937 190 - 2022 1995 193 - 2023 2054 197 - 2024 2113 198 - - 2025 2174 202 - 2026 2236 205 - 2027 2299 207 - 2028 2362 210 - 2029 2427 213 - - For example, should you wish your key to last three years from 2003, - check the RSA keysize values for 2006 in this table. In this case - 1191. - -3.3 Key Rollovers - - Key rollovers are a fact of life when using DNSSEC. A DNSSEC key - cannot be used forever (see RFC2541 [2] and Section 3.2 ). Zone - administrators who are in the process of rolling their keys have to - - - -Kolkman & Gieben Expires August 30, 2004 [Page 9] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - take into account that data published in previous versions of their - zone still lives in caches. When deploying DNSSEC, this becomes an - important consideration; ignoring data that may be in caches may lead - to loss of service for clients. - - The most pressing example of this is when zone material signed with - an old key is being validated by a resolver which does not have the - old zone key cached. If the old key is no longer present in the - current zone, this validation fails, marking the data bogus. - Alternatively, an attempt could be made to validate data which is - signed with a new key against an old key that lives in a local cache, - also resulting in data being marked bogus. - - To appreciate the situation one could think of a number of - authoritative servers that may not be instantaneously running the - same version of a zone and a security aware non-recursive resolver - that sits behind security aware caching forwarders. - - Note that KSK rollovers and ZSK rollovers are different. A zone-key - rollover can be handled in two different ways: pre-publish (Section - Section 3.3.1.1) and double signature (Section Section 3.3.1.2). The - pre-publish technique works because the key-signing key stays the - same during this ZSK rollover. With this KSK a cache is able to - validate the new keyset of a zone. With a KSK rollover a cache can - not validate the new keyset, because it does not trust the new KSK. - - [Editors note: This needs more verbose explanation, nobody will - appreciate the situation just yet. Help with text and examples is - appreciated] - -3.3.1 Zone-signing Key Rollovers - - For zone-signing key rollovers there are two ways to make sure that - during the rollover data still cached can be verified with the new - keysets or newly generated signatures can be verified with the keys - still in caches. One schema uses double signatures, it is described - in Section 3.3.1.2, the other uses key pre-publication (Section - 3.3.1.1). The pros, cons and recommendations are described in Section - 3.3.1.3. - -3.3.1.1 Pre-publish Keyset Rollover - - This section shows how to perform a ZSK rollover without the need to - sign all the data in a zone twice - the so called "prepublish - rollover". We recommend this method because it has advantages in the - case of key compromise. If the old key is compromised, the new key - has already been distributed in the DNS. The zone administrator is - then able to quickly switch to the new key and remove the compromised - - - -Kolkman & Gieben Expires August 30, 2004 [Page 10] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - key from the zone. Another major advantage is that the zone size does - not double, as is the case with the double signature ZSK rollover. A - small "HOWTO" for this kind of rollover can be found in Appendix B. - - normal pre-roll roll after - - SOA0 SOA1 SOA2 SOA3 - RRSIG10(SOA0) RRSIG10(SOA1) RRSIG11(SOA2) RRSIG11(SOA3) - - DNSKEY1 DNSKEY1 DNSKEY1 DNSKEY1 - DNSKEY10 DNSKEY10 DNSKEY10 DNSKEY11 - DNSKEY11 DNSKEY11 - RRSIG1 (DNSKEY) RRSIG1 (DNSKEY) RRSIG1(DNSKEY) RRSIG1 (DNSKEY) - RRSIG10(DNSKEY) RRSIG10(DNSKEY) RRSIG11(DNSKEY) RRSIG11(DNSKEY) - - - normal: Version 0 of the zone: DNSKEY 1 is the key-signing key. - DNSKEY 10 is used to sign all the data of the zone, the - zone-signing key. - pre-roll: DNSKEY 11 is introduced into the keyset. Note that no - signatures are generated with this key yet, but this does not - secure against brute force attacks on the public key. The minimum - duration of this pre-roll phase is the time it takes for the data - to propagate to the authoritative servers plus TTL value of the - keyset. This equates to two times the Maximum Zone TTL. - roll: At the rollover stage (SOA serial 1) DNSKEY 11 is used to sign - the data in the zone exclusively (i.e. all the signatures from - DNSKEY 10 are removed from the zone). DNSKEY 10 remains published - in the keyset. This way data that was loaded into caches from - version 1 of the zone can still be verified with key sets fetched - from version 2 of the zone. - The minimum time that the keyset including DNSKEY 10 is to be - published is the time that it takes for zone data from the - previous version of the zone to expire from old caches i.e. the - time it takes for this zone to propagate to all authoritative - servers plus the Maximum Zone TTL value of any of the data in the - previous version of the zone. - after: DNSKEY 10 is removed from the zone. The keyset, now only - containing DNSKEY 11 is resigned with the DNSKEY 1. - - The above scheme can be simplified by always publishing the "future" - key immediately after the rollover. The scheme would look as follows - (we show two rollovers); the future key is introduced in "after" as - DNSKEY 12 and again a newer one, numbered 13, in "2nd after": - - - - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 11] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - normal roll after 2nd roll 2nd after - - SOA0 SOA2 SOA3 SOA4 SOA5 - RRSIG10(SOA0) RRSIG11(SOA2) RRSIG11(SOA3) RRSIG12(SOA4) RRSIG12(SOA5) - - DNSKEY1 DNSKEY1 DNSKEY1 DNSKEY1 DNSKEY1 - DNSKEY10 DNSKEY10 DNSKEY11 DNSKEY11 DNSKEY12 - DNSKEY11 DNSKEY11 DNSKEY12 DNSKEY12 DNSKEY13 - RRSIG1(DNSKEY) RRSIG1 (DNSKEY) RRSIG1(DNSKEY) RRSIG1(DNSKEY) RRSIG1(DNSKEY) - RRSIG10(DNSKEY) RRSIG11(DNSKEY) RRSIG11(DNSKEY) RRSIG12(DNSKEY) RRSIG12(DNSKEY) - - - Note that the key introduced after the rollover is not used for - production yet; the private key can thus be stored in a physically - secure manner and does not need to be 'fetched' every time a zone - needs to be signed. - - This scheme has the benefit that the key that is intended for future - use: immediately during an emergency rollover assuming that the - private key was stored in a physically secure manner. - -3.3.1.2 Double Signature Zone-signing Key Rollover - - This section shows how to perform a ZSK key rollover using the double - zone data signature scheme, aptly named "double sig rollover". - - During the rollover stage the new version of the zone file will need - to propagate to all authoritative servers and the data that exists in - (distant) caches will need to expire, this will take at least the - maximum Zone TTL . - - normal roll after - - SOA0 SOA1 SOA2 - RRSIG10(SOA0) RRSIG10(SOA1) RRSIG11(SOA2) - RRSIG11(SOA1) - - DNSKEY1 DNSKEY1 DNSKEY1 - DNSKEY10 DNSKEY10 DNSKEY11 - DNSKEY11 - RRSIG1(DNSKEY) RRSIG1(DNSKEY) RRSIG1(DNSKEY) - RRSIG10(DNSKEY) RRSIG10(DNSKEY) RRSIG11(DNSKEY) - RRSIG11(DNSKEY) - - normal: Version 0 of the zone: DNSKEY 1 is the key-signing key. - DNSKEY 10 is used to sign all the data of the zone, the - zone-signing key. - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 12] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - roll: At the rollover stage (SOA serial 1) DNSKEY 11 is introduced - into the keyset and all the data in the zone is signed with DNSKEY - 10 and DNSKEY 11. The rollover period will need to exist until all - data from version 0 of the zone has expired from remote caches. - This will take at least the maximum Zone TTL of version 0 of the - zone. - after: DNSKEY 10 is removed from the zone. All the signatures from - DNSKEY 10 are removed from the zone. The keyset, now only - containing DNSKEY 11, is resigned with DNSKEY 1. - - At every instance the data from the previous version of the zone can - be verified with the key from the current version and vice verse. The - data from the current version can be verified with the data from the - previous version of the zone. The duration of the rollover phase and - the period between rollovers should be at least the "Maximum Zone - TTL". - - Making sure that the rollover phase lasts until the signature - expiration time of the data in version 0 of the zone is recommended. - However, this date could be considerably longer than the Maximum Zone - TTL, making the rollover a lengthy procedure. - - Note that in this example we assumed that the zone was not modified - during the rollover. New data can be introduced in the zone as long - as it is signed with both keys. - -3.3.1.3 Pros and Cons of the Schemes - - Prepublish-keyset rollover: This rollover does not involve signing - the zone data twice. Instead, just before the actual rollover, the - new key is published in the keyset and thus available for - cryptanalysis attacks. A small disavantage is that this process - requires four steps. Also the prepublish scheme will not work for - KSKs as explained in Section 3.3. - Double signature rollover: The drawback of this signing scheme is - that during the rollover the number of signatures in your zone - doubles, this may be prohibitive if you have very big zones. An - advantage is that it only requires three steps. - -3.3.2 Key-signing Key Rollovers - - For the rollover of a key-signing key the same considerations as for - the rollover of a zone-signing key apply. However we can use a double - signature scheme to guarantee that old data (only the apex keyset) in - caches can be verified with a new keyset and vice versa. - - Since only the keyset is signed with a KSK, zone size considerations - do not apply. - - - -Kolkman & Gieben Expires August 30, 2004 [Page 13] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - normal roll after - - SOA0 SOA1 SOA2 - RRSIG10(SOA0) RRSIG10(SOA1) RRSIG10(SOA2) - - DNSKEY1 DNSKEY1 DNSKEY2 - DNSKEY2 - DNSKEY10 DNSKEY10 DNSKEY10 - RRSIG1 (DNSKEY) RRSIG1 (DNSKEY) RRSIG2(DNSKEY) - RRSIG2 (DNSKEY) - RRSIG10(DNSKEY) RRSIG10(DNSKEY) RRSIG10(DNSKEY) - - normal: Version 0 of the zone. The parental DS points to DNSKEY1. - Before the rollover starts the child will have to verify what the - TTL is of the DS RR that points to DNSKEY1 - it is needed during - the rollover and we refer to the value as TTL_DS. - roll: During the rollover phase the zone administrator generates a - second KSK, DNSKEY2. The key is provided to the parent and the - child will have to wait until a new DS RR has been generated that - points to DNSKEY2. After that DS RR has been published on _all_ - servers authoritative for the parents zone, the zone administrator - has to wait at least TTL_DS to make sure that the old DS RR has - expired from distant caches. - after: DNSKEY1 has been removed. - - The scenario above puts the responsibility for maintaining a valid - chain of trust with the child. It also is based on the premises that - the parent only has one DS RR (per algorithm) per zone. St John [The - draft has expired] proposed a mechanism where using an established - trust relation, the interaction can be performed in-band. In this - mechanism there are periods where there are two DS RRs at the parent. - - [Editors note: We probably need to mention more] - -4. Planning for Emergency Key Rollover - - This section deals with preparation for a possible key compromise. - Our advice is to have a documented procedure ready for when a key - compromise is suspected or confirmed. - - [Editors note: We are much in favor of a rollover tactic that keeps - the authentication chain intact as long as possible. This means that - one has to take all the regular rollover properties into account.] - - When the private material of one of your keys is compromised it can - be used for as long as a valid authentication chain exists. An - authentication chain remains intact for: - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 14] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - o as long as a signature over the compromised key in the - authentication chain is valid, - o as long as a parental DS RR (and signature) points to the - compromised key, - o as long as the key is anchored in a resolver and is used as a - starting point for validation. (This is the hardest to update.) - While an authentication chain to your compromised key exists, your - name-space is vulnerable to abuse by the malicious key holder (i.e. - the owner of the compromised key). Zone operators have to make a - trade off if the abuse of the compromised key is worse than having - data in caches that cannot be validated. If the zone operator chooses - to break the authentication chain to the compromised key, data in - caches signed with this key cannot be validated. However, if the zone - administrator chooses to take the path of a regular roll-over, the - malicious key holder can spoof data so that it appears to be valid, - note that this kind of attack will usually be localised in the - Internet topology. - - -4.1 KSK Compromise - - When the KSK has been compromised the parent must be notified as soon - as possible using secure means. The keyset of the zone should be - resigned as soon as possible. Care must be taken to not break the - authentication chain. The local zone can only be resigned with the - new KSK after the parent's zone has been updated with the new KSK. - Before this update takes place it would be best to drop the security - status of a zone all together: the parent removes the DS of the child - at the next zone update. After that the child can be made secure - again. - - An additional danger of a key compromise is that the compromised key - can be used to facilitate a legitimate DNSKEY/DS and/or nameserver - rollover at the parent. When that happens the domain can be in - dispute. An out of band and secure notify mechanism to contact a - parent is needed in this case. - -4.2 ZSK Compromise - - Primarily because there is no parental interaction required when a - ZSK is compromised, the situation is less severe than with with a KSK - compromise. The zone must still be resigned with a new ZSK as soon - as possible. As this is a local operation and requires no - communication between the parent and child this can be achieved - fairly quickly. However, one has to take into account that just as - with a normal rollover the immediate disappearance from the old - compromised key may lead to verification problems. The - pre-publication scheme as discussed above minimises such problems. - - - -Kolkman & Gieben Expires August 30, 2004 [Page 15] - -Internet-Draft DNSSEC Operational Practices March 2004 - - -4.3 Compromises of Keys Anchored in Resolvers - - A key can also be pre-configured in resolvers. If DNSSEC is rolled - out as planned the root key should be pre-configured in every secure - aware resolver on the planet. [Editors Note: add more about - authentication of a newly received resolver key] - - If trust-anchor keys are compromised, the resolvers using these keys - should be notified of this fact. Zone administrators may consider - setting up a mailing list to communicate the fact that a SEP key is - about to be rolled over. This communication will of course need to be - authenticated e.g. by using digital signatures. - -5. Parental Policies - -5.1 Initial Key Exchanges and Parental Policies Considerations - - The initial key exchange is always subject to the policies set by the - parent (or its registry). When designing a key exchange policy one - should take into account that the authentication and authorisation - mechanisms used during a key exchange should be as strong as the - authentication and authorisation mechanisms used for the exchange of - delegation information between parent and child. - - Using the DNS itself as the source for the actual DNSKEY material, - with an off-band check on the validity of the DNSKEY, has the benefit - that it reduces the chances of user error. A parental DNSKEY download - tool can make use of the SEP bit [4] to select the proper key from a - DNSSEC keyset; thereby reducing the chance that the wrong DNSKEY is - sent. It can validate the self-signature over a key; thereby - verifying the ownership of the private key material. Fetching the - DNSKEY from the DNS ensures that the child will not become bogus once - the parent publishes the DS RR indicating the child is secure. - - Note: the off-band verification is still needed when the key-material - is fetched by a tool. The parent can not be sure whether the DNSKEY - RRs have been spoofed. - -5.2 Storing Keys So Hashes Can Be Regenerated - - When designing a registry system one should consider if the DNSKEYs - and/or the corresponding DSs are stored. Storing DNSKEYs will help - during troubleshooting while the overhead of calculating DS records - from them is minimal. - - Having an out-of-band mechanism, such as a Whois database, to find - out which keys are used to generate DS Resource Records for specific - owners may also help with troubleshooting. - - - -Kolkman & Gieben Expires August 30, 2004 [Page 16] - -Internet-Draft DNSSEC Operational Practices March 2004 - - -5.3 Security Lameness Checks - - Security Lameness is defined as what happens when a parent has a DS - Resource Record pointing to a non-existing DNSKEY RR. During key - exchange a parent should make sure that the child's key is actually - configured in the DNS before publishing a DS RR in its zone. Failure - to do so would render the child's zone being marked as bogus. - - Child zones should be very careful removing DNSKEY material, - specifically SEP keys, for which a DS RR exists. - - Once a zone is "security lame" a fix (e.g. by removing a DS RR) will - take time to propagate through the DNS. - -5.4 DS Signature Validity Period - - Since the DS can be replayed as long as it has a valid signature a - short signature validity period over the DS minimises the time a - child is vulnerable in the case of a compromise of the child's - KSK(s). A signature validity period that is too short introduces the - possibility that a zone is marked bogus in case of a configuration - error in the signer; there may not be enough time to fix the problems - before signatures expire. Something as mundane as operator - unavailability during weekends shows the need for DS signature - lifetimes longer than 2 days. We recommend the minimum for a DS - signature validity period to be a few days. - - The maximum signature lifetime of the DS record depends on how long - child zones are willing to be vulnerable after a key compromise. We - consider a signature validity period of around one week to be a good - compromise between the operational constraints of the parent and - minimising damage for the child. - -6. Security Considerations - - DNSSEC adds data integrity to the DNS. This document tries to assess - considerations to operate a stable and secure DNSSEC service. Not - taking into account the 'data propagation' properties in the DNS will - cause validation failures and may make secured zones unavailable to - security aware resolvers. - -7. Acknowledgments - - We, the folk mentioned as authors, only acted as editors. Most of the - ideas in this draft were the result of collective efforts during - workshops, discussions and try outs. - - At the risk of forgetting individuals who where the original - - - -Kolkman & Gieben Expires August 30, 2004 [Page 17] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - contributors of the ideas we would like to acknowledge people who - where actively involved in the compilation of this document. In - random order: Olafur Gudmundsson, Wesley Griffin, Michael Richardson, - Scott Rose, Rick van Rein, Tim McGinnis, Gilles Guette and Olivier - Courtay, Sam Weiler. - - Emma Bretherick and Adrian Bedford corrected many of the spelling and - style issues. - - Kolkman and Gieben take the blame for introducing all miscakes(SIC). - -8. References - -8.1 Normative References - - [1] Eastlake, D., "Domain Name System Security Extensions", RFC - 2535, March 1999. - - [2] Eastlake, D., "DNS Security Operational Considerations", RFC - 2541, March 1999. - - [3] Lewis, E., "DNS Security Extension Clarification on Zone - Status", RFC 3090, March 2001. - - [4] Lewis, E., Kolkman, O. and J. Schlyter, "KEY RR Key-Signing Key - (KSK) Flag", draft-ietf-dnsext-keyrr-key-signing-flag-06 (work - in progress), February 2003. - -8.2 Informative References - - [5] Bradner, S., "Key words for use in RFCs to Indicate Requirement - Levels", BCP 14, RFC 2119, March 1997. - - [6] Andrews, M., "Negative Caching of DNS Queries (DNS NCACHE)", RFC - 2308, March 1998. - - [7] Gudmundsson, O., "Delegation Signer Resource Record", - draft-ietf-dnsext-delegation-signer-13 (work in progress), March - 2003. - - [8] Arends, R., "Protocol Modifications for the DNS Security - Extensions", draft-ietf-dnsext-dnssec-protocol-01 (work in - progress), March 2003. - - [9] Lenstra, A. and E. Verheul, "Selecting Cryptographic Key Sizes", - The Journal of Cryptology 14 (255-293), 2001. - - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 18] - -Internet-Draft DNSSEC Operational Practices March 2004 - - -Authors' Addresses - - Olaf M. Kolkman - RIPE NCC - Singel 256 - Amsterdam 1016 AB - The Netherlands - - Phone: +31 20 535 4444 - EMail: olaf@ripe.net - URI: http://www.ripe.net/ - - - Miek Gieben - NLnet Labs - Kruislaan 419 - Amsterdam 1098 VA - The Netherlands - - EMail: miek@nlnetlabs.nl - URI: http://www.nlnetlabs.nl - -Appendix A. Terminology - - In this document there is some jargon used that is defined in other - documents. In most cases we have not copied the text from the - documents defining the terms but given a more elaborate explanation - of the meaning. Note that these explanations should not be seen as - authoritative. - - Private and Public Keys: DNSSEC secures the DNS through the use of - public key cryptography. Public key cryptography is based on the - existence of two keys, a public key and a private key. The public - keys are published in the DNS by use of the DNSKEY Resource Record - (DNSKEY RR). Private keys should remain private i.e. should not be - exposed to parties not-authorised to do the actual signing. - Signer: The system that has access to the private key material and - signs the Resource Record sets in a zone. A signer may be - configured to sign only parts of the zone e.g. only those RRsets - for which existing signatures are about to expire. - KSK: A Key-Signing Key (KSK) is a key that is used exclusively for - signing the apex keyset. The fact that a key is a KSK is only - relevant to the signing tool. - ZSK: A Zone Signing Key (ZSK) is a key that is used for signing all - data in a zone. The fact that a key is a ZSK is only relevant to - the signing tool. - - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 19] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - SEP Key: A KSK that has a parental DS record pointing to it. Note: - this is not enforced in the protocol. A SEP Key with no parental - DS is security lame. - Anchored Key: A DNSKEY configured in resolvers around the globe. This - Key is hard to update, hence the term anchored. - Bogus: [Editors Note: a reference here] An RRset in DNSSEC is marked - "Bogus" when a signature of a RRset does not validate against the - DNSKEY. Even if the key itself was not marked Bogus. A cache may - choose to cache Bogus data for various reasons. - Singing the Zone File: The term used for the event where an - administrator joyfully signs its zone file while producing melodic - sound patterns. - Zone Administrator: The 'role' that is responsible for signing a zone - and publishing it on the primary authoritative server. - -Appendix B. Zone-signing Key Rollover Howto - - Using the pre-published signature scheme and the most conservative - method to assure oneself that data does not live in distant caches - here follows the "HOWTO". [WES: has some comments about this] - Key notation: - Step 0: The preparation: Create two keys and publish both in your - keyset. Mark one of the keys as "active" and the other as - "published". Use the "active" key for signing your zone data. - Store the private part of the "published" key, preferably - off-line. - Step 1: Determine expiration: At the beginning of the rollover make a - note of the highest expiration time of signatures in your zone - file created with the current key marked as "active". - Wait until the expiration time marked in Step 1 has passed - Step 2: Then start using the key that was marked as "published" to - sign your data i.e. mark it as "active". Stop using the key that - was marked as "active", mark it as "rolled". - Step 3: It is safe to engage in a new rollover (Step 1) after at - least one "signature validity period". - -Appendix C. Typographic Conventions - - The following typographic conventions are used in this document: - Key notation: A key is denoted by KEYx, where x is a number, x could - be thought of as the key id. - RRset notations: RRs are only denoted by the type. All other - information - owner, class, rdata and TTL - is left out. Thus: - example.com 3600 IN A 192.168.1.1 is reduced to: A. RRsets are a - list of RRs. A example of this would be: A1,A2, specifying the - RRset containing two A records. This could again be abbreviated to - just: A. - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 20] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - Signature notation: Signatures are denoted as RRSIGx(RRset), which - means that RRset is signed with DNSKEYx. - Zone representation: Using the above notation we have simplified the - representation of a signed zone by leaving out all unnecessary - details such as the names and by representing all data by "SOAx" - SOA representation: SOA's are represented as SOAx, where x is the - serial number. - Using this notation the following zone : - - - example.net. 600 IN SOA ns.example.net. ernie.example.net. ( - 10 ; serial - 450 ; refresh (7 minutes 30 seconds) - 600 ; retry (10 minutes) - 345600 ; expire (4 days) - 300 ; minimum (5 minutes) - ) - 600 RRSIG SOA 5 2 600 20130522213204 ( - 20130422213204 14 example.net. - cmL62SI6iAX46xGNQAdQ... ) - 600 NS a.iana-servers.net. - 600 NS b.iana-servers.net. - 600 RRSIG NS 5 2 600 20130507213204 ( - 20130407213204 14 example.net. - SO5epiJei19AjXoUpFnQ ... ) - 3600 DNSKEY 256 3 5 ( - EtRB9MP5/AvOuVO0I8XDxy0... - ) ; key id = 14 - 3600 DNSKEY 256 3 5 ( - gsPW/Yy19GzYIY+Gnr8HABU... - ) ; key id = 15 - 3600 RRSIG DNSKEY 5 2 3600 20130522213204 ( - 20130422213204 14 example.net. - J4zCe8QX4tXVGjV4e1r9... ) - 3600 RRSIG DNSKEY 5 2 3600 20130522213204 ( - 20130422213204 15 example.net. - keVDCOpsSeDReyV6O... ) - 600 NSEC a.example.net. NS SOA TXT RRSIG DNSKEY NSEC - 600 RRSIG NSEC 5 2 600 20130507213204 ( - 20130407213204 14 example.net. - obj3HEp1GjnmhRjX... ) - a.example.net. 600 IN TXT "A label" - 600 RRSIG TXT 5 3 600 20130507213204 ( - 20130407213204 14 example.net. - IkDMlRdYLmXH7QJnuF3v... ) - 600 NSEC b.example.com. TXT RRSIG NSEC - 600 RRSIG NSEC 5 3 600 20130507213204 ( - 20130407213204 14 example.net. - - - -Kolkman & Gieben Expires August 30, 2004 [Page 21] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - bZMjoZ3bHjnEz0nIsPMM... ) - - ... - - - is reduced to the following represenation: - - SOA10 - RRSIG14(SOA10) - - DNSKEY14 - DNSKEY15 - - RRSIG14(KEY) - RRSIG15(KEY) - - The rest of the zone data has the same signature as the SOA record, - i.e a RRSIG created with DNSKEY 14. - -Appendix D. Document Details and Changes - - This section is to be removed by the RFC editor if and when the - document is published. - - $Header: /var/cvs/dnssec-key/ - draft-ietf-dnsop-dnssec-operational-practices.xml,v 1.22 2004/05/12 - 08:29:11 dnssec Exp $ - -D.1 draft-ietf-dnsop-dnssec-operational-practices-00 - - Submission as working group document. This document is a modified and - updated version of draft-kolkman-dnssec-operational-practices-00. - -D.2 draft-ietf-dnsop-dnssec-operational-practices-01 - - changed the definition of "Bogus" to reflect the one in the protocol - draft. - - Bad to Bogus - - Style and spelling corrections - - KSK - SEP mapping made explicit. - - Updates from Sam Weiler added - - - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 22] - -Internet-Draft DNSSEC Operational Practices March 2004 - - -Intellectual Property Statement - - The IETF takes no position regarding the validity or scope of any - intellectual property or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; neither does it represent that it - has made any effort to identify any such rights. 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All Rights Reserved. - - This document and translations of it may be copied and furnished to - others, and derivative works that comment on or otherwise explain it - or assist in its implementation may be prepared, copied, published - and distributed, in whole or in part, without restriction of any - kind, provided that the above copyright notice and this paragraph are - included on all such copies and derivative works. However, this - document itself may not be modified in any way, such as by removing - the copyright notice or references to the Internet Society or other - Internet organizations, except as needed for the purpose of - developing Internet standards in which case the procedures for - copyrights defined in the Internet Standards process must be - followed, or as required to translate it into languages other than - English. - - The limited permissions granted above are perpetual and will not be - revoked by the Internet Society or its successors or assignees. - - This document and the information contained herein is provided on an - "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING - TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING - BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION - - - -Kolkman & Gieben Expires August 30, 2004 [Page 23] - -Internet-Draft DNSSEC Operational Practices March 2004 - - - HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF - MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Acknowledgment - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Kolkman & Gieben Expires August 30, 2004 [Page 24] - - diff --git a/doc/draft/draft-ietf-dnsop-dnssec-operational-practices-02.txt b/doc/draft/draft-ietf-dnsop-dnssec-operational-practices-02.txt new file mode 100644 index 0000000000..c8006c2c49 --- /dev/null +++ b/doc/draft/draft-ietf-dnsop-dnssec-operational-practices-02.txt @@ -0,0 +1,1400 @@ + +DNSOP O. Kolkman +Internet-Draft RIPE NCC +Expires: April 11, 2005 R. Gieben + NLnet Labs + October 11, 2004 + + + DNSSEC Operational Practices + draft-ietf-dnsop-dnssec-operational-practices-02.txt + +Status of this Memo + + This document is an Internet-Draft and is subject to all provisions + of section 3 of RFC 3667. By submitting this Internet-Draft, each + author represents that any applicable patent or other IPR claims of + which he or she is aware have been or will be disclosed, and any of + which he or she become aware will be disclosed, in accordance with + RFC 3668. + + Internet-Drafts are working documents of the Internet Engineering + Task Force (IETF), its areas, and its working groups. Note that + other groups may also distribute working documents as + Internet-Drafts. + + Internet-Drafts are draft documents valid for a maximum of six months + and may be updated, replaced, or obsoleted by other documents at any + time. It is inappropriate to use Internet-Drafts as reference + material or to cite them other than as "work in progress." + + The list of current Internet-Drafts can be accessed at + http://www.ietf.org/ietf/1id-abstracts.txt. + + The list of Internet-Draft Shadow Directories can be accessed at + http://www.ietf.org/shadow.html. + + This Internet-Draft will expire on April 11, 2005. + +Copyright Notice + + Copyright (C) The Internet Society (2004). + +Abstract + + This document describes a set of practices for operating a DNSSEC + aware environment. The target audience is zone administrators + deploying DNSSEC that need a guide to help them chose appropriate + values for DNSSEC parameters. It also discusses operational matters + such as key rollovers, KSK and ZSK considerations and related + matters. + + + +Kolkman & Gieben Expires April 11, 2005 [Page 1] + +Internet-Draft DNSSEC Operational Practices October 2004 + + +Table of Contents + + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 1.1 The Use of the Term 'key' . . . . . . . . . . . . . . . . 3 + 1.2 Keeping the Chain of Trust Intact . . . . . . . . . . . . 3 + 2. Time in DNSSEC . . . . . . . . . . . . . . . . . . . . . . . . 4 + 2.1 Time Definitions . . . . . . . . . . . . . . . . . . . . . 4 + 2.2 Time Considerations . . . . . . . . . . . . . . . . . . . 5 + 3. Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 + 3.1 Motivations for the KSK and ZSK Separation . . . . . . . . 7 + 3.2 Key Security Considerations . . . . . . . . . . . . . . . 8 + 3.2.1 Key Validity Period . . . . . . . . . . . . . . . . . 8 + 3.2.2 Key Algorithm . . . . . . . . . . . . . . . . . . . . 8 + 3.2.3 Key Sizes . . . . . . . . . . . . . . . . . . . . . . 9 + 3.3 Key Rollovers . . . . . . . . . . . . . . . . . . . . . . 9 + 3.3.1 Difference Between ZSK and KSK Rollovers . . . . . . . 10 + 3.3.2 Zone-signing Key Rollovers . . . . . . . . . . . . . . 10 + 3.3.3 Key-signing Key Rollovers . . . . . . . . . . . . . . 14 + 3.3.4 Automated Key Rollovers . . . . . . . . . . . . . . . 15 + 4. Planning for Emergency Key Rollover . . . . . . . . . . . . . 15 + 4.1 KSK Compromise . . . . . . . . . . . . . . . . . . . . . . 16 + 4.2 ZSK Compromise . . . . . . . . . . . . . . . . . . . . . . 16 + 4.3 Compromises of Keys Anchored in Resolvers . . . . . . . . 16 + 5. Parental Policies . . . . . . . . . . . . . . . . . . . . . . 17 + 5.1 Initial Key Exchanges and Parental Policies + Considerations . . . . . . . . . . . . . . . . . . . . . . 17 + 5.2 Storing Keys So Hashes Can Be Regenerated . . . . . . . . 17 + 5.3 Security Lameness Checks . . . . . . . . . . . . . . . . . 18 + 5.4 DS Signature Validity Period . . . . . . . . . . . . . . . 18 + 6. Security Considerations . . . . . . . . . . . . . . . . . . . 18 + 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19 + 8.1 Normative References . . . . . . . . . . . . . . . . . . . . 19 + 8.2 Informative References . . . . . . . . . . . . . . . . . . . 19 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 20 + A. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 20 + B. Zone-signing Key Rollover Howto . . . . . . . . . . . . . . . 21 + C. Typographic Conventions . . . . . . . . . . . . . . . . . . . 22 + D. Document Details and Changes . . . . . . . . . . . . . . . . . 23 + D.1 draft-ietf-dnsop-dnssec-operational-practices-00 . . . . . 23 + D.2 draft-ietf-dnsop-dnssec-operational-practices-01 . . . . . 23 + Intellectual Property and Copyright Statements . . . . . . . . 25 + + + + + + + + + +Kolkman & Gieben Expires April 11, 2005 [Page 2] + +Internet-Draft DNSSEC Operational Practices October 2004 + + +1. Introduction + + During workshops and early operational deployment tests, operators + and system administrators gained experience about operating DNSSEC + aware DNS services. This document translates these experiences into + a set of practices for zone administrators. At the time of writing, + there exists very little experience with DNSSEC in production + environments, this document should therefore explicitly not be seen + as representing 'Best Current Practices'. + + The procedures herein are focused on the maintenance of signed zones + (i.e. signing and publishing zones on authoritative servers). It is + intended that maintenance of zones such as resigning or key rollovers + be transparent to any verifying clients on the Internet. + + The structure of this document is as follows: It begins with + discussing some of the considerations with respect to timing + parameters of DNS in relation to DNSSEC (Section 2). Aspects of key + management such as key rollover schemes are described in Section 3. + Emergency rollover considerations are addressed in Section 4. The + typographic conventions used in this document are explained in + Appendix C. + + Since this is a document with operational suggestions and there are + no protocol specifications, the RFC2119 [7] language does not apply. + +1.1 The Use of the Term 'key' + + It is assumed that the reader is familiar with the concept of + asymmetric keys on which DNSSEC is based (Public Key Cryptography + [11]). Therefore, this document will use the term 'key' rather + loosely. Where it is written that 'a key is used to sign data' it is + assumed that the reader understands that it is the private part of + the key-pair that is used for signing. It is also assumed that the + reader understands that the public part of the key-pair is published + in the DNSKEY resource record and that it is the public part that is + used in key-exchanges. + +1.2 Keeping the Chain of Trust Intact + + Maintaining a valid chain of trust is important because broken chains + of trust will result in data being marked as bogus, which may cause + entire (sub)domains to become invisible to verifying clients. The + administrators of secured zones have to realize that their zone is, + to their clients, part of a chain of trust. + + As mentioned in the introduction, the procedures herein are intended + to ensure maintenance of zones, such as resigning or key rollovers, + + + +Kolkman & Gieben Expires April 11, 2005 [Page 3] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + be transparent to the verifying clients on the Internet. + + Administrators of secured zones will have to keep in mind that data + published on an authoritative primary server will not be immediately + seen by verifying clients; it may take some time for the data to be + transfered to other secondary authoritative nameservers, during which + period clients may be fetching data from caching non-authoritative + servers. + + For the verifying clients it is important that data from secured + zones can be used to build chains of trust regardless of whether the + data came directly from an authoritative server, a caching nameserver + or some middle box. Only by carefully using the available timing + parameters can a zone administrator assure that the data necessary + for verification can be obtained. + + The responsibility for maintaining the chain of trust is shared by + administrators of secured zones in the chain of trust. This is most + obvious in the case of a 'key compromise' when a trade off between + maintaining a valid chain of trust and replacing the compromised keys + as soon as possible, must be made. + + The zone administrator will have to make a trade off between keeping + the chain of trust intact - thereby allowing for attacks with the + compromised key - or to deliberately break the chain of trust and + making secured sub domains invisible to security aware resolvers. + Also see Section 4. + +2. Time in DNSSEC + + Without DNSSEC all times in DNS are relative. The SOA's refresh, + retry and expiration timers are counters that are used to determine + the time elapsed after a slave server synchronized (or tried to + synchronize) with a master server. The Time to Live (TTL) value and + the SOA minimum TTL parameter [8] are used to determine how long a + forwarder should cache data after it has been fetched from an + authoritative server. By using a signature validity period, DNSSEC + introduces the notion of an absolute time in the DNS. Signatures in + DNSSEC have an expiration date after which the signature is marked as + invalid and the signed data is to be considered bogus. + +2.1 Time Definitions + + In this document we will be using a number of time related terms. + The following definitions apply: + o "Signature validity period" + + + + + +Kolkman & Gieben Expires April 11, 2005 [Page 4] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + The period that a signature is valid. It starts at the time + specified in the signature inception field of the RRSIG RR and + ends at the time specified in the expiration field of the RRSIG + RR. + o "Signature publication period" + Time after which a signature (made with a specific key) is + replaced with a new signature (made with the same key). This + replacement takes place by publishing the relevant RRSIG in the + master zone file. + If all signatures are refreshed at zone (re)signing then the + signature publication period is equal to the signature validity + period. + o "Maximum/Minimum Zone TTL" + The maximum or minimum value of the TTLs from the complete set + of RRs in a zone. + +2.2 Time Considerations + + Because of the expiration of signatures, one should consider the + following. + o We suggest the Maximum Zone TTL of your zone data to be a fraction + of your signature validity period. + If the TTL would be of similar order as the signature validity + period, then all RRsets fetched during the validity period + would be cached until the signature expiration time. Section + 7.1 [5] suggests that "the resolver may use the time remaining + before expiration of the signature validity period of a signed + RRset as an upper bound for the TTL". As a result query load + on authoritative servers would peak at signature expiration + time, as this is also the time at which records simultaneously + expire from caches. + To avoid query load peaks we suggest the TTL on all the RRs in + your zone to be at least a few times smaller than your + signature validity period. + o We suggest the signature publication period to be at least one + maximum TTL smaller than the signature validity period. + Resigning a zone shortly before the end of the signature + validity period may cause simultaneous expiration of data from + caches. This in turn may lead to peaks in the load on + authoritative servers. + o We suggest the minimum zone TTL to be long enough to both fetch + and verify all the RRs in the authentication chain. A low TTL can + cause two problems: + 1. During validation, some data may expire before the + validation is complete. The validator should be able to keep + all data, until is completed. This applies to all RRs needed + to complete the chain of trust: DSs, DNSKEYs, RRSIGs, and the + final answers i.e. the RR set that is returned for the initial + + + +Kolkman & Gieben Expires April 11, 2005 [Page 5] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + query. + 2. Frequent verification causes load on recursive nameservers. + Data at delegation points, DSs, DNSKEYs and RRSIGs benefit from + caching. The TTL on those should be relatively long. + o Slave servers will need to be able to fetch newly signed zones + well before the RRSIGs in the zone server by the slave server pass + their signature expiration time. + When a slave server is out of sync with its master and data in + a zone is signed by expired signatures it may be better for the + slave server not to give out any answer. + Normally a slave server that is not able to contact a master + server for an extended period will expire a zone. When that + happens the zone will not respond on queries. The time of + expiration is set in the SOA record and is relative to the last + successful refresh between the master and the slave server. + There exists no coupling between the signature expiration of + RRSIGs in the zone and the expire parameter in the SOA. + If the server serves a DNSSEC zone than it may well happen that + the signatures expire well before the SOA expiration timer + counts down to zero. It is not possible to completely prevent + this from happening by tweaking the SOA parameters. + However, the effects can be minimized where the SOA expiration + time is equal or smaller than the signature validity period. + The consequence of an authoritative server not being able to + update a zone, whilst that zone includes expired signatures, is + that non-secure resolvers will continue to be able to resolve + data served by the particular slave servers while security + aware resolvers will experience problems because of answers + being marked as bogus. + We suggest the SOA expiration timer being approximately one + third or one fourth of the signature validity period. It will + allow problems with transfers from the master server to be + noticed before the actual signature time out. + We also suggest that operators of nameservers with slave zones + develop 'watch dogs' to spot upcoming signature expirations in + slave zones, and take appropriate action. + When determining the value for the expiration parameter one has + to take the following into account: What are the chances that + all my secondary zones expire; How quickly can I reach an + administrator and load a valid zone? All these arguments are + not DNSSEC specific but may influence the choice of your + signature validity intervals. + +3. Keys + + The DNSSEC validation protocol does not distinguish between DNSKEYs. + All DNSKEYs can be used during the validation. In practice operators + use Key Singing and Zone Signing Keys and use the so called SEP flag + + + +Kolkman & Gieben Expires April 11, 2005 [Page 6] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + to distinguish between them during operations. The dynamics and + considerations are discussed below. + + To make zone re-signing and key rollovers procedures easier to + implement, it is possible to use one or more keys as Key Signing Keys + (KSK) these keys will only sign the apex DNSKEY RR set in a zone. + Other keys can be used to sign all the RRsets in a zone and are + referred to as Zone Signing Keys (ZSK). In this document we assume + that KSKs are the subset of keys that are used for key exchanges with + the parent and potentially for configuration as trusted anchors - the + so called Secure Entry Point keys (SEP). In this document we assume + a one-to-one mapping between KSK and SEP keys and we assume the SEP + flag [4] to be set on KSKs. + +3.1 Motivations for the KSK and ZSK Separation + + Differentiating between the KSK to ZSK functions has several + advantages: + + o The KSK can be made stronger (i.e. using more bits in the key + material). This has little operational impact since it is only + used to sign a small fraction of the zone data. + o As the KSK is only used to sign a key set, which is most probably + updated less frequently than other data in the zone, it can be + stored separately from and in a safer location than the ZSK. + o A KSK can be used for longer periods. + o No parent/child interaction is required when ZSKs are updated. + + The KSK is used less than ZSK, once a key set is signed with the KSK + all the keys in the key set can be used as ZSK. If a ZSK is + compromised, it can be simply dropped from the key set. The new key + set is then resigned with the KSK. + + Given the assumption that for KSKs the SEP flag is set, the KSK can + be distinguished from a ZSK by examining the flag field in the DNSKEY + RR. If the flag field is an odd number it is a KSK if it is an even + number it is a ZSK. + + The zone-signing key can be used to sign all the data in a zone on a + regular basis. When a zone-signing key is to be rolled, no + interaction with the parent is needed. This allows for "Signature + Validity Periods" in the order of days. + + The key-signing key is only to be used to sign the DNSKEY RRs in a + zone. If a key-signing key is to be rolled over, there will be + interactions with parties other than the zone administrator. These + can include the registry of the parent zone or administrators of + verifying resolvers that have the particular key configured as + + + +Kolkman & Gieben Expires April 11, 2005 [Page 7] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + trusted entry points. Hence, the "Key Usage Time" of these keys can + and should be made much longer. Although, given a long enough key, + the "Key Usage Time" can be on the order of years we suggest to plan + for a "Key Usage Time" of the order of a few months so that a key + rollover remains an operational routine. + +3.2 Key Security Considerations + + Keys in DNSSEC have a number of parameters which should all be chosen + with care, the most important once are: size, algorithm and the key + validity period (its lifetime). + +3.2.1 Key Validity Period + + RFC2541 [2] describes a number of considerations with respect to the + security of keys. The document deals with the generation, lifetime, + size and storage of private keys. + + In Section 3 of RFC2541 [2] there are some suggestions for a key + validity period: 13 months for long-lived keys and 36 days for + transaction keys but suggestions for key sizes are not made. + + If we say long-lived keys are key-signing keys and transactions keys + are zone-signing keys, these recommendations will lead to rollovers + occurring frequently enough to become part of 'operational habits'; + the procedure does not have to be reinvented every time a key is + replaced. + +3.2.2 Key Algorithm + + There are currently three different types of algorithms that can be + used in DNSSEC: RSA, DSA and elliptic curve cryptography. The latter + is fairly new and still needs to be standardized for usage in DNSSEC. + + RSA has been developed in an open and transparent manner. As the + patent on RSA expired in 2000, its use is now also free. + + DSA has been developed by NIST. The creation of signatures creation + is roughly the same speed as with RSA, but is 10 to 40 times as slow + for verification [11]. + + We suggest the use of RSA/SHA-1 as the preferred algorithm for the + key. The current known attacks on RSA can be defeated by making your + key longer. As the MD5 hashing algorithm is showing (theoretical) + cracks, we recommend the usage of SHA1. + + + + + + +Kolkman & Gieben Expires April 11, 2005 [Page 8] + +Internet-Draft DNSSEC Operational Practices October 2004 + + +3.2.3 Key Sizes + + When choosing key sizes, zone administrators will need to take into + account how long a key will be used and how much data will be signed + during the key publication period. It is hard to give precise + recommendations but Lenstra and Verheul [10] supplied the following + table with lower bound estimates for cryptographic key sizes. Their + recommendations are based on a set of explicitly formulated parameter + settings, combined with existing data points about cryptographic + systems. For details we refer to the original paper. + + + Year RSA Key Sizes Year RSA Key Sizes + + 2000 952 2015 1613 + 2001 990 2016 1664 + 2002 1028 2017 1717 + 2003 1068 2018 1771 + 2004 1108 2019 1825 + + + 2005 1149 2020 1881 + 2006 1191 2021 1937 + 2007 1235 2022 1995 + 2008 1279 2023 2054 + 2009 1323 2024 2113 + + + 2026 2236 2025 2174 + 2010 1369 2027 2299 + 2011 1416 2028 2362 + 2012 1464 2029 2427 + 2013 1513 + 2014 1562 + + For example, should you wish your key to last three years from 2003, + check the RSA key size values for 2006 in this table. In this case + 1191. + +3.3 Key Rollovers + + A DNSSEC key cannot be used forever (see RFC2541 [2] and Section + 3.2). So key rollovers are a fact of life when using DNSSEC. Zone + administrators who are in the process of rolling their keys have to + take into account that data published in previous versions of their + zone still lives in caches. When deploying DNSSEC, this becomes an + important consideration; ignoring data that may be in caches may lead + to loss of service for clients. + + + +Kolkman & Gieben Expires April 11, 2005 [Page 9] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + The most pressing example of this is when zone material signed with + an old key is being validated by a resolver which does not have the + old zone key cached. If the old key is no longer present in the + current zone, this validation fails, marking the data bogus. + Alternatively, an attempt could be made to validate data which is + signed with a new key against an old key that lives in a local cache, + also resulting in data being marked bogus. + +3.3.1 Difference Between ZSK and KSK Rollovers + + Note that KSK rollovers and ZSK rollovers are different. A zone-key + rollover can be handled in two different ways: pre-publish (Section + Section 3.3.2.1) and double signature (Section Section 3.3.2.2). + + As the KSK is used to validate the key set and because the KSK is not + changed during a ZSK rollover, a cache is able to validate the new + key set of the zone. The pre-publish method does not work for a KSK + rollover. The following example demonstrates that, here rollover the + KSK from DNSKEY1 to DNSKEY2 using the NONE working pre-publish + method. + + normal pre-roll roll after + + SOA0 SOA1 SOA2 SOA3 + RRSIG10(SOA0) RRSIG10(SOA1) RRSIG11(SOA2) RRSIG11(SOA3) + + DNSKEY1 DNSKEY1 DNSKEY1 DNSKEY2 + DNSKEY10 DNSKEY2 DNSKEY2 DNSKEY10 + DNSKEY10 DNSKEY10 + RRSIG1 (DNSKEY) RRSIG1 (DNSKEY) RRSIG2(DNSKEY) RRSIG2 (DNSKEY) + RRSIG10(DNSKEY) RRSIG10(DNSKEY) RRSIG10(DNSKEY) RRSIG10(DNSKEY) + + A cache that queries the zone during the "normal" step gets back + DNSKEY1. The DS RR and the key set are cached. If the TTL of the DS + RR is large enough, the DS RR remains in the cache until the "after" + step. If in this case, the key set TTL expires, and the cache + queries for the zone again, it will get back the new key set signed + by DNSKEY2. It will then try to validate the key set with DNSKEY1 + and will fail. + +3.3.2 Zone-signing Key Rollovers + + For zone-signing key rollovers there are two ways to make sure that + during the rollover data still cached can be verified with the new + key sets or newly generated signatures can be verified with the keys + still in caches. One schema uses double signatures, it is described + in Section 3.3.2.2, the other uses key pre-publication (Section + 3.3.2.1). The pros, cons and recommendations are described in + + + +Kolkman & Gieben Expires April 11, 2005 [Page 10] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + Section 3.3.2.3. + +3.3.2.1 Pre-publish key set Rollover + + This section shows how to perform a ZSK rollover without the need to + sign all the data in a zone twice - the so called "pre-publish + rollover".This method has advantages in the case of a key compromise. + If the old key is compromised, the new key has already been + distributed in the DNS. The zone administrator is then able to + quickly switch to the new key and remove the compromised key from the + zone. Another major advantage is that the zone size does not double, + as is the case with the double signature ZSK rollover. A small + "HOWTO" for this kind of rollover can be found in Appendix B. + + normal pre-roll roll after + + SOA0 SOA1 SOA2 SOA3 + RRSIG10(SOA0) RRSIG10(SOA1) RRSIG11(SOA2) RRSIG11(SOA3) + + DNSKEY1 DNSKEY1 DNSKEY1 DNSKEY1 + DNSKEY10 DNSKEY10 DNSKEY10 DNSKEY11 + DNSKEY11 DNSKEY11 + RRSIG1 (DNSKEY) RRSIG1 (DNSKEY) RRSIG1(DNSKEY) RRSIG1 (DNSKEY) + RRSIG10(DNSKEY) RRSIG10(DNSKEY) RRSIG11(DNSKEY) RRSIG11(DNSKEY) + + + normal: Version 0 of the zone: DNSKEY 1 is the key-signing key. + DNSKEY 10 is used to sign all the data of the zone, the + zone-signing key. + pre-roll: DNSKEY 11 is introduced into the key set. Note that no + signatures are generated with this key yet, but this does not + secure against brute force attacks on the public key. The minimum + duration of this pre-roll phase is the time it takes for the data + to propagate to the authoritative servers plus TTL value of the + key set. This equates to two times the Maximum Zone TTL. + roll: At the rollover stage (SOA serial 1) DNSKEY 11 is used to sign + the data in the zone exclusively (i.e. all the signatures from + DNSKEY 10 are removed from the zone). DNSKEY 10 remains published + in the key set. This way data that was loaded into caches from + version 1 of the zone can still be verified with key sets fetched + from version 2 of the zone. + The minimum time that the key set including DNSKEY 10 is to be + published is the time that it takes for zone data from the + previous version of the zone to expire from old caches i.e. the + time it takes for this zone to propagate to all authoritative + servers plus the Maximum Zone TTL value of any of the data in the + previous version of the zone. + + + + +Kolkman & Gieben Expires April 11, 2005 [Page 11] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + after: DNSKEY 10 is removed from the zone. The key set, now only + containing DNSKEY 11 is resigned with the DNSKEY 1. + + The above scheme can be simplified by always publishing the "future" + key immediately after the rollover. The scheme would look as follows + (we show two rollovers); the future key is introduced in "after" as + DNSKEY 12 and again a newer one, numbered 13, in "2nd after": + + + normal roll after + + SOA0 SOA2 SOA3 + RRSIG10(SOA0) RRSIG11(SOA2) RRSIG11(SOA3) + + DNSKEY1 DNSKEY1 DNSKEY1 + DNSKEY10 DNSKEY10 DNSKEY11 + DNSKEY11 DNSKEY11 DNSKEY12 + RRSIG1(DNSKEY) RRSIG1 (DNSKEY) RRSIG1(DNSKEY) + RRSIG10(DNSKEY) RRSIG11(DNSKEY) RRSIG11(DNSKEY) + + + 2nd roll 2nd after + + SOA4 SOA5 + RRSIG12(SOA4) RRSIG12(SOA5) + + DNSKEY1 DNSKEY1 + DNSKEY11 DNSKEY12 + DNSKEY12 DNSKEY13 + RRSIG1(DNSKEY) RRSIG1(DNSKEY) + RRSIG12(DNSKEY) RRSIG12(DNSKEY) + + + Note that the key introduced after the rollover is not used for + production yet; the private key can thus be stored in a physically + secure manner and does not need to be 'fetched' every time a zone + needs to be signed. + +3.3.2.2 Double Signature Zone-signing Key Rollover + + This section shows how to perform a ZSK key rollover using the double + zone data signature scheme, aptly named "double sig rollover". + + During the rollover stage the new version of the zone file will need + to propagate to all authoritative servers and the data that exists in + (distant) caches will need to expire, this will take at least the + maximum Zone TTL . + + + + +Kolkman & Gieben Expires April 11, 2005 [Page 12] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + normal roll after + + SOA0 SOA1 SOA2 + RRSIG10(SOA0) RRSIG10(SOA1) RRSIG11(SOA2) + RRSIG11(SOA1) + + DNSKEY1 DNSKEY1 DNSKEY1 + DNSKEY10 DNSKEY10 DNSKEY11 + DNSKEY11 + RRSIG1(DNSKEY) RRSIG1(DNSKEY) RRSIG1(DNSKEY) + RRSIG10(DNSKEY) RRSIG10(DNSKEY) RRSIG11(DNSKEY) + RRSIG11(DNSKEY) + + normal: Version 0 of the zone: DNSKEY 1 is the key-signing key. + DNSKEY 10 is used to sign all the data of the zone, the + zone-signing key. + roll: At the rollover stage (SOA serial 1) DNSKEY 11 is introduced + into the key set and all the data in the zone is signed with + DNSKEY 10 and DNSKEY 11. The rollover period will need to exist + until all data from version 0 of the zone has expired from remote + caches. This will take at least the maximum Zone TTL of version 0 + of the zone. + after: DNSKEY 10 is removed from the zone. All the signatures from + DNSKEY 10 are removed from the zone. The key set, now only + containing DNSKEY 11, is resigned with DNSKEY 1. + + At every instance the data from the previous version of the zone can + be verified with the key from the current version and the other way + around. The data from the current version can be verified with the + data from the previous version of the zone. The duration of the + rollover phase and the period between rollovers should be at least + the "Maximum Zone TTL". + + Making sure that the rollover phase lasts until the signature + expiration time of the data in version 0 of the zone is recommended. + This way all caches are cleared of the old signatures. However, this + date could be considerably longer than the Maximum Zone TTL, making + the rollover a lengthy procedure. + + Note that in this example we assumed that the zone was not modified + during the rollover. New data can be introduced in the zone as long + as it is signed with both keys. + +3.3.2.3 Pros and Cons of the Schemes + + + + + + + +Kolkman & Gieben Expires April 11, 2005 [Page 13] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + Pre-publish-key set rollover: This rollover does not involve signing + the zone data twice. Instead, just before the actual rollover, + the new key is published in the key set and thus available for + cryptanalysis attacks. A small disadvantage is that this process + requires four steps. Also the pre-publish scheme will not work + for KSKs as explained in Section 3.3. + Double signature rollover: The drawback of this signing scheme is + that during the rollover the number of signatures in your zone + doubles, this may be prohibitive if you have very big zones. An + advantage is that it only requires three steps. + +3.3.3 Key-signing Key Rollovers + + For the rollover of a key-signing key the same considerations as for + the rollover of a zone-signing key apply. However we can use a + double signature scheme to guarantee that old data (only the apex key + set) in caches can be verified with a new key set and vice versa. + + Since only the key set is signed with a KSK, zone size considerations + do not apply. + + + normal roll after + + SOA0 SOA1 SOA2 + RRSIG10(SOA0) RRSIG10(SOA1) RRSIG10(SOA2) + + DNSKEY1 DNSKEY1 DNSKEY2 + DNSKEY2 + DNSKEY10 DNSKEY10 DNSKEY10 + RRSIG1 (DNSKEY) RRSIG1 (DNSKEY) RRSIG2(DNSKEY) + RRSIG2 (DNSKEY) + RRSIG10(DNSKEY) RRSIG10(DNSKEY) RRSIG10(DNSKEY) + + normal: Version 0 of the zone. The parental DS points to DNSKEY1. + Before the rollover starts the child will have to verify what the + TTL is of the DS RR that points to DNSKEY1 - it is needed during + the rollover and we refer to the value as TTL_DS. + roll: During the rollover phase the zone administrator generates a + second KSK, DNSKEY2. The key is provided to the parent and the + child will have to wait until a new DS RR has been generated that + points to DNSKEY2. After that DS RR has been published on all + servers authoritative for the parents zone, the zone administrator + has to wait at least TTL_DS to make sure that the old DS RR has + expired from caches. + + + + + + +Kolkman & Gieben Expires April 11, 2005 [Page 14] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + after: DNSKEY1 has been removed. + + The scenario above puts the responsibility for maintaining a valid + chain of trust with the child. It also is based on the premises hat + the parent only has one DS RR (per algorithm) per zone. An + alternative mechanism has been considered. Using an established + trust relation, the interaction can be performed in-band, and where + removal of the keys by the child can be signaled by the parent. In + this mechanism there are periods where there are two DS RRs at the + parent. Since at the moment of writing the protocol for this + interaction has not been developed further discussion is out of scope + for this document. + +3.3.4 Automated Key Rollovers + + As keys must be renewed periodically, there are some motivation to + automate the rollover process (also see [12]) + + o ZSK rollovers are easy to automate as only the local zone is + involved. + o A KSK rollover needs interaction between the parent and child. + Data exchange is needed to provide the new keys to the parent, + consequently, this data must be authenticated and integrity must + be guaranteed in order to avoid attacks on the rollover. + o All time and TTL considerations presented in Section 3.3 apply to + an automated rollover. + +4. Planning for Emergency Key Rollover + + This section deals with preparation for a possible key compromise. + Our advice is to have a documented procedure ready for when a key + compromise is suspected or confirmed. + + When the private material of one of your keys is compromised it can + be used for as long as a valid authentication chain exists. An + authentication chain remains intact for: + o as long as a signature over the compromised key in the + authentication chain is valid, + o as long as a parental DS RR (and signature) points to the + compromised key, + o as long as the key is anchored in a resolver and is used as a + starting point for validation. (This is the hardest to update.) + + While an authentication chain to your compromised key exists, your + name-space is vulnerable to abuse by the malicious key holder (i.e. + the owner of the compromised key). Zone operators have to make a + trade off if the abuse of the compromised key is worse than having + data in caches that cannot be validated. If the zone operator + + + +Kolkman & Gieben Expires April 11, 2005 [Page 15] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + chooses to break the authentication chain to the compromised key, + data in caches signed with this key cannot be validated. However, if + the zone administrator chooses to take the path of a regular + roll-over, the malicious key holder can spoof data so that it appears + to be valid. Note that this kind of attack is more likely to occur + in a localized part of the network topology i.e. downstream from + where the spoof takes place. + + +4.1 KSK Compromise + + When the KSK has been compromised the parent must be notified as soon + as possible using secure means. The key set of the zone should be + resigned as soon as possible. Care must be taken to not break the + authentication chain. The local zone can only be resigned with the + new KSK after the parent's zone has created and reloaded its zone + with the DS created from the new KSK. Before this update takes place + it would be best to drop the security status of a zone all together: + the parent removes the DS of the child at the next zone update. + After that the child can be made secure again. + + An additional danger of a key compromise is that the compromised key + can be used to facilitate a legitimate DNSKEY/DS and/or nameserver + rollover at the parent. When that happens the domain can be in + dispute. An out of band and secure notify mechanism to contact a + parent is needed in this case. + +4.2 ZSK Compromise + + Primarily because there is no parental interaction required when a + ZSK is compromised, the situation is less severe than with with a KSK + compromise. The zone must still be resigned with a new ZSK as soon + as possible. As this is a local operation and requires no + communication between the parent and child this can be achieved + fairly quickly. However, one has to take into account that just as + with a normal rollover the immediate disappearance from the old + compromised key may lead to verification problems. The + pre-publication scheme as discussed above minimizes such problems. + +4.3 Compromises of Keys Anchored in Resolvers + + A key can also be pre-configured in resolvers. For instance, if + DNSSEC is successfully deployed the root key will be pre-configured + in most security aware resolvers. + + If trust-anchor keys are compromised, the resolvers using these keys + should be notified of this fact. Zone administrators may consider + setting up a mailing list to communicate the fact that a SEP key is + + + +Kolkman & Gieben Expires April 11, 2005 [Page 16] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + about to be rolled over. This communication will of course need to + be authenticated e.g. by using digital signatures. + + End-user faced with the task of updating anchored key should always + validate the new key. New keys should be authenticated out of the + DNS, for example, looking them up on an x.509 secured announcement + website. + +5. Parental Policies + +5.1 Initial Key Exchanges and Parental Policies Considerations + + The initial key exchange is always subject to the policies set by the + parent (or its registry). When designing a key exchange policy one + should take into account that the authentication and authorization + mechanisms used during a key exchange should be as strong as the + authentication and authorization mechanisms used for the exchange of + delegation information between parent and child. I.e. there is no + implicit need in DNSSEC to make the authentication process stronger + than it was in DNS. + + Using the DNS itself as the source for the actual DNSKEY material, + with an off-band check on the validity of the DNSKEY, has the benefit + that it reduces the chances of user error. A parental DNSKEY + download tool can make use of the SEP bit [4] to select the proper + key from a DNSSEC key set; thereby reducing the chance that the wrong + DNSKEY is sent. It can validate the self-signature over a key; + thereby verifying the ownership of the private key material. + Fetching the DNSKEY from the DNS ensures that the child will not + become bogus once the parent publishes the DS RR indicating the child + is secure. + + Note: the off-band verification is still needed when the key-material + is fetched via the DNS. The parent can never be sure whether the + DNSKEY RRs have been spoofed or not. + +5.2 Storing Keys So Hashes Can Be Regenerated + + When designing a registry system one should consider if the DNSKEYs + and/or the corresponding DSs are stored. Storing DNSKEYs will help + during troubleshooting while the overhead of calculating DS records + from them is minimal. + + Having an out-of-band mechanism, such as a Whois database, to find + out which keys are used to generate DS Resource Records for specific + owners and/or zones may also help with troubleshooting. + + + + + +Kolkman & Gieben Expires April 11, 2005 [Page 17] + +Internet-Draft DNSSEC Operational Practices October 2004 + + +5.3 Security Lameness Checks + + Security Lameness is defined as what happens when a parent has a DS + RR pointing to a non-existing DNSKEY RR. During key exchange a + parent should make sure that the child's key is actually configured + in the DNS before publishing a DS RR in its zone. Failure to do so + would render the child's zone being marked as bogus. + + Child zones should be very careful removing DNSKEY material, + specifically SEP keys, for which a DS RR exists. + + Once a zone is "security lame" a fix (e.g. by removing a DS RR) will + take time to propagate through the DNS. + +5.4 DS Signature Validity Period + + Since the DS can be replayed as long as it has a valid signature a + short signature validity period over the DS minimizes the time a + child is vulnerable in the case of a compromise of the child's + KSK(s). A signature validity period that is too short introduces the + possibility that a zone is marked bogus in case of a configuration + error in the signer. There may not be enough time to fix the + problems before signatures expire. Something as mundane as operator + unavailability during weekends shows the need for DS signature + lifetimes longer than 2 days. We recommend the minimum for a DS + signature validity period to be a few days. + + The maximum signature lifetime of the DS record depends on how long + child zones are willing to be vulnerable after a key compromise. + Other considerations, such as how often the zone is (re)signed can + also be taken into account. + + We consider a signature validity period of around one week to be a + good compromise between the operational constraints of the parent and + minimizing damage for the child. + +6. Security Considerations + + DNSSEC adds data integrity to the DNS. This document tries to assess + considerations to operate a stable and secure DNSSEC service. Not + taking into account the 'data propagation' properties in the DNS will + cause validation failures and may make secured zones unavailable to + security aware resolvers. + +7. Acknowledgments + + We, the folk mentioned as authors, only acted as editors. Most of + the ideas in this draft were the result of collective efforts during + + + +Kolkman & Gieben Expires April 11, 2005 [Page 18] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + workshops, discussions and try outs. + + At the risk of forgetting individuals who where the original + contributors of the ideas we would like to acknowledge people who + where actively involved in the compilation of this document. In + random order: Olafur Gudmundsson, Wesley Griffin, Michael Richardson, + Scott Rose, Rick van Rein, Tim McGinnis, Gilles Guette and Olivier + Courtay, Sam Weiler, Jelte Jansen. + + Mike StJohns designed the key exchange between parent and child + mentioned in the last paragraph of Section 3.3.3 + + Section 3.3.4 was supplied by G. Guette and O. Courtay. + + Emma Bretherick and Adrian Bedford corrected many of the spelling and + style issues. + + Kolkman and Gieben take the blame for introducing all miscakes(SIC). + +8. References + +8.1 Normative References + + [1] Eastlake, D., "Domain Name System Security Extensions", RFC + 2535, March 1999. + + [2] Eastlake, D., "DNS Security Operational Considerations", RFC + 2541, March 1999. + + [3] Lewis, E., "DNS Security Extension Clarification on Zone + Status", RFC 3090, March 2001. + + [4] Lewis, E., Kolkman, O. and J. Schlyter, "KEY RR Key-Signing Key + (KSK) Flag", draft-ietf-dnsext-keyrr-key-signing-flag-06 (work + in progress), February 2003. + + [5] Arends, R., "DNS Security Introduction and Requirements", + draft-ietf-dnsext-dnssec-intro-11 (work in progress), March + 2003. + + [6] Arends, R., "Protocol Modifications for the DNS Security + Extensions", draft-ietf-dnsext-dnssec-protocol-07 (work in + progress), March 2003. + +8.2 Informative References + + [7] Bradner, S., "Key words for use in RFCs to Indicate Requirement + Levels", BCP 14, RFC 2119, March 1997. + + + +Kolkman & Gieben Expires April 11, 2005 [Page 19] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + [8] Andrews, M., "Negative Caching of DNS Queries (DNS NCACHE)", + RFC 2308, March 1998. + + [9] Gudmundsson, O., "Delegation Signer (DS) Resource Record (RR)", + RFC 3658, December 2003. + + [10] Lenstra, A. and E. Verheul, "Selecting Cryptographic Key + Sizes", The Journal of Cryptology 14 (255-293), 2001. + + [11] Schneier, B., "Applied Cryptography: Protocols, Algorithms, and + Source Code in C", 1996. + + [12] Guette, G., "Requirements for Automated Key Rollover in + DNSsec", draft-ietf-dnsop-key-rollover-requirements-01 (work in + progress), August 2004. + + +Authors' Addresses + + Olaf M. Kolkman + RIPE NCC + Singel 256 + Amsterdam 1016 AB + The Netherlands + + Phone: +31 20 535 4444 + EMail: olaf@ripe.net + URI: http://www.ripe.net/ + + + Miek Gieben + NLnet Labs + Kruislaan 419 + Amsterdam 1098 VA + The Netherlands + + EMail: miek@nlnetlabs.nl + URI: http://www.nlnetlabs.nl + +Appendix A. Terminology + + In this document there is some jargon used that is defined in other + documents. In most cases we have not copied the text from the + documents defining the terms but given a more elaborate explanation + of the meaning. Note that these explanations should not be seen as + authoritative. + + + + + +Kolkman & Gieben Expires April 11, 2005 [Page 20] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + Private and Public Keys: DNSSEC secures the DNS through the use of + public key cryptography. Public key cryptography is based on the + existence of two keys, a public key and a private key. The public + keys are published in the DNS by use of the DNSKEY Resource Record + (DNSKEY RR). Private keys should remain private. + Signer: The system that has access to the private key material and + signs the Resource Record sets in a zone. A signer may be + configured to sign only parts of the zone e.g. only those RRsets + for which existing signatures are about to expire. + KSK: A Key-Signing Key (KSK) is a key that is used exclusively for + signing the apex key set. The fact that a key is a KSK is only + relevant to the signing tool. + ZSK: A Zone Signing Key (ZSK) is a key that is used for signing all + data in a zone. The fact that a key is a ZSK is only relevant to + the signing tool. + SEP Key: A KSK that has a parental DS record pointing to it. Note: + this is not enforced in the protocol. A SEP Key with no parental + DS is security lame. + Anchored Key: A DNSKEY configured in resolvers around the globe. + This key is hard to update, hence the term anchored. + Bogus: Also see Section 5 of [5]. An RRset in DNSSEC is marked + "Bogus" when a signature of a RRset does not validate against a + DNSKEY. + Singing the Zone File: The term used for the event where an + administrator joyfully signs its zone file while producing melodic + sound patterns. + Zone Administrator: The 'role' that is responsible for signing a zone + and publishing it on the primary authoritative server. + +Appendix B. Zone-signing Key Rollover Howto + + Using the pre-published signature scheme and the most conservative + method to assure oneself that data does not live in caches here + follows the "HOWTO". + Key notation: + Step 0: The preparation: Create two keys and publish both in your key + set. Mark one of the keys as "active" and the other as + "published". Use the "active" key for signing your zone data. + Store the private part of the "published" key, preferably + off-line. + Step 1: Determine expiration: At the beginning of the rollover make a + note of the highest expiration time of signatures in your zone + file created with the current key marked as "active". + Wait until the expiration time marked in Step 1 has passed + Step 2: Then start using the key that was marked as "published" to + sign your data i.e. mark it as "active". Stop using the key that + was marked as "active", mark it as "rolled". + + + + +Kolkman & Gieben Expires April 11, 2005 [Page 21] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + Step 3: It is safe to engage in a new rollover (Step 1) after at + least one "signature validity period". + +Appendix C. Typographic Conventions + + The following typographic conventions are used in this document: + Key notation: A key is denoted by KEYx, where x is a number, x could + be thought of as the key id. + RRset notations: RRs are only denoted by the type. All other + information - owner, class, rdata and TTL - is left out. Thus: + "example.com 3600 IN A 192.168.1.1" is reduced to "A". RRsets are + a list of RRs. A example of this would be: "A1,A2", specifying + the RRset containing two "A" records. This could again be + abbreviated to just "A". + Signature notation: Signatures are denoted as RRSIGx(RRset), which + means that RRset is signed with DNSKEYx. + Zone representation: Using the above notation we have simplified the + representation of a signed zone by leaving out all unnecessary + details such as the names and by representing all data by "SOAx" + SOA representation: SOA's are represented as SOAx, where x is the + serial number. + Using this notation the following zone: + + + example.net. 600 IN SOA ns.example.net. bert.example.net. ( + 10 ; serial + 450 ; refresh (7 minutes 30 seconds) + 600 ; retry (10 minutes) + 345600 ; expire (4 days) + 300 ; minimum (5 minutes) + ) + 600 RRSIG SOA 5 2 600 20130522213204 ( + 20130422213204 14 example.net. + cmL62SI6iAX46xGNQAdQ... ) + 600 NS a.iana-servers.net. + 600 NS b.iana-servers.net. + 600 RRSIG NS 5 2 600 20130507213204 ( + 20130407213204 14 example.net. + SO5epiJei19AjXoUpFnQ ... ) + 3600 DNSKEY 256 3 5 ( + EtRB9MP5/AvOuVO0I8XDxy0... + ) ; key id = 14 + 3600 DNSKEY 256 3 5 ( + gsPW/Yy19GzYIY+Gnr8HABU... + ) ; key id = 15 + 3600 RRSIG DNSKEY 5 2 3600 20130522213204 ( + 20130422213204 14 example.net. + J4zCe8QX4tXVGjV4e1r9... ) + + + +Kolkman & Gieben Expires April 11, 2005 [Page 22] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + 3600 RRSIG DNSKEY 5 2 3600 20130522213204 ( + 20130422213204 15 example.net. + keVDCOpsSeDReyV6O... ) + 600 RRSIG NSEC 5 2 600 20130507213204 ( + 20130407213204 14 example.net. + obj3HEp1GjnmhRjX... ) + a.example.net. 600 IN TXT "A label" + 600 RRSIG TXT 5 3 600 20130507213204 ( + 20130407213204 14 example.net. + IkDMlRdYLmXH7QJnuF3v... ) + 600 NSEC b.example.com. TXT RRSIG NSEC + 600 RRSIG NSEC 5 3 600 20130507213204 ( + 20130407213204 14 example.net. + bZMjoZ3bHjnEz0nIsPMM... ) + + ... + + + is reduced to the following representation: + + SOA10 + RRSIG14(SOA10) + + DNSKEY14 + DNSKEY15 + + RRSIG14(KEY) + RRSIG15(KEY) + + The rest of the zone data has the same signature as the SOA record, + i.e a RRSIG created with DNSKEY 14. + +Appendix D. Document Details and Changes + + This section is to be removed by the RFC editor if and when the + document is published. + + $Id: draft-ietf-dnsop-dnssec-operational-practices.xml,v 1.29 2004/ + 10/11 11:27:10 dnssec Exp $ + +D.1 draft-ietf-dnsop-dnssec-operational-practices-00 + + Submission as working group document. This document is a modified + and updated version of draft-kolkman-dnssec-operational-practices-00. + +D.2 draft-ietf-dnsop-dnssec-operational-practices-01 + + changed the definition of "Bogus" to reflect the one in the protocol + + + +Kolkman & Gieben Expires April 11, 2005 [Page 23] + +Internet-Draft DNSSEC Operational Practices October 2004 + + + draft. + + Bad to Bogus + + Style and spelling corrections + + KSK - SEP mapping made explicit. + + Updates from Sam Weiler added + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Kolkman & Gieben Expires April 11, 2005 [Page 24] + +Internet-Draft DNSSEC Operational Practices October 2004 + + +Intellectual Property Statement + + The IETF takes no position regarding the validity or scope of any + Intellectual Property Rights or other rights that might be claimed to + pertain to the implementation or use of the technology described in + this document or the extent to which any license under such rights + might or might not be available; nor does it represent that it has + made any independent effort to identify any such rights. Information + on the procedures with respect to rights in RFC documents can be + found in BCP 78 and BCP 79. + + Copies of IPR disclosures made to the IETF Secretariat and any + assurances of licenses to be made available, or the result of an + attempt made to obtain a general license or permission for the use of + such proprietary rights by implementers or users of this + specification can be obtained from the IETF on-line IPR repository at + http://www.ietf.org/ipr. + + The IETF invites any interested party to bring to its attention any + copyrights, patents or patent applications, or other proprietary + rights that may cover technology that may be required to implement + this standard. Please address the information to the IETF at + ietf-ipr@ietf.org. + + +Disclaimer of Validity + + This document and the information contained herein are provided on an + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET + ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, + INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE + INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED + WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + + +Copyright Statement + + Copyright (C) The Internet Society (2004). This document is subject + to the rights, licenses and restrictions contained in BCP 78, and + except as set forth therein, the authors retain all their rights. + + +Acknowledgment + + Funding for the RFC Editor function is currently provided by the + Internet Society. + + + + +Kolkman & Gieben Expires April 11, 2005 [Page 25] + + diff --git a/doc/draft/draft-ietf-dnsop-inaddr-required-05.txt b/doc/draft/draft-ietf-dnsop-inaddr-required-05.txt new file mode 100644 index 0000000000..8809913a00 --- /dev/null +++ b/doc/draft/draft-ietf-dnsop-inaddr-required-05.txt @@ -0,0 +1,301 @@ + + + + + + +INTERNET-DRAFT D. Senie +Category: BCP Amaranth Networks Inc. +Expires in six months April 2004 + + Encouraging the use of DNS IN-ADDR Mapping + draft-ietf-dnsop-inaddr-required-05.txt + +Status of this Memo + + + This draft, is intended to be become a Best Current Practice RFC. + Distribution of this document is unlimited. Comments should be sent + to the Domain Name Server Operations working group mailing list + or to the author. + + This document is an Internet-Draft and is in full conformance with + all provisions of Section 10 of [RFC2026]. + + Internet-Drafts are working documents of the Internet Engineering + Task Force (IETF), its areas, and its working groups. Note that other + groups may also distribute working documents as Internet-Drafts. + + Internet-Drafts are draft documents valid for a maximum of six months + and may be updated, replaced, or obsoleted by other documents at any + time. It is inappropriate to use Internet-Drafts as reference + material or to cite them other than as "work in progress." + + To view the list Internet-Draft Shadow Directories, see + http://www.ietf.org/shadow.html. + +Copyright Notice + + Copyright (C) The Internet Society (2000-2002). All Rights Reserved. + +Abstract + + Mapping of addresses to names has been a feature of DNS. Many sites, + implement it, many others don’t. Some applications attempt to use it + as a part of a security strategy. The goal of this document is to + encourage proper deployment of address to name mappings, and provide + guidance for their use. + +1. Introduction + + The Domain Name Service has provision for providing mapping of IP + addresses to host names. It is common practice to ensure both name to + address, and address to name mappings are provided for networks. This + practice, while documented, has never been documented as a + requirement placed upon those who control address blocks. This + + + +Senie [Page 1] + + + + + +Internet-Draft Encouraging the use of DNS IN-ADDR Mapping April 2004 + + + document fills this gap. + + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in RFC 2119 [RFC2119]. + +2. Discussion + + From the early days of the Domain Name Service [RFC 883] a special + domain has been set aside for resolving mappings of IP addresses to + domain names. This was refined in [RFC1035], describing the .IN- + ADDR.ARPA in use today. + + The assignment of blocks of IP Address space was delegated to three + regional registries. Guidelines for the registries are specified in + [RFC2050], which requires regional registries to maintain IN-ADDR + records on the large blocks of space issued to ISPs and others. + + ARIN’s policy requires ISPs to maintain IN-ADDR for /16 or larger + allocations. For smaller allocations, ARIN can provide IN-ADDR for + /24 and shorter prefixes. [ARIN]. APNIC provides methods for ISPs to + update IN-ADDR, however the present version of its policy document + for IPv4 [APNIC] dropped the IN-ADDR requirements that were in draft + copies of this document. As of this writing, it appears APNIC has no + actual policy on IN-ADDR. RIPE appears to have the strongest policy + in this area [ripe-185] indicating Local Internet Registries are + required to perform IN-ADDR services, and delegate those as + appropriate when address blocks are delegated. + + As we can see, the regional registries have their own policies for + requirements for IN-ADDR maintenance. It should be noted, however, + that many address blocks were allocated before the creation of the + regional registries, and thus it is unclear whether any of the + policies of the registries are binding on those who hold blocks from + that era. + + Registries allocate address blocks on CIDR [RFC1519] boundaries. + Unfortunately the IN-ADDR zones are based on classful allocations. + Guidelines [RFC2317] for delegating on non-octet-aligned boundaries + exist, but are not always implemented. + +3. Effects of missing IN-ADDR + + Many applications use DNS lookups for security checks. To ensure + validity of claimed names, some applications will look up IN-ADDR + records to get names, and then look up the resultant name to see if + it maps back to the address originally known. Failure to resolve + matching names is seen as a potential security concern. + + + +Senie [Page 2] + + + + + +Internet-Draft Encouraging the use of DNS IN-ADDR Mapping April 2004 + + + Some popular FTP sites will flat-out reject users, even for anonymous + FTP, if the IN-ADDR lookup fails or if the result of the IN-ADDR + lookup when itself resolved, does not match. Some Telnet servers also + implement this check. + + Web sites are in some cases using IN-ADDR checks to verify whether + the client is located within a certain geopolitical entity. This is + being employed for downloads of crypto software, for example, where + export of that software is prohibited to some locales. Credit card + anti-fraud systems also use these methods for geographic placement + purposes. + + The popular TCP Wrappers program found on most Unix and Linux systems + has options to enforce IN-ADDR checks and to reject any client that + does not resolve. + + Wider-scale implementation of IN-ADDR on dialup, CDPD and other such + client-oriented portions of the Internet would result in lower + latency for queries (due to lack of negative caching), and lower name + server load and DNS traffic. + + Some anti-spam (anti junk email) systems use IN-ADDR to verify return + addresses before accepting email. + + Many web servers look up the IN-ADDR of visitors to be used in log + analysis. This adds to the server load, but in the case of IN-ADDR + unavailability, it can lead to delayed responses for users. + + Traceroutes with descriptive IN-ADDR naming proves useful when + debugging problems spanning large areas. When this information is + missing, the traceroutes take longer, and it takes additional steps + to determine that network is the cause of problems. + +4. Requirements + + 4.1 Delegation Requirements + + Regional Registries and any Local Registries to whom they delegate + SHOULD establish and convey a policy to those to whom they delegate + blocks that IN-ADDR mappings are required. Policies SHOULD require + those receiving delegations to provide IN-ADDR service and/or + delegate to downstream customers. + + Network operators SHOULD define and implement policies and procedures + which delegate IN-ADDR to their clients who wish to run their own IN- + ADDR DNS services, and provide IN-ADDR services for those who do not + have the resources to do it themselves. Delegation mechanisms MUST + permit the downstream customer to implement and comply with IETF + + + +Senie [Page 3] + + + + + +Internet-Draft Encouraging the use of DNS IN-ADDR Mapping April 2004 + + + recommendations application of IN-ADDR to CIDR [RFC2317]. + + All IP address space assigned and in use SHOULD be resolved by IN- + ADDR records. All PTR records MUST use canonical names. + + All IP addresses in use within a block SHOULD have an IN-ADDR + mapping. Those addresses not in use, and those that are not valid for + use (zeros or ones broadcast addresses within a CIDR block) need not + have mappings. + + It should be noted that due to CIDR, many addresses that appear to be + otherwise valid host addresses may actually be zeroes or ones + broadcast addresses. As such, attempting to audit a site’s degree of + compliance can only be done with knowledge of the internal routing + structure of the site. However, any host that originates an IP packet + necessarily will have a valid host address, and must therefore have + an IN-ADDR mapping. + + 4.2 Application Requirements + + Applications SHOULD NOT rely on IN-ADDR for proper operation. The use + of IN-ADDR, sometimes in conjunction with a lookup of the name + resulting from the PTR record provides no real security, can lead to + erroneous results and generally just increases load on DNS servers. + Further, in cases where address block holders fail to properly + configure IN-ADDR, users of those blocks are penalized. + +5. Security Considerations + + This document has no negative impact on security. While it could be + argued that lack of PTR record capabilities provides a degree of + anonymity, this is really not valid. Trace routes, whois lookups and + other sources will still provide methods for discovering identity. + + By recommending applications avoid using IN-ADDR as a security + mechanism this document points out that this practice, despite its + use by many applications, is an ineffective form of security. + Applications should use better mechanisms of authentication. + +6. References + + [RFC883] P.V. Mockapetris, "Domain names: Implementation + specification," RFC883, November 1983. + + [RFC1035] P.V. Mockapetris, "Domain Names: Implementation + Specification," RFC 1035, November 1987. + + [RFC1519] V. Fuller, et. al., "Classless Inter-Domain Routing (CIDR): + + + +Senie [Page 4] + + + + + +Internet-Draft Encouraging the use of DNS IN-ADDR Mapping April 2004 + + + an Address Assignment and Aggregation Strategy," RFC 1519, September + 1993. + + [RFC2026] S. Bradner, "The Internet Standards Process -- Revision 3", + RFC 2026, BCP 9, October 1996. + + [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate + Requirement Levels", RFC 2119, BCP 14, March 1997. + + [RFC2050] K. Hubbard, et. al., "Internet Registry IP Allocation + Guidelines", RFC2050, BCP 12, Novebmer 1996. + + [RFC2317] H. Eidnes, et. al., "Classless IN-ADDR.ARPA delegation," + RFC 2317, March 1998. + + [ARIN] "ISP Guidelines for Requesting Initial IP Address Space," date + unknown, http://www.arin.net/regserv/initial-isp.html + + [APNIC] "Policies For IPv4 Address Space Management in the Asia + Pacific Region," APNIC-086, 13 January 2003. + + [RIPE185] "European Internet Registry Policies and Procedures," + ripe-185, October 26, 1998. http://www.ripe.net/docs/ripe-185.html + + +7. Acknowledgements + + Thanks to Peter Koch and Gary Miller for their input, and to many + people who encouraged me to write this document. + +8. Author’s Address + + Daniel Senie + Amaranth Networks Inc. + 324 Still River Road + Bolton, MA 01740 + + Phone: (978) 779-5100 + + EMail: dts@senie.com + + + + + + + + + + + +Senie [Page 5] + + diff --git a/doc/draft/draft-ietf-dnsop-ipv6-dns-configuration-02.txt b/doc/draft/draft-ietf-dnsop-ipv6-dns-configuration-04.txt similarity index 78% rename from doc/draft/draft-ietf-dnsop-ipv6-dns-configuration-02.txt rename to doc/draft/draft-ietf-dnsop-ipv6-dns-configuration-04.txt index 42c3c0b7c7..1a3ccaff12 100644 --- a/doc/draft/draft-ietf-dnsop-ipv6-dns-configuration-02.txt +++ b/doc/draft/draft-ietf-dnsop-ipv6-dns-configuration-04.txt @@ -1,19 +1,19 @@ DNS Operations WG Internet-Draft J. Jeong (ed.) - ETRI + ETRI/University of Minnesota -Expires: January 2005 18 July 2004 +Expires: March 2005 28 September 2004 IPv6 Host Configuration of DNS Server Information Approaches - draft-ietf-dnsop-ipv6-dns-configuration-02.txt + draft-ietf-dnsop-ipv6-dns-configuration-04.txt Status of this Memo By submitting this Internet-Draft, I certify that any applicable - patent or other IPR claims of which I am aware have been disclosed, + patent or other IPR claims of which I am aware have been disclosed, and any of which we become aware will be disclosed, in accordance with RFC3668. @@ -21,7 +21,7 @@ Status of this Memo Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. - + Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts @@ -34,11 +34,11 @@ Status of this Memo The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. - This Internet-Draft will expire on January 17, 2005. + This Internet-Draft will expire on March 27, 2005. Copyright Notice - Copyright (C) The Internet Society (2004). All Rights Reserved. + Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract @@ -51,68 +51,70 @@ Abstract -Jeong, et al. Expires - January 2005 [Page 1] +Jeong, et al. Expires - March 2005 [Page 1] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 - guideline of IPv6 DNS configuration to select approaches suitable + guideline for IPv6 DNS configuration to select approaches suitable for their host DNS configuration. Table of Contents - 1. Introduction...................................................3 - 2. Terminology....................................................3 - 3. IPv6 DNS Configuration Approaches..............................3 - 3.1 RA Option..................................................3 - 3.1.1 Advantages...........................................4 - 3.1.2 Disadvantages........................................5 - 3.1.3 Observations.........................................5 - 3.2 DHCPv6 Option..............................................6 - 3.2.1 Advantages...........................................7 - 3.2.2 Disadvantages........................................8 - 3.2.3 Observations.........................................9 - 3.3 Well-known Anycast Addresses...............................9 - 3.3.1 Advantages...........................................9 - 3.3.2 Disadvantages.......................................10 - 3.3.3 Observations........................................10 - 4. Interworking among IPv6 DNS Configuration Approaches..........11 - 5. Deployment Scenarios..........................................12 - 5.1 ISP Network...............................................12 - 5.1.1 RA Option Approach..................................12 - 5.1.2 DHCPv6 Option Approach..............................13 - 5.1.3 Well-known Addresses Approach.......................13 - 5.2 Enterprise Network........................................14 - 5.3 3GPP Network..............................................14 - 5.3.1 Currently Available Mechanisms and Recommendations..15 - 5.3.2 RA Extension........................................16 - 5.3.3 Stateless DHCPv6....................................16 - 5.3.4 Well-known Addresses................................17 - 5.3.5 Recommendations.....................................17 - 5.4 Unmanaged Network.........................................18 - 5.4.1 Case A: Gateway does not provide IPv6 at all........18 - 5.4.2 Case B: A dual-stack gateway connected to a dual-stack - ISP.........................................18 - 5.4.3 Case C: A dual-stack gateway connected to an IPv4-only - ISP.........................................19 - 5.4.4 Case D: A gateway connected to an IPv6-only ISP.....19 - 6. Security Considerations.......................................19 - 7. Acknowledgements..............................................19 - 8. Normative References..........................................20 - 9. Informative References........................................20 - 10. Authors' Addresses...........................................21 - Intellectual Property Statement..................................23 - Full Copyright Statement.........................................23 - Acknowledgement..................................................24 + 1. Introduction....................................................3 + 2. Terminology.....................................................3 + 3. IPv6 DNS Configuration Approaches...............................3 + 3.1. RA Option..................................................3 + 3.1.1. Advantages..........................................4 + 3.1.2. Disadvantages.......................................5 + 3.1.3. Observations........................................6 + 3.2. DHCPv6 Option..............................................6 + 3.2.1. Advantages..........................................7 + 3.2.2. Disadvantages.......................................8 + 3.2.3. Observations........................................9 + 3.3. Well-known Anycast Addresses...............................9 + 3.3.1. Advantages.........................................10 + 3.3.2. Disadvantages......................................10 + 3.3.3. Observations.......................................10 + 4. Interworking among IPv6 DNS Configuration Approaches...........11 + 5. Deployment Scenarios...........................................12 + 5.1. ISP Network...............................................12 + 5.1.1. RA Option Approach.................................12 + 5.1.2. DHCPv6 Option Approach.............................13 + 5.1.3. Well-known Addresses Approach......................13 + 5.2. Enterprise Network........................................14 + 5.3. 3GPP Network..............................................14 + 5.3.1. Currently Available Mechanisms and Recommendations.15 + 5.3.2. RA Extension.......................................16 + 5.3.3. Stateless DHCPv6...................................16 + 5.3.4. Well-known Addresses...............................17 + 5.3.5. Recommendations....................................17 + 5.4. Unmanaged Network.........................................18 + 5.4.1. Case A: Gateway does not provide IPv6 at all.......18 + 5.4.2. Case B: A dual-stack gateway connected to a + dual-stack ISP.....................................18 + 5.4.3. Case C: A dual-stack gateway connected to an + IPv4-only ISP......................................19 + 5.4.4. Case D: A gateway connected to an IPv6-only ISP....19 + 6. Security Considerations........................................19 + 7. Acknowledgements...............................................19 + 8. Normative References...........................................20 + 9. Informative References.........................................20 + 10. Appendix A - Link-layer Multicast Acknowledgements with RA + Option........................................................21 + 11. Authors' Addresses............................................22 + 12. Intellectual Property Statement...............................23 -Jeong, et al. Expires - January 2005 [Page 2] +Jeong, et al. Expires - March 2005 [Page 2] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 + Full Copyright Statement..........................................24 + Acknowledgement...................................................24 -1. Introduction +1. Introduction Neighbor Discovery (ND) for IP Version 6 and IPv6 Stateless Address Autoconfiguration provide ways to configure either fixed or mobile @@ -138,7 +140,7 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 select approaches suitable for IPv6 host configuration of recursive DNS server. -2. Terminology +2. Terminology This document uses the terminology described in [3]-[9]. In addition, a new term is defined below: @@ -147,57 +149,61 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 server that offers the recursive service of DNS name resolution. -3. IPv6 DNS Configuration Approaches +3. IPv6 DNS Configuration Approaches In this section, the operational attributes of three solutions are described in detail. -3.1 RA Option +3.1. RA Option RA approach is to define a new ND option called RDNSS option that contains a recursive DNS server address. Existing ND transport mechanisms (i.e., advertisements and solicitations) are used. This - works in the same way that nodes learn about routers and prefixes, - etc. An IPv6 host can configure the IPv6 addresses of one or more -Jeong, et al. Expires - January 2005 [Page 3] +Jeong, et al. Expires - March 2005 [Page 3] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 + works in the same way that nodes learn about routers and prefixes. + An IPv6 host can configure the IPv6 addresses of one or more RDNSSes via RA message periodically sent by router or solicited by - a Router Solicitation (RS) [8]. This approach needs RDNSS - information to be configured in the routers doing the - advertisements. The configuration of RDNSS address can be - performed manually by operator or other ways, such as automatic - configuration through DHCPv6 client running on the router. When - advertising more than one RDNSS options, an RA message includes as - many RDNSS options as RDNSSes. Through ND protocol and RDNSS - option along with prefix information option, an IPv6 host can - perform its network configuration of its IPv6 address and RDNSS - simultaneously [3][4]. The RA option for RDNSS can be used on any - network that supports the use of ND. However, RA approach performs - poorly in some wireless environments where RA message is used for - IPv6 address autoconfiguration, such as WLAN networks. + a Router Solicitation (RS) [8]. - The RA approach is useful in some non-WLAN mobile environments - where the addresses of the RDNSSes are changing because the RA - option includes a lifetime field. This can be configured to a - value that will require the client to time out the entry and switch - over to another RDNSS address [8]. However, from the viewpoint of - implementation, lifetime would seem to make matters a bit more - complex. Instead of just writing DNS configuration file, such as - resolv.conf for the list of RDNSS addresses, we have to have a - daemon around (or a program that is called at the defined - intervals) that keeps monitoring the lifetime of RDNSSes all the - time. + This approach needs RDNSS information to be configured in the + routers doing the advertisements. The configuration of RDNSS + address can be performed manually by operator or other ways, such + as automatic configuration through DHCPv6 client running on the + router. When advertising more than one RDNSS options, an RA + message includes as many RDNSS options as RDNSSes. + + Through ND protocol and RDNSS option along with prefix information + option, an IPv6 host can perform its network configuration of its + IPv6 address and RDNSS simultaneously [3][4]. The RA option for + RDNSS can be used on any network that supports the use of ND. + + However, it is worth noting that some link layers (e.g., WLAN) need + to acknowledge multicast packets, which may increase the amount of + link-layer traffic. This is discussed in Appendix A. + + The RA approach is useful in some mobile environments where the + addresses of the RDNSSes are changing because the RA option + includes a lifetime field that allows client to use RDNSSes nearer + to the client. This can be configured to a value that will require + the client to time out the entry and switch over to another RDNSS + address [8]. However, from the viewpoint of implementation, + lifetime would seem to make matters a bit more complex. Instead of + just writing DNS configuration file, such as resolv.conf for the + list of RDNSS addresses, we have to have a daemon around (or a + program that is called at the defined intervals) that keeps + monitoring the lifetime of RDNSSes all the time. The preference value of RDNSS, included in RDNSS option, allows IPv6 hosts to select primary RDNSS among several RDNSSes; this can be used for load balancing of RDNSSes [8]. -3.1.1 Advantages +3.1.1. Advantages The RA option for RDNSS has a number of advantages. These include: @@ -208,27 +214,27 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 2) This approach, like ND, works well on a variety of link types including point-to-point links, point-to-multipoint, and multi- point (i.e., Ethernet LANs), etc. RFC2461 [3] states, however, + + +Jeong, et al. Expires - March 2005 [Page 4] + +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 + + that there may be some link type on which ND is not possible; on such a link, some other mechanism will be needed for DNS configuration. 3) All of the information a host needs to run basic Internet - applications such as email, the web, ftp, etc., can be performed - - -Jeong, et al. Expires - January 2005 [Page 4] - -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 - - + applications such as email, the web, ftp, etc., can be obtained with the addition of this option to ND and address auto- configuration. The use of a single mechanism is more reliable and easier to provide than when the RDNSS information is learned via another protocol mechanism. Debugging problems when multiple - protocol mechanisms are being used is harder and much more complex. + protocol mechanisms are being used is harder and much more complex. 4) This mechanism works over a broad range of scenarios and - leverages IPv6 ND. This works well on links that support broadcast + leverages IPv6 ND. This works well on links that support broadcast reliably (e.g., Ethernet LANs) but not necessarily on other links (e.g., Wireless LANs). Also, this works well on links that are high performance (e.g., Ethernet LANs) and low performance (e.g., @@ -244,44 +250,44 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 addresses that are common to all clients on a subnet would be easy to define. This includes things like NTP servers, SIP servers, etc. -3.1.2 Disadvantages +3.1.2. Disadvantages 1) ND is mostly implemented in kernel part of operating system. Therefore, if ND supports the configuration of some additional services, such as DNS, NTP and SIP servers, ND should be extended - in kernel part. DHCPv6, however, has more flexibility for - extension of service discovery because it is an application layer - protocol. + in kernel part, and complemented by a user-land process. DHCPv6, + however, has more flexibility for extension of service discovery + because it is an application layer protocol. 2) The current ND framework should be modified due to the synchronization between another ND cache for RDNSSes in kernel space and DNS configuration file in user space. Because it is - unacceptable to write and rewrite the DNS configuration file (e.g., + unacceptable to write and rewrite the DNS configuration file (e.g., resolv.conf) from the kernel, another approach is needed. One simple approach to solve this is to have a daemon listening to what the kernel conveys, and to have the daemon do these steps, but such a daemon is not necessary with the current ND framework. + + + +Jeong, et al. Expires - March 2005 [Page 5] + +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 + + 3) It is necessary to configure RDNSS addresses at least at one router on every link where this information needs to be configured by RA option. -3.1.3 Observations +3.1.3. Observations - - - -Jeong, et al. Expires - January 2005 [Page 5] - -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 - - The proposed RDNSS RA option along with IPv6 ND and Auto- configuration allows a host to obtain all of the information it needs to access basic Internet services like the web, email, ftp, etc. This is preferable in environments where hosts use RAs to - autoconfigure their addresses and all hosts on the subnet share the - same router and server addresses. If the configuration information + autoconfigure their addresses and all hosts on the subnet share the + same router and server addresses. If the configuration information can be obtained from a single mechanism, it is preferable because it does not add additional delay, and it uses a minimum of bandwidth. Environments like this include homes, public cellular @@ -297,9 +303,9 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 Note: the observation section is based on what the proponents of each approach think makes a good overall solution. -3.2 DHCPv6 Option +3.2. DHCPv6 Option - DHCPv6 [5] includes the "DNS Recursive Name Server" option, through + DHCPv6 [5] includes the "DNS Recursive Name Server" option, through which a host can obtain a list of IP addresses of recursive DNS servers [7]. The DNS Recursive Name Server option carries a list of IPv6 addresses of RDNSSes to which the host may send DNS queries. @@ -308,7 +314,7 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 The DNS Recursive Name Server option can be carried in any DHCPv6 Reply message, in response to either a Request or an Information- - request message. Thus, the DNS Recursive Name Server option can be + request message. Thus, the DNS Recursive Name Server option can be used either when DHCPv6 is used for address assignment, or when DHCPv6 is used only for other configuration information as stateless DHCPv6 [6]. @@ -318,22 +324,22 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 Several router vendors currently implement stateless DHCPv6 servers. Deploying stateless DHCPv6 in routers has the advantage that no special hardware is required, and should work well for networks + + +Jeong, et al. Expires - March 2005 [Page 6] + +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 + + where DHCPv6 is needed for very straightforward configuration of network devices. However, routers can also act as DHCPv6 relay agents. In this case, the DHCPv6 server need not be on the router - it can be on a general purpose computer. This has the potential to give the - - -Jeong, et al. Expires - January 2005 [Page 6] - -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 - - operator of the DHCPv6 server more flexibility in how the DHCPv6 - server responds to individual clients - clients can easily be given - different configuration information based on their identity, or for + server responds to individual clients - clients can easily be given + different configuration information based on their identity, or for any other reason. Nothing precludes adding this flexibility to a router, but generally in current practice, DHCP servers running on general-purpose hosts tend to have more configuration options than @@ -348,14 +354,14 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 configuration information to DHCPv6 clients as this information changes. - The DHC Working Group is currently studying an additional mechanism + The DHC Working Group is currently studying an additional mechanism through which configuration information, including the list of - RDNSSes, can be updated. The Lifetime Option for DHCPv6 [10], + RDNSSes, can be updated. The lifetime option for DHCPv6 [10] assigns a lifetime to configuration information obtained through DHCPv6. At the expiration of the lifetime, the host contacts the DHCPv6 server to obtain updated configuration information, including the list of RDNSSes. This lifetime gives the network - administrator another mechanism to configure hosts with new RDNSSes + administrator another mechanism to configure hosts with new RDNSSes by controlling the time at which the host refreshes the list. The DHC Working Group has also discussed the possibility of @@ -368,30 +374,30 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 large service provider networks with tens of thousands of hosts that may initiate a DHCPv4 message exchange simultaneously. -3.2.1 Advantages +3.2.1. Advantages The DHCPv6 option for RDNSS has a number of advantages. These include: + + +Jeong, et al. Expires - March 2005 [Page 7] + +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 + + 1) DHCPv6 currently provides a general mechanism for conveying network configuration information to clients. So configuring DHCPv6 servers allows the network administrator to configure - RDNSSes along with the addresses of other network services, as well + RDNSSes along with the addresses of other network services, as well as location-specific information like time zones. - - -Jeong, et al. Expires - January 2005 [Page 7] - -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 - - 2) As a consequence, when the network administrator goes to configure DHCPv6, all the configuration information can be managed through a single service, typically with a single user interface and a single configuration database. - 3) DHCPv6 allows for the configuration of a host with information + 3) DHCPv6 allows for the configuration of a host with information specific to that host, so that hosts on the same link can be configured with different RDNSSes as well as other configuration information. This capability is important in some network @@ -405,14 +411,14 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 addresses of SIP servers and NTP servers are likely to need DHCPv6 for other configuration information. - 6) The specification for configuration of RDNSSes through DHCPv6 is + 6) The specification for configuration of RDNSSes through DHCPv6 is available as an RFC. No new protocol extensions such as new options are necessary. 7) Interoperability among independent implementations has been demonstrated. -3.2.2 Disadvantages +3.2.2. Disadvantages The DHCPv6 option for RDNSS has a few disadvantages. These include: @@ -420,32 +426,31 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 1) Update currently requires message from server (however, see [10]). - 2) Because DNS information is not contained in RA message, the host + 2) Because DNS information is not contained in RA message, the host must receive two messages from the router, and must transmit at - least one message to the router. On networks where bandwidth is at + least one message to the router. On networks where bandwidth is at a premium, this is a disadvantage, although on most networks it is not a practical concern. 3) Increased latency for initial configuration - in addition to waiting for an RA message, the client must now exchange packets + + +Jeong, et al. Expires - March 2005 [Page 8] + +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 + + with a DHCPv6 server; even if it is locally installed on a router, this will slightly extend the time required to configure the client. For clients that are moving rapidly from one network to another, this will be a disadvantage. - - - -Jeong, et al. Expires - January 2005 [Page 8] - -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 - - -3.2.3 Observations +3.2.3. Observations In the general case, on general-purpose networks, stateless DHCPv6 provides significant advantages and no significant disadvantages. - Even in the case where bandwidth is at a premium and low latency is + Even in the case where bandwidth is at a premium and low latency is desired, if hosts require other configuration information in addition to a list of RDNSSes or if hosts must be configured selectively, those hosts will use DHCPv6 and the use of the DHCPv6 @@ -458,13 +463,21 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 draft should be written so as to allow these special applications to be handled using DNS information in the RA packet. -3.3 Well-known Anycast Addresses +3.3. Well-known Anycast Addresses First of all, the well-known anycast addresses approach is much - different from that discussed in IPv6 Working Group in the past. + different from that discussed at IPv6 Working Group in the past [9]. + It should be noted that "anycast" in this memo is simpler than that + of RFC1546 [11] and RFC3513 [12] where it is assumed to be + prohibited to have multiple servers on a single link sharing an + anycast address. That is, on a link, anycast address is assumed to + be unique. DNS clients today already have redundancy by having + multiple well-known anycast addresses configured as RDNSS addresses. + There is no point to have multiple RDNSSes sharing an anycast + address on a single link. - The approach with well-known anycast addresses is to set well-known - anycast addresses in clients' resolver configuration files from the + The approach with well-known anycast addresses is to set well-known + anycast addresses in clients' resolver configuration files from the beginning, say, as factory default. Thus, there is no transport mechanism and no packet format [9]. @@ -476,29 +489,19 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 servers and want to access their ISPs' across their site boundaries. Larger sites may also depend on their ISPs or may have their own RDNSSes within "site" boundaries. - - It should be noted that "anycast" in this memo is simpler than that - of RFC1546 [11] and RFC3513 [12] where it is assumed to be - prohibited to have multiple servers on a single link sharing an - anycast address. That is, on a link, anycast address is assumed to - be unique. DNS clients today already have redundancy by having - multiple well-known anycast addresses configured as RDNSS addresses. - There is no point to have multiple RDNSSes sharing an anycast - address on a single link. - -3.3.1 Advantages - - -Jeong, et al. Expires - January 2005 [Page 9] +Jeong, et al. Expires - March 2005 [Page 9] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 - The basic advantage of the well-known addresses approach is that it + +3.3.1. Advantages + + The basic advantage of the well-known addresses approach is that it uses no transport mechanism. Thus, - 1) There is no delay to get response and no further delay by packet + 1) There is no delay to get response and no further delay by packet losses. 2) The approach can be combined with any other configuration @@ -513,49 +516,49 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 effort is proportional to the number of the DNS servers and scales linearly. It should be noted that, in the simplest case where a subscriber to an ISP does not have any DNS server, the subscriber - naturally access DNS servers of the ISP even though the subscriber + naturally accesses DNS servers of the ISP even though the subscriber and the ISP do nothing and there is no protocol to exchange DNS server information between the subscriber and the ISP. -3.3.2 Disadvantages +3.3.2. Disadvantages - Well-known anycast addresses approach requires that DNS servers (or + Well-known anycast addresses approach requires that DNS servers (or routers near it as a proxy) act as routers to advertise their anycast addresses to the routing system, which requires some configuration (see the last paragraph of the previous section on the scalability of the effort). -3.3.3 Observations +3.3.3. Observations If other approaches are used in addition, the well-known anycast addresses should also be set in RA or DHCP configuration files to - reduce configuration effort of users. + reduce configuration effort of users. Redundancy by multiple RDNSSes is better provided by multiple servers having different anycast addresses than multiple servers sharing same anycast address because the former approach allows - stale servers to still generate routes to their anycast addresses. + stale servers to still generate routes to their anycast addresses. Thus, in a routing domain (or domains sharing DNS servers), there - will be only one server having an anycast address unless the domain + will be only one server having an anycast address unless the domain is so large that load distribution is necessary. Small ISPs will operate one RDNSS at each anycast address which is shared by all the subscribers. Large ISPs may operate multiple + + +Jeong, et al. Expires - March 2005 [Page 10] + +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 + + RDNSSes at each anycast address to distribute and reduce load, where boundary between RDNSSes may be fixed (redundancy is still - provided by multiple addresses) or change dynamically. DNS packets - - -Jeong, et al. Expires - January 2005 [Page 10] - -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 - - + provided by multiple addresses) or change dynamically. DNS packets with the well-known anycast addresses are not expected (though not prohibited) to cross ISP boundaries, as ISPs are expected to be able to take care of themselves. - Because "anycast" in this memo is simpler than that of RFC1546 [11] + Because "anycast" in this memo is simpler than that of RFC1546 [11] and RFC3513 [12] where it is assumed to be administratively prohibited to have multiple servers on a single link sharing an anycast address, anycast in this memo should be implemented as @@ -564,11 +567,11 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 addresses approach can and should use the anycast address as a source unicast (according to RFC3513 [12]) address of packets of UDP and TCP responses. With TCP, if route flips and packets to an - anycast address are routed to a new server, it is expected that the + anycast address are routed to a new server, it is expected that the flip is detected by ICMP or sequence number inconsistency and the - TCP connection is reset and retried. + TCP connection is reset and retried. -4. Interworking among IPv6 DNS Configuration Approaches +4. Interworking among IPv6 DNS Configuration Approaches Three approaches can work together for IPv6 host configuration of RDNSS. This section shows a consideration on how these approaches @@ -576,18 +579,18 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 For ordering between RA and DHCP approaches, O (Other stateful configuration) flag in RA message can be used [8]. If no RDNSS - option is included, an IPv6 Host may perform DNS configuration + option is included, an IPv6 host may perform DNS configuration through DHCPv6 [5]-[7] regardless of whether the O flag is set or not. - The well-known anycast addresses approach fully interworks with the + The well-known anycast addresses approach fully interworks with the other approaches. That is, the other approaches can remove configuration effort on servers by using the well-known addresses - as the default configuration. Moreover, clients preconfigured with - well-known anycast addresses can be further configured to use other + as the default configuration. Moreover, clients preconfigured with + well-known anycast addresses can be further configured to use other approaches to override the well-known addresses, if configuration information from other approaches are available. That is, all the - clients should have the well-known anycast addresses preconfigured, + clients should have the well-known anycast addresses preconfigured, in the case where there are no other mechanisms available. In order to fly anycast approach with the other solutions, there are three options. @@ -596,18 +599,16 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 resort, when an IPv6 host can not get RDNSS information through RA and DHCP. The well-known anycast addresses have to be pre- configured in IPv6 hosts' resolver configuration files. - - - -Jeong, et al. Expires - January 2005 [Page 11] +Jeong, et al. Expires - March 2005 [Page 11] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 + The second is that an IPv6 host can configure well-known addresses - as the most preferable in its configuration file even though either + as the most preferable in its configuration file even though either RA option or DHCP option is available. The last is that the well-known anycast addresses can be set in RA @@ -616,15 +617,15 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 can be obtained by IPv6 host. Because this approach is the most convenient for users, the last option is recommended. - Note: this section does not necessarily mean this document suggests + Note: this section does not necessarily mean this document suggests adopting all these three approaches and making them interwork in the way described here. In fact, some approaches may even not be adopted at all as a result of further discussion. -5. Deployment Scenarios +5. Deployment Scenarios Regarding DNS configuration on the IPv6 host, several mechanisms - have being considered at the DNSOP Working Group such as RA option, + are being considered at the DNSOP Working Group such as RA option, DHCPv6 option and well-known preconfigured anycast addresses as of today, and this document is a final result from the long thread. In this section, we suggest four applicable scenarios of three @@ -634,9 +635,9 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 any specific approaches into the restricted environments. No enforcement is in each scenario and all mentioned scenarios are probable. The main objective of this work is to provide a useful - guideline of IPv6 DNS configuration. + guideline for IPv6 DNS configuration. -5.1 ISP Network +5.1. ISP Network A characteristic of ISP network is that multiple Customer Premises Equipment (CPE) devices are connected to IPv6 PE (Provider Edge) @@ -648,17 +649,16 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 each customer network gets a different IPv6 prefix from an IPv6 PE router, but the same RDNSS configuration will be distributed. - This section discusses how the different approaches to distributing + This section discusses how the different approaches to distributing DNS information are compared in an ISP network. -5.1.1 RA Option Approach +5.1.1. RA Option Approach - -Jeong, et al. Expires - January 2005 [Page 12] +Jeong, et al. Expires - March 2005 [Page 12] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 When the CPE is a host, the RA option for RDNSS can be used to @@ -678,16 +678,16 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 which the host must receive at least an RA message for detecting a new network, than in other scenarios generally although administrator should configure RDNSS information on the routers. - Secure ND [14] can provide extended security when using RA message. + Secure ND [14] can provide extended security when using RA message. -5.1.2 DHCPv6 Option Approach +5.1.2. DHCPv6 Option Approach DHCPv6 can be used for RDNSS configuration through the use of the DNS option, and can provide other configuration information in the same message with RDNSS configuration [5]-[7]. DHCPv6 DNS option is already in place for DHCPv6 as RFC 3646 [7] and moreover DHCPv6- lite or stateless DHCP [6] is nowhere as complex as a full DHCPv6 - implementation. DHCP is a client-server model protocol, so ISP can + implementation. DHCP is a client-server model protocol, so ISP can handle user identification on its network intentionally, and also authenticated DHCP [15] can be used for secure message exchange. @@ -700,32 +700,32 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 can be carried in the same DHCPv6 message exchange used for DHCPv6 to efficiently provide that information, along with any other configuration information needed by the customer gateway or - customer network. This service model can be useful to Home or SOHO - subscribers. The Home or SOHO gateway, which is a customer gateway + customer network. This service model can be useful to Home or SOHO + subscribers. The Home or SOHO gateway, which is a customer gateway for ISP, can then pass that RDNSS configuration information to the hosts in the customer network through DHCP. -5.1.3 Well-known Addresses Approach +5.1.3. Well-known Addresses Approach - Well-known anycast addresses approach is also a feasible and simple + Well-known anycast addresses approach is also a feasible and simple mechanism for ISP [9]. The use of well-known anycast addresses -Jeong, et al. Expires - January 2005 [Page 13] +Jeong, et al. Expires - March 2005 [Page 13] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 - avoids some of the security risks in rogue messages sent through an + avoids some of the security risks in rogue messages sent through an external protocol like RA or DHCPv6. The configuration of hosts - for the use of well-known anycast addresses requires no protocol or + for the use of well-known anycast addresses requires no protocol or manual configuration, but the configuration of routing for the - anycast addresses requires intervention on the part of the network + anycast addresses requires intervention on the part of the network administrator. Also, the number of special addresses would be equal to the number of RDNSSes that could be made available to subscribers. -5.2 Enterprise Network +5.2. Enterprise Network Enterprise network is defined as a network that has multiple internal links, one or more router connections, to one or more @@ -733,13 +733,13 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 [16]. An enterprise network can get network prefixes from ISP by either manual configuration or prefix delegation [17]. In most cases, because an enterprise network manages its own DNS domains, - it operates its own DNS servers for the domains. These DNS servers + it operates its own DNS servers for the domains. These DNS servers within enterprise network process recursive DNS name resolution - requests of IPv6 hosts as RDNSS. RDNSS configuration in enterprise + requests of IPv6 hosts as RDNSS. RDNSS configuration in enterprise network can be performed like in Section 4, in which three approaches can be used together. - IPv6 host can decide which approach is or may be used in its subnet + IPv6 host can decide which approach is or may be used in its subnet with O flag in RA message [8]. As the first option in Section 4, well-known anycast addresses can be used as a last resort when RDNSS information can not be obtained through either RA option or @@ -752,11 +752,11 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 The last option, a more convenient and transparent way, does not need IPv6 hosts to preconfigure the well-known anycast addresses - because the addresses are delivered to IPv6 hosts through either RA + because the addresses are delivered to IPv6 hosts through either RA option or DHCPv6 option as if they were unicast addresses. This way is most recommended for the sake of user's convenience. -5.3 3GPP Network +5.3. 3GPP Network IPv6 DNS configuration is a missing part of IPv6 autoconfiguration and an important part of the basic IPv6 functionality in the 3GPP @@ -766,36 +766,36 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 -Jeong, et al. Expires - January 2005 [Page 14] +Jeong, et al. Expires - March 2005 [Page 14] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 - In 3GPP architecture, there is a dedicated link between the UE and - the GGSN called the Packet Data Protocol (PDP) Context. This link + In 3GPP architecture, there is a dedicated link between the UE and + the GGSN called the Packet Data Protocol (PDP) Context. This link is created through the PDP Context activation procedure [21]. - There is a separate PDP context type for IPv4 and IPv6 traffic. If + There is a separate PDP context type for IPv4 and IPv6 traffic. If a 3GPP UE user is communicating using IPv6 (having an active IPv6 PDP context), it can not be assumed that (s)he has simultaneously - active IPv4 PDP context, and DNS queries could be done using IPv4. + active IPv4 PDP context, and DNS queries could be done using IPv4. A 3GPP UE can thus be an IPv6 node, and it needs to somehow - discover the address of the RDNSS. Before IP-based services (e.g., + discover the address of the RDNSS. Before IP-based services (e.g., web browsing or e-mail) can be used, the IPv6 (and IPv4) RDNSS addresses need to be discovered in the 3GPP UE. - Section 5.3.1 briefly summarizes currently available mechanisms in + Section 5.3.1 briefly summarizes currently available mechanisms in 3GPP networks and recommendations. 5.3.2 analyzes the Router - Advertisement based solution, 5.3.3 analyzes the Stateless DHCPv6 + Advertisement based solution, 5.3.3 analyzes the Stateless DHCPv6 mechanism, and 5.3.4 analyzes the Well-known addresses approach. Section 5.3.5 finally summarizes the recommendations. -5.3.1 Currently Available Mechanisms and Recommendations +5.3.1. Currently Available Mechanisms and Recommendations 3GPP has defined a mechanism, in which RDNSS addresses can be - received in the PDP context activation (a control plane mechanism). + received in the PDP context activation (a control plane mechanism). That is called the Protocol Configuration Options Information Element (PCO-IE) mechanism [22]. The RDNSS addresses can also be - received over the air (using text messages), or typed in manually + received over the air (using text messages), or typed in manually in the UE. Note that the two last mechanisms are not very well scalable. The UE user most probably does not want to type IPv6 RDNSS addresses manually in his/her UE. The use of well-known @@ -805,25 +805,25 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 sufficient for the 3GPP environment. IPv6 is intended to operate in a zero-configuration manner, no matter what the underlying network infrastructure is. Typically, the RDNSS address is needed - to make an IPv6 node operational - and the DNS configuration should + to make an IPv6 node operational - and the DNS configuration should be as simple as the address autoconfiguration mechanism. It must also be noted that there will be additional IP interfaces in some - near future 3GPP UEs, e.g., Wireless LAN (WLAN), and 3GPP-specific - DNS configuration mechanisms (such as PCO-IE [22]) do not work for - those IP interfaces. In other words, a good IPv6 DNS configuration + near future 3GPP UEs, e.g., WLAN, and 3GPP-specific DNS + configuration mechanisms (such as PCO-IE [22]) do not work for + those IP interfaces. In other words, a good IPv6 DNS configuration mechanism should also work in a multi-access network environment. From 3GPP point of view, the best IPv6 DNS configuration solution is feasible for a very large number of IPv6-capable UEs (can be even hundreds of millions in one operator's network), is automatic - and thus requires no user action. It is suggested to standardize a + and thus requires no user action. It is suggested to standardize a lightweight, stateless mechanism that works in all network environments. The solution could then be used for 3GPP, 3GPP2, -Jeong, et al. Expires - January 2005 [Page 15] +Jeong, et al. Expires - March 2005 [Page 15] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 WLAN and other access network technologies. A light, stateless @@ -831,12 +831,12 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 networks, but also 3GPP networks and UEs would certainly benefit from the new mechanism. -5.3.2 RA Extension +5.3.2. RA Extension Router Advertisement extension [8] is a lightweight IPv6 DNS - configuration mechanism that requires minor changes in 3GPP UE IPv6 + configuration mechanism that requires minor changes in 3GPP UE IPv6 stack and Gateway GPRS Support Node (GGSN, the default router in - the 3GPP architecture) IPv6 stack. This solution can be specified + the 3GPP architecture) IPv6 stack. This solution can be specified in the IETF (no action needed in the 3GPP) and taken in use in 3GPP UEs and GGSNs. @@ -846,7 +846,7 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 This solution is easily scalable for a very large number of UEs. The operator can configure the RDNSS addresses in the GGSN as a part of normal GGSN configuration. The IPv6 RDNSS address is - received in the Router Advertisement, and an extra Round Trip Time + received in the Router Advertisement, and an extra Round Trip Time (RTT) for asking RDNSS addresses can be avoided. If thinking about cons, this mechanism still requires @@ -855,17 +855,17 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 should, however, be pretty straightforward, and new IPv6 equipment could support RA extension already from the beginning. -5.3.3 Stateless DHCPv6 +5.3.3. Stateless DHCPv6 DHCPv6-based solution needs the implementation of Stateless DHCP [6] and DHCPv6 DNS options [7] in the UE, and a DHCPv6 server in - the operator's network. A possible configuration is such that the + the operator's network. A possible configuration is such that the GGSN works as a DHCP relay. Pros for Stateless DHCPv6-based solution are 1) Stateless DHCPv6 is a standardized mechanism. - 2) DHCPv6 can be used for receiving other configuration information + 2) DHCPv6 can be used for receiving other configuration information than RDNSS addresses, e.g., SIP server addresses. 3) DHCPv6 works in different network environments. @@ -876,9 +876,9 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 -Jeong, et al. Expires - January 2005 [Page 16] +Jeong, et al. Expires - March 2005 [Page 16] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 Some issues with DHCPv6 in 3GPP networks are listed below: @@ -894,23 +894,23 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 networks (with tens or hundreds of millions of UEs) may be an issue, at least the redundancy needs to be taken care of. However, if the DHCPv6 service is integrated into the network elements, such as - router operating system, scalability and reliability is comparable + router operating system, scalability and reliability is comparable with other DNS configuration approaches. 4) It is sub-optimal to utilize the radio resources in 3GPP networks for DHCPv6 messages if there is a simpler alternative available. - a) Use of Stateless DHCPv6 adds one round trip delay to the case + a) Use of Stateless DHCPv6 adds one round trip delay to the case in which the UE can start transmitting data right after the Router Advertisement. 5) If the DNS information (suddenly) changes, Stateless DHCPv6 can not automatically update the UE, see [23]. -5.3.4 Well-known Addresses +5.3.4. Well-known Addresses - Using well-known addresses is also a feasible and a light mechanism + Using well-known addresses is also a feasible and a light mechanism for 3GPP UEs. Those well-known addresses can be preconfigured in the UE software and the operator makes the corresponding configuration on the network side. So this is a very easy @@ -920,30 +920,30 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 IPv6 anycast addresses are suggested. Note: IPv6 DNS configuration proposal based on the use of well- - known site-local addresses developed at the IPv6 Working Group was + known site-local addresses developed at the IPv6 Working Group was seen as a feasible mechanism for 3GPP UEs, but opposition by some people in the IETF and finally deprecating IPv6 site-local addresses made it impossible to standardize it. Note that this mechanism is implemented in some existing operating systems today - (also in some 3GPP UEs) as a last resort of IPv6 DNS configuration. + (also in some 3GPP UEs) as a last resort of IPv6 DNS configuration. -5.3.5 Recommendations +5.3.5. Recommendations -Jeong, et al. Expires - January 2005 [Page 17] +Jeong, et al. Expires - March 2005 [Page 17] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 - It is suggested that a lightweight, stateless DNS configuration - mechanism is specified as soon as possible. From 3GPP UE's and - networks' point of view, Router Advertisement based mechanism looks - most promising. The sooner a light, stateless mechanism is - specified, the sooner we can get rid of using well-known site-local + It is suggested that a lightweight, stateless DNS configuration + mechanism is specified as soon as possible. From 3GPP UE's and + networks' point of view, Router Advertisement based mechanism looks + most promising. The sooner a light, stateless mechanism is + specified, the sooner we can get rid of using well-known site-local addresses for IPv6 DNS configuration. -5.4 Unmanaged Network +5.4. Unmanaged Network There are 4 deployment scenarios of interest in unmanaged networks [24]: @@ -956,16 +956,16 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 4) A gateway connected to an IPv6-only ISP. -5.4.1 Case A: Gateway does not provide IPv6 at all +5.4.1. Case A: Gateway does not provide IPv6 at all - In this case, the gateway does not provide IPv6; the ISP may or may + In this case, the gateway does not provide IPv6; the ISP may or may not provide IPv6. Automatic or Configured tunnels are the recommended transition mechanisms for this scenario. The case where dual-stack hosts behind an NAT, that need access to an IPv6 RDNSS, can not be entirely ruled out. The DNS configuration mechanism has to work over the tunnel, and the - underlying tunneling mechanism could be implementing NAT traversal. + underlying tunneling mechanism could be implementing NAT traversal. The tunnel server assumes the role of a relay (both for DHCP and Well-known anycast addresses approaches). @@ -976,57 +976,57 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 known anycast addresses in a tunneled environment is unclear or not well understood. -5.4.2 Case B: A dual-stack gateway connected to a dual-stack ISP +5.4.2. Case B: A dual-stack gateway connected to a dual-stack ISP This is similar to a typical IPv4 home user scenario, where DNS configuration parameters are obtained using DHCP. Except that - Stateless DHCPv6 is used, as opposed to the IPv4 scenario where the + Stateless DHCPv6 is used, as opposed to the IPv4 scenario where the DHCP server is stateful (maintains the state for clients). -Jeong, et al. Expires - January 2005 [Page 18] +Jeong, et al. Expires - March 2005 [Page 18] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 -5.4.3 Case C: A dual-stack gateway connected to an IPv4-only ISP +5.4.3. Case C: A dual-stack gateway connected to an IPv4-only ISP - This is similar to Case B. If a gateway provides IPv6 connectivity + This is similar to Case B. If a gateway provides IPv6 connectivity by managing tunnels, then it is also supposed to provide access to an RDNSS. Like this, the tunnel for IPv6 connectivity originates from the dual-stack gateway instead of the host. -5.4.4 Case D: A gateway connected to an IPv6-only ISP +5.4.4. Case D: A gateway connected to an IPv6-only ISP This is similar to Case B. -6. Security Considerations +6. Security Considerations As security requirements depend solely on applications and are different application by application, there can be no generic - requirement defined at higher IP or lower application layer of DNS. + requirement defined at higher IP or lower application layer of DNS. However, it should be noted that cryptographic security requires configured secret information that full autoconfiguration and - cryptographic security are mutually exclusive. People insisting on + cryptographic security are mutually exclusive. People insisting on secure full autoconfiguration will get false security, false autoconfiguration or both. In some deployment scenario [19], where cryptographic security is - required for applications, secret information for the cryptographic + required for applications, secret information for the cryptographic security is preconfigured through which application specific configuration data, including those for DNS, can be securely configured. It should be noted that if applications requiring - cryptographic security depend on DNS, the applications also require + cryptographic security depend on DNS, the applications also require cryptographic security to DNS. Therefore, the full auto- configuration of DNS is not acceptable. However, with full autoconfiguration, weaker but still reasonable security is being widely accepted and will continue to be acceptable. That is, with full autoconfiguration, which means - there is no cryptographic security for the autoconfiguration, it is + there is no cryptographic security for the autoconfiguration, it is already assumed that local environment is secure enough that information from local autoconfiguration server has acceptable security even without cryptographic security. Thus, communication @@ -1036,36 +1036,36 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 For security considerations of each approach, refer to the corresponding drafts [5]-[9]. -7. Acknowledgements +7. Acknowledgements -Jeong, et al. Expires - January 2005 [Page 19] +Jeong, et al. Expires - March 2005 [Page 19] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 This draft has greatly benefited from inputs by David Meyer, Rob Austein, Tatuya Jinmei, Pekka Savola, Tim Chown, Luc Beloeil, - Christian Huitema, and Thomas Narten. The authors appreciate their - contribution. + Christian Huitema, Thomas Narten, Pascal Thubert, and Greg Daley. + The authors appreciate their contribution. -8. Normative References +8. Normative References - [1] S. Bradner, "Intellectual Property Rights in IETF Technology", + [1] S. Bradner, "Intellectual Property Rights in IETF Technology", RFC 3668, February 2004. - [2] S. Bradner, "IETF Rights in Contributions", RFC 3667, February + [2] S. Bradner, "IETF Rights in Contributions", RFC 3667, February 2004. - [3] T. Narten, E. Nordmark and W. Simpson, "Neighbor Discovery for + [3] T. Narten, E. Nordmark and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998. [4] S. Thomson and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462, December 1998. - [5] R. Droms et al., "Dynamic Host Configuration Protocol for IPv6 + [5] R. Droms et al., "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [6] R. Droms, "Stateless Dynamic Host Configuration Protocol @@ -1075,44 +1075,44 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 Configuration Protocol for IPv6 (DHCPv6)", RFC 3646, December 2003. -9. Informative References +9. Informative References [8] J. Jeong, S. Park, L. Beloeil and S. Madanapalli, "IPv6 DNS Discovery based on Router Advertisement", draft-jeong-dnsop- - ipv6-dns-discovery-02.txt, July 2004. + ipv6-dns-discovery-02.txt, July 2004, Work in Progress. [9] M. Ohta, "Preconfigured DNS Server Addresses", draft-ohta- - preconfigured-dns-01.txt, February 2004. + preconfigured-dns-01.txt, February 2004, Work in Progress. - [10] S. Venaas and T. Chown, "Lifetime Option for DHCPv6", draft- - ietf-dhc-lifetime-00.txt, March 2004. + [10] S. Venaas, T. Chown and B. Volz, "Information Refresh Time + Option for DHCPv6", draft-ietf-dhc-lifetime-02.txt, September + 2004, Work in Progress. [11] C. Partridge, T. Mendez and W. Milliken, "Host Anycasting Service", RFC 1546, November 1993. - [12] R. Hinden and S. Deering, "Internet Protocol Version 6 (IPv6) + [12] R. Hinden and S. Deering, "Internet Protocol Version 6 (IPv6) Addressing Architecture", RFC 3513, April 2003. - -Jeong, et al. Expires - January 2005 [Page 20] +Jeong, et al. Expires - March 2005 [Page 20] -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 - [13] M. Lind et al., "Scenarios and Analysis for Introduction IPv6 + [13] M. Lind et al., "Scenarios and Analysis for Introduction IPv6 into ISP Networks", draft-ietf-v6ops-isp-scenarios-analysis- - 02.txt, April 2004. + 03.txt, June 2004, Work in Progress. [14] J. Arkko et al., "SEcure Neighbor Discovery (SEND)", draft- - ietf-send-ndopt-05.txt, April 2004. + ietf-send-ndopt-06.txt, July 2004, Work in Progress. [15] R. Droms and W. Arbaugh, "Authentication for DHCP Messages", RFC 3118, June 2001. [16] J. Bound et al., "IPv6 Enterprise Network Scenarios", draft- - ietf-v6ops-ent-scenarios-01.txt, February 2004. + ietf-v6ops-ent-scenarios-05.txt, July 2004, Work in Progress. [17] O. Troan and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December @@ -1125,40 +1125,66 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 RFC 3574, August 2003. [20] J. Wiljakka, Ed., "Analysis on IPv6 Transition in 3GPP - Networks", draft-ietf-v6ops-3gpp-analysis-09.txt, March 2004. + Networks", draft-ietf-v6ops-3gpp-analysis-10.txt, May 2004, + Work in Progress. [21] 3GPP TS 23.060 V5.4.0, "General Packet Radio Service (GPRS); Service description; Stage 2 (Release 5)", December 2002. [22] 3GPP TS 24.008 V5.8.0, "Mobile radio interface Layer 3 - specification; Core network protocols; Stage 3 (Release 5)", + specification; Core network protocols; Stage 3 (Release 5)", June 2003. [23] T. Chown, S. Venaas and A. Vijayabhaskar, "Renumbering - Requirements for Stateless DHCPv6", draft-ietf-dhc-stateless- - dhcpv6-renumbering-00.txt, March 2004. + Requirements for Stateless DHCPv6", draft-ietf-dhc-stateless- + dhcpv6-renumbering-01.txt, March 2004, Work in Progress. [24] C. Huitema et al., "Unmanaged Networks IPv6 Transition Scenarios", RFC 3750, April 2004. -10. Authors' Addresses +10. Appendix A - Link-layer Multicast Acknowledgements with RA Option + + One benefit of RA option is to be able to multicast the + advertisements, reducing the need for duplicated unicast + communications. + + + + +Jeong, et al. Expires - March 2005 [Page 21] + +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 + + + However, some link-layers may not support this as well as others. + Consider, for example, WLAN networks where multicast is unreliable. + The unreliability problem is caused by lack of ACK for multicast, + especially on the path from the Access Point (AP) to the Station + (STA), which is specific to CSMA/CA of WLAN. Namely, multicast + packet is unacknowledged on the path from the AP to the STA, but + acknowledged in the reverse direction from the STA to the AP. For + example, when a router is placed at wired network connected to an + AP, a host may sometimes not receive RA message advertised through + the AP. + + The fact that this problem has not been addressed in Neighbor + Discovery [3] indicates that the extra link-layer acknowledgements + have not been considered a serious problem till now. + + A possible mitigation technique could be to map all-nodes link- + local multicast address to the link-layer broadcast address, and to + rely on the ND retransmissions for message delivery. + +11. Authors' Addresses Jaehoon Paul Jeong, Editor - ETRI / PEC - 161 Gajeong-dong, Yuseong-gu - Daejeon 305-350 - Korea + ETRI/University of Minnesota at Twin Cities + 117 Pleasant Street SE + Minneapolis, MN 55455 + USA - - -Jeong, et al. Expires - January 2005 [Page 21] - -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 - - - Phone: +82 42 860 1664 - Fax: +82 42 861 5404 - EMail: paul@etri.re.kr + Phone: +1 651 587 7774 + EMail: jjeong@cs.umn.edu Ralph Droms Cisco Systems @@ -1178,6 +1204,13 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 Phone: +1 650 625 2004 EMail: bob.hinden@nokia.com + + +Jeong, et al. Expires - March 2005 [Page 22] + +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 + + Ted Lemon Nominum, Inc. 950 Charter Street @@ -1204,13 +1237,6 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 Korea Phone: +82 31 200 4508 - - -Jeong, et al. Expires - January 2005 [Page 22] - -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 - - EMail: soohong.park@samsung.com Suresh Satapati @@ -1229,14 +1255,21 @@ Internet-Draft IPv6 Host Configuration of DNS Server July 2004 Phone: +358 7180 48372 EMail: juha.wiljakka@nokia.com -Intellectual Property Statement +12. Intellectual Property Statement - The following intellectual property notice is copied from RFC3668, + The following intellectual property notice is copied from RFC3668, Section 5. + + +Jeong, et al. Expires - March 2005 [Page 23] + +Internet-Draft IPv6 Host Configuration of DNS Server September 2004 + + The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed - to pertain to the implementation or use of the technology described + to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. @@ -1250,7 +1283,7 @@ Intellectual Property Statement specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. - The IETF invites any interested party to bring to its attention any + The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- @@ -1258,15 +1291,7 @@ Intellectual Property Statement Full Copyright Statement - - - -Jeong, et al. Expires - January 2005 [Page 23] - -Internet-Draft IPv6 Host Configuration of DNS Server July 2004 - - - The following copyright notice is copied from RFC3667, Section 5.4. + The following copyright notice is copied from RFC3667, Section 5.4. It describes the applicable copyright for this document. Copyright (C) The Internet Society (2004). This document is @@ -1289,33 +1314,8 @@ Acknowledgement Internet Society. - - - - - - - - - - - - - - - - - - - - - - - - - -Jeong, et al. Expires - January 2005 [Page 24] +Jeong, et al. Expires - March 2005 [Page 24] diff --git a/doc/draft/draft-ietf-dnsop-misbehavior-against-aaaa-00.txt b/doc/draft/draft-ietf-dnsop-misbehavior-against-aaaa-00.txt deleted file mode 100644 index 1094275d3e..0000000000 --- a/doc/draft/draft-ietf-dnsop-misbehavior-against-aaaa-00.txt +++ /dev/null @@ -1,505 +0,0 @@ - - -IETF DNSOP Working Group Y. Morishita -Internet-Draft JPRS -Expires: July 11, 2004 T. Jinmei - Toshiba - January 11, 2004 - - - Common Misbehavior against DNS Queries for IPv6 Addresses - draft-ietf-dnsop-misbehavior-against-aaaa-00.txt - -Status of this Memo - - This document is an Internet-Draft and is in full conformance with - all provisions of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that other - groups may also distribute working documents as Internet-Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at http:// - www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on July 11, 2004. - -Copyright Notice - - Copyright (C) The Internet Society (2004). All Rights Reserved. - -Abstract - - There is some known misbehavior of DNS authoritative servers when - they are queried for AAAA resource records. Such behavior can block - IPv4 communication which should actually be available, cause a - significant delay in name resolution, or even make a denial of - service attack. This memo describes details of the known cases and - discusses the effect of the cases. - -1. Introduction - - Many DNS clients (resolvers) that support IPv6 first search for AAAA - Resource Records (RRs) of a target host name, and then for A RRs of - - - -Morishita & Jinmei Expires July 11, 2004 [Page 1] - -Internet-Draft Common Misbehavior against AAAA Queries January 2004 - - - the same name. This fallback mechanism is based on the DNS - specifications, which if not obeyed by authoritative servers can - produce unpleasant results. In some cases, for example, a web browser - fails to connect to a web server it could otherwise. In the following - sections, this memo describes some typical cases of the misbehavior - and its (bad) effects. - - Note that the misbehavior is not specific to AAAA RRs. In fact, all - known examples also apply to the cases of queries for MX, NS, and SOA - RRs. The authors even believe this can be generalized for all types - of queries other than those for A RRs. In this memo, however, we - concentrate on the case for AAAA queries, since the problem is - particularly severe for resolvers that support IPv6, which thus - affects many end users. Resolvers at end users normally send A and/or - AAAA queries only, and so the problem for the other cases is - relatively minor. - -2. Network Model - - In this memo, we assume a typical network model of name resolution - environment using DNS. It consists of three components; stub - resolvers, caching servers, and authoritative servers. A stub - resolver issues a recursive query to a caching server, which then - handles the entire name resolution procedure recursively. The caching - server caches the result of the query as well as sends the result to - the stub resolver. The authoritative servers respond to queries for - names for which they have the authority, normally in a non-recursive - manner. - -3. Expected Behavior - - Suppose that an authoritative server has an A RR but not a AAAA RR - for a host name. Then the server should return a response to a query - for a AAAA RR of the name with the RCODE being 0 (indicating no - error) and with an empty answer section [1]. Such a response - indicates that there is at least one RR of a different type than AAAA - for the queried name, and the stub resolver can then look for A RRs. - - This way, the caching server can cache the fact that the queried name - does not have a AAAA RR (but may have other types of RRs), and thus - can improve the response time to further queries for a AAAA RR of the - name. - -4. Problematic Behaviors - - There are some known cases at authoritative servers that do not - conform to the expected behavior. This section describes those - problematic cases. - - - -Morishita & Jinmei Expires July 11, 2004 [Page 2] - -Internet-Draft Common Misbehavior against AAAA Queries January 2004 - - -4.1 Return NXDOMAIN - - This type of server returns a response with the RCODE being 3 - (NXDOMAIN) to a query for a AAAA RR, indicating it does not have any - RRs of any type for the queried name. - - With this response, the stub resolver may immediately give up and - never fall back. Even if the resolver retries with a query for an A - RR, the negative response for the name has been cached in the caching - server, and the caching server will simply return the negative - response. As a result, the stub resolver considers this as a fatal - error in name resolution. - - There have been several known examples of this behavior, but all the - examples that the authors know have changed their behavior as of this - writing. - -4.2 Return NOTIMP - - Other authoritative servers return a response with the RCODE being 4 - (NOTIMP), indicating the servers do not support the requested type of - query. - - This case is less harmful than the previous one; if the stub resolver - falls back to querying for an A RR, the caching server will process - the query correctly and return an appropriate response. - - In this case, the caching server does not cache the fact that the - queried name has no AAAA RR, resulting in redundant queries for AAAA - RRs in the future. The behavior will waste network bandwidth and - increase the load of the authoritative server. - - Using SERVFAIL or FORMERR would cause the same effect, though the - authors have not seen such implementations yet. - -4.3 Return a Broken Response - - Another different type of authoritative servers returns broken - responses to AAAA queries. A known behavior of this category is to - return a response whose RR type is AAAA, but the length of the RDATA - is 4 bytes. The 4-byte data looks like the IPv4 address of the - queried host name. That is, the RR in the answer section would be - described like this: - - www.bad.example. 600 IN AAAA 192.0.2.1 - - which is, of course, bogus (or at least meaningless). - - - - -Morishita & Jinmei Expires July 11, 2004 [Page 3] - -Internet-Draft Common Misbehavior against AAAA Queries January 2004 - - - A widely deployed caching server implementation transparently returns - the broken response (as well as caches it) to the stub resolver. - Another known server implementation parses the response by - themselves, and sends a separate response with the RCODE being 2 - (SERVFAIL). - - In either case, the broken response does not affect queries for an A - RR of the same name. If the stub resolver falls back to A queries, it - will get an appropriate response. - - The latter case, however, causes the same bad effect as that - described in the previous section: redundant queries for AAAA RRs. - -4.4 Make Lame Delegation - - Some authoritative servers respond to AAAA queries in a way causing - lame delegation. In this case the parent zone specifies that the - authoritative server should have the authority of a zone, but the - server does not return an authoritative response for AAAA queries - within the zone (i.e., the AA bit in the response is not set). On the - other hand, the authoritative server returns an authoritative - response for A queries. - - When a caching server asks the server for AAAA RRs in the zone, it - recognizes the delegation is lame, and return a response with the - RCODE being 2 (SERVFAIL) to the stub resolver. - - Furthermore, some caching servers record the authoritative server as - lame for the zone and will not use it for a certain period of time. - With this type of caching server, even if the stub resolver falls - back to querying for an A RR, the caching server will simply return a - response with the RCODE being SERVFAIL, since all the servers are - known to be "lame." - - There is also an implementation that relaxes the behavior a little - bit. It basically tries to avoid using the lame server, but still - continues to try it as a last resort. With this type of caching - server, the stub resolver will get a correct response if it falls - back after SERVFAIL. However, this still causes redundant AAAA - queries as explained in the previous sections. - -4.5 Ignore Queries for AAAA - - Some authoritative severs seem to ignore queries for a AAAA RR, - causing a delay at the stub resolver to fall back to a query for an A - RR. This behavior may even cause a fatal timeout at the resolver. - - - - - -Morishita & Jinmei Expires July 11, 2004 [Page 4] - -Internet-Draft Common Misbehavior against AAAA Queries January 2004 - - -5. Security Considerations - - The CERT/CC pointed out that the response with NXDOMAIN described in - Section 4.1 can be used for a denial of service attack [2]. The same - argument applies to the case of "lame delegation" described in - Section 4.4 with a certain type of caching server. - -6. Acknowledgements - - Erik Nordmark encouraged the authors to publish this document as an - Internet Draft. Akira Kato and Paul Vixie reviewed a preliminary - version of this document. Pekka Savola carefully reviewed a previous - version and provided detailed comments. - -Informative References - - [1] Mockapetris, P., "DOMAIN NAMES - CONCEPTS AND FACILITIES", RFC - 1034, November 1987. - - [2] The CERT Coordination Center, "Incorrect NXDOMAIN responses from - AAAA queries could cause denial-of-service conditions", March - 2003, . - - -Authors' Addresses - - MORISHITA Orange Yasuhiro - Research and Development Department, Japan Registry Service Co.,Ltd. - Fuundo Bldg 3F, 1-2 Kanda-Ogawamachi - Chiyoda-ku, Tokyo 101-0052 - Japan - - EMail: yasuhiro@jprs.co.jp - - - JINMEI Tatuya - Corporate Research & Development Center, Toshiba Corporation - 1 Komukai Toshiba-cho, Saiwai-ku - Kawasaki-shi, Kanagawa 212-8582 - Japan - - EMail: jinmei@isl.rdc.toshiba.co.jp - -Appendix A. Live Examples - - In this appendix, we show concrete implementations and domain names - that may cause problematic cases so that the behavior can be - reproduced in a practical environment. The examples are for - - - -Morishita & Jinmei Expires July 11, 2004 [Page 5] - -Internet-Draft Common Misbehavior against AAAA Queries January 2004 - - - informational purposes only, and the authors do not intend to accuse - any implementations or zone administrators. - - The behavior described in Section 4.2 (return NOTIMP) can be found by - looking for a AAAA RR of www.css.vtext.com at 66.174.3.4. - - The behavior described in Section 4.3 (broken responses) can be seen - by querying for a AAAA RR of "www.gslb.mainichi.co.jp," which is an - alias of "www.mainichi.co.jp," at 210.173.172.2. The same behavior - can be found with the name "vip.alt.ihp.sony.co.jp," an alias of - "www.sony.co.jp," at 210.139.255.204. - - The behavior described in Section 4.4 (lame delegation) can be found - by querying for a AAAA RR of "www.ual.com" at 209.87.113.4. - - The behavior described in Section 4.5 (ignore queries) can be seen by - trying to ask for a AAAA RR of "ad.3jp.doubleclick.net," which is an - alias of "ad.jp.doubleclick.net," at 210.153.90.9. - - Many authoritative server implementations show the expected behavior - described in Section 3. Some DNS load balancers reportedly have a - problematic behavior shown in Section 4, but the authors do not have - a concrete example. The CERT/CC provides a list of implementations - that behave as described in Section 4.1 [2]. - - The BIND9 caching server implementation is an example of the latter - cases described in Section 4.3 and Section 4.4, respectively. The - BIND8 caching server implementation is an example of the former case - described in Section 4.3. As for the issue shown in Section 4.4, - BIND8 caching servers prior to 8.3.5 show the behavior described as - the former case in this section. The versions 8.3.5 and later of - BIND8 caching server behave like the BIND9 caching server - implementation with this matter. - - Regarding resolver implementations, the authors are only familiar - with the ones derived from the BIND implementation. These - implementations always fall back regardless of the RCODE; NXDOMAIN, - NOTIMP, or SERVFAIL. It even falls back when getting a broken - response. However, the behavior does not help the situation in the - NXDOMAIN case (see Section 4.1). Lame delegation (Section 4.4) also - causes a fatal error at the resolver side if the resolver is using - some older versions of BIND8 caching server. - - The authors hear that a stub resolver routine implemented in some web - browsers interprets the broken response described in Section 4.3 as a - fatal error and does not fall back to A queries. However, we have not - confirmed this information. - - - - -Morishita & Jinmei Expires July 11, 2004 [Page 6] - -Internet-Draft Common Misbehavior against AAAA Queries January 2004 - - -Appendix B. Change History - - Changes since draft-morishita-dnsop-misbehavior-against-aaaa-00 are: - - o Made a separate appendix and moved live examples to appendix so - that we can remove them when this document is (ever) officially - published. - - o Revised some live examples based on the recent status. - - o Noted in introduction that the misbehavior is not specific to AAAA - and that this document still concentrates on the AAAA case. - - o Changed the section title of "delegation loop" to "lame - delegation" in order to reflect the essential point of the issue. - Wording on this matter was updated accordingly. - - o Updated the Acknowledgements list. - - o Changed the reference category from normative to informative (this - is an informational document after all). - - o Changed the draft name to an IETF dnsop working group document (as - agreed). - - o Applied several editorial fixes. - - - - - - - - - - - - - - - - - - - - - - - - - -Morishita & Jinmei Expires July 11, 2004 [Page 7] - -Internet-Draft Common Misbehavior against AAAA Queries January 2004 - - -Intellectual Property Statement - - The IETF takes no position regarding the validity or scope of any - intellectual property or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; neither does it represent that it - has made any effort to identify any such rights. Information on the - IETF's procedures with respect to rights in standards-track and - standards-related documentation can be found in BCP-11. Copies of - claims of rights made available for publication and any assurances of - licenses to be made available, or the result of an attempt made to - obtain a general license or permission for the use of such - proprietary rights by implementors or users of this specification can - be obtained from the IETF Secretariat. - - The IETF invites any interested party to bring to its attention any - copyrights, patents or patent applications, or other proprietary - rights which may cover technology that may be required to practice - this standard. Please address the information to the IETF Executive - Director. - - -Full Copyright Statement - - Copyright (C) The Internet Society (2004). All Rights Reserved. - - This document and translations of it may be copied and furnished to - others, and derivative works that comment on or otherwise explain it - or assist in its implementation may be prepared, copied, published - and distributed, in whole or in part, without restriction of any - kind, provided that the above copyright notice and this paragraph are - included on all such copies and derivative works. However, this - document itself may not be modified in any way, such as by removing - the copyright notice or references to the Internet Society or other - Internet organizations, except as needed for the purpose of - developing Internet standards in which case the procedures for - copyrights defined in the Internet Standards process must be - followed, or as required to translate it into languages other than - English. - - The limited permissions granted above are perpetual and will not be - revoked by the Internet Society or its successors or assignees. - - This document and the information contained herein is provided on an - "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING - TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING - BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION - - - -Morishita & Jinmei Expires July 11, 2004 [Page 8] - -Internet-Draft Common Misbehavior against AAAA Queries January 2004 - - - HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF - MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Acknowledgement - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Morishita & Jinmei Expires July 11, 2004 [Page 9] - - diff --git a/doc/draft/draft-ietf-dnsop-misbehavior-against-aaaa-02.txt b/doc/draft/draft-ietf-dnsop-misbehavior-against-aaaa-02.txt new file mode 100644 index 0000000000..9018f7b5af --- /dev/null +++ b/doc/draft/draft-ietf-dnsop-misbehavior-against-aaaa-02.txt @@ -0,0 +1,451 @@ + + + + +IETF DNSOP Working Group Y. Morishita +Internet-Draft JPRS +Expires: April 23, 2005 T. Jinmei + Toshiba + October 23, 2004 + + + Common Misbehavior against DNS Queries for IPv6 Addresses + draft-ietf-dnsop-misbehavior-against-aaaa-02.txt + +Status of this Memo + + This document is an Internet-Draft and is subject to all provisions + of section 3 of RFC 3667. By submitting this Internet-Draft, each + author represents that any applicable patent or other IPR claims of + which he or she is aware have been or will be disclosed, and any of + which he or she become aware will be disclosed, in accordance with + RFC 3668. + + Internet-Drafts are working documents of the Internet Engineering + Task Force (IETF), its areas, and its working groups. Note that + other groups may also distribute working documents as + Internet-Drafts. + + Internet-Drafts are draft documents valid for a maximum of six months + and may be updated, replaced, or obsoleted by other documents at any + time. It is inappropriate to use Internet-Drafts as reference + material or to cite them other than as "work in progress." + + The list of current Internet-Drafts can be accessed at + http://www.ietf.org/ietf/1id-abstracts.txt. + + The list of Internet-Draft Shadow Directories can be accessed at + http://www.ietf.org/shadow.html. + + This Internet-Draft will expire on April 23, 2005. + +Copyright Notice + + Copyright (C) The Internet Society (2004). + +Abstract + + There is some known misbehavior of DNS authoritative servers when + they are queried for AAAA resource records. Such behavior can block + IPv4 communication which should actually be available, cause a + significant delay in name resolution, or even make a denial of + service attack. This memo describes details of the known cases and + discusses the effect of the cases. + + + +Morishita & Jinmei Expires April 23, 2005 [Page 1] + +Internet-Draft Common Misbehavior against AAAA Queries October 2004 + + +1. Introduction + + Many existing DNS clients (resolvers) that support IPv6 first search + for AAAA Resource Records (RRs) of a target host name, and then for A + RRs of the same name. This fallback mechanism is based on the DNS + specifications, which if not obeyed by authoritative servers can + produce unpleasant results. In some cases, for example, a web + browser fails to connect to a web server it could otherwise reach. + In the following sections, this memo describes some typical cases of + such misbehavior and its (bad) effects. + + Note that the misbehavior is not specific to AAAA RRs. In fact, all + known examples also apply to the cases of queries for MX, NS, and SOA + RRs. The authors even believe this can be generalized for all types + of queries other than those for A RRs. In this memo, however, we + concentrate on the case for AAAA queries, since the problem is + particularly severe for resolvers that support IPv6, which thus + affects many end users. Resolvers at end users normally send A + and/or AAAA queries only, and so the problem for the other cases is + relatively minor. + +2. Network Model + + In this memo, we assume a typical network model of name resolution + environment using DNS. It consists of three components; stub + resolvers, caching servers, and authoritative servers. A stub + resolver issues a recursive query to a caching server, which then + handles the entire name resolution procedure recursively. The + caching server caches the result of the query as well as sends the + result to the stub resolver. The authoritative servers respond to + queries for names for which they have the authority, normally in a + non-recursive manner. + +3. Expected Behavior + + Suppose that an authoritative server has an A RR but not a AAAA RR + for a host name. Then the server should return a response to a query + for a AAAA RR of the name with the response code (RCODE) being 0 + (indicating no error) and with an empty answer section (see Sections + 4.3.2 and 6.2.4 of [1]). Such a response indicates that there is at + least one RR of a different type than AAAA for the queried name, and + the stub resolver can then look for A RRs. + + This way, the caching server can cache the fact that the queried name + does not have a AAAA RR (but may have other types of RRs), and thus + can improve the response time to further queries for a AAAA RR of the + name. + + + + +Morishita & Jinmei Expires April 23, 2005 [Page 2] + +Internet-Draft Common Misbehavior against AAAA Queries October 2004 + + +4. Problematic Behaviors + + There are some known cases at authoritative servers that do not + conform to the expected behavior. This section describes those + problematic cases. + +4.1 Ignore Queries for AAAA + + Some authoritative servers seem to ignore queries for a AAAA RR, + causing a delay at the stub resolver to fall back to a query for an A + RR. This behavior may even cause a fatal timeout at the resolver or + at the application which calls the resolver. Even if the resolver + eventually falls back, the result can be an unacceptable delay for + the application user, especially with interactive applications like + web browsing. + + +4.2 Return "Name Error" + + This type of server returns a response with the RCODE being 3 ("Name + Error") to a query for a AAAA RR, indicating it does not have any RRs + of any type for the queried name. + + With this response, the stub resolver may immediately give up and + never fall back. Even if the resolver retries with a query for an A + RR, the negative response for the name has been cached in the caching + server, and the caching server will simply return the negative + response. As a result, the stub resolver considers this as a fatal + error in name resolution. + + There have been several known examples of this behavior, but all the + examples that the authors know have fixed their behavior as of this + writing. + +4.3 Return Other Erroneous Codes + + Other authoritative servers return a response with other erroneous + response codes than RCODE 3 ("Name Error"). One well-known such + RCODE is 4 ("Not Implemented"), indicating the servers do not support + the requested type of query. + + These cases are less harmful than the previous one; if the stub + resolver falls back to querying for an A RR, the caching server will + process the query correctly and return an appropriate response. + + However, these can still cause a serious effect. There was an + authoritative server implementation that returned RCODE 2 ("Server + failure") to queries for AAAA RRs. One widely deployed mail server + + + +Morishita & Jinmei Expires April 23, 2005 [Page 3] + +Internet-Draft Common Misbehavior against AAAA Queries October 2004 + + + implementation with a certain type of resolver library interpreted + this result as an indication of retry and did not fall back to + queries for A RRs, causing failure of message delivery. + + If the caching server receives a response with these response codes, + it does not cache the fact that the queried name has no AAAA RR, + resulting in redundant queries for AAAA RRs in the future. The + behavior will waste network bandwidth and increase the load of the + authoritative server. + + Using RCODE 1 ("Format error") would cause a similar effect, though + the authors have not seen such implementations yet. + +4.4 Return a Broken Response + + Another different type of authoritative servers returns broken + responses to AAAA queries. A known behavior of this category is to + return a response whose RR type is AAAA, but the length of the RDATA + is 4 bytes. The 4-byte data looks like the IPv4 address of the + queried host name. That is, the RR in the answer section would be + described like this: + + www.bad.example. 600 IN AAAA 192.0.2.1 + + which is, of course, bogus (or at least meaningless). + + A widely deployed caching server implementation transparently returns + the broken response (as well as caches it) to the stub resolver. + Another known server implementation parses the response by + themselves, and sends a separate response with the RCODE being 2 + ("Server failure"). + + In either case, the broken response does not affect queries for an A + RR of the same name. If the stub resolver falls back to A queries, + it will get an appropriate response. + + The latter case, however, causes the same bad effect as that + described in the previous section: redundant queries for AAAA RRs. + +4.5 Make Lame Delegation + + Some authoritative servers respond to AAAA queries in a way causing + lame delegation. In this case the parent zone specifies that the + authoritative server should have the authority of a zone, but the + server does not return an authoritative response for AAAA queries + within the zone (i.e., the AA bit in the response is not set). On + the other hand, the authoritative server returns an authoritative + response for A queries. + + + +Morishita & Jinmei Expires April 23, 2005 [Page 4] + +Internet-Draft Common Misbehavior against AAAA Queries October 2004 + + + When a caching server asks the server for AAAA RRs in the zone, it + recognizes the delegation is lame, and returns a response with the + RCODE being 2 ("Server failure") to the stub resolver. + + Furthermore, some caching servers record the authoritative server as + lame for the zone and will not use it for a certain period of time. + With this type of caching server, even if the stub resolver falls + back to querying for an A RR, the caching server will simply return a + response with the RCODE being 2, since all the servers are known to + be "lame." + + There is also an implementation that relaxes the behavior a little + bit. It basically tries to avoid using the lame server, but still + continues to try it as a last resort. With this type of caching + server, the stub resolver will get a correct response if it falls + back after Sever failure. However, this still causes redundant AAAA + queries as explained in the previous sections. + +5. Security Considerations + + The CERT/CC pointed out that the response with RCODE 3 ("Name Error") + described in Section 4.2 can be used for a denial of service attack + [2]. The same argument applies to the case of "lame delegation" + described in Section 4.5 with a certain type of caching server. + +6. Acknowledgements + + Erik Nordmark encouraged the authors to publish this document as an + Internet Draft. Akira Kato and Paul Vixie reviewed a preliminary + version of this document. Pekka Savola carefully reviewed a previous + version and provided detailed comments. Bill Fenner, Scott + Hollenbeck, Thomas Narten, and Alex Zinin reviewed and helped improve + the document at the last stage for publication. + +7 Informative References + + [1] Mockapetris, P., "DOMAIN NAMES - CONCEPTS AND FACILITIES", RFC + 1034, November 1987. + + [2] The CERT Coordination Center, "Incorrect NXDOMAIN responses from + AAAA queries could cause denial-of-service conditions", March + 2003, . + + + + + + + + + +Morishita & Jinmei Expires April 23, 2005 [Page 5] + +Internet-Draft Common Misbehavior against AAAA Queries October 2004 + + +Authors' Addresses + + MORISHITA Orange Yasuhiro + Research and Development Department, Japan Registry Service Co.,Ltd. + Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda + Chiyoda-ku, Tokyo 101-0065 + Japan + + EMail: yasuhiro@jprs.co.jp + + + JINMEI Tatuya + Corporate Research & Development Center, Toshiba Corporation + 1 Komukai Toshiba-cho, Saiwai-ku + Kawasaki-shi, Kanagawa 212-8582 + Japan + + EMail: jinmei@isl.rdc.toshiba.co.jp + +Appendix A. Change History + + [NOTE TO RFC EDITOR: PLEASE REMOVE THIS SECTION UPON PUBLICATION.] + + Changes since draft-morishita-dnsop-misbehavior-against-aaaa-00 are: + + o Made a separate appendix and moved live examples to appendix so + that we can remove them when this document is (ever) officially + published. + o Revised some live examples based on the recent status. + o Noted in introduction that the misbehavior is not specific to AAAA + and that this document still concentrates on the AAAA case. + o Changed the section title of "delegation loop" to "lame + delegation" in order to reflect the essential point of the issue. + Wording on this matter was updated accordingly. + o Updated the Acknowledgements list. + o Changed the reference category from normative to informative (this + is an informational document after all). + o Changed the draft name to an IETF dnsop working group document (as + agreed). + o Applied several editorial fixes. + + Changes since draft-ietf-dnsop-misbehavior-against-aaaa-00 are: + + o Removed the appendix talking about live examples since these were + not appropriate for official publication. + o Added a note to rfc editor asking to remove this section upon + publication. + + + + +Morishita & Jinmei Expires April 23, 2005 [Page 6] + +Internet-Draft Common Misbehavior against AAAA Queries October 2004 + + + Changes since draft-ietf-dnsop-misbehavior-against-aaaa-01 are: + + o Used the standard keywords for describing RCODEs. + o Provided more specific references for RFC1034. + o Described an additional known issue regarding RCODE 2 ("Server + failure"). Also changed the section title accordingly. + o Moved the "Ignore Queries" section to the first of Section 4, + since it looks the most widely seen misbehavior. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Morishita & Jinmei Expires April 23, 2005 [Page 7] + +Internet-Draft Common Misbehavior against AAAA Queries October 2004 + + +Intellectual Property Statement + + The IETF takes no position regarding the validity or scope of any + Intellectual Property Rights or other rights that might be claimed to + pertain to the implementation or use of the technology described in + this document or the extent to which any license under such rights + might or might not be available; nor does it represent that it has + made any independent effort to identify any such rights. Information + on the procedures with respect to rights in RFC documents can be + found in BCP 78 and BCP 79. + + Copies of IPR disclosures made to the IETF Secretariat and any + assurances of licenses to be made available, or the result of an + attempt made to obtain a general license or permission for the use of + such proprietary rights by implementers or users of this + specification can be obtained from the IETF on-line IPR repository at + http://www.ietf.org/ipr. + + The IETF invites any interested party to bring to its attention any + copyrights, patents or patent applications, or other proprietary + rights that may cover technology that may be required to implement + this standard. Please address the information to the IETF at + ietf-ipr@ietf.org. + + +Disclaimer of Validity + + This document and the information contained herein are provided on an + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET + ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, + INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE + INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED + WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + + +Copyright Statement + + Copyright (C) The Internet Society (2004). This document is subject + to the rights, licenses and restrictions contained in BCP 78, and + except as set forth therein, the authors retain all their rights. + + +Acknowledgment + + Funding for the RFC Editor function is currently provided by the + Internet Society. + + + + +Morishita & Jinmei Expires April 23, 2005 [Page 8] + +