4510. [security] Named mishandled some responses where covering RRSIG

records are returned without the requested data
                        resulting in a assertion failure. (CVE-2016-9147)
                        [RT #43548]

(cherry picked from commit 6adf421e7e)

CHANGES

@@ -97,6 +97,11 @@
 
 4511.	[bug]		win32: mdig.exe-BNFT was missing Configure. [RT #43554]
 
+4510.	[security]	Named mishandled some responses where covering RRSIG
+			records are returned without the requested data
+			resulting in a assertion failure. (CVE-2016-9147)
+			[RT #43548]
+
 4509.	[test]		Make the rrl system test more reliable on slower
 			machines by using mdig instead of dig. [RT #43280]
 

lib/dns/resolver.c

@@ -6984,15 +6984,19 @@ answer_response(fetchctx_t *fctx) {
 						 * a CNAME or DNAME).
 						 */
 						INSIST(!external);
-						if ((rdataset->type !=
-						     dns_rdatatype_cname) ||
-						    !found_dname ||
-						    (aflag ==
-						     DNS_RDATASETATTR_ANSWER))
+						/*
+						 * Don't use found_cname here
+						 * as we have just set it
+						 * above.
+						 */
+						if (cname == NULL &&
+						    !found_dname &&
+						    aflag ==
+						     DNS_RDATASETATTR_ANSWER)
 						{
 							have_answer = ISC_TRUE;
-							if (rdataset->type ==
-							    dns_rdatatype_cname)
+							if (found_cname &&
+							    cname == NULL)
 								cname = name;
 							name->attributes |=
 							    DNS_NAMEATTR_ANSWER;