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Do not provide a shim for SSL_SESSION_is_resumable()

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The recently added TLS client session cache used
SSL_SESSION_is_resumable() to avoid polluting the cache with
non-resumable sessions. However, it turned out that we cannot provide
a shim for this function across the whole range of OpenSSL versions
due to the fact that OpenSSL 1.1.0 does uses opaque pointers for
SSL_SESSION objects.

The commit replaces the shim for SSL_SESSION_is_resumable() with a non
public approximation of it on systems shipped with OpenSSL 1.1.0. It
is not turned into a proper shim because it does not fully emulate the
behaviour of SSL_SESSION_is_resumable(), but in our case it is good
enough, as it still helps to protect the cache from pollution.

For systems shipped with OpenSSL 1.0.X and derivatives (e.g. older
versions of LibreSSL), the provided replacement perfectly mimics the
function it is intended to replace.
This commit is contained in:
Artem Boldariev
2022-05-23 13:41:06 +03:00
parent 31f937cb05
commit 40be3c9263
3 changed files with 28 additions and 14 deletions
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8
lib/isc/openssl_shim.c
View File

@@ -196,11 +196,3 @@ SSL_CTX_up_ref(SSL_CTX *ctx) {
return (CRYPTO_add(&ctx->references, 1, CRYPTO_LOCK_SSL_CTX) > 0);
}
#endif /* !HAVE_SSL_CTX_UP_REF */
#if !HAVE_SSL_SESSION_IS_RESUMABLE
int
SSL_SESSION_is_resumable(const SSL_SESSION *sess) {
return (!sess->not_resumable &&
(sess->session_id_length > 0 || sess->tlsext_ticklen > 0));
}
#endif /* HAVE_SSL_SESSION_IS_RESUMABLE */

5
lib/isc/openssl_shim.h
View File

@@ -135,8 +135,3 @@ SSL_CTX_set1_cert_store(SSL_CTX *ctx, X509_STORE *store);
int
SSL_CTX_up_ref(SSL_CTX *store);
#endif /* !HAVE_SSL_CTX_UP_REF */
#if !HAVE_SSL_SESSION_IS_RESUMABLE
int
SSL_SESSION_is_resumable(const SSL_SESSION *s);
#endif /* HAVE_SSL_SESSION_IS_RESUMABLE */

29
lib/isc/tls.c
View File

@@ -1484,6 +1484,33 @@ isc_tlsctx_client_session_cache_detach(
isc_mem_putanddetach(&cache->mctx, cache, sizeof(*cache));
}
static bool
ssl_session_seems_resumable(const SSL_SESSION *sess) {
#ifdef HAVE_SSL_SESSION_IS_RESUMABLE
/*
* If SSL_SESSION_is_resumable() is available, let's use that. It
* is expected to be available on OpenSSL >= 1.1.1 and its modern
* siblings.
*/
return (SSL_SESSION_is_resumable(sess) != 0);
#elif (OPENSSL_VERSION_NUMBER >= 0x10100000L)
/*
* Taking into consideration that OpenSSL 1.1.0 uses opaque
* pointers for SSL_SESSION, we cannot implement a replacement for
* SSL_SESSION_is_resumable() manually. Let's use a sensible
* approximation for that, then: if there is an associated session
* ticket or session ID, then, most likely, the session is
* resumable.
*/
unsigned int session_id_len = 0;
(void)SSL_SESSION_get_id(sess, &session_id_len);
return (SSL_SESSION_has_ticket(sess) || session_id_len > 0);
#else
return (!sess->not_resumable &&
(sess->session_id_length > 0 || sess->tlsext_ticklen > 0));
#endif
}
void
isc_tlsctx_client_session_cache_keep(isc_tlsctx_client_session_cache_t *cache,
char *remote_peer_name, isc_tls_t *tls) {
@@ -1500,7 +1527,7 @@ isc_tlsctx_client_session_cache_keep(isc_tlsctx_client_session_cache_t *cache,
sess = SSL_get1_session(tls);
if (sess == NULL) {
return;
} else if (SSL_SESSION_is_resumable(sess) == 0) {
} else if (!ssl_session_seems_resumable(sess)) {
SSL_SESSION_free(sess);
return;
}