Fix regression with session cache use by clients

Commit d316cdcf6d8d6934663278145fe0a8191e14a8c5 introduced some extra
checks into the session-cache update procedure, intended to prevent
the caching of sessions whose resumption would lead to a handshake
failure, since if the server is authenticating the client, there needs to
be an application-set "session id context" to match up to the authentication
context.  While that change is effective for its stated purpose, there
was also some collatoral damage introduced along with the fix -- clients
that set SSL_VERIFY_PEER are not expected to set an sid_ctx, and so
their usage of session caching was erroneously denied.

Fix the scope of the original commit by limiting it to only acting
when the SSL is a server SSL.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5967)

diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index 1e24f8446dcc161160405362ff9bcf084162aba3..2a57831bc7b27526e273303874c3ae19505d330f 100644 (file)
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -3336,12 +3336,13 @@ void ssl_update_cache(SSL *s, int mode)
     /*
      * If sid_ctx_length is 0 there is no specific application context
      * associated with this session, so when we try to resume it and
-     * SSL_VERIFY_PEER is requested, we have no indication that this is
-     * actually a session for the proper application context, and the
-     * *handshake* will fail, not just the resumption attempt.
-     * Do not cache these sessions that are not resumable.
+     * SSL_VERIFY_PEER is requested to verify the client identity, we have no
+     * indication that this is actually a session for the proper application
+     * context, and the *handshake* will fail, not just the resumption attempt.
+     * Do not cache (on the server) these sessions that are not resumable
+     * (clients can set SSL_VERIFY_PEER without needing a sid_ctx set).
      */
-    if (s->session->sid_ctx_length == 0
+    if (s->server && s->session->sid_ctx_length == 0
             && (s->verify_mode & SSL_VERIFY_PEER) != 0)
         return;