I tested a Postfix server and client built against OpenSSL 1.1.0, using 1.1.1 run-time libraries. This exercised peer certificate fingerprint matching and session resumption. No major issues.
The only interesting observations are: * With TLS 1.3 a new session is generated even sessions are resumed, because the server responds with a new ticket in the event of session resumption. With TLS 1.2 sessions that had sufficient remaining lifetime did not trigger new ticket generation on the server, and no new session was stored on the client. This causes needless wear-and-tear on the external session cache in Postfix, since each connection writes out a new session, replacing the one it just used. Some might consider this a security feature, but it is not especially desirable with SMTP. Any thoughts about whether this could be tunable? It would have to be server-side tuning I think, since the client does not know why the server issued a new session, perhaps the old one was not (or will soon not) be valid for re-use. * Postfix logs a warning when the compile-time and runtime libraries are not exactly the same (once per process start), this is expected. Perhaps we should provide a means for users to turn that off. * The Postfix logging from the new session callback precedes the OpenSSL message callback that a session ticket was received from the server. It seems that the OpenSSL message callback happens at the completion of session ticket processing, but this results in slightly surprising ordering of the logs. It seems as though the session is stored before the ticket arrives. I think this "cosmetic" issue may be worth addressing. ----- Client-side diagnostics ----- posttls-finger: warning: run-time library vs. compile-time header version mismatch: OpenSSL 1.1.1 may not be compatible with OpenSSL 1.1.0 posttls-finger: SSL_connect:before SSL initialization posttls-finger: SSL_connect:SSLv3/TLS write client hello posttls-finger: SSL_connect:SSLv3/TLS write client hello posttls-finger: SSL_connect:SSLv3/TLS read server hello posttls-finger: SSL_connect:TLSv1.3 read encrypted extensions posttls-finger: SSL_connect:SSLv3/TLS read server certificate posttls-finger: SSL_connect:TLSv1.3 read server certificate verify posttls-finger: SSL_connect:SSLv3/TLS read finished posttls-finger: SSL_connect:SSLv3/TLS write change cipher spec posttls-finger: SSL_connect:SSLv3/TLS write finished posttls-finger: Verified TLS connection established to 127.0.0.1[127.0.0.1]:25: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) posttls-finger: SSL_connect:SSL negotiation finished successfully posttls-finger: SSL_connect:SSL negotiation finished successfully posttls-finger: save session [127.0.0.1]:25&340DAEC7D4C243D38B19F31A405375B4DF69D1A1E5FB70B81C38E9EDC190976D to memory cache posttls-finger: SSL_connect:SSLv3/TLS read server session ticket posttls-finger: Reconnecting after 1 seconds posttls-finger: looking for session [127.0.0.1]:25&340DAEC7D4C243D38B19F31A405375B4DF69D1A1E5FB70B81C38E9EDC190976D in memory cache posttls-finger: reloaded session [127.0.0.1]:25&340DAEC7D4C243D38B19F31A405375B4DF69D1A1E5FB70B81C38E9EDC190976D from memory cache posttls-finger: SSL_connect:before SSL initialization posttls-finger: SSL_connect:SSLv3/TLS write client hello posttls-finger: SSL_connect:SSLv3/TLS write client hello posttls-finger: SSL_connect:SSLv3/TLS read server hello posttls-finger: SSL_connect:TLSv1.3 read encrypted extensions posttls-finger: SSL_connect:SSLv3/TLS read finished posttls-finger: SSL_connect:SSLv3/TLS write change cipher spec posttls-finger: SSL_connect:SSLv3/TLS write finished posttls-finger: 127.0.0.1[127.0.0.1]:25: Reusing old session posttls-finger: Verified TLS connection established to 127.0.0.1[127.0.0.1]:25: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) posttls-finger: SSL_connect:SSL negotiation finished successfully posttls-finger: SSL_connect:SSL negotiation finished successfully posttls-finger: save session [127.0.0.1]:25&340DAEC7D4C243D38B19F31A405375B4DF69D1A1E5FB70B81C38E9EDC190976D to memory cache posttls-finger: SSL_connect:SSLv3/TLS read server session ticket ----- End ----- -- Viktor. _______________________________________________ openssl-project mailing list openssl-project@openssl.org https://mta.openssl.org/mailman/listinfo/openssl-project