Fix session ticket and SNI

When session tickets are used, it's possible that SNI might swtich the
SSL_CTX on an SSL. Normally, this is not a problem, because the
initial_ctx/session_ctx are used for all session ticket/id processes.

However, when the SNI callback occurs, it's possible that the callback
may update the options in the SSL from the SSL_CTX, and this could
cause SSL_OP_NO_TICKET to be set. If this occurs, then two bad things
can happen:

1. The session ticket TLSEXT may not be written when the ticket expected
flag is set. The state machine transistions to writing the ticket, and
the client responds with an error as its not expecting a ticket.
2. When creating the session ticket, if the ticket key cb returns 0
the crypto/hmac contexts are not initialized, and the code crashes when
trying to encrypt the session ticket.

To fix 1, if the ticket TLSEXT is not written out, clear the expected
ticket flag.
To fix 2, consider a return of 0 from the ticket key cb a recoverable
error, and write a 0 length ticket and continue. The client-side code
can explicitly handle this case.

Fix these two cases, and add unit test code to validate ticket behavior.

Reviewed-by: Emilia Käsper <emilia@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1098)

1 files changed, 9 insertions, 0 deletions

diff --git a/test/handshake_helper.h b/test/handshake_helper.h
index 7f7484ab4a..d04655a9ed 100644
--- a/test/handshake_helper.h
+++ b/test/handshake_helper.h
@@ -26,10 +26,19 @@ typedef struct handshake_result {
     /* Negotiated protocol. On success, these should always match. */
     int server_protocol;
     int client_protocol;
+    /* Server connection */
+    int servername;
+    /* Session ticket status */
+    int session_ticket;
+    /* Was this called on the second context? */
+    int session_ticket_do_not_call;
 } HANDSHAKE_RESULT;
 
 /* Do a handshake and report some information about the result. */
 HANDSHAKE_RESULT do_handshake(SSL_CTX *server_ctx, SSL_CTX *client_ctx,
                               const SSL_TEST_CTX *test_ctx);
 
+int do_not_call_session_ticket_callback(SSL* s, unsigned char* key_name, unsigned char *iv,
+                                        EVP_CIPHER_CTX *ctx, HMAC_CTX *hctx, int enc);
+
 #endif  /* HEADER_HANDSHAKE_HELPER_H */