Don't check ciphersuite and compression in SSL session cache lookup
Session-ID based session resumption requires that the resumed session
is consistent with the client's ClientHello in terms of choice of
ciphersuite and choice of compression.
This check was previously assumed to be performed in the session cache
implementation, which seems wrong: The session cache should be an id-based
lookup only, and protocol specific checks should be left to Mbed TLS.
This commit
- adds an explicit ciphersuite and compression consistency check after
the SSL session cache has been queried
- removes the ciphersuite and compression consistency check from
Mbed TLS' session cache reference implementation.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 913a18f..40ad490 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -2765,6 +2765,53 @@
}
#endif /* MBEDTLS_SSL_DTLS_HELLO_VERIFY */
+static void ssl_check_id_based_session_resumption( mbedtls_ssl_context *ssl )
+{
+ int ret;
+ mbedtls_ssl_session session_tmp = { 0 };
+ mbedtls_ssl_session * const session = ssl->session_negotiate;
+
+ /* Resume is 0 by default, see ssl_handshake_init().
+ * It may be already set to 1 by ssl_parse_session_ticket_ext(). */
+ if( ssl->handshake->resume == 1 )
+ return;
+ if( ssl->session_negotiate->id_len == 0 )
+ return;
+ if( ssl->conf->f_get_cache == NULL )
+ return;
+#if defined(MBEDTLS_SSL_RENEGOTIATION)
+ if( ssl->renego_status != MBEDTLS_SSL_INITIAL_HANDSHAKE )
+ return;
+#endif
+
+ session_tmp.id_len = session->id_len;
+ memcpy( session_tmp.id, session->id, session->id_len );
+
+ ret = ssl->conf->f_get_cache( ssl->conf->p_cache,
+ &session_tmp );
+ if( ret != 0 )
+ goto exit;
+
+ if( session->ciphersuite != session_tmp.ciphersuite ||
+ session->compression != session_tmp.compression )
+ {
+ /* Mismatch between cached and negotiated session */
+ goto exit;
+ }
+
+ /* Move semantics */
+ /* Zeroization of session_tmp happens at the end of the function. */
+ mbedtls_ssl_session_free( session );
+ *session = session_tmp;
+
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "session successfully restored from cache" ) );
+ ssl->handshake->resume = 1;
+
+exit:
+
+ mbedtls_platform_zeroize( &session_tmp, sizeof( session_tmp ) );
+}
+
static int ssl_write_server_hello( mbedtls_ssl_context *ssl )
{
#if defined(MBEDTLS_HAVE_TIME)
@@ -2835,22 +2882,7 @@
MBEDTLS_SSL_DEBUG_BUF( 3, "server hello, random bytes", buf + 6, 32 );
- /*
- * Resume is 0 by default, see ssl_handshake_init().
- * It may be already set to 1 by ssl_parse_session_ticket_ext().
- * If not, try looking up session ID in our cache.
- */
- if( ssl->handshake->resume == 0 &&
-#if defined(MBEDTLS_SSL_RENEGOTIATION)
- ssl->renego_status == MBEDTLS_SSL_INITIAL_HANDSHAKE &&
-#endif
- ssl->session_negotiate->id_len != 0 &&
- ssl->conf->f_get_cache != NULL &&
- ssl->conf->f_get_cache( ssl->conf->p_cache, ssl->session_negotiate ) == 0 )
- {
- MBEDTLS_SSL_DEBUG_MSG( 3, ( "session successfully restored from cache" ) );
- ssl->handshake->resume = 1;
- }
+ ssl_check_id_based_session_resumption( ssl );
if( ssl->handshake->resume == 0 )
{