Don't signal SSL_CB_HANDSHAKE_START for TLSv1.3 post-handshake messages

The original 1.1.1 design was to use SSL_CB_HANDSHAKE_START and
SSL_CB_HANDSHAKE_DONE to signal start/end of a post-handshake message
exchange in TLSv1.3. Unfortunately experience has shown that this confuses
some applications who mistake it for a TLSv1.2 renegotiation. This means
that KeyUpdate messages are not handled properly.

This commit removes the use of SSL_CB_HANDSHAKE_START and
SSL_CB_HANDSHAKE_DONE to signal the start/end of a post-handshake
message exchange. Individual post-handshake messages are still signalled in
the normal way.

This is a potentially breaking change if there are any applications already
written that expect to see these TLSv1.3 events. However, without it,
KeyUpdate is not currently usable for many applications.

Fixes #8069
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8096)

(cherry picked from commit 4af5836b55442f31795eff6c8c81ea7a1b8cf94b)

CHANGES

@@ -9,6 +9,17 @@
 
  Changes between 1.1.1a and 1.1.1b [xx XXX xxxx]
 
+  *) Change the info callback signals for the start and end of a post-handshake
+     message exchange in TLSv1.3. In 1.1.1/1.1.1a we used SSL_CB_HANDSHAKE_START
+     and SSL_CB_HANDSHAKE_DONE. Experience has shown that many applications get
+     confused by this and assume that a TLSv1.2 renegotiation has started. This
+     can break KeyUpdate handling. Instead we no longer signal the start and end
+     of a post handshake message exchange (although the messages themselves are
+     still signalled). This could break some applications that were expecting
+     the old signals. However without this KeyUpdate is not usable for many
+     applications.
+     [Matt Caswell]
+
   *) Fix a bug in the computation of the endpoint-pair shared secret used
      by DTLS over SCTP. This breaks interoperability with older versions
      of OpenSSL like OpenSSL 1.1.0 and OpenSSL 1.0.2. There is a runtime

doc/man3/SSL_CTX_set_info_callback.pod

@@ -92,17 +92,13 @@ Callback has been called due to an alert being sent or received.
 
 =item SSL_CB_HANDSHAKE_START
 
-Callback has been called because a new handshake is started. In TLSv1.3 this is
-also used for the start of post-handshake message exchanges such as for the
-exchange of session tickets, or for key updates. It also occurs when resuming a
-handshake following a pause to handle early data.
+Callback has been called because a new handshake is started. It also occurs when
+resuming a handshake following a pause to handle early data.
 
-=item SSL_CB_HANDSHAKE_DONE           0x20
+=item SSL_CB_HANDSHAKE_DONE
 
-Callback has been called because a handshake is finished. In TLSv1.3 this is
-also used at the end of an exchange of post-handshake messages such as for
-session tickets or key updates. It also occurs if the handshake is paused to
-allow the exchange of early data.
+Callback has been called because a handshake is finished.  It also occurs if the
+handshake is paused to allow the exchange of early data.
 
 =back
 

ssl/statem/statem.c

@@ -342,8 +342,10 @@ static int state_machine(SSL *s, int server)
         }
 
         s->server = server;
-        if (cb != NULL)
-            cb(s, SSL_CB_HANDSHAKE_START, 1);
+        if (cb != NULL) {
+            if (SSL_IS_FIRST_HANDSHAKE(s) || !SSL_IS_TLS13(s))
+                cb(s, SSL_CB_HANDSHAKE_START, 1);
+        }
 
         /*
          * Fatal errors in this block don't send an alert because we have

ssl/statem/statem_lib.c

@@ -1030,6 +1030,7 @@ unsigned long ssl3_output_cert_chain(SSL *s, WPACKET *pkt, CERT_PKEY *cpk)
 WORK_STATE tls_finish_handshake(SSL *s, WORK_STATE wst, int clearbufs, int stop)
 {
     void (*cb) (const SSL *ssl, int type, int val) = NULL;
+    int cleanuphand = s->statem.cleanuphand;
 
     if (clearbufs) {
         if (!SSL_IS_DTLS(s)) {
@@ -1056,7 +1057,7 @@ WORK_STATE tls_finish_handshake(SSL *s, WORK_STATE wst, int clearbufs, int stop)
      * Only set if there was a Finished message and this isn't after a TLSv1.3
      * post handshake exchange
      */
-    if (s->statem.cleanuphand) {
+    if (cleanuphand) {
         /* skipped if we just sent a HelloRequest */
         s->renegotiate = 0;
         s->new_session = 0;
@@ -1116,8 +1117,12 @@ WORK_STATE tls_finish_handshake(SSL *s, WORK_STATE wst, int clearbufs, int stop)
     /* The callback may expect us to not be in init at handshake done */
     ossl_statem_set_in_init(s, 0);
 
-    if (cb != NULL)
-        cb(s, SSL_CB_HANDSHAKE_DONE, 1);
+    if (cb != NULL) {
+        if (cleanuphand
+                || !SSL_IS_TLS13(s)
+                || SSL_IS_FIRST_HANDSHAKE(s))
+            cb(s, SSL_CB_HANDSHAKE_DONE, 1);
+    }
 
     if (!stop) {
         /* If we've got more work to do we go back into init */

ssl/statem/statem_srvr.c

@@ -4040,7 +4040,6 @@ int tls_construct_new_session_ticket(SSL *s, WPACKET *pkt)
         uint64_t nonce;
         static const unsigned char nonce_label[] = "resumption";
         const EVP_MD *md = ssl_handshake_md(s);
-        void (*cb) (const SSL *ssl, int type, int val) = NULL;
         int hashleni = EVP_MD_size(md);
 
         /* Ensure cast to size_t is safe */
@@ -4052,24 +4051,6 @@ int tls_construct_new_session_ticket(SSL *s, WPACKET *pkt)
         }
         hashlen = (size_t)hashleni;
 
-        if (s->info_callback != NULL)
-            cb = s->info_callback;
-        else if (s->ctx->info_callback != NULL)
-            cb = s->ctx->info_callback;
-
-        if (cb != NULL) {
-            /*
-             * We don't start and stop the handshake in between each ticket when
-             * sending more than one - but it should appear that way to the info
-             * callback.
-             */
-            if (s->sent_tickets != 0) {
-                ossl_statem_set_in_init(s, 0);
-                cb(s, SSL_CB_HANDSHAKE_DONE, 1);
-                ossl_statem_set_in_init(s, 1);
-            }
-            cb(s, SSL_CB_HANDSHAKE_START, 1);
-        }
         /*
          * If we already sent one NewSessionTicket, or we resumed then
          * s->session may already be in a cache and so we must not modify it.

test/sslapitest.c

@@ -4734,18 +4734,14 @@ static struct info_cb_states_st {
         {SSL_CB_LOOP, "TWCCS"}, {SSL_CB_LOOP, "TWEE"}, {SSL_CB_LOOP, "TWSC"},
         {SSL_CB_LOOP, "TRSCV"}, {SSL_CB_LOOP, "TWFIN"}, {SSL_CB_LOOP, "TED"},
         {SSL_CB_EXIT, NULL}, {SSL_CB_LOOP, "TED"}, {SSL_CB_LOOP, "TRFIN"},
-        {SSL_CB_HANDSHAKE_DONE, NULL}, {SSL_CB_HANDSHAKE_START, NULL},
-        {SSL_CB_LOOP, "TWST"}, {SSL_CB_HANDSHAKE_DONE, NULL},
-        {SSL_CB_HANDSHAKE_START, NULL}, {SSL_CB_LOOP, "TWST"},
-        {SSL_CB_HANDSHAKE_DONE, NULL}, {SSL_CB_EXIT, NULL},
-        {SSL_CB_ALERT, NULL}, {SSL_CB_HANDSHAKE_START, NULL},
-        {SSL_CB_LOOP, "PINIT "}, {SSL_CB_LOOP, "PINIT "}, {SSL_CB_LOOP, "TRCH"},
-        {SSL_CB_LOOP, "TWSH"}, {SSL_CB_LOOP, "TWCCS"}, {SSL_CB_LOOP, "TWEE"},
-        {SSL_CB_LOOP, "TWFIN"}, {SSL_CB_LOOP, "TED"}, {SSL_CB_EXIT, NULL},
-        {SSL_CB_LOOP, "TED"}, {SSL_CB_LOOP, "TRFIN"},
-        {SSL_CB_HANDSHAKE_DONE, NULL}, {SSL_CB_HANDSHAKE_START, NULL},
-        {SSL_CB_LOOP, "TWST"}, {SSL_CB_HANDSHAKE_DONE, NULL},
-        {SSL_CB_EXIT, NULL}, {0, NULL},
+        {SSL_CB_HANDSHAKE_DONE, NULL}, {SSL_CB_LOOP, "TWST"},
+        {SSL_CB_LOOP, "TWST"}, {SSL_CB_EXIT, NULL}, {SSL_CB_ALERT, NULL},
+        {SSL_CB_HANDSHAKE_START, NULL}, {SSL_CB_LOOP, "PINIT "},
+        {SSL_CB_LOOP, "PINIT "}, {SSL_CB_LOOP, "TRCH"}, {SSL_CB_LOOP, "TWSH"},
+        {SSL_CB_LOOP, "TWCCS"}, {SSL_CB_LOOP, "TWEE"}, {SSL_CB_LOOP, "TWFIN"},
+        {SSL_CB_LOOP, "TED"}, {SSL_CB_EXIT, NULL}, {SSL_CB_LOOP, "TED"},
+        {SSL_CB_LOOP, "TRFIN"}, {SSL_CB_HANDSHAKE_DONE, NULL},
+        {SSL_CB_LOOP, "TWST"}, {SSL_CB_EXIT, NULL}, {0, NULL},
     }, {
         /* TLSv1.3 client followed by resumption */
         {SSL_CB_HANDSHAKE_START, NULL}, {SSL_CB_LOOP, "PINIT "},
@@ -4753,20 +4749,16 @@ static struct info_cb_states_st {
         {SSL_CB_LOOP, "TRSH"}, {SSL_CB_LOOP, "TREE"}, {SSL_CB_LOOP, "TRSC"},
         {SSL_CB_LOOP, "TRSCV"}, {SSL_CB_LOOP, "TRFIN"}, {SSL_CB_LOOP, "TWCCS"},
         {SSL_CB_LOOP, "TWFIN"},  {SSL_CB_HANDSHAKE_DONE, NULL},
-        {SSL_CB_EXIT, NULL}, {SSL_CB_HANDSHAKE_START, NULL},
-        {SSL_CB_LOOP, "SSLOK "}, {SSL_CB_LOOP, "SSLOK "}, {SSL_CB_LOOP, "TRST"},
-        {SSL_CB_HANDSHAKE_DONE, NULL},  {SSL_CB_EXIT, NULL},
-        {SSL_CB_HANDSHAKE_START, NULL}, {SSL_CB_LOOP, "SSLOK "},
-        {SSL_CB_LOOP, "SSLOK "}, {SSL_CB_LOOP, "TRST"},
-        {SSL_CB_HANDSHAKE_DONE, NULL},  {SSL_CB_EXIT, NULL},
+        {SSL_CB_EXIT, NULL}, {SSL_CB_LOOP, "SSLOK "}, {SSL_CB_LOOP, "SSLOK "},
+        {SSL_CB_LOOP, "TRST"}, {SSL_CB_EXIT, NULL}, {SSL_CB_LOOP, "SSLOK "},
+        {SSL_CB_LOOP, "SSLOK "}, {SSL_CB_LOOP, "TRST"}, {SSL_CB_EXIT, NULL},
         {SSL_CB_ALERT, NULL}, {SSL_CB_HANDSHAKE_START, NULL},
         {SSL_CB_LOOP, "PINIT "}, {SSL_CB_LOOP, "TWCH"}, {SSL_CB_EXIT, NULL},
         {SSL_CB_LOOP, "TWCH"}, {SSL_CB_LOOP, "TRSH"},  {SSL_CB_LOOP, "TREE"},
         {SSL_CB_LOOP, "TRFIN"}, {SSL_CB_LOOP, "TWCCS"}, {SSL_CB_LOOP, "TWFIN"},
         {SSL_CB_HANDSHAKE_DONE, NULL}, {SSL_CB_EXIT, NULL},
-        {SSL_CB_HANDSHAKE_START, NULL}, {SSL_CB_LOOP, "SSLOK "},
-        {SSL_CB_LOOP, "SSLOK "}, {SSL_CB_LOOP, "TRST"},
-        {SSL_CB_HANDSHAKE_DONE, NULL}, {SSL_CB_EXIT, NULL}, {0, NULL},
+        {SSL_CB_LOOP, "SSLOK "}, {SSL_CB_LOOP, "SSLOK "}, {SSL_CB_LOOP, "TRST"},
+        {SSL_CB_EXIT, NULL}, {0, NULL},
     }, {
         /* TLSv1.3 server, early_data */
         {SSL_CB_HANDSHAKE_START, NULL}, {SSL_CB_LOOP, "PINIT "},
@@ -4775,8 +4767,7 @@ static struct info_cb_states_st {
         {SSL_CB_HANDSHAKE_DONE, NULL}, {SSL_CB_EXIT, NULL},
         {SSL_CB_HANDSHAKE_START, NULL}, {SSL_CB_LOOP, "TED"},
         {SSL_CB_LOOP, "TED"}, {SSL_CB_LOOP, "TWEOED"}, {SSL_CB_LOOP, "TRFIN"},
-        {SSL_CB_HANDSHAKE_DONE, NULL}, {SSL_CB_HANDSHAKE_START, NULL},
-        {SSL_CB_LOOP, "TWST"}, {SSL_CB_HANDSHAKE_DONE, NULL},
+        {SSL_CB_HANDSHAKE_DONE, NULL}, {SSL_CB_LOOP, "TWST"},
         {SSL_CB_EXIT, NULL}, {0, NULL},
     }, {
         /* TLSv1.3 client, early_data */
@@ -4787,9 +4778,8 @@ static struct info_cb_states_st {
         {SSL_CB_LOOP, "TED"}, {SSL_CB_LOOP, "TRSH"}, {SSL_CB_LOOP, "TREE"},
         {SSL_CB_LOOP, "TRFIN"}, {SSL_CB_LOOP, "TPEDE"}, {SSL_CB_LOOP, "TWEOED"},
         {SSL_CB_LOOP, "TWFIN"}, {SSL_CB_HANDSHAKE_DONE, NULL},
-        {SSL_CB_EXIT, NULL}, {SSL_CB_HANDSHAKE_START, NULL},
-        {SSL_CB_LOOP, "SSLOK "}, {SSL_CB_LOOP, "SSLOK "}, {SSL_CB_LOOP, "TRST"},
-        {SSL_CB_HANDSHAKE_DONE, NULL}, {SSL_CB_EXIT, NULL}, {0, NULL},
+        {SSL_CB_EXIT, NULL}, {SSL_CB_LOOP, "SSLOK "}, {SSL_CB_LOOP, "SSLOK "},
+        {SSL_CB_LOOP, "TRST"}, {SSL_CB_EXIT, NULL}, {0, NULL},
     }, {
         {0, NULL},
     }
@@ -4828,8 +4818,11 @@ static void sslapi_info_callback(const SSL *s, int where, int ret)
         return;
     }
 
-    /* Check that, if we've got SSL_CB_HANDSHAKE_DONE we are not in init */
-    if ((where & SSL_CB_HANDSHAKE_DONE) && SSL_in_init((SSL *)s) != 0) {
+    /*
+     * Check that, if we've got SSL_CB_HANDSHAKE_DONE we are not in init
+     */
+    if ((where & SSL_CB_HANDSHAKE_DONE)
+            && SSL_in_init((SSL *)s) != 0) {
         info_cb_failed = 1;
         return;
     }