Change the TLS handshake keys early if we're not doing early data

We change the client TLS handshake keys as late as possible so that we
don't disturb the keys if we are writing early data. However for QUIC we
want to do this as early as possible (after ServerHello). Since we will
never do TLS early data with QUIC we just do it as early as possible if
early data is not being used.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/21810)

2 files changed, 42 insertions, 7 deletions

diff --git a/ssl/statem/statem_clnt.c b/ssl/statem/statem_clnt.c
index 9336363ca1..f2dec2fc0f 100644
--- a/ssl/statem/statem_clnt.c
+++ b/ssl/statem/statem_clnt.c
@@ -1782,12 +1782,29 @@ MSG_PROCESS_RETURN tls_process_server_hello(SSL_CONNECTION *s, PACKET *pkt)
      * In TLSv1.3 we have some post-processing to change cipher state, otherwise
      * we're done with this message
      */
-    if (SSL_CONNECTION_IS_TLS13(s)
-            && (!ssl->method->ssl3_enc->setup_key_block(s)
+    if (SSL_CONNECTION_IS_TLS13(s)) {
+        if (!ssl->method->ssl3_enc->setup_key_block(s)
                 || !ssl->method->ssl3_enc->change_cipher_state(s,
-                    SSL3_CC_HANDSHAKE | SSL3_CHANGE_CIPHER_CLIENT_READ))) {
-        /* SSLfatal() already called */
-        goto err;
+                    SSL3_CC_HANDSHAKE | SSL3_CHANGE_CIPHER_CLIENT_READ)) {
+            /* SSLfatal() already called */
+            goto err;
+        }
+        /*
+         * If we're not doing early-data and we're not going to send a dummy CCS
+         * (i.e. no middlebox compat mode) then we can change the write keys
+         * immediately. Otherwise we have to defer this until after all possible
+         * early data is written. We could just alway defer until the last
+         * moment except QUIC needs it done at the same time as the read keys
+         * are changed. Since QUIC doesn't do TLS early data or need middlebox
+         * compat this doesn't cause a problem.
+         */
+        if (s->early_data_state == SSL_EARLY_DATA_NONE
+                && (s->options & SSL_OP_ENABLE_MIDDLEBOX_COMPAT) == 0
+                && !ssl->method->ssl3_enc->change_cipher_state(s,
+                    SSL3_CC_HANDSHAKE | SSL3_CHANGE_CIPHER_CLIENT_WRITE)) {
+            /* SSLfatal() already called */
+            goto err;
+        }
     }
 
     OPENSSL_free(extensions);
@@ -3772,8 +3789,15 @@ CON_FUNC_RETURN tls_construct_client_certificate(SSL_CONNECTION *s,
         return CON_FUNC_ERROR;
     }
 
+    /*
+     * If we attempted to write early data or we're in middlebox compat mode
+     * then we deferred changing the handshake write keys to the last possible
+     * moment. We need to do it now.
+     */
     if (SSL_CONNECTION_IS_TLS13(s)
             && SSL_IS_FIRST_HANDSHAKE(s)
+            && (s->early_data_state != SSL_EARLY_DATA_NONE
+                || (s->options & SSL_OP_ENABLE_MIDDLEBOX_COMPAT) != 0)
             && (!ssl->method->ssl3_enc->change_cipher_state(s,
                     SSL3_CC_HANDSHAKE | SSL3_CHANGE_CIPHER_CLIENT_WRITE))) {
         /*
@@ -3855,7 +3879,14 @@ CON_FUNC_RETURN tls_construct_client_compressed_certificate(SSL_CONNECTION *sc,
             || !WPACKET_close(pkt))
         goto err;
 
+    /*
+     * If we attempted to write early data or we're in middlebox compat mode
+     * then we deferred changing the handshake write keys to the last possible
+     * moment. We need to do it now.
+     */
     if (SSL_IS_FIRST_HANDSHAKE(sc)
+            && (sc->early_data_state != SSL_EARLY_DATA_NONE
+                || (sc->options & SSL_OP_ENABLE_MIDDLEBOX_COMPAT) != 0)
             && (!ssl->method->ssl3_enc->change_cipher_state(sc,
                     SSL3_CC_HANDSHAKE | SSL3_CHANGE_CIPHER_CLIENT_WRITE))) {
         /*
diff --git a/ssl/statem/statem_lib.c b/ssl/statem/statem_lib.c
index e94b2f76cd..f339b2694c 100644
--- a/ssl/statem/statem_lib.c
+++ b/ssl/statem/statem_lib.c
@@ -615,11 +615,15 @@ CON_FUNC_RETURN tls_construct_finished(SSL_CONNECTION *s, WPACKET *pkt)
         s->statem.cleanuphand = 1;
 
     /*
-     * We only change the keys if we didn't already do this when we sent the
-     * client certificate
+     * If we attempted to write early data or we're in middlebox compat mode
+     * then we deferred changing the handshake write keys to the last possible
+     * moment. If we didn't already do this when we sent the client certificate
+     * then we need to do it now.
      */
     if (SSL_CONNECTION_IS_TLS13(s)
             && !s->server
+            && (s->early_data_state != SSL_EARLY_DATA_NONE
+                || (s->options & SSL_OP_ENABLE_MIDDLEBOX_COMPAT) != 0)
             && s->s3.tmp.cert_req == 0
             && (!ssl->method->ssl3_enc->change_cipher_state(s,
                     SSL3_CC_HANDSHAKE | SSL3_CHANGE_CIPHER_CLIENT_WRITE))) {;