commit e273f7203dfa7d6533ed868a02a4a8ae73138a66
author Ronald Cron <ronald.cron@arm.com> Tue Feb 13 18:22:26 2024 +0100
committer Ronald Cron <ronald.cron@arm.com> Wed Feb 14 10:24:00 2024 +0100
tree 90291dc347f1e97fb61182868285cc89504900c1
parent b3d42fddaee3a2a0051c177ec39494ce24fd028d

tls13: client: Improve CCS handling

Call unconditionally the CCS writing function
when sending a CCS may be necessary in the
course of an handshake. Enforce in the writing
function and only in the writing function that
only one CCS is sent.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>

library/ssl_tls13_client.c

diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index 5d7a495..cedebad 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -3063,23 +3063,17 @@
              */
 #if defined(MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE)
         case MBEDTLS_SSL_CLIENT_CCS_BEFORE_2ND_CLIENT_HELLO:
-            ret = 0;
-            if (ssl->handshake->ccs_count == 0) {
-                ret = mbedtls_ssl_tls13_write_change_cipher_spec(ssl);
-                if (ret != 0) {
-                    break;
-                }
+            ret = mbedtls_ssl_tls13_write_change_cipher_spec(ssl);
+            if (ret != 0) {
+                break;
             }
             mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CLIENT_HELLO);
             break;
 
         case MBEDTLS_SSL_CLIENT_CCS_AFTER_SERVER_FINISHED:
-            ret = 0;
-            if (ssl->handshake->ccs_count == 0) {
-                ret = mbedtls_ssl_tls13_write_change_cipher_spec(ssl);
-                if (ret != 0) {
-                    break;
-                }
+            ret = mbedtls_ssl_tls13_write_change_cipher_spec(ssl);
+            if (ret != 0) {
+                break;
             }
             mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CLIENT_CERTIFICATE);
             break;

library/ssl_tls13_generic.c

diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
index 386a754..c6bb770 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -1379,6 +1379,12 @@
 
     MBEDTLS_SSL_DEBUG_MSG(2, ("=> write change cipher spec"));
 
+    /* Only one CCS to send. */
+    if (ssl->handshake->ccs_count > 0) {
+        ret = 0;
+        goto cleanup;
+    }
+
     /* Write CCS message */
     MBEDTLS_SSL_PROC_CHK(ssl_tls13_write_change_cipher_spec_body(
                              ssl, ssl->out_msg,

library/ssl_tls13_server.c

diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 05693f3..f9f3cc5 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -3482,12 +3482,9 @@
             break;
 
         case MBEDTLS_SSL_SERVER_CCS_AFTER_SERVER_HELLO:
-            ret = 0;
-            if (ssl->handshake->ccs_count == 0) {
-                ret = mbedtls_ssl_tls13_write_change_cipher_spec(ssl);
-                if (ret != 0) {
-                    break;
-                }
+            ret = mbedtls_ssl_tls13_write_change_cipher_spec(ssl);
+            if (ret != 0) {
+                break;
             }
             mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_ENCRYPTED_EXTENSIONS);
             break;