Ensure extensions are only parsed once

Author: lealem47

src/tls13.c

@@ -5324,8 +5324,9 @@ int DoTls13ServerHello(WOLFSSL* ssl, const byte* input, word32* inOutIdx,
     /* restore message type */
     *extMsgType = args->extMsgType;
 
-    if (args->totalExtSz > 0) {
-        /* Parse and handle extensions. */
+    /* Parse and handle extensions, unless lower than TLS1.3. In that case,
+     * extensions will be parsed in DoServerHello. */
+    if (args->totalExtSz > 0 && IsAtLeastTLSv1_3(ssl->version)) {
         ret = TLSX_Parse(ssl, input + args->idx, args->totalExtSz,
             *extMsgType, NULL);
         if (ret != 0) {
@@ -5344,7 +5345,9 @@ int DoTls13ServerHello(WOLFSSL* ssl, const byte* input, word32* inOutIdx,
             ssl->msgsReceived.got_hello_retry_request = 1;
             ssl->msgsReceived.got_server_hello = 0;
         }
+    }
 
+    if (args->totalExtSz > 0) {
         args->idx += args->totalExtSz;
     }