Don't do version neg on an HRR

Previously if a client received an HRR then we would do version negotiation
immediately - because we know we are going to get TLSv1.3. However this
causes a problem when we emit the 2nd ClientHello because we start changing
a whole load of stuff to ommit things that aren't relevant for < TLSv1.3.
The spec requires that the 2nd ClientHello is the same except for changes
required from the HRR. Therefore the simplest thing to do is to defer the
version negotiation until we receive the ServerHello.

Fixes #4292
Reviewed-by: NTim Hudson <tjh@openssl.org>
Reviewed-by: NBen Kaduk <kaduk@mit.edu>
(Merged from https://github.com/openssl/openssl/pull/4527)

ssl/record/ssl3_record.c

@@ -271,8 +271,13 @@ int ssl3_get_record(SSL *s)
                 thisrr->type = type;
                 thisrr->rec_version = version;
 
-                /* Lets check version. In TLSv1.3 we ignore this field */
+                /*
+                 * Lets check version. In TLSv1.3 we ignore this field. For an
+                 * HRR we haven't actually selected TLSv1.3 yet, but we still
+                 * treat it as TLSv1.3, so we must check for that explicitly
+                 */
                 if (!s->first_packet && !SSL_IS_TLS13(s)
+                        && !s->hello_retry_request
                         && version != (unsigned int)s->version) {
                     SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_WRONG_VERSION_NUMBER);
                     if ((s->version & 0xFF00) == (version & 0xFF00)

ssl/statem/extensions.c

@@ -408,13 +408,23 @@ static int verify_extension(SSL *s, unsigned int context, unsigned int type,
  */
 int extension_is_relevant(SSL *s, unsigned int extctx, unsigned int thisctx)
 {
+    int is_tls13;
+
+    /*
+     * For HRR we haven't selected the version yet but we know it will be
+     * TLSv1.3
+     */
+    if ((thisctx & SSL_EXT_TLS1_3_HELLO_RETRY_REQUEST) != 0)
+        is_tls13 = 1;
+    else
+        is_tls13 = SSL_IS_TLS13(s);
+
     if ((SSL_IS_DTLS(s)
                 && (extctx & SSL_EXT_TLS_IMPLEMENTATION_ONLY) != 0)
             || (s->version == SSL3_VERSION
                     && (extctx & SSL_EXT_SSL3_ALLOWED) == 0)
-            || (SSL_IS_TLS13(s)
-                && (extctx & SSL_EXT_TLS1_2_AND_BELOW_ONLY) != 0)
-            || (!SSL_IS_TLS13(s) && (extctx & SSL_EXT_TLS1_3_ONLY) != 0)
+            || (is_tls13 && (extctx & SSL_EXT_TLS1_2_AND_BELOW_ONLY) != 0)
+            || (!is_tls13 && (extctx & SSL_EXT_TLS1_3_ONLY) != 0)
             || (s->hit && (extctx & SSL_EXT_IGNORE_ON_RESUMPTION) != 0))
         return 0;
 

ssl/statem/statem_clnt.c

@@ -391,10 +391,6 @@ static WRITE_TRAN ossl_statem_client13_write_transition(SSL *s)
         /* We only hit this in the case of HelloRetryRequest */
         return WRITE_TRAN_FINISHED;
 
-    case TLS_ST_CR_HELLO_RETRY_REQUEST:
-        st->hand_state = TLS_ST_CW_CLNT_HELLO;
-        return WRITE_TRAN_CONTINUE;
-
     case TLS_ST_CR_FINISHED:
         if (s->early_data_state == SSL_EARLY_DATA_WRITE_RETRY
                 || s->early_data_state == SSL_EARLY_DATA_FINISHED_WRITING)
@@ -500,6 +496,10 @@ WRITE_TRAN ossl_statem_client_write_transition(SSL *s)
          */
         return WRITE_TRAN_FINISHED;
 
+    case TLS_ST_CR_HELLO_RETRY_REQUEST:
+        st->hand_state = TLS_ST_CW_CLNT_HELLO;
+        return WRITE_TRAN_CONTINUE;
+
     case TLS_ST_EARLY_DATA:
         return WRITE_TRAN_FINISHED;
 
@@ -1558,7 +1558,6 @@ MSG_PROCESS_RETURN tls_process_server_hello(SSL *s, PACKET *pkt)
 static MSG_PROCESS_RETURN tls_process_hello_retry_request(SSL *s, PACKET *pkt)
 {
     unsigned int sversion;
-    int errorcode;
     const unsigned char *cipherchars;
     RAW_EXTENSION *extensions = NULL;
     int al;
@@ -1579,13 +1578,6 @@ static MSG_PROCESS_RETURN tls_process_hello_retry_request(SSL *s, PACKET *pkt)
     EVP_CIPHER_CTX_free(s->enc_write_ctx);
     s->enc_write_ctx = NULL;
 
-    /* This will fail if it doesn't choose TLSv1.3+ */
-    errorcode = ssl_choose_client_version(s, sversion, 0, &al);
-    if (errorcode != 0) {
-        SSLerr(SSL_F_TLS_PROCESS_HELLO_RETRY_REQUEST, errorcode);
-        goto f_err;
-    }
-
     if (!PACKET_get_bytes(pkt, &cipherchars, TLS_CIPHER_LEN)) {
         SSLerr(SSL_F_TLS_PROCESS_HELLO_RETRY_REQUEST, SSL_R_LENGTH_MISMATCH);
         al = SSL_AD_DECODE_ERROR;

test/recipes/70-test_tls13kexmodes.t

@@ -99,12 +99,20 @@ $ENV{CTLOG_FILE} = srctop_file("test", "ct", "log_list.conf");
         checkhandshake::STATUS_REQUEST_CLI_EXTENSION],
     [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_SUPPORTED_GROUPS,
         checkhandshake::DEFAULT_EXTENSIONS],
+    [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_EC_POINT_FORMATS,
+        checkhandshake::DEFAULT_EXTENSIONS],
     [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_SIG_ALGS,
         checkhandshake::DEFAULT_EXTENSIONS],
     [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_ALPN,
         checkhandshake::ALPN_CLI_EXTENSION],
     [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_SCT,
         checkhandshake::SCT_CLI_EXTENSION],
+    [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_ENCRYPT_THEN_MAC,
+        checkhandshake::DEFAULT_EXTENSIONS],
+    [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_EXTENDED_MASTER_SECRET,
+        checkhandshake::DEFAULT_EXTENSIONS],
+    [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_SESSION_TICKET,
+        checkhandshake::DEFAULT_EXTENSIONS],
     [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_KEY_SHARE,
         checkhandshake::DEFAULT_EXTENSIONS],
     [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_SUPPORTED_VERSIONS,

test/recipes/70-test_tls13messages.t

@@ -99,12 +99,20 @@ $ENV{CTLOG_FILE} = srctop_file("test", "ct", "log_list.conf");
         checkhandshake::STATUS_REQUEST_CLI_EXTENSION],
     [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_SUPPORTED_GROUPS,
         checkhandshake::DEFAULT_EXTENSIONS],
+    [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_EC_POINT_FORMATS,
+        checkhandshake::DEFAULT_EXTENSIONS],
     [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_SIG_ALGS,
         checkhandshake::DEFAULT_EXTENSIONS],
     [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_ALPN,
         checkhandshake::ALPN_CLI_EXTENSION],
     [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_SCT,
         checkhandshake::SCT_CLI_EXTENSION],
+    [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_ENCRYPT_THEN_MAC,
+        checkhandshake::DEFAULT_EXTENSIONS],
+    [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_EXTENDED_MASTER_SECRET,
+        checkhandshake::DEFAULT_EXTENSIONS],
+    [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_SESSION_TICKET,
+        checkhandshake::DEFAULT_EXTENSIONS],
     [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_KEY_SHARE,
         checkhandshake::DEFAULT_EXTENSIONS],
     [TLSProxy::Message::MT_CLIENT_HELLO, TLSProxy::Message::EXT_SUPPORTED_VERSIONS,