Revise HelloVerifyRequest handling for DTLSv1.2.

Per RFC 6347 section 4.2.1, the HelloVerifyRequest should always contain
DTLSv1.0 - ensure this is the case on the server side, allow both DTLSv1.0
and DTLSv1.2 on the client.

ok tb@

2 files changed, 14 insertions, 4 deletions

diff --git a/src/lib/libssl/ssl_clnt.c b/src/lib/libssl/ssl_clnt.c
index 680cafa8e5..7d55c0dd52 100644
--- a/src/lib/libssl/ssl_clnt.c
+++ b/src/lib/libssl/ssl_clnt.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_clnt.c,v 1.79 2021/02/20 08:19:01 jsing Exp $ */
+/* $OpenBSD: ssl_clnt.c,v 1.80 2021/02/20 08:22:55 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -817,7 +817,12 @@ ssl3_get_dtls_hello_verify(SSL *s)
         if (CBS_len(&hello_verify_request) != 0)
                 goto truncated;
 
-        if (ssl_version != s->version) {
+        /*
+         * Per RFC 6347 section 4.2.1, the HelloVerifyRequest should always
+         * contain DTLSv1.0 the version that is going to be negotiated.
+         * Tolerate DTLSv1.2 just in case.
+         */
+        if (ssl_version != DTLS1_VERSION && ssl_version != DTLS1_2_VERSION) {
                 SSLerror(s, SSL_R_WRONG_SSL_VERSION);
                 s->version = (s->version & 0xff00) | (ssl_version & 0xff);
                 al = SSL_AD_PROTOCOL_VERSION;
diff --git a/src/lib/libssl/ssl_srvr.c b/src/lib/libssl/ssl_srvr.c
index 15768bb565..06ad42c8ff 100644
--- a/src/lib/libssl/ssl_srvr.c
+++ b/src/lib/libssl/ssl_srvr.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_srvr.c,v 1.91 2021/02/07 15:04:10 jsing Exp $ */
+/* $OpenBSD: ssl_srvr.c,v 1.92 2021/02/20 08:22:55 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1171,10 +1171,15 @@ ssl3_send_dtls_hello_verify_request(SSL *s)
                         return 0;
                 }
 
+                /*
+                 * Per RFC 6347 section 4.2.1, the HelloVerifyRequest should
+                 * always contain DTLSv1.0 regardless of the version that is
+                 * going to be negotiated.
+                 */
                 if (!ssl3_handshake_msg_start(s, &cbb, &verify,
                     DTLS1_MT_HELLO_VERIFY_REQUEST))
                         goto err;
-                if (!CBB_add_u16(&verify, s->version))
+                if (!CBB_add_u16(&verify, DTLS1_VERSION))
                         goto err;
                 if (!CBB_add_u8_length_prefixed(&verify, &cookie))
                         goto err;