Fix DTLS transcript handling for HelloVerifyRequest.

If DTLS sees a HelloVerifyRequest the transcript is reset - the previous
tls1_init_finished_mac() function could be called multiple times and would
discard any existing state. The replacement tls1_transcript_init() is more
strict and fails if a transcript already exists.

Provide an explicit tls1_transcript_reset() function and call it from the
appropriate places. This also lets us make DTLS less of a special snowflake
and call tls1_transcript_init() in the same place as used for TLS.

ok beck@ tb@

1 files changed, 2 insertions, 5 deletions

diff --git a/src/lib/libssl/ssl_srvr.c b/src/lib/libssl/ssl_srvr.c
index 27024be856..0667ac8da3 100644
--- a/src/lib/libssl/ssl_srvr.c
+++ b/src/lib/libssl/ssl_srvr.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_srvr.c,v 1.60 2018/11/11 21:54:47 beck Exp $ */
+/* $OpenBSD: ssl_srvr.c,v 1.61 2018/11/21 15:13:29 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -368,10 +368,7 @@ ssl3_accept(SSL *s)
                         S3I(s)->hs.next_state = SSL3_ST_SR_CLNT_HELLO_A;
 
                         /* HelloVerifyRequest resets Finished MAC. */
-                        if (!tls1_transcript_init(s)) {
-                                ret = -1;
-                                goto end;
-                        }
+                        tls1_transcript_reset(s);
                         break;
 
                 case SSL3_ST_SW_SRVR_HELLO_A: