Keep the DTLS timer running after the end of the handshake if appropriate

During a full handshake the server is the last one to "speak". The timer
should continue to run until we know that the client has received our last
flight (e.g. because we receive some application data).

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6170)

1 files changed, 18 insertions, 0 deletions

diff --git a/ssl/statem/statem_lib.c b/ssl/statem/statem_lib.c
index 49b44433f9..74ad6e804a 100644
--- a/ssl/statem/statem_lib.c
+++ b/ssl/statem/statem_lib.c
@@ -1057,6 +1057,15 @@ WORK_STATE tls_finish_handshake(SSL *s, WORK_STATE wst, int clearbufs, int stop)
             CRYPTO_atomic_add(&s->ctx->stats.sess_accept_good, 1, &discard,
                               s->ctx->lock);
             s->handshake_func = ossl_statem_accept;
+
+            if (SSL_IS_DTLS(s) && !s->hit) {
+                /*
+                 * We are finishing after the client. We start the timer going
+                 * in case there are any retransmits of our final flight
+                 * required.
+                 */
+                dtls1_start_timer(s);
+            }
         } else {
             /*
              * In TLSv1.3 we update the cache as part of processing the
@@ -1071,6 +1080,15 @@ WORK_STATE tls_finish_handshake(SSL *s, WORK_STATE wst, int clearbufs, int stop)
             s->handshake_func = ossl_statem_connect;
             CRYPTO_atomic_add(&s->session_ctx->stats.sess_connect_good, 1,
                               &discard, s->session_ctx->lock);
+
+            if (SSL_IS_DTLS(s) && s->hit) {
+                /*
+                 * We are finishing after the server. We start the timer going
+                 * in case there are any retransmits of our final flight
+                 * required.
+                 */
+                dtls1_start_timer(s);
+            }
         }
 
         if (SSL_IS_DTLS(s)) {