Clear state in DTLSv1_listen

This is a backport of commit e83ee04bb7de800cdb71d522fa562e99328003a3 from
the master branch (and this has also been applied to 1.0.2). In 1.0.2 this
was CVE-2015-0207. For other branches there is no known security issue, but
this is being backported as a precautionary measure.

The DTLSv1_listen function is intended to be stateless and processes
the initial ClientHello from many peers. It is common for user code to
loop over the call to DTLSv1_listen until a valid ClientHello is received
with an associated cookie. A defect in the implementation of DTLSv1_listen
means that state is preserved in the SSL object from one invokation to the
next.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit cce3e4adb78a8d3eeb6e0e4efe332fcc5d75f615)

diff --git a/ssl/d1_lib.c b/ssl/d1_lib.c
index f494e045f32447e63cf45789bf78949517bf274f..6e8b7d44e0e1b240dd86fe4cdcc98f1bb1649a62 100644 (file)
--- a/ssl/d1_lib.c
+++ b/ssl/d1_lib.c
@@ -481,6 +481,9 @@ int dtls1_listen(SSL *s, struct sockaddr *client)
 {
     int ret;
 
+    /* Ensure there is no state left over from a previous invocation */
+    SSL_clear(s);
+
     SSL_set_options(s, SSL_OP_COOKIE_EXCHANGE);
     s->d1->listen = 1;