From: Matt Caswell <matt@openssl.org>
Date: Fri, 11 May 2018 09:28:47 +0000 (+0100)
Subject: Don't memcpy the contents of an empty fragment
X-Git-Tag: OpenSSL_1_0_2p~53
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=f54b665e29a0ed8df2ea322a1f9e1b8057f13894;p=oweals%2Fopenssl.git

Don't memcpy the contents of an empty fragment

In DTLS if we have buffered a fragment for a zero length message (e.g.
ServerHelloDone) then, when we unbuffered the fragment, we were attempting
to memcpy the contents of the fragment which is zero length and a NULL
pointer. This is undefined behaviour. We should check first whether we
have a zero length fragment.

Fixes a travis issue.

[extended tests]

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6225)
---

diff --git a/ssl/d1_both.c b/ssl/d1_both.c
index e6bc761e8b..8cf52fac8b 100644
--- a/ssl/d1_both.c
+++ b/ssl/d1_both.c
@@ -656,7 +656,8 @@ static int dtls1_retrieve_buffered_fragment(SSL *s, long max, int *ok)
 
         al = dtls1_preprocess_fragment(s, &frag->msg_header, max);
 
-        if (al == 0) {          /* no alert */
+        /* al will be 0 if no alert */
+        if (al == 0  && frag->msg_header.frag_len > 0) {
             unsigned char *p =
                 (unsigned char *)s->init_buf->data + DTLS1_HM_HEADER_LENGTH;
             memcpy(&p[frag->msg_header.frag_off], frag->fragment,