Fix ssl_get_prev_session overrun

If OpenSSL is configured with no-tlsext then ssl_get_prev_session can read
past the end of the ClientHello message if the session_id length in the
ClientHello is invalid. This should not cause any security issues since the
underlying buffer is 16k in size. It should never be possible to overrun by
that many bytes.

This is probably made redundant by the previous commit - but you can never be
too careful.

With thanks to Qinghao Tang for reporting this issue.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit 5e0a80c1c9b2b06c2d203ad89778ce1b98e0b5ad)

diff --git a/ssl/ssl_sess.c b/ssl/ssl_sess.c
index fb4e8c52598f4d3f7ffc7151d427c00dccdd0a48..4c7f5d8b4e32d3e09690e8f313d62ddd08cbc95b 100644 (file)
--- a/ssl/ssl_sess.c
+++ b/ssl/ssl_sess.c
@@ -481,6 +481,11 @@ int ssl_get_prev_session(SSL *s, unsigned char *session_id, int len,
     if (len > SSL_MAX_SSL_SESSION_ID_LENGTH)
         goto err;
 
+    if (session_id + len > limit) {
+        fatal = 1;
+        goto err;
+    }
+
     if (len == 0)
         try_session_cache = 0;