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>

diff --git a/ssl/ssl_sess.c b/ssl/ssl_sess.c
index a213ea90dfe927cdc27b1bd3153a78773d301b60..3d0f95090df482941a6c736d53fe0c2a32176e0b 100644 (file)
--- a/ssl/ssl_sess.c
+++ b/ssl/ssl_sess.c
@@ -442,6 +442,11 @@ 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;