In SSH2, if decrypting the packet length gave us a negative value,

subsequent packet-receiver code would fail to notice anything was
wrong and segfault. Since this is clearly a silly packet length
anyway, we now explicitly reject it as a daft encryption error.

git-svn-id: svn://svn.tartarus.org/sgt/putty@1852 cda61777-01e9-0310-a592-d414129be87e

diff --git a/ssh.c b/ssh.c
index 0edaf93..acc4598 100644 (file)
--- a/ssh.c
+++ b/ssh.c
@@ -885,6 +885,15 @@ static int ssh2_rdpkt(unsigned char **data, int *datalen)
     st->pad = pktin.data[4];
 
     /*
+     * _Completely_ silly lengths should be stomped on before they
+     * do us any more damage.
+     */
+    if (st->len < 0 || st->pad < 0 || st->len + st->pad < 0) {
+       bombout(("Incoming packet was garbled on decryption"));
+       crReturn(0);
+    }
+
+    /*
      * This enables us to deduce the payload length.
      */
     st->payload = st->len - st->pad - 1;