upstream: fix integer overflow in XMSS private key parsing.

Reported by Adam Zabrocki via SecuriTeam's SSH program.

Note that this code is experimental and not compiled by default.

ok markus@

OpenBSD-Commit-ID: cd0361896d15e8a1bac495ac583ff065ffca2be1

diff --git a/sshkey-xmss.c b/sshkey-xmss.c
index a29e33f395aecd42435aafbb46c7d7d91f81ec81..9e5f5e47565853dc6dab3df35d00c4a0376f2d61 100644 (file)
--- a/sshkey-xmss.c
+++ b/sshkey-xmss.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey-xmss.c,v 1.5 2019/06/28 13:35:04 deraadt Exp $ */
+/* $OpenBSD: sshkey-xmss.c,v 1.6 2019/10/09 00:02:57 djm Exp $ */
 /*
  * Copyright (c) 2017 Markus Friedl.  All rights reserved.
  *
@@ -977,7 +977,8 @@ sshkey_xmss_decrypt_state(const struct sshkey *k, struct sshbuf *encoded,
                goto out;
        }
        /* check that an appropriate amount of auth data is present */
-       if (sshbuf_len(encoded) < encrypted_len + authlen) {
+       if (sshbuf_len(encoded) < authlen ||
+           sshbuf_len(encoded) - authlen < encrypted_len) {
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }