upstream commit

Avoid a theoretical signed integer overflow should
BN_num_bytes() ever violate its manpage and return a negative value. Improve
order of tests to avoid confusing increasingly pedantic compilers.

Reported by Guido Vranken from stack (css.csail.mit.edu/stack)
unstable optimisation analyser output.  ok deraadt@

Upstream-ID: f8508c830c86d8f36c113985e52bf8eedae23505

1 files changed, 6 insertions, 3 deletions

diff --git a/sshkey.c b/sshkey.c
index e6df94aaa..f7197726c 100644
--- a/sshkey.c
+++ b/sshkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.c,v 1.38 2016/09/12 23:31:27 djm Exp $ */
+/* $OpenBSD: sshkey.c,v 1.39 2016/09/26 21:16:11 djm Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Alexander von Gernler.  All rights reserved.
@@ -887,9 +887,12 @@ sshkey_fingerprint_raw(const struct sshkey *k, int dgst_alg,
                 int nlen = BN_num_bytes(k->rsa->n);
                 int elen = BN_num_bytes(k->rsa->e);
 
+                if (nlen < 0 || elen < 0 || nlen >= INT_MAX - elen) {
+                        r = SSH_ERR_INVALID_FORMAT;
+                        goto out;
+                }
                 blob_len = nlen + elen;
-                if (nlen >= INT_MAX - elen ||
-                    (blob = malloc(blob_len)) == NULL) {
+                if ((blob = malloc(blob_len)) == NULL) {
                         r = SSH_ERR_ALLOC_FAIL;
                         goto out;
                 }