more timing paranoia - compare all parts of the expected decrypted

data before returning. AFAIK not exploitable in the SSH protocol.
"groovy" deraadt@

diff --git a/usr.bin/ssh/ssh-rsa.c b/usr.bin/ssh/ssh-rsa.c
index 08ee9e2..b295467 100644 (file)
--- a/usr.bin/ssh/ssh-rsa.c
+++ b/usr.bin/ssh/ssh-rsa.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-rsa.c,v 1.43 2010/07/13 23:13:16 djm Exp $ */
+/* $OpenBSD: ssh-rsa.c,v 1.44 2010/07/16 14:07:35 djm Exp $ */
 /*
  * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
  *
@@ -208,7 +208,7 @@ openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
     u_char *sigbuf, u_int siglen, RSA *rsa)
 {
        u_int ret, rsasize, oidlen = 0, hlen = 0;
-       int len;
+       int len, oidmatch, hashmatch;
        const u_char *oid = NULL;
        u_char *decrypted = NULL;
 
@@ -247,11 +247,13 @@ openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
                error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
                goto done;
        }
-       if (timingsafe_bcmp(decrypted, oid, oidlen) != 0) {
+       oidmatch = timingsafe_bcmp(decrypted, oid, oidlen) == 0;
+       hashmatch = timingsafe_bcmp(decrypted + oidlen, hash, hlen) == 0;
+       if (!oidmatch) {
                error("oid mismatch");
                goto done;
        }
-       if (timingsafe_bcmp(decrypted + oidlen, hash, hlen) != 0) {
+       if (!hashmatch) {
                error("hash mismatch");
                goto done;
        }