- djm@cvs.openbsd.org 2010/07/16 14:07:35

     [ssh-rsa.c]
     more timing paranoia - compare all parts of the expected decrypted
     data before returning. AFAIK not exploitable in the SSH protocol.
     "groovy" deraadt@

2 files changed, 11 insertions, 4 deletions

diff --git a/ChangeLog b/ChangeLog
index 4421f35b..0d51580f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,6 +6,11 @@
    - djm@cvs.openbsd.org 2010/07/16 04:45:30
      [ssh-keygen.c]
      avoid bogus compiler warning
+   - djm@cvs.openbsd.org 2010/07/16 14:07:35
+     [ssh-rsa.c]
+     more timing paranoia - compare all parts of the expected decrypted
+     data before returning. AFAIK not exploitable in the SSH protocol.
+     "groovy" deraadt@
 
 20100819
  - (dtucker) [contrib/ssh-copy-ud.1] Bug #1786: update ssh-copy-id.1 with more
diff --git a/ssh-rsa.c b/ssh-rsa.c
index e3f15615..c471ff32 100644
--- a/ssh-rsa.c
+++ b/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>
  *
@@ -211,7 +211,7 @@ 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;
 
@@ -250,11 +250,13 @@ 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;
 	}