10 files changed, 45 insertions, 23 deletions

diff --git a/ChangeLog b/ChangeLog
index f652e6183..d650f63f8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -22,6 +22,13 @@
         Hostname %h.example.org
      
      "I like it" markus@
+   - djm@cvs.openbsd.org 2010/07/13 11:52:06
+     [auth-rsa.c channels.c jpake.c key.c misc.c misc.h monitor.c]
+     [packet.c ssh-rsa.c]
+     implement a timing_safe_cmp() function to compare memory without leaking
+     timing information by short-circuiting like memcmp() and use it for
+     some of the more sensitive comparisons (though nothing high-value was
+     readily attackable anyway); "looks ok" markus@
 
 20100714
  - (tim) [contrib/redhat/openssh.spec] Bug 1796: Test for skip_x11_askpass
diff --git a/auth-rsa.c b/auth-rsa.c
index ef6767bfb..71abadf6c 100644
--- a/auth-rsa.c
+++ b/auth-rsa.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth-rsa.c,v 1.76 2010/05/11 02:58:04 djm Exp $ */
+/* $OpenBSD: auth-rsa.c,v 1.77 2010/07/13 11:52:06 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -116,7 +116,7 @@ auth_rsa_verify_response(Key *key, BIGNUM *challenge, u_char response[16])
         MD5_Final(mdbuf, &md);
 
         /* Verify that the response is the original challenge. */
-        if (memcmp(response, mdbuf, 16) != 0) {
+        if (timing_safe_cmp(response, mdbuf, 16) != 0) {
                 /* Wrong answer. */
                 return (0);
         }
diff --git a/channels.c b/channels.c
index fe08257df..e52946bcd 100644
--- a/channels.c
+++ b/channels.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.c,v 1.306 2010/06/25 07:20:04 djm Exp $ */
+/* $OpenBSD: channels.c,v 1.307 2010/07/13 11:52:06 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -917,7 +917,7 @@ x11_open_helper(Buffer *b)
         }
         /* Check if authentication data matches our fake data. */
         if (data_len != x11_fake_data_len ||
-            memcmp(ucp + 12 + ((proto_len + 3) & ~3),
+            timing_safe_cmp(ucp + 12 + ((proto_len + 3) & ~3),
                 x11_fake_data, x11_fake_data_len) != 0) {
                 debug2("X11 auth data does not match fake data.");
                 return -1;
diff --git a/jpake.c b/jpake.c
index 130661069..50cf5c82e 100644
--- a/jpake.c
+++ b/jpake.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: jpake.c,v 1.2 2009/03/05 07:18:19 djm Exp $ */
+/* $OpenBSD: jpake.c,v 1.3 2010/07/13 11:52:06 djm Exp $ */
 /*
  * Copyright (c) 2008 Damien Miller.  All rights reserved.
  *
@@ -434,7 +434,7 @@ jpake_check_confirm(const BIGNUM *k,
         if (peer_confirm_hash_len != expected_confirm_hash_len)
                 error("%s: confirmation length mismatch (my %u them %u)",
                     __func__, expected_confirm_hash_len, peer_confirm_hash_len);
-        else if (memcmp(peer_confirm_hash, expected_confirm_hash,
+        else if (timing_safe_cmp(peer_confirm_hash, expected_confirm_hash,
             expected_confirm_hash_len) == 0)
                 success = 1;
         bzero(expected_confirm_hash, expected_confirm_hash_len);
diff --git a/key.c b/key.c
index c4d9d5771..4e31c84e4 100644
--- a/key.c
+++ b/key.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: key.c,v 1.88 2010/05/07 11:30:29 djm Exp $ */
+/* $OpenBSD: key.c,v 1.89 2010/07/13 11:52:06 djm Exp $ */
 /*
  * read_bignum():
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -52,6 +52,7 @@
 #include "uuencode.h"
 #include "buffer.h"
 #include "log.h"
+#include "misc.h"
 #include "ssh2.h"
 
 static struct KeyCert *
@@ -227,7 +228,7 @@ cert_compare(struct KeyCert *a, struct KeyCert *b)
                 return 0;
         if (buffer_len(&a->certblob) != buffer_len(&b->certblob))
                 return 0;
-        if (memcmp(buffer_ptr(&a->certblob), buffer_ptr(&b->certblob),
+        if (timing_safe_cmp(buffer_ptr(&a->certblob), buffer_ptr(&b->certblob),
             buffer_len(&a->certblob)) != 0)
                 return 0;
         return 1;
diff --git a/misc.c b/misc.c
index 4500b7a37..3b98e3fc2 100644
--- a/misc.c
+++ b/misc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: misc.c,v 1.77 2010/07/02 04:32:44 djm Exp $ */
+/* $OpenBSD: misc.c,v 1.78 2010/07/13 11:52:06 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2005,2006 Damien Miller.  All rights reserved.
@@ -850,6 +850,18 @@ ms_to_timeval(struct timeval *tv, int ms)
         tv->tv_usec = (ms % 1000) * 1000;
 }
 
+int
+timing_safe_cmp(const void *_s1, const void *_s2, size_t n)
+{
+        u_char *s1 = (u_char *)_s1;
+        u_char *s2 = (u_char *)_s2;
+        int ret = 0;
+
+        for (; n > 0; n--, s1++, s2++)
+                ret |= *s1 ^ *s2;
+        return ret;
+}
+
 void
 sock_set_v6only(int s)
 {
diff --git a/misc.h b/misc.h
index 32073acd4..7a02a03a5 100644
--- a/misc.h
+++ b/misc.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: misc.h,v 1.41 2010/01/09 23:04:13 dtucker Exp $ */
+/* $OpenBSD: misc.h,v 1.42 2010/07/13 11:52:06 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -36,6 +36,7 @@ void	 sanitise_stdfd(void);
 void     ms_subtract_diff(struct timeval *, int *);
 void     ms_to_timeval(struct timeval *, int);
 void     sock_set_v6only(int);
+int      timing_safe_cmp(const void *, const void *, size_t);
 
 struct passwd *pwcopy(struct passwd *);
 const char *ssh_gai_strerror(int);
diff --git a/monitor.c b/monitor.c
index 334aedde5..920728398 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.c,v 1.106 2010/03/07 11:57:13 dtucker Exp $ */
+/* $OpenBSD: monitor.c,v 1.107 2010/07/13 11:52:06 djm Exp $ */
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -518,7 +518,7 @@ monitor_allowed_key(u_char *blob, u_int bloblen)
 {
         /* make sure key is allowed */
         if (key_blob == NULL || key_bloblen != bloblen ||
-            memcmp(key_blob, blob, key_bloblen))
+            timing_safe_cmp(key_blob, blob, key_bloblen))
                 return (0);
         return (1);
 }
@@ -1103,14 +1103,14 @@ monitor_valid_userblob(u_char *data, u_int datalen)
                 len = buffer_len(&b);
                 if ((session_id2 == NULL) ||
                     (len < session_id2_len) ||
-                    (memcmp(p, session_id2, session_id2_len) != 0))
+                    (timing_safe_cmp(p, session_id2, session_id2_len) != 0))
                         fail++;
                 buffer_consume(&b, session_id2_len);
         } else {
                 p = buffer_get_string(&b, &len);
                 if ((session_id2 == NULL) ||
                     (len != session_id2_len) ||
-                    (memcmp(p, session_id2, session_id2_len) != 0))
+                    (timing_safe_cmp(p, session_id2, session_id2_len) != 0))
                         fail++;
                 xfree(p);
         }
@@ -1158,7 +1158,7 @@ monitor_valid_hostbasedblob(u_char *data, u_int datalen, char *cuser,
         p = buffer_get_string(&b, &len);
         if ((session_id2 == NULL) ||
             (len != session_id2_len) ||
-            (memcmp(p, session_id2, session_id2_len) != 0))
+            (timing_safe_cmp(p, session_id2, session_id2_len) != 0))
                 fail++;
         xfree(p);
 
@@ -1682,9 +1682,9 @@ mm_get_kex(Buffer *m)
 
         kex = xcalloc(1, sizeof(*kex));
         kex->session_id = buffer_get_string(m, &kex->session_id_len);
-        if ((session_id2 == NULL) ||
-            (kex->session_id_len != session_id2_len) ||
-            (memcmp(kex->session_id, session_id2, session_id2_len) != 0))
+        if (session_id2 == NULL ||
+            kex->session_id_len != session_id2_len ||
+            timing_safe_cmp(kex->session_id, session_id2, session_id2_len) != 0)
                 fatal("mm_get_get: internal error: bad session id");
         kex->we_need = buffer_get_int(m);
         kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
diff --git a/packet.c b/packet.c
index 994e35b6d..5c7ec2b5f 100644
--- a/packet.c
+++ b/packet.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.c,v 1.166 2009/06/27 09:29:06 andreas Exp $ */
+/* $OpenBSD: packet.c,v 1.167 2010/07/13 11:52:06 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1307,7 +1307,7 @@ packet_read_poll2(u_int32_t *seqnr_p)
                 macbuf = mac_compute(mac, active_state->p_read.seqnr,
                     buffer_ptr(&active_state->incoming_packet),
                     buffer_len(&active_state->incoming_packet));
-                if (memcmp(macbuf, buffer_ptr(&active_state->input),
+                if (timing_safe_cmp(macbuf, buffer_ptr(&active_state->input),
                     mac->mac_len) != 0) {
                         logit("Corrupted MAC on input.");
                         if (need > PACKET_MAX_SIZE)
diff --git a/ssh-rsa.c b/ssh-rsa.c
index bb9cc8e20..01f27f52c 100644
--- a/ssh-rsa.c
+++ b/ssh-rsa.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-rsa.c,v 1.41 2010/04/16 01:47:26 djm Exp $ */
+/* $OpenBSD: ssh-rsa.c,v 1.42 2010/07/13 11:52:06 djm Exp $ */
 /*
  * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
  *
@@ -30,6 +30,7 @@
 #include "buffer.h"
 #include "key.h"
 #include "compat.h"
+#include "misc.h"
 #include "ssh.h"
 
 static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);
@@ -249,11 +250,11 @@ openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
                 error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
                 goto done;
         }
-        if (memcmp(decrypted, oid, oidlen) != 0) {
+        if (timing_safe_cmp(decrypted, oid, oidlen) != 0) {
                 error("oid mismatch");
                 goto done;
         }
-        if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
+        if (timing_safe_cmp(decrypted + oidlen, hash, hlen) != 0) {
                 error("hash mismatch");
                 goto done;
         }