oss-security - [vs] heimdal: CVE-2022-45142: signature validation failure

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Message-ID: <Y+M28iuYG2lxmLG/@alf.mars>
Date: Wed, 8 Feb 2023 06:45:22 +0100
From: Helmut Grohne <helmut@...divi.de>
To: oss-security@...ts.openwall.com
Subject: [vs] heimdal: CVE-2022-45142: signature validation failure

Hi,

I am hereby publishing a vulnerability in heimdal backports by attaching
the exact mail sent to distros@...openwall.org last week.

----- Forwarded message from Helmut Grohne <helmut@...divi.de> -----

Date: Tue, 31 Jan 2023 15:52:58 +0100
From: Helmut Grohne <helmut@...divi.de>
To: distros@...openwall.org
Cc: heimdal-security@...mdal.team, Andrew Bartlett <abartlet@...ba.org>, Jeffrey Altman <jaltman@...ure-endpoints.com>, Joseph Sutton <josephsutton@...alyst.net.nz>, Nicolas Williams
	<nico@...sigma.com>, "Roberto C. Sánchez" <roberto@...exian.com>, Salvatore Bonaccorso <carnil@...ian.org>
Subject: [vs] heimdal: CVE-2022-45142: signature validation failure

(Resent with proper subject tag)

CVE-2022-3437 was a vulnerability affecting heimdal and samba. It was
fixed in both places. The fix included changing memcmp to be constant
time and a workaround for a compiler bug by adding "!= 0" comparisons to
the result of memcmp. When these patches were backported to the
heimdal-7.7.1 and heimdal-7.8.0 branches (and possibly other branches) a
logic inversion sneaked in causing the validation of message integrity
codes in gssapi/arcfour to be inverted.

This vulnerability does not affect samba nor the main heimdal branch and
only applies to backports. At least the 7.7.1 and 7.8.0 branches are
affected. CVE-2022-45142 has been assigned. All releases of Debian are
affected. At least one release of Fedora and Ubuntu are affected.

Timeline of events

2022-12-09 Issue discovered by me during backporting of patches
2022-12-09 Notified Debian security team
2022-12-09 Notified heimdal and samba
2022-12-09 Jeffrey Altman (heimdal) confirmed the problem
2022-12-10 Andrew Bartlett (samba) replied as not affected
2022-12-13 Patch v1
2022-12-13 Jeffrey Altman (heimdal) reviewed the patch
2022-12-13 Patch v2 (updated commit message)
2022-12-22 Last reply from heimdal (Jeffrey Altman) asking for more time
2022-12-25 Ping
2023-01-04 Ping
2023-01-13 Ping
2023-01-20 Ping and notified Ubuntu security team
2023-01-30 CVE-2022-45142 assigned
2023-01-31 Unilateral disclosure to distros mailinglist
2023-02-08 Proposed public disclosure to oss-sec

I would like to thank Salvatore Bonaccorso for handling most of the
coordination. Thanks also to go Jeffrey Altman and Andrew Bartlett for
their timely replies. My work on this issue is paid by Freexian SARL.

Patch below

Helmut

From: Helmut Grohne <helmut@...divi.de>
Subject: [PATCH v3] CVE-2022-45142: gsskrb5: fix accidental logic inversions

The referenced commit attempted to fix miscompilations with gcc-9 and
gcc-10 by changing `memcmp(...)` to `memcmp(...) != 0`. Unfortunately,
it also inverted the result of the comparison in two occasions. This
inversion happened during backporting the patch to 7.7.1 and 7.8.0.

Fixes: f6edaafcfefd ("gsskrb5: CVE-2022-3437 Use constant-time memcmp()
 for arcfour unwrap")
Signed-off-by: Helmut Grohne <helmut@...divi.de>
---
 lib/gssapi/krb5/arcfour.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Changes since v1:
 * Fix typo in commit message.
 * Mention 7.8.0 in commit message. Thanks to Jeffrey Altman.

Changes since v2:
 * Add CVE identifier.

diff --git a/lib/gssapi/krb5/arcfour.c b/lib/gssapi/krb5/arcfour.c
index e838d007a..eee6ad72f 100644
--- a/lib/gssapi/krb5/arcfour.c
+++ b/lib/gssapi/krb5/arcfour.c
@@ -365,7 +365,7 @@ _gssapi_verify_mic_arcfour(OM_uint32 * minor_status,
 	return GSS_S_FAILURE;
     }

-    cmp = (ct_memcmp(cksum_data, p + 8, 8) == 0);
+    cmp = (ct_memcmp(cksum_data, p + 8, 8) != 0);
     if (cmp) {
 	*minor_status = 0;
 	return GSS_S_BAD_MIC;
@@ -730,7 +730,7 @@ OM_uint32 _gssapi_unwrap_arcfour(OM_uint32 *minor_status,
 	return GSS_S_FAILURE;
     }

-    cmp = (ct_memcmp(cksum_data, p0 + 16, 8) == 0); /* SGN_CKSUM */
+    cmp = (ct_memcmp(cksum_data, p0 + 16, 8) != 0); /* SGN_CKSUM */
     if (cmp) {
 	_gsskrb5_release_buffer(minor_status, output_message_buffer);
 	*minor_status = 0;
--
2.38.1

----- End forwarded message -----
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