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.

NB (Felix Lechner): The message above and the patch below were taken from the
disclosure here: https://www.openwall.com/lists/oss-security/2023/02/08/1

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