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Fix KDC null deref on TGS inner body null server (CVE-2021-37750)

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Resolves: #1997602
Signed-off-by: Antonio Torres <antorres@redhat.com>
This commit is contained in:
Antonio Torres 2021-10-20 17:08:04 +02:00
parent 364706b0c5
commit f34cb373a2
2 changed files with 53 additions and 1 deletions
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47
Fix-KDC-null-deref-on-TGS-inner-body-null-server.patch Normal file
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@ -0,0 +1,47 @@
From 0a8dfc380fe3b210662ba1b1d452fcec2f84841b Mon Sep 17 00:00:00 2001
From: Greg Hudson <ghudson@mit.edu>
Date: Tue, 3 Aug 2021 01:15:27 -0400
Subject: [PATCH] Fix KDC null deref on TGS inner body null server
After the KDC decodes a FAST inner body, it does not check for a null
server. Prior to commit 39548a5b17bbda9eeb63625a201cfd19b9de1c5b this
would typically result in an error from krb5_unparse_name(), but with
the addition of get_local_tgt() it results in a null dereference. Add
a null check.
Reported by Joseph Sutton of Catalyst.
CVE-2021-37750:
In MIT krb5 releases 1.14 and later, an authenticated attacker can
cause a null dereference in the KDC by sending a FAST TGS request with
no server field.
ticket: 9008 (new)
tags: pullup
target_version: 1.19-next
target_version: 1.18-next
(cherry picked from commit d775c95af7606a51bf79547a94fa52ddd1cb7f49)
(cherry picked from commit bb8fa495d00ccd931eec87a01b8920636cf7903e)
(cherry picked from commit dfe383f8251d0edc7e5e08ec5e4fdd9b7f902b2a)
---
src/kdc/do_tgs_req.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/src/kdc/do_tgs_req.c b/src/kdc/do_tgs_req.c
index 463a9c0dd..7c596a111 100644
--- a/src/kdc/do_tgs_req.c
+++ b/src/kdc/do_tgs_req.c
@@ -208,6 +208,11 @@ process_tgs_req(krb5_kdc_req *request, krb5_data *pkt,
status = "FIND_FAST";
goto cleanup;
}
+ if (sprinc == NULL) {
+ status = "NULL_SERVER";
+ errcode = KRB5KDC_ERR_S_PRINCIPAL_UNKNOWN;
+ goto cleanup;
+ }
errcode = get_local_tgt(kdc_context, &sprinc->realm, header_server,
&local_tgt, &local_tgt_storage, &local_tgt_key);

7
krb5.spec
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@ -42,7 +42,7 @@
Summary: The Kerberos network authentication system
Name: krb5
Version: 1.19.1
Release: %{?zdpd}11%{?dist}.1
Release: %{?zdpd}12%{?dist}
# rharwood has trust path to signing key and verifies on check-in
Source0: https://web.mit.edu/kerberos/dist/krb5/%{version}/krb5-%{version}%{?dashpre}.tar.gz
@ -89,6 +89,7 @@ Patch24: Fix-some-principal-realm-canonicalization-cases.patch
Patch25: Allow-kinit-with-keytab-to-defer-canonicalization.patch
Patch26: Fix-kadmin-k-with-fallback-or-referral-realm.patch
Patch27: Fix-KDC-null-deref-on-bad-encrypted-challenge.patch
Patch28: Fix-KDC-null-deref-on-TGS-inner-body-null-server.patch
License: MIT
URL: https://web.mit.edu/kerberos/www/
@ -650,6 +651,10 @@ exit 0
%{_libdir}/libkadm5srv_mit.so.*
%changelog
* Wed Oct 20 2021 Antonio Torres <antorres@redhat.com> - 1.19.1-12
- Fix KDC null deref on TGS inner body null server (CVE-2021-37750)
- Resolves: #1997602
* Mon Aug 09 2021 Mohan Boddu <mboddu@redhat.com> - 1.19.1-11.1
- Rebuilt for IMA sigs, glibc 2.34, aarch64 flags
Related: rhbz#1991688