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package/libkrb5: fix CVE-2021-37750

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The Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) before
1.18.5 and 1.19.x before 1.19.3 has a NULL pointer dereference in
kdc/do_tgs_req.c via a FAST inner body that lacks a server field.

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
This commit is contained in:
Fabrice Fontaine 2021-09-15 21:48:19 +02:00 committed by Yann E. MORIN
parent 868367222b
commit b9646b18bf
2 changed files with 50 additions and 0 deletions
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47
package/libkrb5/0001-Fix-KDC-null-deref-on-TGS-inner-body-null-server.patch Normal file
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@ -0,0 +1,47 @@
From d775c95af7606a51bf79547a94fa52ddd1cb7f49 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
[Retrieved from:
https://github.com/krb5/krb5/commit/d775c95af7606a51bf79547a94fa52ddd1cb7f49]
Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
---
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 582e497cc9..32dc65fa8e 100644
--- a/src/kdc/do_tgs_req.c
+++ b/src/kdc/do_tgs_req.c
@@ -204,6 +204,11 @@ 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);

3
package/libkrb5/libkrb5.mk
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@ -16,6 +16,9 @@ LIBKRB5_CPE_ID_PRODUCT = kerberos_5
LIBKRB5_DEPENDENCIES = host-bison $(TARGET_NLS_DEPENDENCIES)
LIBKRB5_INSTALL_STAGING = YES
# 0001-Fix-KDC-null-deref-on-TGS-inner-body-null-server.patch
LIBKRB5_IGNORE_CVES += CVE-2021-37750
# The configure script uses AC_TRY_RUN tests to check for those values,
# which doesn't work in a cross-compilation scenario. Therefore,
# we feed the configure script with the correct answer for those tests