File 0012-Fix-KDC-null-deref-on-TGS-inner-body-null-server.patch of Package krb5.30217
From f2c45fe33bc51a3340503c2f1cfefdebe131f5a1 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)
---
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 2d2e930ad..8fe12d1b3 100644
--- a/src/kdc/do_tgs_req.c
+++ b/src/kdc/do_tgs_req.c
@@ -201,6 +201,11 @@ 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);
--
2.33.0