krb5: fix CVE-2021-37750

CVE-2021-37750:
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.

References:
https://nvd.nist.gov/vuln/detail/CVE-2021-37750

Patches from:
https://github.com/krb5/krb5/commit/d775c95af7606a51bf79547a94fa52ddd1cb7f49

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-connectivity/krb5/krb5/CVE-2021-37750.patch

@@ -0,0 +1,53 @@
+From b3999be7ab59a5af4b2f1042ce0d6b03ecb17d4e 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
+
+CVE: CVE-2021-37750
+
+Upstream-Status: Backport
+[https://github.com/krb5/krb5/commit/d775c95af7606a51bf79547a94fa52ddd1cb7f49]
+
+Signed-off-by: Yi Zhao <yi.zhao@windriver.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 587342a..622b48f 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);
+-- 
+2.17.1
+

meta-oe/recipes-connectivity/krb5/krb5_1.17.2.bb

@@ -31,6 +31,7 @@ SRC_URI = "http://web.mit.edu/kerberos/dist/${BPN}/${SHRT_VER}/${BP}.tar.gz \
            file://krb5-kdc.service \
            file://krb5-admin-server.service \
            file://CVE-2021-36222.patch;striplevel=2 \
+           file://CVE-2021-37750.patch;striplevel=2 \
 "
 SRC_URI[md5sum] = "aa4337fffa3b61f22dbd0167f708818f"
 SRC_URI[sha256sum] = "1a4bba94df92f6d39a197a10687653e8bfbc9a2076e129f6eb92766974f86134"