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From 5b9b82d0696f1ffd4e693c1f8eafc0915b15e85b Mon Sep 17 00:00:00 2001
From: Greg Hudson <ghudson@mit.edu>
Date: Tue, 19 Jul 2016 11:00:28 -0400
Subject: [PATCH] Fix S4U2Self KDC crash when anon is restricted
cherry-picked from 93b4a6306a0026cf1cc31ac4bd8a49ba5d034ba7 upstream
In validate_as_request(), when enforcing restrict_anonymous_to_tgt,
use client.princ instead of request->client; the latter is NULL when
validating S4U2Self requests.
CVE-2016-3120:
In MIT krb5 1.9 and later, an authenticated attacker can cause krb5kdc
to dereference a null pointer if the restrict_anonymous_to_tgt option
is set to true, by making an S4U2Self request.
CVSSv2 Vector: AV:N/AC:H/Au:S/C:N/I:N/A:C/E:H/RL:OF/RC:C
ticket: 8458 (new)
target_version: 1.14-next
target_version: 1.13-next
Upstream-Status: Backport
Signed-off-by: Alexandru Moise <alexandru.moise@windriver.com>
---
src/kdc/kdc_util.c | 2 +-
src/tests/t_pkinit.py | 5 +++++
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/src/kdc/kdc_util.c b/src/kdc/kdc_util.c
index 48be1ae..10daec4 100644
--- a/src/kdc/kdc_util.c
+++ b/src/kdc/kdc_util.c
@@ -700,7 +700,7 @@ validate_as_request(kdc_realm_t *kdc_active_realm,
return(KDC_ERR_MUST_USE_USER2USER);
}
- if (check_anon(kdc_active_realm, request->client, request->server) != 0) {
+ if (check_anon(kdc_active_realm, client.princ, request->server) != 0) {
*status = "ANONYMOUS NOT ALLOWED";
return(KDC_ERR_POLICY);
}
diff --git a/src/tests/t_pkinit.py b/src/tests/t_pkinit.py
index 762e322..d27d05b 100644
--- a/src/tests/t_pkinit.py
+++ b/src/tests/t_pkinit.py
@@ -94,6 +94,11 @@ out = realm.run([kvno, realm.host_princ], expected_code=1)
if 'KDC policy rejects request' not in out:
fail('Wrong error for restricted anonymous PKINIT')
+# Regression test for #8458: S4U2Self requests crash the KDC if
+# anonymous is restricted.
+realm.kinit(realm.host_princ, flags=['-k'])
+realm.run([kvno, '-U', 'user', realm.host_princ])
+
# Go back to a normal KDC and disable anonymous PKINIT.
realm.stop_kdc()
realm.start_kdc()
--
2.5.0
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