krb5/Allow-aliases-when-matching-U2U-second-ticket.patch

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From ccc5b9663e229f20421c01836aa5ecb06f1f2a48 Mon Sep 17 00:00:00 2001
From: Isaac Boukris <iboukris@gmail.com>
Date: Tue, 22 Sep 2020 01:17:11 +0300
Subject: [PATCH] Allow aliases when matching U2U second ticket
In process_tgs_req() when verifying the user-to-user second ticket,
compare the canonical names of the request server and the second
ticket client.
[ghudson@mit.edu: expanded commit message; trimmed tests]
ticket: 8951 (new)
(cherry picked from commit afc494ef9418e6be7fbb887364efa6606b10034a)
---
src/kdc/do_tgs_req.c | 2 +-
src/tests/t_u2u.py | 25 +++++++++++++++++++++++++
2 files changed, 26 insertions(+), 1 deletion(-)
diff --git a/src/kdc/do_tgs_req.c b/src/kdc/do_tgs_req.c
index 463a9c0dd..74cd19e96 100644
--- a/src/kdc/do_tgs_req.c
+++ b/src/kdc/do_tgs_req.c
@@ -666,7 +666,7 @@ process_tgs_req(krb5_kdc_req *request, krb5_data *pkt,
*/
krb5_enc_tkt_part *t2enc = request->second_ticket[st_idx]->enc_part2;
krb5_principal client2 = t2enc->client;
- if (!krb5_principal_compare(kdc_context, request->server, client2)) {
+ if (!is_client_db_alias(kdc_context, server, client2)) {
altcprinc = client2;
errcode = KRB5KDC_ERR_SERVER_NOMATCH;
status = "2ND_TKT_MISMATCH";
diff --git a/src/tests/t_u2u.py b/src/tests/t_u2u.py
index 1ca6ac87e..4b8a82a2f 100644
--- a/src/tests/t_u2u.py
+++ b/src/tests/t_u2u.py
@@ -32,4 +32,29 @@ realm.run([kvno, '--u2u', realm.ccache, realm.user_princ])
realm.run([klist])
+realm.stop()
+
+# Load the test KDB module to test aliases
+testprincs = {'krbtgt/KRBTEST.COM': {'keys': 'aes128-cts'},
+ 'user': {'keys': 'aes128-cts', 'flags': '+preauth'},
+ 'WIN10': {'keys': 'aes128-cts'}}
+kdcconf = {'realms': {'$realm': {'database_module': 'test'}},
+ 'dbmodules': {'test': {'db_library': 'test',
+ 'princs': testprincs,
+ 'alias': {'HOST/win10': 'WIN10'}}}}
+
+realm = K5Realm(kdc_conf=kdcconf, create_kdb=False)
+realm.start_kdc()
+
+# Create a second user principal and get tickets for it.
+u2u_ccache = 'FILE:' + os.path.join(realm.testdir, 'ccu2u')
+realm.extract_keytab('WIN10', realm.keytab)
+realm.kinit('WIN10', None, ['-k', '-c', u2u_ccache])
+
+realm.extract_keytab(realm.user_princ, realm.keytab)
+realm.kinit(realm.user_princ, None, ['-k'])
+
+realm.run([kvno, '--u2u', u2u_ccache, 'HOST/win10'], expected_msg='kvno = 0')
+realm.run([kvno, '--u2u', u2u_ccache, 'WIN10'], expected_msg='kvno = 0')
+
success('user-to-user tests')