krb5 commit [krb5-1.18]: Fix AS-REQ checking of KDB-modified indicators

https://github.com/krb5/krb5/commit/dc840f670d5b756a773d72fa345aa5e6da298b22
commit dc840f670d5b756a773d72fa345aa5e6da298b22
Author: Greg Hudson <[email protected]>
Date:   Wed Feb 19 15:36:38 2020 -0500

    Fix AS-REQ checking of KDB-modified indicators
    
    Commit 7196c03f18f14695abeb5ae4923004469b172f0f (ticket 8823) gave the
    KDB the ability to modify auth indicators, but it happens after the
    asserted indicators are checked against the server principal
    requirements.  In finish_process_as_req(), move the call to
    check_indicators() after the call to handle_authdata() so that the
    final indicator list is checked.
    
    For the test case, add string attribute functionality to the test KDB
    module, and fix a bug where test_get_principal() would return failure
    if a principal has no keys.  Also add a test case for AS-REQ
    enforcement of normally asserted auth indicators.
    
    (cherry picked from commit 109e30ce22c20f18b8233119f274935bdf573886)
    
    ticket: 8876
    version_fixed: 1.18.1

 src/kdc/do_as_req.c             |   14 ++++++------
 src/plugins/kdb/test/kdb_test.c |   42 +++++++++++++++++++++++++++++++++++++-
 src/tests/t_authdata.py         |   11 ++++++++++
 3 files changed, 58 insertions(+), 9 deletions(-)

diff --git a/src/kdc/do_as_req.c b/src/kdc/do_as_req.c
index 87dd7e9..9ae7b0a 100644
--- a/src/kdc/do_as_req.c
+++ b/src/kdc/do_as_req.c
@@ -211,13 +211,6 @@ finish_process_as_req(struct as_req_state *state, krb5_error_code errcode)
 
     au_state->stage = ENCR_REP;
 
-    errcode = check_indicators(kdc_context, state->server,
-                               state->auth_indicators);
-    if (errcode) {
-        state->status = "HIGHER_AUTHENTICATION_REQUIRED";
-        goto egress;
-    }
-
     state->ticket_reply.enc_part2 = &state->enc_tkt_reply;
 
     errcode = check_kdcpolicy_as(kdc_context, state->request, state->client,
@@ -301,6 +294,13 @@ finish_process_as_req(struct as_req_state *state, krb5_error_code errcode)
         goto egress;
     }
 
+    errcode = check_indicators(kdc_context, state->server,
+                               state->auth_indicators);
+    if (errcode) {
+        state->status = "HIGHER_AUTHENTICATION_REQUIRED";
+        goto egress;
+    }
+
     errcode = krb5_encrypt_tkt_part(kdc_context, &state->server_keyblock,
                                     &state->ticket_reply);
     if (errcode)
diff --git a/src/plugins/kdb/test/kdb_test.c b/src/plugins/kdb/test/kdb_test.c
index 1936cb0..95a6062 100644
--- a/src/plugins/kdb/test/kdb_test.c
+++ b/src/plugins/kdb/test/kdb_test.c
@@ -54,6 +54,8 @@
  *                     # Initial number is kvno; defaults to 1.
  *                     keys = 3 aes256-cts aes128-cts:normal
  *                     keys = 2 rc4-hmac
+ *                     strings = key1:value1
+ *                     strings = key2:value2
  *                 }
  *             }
  *             delegation = {
@@ -282,6 +284,33 @@ make_keys(char **strings, const char *princstr, const krb5_data *realm,
     ent->n_key_data = nkeys;
 }
 
+static void
+make_strings(char **stringattrs, krb5_db_entry *ent)
+{
+    struct k5buf buf;
+    char **p;
+    const char *str, *sep;
+    krb5_tl_data *tl;
+
+    k5_buf_init_dynamic(&buf);
+    for (p = stringattrs; *p != NULL; p++) {
+        str = *p;
+        sep = strchr(str, ':');
+        assert(sep != NULL);
+        k5_buf_add_len(&buf, str, sep - str);
+        k5_buf_add_len(&buf, "\0", 1);
+        k5_buf_add_len(&buf, sep + 1, strlen(sep + 1) + 1);
+    }
+    assert(buf.data != NULL);
+
+    tl = ealloc(sizeof(*ent->tl_data));
+    tl->tl_data_next = NULL;
+    tl->tl_data_type = KRB5_TL_STRING_ATTRS;
+    tl->tl_data_length = buf.len;
+    tl->tl_data_contents = buf.data;
+    ent->tl_data = tl;
+}
+
 static krb5_error_code
 test_init()
 {
@@ -339,7 +368,8 @@ test_get_principal(krb5_context context, krb5_const_principal search_for,
     krb5_principal princ = NULL, tgtprinc;
     krb5_principal_data empty_princ = { KV5M_PRINCIPAL };
     testhandle h = context->dal_handle->db_context;
-    char *search_name = NULL, *canon = NULL, *flagstr, **names, **key_strings;
+    char *search_name = NULL, *canon = NULL, *flagstr;
+    char **names, **key_strings, **stringattrs;
     const char *ename;
     krb5_db_entry *ent;
 
@@ -415,7 +445,7 @@ test_get_principal(krb5_context context, krb5_const_principal search_for,
     ent->pw_expiration = get_time(h, "princs", ename, "pwexpiration");
 
     /* Leave last_success, last_failed, fail_auth_count zeroed. */
-    /* Leave tl_data and e_data empty. */
+    /* Leave e_data empty. */
 
     set_names(h, "princs", ename, "keys");
     ret = profile_get_values(h->profile, h->names, &key_strings);
@@ -424,11 +454,19 @@ test_get_principal(krb5_context context, krb5_const_principal search_for,
         profile_free_list(key_strings);
     }
 
+    set_names(h, "princs", ename, "strings");
+    ret = profile_get_values(h->profile, h->names, &stringattrs);
+    if (ret != PROF_NO_RELATION) {
+        make_strings(stringattrs, ent);
+        profile_free_list(stringattrs);
+    }
+
     /* We must include mod-princ data or kadm5_get_principal() won't work and
      * we can't extract keys with kadmin.local. */
     check(krb5_dbe_update_mod_princ_data(context, ent, 0, &empty_princ));
 
     *entry = ent;
+    ret = 0;
 
 cleanup:
     krb5_free_unparsed_name(context, search_name);
diff --git a/src/tests/t_authdata.py b/src/tests/t_authdata.py
index 378174a..c589adf 100644
--- a/src/tests/t_authdata.py
+++ b/src/tests/t_authdata.py
@@ -158,6 +158,8 @@ realm.run(['./adata', realm.host_princ], expected_msg='+97: [indcl]')
 mark('auth indicator enforcement')
 realm.addprinc('restricted')
 realm.run([kadminl, 'setstr', 'restricted', 'require_auth', 'superstrong'])
+realm.kinit(realm.user_princ, password('user'), ['-S', 'restricted'],
+            expected_code=1, expected_msg='KDC policy rejects request')
 realm.run([kvno, 'restricted'], expected_code=1,
           expected_msg='KDC policy rejects request')
 realm.run([kadminl, 'setstr', 'restricted', 'require_auth', 'indcl'])
@@ -194,6 +196,8 @@ testprincs = {'krbtgt/KRBTEST.COM': {'keys': 'aes128-cts'},
               'krbtgt/FOREIGN': {'keys': 'aes128-cts'},
               'user': {'keys': 'aes128-cts', 'flags': '+preauth'},
               'user2': {'keys': 'aes128-cts', 'flags': '+preauth'},
+              'rservice': {'keys': 'aes128-cts',
+                           'strings': 'require_auth:strong'},
               'service/1': {'keys': 'aes128-cts',
                             'flags': '+ok_to_auth_as_delegate'},
               'service/2': {'keys': 'aes128-cts'},
@@ -208,6 +212,7 @@ usercache = 'FILE:' + os.path.join(realm.testdir, 'usercache')
 realm.extract_keytab(realm.krbtgt_princ, realm.keytab)
 realm.extract_keytab('krbtgt/FOREIGN', realm.keytab)
 realm.extract_keytab(realm.user_princ, realm.keytab)
+realm.extract_keytab('ruser', realm.keytab)
 realm.extract_keytab('service/1', realm.keytab)
 realm.extract_keytab('service/2', realm.keytab)
 realm.extract_keytab('noauthdata', realm.keytab)
@@ -252,6 +257,12 @@ if ' -2: self_ad' not in out or ' -2: proxy_ad' not in out:
 realm.kinit(realm.user_princ, None, ['-k', '-X', 'indicators=dummy dbincr1'])
 realm.run(['./adata', realm.krbtgt_princ], expected_msg='+97: [dbincr2]')
 realm.run(['./adata', 'service/1'], expected_msg='+97: [dbincr3]')
+realm.kinit(realm.user_princ, None,
+            ['-k', '-X', 'indicators=strong', '-S', 'rservice'])
+# Test enforcement of altered indicators during AS request.
+realm.kinit(realm.user_princ, None,
+            ['-k', '-X', 'indicators=strong dbincr1', '-S', 'rservice'],
+            expected_code=1)
 
 # Test that KDB module authdata is included in an AS request, by
 # default or with an explicit PAC request.