[PATCH] Issue 4817 - BUG - locked crypt accounts on import may allow all passwords...

Bug Description: Due to mishanding of short dbpwd hashes, the
crypt_r algorithm was misused and was only comparing salts
in some cases, rather than checking the actual content
of the password.

Fix Description: Stricter checks on dbpwd lengths to ensure
that content passed to crypt_r has at least 2 salt bytes and
1 hash byte, as well as stricter checks on ct_memcmp to ensure
that compared values are the same length, rather than potentially
allowing overruns/short comparisons.

fixes: https://github.com/389ds/389-ds-base/issues/4817

Author: William Brown <william@blackhats.net.au>

Review by: @mreynolds389

Gbp-Pq: Name CVE-2021-3652.patch

diff --git a/dirsrvtests/tests/suites/password/pwd_crypt_asterisk_test.py b/dirsrvtests/tests/suites/password/pwd_crypt_asterisk_test.py
new file mode 100644 (file)
index 0000000..d76614d
--- /dev/null
+++ b/dirsrvtests/tests/suites/password/pwd_crypt_asterisk_test.py
@@ -0,0 +1,50 @@
+# --- BEGIN COPYRIGHT BLOCK ---
+# Copyright (C) 2021 William Brown <william@blackhats.net.au>
+# All rights reserved.
+#
+# License: GPL (version 3 or any later version).
+# See LICENSE for details.
+# --- END COPYRIGHT BLOCK ---
+#
+import ldap
+import pytest
+from lib389.topologies import topology_st
+from lib389.idm.user import UserAccounts
+from lib389._constants import (DEFAULT_SUFFIX, PASSWORD)
+
+pytestmark = pytest.mark.tier1
+
+def test_password_crypt_asterisk_is_rejected(topology_st):
+    """It was reported that {CRYPT}* was allowing all passwords to be
+    valid in the bind process. This checks that we should be rejecting
+    these as they should represent locked accounts. Similar, {CRYPT}!
+
+    :id: 0b8f1a6a-f3eb-4443-985e-da14d0939dc3
+    :setup: Single instance
+    :steps: 1. Set a password hash in with CRYPT and the content *
+            2. Test a bind
+            3. Set a password hash in with CRYPT and the content !
+            4. Test a bind
+    :expectedresults:
+            1. Successfully set the values
+            2. The bind fails
+            3. Successfully set the values
+            4. The bind fails
+    """
+    topology_st.standalone.config.set('nsslapd-allow-hashed-passwords', 'on')
+    topology_st.standalone.config.set('nsslapd-enable-upgrade-hash', 'off')
+
+    users = UserAccounts(topology_st.standalone, DEFAULT_SUFFIX)
+    user = users.create_test_user()
+
+    user.set('userPassword', "{CRYPT}*")
+
+    # Attempt to bind with incorrect password.
+    with pytest.raises(ldap.INVALID_CREDENTIALS):
+        badconn = user.bind('badpassword')
+
+    user.set('userPassword', "{CRYPT}!")
+    # Attempt to bind with incorrect password.
+    with pytest.raises(ldap.INVALID_CREDENTIALS):
+        badconn = user.bind('badpassword')
+

diff --git a/ldap/servers/plugins/pwdstorage/crypt_pwd.c b/ldap/servers/plugins/pwdstorage/crypt_pwd.c
index b4314ad27b8408c1aee760f8722a93979571b908..f8f94dcaedd8883fcbe3c0cb44243cbfa70944e5 100644 (file)
--- a/ldap/servers/plugins/pwdstorage/crypt_pwd.c
+++ b/ldap/servers/plugins/pwdstorage/crypt_pwd.c
@@ -42,15 +42,23 @@ static unsigned char itoa64[] = /* 0 ... 63 => ascii - 64 */
 int
 crypt_pw_cmp(const char *userpwd, const char *dbpwd)
 {
-    int32_t rc;
-    char *cp;
+    int rc = -1;
+    char *cp = NULL;
+    size_t dbpwd_len = strlen(dbpwd);
     struct crypt_data data;
     data.initialized = 0;
 
-    /* we use salt (first 2 chars) of encoded password in call to crypt_r() */
-    cp = crypt_r(userpwd, dbpwd, &data);
-    if (cp) {
-        rc = slapi_ct_memcmp(dbpwd, cp, strlen(dbpwd), strlen(cp));
+    /*
+     * there MUST be at least 2 chars of salt and some pw bytes, else this is INVALID and will
+     * allow any password to bind as we then only compare SALTS.
+     */
+    if (dbpwd_len >= 3) {
+        /* we use salt (first 2 chars) of encoded password in call to crypt_r() */
+        cp = crypt_r(userpwd, dbpwd, &data);
+    }
+    /* If these are not the same length, we can not proceed safely with memcmp. */
+    if (cp && dbpwd_len == strlen(cp)) {
+        rc = slapi_ct_memcmp(dbpwd, cp, dbpwd_len, strlen(cp));
     } else {
         rc = -1;
     }