CVE-2018-10919 tests: Add tests for guessing confidential attributes

Adds tests that assert that a confidential attribute cannot be guessed
by an unprivileged user through wildcard DB searches.

The tests basically consist of a set of DB searches/assertions that
get run for:
- basic searches against a confidential attribute
- confidential attributes that get overridden by giving access to the
  user via an ACE (run against a variety of ACEs)
- protecting a non-confidential attribute via an ACL that denies read-
  access (run against a variety of ACEs)
- querying confidential attributes via the dirsync controls

These tests all pass when run against a Windows Dc and all fail against
a Samba DC.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13434

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Gary Lockyer <gary@catalyst.net.nz>

3 files changed, 938 insertions, 0 deletions

diff --git a/selftest/knownfail.d/confidential_attr b/selftest/knownfail.d/confidential_attr
new file mode 100644
index 00000000000..7a2f2aada57
--- /dev/null
+++ b/selftest/knownfail.d/confidential_attr
@@ -0,0 +1,15 @@
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTest.test_basic_search\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTest.test_search_with_acl_override\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTest.test_search_with_attr_acl_override\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTest.test_search_with_blanket_oa_acl\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTest.test_search_with_neutral_acl\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTest.test_search_with_neutral_acl\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTest.test_search_with_neutral_attr_acl\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTest.test_search_with_neutral_cr_acl\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTest.test_search_with_propset_acl_override\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTestDenyAcl.test_search_with_blanket_oa_deny_acl\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTestDenyAcl.test_search_with_deny_acl\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTestDenyAcl.test_search_with_deny_attr_acl\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTestDenyAcl.test_search_with_deny_propset_acl\(ad_dc_ntvfs\)
+samba4.ldap.confidential_attr.python\(ad_dc_ntvfs\).__main__.ConfidentialAttrTestDirsync.test_search_with_dirsync\(ad_dc_ntvfs\)
+
diff --git a/source4/dsdb/tests/python/confidential_attr.py b/source4/dsdb/tests/python/confidential_attr.py
new file mode 100755
index 00000000000..c3909d5fc2e
--- /dev/null
+++ b/source4/dsdb/tests/python/confidential_attr.py
@@ -0,0 +1,920 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+#
+# Tests that confidential attributes (or attributes protected by a ACL that
+# denies read access) cannot be guessed through wildcard DB searches.
+#
+# Copyright (C) Catalyst.Net Ltd
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+import optparse
+import sys
+sys.path.insert(0, "bin/python")
+
+import samba
+import os
+from samba.tests.subunitrun import SubunitOptions, TestProgram
+import samba.getopt as options
+from ldb import SCOPE_BASE, SCOPE_SUBTREE
+from samba.dsdb import SEARCH_FLAG_CONFIDENTIAL
+from ldb import Message, MessageElement, Dn
+from ldb import FLAG_MOD_REPLACE, FLAG_MOD_ADD
+from samba.auth import system_session
+from samba import gensec, sd_utils
+from samba.samdb import SamDB
+from samba.credentials import Credentials, DONT_USE_KERBEROS
+import samba.tests
+from samba.tests import delete_force
+import samba.dsdb
+
+parser = optparse.OptionParser("confidential_attr.py [options] <host>")
+sambaopts = options.SambaOptions(parser)
+parser.add_option_group(sambaopts)
+parser.add_option_group(options.VersionOptions(parser))
+
+# use command line creds if available
+credopts = options.CredentialsOptions(parser)
+parser.add_option_group(credopts)
+subunitopts = SubunitOptions(parser)
+parser.add_option_group(subunitopts)
+
+opts, args = parser.parse_args()
+
+if len(args) < 1:
+    parser.print_usage()
+    sys.exit(1)
+
+host = args[0]
+if "://" not in host:
+    ldaphost = "ldap://%s" % host
+else:
+    ldaphost = host
+    start = host.rindex("://")
+    host = host.lstrip(start + 3)
+
+lp = sambaopts.get_loadparm()
+creds = credopts.get_credentials(lp)
+creds.set_gensec_features(creds.get_gensec_features() | gensec.FEATURE_SEAL)
+
+# When a user does not have access rights to view the objects' attributes,
+# Windows and Samba behave slightly differently.
+# A windows DC will always act as if the hidden attribute doesn't exist AT ALL
+# (for an unprivileged user). So, even for a user that lacks access rights,
+# the inverse/'!' queries should return ALL objects. This is similar to the
+# kludgeaclredacted behaviour on Samba.
+# However, on Samba (for implementation simplicity) we never return a matching
+# result for an unprivileged user.
+# Either approach is OK, so long as it gets applied consistently and we don't
+# disclose any sensitive details by varying what gets returned by the search.
+DC_MODE_RETURN_NONE = 0
+DC_MODE_RETURN_ALL = 1
+
+#
+# Tests start here
+#
+class ConfidentialAttrCommon(samba.tests.TestCase):
+
+    def setUp(self):
+        super(ConfidentialAttrCommon, self).setUp()
+
+        self.ldb_admin = SamDB(ldaphost, credentials=creds,
+                               session_info=system_session(lp), lp=lp)
+        self.user_pass = "samba123@"
+        self.base_dn = self.ldb_admin.domain_dn()
+        self.schema_dn = self.ldb_admin.get_schema_basedn()
+        self.sd_utils = sd_utils.SDUtils(self.ldb_admin)
+
+        # the tests work by setting the 'Confidential' bit in the searchFlags
+        # for an existing schema attribute. This only works against Windows if
+        # the systemFlags does not have FLAG_SCHEMA_BASE_OBJECT set for the
+        # schema attribute being modified. There are only a few attributes that
+        # meet this criteria (most of which only apply to 'user' objects)
+        self.conf_attr = "homePostalAddress"
+        self.conf_attr_cn = "CN=Address-Home"
+        # schemaIdGuid for homePostalAddress:
+        self.conf_attr_guid = "16775781-47f3-11d1-a9c3-0000f80367c1"
+        self.conf_attr_sec_guid = "77b5b886-944a-11d1-aebd-0000f80367c1"
+        self.attr_dn = "{},{}".format(self.conf_attr_cn, self.schema_dn)
+
+        userou = "OU=conf-attr-test"
+        self.ou = "{},{}".format(userou, self.base_dn)
+        self.ldb_admin.create_ou(self.ou)
+
+        # use a common username prefix, so we can use sAMAccountName=CATC-* as
+        # a search filter to only return the users we're interested in
+        self.user_prefix = "catc-"
+
+        # add a test object with this attribute set
+        self.conf_value = "abcdef"
+        self.conf_user = "{}conf-user".format(self.user_prefix)
+        self.ldb_admin.newuser(self.conf_user, self.user_pass, userou=userou)
+        self.conf_dn = self.get_user_dn(self.conf_user)
+        self.add_attr(self.conf_dn, self.conf_attr, self.conf_value)
+
+        # add a sneaky user that will try to steal our secrets
+        self.user = "{}sneaky-user".format(self.user_prefix)
+        self.ldb_admin.newuser(self.user, self.user_pass, userou=userou)
+        self.ldb_user = self.get_ldb_connection(self.user, self.user_pass)
+
+        self.all_users = [self.user, self.conf_user]
+
+        # add some other users that also have confidential attributes, so we can
+        # check we don't disclose their details, particularly in '!' searches
+        for i in range(1, 3):
+            username = "{}other-user{}".format(self.user_prefix, i)
+            self.ldb_admin.newuser(username, self.user_pass, userou=userou)
+            userdn = self.get_user_dn(username)
+            self.add_attr(userdn, self.conf_attr, "xyz{}".format(i))
+            self.all_users.append(username)
+
+        # there are 4 users in the OU, plus the OU itself
+        self.test_dn = self.ou
+        self.total_objects = len(self.all_users) + 1
+        self.objects_with_attr = 3
+
+        # sanity-check the flag is not already set (this'll cause problems if
+        # previous test run didn't clean up properly)
+        search_flags = self.get_attr_search_flags(self.attr_dn)
+        self.assertTrue(int(search_flags) & SEARCH_FLAG_CONFIDENTIAL == 0,
+                        "{} searchFlags already {}".format(self.conf_attr,
+                                                           search_flags))
+
+    def tearDown(self):
+        super(ConfidentialAttrCommon, self).tearDown()
+        self.ldb_admin.delete(self.ou, ["tree_delete:1"])
+
+    def add_attr(self, dn, attr, value):
+        m = Message()
+        m.dn = Dn(self.ldb_admin, dn)
+        m[attr] = MessageElement(value, FLAG_MOD_ADD, attr)
+        self.ldb_admin.modify(m)
+
+    def set_schema_update_now(self):
+        ldif = """
+dn:
+changetype: modify
+add: schemaUpdateNow
+schemaUpdateNow: 1
+"""
+        self.ldb_admin.modify_ldif(ldif)
+
+    def set_attr_search_flags(self, attr_dn, flags):
+        """Modifies the searchFlags for an object in the schema"""
+        m = Message()
+        m.dn = Dn(self.ldb_admin, attr_dn)
+        m['searchFlags'] = MessageElement(flags, FLAG_MOD_REPLACE,
+                                          'searchFlags')
+        self.ldb_admin.modify(m)
+
+        # note we have to update the schema for this change to take effect (on
+        # Windows, at least)
+        self.set_schema_update_now()
+
+    def get_attr_search_flags(self, attr_dn):
+        """Marks the attribute under test as being confidential"""
+        res = self.ldb_admin.search(attr_dn, scope=SCOPE_BASE,
+                                    attrs=['searchFlags'])
+        return res[0]['searchFlags'][0]
+
+    def make_attr_confidential(self):
+        """Marks the attribute under test as being confidential"""
+
+        # work out the original 'searchFlags' value before we overwrite it
+        old_value = self.get_attr_search_flags(self.attr_dn)
+
+        self.set_attr_search_flags(self.attr_dn, str(SEARCH_FLAG_CONFIDENTIAL))
+
+        # reset the value after the test completes
+        self.addCleanup(self.set_attr_search_flags, self.attr_dn, old_value)
+
+    # The behaviour of the DC can differ in some cases, depending on whether
+    # we're talking to a Windows DC or a Samba DC
+    def guess_dc_mode(self):
+        # if we're in selftest, we can be pretty sure it's a Samba DC
+        if os.environ.get('SAMBA_SELFTEST') == '1':
+            return DC_MODE_RETURN_NONE
+
+        searches = self.get_negative_match_all_searches()
+        res = self.ldb_user.search(self.test_dn, expression=searches[0],
+                                   scope=SCOPE_SUBTREE)
+
+        # we default to DC_MODE_RETURN_NONE (samba).Update this if it
+        # looks like we're talking to a Windows DC
+        if len(res) == self.total_objects:
+            return DC_MODE_RETURN_ALL
+
+        # otherwise assume samba DC behaviour
+        return DC_MODE_RETURN_NONE
+
+    def get_user_dn(self, name):
+        return "CN={},{}".format(name, self.ou)
+
+    def get_user_sid_string(self, username):
+        user_dn = self.get_user_dn(username)
+        user_sid = self.sd_utils.get_object_sid(user_dn)
+        return str(user_sid)
+
+    def get_ldb_connection(self, target_username, target_password):
+        creds_tmp = Credentials()
+        creds_tmp.set_username(target_username)
+        creds_tmp.set_password(target_password)
+        creds_tmp.set_domain(creds.get_domain())
+        creds_tmp.set_realm(creds.get_realm())
+        creds_tmp.set_workstation(creds.get_workstation())
+        features = creds_tmp.get_gensec_features() | gensec.FEATURE_SEAL
+        creds_tmp.set_gensec_features(features)
+        creds_tmp.set_kerberos_state(DONT_USE_KERBEROS)
+        ldb_target = SamDB(url=ldaphost, credentials=creds_tmp, lp=lp)
+        return ldb_target
+
+    def assert_not_in_result(self, res, exclude_dn):
+        for msg in res:
+            self.assertNotEqual(msg.dn, exclude_dn,
+                                "Search revealed object {}".format(exclude_dn))
+
+    def assert_search_result(self, expected_num, expr, samdb):
+
+        # try asking for different attributes back: None/all, the confidential
+        # attribute itself, and a random unrelated attribute
+        attr_filters = [None, ["*"], [self.conf_attr], ['name']]
+        for attr in attr_filters:
+            res = samdb.search(self.test_dn, expression=expr,
+                               scope=SCOPE_SUBTREE, attrs=attr)
+            self.assertTrue(len(res) == expected_num,
+                            "%u results, not %u for search %s, attr %s" %
+                            (len(res), expected_num, expr, str(attr)))
+
+    # return a selection of searches that match exactly against the test object
+    def get_exact_match_searches(self):
+        first_char = self.conf_value[:1]
+        last_char = self.conf_value[-1:]
+        test_attr = self.conf_attr
+
+        searches = [
+            # search for the attribute using a sub-string wildcard
+            # (which could reveal the attribute's actual value)
+            "({}={}*)".format(test_attr, first_char),
+            "({}=*{})".format(test_attr, last_char),
+
+            # sanity-check equality against an exact match on value
+            "({}={})".format(test_attr, self.conf_value),
+
+            # '~=' searches don't work against Samba
+            # sanity-check an approx search against an exact match on value
+            # "({}~={})".format(test_attr, self.conf_value),
+
+            # check wildcard in an AND search...
+            "(&({}={}*)(objectclass=*))".format(test_attr, first_char),
+
+            # ...an OR search (against another term that will never match)
+            "(|({}={}*)(objectclass=banana))".format(test_attr, first_char)]
+
+        return searches
+
+    # return searches that match any object with the attribute under test
+    def get_match_all_searches(self):
+        searches = [
+            # check a full wildcard against the confidential attribute
+            # (which could reveal the attribute's presence/absence)
+            "({}=*)".format(self.conf_attr),
+
+            # check wildcard in an AND search...
+            "(&(objectclass=*)({}=*))".format(self.conf_attr),
+
+            # ...an OR search (against another term that will never match)
+            "(|(objectclass=banana)({}=*))".format(self.conf_attr),
+
+            # check <=, and >= expressions that would normally find a match
+            "({}>=0)".format(self.conf_attr),
+            "({}<=ZZZZZZZZZZZ)".format(self.conf_attr)]
+
+        return searches
+
+    def assert_conf_attr_searches(self, has_rights_to=0, samdb=None):
+        """Check searches against the attribute under test work as expected"""
+
+        if samdb is None:
+            samdb = self.ldb_user
+
+        if has_rights_to == "all":
+            has_rights_to = self.objects_with_attr
+
+        # these first few searches we just expect to match against the one
+        # object under test that we're trying to guess the value of
+        expected_num = 1 if has_rights_to > 0 else 0
+        for search in self.get_exact_match_searches():
+            self.assert_search_result(expected_num, search, samdb)
+
+        # these next searches will match any objects we have rights to see
+        expected_num = has_rights_to
+        for search in self.get_match_all_searches():
+            self.assert_search_result(expected_num, search, samdb)
+
+    # The following are double negative searches (i.e. NOT non-matching-
+    # condition) which will therefore match ALL objects, including the test
+    # object(s).
+    def get_negative_match_all_searches(self):
+        first_char = self.conf_value[:1]
+        last_char = self.conf_value[-1:]
+        not_first_char = chr(ord(first_char) + 1)
+        not_last_char = chr(ord(last_char) + 1)
+
+        searches = [
+            "(!({}={}*))".format(self.conf_attr, not_first_char),
+            "(!({}=*{}))".format(self.conf_attr, not_last_char)]
+        return searches
+
+    # the following searches will not match against the test object(s). So
+    # a user with sufficient rights will see an inverse sub-set of objects.
+    # (An unprivileged user would either see all objects on Windows, or no
+    # objects on Samba)
+    def get_inverse_match_searches(self):
+        first_char = self.conf_value[:1]
+        last_char = self.conf_value[-1:]
+        searches = [
+            "(!({}={}*))".format(self.conf_attr, first_char),
+            "(!({}=*{}))".format(self.conf_attr, last_char)]
+        return searches
+
+    def negative_searches_all_rights(self, total_objects=None):
+        expected_results = {}
+
+        if total_objects is None:
+            total_objects = self.total_objects
+
+        # these searches should match ALL objects (including the OU)
+        for search in self.get_negative_match_all_searches():
+            expected_results[search] = total_objects
+
+        # a ! wildcard should only match the objects without the attribute
+        search = "(!({}=*))".format(self.conf_attr)
+        expected_results[search] = total_objects - self.objects_with_attr
+
+        # whereas the inverse searches should match all objects *except* the
+        # one under test
+        for search in self.get_inverse_match_searches():
+            expected_results[search] = total_objects - 1
+
+        return expected_results
+
+    # Returns the expected negative (i.e. '!') search behaviour when talking to
+    # a DC with DC_MODE_RETURN_ALL behaviour, i.e. we assert that users
+    # without rights always see ALL objects in '!' searches
+    def negative_searches_return_all(self, has_rights_to=0,
+                                     total_objects=None):
+        """Asserts user without rights cannot see objects in '!' searches"""
+        expected_results = {}
+
+        if total_objects is None:
+            total_objects = self.total_objects
+
+        # Windows 'hides' objects by always returning all of them, so negative
+        # searches that match all objects will simply return all objects
+        for search in self.get_negative_match_all_searches():
+            expected_results[search] = total_objects
+
+        # if the search is matching on an inverse subset (everything except the
+        # object under test), the
+        inverse_searches = self.get_inverse_match_searches()
+        inverse_searches += ["(!({}=*))".format(self.conf_attr)]
+
+        for search in inverse_searches:
+            expected_results[search] = total_objects - has_rights_to
+
+        return expected_results
+
+    # Returns the expected negative (i.e. '!') search behaviour when talking to
+    # a DC with DC_MODE_RETURN_NONE behaviour, i.e. we assert that users
+    # without rights cannot see objects in '!' searches at all
+    def negative_searches_return_none(self, has_rights_to=0):
+        expected_results = {}
+
+        # the 'match-all' searches should only return the objects we have
+        # access rights to (if any)
+        for search in self.get_negative_match_all_searches():
+            expected_results[search] = has_rights_to
+
+        # for inverse matches, we should NOT be told about any objects at all
+        inverse_searches = self.get_inverse_match_searches()
+        inverse_searches += ["(!({}=*))".format(self.conf_attr)]
+        for search in inverse_searches:
+            expected_results[search] = 0
+
+        return expected_results
+
+    # Returns the expected negative (i.e. '!') search behaviour. This varies
+    # depending on what type of DC we're talking to (i.e. Windows or Samba)
+    # and what access rights the user has
+    def negative_search_expected_results(self, has_rights_to, dc_mode,
+                                         total_objects=None):
+
+        if has_rights_to == "all":
+            expect_results = self.negative_searches_all_rights(total_objects)
+
+        # if it's a Samba DC, we only expect the 'match-all' searches to return
+        # the objects that we have access rights to (all others are hidden).
+        # Whereas Windows 'hides' the objects by always returning all of them
+        elif dc_mode == DC_MODE_RETURN_NONE:
+            expect_results = self.negative_searches_return_none(has_rights_to)
+        else:
+            expect_results = self.negative_searches_return_all(has_rights_to,
+                                                               total_objects)
+        return expect_results
+
+    def assert_negative_searches(self, has_rights_to=0,
+                                 dc_mode=DC_MODE_RETURN_NONE, samdb=None):
+        """Asserts user without rights cannot see objects in '!' searches"""
+
+        if samdb is None:
+            samdb = self.ldb_user
+
+        # build a dictionary of key=search-expr, value=expected_num assertions
+        expected_results = self.negative_search_expected_results(has_rights_to,
+                                                                 dc_mode)
+
+        for search, expected_num in expected_results.items():
+            self.assert_search_result(expected_num, search, samdb)
+
+    def assert_attr_returned(self, expect_attr, samdb, attrs):
+        # does a query that should always return a successful result, and
+        # checks whether the confidential attribute is present
+        res = samdb.search(self.conf_dn, expression="(objectClass=*)",
+                           scope=SCOPE_SUBTREE, attrs=attrs)
+        self.assertTrue(len(res) == 1)
+
+        attr_returned = False
+        for msg in res:
+            if self.conf_attr in msg:
+                attr_returned = True
+        self.assertEqual(expect_attr, attr_returned)
+
+    def assert_attr_visible(self, expect_attr, samdb=None):
+        if samdb is None:
+            samdb = self.ldb_user
+
+        # sanity-check confidential attribute is/isn't returned as expected
+        # based on the filter attributes we ask for
+        self.assert_attr_returned(expect_attr, samdb, attrs=None)
+        self.assert_attr_returned(expect_attr, samdb, attrs=["*"])
+        self.assert_attr_returned(expect_attr, samdb, attrs=[self.conf_attr])
+
+        # filtering on a different attribute should never return the conf_attr
+        self.assert_attr_returned(expect_attr=False, samdb=samdb,
+                                  attrs=['name'])
+
+    def assert_attr_visible_to_admin(self):
+        # sanity-check the admin user can always see the confidential attribute
+        self.assert_conf_attr_searches(has_rights_to="all", samdb=self.ldb_admin)
+        self.assert_negative_searches(has_rights_to="all", samdb=self.ldb_admin)
+        self.assert_attr_visible(expect_attr=True, samdb=self.ldb_admin)
+
+
+class ConfidentialAttrTest(ConfidentialAttrCommon):
+    def test_basic_search(self):
+        """Basic test confidential attributes aren't disclosed via searches"""
+
+        # check we can see a non-confidential attribute in a basic searches
+        self.assert_conf_attr_searches(has_rights_to="all")
+        self.assert_negative_searches(has_rights_to="all")
+        self.assert_attr_visible(expect_attr=True)
+
+        # now make the attribute confidential. Repeat the tests and check that
+        # an ordinary user can't see the attribute, or indirectly match on the
+        # attribute via the search expression
+        self.make_attr_confidential()
+
+        self.assert_conf_attr_searches(has_rights_to=0)
+        dc_mode = self.guess_dc_mode()
+        self.assert_negative_searches(has_rights_to=0, dc_mode=dc_mode)
+        self.assert_attr_visible(expect_attr=False)
+
+        # sanity-check we haven't hidden the attribute from the admin as well
+        self.assert_attr_visible_to_admin()
+
+    def _test_search_with_allow_acl(self, allow_ace):
+        """Checks a ACE with 'CR' rights can override a confidential attr"""
+        # make the test attribute confidential and check user can't see it
+        self.make_attr_confidential()
+
+        self.assert_conf_attr_searches(has_rights_to=0)
+        dc_mode = self.guess_dc_mode()
+        self.assert_negative_searches(has_rights_to=0, dc_mode=dc_mode)
+        self.assert_attr_visible(expect_attr=False)
+
+        # apply the allow ACE to the object under test
+        self.sd_utils.dacl_add_ace(self.conf_dn, allow_ace)
+
+        # the user should now be able to see the attribute for the one object
+        # we gave it rights to
+        self.assert_conf_attr_searches(has_rights_to=1)
+        self.assert_negative_searches(has_rights_to=1, dc_mode=dc_mode)
+        self.assert_attr_visible(expect_attr=True)
+
+        # sanity-check the admin can still see the attribute
+        self.assert_attr_visible_to_admin()
+
+    def test_search_with_attr_acl_override(self):
+        """Make the confidential attr visible via an OA attr ACE"""
+
+        # set the SEC_ADS_CONTROL_ACCESS bit ('CR') for the user for the
+        # attribute under test, so the user can see it once more
+        user_sid = self.get_user_sid_string(self.user)
+        ace = "(OA;;CR;{};;{})".format(self.conf_attr_guid, user_sid)
+
+        self._test_search_with_allow_acl(ace)
+
+    def test_search_with_propset_acl_override(self):
+        """Make the confidential attr visible via a Property-set ACE"""
+
+        # set the SEC_ADS_CONTROL_ACCESS bit ('CR') for the user for the
+        # property-set containing the attribute under test (i.e. the
+        # attributeSecurityGuid), so the user can see it once more
+        user_sid = self.get_user_sid_string(self.user)
+        ace = "(OA;;CR;{};;{})".format(self.conf_attr_sec_guid, user_sid)
+
+        self._test_search_with_allow_acl(ace)
+
+    def test_search_with_acl_override(self):
+        """Make the confidential attr visible via a general 'allow' ACE"""
+
+        # set the allow SEC_ADS_CONTROL_ACCESS bit ('CR') for the user
+        user_sid = self.get_user_sid_string(self.user)
+        ace = "(A;;CR;;;{})".format(user_sid)
+
+        self._test_search_with_allow_acl(ace)
+
+    def test_search_with_blanket_oa_acl(self):
+        """Make the confidential attr visible via a non-specific OA ACE"""
+
+        # this just checks that an Object Access (OA) ACE without a GUID
+        # specified will work the same as an 'Access' (A) ACE
+        user_sid = self.get_user_sid_string(self.user)
+        ace = "(OA;;CR;;;{})".format(user_sid)
+
+        self._test_search_with_allow_acl(ace)
+
+    def _test_search_with_neutral_acl(self, neutral_ace):
+        """Checks that a user does NOT gain access via an unrelated ACE"""
+
+        # make the test attribute confidential and check user can't see it
+        self.make_attr_confidential()
+
+        self.assert_conf_attr_searches(has_rights_to=0)
+        dc_mode = self.guess_dc_mode()
+        self.assert_negative_searches(has_rights_to=0, dc_mode=dc_mode)
+        self.assert_attr_visible(expect_attr=False)
+
+        # apply the ACE to the object under test
+        self.sd_utils.dacl_add_ace(self.conf_dn, neutral_ace)
+
+        # this should make no difference to the user's ability to see the attr
+        self.assert_conf_attr_searches(has_rights_to=0)
+        self.assert_negative_searches(has_rights_to=0, dc_mode=dc_mode)
+        self.assert_attr_visible(expect_attr=False)
+
+        # sanity-check the admin can still see the attribute
+        self.assert_attr_visible_to_admin()
+
+    def test_search_with_neutral_acl(self):
+        """Give the user all rights *except* CR for any attributes"""
+
+        # give the user all rights *except* CR and check it makes no difference
+        user_sid = self.get_user_sid_string(self.user)
+        ace = "(A;;RPWPCCDCLCLORCWOWDSDDTSW;;;{})".format(user_sid)
+        self._test_search_with_neutral_acl(ace)
+
+    def test_search_with_neutral_attr_acl(self):
+        """Give the user all rights *except* CR for the attribute under test"""
+
+        # giving user all OA rights *except* CR should make no difference
+        user_sid = self.get_user_sid_string(self.user)
+        rights = "RPWPCCDCLCLORCWOWDSDDTSW"
+        ace = "(OA;;{};{};;{})".format(rights, self.conf_attr_guid, user_sid)
+        self._test_search_with_neutral_acl(ace)
+
+    def test_search_with_neutral_cr_acl(self):
+        """Give the user CR rights for *another* unrelated attribute"""
+
+        # giving user object-access CR rights to an unrelated attribute
+        user_sid = self.get_user_sid_string(self.user)
+        # use the GUID for sAMAccountName here (for no particular reason)
+        unrelated_attr = "3e0abfd0-126a-11d0-a060-00aa006c33ed"
+        ace = "(OA;;CR;{};;{})".format(unrelated_attr, user_sid)
+        self._test_search_with_neutral_acl(ace)
+
+
+# Check that a Deny ACL on an attribute doesn't reveal confidential info
+class ConfidentialAttrTestDenyAcl(ConfidentialAttrCommon):
+
+    def assert_not_in_result(self, res, exclude_dn):
+        for msg in res:
+            self.assertNotEqual(msg.dn, exclude_dn,
+                                "Search revealed object {}".format(exclude_dn))
+
+    # deny ACL tests are slightly different as we are only denying access to
+    # the one object under test (rather than any objects with that attribute).
+    # Therefore we need an extra check that we don't reveal the test object
+    # in the search, if we're not supposed to
+    def assert_search_result(self, expected_num, expr, samdb,
+                             excl_testobj=False):
+
+        # try asking for different attributes back: None/all, the confidential
+        # attribute itself, and a random unrelated attribute
+        attr_filters = [None, ["*"], [self.conf_attr], ['name']]
+        for attr in attr_filters:
+            res = samdb.search(self.test_dn, expression=expr,
+                               scope=SCOPE_SUBTREE, attrs=attr)
+            self.assertTrue(len(res) == expected_num,
+                           "%u results, not %u for search %s, attr %s" %
+                            (len(res), expected_num, expr, str(attr)))
+
+            # assert we haven't revealed the hidden test-object
+            if excl_testobj:
+                self.assert_not_in_result(res, exclude_dn=self.conf_dn)
+
+    # we make a few tweaks to the regular version of this function to cater to
+    # denying specifically one object via an ACE
+    def assert_conf_attr_searches(self, has_rights_to=0, samdb=None):
+        """Check searches against the attribute under test work as expected"""
+
+        if samdb is None:
+            samdb = self.ldb_user
+
+        # make sure the test object is not returned if we've been denied rights
+        # to it via an ACE
+        excl_testobj = True if has_rights_to == "deny-one" else False
+
+        # these first few searches we just expect to match against the one
+        # object under test that we're trying to guess the value of
+        expected_num = 1 if has_rights_to == "all" else 0
+
+        for search in self.get_exact_match_searches():
+            self.assert_search_result(expected_num, search, samdb,
+                                      excl_testobj)
+
+        # these next searches will match any objects with the attribute that
+        # we have rights to see (i.e. all except the object under test)
+        if has_rights_to == "all":
+            expected_num = self.objects_with_attr
+        elif has_rights_to == "deny-one":
+            expected_num = self.objects_with_attr - 1
+
+        for search in self.get_match_all_searches():
+            self.assert_search_result(expected_num, search, samdb,
+                                      excl_testobj)
+
+    def negative_searches_return_none(self, has_rights_to=0):
+        expected_results = {}
+
+        # on Samba we will see the objects we have rights to, but the one we
+        # are denied access to will be hidden
+        searches = self.get_negative_match_all_searches()
+        searches += self.get_inverse_match_searches()
+        for search in searches:
+            expected_results[search] = self.total_objects - 1
+
+        # The wildcard returns the objects without this attribute as normal.
+        search = "(!({}=*))".format(self.conf_attr)
+        expected_results[search] = self.total_objects - self.objects_with_attr
+        return expected_results
+
+    def negative_searches_return_all(self, has_rights_to=0,
+                                     total_objects=None):
+        expected_results = {}
+
+        # When a user lacks access rights to an object, Windows 'hides' it in
+        # '!' searches by always returning it, regardless of whether it matches
+        searches = self.get_negative_match_all_searches()
+        searches += self.get_inverse_match_searches()
+        for search in searches:
+            expected_results[search] = self.total_objects
+
+        # in the wildcard case, the one object we don't have rights to gets
+        # bundled in with the objects that don't have the attribute at all
+        search = "(!({}=*))".format(self.conf_attr)
+        has_rights_to = self.objects_with_attr - 1
+        expected_results[search] = self.total_objects - has_rights_to
+        return expected_results
+
+    def assert_negative_searches(self, has_rights_to=0,
+                                 dc_mode=DC_MODE_RETURN_NONE, samdb=None):
+        """Asserts user without rights cannot see objects in '!' searches"""
+
+        if samdb is None:
+            samdb = self.ldb_user
+
+        # As the deny ACL is only denying access to one particular object, add
+        # an extra check that the denied object is not returned. (We can only
+        # assert this if the '!'/negative search behaviour is to suppress any
+        # objects we don't have access rights to)
+        excl_testobj = False
+        if has_rights_to != "all" and dc_mode == DC_MODE_RETURN_NONE:
+            excl_testobj = True
+
+        # build a dictionary of key=search-expr, value=expected_num assertions
+        expected_results = self.negative_search_expected_results(has_rights_to,
+                                                                 dc_mode)
+
+        for search, expected_num in expected_results.items():
+            self.assert_search_result(expected_num, search, samdb,
+                                      excl_testobj=excl_testobj)
+
+    def _test_search_with_deny_acl(self, ace):
+        # check the user can see the attribute initially
+        self.assert_conf_attr_searches(has_rights_to="all")
+        self.assert_negative_searches(has_rights_to="all")
+        self.assert_attr_visible(expect_attr=True)
+
+        # add the ACE that denies access to the attr under test
+        self.sd_utils.dacl_add_ace(self.conf_dn, ace)
+
+        # the user shouldn't be able to see the attribute anymore
+        self.assert_conf_attr_searches(has_rights_to="deny-one")
+        dc_mode = self.guess_dc_mode()
+        self.assert_negative_searches(has_rights_to="deny-one",
+                                      dc_mode=dc_mode)
+        self.assert_attr_visible(expect_attr=False)
+
+        # sanity-check we haven't hidden the attribute from the admin as well
+        self.assert_attr_visible_to_admin()
+
+    def test_search_with_deny_attr_acl(self):
+        """Checks a deny ACE works the same way as a confidential attribute"""
+
+        # add an ACE that denies the user Read Property (RP) access to the attr
+        # (which is similar to making the attribute confidential)
+        user_sid = self.get_user_sid_string(self.user)
+        ace = "(OD;;RP;{};;{})".format(self.conf_attr_guid, user_sid)
+
+        # check the user cannot see the attribute anymore
+        self._test_search_with_deny_acl(ace)
+
+    def test_search_with_deny_acl(self):
+        """Checks a blanket deny ACE denies access to an object's attributes"""
+
+        # add an blanket deny ACE for Read Property (RP) rights
+        user_dn = self.get_user_dn(self.user)
+        user_sid = self.sd_utils.get_object_sid(user_dn)
+        ace = "(D;;RP;;;{})".format(str(user_sid))
+
+        # check the user cannot see the attribute anymore
+        self._test_search_with_deny_acl(ace)
+
+    def test_search_with_deny_propset_acl(self):
+        """Checks a deny ACE on the attribute's Property-Set"""
+
+        # add an blanket deny ACE for Read Property (RP) rights
+        user_sid = self.get_user_sid_string(self.user)
+        ace = "(OD;;RP;{};;{})".format(self.conf_attr_sec_guid, user_sid)
+
+        # check the user cannot see the attribute anymore
+        self._test_search_with_deny_acl(ace)
+
+    def test_search_with_blanket_oa_deny_acl(self):
+        """Checks a non-specific 'OD' ACE works the same as a 'D' ACE"""
+
+        # this just checks that adding a 'Object Deny' (OD) ACE without
+        # specifying a GUID will work the same way as a 'Deny' (D) ACE
+        user_sid = self.get_user_sid_string(self.user)
+        ace = "(OD;;RP;;;{})".format(user_sid)
+
+        # check the user cannot see the attribute anymore
+        self._test_search_with_deny_acl(ace)
+
+
+# Check that using the dirsync controls doesn't reveal confidential attributes
+class ConfidentialAttrTestDirsync(ConfidentialAttrCommon):
+
+    def setUp(self):
+        super(ConfidentialAttrTestDirsync, self).setUp()
+        self.dirsync = ["dirsync:1:1:1000"]
+
+    def assert_search_result(self, expected_num, expr, samdb, base_dn=None):
+
+        # Note dirsync must always search on the partition base DN
+        if base_dn is None:
+            base_dn = self.base_dn
+
+        attr_filters = [None, ["*"], ["name"]]
+
+        # Note dirsync behaviour is slighty different for the attribute under
+        # test - when you have full access rights, it only returns the objects
+        # that actually have this attribute (i.e. it doesn't return an empty
+        # message with just the DN). So we add the 'name' attribute into the
+        # attribute filter to avoid complicating our assertions further
+        attr_filters += [[self.conf_attr, "name"]]
+        for attr in attr_filters:
+            res = samdb.search(base_dn, expression=expr, scope=SCOPE_SUBTREE,
+                               attrs=attr, controls=self.dirsync)
+
+            self.assertTrue(len(res) == expected_num,
+                            "%u results, not %u for search %s, attr %s" %
+                            (len(res), expected_num, expr, str(attr)))
+
+
+    def assert_attr_returned(self, expect_attr, samdb, attrs,
+                             no_result_ok=False):
+
+        # When using dirsync, the base DN we search on needs to be a naming
+        # context. Add an extra filter to ignore all the objects we aren't
+        # interested in
+        expr = "(&(samaccountname={})(!(isDeleted=*)))".format(self.conf_user)
+        res = samdb.search(self.base_dn, expression=expr, scope=SCOPE_SUBTREE,
+                           attrs=attrs, controls=self.dirsync)
+        self.assertTrue(len(res) == 1 or no_result_ok)
+
+        attr_returned = False
+        for msg in res:
+            if self.conf_attr in msg and len(msg[self.conf_attr]) > 0:
+                attr_returned = True
+        self.assertEqual(expect_attr, attr_returned)
+
+    def assert_attr_visible(self, expect_attr, samdb=None):
+        if samdb is None:
+            samdb = self.ldb_user
+
+        # sanity-check confidential attribute is/isn't returned as expected
+        # based on the filter attributes we ask for
+        self.assert_attr_returned(expect_attr, samdb, attrs=None)
+        self.assert_attr_returned(expect_attr, samdb, attrs=["*"])
+
+        if expect_attr:
+            self.assert_attr_returned(expect_attr, samdb,
+                                      attrs=[self.conf_attr])
+        else:
+            # The behaviour with dirsync when asking solely for an attribute
+            # that you don't have rights to is a bit strange. Samba returns
+            # no result rather than an empty message with just the DN.
+            # Presumably this is due to dirsync module behaviour. It's not
+            # disclosive in that the DC behaves the same way as if you asked
+            # for a garbage/non-existent attribute
+            self.assert_attr_returned(expect_attr, samdb,
+                                      attrs=[self.conf_attr],
+                                      no_result_ok=True)
+            self.assert_attr_returned(expect_attr, samdb,
+                                      attrs=["garbage"], no_result_ok=True)
+
+        # filtering on a different attribute should never return the conf_attr
+        self.assert_attr_returned(expect_attr=False, samdb=samdb,
+                                  attrs=['name'])
+
+    def assert_negative_searches(self, has_rights_to=0,
+                                 dc_mode=DC_MODE_RETURN_NONE, samdb=None):
+        """Asserts user without rights cannot see objects in '!' searches"""
+
+        if samdb is None:
+            samdb = self.ldb_user
+
+        # because we need to search on the base DN when using the dirsync
+        # controls, we need an extra filter for the inverse ('!') search,
+        # so we don't get thousands of objects returned
+        extra_filter = \
+            "(samaccountname={}*)(!(isDeleted=*))".format(self.user_prefix)
+
+        # because of this extra filter, the total objects we expect here only
+        # includes the user objects (not the parent OU)
+        total_objects = len(self.all_users)
+        expected_results = self.negative_search_expected_results(has_rights_to,
+                                                                 dc_mode,
+                                                                 total_objects)
+
+        for search, expected_num in expected_results.items():
+            search = "(&{}{})".format(search, extra_filter)
+            self.assert_search_result(expected_num, search, samdb)
+
+    def test_search_with_dirsync(self):
+        """Checks dirsync controls don't reveal confidential attributes"""
+
+        self.assert_conf_attr_searches(has_rights_to="all")
+        self.assert_attr_visible(expect_attr=True)
+        self.assert_negative_searches(has_rights_to="all")
+
+        # make the test attribute confidential and check user can't see it,
+        # even if they use the dirsync controls
+        self.make_attr_confidential()
+
+        self.assert_conf_attr_searches(has_rights_to=0)
+        self.assert_attr_visible(expect_attr=False)
+        dc_mode = self.guess_dc_mode()
+        self.assert_negative_searches(has_rights_to=0, dc_mode=dc_mode)
+
+        # as a final sanity-check, make sure the admin can still see the attr
+        self.assert_conf_attr_searches(has_rights_to="all",
+                                       samdb=self.ldb_admin)
+        self.assert_attr_visible(expect_attr=True, samdb=self.ldb_admin)
+        self.assert_negative_searches(has_rights_to="all",
+                                      samdb=self.ldb_admin)
+
+TestProgram(module=__name__, opts=subunitopts)
diff --git a/source4/selftest/tests.py b/source4/selftest/tests.py
index d814b15a87c..ced12e66b92 100755
--- a/source4/selftest/tests.py
+++ b/source4/selftest/tests.py
@@ -614,6 +614,9 @@ for env in ["ad_dc_ntvfs", "fl2000dc", "fl2003dc", "fl2008r2dc"]:
         # therefore skip it in that configuration
         plantestsuite_loadlist("samba4.ldap.passwords.python(%s)" % env, env, [python, os.path.join(samba4srcdir, "dsdb/tests/python/passwords.py"), "$SERVER", '-U"$USERNAME%$PASSWORD"', "-W$DOMAIN", '$LOADLIST', '$LISTOPT'])
 
+env = "ad_dc_ntvfs"
+plantestsuite_loadlist("samba4.ldap.confidential_attr.python(%s)" % env, env, [python, os.path.join(samba4srcdir, "dsdb/tests/python/confidential_attr.py"), '$SERVER', '-U"$USERNAME%$PASSWORD"', '--workgroup=$DOMAIN', '$LOADLIST', '$LISTOPT'])
+
 for env in ["ad_dc_ntvfs"]:
     # This test takes a lot of time, so we run it against a minimum of
     # environments, please only add new ones if there's really a