source4 dsdb modules: Add new module "unique_object_sids"

New module that sets the LDB_FLAG_INTERNAL_UNIQUE_VALUE on all local
objectSIDS and ensure it is cleared for any foreign security principals.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13004

Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>

4 files changed, 795 insertions, 0 deletions

diff --git a/source4/dsdb/samdb/ldb_modules/tests/test_unique_object_sids.c b/source4/dsdb/samdb/ldb_modules/tests/test_unique_object_sids.c
new file mode 100644
index 00000000000..dfc6d49cfa7
--- /dev/null
+++ b/source4/dsdb/samdb/ldb_modules/tests/test_unique_object_sids.c
@@ -0,0 +1,513 @@
+/*
+   Unit tests for the unique objectSID code in unique_object_sids.c
+
+   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2017
+
+   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/>.
+*/
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <setjmp.h>
+#include <unistd.h>
+#include <cmocka.h>
+
+int ldb_unique_object_sids_init(const char *version);
+#include "../unique_object_sids.c"
+
+#include "../libcli/security/dom_sid.h"
+#include "librpc/gen_ndr/ndr_security.h"
+
+#define TEST_BE "tdb"
+
+#define DOMAIN_SID  "S-1-5-21-2470180966-3899876309-2637894779"
+#define LOCAL_SID   "S-1-5-21-2470180966-3899876309-2637894779-1000"
+#define FOREIGN_SID "S-1-5-21-2470180966-3899876309-2637894778-1000"
+
+static struct ldb_request *last_request;
+
+/*
+ * ldb_next_request mock, records the request passed in last_request
+ * so it can be examined in the test cases.
+ */
+int ldb_next_request(
+	struct ldb_module *module,
+	struct ldb_request *request)
+{
+	last_request = request;
+	return ldb_module_done(request, NULL, NULL, LDB_SUCCESS);
+}
+
+/*
+ * Test context
+ */
+struct ldbtest_ctx {
+	struct tevent_context *ev;
+	struct ldb_context *ldb;
+	struct ldb_module *module;
+
+	const char *dbfile;
+	const char *lockfile;   /* lockfile is separate */
+
+	const char *dbpath;
+	struct dom_sid *domain_sid;
+};
+
+/*
+ * Remove any database files created by the tests
+ */
+static void unlink_old_db(struct ldbtest_ctx *test_ctx)
+{
+	int ret;
+
+	errno = 0;
+	ret = unlink(test_ctx->lockfile);
+	if (ret == -1 && errno != ENOENT) {
+		fail();
+	}
+
+	errno = 0;
+	ret = unlink(test_ctx->dbfile);
+	if (ret == -1 && errno != ENOENT) {
+		fail();
+	}
+}
+
+/*
+ * Empty module to signal the end of the module list
+ */
+static const struct ldb_module_ops eol_ops = {
+	.name              = "eol",
+	.search            = NULL,
+	.add		   = NULL,
+	.modify		   = NULL,
+	.del		   = NULL,
+	.rename		   = NULL,
+	.init_context	   = NULL
+};
+
+/*
+ * Test set up
+ */
+static int setup(void **state)
+{
+	struct ldbtest_ctx *test_ctx	= NULL;
+	struct ldb_module *eol		= NULL;
+	int rc;
+
+	test_ctx = talloc_zero(NULL, struct ldbtest_ctx);
+	assert_non_null(test_ctx);
+
+	test_ctx->ev = tevent_context_init(test_ctx);
+	assert_non_null(test_ctx->ev);
+
+	test_ctx->ldb = ldb_init(test_ctx, test_ctx->ev);
+	assert_non_null(test_ctx->ldb);
+
+	test_ctx->domain_sid = talloc_zero(test_ctx, struct dom_sid);
+	assert_non_null(test_ctx->domain_sid);
+	assert_true(string_to_sid(test_ctx->domain_sid, DOMAIN_SID));
+	ldb_set_opaque(test_ctx->ldb, "cache.domain_sid", test_ctx->domain_sid);
+
+        test_ctx->module = ldb_module_new(
+		test_ctx,
+		test_ctx->ldb,
+		"unique_object_sids",
+		&ldb_unique_object_sids_module_ops);
+	assert_non_null(test_ctx->module);
+	eol = ldb_module_new(test_ctx, test_ctx->ldb, "eol", &eol_ops);
+	assert_non_null(eol);
+	ldb_module_set_next(test_ctx->module, eol);
+
+	test_ctx->dbfile = talloc_strdup(test_ctx, "duptest.ldb");
+	assert_non_null(test_ctx->dbfile);
+
+	test_ctx->lockfile = talloc_asprintf(test_ctx, "%s-lock",
+					     test_ctx->dbfile);
+	assert_non_null(test_ctx->lockfile);
+
+	test_ctx->dbpath = talloc_asprintf(test_ctx,
+			TEST_BE"://%s", test_ctx->dbfile);
+	assert_non_null(test_ctx->dbpath);
+
+	unlink_old_db(test_ctx);
+
+	rc = ldb_connect(test_ctx->ldb, test_ctx->dbpath, 0, NULL);
+	assert_int_equal(rc, LDB_SUCCESS);
+
+	rc = unique_object_sids_init(test_ctx->module);
+	assert_int_equal(rc, LDB_SUCCESS);
+
+	*state = test_ctx;
+
+	last_request = NULL;
+	return 0;
+}
+
+/*
+ * Test clean up
+ */
+static int teardown(void **state)
+{
+	struct ldbtest_ctx *test_ctx = talloc_get_type_abort(*state,
+							struct ldbtest_ctx);
+
+	unlink_old_db(test_ctx);
+	talloc_free(test_ctx);
+	return 0;
+}
+
+/*
+ * Add an objectSID in string form to the supplied message
+ *
+ *
+ */
+static void add_sid(
+	struct ldb_message *msg,
+	const char *sid_str)
+{
+	struct ldb_val v;
+	enum ndr_err_code ndr_err;
+	struct dom_sid *sid = NULL;
+
+	sid = talloc_zero(msg, struct dom_sid);
+	assert_non_null(sid);
+	assert_true(string_to_sid(sid, sid_str));
+	ndr_err = ndr_push_struct_blob(&v, msg, sid,
+				       (ndr_push_flags_fn_t)ndr_push_dom_sid);
+	assert_true(NDR_ERR_CODE_IS_SUCCESS(ndr_err));
+	assert_int_equal(0, ldb_msg_add_value(msg, "objectSID", &v, NULL));
+}
+
+/*
+ * The object is in the current local domain so it should have
+ * DB_FLAG_INTERNAL_UNIQUE_VALUE set
+ */
+static void test_objectSID_in_domain(void **state)
+{
+	struct ldbtest_ctx *test_ctx =
+		talloc_get_type_abort(*state, struct ldbtest_ctx);
+	struct ldb_context *ldb 		= test_ctx->ldb;
+	struct ldb_message *msg			= ldb_msg_new(test_ctx);
+	struct ldb_message_element *el		= NULL;
+	struct ldb_request *request		= NULL;
+	struct ldb_request *original_request	= NULL;
+	int rc;
+
+	msg->dn = ldb_dn_new(msg, ldb, "dc=test");
+	add_sid(msg, LOCAL_SID);
+
+	rc = ldb_build_add_req(
+		&request,
+		test_ctx->ldb,
+		test_ctx,
+		msg,
+		NULL,
+		NULL,
+		ldb_op_default_callback,
+		NULL);
+
+	assert_int_equal(rc, LDB_SUCCESS);
+	assert_non_null(request);
+	original_request = request;
+
+	rc = unique_object_sids_add(test_ctx->module, request);
+	assert_int_equal(rc, LDB_SUCCESS);
+
+	/*
+	 * Check that a copy of the request was passed to the next module
+	 * and not the original request
+	 */
+	assert_ptr_not_equal(last_request, original_request);
+
+	/*
+	 * Check the flag was set on the request passed to the next
+	 * module
+	 */
+	el = ldb_msg_find_element(last_request->op.add.message, "objectSID");
+	assert_non_null(el);
+	assert_true(el->flags & LDB_FLAG_INTERNAL_FORCE_UNIQUE_INDEX);
+
+	/*
+	 * Check the flag was not  set on the original request
+	 */
+	el = ldb_msg_find_element(request->op.add.message, "objectSID");
+	assert_non_null(el);
+	assert_false(el->flags & LDB_FLAG_INTERNAL_FORCE_UNIQUE_INDEX);
+
+}
+
+/*
+ * The object is not in the current local domain so it should NOT have
+ * DB_FLAG_INTERNAL_UNIQUE_VALUE set
+ */
+static void test_objectSID_not_in_domain(void **state)
+{
+	struct ldbtest_ctx *test_ctx =
+		talloc_get_type_abort(*state, struct ldbtest_ctx);
+	struct ldb_context *ldb			= test_ctx->ldb;
+	struct ldb_message *msg			= ldb_msg_new(test_ctx);
+	struct ldb_message_element *el		= NULL;
+	struct ldb_request *request		= NULL;
+	struct ldb_request *original_request	= NULL;
+	int rc;
+
+	msg->dn = ldb_dn_new(msg, ldb, "dc=test");
+	add_sid(msg, FOREIGN_SID);
+
+	rc = ldb_build_add_req(
+		&request,
+		test_ctx->ldb,
+		test_ctx,
+		msg,
+		NULL,
+		NULL,
+		ldb_op_default_callback,
+		NULL);
+
+	assert_int_equal(rc, LDB_SUCCESS);
+	assert_non_null(request);
+	original_request = request;
+
+	rc = unique_object_sids_add(test_ctx->module, request);
+	assert_int_equal(rc, LDB_SUCCESS);
+
+	/*
+	 * Check that the original request was passed to the next module
+	 * and not a copy
+	 */
+	assert_ptr_equal(last_request, original_request);
+
+	/*
+	 * Check that the flag was not set on the objectSID element
+	 */
+	el = ldb_msg_find_element(msg, "objectSID");
+	assert_non_null(el);
+	assert_false(el->flags & LDB_FLAG_INTERNAL_FORCE_UNIQUE_INDEX);
+}
+
+/*
+ * No objectSID on the record so it should pass through the module untouched
+ *
+ */
+static void test_no_objectSID(void **state)
+{
+	struct ldbtest_ctx *test_ctx =
+		talloc_get_type_abort(*state, struct ldbtest_ctx);
+	struct ldb_context *ldb			= test_ctx->ldb;
+	struct ldb_message *msg			= ldb_msg_new(test_ctx);
+	struct ldb_request *request		= NULL;
+	struct ldb_request *original_request	= NULL;
+	int rc;
+
+	msg->dn = ldb_dn_new(msg, ldb, "dc=test");
+	assert_int_equal(LDB_SUCCESS, ldb_msg_add_string(msg, "cn", "test"));
+
+	rc = ldb_build_add_req(
+		&request,
+		test_ctx->ldb,
+		test_ctx,
+		msg,
+		NULL,
+		NULL,
+		ldb_op_default_callback,
+		NULL);
+
+	assert_int_equal(rc, LDB_SUCCESS);
+	assert_non_null(request);
+	original_request = request;
+
+	rc = unique_object_sids_add(test_ctx->module, request);
+	assert_int_equal(rc, LDB_SUCCESS);
+
+	/*
+	 * Check that the original request was passed to the next module
+	 * and not a copy
+	 */
+	assert_ptr_equal(last_request, original_request);
+
+}
+
+/*
+ * Attempt to modify an objectSID DSDB_CONTROL_REPLICATED_UPDATE_OID not set
+ * this should fail with LDB_ERR_UNWILLING_TO_PERFORM
+ */
+static void test_modify_of_objectSID_not_replicated(void **state)
+{
+	struct ldbtest_ctx *test_ctx =
+		talloc_get_type_abort(*state, struct ldbtest_ctx);
+	struct ldb_context *ldb 		= test_ctx->ldb;
+	struct ldb_message *msg			= ldb_msg_new(test_ctx);
+	struct ldb_request *request		= NULL;
+	int rc;
+
+	msg->dn = ldb_dn_new(msg, ldb, "dc=test");
+	add_sid(msg, LOCAL_SID);
+
+	rc = ldb_build_mod_req(
+		&request,
+		test_ctx->ldb,
+		test_ctx,
+		msg,
+		NULL,
+		NULL,
+		ldb_op_default_callback,
+		NULL);
+
+	assert_int_equal(rc, LDB_SUCCESS);
+	assert_non_null(request);
+
+	rc = unique_object_sids_modify(test_ctx->module, request);
+
+	assert_int_equal(rc, LDB_ERR_UNWILLING_TO_PERFORM);
+}
+
+
+/*
+ * Attempt to modify an objectSID DSDB_CONTROL_REPLICATED_UPDATE_OID set
+ * this should succeed
+ */
+static void test_modify_of_objectSID_replicated(void **state)
+{
+	struct ldbtest_ctx *test_ctx =
+		talloc_get_type_abort(*state, struct ldbtest_ctx);
+	struct ldb_context *ldb 		= test_ctx->ldb;
+	struct ldb_message *msg			= ldb_msg_new(test_ctx);
+	struct ldb_message_element *el		= NULL;
+	struct ldb_request *request		= NULL;
+	struct ldb_request *original_request	= NULL;
+	int rc;
+
+	msg->dn = ldb_dn_new(msg, ldb, "dc=test");
+	add_sid(msg, LOCAL_SID);
+
+	rc = ldb_build_mod_req(
+		&request,
+		test_ctx->ldb,
+		test_ctx,
+		msg,
+		NULL,
+		NULL,
+		ldb_op_default_callback,
+		NULL);
+	assert_int_equal(rc, LDB_SUCCESS);
+	assert_non_null(request);
+	original_request = request;
+
+	ldb_request_add_control(
+		request,
+		DSDB_CONTROL_REPLICATED_UPDATE_OID,
+		false,
+		NULL);
+
+	rc = unique_object_sids_modify(test_ctx->module, request);
+
+	assert_int_equal(rc, LDB_SUCCESS);
+
+	/*
+	 * Check that a copy of the request was passed to the next module
+	 * and not the original request
+	 */
+	assert_ptr_not_equal(last_request, original_request);
+
+	/*
+	 * Check the flag was set on the request passed to the next
+	 * module
+	 */
+	el = ldb_msg_find_element(last_request->op.add.message, "objectSID");
+	assert_non_null(el);
+	assert_true(el->flags & LDB_FLAG_INTERNAL_FORCE_UNIQUE_INDEX);
+
+	/*
+	 * Check the flag was not  set on the original request
+	 */
+	el = ldb_msg_find_element(request->op.add.message, "objectSID");
+	assert_non_null(el);
+	assert_false(el->flags & LDB_FLAG_INTERNAL_FORCE_UNIQUE_INDEX);
+
+}
+
+/*
+ * Test the a modify with no object SID is passed through correctly
+ *
+ */
+static void test_modify_no_objectSID(void **state)
+{
+	struct ldbtest_ctx *test_ctx =
+		talloc_get_type_abort(*state, struct ldbtest_ctx);
+	struct ldb_context *ldb			= test_ctx->ldb;
+	struct ldb_message *msg			= ldb_msg_new(test_ctx);
+	struct ldb_request *request		= NULL;
+	struct ldb_request *original_request	= NULL;
+	int rc;
+
+	msg->dn = ldb_dn_new(msg, ldb, "dc=test");
+	assert_int_equal(LDB_SUCCESS, ldb_msg_add_string(msg, "cn", "test"));
+
+	rc = ldb_build_mod_req(
+		&request,
+		test_ctx->ldb,
+		test_ctx,
+		msg,
+		NULL,
+		NULL,
+		ldb_op_default_callback,
+		NULL);
+
+	assert_int_equal(rc, LDB_SUCCESS);
+	assert_non_null(request);
+	original_request = request;
+
+	rc = unique_object_sids_modify(test_ctx->module, request);
+	assert_int_equal(rc, LDB_SUCCESS);
+
+	/*
+	 * Check that the original request was passed to the next module
+	 * and not a copy
+	 */
+	assert_ptr_equal(last_request, original_request);
+
+}
+
+int main(void) {
+	const struct CMUnitTest tests[] = {
+		cmocka_unit_test_setup_teardown(
+			test_objectSID_in_domain,
+			setup,
+			teardown),
+		cmocka_unit_test_setup_teardown(
+			test_objectSID_not_in_domain,
+			setup,
+			teardown),
+		cmocka_unit_test_setup_teardown(
+			test_no_objectSID,
+			setup,
+			teardown),
+		cmocka_unit_test_setup_teardown(
+			test_modify_no_objectSID,
+			setup,
+			teardown),
+		cmocka_unit_test_setup_teardown(
+			test_modify_of_objectSID_not_replicated,
+			setup,
+			teardown),
+		cmocka_unit_test_setup_teardown(
+			test_modify_of_objectSID_replicated,
+			setup,
+			teardown),
+	};
+
+	cmocka_set_message_output(CM_OUTPUT_SUBUNIT);
+	return cmocka_run_group_tests(tests, NULL, NULL);
+}
diff --git a/source4/dsdb/samdb/ldb_modules/unique_object_sids.c b/source4/dsdb/samdb/ldb_modules/unique_object_sids.c
new file mode 100644
index 00000000000..f8427bc2438
--- /dev/null
+++ b/source4/dsdb/samdb/ldb_modules/unique_object_sids.c
@@ -0,0 +1,262 @@
+/*
+   ldb database module to enforce unique local objectSIDs
+
+   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2017
+
+   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/>.
+*/
+
+/*
+
+   Duplicate ObjectSIDs are possible on foreign security principals and
+   replication conflict records.  However a duplicate objectSID within
+   the local domainSID is an error.
+
+   As the uniqueness requirement depends on the source domain it is not possible
+   to enforce this with a unique index.
+
+   This module sets the LDB_FLAG_FORCE_UNIQUE_INDEX for objectSIDs in the
+   local domain.
+*/
+
+#include "includes.h"
+#include "ldb_module.h"
+#include "dsdb/samdb/samdb.h"
+#include "libcli/security/dom_sid.h"
+#include "dsdb/samdb/ldb_modules/util.h"
+
+struct private_data {
+	const struct dom_sid *domain_sid;
+};
+
+
+/*
+ * Does the add request contain a local objectSID
+ */
+static bool message_contains_local_objectSID(
+	struct ldb_module *module,
+	const struct ldb_message *msg)
+{
+	struct dom_sid *objectSID	= NULL;
+
+	struct private_data *data =
+		talloc_get_type(
+			ldb_module_get_private(module),
+			struct private_data);
+
+	TALLOC_CTX *frame = talloc_stackframe();
+
+	objectSID = samdb_result_dom_sid(frame, msg, "objectSID");
+	if (objectSID == NULL) {
+		TALLOC_FREE(frame);
+		return false;
+	}
+
+	/*
+	 * data->domain_sid can be NULL but dom_sid_in_domain handles this
+	 * case correctly. See unique_object_sids_init for more details.
+	 */
+	if (!dom_sid_in_domain(data->domain_sid, objectSID)) {
+		TALLOC_FREE(frame);
+		return false;
+	}
+	TALLOC_FREE(frame);
+	return true;
+}
+
+static int flag_objectSID(
+	struct ldb_module *module,
+	struct ldb_request *req,
+	const struct ldb_message *msg,
+	struct ldb_message **new_msg)
+{
+	struct ldb_message_element *el	= NULL;
+
+	*new_msg = ldb_msg_copy_shallow(req, msg);
+	if (!*new_msg) {
+		return ldb_module_oom(module);
+	}
+
+	el = ldb_msg_find_element(*new_msg, "objectSID");
+	if (el == NULL) {
+		struct ldb_context *ldb = NULL;
+		ldb = ldb_module_get_ctx(module);
+		ldb_asprintf_errstring(
+			ldb,
+			"Unable to locate objectSID in copied request\n");
+		return LDB_ERR_OPERATIONS_ERROR;
+	}
+	el->flags |= LDB_FLAG_INTERNAL_FORCE_UNIQUE_INDEX;
+	return LDB_SUCCESS;
+}
+
+/* add */
+static int unique_object_sids_add(
+	struct ldb_module *module,
+	struct ldb_request *req)
+{
+	const struct ldb_message *msg = req->op.add.message;
+	struct ldb_message *new_msg	= NULL;
+	struct ldb_request *new_req	= NULL;
+	struct ldb_context *ldb		= NULL;
+	int rc;
+
+	if (!message_contains_local_objectSID(module, msg)) {
+		/*
+		 * Request does not contain a local objectSID so chain the
+		 * next module
+		 */
+		return ldb_next_request(module, req);
+	}
+
+	/*
+	 * The add request contains an objectSID for the local domain
+	 */
+
+	rc = flag_objectSID(module, req, msg, &new_msg);
+	if (rc != LDB_SUCCESS) {
+		return rc;
+	}
+
+	ldb = ldb_module_get_ctx(module);
+	rc = ldb_build_add_req(
+		&new_req,
+		ldb,
+		req,
+		new_msg,
+		req->controls,
+		req,
+		dsdb_next_callback,
+		req);
+	if (rc != LDB_SUCCESS) {
+		return rc;
+	}
+
+	return ldb_next_request(module, new_req);
+}
+
+/* modify */
+static int unique_object_sids_modify(
+	struct ldb_module *module,
+	struct ldb_request *req)
+{
+
+	const struct ldb_message *msg	= req->op.mod.message;
+	struct ldb_message *new_msg	= NULL;
+	struct ldb_request *new_req	= NULL;
+	struct ldb_context *ldb		= NULL;
+	int rc;
+
+	if (!message_contains_local_objectSID(module, msg)) {
+		/*
+		 * Request does not contain a local objectSID so chain the
+		 * next module
+		 */
+		return ldb_next_request(module, req);
+	}
+
+	ldb = ldb_module_get_ctx(module);
+
+	/*
+	 * If DSDB_CONTROL_REPLICATED_UPDATE_OID replicated is set we know
+	 * that the modify request is well formed and objectSID only appears
+	 * once.
+	 *
+	 * Enforcing this assumption simplifies the subsequent code.
+	 *
+	 */
+	if(!ldb_request_get_control(req, DSDB_CONTROL_REPLICATED_UPDATE_OID)) {
+		ldb_asprintf_errstring(
+			ldb,
+			"Modify of %s rejected, "
+			"as it is modifying an objectSID\n",
+			ldb_dn_get_linearized(msg->dn));
+		return LDB_ERR_UNWILLING_TO_PERFORM;
+	}
+
+
+	rc = flag_objectSID(module, req, msg, &new_msg);
+	if (rc != LDB_SUCCESS) {
+		return rc;
+	}
+
+	ldb = ldb_module_get_ctx(module);
+	rc = ldb_build_mod_req(
+		&new_req,
+		ldb,
+		req,
+		new_msg,
+		req->controls,
+		req,
+		dsdb_next_callback,
+		req);
+	if (rc != LDB_SUCCESS) {
+		return rc;
+	}
+
+	return ldb_next_request(module, new_req);
+}
+
+/* init */
+static int unique_object_sids_init(
+	struct ldb_module *module)
+{
+	struct ldb_context *ldb = ldb_module_get_ctx(module);
+	struct private_data *data = NULL;
+	int ret;
+
+	ret = ldb_next_init(module);
+
+	if (ret != LDB_SUCCESS) {
+		return ret;
+	}
+
+	data = talloc_zero(module, struct private_data);
+	if (!data) {
+		return ldb_module_oom(module);
+	}
+
+	data->domain_sid = samdb_domain_sid(ldb);
+	if (data->domain_sid == NULL) {
+		/*
+		 * Unable to determine the domainSID, this normally occurs
+		 * when provisioning. As there is no easy way to detect
+		 * that we are provisioning.  We currently just log this as a
+		 * warning.
+		 */
+		ldb_debug(
+			ldb,
+			LDB_DEBUG_WARNING,
+			"Unable to determine the DomainSID, "
+			"can not enforce uniqueness constraint on local "
+			"domainSIDs\n");
+	}
+
+	ldb_module_set_private(module, data);
+
+	return LDB_SUCCESS;
+}
+
+static const struct ldb_module_ops ldb_unique_object_sids_module_ops = {
+	.name		   = "unique_object_sids",
+	.init_context	   = unique_object_sids_init,
+	.add               = unique_object_sids_add,
+	.modify            = unique_object_sids_modify,
+};
+
+int ldb_unique_object_sids_init(const char *version)
+{
+	LDB_MODULE_CHECK_VERSION(version);
+	return ldb_register_module(&ldb_unique_object_sids_module_ops);
+}
diff --git a/source4/dsdb/samdb/ldb_modules/wscript_build b/source4/dsdb/samdb/ldb_modules/wscript_build
index 0df5fe03fff..b0afcf9d826 100644
--- a/source4/dsdb/samdb/ldb_modules/wscript_build
+++ b/source4/dsdb/samdb/ldb_modules/wscript_build
@@ -18,5 +18,16 @@ bld.SAMBA_SUBSYSTEM('DSDB_MODULE_HELPER_RIDALLOC',
 	deps='MESSAGING',
 	)
 
+# Build the cmocka unit tests
+bld.SAMBA_BINARY('test_unique_object_sids',
+        source='tests/test_unique_object_sids.c',
+        deps='''
+            talloc
+            samdb
+            cmocka
+            DSDB_MODULE_HELPERS
+        ''',
+        install=False)
+
 if bld.AD_DC_BUILD_IS_ENABLED():
     bld.PROCESS_SEPARATE_RULE("server")
diff --git a/source4/dsdb/samdb/ldb_modules/wscript_build_server b/source4/dsdb/samdb/ldb_modules/wscript_build_server
index 41b3fe70b37..4aac7f2f9f3 100644
--- a/source4/dsdb/samdb/ldb_modules/wscript_build_server
+++ b/source4/dsdb/samdb/ldb_modules/wscript_build_server
@@ -400,3 +400,12 @@ bld.SAMBA_MODULE('ldb_vlv',
 	deps='samdb-common',
 	subsystem='ldb'
 	)
+
+bld.SAMBA_MODULE('ldb_unique_object_sids',
+	'unique_object_sids.c',
+	init_function='ldb_unique_object_sids_init',
+	module_init_name='ldb_init_module',
+	internal_module=False,
+	deps='samdb-common DSDB_MODULE_HELPERS',
+	subsystem='ldb'
+	)