summaryrefslogtreecommitdiff
path: root/source4/dsdb/samdb/ldb_modules/linked_attributes.c
blob: 29f9d0d697f7ed329d9b429c477c190443b7ae3f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
/*
   ldb database library

   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2007
   Copyright (C) Simo Sorce <idra@samba.org> 2008

   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/>.
*/

/*
 *  Name: ldb
 *
 *  Component: ldb linked_attributes module
 *
 *  Description: Module to ensure linked attribute pairs remain in sync
 *
 *  Author: Andrew Bartlett
 */

#include "includes.h"
#include "ldb_module.h"
#include "util/dlinklist.h"
#include "dsdb/samdb/samdb.h"
#include "librpc/gen_ndr/ndr_misc.h"
#include "dsdb/samdb/ldb_modules/util.h"

struct la_private {
	struct la_context *la_list;
};

struct la_op_store {
	struct la_op_store *next;
	struct la_op_store *prev;
	enum la_op {LA_OP_ADD, LA_OP_DEL} op;
	struct GUID guid;
	char *name;
	char *value;
};

struct replace_context {
	struct la_context *ac;
	unsigned int num_elements;
	struct ldb_message_element *el;
};

struct la_context {
	struct la_context *next, *prev;
	const struct dsdb_schema *schema;
	struct ldb_module *module;
	struct ldb_request *req;
	struct ldb_dn *add_dn;
	struct ldb_dn *del_dn;
	struct replace_context *rc;
	struct la_op_store *ops;
	struct ldb_extended *op_response;
	struct ldb_control **op_controls;
};

static struct la_context *linked_attributes_init(struct ldb_module *module,
						 struct ldb_request *req)
{
	struct ldb_context *ldb;
	struct la_context *ac;

	ldb = ldb_module_get_ctx(module);

	ac = talloc_zero(req, struct la_context);
	if (ac == NULL) {
		ldb_oom(ldb);
		return NULL;
	}

	ac->schema = dsdb_get_schema(ldb, ac);
	ac->module = module;
	ac->req = req;

	return ac;
}

/*
  turn a DN into a GUID
 */
static int la_guid_from_dn(struct la_context *ac, struct ldb_dn *dn, struct GUID *guid)
{
	NTSTATUS status;
	int ret;

	status = dsdb_get_extended_dn_guid(dn, guid, "GUID");
	if (NT_STATUS_IS_OK(status)) {
		return LDB_SUCCESS;
	}
	if (!NT_STATUS_EQUAL(status, NT_STATUS_OBJECT_NAME_NOT_FOUND)) {
		DEBUG(4,(__location__ ": Unable to parse GUID for dn %s\n",
			 ldb_dn_get_linearized(dn)));
		return ldb_operr(ldb_module_get_ctx(ac->module));
	}

	ret = dsdb_find_guid_by_dn(ldb_module_get_ctx(ac->module), dn, guid);
	if (ret != LDB_SUCCESS) {
		DEBUG(4,(__location__ ": Failed to find GUID for dn %s\n",
			 ldb_dn_get_linearized(dn)));
		return ret;
	}
	return LDB_SUCCESS;
}


/* Common routine to handle reading the attributes and creating a
 * series of modify requests */
static int la_store_op(struct la_context *ac,
		       enum la_op op, struct ldb_val *dn,
		       const char *name)
{
	struct ldb_context *ldb;
	struct la_op_store *os;
	struct ldb_dn *op_dn;
	int ret;

	ldb = ldb_module_get_ctx(ac->module);

	op_dn = ldb_dn_from_ldb_val(ac, ldb, dn);
	if (!op_dn) {
		ldb_asprintf_errstring(ldb,
				       "could not parse attribute as a DN");
		return LDB_ERR_INVALID_DN_SYNTAX;
	}

	os = talloc_zero(ac, struct la_op_store);
	if (!os) {
		return ldb_oom(ldb);
	}

	os->op = op;

	ret = la_guid_from_dn(ac, op_dn, &os->guid);
	talloc_free(op_dn);
	if (ret == LDB_ERR_NO_SUCH_OBJECT && ac->req->operation == LDB_DELETE) {
		/* we are deleting an object, and we've found it has a
		 * forward link to a target that no longer
		 * exists. This is not an error in the delete, and we
		 * should just not do the deferred delete of the
		 * target attribute
		 */
		talloc_free(os);
		return LDB_SUCCESS;
	}
	if (ret != LDB_SUCCESS) {
		return ret;
	}

	os->name = talloc_strdup(os, name);
	if (!os->name) {
		return ldb_oom(ldb);
	}

	/* Do deletes before adds */
	if (op == LA_OP_ADD) {
		DLIST_ADD_END(ac->ops, os, struct la_op_store *);
	} else {
		/* By adding to the head of the list, we do deletes before
		 * adds when processing a replace */
		DLIST_ADD(ac->ops, os);
	}

	return LDB_SUCCESS;
}

static int la_queue_mod_request(struct la_context *ac);
static int la_down_req(struct la_context *ac);



/* add */
static int linked_attributes_add(struct ldb_module *module, struct ldb_request *req)
{
	struct ldb_context *ldb;
	const struct dsdb_attribute *target_attr;
	struct la_context *ac;
	const char *attr_name;
	struct ldb_control *ctrl;
	unsigned int i, j;
	int ret;

	ldb = ldb_module_get_ctx(module);

	if (ldb_dn_is_special(req->op.add.message->dn)) {
		/* do not manipulate our control entries */
		return ldb_next_request(module, req);
	}

	if (!(ctrl = ldb_request_get_control(req, DSDB_CONTROL_APPLY_LINKS))) {
		/* don't do anything special for linked attributes, repl_meta_data has done it */
		return ldb_next_request(module, req);
	}
	ctrl->critical = false;

	ac = linked_attributes_init(module, req);
	if (!ac) {
		return ldb_operr(ldb);
	}

	if (!ac->schema) {
		/* without schema, this doesn't make any sense */
		talloc_free(ac);
		return ldb_next_request(module, req);
	}

	/* Need to ensure we only have forward links being specified */
	for (i=0; i < req->op.add.message->num_elements; i++) {
		const struct ldb_message_element *el = &req->op.add.message->elements[i];
		const struct dsdb_attribute *schema_attr
			= dsdb_attribute_by_lDAPDisplayName(ac->schema, el->name);
		if (!schema_attr) {
			ldb_asprintf_errstring(ldb,
					       "attribute %s is not a valid attribute in schema", el->name);
			return LDB_ERR_OBJECT_CLASS_VIOLATION;
		}
		/* We have a valid attribute, now find out if it is a forward link */
		if ((schema_attr->linkID == 0)) {
			continue;
		}

		if ((schema_attr->linkID & 1) == 1) {
			unsigned int functional_level;

			functional_level = dsdb_functional_level(ldb);
			SMB_ASSERT(functional_level > DS_DOMAIN_FUNCTION_2000);
		}

		/* Even link IDs are for the originating attribute */
		target_attr = dsdb_attribute_by_linkID(ac->schema, schema_attr->linkID + 1);
		if (!target_attr) {
			/*
			 * windows 2003 has a broken schema where
			 * the definition of msDS-IsDomainFor
			 * is missing (which is supposed to be
			 * the backlink of the msDS-HasDomainNCs
			 * attribute
			 */
			continue;
		}

		attr_name = target_attr->lDAPDisplayName;

		for (j = 0; j < el->num_values; j++) {
			ret = la_store_op(ac, LA_OP_ADD,
					  &el->values[j],
					  attr_name);
			if (ret != LDB_SUCCESS) {
				return ret;
			}
		}
	}

	/* if no linked attributes are present continue */
	if (ac->ops == NULL) {
		/* nothing to do for this module, proceed */
		talloc_free(ac);
		return ldb_next_request(module, req);
	}

	/* start with the original request */
	return la_down_req(ac);
}

/* For a delete or rename, we need to find out what linked attributes
 * are currently on this DN, and then deal with them.  This is the
 * callback to the base search */

static int la_mod_search_callback(struct ldb_request *req, struct ldb_reply *ares)
{
	struct ldb_context *ldb;
	const struct dsdb_attribute *schema_attr;
	const struct dsdb_attribute *target_attr;
	struct ldb_message_element *search_el;
	struct replace_context *rc;
	struct la_context *ac;
	const char *attr_name;
	unsigned int i, j;
	int ret = LDB_SUCCESS;

	ac = talloc_get_type(req->context, struct la_context);
	ldb = ldb_module_get_ctx(ac->module);
	rc = ac->rc;

	if (!ares) {
		return ldb_module_done(ac->req, NULL, NULL,
					LDB_ERR_OPERATIONS_ERROR);
	}
	if (ares->error != LDB_SUCCESS) {
		return ldb_module_done(ac->req, ares->controls,
					ares->response, ares->error);
	}

	/* Only entries are interesting, and we only want the olddn */
	switch (ares->type) {
	case LDB_REPLY_ENTRY:

		if (ldb_dn_compare(ares->message->dn, ac->req->op.mod.message->dn) != 0) {
			ldb_asprintf_errstring(ldb,
					       "linked_attributes: %s is not the DN we were looking for",
					       ldb_dn_get_linearized(ares->message->dn));
			/* Guh?  We only asked for this DN */
			talloc_free(ares);
			return ldb_module_done(ac->req, NULL, NULL,
						LDB_ERR_OPERATIONS_ERROR);
		}

		ac->add_dn = ac->del_dn = talloc_steal(ac, ares->message->dn);

		/* We don't populate 'rc' for ADD - it can't be deleting elements anyway */
		for (i = 0; rc && i < rc->num_elements; i++) {

			schema_attr = dsdb_attribute_by_lDAPDisplayName(ac->schema, rc->el[i].name);
			if (!schema_attr) {
				ldb_asprintf_errstring(ldb,
					"attribute %s is not a valid attribute in schema",
					rc->el[i].name);
				talloc_free(ares);
				return ldb_module_done(ac->req, NULL, NULL,
						LDB_ERR_OBJECT_CLASS_VIOLATION);
			}

			search_el = ldb_msg_find_element(ares->message,
							 rc->el[i].name);

			/* See if this element already exists */
			/* otherwise just ignore as
			 * the add has already been scheduled */
			if ( ! search_el) {
				continue;
			}

			target_attr = dsdb_attribute_by_linkID(ac->schema, schema_attr->linkID + 1);
			if (!target_attr) {
				/*
				 * windows 2003 has a broken schema where
				 * the definition of msDS-IsDomainFor
				 * is missing (which is supposed to be
				 * the backlink of the msDS-HasDomainNCs
				 * attribute
				 */
				continue;
			}
			attr_name = target_attr->lDAPDisplayName;

			/* Now we know what was there, we can remove it for the re-add */
			for (j = 0; j < search_el->num_values; j++) {
				ret = la_store_op(ac, LA_OP_DEL,
						  &search_el->values[j],
						  attr_name);
				if (ret != LDB_SUCCESS) {
					talloc_free(ares);
					return ldb_module_done(ac->req,
							       NULL, NULL, ret);
				}
			}
		}

		break;

	case LDB_REPLY_REFERRAL:
		/* ignore */
		break;

	case LDB_REPLY_DONE:

		talloc_free(ares);

		if (ac->req->operation == LDB_ADD) {
			/* Start the modifies to the backlinks */
			ret = la_queue_mod_request(ac);

			if (ret != LDB_SUCCESS) {
				return ldb_module_done(ac->req, NULL, NULL,
						       ret);
			}
		} else {
			/* Start with the original request */
			ret = la_down_req(ac);
			if (ret != LDB_SUCCESS) {
				return ldb_module_done(ac->req, NULL, NULL, ret);
			}
		}
		return LDB_SUCCESS;
	}

	talloc_free(ares);
	return ret;
}


/* modify */
static int linked_attributes_modify(struct ldb_module *module, struct ldb_request *req)
{
	/* Look over list of modifications */
	/* Find if any are for linked attributes */
	/* Determine the effect of the modification */
	/* Apply the modify to the linked entry */

	struct ldb_context *ldb;
	unsigned int i, j;
	struct la_context *ac;
	struct ldb_request *search_req;
	const char **attrs;
	struct ldb_control *ctrl;
	int ret;

	ldb = ldb_module_get_ctx(module);

	if (ldb_dn_is_special(req->op.mod.message->dn)) {
		/* do not manipulate our control entries */
		return ldb_next_request(module, req);
	}

	if (!(ctrl = ldb_request_get_control(req, DSDB_CONTROL_APPLY_LINKS))) {
		/* don't do anything special for linked attributes, repl_meta_data has done it */
		return ldb_next_request(module, req);
	}
	ctrl->critical = false;

	ac = linked_attributes_init(module, req);
	if (!ac) {
		return ldb_operr(ldb);
	}

	if (!ac->schema) {
		/* without schema, this doesn't make any sense */
		return ldb_next_request(module, req);
	}

	ac->rc = talloc_zero(ac, struct replace_context);
	if (!ac->rc) {
		return ldb_oom(ldb);
	}

	for (i=0; i < req->op.mod.message->num_elements; i++) {
		bool store_el = false;
		const char *attr_name;
		const struct dsdb_attribute *target_attr;
		const struct ldb_message_element *el = &req->op.mod.message->elements[i];
		const struct dsdb_attribute *schema_attr
			= dsdb_attribute_by_lDAPDisplayName(ac->schema, el->name);
		if (!schema_attr) {
			ldb_asprintf_errstring(ldb,
					       "attribute %s is not a valid attribute in schema", el->name);
			return LDB_ERR_OBJECT_CLASS_VIOLATION;
		}
		/* We have a valid attribute, now find out if it is a forward link
		   (Even link IDs are for the originating attribute) */
		if (schema_attr->linkID == 0) {
			continue;
		}

		if ((schema_attr->linkID & 1) == 1) {
			unsigned int functional_level;

			functional_level = dsdb_functional_level(ldb);
			SMB_ASSERT(functional_level > DS_DOMAIN_FUNCTION_2000);
		}
		/* Now find the target attribute */
		target_attr = dsdb_attribute_by_linkID(ac->schema, schema_attr->linkID + 1);
		if (!target_attr) {
			/*
			 * windows 2003 has a broken schema where
			 * the definition of msDS-IsDomainFor
			 * is missing (which is supposed to be
			 * the backlink of the msDS-HasDomainNCs
			 * attribute
			 */
			continue;
		}

		attr_name = target_attr->lDAPDisplayName;

		switch (el->flags & LDB_FLAG_MOD_MASK) {
		case LDB_FLAG_MOD_REPLACE:
			/* treat as just a normal add the delete part is handled by the callback */
			store_el = true;

			/* break intentionally missing */

		case LDB_FLAG_MOD_ADD:

			/* For each value being added, we need to setup the adds */
			for (j = 0; j < el->num_values; j++) {
				ret = la_store_op(ac, LA_OP_ADD,
						  &el->values[j],
						  attr_name);
				if (ret != LDB_SUCCESS) {
					return ret;
				}
			}
			break;

		case LDB_FLAG_MOD_DELETE:

			if (el->num_values) {
				/* For each value being deleted, we need to setup the delete */
				for (j = 0; j < el->num_values; j++) {
					ret = la_store_op(ac, LA_OP_DEL,
							  &el->values[j],
							  attr_name);
					if (ret != LDB_SUCCESS) {
						return ret;
					}
				}
			} else {
				/* Flag that there was a DELETE
				 * without a value specified, so we
				 * need to look for the old value */
				store_el = true;
			}

			break;
		}

		if (store_el) {
			struct ldb_message_element *search_el;

			search_el = talloc_realloc(ac->rc, ac->rc->el,
						   struct ldb_message_element,
						   ac->rc->num_elements +1);
			if (!search_el) {
				return ldb_oom(ldb);
			}
			ac->rc->el = search_el;

			ac->rc->el[ac->rc->num_elements] = *el;
			ac->rc->num_elements++;
		}
	}

	if (ac->ops || ac->rc->el) {
		/* both replace and delete without values are handled in the callback
		 * after the search on the entry to be modified is performed */

		attrs = talloc_array(ac->rc, const char *, ac->rc->num_elements + 1);
		if (!attrs) {
			return ldb_oom(ldb);
		}
		for (i = 0; ac->rc && i < ac->rc->num_elements; i++) {
			attrs[i] = ac->rc->el[i].name;
		}
		attrs[i] = NULL;

		/* The callback does all the hard work here */
		ret = ldb_build_search_req(&search_req, ldb, ac,
					   req->op.mod.message->dn,
					   LDB_SCOPE_BASE,
					   "(objectClass=*)", attrs,
					   NULL,
					   ac, la_mod_search_callback,
					   req);

		/* We need to figure out our own extended DN, to fill in as the backlink target */
		if (ret == LDB_SUCCESS) {
			ret = ldb_request_add_control(search_req,
						      LDB_CONTROL_EXTENDED_DN_OID,
						      false, NULL);
		}
		if (ret == LDB_SUCCESS) {
			talloc_steal(search_req, attrs);

			ret = ldb_next_request(module, search_req);
		}

	} else {
		/* nothing to do for this module, proceed */
		talloc_free(ac);
		ret = ldb_next_request(module, req);
	}

	return ret;
}

static int linked_attributes_fix_links(struct ldb_module *module,
				       struct ldb_dn *old_dn, struct ldb_dn *new_dn,
				       struct ldb_message_element *el, struct dsdb_schema *schema,
				       const struct dsdb_attribute *schema_attr)
{
	unsigned int i, j;
	TALLOC_CTX *tmp_ctx = talloc_new(module);
	struct ldb_context *ldb = ldb_module_get_ctx(module);
	const struct dsdb_attribute *target;
	const char *attrs[2];
	int ret;

	target = dsdb_attribute_by_linkID(schema, schema_attr->linkID ^ 1);
	if (target == NULL) {
		/* there is no counterpart link to change */
		return LDB_SUCCESS;
	}

	attrs[0] = target->lDAPDisplayName;
	attrs[1] = NULL;

	for (i=0; i<el->num_values; i++) {
		struct dsdb_dn *dsdb_dn;
		struct ldb_result *res;
		struct ldb_message *msg;
		struct ldb_message_element *el2;

		dsdb_dn = dsdb_dn_parse(tmp_ctx, ldb, &el->values[i], schema_attr->syntax->ldap_oid);
		if (dsdb_dn == NULL) {
			talloc_free(tmp_ctx);
			return LDB_ERR_INVALID_DN_SYNTAX;
		}

		ret = dsdb_module_search_dn(module, tmp_ctx, &res, dsdb_dn->dn,
					    attrs,
					    DSDB_FLAG_NEXT_MODULE |
					    DSDB_SEARCH_SHOW_DELETED |
					    DSDB_SEARCH_SHOW_DN_IN_STORAGE_FORMAT |
					    DSDB_SEARCH_REVEAL_INTERNALS);
		if (ret != LDB_SUCCESS) {
			ldb_asprintf_errstring(ldb, "Linked attribute %s->%s between %s and %s - remote not found - %s",
					       el->name, target->lDAPDisplayName,
					       ldb_dn_get_linearized(old_dn),
					       ldb_dn_get_linearized(dsdb_dn->dn),
					       ldb_errstring(ldb));
			talloc_free(tmp_ctx);
			return ret;
		}
		msg = res->msgs[0];

		if (msg->num_elements == 0) {
			/* Forward link without backlink remaining - nothing to do here */
			continue;
		} else if (msg->num_elements != 1) {
			ldb_asprintf_errstring(ldb, "Bad msg elements - got %u elements, expected one element to be returned in linked_attributes_fix_links for %s",
					       msg->num_elements, ldb_dn_get_linearized(msg->dn));
			talloc_free(tmp_ctx);
			return LDB_ERR_OPERATIONS_ERROR;
		}
		if (ldb_attr_cmp(msg->elements[0].name, target->lDAPDisplayName) != 0) {
			ldb_asprintf_errstring(ldb, "Bad returned attribute in linked_attributes_fix_links: got %s, expected %s for %s", msg->elements[0].name, target->lDAPDisplayName, ldb_dn_get_linearized(msg->dn));
			talloc_free(tmp_ctx);
			return LDB_ERR_OPERATIONS_ERROR;
		}
		el2 = &msg->elements[0];

		el2->flags = LDB_FLAG_MOD_REPLACE;

		/* find our DN in the values */
		for (j=0; j<el2->num_values; j++) {
			struct dsdb_dn *dsdb_dn2;
			dsdb_dn2 = dsdb_dn_parse(msg, ldb, &el2->values[j], target->syntax->ldap_oid);
			if (dsdb_dn2 == NULL) {
				talloc_free(tmp_ctx);
				return LDB_ERR_INVALID_DN_SYNTAX;
			}
			if (ldb_dn_compare(old_dn, dsdb_dn2->dn) != 0) {
				continue;
			}
			ret = ldb_dn_update_components(dsdb_dn2->dn, new_dn);
			if (ret != LDB_SUCCESS) {
				talloc_free(tmp_ctx);
				return ret;
			}

			el2->values[j] = data_blob_string_const(
				dsdb_dn_get_extended_linearized(el2->values, dsdb_dn2, 1));
		}

		ret = dsdb_check_single_valued_link(target, el2);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}

		ret = dsdb_module_modify(module, msg, DSDB_FLAG_NEXT_MODULE | DSDB_MODIFY_RELAX);
		if (ret != LDB_SUCCESS) {
			ldb_asprintf_errstring(ldb, "Linked attribute %s->%s between %s and %s - update failed - %s",
					       el->name, target->lDAPDisplayName,
					       ldb_dn_get_linearized(old_dn),
					       ldb_dn_get_linearized(dsdb_dn->dn),
					       ldb_errstring(ldb));
			talloc_free(tmp_ctx);
			return ret;
		}
	}

	talloc_free(tmp_ctx);
	return LDB_SUCCESS;
}


/* rename */
static int linked_attributes_rename(struct ldb_module *module, struct ldb_request *req)
{
	struct ldb_result *res;
	struct ldb_message *msg;
	unsigned int i;
	struct ldb_context *ldb = ldb_module_get_ctx(module);
	struct dsdb_schema *schema;
	int ret;
	/*
	   - load the current msg
	   - find any linked attributes
	   - if its a link then find the target object
	   - modify the target linked attributes with the new DN
	*/
	ret = dsdb_module_search_dn(module, req, &res, req->op.rename.olddn,
				    NULL,
				    DSDB_FLAG_NEXT_MODULE |
				    DSDB_SEARCH_SHOW_DELETED);
	if (ret != LDB_SUCCESS) {
		return ret;
	}

	schema = dsdb_get_schema(ldb, res);
	if (!schema) {
		return ldb_oom(ldb);
	}

	msg = res->msgs[0];

	for (i=0; i<msg->num_elements; i++) {
		struct ldb_message_element *el = &msg->elements[i];
		const struct dsdb_attribute *schema_attr
			= dsdb_attribute_by_lDAPDisplayName(schema, el->name);
		if (!schema_attr || schema_attr->linkID == 0) {
			continue;
		}
		ret = linked_attributes_fix_links(module, msg->dn, req->op.rename.newdn, el,
						  schema, schema_attr);
		if (ret != LDB_SUCCESS) {
			talloc_free(res);
			return ret;
		}
	}

	talloc_free(res);

	return ldb_next_request(module, req);
}


/* queue a linked attributes modify request in the la_private
   structure */
static int la_queue_mod_request(struct la_context *ac)
{
	struct la_private *la_private =
		talloc_get_type(ldb_module_get_private(ac->module), struct la_private);

	if (la_private == NULL) {
		ldb_debug(ldb_module_get_ctx(ac->module), LDB_DEBUG_ERROR, __location__ ": No la_private transaction setup\n");
		return ldb_operr(ldb_module_get_ctx(ac->module));
	}

	talloc_steal(la_private, ac);
	DLIST_ADD(la_private->la_list, ac);

	return ldb_module_done(ac->req, ac->op_controls,
			       ac->op_response, LDB_SUCCESS);
}

/* Having done the original operation, then try to fix up all the linked attributes for modify and delete */
static int la_mod_del_callback(struct ldb_request *req, struct ldb_reply *ares)
{
	struct la_context *ac;
	struct ldb_context *ldb;
	int ret;

	ac = talloc_get_type(req->context, struct la_context);
	ldb = ldb_module_get_ctx(ac->module);

	if (!ares) {
		return ldb_module_done(ac->req, NULL, NULL,
					LDB_ERR_OPERATIONS_ERROR);
	}
	if (ares->error != LDB_SUCCESS) {
		return ldb_module_done(ac->req, ares->controls,
					ares->response, ares->error);
	}

	if (ares->type != LDB_REPLY_DONE) {
		ldb_set_errstring(ldb,
				  "invalid ldb_reply_type in callback");
		talloc_free(ares);
		return ldb_module_done(ac->req, NULL, NULL,
					LDB_ERR_OPERATIONS_ERROR);
	}

	ac->op_controls = talloc_steal(ac, ares->controls);
	ac->op_response = talloc_steal(ac, ares->response);

	/* If we have modfies to make, this is the time to do them for modify and delete */
	ret = la_queue_mod_request(ac);

	if (ret != LDB_SUCCESS) {
		return ldb_module_done(ac->req, NULL, NULL, ret);
	}
	talloc_free(ares);

	/* la_queue_mod_request has already sent the callbacks */
	return LDB_SUCCESS;

}

/* Having done the original add, then try to fix up all the linked attributes

  This is done after the add so the links can get the extended DNs correctly.
 */
static int la_add_callback(struct ldb_request *req, struct ldb_reply *ares)
{
	struct la_context *ac;
	struct ldb_context *ldb;
	int ret;

	ac = talloc_get_type(req->context, struct la_context);
	ldb = ldb_module_get_ctx(ac->module);

	if (!ares) {
		return ldb_module_done(ac->req, NULL, NULL,
					LDB_ERR_OPERATIONS_ERROR);
	}
	if (ares->error != LDB_SUCCESS) {
		return ldb_module_done(ac->req, ares->controls,
					ares->response, ares->error);
	}

	if (ares->type != LDB_REPLY_DONE) {
		ldb_set_errstring(ldb,
				  "invalid ldb_reply_type in callback");
		talloc_free(ares);
		return ldb_module_done(ac->req, NULL, NULL,
					LDB_ERR_OPERATIONS_ERROR);
	}

	if (ac->ops) {
		struct ldb_request *search_req;
		static const char *attrs[] = { NULL };

		/* The callback does all the hard work here - we need
		 * the objectGUID and SID of the added record */
		ret = ldb_build_search_req(&search_req, ldb, ac,
					   ac->req->op.add.message->dn,
					   LDB_SCOPE_BASE,
					   "(objectClass=*)", attrs,
					   NULL,
					   ac, la_mod_search_callback,
					   ac->req);

		if (ret == LDB_SUCCESS) {
			ret = ldb_request_add_control(search_req,
						      LDB_CONTROL_EXTENDED_DN_OID,
						      false, NULL);
		}
		if (ret != LDB_SUCCESS) {
			return ldb_module_done(ac->req, NULL, NULL,
					       ret);
		}

		ac->op_controls = talloc_steal(ac, ares->controls);
		ac->op_response = talloc_steal(ac, ares->response);

		return ldb_next_request(ac->module, search_req);

	} else {
		return ldb_module_done(ac->req, ares->controls,
				       ares->response, ares->error);
	}
}

/* Reconstruct the original request, but pointing at our local callback to finish things off */
static int la_down_req(struct la_context *ac)
{
	struct ldb_request *down_req;
	struct ldb_context *ldb;
	int ret;

	ldb = ldb_module_get_ctx(ac->module);

	switch (ac->req->operation) {
	case LDB_ADD:
		ret = ldb_build_add_req(&down_req, ldb, ac,
					ac->req->op.add.message,
					ac->req->controls,
					ac, la_add_callback,
					ac->req);
		break;
	case LDB_MODIFY:
		ret = ldb_build_mod_req(&down_req, ldb, ac,
					ac->req->op.mod.message,
					ac->req->controls,
					ac, la_mod_del_callback,
					ac->req);
		break;
	default:
		ret = LDB_ERR_OPERATIONS_ERROR;
	}
	if (ret != LDB_SUCCESS) {
		return ret;
	}

	return ldb_next_request(ac->module, down_req);
}

/*
  use the GUID part of an extended DN to find the target DN, in case
  it has moved
 */
static int la_find_dn_target(struct ldb_module *module, struct la_context *ac,
			     struct GUID *guid, struct ldb_dn **dn)
{
	return dsdb_find_dn_by_guid(ldb_module_get_ctx(ac->module), ac, guid, dn);
}

/* apply one la_context op change */
static int la_do_op_request(struct ldb_module *module, struct la_context *ac, struct la_op_store *op)
{
	struct ldb_message_element *ret_el;
	struct ldb_message *new_msg;
	struct ldb_context *ldb;
	int ret;

	ldb = ldb_module_get_ctx(ac->module);

	/* Create the modify request */
	new_msg = ldb_msg_new(ac);
	if (!new_msg) {
		return ldb_oom(ldb);
	}

	ret = la_find_dn_target(module, ac, &op->guid, &new_msg->dn);
	if (ret != LDB_SUCCESS) {
		return ret;
	}

	if (op->op == LA_OP_ADD) {
		ret = ldb_msg_add_empty(new_msg, op->name,
					LDB_FLAG_MOD_ADD, &ret_el);
	} else {
		ret = ldb_msg_add_empty(new_msg, op->name,
					LDB_FLAG_MOD_DELETE, &ret_el);
	}
	if (ret != LDB_SUCCESS) {
		return ret;
	}
	ret_el->values = talloc_array(new_msg, struct ldb_val, 1);
	if (!ret_el->values) {
		return ldb_oom(ldb);
	}
	ret_el->num_values = 1;
	if (op->op == LA_OP_ADD) {
		ret_el->values[0] = data_blob_string_const(ldb_dn_get_extended_linearized(new_msg, ac->add_dn, 1));
	} else {
		ret_el->values[0] = data_blob_string_const(ldb_dn_get_extended_linearized(new_msg, ac->del_dn, 1));
	}

#if 0
	ldb_debug(ldb, LDB_DEBUG_WARNING,
		  "link on %s %s: %s %s\n",
		  ldb_dn_get_linearized(new_msg->dn), ret_el->name,
		  ret_el->values[0].data, ac->ops->op == LA_OP_ADD ? "added" : "deleted");
#endif

	if (DEBUGLVL(4)) {
		DEBUG(4,("Applying linked attribute change:\n%s\n",
			 ldb_ldif_message_string(ldb, op, LDB_CHANGETYPE_MODIFY, new_msg)));
	}

	ret = dsdb_module_modify(module, new_msg, DSDB_FLAG_NEXT_MODULE);
	if (ret != LDB_SUCCESS) {
		ldb_debug(ldb, LDB_DEBUG_WARNING, "Failed to apply linked attribute change '%s'\n%s\n",
			  ldb_errstring(ldb),
			  ldb_ldif_message_string(ldb, op, LDB_CHANGETYPE_MODIFY, new_msg));
	}

	return ret;
}

/* apply one set of la_context changes */
static int la_do_mod_request(struct ldb_module *module, struct la_context *ac)
{
	struct la_op_store *op;

	for (op = ac->ops; op; op=op->next) {
		int ret = la_do_op_request(module, ac, op);
		if (ret != LDB_SUCCESS) {
			if (ret != LDB_ERR_NO_SUCH_OBJECT) {
				return ret;
			}
		}
	}

	return LDB_SUCCESS;
}


/*
  we hook into the transaction operations to allow us to
  perform the linked attribute updates at the end of the whole
  transaction. This allows a forward linked attribute to be created
  before the target is created, as long as the target is created
  in the same transaction
 */
static int linked_attributes_start_transaction(struct ldb_module *module)
{
	/* create our private structure for this transaction */
	struct la_private *la_private = talloc_get_type(ldb_module_get_private(module),
							struct la_private);
	talloc_free(la_private);
	la_private = talloc(module, struct la_private);
	if (la_private == NULL) {
		return ldb_oom(ldb_module_get_ctx(module));
	}
	la_private->la_list = NULL;
	ldb_module_set_private(module, la_private);
	return ldb_next_start_trans(module);
}

/*
  on prepare commit we loop over our queued la_context structures
  and apply each of them
 */
static int linked_attributes_prepare_commit(struct ldb_module *module)
{
	struct la_private *la_private =
		talloc_get_type(ldb_module_get_private(module), struct la_private);
	struct la_context *ac;

	if (!la_private) {
		/* prepare commit without begin_transaction - let someone else return the error, just don't segfault */
		return ldb_next_prepare_commit(module);
	}
	/* walk the list backwards, to do the first entry first, as we
	 * added the entries with DLIST_ADD() which puts them at the
	 * start of the list */

	/* Start at the end of the list - so we can start
	 * there, but ensure we don't create a loop by NULLing
	 * it out in the first element */
	ac = DLIST_TAIL(la_private->la_list);

	for (; ac; ac=DLIST_PREV(ac)) {
		int ret;
		ac->req = NULL;
		ret = la_do_mod_request(module, ac);
		if (ret != LDB_SUCCESS) {
			DEBUG(0,(__location__ ": Failed mod request ret=%d\n", ret));
			talloc_free(la_private);
			ldb_module_set_private(module, NULL);
			return ret;
		}
	}

	talloc_free(la_private);
	ldb_module_set_private(module, NULL);

	return ldb_next_prepare_commit(module);
}

static int linked_attributes_del_transaction(struct ldb_module *module)
{
	struct la_private *la_private =
		talloc_get_type(ldb_module_get_private(module), struct la_private);
	talloc_free(la_private);
	ldb_module_set_private(module, NULL);
	return ldb_next_del_trans(module);
}


_PUBLIC_ const struct ldb_module_ops ldb_linked_attributes_module_ops = {
	.name		   = "linked_attributes",
	.add               = linked_attributes_add,
	.modify            = linked_attributes_modify,
	.rename            = linked_attributes_rename,
	.start_transaction = linked_attributes_start_transaction,
	.prepare_commit    = linked_attributes_prepare_commit,
	.del_transaction   = linked_attributes_del_transaction,
};