summaryrefslogtreecommitdiff
path: root/source3/librpc/crypto/gse.c
blob: fba942bd6407b902ee65ab226139da805987961d (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
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
/*
 *  GSSAPI Security Extensions
 *  RPC Pipe client and server routines
 *  Copyright (C) Simo Sorce 2010.
 *  Copyright (C) Andrew Bartlett 2004-2011.
 *  Copyright (C) Stefan Metzmacher <metze@samba.org> 2004-2005
 *
 *  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/>.
 */

/* We support only GSSAPI/KRB5 here */

#include "includes.h"
#include "gse.h"
#include "libads/kerberos_proto.h"
#include "auth/common_auth.h"
#include "auth/gensec/gensec.h"
#include "auth/credentials/credentials.h"
#include "../librpc/gen_ndr/dcerpc.h"

#if defined(HAVE_KRB5)

#include "auth/kerberos/pac_utils.h"
#include "gse_krb5.h"

static char *gse_errstr(TALLOC_CTX *mem_ctx, OM_uint32 maj, OM_uint32 min);

struct gse_context {
	gss_ctx_id_t gssapi_context;
	gss_name_t server_name;
	gss_name_t client_name;
	OM_uint32 gss_want_flags, gss_got_flags;

	gss_cred_id_t delegated_cred_handle;

	NTTIME expire_time;

	/* gensec_gse only */
	krb5_context k5ctx;
	krb5_ccache ccache;
	krb5_keytab keytab;

	gss_OID_desc gss_mech;
	gss_cred_id_t creds;

	gss_OID ret_mech;
};

#ifndef HAVE_GSS_OID_EQUAL

static bool gss_oid_equal(const gss_OID o1, const gss_OID o2)
{
	if (o1 == o2) {
		return true;
	}
	if ((o1 == NULL && o2 != NULL) || (o1 != NULL && o2 == NULL)) {
		return false;
	}
	if (o1->length != o2->length) {
		return false;
	}
	return memcmp(o1->elements, o2->elements, o1->length) == false;
}

#endif

/* free non talloc dependent contexts */
static int gse_context_destructor(void *ptr)
{
	struct gse_context *gse_ctx;
	OM_uint32 gss_min;

	gse_ctx = talloc_get_type_abort(ptr, struct gse_context);
	if (gse_ctx->k5ctx) {
		if (gse_ctx->ccache) {
			krb5_cc_close(gse_ctx->k5ctx, gse_ctx->ccache);
			gse_ctx->ccache = NULL;
		}
		if (gse_ctx->keytab) {
			krb5_kt_close(gse_ctx->k5ctx, gse_ctx->keytab);
			gse_ctx->keytab = NULL;
		}
		krb5_free_context(gse_ctx->k5ctx);
		gse_ctx->k5ctx = NULL;
	}
	if (gse_ctx->gssapi_context != GSS_C_NO_CONTEXT) {
		(void)gss_delete_sec_context(&gss_min,
						 &gse_ctx->gssapi_context,
						 GSS_C_NO_BUFFER);
	}
	if (gse_ctx->server_name) {
		(void)gss_release_name(&gss_min,
					   &gse_ctx->server_name);
	}
	if (gse_ctx->client_name) {
		(void)gss_release_name(&gss_min,
					   &gse_ctx->client_name);
	}
	if (gse_ctx->creds) {
		(void)gss_release_cred(&gss_min,
					   &gse_ctx->creds);
	}
	if (gse_ctx->delegated_cred_handle) {
		(void)gss_release_cred(&gss_min,
					   &gse_ctx->delegated_cred_handle);
	}

	/* MIT and Heimdal differ as to if you can call
	 * gss_release_oid() on this OID, generated by
	 * gss_{accept,init}_sec_context().  However, as long as the
	 * oid is gss_mech_krb5 (which it always is at the moment),
	 * then this is a moot point, as both declare this particular
	 * OID static, and so no memory is lost.  This assert is in
	 * place to ensure that the programmer who wishes to extend
	 * this code to EAP or other GSS mechanisms determines an
	 * implementation-dependent way of releasing any dynamically
	 * allocated OID */
	SMB_ASSERT(gss_oid_equal(&gse_ctx->gss_mech, GSS_C_NO_OID) || gss_oid_equal(&gse_ctx->gss_mech, gss_mech_krb5));

	return 0;
}

static NTSTATUS gse_context_init(TALLOC_CTX *mem_ctx,
				 bool do_sign, bool do_seal,
				 const char *ccache_name,
				 uint32_t add_gss_c_flags,
				 struct gse_context **_gse_ctx)
{
	struct gse_context *gse_ctx;
	krb5_error_code k5ret;
	NTSTATUS status;

	gse_ctx = talloc_zero(mem_ctx, struct gse_context);
	if (!gse_ctx) {
		return NT_STATUS_NO_MEMORY;
	}
	talloc_set_destructor((TALLOC_CTX *)gse_ctx, gse_context_destructor);

	gse_ctx->expire_time = GENSEC_EXPIRE_TIME_INFINITY;

	memcpy(&gse_ctx->gss_mech, gss_mech_krb5, sizeof(gss_OID_desc));

	gse_ctx->gss_want_flags = GSS_C_MUTUAL_FLAG |
				GSS_C_DELEG_FLAG |
				GSS_C_DELEG_POLICY_FLAG |
				GSS_C_REPLAY_FLAG |
				GSS_C_SEQUENCE_FLAG;
	if (do_sign) {
		gse_ctx->gss_want_flags |= GSS_C_INTEG_FLAG;
	}
	if (do_seal) {
		gse_ctx->gss_want_flags |= GSS_C_INTEG_FLAG;
		gse_ctx->gss_want_flags |= GSS_C_CONF_FLAG;
	}

	gse_ctx->gss_want_flags |= add_gss_c_flags;

	/* Initialize Kerberos Context */
	initialize_krb5_error_table();

	k5ret = krb5_init_context(&gse_ctx->k5ctx);
	if (k5ret) {
		DEBUG(0, ("Failed to initialize kerberos context! (%s)\n",
			  error_message(k5ret)));
		status = NT_STATUS_INTERNAL_ERROR;
		goto err_out;
	}

	if (!ccache_name) {
		ccache_name = krb5_cc_default_name(gse_ctx->k5ctx);
	}
	k5ret = krb5_cc_resolve(gse_ctx->k5ctx, ccache_name,
				&gse_ctx->ccache);
	if (k5ret) {
		DEBUG(1, ("Failed to resolve credential cache! (%s)\n",
			  error_message(k5ret)));
		status = NT_STATUS_INTERNAL_ERROR;
		goto err_out;
	}

	/* TODO: Should we enforce a enc_types list ?
	ret = krb5_set_default_tgs_ktypes(gse_ctx->k5ctx, enc_types);
	*/

	*_gse_ctx = gse_ctx;
	return NT_STATUS_OK;

err_out:
	TALLOC_FREE(gse_ctx);
	return status;
}

static NTSTATUS gse_init_client(TALLOC_CTX *mem_ctx,
				bool do_sign, bool do_seal,
				const char *ccache_name,
				const char *server,
				const char *service,
				const char *username,
				const char *password,
				uint32_t add_gss_c_flags,
				struct gse_context **_gse_ctx)
{
	struct gse_context *gse_ctx;
	OM_uint32 gss_maj, gss_min;
	gss_buffer_desc name_buffer = {0, NULL};
	gss_OID_set_desc mech_set;
	NTSTATUS status;

	if (!server || !service) {
		return NT_STATUS_INVALID_PARAMETER;
	}

	status = gse_context_init(mem_ctx, do_sign, do_seal,
				  ccache_name, add_gss_c_flags,
				  &gse_ctx);
	if (!NT_STATUS_IS_OK(status)) {
		return NT_STATUS_NO_MEMORY;
	}

	/* Guess the realm based on the supplied service, and avoid the GSS libs
	   doing DNS lookups which may fail.

	   TODO: Loop with the KDC on some more combinations (local
	   realm in particular), possibly falling back to
	   GSS_C_NT_HOSTBASED_SERVICE
	*/
	name_buffer.value = kerberos_get_principal_from_service_hostname(
					gse_ctx, service, server, lp_realm());
	if (!name_buffer.value) {
		status = NT_STATUS_NO_MEMORY;
		goto err_out;
	}
	name_buffer.length = strlen((char *)name_buffer.value);
	gss_maj = gss_import_name(&gss_min, &name_buffer,
				  GSS_C_NT_USER_NAME,
				  &gse_ctx->server_name);
	if (gss_maj) {
		DEBUG(0, ("gss_import_name failed for %s, with [%s]\n",
			  (char *)name_buffer.value,
			  gse_errstr(gse_ctx, gss_maj, gss_min)));
		status = NT_STATUS_INTERNAL_ERROR;
		goto err_out;
	}

	/* TODO: get krb5 ticket using username/password, if no valid
	 * one already available in ccache */

	mech_set.count = 1;
	mech_set.elements = &gse_ctx->gss_mech;

	gss_maj = gss_acquire_cred(&gss_min,
				   GSS_C_NO_NAME,
				   GSS_C_INDEFINITE,
				   &mech_set,
				   GSS_C_INITIATE,
				   &gse_ctx->creds,
				   NULL, NULL);
	if (gss_maj) {
		DEBUG(0, ("gss_acquire_creds failed for %s, with [%s]\n",
			  (char *)name_buffer.value,
			  gse_errstr(gse_ctx, gss_maj, gss_min)));
		status = NT_STATUS_INTERNAL_ERROR;
		goto err_out;
	}

	*_gse_ctx = gse_ctx;
	TALLOC_FREE(name_buffer.value);
	return NT_STATUS_OK;

err_out:
	TALLOC_FREE(name_buffer.value);
	TALLOC_FREE(gse_ctx);
	return status;
}

static NTSTATUS gse_get_client_auth_token(TALLOC_CTX *mem_ctx,
					  struct gse_context *gse_ctx,
					  const DATA_BLOB *token_in,
					  DATA_BLOB *token_out)
{
	OM_uint32 gss_maj, gss_min;
	gss_buffer_desc in_data;
	gss_buffer_desc out_data;
	DATA_BLOB blob = data_blob_null;
	NTSTATUS status;
	OM_uint32 time_rec = 0;
	struct timeval tv;

	in_data.value = token_in->data;
	in_data.length = token_in->length;

	gss_maj = gss_init_sec_context(&gss_min,
					gse_ctx->creds,
					&gse_ctx->gssapi_context,
					gse_ctx->server_name,
					&gse_ctx->gss_mech,
					gse_ctx->gss_want_flags,
					0, GSS_C_NO_CHANNEL_BINDINGS,
					&in_data, NULL, &out_data,
					&gse_ctx->gss_got_flags, &time_rec);
	switch (gss_maj) {
	case GSS_S_COMPLETE:
		/* we are done with it */
		tv = timeval_current_ofs(time_rec, 0);
		gse_ctx->expire_time = timeval_to_nttime(&tv);

		status = NT_STATUS_OK;
		break;
	case GSS_S_CONTINUE_NEEDED:
		/* we will need a third leg */
		status = NT_STATUS_MORE_PROCESSING_REQUIRED;
		break;
	default:
		DEBUG(0, ("gss_init_sec_context failed with [%s]\n",
			  gse_errstr(talloc_tos(), gss_maj, gss_min)));
		status = NT_STATUS_INTERNAL_ERROR;
		goto done;
	}

	/* we may be told to return nothing */
	if (out_data.length) {
		blob = data_blob_talloc(mem_ctx, out_data.value, out_data.length);
		if (!blob.data) {
			status = NT_STATUS_NO_MEMORY;
		}

		gss_maj = gss_release_buffer(&gss_min, &out_data);
	}

done:
	*token_out = blob;
	return status;
}

static NTSTATUS gse_init_server(TALLOC_CTX *mem_ctx,
				bool do_sign, bool do_seal,
				uint32_t add_gss_c_flags,
				struct gse_context **_gse_ctx)
{
	struct gse_context *gse_ctx;
	OM_uint32 gss_maj, gss_min;
	krb5_error_code ret;
	NTSTATUS status;

	status = gse_context_init(mem_ctx, do_sign, do_seal,
				  NULL, add_gss_c_flags, &gse_ctx);
	if (!NT_STATUS_IS_OK(status)) {
		return NT_STATUS_NO_MEMORY;
	}

	ret = gse_krb5_get_server_keytab(gse_ctx->k5ctx,
					 &gse_ctx->keytab);
	if (ret) {
		status = NT_STATUS_INTERNAL_ERROR;
		goto done;
	}

#ifdef HAVE_GSS_KRB5_IMPORT_CRED

	/* This creates a GSSAPI cred_id_t with the keytab set */
	gss_maj = gss_krb5_import_cred(&gss_min, NULL, NULL, gse_ctx->keytab, 
				       &gse_ctx->creds);

	if (gss_maj != 0
	    && gss_maj != (GSS_S_CALL_BAD_STRUCTURE|GSS_S_BAD_NAME)) {
		DEBUG(0, ("gss_krb5_import_cred failed with [%s]\n",
			  gse_errstr(gse_ctx, gss_maj, gss_min)));
		status = NT_STATUS_INTERNAL_ERROR;
		goto done;

		/* This is the error the MIT krb5 1.9 gives when it
		 * implements the function, but we do not specify the
		 * principal.  However, when we specify the principal
		 * as host$@REALM the GSS acceptor fails with 'wrong
		 * principal in request'.  Work around the issue by
		 * falling back to the alternate approach below. */
	} else if (gss_maj == (GSS_S_CALL_BAD_STRUCTURE|GSS_S_BAD_NAME))
#endif
	/* FIXME!!!
	 * This call sets the default keytab for the whole server, not
	 * just for this context. Need to find a way that does not alter
	 * the state of the whole server ... */
	{
		const char *ktname;
		gss_OID_set_desc mech_set;

		ret = smb_krb5_keytab_name(gse_ctx, gse_ctx->k5ctx,
				   gse_ctx->keytab, &ktname);
		if (ret) {
			status = NT_STATUS_INTERNAL_ERROR;
			goto done;
		}

		ret = gsskrb5_register_acceptor_identity(ktname);
		if (ret) {
			status = NT_STATUS_INTERNAL_ERROR;
			goto done;
		}

		mech_set.count = 1;
		mech_set.elements = &gse_ctx->gss_mech;

		gss_maj = gss_acquire_cred(&gss_min,
				   GSS_C_NO_NAME,
				   GSS_C_INDEFINITE,
				   &mech_set,
				   GSS_C_ACCEPT,
				   &gse_ctx->creds,
				   NULL, NULL);

		if (gss_maj) {
			DEBUG(0, ("gss_acquire_creds failed with [%s]\n",
				  gse_errstr(gse_ctx, gss_maj, gss_min)));
			status = NT_STATUS_INTERNAL_ERROR;
			goto done;
		}
	}

	status = NT_STATUS_OK;

done:
	if (!NT_STATUS_IS_OK(status)) {
		TALLOC_FREE(gse_ctx);
	}

	*_gse_ctx = gse_ctx;
	return status;
}

static NTSTATUS gse_get_server_auth_token(TALLOC_CTX *mem_ctx,
					  struct gse_context *gse_ctx,
					  const DATA_BLOB *token_in,
					  DATA_BLOB *token_out)
{
	OM_uint32 gss_maj, gss_min;
	gss_buffer_desc in_data;
	gss_buffer_desc out_data;
	DATA_BLOB blob = data_blob_null;
	NTSTATUS status;
	OM_uint32 time_rec = 0;
	struct timeval tv;

	in_data.value = token_in->data;
	in_data.length = token_in->length;

	gss_maj = gss_accept_sec_context(&gss_min,
					 &gse_ctx->gssapi_context,
					 gse_ctx->creds,
					 &in_data,
					 GSS_C_NO_CHANNEL_BINDINGS,
					 &gse_ctx->client_name,
					 &gse_ctx->ret_mech,
					 &out_data,
					 &gse_ctx->gss_got_flags,
					 &time_rec,
					 &gse_ctx->delegated_cred_handle);
	switch (gss_maj) {
	case GSS_S_COMPLETE:
		/* we are done with it */
		tv = timeval_current_ofs(time_rec, 0);
		gse_ctx->expire_time = timeval_to_nttime(&tv);

		status = NT_STATUS_OK;
		break;
	case GSS_S_CONTINUE_NEEDED:
		/* we will need a third leg */
		status = NT_STATUS_MORE_PROCESSING_REQUIRED;
		break;
	default:
		DEBUG(1, ("gss_accept_sec_context failed with [%s]\n",
			  gse_errstr(talloc_tos(), gss_maj, gss_min)));

		if (gse_ctx->gssapi_context) {
			gss_delete_sec_context(&gss_min,
						&gse_ctx->gssapi_context,
						GSS_C_NO_BUFFER);
		}

		status = NT_STATUS_LOGON_FAILURE;
		goto done;
	}

	/* we may be told to return nothing */
	if (out_data.length) {
		blob = data_blob_talloc(mem_ctx, out_data.value, out_data.length);
		if (!blob.data) {
			status = NT_STATUS_NO_MEMORY;
		}
		gss_maj = gss_release_buffer(&gss_min, &out_data);
	}


done:
	*token_out = blob;
	return status;
}

static char *gse_errstr(TALLOC_CTX *mem_ctx, OM_uint32 maj, OM_uint32 min)
{
	OM_uint32 gss_min, gss_maj;
	gss_buffer_desc msg_min;
	gss_buffer_desc msg_maj;
	OM_uint32 msg_ctx = 0;

	char *errstr = NULL;

	ZERO_STRUCT(msg_min);
	ZERO_STRUCT(msg_maj);

	gss_maj = gss_display_status(&gss_min, maj, GSS_C_GSS_CODE,
				     GSS_C_NO_OID, &msg_ctx, &msg_maj);
	if (gss_maj) {
		goto done;
	}
	errstr = talloc_strndup(mem_ctx,
				(char *)msg_maj.value,
					msg_maj.length);
	if (!errstr) {
		goto done;
	}
	gss_maj = gss_display_status(&gss_min, min, GSS_C_MECH_CODE,
				     (gss_OID)discard_const(gss_mech_krb5),
				     &msg_ctx, &msg_min);
	if (gss_maj) {
		goto done;
	}

	errstr = talloc_strdup_append_buffer(errstr, ": ");
	if (!errstr) {
		goto done;
	}
	errstr = talloc_strndup_append_buffer(errstr,
						(char *)msg_min.value,
							msg_min.length);
	if (!errstr) {
		goto done;
	}

done:
	if (msg_min.value) {
		gss_maj = gss_release_buffer(&gss_min, &msg_min);
	}
	if (msg_maj.value) {
		gss_maj = gss_release_buffer(&gss_min, &msg_maj);
	}
	return errstr;
}

static size_t gse_get_signature_length(struct gse_context *gse_ctx,
				       bool seal, size_t payload_size)
{
	OM_uint32 gss_min, gss_maj;
	gss_iov_buffer_desc iov[2];
	int sealed;

	/*
	 * gss_wrap_iov_length() only needs the type and length
	 */
	iov[0].type = GSS_IOV_BUFFER_TYPE_HEADER;
	iov[0].buffer.value = NULL;
	iov[0].buffer.length = 0;
	iov[1].type = GSS_IOV_BUFFER_TYPE_DATA;
	iov[1].buffer.value = NULL;
	iov[1].buffer.length = payload_size;

	gss_maj = gss_wrap_iov_length(&gss_min, gse_ctx->gssapi_context,
					seal, GSS_C_QOP_DEFAULT,
					&sealed, iov, 2);
	if (gss_maj) {
		DEBUG(0, ("gss_wrap_iov_length failed with [%s]\n",
			  gse_errstr(talloc_tos(), gss_maj, gss_min)));
		return 0;
	}

	return iov[0].buffer.length;
}

static NTSTATUS gse_seal(TALLOC_CTX *mem_ctx, struct gse_context *gse_ctx,
			 DATA_BLOB *data, DATA_BLOB *signature)
{
	OM_uint32 gss_min, gss_maj;
	gss_iov_buffer_desc iov[2];
	int req_seal = 1; /* setting to 1 means we request sign+seal */
	int sealed = 1;
	NTSTATUS status;

	/* allocate the memory ourselves so we do not need to talloc_memdup */
	signature->length = gse_get_signature_length(gse_ctx, true, data->length);
	if (!signature->length) {
		return NT_STATUS_INTERNAL_ERROR;
	}
	signature->data = (uint8_t *)talloc_size(mem_ctx, signature->length);
	if (!signature->data) {
		return NT_STATUS_NO_MEMORY;
	}
	iov[0].type = GSS_IOV_BUFFER_TYPE_HEADER;
	iov[0].buffer.value = signature->data;
	iov[0].buffer.length = signature->length;

	/* data is encrypted in place, which is ok */
	iov[1].type = GSS_IOV_BUFFER_TYPE_DATA;
	iov[1].buffer.value = data->data;
	iov[1].buffer.length = data->length;

	gss_maj = gss_wrap_iov(&gss_min, gse_ctx->gssapi_context,
				req_seal, GSS_C_QOP_DEFAULT,
				&sealed, iov, 2);
	if (gss_maj) {
		DEBUG(0, ("gss_wrap_iov failed with [%s]\n",
			  gse_errstr(talloc_tos(), gss_maj, gss_min)));
		status = NT_STATUS_ACCESS_DENIED;
		goto done;
	}

	if (!sealed) {
		DEBUG(0, ("gss_wrap_iov says data was not sealed!\n"));
		status = NT_STATUS_ACCESS_DENIED;
		goto done;
	}

	status = NT_STATUS_OK;

	DEBUG(10, ("Sealed %d bytes, and got %d bytes header/signature.\n",
		   (int)iov[1].buffer.length, (int)iov[0].buffer.length));

done:
	return status;
}

static NTSTATUS gse_unseal(TALLOC_CTX *mem_ctx, struct gse_context *gse_ctx,
			   DATA_BLOB *data, const DATA_BLOB *signature)
{
	OM_uint32 gss_min, gss_maj;
	gss_iov_buffer_desc iov[2];
	int sealed;
	NTSTATUS status;

	iov[0].type = GSS_IOV_BUFFER_TYPE_HEADER;
	iov[0].buffer.value = signature->data;
	iov[0].buffer.length = signature->length;

	/* data is decrypted in place, which is ok */
	iov[1].type = GSS_IOV_BUFFER_TYPE_DATA;
	iov[1].buffer.value = data->data;
	iov[1].buffer.length = data->length;

	gss_maj = gss_unwrap_iov(&gss_min, gse_ctx->gssapi_context,
				 &sealed, NULL, iov, 2);
	if (gss_maj) {
		DEBUG(0, ("gss_unwrap_iov failed with [%s]\n",
			  gse_errstr(talloc_tos(), gss_maj, gss_min)));
		status = NT_STATUS_ACCESS_DENIED;
		goto done;
	}

	if (!sealed) {
		DEBUG(0, ("gss_unwrap_iov says data is not sealed!\n"));
		status = NT_STATUS_ACCESS_DENIED;
		goto done;
	}

	status = NT_STATUS_OK;

	DEBUG(10, ("Unsealed %d bytes, with %d bytes header/signature.\n",
		   (int)iov[1].buffer.length, (int)iov[0].buffer.length));

done:
	return status;
}

static NTSTATUS gse_sign(TALLOC_CTX *mem_ctx, struct gse_context *gse_ctx,
			 DATA_BLOB *data, DATA_BLOB *signature)
{
	OM_uint32 gss_min, gss_maj;
	gss_buffer_desc in_data = { 0, NULL };
	gss_buffer_desc out_data = { 0, NULL};
	NTSTATUS status;

	in_data.value = data->data;
	in_data.length = data->length;

	gss_maj = gss_get_mic(&gss_min, gse_ctx->gssapi_context,
			      GSS_C_QOP_DEFAULT,
			      &in_data, &out_data);
	if (gss_maj) {
		DEBUG(0, ("gss_get_mic failed with [%s]\n",
			  gse_errstr(talloc_tos(), gss_maj, gss_min)));
		status = NT_STATUS_ACCESS_DENIED;
		goto done;
	}

	*signature = data_blob_talloc(mem_ctx,
					out_data.value, out_data.length);
	if (!signature->data) {
		status = NT_STATUS_NO_MEMORY;
		goto done;
	}

	status = NT_STATUS_OK;

done:
	if (out_data.value) {
		gss_maj = gss_release_buffer(&gss_min, &out_data);
	}
	return status;
}

static NTSTATUS gse_sigcheck(TALLOC_CTX *mem_ctx, struct gse_context *gse_ctx,
			     const DATA_BLOB *data, const DATA_BLOB *signature)
{
	OM_uint32 gss_min, gss_maj;
	gss_buffer_desc in_data = { 0, NULL };
	gss_buffer_desc in_token = { 0, NULL};
	NTSTATUS status;

	in_data.value = data->data;
	in_data.length = data->length;
	in_token.value = signature->data;
	in_token.length = signature->length;

	gss_maj = gss_verify_mic(&gss_min, gse_ctx->gssapi_context,
				 &in_data, &in_token, NULL);
	if (gss_maj) {
		DEBUG(0, ("gss_verify_mic failed with [%s]\n",
			  gse_errstr(talloc_tos(), gss_maj, gss_min)));
		status = NT_STATUS_ACCESS_DENIED;
		goto done;
	}

	status = NT_STATUS_OK;

done:
	return status;
}

static NTSTATUS gensec_gse_client_start(struct gensec_security *gensec_security)
{
	struct gse_context *gse_ctx;
	struct cli_credentials *creds = gensec_get_credentials(gensec_security);
	NTSTATUS nt_status;
	OM_uint32 want_flags = 0;
	bool do_sign = false, do_seal = false;
	const char *hostname = gensec_get_target_hostname(gensec_security);
	const char *service = gensec_get_target_service(gensec_security);
	const char *username = cli_credentials_get_username(creds);
	const char *password = cli_credentials_get_password(creds);

	if (!hostname) {
		DEBUG(1, ("Could not determine hostname for target computer, cannot use kerberos\n"));
		return NT_STATUS_INVALID_PARAMETER;
	}
	if (is_ipaddress(hostname)) {
		DEBUG(2, ("Cannot do GSE to an IP address\n"));
		return NT_STATUS_INVALID_PARAMETER;
	}
	if (strcmp(hostname, "localhost") == 0) {
		DEBUG(2, ("GSE to 'localhost' does not make sense\n"));
		return NT_STATUS_INVALID_PARAMETER;
	}

	if (gensec_security->want_features & GENSEC_FEATURE_SIGN) {
		do_sign = true;
	}
	if (gensec_security->want_features & GENSEC_FEATURE_SEAL) {
		do_seal = true;
	}
	if (gensec_security->want_features & GENSEC_FEATURE_DCE_STYLE) {
		want_flags |= GSS_C_DCE_STYLE;
	}

	nt_status = gse_init_client(gensec_security, do_sign, do_seal, NULL,
				    hostname, service,
				    username, password, want_flags,
				    &gse_ctx);
	if (!NT_STATUS_IS_OK(nt_status)) {
		return nt_status;
	}
	gensec_security->private_data = gse_ctx;
	return NT_STATUS_OK;
}

static NTSTATUS gensec_gse_server_start(struct gensec_security *gensec_security)
{
	struct gse_context *gse_ctx;
	NTSTATUS nt_status;
	OM_uint32 want_flags = 0;
	bool do_sign = false, do_seal = false;

	if (gensec_security->want_features & GENSEC_FEATURE_SIGN) {
		do_sign = true;
	}
	if (gensec_security->want_features & GENSEC_FEATURE_SEAL) {
		do_seal = true;
	}
	if (gensec_security->want_features & GENSEC_FEATURE_DCE_STYLE) {
		want_flags |= GSS_C_DCE_STYLE;
	}

	nt_status = gse_init_server(gensec_security, do_sign, do_seal, want_flags,
				    &gse_ctx);
	if (!NT_STATUS_IS_OK(nt_status)) {
		return nt_status;
	}
	gensec_security->private_data = gse_ctx;
	return NT_STATUS_OK;
}

/**
 * Next state function for the GSE GENSEC mechanism
 *
 * @param gensec_gse_state GSE State
 * @param mem_ctx The TALLOC_CTX for *out to be allocated on
 * @param in The request, as a DATA_BLOB
 * @param out The reply, as an talloc()ed DATA_BLOB, on *mem_ctx
 * @return Error, MORE_PROCESSING_REQUIRED if a reply is sent,
 *                or NT_STATUS_OK if the user is authenticated.
 */

static NTSTATUS gensec_gse_update(struct gensec_security *gensec_security,
				  TALLOC_CTX *mem_ctx,
				  struct tevent_context *ev,
				  const DATA_BLOB in, DATA_BLOB *out)
{
	NTSTATUS status;
	struct gse_context *gse_ctx =
		talloc_get_type_abort(gensec_security->private_data,
		struct gse_context);

	switch (gensec_security->gensec_role) {
	case GENSEC_CLIENT:
		status = gse_get_client_auth_token(mem_ctx, gse_ctx,
						   &in, out);
		break;
	case GENSEC_SERVER:
		status = gse_get_server_auth_token(mem_ctx, gse_ctx,
						   &in, out);
		break;
	}
	if (!NT_STATUS_IS_OK(status)) {
		return status;
	}

	return NT_STATUS_OK;
}

static NTSTATUS gensec_gse_wrap(struct gensec_security *gensec_security,
				TALLOC_CTX *mem_ctx,
				const DATA_BLOB *in,
				DATA_BLOB *out)
{
	struct gse_context *gse_ctx =
		talloc_get_type_abort(gensec_security->private_data,
		struct gse_context);
	OM_uint32 maj_stat, min_stat;
	gss_buffer_desc input_token, output_token;
	int conf_state;
	input_token.length = in->length;
	input_token.value = in->data;

	maj_stat = gss_wrap(&min_stat,
			    gse_ctx->gssapi_context,
			    gensec_have_feature(gensec_security, GENSEC_FEATURE_SEAL),
			    GSS_C_QOP_DEFAULT,
			    &input_token,
			    &conf_state,
			    &output_token);
	if (GSS_ERROR(maj_stat)) {
		DEBUG(0, ("gensec_gse_wrap: GSS Wrap failed: %s\n",
			  gse_errstr(talloc_tos(), maj_stat, min_stat)));
		return NT_STATUS_ACCESS_DENIED;
	}

	*out = data_blob_talloc(mem_ctx, output_token.value, output_token.length);
	gss_release_buffer(&min_stat, &output_token);

	if (gensec_have_feature(gensec_security, GENSEC_FEATURE_SEAL)
	    && !conf_state) {
		return NT_STATUS_ACCESS_DENIED;
	}
	return NT_STATUS_OK;
}

static NTSTATUS gensec_gse_unwrap(struct gensec_security *gensec_security,
				     TALLOC_CTX *mem_ctx,
				     const DATA_BLOB *in,
				     DATA_BLOB *out)
{
	struct gse_context *gse_ctx =
		talloc_get_type_abort(gensec_security->private_data,
		struct gse_context);
	OM_uint32 maj_stat, min_stat;
	gss_buffer_desc input_token, output_token;
	int conf_state;
	gss_qop_t qop_state;
	input_token.length = in->length;
	input_token.value = in->data;

	maj_stat = gss_unwrap(&min_stat,
			      gse_ctx->gssapi_context,
			      &input_token,
			      &output_token,
			      &conf_state,
			      &qop_state);
	if (GSS_ERROR(maj_stat)) {
		DEBUG(0, ("gensec_gse_unwrap: GSS UnWrap failed: %s\n",
			  gse_errstr(talloc_tos(), maj_stat, min_stat)));
		return NT_STATUS_ACCESS_DENIED;
	}

	*out = data_blob_talloc(mem_ctx, output_token.value, output_token.length);
	gss_release_buffer(&min_stat, &output_token);

	if (gensec_have_feature(gensec_security, GENSEC_FEATURE_SEAL)
	    && !conf_state) {
		return NT_STATUS_ACCESS_DENIED;
	}
	return NT_STATUS_OK;
}

static NTSTATUS gensec_gse_seal_packet(struct gensec_security *gensec_security,
				       TALLOC_CTX *mem_ctx,
				       uint8_t *data, size_t length,
				       const uint8_t *whole_pdu, size_t pdu_length,
				       DATA_BLOB *sig)
{
	struct gse_context *gse_ctx =
		talloc_get_type_abort(gensec_security->private_data,
		struct gse_context);
	DATA_BLOB payload = data_blob_const(data, length);
	return gse_seal(mem_ctx, gse_ctx, &payload, sig);
}

static NTSTATUS gensec_gse_unseal_packet(struct gensec_security *gensec_security,
					 uint8_t *data, size_t length,
					 const uint8_t *whole_pdu, size_t pdu_length,
					 const DATA_BLOB *sig)
{
	struct gse_context *gse_ctx =
		talloc_get_type_abort(gensec_security->private_data,
		struct gse_context);
	DATA_BLOB payload = data_blob_const(data, length);
	return gse_unseal(talloc_tos() /* unused */, gse_ctx, &payload, sig);
}

static NTSTATUS gensec_gse_sign_packet(struct gensec_security *gensec_security,
				       TALLOC_CTX *mem_ctx,
				       const uint8_t *data, size_t length,
				       const uint8_t *whole_pdu, size_t pdu_length,
				       DATA_BLOB *sig)
{
	struct gse_context *gse_ctx =
		talloc_get_type_abort(gensec_security->private_data,
		struct gse_context);
	DATA_BLOB payload = data_blob_const(data, length);
	return gse_sign(mem_ctx, gse_ctx, &payload, sig);
}

static NTSTATUS gensec_gse_check_packet(struct gensec_security *gensec_security,
					const uint8_t *data, size_t length,
					const uint8_t *whole_pdu, size_t pdu_length,
					const DATA_BLOB *sig)
{
	struct gse_context *gse_ctx =
		talloc_get_type_abort(gensec_security->private_data,
		struct gse_context);
	DATA_BLOB payload = data_blob_const(data, length);
	return gse_sigcheck(NULL, gse_ctx, &payload, sig);
}

/* Try to figure out what features we actually got on the connection */
static bool gensec_gse_have_feature(struct gensec_security *gensec_security,
				    uint32_t feature)
{
	struct gse_context *gse_ctx =
		talloc_get_type_abort(gensec_security->private_data,
		struct gse_context);

	if (feature & GENSEC_FEATURE_SIGN) {
		return gse_ctx->gss_got_flags & GSS_C_INTEG_FLAG;
	}
	if (feature & GENSEC_FEATURE_SEAL) {
		return gse_ctx->gss_got_flags & GSS_C_CONF_FLAG;
	}
	if (feature & GENSEC_FEATURE_SESSION_KEY) {
		/* Only for GSE/Krb5 */
		if (gss_oid_equal(gse_ctx->ret_mech, gss_mech_krb5)) {
			return true;
		}
	}
	if (feature & GENSEC_FEATURE_DCE_STYLE) {
		return gse_ctx->gss_got_flags & GSS_C_DCE_STYLE;
	}
	if (feature & GENSEC_FEATURE_NEW_SPNEGO) {
		NTSTATUS status;
		uint32_t keytype;

		if (!(gse_ctx->gss_got_flags & GSS_C_INTEG_FLAG)) {
			return false;
		}

		status = gssapi_get_session_key(talloc_tos(), 
						gse_ctx->gssapi_context, NULL, &keytype);
		/* 
		 * We should do a proper sig on the mechListMic unless
		 * we know we have to be backwards compatible with
		 * earlier windows versions.  
		 * 
		 * Negotiating a non-krb5
		 * mech for example should be regarded as having
		 * NEW_SPNEGO
		 */
		if (NT_STATUS_IS_OK(status)) {
			switch (keytype) {
			case ENCTYPE_DES_CBC_CRC:
			case ENCTYPE_DES_CBC_MD5:
			case ENCTYPE_ARCFOUR_HMAC:
			case ENCTYPE_DES3_CBC_SHA1:
				return false;
			}
		}
		return true;
	}
	/* We can always do async (rather than strict request/reply) packets.  */
	if (feature & GENSEC_FEATURE_ASYNC_REPLIES) {
		return true;
	}
	return false;
}

static NTTIME gensec_gse_expire_time(struct gensec_security *gensec_security)
{
	struct gse_context *gse_ctx =
		talloc_get_type_abort(gensec_security->private_data,
		struct gse_context);

	return gse_ctx->expire_time;
}

/*
 * Extract the 'sesssion key' needed by SMB signing and ncacn_np
 * (for encrypting some passwords).
 *
 * This breaks all the abstractions, but what do you expect...
 */
static NTSTATUS gensec_gse_session_key(struct gensec_security *gensec_security,
				       TALLOC_CTX *mem_ctx,
				       DATA_BLOB *session_key)
{
	struct gse_context *gse_ctx =
		talloc_get_type_abort(gensec_security->private_data,
		struct gse_context);

	return gssapi_get_session_key(mem_ctx, gse_ctx->gssapi_context, session_key, NULL);
}

/* Get some basic (and authorization) information about the user on
 * this session.  This uses either the PAC (if present) or a local
 * database lookup */
static NTSTATUS gensec_gse_session_info(struct gensec_security *gensec_security,
					TALLOC_CTX *mem_ctx,
					struct auth_session_info **_session_info)
{
	struct gse_context *gse_ctx =
		talloc_get_type_abort(gensec_security->private_data,
		struct gse_context);
	NTSTATUS nt_status;
	TALLOC_CTX *tmp_ctx;
	struct auth_session_info *session_info = NULL;
	OM_uint32 maj_stat, min_stat;
	DATA_BLOB pac_blob, *pac_blob_ptr = NULL;

	gss_buffer_desc name_token;
	char *principal_string;

	tmp_ctx = talloc_named(mem_ctx, 0, "gensec_gse_session_info context");
	NT_STATUS_HAVE_NO_MEMORY(tmp_ctx);

	maj_stat = gss_display_name(&min_stat,
				    gse_ctx->client_name,
				    &name_token,
				    NULL);
	if (GSS_ERROR(maj_stat)) {
		DEBUG(1, ("GSS display_name failed: %s\n",
			  gse_errstr(talloc_tos(), maj_stat, min_stat)));
		talloc_free(tmp_ctx);
		return NT_STATUS_FOOBAR;
	}

	principal_string = talloc_strndup(tmp_ctx,
					  (const char *)name_token.value,
					  name_token.length);

	gss_release_buffer(&min_stat, &name_token);

	if (!principal_string) {
		talloc_free(tmp_ctx);
		return NT_STATUS_NO_MEMORY;
	}

	nt_status = gssapi_obtain_pac_blob(tmp_ctx,  gse_ctx->gssapi_context,
					   gse_ctx->client_name,
					   &pac_blob);

	/* IF we have the PAC - otherwise we need to get this
	 * data from elsewere
	 */
	if (NT_STATUS_IS_OK(nt_status)) {
		pac_blob_ptr = &pac_blob;
	}
	nt_status = gensec_generate_session_info_pac(tmp_ctx,
						     gensec_security,
						     NULL,
						     pac_blob_ptr, principal_string,
						     gensec_get_remote_address(gensec_security),
						     &session_info);
	if (!NT_STATUS_IS_OK(nt_status)) {
		talloc_free(tmp_ctx);
		return nt_status;
	}

	nt_status = gensec_gse_session_key(gensec_security, session_info,
					   &session_info->session_key);
	if (!NT_STATUS_IS_OK(nt_status)) {
		talloc_free(tmp_ctx);
		return nt_status;
	}

	*_session_info = talloc_move(mem_ctx, &session_info);
	talloc_free(tmp_ctx);

	return NT_STATUS_OK;
}

static size_t gensec_gse_sig_size(struct gensec_security *gensec_security,
				  size_t data_size)
{
	struct gse_context *gse_ctx =
		talloc_get_type_abort(gensec_security->private_data,
		struct gse_context);

	return gse_get_signature_length(gse_ctx,
					gensec_security->want_features & GENSEC_FEATURE_SEAL,
					data_size);
}

static const char *gensec_gse_krb5_oids[] = {
	GENSEC_OID_KERBEROS5_OLD,
	GENSEC_OID_KERBEROS5,
	NULL
};

const struct gensec_security_ops gensec_gse_krb5_security_ops = {
	.name		= "gse_krb5",
	.auth_type	= DCERPC_AUTH_TYPE_KRB5,
	.oid            = gensec_gse_krb5_oids,
	.client_start   = gensec_gse_client_start,
	.server_start   = gensec_gse_server_start,
	.magic  	= gensec_magic_check_krb5_oid,
	.update 	= gensec_gse_update,
	.session_key	= gensec_gse_session_key,
	.session_info	= gensec_gse_session_info,
	.sig_size	= gensec_gse_sig_size,
	.sign_packet	= gensec_gse_sign_packet,
	.check_packet	= gensec_gse_check_packet,
	.seal_packet	= gensec_gse_seal_packet,
	.unseal_packet	= gensec_gse_unseal_packet,
	.wrap           = gensec_gse_wrap,
	.unwrap         = gensec_gse_unwrap,
	.have_feature   = gensec_gse_have_feature,
	.expire_time    = gensec_gse_expire_time,
	.enabled        = true,
	.kerberos       = true,
	.priority       = GENSEC_GSSAPI
};

#endif /* HAVE_KRB5 */