summaryrefslogtreecommitdiff
path: root/net/sctp/auth.c
blob: bf812048cf6f7a244c547e0cd31a731351abfab3 (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
/* SCTP kernel implementation
 * (C) Copyright 2007 Hewlett-Packard Development Company, L.P.
 *
 * This file is part of the SCTP kernel implementation
 *
 * This SCTP implementation 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 2, or (at your option)
 * any later version.
 *
 * This SCTP implementation 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 GNU CC; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <lksctp-developers@lists.sourceforge.net>
 *
 * Or submit a bug report through the following website:
 *    http://www.sf.net/projects/lksctp
 *
 * Written or modified by:
 *   Vlad Yasevich     <vladislav.yasevich@hp.com>
 *
 * Any bugs reported given to us we will try to fix... any fixes shared will
 * be incorporated into the next SCTP release.
 */

#include <linux/slab.h>
#include <linux/types.h>
#include <linux/crypto.h>
#include <linux/scatterlist.h>
#include <net/sctp/sctp.h>
#include <net/sctp/auth.h>

static struct sctp_hmac sctp_hmac_list[SCTP_AUTH_NUM_HMACS] = {
	{
		/* id 0 is reserved.  as all 0 */
		.hmac_id = SCTP_AUTH_HMAC_ID_RESERVED_0,
	},
	{
		.hmac_id = SCTP_AUTH_HMAC_ID_SHA1,
		.hmac_name="hmac(sha1)",
		.hmac_len = SCTP_SHA1_SIG_SIZE,
	},
	{
		/* id 2 is reserved as well */
		.hmac_id = SCTP_AUTH_HMAC_ID_RESERVED_2,
	},
#if defined (CONFIG_CRYPTO_SHA256) || defined (CONFIG_CRYPTO_SHA256_MODULE)
	{
		.hmac_id = SCTP_AUTH_HMAC_ID_SHA256,
		.hmac_name="hmac(sha256)",
		.hmac_len = SCTP_SHA256_SIG_SIZE,
	}
#endif
};


void sctp_auth_key_put(struct sctp_auth_bytes *key)
{
	if (!key)
		return;

	if (atomic_dec_and_test(&key->refcnt)) {
		kfree(key);
		SCTP_DBG_OBJCNT_DEC(keys);
	}
}

/* Create a new key structure of a given length */
static struct sctp_auth_bytes *sctp_auth_create_key(__u32 key_len, gfp_t gfp)
{
	struct sctp_auth_bytes *key;

	/* Verify that we are not going to overflow INT_MAX */
	if (key_len > (INT_MAX - sizeof(struct sctp_auth_bytes)))
		return NULL;

	/* Allocate the shared key */
	key = kmalloc(sizeof(struct sctp_auth_bytes) + key_len, gfp);
	if (!key)
		return NULL;

	key->len = key_len;
	atomic_set(&key->refcnt, 1);
	SCTP_DBG_OBJCNT_INC(keys);

	return key;
}

/* Create a new shared key container with a give key id */
struct sctp_shared_key *sctp_auth_shkey_create(__u16 key_id, gfp_t gfp)
{
	struct sctp_shared_key *new;

	/* Allocate the shared key container */
	new = kzalloc(sizeof(struct sctp_shared_key), gfp);
	if (!new)
		return NULL;

	INIT_LIST_HEAD(&new->key_list);
	new->key_id = key_id;

	return new;
}

/* Free the shared key structure */
static void sctp_auth_shkey_free(struct sctp_shared_key *sh_key)
{
	BUG_ON(!list_empty(&sh_key->key_list));
	sctp_auth_key_put(sh_key->key);
	sh_key->key = NULL;
	kfree(sh_key);
}

/* Destroy the entire key list.  This is done during the
 * associon and endpoint free process.
 */
void sctp_auth_destroy_keys(struct list_head *keys)
{
	struct sctp_shared_key *ep_key;
	struct sctp_shared_key *tmp;

	if (list_empty(keys))
		return;

	key_for_each_safe(ep_key, tmp, keys) {
		list_del_init(&ep_key->key_list);
		sctp_auth_shkey_free(ep_key);
	}
}

/* Compare two byte vectors as numbers.  Return values
 * are:
 * 	  0 - vectors are equal
 * 	< 0 - vector 1 is smaller than vector2
 * 	> 0 - vector 1 is greater than vector2
 *
 * Algorithm is:
 * 	This is performed by selecting the numerically smaller key vector...
 *	If the key vectors are equal as numbers but differ in length ...
 *	the shorter vector is considered smaller
 *
 * Examples (with small values):
 * 	000123456789 > 123456789 (first number is longer)
 * 	000123456789 < 234567891 (second number is larger numerically)
 * 	123456789 > 2345678 	 (first number is both larger & longer)
 */
static int sctp_auth_compare_vectors(struct sctp_auth_bytes *vector1,
			      struct sctp_auth_bytes *vector2)
{
	int diff;
	int i;
	const __u8 *longer;

	diff = vector1->len - vector2->len;
	if (diff) {
		longer = (diff > 0) ? vector1->data : vector2->data;

		/* Check to see if the longer number is
		 * lead-zero padded.  If it is not, it
		 * is automatically larger numerically.
		 */
		for (i = 0; i < abs(diff); i++ ) {
			if (longer[i] != 0)
				return diff;
		}
	}

	/* lengths are the same, compare numbers */
	return memcmp(vector1->data, vector2->data, vector1->len);
}

/*
 * Create a key vector as described in SCTP-AUTH, Section 6.1
 *    The RANDOM parameter, the CHUNKS parameter and the HMAC-ALGO
 *    parameter sent by each endpoint are concatenated as byte vectors.
 *    These parameters include the parameter type, parameter length, and
 *    the parameter value, but padding is omitted; all padding MUST be
 *    removed from this concatenation before proceeding with further
 *    computation of keys.  Parameters which were not sent are simply
 *    omitted from the concatenation process.  The resulting two vectors
 *    are called the two key vectors.
 */
static struct sctp_auth_bytes *sctp_auth_make_key_vector(
			sctp_random_param_t *random,
			sctp_chunks_param_t *chunks,
			sctp_hmac_algo_param_t *hmacs,
			gfp_t gfp)
{
	struct sctp_auth_bytes *new;
	__u32	len;
	__u32	offset = 0;

	len = ntohs(random->param_hdr.length) + ntohs(hmacs->param_hdr.length);
        if (chunks)
		len += ntohs(chunks->param_hdr.length);

	new = kmalloc(sizeof(struct sctp_auth_bytes) + len, gfp);
	if (!new)
		return NULL;

	new->len = len;

	memcpy(new->data, random, ntohs(random->param_hdr.length));
	offset += ntohs(random->param_hdr.length);

	if (chunks) {
		memcpy(new->data + offset, chunks,
			ntohs(chunks->param_hdr.length));
		offset += ntohs(chunks->param_hdr.length);
	}

	memcpy(new->data + offset, hmacs, ntohs(hmacs->param_hdr.length));

	return new;
}


/* Make a key vector based on our local parameters */
static struct sctp_auth_bytes *sctp_auth_make_local_vector(
				    const struct sctp_association *asoc,
				    gfp_t gfp)
{
	return sctp_auth_make_key_vector(
				    (sctp_random_param_t*)asoc->c.auth_random,
				    (sctp_chunks_param_t*)asoc->c.auth_chunks,
				    (sctp_hmac_algo_param_t*)asoc->c.auth_hmacs,
				    gfp);
}

/* Make a key vector based on peer's parameters */
static struct sctp_auth_bytes *sctp_auth_make_peer_vector(
				    const struct sctp_association *asoc,
				    gfp_t gfp)
{
	return sctp_auth_make_key_vector(asoc->peer.peer_random,
					 asoc->peer.peer_chunks,
					 asoc->peer.peer_hmacs,
					 gfp);
}


/* Set the value of the association shared key base on the parameters
 * given.  The algorithm is:
 *    From the endpoint pair shared keys and the key vectors the
 *    association shared keys are computed.  This is performed by selecting
 *    the numerically smaller key vector and concatenating it to the
 *    endpoint pair shared key, and then concatenating the numerically
 *    larger key vector to that.  The result of the concatenation is the
 *    association shared key.
 */
static struct sctp_auth_bytes *sctp_auth_asoc_set_secret(
			struct sctp_shared_key *ep_key,
			struct sctp_auth_bytes *first_vector,
			struct sctp_auth_bytes *last_vector,
			gfp_t gfp)
{
	struct sctp_auth_bytes *secret;
	__u32 offset = 0;
	__u32 auth_len;

	auth_len = first_vector->len + last_vector->len;
	if (ep_key->key)
		auth_len += ep_key->key->len;

	secret = sctp_auth_create_key(auth_len, gfp);
	if (!secret)
		return NULL;

	if (ep_key->key) {
		memcpy(secret->data, ep_key->key->data, ep_key->key->len);
		offset += ep_key->key->len;
	}

	memcpy(secret->data + offset, first_vector->data, first_vector->len);
	offset += first_vector->len;

	memcpy(secret->data + offset, last_vector->data, last_vector->len);

	return secret;
}

/* Create an association shared key.  Follow the algorithm
 * described in SCTP-AUTH, Section 6.1
 */
static struct sctp_auth_bytes *sctp_auth_asoc_create_secret(
				 const struct sctp_association *asoc,
				 struct sctp_shared_key *ep_key,
				 gfp_t gfp)
{
	struct sctp_auth_bytes *local_key_vector;
	struct sctp_auth_bytes *peer_key_vector;
	struct sctp_auth_bytes	*first_vector,
				*last_vector;
	struct sctp_auth_bytes	*secret = NULL;
	int	cmp;


	/* Now we need to build the key vectors
	 * SCTP-AUTH , Section 6.1
	 *    The RANDOM parameter, the CHUNKS parameter and the HMAC-ALGO
	 *    parameter sent by each endpoint are concatenated as byte vectors.
	 *    These parameters include the parameter type, parameter length, and
	 *    the parameter value, but padding is omitted; all padding MUST be
	 *    removed from this concatenation before proceeding with further
	 *    computation of keys.  Parameters which were not sent are simply
	 *    omitted from the concatenation process.  The resulting two vectors
	 *    are called the two key vectors.
	 */

	local_key_vector = sctp_auth_make_local_vector(asoc, gfp);
	peer_key_vector = sctp_auth_make_peer_vector(asoc, gfp);

	if (!peer_key_vector || !local_key_vector)
		goto out;

	/* Figure out the order in which the key_vectors will be
	 * added to the endpoint shared key.
	 * SCTP-AUTH, Section 6.1:
	 *   This is performed by selecting the numerically smaller key
	 *   vector and concatenating it to the endpoint pair shared
	 *   key, and then concatenating the numerically larger key
	 *   vector to that.  If the key vectors are equal as numbers
	 *   but differ in length, then the concatenation order is the
	 *   endpoint shared key, followed by the shorter key vector,
	 *   followed by the longer key vector.  Otherwise, the key
	 *   vectors are identical, and may be concatenated to the
	 *   endpoint pair key in any order.
	 */
	cmp = sctp_auth_compare_vectors(local_key_vector,
					peer_key_vector);
	if (cmp < 0) {
		first_vector = local_key_vector;
		last_vector = peer_key_vector;
	} else {
		first_vector = peer_key_vector;
		last_vector = local_key_vector;
	}

	secret = sctp_auth_asoc_set_secret(ep_key, first_vector, last_vector,
					    gfp);
out:
	kfree(local_key_vector);
	kfree(peer_key_vector);

	return secret;
}

/*
 * Populate the association overlay list with the list
 * from the endpoint.
 */
int sctp_auth_asoc_copy_shkeys(const struct sctp_endpoint *ep,
				struct sctp_association *asoc,
				gfp_t gfp)
{
	struct sctp_shared_key *sh_key;
	struct sctp_shared_key *new;

	BUG_ON(!list_empty(&asoc->endpoint_shared_keys));

	key_for_each(sh_key, &ep->endpoint_shared_keys) {
		new = sctp_auth_shkey_create(sh_key->key_id, gfp);
		if (!new)
			goto nomem;

		new->key = sh_key->key;
		sctp_auth_key_hold(new->key);
		list_add(&new->key_list, &asoc->endpoint_shared_keys);
	}

	return 0;

nomem:
	sctp_auth_destroy_keys(&asoc->endpoint_shared_keys);
	return -ENOMEM;
}


/* Public interface to creat the association shared key.
 * See code above for the algorithm.
 */
int sctp_auth_asoc_init_active_key(struct sctp_association *asoc, gfp_t gfp)
{
	struct sctp_auth_bytes	*secret;
	struct sctp_shared_key *ep_key;

	/* If we don't support AUTH, or peer is not capable
	 * we don't need to do anything.
	 */
	if (!sctp_auth_enable || !asoc->peer.auth_capable)
		return 0;

	/* If the key_id is non-zero and we couldn't find an
	 * endpoint pair shared key, we can't compute the
	 * secret.
	 * For key_id 0, endpoint pair shared key is a NULL key.
	 */
	ep_key = sctp_auth_get_shkey(asoc, asoc->active_key_id);
	BUG_ON(!ep_key);

	secret = sctp_auth_asoc_create_secret(asoc, ep_key, gfp);
	if (!secret)
		return -ENOMEM;

	sctp_auth_key_put(asoc->asoc_shared_key);
	asoc->asoc_shared_key = secret;

	return 0;
}


/* Find the endpoint pair shared key based on the key_id */
struct sctp_shared_key *sctp_auth_get_shkey(
				const struct sctp_association *asoc,
				__u16 key_id)
{
	struct sctp_shared_key *key;

	/* First search associations set of endpoint pair shared keys */
	key_for_each(key, &asoc->endpoint_shared_keys) {
		if (key->key_id == key_id)
			return key;
	}

	return NULL;
}

/*
 * Initialize all the possible digest transforms that we can use.  Right now
 * now, the supported digests are SHA1 and SHA256.  We do this here once
 * because of the restrictiong that transforms may only be allocated in
 * user context.  This forces us to pre-allocated all possible transforms
 * at the endpoint init time.
 */
int sctp_auth_init_hmacs(struct sctp_endpoint *ep, gfp_t gfp)
{
	struct crypto_hash *tfm = NULL;
	__u16   id;

	/* if the transforms are already allocted, we are done */
	if (!sctp_auth_enable) {
		ep->auth_hmacs = NULL;
		return 0;
	}

	if (ep->auth_hmacs)
		return 0;

	/* Allocated the array of pointers to transorms */
	ep->auth_hmacs = kzalloc(
			    sizeof(struct crypto_hash *) * SCTP_AUTH_NUM_HMACS,
			    gfp);
	if (!ep->auth_hmacs)
		return -ENOMEM;

	for (id = 0; id < SCTP_AUTH_NUM_HMACS; id++) {

		/* See is we support the id.  Supported IDs have name and
		 * length fields set, so that we can allocated and use
		 * them.  We can safely just check for name, for without the
		 * name, we can't allocate the TFM.
		 */
		if (!sctp_hmac_list[id].hmac_name)
			continue;

		/* If this TFM has been allocated, we are all set */
		if (ep->auth_hmacs[id])
			continue;

		/* Allocate the ID */
		tfm = crypto_alloc_hash(sctp_hmac_list[id].hmac_name, 0,
					CRYPTO_ALG_ASYNC);
		if (IS_ERR(tfm))
			goto out_err;

		ep->auth_hmacs[id] = tfm;
	}

	return 0;

out_err:
	/* Clean up any successful allocations */
	sctp_auth_destroy_hmacs(ep->auth_hmacs);
	return -ENOMEM;
}

/* Destroy the hmac tfm array */
void sctp_auth_destroy_hmacs(struct crypto_hash *auth_hmacs[])
{
	int i;

	if (!auth_hmacs)
		return;

	for (i = 0; i < SCTP_AUTH_NUM_HMACS; i++)
	{
		if (auth_hmacs[i])
			crypto_free_hash(auth_hmacs[i]);
	}
	kfree(auth_hmacs);
}


struct sctp_hmac *sctp_auth_get_hmac(__u16 hmac_id)
{
	return &sctp_hmac_list[hmac_id];
}

/* Get an hmac description information that we can use to build
 * the AUTH chunk
 */
struct sctp_hmac *sctp_auth_asoc_get_hmac(const struct sctp_association *asoc)
{
	struct sctp_hmac_algo_param *hmacs;
	__u16 n_elt;
	__u16 id = 0;
	int i;

	/* If we have a default entry, use it */
	if (asoc->default_hmac_id)
		return &sctp_hmac_list[asoc->default_hmac_id];

	/* Since we do not have a default entry, find the first entry
	 * we support and return that.  Do not cache that id.
	 */
	hmacs = asoc->peer.peer_hmacs;
	if (!hmacs)
		return NULL;

	n_elt = (ntohs(hmacs->param_hdr.length) - sizeof(sctp_paramhdr_t)) >> 1;
	for (i = 0; i < n_elt; i++) {
		id = ntohs(hmacs->hmac_ids[i]);

		/* Check the id is in the supported range */
		if (id > SCTP_AUTH_HMAC_ID_MAX) {
			id = 0;
			continue;
		}

		/* See is we support the id.  Supported IDs have name and
		 * length fields set, so that we can allocated and use
		 * them.  We can safely just check for name, for without the
		 * name, we can't allocate the TFM.
		 */
		if (!sctp_hmac_list[id].hmac_name) {
			id = 0;
			continue;
		}

		break;
	}

	if (id == 0)
		return NULL;

	return &sctp_hmac_list[id];
}

static int __sctp_auth_find_hmacid(__be16 *hmacs, int n_elts, __be16 hmac_id)
{
	int  found = 0;
	int  i;

	for (i = 0; i < n_elts; i++) {
		if (hmac_id == hmacs[i]) {
			found = 1;
			break;
		}
	}

	return found;
}

/* See if the HMAC_ID is one that we claim as supported */
int sctp_auth_asoc_verify_hmac_id(const struct sctp_association *asoc,
				    __be16 hmac_id)
{
	struct sctp_hmac_algo_param *hmacs;
	__u16 n_elt;

	if (!asoc)
		return 0;

	hmacs = (struct sctp_hmac_algo_param *)asoc->c.auth_hmacs;
	n_elt = (ntohs(hmacs->param_hdr.length) - sizeof(sctp_paramhdr_t)) >> 1;

	return __sctp_auth_find_hmacid(hmacs->hmac_ids, n_elt, hmac_id);
}


/* Cache the default HMAC id.  This to follow this text from SCTP-AUTH:
 * Section 6.1:
 *   The receiver of a HMAC-ALGO parameter SHOULD use the first listed
 *   algorithm it supports.
 */
void sctp_auth_asoc_set_default_hmac(struct sctp_association *asoc,
				     struct sctp_hmac_algo_param *hmacs)
{
	struct sctp_endpoint *ep;
	__u16   id;
	int	i;
	int	n_params;

	/* if the default id is already set, use it */
	if (asoc->default_hmac_id)
		return;

	n_params = (ntohs(hmacs->param_hdr.length)
				- sizeof(sctp_paramhdr_t)) >> 1;
	ep = asoc->ep;
	for (i = 0; i < n_params; i++) {
		id = ntohs(hmacs->hmac_ids[i]);

		/* Check the id is in the supported range */
		if (id > SCTP_AUTH_HMAC_ID_MAX)
			continue;

		/* If this TFM has been allocated, use this id */
		if (ep->auth_hmacs[id]) {
			asoc->default_hmac_id = id;
			break;
		}
	}
}


/* Check to see if the given chunk is supposed to be authenticated */
static int __sctp_auth_cid(sctp_cid_t chunk, struct sctp_chunks_param *param)
{
	unsigned short len;
	int found = 0;
	int i;

	if (!param || param->param_hdr.length == 0)
		return 0;

	len = ntohs(param->param_hdr.length) - sizeof(sctp_paramhdr_t);

	/* SCTP-AUTH, Section 3.2
	 *    The chunk types for INIT, INIT-ACK, SHUTDOWN-COMPLETE and AUTH
	 *    chunks MUST NOT be listed in the CHUNKS parameter.  However, if
	 *    a CHUNKS parameter is received then the types for INIT, INIT-ACK,
	 *    SHUTDOWN-COMPLETE and AUTH chunks MUST be ignored.
	 */
	for (i = 0; !found && i < len; i++) {
		switch (param->chunks[i]) {
		    case SCTP_CID_INIT:
		    case SCTP_CID_INIT_ACK:
		    case SCTP_CID_SHUTDOWN_COMPLETE:
		    case SCTP_CID_AUTH:
			break;

		    default:
			if (param->chunks[i] == chunk)
			    found = 1;
			break;
		}
	}

	return found;
}

/* Check if peer requested that this chunk is authenticated */
int sctp_auth_send_cid(sctp_cid_t chunk, const struct sctp_association *asoc)
{
	if (!sctp_auth_enable || !asoc || !asoc->peer.auth_capable)
		return 0;

	return __sctp_auth_cid(chunk, asoc->peer.peer_chunks);
}

/* Check if we requested that peer authenticate this chunk. */
int sctp_auth_recv_cid(sctp_cid_t chunk, const struct sctp_association *asoc)
{
	if (!sctp_auth_enable || !asoc)
		return 0;

	return __sctp_auth_cid(chunk,
			      (struct sctp_chunks_param *)asoc->c.auth_chunks);
}

/* SCTP-AUTH: Section 6.2:
 *    The sender MUST calculate the MAC as described in RFC2104 [2] using
 *    the hash function H as described by the MAC Identifier and the shared
 *    association key K based on the endpoint pair shared key described by
 *    the shared key identifier.  The 'data' used for the computation of
 *    the AUTH-chunk is given by the AUTH chunk with its HMAC field set to
 *    zero (as shown in Figure 6) followed by all chunks that are placed
 *    after the AUTH chunk in the SCTP packet.
 */
void sctp_auth_calculate_hmac(const struct sctp_association *asoc,
			      struct sk_buff *skb,
			      struct sctp_auth_chunk *auth,
			      gfp_t gfp)
{
	struct scatterlist sg;
	struct hash_desc desc;
	struct sctp_auth_bytes *asoc_key;
	__u16 key_id, hmac_id;
	__u8 *digest;
	unsigned char *end;
	int free_key = 0;

	/* Extract the info we need:
	 * - hmac id
	 * - key id
	 */
	key_id = ntohs(auth->auth_hdr.shkey_id);
	hmac_id = ntohs(auth->auth_hdr.hmac_id);

	if (key_id == asoc->active_key_id)
		asoc_key = asoc->asoc_shared_key;
	else {
		struct sctp_shared_key *ep_key;

		ep_key = sctp_auth_get_shkey(asoc, key_id);
		if (!ep_key)
			return;

		asoc_key = sctp_auth_asoc_create_secret(asoc, ep_key, gfp);
		if (!asoc_key)
			return;

		free_key = 1;
	}

	/* set up scatter list */
	end = skb_tail_pointer(skb);
	sg_init_one(&sg, auth, end - (unsigned char *)auth);

	desc.tfm = asoc->ep->auth_hmacs[hmac_id];
	desc.flags = 0;

	digest = auth->auth_hdr.hmac;
	if (crypto_hash_setkey(desc.tfm, &asoc_key->data[0], asoc_key->len))
		goto free;

	crypto_hash_digest(&desc, &sg, sg.length, digest);

free:
	if (free_key)
		sctp_auth_key_put(asoc_key);
}

/* API Helpers */

/* Add a chunk to the endpoint authenticated chunk list */
int sctp_auth_ep_add_chunkid(struct sctp_endpoint *ep, __u8 chunk_id)
{
	struct sctp_chunks_param *p = ep->auth_chunk_list;
	__u16 nchunks;
	__u16 param_len;

	/* If this chunk is already specified, we are done */
	if (__sctp_auth_cid(chunk_id, p))
		return 0;

	/* Check if we can add this chunk to the array */
	param_len = ntohs(p->param_hdr.length);
	nchunks = param_len - sizeof(sctp_paramhdr_t);
	if (nchunks == SCTP_NUM_CHUNK_TYPES)
		return -EINVAL;

	p->chunks[nchunks] = chunk_id;
	p->param_hdr.length = htons(param_len + 1);
	return 0;
}

/* Add hmac identifires to the endpoint list of supported hmac ids */
int sctp_auth_ep_set_hmacs(struct sctp_endpoint *ep,
			   struct sctp_hmacalgo *hmacs)
{
	int has_sha1 = 0;
	__u16 id;
	int i;

	/* Scan the list looking for unsupported id.  Also make sure that
	 * SHA1 is specified.
	 */
	for (i = 0; i < hmacs->shmac_num_idents; i++) {
		id = hmacs->shmac_idents[i];

		if (id > SCTP_AUTH_HMAC_ID_MAX)
			return -EOPNOTSUPP;

		if (SCTP_AUTH_HMAC_ID_SHA1 == id)
			has_sha1 = 1;

		if (!sctp_hmac_list[id].hmac_name)
			return -EOPNOTSUPP;
	}

	if (!has_sha1)
		return -EINVAL;

	memcpy(ep->auth_hmacs_list->hmac_ids, &hmacs->shmac_idents[0],
		hmacs->shmac_num_idents * sizeof(__u16));
	ep->auth_hmacs_list->param_hdr.length = htons(sizeof(sctp_paramhdr_t) +
				hmacs->shmac_num_idents * sizeof(__u16));
	return 0;
}

/* Set a new shared key on either endpoint or association.  If the
 * the key with a same ID already exists, replace the key (remove the
 * old key and add a new one).
 */
int sctp_auth_set_key(struct sctp_endpoint *ep,
		      struct sctp_association *asoc,
		      struct sctp_authkey *auth_key)
{
	struct sctp_shared_key *cur_key = NULL;
	struct sctp_auth_bytes *key;
	struct list_head *sh_keys;
	int replace = 0;

	/* Try to find the given key id to see if
	 * we are doing a replace, or adding a new key
	 */
	if (asoc)
		sh_keys = &asoc->endpoint_shared_keys;
	else
		sh_keys = &ep->endpoint_shared_keys;

	key_for_each(cur_key, sh_keys) {
		if (cur_key->key_id == auth_key->sca_keynumber) {
			replace = 1;
			break;
		}
	}

	/* If we are not replacing a key id, we need to allocate
	 * a shared key.
	 */
	if (!replace) {
		cur_key = sctp_auth_shkey_create(auth_key->sca_keynumber,
						 GFP_KERNEL);
		if (!cur_key)
			return -ENOMEM;
	}

	/* Create a new key data based on the info passed in */
	key = sctp_auth_create_key(auth_key->sca_keylength, GFP_KERNEL);
	if (!key)
		goto nomem;

	memcpy(key->data, &auth_key->sca_key[0], auth_key->sca_keylength);

	/* If we are replacing, remove the old keys data from the
	 * key id.  If we are adding new key id, add it to the
	 * list.
	 */
	if (replace)
		sctp_auth_key_put(cur_key->key);
	else
		list_add(&cur_key->key_list, sh_keys);

	cur_key->key = key;
	sctp_auth_key_hold(key);

	return 0;
nomem:
	if (!replace)
		sctp_auth_shkey_free(cur_key);

	return -ENOMEM;
}

int sctp_auth_set_active_key(struct sctp_endpoint *ep,
			     struct sctp_association *asoc,
			     __u16  key_id)
{
	struct sctp_shared_key *key;
	struct list_head *sh_keys;
	int found = 0;

	/* The key identifier MUST correst to an existing key */
	if (asoc)
		sh_keys = &asoc->endpoint_shared_keys;
	else
		sh_keys = &ep->endpoint_shared_keys;

	key_for_each(key, sh_keys) {
		if (key->key_id == key_id) {
			found = 1;
			break;
		}
	}

	if (!found)
		return -EINVAL;

	if (asoc) {
		asoc->active_key_id = key_id;
		sctp_auth_asoc_init_active_key(asoc, GFP_KERNEL);
	} else
		ep->active_key_id = key_id;

	return 0;
}

int sctp_auth_del_key_id(struct sctp_endpoint *ep,
			 struct sctp_association *asoc,
			 __u16  key_id)
{
	struct sctp_shared_key *key;
	struct list_head *sh_keys;
	int found = 0;

	/* The key identifier MUST NOT be the current active key
	 * The key identifier MUST correst to an existing key
	 */
	if (asoc) {
		if (asoc->active_key_id == key_id)
			return -EINVAL;

		sh_keys = &asoc->endpoint_shared_keys;
	} else {
		if (ep->active_key_id == key_id)
			return -EINVAL;

		sh_keys = &ep->endpoint_shared_keys;
	}

	key_for_each(key, sh_keys) {
		if (key->key_id == key_id) {
			found = 1;
			break;
		}
	}

	if (!found)
		return -EINVAL;

	/* Delete the shared key */
	list_del_init(&key->key_list);
	sctp_auth_shkey_free(key);

	return 0;
}