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Linux/net/sctp/auth.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /* SCTP kernel implementation
  3  * (C) Copyright 2007 Hewlett-Packard Development Company, L.P.
  4  *
  5  * This file is part of the SCTP kernel implementation
  6  *
  7  * Please send any bug reports or fixes you make to the
  8  * email address(es):
  9  *    lksctp developers <linux-sctp@vger.kernel.org>
 10  *
 11  * Written or modified by:
 12  *   Vlad Yasevich     <vladislav.yasevich@hp.com>
 13  */
 14 
 15 #include <crypto/hash.h>
 16 #include <linux/slab.h>
 17 #include <linux/types.h>
 18 #include <linux/scatterlist.h>
 19 #include <net/sctp/sctp.h>
 20 #include <net/sctp/auth.h>
 21 
 22 static struct sctp_hmac sctp_hmac_list[SCTP_AUTH_NUM_HMACS] = {
 23         {
 24                 /* id 0 is reserved.  as all 0 */
 25                 .hmac_id = SCTP_AUTH_HMAC_ID_RESERVED_0,
 26         },
 27         {
 28                 .hmac_id = SCTP_AUTH_HMAC_ID_SHA1,
 29                 .hmac_name = "hmac(sha1)",
 30                 .hmac_len = SCTP_SHA1_SIG_SIZE,
 31         },
 32         {
 33                 /* id 2 is reserved as well */
 34                 .hmac_id = SCTP_AUTH_HMAC_ID_RESERVED_2,
 35         },
 36 #if IS_ENABLED(CONFIG_CRYPTO_SHA256)
 37         {
 38                 .hmac_id = SCTP_AUTH_HMAC_ID_SHA256,
 39                 .hmac_name = "hmac(sha256)",
 40                 .hmac_len = SCTP_SHA256_SIG_SIZE,
 41         }
 42 #endif
 43 };
 44 
 45 
 46 void sctp_auth_key_put(struct sctp_auth_bytes *key)
 47 {
 48         if (!key)
 49                 return;
 50 
 51         if (refcount_dec_and_test(&key->refcnt)) {
 52                 kzfree(key);
 53                 SCTP_DBG_OBJCNT_DEC(keys);
 54         }
 55 }
 56 
 57 /* Create a new key structure of a given length */
 58 static struct sctp_auth_bytes *sctp_auth_create_key(__u32 key_len, gfp_t gfp)
 59 {
 60         struct sctp_auth_bytes *key;
 61 
 62         /* Verify that we are not going to overflow INT_MAX */
 63         if (key_len > (INT_MAX - sizeof(struct sctp_auth_bytes)))
 64                 return NULL;
 65 
 66         /* Allocate the shared key */
 67         key = kmalloc(sizeof(struct sctp_auth_bytes) + key_len, gfp);
 68         if (!key)
 69                 return NULL;
 70 
 71         key->len = key_len;
 72         refcount_set(&key->refcnt, 1);
 73         SCTP_DBG_OBJCNT_INC(keys);
 74 
 75         return key;
 76 }
 77 
 78 /* Create a new shared key container with a give key id */
 79 struct sctp_shared_key *sctp_auth_shkey_create(__u16 key_id, gfp_t gfp)
 80 {
 81         struct sctp_shared_key *new;
 82 
 83         /* Allocate the shared key container */
 84         new = kzalloc(sizeof(struct sctp_shared_key), gfp);
 85         if (!new)
 86                 return NULL;
 87 
 88         INIT_LIST_HEAD(&new->key_list);
 89         refcount_set(&new->refcnt, 1);
 90         new->key_id = key_id;
 91 
 92         return new;
 93 }
 94 
 95 /* Free the shared key structure */
 96 static void sctp_auth_shkey_destroy(struct sctp_shared_key *sh_key)
 97 {
 98         BUG_ON(!list_empty(&sh_key->key_list));
 99         sctp_auth_key_put(sh_key->key);
100         sh_key->key = NULL;
101         kfree(sh_key);
102 }
103 
104 void sctp_auth_shkey_release(struct sctp_shared_key *sh_key)
105 {
106         if (refcount_dec_and_test(&sh_key->refcnt))
107                 sctp_auth_shkey_destroy(sh_key);
108 }
109 
110 void sctp_auth_shkey_hold(struct sctp_shared_key *sh_key)
111 {
112         refcount_inc(&sh_key->refcnt);
113 }
114 
115 /* Destroy the entire key list.  This is done during the
116  * associon and endpoint free process.
117  */
118 void sctp_auth_destroy_keys(struct list_head *keys)
119 {
120         struct sctp_shared_key *ep_key;
121         struct sctp_shared_key *tmp;
122 
123         if (list_empty(keys))
124                 return;
125 
126         key_for_each_safe(ep_key, tmp, keys) {
127                 list_del_init(&ep_key->key_list);
128                 sctp_auth_shkey_release(ep_key);
129         }
130 }
131 
132 /* Compare two byte vectors as numbers.  Return values
133  * are:
134  *        0 - vectors are equal
135  *      < 0 - vector 1 is smaller than vector2
136  *      > 0 - vector 1 is greater than vector2
137  *
138  * Algorithm is:
139  *      This is performed by selecting the numerically smaller key vector...
140  *      If the key vectors are equal as numbers but differ in length ...
141  *      the shorter vector is considered smaller
142  *
143  * Examples (with small values):
144  *      000123456789 > 123456789 (first number is longer)
145  *      000123456789 < 234567891 (second number is larger numerically)
146  *      123456789 > 2345678      (first number is both larger & longer)
147  */
148 static int sctp_auth_compare_vectors(struct sctp_auth_bytes *vector1,
149                               struct sctp_auth_bytes *vector2)
150 {
151         int diff;
152         int i;
153         const __u8 *longer;
154 
155         diff = vector1->len - vector2->len;
156         if (diff) {
157                 longer = (diff > 0) ? vector1->data : vector2->data;
158 
159                 /* Check to see if the longer number is
160                  * lead-zero padded.  If it is not, it
161                  * is automatically larger numerically.
162                  */
163                 for (i = 0; i < abs(diff); i++) {
164                         if (longer[i] != 0)
165                                 return diff;
166                 }
167         }
168 
169         /* lengths are the same, compare numbers */
170         return memcmp(vector1->data, vector2->data, vector1->len);
171 }
172 
173 /*
174  * Create a key vector as described in SCTP-AUTH, Section 6.1
175  *    The RANDOM parameter, the CHUNKS parameter and the HMAC-ALGO
176  *    parameter sent by each endpoint are concatenated as byte vectors.
177  *    These parameters include the parameter type, parameter length, and
178  *    the parameter value, but padding is omitted; all padding MUST be
179  *    removed from this concatenation before proceeding with further
180  *    computation of keys.  Parameters which were not sent are simply
181  *    omitted from the concatenation process.  The resulting two vectors
182  *    are called the two key vectors.
183  */
184 static struct sctp_auth_bytes *sctp_auth_make_key_vector(
185                         struct sctp_random_param *random,
186                         struct sctp_chunks_param *chunks,
187                         struct sctp_hmac_algo_param *hmacs,
188                         gfp_t gfp)
189 {
190         struct sctp_auth_bytes *new;
191         __u32   len;
192         __u32   offset = 0;
193         __u16   random_len, hmacs_len, chunks_len = 0;
194 
195         random_len = ntohs(random->param_hdr.length);
196         hmacs_len = ntohs(hmacs->param_hdr.length);
197         if (chunks)
198                 chunks_len = ntohs(chunks->param_hdr.length);
199 
200         len = random_len + hmacs_len + chunks_len;
201 
202         new = sctp_auth_create_key(len, gfp);
203         if (!new)
204                 return NULL;
205 
206         memcpy(new->data, random, random_len);
207         offset += random_len;
208 
209         if (chunks) {
210                 memcpy(new->data + offset, chunks, chunks_len);
211                 offset += chunks_len;
212         }
213 
214         memcpy(new->data + offset, hmacs, hmacs_len);
215 
216         return new;
217 }
218 
219 
220 /* Make a key vector based on our local parameters */
221 static struct sctp_auth_bytes *sctp_auth_make_local_vector(
222                                     const struct sctp_association *asoc,
223                                     gfp_t gfp)
224 {
225         return sctp_auth_make_key_vector(
226                         (struct sctp_random_param *)asoc->c.auth_random,
227                         (struct sctp_chunks_param *)asoc->c.auth_chunks,
228                         (struct sctp_hmac_algo_param *)asoc->c.auth_hmacs, gfp);
229 }
230 
231 /* Make a key vector based on peer's parameters */
232 static struct sctp_auth_bytes *sctp_auth_make_peer_vector(
233                                     const struct sctp_association *asoc,
234                                     gfp_t gfp)
235 {
236         return sctp_auth_make_key_vector(asoc->peer.peer_random,
237                                          asoc->peer.peer_chunks,
238                                          asoc->peer.peer_hmacs,
239                                          gfp);
240 }
241 
242 
243 /* Set the value of the association shared key base on the parameters
244  * given.  The algorithm is:
245  *    From the endpoint pair shared keys and the key vectors the
246  *    association shared keys are computed.  This is performed by selecting
247  *    the numerically smaller key vector and concatenating it to the
248  *    endpoint pair shared key, and then concatenating the numerically
249  *    larger key vector to that.  The result of the concatenation is the
250  *    association shared key.
251  */
252 static struct sctp_auth_bytes *sctp_auth_asoc_set_secret(
253                         struct sctp_shared_key *ep_key,
254                         struct sctp_auth_bytes *first_vector,
255                         struct sctp_auth_bytes *last_vector,
256                         gfp_t gfp)
257 {
258         struct sctp_auth_bytes *secret;
259         __u32 offset = 0;
260         __u32 auth_len;
261 
262         auth_len = first_vector->len + last_vector->len;
263         if (ep_key->key)
264                 auth_len += ep_key->key->len;
265 
266         secret = sctp_auth_create_key(auth_len, gfp);
267         if (!secret)
268                 return NULL;
269 
270         if (ep_key->key) {
271                 memcpy(secret->data, ep_key->key->data, ep_key->key->len);
272                 offset += ep_key->key->len;
273         }
274 
275         memcpy(secret->data + offset, first_vector->data, first_vector->len);
276         offset += first_vector->len;
277 
278         memcpy(secret->data + offset, last_vector->data, last_vector->len);
279 
280         return secret;
281 }
282 
283 /* Create an association shared key.  Follow the algorithm
284  * described in SCTP-AUTH, Section 6.1
285  */
286 static struct sctp_auth_bytes *sctp_auth_asoc_create_secret(
287                                  const struct sctp_association *asoc,
288                                  struct sctp_shared_key *ep_key,
289                                  gfp_t gfp)
290 {
291         struct sctp_auth_bytes *local_key_vector;
292         struct sctp_auth_bytes *peer_key_vector;
293         struct sctp_auth_bytes  *first_vector,
294                                 *last_vector;
295         struct sctp_auth_bytes  *secret = NULL;
296         int     cmp;
297 
298 
299         /* Now we need to build the key vectors
300          * SCTP-AUTH , Section 6.1
301          *    The RANDOM parameter, the CHUNKS parameter and the HMAC-ALGO
302          *    parameter sent by each endpoint are concatenated as byte vectors.
303          *    These parameters include the parameter type, parameter length, and
304          *    the parameter value, but padding is omitted; all padding MUST be
305          *    removed from this concatenation before proceeding with further
306          *    computation of keys.  Parameters which were not sent are simply
307          *    omitted from the concatenation process.  The resulting two vectors
308          *    are called the two key vectors.
309          */
310 
311         local_key_vector = sctp_auth_make_local_vector(asoc, gfp);
312         peer_key_vector = sctp_auth_make_peer_vector(asoc, gfp);
313 
314         if (!peer_key_vector || !local_key_vector)
315                 goto out;
316 
317         /* Figure out the order in which the key_vectors will be
318          * added to the endpoint shared key.
319          * SCTP-AUTH, Section 6.1:
320          *   This is performed by selecting the numerically smaller key
321          *   vector and concatenating it to the endpoint pair shared
322          *   key, and then concatenating the numerically larger key
323          *   vector to that.  If the key vectors are equal as numbers
324          *   but differ in length, then the concatenation order is the
325          *   endpoint shared key, followed by the shorter key vector,
326          *   followed by the longer key vector.  Otherwise, the key
327          *   vectors are identical, and may be concatenated to the
328          *   endpoint pair key in any order.
329          */
330         cmp = sctp_auth_compare_vectors(local_key_vector,
331                                         peer_key_vector);
332         if (cmp < 0) {
333                 first_vector = local_key_vector;
334                 last_vector = peer_key_vector;
335         } else {
336                 first_vector = peer_key_vector;
337                 last_vector = local_key_vector;
338         }
339 
340         secret = sctp_auth_asoc_set_secret(ep_key, first_vector, last_vector,
341                                             gfp);
342 out:
343         sctp_auth_key_put(local_key_vector);
344         sctp_auth_key_put(peer_key_vector);
345 
346         return secret;
347 }
348 
349 /*
350  * Populate the association overlay list with the list
351  * from the endpoint.
352  */
353 int sctp_auth_asoc_copy_shkeys(const struct sctp_endpoint *ep,
354                                 struct sctp_association *asoc,
355                                 gfp_t gfp)
356 {
357         struct sctp_shared_key *sh_key;
358         struct sctp_shared_key *new;
359 
360         BUG_ON(!list_empty(&asoc->endpoint_shared_keys));
361 
362         key_for_each(sh_key, &ep->endpoint_shared_keys) {
363                 new = sctp_auth_shkey_create(sh_key->key_id, gfp);
364                 if (!new)
365                         goto nomem;
366 
367                 new->key = sh_key->key;
368                 sctp_auth_key_hold(new->key);
369                 list_add(&new->key_list, &asoc->endpoint_shared_keys);
370         }
371 
372         return 0;
373 
374 nomem:
375         sctp_auth_destroy_keys(&asoc->endpoint_shared_keys);
376         return -ENOMEM;
377 }
378 
379 
380 /* Public interface to create the association shared key.
381  * See code above for the algorithm.
382  */
383 int sctp_auth_asoc_init_active_key(struct sctp_association *asoc, gfp_t gfp)
384 {
385         struct sctp_auth_bytes  *secret;
386         struct sctp_shared_key *ep_key;
387         struct sctp_chunk *chunk;
388 
389         /* If we don't support AUTH, or peer is not capable
390          * we don't need to do anything.
391          */
392         if (!asoc->peer.auth_capable)
393                 return 0;
394 
395         /* If the key_id is non-zero and we couldn't find an
396          * endpoint pair shared key, we can't compute the
397          * secret.
398          * For key_id 0, endpoint pair shared key is a NULL key.
399          */
400         ep_key = sctp_auth_get_shkey(asoc, asoc->active_key_id);
401         BUG_ON(!ep_key);
402 
403         secret = sctp_auth_asoc_create_secret(asoc, ep_key, gfp);
404         if (!secret)
405                 return -ENOMEM;
406 
407         sctp_auth_key_put(asoc->asoc_shared_key);
408         asoc->asoc_shared_key = secret;
409         asoc->shkey = ep_key;
410 
411         /* Update send queue in case any chunk already in there now
412          * needs authenticating
413          */
414         list_for_each_entry(chunk, &asoc->outqueue.out_chunk_list, list) {
415                 if (sctp_auth_send_cid(chunk->chunk_hdr->type, asoc)) {
416                         chunk->auth = 1;
417                         if (!chunk->shkey) {
418                                 chunk->shkey = asoc->shkey;
419                                 sctp_auth_shkey_hold(chunk->shkey);
420                         }
421                 }
422         }
423 
424         return 0;
425 }
426 
427 
428 /* Find the endpoint pair shared key based on the key_id */
429 struct sctp_shared_key *sctp_auth_get_shkey(
430                                 const struct sctp_association *asoc,
431                                 __u16 key_id)
432 {
433         struct sctp_shared_key *key;
434 
435         /* First search associations set of endpoint pair shared keys */
436         key_for_each(key, &asoc->endpoint_shared_keys) {
437                 if (key->key_id == key_id) {
438                         if (!key->deactivated)
439                                 return key;
440                         break;
441                 }
442         }
443 
444         return NULL;
445 }
446 
447 /*
448  * Initialize all the possible digest transforms that we can use.  Right now
449  * now, the supported digests are SHA1 and SHA256.  We do this here once
450  * because of the restrictiong that transforms may only be allocated in
451  * user context.  This forces us to pre-allocated all possible transforms
452  * at the endpoint init time.
453  */
454 int sctp_auth_init_hmacs(struct sctp_endpoint *ep, gfp_t gfp)
455 {
456         struct crypto_shash *tfm = NULL;
457         __u16   id;
458 
459         /* If the transforms are already allocated, we are done */
460         if (ep->auth_hmacs)
461                 return 0;
462 
463         /* Allocated the array of pointers to transorms */
464         ep->auth_hmacs = kcalloc(SCTP_AUTH_NUM_HMACS,
465                                  sizeof(struct crypto_shash *),
466                                  gfp);
467         if (!ep->auth_hmacs)
468                 return -ENOMEM;
469 
470         for (id = 0; id < SCTP_AUTH_NUM_HMACS; id++) {
471 
472                 /* See is we support the id.  Supported IDs have name and
473                  * length fields set, so that we can allocated and use
474                  * them.  We can safely just check for name, for without the
475                  * name, we can't allocate the TFM.
476                  */
477                 if (!sctp_hmac_list[id].hmac_name)
478                         continue;
479 
480                 /* If this TFM has been allocated, we are all set */
481                 if (ep->auth_hmacs[id])
482                         continue;
483 
484                 /* Allocate the ID */
485                 tfm = crypto_alloc_shash(sctp_hmac_list[id].hmac_name, 0, 0);
486                 if (IS_ERR(tfm))
487                         goto out_err;
488 
489                 ep->auth_hmacs[id] = tfm;
490         }
491 
492         return 0;
493 
494 out_err:
495         /* Clean up any successful allocations */
496         sctp_auth_destroy_hmacs(ep->auth_hmacs);
497         return -ENOMEM;
498 }
499 
500 /* Destroy the hmac tfm array */
501 void sctp_auth_destroy_hmacs(struct crypto_shash *auth_hmacs[])
502 {
503         int i;
504 
505         if (!auth_hmacs)
506                 return;
507 
508         for (i = 0; i < SCTP_AUTH_NUM_HMACS; i++) {
509                 crypto_free_shash(auth_hmacs[i]);
510         }
511         kfree(auth_hmacs);
512 }
513 
514 
515 struct sctp_hmac *sctp_auth_get_hmac(__u16 hmac_id)
516 {
517         return &sctp_hmac_list[hmac_id];
518 }
519 
520 /* Get an hmac description information that we can use to build
521  * the AUTH chunk
522  */
523 struct sctp_hmac *sctp_auth_asoc_get_hmac(const struct sctp_association *asoc)
524 {
525         struct sctp_hmac_algo_param *hmacs;
526         __u16 n_elt;
527         __u16 id = 0;
528         int i;
529 
530         /* If we have a default entry, use it */
531         if (asoc->default_hmac_id)
532                 return &sctp_hmac_list[asoc->default_hmac_id];
533 
534         /* Since we do not have a default entry, find the first entry
535          * we support and return that.  Do not cache that id.
536          */
537         hmacs = asoc->peer.peer_hmacs;
538         if (!hmacs)
539                 return NULL;
540 
541         n_elt = (ntohs(hmacs->param_hdr.length) -
542                  sizeof(struct sctp_paramhdr)) >> 1;
543         for (i = 0; i < n_elt; i++) {
544                 id = ntohs(hmacs->hmac_ids[i]);
545 
546                 /* Check the id is in the supported range. And
547                  * see if we support the id.  Supported IDs have name and
548                  * length fields set, so that we can allocate and use
549                  * them.  We can safely just check for name, for without the
550                  * name, we can't allocate the TFM.
551                  */
552                 if (id > SCTP_AUTH_HMAC_ID_MAX ||
553                     !sctp_hmac_list[id].hmac_name) {
554                         id = 0;
555                         continue;
556                 }
557 
558                 break;
559         }
560 
561         if (id == 0)
562                 return NULL;
563 
564         return &sctp_hmac_list[id];
565 }
566 
567 static int __sctp_auth_find_hmacid(__be16 *hmacs, int n_elts, __be16 hmac_id)
568 {
569         int  found = 0;
570         int  i;
571 
572         for (i = 0; i < n_elts; i++) {
573                 if (hmac_id == hmacs[i]) {
574                         found = 1;
575                         break;
576                 }
577         }
578 
579         return found;
580 }
581 
582 /* See if the HMAC_ID is one that we claim as supported */
583 int sctp_auth_asoc_verify_hmac_id(const struct sctp_association *asoc,
584                                     __be16 hmac_id)
585 {
586         struct sctp_hmac_algo_param *hmacs;
587         __u16 n_elt;
588 
589         if (!asoc)
590                 return 0;
591 
592         hmacs = (struct sctp_hmac_algo_param *)asoc->c.auth_hmacs;
593         n_elt = (ntohs(hmacs->param_hdr.length) -
594                  sizeof(struct sctp_paramhdr)) >> 1;
595 
596         return __sctp_auth_find_hmacid(hmacs->hmac_ids, n_elt, hmac_id);
597 }
598 
599 
600 /* Cache the default HMAC id.  This to follow this text from SCTP-AUTH:
601  * Section 6.1:
602  *   The receiver of a HMAC-ALGO parameter SHOULD use the first listed
603  *   algorithm it supports.
604  */
605 void sctp_auth_asoc_set_default_hmac(struct sctp_association *asoc,
606                                      struct sctp_hmac_algo_param *hmacs)
607 {
608         struct sctp_endpoint *ep;
609         __u16   id;
610         int     i;
611         int     n_params;
612 
613         /* if the default id is already set, use it */
614         if (asoc->default_hmac_id)
615                 return;
616 
617         n_params = (ntohs(hmacs->param_hdr.length) -
618                     sizeof(struct sctp_paramhdr)) >> 1;
619         ep = asoc->ep;
620         for (i = 0; i < n_params; i++) {
621                 id = ntohs(hmacs->hmac_ids[i]);
622 
623                 /* Check the id is in the supported range */
624                 if (id > SCTP_AUTH_HMAC_ID_MAX)
625                         continue;
626 
627                 /* If this TFM has been allocated, use this id */
628                 if (ep->auth_hmacs[id]) {
629                         asoc->default_hmac_id = id;
630                         break;
631                 }
632         }
633 }
634 
635 
636 /* Check to see if the given chunk is supposed to be authenticated */
637 static int __sctp_auth_cid(enum sctp_cid chunk, struct sctp_chunks_param *param)
638 {
639         unsigned short len;
640         int found = 0;
641         int i;
642 
643         if (!param || param->param_hdr.length == 0)
644                 return 0;
645 
646         len = ntohs(param->param_hdr.length) - sizeof(struct sctp_paramhdr);
647 
648         /* SCTP-AUTH, Section 3.2
649          *    The chunk types for INIT, INIT-ACK, SHUTDOWN-COMPLETE and AUTH
650          *    chunks MUST NOT be listed in the CHUNKS parameter.  However, if
651          *    a CHUNKS parameter is received then the types for INIT, INIT-ACK,
652          *    SHUTDOWN-COMPLETE and AUTH chunks MUST be ignored.
653          */
654         for (i = 0; !found && i < len; i++) {
655                 switch (param->chunks[i]) {
656                 case SCTP_CID_INIT:
657                 case SCTP_CID_INIT_ACK:
658                 case SCTP_CID_SHUTDOWN_COMPLETE:
659                 case SCTP_CID_AUTH:
660                         break;
661 
662                 default:
663                         if (param->chunks[i] == chunk)
664                                 found = 1;
665                         break;
666                 }
667         }
668 
669         return found;
670 }
671 
672 /* Check if peer requested that this chunk is authenticated */
673 int sctp_auth_send_cid(enum sctp_cid chunk, const struct sctp_association *asoc)
674 {
675         if (!asoc)
676                 return 0;
677 
678         if (!asoc->peer.auth_capable)
679                 return 0;
680 
681         return __sctp_auth_cid(chunk, asoc->peer.peer_chunks);
682 }
683 
684 /* Check if we requested that peer authenticate this chunk. */
685 int sctp_auth_recv_cid(enum sctp_cid chunk, const struct sctp_association *asoc)
686 {
687         if (!asoc)
688                 return 0;
689 
690         if (!asoc->peer.auth_capable)
691                 return 0;
692 
693         return __sctp_auth_cid(chunk,
694                               (struct sctp_chunks_param *)asoc->c.auth_chunks);
695 }
696 
697 /* SCTP-AUTH: Section 6.2:
698  *    The sender MUST calculate the MAC as described in RFC2104 [2] using
699  *    the hash function H as described by the MAC Identifier and the shared
700  *    association key K based on the endpoint pair shared key described by
701  *    the shared key identifier.  The 'data' used for the computation of
702  *    the AUTH-chunk is given by the AUTH chunk with its HMAC field set to
703  *    zero (as shown in Figure 6) followed by all chunks that are placed
704  *    after the AUTH chunk in the SCTP packet.
705  */
706 void sctp_auth_calculate_hmac(const struct sctp_association *asoc,
707                               struct sk_buff *skb, struct sctp_auth_chunk *auth,
708                               struct sctp_shared_key *ep_key, gfp_t gfp)
709 {
710         struct sctp_auth_bytes *asoc_key;
711         struct crypto_shash *tfm;
712         __u16 key_id, hmac_id;
713         unsigned char *end;
714         int free_key = 0;
715         __u8 *digest;
716 
717         /* Extract the info we need:
718          * - hmac id
719          * - key id
720          */
721         key_id = ntohs(auth->auth_hdr.shkey_id);
722         hmac_id = ntohs(auth->auth_hdr.hmac_id);
723 
724         if (key_id == asoc->active_key_id)
725                 asoc_key = asoc->asoc_shared_key;
726         else {
727                 /* ep_key can't be NULL here */
728                 asoc_key = sctp_auth_asoc_create_secret(asoc, ep_key, gfp);
729                 if (!asoc_key)
730                         return;
731 
732                 free_key = 1;
733         }
734 
735         /* set up scatter list */
736         end = skb_tail_pointer(skb);
737 
738         tfm = asoc->ep->auth_hmacs[hmac_id];
739 
740         digest = auth->auth_hdr.hmac;
741         if (crypto_shash_setkey(tfm, &asoc_key->data[0], asoc_key->len))
742                 goto free;
743 
744         {
745                 SHASH_DESC_ON_STACK(desc, tfm);
746 
747                 desc->tfm = tfm;
748                 crypto_shash_digest(desc, (u8 *)auth,
749                                     end - (unsigned char *)auth, digest);
750                 shash_desc_zero(desc);
751         }
752 
753 free:
754         if (free_key)
755                 sctp_auth_key_put(asoc_key);
756 }
757 
758 /* API Helpers */
759 
760 /* Add a chunk to the endpoint authenticated chunk list */
761 int sctp_auth_ep_add_chunkid(struct sctp_endpoint *ep, __u8 chunk_id)
762 {
763         struct sctp_chunks_param *p = ep->auth_chunk_list;
764         __u16 nchunks;
765         __u16 param_len;
766 
767         /* If this chunk is already specified, we are done */
768         if (__sctp_auth_cid(chunk_id, p))
769                 return 0;
770 
771         /* Check if we can add this chunk to the array */
772         param_len = ntohs(p->param_hdr.length);
773         nchunks = param_len - sizeof(struct sctp_paramhdr);
774         if (nchunks == SCTP_NUM_CHUNK_TYPES)
775                 return -EINVAL;
776 
777         p->chunks[nchunks] = chunk_id;
778         p->param_hdr.length = htons(param_len + 1);
779         return 0;
780 }
781 
782 /* Add hmac identifires to the endpoint list of supported hmac ids */
783 int sctp_auth_ep_set_hmacs(struct sctp_endpoint *ep,
784                            struct sctp_hmacalgo *hmacs)
785 {
786         int has_sha1 = 0;
787         __u16 id;
788         int i;
789 
790         /* Scan the list looking for unsupported id.  Also make sure that
791          * SHA1 is specified.
792          */
793         for (i = 0; i < hmacs->shmac_num_idents; i++) {
794                 id = hmacs->shmac_idents[i];
795 
796                 if (id > SCTP_AUTH_HMAC_ID_MAX)
797                         return -EOPNOTSUPP;
798 
799                 if (SCTP_AUTH_HMAC_ID_SHA1 == id)
800                         has_sha1 = 1;
801 
802                 if (!sctp_hmac_list[id].hmac_name)
803                         return -EOPNOTSUPP;
804         }
805 
806         if (!has_sha1)
807                 return -EINVAL;
808 
809         for (i = 0; i < hmacs->shmac_num_idents; i++)
810                 ep->auth_hmacs_list->hmac_ids[i] =
811                                 htons(hmacs->shmac_idents[i]);
812         ep->auth_hmacs_list->param_hdr.length =
813                         htons(sizeof(struct sctp_paramhdr) +
814                         hmacs->shmac_num_idents * sizeof(__u16));
815         return 0;
816 }
817 
818 /* Set a new shared key on either endpoint or association.  If the
819  * the key with a same ID already exists, replace the key (remove the
820  * old key and add a new one).
821  */
822 int sctp_auth_set_key(struct sctp_endpoint *ep,
823                       struct sctp_association *asoc,
824                       struct sctp_authkey *auth_key)
825 {
826         struct sctp_shared_key *cur_key, *shkey;
827         struct sctp_auth_bytes *key;
828         struct list_head *sh_keys;
829         int replace = 0;
830 
831         /* Try to find the given key id to see if
832          * we are doing a replace, or adding a new key
833          */
834         if (asoc) {
835                 if (!asoc->peer.auth_capable)
836                         return -EACCES;
837                 sh_keys = &asoc->endpoint_shared_keys;
838         } else {
839                 if (!ep->auth_enable)
840                         return -EACCES;
841                 sh_keys = &ep->endpoint_shared_keys;
842         }
843 
844         key_for_each(shkey, sh_keys) {
845                 if (shkey->key_id == auth_key->sca_keynumber) {
846                         replace = 1;
847                         break;
848                 }
849         }
850 
851         cur_key = sctp_auth_shkey_create(auth_key->sca_keynumber, GFP_KERNEL);
852         if (!cur_key)
853                 return -ENOMEM;
854 
855         /* Create a new key data based on the info passed in */
856         key = sctp_auth_create_key(auth_key->sca_keylength, GFP_KERNEL);
857         if (!key) {
858                 kfree(cur_key);
859                 return -ENOMEM;
860         }
861 
862         memcpy(key->data, &auth_key->sca_key[0], auth_key->sca_keylength);
863         cur_key->key = key;
864 
865         if (replace) {
866                 list_del_init(&shkey->key_list);
867                 sctp_auth_shkey_release(shkey);
868         }
869         list_add(&cur_key->key_list, sh_keys);
870 
871         return 0;
872 }
873 
874 int sctp_auth_set_active_key(struct sctp_endpoint *ep,
875                              struct sctp_association *asoc,
876                              __u16  key_id)
877 {
878         struct sctp_shared_key *key;
879         struct list_head *sh_keys;
880         int found = 0;
881 
882         /* The key identifier MUST correst to an existing key */
883         if (asoc) {
884                 if (!asoc->peer.auth_capable)
885                         return -EACCES;
886                 sh_keys = &asoc->endpoint_shared_keys;
887         } else {
888                 if (!ep->auth_enable)
889                         return -EACCES;
890                 sh_keys = &ep->endpoint_shared_keys;
891         }
892 
893         key_for_each(key, sh_keys) {
894                 if (key->key_id == key_id) {
895                         found = 1;
896                         break;
897                 }
898         }
899 
900         if (!found || key->deactivated)
901                 return -EINVAL;
902 
903         if (asoc) {
904                 asoc->active_key_id = key_id;
905                 sctp_auth_asoc_init_active_key(asoc, GFP_KERNEL);
906         } else
907                 ep->active_key_id = key_id;
908 
909         return 0;
910 }
911 
912 int sctp_auth_del_key_id(struct sctp_endpoint *ep,
913                          struct sctp_association *asoc,
914                          __u16  key_id)
915 {
916         struct sctp_shared_key *key;
917         struct list_head *sh_keys;
918         int found = 0;
919 
920         /* The key identifier MUST NOT be the current active key
921          * The key identifier MUST correst to an existing key
922          */
923         if (asoc) {
924                 if (!asoc->peer.auth_capable)
925                         return -EACCES;
926                 if (asoc->active_key_id == key_id)
927                         return -EINVAL;
928 
929                 sh_keys = &asoc->endpoint_shared_keys;
930         } else {
931                 if (!ep->auth_enable)
932                         return -EACCES;
933                 if (ep->active_key_id == key_id)
934                         return -EINVAL;
935 
936                 sh_keys = &ep->endpoint_shared_keys;
937         }
938 
939         key_for_each(key, sh_keys) {
940                 if (key->key_id == key_id) {
941                         found = 1;
942                         break;
943                 }
944         }
945 
946         if (!found)
947                 return -EINVAL;
948 
949         /* Delete the shared key */
950         list_del_init(&key->key_list);
951         sctp_auth_shkey_release(key);
952 
953         return 0;
954 }
955 
956 int sctp_auth_deact_key_id(struct sctp_endpoint *ep,
957                            struct sctp_association *asoc, __u16  key_id)
958 {
959         struct sctp_shared_key *key;
960         struct list_head *sh_keys;
961         int found = 0;
962 
963         /* The key identifier MUST NOT be the current active key
964          * The key identifier MUST correst to an existing key
965          */
966         if (asoc) {
967                 if (!asoc->peer.auth_capable)
968                         return -EACCES;
969                 if (asoc->active_key_id == key_id)
970                         return -EINVAL;
971 
972                 sh_keys = &asoc->endpoint_shared_keys;
973         } else {
974                 if (!ep->auth_enable)
975                         return -EACCES;
976                 if (ep->active_key_id == key_id)
977                         return -EINVAL;
978 
979                 sh_keys = &ep->endpoint_shared_keys;
980         }
981 
982         key_for_each(key, sh_keys) {
983                 if (key->key_id == key_id) {
984                         found = 1;
985                         break;
986                 }
987         }
988 
989         if (!found)
990                 return -EINVAL;
991 
992         /* refcnt == 1 and !list_empty mean it's not being used anywhere
993          * and deactivated will be set, so it's time to notify userland
994          * that this shkey can be freed.
995          */
996         if (asoc && !list_empty(&key->key_list) &&
997             refcount_read(&key->refcnt) == 1) {
998                 struct sctp_ulpevent *ev;
999 
1000                 ev = sctp_ulpevent_make_authkey(asoc, key->key_id,
1001                                                 SCTP_AUTH_FREE_KEY, GFP_KERNEL);
1002                 if (ev)
1003                         asoc->stream.si->enqueue_event(&asoc->ulpq, ev);
1004         }
1005 
1006         key->deactivated = 1;
1007 
1008         return 0;
1009 }
1010 
1011 int sctp_auth_init(struct sctp_endpoint *ep, gfp_t gfp)
1012 {
1013         int err = -ENOMEM;
1014 
1015         /* Allocate space for HMACS and CHUNKS authentication
1016          * variables.  There are arrays that we encode directly
1017          * into parameters to make the rest of the operations easier.
1018          */
1019         if (!ep->auth_hmacs_list) {
1020                 struct sctp_hmac_algo_param *auth_hmacs;
1021 
1022                 auth_hmacs = kzalloc(struct_size(auth_hmacs, hmac_ids,
1023                                                  SCTP_AUTH_NUM_HMACS), gfp);
1024                 if (!auth_hmacs)
1025                         goto nomem;
1026                 /* Initialize the HMACS parameter.
1027                  * SCTP-AUTH: Section 3.3
1028                  *    Every endpoint supporting SCTP chunk authentication MUST
1029                  *    support the HMAC based on the SHA-1 algorithm.
1030                  */
1031                 auth_hmacs->param_hdr.type = SCTP_PARAM_HMAC_ALGO;
1032                 auth_hmacs->param_hdr.length =
1033                                 htons(sizeof(struct sctp_paramhdr) + 2);
1034                 auth_hmacs->hmac_ids[0] = htons(SCTP_AUTH_HMAC_ID_SHA1);
1035                 ep->auth_hmacs_list = auth_hmacs;
1036         }
1037 
1038         if (!ep->auth_chunk_list) {
1039                 struct sctp_chunks_param *auth_chunks;
1040 
1041                 auth_chunks = kzalloc(sizeof(*auth_chunks) +
1042                                       SCTP_NUM_CHUNK_TYPES, gfp);
1043                 if (!auth_chunks)
1044                         goto nomem;
1045                 /* Initialize the CHUNKS parameter */
1046                 auth_chunks->param_hdr.type = SCTP_PARAM_CHUNKS;
1047                 auth_chunks->param_hdr.length =
1048                                 htons(sizeof(struct sctp_paramhdr));
1049                 ep->auth_chunk_list = auth_chunks;
1050         }
1051 
1052         /* Allocate and initialize transorms arrays for supported
1053          * HMACs.
1054          */
1055         err = sctp_auth_init_hmacs(ep, gfp);
1056         if (err)
1057                 goto nomem;
1058 
1059         return 0;
1060 
1061 nomem:
1062         /* Free all allocations */
1063         kfree(ep->auth_hmacs_list);
1064         kfree(ep->auth_chunk_list);
1065         ep->auth_hmacs_list = NULL;
1066         ep->auth_chunk_list = NULL;
1067         return err;
1068 }
1069 
1070 void sctp_auth_free(struct sctp_endpoint *ep)
1071 {
1072         kfree(ep->auth_hmacs_list);
1073         kfree(ep->auth_chunk_list);
1074         ep->auth_hmacs_list = NULL;
1075         ep->auth_chunk_list = NULL;
1076         sctp_auth_destroy_hmacs(ep->auth_hmacs);
1077         ep->auth_hmacs = NULL;
1078 }
1079 

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