text: /* 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 ((INT_MAX - key_len) < 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 stucture */
  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);
  }
  
  /* Destory 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 wich 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;
  }
  