auth.c

linux 内核源代码

		/* 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 successfull 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)
			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)
			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 (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_keylen, GFP_KERNEL);
	if (!key)
		goto nomem;

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

	/* 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;
}