[SCTP]: Enable the sending of the AUTH chunk.

SCTP-AUTH, Section 6.2:

   Endpoints MUST send all requested chunks authenticated where this has
   been requested by the peer.  The other chunks MAY be sent
   authenticated or not.  If endpoint pair shared keys are used, one of
   them MUST be selected for authentication.

   To send chunks in an authenticated way, the sender MUST include these
   chunks after an AUTH chunk.  This means that a sender MUST bundle
   chunks in order to authenticate them.

   If the endpoint has no endpoint pair shared key for the peer, it MUST
   use Shared Key Identifier 0 with an empty endpoint pair shared key.
   If there are multiple endpoint shared keys the sender selects one and
   uses the corresponding Shared Key Identifier

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 39 insertions, 0 deletions

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 4c02875786ac..fa2ba543183d 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1111,6 +1111,41 @@ nodata:
         return retval;
 }
 
+struct sctp_chunk *sctp_make_auth(const struct sctp_association *asoc)
+{
+        struct sctp_chunk *retval;
+        struct sctp_hmac *hmac_desc;
+        struct sctp_authhdr auth_hdr;
+        __u8 *hmac;
+
+        /* Get the first hmac that the peer told us to use */
+        hmac_desc = sctp_auth_asoc_get_hmac(asoc);
+        if (unlikely(!hmac_desc))
+                return NULL;
+
+        retval = sctp_make_chunk(asoc, SCTP_CID_AUTH, 0,
+                        hmac_desc->hmac_len + sizeof(sctp_authhdr_t));
+        if (!retval)
+                return NULL;
+
+        auth_hdr.hmac_id = htons(hmac_desc->hmac_id);
+        auth_hdr.shkey_id = htons(asoc->active_key_id);
+
+        retval->subh.auth_hdr = sctp_addto_chunk(retval, sizeof(sctp_authhdr_t),
+                                                &auth_hdr);
+
+        hmac = skb_put(retval->skb, hmac_desc->hmac_len);
+        memset(hmac, 0, hmac_desc->hmac_len);
+
+        /* Adjust the chunk header to include the empty MAC */
+        retval->chunk_hdr->length =
+                htons(ntohs(retval->chunk_hdr->length) + hmac_desc->hmac_len);
+        retval->chunk_end = skb_tail_pointer(retval->skb);
+
+        return retval;
+}
+
+
 /********************************************************************
  * 2nd Level Abstractions
  ********************************************************************/
@@ -1225,6 +1260,10 @@ struct sctp_chunk *sctp_make_chunk(const struct sctp_association *asoc,
         retval->chunk_hdr = chunk_hdr;
         retval->chunk_end = ((__u8 *)chunk_hdr) + sizeof(struct sctp_chunkhdr);
 
+        /* Determine if the chunk needs to be authenticated */
+        if (sctp_auth_send_cid(type, asoc))
+                retval->auth = 1;
+
         /* Set the skb to the belonging sock for accounting.  */
         skb->sk = sk;