[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, 12 insertions, 0 deletions

diff --git a/net/sctp/chunk.c b/net/sctp/chunk.c
index 77fb7b06a9c..619d0f2dee5 100644
--- a/net/sctp/chunk.c
+++ b/net/sctp/chunk.c
@@ -194,6 +194,18 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
 
 	max = asoc->frag_point;
 
+	/* If the the peer requested that we authenticate DATA chunks
+	 * we need to accound for bundling of the AUTH chunks along with
+	 * DATA.
+	 */
+	if (sctp_auth_send_cid(SCTP_CID_DATA, asoc)) {
+		struct sctp_hmac *hmac_desc = sctp_auth_asoc_get_hmac(asoc);
+
+		if (hmac_desc)
+			max -= WORD_ROUND(sizeof(sctp_auth_chunk_t) +
+					    hmac_desc->hmac_len);
+	}
+
 	whole = 0;
 	first_len = max;