Commit e4dc99c7 authored by Xin Long's avatar Xin Long Committed by David S. Miller
Browse files

sctp: process duplicated strreset out and addstrm out requests correctly 



Now sctp stream reconf will process a request again even if it's seqno is
less than asoc->strreset_inseq.

If one request has been done successfully and some data chunks have been
accepted and then a duplicated strreset out request comes, the streamin's
ssn will be cleared. It will cause that stream will never receive chunks
any more because of unsynchronized ssn. It allows a replay attack.

A similar issue also exists when processing addstrm out requests. It will
cause more extra streams being added.

This patch is to fix it by saving the last 2 results into asoc. When a
duplicated strreset out or addstrm out request is received, reply it with
bad seqno if it's seqno < asoc->strreset_inseq - 2, and reply it with the
result saved in asoc if it's seqno >= asoc->strreset_inseq - 2.

Note that it saves last 2 results instead of only last 1 result, because
two requests can be sent together in one chunk.

And note that when receiving a duplicated request, the receiver side will
still reply it even if the peer has received the response. It's safe, As
the response will be dropped by the peer.

Signed-off-by: default avatarXin Long <lucien.xin@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b89f04c6

include/net/sctp/structs.h

+1 −0
Original line number Diff line number Diff line
@@ -1889,6 +1889,7 @@ struct sctp_association { 


	__u32 strreset_outseq; /* Update after receiving response */

	__u32 strreset_inseq; /* Update after receiving request */

	__u32 strreset_result[2]; /* save the results of last 2 responses */



	struct sctp_chunk *strreset_chunk; /* save request chunk */

net/sctp/stream.c

+29 −10
Original line number Diff line number Diff line
@@ -344,6 +344,13 @@ static sctp_paramhdr_t *sctp_chunk_lookup_strreset_param( 
	return NULL;

}



static void sctp_update_strreset_result(struct sctp_association *asoc,

					__u32 result)

{

	asoc->strreset_result[1] = asoc->strreset_result[0];

	asoc->strreset_result[0] = result;

}



struct sctp_chunk *sctp_process_strreset_outreq(

				struct sctp_association *asoc,

				union sctp_params param,
@@ -360,15 +367,19 @@ struct sctp_chunk *sctp_process_strreset_outreq( 
	if (ntohl(outreq->send_reset_at_tsn) >

	    sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map)) {

		result = SCTP_STRRESET_IN_PROGRESS;

		goto out;

		goto err;

	}



	if (request_seq > asoc->strreset_inseq) {

	if (TSN_lt(asoc->strreset_inseq, request_seq) ||

	    TSN_lt(request_seq, asoc->strreset_inseq - 2)) {

		result = SCTP_STRRESET_ERR_BAD_SEQNO;

		goto out;

	} else if (request_seq == asoc->strreset_inseq) {

		asoc->strreset_inseq++;

		goto err;

	} else if (TSN_lt(request_seq, asoc->strreset_inseq)) {

		i = asoc->strreset_inseq - request_seq - 1;

		result = asoc->strreset_result[i];

		goto err;

	}

	asoc->strreset_inseq++;



	/* Check strreset_enable after inseq inc, as sender cannot tell

	 * the peer doesn't enable strreset after receiving response with
@@ -427,6 +438,8 @@ struct sctp_chunk *sctp_process_strreset_outreq( 
		GFP_ATOMIC);



out:

	sctp_update_strreset_result(asoc, result);

err:

	return sctp_make_strreset_resp(asoc, result, request_seq);

}
@@ -582,15 +595,19 @@ struct sctp_chunk *sctp_process_strreset_addstrm_out( 
	__u32 result = SCTP_STRRESET_DENIED;

	struct sctp_stream_in *streamin;

	__u32 request_seq, incnt;

	__u16 in;

	__u16 in, i;



	request_seq = ntohl(addstrm->request_seq);

	if (request_seq > asoc->strreset_inseq) {

	if (TSN_lt(asoc->strreset_inseq, request_seq) ||

	    TSN_lt(request_seq, asoc->strreset_inseq - 2)) {

		result = SCTP_STRRESET_ERR_BAD_SEQNO;

		goto out;

	} else if (request_seq == asoc->strreset_inseq) {

		asoc->strreset_inseq++;

		goto err;

	} else if (TSN_lt(request_seq, asoc->strreset_inseq)) {

		i = asoc->strreset_inseq - request_seq - 1;

		result = asoc->strreset_result[i];

		goto err;

	}

	asoc->strreset_inseq++;



	if (!(asoc->strreset_enable & SCTP_ENABLE_CHANGE_ASSOC_REQ))

		goto out;
@@ -638,6 +655,8 @@ struct sctp_chunk *sctp_process_strreset_addstrm_out( 
		0, ntohs(addstrm->number_of_streams), 0, GFP_ATOMIC);



out:

	sctp_update_strreset_result(asoc, result);

err:

	return sctp_make_strreset_resp(asoc, result, request_seq);

}

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