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sctp: process duplicated strreset asoc request correctly

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This patch is to fix the replay attack issue for strreset asoc requests.

When a duplicated strreset asoc 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.

But note that if the result saved in asoc is performed, the sender's next
tsn and receiver's next tsn for the response chunk should be set. It's
safe to get them from asoc. Because if it's changed, which means the peer
has received the response already, the new response with wrong tsn won't
be accepted by peer.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xin Long 2017-04-15 22:00:29 +08:00 committed by David S. Miller
parent d0f025e611
commit 6c80138773
1 changed files with 15 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
net/sctp/stream.c
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@ -529,12 +529,21 @@ struct sctp_chunk *sctp_process_strreset_tsnreq(
__u16 i;
request_seq = ntohl(tsnreq->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];
if (result == SCTP_STRRESET_PERFORMED) {
next_tsn = asoc->next_tsn;
init_tsn =
sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map) + 1;
}
goto err;
}
asoc->strreset_inseq++;
if (!(asoc->strreset_enable & SCTP_ENABLE_RESET_ASSOC_REQ))
goto out;
@ -591,6 +600,8 @@ struct sctp_chunk *sctp_process_strreset_tsnreq(
next_tsn, GFP_ATOMIC);
out:
sctp_update_strreset_result(asoc, result);
err:
return sctp_make_strreset_tsnresp(asoc, result, request_seq,
next_tsn, init_tsn);
}