From e4dc99c7c21ba456fd72a70ada5d8d5f3850bcf5 Mon Sep 17 00:00:00 2001 From: Xin Long Date: Sat, 15 Apr 2017 22:00:27 +0800 Subject: [PATCH] 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: Xin Long Signed-off-by: David S. Miller --- include/net/sctp/structs.h | 1 + net/sctp/stream.c | 39 +++++++++++++++++++++++++++++---------- 2 files changed, 30 insertions(+), 10 deletions(-) diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h index b751399..a8b38e1 100644 --- a/include/net/sctp/structs.h +++ b/include/net/sctp/structs.h @@ -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 */ diff --git a/net/sctp/stream.c b/net/sctp/stream.c index 4ec3679..6cab7c3 100644 --- a/net/sctp/stream.c +++ b/net/sctp/stream.c @@ -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); } -- 2.7.4