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 <lucien.xin@xxxxxxxxx>
---
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);
}
--
2.1.0
--
To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
