Skip to content

Commit

Permalink
dccp: fix bug in sequence number validation during connection setup
Browse files Browse the repository at this point in the history 
This fixes a bug in the sequence number validation during the initial handshake.

The code did not treat the initial sequence numbers ISS and ISR as read-only and
did not keep state for GSR and GSS as required by the specification. This causes
problems with retransmissions during the initial handshake, causing the
budding connection to be reset.

This patch now treats ISS/ISR as read-only and tracks GSS/GSR as required.

Signed-off-by: Samuel Jero <sj323707@ohio.edu>
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
  • Loading branch information
Samuel Jero authored and Gerrit Renker committed Mar 3, 2012
1 parent 793734b commit f541fb7
Show file tree
Hide file tree
Showing 5 changed files with 32 additions and 20 deletions.
8 changes: 6 additions & 2 deletions include/linux/dccp.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -376,8 +376,10 @@ static inline unsigned int dccp_hdr_len(const struct sk_buff *skb)
/**
* struct dccp_request_sock - represent DCCP-specific connection request
* @dreq_inet_rsk: structure inherited from
* @dreq_iss: initial sequence number sent on the Response (RFC 4340, 7.1)
* @dreq_isr: initial sequence number received on the Request
* @dreq_iss: initial sequence number, sent on the first Response (RFC 4340, 7.1)
* @dreq_gss: greatest sequence number sent (for retransmitted Responses)
* @dreq_isr: initial sequence number received in the first Request
* @dreq_gsr: greatest sequence number received (for retransmitted Request(s))
* @dreq_service: service code present on the Request (there is just one)
* @dreq_featneg: feature negotiation options for this connection
* The following two fields are analogous to the ones in dccp_sock:
Expand All @@ -387,7 +389,9 @@ static inline unsigned int dccp_hdr_len(const struct sk_buff *skb)
struct dccp_request_sock {
struct inet_request_sock dreq_inet_rsk;
__u64 dreq_iss;
__u64 dreq_gss;
__u64 dreq_isr;
__u64 dreq_gsr;
__be32 dreq_service;
struct list_head dreq_featneg;
__u32 dreq_timestamp_echo;
Expand Down
8 changes: 5 additions & 3 deletions net/dccp/ipv4.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -300,7 +300,8 @@ static void dccp_v4_err(struct sk_buff *skb, u32 info)
*/
WARN_ON(req->sk);

if (seq != dccp_rsk(req)->dreq_iss) {
if (!between48(seq, dccp_rsk(req)->dreq_iss,
dccp_rsk(req)->dreq_gss)) {
NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
goto out;
}
Expand Down Expand Up @@ -639,11 +640,12 @@ int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
*
* Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
*
* In fact we defer setting S.GSR, S.SWL, S.SWH to
* dccp_create_openreq_child.
* Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
*/
dreq->dreq_isr = dcb->dccpd_seq;
dreq->dreq_gsr = dreq->dreq_isr;
dreq->dreq_iss = dccp_v4_init_sequence(skb);
dreq->dreq_gss = dreq->dreq_iss;
dreq->dreq_service = service;

if (dccp_v4_send_response(sk, req, NULL))
Expand Down
8 changes: 5 additions & 3 deletions net/dccp/ipv6.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -193,7 +193,8 @@ static void dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
*/
WARN_ON(req->sk != NULL);

if (seq != dccp_rsk(req)->dreq_iss) {
if (!between48(seq, dccp_rsk(req)->dreq_iss,
dccp_rsk(req)->dreq_gss)) {
NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
goto out;
}
Expand Down Expand Up @@ -440,11 +441,12 @@ static int dccp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
*
* Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
*
* In fact we defer setting S.GSR, S.SWL, S.SWH to
* dccp_create_openreq_child.
* Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
*/
dreq->dreq_isr = dcb->dccpd_seq;
dreq->dreq_gsr = dreq->dreq_isr;
dreq->dreq_iss = dccp_v6_init_sequence(skb);
dreq->dreq_gss = dreq->dreq_iss;
dreq->dreq_service = service;

if (dccp_v6_send_response(sk, req, NULL))
Expand Down
18 changes: 11 additions & 7 deletions net/dccp/minisocks.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -127,9 +127,11 @@ struct sock *dccp_create_openreq_child(struct sock *sk,
* activation below, as these windows all depend on the local
* and remote Sequence Window feature values (7.5.2).
*/
newdp->dccps_gss = newdp->dccps_iss = dreq->dreq_iss;
newdp->dccps_iss = dreq->dreq_iss;
newdp->dccps_gss = dreq->dreq_gss;
newdp->dccps_gar = newdp->dccps_iss;
newdp->dccps_gsr = newdp->dccps_isr = dreq->dreq_isr;
newdp->dccps_isr = dreq->dreq_isr;
newdp->dccps_gsr = dreq->dreq_gsr;

/*
* Activate features: initialise CCIDs, sequence windows etc.
Expand Down Expand Up @@ -164,9 +166,9 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
/* Check for retransmitted REQUEST */
if (dccp_hdr(skb)->dccph_type == DCCP_PKT_REQUEST) {

if (after48(DCCP_SKB_CB(skb)->dccpd_seq, dreq->dreq_isr)) {
if (after48(DCCP_SKB_CB(skb)->dccpd_seq, dreq->dreq_gsr)) {
dccp_pr_debug("Retransmitted REQUEST\n");
dreq->dreq_isr = DCCP_SKB_CB(skb)->dccpd_seq;
dreq->dreq_gsr = DCCP_SKB_CB(skb)->dccpd_seq;
/*
* Send another RESPONSE packet
* To protect against Request floods, increment retrans
Expand All @@ -186,12 +188,14 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
goto drop;

/* Invalid ACK */
if (DCCP_SKB_CB(skb)->dccpd_ack_seq != dreq->dreq_iss) {
if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
dreq->dreq_iss, dreq->dreq_gss)) {
dccp_pr_debug("Invalid ACK number: ack_seq=%llu, "
"dreq_iss=%llu\n",
"dreq_iss=%llu, dreq_gss=%llu\n",
(unsigned long long)
DCCP_SKB_CB(skb)->dccpd_ack_seq,
(unsigned long long) dreq->dreq_iss);
(unsigned long long) dreq->dreq_iss,
(unsigned long long) dreq->dreq_gss);
goto drop;
}

Expand Down
10 changes: 5 additions & 5 deletions net/dccp/output.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -408,10 +408,10 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
skb_dst_set(skb, dst_clone(dst));

dreq = dccp_rsk(req);
if (inet_rsk(req)->acked) /* increase ISS upon retransmission */
dccp_inc_seqno(&dreq->dreq_iss);
if (inet_rsk(req)->acked) /* increase GSS upon retransmission */
dccp_inc_seqno(&dreq->dreq_gss);
DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
DCCP_SKB_CB(skb)->dccpd_seq = dreq->dreq_iss;
DCCP_SKB_CB(skb)->dccpd_seq = dreq->dreq_gss;

/* Resolve feature dependencies resulting from choice of CCID */
if (dccp_feat_server_ccid_dependencies(dreq))
Expand All @@ -429,8 +429,8 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
dh->dccph_type = DCCP_PKT_RESPONSE;
dh->dccph_x = 1;
dccp_hdr_set_seq(dh, dreq->dreq_iss);
dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
dccp_hdr_set_seq(dh, dreq->dreq_gss);
dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_gsr);
dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;

dccp_csum_outgoing(skb);
Expand Down

0 comments on commit f541fb7

Please sign in to comment.