[PATCH 4.19 19/78] netfilter: conntrack: allow sctp hearbeat after connection re-use

Greg Kroah-Hartman
2020-09-15T23:41:59Z

From: Florian Westphal <fw@strlen.de>

[ Upstream commit cc5453a5b7e90c39f713091a7ebc53c1f87d1700 ]

If an sctp connection gets re-used, heartbeats are flagged as invalid
because their vtag doesn't match.

Handle this in a similar way as TCP conntrack when it suspects that the
endpoints and conntrack are out-of-sync.

When a HEARTBEAT request fails its vtag validation, flag this in the
conntrack state and accept the packet.

When a HEARTBEAT_ACK is received with an invalid vtag in the reverse
direction after we allowed such a HEARTBEAT through, assume we are
out-of-sync and re-set the vtag info.

v2: remove left-over snippet from an older incarnation that moved
new_state/old_state assignments, thats not needed so keep that
as-is.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/netfilter/nf_conntrack_sctp.h | 2 ++
net/netfilter/nf_conntrack_proto_sctp.c | 39 ++++++++++++++++++---
2 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/include/linux/netfilter/nf_conntrack_sctp.h b/include/linux/netfilter/nf_conntrack_sctp.h
index 9a33f171aa822..625f491b95de8 100644
--- a/include/linux/netfilter/nf_conntrack_sctp.h
+++ b/include/linux/netfilter/nf_conntrack_sctp.h
@@ -9,6 +9,8 @@ struct ip_ct_sctp {
enum sctp_conntrack state;

__be32 vtag[IP_CT_DIR_MAX];
+ u8 last_dir;
+ u8 flags;
};

#endif /* _NF_CONNTRACK_SCTP_H */
diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
index 7d7e30ea0ecf9..a937d4f75613f 100644
--- a/net/netfilter/nf_conntrack_proto_sctp.c
+++ b/net/netfilter/nf_conntrack_proto_sctp.c
@@ -65,6 +65,8 @@ static const unsigned int sctp_timeouts[SCTP_CONNTRACK_MAX] = {
[SCTP_CONNTRACK_HEARTBEAT_ACKED] = 210 SECS,
};

+#define SCTP_FLAG_HEARTBEAT_VTAG_FAILED 1
+
#define sNO SCTP_CONNTRACK_NONE
#define sCL SCTP_CONNTRACK_CLOSED
#define sCW SCTP_CONNTRACK_COOKIE_WAIT
@@ -288,6 +290,7 @@ static int sctp_packet(struct nf_conn *ct,
u_int32_t offset, count;
unsigned int *timeouts;
unsigned long map[256 / sizeof(unsigned long)] = { 0 };
+ bool ignore = false;

sh = skb_header_pointer(skb, dataoff, sizeof(_sctph), &_sctph);
if (sh == NULL)
@@ -332,15 +335,39 @@ static int sctp_packet(struct nf_conn *ct,
/* Sec 8.5.1 (D) */
if (sh->vtag != ct->proto.sctp.vtag[dir])
goto out_unlock;
- } else if (sch->type == SCTP_CID_HEARTBEAT ||
- sch->type == SCTP_CID_HEARTBEAT_ACK) {
+ } else if (sch->type == SCTP_CID_HEARTBEAT) {
+ if (ct->proto.sctp.vtag[dir] == 0) {
+ pr_debug("Setting %d vtag %x for dir %d\n", sch->type, sh->vtag, dir);
+ ct->proto.sctp.vtag[dir] = sh->vtag;
+ } else if (sh->vtag != ct->proto.sctp.vtag[dir]) {
+ if (test_bit(SCTP_CID_DATA, map) || ignore)
+ goto out_unlock;
+
+ ct->proto.sctp.flags |= SCTP_FLAG_HEARTBEAT_VTAG_FAILED;
+ ct->proto.sctp.last_dir = dir;
+ ignore = true;
+ continue;
+ } else if (ct->proto.sctp.flags & SCTP_FLAG_HEARTBEAT_VTAG_FAILED) {
+ ct->proto.sctp.flags &= ~SCTP_FLAG_HEARTBEAT_VTAG_FAILED;
+ }
+ } else if (sch->type == SCTP_CID_HEARTBEAT_ACK) {
if (ct->proto.sctp.vtag[dir] == 0) {
pr_debug("Setting vtag %x for dir %d\n",
sh->vtag, dir);
ct->proto.sctp.vtag[dir] = sh->vtag;
} else if (sh->vtag != ct->proto.sctp.vtag[dir]) {
- pr_debug("Verification tag check failed\n");
- goto out_unlock;
+ if (test_bit(SCTP_CID_DATA, map) || ignore)
+ goto out_unlock;
+
+ if ((ct->proto.sctp.flags & SCTP_FLAG_HEARTBEAT_VTAG_FAILED) == 0 ||
+ ct->proto.sctp.last_dir == dir)
+ goto out_unlock;
+
+ ct->proto.sctp.flags &= ~SCTP_FLAG_HEARTBEAT_VTAG_FAILED;
+ ct->proto.sctp.vtag[dir] = sh->vtag;
+ ct->proto.sctp.vtag[!dir] = 0;
+ } else if (ct->proto.sctp.flags & SCTP_FLAG_HEARTBEAT_VTAG_FAILED) {
+ ct->proto.sctp.flags &= ~SCTP_FLAG_HEARTBEAT_VTAG_FAILED;
}
}

@@ -375,6 +402,10 @@ static int sctp_packet(struct nf_conn *ct,
}
spin_unlock_bh(&ct->lock);

+ /* allow but do not refresh timeout */
+ if (ignore)
+ return NF_ACCEPT;
+
timeouts = nf_ct_timeout_lookup(ct);
if (!timeouts)
timeouts = sctp_pernet(nf_ct_net(ct))->timeouts;
--
2.25.1