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netfilter: conntrack: allow sctp hearbeat after connection re-use 

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>
This commit is contained in:
Florian Westphal 2020-08-18 16:15:58 +02:00 committed by Pablo Neira Ayuso
parent cf96d97738
commit cc5453a5b7
2 changed files with 37 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/netfilter/nf_conntrack_sctp.h
View File

@ -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 */

39
net/netfilter/nf_conntrack_proto_sctp.c
View File

@ -62,6 +62,8 @@ 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
@ -369,6 +371,7 @@ int nf_conntrack_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;
if (sctp_error(skb, dataoff, state))
return -NF_ACCEPT;
@ -427,15 +430,39 @@ int nf_conntrack_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;
}
}
@ -470,6 +497,10 @@ int nf_conntrack_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 = nf_sctp_pernet(nf_ct_net(ct))->timeouts;