// SPDX-License-Identifier: GPL-2.0-only
|
/*
|
* Copyright (c) 2013 Patrick McHardy <kaber@trash.net>
|
*/
|
|
#include <linux/netfilter_ipv4/ip_tables.h>
|
#include <linux/netfilter/x_tables.h>
|
#include <linux/netfilter/xt_SYNPROXY.h>
|
|
#include <net/netfilter/nf_synproxy.h>
|
|
static unsigned int
|
synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par)
|
{
|
const struct xt_synproxy_info *info = par->targinfo;
|
struct net *net = xt_net(par);
|
struct synproxy_net *snet = synproxy_pernet(net);
|
struct synproxy_options opts = {};
|
struct tcphdr *th, _th;
|
|
if (nf_ip_checksum(skb, xt_hooknum(par), par->thoff, IPPROTO_TCP))
|
return NF_DROP;
|
|
th = skb_header_pointer(skb, par->thoff, sizeof(_th), &_th);
|
if (th == NULL)
|
return NF_DROP;
|
|
if (!synproxy_parse_options(skb, par->thoff, th, &opts))
|
return NF_DROP;
|
|
if (th->syn && !(th->ack || th->fin || th->rst)) {
|
/* Initial SYN from client */
|
this_cpu_inc(snet->stats->syn_received);
|
|
if (th->ece && th->cwr)
|
opts.options |= XT_SYNPROXY_OPT_ECN;
|
|
opts.options &= info->options;
|
opts.mss_encode = opts.mss_option;
|
opts.mss_option = info->mss;
|
if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP)
|
synproxy_init_timestamp_cookie(info, &opts);
|
else
|
opts.options &= ~(XT_SYNPROXY_OPT_WSCALE |
|
XT_SYNPROXY_OPT_SACK_PERM |
|
XT_SYNPROXY_OPT_ECN);
|
|
synproxy_send_client_synack(net, skb, th, &opts);
|
consume_skb(skb);
|
return NF_STOLEN;
|
} else if (th->ack && !(th->fin || th->rst || th->syn)) {
|
/* ACK from client */
|
if (synproxy_recv_client_ack(net, skb, th, &opts, ntohl(th->seq))) {
|
consume_skb(skb);
|
return NF_STOLEN;
|
} else {
|
return NF_DROP;
|
}
|
}
|
|
return XT_CONTINUE;
|
}
|
|
static int synproxy_tg4_check(const struct xt_tgchk_param *par)
|
{
|
struct synproxy_net *snet = synproxy_pernet(par->net);
|
const struct ipt_entry *e = par->entryinfo;
|
int err;
|
|
if (e->ip.proto != IPPROTO_TCP ||
|
e->ip.invflags & XT_INV_PROTO)
|
return -EINVAL;
|
|
err = nf_ct_netns_get(par->net, par->family);
|
if (err)
|
return err;
|
|
err = nf_synproxy_ipv4_init(snet, par->net);
|
if (err) {
|
nf_ct_netns_put(par->net, par->family);
|
return err;
|
}
|
|
return err;
|
}
|
|
static void synproxy_tg4_destroy(const struct xt_tgdtor_param *par)
|
{
|
struct synproxy_net *snet = synproxy_pernet(par->net);
|
|
nf_synproxy_ipv4_fini(snet, par->net);
|
nf_ct_netns_put(par->net, par->family);
|
}
|
|
static struct xt_target synproxy_tg4_reg __read_mostly = {
|
.name = "SYNPROXY",
|
.family = NFPROTO_IPV4,
|
.hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD),
|
.target = synproxy_tg4,
|
.targetsize = sizeof(struct xt_synproxy_info),
|
.checkentry = synproxy_tg4_check,
|
.destroy = synproxy_tg4_destroy,
|
.me = THIS_MODULE,
|
};
|
|
static int __init synproxy_tg4_init(void)
|
{
|
return xt_register_target(&synproxy_tg4_reg);
|
}
|
|
static void __exit synproxy_tg4_exit(void)
|
{
|
xt_unregister_target(&synproxy_tg4_reg);
|
}
|
|
module_init(synproxy_tg4_init);
|
module_exit(synproxy_tg4_exit);
|
|
MODULE_LICENSE("GPL");
|
MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
|
MODULE_DESCRIPTION("Intercept TCP connections and establish them using syncookies");
|
