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// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/netlink.h>
#include <net/netfilter/nf_tables.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_synproxy.h>
#include <net/netfilter/nf_synproxy.h>
#include <linux/netfilter/nf_tables.h>
#include <linux/netfilter/nf_synproxy.h>
struct nft_synproxy {
struct nf_synproxy_info info;
};
static const struct nla_policy nft_synproxy_policy[NFTA_SYNPROXY_MAX + 1] = {
[NFTA_SYNPROXY_MSS] = { .type = NLA_U16 },
[NFTA_SYNPROXY_WSCALE] = { .type = NLA_U8 },
[NFTA_SYNPROXY_FLAGS] = { .type = NLA_U32 },
};
static void nft_synproxy_tcp_options(struct synproxy_options *opts,
const struct tcphdr *tcp,
struct synproxy_net *snet,
struct nf_synproxy_info *info,
const struct nft_synproxy *priv)
{
this_cpu_inc(snet->stats->syn_received);
if (tcp->ece && tcp->cwr)
opts->options |= NF_SYNPROXY_OPT_ECN;
opts->options &= priv->info.options;
opts->mss_encode = opts->mss_option;
opts->mss_option = info->mss;
if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
synproxy_init_timestamp_cookie(info, opts);
else
opts->options &= ~(NF_SYNPROXY_OPT_WSCALE |
NF_SYNPROXY_OPT_SACK_PERM |
NF_SYNPROXY_OPT_ECN);
}
static void nft_synproxy_eval_v4(const struct nft_synproxy *priv,
struct nft_regs *regs,
const struct nft_pktinfo *pkt,
const struct tcphdr *tcp,
struct tcphdr *_tcph,
struct synproxy_options *opts)
{
struct nf_synproxy_info info = priv->info;
struct net *net = nft_net(pkt);
struct synproxy_net *snet = synproxy_pernet(net);
struct sk_buff *skb = pkt->skb;
if (tcp->syn) {
/* Initial SYN from client */
nft_synproxy_tcp_options(opts, tcp, snet, &info, priv);
synproxy_send_client_synack(net, skb, tcp, opts);
consume_skb(skb);
regs->verdict.code = NF_STOLEN;
} else if (tcp->ack) {
/* ACK from client */
if (synproxy_recv_client_ack(net, skb, tcp, opts,
ntohl(tcp->seq))) {
consume_skb(skb);
regs->verdict.code = NF_STOLEN;
} else {
regs->verdict.code = NF_DROP;
}
}
}
#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
static void nft_synproxy_eval_v6(const struct nft_synproxy *priv,
struct nft_regs *regs,
const struct nft_pktinfo *pkt,
const struct tcphdr *tcp,
struct tcphdr *_tcph,
struct synproxy_options *opts)
{
struct nf_synproxy_info info = priv->info;
struct net *net = nft_net(pkt);
struct synproxy_net *snet = synproxy_pernet(net);
struct sk_buff *skb = pkt->skb;
if (tcp->syn) {
/* Initial SYN from client */
nft_synproxy_tcp_options(opts, tcp, snet, &info, priv);
synproxy_send_client_synack_ipv6(net, skb, tcp, opts);
consume_skb(skb);
regs->verdict.code = NF_STOLEN;
} else if (tcp->ack) {
/* ACK from client */
if (synproxy_recv_client_ack_ipv6(net, skb, tcp, opts,
ntohl(tcp->seq))) {
consume_skb(skb);
regs->verdict.code = NF_STOLEN;
} else {
regs->verdict.code = NF_DROP;
}
}
}
#endif /* CONFIG_NF_TABLES_IPV6*/
static void nft_synproxy_do_eval(const struct nft_synproxy *priv,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
{
struct synproxy_options opts = {};
struct sk_buff *skb = pkt->skb;
int thoff = nft_thoff(pkt);
const struct tcphdr *tcp;
struct tcphdr _tcph;
if (pkt->tprot != IPPROTO_TCP) {
regs->verdict.code = NFT_BREAK;
return;
}
if (nf_ip_checksum(skb, nft_hook(pkt), thoff, IPPROTO_TCP)) {
regs->verdict.code = NF_DROP;
return;
}
tcp = skb_header_pointer(skb, thoff,
sizeof(struct tcphdr),
&_tcph);
if (!tcp) {
regs->verdict.code = NF_DROP;
return;
}
if (!synproxy_parse_options(skb, thoff, tcp, &opts)) {
regs->verdict.code = NF_DROP;
return;
}
switch (skb->protocol) {
case htons(ETH_P_IP):
nft_synproxy_eval_v4(priv, regs, pkt, tcp, &_tcph, &opts);
return;
#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
case htons(ETH_P_IPV6):
nft_synproxy_eval_v6(priv, regs, pkt, tcp, &_tcph, &opts);
return;
#endif
}
regs->verdict.code = NFT_BREAK;
}
static int nft_synproxy_do_init(const struct nft_ctx *ctx,
const struct nlattr * const tb[],
struct nft_synproxy *priv)
{
struct synproxy_net *snet = synproxy_pernet(ctx->net);
u32 flags;
int err;
if (tb[NFTA_SYNPROXY_MSS])
priv->info.mss = ntohs(nla_get_be16(tb[NFTA_SYNPROXY_MSS]));
if (tb[NFTA_SYNPROXY_WSCALE])
priv->info.wscale = nla_get_u8(tb[NFTA_SYNPROXY_WSCALE]);
if (tb[NFTA_SYNPROXY_FLAGS]) {
flags = ntohl(nla_get_be32(tb[NFTA_SYNPROXY_FLAGS]));
if (flags & ~NF_SYNPROXY_OPT_MASK)
return -EOPNOTSUPP;
priv->info.options = flags;
}
err = nf_ct_netns_get(ctx->net, ctx->family);
if (err)
return err;
switch (ctx->family) {
case NFPROTO_IPV4:
err = nf_synproxy_ipv4_init(snet, ctx->net);
if (err)
goto nf_ct_failure;
break;
#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
case NFPROTO_IPV6:
err = nf_synproxy_ipv6_init(snet, ctx->net);
if (err)
goto nf_ct_failure;
break;
#endif
case NFPROTO_INET:
case NFPROTO_BRIDGE:
err = nf_synproxy_ipv4_init(snet, ctx->net);
if (err)
goto nf_ct_failure;
err = nf_synproxy_ipv6_init(snet, ctx->net);
if (err)
goto nf_ct_failure;
break;
}
return 0;
nf_ct_failure:
nf_ct_netns_put(ctx->net, ctx->family);
return err;
}
static void nft_synproxy_do_destroy(const struct nft_ctx *ctx)
{
struct synproxy_net *snet = synproxy_pernet(ctx->net);
switch (ctx->family) {
case NFPROTO_IPV4:
nf_synproxy_ipv4_fini(snet, ctx->net);
break;
#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
case NFPROTO_IPV6:
nf_synproxy_ipv6_fini(snet, ctx->net);
break;
#endif
case NFPROTO_INET:
case NFPROTO_BRIDGE:
nf_synproxy_ipv4_fini(snet, ctx->net);
nf_synproxy_ipv6_fini(snet, ctx->net);
break;
}
nf_ct_netns_put(ctx->net, ctx->family);
}
static int nft_synproxy_do_dump(struct sk_buff *skb, struct nft_synproxy *priv)
{
if (nla_put_be16(skb, NFTA_SYNPROXY_MSS, htons(priv->info.mss)) ||
nla_put_u8(skb, NFTA_SYNPROXY_WSCALE, priv->info.wscale) ||
nla_put_be32(skb, NFTA_SYNPROXY_FLAGS, htonl(priv->info.options)))
goto nla_put_failure;
return 0;
nla_put_failure:
return -1;
}
static void nft_synproxy_eval(const struct nft_expr *expr,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
{
const struct nft_synproxy *priv = nft_expr_priv(expr);
nft_synproxy_do_eval(priv, regs, pkt);
}
static int nft_synproxy_validate(const struct nft_ctx *ctx,
const struct nft_expr *expr,
const struct nft_data **data)
{
return nft_chain_validate_hooks(ctx->chain, (1 << NF_INET_LOCAL_IN) |
(1 << NF_INET_FORWARD));
}
static int nft_synproxy_init(const struct nft_ctx *ctx,
const struct nft_expr *expr,
const struct nlattr * const tb[])
{
struct nft_synproxy *priv = nft_expr_priv(expr);
return nft_synproxy_do_init(ctx, tb, priv);
}
static void nft_synproxy_destroy(const struct nft_ctx *ctx,
const struct nft_expr *expr)
{
nft_synproxy_do_destroy(ctx);
}
static int nft_synproxy_dump(struct sk_buff *skb, const struct nft_expr *expr)
{
struct nft_synproxy *priv = nft_expr_priv(expr);
return nft_synproxy_do_dump(skb, priv);
}
static struct nft_expr_type nft_synproxy_type;
static const struct nft_expr_ops nft_synproxy_ops = {
.eval = nft_synproxy_eval,
.size = NFT_EXPR_SIZE(sizeof(struct nft_synproxy)),
.init = nft_synproxy_init,
.destroy = nft_synproxy_destroy,
.dump = nft_synproxy_dump,
.type = &nft_synproxy_type,
.validate = nft_synproxy_validate,
};
static struct nft_expr_type nft_synproxy_type __read_mostly = {
.ops = &nft_synproxy_ops,
.name = "synproxy",
.owner = THIS_MODULE,
.policy = nft_synproxy_policy,
.maxattr = NFTA_SYNPROXY_MAX,
};
static int nft_synproxy_obj_init(const struct nft_ctx *ctx,
const struct nlattr * const tb[],
struct nft_object *obj)
{
struct nft_synproxy *priv = nft_obj_data(obj);
return nft_synproxy_do_init(ctx, tb, priv);
}
static void nft_synproxy_obj_destroy(const struct nft_ctx *ctx,
struct nft_object *obj)
{
nft_synproxy_do_destroy(ctx);
}
static int nft_synproxy_obj_dump(struct sk_buff *skb,
struct nft_object *obj, bool reset)
{
struct nft_synproxy *priv = nft_obj_data(obj);
return nft_synproxy_do_dump(skb, priv);
}
static void nft_synproxy_obj_eval(struct nft_object *obj,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
{
const struct nft_synproxy *priv = nft_obj_data(obj);
nft_synproxy_do_eval(priv, regs, pkt);
}
static void nft_synproxy_obj_update(struct nft_object *obj,
struct nft_object *newobj)
{
struct nft_synproxy *newpriv = nft_obj_data(newobj);
struct nft_synproxy *priv = nft_obj_data(obj);
priv->info = newpriv->info;
}
static struct nft_object_type nft_synproxy_obj_type;
static const struct nft_object_ops nft_synproxy_obj_ops = {
.type = &nft_synproxy_obj_type,
.size = sizeof(struct nft_synproxy),
.init = nft_synproxy_obj_init,
.destroy = nft_synproxy_obj_destroy,
.dump = nft_synproxy_obj_dump,
.eval = nft_synproxy_obj_eval,
.update = nft_synproxy_obj_update,
};
static struct nft_object_type nft_synproxy_obj_type __read_mostly = {
.type = NFT_OBJECT_SYNPROXY,
.ops = &nft_synproxy_obj_ops,
.maxattr = NFTA_SYNPROXY_MAX,
.policy = nft_synproxy_policy,
.owner = THIS_MODULE,
};
static int __init nft_synproxy_module_init(void)
{
int err;
err = nft_register_obj(&nft_synproxy_obj_type);
if (err < 0)
return err;
err = nft_register_expr(&nft_synproxy_type);
if (err < 0)
goto err;
return 0;
err:
nft_unregister_obj(&nft_synproxy_obj_type);
return err;
}
static void __exit nft_synproxy_module_exit(void)
{
nft_unregister_expr(&nft_synproxy_type);
nft_unregister_obj(&nft_synproxy_obj_type);
}
module_init(nft_synproxy_module_init);
module_exit(nft_synproxy_module_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
MODULE_ALIAS_NFT_EXPR("synproxy");
MODULE_ALIAS_NFT_OBJ(NFT_OBJECT_SYNPROXY);
MODULE_DESCRIPTION("nftables SYNPROXY expression support");
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