Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
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linux
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/types.h>
3#include <net/ip.h>
4#include <net/tcp.h>
5#include <net/netlink.h>
6#include <net/netfilter/nf_tables.h>
7#include <net/netfilter/nf_conntrack.h>
8#include <net/netfilter/nf_conntrack_synproxy.h>
9#include <net/netfilter/nf_synproxy.h>
10#include <linux/netfilter/nf_tables.h>
11#include <linux/netfilter/nf_synproxy.h>
12
13struct nft_synproxy {
14 struct nf_synproxy_info info;
15};
16
17static const struct nla_policy nft_synproxy_policy[NFTA_SYNPROXY_MAX + 1] = {
18 [NFTA_SYNPROXY_MSS] = { .type = NLA_U16 },
19 [NFTA_SYNPROXY_WSCALE] = { .type = NLA_U8 },
20 [NFTA_SYNPROXY_FLAGS] = { .type = NLA_U32 },
21};
22
23static void nft_synproxy_tcp_options(struct synproxy_options *opts,
24 const struct tcphdr *tcp,
25 struct synproxy_net *snet,
26 struct nf_synproxy_info *info,
27 struct nft_synproxy *priv)
28{
29 this_cpu_inc(snet->stats->syn_received);
30 if (tcp->ece && tcp->cwr)
31 opts->options |= NF_SYNPROXY_OPT_ECN;
32
33 opts->options &= priv->info.options;
34 opts->mss_encode = opts->mss;
35 opts->mss = info->mss;
36 if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
37 synproxy_init_timestamp_cookie(info, opts);
38 else
39 opts->options &= ~(NF_SYNPROXY_OPT_WSCALE |
40 NF_SYNPROXY_OPT_SACK_PERM |
41 NF_SYNPROXY_OPT_ECN);
42}
43
44static void nft_synproxy_eval_v4(const struct nft_expr *expr,
45 struct nft_regs *regs,
46 const struct nft_pktinfo *pkt,
47 const struct tcphdr *tcp,
48 struct tcphdr *_tcph,
49 struct synproxy_options *opts)
50{
51 struct nft_synproxy *priv = nft_expr_priv(expr);
52 struct nf_synproxy_info info = priv->info;
53 struct net *net = nft_net(pkt);
54 struct synproxy_net *snet = synproxy_pernet(net);
55 struct sk_buff *skb = pkt->skb;
56
57 if (tcp->syn) {
58 /* Initial SYN from client */
59 nft_synproxy_tcp_options(opts, tcp, snet, &info, priv);
60 synproxy_send_client_synack(net, skb, tcp, opts);
61 consume_skb(skb);
62 regs->verdict.code = NF_STOLEN;
63 } else if (tcp->ack) {
64 /* ACK from client */
65 if (synproxy_recv_client_ack(net, skb, tcp, opts,
66 ntohl(tcp->seq))) {
67 consume_skb(skb);
68 regs->verdict.code = NF_STOLEN;
69 } else {
70 regs->verdict.code = NF_DROP;
71 }
72 }
73}
74
75#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
76static void nft_synproxy_eval_v6(const struct nft_expr *expr,
77 struct nft_regs *regs,
78 const struct nft_pktinfo *pkt,
79 const struct tcphdr *tcp,
80 struct tcphdr *_tcph,
81 struct synproxy_options *opts)
82{
83 struct nft_synproxy *priv = nft_expr_priv(expr);
84 struct nf_synproxy_info info = priv->info;
85 struct net *net = nft_net(pkt);
86 struct synproxy_net *snet = synproxy_pernet(net);
87 struct sk_buff *skb = pkt->skb;
88
89 if (tcp->syn) {
90 /* Initial SYN from client */
91 nft_synproxy_tcp_options(opts, tcp, snet, &info, priv);
92 synproxy_send_client_synack_ipv6(net, skb, tcp, opts);
93 consume_skb(skb);
94 regs->verdict.code = NF_STOLEN;
95 } else if (tcp->ack) {
96 /* ACK from client */
97 if (synproxy_recv_client_ack_ipv6(net, skb, tcp, opts,
98 ntohl(tcp->seq))) {
99 consume_skb(skb);
100 regs->verdict.code = NF_STOLEN;
101 } else {
102 regs->verdict.code = NF_DROP;
103 }
104 }
105}
106#endif /* CONFIG_NF_TABLES_IPV6*/
107
108static void nft_synproxy_eval(const struct nft_expr *expr,
109 struct nft_regs *regs,
110 const struct nft_pktinfo *pkt)
111{
112 struct synproxy_options opts = {};
113 struct sk_buff *skb = pkt->skb;
114 int thoff = pkt->xt.thoff;
115 const struct tcphdr *tcp;
116 struct tcphdr _tcph;
117
118 if (pkt->tprot != IPPROTO_TCP) {
119 regs->verdict.code = NFT_BREAK;
120 return;
121 }
122
123 if (nf_ip_checksum(skb, nft_hook(pkt), thoff, IPPROTO_TCP)) {
124 regs->verdict.code = NF_DROP;
125 return;
126 }
127
128 tcp = skb_header_pointer(skb, pkt->xt.thoff,
129 sizeof(struct tcphdr),
130 &_tcph);
131 if (!tcp) {
132 regs->verdict.code = NF_DROP;
133 return;
134 }
135
136 if (!synproxy_parse_options(skb, thoff, tcp, &opts)) {
137 regs->verdict.code = NF_DROP;
138 return;
139 }
140
141 switch (skb->protocol) {
142 case htons(ETH_P_IP):
143 nft_synproxy_eval_v4(expr, regs, pkt, tcp, &_tcph, &opts);
144 return;
145#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
146 case htons(ETH_P_IPV6):
147 nft_synproxy_eval_v6(expr, regs, pkt, tcp, &_tcph, &opts);
148 return;
149#endif
150 }
151 regs->verdict.code = NFT_BREAK;
152}
153
154static int nft_synproxy_init(const struct nft_ctx *ctx,
155 const struct nft_expr *expr,
156 const struct nlattr * const tb[])
157{
158 struct synproxy_net *snet = synproxy_pernet(ctx->net);
159 struct nft_synproxy *priv = nft_expr_priv(expr);
160 u32 flags;
161 int err;
162
163 if (tb[NFTA_SYNPROXY_MSS])
164 priv->info.mss = ntohs(nla_get_be16(tb[NFTA_SYNPROXY_MSS]));
165 if (tb[NFTA_SYNPROXY_WSCALE])
166 priv->info.wscale = nla_get_u8(tb[NFTA_SYNPROXY_WSCALE]);
167 if (tb[NFTA_SYNPROXY_FLAGS]) {
168 flags = ntohl(nla_get_be32(tb[NFTA_SYNPROXY_FLAGS]));
169 if (flags & ~NF_SYNPROXY_OPT_MASK)
170 return -EOPNOTSUPP;
171 priv->info.options = flags;
172 }
173
174 err = nf_ct_netns_get(ctx->net, ctx->family);
175 if (err)
176 return err;
177
178 switch (ctx->family) {
179 case NFPROTO_IPV4:
180 err = nf_synproxy_ipv4_init(snet, ctx->net);
181 if (err)
182 goto nf_ct_failure;
183 break;
184#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
185 case NFPROTO_IPV6:
186 err = nf_synproxy_ipv6_init(snet, ctx->net);
187 if (err)
188 goto nf_ct_failure;
189 break;
190#endif
191 case NFPROTO_INET:
192 case NFPROTO_BRIDGE:
193 err = nf_synproxy_ipv4_init(snet, ctx->net);
194 if (err)
195 goto nf_ct_failure;
196 err = nf_synproxy_ipv6_init(snet, ctx->net);
197 if (err)
198 goto nf_ct_failure;
199 break;
200 }
201
202 return 0;
203
204nf_ct_failure:
205 nf_ct_netns_put(ctx->net, ctx->family);
206 return err;
207}
208
209static void nft_synproxy_destroy(const struct nft_ctx *ctx,
210 const struct nft_expr *expr)
211{
212 struct synproxy_net *snet = synproxy_pernet(ctx->net);
213
214 switch (ctx->family) {
215 case NFPROTO_IPV4:
216 nf_synproxy_ipv4_fini(snet, ctx->net);
217 break;
218#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
219 case NFPROTO_IPV6:
220 nf_synproxy_ipv6_fini(snet, ctx->net);
221 break;
222#endif
223 case NFPROTO_INET:
224 case NFPROTO_BRIDGE:
225 nf_synproxy_ipv4_fini(snet, ctx->net);
226 nf_synproxy_ipv6_fini(snet, ctx->net);
227 break;
228 }
229 nf_ct_netns_put(ctx->net, ctx->family);
230}
231
232static int nft_synproxy_dump(struct sk_buff *skb, const struct nft_expr *expr)
233{
234 const struct nft_synproxy *priv = nft_expr_priv(expr);
235
236 if (nla_put_be16(skb, NFTA_SYNPROXY_MSS, htons(priv->info.mss)) ||
237 nla_put_u8(skb, NFTA_SYNPROXY_WSCALE, priv->info.wscale) ||
238 nla_put_be32(skb, NFTA_SYNPROXY_FLAGS, htonl(priv->info.options)))
239 goto nla_put_failure;
240
241 return 0;
242
243nla_put_failure:
244 return -1;
245}
246
247static int nft_synproxy_validate(const struct nft_ctx *ctx,
248 const struct nft_expr *expr,
249 const struct nft_data **data)
250{
251 return nft_chain_validate_hooks(ctx->chain, (1 << NF_INET_LOCAL_IN) |
252 (1 << NF_INET_FORWARD));
253}
254
255static struct nft_expr_type nft_synproxy_type;
256static const struct nft_expr_ops nft_synproxy_ops = {
257 .eval = nft_synproxy_eval,
258 .size = NFT_EXPR_SIZE(sizeof(struct nft_synproxy)),
259 .init = nft_synproxy_init,
260 .destroy = nft_synproxy_destroy,
261 .dump = nft_synproxy_dump,
262 .type = &nft_synproxy_type,
263 .validate = nft_synproxy_validate,
264};
265
266static struct nft_expr_type nft_synproxy_type __read_mostly = {
267 .ops = &nft_synproxy_ops,
268 .name = "synproxy",
269 .owner = THIS_MODULE,
270 .policy = nft_synproxy_policy,
271 .maxattr = NFTA_SYNPROXY_MAX,
272};
273
274static int __init nft_synproxy_module_init(void)
275{
276 return nft_register_expr(&nft_synproxy_type);
277}
278
279static void __exit nft_synproxy_module_exit(void)
280{
281 return nft_unregister_expr(&nft_synproxy_type);
282}
283
284module_init(nft_synproxy_module_init);
285module_exit(nft_synproxy_module_exit);
286
287MODULE_LICENSE("GPL");
288MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
289MODULE_ALIAS_NFT_EXPR("synproxy");