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 const 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_option;
35 opts->mss_option = 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_synproxy *priv,
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 nf_synproxy_info info = READ_ONCE(priv->info);
52 struct net *net = nft_net(pkt);
53 struct synproxy_net *snet = synproxy_pernet(net);
54 struct sk_buff *skb = pkt->skb;
55
56 if (tcp->syn) {
57 /* Initial SYN from client */
58 nft_synproxy_tcp_options(opts, tcp, snet, info: &info, priv);
59 synproxy_send_client_synack(net, skb, th: tcp, opts);
60 consume_skb(skb);
61 regs->verdict.code = NF_STOLEN;
62 } else if (tcp->ack) {
63 /* ACK from client */
64 if (synproxy_recv_client_ack(net, skb, th: tcp, opts,
65 ntohl(tcp->seq))) {
66 consume_skb(skb);
67 regs->verdict.code = NF_STOLEN;
68 } else {
69 regs->verdict.code = NF_DROP;
70 }
71 }
72}
73
74#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
75static void nft_synproxy_eval_v6(const struct nft_synproxy *priv,
76 struct nft_regs *regs,
77 const struct nft_pktinfo *pkt,
78 const struct tcphdr *tcp,
79 struct tcphdr *_tcph,
80 struct synproxy_options *opts)
81{
82 struct nf_synproxy_info info = READ_ONCE(priv->info);
83 struct net *net = nft_net(pkt);
84 struct synproxy_net *snet = synproxy_pernet(net);
85 struct sk_buff *skb = pkt->skb;
86
87 if (tcp->syn) {
88 /* Initial SYN from client */
89 nft_synproxy_tcp_options(opts, tcp, snet, info: &info, priv);
90 synproxy_send_client_synack_ipv6(net, skb, th: tcp, opts);
91 consume_skb(skb);
92 regs->verdict.code = NF_STOLEN;
93 } else if (tcp->ack) {
94 /* ACK from client */
95 if (synproxy_recv_client_ack_ipv6(net, skb, th: tcp, opts,
96 ntohl(tcp->seq))) {
97 consume_skb(skb);
98 regs->verdict.code = NF_STOLEN;
99 } else {
100 regs->verdict.code = NF_DROP;
101 }
102 }
103}
104#endif /* CONFIG_NF_TABLES_IPV6*/
105
106static void nft_synproxy_do_eval(const struct nft_synproxy *priv,
107 struct nft_regs *regs,
108 const struct nft_pktinfo *pkt)
109{
110 struct synproxy_options opts = {};
111 struct sk_buff *skb = pkt->skb;
112 int thoff = nft_thoff(pkt);
113 const struct tcphdr *tcp;
114 struct tcphdr _tcph;
115
116 if (pkt->tprot != IPPROTO_TCP) {
117 regs->verdict.code = NFT_BREAK;
118 return;
119 }
120
121 if (nf_ip_checksum(skb, hook: nft_hook(pkt), dataoff: thoff, IPPROTO_TCP)) {
122 regs->verdict.code = NF_DROP;
123 return;
124 }
125
126 tcp = skb_header_pointer(skb, offset: thoff,
127 len: sizeof(struct tcphdr),
128 buffer: &_tcph);
129 if (!tcp) {
130 regs->verdict.code = NF_DROP;
131 return;
132 }
133
134 if (!synproxy_parse_options(skb, doff: thoff, th: tcp, opts: &opts)) {
135 regs->verdict.code = NF_DROP;
136 return;
137 }
138
139 switch (skb->protocol) {
140 case htons(ETH_P_IP):
141 nft_synproxy_eval_v4(priv, regs, pkt, tcp, tcph: &_tcph, opts: &opts);
142 return;
143#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
144 case htons(ETH_P_IPV6):
145 nft_synproxy_eval_v6(priv, regs, pkt, tcp, tcph: &_tcph, opts: &opts);
146 return;
147#endif
148 }
149 regs->verdict.code = NFT_BREAK;
150}
151
152static int nft_synproxy_do_init(const struct nft_ctx *ctx,
153 const struct nlattr * const tb[],
154 struct nft_synproxy *priv)
155{
156 struct synproxy_net *snet = synproxy_pernet(net: ctx->net);
157 u32 flags;
158 int err;
159
160 if (tb[NFTA_SYNPROXY_MSS])
161 priv->info.mss = ntohs(nla_get_be16(tb[NFTA_SYNPROXY_MSS]));
162 if (tb[NFTA_SYNPROXY_WSCALE])
163 priv->info.wscale = nla_get_u8(nla: tb[NFTA_SYNPROXY_WSCALE]);
164 if (tb[NFTA_SYNPROXY_FLAGS]) {
165 flags = ntohl(nla_get_be32(tb[NFTA_SYNPROXY_FLAGS]));
166 if (flags & ~NF_SYNPROXY_OPT_MASK)
167 return -EOPNOTSUPP;
168 priv->info.options = flags;
169 }
170
171 err = nf_ct_netns_get(net: ctx->net, nfproto: ctx->family);
172 if (err)
173 return err;
174
175 switch (ctx->family) {
176 case NFPROTO_IPV4:
177 err = nf_synproxy_ipv4_init(snet, net: ctx->net);
178 if (err)
179 goto nf_ct_failure;
180 break;
181#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
182 case NFPROTO_IPV6:
183 err = nf_synproxy_ipv6_init(snet, net: ctx->net);
184 if (err)
185 goto nf_ct_failure;
186 break;
187#endif
188 case NFPROTO_INET:
189 err = nf_synproxy_ipv4_init(snet, net: ctx->net);
190 if (err)
191 goto nf_ct_failure;
192 err = nf_synproxy_ipv6_init(snet, net: ctx->net);
193 if (err) {
194 nf_synproxy_ipv4_fini(snet, net: ctx->net);
195 goto nf_ct_failure;
196 }
197 break;
198 }
199
200 return 0;
201
202nf_ct_failure:
203 nf_ct_netns_put(net: ctx->net, nfproto: ctx->family);
204 return err;
205}
206
207static void nft_synproxy_do_destroy(const struct nft_ctx *ctx)
208{
209 struct synproxy_net *snet = synproxy_pernet(net: ctx->net);
210
211 switch (ctx->family) {
212 case NFPROTO_IPV4:
213 nf_synproxy_ipv4_fini(snet, net: ctx->net);
214 break;
215#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
216 case NFPROTO_IPV6:
217 nf_synproxy_ipv6_fini(snet, net: ctx->net);
218 break;
219#endif
220 case NFPROTO_INET:
221 nf_synproxy_ipv4_fini(snet, net: ctx->net);
222 nf_synproxy_ipv6_fini(snet, net: ctx->net);
223 break;
224 }
225 nf_ct_netns_put(net: ctx->net, nfproto: ctx->family);
226}
227
228static int nft_synproxy_do_dump(struct sk_buff *skb, struct nft_synproxy *priv)
229{
230 if (nla_put_be16(skb, attrtype: NFTA_SYNPROXY_MSS, htons(priv->info.mss)) ||
231 nla_put_u8(skb, attrtype: NFTA_SYNPROXY_WSCALE, value: priv->info.wscale) ||
232 nla_put_be32(skb, attrtype: NFTA_SYNPROXY_FLAGS, htonl(priv->info.options)))
233 goto nla_put_failure;
234
235 return 0;
236
237nla_put_failure:
238 return -1;
239}
240
241static void nft_synproxy_eval(const struct nft_expr *expr,
242 struct nft_regs *regs,
243 const struct nft_pktinfo *pkt)
244{
245 const struct nft_synproxy *priv = nft_expr_priv(expr);
246
247 nft_synproxy_do_eval(priv, regs, pkt);
248}
249
250static int nft_synproxy_validate(const struct nft_ctx *ctx,
251 const struct nft_expr *expr)
252{
253 if (ctx->family != NFPROTO_IPV4 &&
254 ctx->family != NFPROTO_IPV6 &&
255 ctx->family != NFPROTO_INET)
256 return -EOPNOTSUPP;
257
258 return nft_chain_validate_hooks(chain: ctx->chain, hook_flags: (1 << NF_INET_LOCAL_IN) |
259 (1 << NF_INET_FORWARD));
260}
261
262static int nft_synproxy_init(const struct nft_ctx *ctx,
263 const struct nft_expr *expr,
264 const struct nlattr * const tb[])
265{
266 struct nft_synproxy *priv = nft_expr_priv(expr);
267
268 return nft_synproxy_do_init(ctx, tb, priv);
269}
270
271static void nft_synproxy_destroy(const struct nft_ctx *ctx,
272 const struct nft_expr *expr)
273{
274 nft_synproxy_do_destroy(ctx);
275}
276
277static int nft_synproxy_dump(struct sk_buff *skb,
278 const struct nft_expr *expr, bool reset)
279{
280 struct nft_synproxy *priv = nft_expr_priv(expr);
281
282 return nft_synproxy_do_dump(skb, priv);
283}
284
285static struct nft_expr_type nft_synproxy_type;
286static const struct nft_expr_ops nft_synproxy_ops = {
287 .eval = nft_synproxy_eval,
288 .size = NFT_EXPR_SIZE(sizeof(struct nft_synproxy)),
289 .init = nft_synproxy_init,
290 .destroy = nft_synproxy_destroy,
291 .dump = nft_synproxy_dump,
292 .type = &nft_synproxy_type,
293 .validate = nft_synproxy_validate,
294 .reduce = NFT_REDUCE_READONLY,
295};
296
297static struct nft_expr_type nft_synproxy_type __read_mostly = {
298 .ops = &nft_synproxy_ops,
299 .name = "synproxy",
300 .owner = THIS_MODULE,
301 .policy = nft_synproxy_policy,
302 .maxattr = NFTA_SYNPROXY_MAX,
303};
304
305static int nft_synproxy_obj_init(const struct nft_ctx *ctx,
306 const struct nlattr * const tb[],
307 struct nft_object *obj)
308{
309 struct nft_synproxy *priv = nft_obj_data(obj);
310
311 return nft_synproxy_do_init(ctx, tb, priv);
312}
313
314static void nft_synproxy_obj_destroy(const struct nft_ctx *ctx,
315 struct nft_object *obj)
316{
317 nft_synproxy_do_destroy(ctx);
318}
319
320static int nft_synproxy_obj_dump(struct sk_buff *skb,
321 struct nft_object *obj, bool reset)
322{
323 struct nft_synproxy *priv = nft_obj_data(obj);
324
325 return nft_synproxy_do_dump(skb, priv);
326}
327
328static void nft_synproxy_obj_eval(struct nft_object *obj,
329 struct nft_regs *regs,
330 const struct nft_pktinfo *pkt)
331{
332 const struct nft_synproxy *priv = nft_obj_data(obj);
333
334 nft_synproxy_do_eval(priv, regs, pkt);
335}
336
337static void nft_synproxy_obj_update(struct nft_object *obj,
338 struct nft_object *newobj)
339{
340 struct nft_synproxy *newpriv = nft_obj_data(obj: newobj);
341 struct nft_synproxy *priv = nft_obj_data(obj);
342
343 WRITE_ONCE(priv->info, newpriv->info);
344}
345
346static struct nft_object_type nft_synproxy_obj_type;
347static const struct nft_object_ops nft_synproxy_obj_ops = {
348 .type = &nft_synproxy_obj_type,
349 .size = sizeof(struct nft_synproxy),
350 .init = nft_synproxy_obj_init,
351 .destroy = nft_synproxy_obj_destroy,
352 .dump = nft_synproxy_obj_dump,
353 .eval = nft_synproxy_obj_eval,
354 .update = nft_synproxy_obj_update,
355};
356
357static struct nft_object_type nft_synproxy_obj_type __read_mostly = {
358 .type = NFT_OBJECT_SYNPROXY,
359 .ops = &nft_synproxy_obj_ops,
360 .maxattr = NFTA_SYNPROXY_MAX,
361 .policy = nft_synproxy_policy,
362 .owner = THIS_MODULE,
363};
364
365static int __init nft_synproxy_module_init(void)
366{
367 int err;
368
369 err = nft_register_obj(obj_type: &nft_synproxy_obj_type);
370 if (err < 0)
371 return err;
372
373 err = nft_register_expr(&nft_synproxy_type);
374 if (err < 0)
375 goto err;
376
377 return 0;
378
379err:
380 nft_unregister_obj(obj_type: &nft_synproxy_obj_type);
381 return err;
382}
383
384static void __exit nft_synproxy_module_exit(void)
385{
386 nft_unregister_expr(&nft_synproxy_type);
387 nft_unregister_obj(obj_type: &nft_synproxy_obj_type);
388}
389
390module_init(nft_synproxy_module_init);
391module_exit(nft_synproxy_module_exit);
392
393MODULE_LICENSE("GPL");
394MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
395MODULE_ALIAS_NFT_EXPR("synproxy");
396MODULE_ALIAS_NFT_OBJ(NFT_OBJECT_SYNPROXY);
397MODULE_DESCRIPTION("nftables SYNPROXY expression support");
398

source code of linux/net/netfilter/nft_synproxy.c