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
13 struct nft_synproxy {
14 struct nf_synproxy_info info;
15 };
16
17 static 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
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)23 static 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
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)44 static 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 = 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, priv);
59 synproxy_send_client_synack(net, skb, 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, 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)
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)75 static 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 = 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, priv);
90 synproxy_send_client_synack_ipv6(net, skb, 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, 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
nft_synproxy_do_eval(const struct nft_synproxy * priv,struct nft_regs * regs,const struct nft_pktinfo * pkt)106 static 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, nft_hook(pkt), thoff, IPPROTO_TCP)) {
122 regs->verdict.code = NF_DROP;
123 return;
124 }
125
126 tcp = skb_header_pointer(skb, thoff,
127 sizeof(struct tcphdr),
128 &_tcph);
129 if (!tcp) {
130 regs->verdict.code = NF_DROP;
131 return;
132 }
133
134 if (!synproxy_parse_options(skb, thoff, tcp, &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, &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, &opts);
146 return;
147 #endif
148 }
149 regs->verdict.code = NFT_BREAK;
150 }
151
nft_synproxy_do_init(const struct nft_ctx * ctx,const struct nlattr * const tb[],struct nft_synproxy * priv)152 static 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(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(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(ctx->net, ctx->family);
172 if (err)
173 return err;
174
175 switch (ctx->family) {
176 case NFPROTO_IPV4:
177 err = nf_synproxy_ipv4_init(snet, 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, 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, ctx->net);
190 if (err)
191 goto nf_ct_failure;
192 err = nf_synproxy_ipv6_init(snet, ctx->net);
193 if (err) {
194 nf_synproxy_ipv4_fini(snet, ctx->net);
195 goto nf_ct_failure;
196 }
197 break;
198 }
199
200 return 0;
201
202 nf_ct_failure:
203 nf_ct_netns_put(ctx->net, ctx->family);
204 return err;
205 }
206
nft_synproxy_do_destroy(const struct nft_ctx * ctx)207 static void nft_synproxy_do_destroy(const struct nft_ctx *ctx)
208 {
209 struct synproxy_net *snet = synproxy_pernet(ctx->net);
210
211 switch (ctx->family) {
212 case NFPROTO_IPV4:
213 nf_synproxy_ipv4_fini(snet, ctx->net);
214 break;
215 #if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
216 case NFPROTO_IPV6:
217 nf_synproxy_ipv6_fini(snet, ctx->net);
218 break;
219 #endif
220 case NFPROTO_INET:
221 nf_synproxy_ipv4_fini(snet, ctx->net);
222 nf_synproxy_ipv6_fini(snet, ctx->net);
223 break;
224 }
225 nf_ct_netns_put(ctx->net, ctx->family);
226 }
227
nft_synproxy_do_dump(struct sk_buff * skb,struct nft_synproxy * priv)228 static int nft_synproxy_do_dump(struct sk_buff *skb, struct nft_synproxy *priv)
229 {
230 if (nla_put_be16(skb, NFTA_SYNPROXY_MSS, htons(priv->info.mss)) ||
231 nla_put_u8(skb, NFTA_SYNPROXY_WSCALE, priv->info.wscale) ||
232 nla_put_be32(skb, NFTA_SYNPROXY_FLAGS, htonl(priv->info.options)))
233 goto nla_put_failure;
234
235 return 0;
236
237 nla_put_failure:
238 return -1;
239 }
240
nft_synproxy_eval(const struct nft_expr * expr,struct nft_regs * regs,const struct nft_pktinfo * pkt)241 static 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
nft_synproxy_validate(const struct nft_ctx * ctx,const struct nft_expr * expr,const struct nft_data ** data)250 static int nft_synproxy_validate(const struct nft_ctx *ctx,
251 const struct nft_expr *expr,
252 const struct nft_data **data)
253 {
254 if (ctx->family != NFPROTO_IPV4 &&
255 ctx->family != NFPROTO_IPV6 &&
256 ctx->family != NFPROTO_INET)
257 return -EOPNOTSUPP;
258
259 return nft_chain_validate_hooks(ctx->chain, (1 << NF_INET_LOCAL_IN) |
260 (1 << NF_INET_FORWARD));
261 }
262
nft_synproxy_init(const struct nft_ctx * ctx,const struct nft_expr * expr,const struct nlattr * const tb[])263 static int nft_synproxy_init(const struct nft_ctx *ctx,
264 const struct nft_expr *expr,
265 const struct nlattr * const tb[])
266 {
267 struct nft_synproxy *priv = nft_expr_priv(expr);
268
269 return nft_synproxy_do_init(ctx, tb, priv);
270 }
271
nft_synproxy_destroy(const struct nft_ctx * ctx,const struct nft_expr * expr)272 static void nft_synproxy_destroy(const struct nft_ctx *ctx,
273 const struct nft_expr *expr)
274 {
275 nft_synproxy_do_destroy(ctx);
276 }
277
nft_synproxy_dump(struct sk_buff * skb,const struct nft_expr * expr,bool reset)278 static int nft_synproxy_dump(struct sk_buff *skb,
279 const struct nft_expr *expr, bool reset)
280 {
281 struct nft_synproxy *priv = nft_expr_priv(expr);
282
283 return nft_synproxy_do_dump(skb, priv);
284 }
285
286 static struct nft_expr_type nft_synproxy_type;
287 static const struct nft_expr_ops nft_synproxy_ops = {
288 .eval = nft_synproxy_eval,
289 .size = NFT_EXPR_SIZE(sizeof(struct nft_synproxy)),
290 .init = nft_synproxy_init,
291 .destroy = nft_synproxy_destroy,
292 .dump = nft_synproxy_dump,
293 .type = &nft_synproxy_type,
294 .validate = nft_synproxy_validate,
295 .reduce = NFT_REDUCE_READONLY,
296 };
297
298 static struct nft_expr_type nft_synproxy_type __read_mostly = {
299 .ops = &nft_synproxy_ops,
300 .name = "synproxy",
301 .owner = THIS_MODULE,
302 .policy = nft_synproxy_policy,
303 .maxattr = NFTA_SYNPROXY_MAX,
304 };
305
nft_synproxy_obj_init(const struct nft_ctx * ctx,const struct nlattr * const tb[],struct nft_object * obj)306 static int nft_synproxy_obj_init(const struct nft_ctx *ctx,
307 const struct nlattr * const tb[],
308 struct nft_object *obj)
309 {
310 struct nft_synproxy *priv = nft_obj_data(obj);
311
312 return nft_synproxy_do_init(ctx, tb, priv);
313 }
314
nft_synproxy_obj_destroy(const struct nft_ctx * ctx,struct nft_object * obj)315 static void nft_synproxy_obj_destroy(const struct nft_ctx *ctx,
316 struct nft_object *obj)
317 {
318 nft_synproxy_do_destroy(ctx);
319 }
320
nft_synproxy_obj_dump(struct sk_buff * skb,struct nft_object * obj,bool reset)321 static int nft_synproxy_obj_dump(struct sk_buff *skb,
322 struct nft_object *obj, bool reset)
323 {
324 struct nft_synproxy *priv = nft_obj_data(obj);
325
326 return nft_synproxy_do_dump(skb, priv);
327 }
328
nft_synproxy_obj_eval(struct nft_object * obj,struct nft_regs * regs,const struct nft_pktinfo * pkt)329 static void nft_synproxy_obj_eval(struct nft_object *obj,
330 struct nft_regs *regs,
331 const struct nft_pktinfo *pkt)
332 {
333 const struct nft_synproxy *priv = nft_obj_data(obj);
334
335 nft_synproxy_do_eval(priv, regs, pkt);
336 }
337
nft_synproxy_obj_update(struct nft_object * obj,struct nft_object * newobj)338 static void nft_synproxy_obj_update(struct nft_object *obj,
339 struct nft_object *newobj)
340 {
341 struct nft_synproxy *newpriv = nft_obj_data(newobj);
342 struct nft_synproxy *priv = nft_obj_data(obj);
343
344 priv->info = newpriv->info;
345 }
346
347 static struct nft_object_type nft_synproxy_obj_type;
348 static const struct nft_object_ops nft_synproxy_obj_ops = {
349 .type = &nft_synproxy_obj_type,
350 .size = sizeof(struct nft_synproxy),
351 .init = nft_synproxy_obj_init,
352 .destroy = nft_synproxy_obj_destroy,
353 .dump = nft_synproxy_obj_dump,
354 .eval = nft_synproxy_obj_eval,
355 .update = nft_synproxy_obj_update,
356 };
357
358 static struct nft_object_type nft_synproxy_obj_type __read_mostly = {
359 .type = NFT_OBJECT_SYNPROXY,
360 .ops = &nft_synproxy_obj_ops,
361 .maxattr = NFTA_SYNPROXY_MAX,
362 .policy = nft_synproxy_policy,
363 .owner = THIS_MODULE,
364 };
365
nft_synproxy_module_init(void)366 static int __init nft_synproxy_module_init(void)
367 {
368 int err;
369
370 err = nft_register_obj(&nft_synproxy_obj_type);
371 if (err < 0)
372 return err;
373
374 err = nft_register_expr(&nft_synproxy_type);
375 if (err < 0)
376 goto err;
377
378 return 0;
379
380 err:
381 nft_unregister_obj(&nft_synproxy_obj_type);
382 return err;
383 }
384
nft_synproxy_module_exit(void)385 static void __exit nft_synproxy_module_exit(void)
386 {
387 nft_unregister_expr(&nft_synproxy_type);
388 nft_unregister_obj(&nft_synproxy_obj_type);
389 }
390
391 module_init(nft_synproxy_module_init);
392 module_exit(nft_synproxy_module_exit);
393
394 MODULE_LICENSE("GPL");
395 MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
396 MODULE_ALIAS_NFT_EXPR("synproxy");
397 MODULE_ALIAS_NFT_OBJ(NFT_OBJECT_SYNPROXY);
398 MODULE_DESCRIPTION("nftables SYNPROXY expression support");
399