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 case NFPROTO_BRIDGE:
190 err = nf_synproxy_ipv4_init(snet, ctx->net);
191 if (err)
192 goto nf_ct_failure;
193 err = nf_synproxy_ipv6_init(snet, ctx->net);
194 if (err) {
195 nf_synproxy_ipv4_fini(snet, ctx->net);
196 goto nf_ct_failure;
197 }
198 break;
199 }
200
201 return 0;
202
203 nf_ct_failure:
204 nf_ct_netns_put(ctx->net, ctx->family);
205 return err;
206 }
207
nft_synproxy_do_destroy(const struct nft_ctx * ctx)208 static void nft_synproxy_do_destroy(const struct nft_ctx *ctx)
209 {
210 struct synproxy_net *snet = synproxy_pernet(ctx->net);
211
212 switch (ctx->family) {
213 case NFPROTO_IPV4:
214 nf_synproxy_ipv4_fini(snet, ctx->net);
215 break;
216 #if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
217 case NFPROTO_IPV6:
218 nf_synproxy_ipv6_fini(snet, ctx->net);
219 break;
220 #endif
221 case NFPROTO_INET:
222 case NFPROTO_BRIDGE:
223 nf_synproxy_ipv4_fini(snet, ctx->net);
224 nf_synproxy_ipv6_fini(snet, ctx->net);
225 break;
226 }
227 nf_ct_netns_put(ctx->net, ctx->family);
228 }
229
nft_synproxy_do_dump(struct sk_buff * skb,struct nft_synproxy * priv)230 static int nft_synproxy_do_dump(struct sk_buff *skb, struct nft_synproxy *priv)
231 {
232 if (nla_put_be16(skb, NFTA_SYNPROXY_MSS, htons(priv->info.mss)) ||
233 nla_put_u8(skb, NFTA_SYNPROXY_WSCALE, priv->info.wscale) ||
234 nla_put_be32(skb, NFTA_SYNPROXY_FLAGS, htonl(priv->info.options)))
235 goto nla_put_failure;
236
237 return 0;
238
239 nla_put_failure:
240 return -1;
241 }
242
nft_synproxy_eval(const struct nft_expr * expr,struct nft_regs * regs,const struct nft_pktinfo * pkt)243 static void nft_synproxy_eval(const struct nft_expr *expr,
244 struct nft_regs *regs,
245 const struct nft_pktinfo *pkt)
246 {
247 const struct nft_synproxy *priv = nft_expr_priv(expr);
248
249 nft_synproxy_do_eval(priv, regs, pkt);
250 }
251
nft_synproxy_validate(const struct nft_ctx * ctx,const struct nft_expr * expr,const struct nft_data ** data)252 static int nft_synproxy_validate(const struct nft_ctx *ctx,
253 const struct nft_expr *expr,
254 const struct nft_data **data)
255 {
256 return nft_chain_validate_hooks(ctx->chain, (1 << NF_INET_LOCAL_IN) |
257 (1 << NF_INET_FORWARD));
258 }
259
nft_synproxy_init(const struct nft_ctx * ctx,const struct nft_expr * expr,const struct nlattr * const tb[])260 static int nft_synproxy_init(const struct nft_ctx *ctx,
261 const struct nft_expr *expr,
262 const struct nlattr * const tb[])
263 {
264 struct nft_synproxy *priv = nft_expr_priv(expr);
265
266 return nft_synproxy_do_init(ctx, tb, priv);
267 }
268
nft_synproxy_destroy(const struct nft_ctx * ctx,const struct nft_expr * expr)269 static void nft_synproxy_destroy(const struct nft_ctx *ctx,
270 const struct nft_expr *expr)
271 {
272 nft_synproxy_do_destroy(ctx);
273 }
274
nft_synproxy_dump(struct sk_buff * skb,const struct nft_expr * expr,bool reset)275 static int nft_synproxy_dump(struct sk_buff *skb,
276 const struct nft_expr *expr, bool reset)
277 {
278 struct nft_synproxy *priv = nft_expr_priv(expr);
279
280 return nft_synproxy_do_dump(skb, priv);
281 }
282
283 static struct nft_expr_type nft_synproxy_type;
284 static const struct nft_expr_ops nft_synproxy_ops = {
285 .eval = nft_synproxy_eval,
286 .size = NFT_EXPR_SIZE(sizeof(struct nft_synproxy)),
287 .init = nft_synproxy_init,
288 .destroy = nft_synproxy_destroy,
289 .dump = nft_synproxy_dump,
290 .type = &nft_synproxy_type,
291 .validate = nft_synproxy_validate,
292 .reduce = NFT_REDUCE_READONLY,
293 };
294
295 static struct nft_expr_type nft_synproxy_type __read_mostly = {
296 .ops = &nft_synproxy_ops,
297 .name = "synproxy",
298 .owner = THIS_MODULE,
299 .policy = nft_synproxy_policy,
300 .maxattr = NFTA_SYNPROXY_MAX,
301 };
302
nft_synproxy_obj_init(const struct nft_ctx * ctx,const struct nlattr * const tb[],struct nft_object * obj)303 static int nft_synproxy_obj_init(const struct nft_ctx *ctx,
304 const struct nlattr * const tb[],
305 struct nft_object *obj)
306 {
307 struct nft_synproxy *priv = nft_obj_data(obj);
308
309 return nft_synproxy_do_init(ctx, tb, priv);
310 }
311
nft_synproxy_obj_destroy(const struct nft_ctx * ctx,struct nft_object * obj)312 static void nft_synproxy_obj_destroy(const struct nft_ctx *ctx,
313 struct nft_object *obj)
314 {
315 nft_synproxy_do_destroy(ctx);
316 }
317
nft_synproxy_obj_dump(struct sk_buff * skb,struct nft_object * obj,bool reset)318 static int nft_synproxy_obj_dump(struct sk_buff *skb,
319 struct nft_object *obj, bool reset)
320 {
321 struct nft_synproxy *priv = nft_obj_data(obj);
322
323 return nft_synproxy_do_dump(skb, priv);
324 }
325
nft_synproxy_obj_eval(struct nft_object * obj,struct nft_regs * regs,const struct nft_pktinfo * pkt)326 static void nft_synproxy_obj_eval(struct nft_object *obj,
327 struct nft_regs *regs,
328 const struct nft_pktinfo *pkt)
329 {
330 const struct nft_synproxy *priv = nft_obj_data(obj);
331
332 nft_synproxy_do_eval(priv, regs, pkt);
333 }
334
nft_synproxy_obj_update(struct nft_object * obj,struct nft_object * newobj)335 static void nft_synproxy_obj_update(struct nft_object *obj,
336 struct nft_object *newobj)
337 {
338 struct nft_synproxy *newpriv = nft_obj_data(newobj);
339 struct nft_synproxy *priv = nft_obj_data(obj);
340
341 priv->info = newpriv->info;
342 }
343
344 static struct nft_object_type nft_synproxy_obj_type;
345 static const struct nft_object_ops nft_synproxy_obj_ops = {
346 .type = &nft_synproxy_obj_type,
347 .size = sizeof(struct nft_synproxy),
348 .init = nft_synproxy_obj_init,
349 .destroy = nft_synproxy_obj_destroy,
350 .dump = nft_synproxy_obj_dump,
351 .eval = nft_synproxy_obj_eval,
352 .update = nft_synproxy_obj_update,
353 };
354
355 static struct nft_object_type nft_synproxy_obj_type __read_mostly = {
356 .type = NFT_OBJECT_SYNPROXY,
357 .ops = &nft_synproxy_obj_ops,
358 .maxattr = NFTA_SYNPROXY_MAX,
359 .policy = nft_synproxy_policy,
360 .owner = THIS_MODULE,
361 };
362
nft_synproxy_module_init(void)363 static int __init nft_synproxy_module_init(void)
364 {
365 int err;
366
367 err = nft_register_obj(&nft_synproxy_obj_type);
368 if (err < 0)
369 return err;
370
371 err = nft_register_expr(&nft_synproxy_type);
372 if (err < 0)
373 goto err;
374
375 return 0;
376
377 err:
378 nft_unregister_obj(&nft_synproxy_obj_type);
379 return err;
380 }
381
nft_synproxy_module_exit(void)382 static void __exit nft_synproxy_module_exit(void)
383 {
384 nft_unregister_expr(&nft_synproxy_type);
385 nft_unregister_obj(&nft_synproxy_obj_type);
386 }
387
388 module_init(nft_synproxy_module_init);
389 module_exit(nft_synproxy_module_exit);
390
391 MODULE_LICENSE("GPL");
392 MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
393 MODULE_ALIAS_NFT_EXPR("synproxy");
394 MODULE_ALIAS_NFT_OBJ(NFT_OBJECT_SYNPROXY);
395 MODULE_DESCRIPTION("nftables SYNPROXY expression support");
396
