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netfilter: conntrack: skip identical origin tuple in same zone only
[mirror_ubuntu-hirsute-kernel.git] / net / netfilter / nf_synproxy_core.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (c) 2013 Patrick McHardy <kaber@trash.net>
4 */
5
6 #include <linux/module.h>
7 #include <linux/skbuff.h>
8 #include <asm/unaligned.h>
9 #include <net/tcp.h>
10 #include <net/netns/generic.h>
11 #include <linux/proc_fs.h>
12
13 #include <linux/netfilter_ipv6.h>
14 #include <linux/netfilter/nf_synproxy.h>
15
16 #include <net/netfilter/nf_conntrack.h>
17 #include <net/netfilter/nf_conntrack_ecache.h>
18 #include <net/netfilter/nf_conntrack_extend.h>
19 #include <net/netfilter/nf_conntrack_seqadj.h>
20 #include <net/netfilter/nf_conntrack_synproxy.h>
21 #include <net/netfilter/nf_conntrack_zones.h>
22 #include <net/netfilter/nf_synproxy.h>
23
24 unsigned int synproxy_net_id;
25 EXPORT_SYMBOL_GPL(synproxy_net_id);
26
27 bool
28 synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
29 const struct tcphdr *th, struct synproxy_options *opts)
30 {
31 int length = (th->doff * 4) - sizeof(*th);
32 u8 buf[40], *ptr;
33
34 ptr = skb_header_pointer(skb, doff + sizeof(*th), length, buf);
35 if (ptr == NULL)
36 return false;
37
38 opts->options = 0;
39 while (length > 0) {
40 int opcode = *ptr++;
41 int opsize;
42
43 switch (opcode) {
44 case TCPOPT_EOL:
45 return true;
46 case TCPOPT_NOP:
47 length--;
48 continue;
49 default:
50 opsize = *ptr++;
51 if (opsize < 2)
52 return true;
53 if (opsize > length)
54 return true;
55
56 switch (opcode) {
57 case TCPOPT_MSS:
58 if (opsize == TCPOLEN_MSS) {
59 opts->mss_option = get_unaligned_be16(ptr);
60 opts->options |= NF_SYNPROXY_OPT_MSS;
61 }
62 break;
63 case TCPOPT_WINDOW:
64 if (opsize == TCPOLEN_WINDOW) {
65 opts->wscale = *ptr;
66 if (opts->wscale > TCP_MAX_WSCALE)
67 opts->wscale = TCP_MAX_WSCALE;
68 opts->options |= NF_SYNPROXY_OPT_WSCALE;
69 }
70 break;
71 case TCPOPT_TIMESTAMP:
72 if (opsize == TCPOLEN_TIMESTAMP) {
73 opts->tsval = get_unaligned_be32(ptr);
74 opts->tsecr = get_unaligned_be32(ptr + 4);
75 opts->options |= NF_SYNPROXY_OPT_TIMESTAMP;
76 }
77 break;
78 case TCPOPT_SACK_PERM:
79 if (opsize == TCPOLEN_SACK_PERM)
80 opts->options |= NF_SYNPROXY_OPT_SACK_PERM;
81 break;
82 }
83
84 ptr += opsize - 2;
85 length -= opsize;
86 }
87 }
88 return true;
89 }
90 EXPORT_SYMBOL_GPL(synproxy_parse_options);
91
92 static unsigned int
93 synproxy_options_size(const struct synproxy_options *opts)
94 {
95 unsigned int size = 0;
96
97 if (opts->options & NF_SYNPROXY_OPT_MSS)
98 size += TCPOLEN_MSS_ALIGNED;
99 if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
100 size += TCPOLEN_TSTAMP_ALIGNED;
101 else if (opts->options & NF_SYNPROXY_OPT_SACK_PERM)
102 size += TCPOLEN_SACKPERM_ALIGNED;
103 if (opts->options & NF_SYNPROXY_OPT_WSCALE)
104 size += TCPOLEN_WSCALE_ALIGNED;
105
106 return size;
107 }
108
109 static void
110 synproxy_build_options(struct tcphdr *th, const struct synproxy_options *opts)
111 {
112 __be32 *ptr = (__be32 *)(th + 1);
113 u8 options = opts->options;
114
115 if (options & NF_SYNPROXY_OPT_MSS)
116 *ptr++ = htonl((TCPOPT_MSS << 24) |
117 (TCPOLEN_MSS << 16) |
118 opts->mss_option);
119
120 if (options & NF_SYNPROXY_OPT_TIMESTAMP) {
121 if (options & NF_SYNPROXY_OPT_SACK_PERM)
122 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
123 (TCPOLEN_SACK_PERM << 16) |
124 (TCPOPT_TIMESTAMP << 8) |
125 TCPOLEN_TIMESTAMP);
126 else
127 *ptr++ = htonl((TCPOPT_NOP << 24) |
128 (TCPOPT_NOP << 16) |
129 (TCPOPT_TIMESTAMP << 8) |
130 TCPOLEN_TIMESTAMP);
131
132 *ptr++ = htonl(opts->tsval);
133 *ptr++ = htonl(opts->tsecr);
134 } else if (options & NF_SYNPROXY_OPT_SACK_PERM)
135 *ptr++ = htonl((TCPOPT_NOP << 24) |
136 (TCPOPT_NOP << 16) |
137 (TCPOPT_SACK_PERM << 8) |
138 TCPOLEN_SACK_PERM);
139
140 if (options & NF_SYNPROXY_OPT_WSCALE)
141 *ptr++ = htonl((TCPOPT_NOP << 24) |
142 (TCPOPT_WINDOW << 16) |
143 (TCPOLEN_WINDOW << 8) |
144 opts->wscale);
145 }
146
147 void synproxy_init_timestamp_cookie(const struct nf_synproxy_info *info,
148 struct synproxy_options *opts)
149 {
150 opts->tsecr = opts->tsval;
151 opts->tsval = tcp_time_stamp_raw() & ~0x3f;
152
153 if (opts->options & NF_SYNPROXY_OPT_WSCALE) {
154 opts->tsval |= opts->wscale;
155 opts->wscale = info->wscale;
156 } else
157 opts->tsval |= 0xf;
158
159 if (opts->options & NF_SYNPROXY_OPT_SACK_PERM)
160 opts->tsval |= 1 << 4;
161
162 if (opts->options & NF_SYNPROXY_OPT_ECN)
163 opts->tsval |= 1 << 5;
164 }
165 EXPORT_SYMBOL_GPL(synproxy_init_timestamp_cookie);
166
167 static void
168 synproxy_check_timestamp_cookie(struct synproxy_options *opts)
169 {
170 opts->wscale = opts->tsecr & 0xf;
171 if (opts->wscale != 0xf)
172 opts->options |= NF_SYNPROXY_OPT_WSCALE;
173
174 opts->options |= opts->tsecr & (1 << 4) ? NF_SYNPROXY_OPT_SACK_PERM : 0;
175
176 opts->options |= opts->tsecr & (1 << 5) ? NF_SYNPROXY_OPT_ECN : 0;
177 }
178
179 static unsigned int
180 synproxy_tstamp_adjust(struct sk_buff *skb, unsigned int protoff,
181 struct tcphdr *th, struct nf_conn *ct,
182 enum ip_conntrack_info ctinfo,
183 const struct nf_conn_synproxy *synproxy)
184 {
185 unsigned int optoff, optend;
186 __be32 *ptr, old;
187
188 if (synproxy->tsoff == 0)
189 return 1;
190
191 optoff = protoff + sizeof(struct tcphdr);
192 optend = protoff + th->doff * 4;
193
194 if (skb_ensure_writable(skb, optend))
195 return 0;
196
197 while (optoff < optend) {
198 unsigned char *op = skb->data + optoff;
199
200 switch (op[0]) {
201 case TCPOPT_EOL:
202 return 1;
203 case TCPOPT_NOP:
204 optoff++;
205 continue;
206 default:
207 if (optoff + 1 == optend ||
208 optoff + op[1] > optend ||
209 op[1] < 2)
210 return 0;
211 if (op[0] == TCPOPT_TIMESTAMP &&
212 op[1] == TCPOLEN_TIMESTAMP) {
213 if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
214 ptr = (__be32 *)&op[2];
215 old = *ptr;
216 *ptr = htonl(ntohl(*ptr) -
217 synproxy->tsoff);
218 } else {
219 ptr = (__be32 *)&op[6];
220 old = *ptr;
221 *ptr = htonl(ntohl(*ptr) +
222 synproxy->tsoff);
223 }
224 inet_proto_csum_replace4(&th->check, skb,
225 old, *ptr, false);
226 return 1;
227 }
228 optoff += op[1];
229 }
230 }
231 return 1;
232 }
233
234 static struct nf_ct_ext_type nf_ct_synproxy_extend __read_mostly = {
235 .len = sizeof(struct nf_conn_synproxy),
236 .align = __alignof__(struct nf_conn_synproxy),
237 .id = NF_CT_EXT_SYNPROXY,
238 };
239
240 #ifdef CONFIG_PROC_FS
241 static void *synproxy_cpu_seq_start(struct seq_file *seq, loff_t *pos)
242 {
243 struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
244 int cpu;
245
246 if (*pos == 0)
247 return SEQ_START_TOKEN;
248
249 for (cpu = *pos - 1; cpu < nr_cpu_ids; cpu++) {
250 if (!cpu_possible(cpu))
251 continue;
252 *pos = cpu + 1;
253 return per_cpu_ptr(snet->stats, cpu);
254 }
255
256 return NULL;
257 }
258
259 static void *synproxy_cpu_seq_next(struct seq_file *seq, void *v, loff_t *pos)
260 {
261 struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
262 int cpu;
263
264 for (cpu = *pos; cpu < nr_cpu_ids; cpu++) {
265 if (!cpu_possible(cpu))
266 continue;
267 *pos = cpu + 1;
268 return per_cpu_ptr(snet->stats, cpu);
269 }
270 (*pos)++;
271 return NULL;
272 }
273
274 static void synproxy_cpu_seq_stop(struct seq_file *seq, void *v)
275 {
276 return;
277 }
278
279 static int synproxy_cpu_seq_show(struct seq_file *seq, void *v)
280 {
281 struct synproxy_stats *stats = v;
282
283 if (v == SEQ_START_TOKEN) {
284 seq_puts(seq, "entries\t\tsyn_received\t"
285 "cookie_invalid\tcookie_valid\t"
286 "cookie_retrans\tconn_reopened\n");
287 return 0;
288 }
289
290 seq_printf(seq, "%08x\t%08x\t%08x\t%08x\t%08x\t%08x\n", 0,
291 stats->syn_received,
292 stats->cookie_invalid,
293 stats->cookie_valid,
294 stats->cookie_retrans,
295 stats->conn_reopened);
296
297 return 0;
298 }
299
300 static const struct seq_operations synproxy_cpu_seq_ops = {
301 .start = synproxy_cpu_seq_start,
302 .next = synproxy_cpu_seq_next,
303 .stop = synproxy_cpu_seq_stop,
304 .show = synproxy_cpu_seq_show,
305 };
306
307 static int __net_init synproxy_proc_init(struct net *net)
308 {
309 if (!proc_create_net("synproxy", 0444, net->proc_net_stat,
310 &synproxy_cpu_seq_ops, sizeof(struct seq_net_private)))
311 return -ENOMEM;
312 return 0;
313 }
314
315 static void __net_exit synproxy_proc_exit(struct net *net)
316 {
317 remove_proc_entry("synproxy", net->proc_net_stat);
318 }
319 #else
320 static int __net_init synproxy_proc_init(struct net *net)
321 {
322 return 0;
323 }
324
325 static void __net_exit synproxy_proc_exit(struct net *net)
326 {
327 return;
328 }
329 #endif /* CONFIG_PROC_FS */
330
331 static int __net_init synproxy_net_init(struct net *net)
332 {
333 struct synproxy_net *snet = synproxy_pernet(net);
334 struct nf_conn *ct;
335 int err = -ENOMEM;
336
337 ct = nf_ct_tmpl_alloc(net, &nf_ct_zone_dflt, GFP_KERNEL);
338 if (!ct)
339 goto err1;
340
341 if (!nfct_seqadj_ext_add(ct))
342 goto err2;
343 if (!nfct_synproxy_ext_add(ct))
344 goto err2;
345
346 __set_bit(IPS_CONFIRMED_BIT, &ct->status);
347 nf_conntrack_get(&ct->ct_general);
348 snet->tmpl = ct;
349
350 snet->stats = alloc_percpu(struct synproxy_stats);
351 if (snet->stats == NULL)
352 goto err2;
353
354 err = synproxy_proc_init(net);
355 if (err < 0)
356 goto err3;
357
358 return 0;
359
360 err3:
361 free_percpu(snet->stats);
362 err2:
363 nf_ct_tmpl_free(ct);
364 err1:
365 return err;
366 }
367
368 static void __net_exit synproxy_net_exit(struct net *net)
369 {
370 struct synproxy_net *snet = synproxy_pernet(net);
371
372 nf_ct_put(snet->tmpl);
373 synproxy_proc_exit(net);
374 free_percpu(snet->stats);
375 }
376
377 static struct pernet_operations synproxy_net_ops = {
378 .init = synproxy_net_init,
379 .exit = synproxy_net_exit,
380 .id = &synproxy_net_id,
381 .size = sizeof(struct synproxy_net),
382 };
383
384 static int __init synproxy_core_init(void)
385 {
386 int err;
387
388 err = nf_ct_extend_register(&nf_ct_synproxy_extend);
389 if (err < 0)
390 goto err1;
391
392 err = register_pernet_subsys(&synproxy_net_ops);
393 if (err < 0)
394 goto err2;
395
396 return 0;
397
398 err2:
399 nf_ct_extend_unregister(&nf_ct_synproxy_extend);
400 err1:
401 return err;
402 }
403
404 static void __exit synproxy_core_exit(void)
405 {
406 unregister_pernet_subsys(&synproxy_net_ops);
407 nf_ct_extend_unregister(&nf_ct_synproxy_extend);
408 }
409
410 module_init(synproxy_core_init);
411 module_exit(synproxy_core_exit);
412
413 static struct iphdr *
414 synproxy_build_ip(struct net *net, struct sk_buff *skb, __be32 saddr,
415 __be32 daddr)
416 {
417 struct iphdr *iph;
418
419 skb_reset_network_header(skb);
420 iph = skb_put(skb, sizeof(*iph));
421 iph->version = 4;
422 iph->ihl = sizeof(*iph) / 4;
423 iph->tos = 0;
424 iph->id = 0;
425 iph->frag_off = htons(IP_DF);
426 iph->ttl = net->ipv4.sysctl_ip_default_ttl;
427 iph->protocol = IPPROTO_TCP;
428 iph->check = 0;
429 iph->saddr = saddr;
430 iph->daddr = daddr;
431
432 return iph;
433 }
434
435 static void
436 synproxy_send_tcp(struct net *net,
437 const struct sk_buff *skb, struct sk_buff *nskb,
438 struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
439 struct iphdr *niph, struct tcphdr *nth,
440 unsigned int tcp_hdr_size)
441 {
442 nth->check = ~tcp_v4_check(tcp_hdr_size, niph->saddr, niph->daddr, 0);
443 nskb->ip_summed = CHECKSUM_PARTIAL;
444 nskb->csum_start = (unsigned char *)nth - nskb->head;
445 nskb->csum_offset = offsetof(struct tcphdr, check);
446
447 skb_dst_set_noref(nskb, skb_dst(skb));
448 nskb->protocol = htons(ETH_P_IP);
449 if (ip_route_me_harder(net, nskb->sk, nskb, RTN_UNSPEC))
450 goto free_nskb;
451
452 if (nfct) {
453 nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
454 nf_conntrack_get(nfct);
455 }
456
457 ip_local_out(net, nskb->sk, nskb);
458 return;
459
460 free_nskb:
461 kfree_skb(nskb);
462 }
463
464 void
465 synproxy_send_client_synack(struct net *net,
466 const struct sk_buff *skb, const struct tcphdr *th,
467 const struct synproxy_options *opts)
468 {
469 struct sk_buff *nskb;
470 struct iphdr *iph, *niph;
471 struct tcphdr *nth;
472 unsigned int tcp_hdr_size;
473 u16 mss = opts->mss_encode;
474
475 iph = ip_hdr(skb);
476
477 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
478 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
479 GFP_ATOMIC);
480 if (!nskb)
481 return;
482 skb_reserve(nskb, MAX_TCP_HEADER);
483
484 niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
485
486 skb_reset_transport_header(nskb);
487 nth = skb_put(nskb, tcp_hdr_size);
488 nth->source = th->dest;
489 nth->dest = th->source;
490 nth->seq = htonl(__cookie_v4_init_sequence(iph, th, &mss));
491 nth->ack_seq = htonl(ntohl(th->seq) + 1);
492 tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
493 if (opts->options & NF_SYNPROXY_OPT_ECN)
494 tcp_flag_word(nth) |= TCP_FLAG_ECE;
495 nth->doff = tcp_hdr_size / 4;
496 nth->window = 0;
497 nth->check = 0;
498 nth->urg_ptr = 0;
499
500 synproxy_build_options(nth, opts);
501
502 synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
503 IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
504 }
505 EXPORT_SYMBOL_GPL(synproxy_send_client_synack);
506
507 static void
508 synproxy_send_server_syn(struct net *net,
509 const struct sk_buff *skb, const struct tcphdr *th,
510 const struct synproxy_options *opts, u32 recv_seq)
511 {
512 struct synproxy_net *snet = synproxy_pernet(net);
513 struct sk_buff *nskb;
514 struct iphdr *iph, *niph;
515 struct tcphdr *nth;
516 unsigned int tcp_hdr_size;
517
518 iph = ip_hdr(skb);
519
520 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
521 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
522 GFP_ATOMIC);
523 if (!nskb)
524 return;
525 skb_reserve(nskb, MAX_TCP_HEADER);
526
527 niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
528
529 skb_reset_transport_header(nskb);
530 nth = skb_put(nskb, tcp_hdr_size);
531 nth->source = th->source;
532 nth->dest = th->dest;
533 nth->seq = htonl(recv_seq - 1);
534 /* ack_seq is used to relay our ISN to the synproxy hook to initialize
535 * sequence number translation once a connection tracking entry exists.
536 */
537 nth->ack_seq = htonl(ntohl(th->ack_seq) - 1);
538 tcp_flag_word(nth) = TCP_FLAG_SYN;
539 if (opts->options & NF_SYNPROXY_OPT_ECN)
540 tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
541 nth->doff = tcp_hdr_size / 4;
542 nth->window = th->window;
543 nth->check = 0;
544 nth->urg_ptr = 0;
545
546 synproxy_build_options(nth, opts);
547
548 synproxy_send_tcp(net, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
549 niph, nth, tcp_hdr_size);
550 }
551
552 static void
553 synproxy_send_server_ack(struct net *net,
554 const struct ip_ct_tcp *state,
555 const struct sk_buff *skb, const struct tcphdr *th,
556 const struct synproxy_options *opts)
557 {
558 struct sk_buff *nskb;
559 struct iphdr *iph, *niph;
560 struct tcphdr *nth;
561 unsigned int tcp_hdr_size;
562
563 iph = ip_hdr(skb);
564
565 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
566 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
567 GFP_ATOMIC);
568 if (!nskb)
569 return;
570 skb_reserve(nskb, MAX_TCP_HEADER);
571
572 niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
573
574 skb_reset_transport_header(nskb);
575 nth = skb_put(nskb, tcp_hdr_size);
576 nth->source = th->dest;
577 nth->dest = th->source;
578 nth->seq = htonl(ntohl(th->ack_seq));
579 nth->ack_seq = htonl(ntohl(th->seq) + 1);
580 tcp_flag_word(nth) = TCP_FLAG_ACK;
581 nth->doff = tcp_hdr_size / 4;
582 nth->window = htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
583 nth->check = 0;
584 nth->urg_ptr = 0;
585
586 synproxy_build_options(nth, opts);
587
588 synproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
589 }
590
591 static void
592 synproxy_send_client_ack(struct net *net,
593 const struct sk_buff *skb, const struct tcphdr *th,
594 const struct synproxy_options *opts)
595 {
596 struct sk_buff *nskb;
597 struct iphdr *iph, *niph;
598 struct tcphdr *nth;
599 unsigned int tcp_hdr_size;
600
601 iph = ip_hdr(skb);
602
603 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
604 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
605 GFP_ATOMIC);
606 if (!nskb)
607 return;
608 skb_reserve(nskb, MAX_TCP_HEADER);
609
610 niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
611
612 skb_reset_transport_header(nskb);
613 nth = skb_put(nskb, tcp_hdr_size);
614 nth->source = th->source;
615 nth->dest = th->dest;
616 nth->seq = htonl(ntohl(th->seq) + 1);
617 nth->ack_seq = th->ack_seq;
618 tcp_flag_word(nth) = TCP_FLAG_ACK;
619 nth->doff = tcp_hdr_size / 4;
620 nth->window = htons(ntohs(th->window) >> opts->wscale);
621 nth->check = 0;
622 nth->urg_ptr = 0;
623
624 synproxy_build_options(nth, opts);
625
626 synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
627 IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
628 }
629
630 bool
631 synproxy_recv_client_ack(struct net *net,
632 const struct sk_buff *skb, const struct tcphdr *th,
633 struct synproxy_options *opts, u32 recv_seq)
634 {
635 struct synproxy_net *snet = synproxy_pernet(net);
636 int mss;
637
638 mss = __cookie_v4_check(ip_hdr(skb), th, ntohl(th->ack_seq) - 1);
639 if (mss == 0) {
640 this_cpu_inc(snet->stats->cookie_invalid);
641 return false;
642 }
643
644 this_cpu_inc(snet->stats->cookie_valid);
645 opts->mss_option = mss;
646 opts->options |= NF_SYNPROXY_OPT_MSS;
647
648 if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
649 synproxy_check_timestamp_cookie(opts);
650
651 synproxy_send_server_syn(net, skb, th, opts, recv_seq);
652 return true;
653 }
654 EXPORT_SYMBOL_GPL(synproxy_recv_client_ack);
655
656 unsigned int
657 ipv4_synproxy_hook(void *priv, struct sk_buff *skb,
658 const struct nf_hook_state *nhs)
659 {
660 struct net *net = nhs->net;
661 struct synproxy_net *snet = synproxy_pernet(net);
662 enum ip_conntrack_info ctinfo;
663 struct nf_conn *ct;
664 struct nf_conn_synproxy *synproxy;
665 struct synproxy_options opts = {};
666 const struct ip_ct_tcp *state;
667 struct tcphdr *th, _th;
668 unsigned int thoff;
669
670 ct = nf_ct_get(skb, &ctinfo);
671 if (!ct)
672 return NF_ACCEPT;
673
674 synproxy = nfct_synproxy(ct);
675 if (!synproxy)
676 return NF_ACCEPT;
677
678 if (nf_is_loopback_packet(skb) ||
679 ip_hdr(skb)->protocol != IPPROTO_TCP)
680 return NF_ACCEPT;
681
682 thoff = ip_hdrlen(skb);
683 th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
684 if (!th)
685 return NF_DROP;
686
687 state = &ct->proto.tcp;
688 switch (state->state) {
689 case TCP_CONNTRACK_CLOSE:
690 if (th->rst && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
691 nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
692 ntohl(th->seq) + 1);
693 break;
694 }
695
696 if (!th->syn || th->ack ||
697 CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
698 break;
699
700 /* Reopened connection - reset the sequence number and timestamp
701 * adjustments, they will get initialized once the connection is
702 * reestablished.
703 */
704 nf_ct_seqadj_init(ct, ctinfo, 0);
705 synproxy->tsoff = 0;
706 this_cpu_inc(snet->stats->conn_reopened);
707 fallthrough;
708 case TCP_CONNTRACK_SYN_SENT:
709 if (!synproxy_parse_options(skb, thoff, th, &opts))
710 return NF_DROP;
711
712 if (!th->syn && th->ack &&
713 CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
714 /* Keep-Alives are sent with SEG.SEQ = SND.NXT-1,
715 * therefore we need to add 1 to make the SYN sequence
716 * number match the one of first SYN.
717 */
718 if (synproxy_recv_client_ack(net, skb, th, &opts,
719 ntohl(th->seq) + 1)) {
720 this_cpu_inc(snet->stats->cookie_retrans);
721 consume_skb(skb);
722 return NF_STOLEN;
723 } else {
724 return NF_DROP;
725 }
726 }
727
728 synproxy->isn = ntohl(th->ack_seq);
729 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP)
730 synproxy->its = opts.tsecr;
731
732 nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
733 break;
734 case TCP_CONNTRACK_SYN_RECV:
735 if (!th->syn || !th->ack)
736 break;
737
738 if (!synproxy_parse_options(skb, thoff, th, &opts))
739 return NF_DROP;
740
741 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP) {
742 synproxy->tsoff = opts.tsval - synproxy->its;
743 nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
744 }
745
746 opts.options &= ~(NF_SYNPROXY_OPT_MSS |
747 NF_SYNPROXY_OPT_WSCALE |
748 NF_SYNPROXY_OPT_SACK_PERM);
749
750 swap(opts.tsval, opts.tsecr);
751 synproxy_send_server_ack(net, state, skb, th, &opts);
752
753 nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
754 nf_conntrack_event_cache(IPCT_SEQADJ, ct);
755
756 swap(opts.tsval, opts.tsecr);
757 synproxy_send_client_ack(net, skb, th, &opts);
758
759 consume_skb(skb);
760 return NF_STOLEN;
761 default:
762 break;
763 }
764
765 synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
766 return NF_ACCEPT;
767 }
768 EXPORT_SYMBOL_GPL(ipv4_synproxy_hook);
769
770 static const struct nf_hook_ops ipv4_synproxy_ops[] = {
771 {
772 .hook = ipv4_synproxy_hook,
773 .pf = NFPROTO_IPV4,
774 .hooknum = NF_INET_LOCAL_IN,
775 .priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
776 },
777 {
778 .hook = ipv4_synproxy_hook,
779 .pf = NFPROTO_IPV4,
780 .hooknum = NF_INET_POST_ROUTING,
781 .priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
782 },
783 };
784
785 int nf_synproxy_ipv4_init(struct synproxy_net *snet, struct net *net)
786 {
787 int err;
788
789 if (snet->hook_ref4 == 0) {
790 err = nf_register_net_hooks(net, ipv4_synproxy_ops,
791 ARRAY_SIZE(ipv4_synproxy_ops));
792 if (err)
793 return err;
794 }
795
796 snet->hook_ref4++;
797 return 0;
798 }
799 EXPORT_SYMBOL_GPL(nf_synproxy_ipv4_init);
800
801 void nf_synproxy_ipv4_fini(struct synproxy_net *snet, struct net *net)
802 {
803 snet->hook_ref4--;
804 if (snet->hook_ref4 == 0)
805 nf_unregister_net_hooks(net, ipv4_synproxy_ops,
806 ARRAY_SIZE(ipv4_synproxy_ops));
807 }
808 EXPORT_SYMBOL_GPL(nf_synproxy_ipv4_fini);
809
810 #if IS_ENABLED(CONFIG_IPV6)
811 static struct ipv6hdr *
812 synproxy_build_ip_ipv6(struct net *net, struct sk_buff *skb,
813 const struct in6_addr *saddr,
814 const struct in6_addr *daddr)
815 {
816 struct ipv6hdr *iph;
817
818 skb_reset_network_header(skb);
819 iph = skb_put(skb, sizeof(*iph));
820 ip6_flow_hdr(iph, 0, 0);
821 iph->hop_limit = net->ipv6.devconf_all->hop_limit;
822 iph->nexthdr = IPPROTO_TCP;
823 iph->saddr = *saddr;
824 iph->daddr = *daddr;
825
826 return iph;
827 }
828
829 static void
830 synproxy_send_tcp_ipv6(struct net *net,
831 const struct sk_buff *skb, struct sk_buff *nskb,
832 struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
833 struct ipv6hdr *niph, struct tcphdr *nth,
834 unsigned int tcp_hdr_size)
835 {
836 struct dst_entry *dst;
837 struct flowi6 fl6;
838 int err;
839
840 nth->check = ~tcp_v6_check(tcp_hdr_size, &niph->saddr, &niph->daddr, 0);
841 nskb->ip_summed = CHECKSUM_PARTIAL;
842 nskb->csum_start = (unsigned char *)nth - nskb->head;
843 nskb->csum_offset = offsetof(struct tcphdr, check);
844
845 memset(&fl6, 0, sizeof(fl6));
846 fl6.flowi6_proto = IPPROTO_TCP;
847 fl6.saddr = niph->saddr;
848 fl6.daddr = niph->daddr;
849 fl6.fl6_sport = nth->source;
850 fl6.fl6_dport = nth->dest;
851 security_skb_classify_flow((struct sk_buff *)skb,
852 flowi6_to_flowi_common(&fl6));
853 err = nf_ip6_route(net, &dst, flowi6_to_flowi(&fl6), false);
854 if (err) {
855 goto free_nskb;
856 }
857
858 dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
859 if (IS_ERR(dst))
860 goto free_nskb;
861
862 skb_dst_set(nskb, dst);
863
864 if (nfct) {
865 nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
866 nf_conntrack_get(nfct);
867 }
868
869 ip6_local_out(net, nskb->sk, nskb);
870 return;
871
872 free_nskb:
873 kfree_skb(nskb);
874 }
875
876 void
877 synproxy_send_client_synack_ipv6(struct net *net,
878 const struct sk_buff *skb,
879 const struct tcphdr *th,
880 const struct synproxy_options *opts)
881 {
882 struct sk_buff *nskb;
883 struct ipv6hdr *iph, *niph;
884 struct tcphdr *nth;
885 unsigned int tcp_hdr_size;
886 u16 mss = opts->mss_encode;
887
888 iph = ipv6_hdr(skb);
889
890 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
891 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
892 GFP_ATOMIC);
893 if (!nskb)
894 return;
895 skb_reserve(nskb, MAX_TCP_HEADER);
896
897 niph = synproxy_build_ip_ipv6(net, nskb, &iph->daddr, &iph->saddr);
898
899 skb_reset_transport_header(nskb);
900 nth = skb_put(nskb, tcp_hdr_size);
901 nth->source = th->dest;
902 nth->dest = th->source;
903 nth->seq = htonl(nf_ipv6_cookie_init_sequence(iph, th, &mss));
904 nth->ack_seq = htonl(ntohl(th->seq) + 1);
905 tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
906 if (opts->options & NF_SYNPROXY_OPT_ECN)
907 tcp_flag_word(nth) |= TCP_FLAG_ECE;
908 nth->doff = tcp_hdr_size / 4;
909 nth->window = 0;
910 nth->check = 0;
911 nth->urg_ptr = 0;
912
913 synproxy_build_options(nth, opts);
914
915 synproxy_send_tcp_ipv6(net, skb, nskb, skb_nfct(skb),
916 IP_CT_ESTABLISHED_REPLY, niph, nth,
917 tcp_hdr_size);
918 }
919 EXPORT_SYMBOL_GPL(synproxy_send_client_synack_ipv6);
920
921 static void
922 synproxy_send_server_syn_ipv6(struct net *net, const struct sk_buff *skb,
923 const struct tcphdr *th,
924 const struct synproxy_options *opts, u32 recv_seq)
925 {
926 struct synproxy_net *snet = synproxy_pernet(net);
927 struct sk_buff *nskb;
928 struct ipv6hdr *iph, *niph;
929 struct tcphdr *nth;
930 unsigned int tcp_hdr_size;
931
932 iph = ipv6_hdr(skb);
933
934 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
935 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
936 GFP_ATOMIC);
937 if (!nskb)
938 return;
939 skb_reserve(nskb, MAX_TCP_HEADER);
940
941 niph = synproxy_build_ip_ipv6(net, nskb, &iph->saddr, &iph->daddr);
942
943 skb_reset_transport_header(nskb);
944 nth = skb_put(nskb, tcp_hdr_size);
945 nth->source = th->source;
946 nth->dest = th->dest;
947 nth->seq = htonl(recv_seq - 1);
948 /* ack_seq is used to relay our ISN to the synproxy hook to initialize
949 * sequence number translation once a connection tracking entry exists.
950 */
951 nth->ack_seq = htonl(ntohl(th->ack_seq) - 1);
952 tcp_flag_word(nth) = TCP_FLAG_SYN;
953 if (opts->options & NF_SYNPROXY_OPT_ECN)
954 tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
955 nth->doff = tcp_hdr_size / 4;
956 nth->window = th->window;
957 nth->check = 0;
958 nth->urg_ptr = 0;
959
960 synproxy_build_options(nth, opts);
961
962 synproxy_send_tcp_ipv6(net, skb, nskb, &snet->tmpl->ct_general,
963 IP_CT_NEW, niph, nth, tcp_hdr_size);
964 }
965
966 static void
967 synproxy_send_server_ack_ipv6(struct net *net, const struct ip_ct_tcp *state,
968 const struct sk_buff *skb,
969 const struct tcphdr *th,
970 const struct synproxy_options *opts)
971 {
972 struct sk_buff *nskb;
973 struct ipv6hdr *iph, *niph;
974 struct tcphdr *nth;
975 unsigned int tcp_hdr_size;
976
977 iph = ipv6_hdr(skb);
978
979 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
980 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
981 GFP_ATOMIC);
982 if (!nskb)
983 return;
984 skb_reserve(nskb, MAX_TCP_HEADER);
985
986 niph = synproxy_build_ip_ipv6(net, nskb, &iph->daddr, &iph->saddr);
987
988 skb_reset_transport_header(nskb);
989 nth = skb_put(nskb, tcp_hdr_size);
990 nth->source = th->dest;
991 nth->dest = th->source;
992 nth->seq = htonl(ntohl(th->ack_seq));
993 nth->ack_seq = htonl(ntohl(th->seq) + 1);
994 tcp_flag_word(nth) = TCP_FLAG_ACK;
995 nth->doff = tcp_hdr_size / 4;
996 nth->window = htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
997 nth->check = 0;
998 nth->urg_ptr = 0;
999
1000 synproxy_build_options(nth, opts);
1001
1002 synproxy_send_tcp_ipv6(net, skb, nskb, NULL, 0, niph, nth,
1003 tcp_hdr_size);
1004 }
1005
1006 static void
1007 synproxy_send_client_ack_ipv6(struct net *net, const struct sk_buff *skb,
1008 const struct tcphdr *th,
1009 const struct synproxy_options *opts)
1010 {
1011 struct sk_buff *nskb;
1012 struct ipv6hdr *iph, *niph;
1013 struct tcphdr *nth;
1014 unsigned int tcp_hdr_size;
1015
1016 iph = ipv6_hdr(skb);
1017
1018 tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
1019 nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
1020 GFP_ATOMIC);
1021 if (!nskb)
1022 return;
1023 skb_reserve(nskb, MAX_TCP_HEADER);
1024
1025 niph = synproxy_build_ip_ipv6(net, nskb, &iph->saddr, &iph->daddr);
1026
1027 skb_reset_transport_header(nskb);
1028 nth = skb_put(nskb, tcp_hdr_size);
1029 nth->source = th->source;
1030 nth->dest = th->dest;
1031 nth->seq = htonl(ntohl(th->seq) + 1);
1032 nth->ack_seq = th->ack_seq;
1033 tcp_flag_word(nth) = TCP_FLAG_ACK;
1034 nth->doff = tcp_hdr_size / 4;
1035 nth->window = htons(ntohs(th->window) >> opts->wscale);
1036 nth->check = 0;
1037 nth->urg_ptr = 0;
1038
1039 synproxy_build_options(nth, opts);
1040
1041 synproxy_send_tcp_ipv6(net, skb, nskb, skb_nfct(skb),
1042 IP_CT_ESTABLISHED_REPLY, niph, nth,
1043 tcp_hdr_size);
1044 }
1045
1046 bool
1047 synproxy_recv_client_ack_ipv6(struct net *net,
1048 const struct sk_buff *skb,
1049 const struct tcphdr *th,
1050 struct synproxy_options *opts, u32 recv_seq)
1051 {
1052 struct synproxy_net *snet = synproxy_pernet(net);
1053 int mss;
1054
1055 mss = nf_cookie_v6_check(ipv6_hdr(skb), th, ntohl(th->ack_seq) - 1);
1056 if (mss == 0) {
1057 this_cpu_inc(snet->stats->cookie_invalid);
1058 return false;
1059 }
1060
1061 this_cpu_inc(snet->stats->cookie_valid);
1062 opts->mss_option = mss;
1063 opts->options |= NF_SYNPROXY_OPT_MSS;
1064
1065 if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
1066 synproxy_check_timestamp_cookie(opts);
1067
1068 synproxy_send_server_syn_ipv6(net, skb, th, opts, recv_seq);
1069 return true;
1070 }
1071 EXPORT_SYMBOL_GPL(synproxy_recv_client_ack_ipv6);
1072
1073 unsigned int
1074 ipv6_synproxy_hook(void *priv, struct sk_buff *skb,
1075 const struct nf_hook_state *nhs)
1076 {
1077 struct net *net = nhs->net;
1078 struct synproxy_net *snet = synproxy_pernet(net);
1079 enum ip_conntrack_info ctinfo;
1080 struct nf_conn *ct;
1081 struct nf_conn_synproxy *synproxy;
1082 struct synproxy_options opts = {};
1083 const struct ip_ct_tcp *state;
1084 struct tcphdr *th, _th;
1085 __be16 frag_off;
1086 u8 nexthdr;
1087 int thoff;
1088
1089 ct = nf_ct_get(skb, &ctinfo);
1090 if (!ct)
1091 return NF_ACCEPT;
1092
1093 synproxy = nfct_synproxy(ct);
1094 if (!synproxy)
1095 return NF_ACCEPT;
1096
1097 if (nf_is_loopback_packet(skb))
1098 return NF_ACCEPT;
1099
1100 nexthdr = ipv6_hdr(skb)->nexthdr;
1101 thoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr,
1102 &frag_off);
1103 if (thoff < 0 || nexthdr != IPPROTO_TCP)
1104 return NF_ACCEPT;
1105
1106 th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
1107 if (!th)
1108 return NF_DROP;
1109
1110 state = &ct->proto.tcp;
1111 switch (state->state) {
1112 case TCP_CONNTRACK_CLOSE:
1113 if (th->rst && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
1114 nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
1115 ntohl(th->seq) + 1);
1116 break;
1117 }
1118
1119 if (!th->syn || th->ack ||
1120 CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
1121 break;
1122
1123 /* Reopened connection - reset the sequence number and timestamp
1124 * adjustments, they will get initialized once the connection is
1125 * reestablished.
1126 */
1127 nf_ct_seqadj_init(ct, ctinfo, 0);
1128 synproxy->tsoff = 0;
1129 this_cpu_inc(snet->stats->conn_reopened);
1130 fallthrough;
1131 case TCP_CONNTRACK_SYN_SENT:
1132 if (!synproxy_parse_options(skb, thoff, th, &opts))
1133 return NF_DROP;
1134
1135 if (!th->syn && th->ack &&
1136 CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
1137 /* Keep-Alives are sent with SEG.SEQ = SND.NXT-1,
1138 * therefore we need to add 1 to make the SYN sequence
1139 * number match the one of first SYN.
1140 */
1141 if (synproxy_recv_client_ack_ipv6(net, skb, th, &opts,
1142 ntohl(th->seq) + 1)) {
1143 this_cpu_inc(snet->stats->cookie_retrans);
1144 consume_skb(skb);
1145 return NF_STOLEN;
1146 } else {
1147 return NF_DROP;
1148 }
1149 }
1150
1151 synproxy->isn = ntohl(th->ack_seq);
1152 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP)
1153 synproxy->its = opts.tsecr;
1154
1155 nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
1156 break;
1157 case TCP_CONNTRACK_SYN_RECV:
1158 if (!th->syn || !th->ack)
1159 break;
1160
1161 if (!synproxy_parse_options(skb, thoff, th, &opts))
1162 return NF_DROP;
1163
1164 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP) {
1165 synproxy->tsoff = opts.tsval - synproxy->its;
1166 nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
1167 }
1168
1169 opts.options &= ~(NF_SYNPROXY_OPT_MSS |
1170 NF_SYNPROXY_OPT_WSCALE |
1171 NF_SYNPROXY_OPT_SACK_PERM);
1172
1173 swap(opts.tsval, opts.tsecr);
1174 synproxy_send_server_ack_ipv6(net, state, skb, th, &opts);
1175
1176 nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
1177 nf_conntrack_event_cache(IPCT_SEQADJ, ct);
1178
1179 swap(opts.tsval, opts.tsecr);
1180 synproxy_send_client_ack_ipv6(net, skb, th, &opts);
1181
1182 consume_skb(skb);
1183 return NF_STOLEN;
1184 default:
1185 break;
1186 }
1187
1188 synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
1189 return NF_ACCEPT;
1190 }
1191 EXPORT_SYMBOL_GPL(ipv6_synproxy_hook);
1192
1193 static const struct nf_hook_ops ipv6_synproxy_ops[] = {
1194 {
1195 .hook = ipv6_synproxy_hook,
1196 .pf = NFPROTO_IPV6,
1197 .hooknum = NF_INET_LOCAL_IN,
1198 .priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
1199 },
1200 {
1201 .hook = ipv6_synproxy_hook,
1202 .pf = NFPROTO_IPV6,
1203 .hooknum = NF_INET_POST_ROUTING,
1204 .priority = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
1205 },
1206 };
1207
1208 int
1209 nf_synproxy_ipv6_init(struct synproxy_net *snet, struct net *net)
1210 {
1211 int err;
1212
1213 if (snet->hook_ref6 == 0) {
1214 err = nf_register_net_hooks(net, ipv6_synproxy_ops,
1215 ARRAY_SIZE(ipv6_synproxy_ops));
1216 if (err)
1217 return err;
1218 }
1219
1220 snet->hook_ref6++;
1221 return 0;
1222 }
1223 EXPORT_SYMBOL_GPL(nf_synproxy_ipv6_init);
1224
1225 void
1226 nf_synproxy_ipv6_fini(struct synproxy_net *snet, struct net *net)
1227 {
1228 snet->hook_ref6--;
1229 if (snet->hook_ref6 == 0)
1230 nf_unregister_net_hooks(net, ipv6_synproxy_ops,
1231 ARRAY_SIZE(ipv6_synproxy_ops));
1232 }
1233 EXPORT_SYMBOL_GPL(nf_synproxy_ipv6_fini);
1234 #endif /* CONFIG_IPV6 */
1235
1236 MODULE_LICENSE("GPL");
1237 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
1238 MODULE_DESCRIPTION("nftables SYNPROXY expression support");
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