1 /*
2 * Copyright (c) 2013 Patrick McHardy <kaber@trash.net>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 */
8
9 #include <linux/module.h>
10 #include <linux/skbuff.h>
11 #include <asm/unaligned.h>
12 #include <net/tcp.h>
13 #include <net/netns/generic.h>
14
15 #include <linux/netfilter_ipv4/ip_tables.h>
16 #include <linux/netfilter/x_tables.h>
17 #include <linux/netfilter/xt_tcpudp.h>
18 #include <linux/netfilter/xt_SYNPROXY.h>
19 #include <net/netfilter/nf_conntrack.h>
20 #include <net/netfilter/nf_conntrack_extend.h>
21 #include <net/netfilter/nf_conntrack_seqadj.h>
22 #include <net/netfilter/nf_conntrack_synproxy.h>
23
24 int synproxy_net_id;
25 EXPORT_SYMBOL_GPL(synproxy_net_id);
26
27 bool
synproxy_parse_options(const struct sk_buff * skb,unsigned int doff,const struct tcphdr * th,struct synproxy_options * opts)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 = get_unaligned_be16(ptr);
60 opts->options |= XT_SYNPROXY_OPT_MSS;
61 }
62 break;
63 case TCPOPT_WINDOW:
64 if (opsize == TCPOLEN_WINDOW) {
65 opts->wscale = *ptr;
66 if (opts->wscale > 14)
67 opts->wscale = 14;
68 opts->options |= XT_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 |= XT_SYNPROXY_OPT_TIMESTAMP;
76 }
77 break;
78 case TCPOPT_SACK_PERM:
79 if (opsize == TCPOLEN_SACK_PERM)
80 opts->options |= XT_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
synproxy_options_size(const struct synproxy_options * opts)92 unsigned int synproxy_options_size(const struct synproxy_options *opts)
93 {
94 unsigned int size = 0;
95
96 if (opts->options & XT_SYNPROXY_OPT_MSS)
97 size += TCPOLEN_MSS_ALIGNED;
98 if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP)
99 size += TCPOLEN_TSTAMP_ALIGNED;
100 else if (opts->options & XT_SYNPROXY_OPT_SACK_PERM)
101 size += TCPOLEN_SACKPERM_ALIGNED;
102 if (opts->options & XT_SYNPROXY_OPT_WSCALE)
103 size += TCPOLEN_WSCALE_ALIGNED;
104
105 return size;
106 }
107 EXPORT_SYMBOL_GPL(synproxy_options_size);
108
109 void
synproxy_build_options(struct tcphdr * th,const struct synproxy_options * opts)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 & XT_SYNPROXY_OPT_MSS)
116 *ptr++ = htonl((TCPOPT_MSS << 24) |
117 (TCPOLEN_MSS << 16) |
118 opts->mss);
119
120 if (options & XT_SYNPROXY_OPT_TIMESTAMP) {
121 if (options & XT_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 & XT_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 & XT_SYNPROXY_OPT_WSCALE)
141 *ptr++ = htonl((TCPOPT_NOP << 24) |
142 (TCPOPT_WINDOW << 16) |
143 (TCPOLEN_WINDOW << 8) |
144 opts->wscale);
145 }
146 EXPORT_SYMBOL_GPL(synproxy_build_options);
147
synproxy_init_timestamp_cookie(const struct xt_synproxy_info * info,struct synproxy_options * opts)148 void synproxy_init_timestamp_cookie(const struct xt_synproxy_info *info,
149 struct synproxy_options *opts)
150 {
151 opts->tsecr = opts->tsval;
152 opts->tsval = tcp_time_stamp & ~0x3f;
153
154 if (opts->options & XT_SYNPROXY_OPT_WSCALE) {
155 opts->tsval |= opts->wscale;
156 opts->wscale = info->wscale;
157 } else
158 opts->tsval |= 0xf;
159
160 if (opts->options & XT_SYNPROXY_OPT_SACK_PERM)
161 opts->tsval |= 1 << 4;
162
163 if (opts->options & XT_SYNPROXY_OPT_ECN)
164 opts->tsval |= 1 << 5;
165 }
166 EXPORT_SYMBOL_GPL(synproxy_init_timestamp_cookie);
167
synproxy_check_timestamp_cookie(struct synproxy_options * opts)168 void synproxy_check_timestamp_cookie(struct synproxy_options *opts)
169 {
170 opts->wscale = opts->tsecr & 0xf;
171 if (opts->wscale != 0xf)
172 opts->options |= XT_SYNPROXY_OPT_WSCALE;
173
174 opts->options |= opts->tsecr & (1 << 4) ? XT_SYNPROXY_OPT_SACK_PERM : 0;
175
176 opts->options |= opts->tsecr & (1 << 5) ? XT_SYNPROXY_OPT_ECN : 0;
177 }
178 EXPORT_SYMBOL_GPL(synproxy_check_timestamp_cookie);
179
synproxy_tstamp_adjust(struct sk_buff * skb,unsigned int protoff,struct tcphdr * th,struct nf_conn * ct,enum ip_conntrack_info ctinfo,const struct nf_conn_synproxy * synproxy)180 unsigned int synproxy_tstamp_adjust(struct sk_buff *skb,
181 unsigned int protoff,
182 struct tcphdr *th,
183 struct nf_conn *ct,
184 enum ip_conntrack_info ctinfo,
185 const struct nf_conn_synproxy *synproxy)
186 {
187 unsigned int optoff, optend;
188 u32 *ptr, old;
189
190 if (synproxy->tsoff == 0)
191 return 1;
192
193 optoff = protoff + sizeof(struct tcphdr);
194 optend = protoff + th->doff * 4;
195
196 if (!skb_make_writable(skb, optend))
197 return 0;
198
199 while (optoff < optend) {
200 unsigned char *op = skb->data + optoff;
201
202 switch (op[0]) {
203 case TCPOPT_EOL:
204 return 1;
205 case TCPOPT_NOP:
206 optoff++;
207 continue;
208 default:
209 if (optoff + 1 == optend ||
210 optoff + op[1] > optend ||
211 op[1] < 2)
212 return 0;
213 if (op[0] == TCPOPT_TIMESTAMP &&
214 op[1] == TCPOLEN_TIMESTAMP) {
215 if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
216 ptr = (u32 *)&op[2];
217 old = *ptr;
218 *ptr = htonl(ntohl(*ptr) -
219 synproxy->tsoff);
220 } else {
221 ptr = (u32 *)&op[6];
222 old = *ptr;
223 *ptr = htonl(ntohl(*ptr) +
224 synproxy->tsoff);
225 }
226 inet_proto_csum_replace4(&th->check, skb,
227 old, *ptr, 0);
228 return 1;
229 }
230 optoff += op[1];
231 }
232 }
233 return 1;
234 }
235 EXPORT_SYMBOL_GPL(synproxy_tstamp_adjust);
236
237 static struct nf_ct_ext_type nf_ct_synproxy_extend __read_mostly = {
238 .len = sizeof(struct nf_conn_synproxy),
239 .align = __alignof__(struct nf_conn_synproxy),
240 .id = NF_CT_EXT_SYNPROXY,
241 };
242
243 #ifdef CONFIG_PROC_FS
synproxy_cpu_seq_start(struct seq_file * seq,loff_t * pos)244 static void *synproxy_cpu_seq_start(struct seq_file *seq, loff_t *pos)
245 {
246 struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
247 int cpu;
248
249 if (*pos == 0)
250 return SEQ_START_TOKEN;
251
252 for (cpu = *pos - 1; cpu < nr_cpu_ids; cpu++) {
253 if (!cpu_possible(cpu))
254 continue;
255 *pos = cpu + 1;
256 return per_cpu_ptr(snet->stats, cpu);
257 }
258
259 return NULL;
260 }
261
synproxy_cpu_seq_next(struct seq_file * seq,void * v,loff_t * pos)262 static void *synproxy_cpu_seq_next(struct seq_file *seq, void *v, loff_t *pos)
263 {
264 struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
265 int cpu;
266
267 for (cpu = *pos; cpu < nr_cpu_ids; cpu++) {
268 if (!cpu_possible(cpu))
269 continue;
270 *pos = cpu + 1;
271 return per_cpu_ptr(snet->stats, cpu);
272 }
273
274 return NULL;
275 }
276
synproxy_cpu_seq_stop(struct seq_file * seq,void * v)277 static void synproxy_cpu_seq_stop(struct seq_file *seq, void *v)
278 {
279 return;
280 }
281
synproxy_cpu_seq_show(struct seq_file * seq,void * v)282 static int synproxy_cpu_seq_show(struct seq_file *seq, void *v)
283 {
284 struct synproxy_stats *stats = v;
285
286 if (v == SEQ_START_TOKEN) {
287 seq_printf(seq, "entries\t\tsyn_received\t"
288 "cookie_invalid\tcookie_valid\t"
289 "cookie_retrans\tconn_reopened\n");
290 return 0;
291 }
292
293 seq_printf(seq, "%08x\t%08x\t%08x\t%08x\t%08x\t%08x\n", 0,
294 stats->syn_received,
295 stats->cookie_invalid,
296 stats->cookie_valid,
297 stats->cookie_retrans,
298 stats->conn_reopened);
299
300 return 0;
301 }
302
303 static const struct seq_operations synproxy_cpu_seq_ops = {
304 .start = synproxy_cpu_seq_start,
305 .next = synproxy_cpu_seq_next,
306 .stop = synproxy_cpu_seq_stop,
307 .show = synproxy_cpu_seq_show,
308 };
309
synproxy_cpu_seq_open(struct inode * inode,struct file * file)310 static int synproxy_cpu_seq_open(struct inode *inode, struct file *file)
311 {
312 return seq_open_net(inode, file, &synproxy_cpu_seq_ops,
313 sizeof(struct seq_net_private));
314 }
315
316 static const struct file_operations synproxy_cpu_seq_fops = {
317 .owner = THIS_MODULE,
318 .open = synproxy_cpu_seq_open,
319 .read = seq_read,
320 .llseek = seq_lseek,
321 .release = seq_release_net,
322 };
323
synproxy_proc_init(struct net * net)324 static int __net_init synproxy_proc_init(struct net *net)
325 {
326 if (!proc_create("synproxy", S_IRUGO, net->proc_net_stat,
327 &synproxy_cpu_seq_fops))
328 return -ENOMEM;
329 return 0;
330 }
331
synproxy_proc_exit(struct net * net)332 static void __net_exit synproxy_proc_exit(struct net *net)
333 {
334 remove_proc_entry("synproxy", net->proc_net_stat);
335 }
336 #else
synproxy_proc_init(struct net * net)337 static int __net_init synproxy_proc_init(struct net *net)
338 {
339 return 0;
340 }
341
synproxy_proc_exit(struct net * net)342 static void __net_exit synproxy_proc_exit(struct net *net)
343 {
344 return;
345 }
346 #endif /* CONFIG_PROC_FS */
347
synproxy_net_init(struct net * net)348 static int __net_init synproxy_net_init(struct net *net)
349 {
350 struct synproxy_net *snet = synproxy_pernet(net);
351 struct nf_conntrack_tuple t;
352 struct nf_conn *ct;
353 int err = -ENOMEM;
354
355 memset(&t, 0, sizeof(t));
356 ct = nf_conntrack_alloc(net, 0, &t, &t, GFP_KERNEL);
357 if (IS_ERR(ct)) {
358 err = PTR_ERR(ct);
359 goto err1;
360 }
361
362 if (!nfct_seqadj_ext_add(ct))
363 goto err2;
364 if (!nfct_synproxy_ext_add(ct))
365 goto err2;
366
367 nf_conntrack_tmpl_insert(net, ct);
368 snet->tmpl = ct;
369
370 snet->stats = alloc_percpu(struct synproxy_stats);
371 if (snet->stats == NULL)
372 goto err2;
373
374 err = synproxy_proc_init(net);
375 if (err < 0)
376 goto err3;
377
378 return 0;
379
380 err3:
381 free_percpu(snet->stats);
382 err2:
383 nf_conntrack_free(ct);
384 err1:
385 return err;
386 }
387
synproxy_net_exit(struct net * net)388 static void __net_exit synproxy_net_exit(struct net *net)
389 {
390 struct synproxy_net *snet = synproxy_pernet(net);
391
392 nf_ct_put(snet->tmpl);
393 synproxy_proc_exit(net);
394 free_percpu(snet->stats);
395 }
396
397 static struct pernet_operations synproxy_net_ops = {
398 .init = synproxy_net_init,
399 .exit = synproxy_net_exit,
400 .id = &synproxy_net_id,
401 .size = sizeof(struct synproxy_net),
402 };
403
synproxy_core_init(void)404 static int __init synproxy_core_init(void)
405 {
406 int err;
407
408 err = nf_ct_extend_register(&nf_ct_synproxy_extend);
409 if (err < 0)
410 goto err1;
411
412 err = register_pernet_subsys(&synproxy_net_ops);
413 if (err < 0)
414 goto err2;
415
416 return 0;
417
418 err2:
419 nf_ct_extend_unregister(&nf_ct_synproxy_extend);
420 err1:
421 return err;
422 }
423
synproxy_core_exit(void)424 static void __exit synproxy_core_exit(void)
425 {
426 unregister_pernet_subsys(&synproxy_net_ops);
427 nf_ct_extend_unregister(&nf_ct_synproxy_extend);
428 }
429
430 module_init(synproxy_core_init);
431 module_exit(synproxy_core_exit);
432
433 MODULE_LICENSE("GPL");
434 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
435