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Committer: Michael Beasley <mike@snafu.setup>
[mikesnafu-overlay.git] / net / netfilter / nf_conntrack_ftp.c
blob6770baf2e845f1fafc0904f5251a3a6ed53e7a5a
1 /* FTP extension for connection tracking. */
2
3 /* (C) 1999-2001 Paul `Rusty' Russell
4 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
5 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 */
11
12 #include <linux/module.h>
13 #include <linux/moduleparam.h>
14 #include <linux/netfilter.h>
15 #include <linux/ip.h>
16 #include <linux/ipv6.h>
17 #include <linux/ctype.h>
18 #include <linux/inet.h>
19 #include <net/checksum.h>
20 #include <net/tcp.h>
21
22 #include <net/netfilter/nf_conntrack.h>
23 #include <net/netfilter/nf_conntrack_expect.h>
24 #include <net/netfilter/nf_conntrack_ecache.h>
25 #include <net/netfilter/nf_conntrack_helper.h>
26 #include <linux/netfilter/nf_conntrack_ftp.h>
27
28 MODULE_LICENSE("GPL");
29 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
30 MODULE_DESCRIPTION("ftp connection tracking helper");
31 MODULE_ALIAS("ip_conntrack_ftp");
32
33 /* This is slow, but it's simple. --RR */
34 static char *ftp_buffer;
35
36 static DEFINE_SPINLOCK(nf_ftp_lock);
37
38 #define MAX_PORTS 8
39 static u_int16_t ports[MAX_PORTS];
40 static unsigned int ports_c;
41 module_param_array(ports, ushort, &ports_c, 0400);
42
43 static int loose;
44 module_param(loose, bool, 0600);
45
46 unsigned int (*nf_nat_ftp_hook)(struct sk_buff *skb,
47 enum ip_conntrack_info ctinfo,
48 enum nf_ct_ftp_type type,
49 unsigned int matchoff,
50 unsigned int matchlen,
51 struct nf_conntrack_expect *exp);
52 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
53
54 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
55 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
56 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
57 char);
58
59 static struct ftp_search {
60 const char *pattern;
61 size_t plen;
62 char skip;
63 char term;
64 enum nf_ct_ftp_type ftptype;
65 int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
66 } search[IP_CT_DIR_MAX][2] = {
67 [IP_CT_DIR_ORIGINAL] = {
68 {
69 .pattern = "PORT",
70 .plen = sizeof("PORT") - 1,
71 .skip = ' ',
72 .term = '\r',
73 .ftptype = NF_CT_FTP_PORT,
74 .getnum = try_rfc959,
75 },
76 {
77 .pattern = "EPRT",
78 .plen = sizeof("EPRT") - 1,
79 .skip = ' ',
80 .term = '\r',
81 .ftptype = NF_CT_FTP_EPRT,
82 .getnum = try_eprt,
83 },
84 },
85 [IP_CT_DIR_REPLY] = {
86 {
87 .pattern = "227 ",
88 .plen = sizeof("227 ") - 1,
89 .skip = '(',
90 .term = ')',
91 .ftptype = NF_CT_FTP_PASV,
92 .getnum = try_rfc959,
93 },
94 {
95 .pattern = "229 ",
96 .plen = sizeof("229 ") - 1,
97 .skip = '(',
98 .term = ')',
99 .ftptype = NF_CT_FTP_EPSV,
100 .getnum = try_epsv_response,
101 },
102 },
103 };
104
105 static int
106 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
107 {
108 const char *end;
109 int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
110 if (ret > 0)
111 return (int)(end - src);
112 return 0;
113 }
114
115 static int try_number(const char *data, size_t dlen, u_int32_t array[],
116 int array_size, char sep, char term)
117 {
118 u_int32_t i, len;
119
120 memset(array, 0, sizeof(array[0])*array_size);
121
122 /* Keep data pointing at next char. */
123 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
124 if (*data >= '0' && *data <= '9') {
125 array[i] = array[i]*10 + *data - '0';
126 }
127 else if (*data == sep)
128 i++;
129 else {
130 /* Unexpected character; true if it's the
131 terminator and we're finished. */
132 if (*data == term && i == array_size - 1)
133 return len;
134
135 pr_debug("Char %u (got %u nums) `%u' unexpected\n",
136 len, i, *data);
137 return 0;
138 }
139 }
140 pr_debug("Failed to fill %u numbers separated by %c\n",
141 array_size, sep);
142 return 0;
143 }
144
145 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
146 static int try_rfc959(const char *data, size_t dlen,
147 struct nf_conntrack_man *cmd, char term)
148 {
149 int length;
150 u_int32_t array[6];
151
152 length = try_number(data, dlen, array, 6, ',', term);
153 if (length == 0)
154 return 0;
155
156 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
157 (array[2] << 8) | array[3]);
158 cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
159 return length;
160 }
161
162 /* Grab port: number up to delimiter */
163 static int get_port(const char *data, int start, size_t dlen, char delim,
164 __be16 *port)
165 {
166 u_int16_t tmp_port = 0;
167 int i;
168
169 for (i = start; i < dlen; i++) {
170 /* Finished? */
171 if (data[i] == delim) {
172 if (tmp_port == 0)
173 break;
174 *port = htons(tmp_port);
175 pr_debug("get_port: return %d\n", tmp_port);
176 return i + 1;
177 }
178 else if (data[i] >= '0' && data[i] <= '9')
179 tmp_port = tmp_port*10 + data[i] - '0';
180 else { /* Some other crap */
181 pr_debug("get_port: invalid char.\n");
182 break;
183 }
184 }
185 return 0;
186 }
187
188 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
189 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
190 char term)
191 {
192 char delim;
193 int length;
194
195 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
196 then delimiter again. */
197 if (dlen <= 3) {
198 pr_debug("EPRT: too short\n");
199 return 0;
200 }
201 delim = data[0];
202 if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
203 pr_debug("try_eprt: invalid delimitter.\n");
204 return 0;
205 }
206
207 if ((cmd->l3num == PF_INET && data[1] != '1') ||
208 (cmd->l3num == PF_INET6 && data[1] != '2')) {
209 pr_debug("EPRT: invalid protocol number.\n");
210 return 0;
211 }
212
213 pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
214
215 if (data[1] == '1') {
216 u_int32_t array[4];
217
218 /* Now we have IP address. */
219 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
220 if (length != 0)
221 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
222 | (array[2] << 8) | array[3]);
223 } else {
224 /* Now we have IPv6 address. */
225 length = get_ipv6_addr(data + 3, dlen - 3,
226 (struct in6_addr *)cmd->u3.ip6, delim);
227 }
228
229 if (length == 0)
230 return 0;
231 pr_debug("EPRT: Got IP address!\n");
232 /* Start offset includes initial "|1|", and trailing delimiter */
233 return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
234 }
235
236 /* Returns 0, or length of numbers: |||6446| */
237 static int try_epsv_response(const char *data, size_t dlen,
238 struct nf_conntrack_man *cmd, char term)
239 {
240 char delim;
241
242 /* Three delimiters. */
243 if (dlen <= 3) return 0;
244 delim = data[0];
245 if (isdigit(delim) || delim < 33 || delim > 126
246 || data[1] != delim || data[2] != delim)
247 return 0;
248
249 return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
250 }
251
252 /* Return 1 for match, 0 for accept, -1 for partial. */
253 static int find_pattern(const char *data, size_t dlen,
254 const char *pattern, size_t plen,
255 char skip, char term,
256 unsigned int *numoff,
257 unsigned int *numlen,
258 struct nf_conntrack_man *cmd,
259 int (*getnum)(const char *, size_t,
260 struct nf_conntrack_man *, char))
261 {
262 size_t i;
263
264 pr_debug("find_pattern `%s': dlen = %Zu\n", pattern, dlen);
265 if (dlen == 0)
266 return 0;
267
268 if (dlen <= plen) {
269 /* Short packet: try for partial? */
270 if (strnicmp(data, pattern, dlen) == 0)
271 return -1;
272 else return 0;
273 }
274
275 if (strnicmp(data, pattern, plen) != 0) {
276 #if 0
277 size_t i;
278
279 pr_debug("ftp: string mismatch\n");
280 for (i = 0; i < plen; i++) {
281 pr_debug("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
282 i, data[i], data[i],
283 pattern[i], pattern[i]);
284 }
285 #endif
286 return 0;
287 }
288
289 pr_debug("Pattern matches!\n");
290 /* Now we've found the constant string, try to skip
291 to the 'skip' character */
292 for (i = plen; data[i] != skip; i++)
293 if (i == dlen - 1) return -1;
294
295 /* Skip over the last character */
296 i++;
297
298 pr_debug("Skipped up to `%c'!\n", skip);
299
300 *numoff = i;
301 *numlen = getnum(data + i, dlen - i, cmd, term);
302 if (!*numlen)
303 return -1;
304
305 pr_debug("Match succeeded!\n");
306 return 1;
307 }
308
309 /* Look up to see if we're just after a \n. */
310 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
311 {
312 unsigned int i;
313
314 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
315 if (info->seq_aft_nl[dir][i] == seq)
316 return 1;
317 return 0;
318 }
319
320 /* We don't update if it's older than what we have. */
321 static void update_nl_seq(u32 nl_seq, struct nf_ct_ftp_master *info, int dir,
322 struct sk_buff *skb)
323 {
324 unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
325
326 /* Look for oldest: if we find exact match, we're done. */
327 for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
328 if (info->seq_aft_nl[dir][i] == nl_seq)
329 return;
330
331 if (oldest == info->seq_aft_nl_num[dir] ||
332 before(info->seq_aft_nl[dir][i],
333 info->seq_aft_nl[dir][oldest]))
334 oldest = i;
335 }
336
337 if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
338 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
339 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
340 } else if (oldest != NUM_SEQ_TO_REMEMBER &&
341 after(nl_seq, info->seq_aft_nl[dir][oldest])) {
342 info->seq_aft_nl[dir][oldest] = nl_seq;
343 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
344 }
345 }
346
347 static int help(struct sk_buff *skb,
348 unsigned int protoff,
349 struct nf_conn *ct,
350 enum ip_conntrack_info ctinfo)
351 {
352 unsigned int dataoff, datalen;
353 struct tcphdr _tcph, *th;
354 char *fb_ptr;
355 int ret;
356 u32 seq;
357 int dir = CTINFO2DIR(ctinfo);
358 unsigned int matchlen, matchoff;
359 struct nf_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
360 struct nf_conntrack_expect *exp;
361 union nf_inet_addr *daddr;
362 struct nf_conntrack_man cmd = {};
363 unsigned int i;
364 int found = 0, ends_in_nl;
365 typeof(nf_nat_ftp_hook) nf_nat_ftp;
366
367 /* Until there's been traffic both ways, don't look in packets. */
368 if (ctinfo != IP_CT_ESTABLISHED
369 && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
370 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
371 return NF_ACCEPT;
372 }
373
374 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
375 if (th == NULL)
376 return NF_ACCEPT;
377
378 dataoff = protoff + th->doff * 4;
379 /* No data? */
380 if (dataoff >= skb->len) {
381 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
382 skb->len);
383 return NF_ACCEPT;
384 }
385 datalen = skb->len - dataoff;
386
387 spin_lock_bh(&nf_ftp_lock);
388 fb_ptr = skb_header_pointer(skb, dataoff, datalen, ftp_buffer);
389 BUG_ON(fb_ptr == NULL);
390
391 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
392 seq = ntohl(th->seq) + datalen;
393
394 /* Look up to see if we're just after a \n. */
395 if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
396 /* Now if this ends in \n, update ftp info. */
397 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
398 ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
399 ct_ftp_info->seq_aft_nl[dir][0],
400 ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
401 ct_ftp_info->seq_aft_nl[dir][1]);
402 ret = NF_ACCEPT;
403 goto out_update_nl;
404 }
405
406 /* Initialize IP/IPv6 addr to expected address (it's not mentioned
407 in EPSV responses) */
408 cmd.l3num = ct->tuplehash[dir].tuple.src.l3num;
409 memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
410 sizeof(cmd.u3.all));
411
412 for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
413 found = find_pattern(fb_ptr, datalen,
414 search[dir][i].pattern,
415 search[dir][i].plen,
416 search[dir][i].skip,
417 search[dir][i].term,
418 &matchoff, &matchlen,
419 &cmd,
420 search[dir][i].getnum);
421 if (found) break;
422 }
423 if (found == -1) {
424 /* We don't usually drop packets. After all, this is
425 connection tracking, not packet filtering.
426 However, it is necessary for accurate tracking in
427 this case. */
428 if (net_ratelimit())
429 printk("conntrack_ftp: partial %s %u+%u\n",
430 search[dir][i].pattern,
431 ntohl(th->seq), datalen);
432 ret = NF_DROP;
433 goto out;
434 } else if (found == 0) { /* No match */
435 ret = NF_ACCEPT;
436 goto out_update_nl;
437 }
438
439 pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
440 matchlen, fb_ptr + matchoff,
441 matchlen, ntohl(th->seq) + matchoff);
442
443 exp = nf_ct_expect_alloc(ct);
444 if (exp == NULL) {
445 ret = NF_DROP;
446 goto out;
447 }
448
449 /* We refer to the reverse direction ("!dir") tuples here,
450 * because we're expecting something in the other direction.
451 * Doesn't matter unless NAT is happening. */
452 daddr = &ct->tuplehash[!dir].tuple.dst.u3;
453
454 /* Update the ftp info */
455 if ((cmd.l3num == ct->tuplehash[dir].tuple.src.l3num) &&
456 memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
457 sizeof(cmd.u3.all))) {
458 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
459 server: it really wants us to connect to a
460 different IP address. Simply don't record it for
461 NAT. */
462 if (cmd.l3num == PF_INET) {
463 pr_debug("conntrack_ftp: NOT RECORDING: " NIPQUAD_FMT
464 " != " NIPQUAD_FMT "\n",
465 NIPQUAD(cmd.u3.ip),
466 NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
467 } else {
468 pr_debug("conntrack_ftp: NOT RECORDING: " NIP6_FMT
469 " != " NIP6_FMT "\n",
470 NIP6(*((struct in6_addr *)cmd.u3.ip6)),
471 NIP6(*((struct in6_addr *)
472 ct->tuplehash[dir].tuple.src.u3.ip6)));
473 }
474
475 /* Thanks to Cristiano Lincoln Mattos
476 <lincoln@cesar.org.br> for reporting this potential
477 problem (DMZ machines opening holes to internal
478 networks, or the packet filter itself). */
479 if (!loose) {
480 ret = NF_ACCEPT;
481 goto out_put_expect;
482 }
483 daddr = &cmd.u3;
484 }
485
486 nf_ct_expect_init(exp, cmd.l3num,
487 &ct->tuplehash[!dir].tuple.src.u3, daddr,
488 IPPROTO_TCP, NULL, &cmd.u.tcp.port);
489
490 /* Now, NAT might want to mangle the packet, and register the
491 * (possibly changed) expectation itself. */
492 nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
493 if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
494 ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
495 matchoff, matchlen, exp);
496 else {
497 /* Can't expect this? Best to drop packet now. */
498 if (nf_ct_expect_related(exp) != 0)
499 ret = NF_DROP;
500 else
501 ret = NF_ACCEPT;
502 }
503
504 out_put_expect:
505 nf_ct_expect_put(exp);
506
507 out_update_nl:
508 /* Now if this ends in \n, update ftp info. Seq may have been
509 * adjusted by NAT code. */
510 if (ends_in_nl)
511 update_nl_seq(seq, ct_ftp_info, dir, skb);
512 out:
513 spin_unlock_bh(&nf_ftp_lock);
514 return ret;
515 }
516
517 static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
518 static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")] __read_mostly;
519
520 /* don't make this __exit, since it's called from __init ! */
521 static void nf_conntrack_ftp_fini(void)
522 {
523 int i, j;
524 for (i = 0; i < ports_c; i++) {
525 for (j = 0; j < 2; j++) {
526 if (ftp[i][j].me == NULL)
527 continue;
528
529 pr_debug("nf_ct_ftp: unregistering helper for pf: %d "
530 "port: %d\n",
531 ftp[i][j].tuple.src.l3num, ports[i]);
532 nf_conntrack_helper_unregister(&ftp[i][j]);
533 }
534 }
535
536 kfree(ftp_buffer);
537 }
538
539 static int __init nf_conntrack_ftp_init(void)
540 {
541 int i, j = -1, ret = 0;
542 char *tmpname;
543
544 ftp_buffer = kmalloc(65536, GFP_KERNEL);
545 if (!ftp_buffer)
546 return -ENOMEM;
547
548 if (ports_c == 0)
549 ports[ports_c++] = FTP_PORT;
550
551 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
552 are tracked or not - YK */
553 for (i = 0; i < ports_c; i++) {
554 ftp[i][0].tuple.src.l3num = PF_INET;
555 ftp[i][1].tuple.src.l3num = PF_INET6;
556 for (j = 0; j < 2; j++) {
557 ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
558 ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
559 ftp[i][j].max_expected = 1;
560 ftp[i][j].timeout = 5 * 60; /* 5 Minutes */
561 ftp[i][j].me = THIS_MODULE;
562 ftp[i][j].help = help;
563 tmpname = &ftp_names[i][j][0];
564 if (ports[i] == FTP_PORT)
565 sprintf(tmpname, "ftp");
566 else
567 sprintf(tmpname, "ftp-%d", ports[i]);
568 ftp[i][j].name = tmpname;
569
570 pr_debug("nf_ct_ftp: registering helper for pf: %d "
571 "port: %d\n",
572 ftp[i][j].tuple.src.l3num, ports[i]);
573 ret = nf_conntrack_helper_register(&ftp[i][j]);
574 if (ret) {
575 printk("nf_ct_ftp: failed to register helper "
576 " for pf: %d port: %d\n",
577 ftp[i][j].tuple.src.l3num, ports[i]);
578 nf_conntrack_ftp_fini();
579 return ret;
580 }
581 }
582 }
583
584 return 0;
585 }
586
587 module_init(nf_conntrack_ftp_init);
588 module_exit(nf_conntrack_ftp_fini);
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