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inotify: fix race
[linux-2.6.22.y-op.git] / net / netfilter / nf_conntrack_ftp.c
blob82db2aa53bfce5acecac166f4d10e493dc2fe478
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 **pskb,
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 #if 0
55 #define DEBUGP printk
56 #else
57 #define DEBUGP(format, args...)
58 #endif
59
60 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
61 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
62 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
63 char);
64
65 static struct ftp_search {
66 const char *pattern;
67 size_t plen;
68 char skip;
69 char term;
70 enum nf_ct_ftp_type ftptype;
71 int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
72 } search[IP_CT_DIR_MAX][2] = {
73 [IP_CT_DIR_ORIGINAL] = {
74 {
75 .pattern = "PORT",
76 .plen = sizeof("PORT") - 1,
77 .skip = ' ',
78 .term = '\r',
79 .ftptype = NF_CT_FTP_PORT,
80 .getnum = try_rfc959,
81 },
82 {
83 .pattern = "EPRT",
84 .plen = sizeof("EPRT") - 1,
85 .skip = ' ',
86 .term = '\r',
87 .ftptype = NF_CT_FTP_EPRT,
88 .getnum = try_eprt,
89 },
90 },
91 [IP_CT_DIR_REPLY] = {
92 {
93 .pattern = "227 ",
94 .plen = sizeof("227 ") - 1,
95 .skip = '(',
96 .term = ')',
97 .ftptype = NF_CT_FTP_PASV,
98 .getnum = try_rfc959,
99 },
100 {
101 .pattern = "229 ",
102 .plen = sizeof("229 ") - 1,
103 .skip = '(',
104 .term = ')',
105 .ftptype = NF_CT_FTP_EPSV,
106 .getnum = try_epsv_response,
107 },
108 },
109 };
110
111 static int
112 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
113 {
114 const char *end;
115 int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
116 if (ret > 0)
117 return (int)(end - src);
118 return 0;
119 }
120
121 static int try_number(const char *data, size_t dlen, u_int32_t array[],
122 int array_size, char sep, char term)
123 {
124 u_int32_t i, len;
125
126 memset(array, 0, sizeof(array[0])*array_size);
127
128 /* Keep data pointing at next char. */
129 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
130 if (*data >= '0' && *data <= '9') {
131 array[i] = array[i]*10 + *data - '0';
132 }
133 else if (*data == sep)
134 i++;
135 else {
136 /* Unexpected character; true if it's the
137 terminator and we're finished. */
138 if (*data == term && i == array_size - 1)
139 return len;
140
141 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
142 len, i, *data);
143 return 0;
144 }
145 }
146 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
147
148 return 0;
149 }
150
151 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
152 static int try_rfc959(const char *data, size_t dlen,
153 struct nf_conntrack_man *cmd, char term)
154 {
155 int length;
156 u_int32_t array[6];
157
158 length = try_number(data, dlen, array, 6, ',', term);
159 if (length == 0)
160 return 0;
161
162 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
163 (array[2] << 8) | array[3]);
164 cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
165 return length;
166 }
167
168 /* Grab port: number up to delimiter */
169 static int get_port(const char *data, int start, size_t dlen, char delim,
170 __be16 *port)
171 {
172 u_int16_t tmp_port = 0;
173 int i;
174
175 for (i = start; i < dlen; i++) {
176 /* Finished? */
177 if (data[i] == delim) {
178 if (tmp_port == 0)
179 break;
180 *port = htons(tmp_port);
181 DEBUGP("get_port: return %d\n", tmp_port);
182 return i + 1;
183 }
184 else if (data[i] >= '0' && data[i] <= '9')
185 tmp_port = tmp_port*10 + data[i] - '0';
186 else { /* Some other crap */
187 DEBUGP("get_port: invalid char.\n");
188 break;
189 }
190 }
191 return 0;
192 }
193
194 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
195 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
196 char term)
197 {
198 char delim;
199 int length;
200
201 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
202 then delimiter again. */
203 if (dlen <= 3) {
204 DEBUGP("EPRT: too short\n");
205 return 0;
206 }
207 delim = data[0];
208 if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
209 DEBUGP("try_eprt: invalid delimitter.\n");
210 return 0;
211 }
212
213 if ((cmd->l3num == PF_INET && data[1] != '1') ||
214 (cmd->l3num == PF_INET6 && data[1] != '2')) {
215 DEBUGP("EPRT: invalid protocol number.\n");
216 return 0;
217 }
218
219 DEBUGP("EPRT: Got %c%c%c\n", delim, data[1], delim);
220
221 if (data[1] == '1') {
222 u_int32_t array[4];
223
224 /* Now we have IP address. */
225 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
226 if (length != 0)
227 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
228 | (array[2] << 8) | array[3]);
229 } else {
230 /* Now we have IPv6 address. */
231 length = get_ipv6_addr(data + 3, dlen - 3,
232 (struct in6_addr *)cmd->u3.ip6, delim);
233 }
234
235 if (length == 0)
236 return 0;
237 DEBUGP("EPRT: Got IP address!\n");
238 /* Start offset includes initial "|1|", and trailing delimiter */
239 return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
240 }
241
242 /* Returns 0, or length of numbers: |||6446| */
243 static int try_epsv_response(const char *data, size_t dlen,
244 struct nf_conntrack_man *cmd, char term)
245 {
246 char delim;
247
248 /* Three delimiters. */
249 if (dlen <= 3) return 0;
250 delim = data[0];
251 if (isdigit(delim) || delim < 33 || delim > 126
252 || data[1] != delim || data[2] != delim)
253 return 0;
254
255 return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
256 }
257
258 /* Return 1 for match, 0 for accept, -1 for partial. */
259 static int find_pattern(const char *data, size_t dlen,
260 const char *pattern, size_t plen,
261 char skip, char term,
262 unsigned int *numoff,
263 unsigned int *numlen,
264 struct nf_conntrack_man *cmd,
265 int (*getnum)(const char *, size_t,
266 struct nf_conntrack_man *, char))
267 {
268 size_t i;
269
270 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
271 if (dlen == 0)
272 return 0;
273
274 if (dlen <= plen) {
275 /* Short packet: try for partial? */
276 if (strnicmp(data, pattern, dlen) == 0)
277 return -1;
278 else return 0;
279 }
280
281 if (strnicmp(data, pattern, plen) != 0) {
282 #if 0
283 size_t i;
284
285 DEBUGP("ftp: string mismatch\n");
286 for (i = 0; i < plen; i++) {
287 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
288 i, data[i], data[i],
289 pattern[i], pattern[i]);
290 }
291 #endif
292 return 0;
293 }
294
295 DEBUGP("Pattern matches!\n");
296 /* Now we've found the constant string, try to skip
297 to the 'skip' character */
298 for (i = plen; data[i] != skip; i++)
299 if (i == dlen - 1) return -1;
300
301 /* Skip over the last character */
302 i++;
303
304 DEBUGP("Skipped up to `%c'!\n", skip);
305
306 *numoff = i;
307 *numlen = getnum(data + i, dlen - i, cmd, term);
308 if (!*numlen)
309 return -1;
310
311 DEBUGP("Match succeeded!\n");
312 return 1;
313 }
314
315 /* Look up to see if we're just after a \n. */
316 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
317 {
318 unsigned int i;
319
320 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
321 if (info->seq_aft_nl[dir][i] == seq)
322 return 1;
323 return 0;
324 }
325
326 /* We don't update if it's older than what we have. */
327 static void update_nl_seq(u32 nl_seq, struct nf_ct_ftp_master *info, int dir,
328 struct sk_buff *skb)
329 {
330 unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
331
332 /* Look for oldest: if we find exact match, we're done. */
333 for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
334 if (info->seq_aft_nl[dir][i] == nl_seq)
335 return;
336
337 if (oldest == info->seq_aft_nl_num[dir] ||
338 before(info->seq_aft_nl[dir][i],
339 info->seq_aft_nl[dir][oldest]))
340 oldest = i;
341 }
342
343 if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
344 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
345 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
346 } else if (oldest != NUM_SEQ_TO_REMEMBER &&
347 after(nl_seq, info->seq_aft_nl[dir][oldest])) {
348 info->seq_aft_nl[dir][oldest] = nl_seq;
349 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
350 }
351 }
352
353 static int help(struct sk_buff **pskb,
354 unsigned int protoff,
355 struct nf_conn *ct,
356 enum ip_conntrack_info ctinfo)
357 {
358 unsigned int dataoff, datalen;
359 struct tcphdr _tcph, *th;
360 char *fb_ptr;
361 int ret;
362 u32 seq;
363 int dir = CTINFO2DIR(ctinfo);
364 unsigned int matchlen, matchoff;
365 struct nf_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
366 struct nf_conntrack_expect *exp;
367 struct nf_conntrack_man cmd = {};
368 unsigned int i;
369 int found = 0, ends_in_nl;
370 typeof(nf_nat_ftp_hook) nf_nat_ftp;
371
372 /* Until there's been traffic both ways, don't look in packets. */
373 if (ctinfo != IP_CT_ESTABLISHED
374 && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
375 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
376 return NF_ACCEPT;
377 }
378
379 th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph);
380 if (th == NULL)
381 return NF_ACCEPT;
382
383 dataoff = protoff + th->doff * 4;
384 /* No data? */
385 if (dataoff >= (*pskb)->len) {
386 DEBUGP("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
387 (*pskb)->len);
388 return NF_ACCEPT;
389 }
390 datalen = (*pskb)->len - dataoff;
391
392 spin_lock_bh(&nf_ftp_lock);
393 fb_ptr = skb_header_pointer(*pskb, dataoff, datalen, ftp_buffer);
394 BUG_ON(fb_ptr == NULL);
395
396 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
397 seq = ntohl(th->seq) + datalen;
398
399 /* Look up to see if we're just after a \n. */
400 if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
401 /* Now if this ends in \n, update ftp info. */
402 DEBUGP("nf_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
403 ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
404 ct_ftp_info->seq_aft_nl[dir][0],
405 ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
406 ct_ftp_info->seq_aft_nl[dir][1]);
407 ret = NF_ACCEPT;
408 goto out_update_nl;
409 }
410
411 /* Initialize IP/IPv6 addr to expected address (it's not mentioned
412 in EPSV responses) */
413 cmd.l3num = ct->tuplehash[dir].tuple.src.l3num;
414 memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
415 sizeof(cmd.u3.all));
416
417 for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
418 found = find_pattern(fb_ptr, datalen,
419 search[dir][i].pattern,
420 search[dir][i].plen,
421 search[dir][i].skip,
422 search[dir][i].term,
423 &matchoff, &matchlen,
424 &cmd,
425 search[dir][i].getnum);
426 if (found) break;
427 }
428 if (found == -1) {
429 /* We don't usually drop packets. After all, this is
430 connection tracking, not packet filtering.
431 However, it is necessary for accurate tracking in
432 this case. */
433 if (net_ratelimit())
434 printk("conntrack_ftp: partial %s %u+%u\n",
435 search[dir][i].pattern,
436 ntohl(th->seq), datalen);
437 ret = NF_DROP;
438 goto out;
439 } else if (found == 0) { /* No match */
440 ret = NF_ACCEPT;
441 goto out_update_nl;
442 }
443
444 DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
445 (int)matchlen, fb_ptr + matchoff,
446 matchlen, ntohl(th->seq) + matchoff);
447
448 exp = nf_conntrack_expect_alloc(ct);
449 if (exp == NULL) {
450 ret = NF_DROP;
451 goto out;
452 }
453
454 /* We refer to the reverse direction ("!dir") tuples here,
455 * because we're expecting something in the other direction.
456 * Doesn't matter unless NAT is happening. */
457 exp->tuple.dst.u3 = ct->tuplehash[!dir].tuple.dst.u3;
458
459 /* Update the ftp info */
460 if ((cmd.l3num == ct->tuplehash[dir].tuple.src.l3num) &&
461 memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
462 sizeof(cmd.u3.all))) {
463 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
464 server: it really wants us to connect to a
465 different IP address. Simply don't record it for
466 NAT. */
467 if (cmd.l3num == PF_INET) {
468 DEBUGP("conntrack_ftp: NOT RECORDING: " NIPQUAD_FMT " != " NIPQUAD_FMT "\n",
469 NIPQUAD(cmd.u3.ip),
470 NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
471 } else {
472 DEBUGP("conntrack_ftp: NOT RECORDING: " NIP6_FMT " != " NIP6_FMT "\n",
473 NIP6(*((struct in6_addr *)cmd.u3.ip6)),
474 NIP6(*((struct in6_addr *)ct->tuplehash[dir]
475 .tuple.src.u3.ip6)));
476 }
477
478 /* Thanks to Cristiano Lincoln Mattos
479 <lincoln@cesar.org.br> for reporting this potential
480 problem (DMZ machines opening holes to internal
481 networks, or the packet filter itself). */
482 if (!loose) {
483 ret = NF_ACCEPT;
484 goto out_put_expect;
485 }
486 memcpy(&exp->tuple.dst.u3, &cmd.u3.all,
487 sizeof(exp->tuple.dst.u3));
488 }
489
490 exp->tuple.src.u3 = ct->tuplehash[!dir].tuple.src.u3;
491 exp->tuple.src.l3num = cmd.l3num;
492 exp->tuple.src.u.tcp.port = 0;
493 exp->tuple.dst.u.tcp.port = cmd.u.tcp.port;
494 exp->tuple.dst.protonum = IPPROTO_TCP;
495
496 exp->mask = (struct nf_conntrack_tuple)
497 { .src = { .l3num = 0xFFFF,
498 .u = { .tcp = { 0 }},
499 },
500 .dst = { .protonum = 0xFF,
501 .u = { .tcp = { __constant_htons(0xFFFF) }},
502 },
503 };
504 if (cmd.l3num == PF_INET) {
505 exp->mask.src.u3.ip = htonl(0xFFFFFFFF);
506 exp->mask.dst.u3.ip = htonl(0xFFFFFFFF);
507 } else {
508 memset(exp->mask.src.u3.ip6, 0xFF,
509 sizeof(exp->mask.src.u3.ip6));
510 memset(exp->mask.dst.u3.ip6, 0xFF,
511 sizeof(exp->mask.src.u3.ip6));
512 }
513
514 exp->expectfn = NULL;
515 exp->helper = NULL;
516 exp->flags = 0;
517
518 /* Now, NAT might want to mangle the packet, and register the
519 * (possibly changed) expectation itself. */
520 nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
521 if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
522 ret = nf_nat_ftp(pskb, ctinfo, search[dir][i].ftptype,
523 matchoff, matchlen, exp);
524 else {
525 /* Can't expect this? Best to drop packet now. */
526 if (nf_conntrack_expect_related(exp) != 0)
527 ret = NF_DROP;
528 else
529 ret = NF_ACCEPT;
530 }
531
532 out_put_expect:
533 nf_conntrack_expect_put(exp);
534
535 out_update_nl:
536 /* Now if this ends in \n, update ftp info. Seq may have been
537 * adjusted by NAT code. */
538 if (ends_in_nl)
539 update_nl_seq(seq, ct_ftp_info, dir, *pskb);
540 out:
541 spin_unlock_bh(&nf_ftp_lock);
542 return ret;
543 }
544
545 static struct nf_conntrack_helper ftp[MAX_PORTS][2];
546 static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")];
547
548 /* don't make this __exit, since it's called from __init ! */
549 static void nf_conntrack_ftp_fini(void)
550 {
551 int i, j;
552 for (i = 0; i < ports_c; i++) {
553 for (j = 0; j < 2; j++) {
554 if (ftp[i][j].me == NULL)
555 continue;
556
557 DEBUGP("nf_ct_ftp: unregistering helper for pf: %d "
558 "port: %d\n",
559 ftp[i][j].tuple.src.l3num, ports[i]);
560 nf_conntrack_helper_unregister(&ftp[i][j]);
561 }
562 }
563
564 kfree(ftp_buffer);
565 }
566
567 static int __init nf_conntrack_ftp_init(void)
568 {
569 int i, j = -1, ret = 0;
570 char *tmpname;
571
572 ftp_buffer = kmalloc(65536, GFP_KERNEL);
573 if (!ftp_buffer)
574 return -ENOMEM;
575
576 if (ports_c == 0)
577 ports[ports_c++] = FTP_PORT;
578
579 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
580 are tracked or not - YK */
581 for (i = 0; i < ports_c; i++) {
582 ftp[i][0].tuple.src.l3num = PF_INET;
583 ftp[i][1].tuple.src.l3num = PF_INET6;
584 for (j = 0; j < 2; j++) {
585 ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
586 ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
587 ftp[i][j].mask.src.l3num = 0xFFFF;
588 ftp[i][j].mask.src.u.tcp.port = htons(0xFFFF);
589 ftp[i][j].mask.dst.protonum = 0xFF;
590 ftp[i][j].max_expected = 1;
591 ftp[i][j].timeout = 5 * 60; /* 5 Minutes */
592 ftp[i][j].me = THIS_MODULE;
593 ftp[i][j].help = help;
594 tmpname = &ftp_names[i][j][0];
595 if (ports[i] == FTP_PORT)
596 sprintf(tmpname, "ftp");
597 else
598 sprintf(tmpname, "ftp-%d", ports[i]);
599 ftp[i][j].name = tmpname;
600
601 DEBUGP("nf_ct_ftp: registering helper for pf: %d "
602 "port: %d\n",
603 ftp[i][j].tuple.src.l3num, ports[i]);
604 ret = nf_conntrack_helper_register(&ftp[i][j]);
605 if (ret) {
606 printk("nf_ct_ftp: failed to register helper "
607 " for pf: %d port: %d\n",
608 ftp[i][j].tuple.src.l3num, ports[i]);
609 nf_conntrack_ftp_fini();
610 return ret;
611 }
612 }
613 }
614
615 return 0;
616 }
617
618 module_init(nf_conntrack_ftp_init);
619 module_exit(nf_conntrack_ftp_fini);
linux v2.6.22.y-op