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[NETFILTER]: nf_conntrack: endian annotations
[linux-2.6/linux-mips.git] / net / netfilter / nf_conntrack_ftp.c
blobfdac52beeb8cd6b5950fb36d9857a00167618bba
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 * 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
12 * - enable working with Layer 3 protocol independent connection tracking.
13 * - track EPRT and EPSV commands with IPv6 address.
14 *
15 * Derived from net/ipv4/netfilter/ip_conntrack_ftp.c
16 */
17
18 #include <linux/module.h>
19 #include <linux/moduleparam.h>
20 #include <linux/netfilter.h>
21 #include <linux/ip.h>
22 #include <linux/ipv6.h>
23 #include <linux/ctype.h>
24 #include <linux/inet.h>
25 #include <net/checksum.h>
26 #include <net/tcp.h>
27
28 #include <net/netfilter/nf_conntrack.h>
29 #include <net/netfilter/nf_conntrack_expect.h>
30 #include <net/netfilter/nf_conntrack_ecache.h>
31 #include <net/netfilter/nf_conntrack_helper.h>
32 #include <linux/netfilter/nf_conntrack_ftp.h>
33
34 MODULE_LICENSE("GPL");
35 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
36 MODULE_DESCRIPTION("ftp connection tracking helper");
37
38 /* This is slow, but it's simple. --RR */
39 static char *ftp_buffer;
40
41 static DEFINE_SPINLOCK(nf_ftp_lock);
42
43 #define MAX_PORTS 8
44 static u_int16_t ports[MAX_PORTS];
45 static unsigned int ports_c;
46 module_param_array(ports, ushort, &ports_c, 0400);
47
48 static int loose;
49 module_param(loose, bool, 0600);
50
51 unsigned int (*nf_nat_ftp_hook)(struct sk_buff **pskb,
52 enum ip_conntrack_info ctinfo,
53 enum ip_ct_ftp_type type,
54 unsigned int matchoff,
55 unsigned int matchlen,
56 struct nf_conntrack_expect *exp,
57 u32 *seq);
58 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
59
60 #if 0
61 #define DEBUGP printk
62 #else
63 #define DEBUGP(format, args...)
64 #endif
65
66 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
67 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
68 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
69 char);
70
71 static struct ftp_search {
72 const char *pattern;
73 size_t plen;
74 char skip;
75 char term;
76 enum ip_ct_ftp_type ftptype;
77 int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
78 } search[IP_CT_DIR_MAX][2] = {
79 [IP_CT_DIR_ORIGINAL] = {
80 {
81 .pattern = "PORT",
82 .plen = sizeof("PORT") - 1,
83 .skip = ' ',
84 .term = '\r',
85 .ftptype = IP_CT_FTP_PORT,
86 .getnum = try_rfc959,
87 },
88 {
89 .pattern = "EPRT",
90 .plen = sizeof("EPRT") - 1,
91 .skip = ' ',
92 .term = '\r',
93 .ftptype = IP_CT_FTP_EPRT,
94 .getnum = try_eprt,
95 },
96 },
97 [IP_CT_DIR_REPLY] = {
98 {
99 .pattern = "227 ",
100 .plen = sizeof("227 ") - 1,
101 .skip = '(',
102 .term = ')',
103 .ftptype = IP_CT_FTP_PASV,
104 .getnum = try_rfc959,
105 },
106 {
107 .pattern = "229 ",
108 .plen = sizeof("229 ") - 1,
109 .skip = '(',
110 .term = ')',
111 .ftptype = IP_CT_FTP_EPSV,
112 .getnum = try_epsv_response,
113 },
114 },
115 };
116
117 static int
118 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
119 {
120 const char *end;
121 int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
122 if (ret > 0)
123 return (int)(end - src);
124 return 0;
125 }
126
127 static int try_number(const char *data, size_t dlen, u_int32_t array[],
128 int array_size, char sep, char term)
129 {
130 u_int32_t i, len;
131
132 memset(array, 0, sizeof(array[0])*array_size);
133
134 /* Keep data pointing at next char. */
135 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
136 if (*data >= '0' && *data <= '9') {
137 array[i] = array[i]*10 + *data - '0';
138 }
139 else if (*data == sep)
140 i++;
141 else {
142 /* Unexpected character; true if it's the
143 terminator and we're finished. */
144 if (*data == term && i == array_size - 1)
145 return len;
146
147 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
148 len, i, *data);
149 return 0;
150 }
151 }
152 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
153
154 return 0;
155 }
156
157 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
158 static int try_rfc959(const char *data, size_t dlen,
159 struct nf_conntrack_man *cmd, char term)
160 {
161 int length;
162 u_int32_t array[6];
163
164 length = try_number(data, dlen, array, 6, ',', term);
165 if (length == 0)
166 return 0;
167
168 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
169 (array[2] << 8) | array[3]);
170 cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
171 return length;
172 }
173
174 /* Grab port: number up to delimiter */
175 static int get_port(const char *data, int start, size_t dlen, char delim,
176 __be16 *port)
177 {
178 u_int16_t tmp_port = 0;
179 int i;
180
181 for (i = start; i < dlen; i++) {
182 /* Finished? */
183 if (data[i] == delim) {
184 if (tmp_port == 0)
185 break;
186 *port = htons(tmp_port);
187 DEBUGP("get_port: return %d\n", tmp_port);
188 return i + 1;
189 }
190 else if (data[i] >= '0' && data[i] <= '9')
191 tmp_port = tmp_port*10 + data[i] - '0';
192 else { /* Some other crap */
193 DEBUGP("get_port: invalid char.\n");
194 break;
195 }
196 }
197 return 0;
198 }
199
200 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
201 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
202 char term)
203 {
204 char delim;
205 int length;
206
207 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
208 then delimiter again. */
209 if (dlen <= 3) {
210 DEBUGP("EPRT: too short\n");
211 return 0;
212 }
213 delim = data[0];
214 if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
215 DEBUGP("try_eprt: invalid delimitter.\n");
216 return 0;
217 }
218
219 if ((cmd->l3num == PF_INET && data[1] != '1') ||
220 (cmd->l3num == PF_INET6 && data[1] != '2')) {
221 DEBUGP("EPRT: invalid protocol number.\n");
222 return 0;
223 }
224
225 DEBUGP("EPRT: Got %c%c%c\n", delim, data[1], delim);
226
227 if (data[1] == '1') {
228 u_int32_t array[4];
229
230 /* Now we have IP address. */
231 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
232 if (length != 0)
233 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
234 | (array[2] << 8) | array[3]);
235 } else {
236 /* Now we have IPv6 address. */
237 length = get_ipv6_addr(data + 3, dlen - 3,
238 (struct in6_addr *)cmd->u3.ip6, delim);
239 }
240
241 if (length == 0)
242 return 0;
243 DEBUGP("EPRT: Got IP address!\n");
244 /* Start offset includes initial "|1|", and trailing delimiter */
245 return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
246 }
247
248 /* Returns 0, or length of numbers: |||6446| */
249 static int try_epsv_response(const char *data, size_t dlen,
250 struct nf_conntrack_man *cmd, char term)
251 {
252 char delim;
253
254 /* Three delimiters. */
255 if (dlen <= 3) return 0;
256 delim = data[0];
257 if (isdigit(delim) || delim < 33 || delim > 126
258 || data[1] != delim || data[2] != delim)
259 return 0;
260
261 return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
262 }
263
264 /* Return 1 for match, 0 for accept, -1 for partial. */
265 static int find_pattern(const char *data, size_t dlen,
266 const char *pattern, size_t plen,
267 char skip, char term,
268 unsigned int *numoff,
269 unsigned int *numlen,
270 struct nf_conntrack_man *cmd,
271 int (*getnum)(const char *, size_t,
272 struct nf_conntrack_man *, char))
273 {
274 size_t i;
275
276 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
277 if (dlen == 0)
278 return 0;
279
280 if (dlen <= plen) {
281 /* Short packet: try for partial? */
282 if (strnicmp(data, pattern, dlen) == 0)
283 return -1;
284 else return 0;
285 }
286
287 if (strnicmp(data, pattern, plen) != 0) {
288 #if 0
289 size_t i;
290
291 DEBUGP("ftp: string mismatch\n");
292 for (i = 0; i < plen; i++) {
293 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
294 i, data[i], data[i],
295 pattern[i], pattern[i]);
296 }
297 #endif
298 return 0;
299 }
300
301 DEBUGP("Pattern matches!\n");
302 /* Now we've found the constant string, try to skip
303 to the 'skip' character */
304 for (i = plen; data[i] != skip; i++)
305 if (i == dlen - 1) return -1;
306
307 /* Skip over the last character */
308 i++;
309
310 DEBUGP("Skipped up to `%c'!\n", skip);
311
312 *numoff = i;
313 *numlen = getnum(data + i, dlen - i, cmd, term);
314 if (!*numlen)
315 return -1;
316
317 DEBUGP("Match succeeded!\n");
318 return 1;
319 }
320
321 /* Look up to see if we're just after a \n. */
322 static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
323 {
324 unsigned int i;
325
326 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
327 if (info->seq_aft_nl[dir][i] == seq)
328 return 1;
329 return 0;
330 }
331
332 /* We don't update if it's older than what we have. */
333 static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir,
334 struct sk_buff *skb)
335 {
336 unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
337
338 /* Look for oldest: if we find exact match, we're done. */
339 for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
340 if (info->seq_aft_nl[dir][i] == nl_seq)
341 return;
342
343 if (oldest == info->seq_aft_nl_num[dir]
344 || before(info->seq_aft_nl[dir][i], oldest))
345 oldest = i;
346 }
347
348 if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
349 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
350 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
351 } else if (oldest != NUM_SEQ_TO_REMEMBER) {
352 info->seq_aft_nl[dir][oldest] = nl_seq;
353 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
354 }
355 }
356
357 static int help(struct sk_buff **pskb,
358 unsigned int protoff,
359 struct nf_conn *ct,
360 enum ip_conntrack_info ctinfo)
361 {
362 unsigned int dataoff, datalen;
363 struct tcphdr _tcph, *th;
364 char *fb_ptr;
365 int ret;
366 u32 seq;
367 int dir = CTINFO2DIR(ctinfo);
368 unsigned int matchlen, matchoff;
369 struct ip_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
370 struct nf_conntrack_expect *exp;
371 struct nf_conntrack_man cmd = {};
372 unsigned int i;
373 int found = 0, ends_in_nl;
374 typeof(nf_nat_ftp_hook) nf_nat_ftp;
375
376 /* Until there's been traffic both ways, don't look in packets. */
377 if (ctinfo != IP_CT_ESTABLISHED
378 && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
379 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
380 return NF_ACCEPT;
381 }
382
383 th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph);
384 if (th == NULL)
385 return NF_ACCEPT;
386
387 dataoff = protoff + th->doff * 4;
388 /* No data? */
389 if (dataoff >= (*pskb)->len) {
390 DEBUGP("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
391 (*pskb)->len);
392 return NF_ACCEPT;
393 }
394 datalen = (*pskb)->len - dataoff;
395
396 spin_lock_bh(&nf_ftp_lock);
397 fb_ptr = skb_header_pointer(*pskb, dataoff, datalen, ftp_buffer);
398 BUG_ON(fb_ptr == NULL);
399
400 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
401 seq = ntohl(th->seq) + datalen;
402
403 /* Look up to see if we're just after a \n. */
404 if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
405 /* Now if this ends in \n, update ftp info. */
406 DEBUGP("nf_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
407 ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
408 ct_ftp_info->seq_aft_nl[dir][0],
409 ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
410 ct_ftp_info->seq_aft_nl[dir][1]);
411 ret = NF_ACCEPT;
412 goto out_update_nl;
413 }
414
415 /* Initialize IP/IPv6 addr to expected address (it's not mentioned
416 in EPSV responses) */
417 cmd.l3num = ct->tuplehash[dir].tuple.src.l3num;
418 memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
419 sizeof(cmd.u3.all));
420
421 for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
422 found = find_pattern(fb_ptr, datalen,
423 search[dir][i].pattern,
424 search[dir][i].plen,
425 search[dir][i].skip,
426 search[dir][i].term,
427 &matchoff, &matchlen,
428 &cmd,
429 search[dir][i].getnum);
430 if (found) break;
431 }
432 if (found == -1) {
433 /* We don't usually drop packets. After all, this is
434 connection tracking, not packet filtering.
435 However, it is necessary for accurate tracking in
436 this case. */
437 if (net_ratelimit())
438 printk("conntrack_ftp: partial %s %u+%u\n",
439 search[dir][i].pattern,
440 ntohl(th->seq), datalen);
441 ret = NF_DROP;
442 goto out;
443 } else if (found == 0) { /* No match */
444 ret = NF_ACCEPT;
445 goto out_update_nl;
446 }
447
448 DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
449 (int)matchlen, fb_ptr + matchoff,
450 matchlen, ntohl(th->seq) + matchoff);
451
452 exp = nf_conntrack_expect_alloc(ct);
453 if (exp == NULL) {
454 ret = NF_DROP;
455 goto out;
456 }
457
458 /* We refer to the reverse direction ("!dir") tuples here,
459 * because we're expecting something in the other direction.
460 * Doesn't matter unless NAT is happening. */
461 exp->tuple.dst.u3 = ct->tuplehash[!dir].tuple.dst.u3;
462
463 /* Update the ftp info */
464 if ((cmd.l3num == ct->tuplehash[dir].tuple.src.l3num) &&
465 memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
466 sizeof(cmd.u3.all))) {
467 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
468 server: it really wants us to connect to a
469 different IP address. Simply don't record it for
470 NAT. */
471 if (cmd.l3num == PF_INET) {
472 DEBUGP("conntrack_ftp: NOT RECORDING: " NIPQUAD_FMT " != " NIPQUAD_FMT "\n",
473 NIPQUAD(cmd.u3.ip),
474 NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
475 } else {
476 DEBUGP("conntrack_ftp: NOT RECORDING: " NIP6_FMT " != " NIP6_FMT "\n",
477 NIP6(*((struct in6_addr *)cmd.u3.ip6)),
478 NIP6(*((struct in6_addr *)ct->tuplehash[dir]
479 .tuple.src.u3.ip6)));
480 }
481
482 /* Thanks to Cristiano Lincoln Mattos
483 <lincoln@cesar.org.br> for reporting this potential
484 problem (DMZ machines opening holes to internal
485 networks, or the packet filter itself). */
486 if (!loose) {
487 ret = NF_ACCEPT;
488 goto out_put_expect;
489 }
490 memcpy(&exp->tuple.dst.u3, &cmd.u3.all,
491 sizeof(exp->tuple.dst.u3));
492 }
493
494 exp->tuple.src.u3 = ct->tuplehash[!dir].tuple.src.u3;
495 exp->tuple.src.l3num = cmd.l3num;
496 exp->tuple.src.u.tcp.port = 0;
497 exp->tuple.dst.u.tcp.port = cmd.u.tcp.port;
498 exp->tuple.dst.protonum = IPPROTO_TCP;
499
500 exp->mask = (struct nf_conntrack_tuple)
501 { .src = { .l3num = 0xFFFF,
502 .u = { .tcp = { 0 }},
503 },
504 .dst = { .protonum = 0xFF,
505 .u = { .tcp = { __constant_htons(0xFFFF) }},
506 },
507 };
508 if (cmd.l3num == PF_INET) {
509 exp->mask.src.u3.ip = htonl(0xFFFFFFFF);
510 exp->mask.dst.u3.ip = htonl(0xFFFFFFFF);
511 } else {
512 memset(exp->mask.src.u3.ip6, 0xFF,
513 sizeof(exp->mask.src.u3.ip6));
514 memset(exp->mask.dst.u3.ip6, 0xFF,
515 sizeof(exp->mask.src.u3.ip6));
516 }
517
518 exp->expectfn = NULL;
519 exp->flags = 0;
520
521 /* Now, NAT might want to mangle the packet, and register the
522 * (possibly changed) expectation itself. */
523 nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
524 if (nf_nat_ftp)
525 ret = nf_nat_ftp(pskb, ctinfo, search[dir][i].ftptype,
526 matchoff, matchlen, exp, &seq);
527 else {
528 /* Can't expect this? Best to drop packet now. */
529 if (nf_conntrack_expect_related(exp) != 0)
530 ret = NF_DROP;
531 else
532 ret = NF_ACCEPT;
533 }
534
535 out_put_expect:
536 nf_conntrack_expect_put(exp);
537
538 out_update_nl:
539 /* Now if this ends in \n, update ftp info. Seq may have been
540 * adjusted by NAT code. */
541 if (ends_in_nl)
542 update_nl_seq(seq, ct_ftp_info, dir, *pskb);
543 out:
544 spin_unlock_bh(&nf_ftp_lock);
545 return ret;
546 }
547
548 static struct nf_conntrack_helper ftp[MAX_PORTS][2];
549 static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")];
550
551 /* don't make this __exit, since it's called from __init ! */
552 static void nf_conntrack_ftp_fini(void)
553 {
554 int i, j;
555 for (i = 0; i < ports_c; i++) {
556 for (j = 0; j < 2; j++) {
557 if (ftp[i][j].me == NULL)
558 continue;
559
560 DEBUGP("nf_ct_ftp: unregistering helper for pf: %d "
561 "port: %d\n",
562 ftp[i][j].tuple.src.l3num, ports[i]);
563 nf_conntrack_helper_unregister(&ftp[i][j]);
564 }
565 }
566
567 kfree(ftp_buffer);
568 }
569
570 static int __init nf_conntrack_ftp_init(void)
571 {
572 int i, j = -1, ret = 0;
573 char *tmpname;
574
575 ftp_buffer = kmalloc(65536, GFP_KERNEL);
576 if (!ftp_buffer)
577 return -ENOMEM;
578
579 if (ports_c == 0)
580 ports[ports_c++] = FTP_PORT;
581
582 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
583 are tracked or not - YK */
584 for (i = 0; i < ports_c; i++) {
585 ftp[i][0].tuple.src.l3num = PF_INET;
586 ftp[i][1].tuple.src.l3num = PF_INET6;
587 for (j = 0; j < 2; j++) {
588 ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
589 ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
590 ftp[i][j].mask.src.l3num = 0xFFFF;
591 ftp[i][j].mask.src.u.tcp.port = htons(0xFFFF);
592 ftp[i][j].mask.dst.protonum = 0xFF;
593 ftp[i][j].max_expected = 1;
594 ftp[i][j].timeout = 5 * 60; /* 5 Minutes */
595 ftp[i][j].me = THIS_MODULE;
596 ftp[i][j].help = help;
597 tmpname = &ftp_names[i][j][0];
598 if (ports[i] == FTP_PORT)
599 sprintf(tmpname, "ftp");
600 else
601 sprintf(tmpname, "ftp-%d", ports[i]);
602 ftp[i][j].name = tmpname;
603
604 DEBUGP("nf_ct_ftp: registering helper for pf: %d "
605 "port: %d\n",
606 ftp[i][j].tuple.src.l3num, ports[i]);
607 ret = nf_conntrack_helper_register(&ftp[i][j]);
608 if (ret) {
609 printk("nf_ct_ftp: failed to register helper "
610 " for pf: %d port: %d\n",
611 ftp[i][j].tuple.src.l3num, ports[i]);
612 nf_conntrack_ftp_fini();
613 return ret;
614 }
615 }
616 }
617
618 return 0;
619 }
620
621 module_init(nf_conntrack_ftp_init);
622 module_exit(nf_conntrack_ftp_fini);
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