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Merge tag 'rdma-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland...
[deliverable/linux.git] / net / netfilter / nf_conntrack_ftp.c
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/slab.h>
17 #include <linux/ipv6.h>
18 #include <linux/ctype.h>
19 #include <linux/inet.h>
20 #include <net/checksum.h>
21 #include <net/tcp.h>
22
23 #include <net/netfilter/nf_conntrack.h>
24 #include <net/netfilter/nf_conntrack_expect.h>
25 #include <net/netfilter/nf_conntrack_ecache.h>
26 #include <net/netfilter/nf_conntrack_helper.h>
27 #include <linux/netfilter/nf_conntrack_ftp.h>
28
29 MODULE_LICENSE("GPL");
30 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
31 MODULE_DESCRIPTION("ftp connection tracking helper");
32 MODULE_ALIAS("ip_conntrack_ftp");
33 MODULE_ALIAS_NFCT_HELPER("ftp");
34
35 /* This is slow, but it's simple. --RR */
36 static char *ftp_buffer;
37
38 static DEFINE_SPINLOCK(nf_ftp_lock);
39
40 #define MAX_PORTS 8
41 static u_int16_t ports[MAX_PORTS];
42 static unsigned int ports_c;
43 module_param_array(ports, ushort, &ports_c, 0400);
44
45 static bool loose;
46 module_param(loose, bool, 0600);
47
48 unsigned int (*nf_nat_ftp_hook)(struct sk_buff *skb,
49 enum ip_conntrack_info ctinfo,
50 enum nf_ct_ftp_type type,
51 unsigned int protoff,
52 unsigned int matchoff,
53 unsigned int matchlen,
54 struct nf_conntrack_expect *exp);
55 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
56
57 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
58 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
59 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
60 char);
61
62 static struct ftp_search {
63 const char *pattern;
64 size_t plen;
65 char skip;
66 char term;
67 enum nf_ct_ftp_type ftptype;
68 int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
69 } search[IP_CT_DIR_MAX][2] = {
70 [IP_CT_DIR_ORIGINAL] = {
71 {
72 .pattern = "PORT",
73 .plen = sizeof("PORT") - 1,
74 .skip = ' ',
75 .term = '\r',
76 .ftptype = NF_CT_FTP_PORT,
77 .getnum = try_rfc959,
78 },
79 {
80 .pattern = "EPRT",
81 .plen = sizeof("EPRT") - 1,
82 .skip = ' ',
83 .term = '\r',
84 .ftptype = NF_CT_FTP_EPRT,
85 .getnum = try_eprt,
86 },
87 },
88 [IP_CT_DIR_REPLY] = {
89 {
90 .pattern = "227 ",
91 .plen = sizeof("227 ") - 1,
92 .skip = '(',
93 .term = ')',
94 .ftptype = NF_CT_FTP_PASV,
95 .getnum = try_rfc959,
96 },
97 {
98 .pattern = "229 ",
99 .plen = sizeof("229 ") - 1,
100 .skip = '(',
101 .term = ')',
102 .ftptype = NF_CT_FTP_EPSV,
103 .getnum = try_epsv_response,
104 },
105 },
106 };
107
108 static int
109 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
110 {
111 const char *end;
112 int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
113 if (ret > 0)
114 return (int)(end - src);
115 return 0;
116 }
117
118 static int try_number(const char *data, size_t dlen, u_int32_t array[],
119 int array_size, char sep, char term)
120 {
121 u_int32_t i, len;
122
123 memset(array, 0, sizeof(array[0])*array_size);
124
125 /* Keep data pointing at next char. */
126 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
127 if (*data >= '0' && *data <= '9') {
128 array[i] = array[i]*10 + *data - '0';
129 }
130 else if (*data == sep)
131 i++;
132 else {
133 /* Unexpected character; true if it's the
134 terminator and we're finished. */
135 if (*data == term && i == array_size - 1)
136 return len;
137
138 pr_debug("Char %u (got %u nums) `%u' unexpected\n",
139 len, i, *data);
140 return 0;
141 }
142 }
143 pr_debug("Failed to fill %u numbers separated by %c\n",
144 array_size, sep);
145 return 0;
146 }
147
148 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
149 static int try_rfc959(const char *data, size_t dlen,
150 struct nf_conntrack_man *cmd, char term)
151 {
152 int length;
153 u_int32_t array[6];
154
155 length = try_number(data, dlen, array, 6, ',', term);
156 if (length == 0)
157 return 0;
158
159 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
160 (array[2] << 8) | array[3]);
161 cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
162 return length;
163 }
164
165 /* Grab port: number up to delimiter */
166 static int get_port(const char *data, int start, size_t dlen, char delim,
167 __be16 *port)
168 {
169 u_int16_t tmp_port = 0;
170 int i;
171
172 for (i = start; i < dlen; i++) {
173 /* Finished? */
174 if (data[i] == delim) {
175 if (tmp_port == 0)
176 break;
177 *port = htons(tmp_port);
178 pr_debug("get_port: return %d\n", tmp_port);
179 return i + 1;
180 }
181 else if (data[i] >= '0' && data[i] <= '9')
182 tmp_port = tmp_port*10 + data[i] - '0';
183 else { /* Some other crap */
184 pr_debug("get_port: invalid char.\n");
185 break;
186 }
187 }
188 return 0;
189 }
190
191 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
192 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
193 char term)
194 {
195 char delim;
196 int length;
197
198 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
199 then delimiter again. */
200 if (dlen <= 3) {
201 pr_debug("EPRT: too short\n");
202 return 0;
203 }
204 delim = data[0];
205 if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
206 pr_debug("try_eprt: invalid delimitter.\n");
207 return 0;
208 }
209
210 if ((cmd->l3num == PF_INET && data[1] != '1') ||
211 (cmd->l3num == PF_INET6 && data[1] != '2')) {
212 pr_debug("EPRT: invalid protocol number.\n");
213 return 0;
214 }
215
216 pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
217
218 if (data[1] == '1') {
219 u_int32_t array[4];
220
221 /* Now we have IP address. */
222 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
223 if (length != 0)
224 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
225 | (array[2] << 8) | array[3]);
226 } else {
227 /* Now we have IPv6 address. */
228 length = get_ipv6_addr(data + 3, dlen - 3,
229 (struct in6_addr *)cmd->u3.ip6, delim);
230 }
231
232 if (length == 0)
233 return 0;
234 pr_debug("EPRT: Got IP address!\n");
235 /* Start offset includes initial "|1|", and trailing delimiter */
236 return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
237 }
238
239 /* Returns 0, or length of numbers: |||6446| */
240 static int try_epsv_response(const char *data, size_t dlen,
241 struct nf_conntrack_man *cmd, char term)
242 {
243 char delim;
244
245 /* Three delimiters. */
246 if (dlen <= 3) return 0;
247 delim = data[0];
248 if (isdigit(delim) || delim < 33 || delim > 126 ||
249 data[1] != delim || data[2] != delim)
250 return 0;
251
252 return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
253 }
254
255 /* Return 1 for match, 0 for accept, -1 for partial. */
256 static int find_pattern(const char *data, size_t dlen,
257 const char *pattern, size_t plen,
258 char skip, char term,
259 unsigned int *numoff,
260 unsigned int *numlen,
261 struct nf_conntrack_man *cmd,
262 int (*getnum)(const char *, size_t,
263 struct nf_conntrack_man *, char))
264 {
265 size_t i;
266
267 pr_debug("find_pattern `%s': dlen = %Zu\n", pattern, dlen);
268 if (dlen == 0)
269 return 0;
270
271 if (dlen <= plen) {
272 /* Short packet: try for partial? */
273 if (strnicmp(data, pattern, dlen) == 0)
274 return -1;
275 else return 0;
276 }
277
278 if (strnicmp(data, pattern, plen) != 0) {
279 #if 0
280 size_t i;
281
282 pr_debug("ftp: string mismatch\n");
283 for (i = 0; i < plen; i++) {
284 pr_debug("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
285 i, data[i], data[i],
286 pattern[i], pattern[i]);
287 }
288 #endif
289 return 0;
290 }
291
292 pr_debug("Pattern matches!\n");
293 /* Now we've found the constant string, try to skip
294 to the 'skip' character */
295 for (i = plen; data[i] != skip; i++)
296 if (i == dlen - 1) return -1;
297
298 /* Skip over the last character */
299 i++;
300
301 pr_debug("Skipped up to `%c'!\n", skip);
302
303 *numoff = i;
304 *numlen = getnum(data + i, dlen - i, cmd, term);
305 if (!*numlen)
306 return -1;
307
308 pr_debug("Match succeeded!\n");
309 return 1;
310 }
311
312 /* Look up to see if we're just after a \n. */
313 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
314 {
315 unsigned int i;
316
317 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
318 if (info->seq_aft_nl[dir][i] == seq)
319 return 1;
320 return 0;
321 }
322
323 /* We don't update if it's older than what we have. */
324 static void update_nl_seq(struct nf_conn *ct, u32 nl_seq,
325 struct nf_ct_ftp_master *info, int dir,
326 struct sk_buff *skb)
327 {
328 unsigned int i, oldest;
329
330 /* Look for oldest: if we find exact match, we're done. */
331 for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
332 if (info->seq_aft_nl[dir][i] == nl_seq)
333 return;
334 }
335
336 if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
337 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
338 } else {
339 if (before(info->seq_aft_nl[dir][0], info->seq_aft_nl[dir][1]))
340 oldest = 0;
341 else
342 oldest = 1;
343
344 if (after(nl_seq, info->seq_aft_nl[dir][oldest]))
345 info->seq_aft_nl[dir][oldest] = nl_seq;
346 }
347 }
348
349 static int help(struct sk_buff *skb,
350 unsigned int protoff,
351 struct nf_conn *ct,
352 enum ip_conntrack_info ctinfo)
353 {
354 unsigned int dataoff, datalen;
355 const struct tcphdr *th;
356 struct tcphdr _tcph;
357 const char *fb_ptr;
358 int ret;
359 u32 seq;
360 int dir = CTINFO2DIR(ctinfo);
361 unsigned int uninitialized_var(matchlen), uninitialized_var(matchoff);
362 struct nf_ct_ftp_master *ct_ftp_info = nfct_help_data(ct);
363 struct nf_conntrack_expect *exp;
364 union nf_inet_addr *daddr;
365 struct nf_conntrack_man cmd = {};
366 unsigned int i;
367 int found = 0, ends_in_nl;
368 typeof(nf_nat_ftp_hook) nf_nat_ftp;
369
370 /* Until there's been traffic both ways, don't look in packets. */
371 if (ctinfo != IP_CT_ESTABLISHED &&
372 ctinfo != IP_CT_ESTABLISHED_REPLY) {
373 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
374 return NF_ACCEPT;
375 }
376
377 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
378 if (th == NULL)
379 return NF_ACCEPT;
380
381 dataoff = protoff + th->doff * 4;
382 /* No data? */
383 if (dataoff >= skb->len) {
384 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
385 skb->len);
386 return NF_ACCEPT;
387 }
388 datalen = skb->len - dataoff;
389
390 spin_lock_bh(&nf_ftp_lock);
391 fb_ptr = skb_header_pointer(skb, dataoff, datalen, ftp_buffer);
392 BUG_ON(fb_ptr == NULL);
393
394 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
395 seq = ntohl(th->seq) + datalen;
396
397 /* Look up to see if we're just after a \n. */
398 if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
399 /* We're picking up this, clear flags and let it continue */
400 if (unlikely(ct_ftp_info->flags[dir] & NF_CT_FTP_SEQ_PICKUP)) {
401 ct_ftp_info->flags[dir] ^= NF_CT_FTP_SEQ_PICKUP;
402 goto skip_nl_seq;
403 }
404
405 /* Now if this ends in \n, update ftp info. */
406 pr_debug("nf_conntrack_ftp: 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 skip_nl_seq:
416 /* Initialize IP/IPv6 addr to expected address (it's not mentioned
417 in EPSV responses) */
418 cmd.l3num = nf_ct_l3num(ct);
419 memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
420 sizeof(cmd.u3.all));
421
422 for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
423 found = find_pattern(fb_ptr, datalen,
424 search[dir][i].pattern,
425 search[dir][i].plen,
426 search[dir][i].skip,
427 search[dir][i].term,
428 &matchoff, &matchlen,
429 &cmd,
430 search[dir][i].getnum);
431 if (found) break;
432 }
433 if (found == -1) {
434 /* We don't usually drop packets. After all, this is
435 connection tracking, not packet filtering.
436 However, it is necessary for accurate tracking in
437 this case. */
438 nf_ct_helper_log(skb, ct, "partial matching of `%s'",
439 search[dir][i].pattern);
440 ret = NF_DROP;
441 goto out;
442 } else if (found == 0) { /* No match */
443 ret = NF_ACCEPT;
444 goto out_update_nl;
445 }
446
447 pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
448 matchlen, fb_ptr + matchoff,
449 matchlen, ntohl(th->seq) + matchoff);
450
451 exp = nf_ct_expect_alloc(ct);
452 if (exp == NULL) {
453 nf_ct_helper_log(skb, ct, "cannot alloc expectation");
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 daddr = &ct->tuplehash[!dir].tuple.dst.u3;
462
463 /* Update the ftp info */
464 if ((cmd.l3num == nf_ct_l3num(ct)) &&
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 pr_debug("conntrack_ftp: NOT RECORDING: %pI4 != %pI4\n",
473 &cmd.u3.ip,
474 &ct->tuplehash[dir].tuple.src.u3.ip);
475 } else {
476 pr_debug("conntrack_ftp: NOT RECORDING: %pI6 != %pI6\n",
477 cmd.u3.ip6,
478 ct->tuplehash[dir].tuple.src.u3.ip6);
479 }
480
481 /* Thanks to Cristiano Lincoln Mattos
482 <lincoln@cesar.org.br> for reporting this potential
483 problem (DMZ machines opening holes to internal
484 networks, or the packet filter itself). */
485 if (!loose) {
486 ret = NF_ACCEPT;
487 goto out_put_expect;
488 }
489 daddr = &cmd.u3;
490 }
491
492 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, cmd.l3num,
493 &ct->tuplehash[!dir].tuple.src.u3, daddr,
494 IPPROTO_TCP, NULL, &cmd.u.tcp.port);
495
496 /* Now, NAT might want to mangle the packet, and register the
497 * (possibly changed) expectation itself. */
498 nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
499 if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
500 ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
501 protoff, matchoff, matchlen, exp);
502 else {
503 /* Can't expect this? Best to drop packet now. */
504 if (nf_ct_expect_related(exp) != 0) {
505 nf_ct_helper_log(skb, ct, "cannot add expectation");
506 ret = NF_DROP;
507 } else
508 ret = NF_ACCEPT;
509 }
510
511 out_put_expect:
512 nf_ct_expect_put(exp);
513
514 out_update_nl:
515 /* Now if this ends in \n, update ftp info. Seq may have been
516 * adjusted by NAT code. */
517 if (ends_in_nl)
518 update_nl_seq(ct, seq, ct_ftp_info, dir, skb);
519 out:
520 spin_unlock_bh(&nf_ftp_lock);
521 return ret;
522 }
523
524 static int nf_ct_ftp_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
525 {
526 struct nf_ct_ftp_master *ftp = nfct_help_data(ct);
527
528 /* This conntrack has been injected from user-space, always pick up
529 * sequence tracking. Otherwise, the first FTP command after the
530 * failover breaks.
531 */
532 ftp->flags[IP_CT_DIR_ORIGINAL] |= NF_CT_FTP_SEQ_PICKUP;
533 ftp->flags[IP_CT_DIR_REPLY] |= NF_CT_FTP_SEQ_PICKUP;
534 return 0;
535 }
536
537 static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
538
539 static const struct nf_conntrack_expect_policy ftp_exp_policy = {
540 .max_expected = 1,
541 .timeout = 5 * 60,
542 };
543
544 /* don't make this __exit, since it's called from __init ! */
545 static void nf_conntrack_ftp_fini(void)
546 {
547 int i, j;
548 for (i = 0; i < ports_c; i++) {
549 for (j = 0; j < 2; j++) {
550 if (ftp[i][j].me == NULL)
551 continue;
552
553 pr_debug("nf_ct_ftp: unregistering helper for pf: %d "
554 "port: %d\n",
555 ftp[i][j].tuple.src.l3num, ports[i]);
556 nf_conntrack_helper_unregister(&ftp[i][j]);
557 }
558 }
559
560 kfree(ftp_buffer);
561 }
562
563 static int __init nf_conntrack_ftp_init(void)
564 {
565 int i, j = -1, ret = 0;
566
567 ftp_buffer = kmalloc(65536, GFP_KERNEL);
568 if (!ftp_buffer)
569 return -ENOMEM;
570
571 if (ports_c == 0)
572 ports[ports_c++] = FTP_PORT;
573
574 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
575 are tracked or not - YK */
576 for (i = 0; i < ports_c; i++) {
577 ftp[i][0].tuple.src.l3num = PF_INET;
578 ftp[i][1].tuple.src.l3num = PF_INET6;
579 for (j = 0; j < 2; j++) {
580 ftp[i][j].data_len = sizeof(struct nf_ct_ftp_master);
581 ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
582 ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
583 ftp[i][j].expect_policy = &ftp_exp_policy;
584 ftp[i][j].me = THIS_MODULE;
585 ftp[i][j].help = help;
586 ftp[i][j].from_nlattr = nf_ct_ftp_from_nlattr;
587 if (ports[i] == FTP_PORT)
588 sprintf(ftp[i][j].name, "ftp");
589 else
590 sprintf(ftp[i][j].name, "ftp-%d", ports[i]);
591
592 pr_debug("nf_ct_ftp: registering helper for pf: %d "
593 "port: %d\n",
594 ftp[i][j].tuple.src.l3num, ports[i]);
595 ret = nf_conntrack_helper_register(&ftp[i][j]);
596 if (ret) {
597 printk(KERN_ERR "nf_ct_ftp: failed to register"
598 " helper for pf: %d port: %d\n",
599 ftp[i][j].tuple.src.l3num, ports[i]);
600 nf_conntrack_ftp_fini();
601 return ret;
602 }
603 }
604 }
605
606 return 0;
607 }
608
609 module_init(nf_conntrack_ftp_init);
610 module_exit(nf_conntrack_ftp_fini);
Linux kernel - Deliverables
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