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[GitHub/mt8127/android_kernel_alcatel_ttab.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 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 */
12
13 #include <linux/module.h>
14 #include <linux/moduleparam.h>
15 #include <linux/netfilter.h>
16 #include <linux/ip.h>
17 #include <linux/slab.h>
18 #include <linux/ipv6.h>
19 #include <linux/ctype.h>
20 #include <linux/inet.h>
21 #include <net/checksum.h>
22 #include <net/tcp.h>
23
24 #include <net/netfilter/nf_conntrack.h>
25 #include <net/netfilter/nf_conntrack_expect.h>
26 #include <net/netfilter/nf_conntrack_ecache.h>
27 #include <net/netfilter/nf_conntrack_helper.h>
28 #include <linux/netfilter/nf_conntrack_ftp.h>
29
30 MODULE_LICENSE("GPL");
31 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
32 MODULE_DESCRIPTION("ftp connection tracking helper");
33 MODULE_ALIAS("ip_conntrack_ftp");
34 MODULE_ALIAS_NFCT_HELPER("ftp");
35
36 /* This is slow, but it's simple. --RR */
37 static char *ftp_buffer;
38
39 static DEFINE_SPINLOCK(nf_ftp_lock);
40
41 #define MAX_PORTS 8
42 static u_int16_t ports[MAX_PORTS];
43 static unsigned int ports_c;
44 module_param_array(ports, ushort, &ports_c, 0400);
45
46 static bool loose;
47 module_param(loose, bool, 0600);
48
49 unsigned int (*nf_nat_ftp_hook)(struct sk_buff *skb,
50 enum ip_conntrack_info ctinfo,
51 enum nf_ct_ftp_type type,
52 unsigned int protoff,
53 unsigned int matchoff,
54 unsigned int matchlen,
55 struct nf_conntrack_expect *exp);
56 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
57
58 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
59 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
60 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
61 char);
62
63 static struct ftp_search {
64 const char *pattern;
65 size_t plen;
66 char skip;
67 char term;
68 enum nf_ct_ftp_type ftptype;
69 int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
70 } search[IP_CT_DIR_MAX][2] = {
71 [IP_CT_DIR_ORIGINAL] = {
72 {
73 .pattern = "PORT",
74 .plen = sizeof("PORT") - 1,
75 .skip = ' ',
76 .term = '\r',
77 .ftptype = NF_CT_FTP_PORT,
78 .getnum = try_rfc959,
79 },
80 {
81 .pattern = "EPRT",
82 .plen = sizeof("EPRT") - 1,
83 .skip = ' ',
84 .term = '\r',
85 .ftptype = NF_CT_FTP_EPRT,
86 .getnum = try_eprt,
87 },
88 },
89 [IP_CT_DIR_REPLY] = {
90 {
91 .pattern = "227 ",
92 .plen = sizeof("227 ") - 1,
93 .skip = '(',
94 .term = ')',
95 .ftptype = NF_CT_FTP_PASV,
96 .getnum = try_rfc959,
97 },
98 {
99 .pattern = "229 ",
100 .plen = sizeof("229 ") - 1,
101 .skip = '(',
102 .term = ')',
103 .ftptype = NF_CT_FTP_EPSV,
104 .getnum = try_epsv_response,
105 },
106 },
107 };
108
109 static int
110 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
111 {
112 const char *end;
113 int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
114 if (ret > 0)
115 return (int)(end - src);
116 return 0;
117 }
118
119 static int try_number(const char *data, size_t dlen, u_int32_t array[],
120 int array_size, char sep, char term)
121 {
122 u_int32_t i, len;
123
124 memset(array, 0, sizeof(array[0])*array_size);
125
126 /* Keep data pointing at next char. */
127 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
128 if (*data >= '0' && *data <= '9') {
129 array[i] = array[i]*10 + *data - '0';
130 }
131 else if (*data == sep)
132 i++;
133 else {
134 /* Unexpected character; true if it's the
135 terminator and we're finished. */
136 if (*data == term && i == array_size - 1)
137 return len;
138
139 pr_debug("Char %u (got %u nums) `%u' unexpected\n",
140 len, i, *data);
141 return 0;
142 }
143 }
144 pr_debug("Failed to fill %u numbers separated by %c\n",
145 array_size, sep);
146 return 0;
147 }
148
149 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
150 static int try_rfc959(const char *data, size_t dlen,
151 struct nf_conntrack_man *cmd, char term)
152 {
153 int length;
154 u_int32_t array[6];
155
156 length = try_number(data, dlen, array, 6, ',', term);
157 if (length == 0)
158 return 0;
159
160 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
161 (array[2] << 8) | array[3]);
162 cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
163 return length;
164 }
165
166 /* Grab port: number up to delimiter */
167 static int get_port(const char *data, int start, size_t dlen, char delim,
168 __be16 *port)
169 {
170 u_int16_t tmp_port = 0;
171 int i;
172
173 for (i = start; i < dlen; i++) {
174 /* Finished? */
175 if (data[i] == delim) {
176 if (tmp_port == 0)
177 break;
178 *port = htons(tmp_port);
179 pr_debug("get_port: return %d\n", tmp_port);
180 return i + 1;
181 }
182 else if (data[i] >= '0' && data[i] <= '9')
183 tmp_port = tmp_port*10 + data[i] - '0';
184 else { /* Some other crap */
185 pr_debug("get_port: invalid char.\n");
186 break;
187 }
188 }
189 return 0;
190 }
191
192 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
193 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
194 char term)
195 {
196 char delim;
197 int length;
198
199 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
200 then delimiter again. */
201 if (dlen <= 3) {
202 pr_debug("EPRT: too short\n");
203 return 0;
204 }
205 delim = data[0];
206 if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
207 pr_debug("try_eprt: invalid delimitter.\n");
208 return 0;
209 }
210
211 if ((cmd->l3num == PF_INET && data[1] != '1') ||
212 (cmd->l3num == PF_INET6 && data[1] != '2')) {
213 pr_debug("EPRT: invalid protocol number.\n");
214 return 0;
215 }
216
217 pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
218
219 if (data[1] == '1') {
220 u_int32_t array[4];
221
222 /* Now we have IP address. */
223 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
224 if (length != 0)
225 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
226 | (array[2] << 8) | array[3]);
227 } else {
228 /* Now we have IPv6 address. */
229 length = get_ipv6_addr(data + 3, dlen - 3,
230 (struct in6_addr *)cmd->u3.ip6, delim);
231 }
232
233 if (length == 0)
234 return 0;
235 pr_debug("EPRT: Got IP address!\n");
236 /* Start offset includes initial "|1|", and trailing delimiter */
237 return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
238 }
239
240 /* Returns 0, or length of numbers: |||6446| */
241 static int try_epsv_response(const char *data, size_t dlen,
242 struct nf_conntrack_man *cmd, char term)
243 {
244 char delim;
245
246 /* Three delimiters. */
247 if (dlen <= 3) return 0;
248 delim = data[0];
249 if (isdigit(delim) || delim < 33 || delim > 126 ||
250 data[1] != delim || data[2] != delim)
251 return 0;
252
253 return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
254 }
255
256 /* Return 1 for match, 0 for accept, -1 for partial. */
257 static int find_pattern(const char *data, size_t dlen,
258 const char *pattern, size_t plen,
259 char skip, char term,
260 unsigned int *numoff,
261 unsigned int *numlen,
262 struct nf_conntrack_man *cmd,
263 int (*getnum)(const char *, size_t,
264 struct nf_conntrack_man *, char))
265 {
266 size_t i;
267
268 pr_debug("find_pattern `%s': dlen = %Zu\n", pattern, dlen);
269 if (dlen == 0)
270 return 0;
271
272 if (dlen <= plen) {
273 /* Short packet: try for partial? */
274 if (strnicmp(data, pattern, dlen) == 0)
275 return -1;
276 else return 0;
277 }
278
279 if (strnicmp(data, pattern, plen) != 0) {
280 #if 0
281 size_t i;
282
283 pr_debug("ftp: string mismatch\n");
284 for (i = 0; i < plen; i++) {
285 pr_debug("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
286 i, data[i], data[i],
287 pattern[i], pattern[i]);
288 }
289 #endif
290 return 0;
291 }
292
293 pr_debug("Pattern matches!\n");
294 /* Now we've found the constant string, try to skip
295 to the 'skip' character */
296 for (i = plen; data[i] != skip; i++)
297 if (i == dlen - 1) return -1;
298
299 /* Skip over the last character */
300 i++;
301
302 pr_debug("Skipped up to `%c'!\n", skip);
303
304 *numoff = i;
305 *numlen = getnum(data + i, dlen - i, cmd, term);
306 if (!*numlen)
307 return -1;
308
309 pr_debug("Match succeeded!\n");
310 return 1;
311 }
312
313 /* Look up to see if we're just after a \n. */
314 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
315 {
316 unsigned int i;
317
318 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
319 if (info->seq_aft_nl[dir][i] == seq)
320 return 1;
321 return 0;
322 }
323
324 /* We don't update if it's older than what we have. */
325 static void update_nl_seq(struct nf_conn *ct, u32 nl_seq,
326 struct nf_ct_ftp_master *info, int dir,
327 struct sk_buff *skb)
328 {
329 unsigned int i, oldest;
330
331 /* Look for oldest: if we find exact match, we're done. */
332 for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
333 if (info->seq_aft_nl[dir][i] == nl_seq)
334 return;
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 } else {
340 if (before(info->seq_aft_nl[dir][0], info->seq_aft_nl[dir][1]))
341 oldest = 0;
342 else
343 oldest = 1;
344
345 if (after(nl_seq, info->seq_aft_nl[dir][oldest]))
346 info->seq_aft_nl[dir][oldest] = nl_seq;
347 }
348 }
349
350 static int help(struct sk_buff *skb,
351 unsigned int protoff,
352 struct nf_conn *ct,
353 enum ip_conntrack_info ctinfo)
354 {
355 unsigned int dataoff, datalen;
356 const struct tcphdr *th;
357 struct tcphdr _tcph;
358 const char *fb_ptr;
359 int ret;
360 u32 seq;
361 int dir = CTINFO2DIR(ctinfo);
362 unsigned int uninitialized_var(matchlen), uninitialized_var(matchoff);
363 struct nf_ct_ftp_master *ct_ftp_info = nfct_help_data(ct);
364 struct nf_conntrack_expect *exp;
365 union nf_inet_addr *daddr;
366 struct nf_conntrack_man cmd = {};
367 unsigned int i;
368 int found = 0, ends_in_nl;
369 typeof(nf_nat_ftp_hook) nf_nat_ftp;
370
371 /* Until there's been traffic both ways, don't look in packets. */
372 if (ctinfo != IP_CT_ESTABLISHED &&
373 ctinfo != IP_CT_ESTABLISHED_REPLY) {
374 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
375 return NF_ACCEPT;
376 }
377
378 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
379 if (th == NULL)
380 return NF_ACCEPT;
381
382 dataoff = protoff + th->doff * 4;
383 /* No data? */
384 if (dataoff >= skb->len) {
385 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
386 skb->len);
387 return NF_ACCEPT;
388 }
389 datalen = skb->len - dataoff;
390
391 spin_lock_bh(&nf_ftp_lock);
392 fb_ptr = skb_header_pointer(skb, dataoff, datalen, ftp_buffer);
393 BUG_ON(fb_ptr == NULL);
394
395 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
396 seq = ntohl(th->seq) + datalen;
397
398 /* Look up to see if we're just after a \n. */
399 if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
400 /* We're picking up this, clear flags and let it continue */
401 if (unlikely(ct_ftp_info->flags[dir] & NF_CT_FTP_SEQ_PICKUP)) {
402 ct_ftp_info->flags[dir] ^= NF_CT_FTP_SEQ_PICKUP;
403 goto skip_nl_seq;
404 }
405
406 /* Now if this ends in \n, update ftp info. */
407 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
408 ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
409 ct_ftp_info->seq_aft_nl[dir][0],
410 ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
411 ct_ftp_info->seq_aft_nl[dir][1]);
412 ret = NF_ACCEPT;
413 goto out_update_nl;
414 }
415
416 skip_nl_seq:
417 /* Initialize IP/IPv6 addr to expected address (it's not mentioned
418 in EPSV responses) */
419 cmd.l3num = nf_ct_l3num(ct);
420 memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
421 sizeof(cmd.u3.all));
422
423 for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
424 found = find_pattern(fb_ptr, datalen,
425 search[dir][i].pattern,
426 search[dir][i].plen,
427 search[dir][i].skip,
428 search[dir][i].term,
429 &matchoff, &matchlen,
430 &cmd,
431 search[dir][i].getnum);
432 if (found) break;
433 }
434 if (found == -1) {
435 /* We don't usually drop packets. After all, this is
436 connection tracking, not packet filtering.
437 However, it is necessary for accurate tracking in
438 this case. */
439 nf_ct_helper_log(skb, ct, "partial matching of `%s'",
440 search[dir][i].pattern);
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 pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
449 matchlen, fb_ptr + matchoff,
450 matchlen, ntohl(th->seq) + matchoff);
451
452 exp = nf_ct_expect_alloc(ct);
453 if (exp == NULL) {
454 nf_ct_helper_log(skb, ct, "cannot alloc expectation");
455 ret = NF_DROP;
456 goto out;
457 }
458
459 /* We refer to the reverse direction ("!dir") tuples here,
460 * because we're expecting something in the other direction.
461 * Doesn't matter unless NAT is happening. */
462 daddr = &ct->tuplehash[!dir].tuple.dst.u3;
463
464 /* Update the ftp info */
465 if ((cmd.l3num == nf_ct_l3num(ct)) &&
466 memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
467 sizeof(cmd.u3.all))) {
468 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
469 server: it really wants us to connect to a
470 different IP address. Simply don't record it for
471 NAT. */
472 if (cmd.l3num == PF_INET) {
473 pr_debug("conntrack_ftp: NOT RECORDING: %pI4 != %pI4\n",
474 &cmd.u3.ip,
475 &ct->tuplehash[dir].tuple.src.u3.ip);
476 } else {
477 pr_debug("conntrack_ftp: NOT RECORDING: %pI6 != %pI6\n",
478 cmd.u3.ip6,
479 ct->tuplehash[dir].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 daddr = &cmd.u3;
491 }
492
493 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, cmd.l3num,
494 &ct->tuplehash[!dir].tuple.src.u3, daddr,
495 IPPROTO_TCP, NULL, &cmd.u.tcp.port);
496
497 /* Now, NAT might want to mangle the packet, and register the
498 * (possibly changed) expectation itself. */
499 nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
500 if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
501 ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
502 protoff, matchoff, matchlen, exp);
503 else {
504 /* Can't expect this? Best to drop packet now. */
505 if (nf_ct_expect_related(exp) != 0) {
506 nf_ct_helper_log(skb, ct, "cannot add expectation");
507 ret = NF_DROP;
508 } else
509 ret = NF_ACCEPT;
510 }
511
512 out_put_expect:
513 nf_ct_expect_put(exp);
514
515 out_update_nl:
516 /* Now if this ends in \n, update ftp info. Seq may have been
517 * adjusted by NAT code. */
518 if (ends_in_nl)
519 update_nl_seq(ct, seq, ct_ftp_info, dir, skb);
520 out:
521 spin_unlock_bh(&nf_ftp_lock);
522 return ret;
523 }
524
525 static int nf_ct_ftp_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
526 {
527 struct nf_ct_ftp_master *ftp = nfct_help_data(ct);
528
529 /* This conntrack has been injected from user-space, always pick up
530 * sequence tracking. Otherwise, the first FTP command after the
531 * failover breaks.
532 */
533 ftp->flags[IP_CT_DIR_ORIGINAL] |= NF_CT_FTP_SEQ_PICKUP;
534 ftp->flags[IP_CT_DIR_REPLY] |= NF_CT_FTP_SEQ_PICKUP;
535 return 0;
536 }
537
538 static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
539
540 static const struct nf_conntrack_expect_policy ftp_exp_policy = {
541 .max_expected = 1,
542 .timeout = 5 * 60,
543 };
544
545 /* don't make this __exit, since it's called from __init ! */
546 static void nf_conntrack_ftp_fini(void)
547 {
548 int i, j;
549 for (i = 0; i < ports_c; i++) {
550 for (j = 0; j < 2; j++) {
551 if (ftp[i][j].me == NULL)
552 continue;
553
554 pr_debug("nf_ct_ftp: unregistering helper for pf: %d "
555 "port: %d\n",
556 ftp[i][j].tuple.src.l3num, ports[i]);
557 nf_conntrack_helper_unregister(&ftp[i][j]);
558 }
559 }
560
561 kfree(ftp_buffer);
562 }
563
564 static int __init nf_conntrack_ftp_init(void)
565 {
566 int i, j = -1, ret = 0;
567
568 ftp_buffer = kmalloc(65536, GFP_KERNEL);
569 if (!ftp_buffer)
570 return -ENOMEM;
571
572 if (ports_c == 0)
573 ports[ports_c++] = FTP_PORT;
574
575 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
576 are tracked or not - YK */
577 for (i = 0; i < ports_c; i++) {
578 ftp[i][0].tuple.src.l3num = PF_INET;
579 ftp[i][1].tuple.src.l3num = PF_INET6;
580 for (j = 0; j < 2; j++) {
581 ftp[i][j].data_len = sizeof(struct nf_ct_ftp_master);
582 ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
583 ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
584 ftp[i][j].expect_policy = &ftp_exp_policy;
585 ftp[i][j].me = THIS_MODULE;
586 ftp[i][j].help = help;
587 ftp[i][j].from_nlattr = nf_ct_ftp_from_nlattr;
588 if (ports[i] == FTP_PORT)
589 sprintf(ftp[i][j].name, "ftp");
590 else
591 sprintf(ftp[i][j].name, "ftp-%d", ports[i]);
592
593 pr_debug("nf_ct_ftp: registering helper for pf: %d "
594 "port: %d\n",
595 ftp[i][j].tuple.src.l3num, ports[i]);
596 ret = nf_conntrack_helper_register(&ftp[i][j]);
597 if (ret) {
598 printk(KERN_ERR "nf_ct_ftp: failed to register"
599 " helper for pf: %d port: %d\n",
600 ftp[i][j].tuple.src.l3num, ports[i]);
601 nf_conntrack_ftp_fini();
602 return ret;
603 }
604 }
605 }
606
607 return 0;
608 }
609
610 module_init(nf_conntrack_ftp_init);
611 module_exit(nf_conntrack_ftp_fini);
kernel source for telekom puls (alcatel/mediatek)