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MOXA linux-2.6.x / linux-2.6.19-uc1 from UC-7110-LX-BOOTLOADER-1.9_VERSION-4.2.tgz
[linux-2.6.19-moxart.git] / net / ipv4 / netfilter / ip_conntrack_ftp.c
blob0eac6c1605580d22397cbe612657f64e2e13035d
1 /* FTP extension for IP connection tracking. */
2
3 /* (C) 1999-2001 Paul `Rusty' Russell
4 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
10
11 #include <linux/module.h>
12 #include <linux/netfilter.h>
13 #include <linux/ip.h>
14 #include <linux/ctype.h>
15 #include <net/checksum.h>
16 #include <net/tcp.h>
17
18 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
19 #include <linux/netfilter_ipv4/ip_conntrack_ftp.h>
20 #include <linux/moduleparam.h>
21
22 MODULE_LICENSE("GPL");
23 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
24 MODULE_DESCRIPTION("ftp connection tracking helper");
25
26 /* This is slow, but it's simple. --RR */
27 static char *ftp_buffer;
28 static DEFINE_SPINLOCK(ip_ftp_lock);
29
30 #define MAX_PORTS 8
31 static unsigned short ports[MAX_PORTS];
32 static int ports_c;
33 module_param_array(ports, ushort, &ports_c, 0400);
34
35 static int loose;
36 module_param(loose, bool, 0600);
37
38 unsigned int (*ip_nat_ftp_hook)(struct sk_buff **pskb,
39 enum ip_conntrack_info ctinfo,
40 enum ip_ct_ftp_type type,
41 unsigned int matchoff,
42 unsigned int matchlen,
43 struct ip_conntrack_expect *exp,
44 u32 *seq);
45 EXPORT_SYMBOL_GPL(ip_nat_ftp_hook);
46
47 #if 0
48 #define DEBUGP printk
49 #else
50 #define DEBUGP(format, args...)
51 #endif
52
53 static int try_rfc959(const char *, size_t, u_int32_t [], char);
54 static int try_eprt(const char *, size_t, u_int32_t [], char);
55 static int try_epsv_response(const char *, size_t, u_int32_t [], char);
56
57 static const struct ftp_search {
58 const char *pattern;
59 size_t plen;
60 char skip;
61 char term;
62 enum ip_ct_ftp_type ftptype;
63 int (*getnum)(const char *, size_t, u_int32_t[], char);
64 } search[IP_CT_DIR_MAX][2] = {
65 [IP_CT_DIR_ORIGINAL] = {
66 {
67 .pattern = "PORT",
68 .plen = sizeof("PORT") - 1,
69 .skip = ' ',
70 .term = '\r',
71 .ftptype = IP_CT_FTP_PORT,
72 .getnum = try_rfc959,
73 },
74 {
75 .pattern = "EPRT",
76 .plen = sizeof("EPRT") - 1,
77 .skip = ' ',
78 .term = '\r',
79 .ftptype = IP_CT_FTP_EPRT,
80 .getnum = try_eprt,
81 },
82 },
83 [IP_CT_DIR_REPLY] = {
84 {
85 .pattern = "227 ",
86 .plen = sizeof("227 ") - 1,
87 .skip = '(',
88 .term = ')',
89 .ftptype = IP_CT_FTP_PASV,
90 .getnum = try_rfc959,
91 },
92 {
93 .pattern = "229 ",
94 .plen = sizeof("229 ") - 1,
95 .skip = '(',
96 .term = ')',
97 .ftptype = IP_CT_FTP_EPSV,
98 .getnum = try_epsv_response,
99 },
100 },
101 };
102
103 static int try_number(const char *data, size_t dlen, u_int32_t array[],
104 int array_size, char sep, char term)
105 {
106 u_int32_t i, len;
107
108 memset(array, 0, sizeof(array[0])*array_size);
109
110 /* Keep data pointing at next char. */
111 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
112 if (*data >= '0' && *data <= '9') {
113 array[i] = array[i]*10 + *data - '0';
114 }
115 else if (*data == sep)
116 i++;
117 else {
118 /* Unexpected character; true if it's the
119 terminator and we're finished. */
120 if (*data == term && i == array_size - 1)
121 return len;
122
123 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
124 len, i, *data);
125 return 0;
126 }
127 }
128 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
129
130 return 0;
131 }
132
133 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
134 static int try_rfc959(const char *data, size_t dlen, u_int32_t array[6],
135 char term)
136 {
137 return try_number(data, dlen, array, 6, ',', term);
138 }
139
140 /* Grab port: number up to delimiter */
141 static int get_port(const char *data, int start, size_t dlen, char delim,
142 u_int32_t array[2])
143 {
144 u_int16_t port = 0;
145 int i;
146
147 for (i = start; i < dlen; i++) {
148 /* Finished? */
149 if (data[i] == delim) {
150 if (port == 0)
151 break;
152 array[0] = port >> 8;
153 array[1] = port;
154 return i + 1;
155 }
156 else if (data[i] >= '0' && data[i] <= '9')
157 port = port*10 + data[i] - '0';
158 else /* Some other crap */
159 break;
160 }
161 return 0;
162 }
163
164 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */
165 static int try_eprt(const char *data, size_t dlen, u_int32_t array[6],
166 char term)
167 {
168 char delim;
169 int length;
170
171 /* First character is delimiter, then "1" for IPv4, then
172 delimiter again. */
173 if (dlen <= 3) return 0;
174 delim = data[0];
175 if (isdigit(delim) || delim < 33 || delim > 126
176 || data[1] != '1' || data[2] != delim)
177 return 0;
178
179 DEBUGP("EPRT: Got |1|!\n");
180 /* Now we have IP address. */
181 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
182 if (length == 0)
183 return 0;
184
185 DEBUGP("EPRT: Got IP address!\n");
186 /* Start offset includes initial "|1|", and trailing delimiter */
187 return get_port(data, 3 + length + 1, dlen, delim, array+4);
188 }
189
190 /* Returns 0, or length of numbers: |||6446| */
191 static int try_epsv_response(const char *data, size_t dlen, u_int32_t array[6],
192 char term)
193 {
194 char delim;
195
196 /* Three delimiters. */
197 if (dlen <= 3) return 0;
198 delim = data[0];
199 if (isdigit(delim) || delim < 33 || delim > 126
200 || data[1] != delim || data[2] != delim)
201 return 0;
202
203 return get_port(data, 3, dlen, delim, array+4);
204 }
205
206 /* Return 1 for match, 0 for accept, -1 for partial. */
207 static int find_pattern(const char *data, size_t dlen,
208 const char *pattern, size_t plen,
209 char skip, char term,
210 unsigned int *numoff,
211 unsigned int *numlen,
212 u_int32_t array[6],
213 int (*getnum)(const char *, size_t, u_int32_t[], char))
214 {
215 size_t i;
216
217 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
218 if (dlen == 0)
219 return 0;
220
221 if (dlen <= plen) {
222 /* Short packet: try for partial? */
223 if (strnicmp(data, pattern, dlen) == 0)
224 return -1;
225 else return 0;
226 }
227
228 if (strnicmp(data, pattern, plen) != 0) {
229 #if 0
230 size_t i;
231
232 DEBUGP("ftp: string mismatch\n");
233 for (i = 0; i < plen; i++) {
234 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
235 i, data[i], data[i],
236 pattern[i], pattern[i]);
237 }
238 #endif
239 return 0;
240 }
241
242 DEBUGP("Pattern matches!\n");
243 /* Now we've found the constant string, try to skip
244 to the 'skip' character */
245 for (i = plen; data[i] != skip; i++)
246 if (i == dlen - 1) return -1;
247
248 /* Skip over the last character */
249 i++;
250
251 DEBUGP("Skipped up to `%c'!\n", skip);
252
253 *numoff = i;
254 *numlen = getnum(data + i, dlen - i, array, term);
255 if (!*numlen)
256 return -1;
257
258 DEBUGP("Match succeeded!\n");
259 return 1;
260 }
261
262 /* Look up to see if we're just after a \n. */
263 static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
264 {
265 unsigned int i;
266
267 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
268 if (info->seq_aft_nl[dir][i] == seq)
269 return 1;
270 return 0;
271 }
272
273 /* We don't update if it's older than what we have. */
274 static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir,
275 struct sk_buff *skb)
276 {
277 unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
278
279 /* Look for oldest: if we find exact match, we're done. */
280 for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
281 if (info->seq_aft_nl[dir][i] == nl_seq)
282 return;
283
284 if (oldest == info->seq_aft_nl_num[dir]
285 || before(info->seq_aft_nl[dir][i], oldest))
286 oldest = i;
287 }
288
289 if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
290 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
291 ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
292 } else if (oldest != NUM_SEQ_TO_REMEMBER) {
293 info->seq_aft_nl[dir][oldest] = nl_seq;
294 ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
295 }
296 }
297
298 static int help(struct sk_buff **pskb,
299 struct ip_conntrack *ct,
300 enum ip_conntrack_info ctinfo)
301 {
302 unsigned int dataoff, datalen;
303 struct tcphdr _tcph, *th;
304 char *fb_ptr;
305 int ret;
306 u32 seq, array[6] = { 0 };
307 int dir = CTINFO2DIR(ctinfo);
308 unsigned int matchlen, matchoff;
309 struct ip_ct_ftp_master *ct_ftp_info = &ct->help.ct_ftp_info;
310 struct ip_conntrack_expect *exp;
311 unsigned int i;
312 int found = 0, ends_in_nl;
313
314 /* Until there's been traffic both ways, don't look in packets. */
315 if (ctinfo != IP_CT_ESTABLISHED
316 && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
317 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
318 return NF_ACCEPT;
319 }
320
321 th = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4,
322 sizeof(_tcph), &_tcph);
323 if (th == NULL)
324 return NF_ACCEPT;
325
326 dataoff = (*pskb)->nh.iph->ihl*4 + th->doff*4;
327 /* No data? */
328 if (dataoff >= (*pskb)->len) {
329 DEBUGP("ftp: pskblen = %u\n", (*pskb)->len);
330 return NF_ACCEPT;
331 }
332 datalen = (*pskb)->len - dataoff;
333
334 spin_lock_bh(&ip_ftp_lock);
335 fb_ptr = skb_header_pointer(*pskb, dataoff,
336 (*pskb)->len - dataoff, ftp_buffer);
337 BUG_ON(fb_ptr == NULL);
338
339 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
340 seq = ntohl(th->seq) + datalen;
341
342 /* Look up to see if we're just after a \n. */
343 if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
344 /* Now if this ends in \n, update ftp info. */
345 DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
346 ct_ftp_info->seq_aft_nl[0][dir]
347 old_seq_aft_nl_set ? "":"(UNSET) ", old_seq_aft_nl);
348 ret = NF_ACCEPT;
349 goto out_update_nl;
350 }
351
352 /* Initialize IP array to expected address (it's not mentioned
353 in EPSV responses) */
354 array[0] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 24) & 0xFF;
355 array[1] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 16) & 0xFF;
356 array[2] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 8) & 0xFF;
357 array[3] = ntohl(ct->tuplehash[dir].tuple.src.ip) & 0xFF;
358
359 for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
360 found = find_pattern(fb_ptr, (*pskb)->len - dataoff,
361 search[dir][i].pattern,
362 search[dir][i].plen,
363 search[dir][i].skip,
364 search[dir][i].term,
365 &matchoff, &matchlen,
366 array,
367 search[dir][i].getnum);
368 if (found) break;
369 }
370 if (found == -1) {
371 /* We don't usually drop packets. After all, this is
372 connection tracking, not packet filtering.
373 However, it is necessary for accurate tracking in
374 this case. */
375 if (net_ratelimit())
376 printk("conntrack_ftp: partial %s %u+%u\n",
377 search[dir][i].pattern,
378 ntohl(th->seq), datalen);
379 ret = NF_DROP;
380 goto out;
381 } else if (found == 0) { /* No match */
382 ret = NF_ACCEPT;
383 goto out_update_nl;
384 }
385
386 DEBUGP("conntrack_ftp: match `%s' (%u bytes at %u)\n",
387 fb_ptr + matchoff, matchlen, ntohl(th->seq) + matchoff);
388
389 /* Allocate expectation which will be inserted */
390 exp = ip_conntrack_expect_alloc(ct);
391 if (exp == NULL) {
392 ret = NF_DROP;
393 goto out;
394 }
395
396 /* We refer to the reverse direction ("!dir") tuples here,
397 * because we're expecting something in the other direction.
398 * Doesn't matter unless NAT is happening. */
399 exp->tuple.dst.ip = ct->tuplehash[!dir].tuple.dst.ip;
400
401 if (htonl((array[0] << 24) | (array[1] << 16) | (array[2] << 8) | array[3])
402 != ct->tuplehash[dir].tuple.src.ip) {
403 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
404 server: it really wants us to connect to a
405 different IP address. Simply don't record it for
406 NAT. */
407 DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n",
408 array[0], array[1], array[2], array[3],
409 NIPQUAD(ct->tuplehash[dir].tuple.src.ip));
410
411 /* Thanks to Cristiano Lincoln Mattos
412 <lincoln@cesar.org.br> for reporting this potential
413 problem (DMZ machines opening holes to internal
414 networks, or the packet filter itself). */
415 if (!loose) {
416 if (net_ratelimit())
417 printk("conntrack_ftp: ip mismatch: "
418 "%u,%u,%u,%u != %u.%u.%u.%u\n",
419 array[0], array[1], array[2], array[3],
420 NIPQUAD(ct->tuplehash[dir].tuple.src.ip));
421 ret = NF_DROP;
422 ip_conntrack_expect_put(exp);
423 goto out;
424 }
425 exp->tuple.dst.ip = htonl((array[0] << 24) | (array[1] << 16)
426 | (array[2] << 8) | array[3]);
427 }
428
429 exp->tuple.src.ip = ct->tuplehash[!dir].tuple.src.ip;
430 exp->tuple.dst.u.tcp.port = htons(array[4] << 8 | array[5]);
431 exp->tuple.src.u.tcp.port = 0; /* Don't care. */
432 exp->tuple.dst.protonum = IPPROTO_TCP;
433 exp->mask = ((struct ip_conntrack_tuple)
434 { { htonl(0xFFFFFFFF), { 0 } },
435 { htonl(0xFFFFFFFF), { .tcp = { htons(0xFFFF) } }, 0xFF }});
436
437 exp->expectfn = NULL;
438 exp->flags = 0;
439
440 /* Now, NAT might want to mangle the packet, and register the
441 * (possibly changed) expectation itself. */
442 if (ip_nat_ftp_hook)
443 ret = ip_nat_ftp_hook(pskb, ctinfo, search[dir][i].ftptype,
444 matchoff, matchlen, exp, &seq);
445 else {
446 /* Can't expect this? Best to drop packet now. */
447 if (ip_conntrack_expect_related(exp) != 0)
448 ret = NF_DROP;
449 else
450 ret = NF_ACCEPT;
451 }
452
453 ip_conntrack_expect_put(exp);
454
455 out_update_nl:
456 /* Now if this ends in \n, update ftp info. Seq may have been
457 * adjusted by NAT code. */
458 if (ends_in_nl)
459 update_nl_seq(seq, ct_ftp_info,dir, *pskb);
460 out:
461 spin_unlock_bh(&ip_ftp_lock);
462 return ret;
463 }
464
465 static struct ip_conntrack_helper ftp[MAX_PORTS];
466 static char ftp_names[MAX_PORTS][sizeof("ftp-65535")];
467
468 /* Not __exit: called from init() */
469 static void ip_conntrack_ftp_fini(void)
470 {
471 int i;
472 for (i = 0; i < ports_c; i++) {
473 DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
474 ports[i]);
475 ip_conntrack_helper_unregister(&ftp[i]);
476 }
477
478 kfree(ftp_buffer);
479 }
480
481 static int __init ip_conntrack_ftp_init(void)
482 {
483 int i, ret;
484 char *tmpname;
485
486 ftp_buffer = kmalloc(65536, GFP_KERNEL);
487 if (!ftp_buffer)
488 return -ENOMEM;
489
490 if (ports_c == 0)
491 ports[ports_c++] = FTP_PORT;
492
493 for (i = 0; i < ports_c; i++) {
494 ftp[i].tuple.src.u.tcp.port = htons(ports[i]);
495 ftp[i].tuple.dst.protonum = IPPROTO_TCP;
496 ftp[i].mask.src.u.tcp.port = htons(0xFFFF);
497 ftp[i].mask.dst.protonum = 0xFF;
498 ftp[i].max_expected = 1;
499 ftp[i].timeout = 5 * 60; /* 5 minutes */
500 ftp[i].me = THIS_MODULE;
501 ftp[i].help = help;
502
503 tmpname = &ftp_names[i][0];
504 if (ports[i] == FTP_PORT)
505 sprintf(tmpname, "ftp");
506 else
507 sprintf(tmpname, "ftp-%d", ports[i]);
508 ftp[i].name = tmpname;
509
510 DEBUGP("ip_ct_ftp: registering helper for port %d\n",
511 ports[i]);
512 ret = ip_conntrack_helper_register(&ftp[i]);
513
514 if (ret) {
515 ip_conntrack_ftp_fini();
516 return ret;
517 }
518 }
519 return 0;
520 }
521
522 module_init(ip_conntrack_ftp_init);
523 module_exit(ip_conntrack_ftp_fini);
MOXA 2.6.19 from UC-7110-LX-BOOTLOADER-1.9_VERSION-4.2.tgz