Commit | Line | Data |
---|---|---|
1da177e4 LT |
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/config.h> | |
12 | #include <linux/module.h> | |
13 | #include <linux/netfilter.h> | |
14 | #include <linux/ip.h> | |
15 | #include <linux/ctype.h> | |
16 | #include <net/checksum.h> | |
17 | #include <net/tcp.h> | |
18 | ||
19 | #include <linux/netfilter_ipv4/lockhelp.h> | |
20 | #include <linux/netfilter_ipv4/ip_conntrack_helper.h> | |
21 | #include <linux/netfilter_ipv4/ip_conntrack_ftp.h> | |
22 | #include <linux/moduleparam.h> | |
23 | ||
24 | MODULE_LICENSE("GPL"); | |
25 | MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>"); | |
26 | MODULE_DESCRIPTION("ftp connection tracking helper"); | |
27 | ||
28 | /* This is slow, but it's simple. --RR */ | |
29 | static char ftp_buffer[65536]; | |
30 | ||
31 | static DECLARE_LOCK(ip_ftp_lock); | |
32 | ||
33 | #define MAX_PORTS 8 | |
34 | static int ports[MAX_PORTS]; | |
35 | static int ports_c; | |
36 | module_param_array(ports, int, &ports_c, 0400); | |
37 | ||
38 | static int loose; | |
39 | module_param(loose, int, 0600); | |
40 | ||
41 | unsigned int (*ip_nat_ftp_hook)(struct sk_buff **pskb, | |
42 | enum ip_conntrack_info ctinfo, | |
43 | enum ip_ct_ftp_type type, | |
44 | unsigned int matchoff, | |
45 | unsigned int matchlen, | |
46 | struct ip_conntrack_expect *exp, | |
47 | u32 *seq); | |
48 | EXPORT_SYMBOL_GPL(ip_nat_ftp_hook); | |
49 | ||
50 | #if 0 | |
51 | #define DEBUGP printk | |
52 | #else | |
53 | #define DEBUGP(format, args...) | |
54 | #endif | |
55 | ||
56 | static int try_rfc959(const char *, size_t, u_int32_t [], char); | |
57 | static int try_eprt(const char *, size_t, u_int32_t [], char); | |
58 | static int try_epsv_response(const char *, size_t, u_int32_t [], char); | |
59 | ||
60 | static struct ftp_search { | |
61 | enum ip_conntrack_dir dir; | |
62 | const char *pattern; | |
63 | size_t plen; | |
64 | char skip; | |
65 | char term; | |
66 | enum ip_ct_ftp_type ftptype; | |
67 | int (*getnum)(const char *, size_t, u_int32_t[], char); | |
68 | } search[] = { | |
69 | { | |
70 | IP_CT_DIR_ORIGINAL, | |
71 | "PORT", sizeof("PORT") - 1, ' ', '\r', | |
72 | IP_CT_FTP_PORT, | |
73 | try_rfc959, | |
74 | }, | |
75 | { | |
76 | IP_CT_DIR_REPLY, | |
77 | "227 ", sizeof("227 ") - 1, '(', ')', | |
78 | IP_CT_FTP_PASV, | |
79 | try_rfc959, | |
80 | }, | |
81 | { | |
82 | IP_CT_DIR_ORIGINAL, | |
83 | "EPRT", sizeof("EPRT") - 1, ' ', '\r', | |
84 | IP_CT_FTP_EPRT, | |
85 | try_eprt, | |
86 | }, | |
87 | { | |
88 | IP_CT_DIR_REPLY, | |
89 | "229 ", sizeof("229 ") - 1, '(', ')', | |
90 | IP_CT_FTP_EPSV, | |
91 | try_epsv_response, | |
92 | }, | |
93 | }; | |
94 | ||
95 | static int try_number(const char *data, size_t dlen, u_int32_t array[], | |
96 | int array_size, char sep, char term) | |
97 | { | |
98 | u_int32_t i, len; | |
99 | ||
100 | memset(array, 0, sizeof(array[0])*array_size); | |
101 | ||
102 | /* Keep data pointing at next char. */ | |
103 | for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) { | |
104 | if (*data >= '0' && *data <= '9') { | |
105 | array[i] = array[i]*10 + *data - '0'; | |
106 | } | |
107 | else if (*data == sep) | |
108 | i++; | |
109 | else { | |
110 | /* Unexpected character; true if it's the | |
111 | terminator and we're finished. */ | |
112 | if (*data == term && i == array_size - 1) | |
113 | return len; | |
114 | ||
115 | DEBUGP("Char %u (got %u nums) `%u' unexpected\n", | |
116 | len, i, *data); | |
117 | return 0; | |
118 | } | |
119 | } | |
120 | DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep); | |
121 | ||
122 | return 0; | |
123 | } | |
124 | ||
125 | /* Returns 0, or length of numbers: 192,168,1,1,5,6 */ | |
126 | static int try_rfc959(const char *data, size_t dlen, u_int32_t array[6], | |
127 | char term) | |
128 | { | |
129 | return try_number(data, dlen, array, 6, ',', term); | |
130 | } | |
131 | ||
132 | /* Grab port: number up to delimiter */ | |
133 | static int get_port(const char *data, int start, size_t dlen, char delim, | |
134 | u_int32_t array[2]) | |
135 | { | |
136 | u_int16_t port = 0; | |
137 | int i; | |
138 | ||
139 | for (i = start; i < dlen; i++) { | |
140 | /* Finished? */ | |
141 | if (data[i] == delim) { | |
142 | if (port == 0) | |
143 | break; | |
144 | array[0] = port >> 8; | |
145 | array[1] = port; | |
146 | return i + 1; | |
147 | } | |
148 | else if (data[i] >= '0' && data[i] <= '9') | |
149 | port = port*10 + data[i] - '0'; | |
150 | else /* Some other crap */ | |
151 | break; | |
152 | } | |
153 | return 0; | |
154 | } | |
155 | ||
156 | /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */ | |
157 | static int try_eprt(const char *data, size_t dlen, u_int32_t array[6], | |
158 | char term) | |
159 | { | |
160 | char delim; | |
161 | int length; | |
162 | ||
163 | /* First character is delimiter, then "1" for IPv4, then | |
164 | delimiter again. */ | |
165 | if (dlen <= 3) return 0; | |
166 | delim = data[0]; | |
167 | if (isdigit(delim) || delim < 33 || delim > 126 | |
168 | || data[1] != '1' || data[2] != delim) | |
169 | return 0; | |
170 | ||
171 | DEBUGP("EPRT: Got |1|!\n"); | |
172 | /* Now we have IP address. */ | |
173 | length = try_number(data + 3, dlen - 3, array, 4, '.', delim); | |
174 | if (length == 0) | |
175 | return 0; | |
176 | ||
177 | DEBUGP("EPRT: Got IP address!\n"); | |
178 | /* Start offset includes initial "|1|", and trailing delimiter */ | |
179 | return get_port(data, 3 + length + 1, dlen, delim, array+4); | |
180 | } | |
181 | ||
182 | /* Returns 0, or length of numbers: |||6446| */ | |
183 | static int try_epsv_response(const char *data, size_t dlen, u_int32_t array[6], | |
184 | char term) | |
185 | { | |
186 | char delim; | |
187 | ||
188 | /* Three delimiters. */ | |
189 | if (dlen <= 3) return 0; | |
190 | delim = data[0]; | |
191 | if (isdigit(delim) || delim < 33 || delim > 126 | |
192 | || data[1] != delim || data[2] != delim) | |
193 | return 0; | |
194 | ||
195 | return get_port(data, 3, dlen, delim, array+4); | |
196 | } | |
197 | ||
198 | /* Return 1 for match, 0 for accept, -1 for partial. */ | |
199 | static int find_pattern(const char *data, size_t dlen, | |
200 | const char *pattern, size_t plen, | |
201 | char skip, char term, | |
202 | unsigned int *numoff, | |
203 | unsigned int *numlen, | |
204 | u_int32_t array[6], | |
205 | int (*getnum)(const char *, size_t, u_int32_t[], char)) | |
206 | { | |
207 | size_t i; | |
208 | ||
209 | DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen); | |
210 | if (dlen == 0) | |
211 | return 0; | |
212 | ||
213 | if (dlen <= plen) { | |
214 | /* Short packet: try for partial? */ | |
215 | if (strnicmp(data, pattern, dlen) == 0) | |
216 | return -1; | |
217 | else return 0; | |
218 | } | |
219 | ||
220 | if (strnicmp(data, pattern, plen) != 0) { | |
221 | #if 0 | |
222 | size_t i; | |
223 | ||
224 | DEBUGP("ftp: string mismatch\n"); | |
225 | for (i = 0; i < plen; i++) { | |
226 | DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n", | |
227 | i, data[i], data[i], | |
228 | pattern[i], pattern[i]); | |
229 | } | |
230 | #endif | |
231 | return 0; | |
232 | } | |
233 | ||
234 | DEBUGP("Pattern matches!\n"); | |
235 | /* Now we've found the constant string, try to skip | |
236 | to the 'skip' character */ | |
237 | for (i = plen; data[i] != skip; i++) | |
238 | if (i == dlen - 1) return -1; | |
239 | ||
240 | /* Skip over the last character */ | |
241 | i++; | |
242 | ||
243 | DEBUGP("Skipped up to `%c'!\n", skip); | |
244 | ||
245 | *numoff = i; | |
246 | *numlen = getnum(data + i, dlen - i, array, term); | |
247 | if (!*numlen) | |
248 | return -1; | |
249 | ||
250 | DEBUGP("Match succeeded!\n"); | |
251 | return 1; | |
252 | } | |
253 | ||
254 | /* Look up to see if we're just after a \n. */ | |
255 | static int find_nl_seq(u16 seq, const struct ip_ct_ftp_master *info, int dir) | |
256 | { | |
257 | unsigned int i; | |
258 | ||
259 | for (i = 0; i < info->seq_aft_nl_num[dir]; i++) | |
260 | if (info->seq_aft_nl[dir][i] == seq) | |
261 | return 1; | |
262 | return 0; | |
263 | } | |
264 | ||
265 | /* We don't update if it's older than what we have. */ | |
266 | static void update_nl_seq(u16 nl_seq, struct ip_ct_ftp_master *info, int dir) | |
267 | { | |
268 | unsigned int i, oldest = NUM_SEQ_TO_REMEMBER; | |
269 | ||
270 | /* Look for oldest: if we find exact match, we're done. */ | |
271 | for (i = 0; i < info->seq_aft_nl_num[dir]; i++) { | |
272 | if (info->seq_aft_nl[dir][i] == nl_seq) | |
273 | return; | |
274 | ||
275 | if (oldest == info->seq_aft_nl_num[dir] | |
276 | || before(info->seq_aft_nl[dir][i], oldest)) | |
277 | oldest = i; | |
278 | } | |
279 | ||
280 | if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) | |
281 | info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq; | |
282 | else if (oldest != NUM_SEQ_TO_REMEMBER) | |
283 | info->seq_aft_nl[dir][oldest] = nl_seq; | |
284 | } | |
285 | ||
286 | static int help(struct sk_buff **pskb, | |
287 | struct ip_conntrack *ct, | |
288 | enum ip_conntrack_info ctinfo) | |
289 | { | |
290 | unsigned int dataoff, datalen; | |
291 | struct tcphdr _tcph, *th; | |
292 | char *fb_ptr; | |
293 | int ret; | |
294 | u32 seq, array[6] = { 0 }; | |
295 | int dir = CTINFO2DIR(ctinfo); | |
296 | unsigned int matchlen, matchoff; | |
297 | struct ip_ct_ftp_master *ct_ftp_info = &ct->help.ct_ftp_info; | |
298 | struct ip_conntrack_expect *exp; | |
299 | unsigned int i; | |
300 | int found = 0, ends_in_nl; | |
301 | ||
302 | /* Until there's been traffic both ways, don't look in packets. */ | |
303 | if (ctinfo != IP_CT_ESTABLISHED | |
304 | && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) { | |
305 | DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo); | |
306 | return NF_ACCEPT; | |
307 | } | |
308 | ||
309 | th = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4, | |
310 | sizeof(_tcph), &_tcph); | |
311 | if (th == NULL) | |
312 | return NF_ACCEPT; | |
313 | ||
314 | dataoff = (*pskb)->nh.iph->ihl*4 + th->doff*4; | |
315 | /* No data? */ | |
316 | if (dataoff >= (*pskb)->len) { | |
317 | DEBUGP("ftp: pskblen = %u\n", (*pskb)->len); | |
318 | return NF_ACCEPT; | |
319 | } | |
320 | datalen = (*pskb)->len - dataoff; | |
321 | ||
322 | LOCK_BH(&ip_ftp_lock); | |
323 | fb_ptr = skb_header_pointer(*pskb, dataoff, | |
324 | (*pskb)->len - dataoff, ftp_buffer); | |
325 | BUG_ON(fb_ptr == NULL); | |
326 | ||
327 | ends_in_nl = (fb_ptr[datalen - 1] == '\n'); | |
328 | seq = ntohl(th->seq) + datalen; | |
329 | ||
330 | /* Look up to see if we're just after a \n. */ | |
331 | if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) { | |
332 | /* Now if this ends in \n, update ftp info. */ | |
333 | DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n", | |
334 | ct_ftp_info->seq_aft_nl[0][dir] | |
335 | old_seq_aft_nl_set ? "":"(UNSET) ", old_seq_aft_nl); | |
336 | ret = NF_ACCEPT; | |
337 | goto out_update_nl; | |
338 | } | |
339 | ||
340 | /* Initialize IP array to expected address (it's not mentioned | |
341 | in EPSV responses) */ | |
342 | array[0] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 24) & 0xFF; | |
343 | array[1] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 16) & 0xFF; | |
344 | array[2] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 8) & 0xFF; | |
345 | array[3] = ntohl(ct->tuplehash[dir].tuple.src.ip) & 0xFF; | |
346 | ||
347 | for (i = 0; i < ARRAY_SIZE(search); i++) { | |
348 | if (search[i].dir != dir) continue; | |
349 | ||
350 | found = find_pattern(fb_ptr, (*pskb)->len - dataoff, | |
351 | search[i].pattern, | |
352 | search[i].plen, | |
353 | search[i].skip, | |
354 | search[i].term, | |
355 | &matchoff, &matchlen, | |
356 | array, | |
357 | search[i].getnum); | |
358 | if (found) break; | |
359 | } | |
360 | if (found == -1) { | |
361 | /* We don't usually drop packets. After all, this is | |
362 | connection tracking, not packet filtering. | |
363 | However, it is necessary for accurate tracking in | |
364 | this case. */ | |
365 | if (net_ratelimit()) | |
366 | printk("conntrack_ftp: partial %s %u+%u\n", | |
367 | search[i].pattern, | |
368 | ntohl(th->seq), datalen); | |
369 | ret = NF_DROP; | |
370 | goto out; | |
371 | } else if (found == 0) { /* No match */ | |
372 | ret = NF_ACCEPT; | |
373 | goto out_update_nl; | |
374 | } | |
375 | ||
376 | DEBUGP("conntrack_ftp: match `%s' (%u bytes at %u)\n", | |
377 | fb_ptr + matchoff, matchlen, ntohl(th->seq) + matchoff); | |
378 | ||
379 | /* Allocate expectation which will be inserted */ | |
380 | exp = ip_conntrack_expect_alloc(); | |
381 | if (exp == NULL) { | |
382 | ret = NF_DROP; | |
383 | goto out; | |
384 | } | |
385 | ||
386 | /* We refer to the reverse direction ("!dir") tuples here, | |
387 | * because we're expecting something in the other direction. | |
388 | * Doesn't matter unless NAT is happening. */ | |
389 | exp->tuple.dst.ip = ct->tuplehash[!dir].tuple.dst.ip; | |
390 | ||
391 | if (htonl((array[0] << 24) | (array[1] << 16) | (array[2] << 8) | array[3]) | |
392 | != ct->tuplehash[dir].tuple.src.ip) { | |
393 | /* Enrico Scholz's passive FTP to partially RNAT'd ftp | |
394 | server: it really wants us to connect to a | |
395 | different IP address. Simply don't record it for | |
396 | NAT. */ | |
397 | DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n", | |
398 | array[0], array[1], array[2], array[3], | |
399 | NIPQUAD(ct->tuplehash[dir].tuple.src.ip)); | |
400 | ||
401 | /* Thanks to Cristiano Lincoln Mattos | |
402 | <lincoln@cesar.org.br> for reporting this potential | |
403 | problem (DMZ machines opening holes to internal | |
404 | networks, or the packet filter itself). */ | |
405 | if (!loose) { | |
406 | ret = NF_ACCEPT; | |
407 | ip_conntrack_expect_free(exp); | |
408 | goto out_update_nl; | |
409 | } | |
410 | exp->tuple.dst.ip = htonl((array[0] << 24) | (array[1] << 16) | |
411 | | (array[2] << 8) | array[3]); | |
412 | } | |
413 | ||
414 | exp->tuple.src.ip = ct->tuplehash[!dir].tuple.src.ip; | |
415 | exp->tuple.dst.u.tcp.port = htons(array[4] << 8 | array[5]); | |
416 | exp->tuple.src.u.tcp.port = 0; /* Don't care. */ | |
417 | exp->tuple.dst.protonum = IPPROTO_TCP; | |
418 | exp->mask = ((struct ip_conntrack_tuple) | |
419 | { { 0xFFFFFFFF, { 0 } }, | |
420 | { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFF }}); | |
421 | ||
422 | exp->expectfn = NULL; | |
423 | exp->master = ct; | |
424 | ||
425 | /* Now, NAT might want to mangle the packet, and register the | |
426 | * (possibly changed) expectation itself. */ | |
427 | if (ip_nat_ftp_hook) | |
428 | ret = ip_nat_ftp_hook(pskb, ctinfo, search[i].ftptype, | |
429 | matchoff, matchlen, exp, &seq); | |
430 | else { | |
431 | /* Can't expect this? Best to drop packet now. */ | |
432 | if (ip_conntrack_expect_related(exp) != 0) { | |
433 | ip_conntrack_expect_free(exp); | |
434 | ret = NF_DROP; | |
435 | } else | |
436 | ret = NF_ACCEPT; | |
437 | } | |
438 | ||
439 | out_update_nl: | |
440 | /* Now if this ends in \n, update ftp info. Seq may have been | |
441 | * adjusted by NAT code. */ | |
442 | if (ends_in_nl) | |
443 | update_nl_seq(seq, ct_ftp_info,dir); | |
444 | out: | |
445 | UNLOCK_BH(&ip_ftp_lock); | |
446 | return ret; | |
447 | } | |
448 | ||
449 | static struct ip_conntrack_helper ftp[MAX_PORTS]; | |
450 | static char ftp_names[MAX_PORTS][10]; | |
451 | ||
452 | /* Not __exit: called from init() */ | |
453 | static void fini(void) | |
454 | { | |
455 | int i; | |
456 | for (i = 0; i < ports_c; i++) { | |
457 | DEBUGP("ip_ct_ftp: unregistering helper for port %d\n", | |
458 | ports[i]); | |
459 | ip_conntrack_helper_unregister(&ftp[i]); | |
460 | } | |
461 | } | |
462 | ||
463 | static int __init init(void) | |
464 | { | |
465 | int i, ret; | |
466 | char *tmpname; | |
467 | ||
468 | if (ports_c == 0) | |
469 | ports[ports_c++] = FTP_PORT; | |
470 | ||
471 | for (i = 0; i < ports_c; i++) { | |
472 | ftp[i].tuple.src.u.tcp.port = htons(ports[i]); | |
473 | ftp[i].tuple.dst.protonum = IPPROTO_TCP; | |
474 | ftp[i].mask.src.u.tcp.port = 0xFFFF; | |
475 | ftp[i].mask.dst.protonum = 0xFF; | |
476 | ftp[i].max_expected = 1; | |
477 | ftp[i].timeout = 5 * 60; /* 5 minutes */ | |
478 | ftp[i].me = THIS_MODULE; | |
479 | ftp[i].help = help; | |
480 | ||
481 | tmpname = &ftp_names[i][0]; | |
482 | if (ports[i] == FTP_PORT) | |
483 | sprintf(tmpname, "ftp"); | |
484 | else | |
485 | sprintf(tmpname, "ftp-%d", ports[i]); | |
486 | ftp[i].name = tmpname; | |
487 | ||
488 | DEBUGP("ip_ct_ftp: registering helper for port %d\n", | |
489 | ports[i]); | |
490 | ret = ip_conntrack_helper_register(&ftp[i]); | |
491 | ||
492 | if (ret) { | |
493 | fini(); | |
494 | return ret; | |
495 | } | |
496 | } | |
497 | return 0; | |
498 | } | |
499 | ||
500 | module_init(init); | |
501 | module_exit(fini); |