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 | ||
1da177e4 LT |
19 | #include <linux/netfilter_ipv4/ip_conntrack_helper.h> |
20 | #include <linux/netfilter_ipv4/ip_conntrack_ftp.h> | |
21 | #include <linux/moduleparam.h> | |
22 | ||
23 | MODULE_LICENSE("GPL"); | |
24 | MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>"); | |
25 | MODULE_DESCRIPTION("ftp connection tracking helper"); | |
26 | ||
27 | /* This is slow, but it's simple. --RR */ | |
28 | static char ftp_buffer[65536]; | |
29 | ||
e45b1be8 | 30 | static DEFINE_SPINLOCK(ip_ftp_lock); |
1da177e4 LT |
31 | |
32 | #define MAX_PORTS 8 | |
33 | static int ports[MAX_PORTS]; | |
34 | static int ports_c; | |
35 | module_param_array(ports, int, &ports_c, 0400); | |
36 | ||
37 | static int loose; | |
38 | module_param(loose, int, 0600); | |
39 | ||
40 | unsigned int (*ip_nat_ftp_hook)(struct sk_buff **pskb, | |
41 | enum ip_conntrack_info ctinfo, | |
42 | enum ip_ct_ftp_type type, | |
43 | unsigned int matchoff, | |
44 | unsigned int matchlen, | |
45 | struct ip_conntrack_expect *exp, | |
46 | u32 *seq); | |
47 | EXPORT_SYMBOL_GPL(ip_nat_ftp_hook); | |
48 | ||
49 | #if 0 | |
50 | #define DEBUGP printk | |
51 | #else | |
52 | #define DEBUGP(format, args...) | |
53 | #endif | |
54 | ||
55 | static int try_rfc959(const char *, size_t, u_int32_t [], char); | |
56 | static int try_eprt(const char *, size_t, u_int32_t [], char); | |
57 | static int try_epsv_response(const char *, size_t, u_int32_t [], char); | |
58 | ||
59 | static struct ftp_search { | |
60 | enum ip_conntrack_dir dir; | |
61 | const char *pattern; | |
62 | size_t plen; | |
63 | char skip; | |
64 | char term; | |
65 | enum ip_ct_ftp_type ftptype; | |
66 | int (*getnum)(const char *, size_t, u_int32_t[], char); | |
67 | } search[] = { | |
68 | { | |
69 | IP_CT_DIR_ORIGINAL, | |
70 | "PORT", sizeof("PORT") - 1, ' ', '\r', | |
71 | IP_CT_FTP_PORT, | |
72 | try_rfc959, | |
73 | }, | |
74 | { | |
75 | IP_CT_DIR_REPLY, | |
76 | "227 ", sizeof("227 ") - 1, '(', ')', | |
77 | IP_CT_FTP_PASV, | |
78 | try_rfc959, | |
79 | }, | |
80 | { | |
81 | IP_CT_DIR_ORIGINAL, | |
82 | "EPRT", sizeof("EPRT") - 1, ' ', '\r', | |
83 | IP_CT_FTP_EPRT, | |
84 | try_eprt, | |
85 | }, | |
86 | { | |
87 | IP_CT_DIR_REPLY, | |
88 | "229 ", sizeof("229 ") - 1, '(', ')', | |
89 | IP_CT_FTP_EPSV, | |
90 | try_epsv_response, | |
91 | }, | |
92 | }; | |
93 | ||
94 | static int try_number(const char *data, size_t dlen, u_int32_t array[], | |
95 | int array_size, char sep, char term) | |
96 | { | |
97 | u_int32_t i, len; | |
98 | ||
99 | memset(array, 0, sizeof(array[0])*array_size); | |
100 | ||
101 | /* Keep data pointing at next char. */ | |
102 | for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) { | |
103 | if (*data >= '0' && *data <= '9') { | |
104 | array[i] = array[i]*10 + *data - '0'; | |
105 | } | |
106 | else if (*data == sep) | |
107 | i++; | |
108 | else { | |
109 | /* Unexpected character; true if it's the | |
110 | terminator and we're finished. */ | |
111 | if (*data == term && i == array_size - 1) | |
112 | return len; | |
113 | ||
114 | DEBUGP("Char %u (got %u nums) `%u' unexpected\n", | |
115 | len, i, *data); | |
116 | return 0; | |
117 | } | |
118 | } | |
119 | DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep); | |
120 | ||
121 | return 0; | |
122 | } | |
123 | ||
124 | /* Returns 0, or length of numbers: 192,168,1,1,5,6 */ | |
125 | static int try_rfc959(const char *data, size_t dlen, u_int32_t array[6], | |
126 | char term) | |
127 | { | |
128 | return try_number(data, dlen, array, 6, ',', term); | |
129 | } | |
130 | ||
131 | /* Grab port: number up to delimiter */ | |
132 | static int get_port(const char *data, int start, size_t dlen, char delim, | |
133 | u_int32_t array[2]) | |
134 | { | |
135 | u_int16_t port = 0; | |
136 | int i; | |
137 | ||
138 | for (i = start; i < dlen; i++) { | |
139 | /* Finished? */ | |
140 | if (data[i] == delim) { | |
141 | if (port == 0) | |
142 | break; | |
143 | array[0] = port >> 8; | |
144 | array[1] = port; | |
145 | return i + 1; | |
146 | } | |
147 | else if (data[i] >= '0' && data[i] <= '9') | |
148 | port = port*10 + data[i] - '0'; | |
149 | else /* Some other crap */ | |
150 | break; | |
151 | } | |
152 | return 0; | |
153 | } | |
154 | ||
155 | /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */ | |
156 | static int try_eprt(const char *data, size_t dlen, u_int32_t array[6], | |
157 | char term) | |
158 | { | |
159 | char delim; | |
160 | int length; | |
161 | ||
162 | /* First character is delimiter, then "1" for IPv4, then | |
163 | delimiter again. */ | |
164 | if (dlen <= 3) return 0; | |
165 | delim = data[0]; | |
166 | if (isdigit(delim) || delim < 33 || delim > 126 | |
167 | || data[1] != '1' || data[2] != delim) | |
168 | return 0; | |
169 | ||
170 | DEBUGP("EPRT: Got |1|!\n"); | |
171 | /* Now we have IP address. */ | |
172 | length = try_number(data + 3, dlen - 3, array, 4, '.', delim); | |
173 | if (length == 0) | |
174 | return 0; | |
175 | ||
176 | DEBUGP("EPRT: Got IP address!\n"); | |
177 | /* Start offset includes initial "|1|", and trailing delimiter */ | |
178 | return get_port(data, 3 + length + 1, dlen, delim, array+4); | |
179 | } | |
180 | ||
181 | /* Returns 0, or length of numbers: |||6446| */ | |
182 | static int try_epsv_response(const char *data, size_t dlen, u_int32_t array[6], | |
183 | char term) | |
184 | { | |
185 | char delim; | |
186 | ||
187 | /* Three delimiters. */ | |
188 | if (dlen <= 3) return 0; | |
189 | delim = data[0]; | |
190 | if (isdigit(delim) || delim < 33 || delim > 126 | |
191 | || data[1] != delim || data[2] != delim) | |
192 | return 0; | |
193 | ||
194 | return get_port(data, 3, dlen, delim, array+4); | |
195 | } | |
196 | ||
197 | /* Return 1 for match, 0 for accept, -1 for partial. */ | |
198 | static int find_pattern(const char *data, size_t dlen, | |
199 | const char *pattern, size_t plen, | |
200 | char skip, char term, | |
201 | unsigned int *numoff, | |
202 | unsigned int *numlen, | |
203 | u_int32_t array[6], | |
204 | int (*getnum)(const char *, size_t, u_int32_t[], char)) | |
205 | { | |
206 | size_t i; | |
207 | ||
208 | DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen); | |
209 | if (dlen == 0) | |
210 | return 0; | |
211 | ||
212 | if (dlen <= plen) { | |
213 | /* Short packet: try for partial? */ | |
214 | if (strnicmp(data, pattern, dlen) == 0) | |
215 | return -1; | |
216 | else return 0; | |
217 | } | |
218 | ||
219 | if (strnicmp(data, pattern, plen) != 0) { | |
220 | #if 0 | |
221 | size_t i; | |
222 | ||
223 | DEBUGP("ftp: string mismatch\n"); | |
224 | for (i = 0; i < plen; i++) { | |
225 | DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n", | |
226 | i, data[i], data[i], | |
227 | pattern[i], pattern[i]); | |
228 | } | |
229 | #endif | |
230 | return 0; | |
231 | } | |
232 | ||
233 | DEBUGP("Pattern matches!\n"); | |
234 | /* Now we've found the constant string, try to skip | |
235 | to the 'skip' character */ | |
236 | for (i = plen; data[i] != skip; i++) | |
237 | if (i == dlen - 1) return -1; | |
238 | ||
239 | /* Skip over the last character */ | |
240 | i++; | |
241 | ||
242 | DEBUGP("Skipped up to `%c'!\n", skip); | |
243 | ||
244 | *numoff = i; | |
245 | *numlen = getnum(data + i, dlen - i, array, term); | |
246 | if (!*numlen) | |
247 | return -1; | |
248 | ||
249 | DEBUGP("Match succeeded!\n"); | |
250 | return 1; | |
251 | } | |
252 | ||
253 | /* Look up to see if we're just after a \n. */ | |
f649a3bf | 254 | static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir) |
1da177e4 LT |
255 | { |
256 | unsigned int i; | |
257 | ||
258 | for (i = 0; i < info->seq_aft_nl_num[dir]; i++) | |
259 | if (info->seq_aft_nl[dir][i] == seq) | |
260 | return 1; | |
261 | return 0; | |
262 | } | |
263 | ||
264 | /* We don't update if it's older than what we have. */ | |
ac3247ba HW |
265 | static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir, |
266 | struct sk_buff *skb) | |
1da177e4 LT |
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 | ||
ac3247ba | 280 | if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) { |
1da177e4 | 281 | info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq; |
ac3247ba HW |
282 | ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb); |
283 | } else if (oldest != NUM_SEQ_TO_REMEMBER) { | |
1da177e4 | 284 | info->seq_aft_nl[dir][oldest] = nl_seq; |
ac3247ba HW |
285 | ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb); |
286 | } | |
1da177e4 LT |
287 | } |
288 | ||
289 | static int help(struct sk_buff **pskb, | |
290 | struct ip_conntrack *ct, | |
291 | enum ip_conntrack_info ctinfo) | |
292 | { | |
293 | unsigned int dataoff, datalen; | |
294 | struct tcphdr _tcph, *th; | |
295 | char *fb_ptr; | |
296 | int ret; | |
297 | u32 seq, array[6] = { 0 }; | |
298 | int dir = CTINFO2DIR(ctinfo); | |
299 | unsigned int matchlen, matchoff; | |
300 | struct ip_ct_ftp_master *ct_ftp_info = &ct->help.ct_ftp_info; | |
301 | struct ip_conntrack_expect *exp; | |
302 | unsigned int i; | |
303 | int found = 0, ends_in_nl; | |
304 | ||
305 | /* Until there's been traffic both ways, don't look in packets. */ | |
306 | if (ctinfo != IP_CT_ESTABLISHED | |
307 | && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) { | |
308 | DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo); | |
309 | return NF_ACCEPT; | |
310 | } | |
311 | ||
312 | th = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4, | |
313 | sizeof(_tcph), &_tcph); | |
314 | if (th == NULL) | |
315 | return NF_ACCEPT; | |
316 | ||
317 | dataoff = (*pskb)->nh.iph->ihl*4 + th->doff*4; | |
318 | /* No data? */ | |
319 | if (dataoff >= (*pskb)->len) { | |
320 | DEBUGP("ftp: pskblen = %u\n", (*pskb)->len); | |
321 | return NF_ACCEPT; | |
322 | } | |
323 | datalen = (*pskb)->len - dataoff; | |
324 | ||
e45b1be8 | 325 | spin_lock_bh(&ip_ftp_lock); |
1da177e4 LT |
326 | fb_ptr = skb_header_pointer(*pskb, dataoff, |
327 | (*pskb)->len - dataoff, ftp_buffer); | |
328 | BUG_ON(fb_ptr == NULL); | |
329 | ||
330 | ends_in_nl = (fb_ptr[datalen - 1] == '\n'); | |
331 | seq = ntohl(th->seq) + datalen; | |
332 | ||
333 | /* Look up to see if we're just after a \n. */ | |
334 | if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) { | |
335 | /* Now if this ends in \n, update ftp info. */ | |
336 | DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n", | |
337 | ct_ftp_info->seq_aft_nl[0][dir] | |
338 | old_seq_aft_nl_set ? "":"(UNSET) ", old_seq_aft_nl); | |
339 | ret = NF_ACCEPT; | |
340 | goto out_update_nl; | |
341 | } | |
342 | ||
343 | /* Initialize IP array to expected address (it's not mentioned | |
344 | in EPSV responses) */ | |
345 | array[0] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 24) & 0xFF; | |
346 | array[1] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 16) & 0xFF; | |
347 | array[2] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 8) & 0xFF; | |
348 | array[3] = ntohl(ct->tuplehash[dir].tuple.src.ip) & 0xFF; | |
349 | ||
350 | for (i = 0; i < ARRAY_SIZE(search); i++) { | |
351 | if (search[i].dir != dir) continue; | |
352 | ||
353 | found = find_pattern(fb_ptr, (*pskb)->len - dataoff, | |
354 | search[i].pattern, | |
355 | search[i].plen, | |
356 | search[i].skip, | |
357 | search[i].term, | |
358 | &matchoff, &matchlen, | |
359 | array, | |
360 | search[i].getnum); | |
361 | if (found) break; | |
362 | } | |
363 | if (found == -1) { | |
364 | /* We don't usually drop packets. After all, this is | |
365 | connection tracking, not packet filtering. | |
366 | However, it is necessary for accurate tracking in | |
367 | this case. */ | |
368 | if (net_ratelimit()) | |
369 | printk("conntrack_ftp: partial %s %u+%u\n", | |
370 | search[i].pattern, | |
371 | ntohl(th->seq), datalen); | |
372 | ret = NF_DROP; | |
373 | goto out; | |
374 | } else if (found == 0) { /* No match */ | |
375 | ret = NF_ACCEPT; | |
376 | goto out_update_nl; | |
377 | } | |
378 | ||
379 | DEBUGP("conntrack_ftp: match `%s' (%u bytes at %u)\n", | |
380 | fb_ptr + matchoff, matchlen, ntohl(th->seq) + matchoff); | |
381 | ||
382 | /* Allocate expectation which will be inserted */ | |
4acdbdbe | 383 | exp = ip_conntrack_expect_alloc(ct); |
1da177e4 LT |
384 | if (exp == NULL) { |
385 | ret = NF_DROP; | |
386 | goto out; | |
387 | } | |
388 | ||
389 | /* We refer to the reverse direction ("!dir") tuples here, | |
390 | * because we're expecting something in the other direction. | |
391 | * Doesn't matter unless NAT is happening. */ | |
392 | exp->tuple.dst.ip = ct->tuplehash[!dir].tuple.dst.ip; | |
393 | ||
394 | if (htonl((array[0] << 24) | (array[1] << 16) | (array[2] << 8) | array[3]) | |
395 | != ct->tuplehash[dir].tuple.src.ip) { | |
396 | /* Enrico Scholz's passive FTP to partially RNAT'd ftp | |
397 | server: it really wants us to connect to a | |
398 | different IP address. Simply don't record it for | |
399 | NAT. */ | |
400 | DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n", | |
401 | array[0], array[1], array[2], array[3], | |
402 | NIPQUAD(ct->tuplehash[dir].tuple.src.ip)); | |
403 | ||
404 | /* Thanks to Cristiano Lincoln Mattos | |
405 | <lincoln@cesar.org.br> for reporting this potential | |
406 | problem (DMZ machines opening holes to internal | |
407 | networks, or the packet filter itself). */ | |
408 | if (!loose) { | |
409 | ret = NF_ACCEPT; | |
4acdbdbe | 410 | goto out_put_expect; |
1da177e4 LT |
411 | } |
412 | exp->tuple.dst.ip = htonl((array[0] << 24) | (array[1] << 16) | |
413 | | (array[2] << 8) | array[3]); | |
414 | } | |
415 | ||
416 | exp->tuple.src.ip = ct->tuplehash[!dir].tuple.src.ip; | |
417 | exp->tuple.dst.u.tcp.port = htons(array[4] << 8 | array[5]); | |
418 | exp->tuple.src.u.tcp.port = 0; /* Don't care. */ | |
419 | exp->tuple.dst.protonum = IPPROTO_TCP; | |
420 | exp->mask = ((struct ip_conntrack_tuple) | |
421 | { { 0xFFFFFFFF, { 0 } }, | |
422 | { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFF }}); | |
423 | ||
424 | exp->expectfn = NULL; | |
1da177e4 LT |
425 | |
426 | /* Now, NAT might want to mangle the packet, and register the | |
427 | * (possibly changed) expectation itself. */ | |
428 | if (ip_nat_ftp_hook) | |
429 | ret = ip_nat_ftp_hook(pskb, ctinfo, search[i].ftptype, | |
430 | matchoff, matchlen, exp, &seq); | |
431 | else { | |
432 | /* Can't expect this? Best to drop packet now. */ | |
4acdbdbe | 433 | if (ip_conntrack_expect_related(exp) != 0) |
1da177e4 | 434 | ret = NF_DROP; |
4acdbdbe | 435 | else |
1da177e4 LT |
436 | ret = NF_ACCEPT; |
437 | } | |
438 | ||
4acdbdbe RR |
439 | out_put_expect: |
440 | ip_conntrack_expect_put(exp); | |
441 | ||
1da177e4 LT |
442 | out_update_nl: |
443 | /* Now if this ends in \n, update ftp info. Seq may have been | |
444 | * adjusted by NAT code. */ | |
445 | if (ends_in_nl) | |
ac3247ba | 446 | update_nl_seq(seq, ct_ftp_info,dir, *pskb); |
1da177e4 | 447 | out: |
e45b1be8 | 448 | spin_unlock_bh(&ip_ftp_lock); |
1da177e4 LT |
449 | return ret; |
450 | } | |
451 | ||
452 | static struct ip_conntrack_helper ftp[MAX_PORTS]; | |
453 | static char ftp_names[MAX_PORTS][10]; | |
454 | ||
455 | /* Not __exit: called from init() */ | |
456 | static void fini(void) | |
457 | { | |
458 | int i; | |
459 | for (i = 0; i < ports_c; i++) { | |
460 | DEBUGP("ip_ct_ftp: unregistering helper for port %d\n", | |
461 | ports[i]); | |
462 | ip_conntrack_helper_unregister(&ftp[i]); | |
463 | } | |
464 | } | |
465 | ||
466 | static int __init init(void) | |
467 | { | |
468 | int i, ret; | |
469 | char *tmpname; | |
470 | ||
471 | if (ports_c == 0) | |
472 | ports[ports_c++] = FTP_PORT; | |
473 | ||
474 | for (i = 0; i < ports_c; i++) { | |
475 | ftp[i].tuple.src.u.tcp.port = htons(ports[i]); | |
476 | ftp[i].tuple.dst.protonum = IPPROTO_TCP; | |
477 | ftp[i].mask.src.u.tcp.port = 0xFFFF; | |
478 | ftp[i].mask.dst.protonum = 0xFF; | |
479 | ftp[i].max_expected = 1; | |
480 | ftp[i].timeout = 5 * 60; /* 5 minutes */ | |
481 | ftp[i].me = THIS_MODULE; | |
482 | ftp[i].help = help; | |
483 | ||
484 | tmpname = &ftp_names[i][0]; | |
485 | if (ports[i] == FTP_PORT) | |
486 | sprintf(tmpname, "ftp"); | |
487 | else | |
488 | sprintf(tmpname, "ftp-%d", ports[i]); | |
489 | ftp[i].name = tmpname; | |
490 | ||
491 | DEBUGP("ip_ct_ftp: registering helper for port %d\n", | |
492 | ports[i]); | |
493 | ret = ip_conntrack_helper_register(&ftp[i]); | |
494 | ||
495 | if (ret) { | |
496 | fini(); | |
497 | return ret; | |
498 | } | |
499 | } | |
500 | return 0; | |
501 | } | |
502 | ||
503 | module_init(init); | |
504 | module_exit(fini); |