1 /* FTP extension for IP connection tracking. */
3 /* (C) 1999-2001 Paul `Rusty' Russell
4 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
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.
11 #include <linux/config.h>
12 #include <linux/module.h>
13 #include <linux/netfilter.h>
15 #include <linux/ctype.h>
16 #include <net/checksum.h>
19 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
20 #include <linux/netfilter_ipv4/ip_conntrack_ftp.h>
21 #include <linux/moduleparam.h>
23 MODULE_LICENSE("GPL");
24 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
25 MODULE_DESCRIPTION("ftp connection tracking helper");
27 /* This is slow, but it's simple. --RR */
28 static char *ftp_buffer;
29 static DEFINE_SPINLOCK(ip_ftp_lock);
32 static int ports[MAX_PORTS];
34 module_param_array(ports, int, &ports_c, 0400);
37 module_param(loose, int, 0600);
39 unsigned int (*ip_nat_ftp_hook)(struct sk_buff **pskb,
40 enum ip_conntrack_info ctinfo,
41 enum ip_ct_ftp_type type,
42 unsigned int matchoff,
43 unsigned int matchlen,
44 struct ip_conntrack_expect *exp,
46 EXPORT_SYMBOL_GPL(ip_nat_ftp_hook);
51 #define DEBUGP(format, args...)
54 static int try_rfc959(const char *, size_t, u_int32_t [], char);
55 static int try_eprt(const char *, size_t, u_int32_t [], char);
56 static int try_epsv_response(const char *, size_t, u_int32_t [], char);
58 static struct ftp_search {
59 enum ip_conntrack_dir dir;
64 enum ip_ct_ftp_type ftptype;
65 int (*getnum)(const char *, size_t, u_int32_t[], char);
69 "PORT", sizeof("PORT") - 1, ' ', '\r',
75 "227 ", sizeof("227 ") - 1, '(', ')',
81 "EPRT", sizeof("EPRT") - 1, ' ', '\r',
87 "229 ", sizeof("229 ") - 1, '(', ')',
93 static int try_number(const char *data, size_t dlen, u_int32_t array[],
94 int array_size, char sep, char term)
98 memset(array, 0, sizeof(array[0])*array_size);
100 /* Keep data pointing at next char. */
101 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
102 if (*data >= '0' && *data <= '9') {
103 array[i] = array[i]*10 + *data - '0';
105 else if (*data == sep)
108 /* Unexpected character; true if it's the
109 terminator and we're finished. */
110 if (*data == term && i == array_size - 1)
113 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
118 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
123 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
124 static int try_rfc959(const char *data, size_t dlen, u_int32_t array[6],
127 return try_number(data, dlen, array, 6, ',', term);
130 /* Grab port: number up to delimiter */
131 static int get_port(const char *data, int start, size_t dlen, char delim,
137 for (i = start; i < dlen; i++) {
139 if (data[i] == delim) {
142 array[0] = port >> 8;
146 else if (data[i] >= '0' && data[i] <= '9')
147 port = port*10 + data[i] - '0';
148 else /* Some other crap */
154 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */
155 static int try_eprt(const char *data, size_t dlen, u_int32_t array[6],
161 /* First character is delimiter, then "1" for IPv4, then
163 if (dlen <= 3) return 0;
165 if (isdigit(delim) || delim < 33 || delim > 126
166 || data[1] != '1' || data[2] != delim)
169 DEBUGP("EPRT: Got |1|!\n");
170 /* Now we have IP address. */
171 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
175 DEBUGP("EPRT: Got IP address!\n");
176 /* Start offset includes initial "|1|", and trailing delimiter */
177 return get_port(data, 3 + length + 1, dlen, delim, array+4);
180 /* Returns 0, or length of numbers: |||6446| */
181 static int try_epsv_response(const char *data, size_t dlen, u_int32_t array[6],
186 /* Three delimiters. */
187 if (dlen <= 3) return 0;
189 if (isdigit(delim) || delim < 33 || delim > 126
190 || data[1] != delim || data[2] != delim)
193 return get_port(data, 3, dlen, delim, array+4);
196 /* Return 1 for match, 0 for accept, -1 for partial. */
197 static int find_pattern(const char *data, size_t dlen,
198 const char *pattern, size_t plen,
199 char skip, char term,
200 unsigned int *numoff,
201 unsigned int *numlen,
203 int (*getnum)(const char *, size_t, u_int32_t[], char))
207 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
212 /* Short packet: try for partial? */
213 if (strnicmp(data, pattern, dlen) == 0)
218 if (strnicmp(data, pattern, plen) != 0) {
222 DEBUGP("ftp: string mismatch\n");
223 for (i = 0; i < plen; i++) {
224 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
226 pattern[i], pattern[i]);
232 DEBUGP("Pattern matches!\n");
233 /* Now we've found the constant string, try to skip
234 to the 'skip' character */
235 for (i = plen; data[i] != skip; i++)
236 if (i == dlen - 1) return -1;
238 /* Skip over the last character */
241 DEBUGP("Skipped up to `%c'!\n", skip);
244 *numlen = getnum(data + i, dlen - i, array, term);
248 DEBUGP("Match succeeded!\n");
252 /* Look up to see if we're just after a \n. */
253 static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
257 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
258 if (info->seq_aft_nl[dir][i] == seq)
263 /* We don't update if it's older than what we have. */
264 static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir,
267 unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
269 /* Look for oldest: if we find exact match, we're done. */
270 for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
271 if (info->seq_aft_nl[dir][i] == nl_seq)
274 if (oldest == info->seq_aft_nl_num[dir]
275 || before(info->seq_aft_nl[dir][i], oldest))
279 if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
280 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
281 ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
282 } else if (oldest != NUM_SEQ_TO_REMEMBER) {
283 info->seq_aft_nl[dir][oldest] = nl_seq;
284 ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
288 static int help(struct sk_buff **pskb,
289 struct ip_conntrack *ct,
290 enum ip_conntrack_info ctinfo)
292 unsigned int dataoff, datalen;
293 struct tcphdr _tcph, *th;
296 u32 seq, array[6] = { 0 };
297 int dir = CTINFO2DIR(ctinfo);
298 unsigned int matchlen, matchoff;
299 struct ip_ct_ftp_master *ct_ftp_info = &ct->help.ct_ftp_info;
300 struct ip_conntrack_expect *exp;
302 int found = 0, ends_in_nl;
304 /* Until there's been traffic both ways, don't look in packets. */
305 if (ctinfo != IP_CT_ESTABLISHED
306 && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
307 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
311 th = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4,
312 sizeof(_tcph), &_tcph);
316 dataoff = (*pskb)->nh.iph->ihl*4 + th->doff*4;
318 if (dataoff >= (*pskb)->len) {
319 DEBUGP("ftp: pskblen = %u\n", (*pskb)->len);
322 datalen = (*pskb)->len - dataoff;
324 spin_lock_bh(&ip_ftp_lock);
325 fb_ptr = skb_header_pointer(*pskb, dataoff,
326 (*pskb)->len - dataoff, ftp_buffer);
327 BUG_ON(fb_ptr == NULL);
329 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
330 seq = ntohl(th->seq) + datalen;
332 /* Look up to see if we're just after a \n. */
333 if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
334 /* Now if this ends in \n, update ftp info. */
335 DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
336 ct_ftp_info->seq_aft_nl[0][dir]
337 old_seq_aft_nl_set ? "":"(UNSET) ", old_seq_aft_nl);
342 /* Initialize IP array to expected address (it's not mentioned
343 in EPSV responses) */
344 array[0] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 24) & 0xFF;
345 array[1] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 16) & 0xFF;
346 array[2] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 8) & 0xFF;
347 array[3] = ntohl(ct->tuplehash[dir].tuple.src.ip) & 0xFF;
349 for (i = 0; i < ARRAY_SIZE(search); i++) {
350 if (search[i].dir != dir) continue;
352 found = find_pattern(fb_ptr, (*pskb)->len - dataoff,
357 &matchoff, &matchlen,
363 /* We don't usually drop packets. After all, this is
364 connection tracking, not packet filtering.
365 However, it is necessary for accurate tracking in
368 printk("conntrack_ftp: partial %s %u+%u\n",
370 ntohl(th->seq), datalen);
373 } else if (found == 0) { /* No match */
378 DEBUGP("conntrack_ftp: match `%s' (%u bytes at %u)\n",
379 fb_ptr + matchoff, matchlen, ntohl(th->seq) + matchoff);
381 /* Allocate expectation which will be inserted */
382 exp = ip_conntrack_expect_alloc(ct);
388 /* We refer to the reverse direction ("!dir") tuples here,
389 * because we're expecting something in the other direction.
390 * Doesn't matter unless NAT is happening. */
391 exp->tuple.dst.ip = ct->tuplehash[!dir].tuple.dst.ip;
393 if (htonl((array[0] << 24) | (array[1] << 16) | (array[2] << 8) | array[3])
394 != ct->tuplehash[dir].tuple.src.ip) {
395 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
396 server: it really wants us to connect to a
397 different IP address. Simply don't record it for
399 DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n",
400 array[0], array[1], array[2], array[3],
401 NIPQUAD(ct->tuplehash[dir].tuple.src.ip));
403 /* Thanks to Cristiano Lincoln Mattos
404 <lincoln@cesar.org.br> for reporting this potential
405 problem (DMZ machines opening holes to internal
406 networks, or the packet filter itself). */
411 exp->tuple.dst.ip = htonl((array[0] << 24) | (array[1] << 16)
412 | (array[2] << 8) | array[3]);
415 exp->tuple.src.ip = ct->tuplehash[!dir].tuple.src.ip;
416 exp->tuple.dst.u.tcp.port = htons(array[4] << 8 | array[5]);
417 exp->tuple.src.u.tcp.port = 0; /* Don't care. */
418 exp->tuple.dst.protonum = IPPROTO_TCP;
419 exp->mask = ((struct ip_conntrack_tuple)
420 { { 0xFFFFFFFF, { 0 } },
421 { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFF }});
423 exp->expectfn = NULL;
426 /* Now, NAT might want to mangle the packet, and register the
427 * (possibly changed) expectation itself. */
429 ret = ip_nat_ftp_hook(pskb, ctinfo, search[i].ftptype,
430 matchoff, matchlen, exp, &seq);
432 /* Can't expect this? Best to drop packet now. */
433 if (ip_conntrack_expect_related(exp) != 0)
440 ip_conntrack_expect_put(exp);
443 /* Now if this ends in \n, update ftp info. Seq may have been
444 * adjusted by NAT code. */
446 update_nl_seq(seq, ct_ftp_info,dir, *pskb);
448 spin_unlock_bh(&ip_ftp_lock);
452 static struct ip_conntrack_helper ftp[MAX_PORTS];
453 static char ftp_names[MAX_PORTS][10];
455 /* Not __exit: called from init() */
456 static void fini(void)
459 for (i = 0; i < ports_c; i++) {
460 DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
462 ip_conntrack_helper_unregister(&ftp[i]);
468 static int __init init(void)
473 ftp_buffer = kmalloc(65536, GFP_KERNEL);
478 ports[ports_c++] = FTP_PORT;
480 for (i = 0; i < ports_c; i++) {
481 ftp[i].tuple.src.u.tcp.port = htons(ports[i]);
482 ftp[i].tuple.dst.protonum = IPPROTO_TCP;
483 ftp[i].mask.src.u.tcp.port = 0xFFFF;
484 ftp[i].mask.dst.protonum = 0xFF;
485 ftp[i].max_expected = 1;
486 ftp[i].timeout = 5 * 60; /* 5 minutes */
487 ftp[i].me = THIS_MODULE;
490 tmpname = &ftp_names[i][0];
491 if (ports[i] == FTP_PORT)
492 sprintf(tmpname, "ftp");
494 sprintf(tmpname, "ftp-%d", ports[i]);
495 ftp[i].name = tmpname;
497 DEBUGP("ip_ct_ftp: registering helper for port %d\n",
499 ret = ip_conntrack_helper_register(&ftp[i]);