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/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>
24 MODULE_LICENSE("GPL");
25 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
26 MODULE_DESCRIPTION("ftp connection tracking helper");
28 /* This is slow, but it's simple. --RR */
29 static char ftp_buffer[65536];
31 static DECLARE_LOCK(ip_ftp_lock);
34 static int ports[MAX_PORTS];
36 module_param_array(ports, int, &ports_c, 0400);
39 module_param(loose, int, 0600);
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,
48 EXPORT_SYMBOL_GPL(ip_nat_ftp_hook);
53 #define DEBUGP(format, args...)
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);
60 static struct ftp_search {
61 enum ip_conntrack_dir dir;
66 enum ip_ct_ftp_type ftptype;
67 int (*getnum)(const char *, size_t, u_int32_t[], char);
71 "PORT", sizeof("PORT") - 1, ' ', '\r',
77 "227 ", sizeof("227 ") - 1, '(', ')',
83 "EPRT", sizeof("EPRT") - 1, ' ', '\r',
89 "229 ", sizeof("229 ") - 1, '(', ')',
95 static int try_number(const char *data, size_t dlen, u_int32_t array[],
96 int array_size, char sep, char term)
100 memset(array, 0, sizeof(array[0])*array_size);
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';
107 else if (*data == sep)
110 /* Unexpected character; true if it's the
111 terminator and we're finished. */
112 if (*data == term && i == array_size - 1)
115 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
120 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
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],
129 return try_number(data, dlen, array, 6, ',', term);
132 /* Grab port: number up to delimiter */
133 static int get_port(const char *data, int start, size_t dlen, char delim,
139 for (i = start; i < dlen; i++) {
141 if (data[i] == delim) {
144 array[0] = port >> 8;
148 else if (data[i] >= '0' && data[i] <= '9')
149 port = port*10 + data[i] - '0';
150 else /* Some other crap */
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],
163 /* First character is delimiter, then "1" for IPv4, then
165 if (dlen <= 3) return 0;
167 if (isdigit(delim) || delim < 33 || delim > 126
168 || data[1] != '1' || data[2] != delim)
171 DEBUGP("EPRT: Got |1|!\n");
172 /* Now we have IP address. */
173 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
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);
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],
188 /* Three delimiters. */
189 if (dlen <= 3) return 0;
191 if (isdigit(delim) || delim < 33 || delim > 126
192 || data[1] != delim || data[2] != delim)
195 return get_port(data, 3, dlen, delim, array+4);
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,
205 int (*getnum)(const char *, size_t, u_int32_t[], char))
209 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
214 /* Short packet: try for partial? */
215 if (strnicmp(data, pattern, dlen) == 0)
220 if (strnicmp(data, pattern, plen) != 0) {
224 DEBUGP("ftp: string mismatch\n");
225 for (i = 0; i < plen; i++) {
226 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
228 pattern[i], pattern[i]);
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;
240 /* Skip over the last character */
243 DEBUGP("Skipped up to `%c'!\n", skip);
246 *numlen = getnum(data + i, dlen - i, array, term);
250 DEBUGP("Match succeeded!\n");
254 /* Look up to see if we're just after a \n. */
255 static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
259 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
260 if (info->seq_aft_nl[dir][i] == seq)
265 /* We don't update if it's older than what we have. */
266 static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir)
268 unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
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)
275 if (oldest == info->seq_aft_nl_num[dir]
276 || before(info->seq_aft_nl[dir][i], oldest))
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;
286 static int help(struct sk_buff **pskb,
287 struct ip_conntrack *ct,
288 enum ip_conntrack_info ctinfo)
290 unsigned int dataoff, datalen;
291 struct tcphdr _tcph, *th;
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;
300 int found = 0, ends_in_nl;
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);
309 th = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4,
310 sizeof(_tcph), &_tcph);
314 dataoff = (*pskb)->nh.iph->ihl*4 + th->doff*4;
316 if (dataoff >= (*pskb)->len) {
317 DEBUGP("ftp: pskblen = %u\n", (*pskb)->len);
320 datalen = (*pskb)->len - dataoff;
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);
327 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
328 seq = ntohl(th->seq) + datalen;
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);
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;
347 for (i = 0; i < ARRAY_SIZE(search); i++) {
348 if (search[i].dir != dir) continue;
350 found = find_pattern(fb_ptr, (*pskb)->len - dataoff,
355 &matchoff, &matchlen,
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
366 printk("conntrack_ftp: partial %s %u+%u\n",
368 ntohl(th->seq), datalen);
371 } else if (found == 0) { /* No match */
376 DEBUGP("conntrack_ftp: match `%s' (%u bytes at %u)\n",
377 fb_ptr + matchoff, matchlen, ntohl(th->seq) + matchoff);
379 /* Allocate expectation which will be inserted */
380 exp = ip_conntrack_expect_alloc();
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;
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
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));
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). */
407 ip_conntrack_expect_free(exp);
410 exp->tuple.dst.ip = htonl((array[0] << 24) | (array[1] << 16)
411 | (array[2] << 8) | array[3]);
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 }});
422 exp->expectfn = NULL;
425 /* Now, NAT might want to mangle the packet, and register the
426 * (possibly changed) expectation itself. */
428 ret = ip_nat_ftp_hook(pskb, ctinfo, search[i].ftptype,
429 matchoff, matchlen, exp, &seq);
431 /* Can't expect this? Best to drop packet now. */
432 if (ip_conntrack_expect_related(exp) != 0) {
433 ip_conntrack_expect_free(exp);
440 /* Now if this ends in \n, update ftp info. Seq may have been
441 * adjusted by NAT code. */
443 update_nl_seq(seq, ct_ftp_info,dir);
445 UNLOCK_BH(&ip_ftp_lock);
449 static struct ip_conntrack_helper ftp[MAX_PORTS];
450 static char ftp_names[MAX_PORTS][10];
452 /* Not __exit: called from init() */
453 static void fini(void)
456 for (i = 0; i < ports_c; i++) {
457 DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
459 ip_conntrack_helper_unregister(&ftp[i]);
463 static int __init init(void)
469 ports[ports_c++] = FTP_PORT;
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;
481 tmpname = &ftp_names[i][0];
482 if (ports[i] == FTP_PORT)
483 sprintf(tmpname, "ftp");
485 sprintf(tmpname, "ftp-%d", ports[i]);
486 ftp[i].name = tmpname;
488 DEBUGP("ip_ct_ftp: registering helper for port %d\n",
490 ret = ip_conntrack_helper_register(&ftp[i]);