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[65536];
30 static DEFINE_SPINLOCK(ip_ftp_lock);
33 static int ports[MAX_PORTS];
35 module_param_array(ports, int, &ports_c, 0400);
38 module_param(loose, int, 0600);
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,
47 EXPORT_SYMBOL_GPL(ip_nat_ftp_hook);
52 #define DEBUGP(format, args...)
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);
59 static struct ftp_search {
60 enum ip_conntrack_dir dir;
65 enum ip_ct_ftp_type ftptype;
66 int (*getnum)(const char *, size_t, u_int32_t[], char);
70 "PORT", sizeof("PORT") - 1, ' ', '\r',
76 "227 ", sizeof("227 ") - 1, '(', ')',
82 "EPRT", sizeof("EPRT") - 1, ' ', '\r',
88 "229 ", sizeof("229 ") - 1, '(', ')',
94 static int try_number(const char *data, size_t dlen, u_int32_t array[],
95 int array_size, char sep, char term)
99 memset(array, 0, sizeof(array[0])*array_size);
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';
106 else if (*data == sep)
109 /* Unexpected character; true if it's the
110 terminator and we're finished. */
111 if (*data == term && i == array_size - 1)
114 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
119 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
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],
128 return try_number(data, dlen, array, 6, ',', term);
131 /* Grab port: number up to delimiter */
132 static int get_port(const char *data, int start, size_t dlen, char delim,
138 for (i = start; i < dlen; i++) {
140 if (data[i] == delim) {
143 array[0] = port >> 8;
147 else if (data[i] >= '0' && data[i] <= '9')
148 port = port*10 + data[i] - '0';
149 else /* Some other crap */
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],
162 /* First character is delimiter, then "1" for IPv4, then
164 if (dlen <= 3) return 0;
166 if (isdigit(delim) || delim < 33 || delim > 126
167 || data[1] != '1' || data[2] != delim)
170 DEBUGP("EPRT: Got |1|!\n");
171 /* Now we have IP address. */
172 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
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);
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],
187 /* Three delimiters. */
188 if (dlen <= 3) return 0;
190 if (isdigit(delim) || delim < 33 || delim > 126
191 || data[1] != delim || data[2] != delim)
194 return get_port(data, 3, dlen, delim, array+4);
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,
204 int (*getnum)(const char *, size_t, u_int32_t[], char))
208 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
213 /* Short packet: try for partial? */
214 if (strnicmp(data, pattern, dlen) == 0)
219 if (strnicmp(data, pattern, plen) != 0) {
223 DEBUGP("ftp: string mismatch\n");
224 for (i = 0; i < plen; i++) {
225 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
227 pattern[i], pattern[i]);
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;
239 /* Skip over the last character */
242 DEBUGP("Skipped up to `%c'!\n", skip);
245 *numlen = getnum(data + i, dlen - i, array, term);
249 DEBUGP("Match succeeded!\n");
253 /* Look up to see if we're just after a \n. */
254 static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
258 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
259 if (info->seq_aft_nl[dir][i] == seq)
264 /* We don't update if it's older than what we have. */
265 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 ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
283 } else if (oldest != NUM_SEQ_TO_REMEMBER) {
284 info->seq_aft_nl[dir][oldest] = nl_seq;
285 ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
289 static int help(struct sk_buff **pskb,
290 struct ip_conntrack *ct,
291 enum ip_conntrack_info ctinfo)
293 unsigned int dataoff, datalen;
294 struct tcphdr _tcph, *th;
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;
303 int found = 0, ends_in_nl;
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);
312 th = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4,
313 sizeof(_tcph), &_tcph);
317 dataoff = (*pskb)->nh.iph->ihl*4 + th->doff*4;
319 if (dataoff >= (*pskb)->len) {
320 DEBUGP("ftp: pskblen = %u\n", (*pskb)->len);
323 datalen = (*pskb)->len - dataoff;
325 spin_lock_bh(&ip_ftp_lock);
326 fb_ptr = skb_header_pointer(*pskb, dataoff,
327 (*pskb)->len - dataoff, ftp_buffer);
328 BUG_ON(fb_ptr == NULL);
330 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
331 seq = ntohl(th->seq) + datalen;
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);
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;
350 for (i = 0; i < ARRAY_SIZE(search); i++) {
351 if (search[i].dir != dir) continue;
353 found = find_pattern(fb_ptr, (*pskb)->len - dataoff,
358 &matchoff, &matchlen,
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
369 printk("conntrack_ftp: partial %s %u+%u\n",
371 ntohl(th->seq), datalen);
374 } else if (found == 0) { /* No match */
379 DEBUGP("conntrack_ftp: match `%s' (%u bytes at %u)\n",
380 fb_ptr + matchoff, matchlen, ntohl(th->seq) + matchoff);
382 /* Allocate expectation which will be inserted */
383 exp = ip_conntrack_expect_alloc(ct);
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;
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
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));
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). */
412 exp->tuple.dst.ip = htonl((array[0] << 24) | (array[1] << 16)
413 | (array[2] << 8) | array[3]);
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 }});
424 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]);
466 static int __init init(void)
472 ports[ports_c++] = FTP_PORT;
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;
484 tmpname = &ftp_names[i][0];
485 if (ports[i] == FTP_PORT)
486 sprintf(tmpname, "ftp");
488 sprintf(tmpname, "ftp-%d", ports[i]);
489 ftp[i].name = tmpname;
491 DEBUGP("ip_ct_ftp: registering helper for port %d\n",
493 ret = ip_conntrack_helper_register(&ftp[i]);