1 /* FTP extension for connection tracking. */
3 /* (C) 1999-2001 Paul `Rusty' Russell
4 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
5 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
12 #include <linux/module.h>
13 #include <linux/moduleparam.h>
14 #include <linux/netfilter.h>
16 #include <linux/slab.h>
17 #include <linux/ipv6.h>
18 #include <linux/ctype.h>
19 #include <linux/inet.h>
20 #include <net/checksum.h>
23 #include <net/netfilter/nf_conntrack.h>
24 #include <net/netfilter/nf_conntrack_expect.h>
25 #include <net/netfilter/nf_conntrack_ecache.h>
26 #include <net/netfilter/nf_conntrack_helper.h>
27 #include <linux/netfilter/nf_conntrack_ftp.h>
29 MODULE_LICENSE("GPL");
30 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
31 MODULE_DESCRIPTION("ftp connection tracking helper");
32 MODULE_ALIAS("ip_conntrack_ftp");
33 MODULE_ALIAS_NFCT_HELPER("ftp");
35 /* This is slow, but it's simple. --RR */
36 static char *ftp_buffer;
38 static DEFINE_SPINLOCK(nf_ftp_lock);
41 static u_int16_t ports[MAX_PORTS];
42 static unsigned int ports_c;
43 module_param_array(ports, ushort, &ports_c, 0400);
46 module_param(loose, bool, 0600);
48 unsigned int (*nf_nat_ftp_hook)(struct sk_buff *skb,
49 enum ip_conntrack_info ctinfo,
50 enum nf_ct_ftp_type type,
52 unsigned int matchoff,
53 unsigned int matchlen,
54 struct nf_conntrack_expect *exp);
55 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
57 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
58 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
59 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
62 static struct ftp_search {
67 enum nf_ct_ftp_type ftptype;
68 int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
69 } search[IP_CT_DIR_MAX][2] = {
70 [IP_CT_DIR_ORIGINAL] = {
73 .plen = sizeof("PORT") - 1,
76 .ftptype = NF_CT_FTP_PORT,
81 .plen = sizeof("EPRT") - 1,
84 .ftptype = NF_CT_FTP_EPRT,
91 .plen = sizeof("227 ") - 1,
94 .ftptype = NF_CT_FTP_PASV,
99 .plen = sizeof("229 ") - 1,
102 .ftptype = NF_CT_FTP_EPSV,
103 .getnum = try_epsv_response,
109 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
112 int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
114 return (int)(end - src);
118 static int try_number(const char *data, size_t dlen, u_int32_t array[],
119 int array_size, char sep, char term)
123 memset(array, 0, sizeof(array[0])*array_size);
125 /* Keep data pointing at next char. */
126 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
127 if (*data >= '0' && *data <= '9') {
128 array[i] = array[i]*10 + *data - '0';
130 else if (*data == sep)
133 /* Unexpected character; true if it's the
134 terminator and we're finished. */
135 if (*data == term && i == array_size - 1)
138 pr_debug("Char %u (got %u nums) `%u' unexpected\n",
143 pr_debug("Failed to fill %u numbers separated by %c\n",
148 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
149 static int try_rfc959(const char *data, size_t dlen,
150 struct nf_conntrack_man *cmd, char term)
155 length = try_number(data, dlen, array, 6, ',', term);
159 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
160 (array[2] << 8) | array[3]);
161 cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
165 /* Grab port: number up to delimiter */
166 static int get_port(const char *data, int start, size_t dlen, char delim,
169 u_int16_t tmp_port = 0;
172 for (i = start; i < dlen; i++) {
174 if (data[i] == delim) {
177 *port = htons(tmp_port);
178 pr_debug("get_port: return %d\n", tmp_port);
181 else if (data[i] >= '0' && data[i] <= '9')
182 tmp_port = tmp_port*10 + data[i] - '0';
183 else { /* Some other crap */
184 pr_debug("get_port: invalid char.\n");
191 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
192 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
198 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
199 then delimiter again. */
201 pr_debug("EPRT: too short\n");
205 if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
206 pr_debug("try_eprt: invalid delimitter.\n");
210 if ((cmd->l3num == PF_INET && data[1] != '1') ||
211 (cmd->l3num == PF_INET6 && data[1] != '2')) {
212 pr_debug("EPRT: invalid protocol number.\n");
216 pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
218 if (data[1] == '1') {
221 /* Now we have IP address. */
222 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
224 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
225 | (array[2] << 8) | array[3]);
227 /* Now we have IPv6 address. */
228 length = get_ipv6_addr(data + 3, dlen - 3,
229 (struct in6_addr *)cmd->u3.ip6, delim);
234 pr_debug("EPRT: Got IP address!\n");
235 /* Start offset includes initial "|1|", and trailing delimiter */
236 return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
239 /* Returns 0, or length of numbers: |||6446| */
240 static int try_epsv_response(const char *data, size_t dlen,
241 struct nf_conntrack_man *cmd, char term)
245 /* Three delimiters. */
246 if (dlen <= 3) return 0;
248 if (isdigit(delim) || delim < 33 || delim > 126 ||
249 data[1] != delim || data[2] != delim)
252 return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
255 /* Return 1 for match, 0 for accept, -1 for partial. */
256 static int find_pattern(const char *data, size_t dlen,
257 const char *pattern, size_t plen,
258 char skip, char term,
259 unsigned int *numoff,
260 unsigned int *numlen,
261 struct nf_conntrack_man *cmd,
262 int (*getnum)(const char *, size_t,
263 struct nf_conntrack_man *, char))
267 pr_debug("find_pattern `%s': dlen = %Zu\n", pattern, dlen);
272 /* Short packet: try for partial? */
273 if (strnicmp(data, pattern, dlen) == 0)
278 if (strnicmp(data, pattern, plen) != 0) {
282 pr_debug("ftp: string mismatch\n");
283 for (i = 0; i < plen; i++) {
284 pr_debug("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
286 pattern[i], pattern[i]);
292 pr_debug("Pattern matches!\n");
293 /* Now we've found the constant string, try to skip
294 to the 'skip' character */
295 for (i = plen; data[i] != skip; i++)
296 if (i == dlen - 1) return -1;
298 /* Skip over the last character */
301 pr_debug("Skipped up to `%c'!\n", skip);
304 *numlen = getnum(data + i, dlen - i, cmd, term);
308 pr_debug("Match succeeded!\n");
312 /* Look up to see if we're just after a \n. */
313 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
317 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
318 if (info->seq_aft_nl[dir][i] == seq)
323 /* We don't update if it's older than what we have. */
324 static void update_nl_seq(struct nf_conn *ct, u32 nl_seq,
325 struct nf_ct_ftp_master *info, int dir,
328 unsigned int i, oldest;
330 /* Look for oldest: if we find exact match, we're done. */
331 for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
332 if (info->seq_aft_nl[dir][i] == nl_seq)
336 if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
337 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
339 if (before(info->seq_aft_nl[dir][0], info->seq_aft_nl[dir][1]))
344 if (after(nl_seq, info->seq_aft_nl[dir][oldest]))
345 info->seq_aft_nl[dir][oldest] = nl_seq;
349 static int help(struct sk_buff *skb,
350 unsigned int protoff,
352 enum ip_conntrack_info ctinfo)
354 unsigned int dataoff, datalen;
355 const struct tcphdr *th;
360 int dir = CTINFO2DIR(ctinfo);
361 unsigned int uninitialized_var(matchlen), uninitialized_var(matchoff);
362 struct nf_ct_ftp_master *ct_ftp_info = nfct_help_data(ct);
363 struct nf_conntrack_expect *exp;
364 union nf_inet_addr *daddr;
365 struct nf_conntrack_man cmd = {};
367 int found = 0, ends_in_nl;
368 typeof(nf_nat_ftp_hook) nf_nat_ftp;
370 /* Until there's been traffic both ways, don't look in packets. */
371 if (ctinfo != IP_CT_ESTABLISHED &&
372 ctinfo != IP_CT_ESTABLISHED_REPLY) {
373 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
377 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
381 dataoff = protoff + th->doff * 4;
383 if (dataoff >= skb->len) {
384 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
388 datalen = skb->len - dataoff;
390 spin_lock_bh(&nf_ftp_lock);
391 fb_ptr = skb_header_pointer(skb, dataoff, datalen, ftp_buffer);
392 BUG_ON(fb_ptr == NULL);
394 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
395 seq = ntohl(th->seq) + datalen;
397 /* Look up to see if we're just after a \n. */
398 if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
399 /* We're picking up this, clear flags and let it continue */
400 if (unlikely(ct_ftp_info->flags[dir] & NF_CT_FTP_SEQ_PICKUP)) {
401 ct_ftp_info->flags[dir] ^= NF_CT_FTP_SEQ_PICKUP;
405 /* Now if this ends in \n, update ftp info. */
406 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
407 ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
408 ct_ftp_info->seq_aft_nl[dir][0],
409 ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
410 ct_ftp_info->seq_aft_nl[dir][1]);
416 /* Initialize IP/IPv6 addr to expected address (it's not mentioned
417 in EPSV responses) */
418 cmd.l3num = nf_ct_l3num(ct);
419 memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
422 for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
423 found = find_pattern(fb_ptr, datalen,
424 search[dir][i].pattern,
428 &matchoff, &matchlen,
430 search[dir][i].getnum);
434 /* We don't usually drop packets. After all, this is
435 connection tracking, not packet filtering.
436 However, it is necessary for accurate tracking in
438 nf_ct_helper_log(skb, ct, "partial matching of `%s'",
439 search[dir][i].pattern);
442 } else if (found == 0) { /* No match */
447 pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
448 matchlen, fb_ptr + matchoff,
449 matchlen, ntohl(th->seq) + matchoff);
451 exp = nf_ct_expect_alloc(ct);
453 nf_ct_helper_log(skb, ct, "cannot alloc expectation");
458 /* We refer to the reverse direction ("!dir") tuples here,
459 * because we're expecting something in the other direction.
460 * Doesn't matter unless NAT is happening. */
461 daddr = &ct->tuplehash[!dir].tuple.dst.u3;
463 /* Update the ftp info */
464 if ((cmd.l3num == nf_ct_l3num(ct)) &&
465 memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
466 sizeof(cmd.u3.all))) {
467 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
468 server: it really wants us to connect to a
469 different IP address. Simply don't record it for
471 if (cmd.l3num == PF_INET) {
472 pr_debug("conntrack_ftp: NOT RECORDING: %pI4 != %pI4\n",
474 &ct->tuplehash[dir].tuple.src.u3.ip);
476 pr_debug("conntrack_ftp: NOT RECORDING: %pI6 != %pI6\n",
478 ct->tuplehash[dir].tuple.src.u3.ip6);
481 /* Thanks to Cristiano Lincoln Mattos
482 <lincoln@cesar.org.br> for reporting this potential
483 problem (DMZ machines opening holes to internal
484 networks, or the packet filter itself). */
492 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, cmd.l3num,
493 &ct->tuplehash[!dir].tuple.src.u3, daddr,
494 IPPROTO_TCP, NULL, &cmd.u.tcp.port);
496 /* Now, NAT might want to mangle the packet, and register the
497 * (possibly changed) expectation itself. */
498 nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
499 if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
500 ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
501 protoff, matchoff, matchlen, exp);
503 /* Can't expect this? Best to drop packet now. */
504 if (nf_ct_expect_related(exp) != 0) {
505 nf_ct_helper_log(skb, ct, "cannot add expectation");
512 nf_ct_expect_put(exp);
515 /* Now if this ends in \n, update ftp info. Seq may have been
516 * adjusted by NAT code. */
518 update_nl_seq(ct, seq, ct_ftp_info, dir, skb);
520 spin_unlock_bh(&nf_ftp_lock);
524 static int nf_ct_ftp_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
526 struct nf_ct_ftp_master *ftp = nfct_help_data(ct);
528 /* This conntrack has been injected from user-space, always pick up
529 * sequence tracking. Otherwise, the first FTP command after the
532 ftp->flags[IP_CT_DIR_ORIGINAL] |= NF_CT_FTP_SEQ_PICKUP;
533 ftp->flags[IP_CT_DIR_REPLY] |= NF_CT_FTP_SEQ_PICKUP;
537 static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
539 static const struct nf_conntrack_expect_policy ftp_exp_policy = {
544 /* don't make this __exit, since it's called from __init ! */
545 static void nf_conntrack_ftp_fini(void)
548 for (i = 0; i < ports_c; i++) {
549 for (j = 0; j < 2; j++) {
550 if (ftp[i][j].me == NULL)
553 pr_debug("nf_ct_ftp: unregistering helper for pf: %d "
555 ftp[i][j].tuple.src.l3num, ports[i]);
556 nf_conntrack_helper_unregister(&ftp[i][j]);
563 static int __init nf_conntrack_ftp_init(void)
565 int i, j = -1, ret = 0;
567 ftp_buffer = kmalloc(65536, GFP_KERNEL);
572 ports[ports_c++] = FTP_PORT;
574 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
575 are tracked or not - YK */
576 for (i = 0; i < ports_c; i++) {
577 ftp[i][0].tuple.src.l3num = PF_INET;
578 ftp[i][1].tuple.src.l3num = PF_INET6;
579 for (j = 0; j < 2; j++) {
580 ftp[i][j].data_len = sizeof(struct nf_ct_ftp_master);
581 ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
582 ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
583 ftp[i][j].expect_policy = &ftp_exp_policy;
584 ftp[i][j].me = THIS_MODULE;
585 ftp[i][j].help = help;
586 ftp[i][j].from_nlattr = nf_ct_ftp_from_nlattr;
587 if (ports[i] == FTP_PORT)
588 sprintf(ftp[i][j].name, "ftp");
590 sprintf(ftp[i][j].name, "ftp-%d", ports[i]);
592 pr_debug("nf_ct_ftp: registering helper for pf: %d "
594 ftp[i][j].tuple.src.l3num, ports[i]);
595 ret = nf_conntrack_helper_register(&ftp[i][j]);
597 printk(KERN_ERR "nf_ct_ftp: failed to register"
598 " helper for pf: %d port: %d\n",
599 ftp[i][j].tuple.src.l3num, ports[i]);
600 nf_conntrack_ftp_fini();
609 module_init(nf_conntrack_ftp_init);
610 module_exit(nf_conntrack_ftp_fini);