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,
51 unsigned int matchoff,
52 unsigned int matchlen,
53 struct nf_conntrack_expect *exp);
54 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
56 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
57 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
58 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
61 static struct ftp_search {
66 enum nf_ct_ftp_type ftptype;
67 int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
68 } search[IP_CT_DIR_MAX][2] = {
69 [IP_CT_DIR_ORIGINAL] = {
72 .plen = sizeof("PORT") - 1,
75 .ftptype = NF_CT_FTP_PORT,
80 .plen = sizeof("EPRT") - 1,
83 .ftptype = NF_CT_FTP_EPRT,
90 .plen = sizeof("227 ") - 1,
93 .ftptype = NF_CT_FTP_PASV,
98 .plen = sizeof("229 ") - 1,
101 .ftptype = NF_CT_FTP_EPSV,
102 .getnum = try_epsv_response,
108 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
111 int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
113 return (int)(end - src);
117 static int try_number(const char *data, size_t dlen, u_int32_t array[],
118 int array_size, char sep, char term)
122 memset(array, 0, sizeof(array[0])*array_size);
124 /* Keep data pointing at next char. */
125 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
126 if (*data >= '0' && *data <= '9') {
127 array[i] = array[i]*10 + *data - '0';
129 else if (*data == sep)
132 /* Unexpected character; true if it's the
133 terminator and we're finished. */
134 if (*data == term && i == array_size - 1)
137 pr_debug("Char %u (got %u nums) `%u' unexpected\n",
142 pr_debug("Failed to fill %u numbers separated by %c\n",
147 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
148 static int try_rfc959(const char *data, size_t dlen,
149 struct nf_conntrack_man *cmd, char term)
154 length = try_number(data, dlen, array, 6, ',', term);
158 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
159 (array[2] << 8) | array[3]);
160 cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
164 /* Grab port: number up to delimiter */
165 static int get_port(const char *data, int start, size_t dlen, char delim,
168 u_int16_t tmp_port = 0;
171 for (i = start; i < dlen; i++) {
173 if (data[i] == delim) {
176 *port = htons(tmp_port);
177 pr_debug("get_port: return %d\n", tmp_port);
180 else if (data[i] >= '0' && data[i] <= '9')
181 tmp_port = tmp_port*10 + data[i] - '0';
182 else { /* Some other crap */
183 pr_debug("get_port: invalid char.\n");
190 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
191 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
197 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
198 then delimiter again. */
200 pr_debug("EPRT: too short\n");
204 if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
205 pr_debug("try_eprt: invalid delimitter.\n");
209 if ((cmd->l3num == PF_INET && data[1] != '1') ||
210 (cmd->l3num == PF_INET6 && data[1] != '2')) {
211 pr_debug("EPRT: invalid protocol number.\n");
215 pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
217 if (data[1] == '1') {
220 /* Now we have IP address. */
221 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
223 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
224 | (array[2] << 8) | array[3]);
226 /* Now we have IPv6 address. */
227 length = get_ipv6_addr(data + 3, dlen - 3,
228 (struct in6_addr *)cmd->u3.ip6, delim);
233 pr_debug("EPRT: Got IP address!\n");
234 /* Start offset includes initial "|1|", and trailing delimiter */
235 return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
238 /* Returns 0, or length of numbers: |||6446| */
239 static int try_epsv_response(const char *data, size_t dlen,
240 struct nf_conntrack_man *cmd, char term)
244 /* Three delimiters. */
245 if (dlen <= 3) return 0;
247 if (isdigit(delim) || delim < 33 || delim > 126 ||
248 data[1] != delim || data[2] != delim)
251 return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
254 /* Return 1 for match, 0 for accept, -1 for partial. */
255 static int find_pattern(const char *data, size_t dlen,
256 const char *pattern, size_t plen,
257 char skip, char term,
258 unsigned int *numoff,
259 unsigned int *numlen,
260 struct nf_conntrack_man *cmd,
261 int (*getnum)(const char *, size_t,
262 struct nf_conntrack_man *, char))
266 pr_debug("find_pattern `%s': dlen = %Zu\n", pattern, dlen);
271 /* Short packet: try for partial? */
272 if (strnicmp(data, pattern, dlen) == 0)
277 if (strnicmp(data, pattern, plen) != 0) {
281 pr_debug("ftp: string mismatch\n");
282 for (i = 0; i < plen; i++) {
283 pr_debug("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
285 pattern[i], pattern[i]);
291 pr_debug("Pattern matches!\n");
292 /* Now we've found the constant string, try to skip
293 to the 'skip' character */
294 for (i = plen; data[i] != skip; i++)
295 if (i == dlen - 1) return -1;
297 /* Skip over the last character */
300 pr_debug("Skipped up to `%c'!\n", skip);
303 *numlen = getnum(data + i, dlen - i, cmd, term);
307 pr_debug("Match succeeded!\n");
311 /* Look up to see if we're just after a \n. */
312 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
316 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
317 if (info->seq_aft_nl[dir][i] == seq)
322 /* We don't update if it's older than what we have. */
323 static void update_nl_seq(struct nf_conn *ct, u32 nl_seq,
324 struct nf_ct_ftp_master *info, int dir,
327 unsigned int i, oldest;
329 /* Look for oldest: if we find exact match, we're done. */
330 for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
331 if (info->seq_aft_nl[dir][i] == nl_seq)
335 if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
336 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
338 if (before(info->seq_aft_nl[dir][0], info->seq_aft_nl[dir][1]))
343 if (after(nl_seq, info->seq_aft_nl[dir][oldest]))
344 info->seq_aft_nl[dir][oldest] = nl_seq;
348 static int help(struct sk_buff *skb,
349 unsigned int protoff,
351 enum ip_conntrack_info ctinfo)
353 unsigned int dataoff, datalen;
354 const struct tcphdr *th;
359 int dir = CTINFO2DIR(ctinfo);
360 unsigned int uninitialized_var(matchlen), uninitialized_var(matchoff);
361 struct nf_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
362 struct nf_conntrack_expect *exp;
363 union nf_inet_addr *daddr;
364 struct nf_conntrack_man cmd = {};
366 int found = 0, ends_in_nl;
367 typeof(nf_nat_ftp_hook) nf_nat_ftp;
369 /* Until there's been traffic both ways, don't look in packets. */
370 if (ctinfo != IP_CT_ESTABLISHED &&
371 ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) {
372 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
376 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
380 dataoff = protoff + th->doff * 4;
382 if (dataoff >= skb->len) {
383 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
387 datalen = skb->len - dataoff;
389 spin_lock_bh(&nf_ftp_lock);
390 fb_ptr = skb_header_pointer(skb, dataoff, datalen, ftp_buffer);
391 BUG_ON(fb_ptr == NULL);
393 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
394 seq = ntohl(th->seq) + datalen;
396 /* Look up to see if we're just after a \n. */
397 if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
398 /* Now if this ends in \n, update ftp info. */
399 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
400 ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
401 ct_ftp_info->seq_aft_nl[dir][0],
402 ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
403 ct_ftp_info->seq_aft_nl[dir][1]);
408 /* Initialize IP/IPv6 addr to expected address (it's not mentioned
409 in EPSV responses) */
410 cmd.l3num = nf_ct_l3num(ct);
411 memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
414 for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
415 found = find_pattern(fb_ptr, datalen,
416 search[dir][i].pattern,
420 &matchoff, &matchlen,
422 search[dir][i].getnum);
426 /* We don't usually drop packets. After all, this is
427 connection tracking, not packet filtering.
428 However, it is necessary for accurate tracking in
430 pr_debug("conntrack_ftp: partial %s %u+%u\n",
431 search[dir][i].pattern, ntohl(th->seq), datalen);
434 } else if (found == 0) { /* No match */
439 pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
440 matchlen, fb_ptr + matchoff,
441 matchlen, ntohl(th->seq) + matchoff);
443 exp = nf_ct_expect_alloc(ct);
449 /* We refer to the reverse direction ("!dir") tuples here,
450 * because we're expecting something in the other direction.
451 * Doesn't matter unless NAT is happening. */
452 daddr = &ct->tuplehash[!dir].tuple.dst.u3;
454 /* Update the ftp info */
455 if ((cmd.l3num == nf_ct_l3num(ct)) &&
456 memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
457 sizeof(cmd.u3.all))) {
458 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
459 server: it really wants us to connect to a
460 different IP address. Simply don't record it for
462 if (cmd.l3num == PF_INET) {
463 pr_debug("conntrack_ftp: NOT RECORDING: %pI4 != %pI4\n",
465 &ct->tuplehash[dir].tuple.src.u3.ip);
467 pr_debug("conntrack_ftp: NOT RECORDING: %pI6 != %pI6\n",
469 ct->tuplehash[dir].tuple.src.u3.ip6);
472 /* Thanks to Cristiano Lincoln Mattos
473 <lincoln@cesar.org.br> for reporting this potential
474 problem (DMZ machines opening holes to internal
475 networks, or the packet filter itself). */
483 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, cmd.l3num,
484 &ct->tuplehash[!dir].tuple.src.u3, daddr,
485 IPPROTO_TCP, NULL, &cmd.u.tcp.port);
487 /* Now, NAT might want to mangle the packet, and register the
488 * (possibly changed) expectation itself. */
489 nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
490 if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
491 ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
492 matchoff, matchlen, exp);
494 /* Can't expect this? Best to drop packet now. */
495 if (nf_ct_expect_related(exp) != 0)
502 nf_ct_expect_put(exp);
505 /* Now if this ends in \n, update ftp info. Seq may have been
506 * adjusted by NAT code. */
508 update_nl_seq(ct, seq, ct_ftp_info, dir, skb);
510 spin_unlock_bh(&nf_ftp_lock);
514 static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
515 static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")] __read_mostly;
517 static const struct nf_conntrack_expect_policy ftp_exp_policy = {
522 /* don't make this __exit, since it's called from __init ! */
523 static void nf_conntrack_ftp_fini(void)
526 for (i = 0; i < ports_c; i++) {
527 for (j = 0; j < 2; j++) {
528 if (ftp[i][j].me == NULL)
531 pr_debug("nf_ct_ftp: unregistering helper for pf: %d "
533 ftp[i][j].tuple.src.l3num, ports[i]);
534 nf_conntrack_helper_unregister(&ftp[i][j]);
541 static int __init nf_conntrack_ftp_init(void)
543 int i, j = -1, ret = 0;
546 ftp_buffer = kmalloc(65536, GFP_KERNEL);
551 ports[ports_c++] = FTP_PORT;
553 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
554 are tracked or not - YK */
555 for (i = 0; i < ports_c; i++) {
556 ftp[i][0].tuple.src.l3num = PF_INET;
557 ftp[i][1].tuple.src.l3num = PF_INET6;
558 for (j = 0; j < 2; j++) {
559 ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
560 ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
561 ftp[i][j].expect_policy = &ftp_exp_policy;
562 ftp[i][j].me = THIS_MODULE;
563 ftp[i][j].help = help;
564 tmpname = &ftp_names[i][j][0];
565 if (ports[i] == FTP_PORT)
566 sprintf(tmpname, "ftp");
568 sprintf(tmpname, "ftp-%d", ports[i]);
569 ftp[i][j].name = tmpname;
571 pr_debug("nf_ct_ftp: registering helper for pf: %d "
573 ftp[i][j].tuple.src.l3num, ports[i]);
574 ret = nf_conntrack_helper_register(&ftp[i][j]);
576 printk(KERN_ERR "nf_ct_ftp: failed to register"
577 " helper for pf: %d port: %d\n",
578 ftp[i][j].tuple.src.l3num, ports[i]);
579 nf_conntrack_ftp_fini();
588 module_init(nf_conntrack_ftp_init);
589 module_exit(nf_conntrack_ftp_fini);