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.
11 * 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
12 * - enable working with Layer 3 protocol independent connection tracking.
13 * - track EPRT and EPSV commands with IPv6 address.
15 * Derived from net/ipv4/netfilter/ip_conntrack_ftp.c
18 #include <linux/config.h>
19 #include <linux/module.h>
20 #include <linux/moduleparam.h>
21 #include <linux/netfilter.h>
23 #include <linux/ipv6.h>
24 #include <linux/ctype.h>
25 #include <net/checksum.h>
28 #include <net/netfilter/nf_conntrack.h>
29 #include <net/netfilter/nf_conntrack_helper.h>
30 #include <linux/netfilter/nf_conntrack_ftp.h>
32 MODULE_LICENSE("GPL");
33 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
34 MODULE_DESCRIPTION("ftp connection tracking helper");
36 /* This is slow, but it's simple. --RR */
37 static char *ftp_buffer;
39 static DEFINE_SPINLOCK(nf_ftp_lock);
42 static u_int16_t ports[MAX_PORTS];
43 static unsigned int ports_c;
44 module_param_array(ports, ushort, &ports_c, 0400);
47 module_param(loose, bool, 0600);
49 unsigned int (*nf_nat_ftp_hook)(struct sk_buff **pskb,
50 enum ip_conntrack_info ctinfo,
51 enum ip_ct_ftp_type type,
52 unsigned int matchoff,
53 unsigned int matchlen,
54 struct nf_conntrack_expect *exp,
56 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
61 #define DEBUGP(format, args...)
64 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
65 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
66 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
69 static struct ftp_search {
74 enum ip_ct_ftp_type ftptype;
75 int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
76 } search[IP_CT_DIR_MAX][2] = {
77 [IP_CT_DIR_ORIGINAL] = {
80 .plen = sizeof("PORT") - 1,
83 .ftptype = IP_CT_FTP_PORT,
88 .plen = sizeof("EPRT") - 1,
91 .ftptype = IP_CT_FTP_EPRT,
98 .plen = sizeof("227 ") - 1,
101 .ftptype = IP_CT_FTP_PASV,
102 .getnum = try_rfc959,
106 .plen = sizeof("229 ") - 1,
109 .ftptype = IP_CT_FTP_EPSV,
110 .getnum = try_epsv_response,
115 /* This code is based on inet_pton() in glibc-2.2.4 */
117 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
119 static const char xdigits[] = "0123456789abcdef";
120 u_int8_t tmp[16], *tp, *endp, *colonp;
125 tp = memset(tmp, '\0', sizeof(tmp));
126 endp = tp + sizeof(tmp);
129 /* Leading :: requires some special handling. */
132 DEBUGP("invalid \":\" at the head of addr\n");
140 while ((clen < dlen) && (*src != term)) {
143 ch = tolower(*src++);
146 pch = strchr(xdigits, ch);
149 val |= (pch - xdigits);
157 DEBUGP("get_ipv6_addr: invalid char. \'%c\'\n", ch);
163 DEBUGP("invalid location of \"::\".\n");
168 } else if (*src == term) {
169 DEBUGP("trancated IPv6 addr\n");
175 *tp++ = (u_int8_t) (val >> 8) & 0xff;
176 *tp++ = (u_int8_t) val & 0xff;
185 *tp++ = (u_int8_t) (val >> 8) & 0xff;
186 *tp++ = (u_int8_t) val & 0xff;
188 if (colonp != NULL) {
190 * Since some memmove()'s erroneously fail to handle
191 * overlapping regions, we'll do the shift by hand.
193 const int n = tp - colonp;
199 for (i = 1; i <= n; i++) {
200 endp[- i] = colonp[n - i];
205 if (tp != endp || (*src != term))
208 memcpy(dst->s6_addr, tmp, sizeof(dst->s6_addr));
212 static int try_number(const char *data, size_t dlen, u_int32_t array[],
213 int array_size, char sep, char term)
217 memset(array, 0, sizeof(array[0])*array_size);
219 /* Keep data pointing at next char. */
220 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
221 if (*data >= '0' && *data <= '9') {
222 array[i] = array[i]*10 + *data - '0';
224 else if (*data == sep)
227 /* Unexpected character; true if it's the
228 terminator and we're finished. */
229 if (*data == term && i == array_size - 1)
232 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
237 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
242 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
243 static int try_rfc959(const char *data, size_t dlen,
244 struct nf_conntrack_man *cmd, char term)
249 length = try_number(data, dlen, array, 6, ',', term);
253 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
254 (array[2] << 8) | array[3]);
255 cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
259 /* Grab port: number up to delimiter */
260 static int get_port(const char *data, int start, size_t dlen, char delim,
263 u_int16_t tmp_port = 0;
266 for (i = start; i < dlen; i++) {
268 if (data[i] == delim) {
271 *port = htons(tmp_port);
272 DEBUGP("get_port: return %d\n", tmp_port);
275 else if (data[i] >= '0' && data[i] <= '9')
276 tmp_port = tmp_port*10 + data[i] - '0';
277 else { /* Some other crap */
278 DEBUGP("get_port: invalid char.\n");
285 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
286 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
292 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
293 then delimiter again. */
295 DEBUGP("EPRT: too short\n");
299 if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
300 DEBUGP("try_eprt: invalid delimitter.\n");
304 if ((cmd->l3num == PF_INET && data[1] != '1') ||
305 (cmd->l3num == PF_INET6 && data[1] != '2')) {
306 DEBUGP("EPRT: invalid protocol number.\n");
310 DEBUGP("EPRT: Got %c%c%c\n", delim, data[1], delim);
312 if (data[1] == '1') {
315 /* Now we have IP address. */
316 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
318 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
319 | (array[2] << 8) | array[3]);
321 /* Now we have IPv6 address. */
322 length = get_ipv6_addr(data + 3, dlen - 3,
323 (struct in6_addr *)cmd->u3.ip6, delim);
328 DEBUGP("EPRT: Got IP address!\n");
329 /* Start offset includes initial "|1|", and trailing delimiter */
330 return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
333 /* Returns 0, or length of numbers: |||6446| */
334 static int try_epsv_response(const char *data, size_t dlen,
335 struct nf_conntrack_man *cmd, char term)
339 /* Three delimiters. */
340 if (dlen <= 3) return 0;
342 if (isdigit(delim) || delim < 33 || delim > 126
343 || data[1] != delim || data[2] != delim)
346 return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
349 /* Return 1 for match, 0 for accept, -1 for partial. */
350 static int find_pattern(const char *data, size_t dlen,
351 const char *pattern, size_t plen,
352 char skip, char term,
353 unsigned int *numoff,
354 unsigned int *numlen,
355 struct nf_conntrack_man *cmd,
356 int (*getnum)(const char *, size_t,
357 struct nf_conntrack_man *, char))
361 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
366 /* Short packet: try for partial? */
367 if (strnicmp(data, pattern, dlen) == 0)
372 if (strnicmp(data, pattern, plen) != 0) {
376 DEBUGP("ftp: string mismatch\n");
377 for (i = 0; i < plen; i++) {
378 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
380 pattern[i], pattern[i]);
386 DEBUGP("Pattern matches!\n");
387 /* Now we've found the constant string, try to skip
388 to the 'skip' character */
389 for (i = plen; data[i] != skip; i++)
390 if (i == dlen - 1) return -1;
392 /* Skip over the last character */
395 DEBUGP("Skipped up to `%c'!\n", skip);
398 *numlen = getnum(data + i, dlen - i, cmd, term);
402 DEBUGP("Match succeeded!\n");
406 /* Look up to see if we're just after a \n. */
407 static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
411 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
412 if (info->seq_aft_nl[dir][i] == seq)
417 /* We don't update if it's older than what we have. */
418 static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir,
421 unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
423 /* Look for oldest: if we find exact match, we're done. */
424 for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
425 if (info->seq_aft_nl[dir][i] == nl_seq)
428 if (oldest == info->seq_aft_nl_num[dir]
429 || before(info->seq_aft_nl[dir][i], oldest))
433 if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
434 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
435 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
436 } else if (oldest != NUM_SEQ_TO_REMEMBER) {
437 info->seq_aft_nl[dir][oldest] = nl_seq;
438 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
442 static int help(struct sk_buff **pskb,
443 unsigned int protoff,
445 enum ip_conntrack_info ctinfo)
447 unsigned int dataoff, datalen;
448 struct tcphdr _tcph, *th;
452 int dir = CTINFO2DIR(ctinfo);
453 unsigned int matchlen, matchoff;
454 struct ip_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
455 struct nf_conntrack_expect *exp;
456 struct nf_conntrack_man cmd = {};
459 int found = 0, ends_in_nl;
461 /* Until there's been traffic both ways, don't look in packets. */
462 if (ctinfo != IP_CT_ESTABLISHED
463 && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
464 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
468 th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph);
472 dataoff = protoff + th->doff * 4;
474 if (dataoff >= (*pskb)->len) {
475 DEBUGP("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
479 datalen = (*pskb)->len - dataoff;
481 spin_lock_bh(&nf_ftp_lock);
482 fb_ptr = skb_header_pointer(*pskb, dataoff, datalen, ftp_buffer);
483 BUG_ON(fb_ptr == NULL);
485 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
486 seq = ntohl(th->seq) + datalen;
488 /* Look up to see if we're just after a \n. */
489 if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
490 /* Now if this ends in \n, update ftp info. */
491 DEBUGP("nf_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
492 ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
493 ct_ftp_info->seq_aft_nl[dir][0],
494 ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
495 ct_ftp_info->seq_aft_nl[dir][1]);
500 /* Initialize IP/IPv6 addr to expected address (it's not mentioned
501 in EPSV responses) */
502 cmd.l3num = ct->tuplehash[dir].tuple.src.l3num;
503 memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
506 for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
507 found = find_pattern(fb_ptr, datalen,
508 search[dir][i].pattern,
512 &matchoff, &matchlen,
514 search[dir][i].getnum);
518 /* We don't usually drop packets. After all, this is
519 connection tracking, not packet filtering.
520 However, it is necessary for accurate tracking in
523 printk("conntrack_ftp: partial %s %u+%u\n",
524 search[dir][i].pattern,
525 ntohl(th->seq), datalen);
528 } else if (found == 0) { /* No match */
533 DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
534 (int)matchlen, fb_ptr + matchoff,
535 matchlen, ntohl(th->seq) + matchoff);
537 exp = nf_conntrack_expect_alloc(ct);
543 /* We refer to the reverse direction ("!dir") tuples here,
544 * because we're expecting something in the other direction.
545 * Doesn't matter unless NAT is happening. */
546 exp->tuple.dst.u3 = ct->tuplehash[!dir].tuple.dst.u3;
548 /* Update the ftp info */
549 if ((cmd.l3num == ct->tuplehash[dir].tuple.src.l3num) &&
550 memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
551 sizeof(cmd.u3.all))) {
552 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
553 server: it really wants us to connect to a
554 different IP address. Simply don't record it for
556 if (cmd.l3num == PF_INET) {
557 DEBUGP("conntrack_ftp: NOT RECORDING: " NIPQUAD_FMT " != " NIPQUAD_FMT "\n",
559 NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
561 DEBUGP("conntrack_ftp: NOT RECORDING: " NIP6_FMT " != " NIP6_FMT "\n",
562 NIP6(*((struct in6_addr *)cmd.u3.ip6)),
563 NIP6(*((struct in6_addr *)ct->tuplehash[dir]
564 .tuple.src.u3.ip6)));
567 /* Thanks to Cristiano Lincoln Mattos
568 <lincoln@cesar.org.br> for reporting this potential
569 problem (DMZ machines opening holes to internal
570 networks, or the packet filter itself). */
575 memcpy(&exp->tuple.dst.u3, &cmd.u3.all,
576 sizeof(exp->tuple.dst.u3));
579 exp->tuple.src.u3 = ct->tuplehash[!dir].tuple.src.u3;
580 exp->tuple.src.l3num = cmd.l3num;
581 exp->tuple.src.u.tcp.port = 0;
582 exp->tuple.dst.u.tcp.port = cmd.u.tcp.port;
583 exp->tuple.dst.protonum = IPPROTO_TCP;
585 exp->mask = (struct nf_conntrack_tuple)
586 { .src = { .l3num = 0xFFFF,
587 .u = { .tcp = { 0 }},
589 .dst = { .protonum = 0xFF,
590 .u = { .tcp = { 0xFFFF }},
593 if (cmd.l3num == PF_INET) {
594 exp->mask.src.u3.ip = 0xFFFFFFFF;
595 exp->mask.dst.u3.ip = 0xFFFFFFFF;
597 memset(exp->mask.src.u3.ip6, 0xFF,
598 sizeof(exp->mask.src.u3.ip6));
599 memset(exp->mask.dst.u3.ip6, 0xFF,
600 sizeof(exp->mask.src.u3.ip6));
603 exp->expectfn = NULL;
606 /* Now, NAT might want to mangle the packet, and register the
607 * (possibly changed) expectation itself. */
609 ret = nf_nat_ftp_hook(pskb, ctinfo, search[dir][i].ftptype,
610 matchoff, matchlen, exp, &seq);
612 /* Can't expect this? Best to drop packet now. */
613 if (nf_conntrack_expect_related(exp) != 0)
620 nf_conntrack_expect_put(exp);
623 /* Now if this ends in \n, update ftp info. Seq may have been
624 * adjusted by NAT code. */
626 update_nl_seq(seq, ct_ftp_info, dir, *pskb);
628 spin_unlock_bh(&nf_ftp_lock);
632 static struct nf_conntrack_helper ftp[MAX_PORTS][2];
633 static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")];
635 /* don't make this __exit, since it's called from __init ! */
636 static void nf_conntrack_ftp_fini(void)
639 for (i = 0; i < ports_c; i++) {
640 for (j = 0; j < 2; j++) {
641 if (ftp[i][j].me == NULL)
644 DEBUGP("nf_ct_ftp: unregistering helper for pf: %d "
646 ftp[i][j].tuple.src.l3num, ports[i]);
647 nf_conntrack_helper_unregister(&ftp[i][j]);
654 static int __init nf_conntrack_ftp_init(void)
656 int i, j = -1, ret = 0;
659 ftp_buffer = kmalloc(65536, GFP_KERNEL);
664 ports[ports_c++] = FTP_PORT;
666 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
667 are tracked or not - YK */
668 for (i = 0; i < ports_c; i++) {
669 ftp[i][0].tuple.src.l3num = PF_INET;
670 ftp[i][1].tuple.src.l3num = PF_INET6;
671 for (j = 0; j < 2; j++) {
672 ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
673 ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
674 ftp[i][j].mask.src.u.tcp.port = 0xFFFF;
675 ftp[i][j].mask.dst.protonum = 0xFF;
676 ftp[i][j].max_expected = 1;
677 ftp[i][j].timeout = 5 * 60; /* 5 Minutes */
678 ftp[i][j].me = THIS_MODULE;
679 ftp[i][j].help = help;
680 tmpname = &ftp_names[i][j][0];
681 if (ports[i] == FTP_PORT)
682 sprintf(tmpname, "ftp");
684 sprintf(tmpname, "ftp-%d", ports[i]);
685 ftp[i][j].name = tmpname;
687 DEBUGP("nf_ct_ftp: registering helper for pf: %d "
689 ftp[i][j].tuple.src.l3num, ports[i]);
690 ret = nf_conntrack_helper_register(&ftp[i][j]);
692 printk("nf_ct_ftp: failed to register helper "
693 " for pf: %d port: %d\n",
694 ftp[i][j].tuple.src.l3num, ports[i]);
695 nf_conntrack_ftp_fini();
704 module_init(nf_conntrack_ftp_init);
705 module_exit(nf_conntrack_ftp_fini);