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/module.h>
19 #include <linux/moduleparam.h>
20 #include <linux/netfilter.h>
22 #include <linux/ipv6.h>
23 #include <linux/ctype.h>
24 #include <net/checksum.h>
27 #include <net/netfilter/nf_conntrack.h>
28 #include <net/netfilter/nf_conntrack_helper.h>
29 #include <linux/netfilter/nf_conntrack_ftp.h>
31 MODULE_LICENSE("GPL");
32 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
33 MODULE_DESCRIPTION("ftp connection tracking helper");
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 **pskb,
49 enum ip_conntrack_info ctinfo,
50 enum ip_ct_ftp_type type,
51 unsigned int matchoff,
52 unsigned int matchlen,
53 struct nf_conntrack_expect *exp,
55 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
60 #define DEBUGP(format, args...)
63 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
64 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
65 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
68 static struct ftp_search {
73 enum ip_ct_ftp_type ftptype;
74 int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
75 } search[IP_CT_DIR_MAX][2] = {
76 [IP_CT_DIR_ORIGINAL] = {
79 .plen = sizeof("PORT") - 1,
82 .ftptype = IP_CT_FTP_PORT,
87 .plen = sizeof("EPRT") - 1,
90 .ftptype = IP_CT_FTP_EPRT,
97 .plen = sizeof("227 ") - 1,
100 .ftptype = IP_CT_FTP_PASV,
101 .getnum = try_rfc959,
105 .plen = sizeof("229 ") - 1,
108 .ftptype = IP_CT_FTP_EPSV,
109 .getnum = try_epsv_response,
114 /* This code is based on inet_pton() in glibc-2.2.4 */
116 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
118 static const char xdigits[] = "0123456789abcdef";
119 u_int8_t tmp[16], *tp, *endp, *colonp;
124 tp = memset(tmp, '\0', sizeof(tmp));
125 endp = tp + sizeof(tmp);
128 /* Leading :: requires some special handling. */
131 DEBUGP("invalid \":\" at the head of addr\n");
139 while ((clen < dlen) && (*src != term)) {
142 ch = tolower(*src++);
145 pch = strchr(xdigits, ch);
148 val |= (pch - xdigits);
156 DEBUGP("get_ipv6_addr: invalid char. \'%c\'\n", ch);
162 DEBUGP("invalid location of \"::\".\n");
167 } else if (*src == term) {
168 DEBUGP("trancated IPv6 addr\n");
174 *tp++ = (u_int8_t) (val >> 8) & 0xff;
175 *tp++ = (u_int8_t) val & 0xff;
184 *tp++ = (u_int8_t) (val >> 8) & 0xff;
185 *tp++ = (u_int8_t) val & 0xff;
187 if (colonp != NULL) {
189 * Since some memmove()'s erroneously fail to handle
190 * overlapping regions, we'll do the shift by hand.
192 const int n = tp - colonp;
198 for (i = 1; i <= n; i++) {
199 endp[- i] = colonp[n - i];
204 if (tp != endp || (*src != term))
207 memcpy(dst->s6_addr, tmp, sizeof(dst->s6_addr));
211 static int try_number(const char *data, size_t dlen, u_int32_t array[],
212 int array_size, char sep, char term)
216 memset(array, 0, sizeof(array[0])*array_size);
218 /* Keep data pointing at next char. */
219 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
220 if (*data >= '0' && *data <= '9') {
221 array[i] = array[i]*10 + *data - '0';
223 else if (*data == sep)
226 /* Unexpected character; true if it's the
227 terminator and we're finished. */
228 if (*data == term && i == array_size - 1)
231 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
236 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
241 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
242 static int try_rfc959(const char *data, size_t dlen,
243 struct nf_conntrack_man *cmd, char term)
248 length = try_number(data, dlen, array, 6, ',', term);
252 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
253 (array[2] << 8) | array[3]);
254 cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
258 /* Grab port: number up to delimiter */
259 static int get_port(const char *data, int start, size_t dlen, char delim,
262 u_int16_t tmp_port = 0;
265 for (i = start; i < dlen; i++) {
267 if (data[i] == delim) {
270 *port = htons(tmp_port);
271 DEBUGP("get_port: return %d\n", tmp_port);
274 else if (data[i] >= '0' && data[i] <= '9')
275 tmp_port = tmp_port*10 + data[i] - '0';
276 else { /* Some other crap */
277 DEBUGP("get_port: invalid char.\n");
284 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
285 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
291 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
292 then delimiter again. */
294 DEBUGP("EPRT: too short\n");
298 if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
299 DEBUGP("try_eprt: invalid delimitter.\n");
303 if ((cmd->l3num == PF_INET && data[1] != '1') ||
304 (cmd->l3num == PF_INET6 && data[1] != '2')) {
305 DEBUGP("EPRT: invalid protocol number.\n");
309 DEBUGP("EPRT: Got %c%c%c\n", delim, data[1], delim);
311 if (data[1] == '1') {
314 /* Now we have IP address. */
315 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
317 cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
318 | (array[2] << 8) | array[3]);
320 /* Now we have IPv6 address. */
321 length = get_ipv6_addr(data + 3, dlen - 3,
322 (struct in6_addr *)cmd->u3.ip6, delim);
327 DEBUGP("EPRT: Got IP address!\n");
328 /* Start offset includes initial "|1|", and trailing delimiter */
329 return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
332 /* Returns 0, or length of numbers: |||6446| */
333 static int try_epsv_response(const char *data, size_t dlen,
334 struct nf_conntrack_man *cmd, char term)
338 /* Three delimiters. */
339 if (dlen <= 3) return 0;
341 if (isdigit(delim) || delim < 33 || delim > 126
342 || data[1] != delim || data[2] != delim)
345 return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
348 /* Return 1 for match, 0 for accept, -1 for partial. */
349 static int find_pattern(const char *data, size_t dlen,
350 const char *pattern, size_t plen,
351 char skip, char term,
352 unsigned int *numoff,
353 unsigned int *numlen,
354 struct nf_conntrack_man *cmd,
355 int (*getnum)(const char *, size_t,
356 struct nf_conntrack_man *, char))
360 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
365 /* Short packet: try for partial? */
366 if (strnicmp(data, pattern, dlen) == 0)
371 if (strnicmp(data, pattern, plen) != 0) {
375 DEBUGP("ftp: string mismatch\n");
376 for (i = 0; i < plen; i++) {
377 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
379 pattern[i], pattern[i]);
385 DEBUGP("Pattern matches!\n");
386 /* Now we've found the constant string, try to skip
387 to the 'skip' character */
388 for (i = plen; data[i] != skip; i++)
389 if (i == dlen - 1) return -1;
391 /* Skip over the last character */
394 DEBUGP("Skipped up to `%c'!\n", skip);
397 *numlen = getnum(data + i, dlen - i, cmd, term);
401 DEBUGP("Match succeeded!\n");
405 /* Look up to see if we're just after a \n. */
406 static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
410 for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
411 if (info->seq_aft_nl[dir][i] == seq)
416 /* We don't update if it's older than what we have. */
417 static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir,
420 unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
422 /* Look for oldest: if we find exact match, we're done. */
423 for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
424 if (info->seq_aft_nl[dir][i] == nl_seq)
427 if (oldest == info->seq_aft_nl_num[dir]
428 || before(info->seq_aft_nl[dir][i], oldest))
432 if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
433 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
434 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
435 } else if (oldest != NUM_SEQ_TO_REMEMBER) {
436 info->seq_aft_nl[dir][oldest] = nl_seq;
437 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
441 static int help(struct sk_buff **pskb,
442 unsigned int protoff,
444 enum ip_conntrack_info ctinfo)
446 unsigned int dataoff, datalen;
447 struct tcphdr _tcph, *th;
451 int dir = CTINFO2DIR(ctinfo);
452 unsigned int matchlen, matchoff;
453 struct ip_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
454 struct nf_conntrack_expect *exp;
455 struct nf_conntrack_man cmd = {};
458 int found = 0, ends_in_nl;
460 /* Until there's been traffic both ways, don't look in packets. */
461 if (ctinfo != IP_CT_ESTABLISHED
462 && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
463 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
467 th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph);
471 dataoff = protoff + th->doff * 4;
473 if (dataoff >= (*pskb)->len) {
474 DEBUGP("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
478 datalen = (*pskb)->len - dataoff;
480 spin_lock_bh(&nf_ftp_lock);
481 fb_ptr = skb_header_pointer(*pskb, dataoff, datalen, ftp_buffer);
482 BUG_ON(fb_ptr == NULL);
484 ends_in_nl = (fb_ptr[datalen - 1] == '\n');
485 seq = ntohl(th->seq) + datalen;
487 /* Look up to see if we're just after a \n. */
488 if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
489 /* Now if this ends in \n, update ftp info. */
490 DEBUGP("nf_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
491 ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
492 ct_ftp_info->seq_aft_nl[dir][0],
493 ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
494 ct_ftp_info->seq_aft_nl[dir][1]);
499 /* Initialize IP/IPv6 addr to expected address (it's not mentioned
500 in EPSV responses) */
501 cmd.l3num = ct->tuplehash[dir].tuple.src.l3num;
502 memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
505 for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
506 found = find_pattern(fb_ptr, datalen,
507 search[dir][i].pattern,
511 &matchoff, &matchlen,
513 search[dir][i].getnum);
517 /* We don't usually drop packets. After all, this is
518 connection tracking, not packet filtering.
519 However, it is necessary for accurate tracking in
522 printk("conntrack_ftp: partial %s %u+%u\n",
523 search[dir][i].pattern,
524 ntohl(th->seq), datalen);
527 } else if (found == 0) { /* No match */
532 DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
533 (int)matchlen, fb_ptr + matchoff,
534 matchlen, ntohl(th->seq) + matchoff);
536 exp = nf_conntrack_expect_alloc(ct);
542 /* We refer to the reverse direction ("!dir") tuples here,
543 * because we're expecting something in the other direction.
544 * Doesn't matter unless NAT is happening. */
545 exp->tuple.dst.u3 = ct->tuplehash[!dir].tuple.dst.u3;
547 /* Update the ftp info */
548 if ((cmd.l3num == ct->tuplehash[dir].tuple.src.l3num) &&
549 memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
550 sizeof(cmd.u3.all))) {
551 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
552 server: it really wants us to connect to a
553 different IP address. Simply don't record it for
555 if (cmd.l3num == PF_INET) {
556 DEBUGP("conntrack_ftp: NOT RECORDING: " NIPQUAD_FMT " != " NIPQUAD_FMT "\n",
558 NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
560 DEBUGP("conntrack_ftp: NOT RECORDING: " NIP6_FMT " != " NIP6_FMT "\n",
561 NIP6(*((struct in6_addr *)cmd.u3.ip6)),
562 NIP6(*((struct in6_addr *)ct->tuplehash[dir]
563 .tuple.src.u3.ip6)));
566 /* Thanks to Cristiano Lincoln Mattos
567 <lincoln@cesar.org.br> for reporting this potential
568 problem (DMZ machines opening holes to internal
569 networks, or the packet filter itself). */
574 memcpy(&exp->tuple.dst.u3, &cmd.u3.all,
575 sizeof(exp->tuple.dst.u3));
578 exp->tuple.src.u3 = ct->tuplehash[!dir].tuple.src.u3;
579 exp->tuple.src.l3num = cmd.l3num;
580 exp->tuple.src.u.tcp.port = 0;
581 exp->tuple.dst.u.tcp.port = cmd.u.tcp.port;
582 exp->tuple.dst.protonum = IPPROTO_TCP;
584 exp->mask = (struct nf_conntrack_tuple)
585 { .src = { .l3num = 0xFFFF,
586 .u = { .tcp = { 0 }},
588 .dst = { .protonum = 0xFF,
589 .u = { .tcp = { 0xFFFF }},
592 if (cmd.l3num == PF_INET) {
593 exp->mask.src.u3.ip = 0xFFFFFFFF;
594 exp->mask.dst.u3.ip = 0xFFFFFFFF;
596 memset(exp->mask.src.u3.ip6, 0xFF,
597 sizeof(exp->mask.src.u3.ip6));
598 memset(exp->mask.dst.u3.ip6, 0xFF,
599 sizeof(exp->mask.src.u3.ip6));
602 exp->expectfn = NULL;
605 /* Now, NAT might want to mangle the packet, and register the
606 * (possibly changed) expectation itself. */
608 ret = nf_nat_ftp_hook(pskb, ctinfo, search[dir][i].ftptype,
609 matchoff, matchlen, exp, &seq);
611 /* Can't expect this? Best to drop packet now. */
612 if (nf_conntrack_expect_related(exp) != 0)
619 nf_conntrack_expect_put(exp);
622 /* Now if this ends in \n, update ftp info. Seq may have been
623 * adjusted by NAT code. */
625 update_nl_seq(seq, ct_ftp_info, dir, *pskb);
627 spin_unlock_bh(&nf_ftp_lock);
631 static struct nf_conntrack_helper ftp[MAX_PORTS][2];
632 static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")];
634 /* don't make this __exit, since it's called from __init ! */
635 static void nf_conntrack_ftp_fini(void)
638 for (i = 0; i < ports_c; i++) {
639 for (j = 0; j < 2; j++) {
640 if (ftp[i][j].me == NULL)
643 DEBUGP("nf_ct_ftp: unregistering helper for pf: %d "
645 ftp[i][j].tuple.src.l3num, ports[i]);
646 nf_conntrack_helper_unregister(&ftp[i][j]);
653 static int __init nf_conntrack_ftp_init(void)
655 int i, j = -1, ret = 0;
658 ftp_buffer = kmalloc(65536, GFP_KERNEL);
663 ports[ports_c++] = FTP_PORT;
665 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
666 are tracked or not - YK */
667 for (i = 0; i < ports_c; i++) {
668 ftp[i][0].tuple.src.l3num = PF_INET;
669 ftp[i][1].tuple.src.l3num = PF_INET6;
670 for (j = 0; j < 2; j++) {
671 ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
672 ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
673 ftp[i][j].mask.src.u.tcp.port = 0xFFFF;
674 ftp[i][j].mask.dst.protonum = 0xFF;
675 ftp[i][j].max_expected = 1;
676 ftp[i][j].timeout = 5 * 60; /* 5 Minutes */
677 ftp[i][j].me = THIS_MODULE;
678 ftp[i][j].help = help;
679 tmpname = &ftp_names[i][j][0];
680 if (ports[i] == FTP_PORT)
681 sprintf(tmpname, "ftp");
683 sprintf(tmpname, "ftp-%d", ports[i]);
684 ftp[i][j].name = tmpname;
686 DEBUGP("nf_ct_ftp: registering helper for pf: %d "
688 ftp[i][j].tuple.src.l3num, ports[i]);
689 ret = nf_conntrack_helper_register(&ftp[i][j]);
691 printk("nf_ct_ftp: failed to register helper "
692 " for pf: %d port: %d\n",
693 ftp[i][j].tuple.src.l3num, ports[i]);
694 nf_conntrack_ftp_fini();
703 module_init(nf_conntrack_ftp_init);
704 module_exit(nf_conntrack_ftp_fini);