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 <linux/inet.h>
25 #include <net/checksum.h>
28 #include <net/netfilter/nf_conntrack.h>
29 #include <net/netfilter/nf_conntrack_expect.h>
30 #include <net/netfilter/nf_conntrack_ecache.h>
31 #include <net/netfilter/nf_conntrack_helper.h>
32 #include <linux/netfilter/nf_conntrack_ftp.h>
34 MODULE_LICENSE("GPL");
35 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
36 MODULE_DESCRIPTION("ftp connection tracking helper");
37 MODULE_ALIAS("ip_conntrack_ftp");
39 /* This is slow, but it's simple. --RR */
40 static char *ftp_buffer
;
42 static DEFINE_SPINLOCK(nf_ftp_lock
);
45 static u_int16_t ports
[MAX_PORTS
];
46 static unsigned int ports_c
;
47 module_param_array(ports
, ushort
, &ports_c
, 0400);
50 module_param(loose
, bool, 0600);
52 unsigned int (*nf_nat_ftp_hook
)(struct sk_buff
**pskb
,
53 enum ip_conntrack_info ctinfo
,
54 enum nf_ct_ftp_type type
,
55 unsigned int matchoff
,
56 unsigned int matchlen
,
57 struct nf_conntrack_expect
*exp
,
59 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook
);
64 #define DEBUGP(format, args...)
67 static int try_rfc959(const char *, size_t, struct nf_conntrack_man
*, char);
68 static int try_eprt(const char *, size_t, struct nf_conntrack_man
*, char);
69 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man
*,
72 static struct ftp_search
{
77 enum nf_ct_ftp_type ftptype
;
78 int (*getnum
)(const char *, size_t, struct nf_conntrack_man
*, char);
79 } search
[IP_CT_DIR_MAX
][2] = {
80 [IP_CT_DIR_ORIGINAL
] = {
83 .plen
= sizeof("PORT") - 1,
86 .ftptype
= NF_CT_FTP_PORT
,
91 .plen
= sizeof("EPRT") - 1,
94 .ftptype
= NF_CT_FTP_EPRT
,
101 .plen
= sizeof("227 ") - 1,
104 .ftptype
= NF_CT_FTP_PASV
,
105 .getnum
= try_rfc959
,
109 .plen
= sizeof("229 ") - 1,
112 .ftptype
= NF_CT_FTP_EPSV
,
113 .getnum
= try_epsv_response
,
119 get_ipv6_addr(const char *src
, size_t dlen
, struct in6_addr
*dst
, u_int8_t term
)
122 int ret
= in6_pton(src
, min_t(size_t, dlen
, 0xffff), (u8
*)dst
, term
, &end
);
124 return (int)(end
- src
);
128 static int try_number(const char *data
, size_t dlen
, u_int32_t array
[],
129 int array_size
, char sep
, char term
)
133 memset(array
, 0, sizeof(array
[0])*array_size
);
135 /* Keep data pointing at next char. */
136 for (i
= 0, len
= 0; len
< dlen
&& i
< array_size
; len
++, data
++) {
137 if (*data
>= '0' && *data
<= '9') {
138 array
[i
] = array
[i
]*10 + *data
- '0';
140 else if (*data
== sep
)
143 /* Unexpected character; true if it's the
144 terminator and we're finished. */
145 if (*data
== term
&& i
== array_size
- 1)
148 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
153 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size
, sep
);
158 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
159 static int try_rfc959(const char *data
, size_t dlen
,
160 struct nf_conntrack_man
*cmd
, char term
)
165 length
= try_number(data
, dlen
, array
, 6, ',', term
);
169 cmd
->u3
.ip
= htonl((array
[0] << 24) | (array
[1] << 16) |
170 (array
[2] << 8) | array
[3]);
171 cmd
->u
.tcp
.port
= htons((array
[4] << 8) | array
[5]);
175 /* Grab port: number up to delimiter */
176 static int get_port(const char *data
, int start
, size_t dlen
, char delim
,
179 u_int16_t tmp_port
= 0;
182 for (i
= start
; i
< dlen
; i
++) {
184 if (data
[i
] == delim
) {
187 *port
= htons(tmp_port
);
188 DEBUGP("get_port: return %d\n", tmp_port
);
191 else if (data
[i
] >= '0' && data
[i
] <= '9')
192 tmp_port
= tmp_port
*10 + data
[i
] - '0';
193 else { /* Some other crap */
194 DEBUGP("get_port: invalid char.\n");
201 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
202 static int try_eprt(const char *data
, size_t dlen
, struct nf_conntrack_man
*cmd
,
208 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
209 then delimiter again. */
211 DEBUGP("EPRT: too short\n");
215 if (isdigit(delim
) || delim
< 33 || delim
> 126 || data
[2] != delim
) {
216 DEBUGP("try_eprt: invalid delimitter.\n");
220 if ((cmd
->l3num
== PF_INET
&& data
[1] != '1') ||
221 (cmd
->l3num
== PF_INET6
&& data
[1] != '2')) {
222 DEBUGP("EPRT: invalid protocol number.\n");
226 DEBUGP("EPRT: Got %c%c%c\n", delim
, data
[1], delim
);
228 if (data
[1] == '1') {
231 /* Now we have IP address. */
232 length
= try_number(data
+ 3, dlen
- 3, array
, 4, '.', delim
);
234 cmd
->u3
.ip
= htonl((array
[0] << 24) | (array
[1] << 16)
235 | (array
[2] << 8) | array
[3]);
237 /* Now we have IPv6 address. */
238 length
= get_ipv6_addr(data
+ 3, dlen
- 3,
239 (struct in6_addr
*)cmd
->u3
.ip6
, delim
);
244 DEBUGP("EPRT: Got IP address!\n");
245 /* Start offset includes initial "|1|", and trailing delimiter */
246 return get_port(data
, 3 + length
+ 1, dlen
, delim
, &cmd
->u
.tcp
.port
);
249 /* Returns 0, or length of numbers: |||6446| */
250 static int try_epsv_response(const char *data
, size_t dlen
,
251 struct nf_conntrack_man
*cmd
, char term
)
255 /* Three delimiters. */
256 if (dlen
<= 3) return 0;
258 if (isdigit(delim
) || delim
< 33 || delim
> 126
259 || data
[1] != delim
|| data
[2] != delim
)
262 return get_port(data
, 3, dlen
, delim
, &cmd
->u
.tcp
.port
);
265 /* Return 1 for match, 0 for accept, -1 for partial. */
266 static int find_pattern(const char *data
, size_t dlen
,
267 const char *pattern
, size_t plen
,
268 char skip
, char term
,
269 unsigned int *numoff
,
270 unsigned int *numlen
,
271 struct nf_conntrack_man
*cmd
,
272 int (*getnum
)(const char *, size_t,
273 struct nf_conntrack_man
*, char))
277 DEBUGP("find_pattern `%s': dlen = %u\n", pattern
, dlen
);
282 /* Short packet: try for partial? */
283 if (strnicmp(data
, pattern
, dlen
) == 0)
288 if (strnicmp(data
, pattern
, plen
) != 0) {
292 DEBUGP("ftp: string mismatch\n");
293 for (i
= 0; i
< plen
; i
++) {
294 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
296 pattern
[i
], pattern
[i
]);
302 DEBUGP("Pattern matches!\n");
303 /* Now we've found the constant string, try to skip
304 to the 'skip' character */
305 for (i
= plen
; data
[i
] != skip
; i
++)
306 if (i
== dlen
- 1) return -1;
308 /* Skip over the last character */
311 DEBUGP("Skipped up to `%c'!\n", skip
);
314 *numlen
= getnum(data
+ i
, dlen
- i
, cmd
, term
);
318 DEBUGP("Match succeeded!\n");
322 /* Look up to see if we're just after a \n. */
323 static int find_nl_seq(u32 seq
, const struct nf_ct_ftp_master
*info
, int dir
)
327 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++)
328 if (info
->seq_aft_nl
[dir
][i
] == seq
)
333 /* We don't update if it's older than what we have. */
334 static void update_nl_seq(u32 nl_seq
, struct nf_ct_ftp_master
*info
, int dir
,
337 unsigned int i
, oldest
= NUM_SEQ_TO_REMEMBER
;
339 /* Look for oldest: if we find exact match, we're done. */
340 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++) {
341 if (info
->seq_aft_nl
[dir
][i
] == nl_seq
)
344 if (oldest
== info
->seq_aft_nl_num
[dir
]
345 || before(info
->seq_aft_nl
[dir
][i
], oldest
))
349 if (info
->seq_aft_nl_num
[dir
] < NUM_SEQ_TO_REMEMBER
) {
350 info
->seq_aft_nl
[dir
][info
->seq_aft_nl_num
[dir
]++] = nl_seq
;
351 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE
, skb
);
352 } else if (oldest
!= NUM_SEQ_TO_REMEMBER
) {
353 info
->seq_aft_nl
[dir
][oldest
] = nl_seq
;
354 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE
, skb
);
358 static int help(struct sk_buff
**pskb
,
359 unsigned int protoff
,
361 enum ip_conntrack_info ctinfo
)
363 unsigned int dataoff
, datalen
;
364 struct tcphdr _tcph
, *th
;
368 int dir
= CTINFO2DIR(ctinfo
);
369 unsigned int matchlen
, matchoff
;
370 struct nf_ct_ftp_master
*ct_ftp_info
= &nfct_help(ct
)->help
.ct_ftp_info
;
371 struct nf_conntrack_expect
*exp
;
372 struct nf_conntrack_man cmd
= {};
374 int found
= 0, ends_in_nl
;
375 typeof(nf_nat_ftp_hook
) nf_nat_ftp
;
377 /* Until there's been traffic both ways, don't look in packets. */
378 if (ctinfo
!= IP_CT_ESTABLISHED
379 && ctinfo
!= IP_CT_ESTABLISHED
+IP_CT_IS_REPLY
) {
380 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo
);
384 th
= skb_header_pointer(*pskb
, protoff
, sizeof(_tcph
), &_tcph
);
388 dataoff
= protoff
+ th
->doff
* 4;
390 if (dataoff
>= (*pskb
)->len
) {
391 DEBUGP("ftp: dataoff(%u) >= skblen(%u)\n", dataoff
,
395 datalen
= (*pskb
)->len
- dataoff
;
397 spin_lock_bh(&nf_ftp_lock
);
398 fb_ptr
= skb_header_pointer(*pskb
, dataoff
, datalen
, ftp_buffer
);
399 BUG_ON(fb_ptr
== NULL
);
401 ends_in_nl
= (fb_ptr
[datalen
- 1] == '\n');
402 seq
= ntohl(th
->seq
) + datalen
;
404 /* Look up to see if we're just after a \n. */
405 if (!find_nl_seq(ntohl(th
->seq
), ct_ftp_info
, dir
)) {
406 /* Now if this ends in \n, update ftp info. */
407 DEBUGP("nf_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
408 ct_ftp_info
->seq_aft_nl_num
[dir
] > 0 ? "" : "(UNSET)",
409 ct_ftp_info
->seq_aft_nl
[dir
][0],
410 ct_ftp_info
->seq_aft_nl_num
[dir
] > 1 ? "" : "(UNSET)",
411 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
= ct
->tuplehash
[dir
].tuple
.src
.l3num
;
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
439 printk("conntrack_ftp: partial %s %u+%u\n",
440 search
[dir
][i
].pattern
,
441 ntohl(th
->seq
), datalen
);
444 } else if (found
== 0) { /* No match */
449 DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
450 (int)matchlen
, fb_ptr
+ matchoff
,
451 matchlen
, ntohl(th
->seq
) + matchoff
);
453 exp
= nf_conntrack_expect_alloc(ct
);
459 /* We refer to the reverse direction ("!dir") tuples here,
460 * because we're expecting something in the other direction.
461 * Doesn't matter unless NAT is happening. */
462 exp
->tuple
.dst
.u3
= ct
->tuplehash
[!dir
].tuple
.dst
.u3
;
464 /* Update the ftp info */
465 if ((cmd
.l3num
== ct
->tuplehash
[dir
].tuple
.src
.l3num
) &&
466 memcmp(&cmd
.u3
.all
, &ct
->tuplehash
[dir
].tuple
.src
.u3
.all
,
467 sizeof(cmd
.u3
.all
))) {
468 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
469 server: it really wants us to connect to a
470 different IP address. Simply don't record it for
472 if (cmd
.l3num
== PF_INET
) {
473 DEBUGP("conntrack_ftp: NOT RECORDING: " NIPQUAD_FMT
" != " NIPQUAD_FMT
"\n",
475 NIPQUAD(ct
->tuplehash
[dir
].tuple
.src
.u3
.ip
));
477 DEBUGP("conntrack_ftp: NOT RECORDING: " NIP6_FMT
" != " NIP6_FMT
"\n",
478 NIP6(*((struct in6_addr
*)cmd
.u3
.ip6
)),
479 NIP6(*((struct in6_addr
*)ct
->tuplehash
[dir
]
480 .tuple
.src
.u3
.ip6
)));
483 /* Thanks to Cristiano Lincoln Mattos
484 <lincoln@cesar.org.br> for reporting this potential
485 problem (DMZ machines opening holes to internal
486 networks, or the packet filter itself). */
491 memcpy(&exp
->tuple
.dst
.u3
, &cmd
.u3
.all
,
492 sizeof(exp
->tuple
.dst
.u3
));
495 exp
->tuple
.src
.u3
= ct
->tuplehash
[!dir
].tuple
.src
.u3
;
496 exp
->tuple
.src
.l3num
= cmd
.l3num
;
497 exp
->tuple
.src
.u
.tcp
.port
= 0;
498 exp
->tuple
.dst
.u
.tcp
.port
= cmd
.u
.tcp
.port
;
499 exp
->tuple
.dst
.protonum
= IPPROTO_TCP
;
501 exp
->mask
= (struct nf_conntrack_tuple
)
502 { .src
= { .l3num
= 0xFFFF,
503 .u
= { .tcp
= { 0 }},
505 .dst
= { .protonum
= 0xFF,
506 .u
= { .tcp
= { __constant_htons(0xFFFF) }},
509 if (cmd
.l3num
== PF_INET
) {
510 exp
->mask
.src
.u3
.ip
= htonl(0xFFFFFFFF);
511 exp
->mask
.dst
.u3
.ip
= htonl(0xFFFFFFFF);
513 memset(exp
->mask
.src
.u3
.ip6
, 0xFF,
514 sizeof(exp
->mask
.src
.u3
.ip6
));
515 memset(exp
->mask
.dst
.u3
.ip6
, 0xFF,
516 sizeof(exp
->mask
.src
.u3
.ip6
));
519 exp
->expectfn
= NULL
;
523 /* Now, NAT might want to mangle the packet, and register the
524 * (possibly changed) expectation itself. */
525 nf_nat_ftp
= rcu_dereference(nf_nat_ftp_hook
);
526 if (nf_nat_ftp
&& ct
->status
& IPS_NAT_MASK
)
527 ret
= nf_nat_ftp(pskb
, ctinfo
, search
[dir
][i
].ftptype
,
528 matchoff
, matchlen
, exp
, &seq
);
530 /* Can't expect this? Best to drop packet now. */
531 if (nf_conntrack_expect_related(exp
) != 0)
538 nf_conntrack_expect_put(exp
);
541 /* Now if this ends in \n, update ftp info. Seq may have been
542 * adjusted by NAT code. */
544 update_nl_seq(seq
, ct_ftp_info
, dir
, *pskb
);
546 spin_unlock_bh(&nf_ftp_lock
);
550 static struct nf_conntrack_helper ftp
[MAX_PORTS
][2];
551 static char ftp_names
[MAX_PORTS
][2][sizeof("ftp-65535")];
553 /* don't make this __exit, since it's called from __init ! */
554 static void nf_conntrack_ftp_fini(void)
557 for (i
= 0; i
< ports_c
; i
++) {
558 for (j
= 0; j
< 2; j
++) {
559 if (ftp
[i
][j
].me
== NULL
)
562 DEBUGP("nf_ct_ftp: unregistering helper for pf: %d "
564 ftp
[i
][j
].tuple
.src
.l3num
, ports
[i
]);
565 nf_conntrack_helper_unregister(&ftp
[i
][j
]);
572 static int __init
nf_conntrack_ftp_init(void)
574 int i
, j
= -1, ret
= 0;
577 ftp_buffer
= kmalloc(65536, GFP_KERNEL
);
582 ports
[ports_c
++] = FTP_PORT
;
584 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
585 are tracked or not - YK */
586 for (i
= 0; i
< ports_c
; i
++) {
587 ftp
[i
][0].tuple
.src
.l3num
= PF_INET
;
588 ftp
[i
][1].tuple
.src
.l3num
= PF_INET6
;
589 for (j
= 0; j
< 2; j
++) {
590 ftp
[i
][j
].tuple
.src
.u
.tcp
.port
= htons(ports
[i
]);
591 ftp
[i
][j
].tuple
.dst
.protonum
= IPPROTO_TCP
;
592 ftp
[i
][j
].mask
.src
.l3num
= 0xFFFF;
593 ftp
[i
][j
].mask
.src
.u
.tcp
.port
= htons(0xFFFF);
594 ftp
[i
][j
].mask
.dst
.protonum
= 0xFF;
595 ftp
[i
][j
].max_expected
= 1;
596 ftp
[i
][j
].timeout
= 5 * 60; /* 5 Minutes */
597 ftp
[i
][j
].me
= THIS_MODULE
;
598 ftp
[i
][j
].help
= help
;
599 tmpname
= &ftp_names
[i
][j
][0];
600 if (ports
[i
] == FTP_PORT
)
601 sprintf(tmpname
, "ftp");
603 sprintf(tmpname
, "ftp-%d", ports
[i
]);
604 ftp
[i
][j
].name
= tmpname
;
606 DEBUGP("nf_ct_ftp: registering helper for pf: %d "
608 ftp
[i
][j
].tuple
.src
.l3num
, ports
[i
]);
609 ret
= nf_conntrack_helper_register(&ftp
[i
][j
]);
611 printk("nf_ct_ftp: failed to register helper "
612 " for pf: %d port: %d\n",
613 ftp
[i
][j
].tuple
.src
.l3num
, ports
[i
]);
614 nf_conntrack_ftp_fini();
623 module_init(nf_conntrack_ftp_init
);
624 module_exit(nf_conntrack_ftp_fini
);