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_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
,
116 get_ipv6_addr(const char *src
, size_t dlen
, struct in6_addr
*dst
, u_int8_t term
)
119 int ret
= in6_pton(src
, min_t(size_t, dlen
, 0xffff), (u8
*)dst
, term
, &end
);
121 return (int)(end
- src
);
125 static int try_number(const char *data
, size_t dlen
, u_int32_t array
[],
126 int array_size
, char sep
, char term
)
130 memset(array
, 0, sizeof(array
[0])*array_size
);
132 /* Keep data pointing at next char. */
133 for (i
= 0, len
= 0; len
< dlen
&& i
< array_size
; len
++, data
++) {
134 if (*data
>= '0' && *data
<= '9') {
135 array
[i
] = array
[i
]*10 + *data
- '0';
137 else if (*data
== sep
)
140 /* Unexpected character; true if it's the
141 terminator and we're finished. */
142 if (*data
== term
&& i
== array_size
- 1)
145 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
150 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size
, sep
);
155 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
156 static int try_rfc959(const char *data
, size_t dlen
,
157 struct nf_conntrack_man
*cmd
, char term
)
162 length
= try_number(data
, dlen
, array
, 6, ',', term
);
166 cmd
->u3
.ip
= htonl((array
[0] << 24) | (array
[1] << 16) |
167 (array
[2] << 8) | array
[3]);
168 cmd
->u
.tcp
.port
= htons((array
[4] << 8) | array
[5]);
172 /* Grab port: number up to delimiter */
173 static int get_port(const char *data
, int start
, size_t dlen
, char delim
,
176 u_int16_t tmp_port
= 0;
179 for (i
= start
; i
< dlen
; i
++) {
181 if (data
[i
] == delim
) {
184 *port
= htons(tmp_port
);
185 DEBUGP("get_port: return %d\n", tmp_port
);
188 else if (data
[i
] >= '0' && data
[i
] <= '9')
189 tmp_port
= tmp_port
*10 + data
[i
] - '0';
190 else { /* Some other crap */
191 DEBUGP("get_port: invalid char.\n");
198 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
199 static int try_eprt(const char *data
, size_t dlen
, struct nf_conntrack_man
*cmd
,
205 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
206 then delimiter again. */
208 DEBUGP("EPRT: too short\n");
212 if (isdigit(delim
) || delim
< 33 || delim
> 126 || data
[2] != delim
) {
213 DEBUGP("try_eprt: invalid delimitter.\n");
217 if ((cmd
->l3num
== PF_INET
&& data
[1] != '1') ||
218 (cmd
->l3num
== PF_INET6
&& data
[1] != '2')) {
219 DEBUGP("EPRT: invalid protocol number.\n");
223 DEBUGP("EPRT: Got %c%c%c\n", delim
, data
[1], delim
);
225 if (data
[1] == '1') {
228 /* Now we have IP address. */
229 length
= try_number(data
+ 3, dlen
- 3, array
, 4, '.', delim
);
231 cmd
->u3
.ip
= htonl((array
[0] << 24) | (array
[1] << 16)
232 | (array
[2] << 8) | array
[3]);
234 /* Now we have IPv6 address. */
235 length
= get_ipv6_addr(data
+ 3, dlen
- 3,
236 (struct in6_addr
*)cmd
->u3
.ip6
, delim
);
241 DEBUGP("EPRT: Got IP address!\n");
242 /* Start offset includes initial "|1|", and trailing delimiter */
243 return get_port(data
, 3 + length
+ 1, dlen
, delim
, &cmd
->u
.tcp
.port
);
246 /* Returns 0, or length of numbers: |||6446| */
247 static int try_epsv_response(const char *data
, size_t dlen
,
248 struct nf_conntrack_man
*cmd
, char term
)
252 /* Three delimiters. */
253 if (dlen
<= 3) return 0;
255 if (isdigit(delim
) || delim
< 33 || delim
> 126
256 || data
[1] != delim
|| data
[2] != delim
)
259 return get_port(data
, 3, dlen
, delim
, &cmd
->u
.tcp
.port
);
262 /* Return 1 for match, 0 for accept, -1 for partial. */
263 static int find_pattern(const char *data
, size_t dlen
,
264 const char *pattern
, size_t plen
,
265 char skip
, char term
,
266 unsigned int *numoff
,
267 unsigned int *numlen
,
268 struct nf_conntrack_man
*cmd
,
269 int (*getnum
)(const char *, size_t,
270 struct nf_conntrack_man
*, char))
274 DEBUGP("find_pattern `%s': dlen = %u\n", pattern
, dlen
);
279 /* Short packet: try for partial? */
280 if (strnicmp(data
, pattern
, dlen
) == 0)
285 if (strnicmp(data
, pattern
, plen
) != 0) {
289 DEBUGP("ftp: string mismatch\n");
290 for (i
= 0; i
< plen
; i
++) {
291 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
293 pattern
[i
], pattern
[i
]);
299 DEBUGP("Pattern matches!\n");
300 /* Now we've found the constant string, try to skip
301 to the 'skip' character */
302 for (i
= plen
; data
[i
] != skip
; i
++)
303 if (i
== dlen
- 1) return -1;
305 /* Skip over the last character */
308 DEBUGP("Skipped up to `%c'!\n", skip
);
311 *numlen
= getnum(data
+ i
, dlen
- i
, cmd
, term
);
315 DEBUGP("Match succeeded!\n");
319 /* Look up to see if we're just after a \n. */
320 static int find_nl_seq(u32 seq
, const struct ip_ct_ftp_master
*info
, int dir
)
324 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++)
325 if (info
->seq_aft_nl
[dir
][i
] == seq
)
330 /* We don't update if it's older than what we have. */
331 static void update_nl_seq(u32 nl_seq
, struct ip_ct_ftp_master
*info
, int dir
,
334 unsigned int i
, oldest
= NUM_SEQ_TO_REMEMBER
;
336 /* Look for oldest: if we find exact match, we're done. */
337 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++) {
338 if (info
->seq_aft_nl
[dir
][i
] == nl_seq
)
341 if (oldest
== info
->seq_aft_nl_num
[dir
]
342 || before(info
->seq_aft_nl
[dir
][i
], oldest
))
346 if (info
->seq_aft_nl_num
[dir
] < NUM_SEQ_TO_REMEMBER
) {
347 info
->seq_aft_nl
[dir
][info
->seq_aft_nl_num
[dir
]++] = nl_seq
;
348 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE
, skb
);
349 } else if (oldest
!= NUM_SEQ_TO_REMEMBER
) {
350 info
->seq_aft_nl
[dir
][oldest
] = nl_seq
;
351 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE
, skb
);
355 static int help(struct sk_buff
**pskb
,
356 unsigned int protoff
,
358 enum ip_conntrack_info ctinfo
)
360 unsigned int dataoff
, datalen
;
361 struct tcphdr _tcph
, *th
;
365 int dir
= CTINFO2DIR(ctinfo
);
366 unsigned int matchlen
, matchoff
;
367 struct ip_ct_ftp_master
*ct_ftp_info
= &nfct_help(ct
)->help
.ct_ftp_info
;
368 struct nf_conntrack_expect
*exp
;
369 struct nf_conntrack_man cmd
= {};
372 int found
= 0, ends_in_nl
;
374 /* Until there's been traffic both ways, don't look in packets. */
375 if (ctinfo
!= IP_CT_ESTABLISHED
376 && ctinfo
!= IP_CT_ESTABLISHED
+IP_CT_IS_REPLY
) {
377 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo
);
381 th
= skb_header_pointer(*pskb
, protoff
, sizeof(_tcph
), &_tcph
);
385 dataoff
= protoff
+ th
->doff
* 4;
387 if (dataoff
>= (*pskb
)->len
) {
388 DEBUGP("ftp: dataoff(%u) >= skblen(%u)\n", dataoff
,
392 datalen
= (*pskb
)->len
- dataoff
;
394 spin_lock_bh(&nf_ftp_lock
);
395 fb_ptr
= skb_header_pointer(*pskb
, dataoff
, datalen
, ftp_buffer
);
396 BUG_ON(fb_ptr
== NULL
);
398 ends_in_nl
= (fb_ptr
[datalen
- 1] == '\n');
399 seq
= ntohl(th
->seq
) + datalen
;
401 /* Look up to see if we're just after a \n. */
402 if (!find_nl_seq(ntohl(th
->seq
), ct_ftp_info
, dir
)) {
403 /* Now if this ends in \n, update ftp info. */
404 DEBUGP("nf_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
405 ct_ftp_info
->seq_aft_nl_num
[dir
] > 0 ? "" : "(UNSET)",
406 ct_ftp_info
->seq_aft_nl
[dir
][0],
407 ct_ftp_info
->seq_aft_nl_num
[dir
] > 1 ? "" : "(UNSET)",
408 ct_ftp_info
->seq_aft_nl
[dir
][1]);
413 /* Initialize IP/IPv6 addr to expected address (it's not mentioned
414 in EPSV responses) */
415 cmd
.l3num
= ct
->tuplehash
[dir
].tuple
.src
.l3num
;
416 memcpy(cmd
.u3
.all
, &ct
->tuplehash
[dir
].tuple
.src
.u3
.all
,
419 for (i
= 0; i
< ARRAY_SIZE(search
[dir
]); i
++) {
420 found
= find_pattern(fb_ptr
, datalen
,
421 search
[dir
][i
].pattern
,
425 &matchoff
, &matchlen
,
427 search
[dir
][i
].getnum
);
431 /* We don't usually drop packets. After all, this is
432 connection tracking, not packet filtering.
433 However, it is necessary for accurate tracking in
436 printk("conntrack_ftp: partial %s %u+%u\n",
437 search
[dir
][i
].pattern
,
438 ntohl(th
->seq
), datalen
);
441 } else if (found
== 0) { /* No match */
446 DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
447 (int)matchlen
, fb_ptr
+ matchoff
,
448 matchlen
, ntohl(th
->seq
) + matchoff
);
450 exp
= nf_conntrack_expect_alloc(ct
);
456 /* We refer to the reverse direction ("!dir") tuples here,
457 * because we're expecting something in the other direction.
458 * Doesn't matter unless NAT is happening. */
459 exp
->tuple
.dst
.u3
= ct
->tuplehash
[!dir
].tuple
.dst
.u3
;
461 /* Update the ftp info */
462 if ((cmd
.l3num
== ct
->tuplehash
[dir
].tuple
.src
.l3num
) &&
463 memcmp(&cmd
.u3
.all
, &ct
->tuplehash
[dir
].tuple
.src
.u3
.all
,
464 sizeof(cmd
.u3
.all
))) {
465 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
466 server: it really wants us to connect to a
467 different IP address. Simply don't record it for
469 if (cmd
.l3num
== PF_INET
) {
470 DEBUGP("conntrack_ftp: NOT RECORDING: " NIPQUAD_FMT
" != " NIPQUAD_FMT
"\n",
472 NIPQUAD(ct
->tuplehash
[dir
].tuple
.src
.u3
.ip
));
474 DEBUGP("conntrack_ftp: NOT RECORDING: " NIP6_FMT
" != " NIP6_FMT
"\n",
475 NIP6(*((struct in6_addr
*)cmd
.u3
.ip6
)),
476 NIP6(*((struct in6_addr
*)ct
->tuplehash
[dir
]
477 .tuple
.src
.u3
.ip6
)));
480 /* Thanks to Cristiano Lincoln Mattos
481 <lincoln@cesar.org.br> for reporting this potential
482 problem (DMZ machines opening holes to internal
483 networks, or the packet filter itself). */
488 memcpy(&exp
->tuple
.dst
.u3
, &cmd
.u3
.all
,
489 sizeof(exp
->tuple
.dst
.u3
));
492 exp
->tuple
.src
.u3
= ct
->tuplehash
[!dir
].tuple
.src
.u3
;
493 exp
->tuple
.src
.l3num
= cmd
.l3num
;
494 exp
->tuple
.src
.u
.tcp
.port
= 0;
495 exp
->tuple
.dst
.u
.tcp
.port
= cmd
.u
.tcp
.port
;
496 exp
->tuple
.dst
.protonum
= IPPROTO_TCP
;
498 exp
->mask
= (struct nf_conntrack_tuple
)
499 { .src
= { .l3num
= 0xFFFF,
500 .u
= { .tcp
= { 0 }},
502 .dst
= { .protonum
= 0xFF,
503 .u
= { .tcp
= { 0xFFFF }},
506 if (cmd
.l3num
== PF_INET
) {
507 exp
->mask
.src
.u3
.ip
= 0xFFFFFFFF;
508 exp
->mask
.dst
.u3
.ip
= 0xFFFFFFFF;
510 memset(exp
->mask
.src
.u3
.ip6
, 0xFF,
511 sizeof(exp
->mask
.src
.u3
.ip6
));
512 memset(exp
->mask
.dst
.u3
.ip6
, 0xFF,
513 sizeof(exp
->mask
.src
.u3
.ip6
));
516 exp
->expectfn
= NULL
;
519 /* Now, NAT might want to mangle the packet, and register the
520 * (possibly changed) expectation itself. */
522 ret
= nf_nat_ftp_hook(pskb
, ctinfo
, search
[dir
][i
].ftptype
,
523 matchoff
, matchlen
, exp
, &seq
);
525 /* Can't expect this? Best to drop packet now. */
526 if (nf_conntrack_expect_related(exp
) != 0)
533 nf_conntrack_expect_put(exp
);
536 /* Now if this ends in \n, update ftp info. Seq may have been
537 * adjusted by NAT code. */
539 update_nl_seq(seq
, ct_ftp_info
, dir
, *pskb
);
541 spin_unlock_bh(&nf_ftp_lock
);
545 static struct nf_conntrack_helper ftp
[MAX_PORTS
][2];
546 static char ftp_names
[MAX_PORTS
][2][sizeof("ftp-65535")];
548 /* don't make this __exit, since it's called from __init ! */
549 static void nf_conntrack_ftp_fini(void)
552 for (i
= 0; i
< ports_c
; i
++) {
553 for (j
= 0; j
< 2; j
++) {
554 if (ftp
[i
][j
].me
== NULL
)
557 DEBUGP("nf_ct_ftp: unregistering helper for pf: %d "
559 ftp
[i
][j
].tuple
.src
.l3num
, ports
[i
]);
560 nf_conntrack_helper_unregister(&ftp
[i
][j
]);
567 static int __init
nf_conntrack_ftp_init(void)
569 int i
, j
= -1, ret
= 0;
572 ftp_buffer
= kmalloc(65536, GFP_KERNEL
);
577 ports
[ports_c
++] = FTP_PORT
;
579 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
580 are tracked or not - YK */
581 for (i
= 0; i
< ports_c
; i
++) {
582 ftp
[i
][0].tuple
.src
.l3num
= PF_INET
;
583 ftp
[i
][1].tuple
.src
.l3num
= PF_INET6
;
584 for (j
= 0; j
< 2; j
++) {
585 ftp
[i
][j
].tuple
.src
.u
.tcp
.port
= htons(ports
[i
]);
586 ftp
[i
][j
].tuple
.dst
.protonum
= IPPROTO_TCP
;
587 ftp
[i
][j
].mask
.src
.u
.tcp
.port
= 0xFFFF;
588 ftp
[i
][j
].mask
.dst
.protonum
= 0xFF;
589 ftp
[i
][j
].max_expected
= 1;
590 ftp
[i
][j
].timeout
= 5 * 60; /* 5 Minutes */
591 ftp
[i
][j
].me
= THIS_MODULE
;
592 ftp
[i
][j
].help
= help
;
593 tmpname
= &ftp_names
[i
][j
][0];
594 if (ports
[i
] == FTP_PORT
)
595 sprintf(tmpname
, "ftp");
597 sprintf(tmpname
, "ftp-%d", ports
[i
]);
598 ftp
[i
][j
].name
= tmpname
;
600 DEBUGP("nf_ct_ftp: registering helper for pf: %d "
602 ftp
[i
][j
].tuple
.src
.l3num
, ports
[i
]);
603 ret
= nf_conntrack_helper_register(&ftp
[i
][j
]);
605 printk("nf_ct_ftp: failed to register helper "
606 " for pf: %d port: %d\n",
607 ftp
[i
][j
].tuple
.src
.l3num
, ports
[i
]);
608 nf_conntrack_ftp_fini();
617 module_init(nf_conntrack_ftp_init
);
618 module_exit(nf_conntrack_ftp_fini
);