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>
6 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15 #include <linux/module.h>
16 #include <linux/moduleparam.h>
17 #include <linux/netfilter.h>
19 #include <linux/slab.h>
20 #include <linux/ipv6.h>
21 #include <linux/ctype.h>
22 #include <linux/inet.h>
23 #include <net/checksum.h>
26 #include <net/netfilter/nf_conntrack.h>
27 #include <net/netfilter/nf_conntrack_expect.h>
28 #include <net/netfilter/nf_conntrack_ecache.h>
29 #include <net/netfilter/nf_conntrack_helper.h>
30 #include <linux/netfilter/nf_conntrack_ftp.h>
32 #define HELPER_NAME "ftp"
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");
38 MODULE_ALIAS_NFCT_HELPER(HELPER_NAME
);
40 /* This is slow, but it's simple. --RR */
41 static char *ftp_buffer
;
43 static DEFINE_SPINLOCK(nf_ftp_lock
);
46 static u_int16_t ports
[MAX_PORTS
];
47 static unsigned int ports_c
;
48 module_param_array(ports
, ushort
, &ports_c
, 0400);
51 module_param(loose
, bool, 0600);
53 unsigned int (*nf_nat_ftp_hook
)(struct sk_buff
*skb
,
54 enum ip_conntrack_info ctinfo
,
55 enum nf_ct_ftp_type type
,
57 unsigned int matchoff
,
58 unsigned int matchlen
,
59 struct nf_conntrack_expect
*exp
);
60 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook
);
62 static int try_rfc959(const char *, size_t, struct nf_conntrack_man
*,
63 char, unsigned int *);
64 static int try_rfc1123(const char *, size_t, struct nf_conntrack_man
*,
65 char, unsigned int *);
66 static int try_eprt(const char *, size_t, struct nf_conntrack_man
*,
67 char, unsigned int *);
68 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man
*,
69 char, unsigned int *);
71 static struct ftp_search
{
76 enum nf_ct_ftp_type ftptype
;
77 int (*getnum
)(const char *, size_t, struct nf_conntrack_man
*, char, unsigned int *);
78 } search
[IP_CT_DIR_MAX
][2] = {
79 [IP_CT_DIR_ORIGINAL
] = {
82 .plen
= sizeof("PORT") - 1,
85 .ftptype
= NF_CT_FTP_PORT
,
90 .plen
= sizeof("EPRT") - 1,
93 .ftptype
= NF_CT_FTP_EPRT
,
100 .plen
= sizeof("227 ") - 1,
101 .ftptype
= NF_CT_FTP_PASV
,
102 .getnum
= try_rfc1123
,
106 .plen
= sizeof("229 ") - 1,
109 .ftptype
= NF_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 (or we don't care about one)
142 and we're finished. */
143 if ((*data
== term
|| !term
) && i
== array_size
- 1)
146 pr_debug("Char %u (got %u nums) `%u' unexpected\n",
151 pr_debug("Failed to fill %u numbers separated by %c\n",
156 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
157 static int try_rfc959(const char *data
, size_t dlen
,
158 struct nf_conntrack_man
*cmd
, char term
,
159 unsigned int *offset
)
164 length
= try_number(data
, dlen
, array
, 6, ',', term
);
168 cmd
->u3
.ip
= htonl((array
[0] << 24) | (array
[1] << 16) |
169 (array
[2] << 8) | array
[3]);
170 cmd
->u
.tcp
.port
= htons((array
[4] << 8) | array
[5]);
176 * The format of the 227 reply to a PASV command is not
177 * well standardized. In particular, an FTP client cannot
178 * assume that the parentheses shown on page 40 of RFC-959
179 * will be present (and in fact, Figure 3 on page 43 omits
180 * them). Therefore, a User-FTP program that interprets
181 * the PASV reply must scan the reply for the first digit
182 * of the host and port numbers.
184 static int try_rfc1123(const char *data
, size_t dlen
,
185 struct nf_conntrack_man
*cmd
, char term
,
186 unsigned int *offset
)
189 for (i
= 0; i
< dlen
; i
++)
190 if (isdigit(data
[i
]))
198 return try_rfc959(data
+ i
, dlen
- i
, cmd
, 0, offset
);
201 /* Grab port: number up to delimiter */
202 static int get_port(const char *data
, int start
, size_t dlen
, char delim
,
205 u_int16_t tmp_port
= 0;
208 for (i
= start
; i
< dlen
; i
++) {
210 if (data
[i
] == delim
) {
213 *port
= htons(tmp_port
);
214 pr_debug("get_port: return %d\n", tmp_port
);
217 else if (data
[i
] >= '0' && data
[i
] <= '9')
218 tmp_port
= tmp_port
*10 + data
[i
] - '0';
219 else { /* Some other crap */
220 pr_debug("get_port: invalid char.\n");
227 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
228 static int try_eprt(const char *data
, size_t dlen
, struct nf_conntrack_man
*cmd
,
229 char term
, unsigned int *offset
)
234 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
235 then delimiter again. */
237 pr_debug("EPRT: too short\n");
241 if (isdigit(delim
) || delim
< 33 || delim
> 126 || data
[2] != delim
) {
242 pr_debug("try_eprt: invalid delimiter.\n");
246 if ((cmd
->l3num
== PF_INET
&& data
[1] != '1') ||
247 (cmd
->l3num
== PF_INET6
&& data
[1] != '2')) {
248 pr_debug("EPRT: invalid protocol number.\n");
252 pr_debug("EPRT: Got %c%c%c\n", delim
, data
[1], delim
);
254 if (data
[1] == '1') {
257 /* Now we have IP address. */
258 length
= try_number(data
+ 3, dlen
- 3, array
, 4, '.', delim
);
260 cmd
->u3
.ip
= htonl((array
[0] << 24) | (array
[1] << 16)
261 | (array
[2] << 8) | array
[3]);
263 /* Now we have IPv6 address. */
264 length
= get_ipv6_addr(data
+ 3, dlen
- 3,
265 (struct in6_addr
*)cmd
->u3
.ip6
, delim
);
270 pr_debug("EPRT: Got IP address!\n");
271 /* Start offset includes initial "|1|", and trailing delimiter */
272 return get_port(data
, 3 + length
+ 1, dlen
, delim
, &cmd
->u
.tcp
.port
);
275 /* Returns 0, or length of numbers: |||6446| */
276 static int try_epsv_response(const char *data
, size_t dlen
,
277 struct nf_conntrack_man
*cmd
, char term
,
278 unsigned int *offset
)
282 /* Three delimiters. */
283 if (dlen
<= 3) return 0;
285 if (isdigit(delim
) || delim
< 33 || delim
> 126 ||
286 data
[1] != delim
|| data
[2] != delim
)
289 return get_port(data
, 3, dlen
, delim
, &cmd
->u
.tcp
.port
);
292 /* Return 1 for match, 0 for accept, -1 for partial. */
293 static int find_pattern(const char *data
, size_t dlen
,
294 const char *pattern
, size_t plen
,
295 char skip
, char term
,
296 unsigned int *numoff
,
297 unsigned int *numlen
,
298 struct nf_conntrack_man
*cmd
,
299 int (*getnum
)(const char *, size_t,
300 struct nf_conntrack_man
*, char,
305 pr_debug("find_pattern `%s': dlen = %zu\n", pattern
, dlen
);
308 /* Short packet: try for partial? */
309 if (strncasecmp(data
, pattern
, dlen
) == 0)
314 if (strncasecmp(data
, pattern
, plen
) != 0)
317 pr_debug("Pattern matches!\n");
318 /* Now we've found the constant string, try to skip
319 to the 'skip' character */
321 for (i
= plen
; data
[i
] != skip
; i
++)
322 if (i
== dlen
- 1) return -1;
324 /* Skip over the last character */
328 pr_debug("Skipped up to `%c'!\n", skip
);
331 *numlen
= getnum(data
+ i
, dlen
- i
, cmd
, term
, numoff
);
335 pr_debug("Match succeeded!\n");
339 /* Look up to see if we're just after a \n. */
340 static int find_nl_seq(u32 seq
, const struct nf_ct_ftp_master
*info
, int dir
)
344 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++)
345 if (info
->seq_aft_nl
[dir
][i
] == seq
)
350 /* We don't update if it's older than what we have. */
351 static void update_nl_seq(struct nf_conn
*ct
, u32 nl_seq
,
352 struct nf_ct_ftp_master
*info
, int dir
,
355 unsigned int i
, oldest
;
357 /* Look for oldest: if we find exact match, we're done. */
358 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++) {
359 if (info
->seq_aft_nl
[dir
][i
] == nl_seq
)
363 if (info
->seq_aft_nl_num
[dir
] < NUM_SEQ_TO_REMEMBER
) {
364 info
->seq_aft_nl
[dir
][info
->seq_aft_nl_num
[dir
]++] = nl_seq
;
366 if (before(info
->seq_aft_nl
[dir
][0], info
->seq_aft_nl
[dir
][1]))
371 if (after(nl_seq
, info
->seq_aft_nl
[dir
][oldest
]))
372 info
->seq_aft_nl
[dir
][oldest
] = nl_seq
;
376 static int help(struct sk_buff
*skb
,
377 unsigned int protoff
,
379 enum ip_conntrack_info ctinfo
)
381 unsigned int dataoff
, datalen
;
382 const struct tcphdr
*th
;
387 int dir
= CTINFO2DIR(ctinfo
);
388 unsigned int uninitialized_var(matchlen
), uninitialized_var(matchoff
);
389 struct nf_ct_ftp_master
*ct_ftp_info
= nfct_help_data(ct
);
390 struct nf_conntrack_expect
*exp
;
391 union nf_inet_addr
*daddr
;
392 struct nf_conntrack_man cmd
= {};
394 int found
= 0, ends_in_nl
;
395 typeof(nf_nat_ftp_hook
) nf_nat_ftp
;
397 /* Until there's been traffic both ways, don't look in packets. */
398 if (ctinfo
!= IP_CT_ESTABLISHED
&&
399 ctinfo
!= IP_CT_ESTABLISHED_REPLY
) {
400 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo
);
404 th
= skb_header_pointer(skb
, protoff
, sizeof(_tcph
), &_tcph
);
408 dataoff
= protoff
+ th
->doff
* 4;
410 if (dataoff
>= skb
->len
) {
411 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff
,
415 datalen
= skb
->len
- dataoff
;
417 spin_lock_bh(&nf_ftp_lock
);
418 fb_ptr
= skb_header_pointer(skb
, dataoff
, datalen
, ftp_buffer
);
419 BUG_ON(fb_ptr
== NULL
);
421 ends_in_nl
= (fb_ptr
[datalen
- 1] == '\n');
422 seq
= ntohl(th
->seq
) + datalen
;
424 /* Look up to see if we're just after a \n. */
425 if (!find_nl_seq(ntohl(th
->seq
), ct_ftp_info
, dir
)) {
426 /* We're picking up this, clear flags and let it continue */
427 if (unlikely(ct_ftp_info
->flags
[dir
] & NF_CT_FTP_SEQ_PICKUP
)) {
428 ct_ftp_info
->flags
[dir
] ^= NF_CT_FTP_SEQ_PICKUP
;
432 /* Now if this ends in \n, update ftp info. */
433 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
434 ct_ftp_info
->seq_aft_nl_num
[dir
] > 0 ? "" : "(UNSET)",
435 ct_ftp_info
->seq_aft_nl
[dir
][0],
436 ct_ftp_info
->seq_aft_nl_num
[dir
] > 1 ? "" : "(UNSET)",
437 ct_ftp_info
->seq_aft_nl
[dir
][1]);
443 /* Initialize IP/IPv6 addr to expected address (it's not mentioned
444 in EPSV responses) */
445 cmd
.l3num
= nf_ct_l3num(ct
);
446 memcpy(cmd
.u3
.all
, &ct
->tuplehash
[dir
].tuple
.src
.u3
.all
,
449 for (i
= 0; i
< ARRAY_SIZE(search
[dir
]); i
++) {
450 found
= find_pattern(fb_ptr
, datalen
,
451 search
[dir
][i
].pattern
,
455 &matchoff
, &matchlen
,
457 search
[dir
][i
].getnum
);
461 /* We don't usually drop packets. After all, this is
462 connection tracking, not packet filtering.
463 However, it is necessary for accurate tracking in
465 nf_ct_helper_log(skb
, ct
, "partial matching of `%s'",
466 search
[dir
][i
].pattern
);
469 } else if (found
== 0) { /* No match */
474 pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
475 matchlen
, fb_ptr
+ matchoff
,
476 matchlen
, ntohl(th
->seq
) + matchoff
);
478 exp
= nf_ct_expect_alloc(ct
);
480 nf_ct_helper_log(skb
, ct
, "cannot alloc expectation");
485 /* We refer to the reverse direction ("!dir") tuples here,
486 * because we're expecting something in the other direction.
487 * Doesn't matter unless NAT is happening. */
488 daddr
= &ct
->tuplehash
[!dir
].tuple
.dst
.u3
;
490 /* Update the ftp info */
491 if ((cmd
.l3num
== nf_ct_l3num(ct
)) &&
492 memcmp(&cmd
.u3
.all
, &ct
->tuplehash
[dir
].tuple
.src
.u3
.all
,
493 sizeof(cmd
.u3
.all
))) {
494 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
495 server: it really wants us to connect to a
496 different IP address. Simply don't record it for
498 if (cmd
.l3num
== PF_INET
) {
499 pr_debug("NOT RECORDING: %pI4 != %pI4\n",
501 &ct
->tuplehash
[dir
].tuple
.src
.u3
.ip
);
503 pr_debug("NOT RECORDING: %pI6 != %pI6\n",
505 ct
->tuplehash
[dir
].tuple
.src
.u3
.ip6
);
508 /* Thanks to Cristiano Lincoln Mattos
509 <lincoln@cesar.org.br> for reporting this potential
510 problem (DMZ machines opening holes to internal
511 networks, or the packet filter itself). */
519 nf_ct_expect_init(exp
, NF_CT_EXPECT_CLASS_DEFAULT
, cmd
.l3num
,
520 &ct
->tuplehash
[!dir
].tuple
.src
.u3
, daddr
,
521 IPPROTO_TCP
, NULL
, &cmd
.u
.tcp
.port
);
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(skb
, ctinfo
, search
[dir
][i
].ftptype
,
528 protoff
, matchoff
, matchlen
, exp
);
530 /* Can't expect this? Best to drop packet now. */
531 if (nf_ct_expect_related(exp
) != 0) {
532 nf_ct_helper_log(skb
, ct
, "cannot add expectation");
539 nf_ct_expect_put(exp
);
542 /* Now if this ends in \n, update ftp info. Seq may have been
543 * adjusted by NAT code. */
545 update_nl_seq(ct
, seq
, ct_ftp_info
, dir
, skb
);
547 spin_unlock_bh(&nf_ftp_lock
);
551 static int nf_ct_ftp_from_nlattr(struct nlattr
*attr
, struct nf_conn
*ct
)
553 struct nf_ct_ftp_master
*ftp
= nfct_help_data(ct
);
555 /* This conntrack has been injected from user-space, always pick up
556 * sequence tracking. Otherwise, the first FTP command after the
559 ftp
->flags
[IP_CT_DIR_ORIGINAL
] |= NF_CT_FTP_SEQ_PICKUP
;
560 ftp
->flags
[IP_CT_DIR_REPLY
] |= NF_CT_FTP_SEQ_PICKUP
;
564 static struct nf_conntrack_helper ftp
[MAX_PORTS
* 2] __read_mostly
;
566 static const struct nf_conntrack_expect_policy ftp_exp_policy
= {
571 static void __exit
nf_conntrack_ftp_fini(void)
573 nf_conntrack_helpers_unregister(ftp
, ports_c
* 2);
577 static int __init
nf_conntrack_ftp_init(void)
581 NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_ftp_master
));
583 ftp_buffer
= kmalloc(65536, GFP_KERNEL
);
588 ports
[ports_c
++] = FTP_PORT
;
590 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
591 are tracked or not - YK */
592 for (i
= 0; i
< ports_c
; i
++) {
593 nf_ct_helper_init(&ftp
[2 * i
], AF_INET
, IPPROTO_TCP
,
594 HELPER_NAME
, FTP_PORT
, ports
[i
], ports
[i
],
595 &ftp_exp_policy
, 0, help
,
596 nf_ct_ftp_from_nlattr
, THIS_MODULE
);
597 nf_ct_helper_init(&ftp
[2 * i
+ 1], AF_INET6
, IPPROTO_TCP
,
598 HELPER_NAME
, FTP_PORT
, ports
[i
], ports
[i
],
599 &ftp_exp_policy
, 0, help
,
600 nf_ct_ftp_from_nlattr
, THIS_MODULE
);
603 ret
= nf_conntrack_helpers_register(ftp
, ports_c
* 2);
605 pr_err("failed to register helpers\n");
613 module_init(nf_conntrack_ftp_init
);
614 module_exit(nf_conntrack_ftp_fini
);