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 MODULE_LICENSE("GPL");
33 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
34 MODULE_DESCRIPTION("ftp connection tracking helper");
35 MODULE_ALIAS("ip_conntrack_ftp");
36 MODULE_ALIAS_NFCT_HELPER("ftp");
38 /* This is slow, but it's simple. --RR */
39 static char *ftp_buffer
;
41 static DEFINE_SPINLOCK(nf_ftp_lock
);
44 static u_int16_t ports
[MAX_PORTS
];
45 static unsigned int ports_c
;
46 module_param_array(ports
, ushort
, &ports_c
, 0400);
49 module_param(loose
, bool, 0600);
51 unsigned int (*nf_nat_ftp_hook
)(struct sk_buff
*skb
,
52 enum ip_conntrack_info ctinfo
,
53 enum nf_ct_ftp_type type
,
55 unsigned int matchoff
,
56 unsigned int matchlen
,
57 struct nf_conntrack_expect
*exp
);
58 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook
);
60 static int try_rfc959(const char *, size_t, struct nf_conntrack_man
*,
61 char, unsigned int *);
62 static int try_rfc1123(const char *, size_t, struct nf_conntrack_man
*,
63 char, unsigned int *);
64 static int try_eprt(const char *, size_t, struct nf_conntrack_man
*,
65 char, unsigned int *);
66 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man
*,
67 char, unsigned int *);
69 static struct ftp_search
{
74 enum nf_ct_ftp_type ftptype
;
75 int (*getnum
)(const char *, size_t, struct nf_conntrack_man
*, char, unsigned int *);
76 } search
[IP_CT_DIR_MAX
][2] = {
77 [IP_CT_DIR_ORIGINAL
] = {
80 .plen
= sizeof("PORT") - 1,
83 .ftptype
= NF_CT_FTP_PORT
,
88 .plen
= sizeof("EPRT") - 1,
91 .ftptype
= NF_CT_FTP_EPRT
,
98 .plen
= sizeof("227 ") - 1,
99 .ftptype
= NF_CT_FTP_PASV
,
100 .getnum
= try_rfc1123
,
104 .plen
= sizeof("229 ") - 1,
107 .ftptype
= NF_CT_FTP_EPSV
,
108 .getnum
= try_epsv_response
,
114 get_ipv6_addr(const char *src
, size_t dlen
, struct in6_addr
*dst
, u_int8_t term
)
117 int ret
= in6_pton(src
, min_t(size_t, dlen
, 0xffff), (u8
*)dst
, term
, &end
);
119 return (int)(end
- src
);
123 static int try_number(const char *data
, size_t dlen
, u_int32_t array
[],
124 int array_size
, char sep
, char term
)
128 memset(array
, 0, sizeof(array
[0])*array_size
);
130 /* Keep data pointing at next char. */
131 for (i
= 0, len
= 0; len
< dlen
&& i
< array_size
; len
++, data
++) {
132 if (*data
>= '0' && *data
<= '9') {
133 array
[i
] = array
[i
]*10 + *data
- '0';
135 else if (*data
== sep
)
138 /* Unexpected character; true if it's the
139 terminator (or we don't care about one)
140 and we're finished. */
141 if ((*data
== term
|| !term
) && i
== array_size
- 1)
144 pr_debug("Char %u (got %u nums) `%u' unexpected\n",
149 pr_debug("Failed to fill %u numbers separated by %c\n",
154 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
155 static int try_rfc959(const char *data
, size_t dlen
,
156 struct nf_conntrack_man
*cmd
, char term
,
157 unsigned int *offset
)
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]);
174 * The format of the 227 reply to a PASV command is not
175 * well standardized. In particular, an FTP client cannot
176 * assume that the parentheses shown on page 40 of RFC-959
177 * will be present (and in fact, Figure 3 on page 43 omits
178 * them). Therefore, a User-FTP program that interprets
179 * the PASV reply must scan the reply for the first digit
180 * of the host and port numbers.
182 static int try_rfc1123(const char *data
, size_t dlen
,
183 struct nf_conntrack_man
*cmd
, char term
,
184 unsigned int *offset
)
187 for (i
= 0; i
< dlen
; i
++)
188 if (isdigit(data
[i
]))
196 return try_rfc959(data
+ i
, dlen
- i
, cmd
, 0, offset
);
199 /* Grab port: number up to delimiter */
200 static int get_port(const char *data
, int start
, size_t dlen
, char delim
,
203 u_int16_t tmp_port
= 0;
206 for (i
= start
; i
< dlen
; i
++) {
208 if (data
[i
] == delim
) {
211 *port
= htons(tmp_port
);
212 pr_debug("get_port: return %d\n", tmp_port
);
215 else if (data
[i
] >= '0' && data
[i
] <= '9')
216 tmp_port
= tmp_port
*10 + data
[i
] - '0';
217 else { /* Some other crap */
218 pr_debug("get_port: invalid char.\n");
225 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
226 static int try_eprt(const char *data
, size_t dlen
, struct nf_conntrack_man
*cmd
,
227 char term
, unsigned int *offset
)
232 /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
233 then delimiter again. */
235 pr_debug("EPRT: too short\n");
239 if (isdigit(delim
) || delim
< 33 || delim
> 126 || data
[2] != delim
) {
240 pr_debug("try_eprt: invalid delimiter.\n");
244 if ((cmd
->l3num
== PF_INET
&& data
[1] != '1') ||
245 (cmd
->l3num
== PF_INET6
&& data
[1] != '2')) {
246 pr_debug("EPRT: invalid protocol number.\n");
250 pr_debug("EPRT: Got %c%c%c\n", delim
, data
[1], delim
);
252 if (data
[1] == '1') {
255 /* Now we have IP address. */
256 length
= try_number(data
+ 3, dlen
- 3, array
, 4, '.', delim
);
258 cmd
->u3
.ip
= htonl((array
[0] << 24) | (array
[1] << 16)
259 | (array
[2] << 8) | array
[3]);
261 /* Now we have IPv6 address. */
262 length
= get_ipv6_addr(data
+ 3, dlen
- 3,
263 (struct in6_addr
*)cmd
->u3
.ip6
, delim
);
268 pr_debug("EPRT: Got IP address!\n");
269 /* Start offset includes initial "|1|", and trailing delimiter */
270 return get_port(data
, 3 + length
+ 1, dlen
, delim
, &cmd
->u
.tcp
.port
);
273 /* Returns 0, or length of numbers: |||6446| */
274 static int try_epsv_response(const char *data
, size_t dlen
,
275 struct nf_conntrack_man
*cmd
, char term
,
276 unsigned int *offset
)
280 /* Three delimiters. */
281 if (dlen
<= 3) return 0;
283 if (isdigit(delim
) || delim
< 33 || delim
> 126 ||
284 data
[1] != delim
|| data
[2] != delim
)
287 return get_port(data
, 3, dlen
, delim
, &cmd
->u
.tcp
.port
);
290 /* Return 1 for match, 0 for accept, -1 for partial. */
291 static int find_pattern(const char *data
, size_t dlen
,
292 const char *pattern
, size_t plen
,
293 char skip
, char term
,
294 unsigned int *numoff
,
295 unsigned int *numlen
,
296 struct nf_conntrack_man
*cmd
,
297 int (*getnum
)(const char *, size_t,
298 struct nf_conntrack_man
*, char,
303 pr_debug("find_pattern `%s': dlen = %Zu\n", pattern
, dlen
);
306 /* Short packet: try for partial? */
307 if (strncasecmp(data
, pattern
, dlen
) == 0)
312 if (strncasecmp(data
, pattern
, plen
) != 0)
315 pr_debug("Pattern matches!\n");
316 /* Now we've found the constant string, try to skip
317 to the 'skip' character */
319 for (i
= plen
; data
[i
] != skip
; i
++)
320 if (i
== dlen
- 1) return -1;
322 /* Skip over the last character */
326 pr_debug("Skipped up to `%c'!\n", skip
);
329 *numlen
= getnum(data
+ i
, dlen
- i
, cmd
, term
, numoff
);
333 pr_debug("Match succeeded!\n");
337 /* Look up to see if we're just after a \n. */
338 static int find_nl_seq(u32 seq
, const struct nf_ct_ftp_master
*info
, int dir
)
342 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++)
343 if (info
->seq_aft_nl
[dir
][i
] == seq
)
348 /* We don't update if it's older than what we have. */
349 static void update_nl_seq(struct nf_conn
*ct
, u32 nl_seq
,
350 struct nf_ct_ftp_master
*info
, int dir
,
353 unsigned int i
, oldest
;
355 /* Look for oldest: if we find exact match, we're done. */
356 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++) {
357 if (info
->seq_aft_nl
[dir
][i
] == nl_seq
)
361 if (info
->seq_aft_nl_num
[dir
] < NUM_SEQ_TO_REMEMBER
) {
362 info
->seq_aft_nl
[dir
][info
->seq_aft_nl_num
[dir
]++] = nl_seq
;
364 if (before(info
->seq_aft_nl
[dir
][0], info
->seq_aft_nl
[dir
][1]))
369 if (after(nl_seq
, info
->seq_aft_nl
[dir
][oldest
]))
370 info
->seq_aft_nl
[dir
][oldest
] = nl_seq
;
374 static int help(struct sk_buff
*skb
,
375 unsigned int protoff
,
377 enum ip_conntrack_info ctinfo
)
379 unsigned int dataoff
, datalen
;
380 const struct tcphdr
*th
;
385 int dir
= CTINFO2DIR(ctinfo
);
386 unsigned int uninitialized_var(matchlen
), uninitialized_var(matchoff
);
387 struct nf_ct_ftp_master
*ct_ftp_info
= nfct_help_data(ct
);
388 struct nf_conntrack_expect
*exp
;
389 union nf_inet_addr
*daddr
;
390 struct nf_conntrack_man cmd
= {};
392 int found
= 0, ends_in_nl
;
393 typeof(nf_nat_ftp_hook
) nf_nat_ftp
;
395 /* Until there's been traffic both ways, don't look in packets. */
396 if (ctinfo
!= IP_CT_ESTABLISHED
&&
397 ctinfo
!= IP_CT_ESTABLISHED_REPLY
) {
398 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo
);
402 th
= skb_header_pointer(skb
, protoff
, sizeof(_tcph
), &_tcph
);
406 dataoff
= protoff
+ th
->doff
* 4;
408 if (dataoff
>= skb
->len
) {
409 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff
,
413 datalen
= skb
->len
- dataoff
;
415 spin_lock_bh(&nf_ftp_lock
);
416 fb_ptr
= skb_header_pointer(skb
, dataoff
, datalen
, ftp_buffer
);
417 BUG_ON(fb_ptr
== NULL
);
419 ends_in_nl
= (fb_ptr
[datalen
- 1] == '\n');
420 seq
= ntohl(th
->seq
) + datalen
;
422 /* Look up to see if we're just after a \n. */
423 if (!find_nl_seq(ntohl(th
->seq
), ct_ftp_info
, dir
)) {
424 /* We're picking up this, clear flags and let it continue */
425 if (unlikely(ct_ftp_info
->flags
[dir
] & NF_CT_FTP_SEQ_PICKUP
)) {
426 ct_ftp_info
->flags
[dir
] ^= NF_CT_FTP_SEQ_PICKUP
;
430 /* Now if this ends in \n, update ftp info. */
431 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
432 ct_ftp_info
->seq_aft_nl_num
[dir
] > 0 ? "" : "(UNSET)",
433 ct_ftp_info
->seq_aft_nl
[dir
][0],
434 ct_ftp_info
->seq_aft_nl_num
[dir
] > 1 ? "" : "(UNSET)",
435 ct_ftp_info
->seq_aft_nl
[dir
][1]);
441 /* Initialize IP/IPv6 addr to expected address (it's not mentioned
442 in EPSV responses) */
443 cmd
.l3num
= nf_ct_l3num(ct
);
444 memcpy(cmd
.u3
.all
, &ct
->tuplehash
[dir
].tuple
.src
.u3
.all
,
447 for (i
= 0; i
< ARRAY_SIZE(search
[dir
]); i
++) {
448 found
= find_pattern(fb_ptr
, datalen
,
449 search
[dir
][i
].pattern
,
453 &matchoff
, &matchlen
,
455 search
[dir
][i
].getnum
);
459 /* We don't usually drop packets. After all, this is
460 connection tracking, not packet filtering.
461 However, it is necessary for accurate tracking in
463 nf_ct_helper_log(skb
, ct
, "partial matching of `%s'",
464 search
[dir
][i
].pattern
);
467 } else if (found
== 0) { /* No match */
472 pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
473 matchlen
, fb_ptr
+ matchoff
,
474 matchlen
, ntohl(th
->seq
) + matchoff
);
476 exp
= nf_ct_expect_alloc(ct
);
478 nf_ct_helper_log(skb
, ct
, "cannot alloc expectation");
483 /* We refer to the reverse direction ("!dir") tuples here,
484 * because we're expecting something in the other direction.
485 * Doesn't matter unless NAT is happening. */
486 daddr
= &ct
->tuplehash
[!dir
].tuple
.dst
.u3
;
488 /* Update the ftp info */
489 if ((cmd
.l3num
== nf_ct_l3num(ct
)) &&
490 memcmp(&cmd
.u3
.all
, &ct
->tuplehash
[dir
].tuple
.src
.u3
.all
,
491 sizeof(cmd
.u3
.all
))) {
492 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
493 server: it really wants us to connect to a
494 different IP address. Simply don't record it for
496 if (cmd
.l3num
== PF_INET
) {
497 pr_debug("NOT RECORDING: %pI4 != %pI4\n",
499 &ct
->tuplehash
[dir
].tuple
.src
.u3
.ip
);
501 pr_debug("NOT RECORDING: %pI6 != %pI6\n",
503 ct
->tuplehash
[dir
].tuple
.src
.u3
.ip6
);
506 /* Thanks to Cristiano Lincoln Mattos
507 <lincoln@cesar.org.br> for reporting this potential
508 problem (DMZ machines opening holes to internal
509 networks, or the packet filter itself). */
517 nf_ct_expect_init(exp
, NF_CT_EXPECT_CLASS_DEFAULT
, cmd
.l3num
,
518 &ct
->tuplehash
[!dir
].tuple
.src
.u3
, daddr
,
519 IPPROTO_TCP
, NULL
, &cmd
.u
.tcp
.port
);
521 /* Now, NAT might want to mangle the packet, and register the
522 * (possibly changed) expectation itself. */
523 nf_nat_ftp
= rcu_dereference(nf_nat_ftp_hook
);
524 if (nf_nat_ftp
&& ct
->status
& IPS_NAT_MASK
)
525 ret
= nf_nat_ftp(skb
, ctinfo
, search
[dir
][i
].ftptype
,
526 protoff
, matchoff
, matchlen
, exp
);
528 /* Can't expect this? Best to drop packet now. */
529 if (nf_ct_expect_related(exp
) != 0) {
530 nf_ct_helper_log(skb
, ct
, "cannot add expectation");
537 nf_ct_expect_put(exp
);
540 /* Now if this ends in \n, update ftp info. Seq may have been
541 * adjusted by NAT code. */
543 update_nl_seq(ct
, seq
, ct_ftp_info
, dir
, skb
);
545 spin_unlock_bh(&nf_ftp_lock
);
549 static int nf_ct_ftp_from_nlattr(struct nlattr
*attr
, struct nf_conn
*ct
)
551 struct nf_ct_ftp_master
*ftp
= nfct_help_data(ct
);
553 /* This conntrack has been injected from user-space, always pick up
554 * sequence tracking. Otherwise, the first FTP command after the
557 ftp
->flags
[IP_CT_DIR_ORIGINAL
] |= NF_CT_FTP_SEQ_PICKUP
;
558 ftp
->flags
[IP_CT_DIR_REPLY
] |= NF_CT_FTP_SEQ_PICKUP
;
562 static struct nf_conntrack_helper ftp
[MAX_PORTS
* 2] __read_mostly
;
564 static const struct nf_conntrack_expect_policy ftp_exp_policy
= {
569 /* don't make this __exit, since it's called from __init ! */
570 static void nf_conntrack_ftp_fini(void)
572 nf_conntrack_helpers_unregister(ftp
, ports_c
* 2);
576 static int __init
nf_conntrack_ftp_init(void)
580 ftp_buffer
= kmalloc(65536, GFP_KERNEL
);
585 ports
[ports_c
++] = FTP_PORT
;
587 /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
588 are tracked or not - YK */
589 for (i
= 0; i
< ports_c
; i
++) {
590 nf_ct_helper_init(&ftp
[2 * i
], AF_INET
, IPPROTO_TCP
, "ftp",
591 FTP_PORT
, ports
[i
], ports
[i
], &ftp_exp_policy
,
592 0, sizeof(struct nf_ct_ftp_master
), help
,
593 nf_ct_ftp_from_nlattr
, THIS_MODULE
);
594 nf_ct_helper_init(&ftp
[2 * i
+ 1], AF_INET6
, IPPROTO_TCP
, "ftp",
595 FTP_PORT
, ports
[i
], ports
[i
], &ftp_exp_policy
,
596 0, sizeof(struct nf_ct_ftp_master
), help
,
597 nf_ct_ftp_from_nlattr
, THIS_MODULE
);
600 ret
= nf_conntrack_helpers_register(ftp
, ports_c
* 2);
602 pr_err("failed to register helpers\n");
610 module_init(nf_conntrack_ftp_init
);
611 module_exit(nf_conntrack_ftp_fini
);