1 /* FTP extension for IP connection tracking. */
3 /* (C) 1999-2001 Paul `Rusty' Russell
4 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
11 #include <linux/config.h>
12 #include <linux/module.h>
13 #include <linux/netfilter.h>
15 #include <linux/ctype.h>
16 #include <net/checksum.h>
19 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
20 #include <linux/netfilter_ipv4/ip_conntrack_ftp.h>
21 #include <linux/moduleparam.h>
23 MODULE_LICENSE("GPL");
24 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
25 MODULE_DESCRIPTION("ftp connection tracking helper");
27 /* This is slow, but it's simple. --RR */
28 static char *ftp_buffer
;
29 static DEFINE_SPINLOCK(ip_ftp_lock
);
32 static unsigned short ports
[MAX_PORTS
];
34 module_param_array(ports
, ushort
, &ports_c
, 0400);
37 module_param(loose
, bool, 0600);
39 unsigned int (*ip_nat_ftp_hook
)(struct sk_buff
**pskb
,
40 enum ip_conntrack_info ctinfo
,
41 enum ip_ct_ftp_type type
,
42 unsigned int matchoff
,
43 unsigned int matchlen
,
44 struct ip_conntrack_expect
*exp
,
46 EXPORT_SYMBOL_GPL(ip_nat_ftp_hook
);
51 #define DEBUGP(format, args...)
54 static int try_rfc959(const char *, size_t, u_int32_t
[], char);
55 static int try_eprt(const char *, size_t, u_int32_t
[], char);
56 static int try_epsv_response(const char *, size_t, u_int32_t
[], char);
58 static const struct ftp_search
{
63 enum ip_ct_ftp_type ftptype
;
64 int (*getnum
)(const char *, size_t, u_int32_t
[], char);
65 } search
[IP_CT_DIR_MAX
][2] = {
66 [IP_CT_DIR_ORIGINAL
] = {
69 .plen
= sizeof("PORT") - 1,
72 .ftptype
= IP_CT_FTP_PORT
,
77 .plen
= sizeof("EPRT") - 1,
80 .ftptype
= IP_CT_FTP_EPRT
,
87 .plen
= sizeof("227 ") - 1,
90 .ftptype
= IP_CT_FTP_PASV
,
95 .plen
= sizeof("229 ") - 1,
98 .ftptype
= IP_CT_FTP_EPSV
,
99 .getnum
= try_epsv_response
,
104 static int try_number(const char *data
, size_t dlen
, u_int32_t array
[],
105 int array_size
, char sep
, char term
)
109 memset(array
, 0, sizeof(array
[0])*array_size
);
111 /* Keep data pointing at next char. */
112 for (i
= 0, len
= 0; len
< dlen
&& i
< array_size
; len
++, data
++) {
113 if (*data
>= '0' && *data
<= '9') {
114 array
[i
] = array
[i
]*10 + *data
- '0';
116 else if (*data
== sep
)
119 /* Unexpected character; true if it's the
120 terminator and we're finished. */
121 if (*data
== term
&& i
== array_size
- 1)
124 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
129 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size
, sep
);
134 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
135 static int try_rfc959(const char *data
, size_t dlen
, u_int32_t array
[6],
138 return try_number(data
, dlen
, array
, 6, ',', term
);
141 /* Grab port: number up to delimiter */
142 static int get_port(const char *data
, int start
, size_t dlen
, char delim
,
148 for (i
= start
; i
< dlen
; i
++) {
150 if (data
[i
] == delim
) {
153 array
[0] = port
>> 8;
157 else if (data
[i
] >= '0' && data
[i
] <= '9')
158 port
= port
*10 + data
[i
] - '0';
159 else /* Some other crap */
165 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */
166 static int try_eprt(const char *data
, size_t dlen
, u_int32_t array
[6],
172 /* First character is delimiter, then "1" for IPv4, then
174 if (dlen
<= 3) return 0;
176 if (isdigit(delim
) || delim
< 33 || delim
> 126
177 || data
[1] != '1' || data
[2] != delim
)
180 DEBUGP("EPRT: Got |1|!\n");
181 /* Now we have IP address. */
182 length
= try_number(data
+ 3, dlen
- 3, array
, 4, '.', delim
);
186 DEBUGP("EPRT: Got IP address!\n");
187 /* Start offset includes initial "|1|", and trailing delimiter */
188 return get_port(data
, 3 + length
+ 1, dlen
, delim
, array
+4);
191 /* Returns 0, or length of numbers: |||6446| */
192 static int try_epsv_response(const char *data
, size_t dlen
, u_int32_t array
[6],
197 /* Three delimiters. */
198 if (dlen
<= 3) return 0;
200 if (isdigit(delim
) || delim
< 33 || delim
> 126
201 || data
[1] != delim
|| data
[2] != delim
)
204 return get_port(data
, 3, dlen
, delim
, array
+4);
207 /* Return 1 for match, 0 for accept, -1 for partial. */
208 static int find_pattern(const char *data
, size_t dlen
,
209 const char *pattern
, size_t plen
,
210 char skip
, char term
,
211 unsigned int *numoff
,
212 unsigned int *numlen
,
214 int (*getnum
)(const char *, size_t, u_int32_t
[], char))
218 DEBUGP("find_pattern `%s': dlen = %u\n", pattern
, dlen
);
223 /* Short packet: try for partial? */
224 if (strnicmp(data
, pattern
, dlen
) == 0)
229 if (strnicmp(data
, pattern
, plen
) != 0) {
233 DEBUGP("ftp: string mismatch\n");
234 for (i
= 0; i
< plen
; i
++) {
235 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
237 pattern
[i
], pattern
[i
]);
243 DEBUGP("Pattern matches!\n");
244 /* Now we've found the constant string, try to skip
245 to the 'skip' character */
246 for (i
= plen
; data
[i
] != skip
; i
++)
247 if (i
== dlen
- 1) return -1;
249 /* Skip over the last character */
252 DEBUGP("Skipped up to `%c'!\n", skip
);
255 *numlen
= getnum(data
+ i
, dlen
- i
, array
, term
);
259 DEBUGP("Match succeeded!\n");
263 /* Look up to see if we're just after a \n. */
264 static int find_nl_seq(u32 seq
, const struct ip_ct_ftp_master
*info
, int dir
)
268 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++)
269 if (info
->seq_aft_nl
[dir
][i
] == seq
)
274 /* We don't update if it's older than what we have. */
275 static void update_nl_seq(u32 nl_seq
, struct ip_ct_ftp_master
*info
, int dir
,
278 unsigned int i
, oldest
= NUM_SEQ_TO_REMEMBER
;
280 /* Look for oldest: if we find exact match, we're done. */
281 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++) {
282 if (info
->seq_aft_nl
[dir
][i
] == nl_seq
)
285 if (oldest
== info
->seq_aft_nl_num
[dir
]
286 || before(info
->seq_aft_nl
[dir
][i
], oldest
))
290 if (info
->seq_aft_nl_num
[dir
] < NUM_SEQ_TO_REMEMBER
) {
291 info
->seq_aft_nl
[dir
][info
->seq_aft_nl_num
[dir
]++] = nl_seq
;
292 ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE
, skb
);
293 } else if (oldest
!= NUM_SEQ_TO_REMEMBER
) {
294 info
->seq_aft_nl
[dir
][oldest
] = nl_seq
;
295 ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE
, skb
);
299 static int help(struct sk_buff
**pskb
,
300 struct ip_conntrack
*ct
,
301 enum ip_conntrack_info ctinfo
)
303 unsigned int dataoff
, datalen
;
304 struct tcphdr _tcph
, *th
;
307 u32 seq
, array
[6] = { 0 };
308 int dir
= CTINFO2DIR(ctinfo
);
309 unsigned int matchlen
, matchoff
;
310 struct ip_ct_ftp_master
*ct_ftp_info
= &ct
->help
.ct_ftp_info
;
311 struct ip_conntrack_expect
*exp
;
313 int found
= 0, ends_in_nl
;
315 /* Until there's been traffic both ways, don't look in packets. */
316 if (ctinfo
!= IP_CT_ESTABLISHED
317 && ctinfo
!= IP_CT_ESTABLISHED
+IP_CT_IS_REPLY
) {
318 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo
);
322 th
= skb_header_pointer(*pskb
, (*pskb
)->nh
.iph
->ihl
*4,
323 sizeof(_tcph
), &_tcph
);
327 dataoff
= (*pskb
)->nh
.iph
->ihl
*4 + th
->doff
*4;
329 if (dataoff
>= (*pskb
)->len
) {
330 DEBUGP("ftp: pskblen = %u\n", (*pskb
)->len
);
333 datalen
= (*pskb
)->len
- dataoff
;
335 spin_lock_bh(&ip_ftp_lock
);
336 fb_ptr
= skb_header_pointer(*pskb
, dataoff
,
337 (*pskb
)->len
- dataoff
, ftp_buffer
);
338 BUG_ON(fb_ptr
== NULL
);
340 ends_in_nl
= (fb_ptr
[datalen
- 1] == '\n');
341 seq
= ntohl(th
->seq
) + datalen
;
343 /* Look up to see if we're just after a \n. */
344 if (!find_nl_seq(ntohl(th
->seq
), ct_ftp_info
, dir
)) {
345 /* Now if this ends in \n, update ftp info. */
346 DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
347 ct_ftp_info
->seq_aft_nl
[0][dir
]
348 old_seq_aft_nl_set
? "":"(UNSET) ", old_seq_aft_nl
);
353 /* Initialize IP array to expected address (it's not mentioned
354 in EPSV responses) */
355 array
[0] = (ntohl(ct
->tuplehash
[dir
].tuple
.src
.ip
) >> 24) & 0xFF;
356 array
[1] = (ntohl(ct
->tuplehash
[dir
].tuple
.src
.ip
) >> 16) & 0xFF;
357 array
[2] = (ntohl(ct
->tuplehash
[dir
].tuple
.src
.ip
) >> 8) & 0xFF;
358 array
[3] = ntohl(ct
->tuplehash
[dir
].tuple
.src
.ip
) & 0xFF;
360 for (i
= 0; i
< ARRAY_SIZE(search
[dir
]); i
++) {
361 found
= find_pattern(fb_ptr
, (*pskb
)->len
- dataoff
,
362 search
[dir
][i
].pattern
,
366 &matchoff
, &matchlen
,
368 search
[dir
][i
].getnum
);
372 /* We don't usually drop packets. After all, this is
373 connection tracking, not packet filtering.
374 However, it is necessary for accurate tracking in
377 printk("conntrack_ftp: partial %s %u+%u\n",
378 search
[dir
][i
].pattern
,
379 ntohl(th
->seq
), datalen
);
382 } else if (found
== 0) { /* No match */
387 DEBUGP("conntrack_ftp: match `%s' (%u bytes at %u)\n",
388 fb_ptr
+ matchoff
, matchlen
, ntohl(th
->seq
) + matchoff
);
390 /* Allocate expectation which will be inserted */
391 exp
= ip_conntrack_expect_alloc(ct
);
397 /* We refer to the reverse direction ("!dir") tuples here,
398 * because we're expecting something in the other direction.
399 * Doesn't matter unless NAT is happening. */
400 exp
->tuple
.dst
.ip
= ct
->tuplehash
[!dir
].tuple
.dst
.ip
;
402 if (htonl((array
[0] << 24) | (array
[1] << 16) | (array
[2] << 8) | array
[3])
403 != ct
->tuplehash
[dir
].tuple
.src
.ip
) {
404 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
405 server: it really wants us to connect to a
406 different IP address. Simply don't record it for
408 DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n",
409 array
[0], array
[1], array
[2], array
[3],
410 NIPQUAD(ct
->tuplehash
[dir
].tuple
.src
.ip
));
412 /* Thanks to Cristiano Lincoln Mattos
413 <lincoln@cesar.org.br> for reporting this potential
414 problem (DMZ machines opening holes to internal
415 networks, or the packet filter itself). */
420 exp
->tuple
.dst
.ip
= htonl((array
[0] << 24) | (array
[1] << 16)
421 | (array
[2] << 8) | array
[3]);
424 exp
->tuple
.src
.ip
= ct
->tuplehash
[!dir
].tuple
.src
.ip
;
425 exp
->tuple
.dst
.u
.tcp
.port
= htons(array
[4] << 8 | array
[5]);
426 exp
->tuple
.src
.u
.tcp
.port
= 0; /* Don't care. */
427 exp
->tuple
.dst
.protonum
= IPPROTO_TCP
;
428 exp
->mask
= ((struct ip_conntrack_tuple
)
429 { { 0xFFFFFFFF, { 0 } },
430 { 0xFFFFFFFF, { .tcp
= { 0xFFFF } }, 0xFF }});
432 exp
->expectfn
= NULL
;
435 /* Now, NAT might want to mangle the packet, and register the
436 * (possibly changed) expectation itself. */
438 ret
= ip_nat_ftp_hook(pskb
, ctinfo
, search
[dir
][i
].ftptype
,
439 matchoff
, matchlen
, exp
, &seq
);
441 /* Can't expect this? Best to drop packet now. */
442 if (ip_conntrack_expect_related(exp
) != 0)
449 ip_conntrack_expect_put(exp
);
452 /* Now if this ends in \n, update ftp info. Seq may have been
453 * adjusted by NAT code. */
455 update_nl_seq(seq
, ct_ftp_info
,dir
, *pskb
);
457 spin_unlock_bh(&ip_ftp_lock
);
461 static struct ip_conntrack_helper ftp
[MAX_PORTS
];
462 static char ftp_names
[MAX_PORTS
][sizeof("ftp-65535")];
464 /* Not __exit: called from init() */
465 static void ip_conntrack_ftp_fini(void)
468 for (i
= 0; i
< ports_c
; i
++) {
469 DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
471 ip_conntrack_helper_unregister(&ftp
[i
]);
477 static int __init
ip_conntrack_ftp_init(void)
482 ftp_buffer
= kmalloc(65536, GFP_KERNEL
);
487 ports
[ports_c
++] = FTP_PORT
;
489 for (i
= 0; i
< ports_c
; i
++) {
490 ftp
[i
].tuple
.src
.u
.tcp
.port
= htons(ports
[i
]);
491 ftp
[i
].tuple
.dst
.protonum
= IPPROTO_TCP
;
492 ftp
[i
].mask
.src
.u
.tcp
.port
= 0xFFFF;
493 ftp
[i
].mask
.dst
.protonum
= 0xFF;
494 ftp
[i
].max_expected
= 1;
495 ftp
[i
].timeout
= 5 * 60; /* 5 minutes */
496 ftp
[i
].me
= THIS_MODULE
;
499 tmpname
= &ftp_names
[i
][0];
500 if (ports
[i
] == FTP_PORT
)
501 sprintf(tmpname
, "ftp");
503 sprintf(tmpname
, "ftp-%d", ports
[i
]);
504 ftp
[i
].name
= tmpname
;
506 DEBUGP("ip_ct_ftp: registering helper for port %d\n",
508 ret
= ip_conntrack_helper_register(&ftp
[i
]);
511 ip_conntrack_ftp_fini();
518 module_init(ip_conntrack_ftp_init
);
519 module_exit(ip_conntrack_ftp_fini
);