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/lockhelp.h>
20 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
21 #include <linux/netfilter_ipv4/ip_conntrack_ftp.h>
22 #include <linux/moduleparam.h>
24 MODULE_LICENSE("GPL");
25 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
26 MODULE_DESCRIPTION("ftp connection tracking helper");
28 /* This is slow, but it's simple. --RR */
29 static char ftp_buffer
[65536];
31 static DECLARE_LOCK(ip_ftp_lock
);
34 static int ports
[MAX_PORTS
];
36 module_param_array(ports
, int, &ports_c
, 0400);
39 module_param(loose
, int, 0600);
41 unsigned int (*ip_nat_ftp_hook
)(struct sk_buff
**pskb
,
42 enum ip_conntrack_info ctinfo
,
43 enum ip_ct_ftp_type type
,
44 unsigned int matchoff
,
45 unsigned int matchlen
,
46 struct ip_conntrack_expect
*exp
,
48 EXPORT_SYMBOL_GPL(ip_nat_ftp_hook
);
53 #define DEBUGP(format, args...)
56 static int try_rfc959(const char *, size_t, u_int32_t
[], char);
57 static int try_eprt(const char *, size_t, u_int32_t
[], char);
58 static int try_epsv_response(const char *, size_t, u_int32_t
[], char);
60 static struct ftp_search
{
61 enum ip_conntrack_dir dir
;
66 enum ip_ct_ftp_type ftptype
;
67 int (*getnum
)(const char *, size_t, u_int32_t
[], char);
71 "PORT", sizeof("PORT") - 1, ' ', '\r',
77 "227 ", sizeof("227 ") - 1, '(', ')',
83 "EPRT", sizeof("EPRT") - 1, ' ', '\r',
89 "229 ", sizeof("229 ") - 1, '(', ')',
95 static int try_number(const char *data
, size_t dlen
, u_int32_t array
[],
96 int array_size
, char sep
, char term
)
100 memset(array
, 0, sizeof(array
[0])*array_size
);
102 /* Keep data pointing at next char. */
103 for (i
= 0, len
= 0; len
< dlen
&& i
< array_size
; len
++, data
++) {
104 if (*data
>= '0' && *data
<= '9') {
105 array
[i
] = array
[i
]*10 + *data
- '0';
107 else if (*data
== sep
)
110 /* Unexpected character; true if it's the
111 terminator and we're finished. */
112 if (*data
== term
&& i
== array_size
- 1)
115 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
120 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size
, sep
);
125 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
126 static int try_rfc959(const char *data
, size_t dlen
, u_int32_t array
[6],
129 return try_number(data
, dlen
, array
, 6, ',', term
);
132 /* Grab port: number up to delimiter */
133 static int get_port(const char *data
, int start
, size_t dlen
, char delim
,
139 for (i
= start
; i
< dlen
; i
++) {
141 if (data
[i
] == delim
) {
144 array
[0] = port
>> 8;
148 else if (data
[i
] >= '0' && data
[i
] <= '9')
149 port
= port
*10 + data
[i
] - '0';
150 else /* Some other crap */
156 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */
157 static int try_eprt(const char *data
, size_t dlen
, u_int32_t array
[6],
163 /* First character is delimiter, then "1" for IPv4, then
165 if (dlen
<= 3) return 0;
167 if (isdigit(delim
) || delim
< 33 || delim
> 126
168 || data
[1] != '1' || data
[2] != delim
)
171 DEBUGP("EPRT: Got |1|!\n");
172 /* Now we have IP address. */
173 length
= try_number(data
+ 3, dlen
- 3, array
, 4, '.', delim
);
177 DEBUGP("EPRT: Got IP address!\n");
178 /* Start offset includes initial "|1|", and trailing delimiter */
179 return get_port(data
, 3 + length
+ 1, dlen
, delim
, array
+4);
182 /* Returns 0, or length of numbers: |||6446| */
183 static int try_epsv_response(const char *data
, size_t dlen
, u_int32_t array
[6],
188 /* Three delimiters. */
189 if (dlen
<= 3) return 0;
191 if (isdigit(delim
) || delim
< 33 || delim
> 126
192 || data
[1] != delim
|| data
[2] != delim
)
195 return get_port(data
, 3, dlen
, delim
, array
+4);
198 /* Return 1 for match, 0 for accept, -1 for partial. */
199 static int find_pattern(const char *data
, size_t dlen
,
200 const char *pattern
, size_t plen
,
201 char skip
, char term
,
202 unsigned int *numoff
,
203 unsigned int *numlen
,
205 int (*getnum
)(const char *, size_t, u_int32_t
[], char))
209 DEBUGP("find_pattern `%s': dlen = %u\n", pattern
, dlen
);
214 /* Short packet: try for partial? */
215 if (strnicmp(data
, pattern
, dlen
) == 0)
220 if (strnicmp(data
, pattern
, plen
) != 0) {
224 DEBUGP("ftp: string mismatch\n");
225 for (i
= 0; i
< plen
; i
++) {
226 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
228 pattern
[i
], pattern
[i
]);
234 DEBUGP("Pattern matches!\n");
235 /* Now we've found the constant string, try to skip
236 to the 'skip' character */
237 for (i
= plen
; data
[i
] != skip
; i
++)
238 if (i
== dlen
- 1) return -1;
240 /* Skip over the last character */
243 DEBUGP("Skipped up to `%c'!\n", skip
);
246 *numlen
= getnum(data
+ i
, dlen
- i
, array
, term
);
250 DEBUGP("Match succeeded!\n");
254 /* Look up to see if we're just after a \n. */
255 static int find_nl_seq(u32 seq
, const struct ip_ct_ftp_master
*info
, int dir
)
259 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++)
260 if (info
->seq_aft_nl
[dir
][i
] == seq
)
265 /* We don't update if it's older than what we have. */
266 static void update_nl_seq(u32 nl_seq
, struct ip_ct_ftp_master
*info
, int dir
)
268 unsigned int i
, oldest
= NUM_SEQ_TO_REMEMBER
;
270 /* Look for oldest: if we find exact match, we're done. */
271 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++) {
272 if (info
->seq_aft_nl
[dir
][i
] == nl_seq
)
275 if (oldest
== info
->seq_aft_nl_num
[dir
]
276 || before(info
->seq_aft_nl
[dir
][i
], oldest
))
280 if (info
->seq_aft_nl_num
[dir
] < NUM_SEQ_TO_REMEMBER
)
281 info
->seq_aft_nl
[dir
][info
->seq_aft_nl_num
[dir
]++] = nl_seq
;
282 else if (oldest
!= NUM_SEQ_TO_REMEMBER
)
283 info
->seq_aft_nl
[dir
][oldest
] = nl_seq
;
286 static int help(struct sk_buff
**pskb
,
287 struct ip_conntrack
*ct
,
288 enum ip_conntrack_info ctinfo
)
290 unsigned int dataoff
, datalen
;
291 struct tcphdr _tcph
, *th
;
294 u32 seq
, array
[6] = { 0 };
295 int dir
= CTINFO2DIR(ctinfo
);
296 unsigned int matchlen
, matchoff
;
297 struct ip_ct_ftp_master
*ct_ftp_info
= &ct
->help
.ct_ftp_info
;
298 struct ip_conntrack_expect
*exp
;
300 int found
= 0, ends_in_nl
;
302 /* Until there's been traffic both ways, don't look in packets. */
303 if (ctinfo
!= IP_CT_ESTABLISHED
304 && ctinfo
!= IP_CT_ESTABLISHED
+IP_CT_IS_REPLY
) {
305 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo
);
309 th
= skb_header_pointer(*pskb
, (*pskb
)->nh
.iph
->ihl
*4,
310 sizeof(_tcph
), &_tcph
);
314 dataoff
= (*pskb
)->nh
.iph
->ihl
*4 + th
->doff
*4;
316 if (dataoff
>= (*pskb
)->len
) {
317 DEBUGP("ftp: pskblen = %u\n", (*pskb
)->len
);
320 datalen
= (*pskb
)->len
- dataoff
;
322 LOCK_BH(&ip_ftp_lock
);
323 fb_ptr
= skb_header_pointer(*pskb
, dataoff
,
324 (*pskb
)->len
- dataoff
, ftp_buffer
);
325 BUG_ON(fb_ptr
== NULL
);
327 ends_in_nl
= (fb_ptr
[datalen
- 1] == '\n');
328 seq
= ntohl(th
->seq
) + datalen
;
330 /* Look up to see if we're just after a \n. */
331 if (!find_nl_seq(ntohl(th
->seq
), ct_ftp_info
, dir
)) {
332 /* Now if this ends in \n, update ftp info. */
333 DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
334 ct_ftp_info
->seq_aft_nl
[0][dir
]
335 old_seq_aft_nl_set
? "":"(UNSET) ", old_seq_aft_nl
);
340 /* Initialize IP array to expected address (it's not mentioned
341 in EPSV responses) */
342 array
[0] = (ntohl(ct
->tuplehash
[dir
].tuple
.src
.ip
) >> 24) & 0xFF;
343 array
[1] = (ntohl(ct
->tuplehash
[dir
].tuple
.src
.ip
) >> 16) & 0xFF;
344 array
[2] = (ntohl(ct
->tuplehash
[dir
].tuple
.src
.ip
) >> 8) & 0xFF;
345 array
[3] = ntohl(ct
->tuplehash
[dir
].tuple
.src
.ip
) & 0xFF;
347 for (i
= 0; i
< ARRAY_SIZE(search
); i
++) {
348 if (search
[i
].dir
!= dir
) continue;
350 found
= find_pattern(fb_ptr
, (*pskb
)->len
- dataoff
,
355 &matchoff
, &matchlen
,
361 /* We don't usually drop packets. After all, this is
362 connection tracking, not packet filtering.
363 However, it is necessary for accurate tracking in
366 printk("conntrack_ftp: partial %s %u+%u\n",
368 ntohl(th
->seq
), datalen
);
371 } else if (found
== 0) { /* No match */
376 DEBUGP("conntrack_ftp: match `%s' (%u bytes at %u)\n",
377 fb_ptr
+ matchoff
, matchlen
, ntohl(th
->seq
) + matchoff
);
379 /* Allocate expectation which will be inserted */
380 exp
= ip_conntrack_expect_alloc();
386 /* We refer to the reverse direction ("!dir") tuples here,
387 * because we're expecting something in the other direction.
388 * Doesn't matter unless NAT is happening. */
389 exp
->tuple
.dst
.ip
= ct
->tuplehash
[!dir
].tuple
.dst
.ip
;
391 if (htonl((array
[0] << 24) | (array
[1] << 16) | (array
[2] << 8) | array
[3])
392 != ct
->tuplehash
[dir
].tuple
.src
.ip
) {
393 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
394 server: it really wants us to connect to a
395 different IP address. Simply don't record it for
397 DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n",
398 array
[0], array
[1], array
[2], array
[3],
399 NIPQUAD(ct
->tuplehash
[dir
].tuple
.src
.ip
));
401 /* Thanks to Cristiano Lincoln Mattos
402 <lincoln@cesar.org.br> for reporting this potential
403 problem (DMZ machines opening holes to internal
404 networks, or the packet filter itself). */
407 ip_conntrack_expect_free(exp
);
410 exp
->tuple
.dst
.ip
= htonl((array
[0] << 24) | (array
[1] << 16)
411 | (array
[2] << 8) | array
[3]);
414 exp
->tuple
.src
.ip
= ct
->tuplehash
[!dir
].tuple
.src
.ip
;
415 exp
->tuple
.dst
.u
.tcp
.port
= htons(array
[4] << 8 | array
[5]);
416 exp
->tuple
.src
.u
.tcp
.port
= 0; /* Don't care. */
417 exp
->tuple
.dst
.protonum
= IPPROTO_TCP
;
418 exp
->mask
= ((struct ip_conntrack_tuple
)
419 { { 0xFFFFFFFF, { 0 } },
420 { 0xFFFFFFFF, { .tcp
= { 0xFFFF } }, 0xFF }});
422 exp
->expectfn
= NULL
;
425 /* Now, NAT might want to mangle the packet, and register the
426 * (possibly changed) expectation itself. */
428 ret
= ip_nat_ftp_hook(pskb
, ctinfo
, search
[i
].ftptype
,
429 matchoff
, matchlen
, exp
, &seq
);
431 /* Can't expect this? Best to drop packet now. */
432 if (ip_conntrack_expect_related(exp
) != 0) {
433 ip_conntrack_expect_free(exp
);
440 /* Now if this ends in \n, update ftp info. Seq may have been
441 * adjusted by NAT code. */
443 update_nl_seq(seq
, ct_ftp_info
,dir
);
445 UNLOCK_BH(&ip_ftp_lock
);
449 static struct ip_conntrack_helper ftp
[MAX_PORTS
];
450 static char ftp_names
[MAX_PORTS
][10];
452 /* Not __exit: called from init() */
453 static void fini(void)
456 for (i
= 0; i
< ports_c
; i
++) {
457 DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
459 ip_conntrack_helper_unregister(&ftp
[i
]);
463 static int __init
init(void)
469 ports
[ports_c
++] = FTP_PORT
;
471 for (i
= 0; i
< ports_c
; i
++) {
472 ftp
[i
].tuple
.src
.u
.tcp
.port
= htons(ports
[i
]);
473 ftp
[i
].tuple
.dst
.protonum
= IPPROTO_TCP
;
474 ftp
[i
].mask
.src
.u
.tcp
.port
= 0xFFFF;
475 ftp
[i
].mask
.dst
.protonum
= 0xFF;
476 ftp
[i
].max_expected
= 1;
477 ftp
[i
].timeout
= 5 * 60; /* 5 minutes */
478 ftp
[i
].me
= THIS_MODULE
;
481 tmpname
= &ftp_names
[i
][0];
482 if (ports
[i
] == FTP_PORT
)
483 sprintf(tmpname
, "ftp");
485 sprintf(tmpname
, "ftp-%d", ports
[i
]);
486 ftp
[i
].name
= tmpname
;
488 DEBUGP("ip_ct_ftp: registering helper for port %d\n",
490 ret
= ip_conntrack_helper_register(&ftp
[i
]);