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
{
59 enum ip_conntrack_dir dir
;
64 enum ip_ct_ftp_type ftptype
;
65 int (*getnum
)(const char *, size_t, u_int32_t
[], char);
69 "PORT", sizeof("PORT") - 1, ' ', '\r',
75 "227 ", sizeof("227 ") - 1, '(', ')',
81 "EPRT", sizeof("EPRT") - 1, ' ', '\r',
87 "229 ", sizeof("229 ") - 1, '(', ')',
93 static int try_number(const char *data
, size_t dlen
, u_int32_t array
[],
94 int array_size
, char sep
, char term
)
98 memset(array
, 0, sizeof(array
[0])*array_size
);
100 /* Keep data pointing at next char. */
101 for (i
= 0, len
= 0; len
< dlen
&& i
< array_size
; len
++, data
++) {
102 if (*data
>= '0' && *data
<= '9') {
103 array
[i
] = array
[i
]*10 + *data
- '0';
105 else if (*data
== sep
)
108 /* Unexpected character; true if it's the
109 terminator and we're finished. */
110 if (*data
== term
&& i
== array_size
- 1)
113 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
118 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size
, sep
);
123 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
124 static int try_rfc959(const char *data
, size_t dlen
, u_int32_t array
[6],
127 return try_number(data
, dlen
, array
, 6, ',', term
);
130 /* Grab port: number up to delimiter */
131 static int get_port(const char *data
, int start
, size_t dlen
, char delim
,
137 for (i
= start
; i
< dlen
; i
++) {
139 if (data
[i
] == delim
) {
142 array
[0] = port
>> 8;
146 else if (data
[i
] >= '0' && data
[i
] <= '9')
147 port
= port
*10 + data
[i
] - '0';
148 else /* Some other crap */
154 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */
155 static int try_eprt(const char *data
, size_t dlen
, u_int32_t array
[6],
161 /* First character is delimiter, then "1" for IPv4, then
163 if (dlen
<= 3) return 0;
165 if (isdigit(delim
) || delim
< 33 || delim
> 126
166 || data
[1] != '1' || data
[2] != delim
)
169 DEBUGP("EPRT: Got |1|!\n");
170 /* Now we have IP address. */
171 length
= try_number(data
+ 3, dlen
- 3, array
, 4, '.', delim
);
175 DEBUGP("EPRT: Got IP address!\n");
176 /* Start offset includes initial "|1|", and trailing delimiter */
177 return get_port(data
, 3 + length
+ 1, dlen
, delim
, array
+4);
180 /* Returns 0, or length of numbers: |||6446| */
181 static int try_epsv_response(const char *data
, size_t dlen
, u_int32_t array
[6],
186 /* Three delimiters. */
187 if (dlen
<= 3) return 0;
189 if (isdigit(delim
) || delim
< 33 || delim
> 126
190 || data
[1] != delim
|| data
[2] != delim
)
193 return get_port(data
, 3, dlen
, delim
, array
+4);
196 /* Return 1 for match, 0 for accept, -1 for partial. */
197 static int find_pattern(const char *data
, size_t dlen
,
198 const char *pattern
, size_t plen
,
199 char skip
, char term
,
200 unsigned int *numoff
,
201 unsigned int *numlen
,
203 int (*getnum
)(const char *, size_t, u_int32_t
[], char))
207 DEBUGP("find_pattern `%s': dlen = %u\n", pattern
, dlen
);
212 /* Short packet: try for partial? */
213 if (strnicmp(data
, pattern
, dlen
) == 0)
218 if (strnicmp(data
, pattern
, plen
) != 0) {
222 DEBUGP("ftp: string mismatch\n");
223 for (i
= 0; i
< plen
; i
++) {
224 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
226 pattern
[i
], pattern
[i
]);
232 DEBUGP("Pattern matches!\n");
233 /* Now we've found the constant string, try to skip
234 to the 'skip' character */
235 for (i
= plen
; data
[i
] != skip
; i
++)
236 if (i
== dlen
- 1) return -1;
238 /* Skip over the last character */
241 DEBUGP("Skipped up to `%c'!\n", skip
);
244 *numlen
= getnum(data
+ i
, dlen
- i
, array
, term
);
248 DEBUGP("Match succeeded!\n");
252 /* Look up to see if we're just after a \n. */
253 static int find_nl_seq(u32 seq
, const struct ip_ct_ftp_master
*info
, int dir
)
257 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++)
258 if (info
->seq_aft_nl
[dir
][i
] == seq
)
263 /* We don't update if it's older than what we have. */
264 static void update_nl_seq(u32 nl_seq
, struct ip_ct_ftp_master
*info
, int dir
,
267 unsigned int i
, oldest
= NUM_SEQ_TO_REMEMBER
;
269 /* Look for oldest: if we find exact match, we're done. */
270 for (i
= 0; i
< info
->seq_aft_nl_num
[dir
]; i
++) {
271 if (info
->seq_aft_nl
[dir
][i
] == nl_seq
)
274 if (oldest
== info
->seq_aft_nl_num
[dir
]
275 || before(info
->seq_aft_nl
[dir
][i
], oldest
))
279 if (info
->seq_aft_nl_num
[dir
] < NUM_SEQ_TO_REMEMBER
) {
280 info
->seq_aft_nl
[dir
][info
->seq_aft_nl_num
[dir
]++] = nl_seq
;
281 ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE
, skb
);
282 } else if (oldest
!= NUM_SEQ_TO_REMEMBER
) {
283 info
->seq_aft_nl
[dir
][oldest
] = nl_seq
;
284 ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE
, skb
);
288 static int help(struct sk_buff
**pskb
,
289 struct ip_conntrack
*ct
,
290 enum ip_conntrack_info ctinfo
)
292 unsigned int dataoff
, datalen
;
293 struct tcphdr _tcph
, *th
;
296 u32 seq
, array
[6] = { 0 };
297 int dir
= CTINFO2DIR(ctinfo
);
298 unsigned int matchlen
, matchoff
;
299 struct ip_ct_ftp_master
*ct_ftp_info
= &ct
->help
.ct_ftp_info
;
300 struct ip_conntrack_expect
*exp
;
302 int found
= 0, ends_in_nl
;
304 /* Until there's been traffic both ways, don't look in packets. */
305 if (ctinfo
!= IP_CT_ESTABLISHED
306 && ctinfo
!= IP_CT_ESTABLISHED
+IP_CT_IS_REPLY
) {
307 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo
);
311 th
= skb_header_pointer(*pskb
, (*pskb
)->nh
.iph
->ihl
*4,
312 sizeof(_tcph
), &_tcph
);
316 dataoff
= (*pskb
)->nh
.iph
->ihl
*4 + th
->doff
*4;
318 if (dataoff
>= (*pskb
)->len
) {
319 DEBUGP("ftp: pskblen = %u\n", (*pskb
)->len
);
322 datalen
= (*pskb
)->len
- dataoff
;
324 spin_lock_bh(&ip_ftp_lock
);
325 fb_ptr
= skb_header_pointer(*pskb
, dataoff
,
326 (*pskb
)->len
- dataoff
, ftp_buffer
);
327 BUG_ON(fb_ptr
== NULL
);
329 ends_in_nl
= (fb_ptr
[datalen
- 1] == '\n');
330 seq
= ntohl(th
->seq
) + datalen
;
332 /* Look up to see if we're just after a \n. */
333 if (!find_nl_seq(ntohl(th
->seq
), ct_ftp_info
, dir
)) {
334 /* Now if this ends in \n, update ftp info. */
335 DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
336 ct_ftp_info
->seq_aft_nl
[0][dir
]
337 old_seq_aft_nl_set
? "":"(UNSET) ", old_seq_aft_nl
);
342 /* Initialize IP array to expected address (it's not mentioned
343 in EPSV responses) */
344 array
[0] = (ntohl(ct
->tuplehash
[dir
].tuple
.src
.ip
) >> 24) & 0xFF;
345 array
[1] = (ntohl(ct
->tuplehash
[dir
].tuple
.src
.ip
) >> 16) & 0xFF;
346 array
[2] = (ntohl(ct
->tuplehash
[dir
].tuple
.src
.ip
) >> 8) & 0xFF;
347 array
[3] = ntohl(ct
->tuplehash
[dir
].tuple
.src
.ip
) & 0xFF;
349 for (i
= 0; i
< ARRAY_SIZE(search
); i
++) {
350 if (search
[i
].dir
!= dir
) continue;
352 found
= find_pattern(fb_ptr
, (*pskb
)->len
- dataoff
,
357 &matchoff
, &matchlen
,
363 /* We don't usually drop packets. After all, this is
364 connection tracking, not packet filtering.
365 However, it is necessary for accurate tracking in
368 printk("conntrack_ftp: partial %s %u+%u\n",
370 ntohl(th
->seq
), datalen
);
373 } else if (found
== 0) { /* No match */
378 DEBUGP("conntrack_ftp: match `%s' (%u bytes at %u)\n",
379 fb_ptr
+ matchoff
, matchlen
, ntohl(th
->seq
) + matchoff
);
381 /* Allocate expectation which will be inserted */
382 exp
= ip_conntrack_expect_alloc(ct
);
388 /* We refer to the reverse direction ("!dir") tuples here,
389 * because we're expecting something in the other direction.
390 * Doesn't matter unless NAT is happening. */
391 exp
->tuple
.dst
.ip
= ct
->tuplehash
[!dir
].tuple
.dst
.ip
;
393 if (htonl((array
[0] << 24) | (array
[1] << 16) | (array
[2] << 8) | array
[3])
394 != ct
->tuplehash
[dir
].tuple
.src
.ip
) {
395 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
396 server: it really wants us to connect to a
397 different IP address. Simply don't record it for
399 DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n",
400 array
[0], array
[1], array
[2], array
[3],
401 NIPQUAD(ct
->tuplehash
[dir
].tuple
.src
.ip
));
403 /* Thanks to Cristiano Lincoln Mattos
404 <lincoln@cesar.org.br> for reporting this potential
405 problem (DMZ machines opening holes to internal
406 networks, or the packet filter itself). */
411 exp
->tuple
.dst
.ip
= htonl((array
[0] << 24) | (array
[1] << 16)
412 | (array
[2] << 8) | array
[3]);
415 exp
->tuple
.src
.ip
= ct
->tuplehash
[!dir
].tuple
.src
.ip
;
416 exp
->tuple
.dst
.u
.tcp
.port
= htons(array
[4] << 8 | array
[5]);
417 exp
->tuple
.src
.u
.tcp
.port
= 0; /* Don't care. */
418 exp
->tuple
.dst
.protonum
= IPPROTO_TCP
;
419 exp
->mask
= ((struct ip_conntrack_tuple
)
420 { { 0xFFFFFFFF, { 0 } },
421 { 0xFFFFFFFF, { .tcp
= { 0xFFFF } }, 0xFF }});
423 exp
->expectfn
= NULL
;
426 /* Now, NAT might want to mangle the packet, and register the
427 * (possibly changed) expectation itself. */
429 ret
= ip_nat_ftp_hook(pskb
, ctinfo
, search
[i
].ftptype
,
430 matchoff
, matchlen
, exp
, &seq
);
432 /* Can't expect this? Best to drop packet now. */
433 if (ip_conntrack_expect_related(exp
) != 0)
440 ip_conntrack_expect_put(exp
);
443 /* Now if this ends in \n, update ftp info. Seq may have been
444 * adjusted by NAT code. */
446 update_nl_seq(seq
, ct_ftp_info
,dir
, *pskb
);
448 spin_unlock_bh(&ip_ftp_lock
);
452 static struct ip_conntrack_helper ftp
[MAX_PORTS
];
453 static char ftp_names
[MAX_PORTS
][sizeof("ftp-65535")];
455 /* Not __exit: called from init() */
456 static void fini(void)
459 for (i
= 0; i
< ports_c
; i
++) {
460 DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
462 ip_conntrack_helper_unregister(&ftp
[i
]);
468 static int __init
init(void)
473 ftp_buffer
= kmalloc(65536, GFP_KERNEL
);
478 ports
[ports_c
++] = FTP_PORT
;
480 for (i
= 0; i
< ports_c
; i
++) {
481 ftp
[i
].tuple
.src
.u
.tcp
.port
= htons(ports
[i
]);
482 ftp
[i
].tuple
.dst
.protonum
= IPPROTO_TCP
;
483 ftp
[i
].mask
.src
.u
.tcp
.port
= 0xFFFF;
484 ftp
[i
].mask
.dst
.protonum
= 0xFF;
485 ftp
[i
].max_expected
= 1;
486 ftp
[i
].timeout
= 5 * 60; /* 5 minutes */
487 ftp
[i
].me
= THIS_MODULE
;
490 tmpname
= &ftp_names
[i
][0];
491 if (ports
[i
] == FTP_PORT
)
492 sprintf(tmpname
, "ftp");
494 sprintf(tmpname
, "ftp-%d", ports
[i
]);
495 ftp
[i
].name
= tmpname
;
497 DEBUGP("ip_ct_ftp: registering helper for port %d\n",
499 ret
= ip_conntrack_helper_register(&ftp
[i
]);