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>
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 //#if defined(CONFIG_MIPS_BRCM)
29 //static char ftp_buffer[16384];
31 //static char ftp_buffer[65536];
34 static char ftp_buffer[4096];
36 DECLARE_LOCK(ip_ftp_lock);
37 struct module *ip_conntrack_ftp = THIS_MODULE;
40 static int ports[MAX_PORTS];
42 MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_PORTS) "i");
45 MODULE_PARM(loose, "i");
50 #define DEBUGP(format, args...)
53 static int try_rfc959(const char *, size_t, u_int32_t [], char);
54 static int try_eprt(const char *, size_t, u_int32_t [], char);
55 static int try_epsv_response(const char *, size_t, u_int32_t [], char);
57 static struct ftp_search {
58 enum ip_conntrack_dir dir;
63 enum ip_ct_ftp_type ftptype;
64 int (*getnum)(const char *, size_t, u_int32_t[], char);
68 "PORT", sizeof("PORT") - 1, ' ', '\r',
74 "227 ", sizeof("227 ") - 1, '(', ')',
80 "EPRT", sizeof("EPRT") - 1, ' ', '\r',
86 "229 ", sizeof("229 ") - 1, '(', ')',
92 static int try_number(const char *data, size_t dlen, u_int32_t array[],
93 int array_size, char sep, char term)
97 memset(array, 0, sizeof(array[0])*array_size);
99 /* Keep data pointing at next char. */
100 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
101 if (*data >= '0' && *data <= '9') {
102 array[i] = array[i]*10 + *data - '0';
104 else if (*data == sep)
107 /* Unexpected character; true if it's the
108 terminator and we're finished. */
109 if (*data == term && i == array_size - 1)
112 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
117 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
122 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
123 static int try_rfc959(const char *data, size_t dlen, u_int32_t array[6],
126 return try_number(data, dlen, array, 6, ',', term);
129 /* Grab port: number up to delimiter */
130 static int get_port(const char *data, int start, size_t dlen, char delim,
136 for (i = start; i < dlen; i++) {
138 if (data[i] == delim) {
141 array[0] = port >> 8;
145 else if (data[i] >= '0' && data[i] <= '9')
146 port = port*10 + data[i] - '0';
147 else /* Some other crap */
153 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */
154 static int try_eprt(const char *data, size_t dlen, u_int32_t array[6],
160 /* First character is delimiter, then "1" for IPv4, then
162 if (dlen <= 3) return 0;
164 if (isdigit(delim) || delim < 33 || delim > 126
165 || data[1] != '1' || data[2] != delim)
168 DEBUGP("EPRT: Got |1|!\n");
169 /* Now we have IP address. */
170 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
174 DEBUGP("EPRT: Got IP address!\n");
175 /* Start offset includes initial "|1|", and trailing delimiter */
176 return get_port(data, 3 + length + 1, dlen, delim, array+4);
179 /* Returns 0, or length of numbers: |||6446| */
180 static int try_epsv_response(const char *data, size_t dlen, u_int32_t array[6],
185 /* Three delimiters. */
186 if (dlen <= 3) return 0;
188 if (isdigit(delim) || delim < 33 || delim > 126
189 || data[1] != delim || data[2] != delim)
192 return get_port(data, 3, dlen, delim, array+4);
195 /* Return 1 for match, 0 for accept, -1 for partial. */
196 static int find_pattern(const char *data, size_t dlen,
197 const char *pattern, size_t plen,
198 char skip, char term,
199 unsigned int *numoff,
200 unsigned int *numlen,
202 int (*getnum)(const char *, size_t, u_int32_t[], char))
206 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
211 /* Short packet: try for partial? */
212 if (strnicmp(data, pattern, dlen) == 0)
217 if (strnicmp(data, pattern, plen) != 0) {
221 DEBUGP("ftp: string mismatch\n");
222 for (i = 0; i < plen; i++) {
223 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
225 pattern[i], pattern[i]);
231 DEBUGP("Pattern matches!\n");
232 /* Now we've found the constant string, try to skip
233 to the 'skip' character */
234 for (i = plen; data[i] != skip; i++)
235 if (i == dlen - 1) return -1;
237 /* Skip over the last character */
240 DEBUGP("Skipped up to `%c'!\n", skip);
243 *numlen = getnum(data + i, dlen - i, array, term);
247 DEBUGP("Match succeeded!\n");
251 static int help(struct sk_buff *skb,
252 struct ip_conntrack *ct,
253 enum ip_conntrack_info ctinfo)
255 unsigned int dataoff, datalen;
257 u_int32_t old_seq_aft_nl;
258 int old_seq_aft_nl_set, ret;
259 u_int32_t array[6] = { 0 };
260 int dir = CTINFO2DIR(ctinfo);
261 unsigned int matchlen, matchoff;
262 struct ip_ct_ftp_master *ct_ftp_info = &ct->help.ct_ftp_info;
263 struct ip_conntrack_expect *exp;
264 struct ip_ct_ftp_expect *exp_ftp_info;
269 /* Until there's been traffic both ways, don't look in packets. */
270 if (ctinfo != IP_CT_ESTABLISHED
271 && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
272 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
276 if (skb_copy_bits(skb, skb->nh.iph->ihl*4, &tcph, sizeof(tcph)) != 0)
279 dataoff = skb->nh.iph->ihl*4 + tcph.doff*4;
281 if (dataoff >= skb->len) {
282 DEBUGP("ftp: skblen = %u\n", skb->len);
285 datalen = skb->len - dataoff;
287 LOCK_BH(&ip_ftp_lock);
288 skb_copy_bits(skb, dataoff, ftp_buffer, skb->len - dataoff);
290 old_seq_aft_nl_set = ct_ftp_info->seq_aft_nl_set[dir];
291 old_seq_aft_nl = ct_ftp_info->seq_aft_nl[dir];
293 DEBUGP("conntrack_ftp: datalen %u\n", datalen);
294 if (ftp_buffer[datalen - 1] == '\n') {
295 DEBUGP("conntrack_ftp: datalen %u ends in \\n\n", datalen);
296 if (!old_seq_aft_nl_set
297 || after(ntohl(tcph.seq) + datalen, old_seq_aft_nl)) {
298 DEBUGP("conntrack_ftp: updating nl to %u\n",
299 ntohl(tcph.seq) + datalen);
300 ct_ftp_info->seq_aft_nl[dir] =
301 ntohl(tcph.seq) + datalen;
302 ct_ftp_info->seq_aft_nl_set[dir] = 1;
306 if(!old_seq_aft_nl_set ||
307 (ntohl(tcph.seq) != old_seq_aft_nl)) {
308 DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u)\n",
309 old_seq_aft_nl_set ? "":"(UNSET) ", old_seq_aft_nl);
314 /* Initialize IP array to expected address (it's not mentioned
315 in EPSV responses) */
316 array[0] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 24) & 0xFF;
317 array[1] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 16) & 0xFF;
318 array[2] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 8) & 0xFF;
319 array[3] = ntohl(ct->tuplehash[dir].tuple.src.ip) & 0xFF;
321 for (i = 0; i < ARRAY_SIZE(search); i++) {
322 if (search[i].dir != dir) continue;
324 found = find_pattern(ftp_buffer, skb->len - dataoff,
329 &matchoff, &matchlen,
335 /* We don't usually drop packets. After all, this is
336 connection tracking, not packet filtering.
337 However, it is necessary for accurate tracking in
340 printk("conntrack_ftp: partial %s %u+%u\n",
342 ntohl(tcph.seq), datalen);
345 } else if (found == 0) { /* No match */
350 DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
351 (int)matchlen, data + matchoff,
352 matchlen, ntohl(tcph.seq) + matchoff);
354 /* Allocate expectation which will be inserted */
355 exp = ip_conntrack_expect_alloc();
361 exp_ftp_info = &exp->help.exp_ftp_info;
363 /* Update the ftp info */
364 if (htonl((array[0] << 24) | (array[1] << 16) | (array[2] << 8) | array[3])
365 == ct->tuplehash[dir].tuple.src.ip) {
366 exp->seq = ntohl(tcph.seq) + matchoff;
367 exp_ftp_info->len = matchlen;
368 exp_ftp_info->ftptype = search[i].ftptype;
369 exp_ftp_info->port = array[4] << 8 | array[5];
371 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
372 server: it really wants us to connect to a
373 different IP address. Simply don't record it for
375 DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n",
376 array[0], array[1], array[2], array[3],
377 NIPQUAD(ct->tuplehash[dir].tuple.src.ip));
379 /* Thanks to Cristiano Lincoln Mattos
380 <lincoln@cesar.org.br> for reporting this potential
381 problem (DMZ machines opening holes to internal
382 networks, or the packet filter itself). */
389 exp->tuple = ((struct ip_conntrack_tuple)
390 { { ct->tuplehash[!dir].tuple.src.ip,
392 { htonl((array[0] << 24) | (array[1] << 16)
393 | (array[2] << 8) | array[3]),
394 { .tcp = { htons(array[4] << 8 | array[5]) } },
396 exp->mask = ((struct ip_conntrack_tuple)
397 { { 0xFFFFFFFF, { 0 } },
398 { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFFFF }});
400 exp->expectfn = NULL;
402 /* Ignore failure; should only happen with NAT */
403 ip_conntrack_expect_related(exp, ct);
406 UNLOCK_BH(&ip_ftp_lock);
410 static struct ip_conntrack_helper ftp[MAX_PORTS];
411 static char ftp_names[MAX_PORTS][10];
413 /* Not __exit: called from init() */
414 static void fini(void)
417 for (i = 0; i < ports_c; i++) {
418 DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
420 ip_conntrack_helper_unregister(&ftp[i]);
424 static int __init init(void)
432 for (i = 0; (i < MAX_PORTS) && ports[i]; i++) {
433 ftp[i].tuple.src.u.tcp.port = htons(ports[i]);
434 ftp[i].tuple.dst.protonum = IPPROTO_TCP;
435 ftp[i].mask.src.u.tcp.port = 0xFFFF;
436 ftp[i].mask.dst.protonum = 0xFFFF;
437 ftp[i].max_expected = 1;
439 ftp[i].flags = IP_CT_HELPER_F_REUSE_EXPECT;
440 ftp[i].me = ip_conntrack_ftp;
443 tmpname = &ftp_names[i][0];
444 if (ports[i] == FTP_PORT)
445 sprintf(tmpname, "ftp");
447 sprintf(tmpname, "ftp-%d", ports[i]);
448 ftp[i].name = tmpname;
450 DEBUGP("ip_ct_ftp: registering helper for port %d\n",
452 ret = ip_conntrack_helper_register(&ftp[i]);
463 PROVIDES_CONNTRACK(ftp);
464 EXPORT_SYMBOL(ip_ftp_lock);