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 static char ftp_buffer[65536];
30 DECLARE_LOCK(ip_ftp_lock);
31 struct module *ip_conntrack_ftp = THIS_MODULE;
34 static int ports[MAX_PORTS];
37 MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_PORTS) "i");
41 MODULE_PARM(loose, "i");
46 #define DEBUGP(format, args...)
49 static int try_rfc959(const char *, size_t, u_int32_t [], char);
50 static int try_eprt(const char *, size_t, u_int32_t [], char);
51 static int try_epsv_response(const char *, size_t, u_int32_t [], char);
53 static struct ftp_search {
54 enum ip_conntrack_dir dir;
59 enum ip_ct_ftp_type ftptype;
60 int (*getnum)(const char *, size_t, u_int32_t[], char);
64 "PORT", sizeof("PORT") - 1, ' ', '\r',
70 "227 ", sizeof("227 ") - 1, '(', ')',
76 "EPRT", sizeof("EPRT") - 1, ' ', '\r',
82 "229 ", sizeof("229 ") - 1, '(', ')',
88 static int try_number(const char *data, size_t dlen, u_int32_t array[],
89 int array_size, char sep, char term)
93 memset(array, 0, sizeof(array[0])*array_size);
95 /* Keep data pointing at next char. */
96 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
97 if (*data >= '0' && *data <= '9') {
98 array[i] = array[i]*10 + *data - '0';
100 else if (*data == sep)
103 /* Unexpected character; true if it's the
104 terminator and we're finished. */
105 if (*data == term && i == array_size - 1)
108 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
113 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
118 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
119 static int try_rfc959(const char *data, size_t dlen, u_int32_t array[6],
122 return try_number(data, dlen, array, 6, ',', term);
125 /* Grab port: number up to delimiter */
126 static int get_port(const char *data, int start, size_t dlen, char delim,
132 for (i = start; i < dlen; i++) {
134 if (data[i] == delim) {
137 array[0] = port >> 8;
141 else if (data[i] >= '0' && data[i] <= '9')
142 port = port*10 + data[i] - '0';
143 else /* Some other crap */
149 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */
150 static int try_eprt(const char *data, size_t dlen, u_int32_t array[6],
156 /* First character is delimiter, then "1" for IPv4, then
158 if (dlen <= 3) return 0;
160 if (isdigit(delim) || delim < 33 || delim > 126
161 || data[1] != '1' || data[2] != delim)
164 DEBUGP("EPRT: Got |1|!\n");
165 /* Now we have IP address. */
166 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
170 DEBUGP("EPRT: Got IP address!\n");
171 /* Start offset includes initial "|1|", and trailing delimiter */
172 return get_port(data, 3 + length + 1, dlen, delim, array+4);
175 /* Returns 0, or length of numbers: |||6446| */
176 static int try_epsv_response(const char *data, size_t dlen, u_int32_t array[6],
181 /* Three delimiters. */
182 if (dlen <= 3) return 0;
184 if (isdigit(delim) || delim < 33 || delim > 126
185 || data[1] != delim || data[2] != delim)
188 return get_port(data, 3, dlen, delim, array+4);
191 /* Return 1 for match, 0 for accept, -1 for partial. */
192 static int find_pattern(const char *data, size_t dlen,
193 const char *pattern, size_t plen,
194 char skip, char term,
195 unsigned int *numoff,
196 unsigned int *numlen,
198 int (*getnum)(const char *, size_t, u_int32_t[], char))
202 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
207 /* Short packet: try for partial? */
208 if (strnicmp(data, pattern, dlen) == 0)
213 if (strnicmp(data, pattern, plen) != 0) {
217 DEBUGP("ftp: string mismatch\n");
218 for (i = 0; i < plen; i++) {
219 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
221 pattern[i], pattern[i]);
227 DEBUGP("Pattern matches!\n");
228 /* Now we've found the constant string, try to skip
229 to the 'skip' character */
230 for (i = plen; data[i] != skip; i++)
231 if (i == dlen - 1) return -1;
233 /* Skip over the last character */
236 DEBUGP("Skipped up to `%c'!\n", skip);
239 *numlen = getnum(data + i, dlen - i, array, term);
243 DEBUGP("Match succeeded!\n");
247 static int help(struct sk_buff *skb,
248 struct ip_conntrack *ct,
249 enum ip_conntrack_info ctinfo)
251 unsigned int dataoff, datalen;
253 u_int32_t old_seq_aft_nl;
254 int old_seq_aft_nl_set, ret;
255 u_int32_t array[6] = { 0 };
256 int dir = CTINFO2DIR(ctinfo);
257 unsigned int matchlen, matchoff;
258 struct ip_ct_ftp_master *ct_ftp_info = &ct->help.ct_ftp_info;
259 struct ip_conntrack_expect *exp;
260 struct ip_ct_ftp_expect *exp_ftp_info;
265 /* Until there's been traffic both ways, don't look in packets. */
266 if (ctinfo != IP_CT_ESTABLISHED
267 && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
268 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
272 if (skb_copy_bits(skb, skb->nh.iph->ihl*4, &tcph, sizeof(tcph)) != 0)
275 dataoff = skb->nh.iph->ihl*4 + tcph.doff*4;
277 if (dataoff >= skb->len) {
278 DEBUGP("ftp: skblen = %u\n", skb->len);
281 datalen = skb->len - dataoff;
283 LOCK_BH(&ip_ftp_lock);
284 skb_copy_bits(skb, dataoff, ftp_buffer, skb->len - dataoff);
286 old_seq_aft_nl_set = ct_ftp_info->seq_aft_nl_set[dir];
287 old_seq_aft_nl = ct_ftp_info->seq_aft_nl[dir];
289 DEBUGP("conntrack_ftp: datalen %u\n", datalen);
290 if (ftp_buffer[datalen - 1] == '\n') {
291 DEBUGP("conntrack_ftp: datalen %u ends in \\n\n", datalen);
292 if (!old_seq_aft_nl_set
293 || after(ntohl(tcph.seq) + datalen, old_seq_aft_nl)) {
294 DEBUGP("conntrack_ftp: updating nl to %u\n",
295 ntohl(tcph.seq) + datalen);
296 ct_ftp_info->seq_aft_nl[dir] =
297 ntohl(tcph.seq) + datalen;
298 ct_ftp_info->seq_aft_nl_set[dir] = 1;
302 if(!old_seq_aft_nl_set ||
303 (ntohl(tcph.seq) != old_seq_aft_nl)) {
304 DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u)\n",
305 old_seq_aft_nl_set ? "":"(UNSET) ", old_seq_aft_nl);
310 /* Initialize IP array to expected address (it's not mentioned
311 in EPSV responses) */
312 array[0] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 24) & 0xFF;
313 array[1] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 16) & 0xFF;
314 array[2] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 8) & 0xFF;
315 array[3] = ntohl(ct->tuplehash[dir].tuple.src.ip) & 0xFF;
317 for (i = 0; i < ARRAY_SIZE(search); i++) {
318 if (search[i].dir != dir) continue;
320 found = find_pattern(ftp_buffer, skb->len - dataoff,
325 &matchoff, &matchlen,
331 /* We don't usually drop packets. After all, this is
332 connection tracking, not packet filtering.
333 However, it is necessary for accurate tracking in
336 printk("conntrack_ftp: partial %s %u+%u\n",
338 ntohl(tcph.seq), datalen);
341 } else if (found == 0) { /* No match */
346 DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
347 (int)matchlen, data + matchoff,
348 matchlen, ntohl(tcph.seq) + matchoff);
350 /* Allocate expectation which will be inserted */
351 exp = ip_conntrack_expect_alloc();
357 exp_ftp_info = &exp->help.exp_ftp_info;
359 /* Update the ftp info */
360 if (htonl((array[0] << 24) | (array[1] << 16) | (array[2] << 8) | array[3])
361 == ct->tuplehash[dir].tuple.src.ip) {
362 exp->seq = ntohl(tcph.seq) + matchoff;
363 exp_ftp_info->len = matchlen;
364 exp_ftp_info->ftptype = search[i].ftptype;
365 exp_ftp_info->port = array[4] << 8 | array[5];
367 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
368 server: it really wants us to connect to a
369 different IP address. Simply don't record it for
371 DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n",
372 array[0], array[1], array[2], array[3],
373 NIPQUAD(ct->tuplehash[dir].tuple.src.ip));
375 /* Thanks to Cristiano Lincoln Mattos
376 <lincoln@cesar.org.br> for reporting this potential
377 problem (DMZ machines opening holes to internal
378 networks, or the packet filter itself). */
385 exp->tuple = ((struct ip_conntrack_tuple)
386 { { ct->tuplehash[!dir].tuple.src.ip,
388 { htonl((array[0] << 24) | (array[1] << 16)
389 | (array[2] << 8) | array[3]),
390 { .tcp = { htons(array[4] << 8 | array[5]) } },
392 exp->mask = ((struct ip_conntrack_tuple)
393 { { 0xFFFFFFFF, { 0 } },
394 { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFFFF }});
396 exp->expectfn = NULL;
398 /* Ignore failure; should only happen with NAT */
399 ip_conntrack_expect_related(exp, ct);
402 UNLOCK_BH(&ip_ftp_lock);
406 static struct ip_conntrack_helper ftp[MAX_PORTS];
407 static char ftp_names[MAX_PORTS][10];
409 /* Not __exit: called from init() */
410 static void fini(void)
413 for (i = 0; i < ports_c; i++) {
414 DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
416 ip_conntrack_helper_unregister(&ftp[i]);
420 static int __init init(void)
428 for (i = 0; (i < MAX_PORTS) && ports[i]; i++) {
429 ftp[i].tuple.src.u.tcp.port = htons(ports[i]);
430 ftp[i].tuple.dst.protonum = IPPROTO_TCP;
431 ftp[i].mask.src.u.tcp.port = 0xFFFF;
432 ftp[i].mask.dst.protonum = 0xFFFF;
433 ftp[i].max_expected = 1;
435 ftp[i].flags = IP_CT_HELPER_F_REUSE_EXPECT;
436 ftp[i].me = ip_conntrack_ftp;
439 tmpname = &ftp_names[i][0];
440 if (ports[i] == FTP_PORT)
441 sprintf(tmpname, "ftp");
443 sprintf(tmpname, "ftp-%d", ports[i]);
444 ftp[i].name = tmpname;
446 DEBUGP("ip_ct_ftp: registering helper for port %d\n",
448 ret = ip_conntrack_helper_register(&ftp[i]);
459 PROVIDES_CONNTRACK(ftp);
460 EXPORT_SYMBOL(ip_ftp_lock);