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);
32 struct module *ip_conntrack_ftp = THIS_MODULE;
35 static int ports[MAX_PORTS];
37 module_param_array(ports, int, ports_c, 0400);
40 module_param(loose, int, 0600);
45 #define DEBUGP(format, args...)
48 static int try_rfc959(const char *, size_t, u_int32_t [], char);
49 static int try_eprt(const char *, size_t, u_int32_t [], char);
50 static int try_epsv_response(const char *, size_t, u_int32_t [], char);
52 static struct ftp_search {
53 enum ip_conntrack_dir dir;
58 enum ip_ct_ftp_type ftptype;
59 int (*getnum)(const char *, size_t, u_int32_t[], char);
63 "PORT", sizeof("PORT") - 1, ' ', '\r',
69 "227 ", sizeof("227 ") - 1, '(', ')',
75 "EPRT", sizeof("EPRT") - 1, ' ', '\r',
81 "229 ", sizeof("229 ") - 1, '(', ')',
87 static int try_number(const char *data, size_t dlen, u_int32_t array[],
88 int array_size, char sep, char term)
92 memset(array, 0, sizeof(array[0])*array_size);
94 /* Keep data pointing at next char. */
95 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
96 if (*data >= '0' && *data <= '9') {
97 array[i] = array[i]*10 + *data - '0';
99 else if (*data == sep)
102 /* Unexpected character; true if it's the
103 terminator and we're finished. */
104 if (*data == term && i == array_size - 1)
107 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
112 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
117 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
118 static int try_rfc959(const char *data, size_t dlen, u_int32_t array[6],
121 return try_number(data, dlen, array, 6, ',', term);
124 /* Grab port: number up to delimiter */
125 static int get_port(const char *data, int start, size_t dlen, char delim,
131 for (i = start; i < dlen; i++) {
133 if (data[i] == delim) {
136 array[0] = port >> 8;
140 else if (data[i] >= '0' && data[i] <= '9')
141 port = port*10 + data[i] - '0';
142 else /* Some other crap */
148 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */
149 static int try_eprt(const char *data, size_t dlen, u_int32_t array[6],
155 /* First character is delimiter, then "1" for IPv4, then
157 if (dlen <= 3) return 0;
159 if (isdigit(delim) || delim < 33 || delim > 126
160 || data[1] != '1' || data[2] != delim)
163 DEBUGP("EPRT: Got |1|!\n");
164 /* Now we have IP address. */
165 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
169 DEBUGP("EPRT: Got IP address!\n");
170 /* Start offset includes initial "|1|", and trailing delimiter */
171 return get_port(data, 3 + length + 1, dlen, delim, array+4);
174 /* Returns 0, or length of numbers: |||6446| */
175 static int try_epsv_response(const char *data, size_t dlen, u_int32_t array[6],
180 /* Three delimiters. */
181 if (dlen <= 3) return 0;
183 if (isdigit(delim) || delim < 33 || delim > 126
184 || data[1] != delim || data[2] != delim)
187 return get_port(data, 3, dlen, delim, array+4);
190 /* Return 1 for match, 0 for accept, -1 for partial. */
191 static int find_pattern(const char *data, size_t dlen,
192 const char *pattern, size_t plen,
193 char skip, char term,
194 unsigned int *numoff,
195 unsigned int *numlen,
197 int (*getnum)(const char *, size_t, u_int32_t[], char))
201 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
206 /* Short packet: try for partial? */
207 if (strnicmp(data, pattern, dlen) == 0)
212 if (strnicmp(data, pattern, plen) != 0) {
216 DEBUGP("ftp: string mismatch\n");
217 for (i = 0; i < plen; i++) {
218 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
220 pattern[i], pattern[i]);
226 DEBUGP("Pattern matches!\n");
227 /* Now we've found the constant string, try to skip
228 to the 'skip' character */
229 for (i = plen; data[i] != skip; i++)
230 if (i == dlen - 1) return -1;
232 /* Skip over the last character */
235 DEBUGP("Skipped up to `%c'!\n", skip);
238 *numlen = getnum(data + i, dlen - i, array, term);
242 DEBUGP("Match succeeded!\n");
246 static int help(struct sk_buff *skb,
247 struct ip_conntrack *ct,
248 enum ip_conntrack_info ctinfo)
250 unsigned int dataoff, datalen;
251 struct tcphdr _tcph, *th;
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 th = skb_header_pointer(skb, skb->nh.iph->ihl*4,
273 sizeof(_tcph), &_tcph);
277 dataoff = skb->nh.iph->ihl*4 + th->doff*4;
279 if (dataoff >= skb->len) {
280 DEBUGP("ftp: skblen = %u\n", skb->len);
283 datalen = skb->len - dataoff;
285 LOCK_BH(&ip_ftp_lock);
286 fb_ptr = skb_header_pointer(skb, dataoff,
287 skb->len - dataoff, ftp_buffer);
288 BUG_ON(fb_ptr == NULL);
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 (fb_ptr[datalen - 1] == '\n') {
295 DEBUGP("conntrack_ftp: datalen %u ends in \\n\n", datalen);
296 if (!old_seq_aft_nl_set
297 || after(ntohl(th->seq) + datalen, old_seq_aft_nl)) {
298 DEBUGP("conntrack_ftp: updating nl to %u\n",
299 ntohl(th->seq) + datalen);
300 ct_ftp_info->seq_aft_nl[dir] =
301 ntohl(th->seq) + datalen;
302 ct_ftp_info->seq_aft_nl_set[dir] = 1;
306 if(!old_seq_aft_nl_set ||
307 (ntohl(th->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(fb_ptr, 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(th->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(th->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(th->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)
430 ports[ports_c++] = FTP_PORT;
432 for (i = 0; i < ports_c; 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]);
462 PROVIDES_CONNTRACK(ftp);