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 DECLARE_LOCK(ip_ftp_lock);
35 struct module *ip_conntrack_ftp = THIS_MODULE;
38 static int ports[MAX_PORTS];
40 MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_PORTS) "i");
43 MODULE_PARM(loose, "i");
48 #define DEBUGP(format, args...)
51 static int try_rfc959(const char *, size_t, u_int32_t [], char);
52 static int try_eprt(const char *, size_t, u_int32_t [], char);
53 static int try_epsv_response(const char *, size_t, u_int32_t [], char);
55 static struct ftp_search {
56 enum ip_conntrack_dir dir;
61 enum ip_ct_ftp_type ftptype;
62 int (*getnum)(const char *, size_t, u_int32_t[], char);
66 "PORT", sizeof("PORT") - 1, ' ', '\r',
72 "227 ", sizeof("227 ") - 1, '(', ')',
78 "EPRT", sizeof("EPRT") - 1, ' ', '\r',
84 "229 ", sizeof("229 ") - 1, '(', ')',
90 static int try_number(const char *data, size_t dlen, u_int32_t array[],
91 int array_size, char sep, char term)
95 memset(array, 0, sizeof(array[0])*array_size);
97 /* Keep data pointing at next char. */
98 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
99 if (*data >= '0' && *data <= '9') {
100 array[i] = array[i]*10 + *data - '0';
102 else if (*data == sep)
105 /* Unexpected character; true if it's the
106 terminator and we're finished. */
107 if (*data == term && i == array_size - 1)
110 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
115 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
120 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
121 static int try_rfc959(const char *data, size_t dlen, u_int32_t array[6],
124 return try_number(data, dlen, array, 6, ',', term);
127 /* Grab port: number up to delimiter */
128 static int get_port(const char *data, int start, size_t dlen, char delim,
134 for (i = start; i < dlen; i++) {
136 if (data[i] == delim) {
139 array[0] = port >> 8;
143 else if (data[i] >= '0' && data[i] <= '9')
144 port = port*10 + data[i] - '0';
145 else /* Some other crap */
151 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */
152 static int try_eprt(const char *data, size_t dlen, u_int32_t array[6],
158 /* First character is delimiter, then "1" for IPv4, then
160 if (dlen <= 3) return 0;
162 if (isdigit(delim) || delim < 33 || delim > 126
163 || data[1] != '1' || data[2] != delim)
166 DEBUGP("EPRT: Got |1|!\n");
167 /* Now we have IP address. */
168 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
172 DEBUGP("EPRT: Got IP address!\n");
173 /* Start offset includes initial "|1|", and trailing delimiter */
174 return get_port(data, 3 + length + 1, dlen, delim, array+4);
177 /* Returns 0, or length of numbers: |||6446| */
178 static int try_epsv_response(const char *data, size_t dlen, u_int32_t array[6],
183 /* Three delimiters. */
184 if (dlen <= 3) return 0;
186 if (isdigit(delim) || delim < 33 || delim > 126
187 || data[1] != delim || data[2] != delim)
190 return get_port(data, 3, dlen, delim, array+4);
193 /* Return 1 for match, 0 for accept, -1 for partial. */
194 static int find_pattern(const char *data, size_t dlen,
195 const char *pattern, size_t plen,
196 char skip, char term,
197 unsigned int *numoff,
198 unsigned int *numlen,
200 int (*getnum)(const char *, size_t, u_int32_t[], char))
204 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
209 /* Short packet: try for partial? */
210 if (strnicmp(data, pattern, dlen) == 0)
215 if (strnicmp(data, pattern, plen) != 0) {
219 DEBUGP("ftp: string mismatch\n");
220 for (i = 0; i < plen; i++) {
221 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
223 pattern[i], pattern[i]);
229 DEBUGP("Pattern matches!\n");
230 /* Now we've found the constant string, try to skip
231 to the 'skip' character */
232 for (i = plen; data[i] != skip; i++)
233 if (i == dlen - 1) return -1;
235 /* Skip over the last character */
238 DEBUGP("Skipped up to `%c'!\n", skip);
241 *numlen = getnum(data + i, dlen - i, array, term);
245 DEBUGP("Match succeeded!\n");
249 static int help(struct sk_buff *skb,
250 struct ip_conntrack *ct,
251 enum ip_conntrack_info ctinfo)
253 unsigned int dataoff, datalen;
255 u_int32_t old_seq_aft_nl;
256 int old_seq_aft_nl_set, ret;
257 u_int32_t array[6] = { 0 };
258 int dir = CTINFO2DIR(ctinfo);
259 unsigned int matchlen, matchoff;
260 struct ip_ct_ftp_master *ct_ftp_info = &ct->help.ct_ftp_info;
261 struct ip_conntrack_expect *exp;
262 struct ip_ct_ftp_expect *exp_ftp_info;
267 /* Until there's been traffic both ways, don't look in packets. */
268 if (ctinfo != IP_CT_ESTABLISHED
269 && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
270 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
274 if (skb_copy_bits(skb, skb->nh.iph->ihl*4, &tcph, sizeof(tcph)) != 0)
277 dataoff = skb->nh.iph->ihl*4 + tcph.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 skb_copy_bits(skb, dataoff, ftp_buffer, skb->len - dataoff);
288 old_seq_aft_nl_set = ct_ftp_info->seq_aft_nl_set[dir];
289 old_seq_aft_nl = ct_ftp_info->seq_aft_nl[dir];
291 DEBUGP("conntrack_ftp: datalen %u\n", datalen);
292 if (ftp_buffer[datalen - 1] == '\n') {
293 DEBUGP("conntrack_ftp: datalen %u ends in \\n\n", datalen);
294 if (!old_seq_aft_nl_set
295 || after(ntohl(tcph.seq) + datalen, old_seq_aft_nl)) {
296 DEBUGP("conntrack_ftp: updating nl to %u\n",
297 ntohl(tcph.seq) + datalen);
298 ct_ftp_info->seq_aft_nl[dir] =
299 ntohl(tcph.seq) + datalen;
300 ct_ftp_info->seq_aft_nl_set[dir] = 1;
304 if(!old_seq_aft_nl_set ||
305 (ntohl(tcph.seq) != old_seq_aft_nl)) {
306 DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u)\n",
307 old_seq_aft_nl_set ? "":"(UNSET) ", old_seq_aft_nl);
312 /* Initialize IP array to expected address (it's not mentioned
313 in EPSV responses) */
314 array[0] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 24) & 0xFF;
315 array[1] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 16) & 0xFF;
316 array[2] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 8) & 0xFF;
317 array[3] = ntohl(ct->tuplehash[dir].tuple.src.ip) & 0xFF;
319 for (i = 0; i < ARRAY_SIZE(search); i++) {
320 if (search[i].dir != dir) continue;
322 found = find_pattern(ftp_buffer, skb->len - dataoff,
327 &matchoff, &matchlen,
333 /* We don't usually drop packets. After all, this is
334 connection tracking, not packet filtering.
335 However, it is necessary for accurate tracking in
338 printk("conntrack_ftp: partial %s %u+%u\n",
340 ntohl(tcph.seq), datalen);
343 } else if (found == 0) { /* No match */
348 DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
349 (int)matchlen, data + matchoff,
350 matchlen, ntohl(tcph.seq) + matchoff);
352 /* Allocate expectation which will be inserted */
353 exp = ip_conntrack_expect_alloc();
359 exp_ftp_info = &exp->help.exp_ftp_info;
361 /* Update the ftp info */
362 if (htonl((array[0] << 24) | (array[1] << 16) | (array[2] << 8) | array[3])
363 == ct->tuplehash[dir].tuple.src.ip) {
364 exp->seq = ntohl(tcph.seq) + matchoff;
365 exp_ftp_info->len = matchlen;
366 exp_ftp_info->ftptype = search[i].ftptype;
367 exp_ftp_info->port = array[4] << 8 | array[5];
369 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
370 server: it really wants us to connect to a
371 different IP address. Simply don't record it for
373 DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n",
374 array[0], array[1], array[2], array[3],
375 NIPQUAD(ct->tuplehash[dir].tuple.src.ip));
377 /* Thanks to Cristiano Lincoln Mattos
378 <lincoln@cesar.org.br> for reporting this potential
379 problem (DMZ machines opening holes to internal
380 networks, or the packet filter itself). */
387 exp->tuple = ((struct ip_conntrack_tuple)
388 { { ct->tuplehash[!dir].tuple.src.ip,
390 { htonl((array[0] << 24) | (array[1] << 16)
391 | (array[2] << 8) | array[3]),
392 { .tcp = { htons(array[4] << 8 | array[5]) } },
394 exp->mask = ((struct ip_conntrack_tuple)
395 { { 0xFFFFFFFF, { 0 } },
396 { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFFFF }});
398 exp->expectfn = NULL;
400 /* Ignore failure; should only happen with NAT */
401 ip_conntrack_expect_related(exp, ct);
404 UNLOCK_BH(&ip_ftp_lock);
408 static struct ip_conntrack_helper ftp[MAX_PORTS];
409 static char ftp_names[MAX_PORTS][10];
411 /* Not __exit: called from init() */
412 static void fini(void)
415 for (i = 0; i < ports_c; i++) {
416 DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
418 ip_conntrack_helper_unregister(&ftp[i]);
422 static int __init init(void)
430 for (i = 0; (i < MAX_PORTS) && ports[i]; i++) {
431 ftp[i].tuple.src.u.tcp.port = htons(ports[i]);
432 ftp[i].tuple.dst.protonum = IPPROTO_TCP;
433 ftp[i].mask.src.u.tcp.port = 0xFFFF;
434 ftp[i].mask.dst.protonum = 0xFFFF;
435 ftp[i].max_expected = 1;
437 ftp[i].flags = IP_CT_HELPER_F_REUSE_EXPECT;
438 ftp[i].me = ip_conntrack_ftp;
441 tmpname = &ftp_names[i][0];
442 if (ports[i] == FTP_PORT)
443 sprintf(tmpname, "ftp");
445 sprintf(tmpname, "ftp-%d", ports[i]);
446 ftp[i].name = tmpname;
448 DEBUGP("ip_ct_ftp: registering helper for port %d\n",
450 ret = ip_conntrack_helper_register(&ftp[i]);
461 PROVIDES_CONNTRACK(ftp);
462 EXPORT_SYMBOL(ip_ftp_lock);