1 /* FTP extension for IP connection tracking. */
2 #include <linux/config.h>
3 #include <linux/module.h>
4 #include <linux/netfilter.h>
6 #include <linux/ctype.h>
7 #include <net/checksum.h>
10 #include <linux/netfilter_ipv4/lockhelp.h>
11 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
12 #include <linux/netfilter_ipv4/ip_conntrack_ftp.h>
14 /* This is slow, but it's simple. --RR */
15 static char ftp_buffer[65536];
17 DECLARE_LOCK(ip_ftp_lock);
18 struct module *ip_conntrack_ftp = THIS_MODULE;
21 static int ports[MAX_PORTS];
22 static int ports_c = 0;
24 MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_PORTS) "i");
28 MODULE_PARM(loose, "i");
33 #define DEBUGP(format, args...)
36 static int try_rfc959(const char *, size_t, u_int32_t [], char);
37 static int try_eprt(const char *, size_t, u_int32_t [], char);
38 static int try_epsv_response(const char *, size_t, u_int32_t [], char);
40 static struct ftp_search {
41 enum ip_conntrack_dir dir;
46 enum ip_ct_ftp_type ftptype;
47 int (*getnum)(const char *, size_t, u_int32_t[], char);
51 "PORT", sizeof("PORT") - 1, ' ', '\r',
57 "227 ", sizeof("227 ") - 1, '(', ')',
63 "EPRT", sizeof("EPRT") - 1, ' ', '\r',
69 "229 ", sizeof("229 ") - 1, '(', ')',
75 static int try_number(const char *data, size_t dlen, u_int32_t array[],
76 int array_size, char sep, char term)
80 memset(array, 0, sizeof(array[0])*array_size);
82 /* Keep data pointing at next char. */
83 for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
84 if (*data >= '0' && *data <= '9') {
85 array[i] = array[i]*10 + *data - '0';
87 else if (*data == sep)
90 /* Unexpected character; true if it's the
91 terminator and we're finished. */
92 if (*data == term && i == array_size - 1)
95 DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
100 DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
105 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
106 static int try_rfc959(const char *data, size_t dlen, u_int32_t array[6],
109 return try_number(data, dlen, array, 6, ',', term);
112 /* Grab port: number up to delimiter */
113 static int get_port(const char *data, int start, size_t dlen, char delim,
119 for (i = start; i < dlen; i++) {
121 if (data[i] == delim) {
124 array[0] = port >> 8;
128 else if (data[i] >= '0' && data[i] <= '9')
129 port = port*10 + data[i] - '0';
130 else /* Some other crap */
136 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| */
137 static int try_eprt(const char *data, size_t dlen, u_int32_t array[6],
143 /* First character is delimiter, then "1" for IPv4, then
145 if (dlen <= 3) return 0;
147 if (isdigit(delim) || delim < 33 || delim > 126
148 || data[1] != '1' || data[2] != delim)
151 DEBUGP("EPRT: Got |1|!\n");
152 /* Now we have IP address. */
153 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
157 DEBUGP("EPRT: Got IP address!\n");
158 /* Start offset includes initial "|1|", and trailing delimiter */
159 return get_port(data, 3 + length + 1, dlen, delim, array+4);
162 /* Returns 0, or length of numbers: |||6446| */
163 static int try_epsv_response(const char *data, size_t dlen, u_int32_t array[6],
168 /* Three delimiters. */
169 if (dlen <= 3) return 0;
171 if (isdigit(delim) || delim < 33 || delim > 126
172 || data[1] != delim || data[2] != delim)
175 return get_port(data, 3, dlen, delim, array+4);
178 /* Return 1 for match, 0 for accept, -1 for partial. */
179 static int find_pattern(const char *data, size_t dlen,
180 const char *pattern, size_t plen,
181 char skip, char term,
182 unsigned int *numoff,
183 unsigned int *numlen,
185 int (*getnum)(const char *, size_t, u_int32_t[], char))
189 DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
194 /* Short packet: try for partial? */
195 if (strnicmp(data, pattern, dlen) == 0)
200 if (strnicmp(data, pattern, plen) != 0) {
204 DEBUGP("ftp: string mismatch\n");
205 for (i = 0; i < plen; i++) {
206 DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
208 pattern[i], pattern[i]);
214 DEBUGP("Pattern matches!\n");
215 /* Now we've found the constant string, try to skip
216 to the 'skip' character */
217 for (i = plen; data[i] != skip; i++)
218 if (i == dlen - 1) return -1;
220 /* Skip over the last character */
223 DEBUGP("Skipped up to `%c'!\n", skip);
226 *numlen = getnum(data + i, dlen - i, array, term);
230 DEBUGP("Match succeeded!\n");
234 static int help(struct sk_buff *skb,
235 struct ip_conntrack *ct,
236 enum ip_conntrack_info ctinfo)
238 unsigned int dataoff, datalen;
240 u_int32_t old_seq_aft_nl;
241 int old_seq_aft_nl_set, ret;
242 u_int32_t array[6] = { 0 };
243 int dir = CTINFO2DIR(ctinfo);
244 unsigned int matchlen, matchoff;
245 struct ip_ct_ftp_master *ct_ftp_info = &ct->help.ct_ftp_info;
246 struct ip_conntrack_expect expect, *exp = &expect;
247 struct ip_ct_ftp_expect *exp_ftp_info = &exp->help.exp_ftp_info;
252 /* Until there's been traffic both ways, don't look in packets. */
253 if (ctinfo != IP_CT_ESTABLISHED
254 && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
255 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
259 if (skb_copy_bits(skb, skb->nh.iph->ihl*4, &tcph, sizeof(tcph)) != 0)
262 dataoff = skb->nh.iph->ihl*4 + tcph.doff*4;
264 if (dataoff >= skb->len) {
265 DEBUGP("ftp: skblen = %u\n", skb->len);
268 datalen = skb->len - dataoff;
270 LOCK_BH(&ip_ftp_lock);
271 skb_copy_bits(skb, dataoff, ftp_buffer, skb->len - dataoff);
273 old_seq_aft_nl_set = ct_ftp_info->seq_aft_nl_set[dir];
274 old_seq_aft_nl = ct_ftp_info->seq_aft_nl[dir];
276 DEBUGP("conntrack_ftp: datalen %u\n", datalen);
277 if (ftp_buffer[datalen - 1] == '\n') {
278 DEBUGP("conntrack_ftp: datalen %u ends in \\n\n", datalen);
279 if (!old_seq_aft_nl_set
280 || after(ntohl(tcph.seq) + datalen, old_seq_aft_nl)) {
281 DEBUGP("conntrack_ftp: updating nl to %u\n",
282 ntohl(tcph.seq) + datalen);
283 ct_ftp_info->seq_aft_nl[dir] =
284 ntohl(tcph.seq) + datalen;
285 ct_ftp_info->seq_aft_nl_set[dir] = 1;
289 if(!old_seq_aft_nl_set ||
290 (ntohl(tcph.seq) != old_seq_aft_nl)) {
291 DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u)\n",
292 old_seq_aft_nl_set ? "":"(UNSET) ", old_seq_aft_nl);
297 /* Initialize IP array to expected address (it's not mentioned
298 in EPSV responses) */
299 array[0] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 24) & 0xFF;
300 array[1] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 16) & 0xFF;
301 array[2] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 8) & 0xFF;
302 array[3] = ntohl(ct->tuplehash[dir].tuple.src.ip) & 0xFF;
304 for (i = 0; i < ARRAY_SIZE(search); i++) {
305 if (search[i].dir != dir) continue;
307 found = find_pattern(ftp_buffer, skb->len - dataoff,
312 &matchoff, &matchlen,
318 /* We don't usually drop packets. After all, this is
319 connection tracking, not packet filtering.
320 However, it is necessary for accurate tracking in
323 printk("conntrack_ftp: partial %s %u+%u\n",
325 ntohl(tcph.seq), datalen);
328 } else if (found == 0) { /* No match */
333 DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
334 (int)matchlen, data + matchoff,
335 matchlen, ntohl(tcph.seq) + matchoff);
337 memset(&expect, 0, sizeof(expect));
339 /* Update the ftp info */
340 if (htonl((array[0] << 24) | (array[1] << 16) | (array[2] << 8) | array[3])
341 == ct->tuplehash[dir].tuple.src.ip) {
342 exp->seq = ntohl(tcph.seq) + matchoff;
343 exp_ftp_info->len = matchlen;
344 exp_ftp_info->ftptype = search[i].ftptype;
345 exp_ftp_info->port = array[4] << 8 | array[5];
347 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
348 server: it really wants us to connect to a
349 different IP address. Simply don't record it for
351 DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n",
352 array[0], array[1], array[2], array[3],
353 NIPQUAD(ct->tuplehash[dir].tuple.src.ip));
355 /* Thanks to Cristiano Lincoln Mattos
356 <lincoln@cesar.org.br> for reporting this potential
357 problem (DMZ machines opening holes to internal
358 networks, or the packet filter itself). */
365 exp->tuple = ((struct ip_conntrack_tuple)
366 { { ct->tuplehash[!dir].tuple.src.ip,
368 { htonl((array[0] << 24) | (array[1] << 16)
369 | (array[2] << 8) | array[3]),
370 { .tcp = { htons(array[4] << 8 | array[5]) } },
372 exp->mask = ((struct ip_conntrack_tuple)
373 { { 0xFFFFFFFF, { 0 } },
374 { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFFFF }});
376 exp->expectfn = NULL;
378 /* Ignore failure; should only happen with NAT */
379 ip_conntrack_expect_related(ct, &expect);
382 UNLOCK_BH(&ip_ftp_lock);
386 static struct ip_conntrack_helper ftp[MAX_PORTS];
387 static char ftp_names[MAX_PORTS][10];
389 /* Not __exit: called from init() */
390 static void fini(void)
393 for (i = 0; i < ports_c; i++) {
394 DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
396 ip_conntrack_helper_unregister(&ftp[i]);
400 static int __init init(void)
408 for (i = 0; (i < MAX_PORTS) && ports[i]; i++) {
409 ftp[i].tuple.src.u.tcp.port = htons(ports[i]);
410 ftp[i].tuple.dst.protonum = IPPROTO_TCP;
411 ftp[i].mask.src.u.tcp.port = 0xFFFF;
412 ftp[i].mask.dst.protonum = 0xFFFF;
413 ftp[i].max_expected = 1;
415 ftp[i].flags = IP_CT_HELPER_F_REUSE_EXPECT;
416 ftp[i].me = ip_conntrack_ftp;
419 tmpname = &ftp_names[i][0];
420 if (ports[i] == FTP_PORT)
421 sprintf(tmpname, "ftp");
423 sprintf(tmpname, "ftp-%d", ports[i]);
424 ftp[i].name = tmpname;
426 DEBUGP("ip_ct_ftp: registering helper for port %d\n",
428 ret = ip_conntrack_helper_register(&ftp[i]);
439 PROVIDES_CONNTRACK(ftp);
440 EXPORT_SYMBOL(ip_ftp_lock);
442 MODULE_LICENSE("GPL");