8cab6d5959097962099b7d3c194cc829828caf81
[linux-2.6.git] / net / netfilter / nf_conntrack_ftp.c
1 /* FTP extension for connection tracking. */
2
3 /* (C) 1999-2001 Paul `Rusty' Russell
4  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
5  * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  */
11
12 #include <linux/module.h>
13 #include <linux/moduleparam.h>
14 #include <linux/netfilter.h>
15 #include <linux/ip.h>
16 #include <linux/ipv6.h>
17 #include <linux/ctype.h>
18 #include <linux/inet.h>
19 #include <net/checksum.h>
20 #include <net/tcp.h>
21
22 #include <net/netfilter/nf_conntrack.h>
23 #include <net/netfilter/nf_conntrack_expect.h>
24 #include <net/netfilter/nf_conntrack_ecache.h>
25 #include <net/netfilter/nf_conntrack_helper.h>
26 #include <linux/netfilter/nf_conntrack_ftp.h>
27
28 MODULE_LICENSE("GPL");
29 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
30 MODULE_DESCRIPTION("ftp connection tracking helper");
31 MODULE_ALIAS("ip_conntrack_ftp");
32
33 /* This is slow, but it's simple. --RR */
34 static char *ftp_buffer;
35
36 static DEFINE_SPINLOCK(nf_ftp_lock);
37
38 #define MAX_PORTS 8
39 static u_int16_t ports[MAX_PORTS];
40 static unsigned int ports_c;
41 module_param_array(ports, ushort, &ports_c, 0400);
42
43 static int loose;
44 module_param(loose, bool, 0600);
45
46 unsigned int (*nf_nat_ftp_hook)(struct sk_buff *skb,
47                                 enum ip_conntrack_info ctinfo,
48                                 enum nf_ct_ftp_type type,
49                                 unsigned int matchoff,
50                                 unsigned int matchlen,
51                                 struct nf_conntrack_expect *exp);
52 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
53
54 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
55 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
56 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
57                              char);
58
59 static struct ftp_search {
60         const char *pattern;
61         size_t plen;
62         char skip;
63         char term;
64         enum nf_ct_ftp_type ftptype;
65         int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
66 } search[IP_CT_DIR_MAX][2] = {
67         [IP_CT_DIR_ORIGINAL] = {
68                 {
69                         .pattern        = "PORT",
70                         .plen           = sizeof("PORT") - 1,
71                         .skip           = ' ',
72                         .term           = '\r',
73                         .ftptype        = NF_CT_FTP_PORT,
74                         .getnum         = try_rfc959,
75                 },
76                 {
77                         .pattern        = "EPRT",
78                         .plen           = sizeof("EPRT") - 1,
79                         .skip           = ' ',
80                         .term           = '\r',
81                         .ftptype        = NF_CT_FTP_EPRT,
82                         .getnum         = try_eprt,
83                 },
84         },
85         [IP_CT_DIR_REPLY] = {
86                 {
87                         .pattern        = "227 ",
88                         .plen           = sizeof("227 ") - 1,
89                         .skip           = '(',
90                         .term           = ')',
91                         .ftptype        = NF_CT_FTP_PASV,
92                         .getnum         = try_rfc959,
93                 },
94                 {
95                         .pattern        = "229 ",
96                         .plen           = sizeof("229 ") - 1,
97                         .skip           = '(',
98                         .term           = ')',
99                         .ftptype        = NF_CT_FTP_EPSV,
100                         .getnum         = try_epsv_response,
101                 },
102         },
103 };
104
105 static int
106 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
107 {
108         const char *end;
109         int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
110         if (ret > 0)
111                 return (int)(end - src);
112         return 0;
113 }
114
115 static int try_number(const char *data, size_t dlen, u_int32_t array[],
116                       int array_size, char sep, char term)
117 {
118         u_int32_t i, len;
119
120         memset(array, 0, sizeof(array[0])*array_size);
121
122         /* Keep data pointing at next char. */
123         for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
124                 if (*data >= '0' && *data <= '9') {
125                         array[i] = array[i]*10 + *data - '0';
126                 }
127                 else if (*data == sep)
128                         i++;
129                 else {
130                         /* Unexpected character; true if it's the
131                            terminator and we're finished. */
132                         if (*data == term && i == array_size - 1)
133                                 return len;
134
135                         pr_debug("Char %u (got %u nums) `%u' unexpected\n",
136                                  len, i, *data);
137                         return 0;
138                 }
139         }
140         pr_debug("Failed to fill %u numbers separated by %c\n",
141                  array_size, sep);
142         return 0;
143 }
144
145 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
146 static int try_rfc959(const char *data, size_t dlen,
147                       struct nf_conntrack_man *cmd, char term)
148 {
149         int length;
150         u_int32_t array[6];
151
152         length = try_number(data, dlen, array, 6, ',', term);
153         if (length == 0)
154                 return 0;
155
156         cmd->u3.ip =  htonl((array[0] << 24) | (array[1] << 16) |
157                                     (array[2] << 8) | array[3]);
158         cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
159         return length;
160 }
161
162 /* Grab port: number up to delimiter */
163 static int get_port(const char *data, int start, size_t dlen, char delim,
164                     __be16 *port)
165 {
166         u_int16_t tmp_port = 0;
167         int i;
168
169         for (i = start; i < dlen; i++) {
170                 /* Finished? */
171                 if (data[i] == delim) {
172                         if (tmp_port == 0)
173                                 break;
174                         *port = htons(tmp_port);
175                         pr_debug("get_port: return %d\n", tmp_port);
176                         return i + 1;
177                 }
178                 else if (data[i] >= '0' && data[i] <= '9')
179                         tmp_port = tmp_port*10 + data[i] - '0';
180                 else { /* Some other crap */
181                         pr_debug("get_port: invalid char.\n");
182                         break;
183                 }
184         }
185         return 0;
186 }
187
188 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
189 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
190                     char term)
191 {
192         char delim;
193         int length;
194
195         /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
196            then delimiter again. */
197         if (dlen <= 3) {
198                 pr_debug("EPRT: too short\n");
199                 return 0;
200         }
201         delim = data[0];
202         if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
203                 pr_debug("try_eprt: invalid delimitter.\n");
204                 return 0;
205         }
206
207         if ((cmd->l3num == PF_INET && data[1] != '1') ||
208             (cmd->l3num == PF_INET6 && data[1] != '2')) {
209                 pr_debug("EPRT: invalid protocol number.\n");
210                 return 0;
211         }
212
213         pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
214
215         if (data[1] == '1') {
216                 u_int32_t array[4];
217
218                 /* Now we have IP address. */
219                 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
220                 if (length != 0)
221                         cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
222                                            | (array[2] << 8) | array[3]);
223         } else {
224                 /* Now we have IPv6 address. */
225                 length = get_ipv6_addr(data + 3, dlen - 3,
226                                        (struct in6_addr *)cmd->u3.ip6, delim);
227         }
228
229         if (length == 0)
230                 return 0;
231         pr_debug("EPRT: Got IP address!\n");
232         /* Start offset includes initial "|1|", and trailing delimiter */
233         return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
234 }
235
236 /* Returns 0, or length of numbers: |||6446| */
237 static int try_epsv_response(const char *data, size_t dlen,
238                              struct nf_conntrack_man *cmd, char term)
239 {
240         char delim;
241
242         /* Three delimiters. */
243         if (dlen <= 3) return 0;
244         delim = data[0];
245         if (isdigit(delim) || delim < 33 || delim > 126
246             || data[1] != delim || data[2] != delim)
247                 return 0;
248
249         return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
250 }
251
252 /* Return 1 for match, 0 for accept, -1 for partial. */
253 static int find_pattern(const char *data, size_t dlen,
254                         const char *pattern, size_t plen,
255                         char skip, char term,
256                         unsigned int *numoff,
257                         unsigned int *numlen,
258                         struct nf_conntrack_man *cmd,
259                         int (*getnum)(const char *, size_t,
260                                       struct nf_conntrack_man *, char))
261 {
262         size_t i;
263
264         pr_debug("find_pattern `%s': dlen = %Zu\n", pattern, dlen);
265         if (dlen == 0)
266                 return 0;
267
268         if (dlen <= plen) {
269                 /* Short packet: try for partial? */
270                 if (strnicmp(data, pattern, dlen) == 0)
271                         return -1;
272                 else return 0;
273         }
274
275         if (strnicmp(data, pattern, plen) != 0) {
276 #if 0
277                 size_t i;
278
279                 pr_debug("ftp: string mismatch\n");
280                 for (i = 0; i < plen; i++) {
281                         pr_debug("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
282                                  i, data[i], data[i],
283                                  pattern[i], pattern[i]);
284                 }
285 #endif
286                 return 0;
287         }
288
289         pr_debug("Pattern matches!\n");
290         /* Now we've found the constant string, try to skip
291            to the 'skip' character */
292         for (i = plen; data[i] != skip; i++)
293                 if (i == dlen - 1) return -1;
294
295         /* Skip over the last character */
296         i++;
297
298         pr_debug("Skipped up to `%c'!\n", skip);
299
300         *numoff = i;
301         *numlen = getnum(data + i, dlen - i, cmd, term);
302         if (!*numlen)
303                 return -1;
304
305         pr_debug("Match succeeded!\n");
306         return 1;
307 }
308
309 /* Look up to see if we're just after a \n. */
310 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
311 {
312         unsigned int i;
313
314         for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
315                 if (info->seq_aft_nl[dir][i] == seq)
316                         return 1;
317         return 0;
318 }
319
320 /* We don't update if it's older than what we have. */
321 static void update_nl_seq(struct nf_conn *ct, u32 nl_seq,
322                           struct nf_ct_ftp_master *info, int dir,
323                           struct sk_buff *skb)
324 {
325         unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
326
327         /* Look for oldest: if we find exact match, we're done. */
328         for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
329                 if (info->seq_aft_nl[dir][i] == nl_seq)
330                         return;
331
332                 if (oldest == info->seq_aft_nl_num[dir] ||
333                     before(info->seq_aft_nl[dir][i],
334                            info->seq_aft_nl[dir][oldest]))
335                         oldest = i;
336         }
337
338         if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
339                 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
340                 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, ct);
341         } else if (oldest != NUM_SEQ_TO_REMEMBER &&
342                    after(nl_seq, info->seq_aft_nl[dir][oldest])) {
343                 info->seq_aft_nl[dir][oldest] = nl_seq;
344                 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, ct);
345         }
346 }
347
348 static int help(struct sk_buff *skb,
349                 unsigned int protoff,
350                 struct nf_conn *ct,
351                 enum ip_conntrack_info ctinfo)
352 {
353         unsigned int dataoff, datalen;
354         const struct tcphdr *th;
355         struct tcphdr _tcph;
356         const char *fb_ptr;
357         int ret;
358         u32 seq;
359         int dir = CTINFO2DIR(ctinfo);
360         unsigned int matchlen, matchoff;
361         struct nf_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
362         struct nf_conntrack_expect *exp;
363         union nf_inet_addr *daddr;
364         struct nf_conntrack_man cmd = {};
365         unsigned int i;
366         int found = 0, ends_in_nl;
367         typeof(nf_nat_ftp_hook) nf_nat_ftp;
368
369         /* Until there's been traffic both ways, don't look in packets. */
370         if (ctinfo != IP_CT_ESTABLISHED
371             && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
372                 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
373                 return NF_ACCEPT;
374         }
375
376         th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
377         if (th == NULL)
378                 return NF_ACCEPT;
379
380         dataoff = protoff + th->doff * 4;
381         /* No data? */
382         if (dataoff >= skb->len) {
383                 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
384                          skb->len);
385                 return NF_ACCEPT;
386         }
387         datalen = skb->len - dataoff;
388
389         spin_lock_bh(&nf_ftp_lock);
390         fb_ptr = skb_header_pointer(skb, dataoff, datalen, ftp_buffer);
391         BUG_ON(fb_ptr == NULL);
392
393         ends_in_nl = (fb_ptr[datalen - 1] == '\n');
394         seq = ntohl(th->seq) + datalen;
395
396         /* Look up to see if we're just after a \n. */
397         if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
398                 /* Now if this ends in \n, update ftp info. */
399                 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
400                          ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
401                          ct_ftp_info->seq_aft_nl[dir][0],
402                          ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
403                          ct_ftp_info->seq_aft_nl[dir][1]);
404                 ret = NF_ACCEPT;
405                 goto out_update_nl;
406         }
407
408         /* Initialize IP/IPv6 addr to expected address (it's not mentioned
409            in EPSV responses) */
410         cmd.l3num = nf_ct_l3num(ct);
411         memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
412                sizeof(cmd.u3.all));
413
414         for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
415                 found = find_pattern(fb_ptr, datalen,
416                                      search[dir][i].pattern,
417                                      search[dir][i].plen,
418                                      search[dir][i].skip,
419                                      search[dir][i].term,
420                                      &matchoff, &matchlen,
421                                      &cmd,
422                                      search[dir][i].getnum);
423                 if (found) break;
424         }
425         if (found == -1) {
426                 /* We don't usually drop packets.  After all, this is
427                    connection tracking, not packet filtering.
428                    However, it is necessary for accurate tracking in
429                    this case. */
430                 if (net_ratelimit())
431                         printk("conntrack_ftp: partial %s %u+%u\n",
432                                search[dir][i].pattern,
433                                ntohl(th->seq), datalen);
434                 ret = NF_DROP;
435                 goto out;
436         } else if (found == 0) { /* No match */
437                 ret = NF_ACCEPT;
438                 goto out_update_nl;
439         }
440
441         pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
442                  matchlen, fb_ptr + matchoff,
443                  matchlen, ntohl(th->seq) + matchoff);
444
445         exp = nf_ct_expect_alloc(ct);
446         if (exp == NULL) {
447                 ret = NF_DROP;
448                 goto out;
449         }
450
451         /* We refer to the reverse direction ("!dir") tuples here,
452          * because we're expecting something in the other direction.
453          * Doesn't matter unless NAT is happening.  */
454         daddr = &ct->tuplehash[!dir].tuple.dst.u3;
455
456         /* Update the ftp info */
457         if ((cmd.l3num == nf_ct_l3num(ct)) &&
458             memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
459                      sizeof(cmd.u3.all))) {
460                 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
461                    server: it really wants us to connect to a
462                    different IP address.  Simply don't record it for
463                    NAT. */
464                 if (cmd.l3num == PF_INET) {
465                         pr_debug("conntrack_ftp: NOT RECORDING: " NIPQUAD_FMT
466                                  " != " NIPQUAD_FMT "\n",
467                                  NIPQUAD(cmd.u3.ip),
468                                  NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
469                 } else {
470                         pr_debug("conntrack_ftp: NOT RECORDING: %pI6 != %pI6\n",
471                                  cmd.u3.ip6,
472                                  ct->tuplehash[dir].tuple.src.u3.ip6);
473                 }
474
475                 /* Thanks to Cristiano Lincoln Mattos
476                    <lincoln@cesar.org.br> for reporting this potential
477                    problem (DMZ machines opening holes to internal
478                    networks, or the packet filter itself). */
479                 if (!loose) {
480                         ret = NF_ACCEPT;
481                         goto out_put_expect;
482                 }
483                 daddr = &cmd.u3;
484         }
485
486         nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, cmd.l3num,
487                           &ct->tuplehash[!dir].tuple.src.u3, daddr,
488                           IPPROTO_TCP, NULL, &cmd.u.tcp.port);
489
490         /* Now, NAT might want to mangle the packet, and register the
491          * (possibly changed) expectation itself. */
492         nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
493         if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
494                 ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
495                                  matchoff, matchlen, exp);
496         else {
497                 /* Can't expect this?  Best to drop packet now. */
498                 if (nf_ct_expect_related(exp) != 0)
499                         ret = NF_DROP;
500                 else
501                         ret = NF_ACCEPT;
502         }
503
504 out_put_expect:
505         nf_ct_expect_put(exp);
506
507 out_update_nl:
508         /* Now if this ends in \n, update ftp info.  Seq may have been
509          * adjusted by NAT code. */
510         if (ends_in_nl)
511                 update_nl_seq(ct, seq, ct_ftp_info, dir, skb);
512  out:
513         spin_unlock_bh(&nf_ftp_lock);
514         return ret;
515 }
516
517 static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
518 static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")] __read_mostly;
519
520 static const struct nf_conntrack_expect_policy ftp_exp_policy = {
521         .max_expected   = 1,
522         .timeout        = 5 * 60,
523 };
524
525 /* don't make this __exit, since it's called from __init ! */
526 static void nf_conntrack_ftp_fini(void)
527 {
528         int i, j;
529         for (i = 0; i < ports_c; i++) {
530                 for (j = 0; j < 2; j++) {
531                         if (ftp[i][j].me == NULL)
532                                 continue;
533
534                         pr_debug("nf_ct_ftp: unregistering helper for pf: %d "
535                                  "port: %d\n",
536                                  ftp[i][j].tuple.src.l3num, ports[i]);
537                         nf_conntrack_helper_unregister(&ftp[i][j]);
538                 }
539         }
540
541         kfree(ftp_buffer);
542 }
543
544 static int __init nf_conntrack_ftp_init(void)
545 {
546         int i, j = -1, ret = 0;
547         char *tmpname;
548
549         ftp_buffer = kmalloc(65536, GFP_KERNEL);
550         if (!ftp_buffer)
551                 return -ENOMEM;
552
553         if (ports_c == 0)
554                 ports[ports_c++] = FTP_PORT;
555
556         /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
557                  are tracked or not - YK */
558         for (i = 0; i < ports_c; i++) {
559                 ftp[i][0].tuple.src.l3num = PF_INET;
560                 ftp[i][1].tuple.src.l3num = PF_INET6;
561                 for (j = 0; j < 2; j++) {
562                         ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
563                         ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
564                         ftp[i][j].expect_policy = &ftp_exp_policy;
565                         ftp[i][j].me = THIS_MODULE;
566                         ftp[i][j].help = help;
567                         tmpname = &ftp_names[i][j][0];
568                         if (ports[i] == FTP_PORT)
569                                 sprintf(tmpname, "ftp");
570                         else
571                                 sprintf(tmpname, "ftp-%d", ports[i]);
572                         ftp[i][j].name = tmpname;
573
574                         pr_debug("nf_ct_ftp: registering helper for pf: %d "
575                                  "port: %d\n",
576                                  ftp[i][j].tuple.src.l3num, ports[i]);
577                         ret = nf_conntrack_helper_register(&ftp[i][j]);
578                         if (ret) {
579                                 printk("nf_ct_ftp: failed to register helper "
580                                        " for pf: %d port: %d\n",
581                                         ftp[i][j].tuple.src.l3num, ports[i]);
582                                 nf_conntrack_ftp_fini();
583                                 return ret;
584                         }
585                 }
586         }
587
588         return 0;
589 }
590
591 module_init(nf_conntrack_ftp_init);
592 module_exit(nf_conntrack_ftp_fini);