ipvs: convert lblc scheduler to rcu
[linux-3.10.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/slab.h>
17 #include <linux/ipv6.h>
18 #include <linux/ctype.h>
19 #include <linux/inet.h>
20 #include <net/checksum.h>
21 #include <net/tcp.h>
22
23 #include <net/netfilter/nf_conntrack.h>
24 #include <net/netfilter/nf_conntrack_expect.h>
25 #include <net/netfilter/nf_conntrack_ecache.h>
26 #include <net/netfilter/nf_conntrack_helper.h>
27 #include <linux/netfilter/nf_conntrack_ftp.h>
28
29 MODULE_LICENSE("GPL");
30 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
31 MODULE_DESCRIPTION("ftp connection tracking helper");
32 MODULE_ALIAS("ip_conntrack_ftp");
33 MODULE_ALIAS_NFCT_HELPER("ftp");
34
35 /* This is slow, but it's simple. --RR */
36 static char *ftp_buffer;
37
38 static DEFINE_SPINLOCK(nf_ftp_lock);
39
40 #define MAX_PORTS 8
41 static u_int16_t ports[MAX_PORTS];
42 static unsigned int ports_c;
43 module_param_array(ports, ushort, &ports_c, 0400);
44
45 static bool loose;
46 module_param(loose, bool, 0600);
47
48 unsigned int (*nf_nat_ftp_hook)(struct sk_buff *skb,
49                                 enum ip_conntrack_info ctinfo,
50                                 enum nf_ct_ftp_type type,
51                                 unsigned int protoff,
52                                 unsigned int matchoff,
53                                 unsigned int matchlen,
54                                 struct nf_conntrack_expect *exp);
55 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
56
57 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
58 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
59 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
60                              char);
61
62 static struct ftp_search {
63         const char *pattern;
64         size_t plen;
65         char skip;
66         char term;
67         enum nf_ct_ftp_type ftptype;
68         int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
69 } search[IP_CT_DIR_MAX][2] = {
70         [IP_CT_DIR_ORIGINAL] = {
71                 {
72                         .pattern        = "PORT",
73                         .plen           = sizeof("PORT") - 1,
74                         .skip           = ' ',
75                         .term           = '\r',
76                         .ftptype        = NF_CT_FTP_PORT,
77                         .getnum         = try_rfc959,
78                 },
79                 {
80                         .pattern        = "EPRT",
81                         .plen           = sizeof("EPRT") - 1,
82                         .skip           = ' ',
83                         .term           = '\r',
84                         .ftptype        = NF_CT_FTP_EPRT,
85                         .getnum         = try_eprt,
86                 },
87         },
88         [IP_CT_DIR_REPLY] = {
89                 {
90                         .pattern        = "227 ",
91                         .plen           = sizeof("227 ") - 1,
92                         .skip           = '(',
93                         .term           = ')',
94                         .ftptype        = NF_CT_FTP_PASV,
95                         .getnum         = try_rfc959,
96                 },
97                 {
98                         .pattern        = "229 ",
99                         .plen           = sizeof("229 ") - 1,
100                         .skip           = '(',
101                         .term           = ')',
102                         .ftptype        = NF_CT_FTP_EPSV,
103                         .getnum         = try_epsv_response,
104                 },
105         },
106 };
107
108 static int
109 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
110 {
111         const char *end;
112         int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
113         if (ret > 0)
114                 return (int)(end - src);
115         return 0;
116 }
117
118 static int try_number(const char *data, size_t dlen, u_int32_t array[],
119                       int array_size, char sep, char term)
120 {
121         u_int32_t i, len;
122
123         memset(array, 0, sizeof(array[0])*array_size);
124
125         /* Keep data pointing at next char. */
126         for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
127                 if (*data >= '0' && *data <= '9') {
128                         array[i] = array[i]*10 + *data - '0';
129                 }
130                 else if (*data == sep)
131                         i++;
132                 else {
133                         /* Unexpected character; true if it's the
134                            terminator and we're finished. */
135                         if (*data == term && i == array_size - 1)
136                                 return len;
137
138                         pr_debug("Char %u (got %u nums) `%u' unexpected\n",
139                                  len, i, *data);
140                         return 0;
141                 }
142         }
143         pr_debug("Failed to fill %u numbers separated by %c\n",
144                  array_size, sep);
145         return 0;
146 }
147
148 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
149 static int try_rfc959(const char *data, size_t dlen,
150                       struct nf_conntrack_man *cmd, char term)
151 {
152         int length;
153         u_int32_t array[6];
154
155         length = try_number(data, dlen, array, 6, ',', term);
156         if (length == 0)
157                 return 0;
158
159         cmd->u3.ip =  htonl((array[0] << 24) | (array[1] << 16) |
160                                     (array[2] << 8) | array[3]);
161         cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
162         return length;
163 }
164
165 /* Grab port: number up to delimiter */
166 static int get_port(const char *data, int start, size_t dlen, char delim,
167                     __be16 *port)
168 {
169         u_int16_t tmp_port = 0;
170         int i;
171
172         for (i = start; i < dlen; i++) {
173                 /* Finished? */
174                 if (data[i] == delim) {
175                         if (tmp_port == 0)
176                                 break;
177                         *port = htons(tmp_port);
178                         pr_debug("get_port: return %d\n", tmp_port);
179                         return i + 1;
180                 }
181                 else if (data[i] >= '0' && data[i] <= '9')
182                         tmp_port = tmp_port*10 + data[i] - '0';
183                 else { /* Some other crap */
184                         pr_debug("get_port: invalid char.\n");
185                         break;
186                 }
187         }
188         return 0;
189 }
190
191 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
192 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
193                     char term)
194 {
195         char delim;
196         int length;
197
198         /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
199            then delimiter again. */
200         if (dlen <= 3) {
201                 pr_debug("EPRT: too short\n");
202                 return 0;
203         }
204         delim = data[0];
205         if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
206                 pr_debug("try_eprt: invalid delimitter.\n");
207                 return 0;
208         }
209
210         if ((cmd->l3num == PF_INET && data[1] != '1') ||
211             (cmd->l3num == PF_INET6 && data[1] != '2')) {
212                 pr_debug("EPRT: invalid protocol number.\n");
213                 return 0;
214         }
215
216         pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
217
218         if (data[1] == '1') {
219                 u_int32_t array[4];
220
221                 /* Now we have IP address. */
222                 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
223                 if (length != 0)
224                         cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
225                                            | (array[2] << 8) | array[3]);
226         } else {
227                 /* Now we have IPv6 address. */
228                 length = get_ipv6_addr(data + 3, dlen - 3,
229                                        (struct in6_addr *)cmd->u3.ip6, delim);
230         }
231
232         if (length == 0)
233                 return 0;
234         pr_debug("EPRT: Got IP address!\n");
235         /* Start offset includes initial "|1|", and trailing delimiter */
236         return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
237 }
238
239 /* Returns 0, or length of numbers: |||6446| */
240 static int try_epsv_response(const char *data, size_t dlen,
241                              struct nf_conntrack_man *cmd, char term)
242 {
243         char delim;
244
245         /* Three delimiters. */
246         if (dlen <= 3) return 0;
247         delim = data[0];
248         if (isdigit(delim) || delim < 33 || delim > 126 ||
249             data[1] != delim || data[2] != delim)
250                 return 0;
251
252         return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
253 }
254
255 /* Return 1 for match, 0 for accept, -1 for partial. */
256 static int find_pattern(const char *data, size_t dlen,
257                         const char *pattern, size_t plen,
258                         char skip, char term,
259                         unsigned int *numoff,
260                         unsigned int *numlen,
261                         struct nf_conntrack_man *cmd,
262                         int (*getnum)(const char *, size_t,
263                                       struct nf_conntrack_man *, char))
264 {
265         size_t i;
266
267         pr_debug("find_pattern `%s': dlen = %Zu\n", pattern, dlen);
268         if (dlen == 0)
269                 return 0;
270
271         if (dlen <= plen) {
272                 /* Short packet: try for partial? */
273                 if (strnicmp(data, pattern, dlen) == 0)
274                         return -1;
275                 else return 0;
276         }
277
278         if (strnicmp(data, pattern, plen) != 0) {
279 #if 0
280                 size_t i;
281
282                 pr_debug("ftp: string mismatch\n");
283                 for (i = 0; i < plen; i++) {
284                         pr_debug("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
285                                  i, data[i], data[i],
286                                  pattern[i], pattern[i]);
287                 }
288 #endif
289                 return 0;
290         }
291
292         pr_debug("Pattern matches!\n");
293         /* Now we've found the constant string, try to skip
294            to the 'skip' character */
295         for (i = plen; data[i] != skip; i++)
296                 if (i == dlen - 1) return -1;
297
298         /* Skip over the last character */
299         i++;
300
301         pr_debug("Skipped up to `%c'!\n", skip);
302
303         *numoff = i;
304         *numlen = getnum(data + i, dlen - i, cmd, term);
305         if (!*numlen)
306                 return -1;
307
308         pr_debug("Match succeeded!\n");
309         return 1;
310 }
311
312 /* Look up to see if we're just after a \n. */
313 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
314 {
315         unsigned int i;
316
317         for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
318                 if (info->seq_aft_nl[dir][i] == seq)
319                         return 1;
320         return 0;
321 }
322
323 /* We don't update if it's older than what we have. */
324 static void update_nl_seq(struct nf_conn *ct, u32 nl_seq,
325                           struct nf_ct_ftp_master *info, int dir,
326                           struct sk_buff *skb)
327 {
328         unsigned int i, oldest;
329
330         /* Look for oldest: if we find exact match, we're done. */
331         for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
332                 if (info->seq_aft_nl[dir][i] == nl_seq)
333                         return;
334         }
335
336         if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
337                 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
338         } else {
339                 if (before(info->seq_aft_nl[dir][0], info->seq_aft_nl[dir][1]))
340                         oldest = 0;
341                 else
342                         oldest = 1;
343
344                 if (after(nl_seq, info->seq_aft_nl[dir][oldest]))
345                         info->seq_aft_nl[dir][oldest] = nl_seq;
346         }
347 }
348
349 static int help(struct sk_buff *skb,
350                 unsigned int protoff,
351                 struct nf_conn *ct,
352                 enum ip_conntrack_info ctinfo)
353 {
354         unsigned int dataoff, datalen;
355         const struct tcphdr *th;
356         struct tcphdr _tcph;
357         const char *fb_ptr;
358         int ret;
359         u32 seq;
360         int dir = CTINFO2DIR(ctinfo);
361         unsigned int uninitialized_var(matchlen), uninitialized_var(matchoff);
362         struct nf_ct_ftp_master *ct_ftp_info = nfct_help_data(ct);
363         struct nf_conntrack_expect *exp;
364         union nf_inet_addr *daddr;
365         struct nf_conntrack_man cmd = {};
366         unsigned int i;
367         int found = 0, ends_in_nl;
368         typeof(nf_nat_ftp_hook) nf_nat_ftp;
369
370         /* Until there's been traffic both ways, don't look in packets. */
371         if (ctinfo != IP_CT_ESTABLISHED &&
372             ctinfo != IP_CT_ESTABLISHED_REPLY) {
373                 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
374                 return NF_ACCEPT;
375         }
376
377         th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
378         if (th == NULL)
379                 return NF_ACCEPT;
380
381         dataoff = protoff + th->doff * 4;
382         /* No data? */
383         if (dataoff >= skb->len) {
384                 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
385                          skb->len);
386                 return NF_ACCEPT;
387         }
388         datalen = skb->len - dataoff;
389
390         spin_lock_bh(&nf_ftp_lock);
391         fb_ptr = skb_header_pointer(skb, dataoff, datalen, ftp_buffer);
392         BUG_ON(fb_ptr == NULL);
393
394         ends_in_nl = (fb_ptr[datalen - 1] == '\n');
395         seq = ntohl(th->seq) + datalen;
396
397         /* Look up to see if we're just after a \n. */
398         if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
399                 /* We're picking up this, clear flags and let it continue */
400                 if (unlikely(ct_ftp_info->flags[dir] & NF_CT_FTP_SEQ_PICKUP)) {
401                         ct_ftp_info->flags[dir] ^= NF_CT_FTP_SEQ_PICKUP;
402                         goto skip_nl_seq;
403                 }
404
405                 /* Now if this ends in \n, update ftp info. */
406                 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
407                          ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
408                          ct_ftp_info->seq_aft_nl[dir][0],
409                          ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
410                          ct_ftp_info->seq_aft_nl[dir][1]);
411                 ret = NF_ACCEPT;
412                 goto out_update_nl;
413         }
414
415 skip_nl_seq:
416         /* Initialize IP/IPv6 addr to expected address (it's not mentioned
417            in EPSV responses) */
418         cmd.l3num = nf_ct_l3num(ct);
419         memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
420                sizeof(cmd.u3.all));
421
422         for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
423                 found = find_pattern(fb_ptr, datalen,
424                                      search[dir][i].pattern,
425                                      search[dir][i].plen,
426                                      search[dir][i].skip,
427                                      search[dir][i].term,
428                                      &matchoff, &matchlen,
429                                      &cmd,
430                                      search[dir][i].getnum);
431                 if (found) break;
432         }
433         if (found == -1) {
434                 /* We don't usually drop packets.  After all, this is
435                    connection tracking, not packet filtering.
436                    However, it is necessary for accurate tracking in
437                    this case. */
438                 nf_ct_helper_log(skb, ct, "partial matching of `%s'",
439                                  search[dir][i].pattern);
440                 ret = NF_DROP;
441                 goto out;
442         } else if (found == 0) { /* No match */
443                 ret = NF_ACCEPT;
444                 goto out_update_nl;
445         }
446
447         pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
448                  matchlen, fb_ptr + matchoff,
449                  matchlen, ntohl(th->seq) + matchoff);
450
451         exp = nf_ct_expect_alloc(ct);
452         if (exp == NULL) {
453                 nf_ct_helper_log(skb, ct, "cannot alloc expectation");
454                 ret = NF_DROP;
455                 goto out;
456         }
457
458         /* We refer to the reverse direction ("!dir") tuples here,
459          * because we're expecting something in the other direction.
460          * Doesn't matter unless NAT is happening.  */
461         daddr = &ct->tuplehash[!dir].tuple.dst.u3;
462
463         /* Update the ftp info */
464         if ((cmd.l3num == nf_ct_l3num(ct)) &&
465             memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
466                      sizeof(cmd.u3.all))) {
467                 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
468                    server: it really wants us to connect to a
469                    different IP address.  Simply don't record it for
470                    NAT. */
471                 if (cmd.l3num == PF_INET) {
472                         pr_debug("conntrack_ftp: NOT RECORDING: %pI4 != %pI4\n",
473                                  &cmd.u3.ip,
474                                  &ct->tuplehash[dir].tuple.src.u3.ip);
475                 } else {
476                         pr_debug("conntrack_ftp: NOT RECORDING: %pI6 != %pI6\n",
477                                  cmd.u3.ip6,
478                                  ct->tuplehash[dir].tuple.src.u3.ip6);
479                 }
480
481                 /* Thanks to Cristiano Lincoln Mattos
482                    <lincoln@cesar.org.br> for reporting this potential
483                    problem (DMZ machines opening holes to internal
484                    networks, or the packet filter itself). */
485                 if (!loose) {
486                         ret = NF_ACCEPT;
487                         goto out_put_expect;
488                 }
489                 daddr = &cmd.u3;
490         }
491
492         nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, cmd.l3num,
493                           &ct->tuplehash[!dir].tuple.src.u3, daddr,
494                           IPPROTO_TCP, NULL, &cmd.u.tcp.port);
495
496         /* Now, NAT might want to mangle the packet, and register the
497          * (possibly changed) expectation itself. */
498         nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
499         if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
500                 ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
501                                  protoff, matchoff, matchlen, exp);
502         else {
503                 /* Can't expect this?  Best to drop packet now. */
504                 if (nf_ct_expect_related(exp) != 0) {
505                         nf_ct_helper_log(skb, ct, "cannot add expectation");
506                         ret = NF_DROP;
507                 } else
508                         ret = NF_ACCEPT;
509         }
510
511 out_put_expect:
512         nf_ct_expect_put(exp);
513
514 out_update_nl:
515         /* Now if this ends in \n, update ftp info.  Seq may have been
516          * adjusted by NAT code. */
517         if (ends_in_nl)
518                 update_nl_seq(ct, seq, ct_ftp_info, dir, skb);
519  out:
520         spin_unlock_bh(&nf_ftp_lock);
521         return ret;
522 }
523
524 static int nf_ct_ftp_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
525 {
526         struct nf_ct_ftp_master *ftp = nfct_help_data(ct);
527
528         /* This conntrack has been injected from user-space, always pick up
529          * sequence tracking. Otherwise, the first FTP command after the
530          * failover breaks.
531          */
532         ftp->flags[IP_CT_DIR_ORIGINAL] |= NF_CT_FTP_SEQ_PICKUP;
533         ftp->flags[IP_CT_DIR_REPLY] |= NF_CT_FTP_SEQ_PICKUP;
534         return 0;
535 }
536
537 static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
538
539 static const struct nf_conntrack_expect_policy ftp_exp_policy = {
540         .max_expected   = 1,
541         .timeout        = 5 * 60,
542 };
543
544 /* don't make this __exit, since it's called from __init ! */
545 static void nf_conntrack_ftp_fini(void)
546 {
547         int i, j;
548         for (i = 0; i < ports_c; i++) {
549                 for (j = 0; j < 2; j++) {
550                         if (ftp[i][j].me == NULL)
551                                 continue;
552
553                         pr_debug("nf_ct_ftp: unregistering helper for pf: %d "
554                                  "port: %d\n",
555                                  ftp[i][j].tuple.src.l3num, ports[i]);
556                         nf_conntrack_helper_unregister(&ftp[i][j]);
557                 }
558         }
559
560         kfree(ftp_buffer);
561 }
562
563 static int __init nf_conntrack_ftp_init(void)
564 {
565         int i, j = -1, ret = 0;
566
567         ftp_buffer = kmalloc(65536, GFP_KERNEL);
568         if (!ftp_buffer)
569                 return -ENOMEM;
570
571         if (ports_c == 0)
572                 ports[ports_c++] = FTP_PORT;
573
574         /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
575                  are tracked or not - YK */
576         for (i = 0; i < ports_c; i++) {
577                 ftp[i][0].tuple.src.l3num = PF_INET;
578                 ftp[i][1].tuple.src.l3num = PF_INET6;
579                 for (j = 0; j < 2; j++) {
580                         ftp[i][j].data_len = sizeof(struct nf_ct_ftp_master);
581                         ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
582                         ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
583                         ftp[i][j].expect_policy = &ftp_exp_policy;
584                         ftp[i][j].me = THIS_MODULE;
585                         ftp[i][j].help = help;
586                         ftp[i][j].from_nlattr = nf_ct_ftp_from_nlattr;
587                         if (ports[i] == FTP_PORT)
588                                 sprintf(ftp[i][j].name, "ftp");
589                         else
590                                 sprintf(ftp[i][j].name, "ftp-%d", ports[i]);
591
592                         pr_debug("nf_ct_ftp: registering helper for pf: %d "
593                                  "port: %d\n",
594                                  ftp[i][j].tuple.src.l3num, ports[i]);
595                         ret = nf_conntrack_helper_register(&ftp[i][j]);
596                         if (ret) {
597                                 printk(KERN_ERR "nf_ct_ftp: failed to register"
598                                        " helper for pf: %d port: %d\n",
599                                         ftp[i][j].tuple.src.l3num, ports[i]);
600                                 nf_conntrack_ftp_fini();
601                                 return ret;
602                         }
603                 }
604         }
605
606         return 0;
607 }
608
609 module_init(nf_conntrack_ftp_init);
610 module_exit(nf_conntrack_ftp_fini);