netfilter: nf_ct_ftp: fix out of bounds read in update_nl_seq()
[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 MODULE_ALIAS_NFCT_HELPER("ftp");
33
34 /* This is slow, but it's simple. --RR */
35 static char *ftp_buffer;
36
37 static DEFINE_SPINLOCK(nf_ftp_lock);
38
39 #define MAX_PORTS 8
40 static u_int16_t ports[MAX_PORTS];
41 static unsigned int ports_c;
42 module_param_array(ports, ushort, &ports_c, 0400);
43
44 static int loose;
45 module_param(loose, bool, 0600);
46
47 unsigned int (*nf_nat_ftp_hook)(struct sk_buff *skb,
48                                 enum ip_conntrack_info ctinfo,
49                                 enum nf_ct_ftp_type type,
50                                 unsigned int matchoff,
51                                 unsigned int matchlen,
52                                 struct nf_conntrack_expect *exp);
53 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
54
55 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
56 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
57 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
58                              char);
59
60 static struct ftp_search {
61         const char *pattern;
62         size_t plen;
63         char skip;
64         char term;
65         enum nf_ct_ftp_type ftptype;
66         int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
67 } search[IP_CT_DIR_MAX][2] = {
68         [IP_CT_DIR_ORIGINAL] = {
69                 {
70                         .pattern        = "PORT",
71                         .plen           = sizeof("PORT") - 1,
72                         .skip           = ' ',
73                         .term           = '\r',
74                         .ftptype        = NF_CT_FTP_PORT,
75                         .getnum         = try_rfc959,
76                 },
77                 {
78                         .pattern        = "EPRT",
79                         .plen           = sizeof("EPRT") - 1,
80                         .skip           = ' ',
81                         .term           = '\r',
82                         .ftptype        = NF_CT_FTP_EPRT,
83                         .getnum         = try_eprt,
84                 },
85         },
86         [IP_CT_DIR_REPLY] = {
87                 {
88                         .pattern        = "227 ",
89                         .plen           = sizeof("227 ") - 1,
90                         .skip           = '(',
91                         .term           = ')',
92                         .ftptype        = NF_CT_FTP_PASV,
93                         .getnum         = try_rfc959,
94                 },
95                 {
96                         .pattern        = "229 ",
97                         .plen           = sizeof("229 ") - 1,
98                         .skip           = '(',
99                         .term           = ')',
100                         .ftptype        = NF_CT_FTP_EPSV,
101                         .getnum         = try_epsv_response,
102                 },
103         },
104 };
105
106 static int
107 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
108 {
109         const char *end;
110         int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
111         if (ret > 0)
112                 return (int)(end - src);
113         return 0;
114 }
115
116 static int try_number(const char *data, size_t dlen, u_int32_t array[],
117                       int array_size, char sep, char term)
118 {
119         u_int32_t i, len;
120
121         memset(array, 0, sizeof(array[0])*array_size);
122
123         /* Keep data pointing at next char. */
124         for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
125                 if (*data >= '0' && *data <= '9') {
126                         array[i] = array[i]*10 + *data - '0';
127                 }
128                 else if (*data == sep)
129                         i++;
130                 else {
131                         /* Unexpected character; true if it's the
132                            terminator and we're finished. */
133                         if (*data == term && i == array_size - 1)
134                                 return len;
135
136                         pr_debug("Char %u (got %u nums) `%u' unexpected\n",
137                                  len, i, *data);
138                         return 0;
139                 }
140         }
141         pr_debug("Failed to fill %u numbers separated by %c\n",
142                  array_size, sep);
143         return 0;
144 }
145
146 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
147 static int try_rfc959(const char *data, size_t dlen,
148                       struct nf_conntrack_man *cmd, char term)
149 {
150         int length;
151         u_int32_t array[6];
152
153         length = try_number(data, dlen, array, 6, ',', term);
154         if (length == 0)
155                 return 0;
156
157         cmd->u3.ip =  htonl((array[0] << 24) | (array[1] << 16) |
158                                     (array[2] << 8) | array[3]);
159         cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
160         return length;
161 }
162
163 /* Grab port: number up to delimiter */
164 static int get_port(const char *data, int start, size_t dlen, char delim,
165                     __be16 *port)
166 {
167         u_int16_t tmp_port = 0;
168         int i;
169
170         for (i = start; i < dlen; i++) {
171                 /* Finished? */
172                 if (data[i] == delim) {
173                         if (tmp_port == 0)
174                                 break;
175                         *port = htons(tmp_port);
176                         pr_debug("get_port: return %d\n", tmp_port);
177                         return i + 1;
178                 }
179                 else if (data[i] >= '0' && data[i] <= '9')
180                         tmp_port = tmp_port*10 + data[i] - '0';
181                 else { /* Some other crap */
182                         pr_debug("get_port: invalid char.\n");
183                         break;
184                 }
185         }
186         return 0;
187 }
188
189 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
190 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
191                     char term)
192 {
193         char delim;
194         int length;
195
196         /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
197            then delimiter again. */
198         if (dlen <= 3) {
199                 pr_debug("EPRT: too short\n");
200                 return 0;
201         }
202         delim = data[0];
203         if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
204                 pr_debug("try_eprt: invalid delimitter.\n");
205                 return 0;
206         }
207
208         if ((cmd->l3num == PF_INET && data[1] != '1') ||
209             (cmd->l3num == PF_INET6 && data[1] != '2')) {
210                 pr_debug("EPRT: invalid protocol number.\n");
211                 return 0;
212         }
213
214         pr_debug("EPRT: Got %c%c%c\n", delim, data[1], delim);
215
216         if (data[1] == '1') {
217                 u_int32_t array[4];
218
219                 /* Now we have IP address. */
220                 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
221                 if (length != 0)
222                         cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
223                                            | (array[2] << 8) | array[3]);
224         } else {
225                 /* Now we have IPv6 address. */
226                 length = get_ipv6_addr(data + 3, dlen - 3,
227                                        (struct in6_addr *)cmd->u3.ip6, delim);
228         }
229
230         if (length == 0)
231                 return 0;
232         pr_debug("EPRT: Got IP address!\n");
233         /* Start offset includes initial "|1|", and trailing delimiter */
234         return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
235 }
236
237 /* Returns 0, or length of numbers: |||6446| */
238 static int try_epsv_response(const char *data, size_t dlen,
239                              struct nf_conntrack_man *cmd, char term)
240 {
241         char delim;
242
243         /* Three delimiters. */
244         if (dlen <= 3) return 0;
245         delim = data[0];
246         if (isdigit(delim) || delim < 33 || delim > 126 ||
247             data[1] != delim || data[2] != delim)
248                 return 0;
249
250         return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
251 }
252
253 /* Return 1 for match, 0 for accept, -1 for partial. */
254 static int find_pattern(const char *data, size_t dlen,
255                         const char *pattern, size_t plen,
256                         char skip, char term,
257                         unsigned int *numoff,
258                         unsigned int *numlen,
259                         struct nf_conntrack_man *cmd,
260                         int (*getnum)(const char *, size_t,
261                                       struct nf_conntrack_man *, char))
262 {
263         size_t i;
264
265         pr_debug("find_pattern `%s': dlen = %Zu\n", pattern, dlen);
266         if (dlen == 0)
267                 return 0;
268
269         if (dlen <= plen) {
270                 /* Short packet: try for partial? */
271                 if (strnicmp(data, pattern, dlen) == 0)
272                         return -1;
273                 else return 0;
274         }
275
276         if (strnicmp(data, pattern, plen) != 0) {
277 #if 0
278                 size_t i;
279
280                 pr_debug("ftp: string mismatch\n");
281                 for (i = 0; i < plen; i++) {
282                         pr_debug("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
283                                  i, data[i], data[i],
284                                  pattern[i], pattern[i]);
285                 }
286 #endif
287                 return 0;
288         }
289
290         pr_debug("Pattern matches!\n");
291         /* Now we've found the constant string, try to skip
292            to the 'skip' character */
293         for (i = plen; data[i] != skip; i++)
294                 if (i == dlen - 1) return -1;
295
296         /* Skip over the last character */
297         i++;
298
299         pr_debug("Skipped up to `%c'!\n", skip);
300
301         *numoff = i;
302         *numlen = getnum(data + i, dlen - i, cmd, term);
303         if (!*numlen)
304                 return -1;
305
306         pr_debug("Match succeeded!\n");
307         return 1;
308 }
309
310 /* Look up to see if we're just after a \n. */
311 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
312 {
313         unsigned int i;
314
315         for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
316                 if (info->seq_aft_nl[dir][i] == seq)
317                         return 1;
318         return 0;
319 }
320
321 /* We don't update if it's older than what we have. */
322 static void update_nl_seq(struct nf_conn *ct, u32 nl_seq,
323                           struct nf_ct_ftp_master *info, int dir,
324                           struct sk_buff *skb)
325 {
326         unsigned int i, oldest;
327
328         /* Look for oldest: if we find exact match, we're done. */
329         for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
330                 if (info->seq_aft_nl[dir][i] == nl_seq)
331                         return;
332         }
333
334         if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
335                 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
336         } else {
337                 if (before(info->seq_aft_nl[dir][0], info->seq_aft_nl[dir][1]))
338                         oldest = 0;
339                 else
340                         oldest = 1;
341
342                 if (after(nl_seq, info->seq_aft_nl[dir][oldest]))
343                         info->seq_aft_nl[dir][oldest] = nl_seq;
344         }
345 }
346
347 static int help(struct sk_buff *skb,
348                 unsigned int protoff,
349                 struct nf_conn *ct,
350                 enum ip_conntrack_info ctinfo)
351 {
352         unsigned int dataoff, datalen;
353         const struct tcphdr *th;
354         struct tcphdr _tcph;
355         const char *fb_ptr;
356         int ret;
357         u32 seq;
358         int dir = CTINFO2DIR(ctinfo);
359         unsigned int uninitialized_var(matchlen), uninitialized_var(matchoff);
360         struct nf_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
361         struct nf_conntrack_expect *exp;
362         union nf_inet_addr *daddr;
363         struct nf_conntrack_man cmd = {};
364         unsigned int i;
365         int found = 0, ends_in_nl;
366         typeof(nf_nat_ftp_hook) nf_nat_ftp;
367
368         /* Until there's been traffic both ways, don't look in packets. */
369         if (ctinfo != IP_CT_ESTABLISHED &&
370             ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) {
371                 pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
372                 return NF_ACCEPT;
373         }
374
375         th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
376         if (th == NULL)
377                 return NF_ACCEPT;
378
379         dataoff = protoff + th->doff * 4;
380         /* No data? */
381         if (dataoff >= skb->len) {
382                 pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
383                          skb->len);
384                 return NF_ACCEPT;
385         }
386         datalen = skb->len - dataoff;
387
388         spin_lock_bh(&nf_ftp_lock);
389         fb_ptr = skb_header_pointer(skb, dataoff, datalen, ftp_buffer);
390         BUG_ON(fb_ptr == NULL);
391
392         ends_in_nl = (fb_ptr[datalen - 1] == '\n');
393         seq = ntohl(th->seq) + datalen;
394
395         /* Look up to see if we're just after a \n. */
396         if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
397                 /* Now if this ends in \n, update ftp info. */
398                 pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
399                          ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
400                          ct_ftp_info->seq_aft_nl[dir][0],
401                          ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
402                          ct_ftp_info->seq_aft_nl[dir][1]);
403                 ret = NF_ACCEPT;
404                 goto out_update_nl;
405         }
406
407         /* Initialize IP/IPv6 addr to expected address (it's not mentioned
408            in EPSV responses) */
409         cmd.l3num = nf_ct_l3num(ct);
410         memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
411                sizeof(cmd.u3.all));
412
413         for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
414                 found = find_pattern(fb_ptr, datalen,
415                                      search[dir][i].pattern,
416                                      search[dir][i].plen,
417                                      search[dir][i].skip,
418                                      search[dir][i].term,
419                                      &matchoff, &matchlen,
420                                      &cmd,
421                                      search[dir][i].getnum);
422                 if (found) break;
423         }
424         if (found == -1) {
425                 /* We don't usually drop packets.  After all, this is
426                    connection tracking, not packet filtering.
427                    However, it is necessary for accurate tracking in
428                    this case. */
429                 pr_debug("conntrack_ftp: partial %s %u+%u\n",
430                          search[dir][i].pattern,  ntohl(th->seq), datalen);
431                 ret = NF_DROP;
432                 goto out;
433         } else if (found == 0) { /* No match */
434                 ret = NF_ACCEPT;
435                 goto out_update_nl;
436         }
437
438         pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
439                  matchlen, fb_ptr + matchoff,
440                  matchlen, ntohl(th->seq) + matchoff);
441
442         exp = nf_ct_expect_alloc(ct);
443         if (exp == NULL) {
444                 ret = NF_DROP;
445                 goto out;
446         }
447
448         /* We refer to the reverse direction ("!dir") tuples here,
449          * because we're expecting something in the other direction.
450          * Doesn't matter unless NAT is happening.  */
451         daddr = &ct->tuplehash[!dir].tuple.dst.u3;
452
453         /* Update the ftp info */
454         if ((cmd.l3num == nf_ct_l3num(ct)) &&
455             memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
456                      sizeof(cmd.u3.all))) {
457                 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
458                    server: it really wants us to connect to a
459                    different IP address.  Simply don't record it for
460                    NAT. */
461                 if (cmd.l3num == PF_INET) {
462                         pr_debug("conntrack_ftp: NOT RECORDING: %pI4 != %pI4\n",
463                                  &cmd.u3.ip,
464                                  &ct->tuplehash[dir].tuple.src.u3.ip);
465                 } else {
466                         pr_debug("conntrack_ftp: NOT RECORDING: %pI6 != %pI6\n",
467                                  cmd.u3.ip6,
468                                  ct->tuplehash[dir].tuple.src.u3.ip6);
469                 }
470
471                 /* Thanks to Cristiano Lincoln Mattos
472                    <lincoln@cesar.org.br> for reporting this potential
473                    problem (DMZ machines opening holes to internal
474                    networks, or the packet filter itself). */
475                 if (!loose) {
476                         ret = NF_ACCEPT;
477                         goto out_put_expect;
478                 }
479                 daddr = &cmd.u3;
480         }
481
482         nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, cmd.l3num,
483                           &ct->tuplehash[!dir].tuple.src.u3, daddr,
484                           IPPROTO_TCP, NULL, &cmd.u.tcp.port);
485
486         /* Now, NAT might want to mangle the packet, and register the
487          * (possibly changed) expectation itself. */
488         nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
489         if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
490                 ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
491                                  matchoff, matchlen, exp);
492         else {
493                 /* Can't expect this?  Best to drop packet now. */
494                 if (nf_ct_expect_related(exp) != 0)
495                         ret = NF_DROP;
496                 else
497                         ret = NF_ACCEPT;
498         }
499
500 out_put_expect:
501         nf_ct_expect_put(exp);
502
503 out_update_nl:
504         /* Now if this ends in \n, update ftp info.  Seq may have been
505          * adjusted by NAT code. */
506         if (ends_in_nl)
507                 update_nl_seq(ct, seq, ct_ftp_info, dir, skb);
508  out:
509         spin_unlock_bh(&nf_ftp_lock);
510         return ret;
511 }
512
513 static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
514 static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")] __read_mostly;
515
516 static const struct nf_conntrack_expect_policy ftp_exp_policy = {
517         .max_expected   = 1,
518         .timeout        = 5 * 60,
519 };
520
521 /* don't make this __exit, since it's called from __init ! */
522 static void nf_conntrack_ftp_fini(void)
523 {
524         int i, j;
525         for (i = 0; i < ports_c; i++) {
526                 for (j = 0; j < 2; j++) {
527                         if (ftp[i][j].me == NULL)
528                                 continue;
529
530                         pr_debug("nf_ct_ftp: unregistering helper for pf: %d "
531                                  "port: %d\n",
532                                  ftp[i][j].tuple.src.l3num, ports[i]);
533                         nf_conntrack_helper_unregister(&ftp[i][j]);
534                 }
535         }
536
537         kfree(ftp_buffer);
538 }
539
540 static int __init nf_conntrack_ftp_init(void)
541 {
542         int i, j = -1, ret = 0;
543         char *tmpname;
544
545         ftp_buffer = kmalloc(65536, GFP_KERNEL);
546         if (!ftp_buffer)
547                 return -ENOMEM;
548
549         if (ports_c == 0)
550                 ports[ports_c++] = FTP_PORT;
551
552         /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
553                  are tracked or not - YK */
554         for (i = 0; i < ports_c; i++) {
555                 ftp[i][0].tuple.src.l3num = PF_INET;
556                 ftp[i][1].tuple.src.l3num = PF_INET6;
557                 for (j = 0; j < 2; j++) {
558                         ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
559                         ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
560                         ftp[i][j].expect_policy = &ftp_exp_policy;
561                         ftp[i][j].me = THIS_MODULE;
562                         ftp[i][j].help = help;
563                         tmpname = &ftp_names[i][j][0];
564                         if (ports[i] == FTP_PORT)
565                                 sprintf(tmpname, "ftp");
566                         else
567                                 sprintf(tmpname, "ftp-%d", ports[i]);
568                         ftp[i][j].name = tmpname;
569
570                         pr_debug("nf_ct_ftp: registering helper for pf: %d "
571                                  "port: %d\n",
572                                  ftp[i][j].tuple.src.l3num, ports[i]);
573                         ret = nf_conntrack_helper_register(&ftp[i][j]);
574                         if (ret) {
575                                 printk("nf_ct_ftp: failed to register helper "
576                                        " for pf: %d port: %d\n",
577                                         ftp[i][j].tuple.src.l3num, ports[i]);
578                                 nf_conntrack_ftp_fini();
579                                 return ret;
580                         }
581                 }
582         }
583
584         return 0;
585 }
586
587 module_init(nf_conntrack_ftp_init);
588 module_exit(nf_conntrack_ftp_fini);