[NETFILTER]: nf_conntrack_ftp: fix newline sequence number update
[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 **pskb,
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                                 u32 *seq);
53 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
54
55 #if 0
56 #define DEBUGP printk
57 #else
58 #define DEBUGP(format, args...)
59 #endif
60
61 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
62 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
63 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
64                              char);
65
66 static struct ftp_search {
67         const char *pattern;
68         size_t plen;
69         char skip;
70         char term;
71         enum nf_ct_ftp_type ftptype;
72         int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
73 } search[IP_CT_DIR_MAX][2] = {
74         [IP_CT_DIR_ORIGINAL] = {
75                 {
76                         .pattern        = "PORT",
77                         .plen           = sizeof("PORT") - 1,
78                         .skip           = ' ',
79                         .term           = '\r',
80                         .ftptype        = NF_CT_FTP_PORT,
81                         .getnum         = try_rfc959,
82                 },
83                 {
84                         .pattern        = "EPRT",
85                         .plen           = sizeof("EPRT") - 1,
86                         .skip           = ' ',
87                         .term           = '\r',
88                         .ftptype        = NF_CT_FTP_EPRT,
89                         .getnum         = try_eprt,
90                 },
91         },
92         [IP_CT_DIR_REPLY] = {
93                 {
94                         .pattern        = "227 ",
95                         .plen           = sizeof("227 ") - 1,
96                         .skip           = '(',
97                         .term           = ')',
98                         .ftptype        = NF_CT_FTP_PASV,
99                         .getnum         = try_rfc959,
100                 },
101                 {
102                         .pattern        = "229 ",
103                         .plen           = sizeof("229 ") - 1,
104                         .skip           = '(',
105                         .term           = ')',
106                         .ftptype        = NF_CT_FTP_EPSV,
107                         .getnum         = try_epsv_response,
108                 },
109         },
110 };
111
112 static int
113 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
114 {
115         const char *end;
116         int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
117         if (ret > 0)
118                 return (int)(end - src);
119         return 0;
120 }
121
122 static int try_number(const char *data, size_t dlen, u_int32_t array[],
123                       int array_size, char sep, char term)
124 {
125         u_int32_t i, len;
126
127         memset(array, 0, sizeof(array[0])*array_size);
128
129         /* Keep data pointing at next char. */
130         for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
131                 if (*data >= '0' && *data <= '9') {
132                         array[i] = array[i]*10 + *data - '0';
133                 }
134                 else if (*data == sep)
135                         i++;
136                 else {
137                         /* Unexpected character; true if it's the
138                            terminator and we're finished. */
139                         if (*data == term && i == array_size - 1)
140                                 return len;
141
142                         DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
143                                len, i, *data);
144                         return 0;
145                 }
146         }
147         DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
148
149         return 0;
150 }
151
152 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
153 static int try_rfc959(const char *data, size_t dlen,
154                       struct nf_conntrack_man *cmd, char term)
155 {
156         int length;
157         u_int32_t array[6];
158
159         length = try_number(data, dlen, array, 6, ',', term);
160         if (length == 0)
161                 return 0;
162
163         cmd->u3.ip =  htonl((array[0] << 24) | (array[1] << 16) |
164                                     (array[2] << 8) | array[3]);
165         cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
166         return length;
167 }
168
169 /* Grab port: number up to delimiter */
170 static int get_port(const char *data, int start, size_t dlen, char delim,
171                     __be16 *port)
172 {
173         u_int16_t tmp_port = 0;
174         int i;
175
176         for (i = start; i < dlen; i++) {
177                 /* Finished? */
178                 if (data[i] == delim) {
179                         if (tmp_port == 0)
180                                 break;
181                         *port = htons(tmp_port);
182                         DEBUGP("get_port: return %d\n", tmp_port);
183                         return i + 1;
184                 }
185                 else if (data[i] >= '0' && data[i] <= '9')
186                         tmp_port = tmp_port*10 + data[i] - '0';
187                 else { /* Some other crap */
188                         DEBUGP("get_port: invalid char.\n");
189                         break;
190                 }
191         }
192         return 0;
193 }
194
195 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
196 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
197                     char term)
198 {
199         char delim;
200         int length;
201
202         /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
203            then delimiter again. */
204         if (dlen <= 3) {
205                 DEBUGP("EPRT: too short\n");
206                 return 0;
207         }
208         delim = data[0];
209         if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
210                 DEBUGP("try_eprt: invalid delimitter.\n");
211                 return 0;
212         }
213
214         if ((cmd->l3num == PF_INET && data[1] != '1') ||
215             (cmd->l3num == PF_INET6 && data[1] != '2')) {
216                 DEBUGP("EPRT: invalid protocol number.\n");
217                 return 0;
218         }
219
220         DEBUGP("EPRT: Got %c%c%c\n", delim, data[1], delim);
221
222         if (data[1] == '1') {
223                 u_int32_t array[4];
224
225                 /* Now we have IP address. */
226                 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
227                 if (length != 0)
228                         cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
229                                            | (array[2] << 8) | array[3]);
230         } else {
231                 /* Now we have IPv6 address. */
232                 length = get_ipv6_addr(data + 3, dlen - 3,
233                                        (struct in6_addr *)cmd->u3.ip6, delim);
234         }
235
236         if (length == 0)
237                 return 0;
238         DEBUGP("EPRT: Got IP address!\n");
239         /* Start offset includes initial "|1|", and trailing delimiter */
240         return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
241 }
242
243 /* Returns 0, or length of numbers: |||6446| */
244 static int try_epsv_response(const char *data, size_t dlen,
245                              struct nf_conntrack_man *cmd, char term)
246 {
247         char delim;
248
249         /* Three delimiters. */
250         if (dlen <= 3) return 0;
251         delim = data[0];
252         if (isdigit(delim) || delim < 33 || delim > 126
253             || data[1] != delim || data[2] != delim)
254                 return 0;
255
256         return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
257 }
258
259 /* Return 1 for match, 0 for accept, -1 for partial. */
260 static int find_pattern(const char *data, size_t dlen,
261                         const char *pattern, size_t plen,
262                         char skip, char term,
263                         unsigned int *numoff,
264                         unsigned int *numlen,
265                         struct nf_conntrack_man *cmd,
266                         int (*getnum)(const char *, size_t,
267                                       struct nf_conntrack_man *, char))
268 {
269         size_t i;
270
271         DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
272         if (dlen == 0)
273                 return 0;
274
275         if (dlen <= plen) {
276                 /* Short packet: try for partial? */
277                 if (strnicmp(data, pattern, dlen) == 0)
278                         return -1;
279                 else return 0;
280         }
281
282         if (strnicmp(data, pattern, plen) != 0) {
283 #if 0
284                 size_t i;
285
286                 DEBUGP("ftp: string mismatch\n");
287                 for (i = 0; i < plen; i++) {
288                         DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
289                                 i, data[i], data[i],
290                                 pattern[i], pattern[i]);
291                 }
292 #endif
293                 return 0;
294         }
295
296         DEBUGP("Pattern matches!\n");
297         /* Now we've found the constant string, try to skip
298            to the 'skip' character */
299         for (i = plen; data[i] != skip; i++)
300                 if (i == dlen - 1) return -1;
301
302         /* Skip over the last character */
303         i++;
304
305         DEBUGP("Skipped up to `%c'!\n", skip);
306
307         *numoff = i;
308         *numlen = getnum(data + i, dlen - i, cmd, term);
309         if (!*numlen)
310                 return -1;
311
312         DEBUGP("Match succeeded!\n");
313         return 1;
314 }
315
316 /* Look up to see if we're just after a \n. */
317 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
318 {
319         unsigned int i;
320
321         for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
322                 if (info->seq_aft_nl[dir][i] == seq)
323                         return 1;
324         return 0;
325 }
326
327 /* We don't update if it's older than what we have. */
328 static void update_nl_seq(u32 nl_seq, struct nf_ct_ftp_master *info, int dir,
329                           struct sk_buff *skb)
330 {
331         unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
332
333         /* Look for oldest: if we find exact match, we're done. */
334         for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
335                 if (info->seq_aft_nl[dir][i] == nl_seq)
336                         return;
337
338                 if (oldest == info->seq_aft_nl_num[dir] ||
339                     before(info->seq_aft_nl[dir][i],
340                            info->seq_aft_nl[dir][oldest]))
341                         oldest = i;
342         }
343
344         if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
345                 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
346                 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
347         } else if (oldest != NUM_SEQ_TO_REMEMBER &&
348                    after(nl_seq, info->seq_aft_nl[dir][oldest])) {
349                 info->seq_aft_nl[dir][oldest] = nl_seq;
350                 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
351         }
352 }
353
354 static int help(struct sk_buff **pskb,
355                 unsigned int protoff,
356                 struct nf_conn *ct,
357                 enum ip_conntrack_info ctinfo)
358 {
359         unsigned int dataoff, datalen;
360         struct tcphdr _tcph, *th;
361         char *fb_ptr;
362         int ret;
363         u32 seq;
364         int dir = CTINFO2DIR(ctinfo);
365         unsigned int matchlen, matchoff;
366         struct nf_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
367         struct nf_conntrack_expect *exp;
368         struct nf_conntrack_man cmd = {};
369         unsigned int i;
370         int found = 0, ends_in_nl;
371         typeof(nf_nat_ftp_hook) nf_nat_ftp;
372
373         /* Until there's been traffic both ways, don't look in packets. */
374         if (ctinfo != IP_CT_ESTABLISHED
375             && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
376                 DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
377                 return NF_ACCEPT;
378         }
379
380         th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph);
381         if (th == NULL)
382                 return NF_ACCEPT;
383
384         dataoff = protoff + th->doff * 4;
385         /* No data? */
386         if (dataoff >= (*pskb)->len) {
387                 DEBUGP("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
388                         (*pskb)->len);
389                 return NF_ACCEPT;
390         }
391         datalen = (*pskb)->len - dataoff;
392
393         spin_lock_bh(&nf_ftp_lock);
394         fb_ptr = skb_header_pointer(*pskb, dataoff, datalen, ftp_buffer);
395         BUG_ON(fb_ptr == NULL);
396
397         ends_in_nl = (fb_ptr[datalen - 1] == '\n');
398         seq = ntohl(th->seq) + datalen;
399
400         /* Look up to see if we're just after a \n. */
401         if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
402                 /* Now if this ends in \n, update ftp info. */
403                 DEBUGP("nf_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
404                        ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
405                        ct_ftp_info->seq_aft_nl[dir][0],
406                        ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
407                        ct_ftp_info->seq_aft_nl[dir][1]);
408                 ret = NF_ACCEPT;
409                 goto out_update_nl;
410         }
411
412         /* Initialize IP/IPv6 addr to expected address (it's not mentioned
413            in EPSV responses) */
414         cmd.l3num = ct->tuplehash[dir].tuple.src.l3num;
415         memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
416                sizeof(cmd.u3.all));
417
418         for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
419                 found = find_pattern(fb_ptr, datalen,
420                                      search[dir][i].pattern,
421                                      search[dir][i].plen,
422                                      search[dir][i].skip,
423                                      search[dir][i].term,
424                                      &matchoff, &matchlen,
425                                      &cmd,
426                                      search[dir][i].getnum);
427                 if (found) break;
428         }
429         if (found == -1) {
430                 /* We don't usually drop packets.  After all, this is
431                    connection tracking, not packet filtering.
432                    However, it is necessary for accurate tracking in
433                    this case. */
434                 if (net_ratelimit())
435                         printk("conntrack_ftp: partial %s %u+%u\n",
436                                search[dir][i].pattern,
437                                ntohl(th->seq), datalen);
438                 ret = NF_DROP;
439                 goto out;
440         } else if (found == 0) { /* No match */
441                 ret = NF_ACCEPT;
442                 goto out_update_nl;
443         }
444
445         DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
446                (int)matchlen, fb_ptr + matchoff,
447                matchlen, ntohl(th->seq) + matchoff);
448
449         exp = nf_conntrack_expect_alloc(ct);
450         if (exp == NULL) {
451                 ret = NF_DROP;
452                 goto out;
453         }
454
455         /* We refer to the reverse direction ("!dir") tuples here,
456          * because we're expecting something in the other direction.
457          * Doesn't matter unless NAT is happening.  */
458         exp->tuple.dst.u3 = ct->tuplehash[!dir].tuple.dst.u3;
459
460         /* Update the ftp info */
461         if ((cmd.l3num == ct->tuplehash[dir].tuple.src.l3num) &&
462             memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
463                      sizeof(cmd.u3.all))) {
464                 /* Enrico Scholz's passive FTP to partially RNAT'd ftp
465                    server: it really wants us to connect to a
466                    different IP address.  Simply don't record it for
467                    NAT. */
468                 if (cmd.l3num == PF_INET) {
469                         DEBUGP("conntrack_ftp: NOT RECORDING: " NIPQUAD_FMT " != " NIPQUAD_FMT "\n",
470                                NIPQUAD(cmd.u3.ip),
471                                NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
472                 } else {
473                         DEBUGP("conntrack_ftp: NOT RECORDING: " NIP6_FMT " != " NIP6_FMT "\n",
474                                NIP6(*((struct in6_addr *)cmd.u3.ip6)),
475                                NIP6(*((struct in6_addr *)ct->tuplehash[dir]
476                                                         .tuple.src.u3.ip6)));
477                 }
478
479                 /* Thanks to Cristiano Lincoln Mattos
480                    <lincoln@cesar.org.br> for reporting this potential
481                    problem (DMZ machines opening holes to internal
482                    networks, or the packet filter itself). */
483                 if (!loose) {
484                         ret = NF_ACCEPT;
485                         goto out_put_expect;
486                 }
487                 memcpy(&exp->tuple.dst.u3, &cmd.u3.all,
488                        sizeof(exp->tuple.dst.u3));
489         }
490
491         exp->tuple.src.u3 = ct->tuplehash[!dir].tuple.src.u3;
492         exp->tuple.src.l3num = cmd.l3num;
493         exp->tuple.src.u.tcp.port = 0;
494         exp->tuple.dst.u.tcp.port = cmd.u.tcp.port;
495         exp->tuple.dst.protonum = IPPROTO_TCP;
496
497         exp->mask = (struct nf_conntrack_tuple)
498                     { .src = { .l3num = 0xFFFF,
499                                .u = { .tcp = { 0 }},
500                              },
501                       .dst = { .protonum = 0xFF,
502                                .u = { .tcp = { __constant_htons(0xFFFF) }},
503                              },
504                     };
505         if (cmd.l3num == PF_INET) {
506                 exp->mask.src.u3.ip = htonl(0xFFFFFFFF);
507                 exp->mask.dst.u3.ip = htonl(0xFFFFFFFF);
508         } else {
509                 memset(exp->mask.src.u3.ip6, 0xFF,
510                        sizeof(exp->mask.src.u3.ip6));
511                 memset(exp->mask.dst.u3.ip6, 0xFF,
512                        sizeof(exp->mask.src.u3.ip6));
513         }
514
515         exp->expectfn = NULL;
516         exp->helper = NULL;
517         exp->flags = 0;
518
519         /* Now, NAT might want to mangle the packet, and register the
520          * (possibly changed) expectation itself. */
521         nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
522         if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
523                 ret = nf_nat_ftp(pskb, ctinfo, search[dir][i].ftptype,
524                                  matchoff, matchlen, exp, &seq);
525         else {
526                 /* Can't expect this?  Best to drop packet now. */
527                 if (nf_conntrack_expect_related(exp) != 0)
528                         ret = NF_DROP;
529                 else
530                         ret = NF_ACCEPT;
531         }
532
533 out_put_expect:
534         nf_conntrack_expect_put(exp);
535
536 out_update_nl:
537         /* Now if this ends in \n, update ftp info.  Seq may have been
538          * adjusted by NAT code. */
539         if (ends_in_nl)
540                 update_nl_seq(seq, ct_ftp_info, dir, *pskb);
541  out:
542         spin_unlock_bh(&nf_ftp_lock);
543         return ret;
544 }
545
546 static struct nf_conntrack_helper ftp[MAX_PORTS][2];
547 static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")];
548
549 /* don't make this __exit, since it's called from __init ! */
550 static void nf_conntrack_ftp_fini(void)
551 {
552         int i, j;
553         for (i = 0; i < ports_c; i++) {
554                 for (j = 0; j < 2; j++) {
555                         if (ftp[i][j].me == NULL)
556                                 continue;
557
558                         DEBUGP("nf_ct_ftp: unregistering helper for pf: %d "
559                                "port: %d\n",
560                                 ftp[i][j].tuple.src.l3num, ports[i]);
561                         nf_conntrack_helper_unregister(&ftp[i][j]);
562                 }
563         }
564
565         kfree(ftp_buffer);
566 }
567
568 static int __init nf_conntrack_ftp_init(void)
569 {
570         int i, j = -1, ret = 0;
571         char *tmpname;
572
573         ftp_buffer = kmalloc(65536, GFP_KERNEL);
574         if (!ftp_buffer)
575                 return -ENOMEM;
576
577         if (ports_c == 0)
578                 ports[ports_c++] = FTP_PORT;
579
580         /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
581                  are tracked or not - YK */
582         for (i = 0; i < ports_c; i++) {
583                 ftp[i][0].tuple.src.l3num = PF_INET;
584                 ftp[i][1].tuple.src.l3num = PF_INET6;
585                 for (j = 0; j < 2; j++) {
586                         ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
587                         ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
588                         ftp[i][j].mask.src.l3num = 0xFFFF;
589                         ftp[i][j].mask.src.u.tcp.port = htons(0xFFFF);
590                         ftp[i][j].mask.dst.protonum = 0xFF;
591                         ftp[i][j].max_expected = 1;
592                         ftp[i][j].timeout = 5 * 60;     /* 5 Minutes */
593                         ftp[i][j].me = THIS_MODULE;
594                         ftp[i][j].help = help;
595                         tmpname = &ftp_names[i][j][0];
596                         if (ports[i] == FTP_PORT)
597                                 sprintf(tmpname, "ftp");
598                         else
599                                 sprintf(tmpname, "ftp-%d", ports[i]);
600                         ftp[i][j].name = tmpname;
601
602                         DEBUGP("nf_ct_ftp: registering helper for pf: %d "
603                                "port: %d\n",
604                                 ftp[i][j].tuple.src.l3num, ports[i]);
605                         ret = nf_conntrack_helper_register(&ftp[i][j]);
606                         if (ret) {
607                                 printk("nf_ct_ftp: failed to register helper "
608                                        " for pf: %d port: %d\n",
609                                         ftp[i][j].tuple.src.l3num, ports[i]);
610                                 nf_conntrack_ftp_fini();
611                                 return ret;
612                         }
613                 }
614         }
615
616         return 0;
617 }
618
619 module_init(nf_conntrack_ftp_init);
620 module_exit(nf_conntrack_ftp_fini);