SAFE public projects git trees. - safe/jmp/linux-2.6/blob - 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 EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
  53
  54 #if 0
  55 #define DEBUGP printk
  56 #else
  57 #define DEBUGP(format, args...)
  58 #endif
  59
  60 static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
  61 static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
  62 static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
  63                              char);
  64
  65 static struct ftp_search {
  66         const char *pattern;
  67         size_t plen;
  68         char skip;
  69         char term;
  70         enum nf_ct_ftp_type ftptype;
  71         int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char);
  72 } search[IP_CT_DIR_MAX][2] = {
  73         [IP_CT_DIR_ORIGINAL] = {
  74                 {
  75                         .pattern        = "PORT",
  76                         .plen           = sizeof("PORT") - 1,
  77                         .skip           = ' ',
  78                         .term           = '\r',
  79                         .ftptype        = NF_CT_FTP_PORT,
  80                         .getnum         = try_rfc959,
  81                 },
  82                 {
  83                         .pattern        = "EPRT",
  84                         .plen           = sizeof("EPRT") - 1,
  85                         .skip           = ' ',
  86                         .term           = '\r',
  87                         .ftptype        = NF_CT_FTP_EPRT,
  88                         .getnum         = try_eprt,
  89                 },
  90         },
  91         [IP_CT_DIR_REPLY] = {
  92                 {
  93                         .pattern        = "227 ",
  94                         .plen           = sizeof("227 ") - 1,
  95                         .skip           = '(',
  96                         .term           = ')',
  97                         .ftptype        = NF_CT_FTP_PASV,
  98                         .getnum         = try_rfc959,
  99                 },
 100                 {
 101                         .pattern        = "229 ",
 102                         .plen           = sizeof("229 ") - 1,
 103                         .skip           = '(',
 104                         .term           = ')',
 105                         .ftptype        = NF_CT_FTP_EPSV,
 106                         .getnum         = try_epsv_response,
 107                 },
 108         },
 109 };
 110
 111 static int
 112 get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
 113 {
 114         const char *end;
 115         int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
 116         if (ret > 0)
 117                 return (int)(end - src);
 118         return 0;
 119 }
 120
 121 static int try_number(const char *data, size_t dlen, u_int32_t array[],
 122                       int array_size, char sep, char term)
 123 {
 124         u_int32_t i, len;
 125
 126         memset(array, 0, sizeof(array[0])*array_size);
 127
 128         /* Keep data pointing at next char. */
 129         for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
 130                 if (*data >= '0' && *data <= '9') {
 131                         array[i] = array[i]*10 + *data - '0';
 132                 }
 133                 else if (*data == sep)
 134                         i++;
 135                 else {
 136                         /* Unexpected character; true if it's the
 137                            terminator and we're finished. */
 138                         if (*data == term && i == array_size - 1)
 139                                 return len;
 140
 141                         DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
 142                                len, i, *data);
 143                         return 0;
 144                 }
 145         }
 146         DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
 147
 148         return 0;
 149 }
 150
 151 /* Returns 0, or length of numbers: 192,168,1,1,5,6 */
 152 static int try_rfc959(const char *data, size_t dlen,
 153                       struct nf_conntrack_man *cmd, char term)
 154 {
 155         int length;
 156         u_int32_t array[6];
 157
 158         length = try_number(data, dlen, array, 6, ',', term);
 159         if (length == 0)
 160                 return 0;
 161
 162         cmd->u3.ip =  htonl((array[0] << 24) | (array[1] << 16) |
 163                                     (array[2] << 8) | array[3]);
 164         cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
 165         return length;
 166 }
 167
 168 /* Grab port: number up to delimiter */
 169 static int get_port(const char *data, int start, size_t dlen, char delim,
 170                     __be16 *port)
 171 {
 172         u_int16_t tmp_port = 0;
 173         int i;
 174
 175         for (i = start; i < dlen; i++) {
 176                 /* Finished? */
 177                 if (data[i] == delim) {
 178                         if (tmp_port == 0)
 179                                 break;
 180                         *port = htons(tmp_port);
 181                         DEBUGP("get_port: return %d\n", tmp_port);
 182                         return i + 1;
 183                 }
 184                 else if (data[i] >= '0' && data[i] <= '9')
 185                         tmp_port = tmp_port*10 + data[i] - '0';
 186                 else { /* Some other crap */
 187                         DEBUGP("get_port: invalid char.\n");
 188                         break;
 189                 }
 190         }
 191         return 0;
 192 }
 193
 194 /* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
 195 static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
 196                     char term)
 197 {
 198         char delim;
 199         int length;
 200
 201         /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
 202            then delimiter again. */
 203         if (dlen <= 3) {
 204                 DEBUGP("EPRT: too short\n");
 205                 return 0;
 206         }
 207         delim = data[0];
 208         if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
 209                 DEBUGP("try_eprt: invalid delimitter.\n");
 210                 return 0;
 211         }
 212
 213         if ((cmd->l3num == PF_INET && data[1] != '1') ||
 214             (cmd->l3num == PF_INET6 && data[1] != '2')) {
 215                 DEBUGP("EPRT: invalid protocol number.\n");
 216                 return 0;
 217         }
 218
 219         DEBUGP("EPRT: Got %c%c%c\n", delim, data[1], delim);
 220
 221         if (data[1] == '1') {
 222                 u_int32_t array[4];
 223
 224                 /* Now we have IP address. */
 225                 length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
 226                 if (length != 0)
 227                         cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
 228                                            | (array[2] << 8) | array[3]);
 229         } else {
 230                 /* Now we have IPv6 address. */
 231                 length = get_ipv6_addr(data + 3, dlen - 3,
 232                                        (struct in6_addr *)cmd->u3.ip6, delim);
 233         }
 234
 235         if (length == 0)
 236                 return 0;
 237         DEBUGP("EPRT: Got IP address!\n");
 238         /* Start offset includes initial "|1|", and trailing delimiter */
 239         return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
 240 }
 241
 242 /* Returns 0, or length of numbers: |||6446| */
 243 static int try_epsv_response(const char *data, size_t dlen,
 244                              struct nf_conntrack_man *cmd, char term)
 245 {
 246         char delim;
 247
 248         /* Three delimiters. */
 249         if (dlen <= 3) return 0;
 250         delim = data[0];
 251         if (isdigit(delim) || delim < 33 || delim > 126
 252             || data[1] != delim || data[2] != delim)
 253                 return 0;
 254
 255         return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
 256 }
 257
 258 /* Return 1 for match, 0 for accept, -1 for partial. */
 259 static int find_pattern(const char *data, size_t dlen,
 260                         const char *pattern, size_t plen,
 261                         char skip, char term,
 262                         unsigned int *numoff,
 263                         unsigned int *numlen,
 264                         struct nf_conntrack_man *cmd,
 265                         int (*getnum)(const char *, size_t,
 266                                       struct nf_conntrack_man *, char))
 267 {
 268         size_t i;
 269
 270         DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
 271         if (dlen == 0)
 272                 return 0;
 273
 274         if (dlen <= plen) {
 275                 /* Short packet: try for partial? */
 276                 if (strnicmp(data, pattern, dlen) == 0)
 277                         return -1;
 278                 else return 0;
 279         }
 280
 281         if (strnicmp(data, pattern, plen) != 0) {
 282 #if 0
 283                 size_t i;
 284
 285                 DEBUGP("ftp: string mismatch\n");
 286                 for (i = 0; i < plen; i++) {
 287                         DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
 288                                 i, data[i], data[i],
 289                                 pattern[i], pattern[i]);
 290                 }
 291 #endif
 292                 return 0;
 293         }
 294
 295         DEBUGP("Pattern matches!\n");
 296         /* Now we've found the constant string, try to skip
 297            to the 'skip' character */
 298         for (i = plen; data[i] != skip; i++)
 299                 if (i == dlen - 1) return -1;
 300
 301         /* Skip over the last character */
 302         i++;
 303
 304         DEBUGP("Skipped up to `%c'!\n", skip);
 305
 306         *numoff = i;
 307         *numlen = getnum(data + i, dlen - i, cmd, term);
 308         if (!*numlen)
 309                 return -1;
 310
 311         DEBUGP("Match succeeded!\n");
 312         return 1;
 313 }
 314
 315 /* Look up to see if we're just after a \n. */
 316 static int find_nl_seq(u32 seq, const struct nf_ct_ftp_master *info, int dir)
 317 {
 318         unsigned int i;
 319
 320         for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
 321                 if (info->seq_aft_nl[dir][i] == seq)
 322                         return 1;
 323         return 0;
 324 }
 325
 326 /* We don't update if it's older than what we have. */
 327 static void update_nl_seq(u32 nl_seq, struct nf_ct_ftp_master *info, int dir,
 328                           struct sk_buff *skb)
 329 {
 330         unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
 331
 332         /* Look for oldest: if we find exact match, we're done. */
 333         for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
 334                 if (info->seq_aft_nl[dir][i] == nl_seq)
 335                         return;
 336
 337                 if (oldest == info->seq_aft_nl_num[dir] ||
 338                     before(info->seq_aft_nl[dir][i],
 339                            info->seq_aft_nl[dir][oldest]))
 340                         oldest = i;
 341         }
 342
 343         if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
 344                 info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
 345                 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
 346         } else if (oldest != NUM_SEQ_TO_REMEMBER &&
 347                    after(nl_seq, info->seq_aft_nl[dir][oldest])) {
 348                 info->seq_aft_nl[dir][oldest] = nl_seq;
 349                 nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
 350         }
 351 }
 352
 353 static int help(struct sk_buff **pskb,
 354                 unsigned int protoff,
 355                 struct nf_conn *ct,
 356                 enum ip_conntrack_info ctinfo)
 357 {
 358         unsigned int dataoff, datalen;
 359         struct tcphdr _tcph, *th;
 360         char *fb_ptr;
 361         int ret;
 362         u32 seq;
 363         int dir = CTINFO2DIR(ctinfo);
 364         unsigned int matchlen, matchoff;
 365         struct nf_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
 366         struct nf_conntrack_expect *exp;
 367         union nf_conntrack_address *daddr;
 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_ct_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         daddr = &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                 daddr = &cmd.u3;
 488         }
 489
 490         nf_ct_expect_init(exp, cmd.l3num,
 491                           &ct->tuplehash[!dir].tuple.src.u3, daddr,
 492                           IPPROTO_TCP, NULL, &cmd.u.tcp.port);
 493
 494         /* Now, NAT might want to mangle the packet, and register the
 495          * (possibly changed) expectation itself. */
 496         nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
 497         if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
 498                 ret = nf_nat_ftp(pskb, ctinfo, search[dir][i].ftptype,
 499                                  matchoff, matchlen, exp);
 500         else {
 501                 /* Can't expect this?  Best to drop packet now. */
 502                 if (nf_ct_expect_related(exp) != 0)
 503                         ret = NF_DROP;
 504                 else
 505                         ret = NF_ACCEPT;
 506         }
 507
 508 out_put_expect:
 509         nf_ct_expect_put(exp);
 510
 511 out_update_nl:
 512         /* Now if this ends in \n, update ftp info.  Seq may have been
 513          * adjusted by NAT code. */
 514         if (ends_in_nl)
 515                 update_nl_seq(seq, ct_ftp_info, dir, *pskb);
 516  out:
 517         spin_unlock_bh(&nf_ftp_lock);
 518         return ret;
 519 }
 520
 521 static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
 522 static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")] __read_mostly;
 523
 524 /* don't make this __exit, since it's called from __init ! */
 525 static void nf_conntrack_ftp_fini(void)
 526 {
 527         int i, j;
 528         for (i = 0; i < ports_c; i++) {
 529                 for (j = 0; j < 2; j++) {
 530                         if (ftp[i][j].me == NULL)
 531                                 continue;
 532
 533                         DEBUGP("nf_ct_ftp: unregistering helper for pf: %d "
 534                                "port: %d\n",
 535                                 ftp[i][j].tuple.src.l3num, ports[i]);
 536                         nf_conntrack_helper_unregister(&ftp[i][j]);
 537                 }
 538         }
 539
 540         kfree(ftp_buffer);
 541 }
 542
 543 static int __init nf_conntrack_ftp_init(void)
 544 {
 545         int i, j = -1, ret = 0;
 546         char *tmpname;
 547
 548         ftp_buffer = kmalloc(65536, GFP_KERNEL);
 549         if (!ftp_buffer)
 550                 return -ENOMEM;
 551
 552         if (ports_c == 0)
 553                 ports[ports_c++] = FTP_PORT;
 554
 555         /* FIXME should be configurable whether IPv4 and IPv6 FTP connections
 556                  are tracked or not - YK */
 557         for (i = 0; i < ports_c; i++) {
 558                 ftp[i][0].tuple.src.l3num = PF_INET;
 559                 ftp[i][1].tuple.src.l3num = PF_INET6;
 560                 for (j = 0; j < 2; j++) {
 561                         ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
 562                         ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
 563                         ftp[i][j].max_expected = 1;
 564                         ftp[i][j].timeout = 5 * 60;     /* 5 Minutes */
 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                         DEBUGP("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);