1 /* 2 * Transparent proxy support for Linux/iptables 3 * 4 * Copyright (C) 2007-2008 BalaBit IT Ltd. 5 * Author: Krisztian Kovacs 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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 13 #include <linux/module.h> 14 #include <linux/skbuff.h> 15 #include <linux/netfilter/x_tables.h> 16 #include <linux/netfilter_ipv4/ip_tables.h> 17 #include <net/tcp.h> 18 #include <net/udp.h> 19 #include <net/icmp.h> 20 #include <net/sock.h> 21 #include <net/inet_sock.h> 22 #include <net/netfilter/ipv4/nf_defrag_ipv4.h> 23 24 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) 25 #define XT_SOCKET_HAVE_IPV6 1 26 #include <linux/netfilter_ipv6/ip6_tables.h> 27 #include <net/inet6_hashtables.h> 28 #include <net/netfilter/ipv6/nf_defrag_ipv6.h> 29 #endif 30 31 #include <linux/netfilter/xt_socket.h> 32 33 #if IS_ENABLED(CONFIG_NF_CONNTRACK) 34 #define XT_SOCKET_HAVE_CONNTRACK 1 35 #include <net/netfilter/nf_conntrack.h> 36 #endif 37 38 static int 39 extract_icmp4_fields(const struct sk_buff *skb, 40 u8 *protocol, 41 __be32 *raddr, 42 __be32 *laddr, 43 __be16 *rport, 44 __be16 *lport) 45 { 46 unsigned int outside_hdrlen = ip_hdrlen(skb); 47 struct iphdr *inside_iph, _inside_iph; 48 struct icmphdr *icmph, _icmph; 49 __be16 *ports, _ports[2]; 50 51 icmph = skb_header_pointer(skb, outside_hdrlen, 52 sizeof(_icmph), &_icmph); 53 if (icmph == NULL) 54 return 1; 55 56 switch (icmph->type) { 57 case ICMP_DEST_UNREACH: 58 case ICMP_SOURCE_QUENCH: 59 case ICMP_REDIRECT: 60 case ICMP_TIME_EXCEEDED: 61 case ICMP_PARAMETERPROB: 62 break; 63 default: 64 return 1; 65 } 66 67 inside_iph = skb_header_pointer(skb, outside_hdrlen + 68 sizeof(struct icmphdr), 69 sizeof(_inside_iph), &_inside_iph); 70 if (inside_iph == NULL) 71 return 1; 72 73 if (inside_iph->protocol != IPPROTO_TCP && 74 inside_iph->protocol != IPPROTO_UDP) 75 return 1; 76 77 ports = skb_header_pointer(skb, outside_hdrlen + 78 sizeof(struct icmphdr) + 79 (inside_iph->ihl << 2), 80 sizeof(_ports), &_ports); 81 if (ports == NULL) 82 return 1; 83 84 /* the inside IP packet is the one quoted from our side, thus 85 * its saddr is the local address */ 86 *protocol = inside_iph->protocol; 87 *laddr = inside_iph->saddr; 88 *lport = ports[0]; 89 *raddr = inside_iph->daddr; 90 *rport = ports[1]; 91 92 return 0; 93 } 94 95 /* "socket" match based redirection (no specific rule) 96 * =================================================== 97 * 98 * There are connections with dynamic endpoints (e.g. FTP data 99 * connection) that the user is unable to add explicit rules 100 * for. These are taken care of by a generic "socket" rule. It is 101 * assumed that the proxy application is trusted to open such 102 * connections without explicit iptables rule (except of course the 103 * generic 'socket' rule). In this case the following sockets are 104 * matched in preference order: 105 * 106 * - match: if there's a fully established connection matching the 107 * _packet_ tuple 108 * 109 * - match: if there's a non-zero bound listener (possibly with a 110 * non-local address) We don't accept zero-bound listeners, since 111 * then local services could intercept traffic going through the 112 * box. 113 */ 114 static struct sock * 115 xt_socket_get_sock_v4(struct net *net, struct sk_buff *skb, const int doff, 116 const u8 protocol, 117 const __be32 saddr, const __be32 daddr, 118 const __be16 sport, const __be16 dport, 119 const struct net_device *in) 120 { 121 switch (protocol) { 122 case IPPROTO_TCP: 123 return inet_lookup(net, &tcp_hashinfo, skb, doff, 124 saddr, sport, daddr, dport, 125 in->ifindex); 126 case IPPROTO_UDP: 127 return udp4_lib_lookup(net, saddr, sport, daddr, dport, 128 in->ifindex); 129 } 130 return NULL; 131 } 132 133 static bool xt_socket_sk_is_transparent(struct sock *sk) 134 { 135 switch (sk->sk_state) { 136 case TCP_TIME_WAIT: 137 return inet_twsk(sk)->tw_transparent; 138 139 case TCP_NEW_SYN_RECV: 140 return inet_rsk(inet_reqsk(sk))->no_srccheck; 141 142 default: 143 return inet_sk(sk)->transparent; 144 } 145 } 146 147 static struct sock *xt_socket_lookup_slow_v4(struct net *net, 148 const struct sk_buff *skb, 149 const struct net_device *indev) 150 { 151 const struct iphdr *iph = ip_hdr(skb); 152 struct sk_buff *data_skb = NULL; 153 int doff = 0; 154 __be32 uninitialized_var(daddr), uninitialized_var(saddr); 155 __be16 uninitialized_var(dport), uninitialized_var(sport); 156 u8 uninitialized_var(protocol); 157 #ifdef XT_SOCKET_HAVE_CONNTRACK 158 struct nf_conn const *ct; 159 enum ip_conntrack_info ctinfo; 160 #endif 161 162 if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) { 163 struct udphdr _hdr, *hp; 164 165 hp = skb_header_pointer(skb, ip_hdrlen(skb), 166 sizeof(_hdr), &_hdr); 167 if (hp == NULL) 168 return NULL; 169 170 protocol = iph->protocol; 171 saddr = iph->saddr; 172 sport = hp->source; 173 daddr = iph->daddr; 174 dport = hp->dest; 175 data_skb = (struct sk_buff *)skb; 176 doff = iph->protocol == IPPROTO_TCP ? 177 ip_hdrlen(skb) + __tcp_hdrlen((struct tcphdr *)hp) : 178 ip_hdrlen(skb) + sizeof(*hp); 179 180 } else if (iph->protocol == IPPROTO_ICMP) { 181 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr, 182 &sport, &dport)) 183 return NULL; 184 } else { 185 return NULL; 186 } 187 188 #ifdef XT_SOCKET_HAVE_CONNTRACK 189 /* Do the lookup with the original socket address in 190 * case this is a reply packet of an established 191 * SNAT-ted connection. 192 */ 193 ct = nf_ct_get(skb, &ctinfo); 194 if (ct && !nf_ct_is_untracked(ct) && 195 ((iph->protocol != IPPROTO_ICMP && 196 ctinfo == IP_CT_ESTABLISHED_REPLY) || 197 (iph->protocol == IPPROTO_ICMP && 198 ctinfo == IP_CT_RELATED_REPLY)) && 199 (ct->status & IPS_SRC_NAT_DONE)) { 200 201 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip; 202 dport = (iph->protocol == IPPROTO_TCP) ? 203 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port : 204 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port; 205 } 206 #endif 207 208 return xt_socket_get_sock_v4(net, data_skb, doff, protocol, saddr, 209 daddr, sport, dport, indev); 210 } 211 212 static bool 213 socket_match(const struct sk_buff *skb, struct xt_action_param *par, 214 const struct xt_socket_mtinfo1 *info) 215 { 216 struct sk_buff *pskb = (struct sk_buff *)skb; 217 struct sock *sk = skb->sk; 218 219 if (!sk) 220 sk = xt_socket_lookup_slow_v4(par->net, skb, par->in); 221 if (sk) { 222 bool wildcard; 223 bool transparent = true; 224 225 /* Ignore sockets listening on INADDR_ANY, 226 * unless XT_SOCKET_NOWILDCARD is set 227 */ 228 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 229 sk_fullsock(sk) && 230 inet_sk(sk)->inet_rcv_saddr == 0); 231 232 /* Ignore non-transparent sockets, 233 * if XT_SOCKET_TRANSPARENT is used 234 */ 235 if (info->flags & XT_SOCKET_TRANSPARENT) 236 transparent = xt_socket_sk_is_transparent(sk); 237 238 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard && 239 transparent) 240 pskb->mark = sk->sk_mark; 241 242 if (sk != skb->sk) 243 sock_gen_put(sk); 244 245 if (wildcard || !transparent) 246 sk = NULL; 247 } 248 249 return sk != NULL; 250 } 251 252 static bool 253 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par) 254 { 255 static struct xt_socket_mtinfo1 xt_info_v0 = { 256 .flags = 0, 257 }; 258 259 return socket_match(skb, par, &xt_info_v0); 260 } 261 262 static bool 263 socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par) 264 { 265 return socket_match(skb, par, par->matchinfo); 266 } 267 268 #ifdef XT_SOCKET_HAVE_IPV6 269 270 static int 271 extract_icmp6_fields(const struct sk_buff *skb, 272 unsigned int outside_hdrlen, 273 int *protocol, 274 const struct in6_addr **raddr, 275 const struct in6_addr **laddr, 276 __be16 *rport, 277 __be16 *lport, 278 struct ipv6hdr *ipv6_var) 279 { 280 const struct ipv6hdr *inside_iph; 281 struct icmp6hdr *icmph, _icmph; 282 __be16 *ports, _ports[2]; 283 u8 inside_nexthdr; 284 __be16 inside_fragoff; 285 int inside_hdrlen; 286 287 icmph = skb_header_pointer(skb, outside_hdrlen, 288 sizeof(_icmph), &_icmph); 289 if (icmph == NULL) 290 return 1; 291 292 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK) 293 return 1; 294 295 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), 296 sizeof(*ipv6_var), ipv6_var); 297 if (inside_iph == NULL) 298 return 1; 299 inside_nexthdr = inside_iph->nexthdr; 300 301 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + 302 sizeof(*ipv6_var), 303 &inside_nexthdr, &inside_fragoff); 304 if (inside_hdrlen < 0) 305 return 1; /* hjm: Packet has no/incomplete transport layer headers. */ 306 307 if (inside_nexthdr != IPPROTO_TCP && 308 inside_nexthdr != IPPROTO_UDP) 309 return 1; 310 311 ports = skb_header_pointer(skb, inside_hdrlen, 312 sizeof(_ports), &_ports); 313 if (ports == NULL) 314 return 1; 315 316 /* the inside IP packet is the one quoted from our side, thus 317 * its saddr is the local address */ 318 *protocol = inside_nexthdr; 319 *laddr = &inside_iph->saddr; 320 *lport = ports[0]; 321 *raddr = &inside_iph->daddr; 322 *rport = ports[1]; 323 324 return 0; 325 } 326 327 static struct sock * 328 xt_socket_get_sock_v6(struct net *net, struct sk_buff *skb, int doff, 329 const u8 protocol, 330 const struct in6_addr *saddr, const struct in6_addr *daddr, 331 const __be16 sport, const __be16 dport, 332 const struct net_device *in) 333 { 334 switch (protocol) { 335 case IPPROTO_TCP: 336 return inet6_lookup(net, &tcp_hashinfo, skb, doff, 337 saddr, sport, daddr, dport, 338 in->ifindex); 339 case IPPROTO_UDP: 340 return udp6_lib_lookup(net, saddr, sport, daddr, dport, 341 in->ifindex); 342 } 343 344 return NULL; 345 } 346 347 static struct sock *xt_socket_lookup_slow_v6(struct net *net, 348 const struct sk_buff *skb, 349 const struct net_device *indev) 350 { 351 __be16 uninitialized_var(dport), uninitialized_var(sport); 352 const struct in6_addr *daddr = NULL, *saddr = NULL; 353 struct ipv6hdr *iph = ipv6_hdr(skb); 354 struct sk_buff *data_skb = NULL; 355 int doff = 0; 356 int thoff = 0, tproto; 357 358 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); 359 if (tproto < 0) { 360 pr_debug("unable to find transport header in IPv6 packet, dropping\n"); 361 return NULL; 362 } 363 364 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) { 365 struct udphdr _hdr, *hp; 366 367 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); 368 if (hp == NULL) 369 return NULL; 370 371 saddr = &iph->saddr; 372 sport = hp->source; 373 daddr = &iph->daddr; 374 dport = hp->dest; 375 data_skb = (struct sk_buff *)skb; 376 doff = tproto == IPPROTO_TCP ? 377 thoff + __tcp_hdrlen((struct tcphdr *)hp) : 378 thoff + sizeof(*hp); 379 380 } else if (tproto == IPPROTO_ICMPV6) { 381 struct ipv6hdr ipv6_var; 382 383 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr, 384 &sport, &dport, &ipv6_var)) 385 return NULL; 386 } else { 387 return NULL; 388 } 389 390 return xt_socket_get_sock_v6(net, data_skb, doff, tproto, saddr, daddr, 391 sport, dport, indev); 392 } 393 394 static bool 395 socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par) 396 { 397 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 398 struct sk_buff *pskb = (struct sk_buff *)skb; 399 struct sock *sk = skb->sk; 400 401 if (!sk) 402 sk = xt_socket_lookup_slow_v6(par->net, skb, par->in); 403 if (sk) { 404 bool wildcard; 405 bool transparent = true; 406 407 /* Ignore sockets listening on INADDR_ANY 408 * unless XT_SOCKET_NOWILDCARD is set 409 */ 410 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 411 sk_fullsock(sk) && 412 ipv6_addr_any(&sk->sk_v6_rcv_saddr)); 413 414 /* Ignore non-transparent sockets, 415 * if XT_SOCKET_TRANSPARENT is used 416 */ 417 if (info->flags & XT_SOCKET_TRANSPARENT) 418 transparent = xt_socket_sk_is_transparent(sk); 419 420 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard && 421 transparent) 422 pskb->mark = sk->sk_mark; 423 424 if (sk != skb->sk) 425 sock_gen_put(sk); 426 427 if (wildcard || !transparent) 428 sk = NULL; 429 } 430 431 return sk != NULL; 432 } 433 #endif 434 435 static int socket_mt_v1_check(const struct xt_mtchk_param *par) 436 { 437 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 438 439 if (info->flags & ~XT_SOCKET_FLAGS_V1) { 440 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1); 441 return -EINVAL; 442 } 443 return 0; 444 } 445 446 static int socket_mt_v2_check(const struct xt_mtchk_param *par) 447 { 448 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo; 449 450 if (info->flags & ~XT_SOCKET_FLAGS_V2) { 451 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2); 452 return -EINVAL; 453 } 454 return 0; 455 } 456 457 static int socket_mt_v3_check(const struct xt_mtchk_param *par) 458 { 459 const struct xt_socket_mtinfo3 *info = 460 (struct xt_socket_mtinfo3 *)par->matchinfo; 461 462 if (info->flags & ~XT_SOCKET_FLAGS_V3) { 463 pr_info("unknown flags 0x%x\n", 464 info->flags & ~XT_SOCKET_FLAGS_V3); 465 return -EINVAL; 466 } 467 return 0; 468 } 469 470 static struct xt_match socket_mt_reg[] __read_mostly = { 471 { 472 .name = "socket", 473 .revision = 0, 474 .family = NFPROTO_IPV4, 475 .match = socket_mt4_v0, 476 .hooks = (1 << NF_INET_PRE_ROUTING) | 477 (1 << NF_INET_LOCAL_IN), 478 .me = THIS_MODULE, 479 }, 480 { 481 .name = "socket", 482 .revision = 1, 483 .family = NFPROTO_IPV4, 484 .match = socket_mt4_v1_v2_v3, 485 .checkentry = socket_mt_v1_check, 486 .matchsize = sizeof(struct xt_socket_mtinfo1), 487 .hooks = (1 << NF_INET_PRE_ROUTING) | 488 (1 << NF_INET_LOCAL_IN), 489 .me = THIS_MODULE, 490 }, 491 #ifdef XT_SOCKET_HAVE_IPV6 492 { 493 .name = "socket", 494 .revision = 1, 495 .family = NFPROTO_IPV6, 496 .match = socket_mt6_v1_v2_v3, 497 .checkentry = socket_mt_v1_check, 498 .matchsize = sizeof(struct xt_socket_mtinfo1), 499 .hooks = (1 << NF_INET_PRE_ROUTING) | 500 (1 << NF_INET_LOCAL_IN), 501 .me = THIS_MODULE, 502 }, 503 #endif 504 { 505 .name = "socket", 506 .revision = 2, 507 .family = NFPROTO_IPV4, 508 .match = socket_mt4_v1_v2_v3, 509 .checkentry = socket_mt_v2_check, 510 .matchsize = sizeof(struct xt_socket_mtinfo1), 511 .hooks = (1 << NF_INET_PRE_ROUTING) | 512 (1 << NF_INET_LOCAL_IN), 513 .me = THIS_MODULE, 514 }, 515 #ifdef XT_SOCKET_HAVE_IPV6 516 { 517 .name = "socket", 518 .revision = 2, 519 .family = NFPROTO_IPV6, 520 .match = socket_mt6_v1_v2_v3, 521 .checkentry = socket_mt_v2_check, 522 .matchsize = sizeof(struct xt_socket_mtinfo1), 523 .hooks = (1 << NF_INET_PRE_ROUTING) | 524 (1 << NF_INET_LOCAL_IN), 525 .me = THIS_MODULE, 526 }, 527 #endif 528 { 529 .name = "socket", 530 .revision = 3, 531 .family = NFPROTO_IPV4, 532 .match = socket_mt4_v1_v2_v3, 533 .checkentry = socket_mt_v3_check, 534 .matchsize = sizeof(struct xt_socket_mtinfo1), 535 .hooks = (1 << NF_INET_PRE_ROUTING) | 536 (1 << NF_INET_LOCAL_IN), 537 .me = THIS_MODULE, 538 }, 539 #ifdef XT_SOCKET_HAVE_IPV6 540 { 541 .name = "socket", 542 .revision = 3, 543 .family = NFPROTO_IPV6, 544 .match = socket_mt6_v1_v2_v3, 545 .checkentry = socket_mt_v3_check, 546 .matchsize = sizeof(struct xt_socket_mtinfo1), 547 .hooks = (1 << NF_INET_PRE_ROUTING) | 548 (1 << NF_INET_LOCAL_IN), 549 .me = THIS_MODULE, 550 }, 551 #endif 552 }; 553 554 static int __init socket_mt_init(void) 555 { 556 nf_defrag_ipv4_enable(); 557 #ifdef XT_SOCKET_HAVE_IPV6 558 nf_defrag_ipv6_enable(); 559 #endif 560 561 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 562 } 563 564 static void __exit socket_mt_exit(void) 565 { 566 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 567 } 568 569 module_init(socket_mt_init); 570 module_exit(socket_mt_exit); 571 572 MODULE_LICENSE("GPL"); 573 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler"); 574 MODULE_DESCRIPTION("x_tables socket match module"); 575 MODULE_ALIAS("ipt_socket"); 576 MODULE_ALIAS("ip6t_socket"); 577