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, const u8 protocol, 116 const __be32 saddr, const __be32 daddr, 117 const __be16 sport, const __be16 dport, 118 const struct net_device *in) 119 { 120 switch (protocol) { 121 case IPPROTO_TCP: 122 return __inet_lookup(net, &tcp_hashinfo, 123 saddr, sport, daddr, dport, 124 in->ifindex); 125 case IPPROTO_UDP: 126 return udp4_lib_lookup(net, saddr, sport, daddr, dport, 127 in->ifindex); 128 } 129 return NULL; 130 } 131 132 static bool xt_socket_sk_is_transparent(struct sock *sk) 133 { 134 switch (sk->sk_state) { 135 case TCP_TIME_WAIT: 136 return inet_twsk(sk)->tw_transparent; 137 138 case TCP_NEW_SYN_RECV: 139 return inet_rsk(inet_reqsk(sk))->no_srccheck; 140 141 default: 142 return inet_sk(sk)->transparent; 143 } 144 } 145 146 static struct sock *xt_socket_lookup_slow_v4(const struct sk_buff *skb, 147 const struct net_device *indev) 148 { 149 const struct iphdr *iph = ip_hdr(skb); 150 __be32 uninitialized_var(daddr), uninitialized_var(saddr); 151 __be16 uninitialized_var(dport), uninitialized_var(sport); 152 u8 uninitialized_var(protocol); 153 #ifdef XT_SOCKET_HAVE_CONNTRACK 154 struct nf_conn const *ct; 155 enum ip_conntrack_info ctinfo; 156 #endif 157 158 if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) { 159 struct udphdr _hdr, *hp; 160 161 hp = skb_header_pointer(skb, ip_hdrlen(skb), 162 sizeof(_hdr), &_hdr); 163 if (hp == NULL) 164 return NULL; 165 166 protocol = iph->protocol; 167 saddr = iph->saddr; 168 sport = hp->source; 169 daddr = iph->daddr; 170 dport = hp->dest; 171 172 } else if (iph->protocol == IPPROTO_ICMP) { 173 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr, 174 &sport, &dport)) 175 return NULL; 176 } else { 177 return NULL; 178 } 179 180 #ifdef XT_SOCKET_HAVE_CONNTRACK 181 /* Do the lookup with the original socket address in 182 * case this is a reply packet of an established 183 * SNAT-ted connection. 184 */ 185 ct = nf_ct_get(skb, &ctinfo); 186 if (ct && !nf_ct_is_untracked(ct) && 187 ((iph->protocol != IPPROTO_ICMP && 188 ctinfo == IP_CT_ESTABLISHED_REPLY) || 189 (iph->protocol == IPPROTO_ICMP && 190 ctinfo == IP_CT_RELATED_REPLY)) && 191 (ct->status & IPS_SRC_NAT_DONE)) { 192 193 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip; 194 dport = (iph->protocol == IPPROTO_TCP) ? 195 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port : 196 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port; 197 } 198 #endif 199 200 return xt_socket_get_sock_v4(dev_net(skb->dev), protocol, saddr, daddr, 201 sport, dport, indev); 202 } 203 204 static bool 205 socket_match(const struct sk_buff *skb, struct xt_action_param *par, 206 const struct xt_socket_mtinfo1 *info) 207 { 208 struct sk_buff *pskb = (struct sk_buff *)skb; 209 struct sock *sk = skb->sk; 210 211 if (!sk) 212 sk = xt_socket_lookup_slow_v4(skb, par->in); 213 if (sk) { 214 bool wildcard; 215 bool transparent = true; 216 217 /* Ignore sockets listening on INADDR_ANY, 218 * unless XT_SOCKET_NOWILDCARD is set 219 */ 220 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 221 sk_fullsock(sk) && 222 inet_sk(sk)->inet_rcv_saddr == 0); 223 224 /* Ignore non-transparent sockets, 225 * if XT_SOCKET_TRANSPARENT is used 226 */ 227 if (info->flags & XT_SOCKET_TRANSPARENT) 228 transparent = xt_socket_sk_is_transparent(sk); 229 230 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard && 231 transparent) 232 pskb->mark = sk->sk_mark; 233 234 if (sk != skb->sk) 235 sock_gen_put(sk); 236 237 if (wildcard || !transparent) 238 sk = NULL; 239 } 240 241 return sk != NULL; 242 } 243 244 static bool 245 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par) 246 { 247 static struct xt_socket_mtinfo1 xt_info_v0 = { 248 .flags = 0, 249 }; 250 251 return socket_match(skb, par, &xt_info_v0); 252 } 253 254 static bool 255 socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par) 256 { 257 return socket_match(skb, par, par->matchinfo); 258 } 259 260 #ifdef XT_SOCKET_HAVE_IPV6 261 262 static int 263 extract_icmp6_fields(const struct sk_buff *skb, 264 unsigned int outside_hdrlen, 265 int *protocol, 266 const struct in6_addr **raddr, 267 const struct in6_addr **laddr, 268 __be16 *rport, 269 __be16 *lport, 270 struct ipv6hdr *ipv6_var) 271 { 272 const struct ipv6hdr *inside_iph; 273 struct icmp6hdr *icmph, _icmph; 274 __be16 *ports, _ports[2]; 275 u8 inside_nexthdr; 276 __be16 inside_fragoff; 277 int inside_hdrlen; 278 279 icmph = skb_header_pointer(skb, outside_hdrlen, 280 sizeof(_icmph), &_icmph); 281 if (icmph == NULL) 282 return 1; 283 284 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK) 285 return 1; 286 287 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), 288 sizeof(*ipv6_var), ipv6_var); 289 if (inside_iph == NULL) 290 return 1; 291 inside_nexthdr = inside_iph->nexthdr; 292 293 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + 294 sizeof(*ipv6_var), 295 &inside_nexthdr, &inside_fragoff); 296 if (inside_hdrlen < 0) 297 return 1; /* hjm: Packet has no/incomplete transport layer headers. */ 298 299 if (inside_nexthdr != IPPROTO_TCP && 300 inside_nexthdr != IPPROTO_UDP) 301 return 1; 302 303 ports = skb_header_pointer(skb, inside_hdrlen, 304 sizeof(_ports), &_ports); 305 if (ports == NULL) 306 return 1; 307 308 /* the inside IP packet is the one quoted from our side, thus 309 * its saddr is the local address */ 310 *protocol = inside_nexthdr; 311 *laddr = &inside_iph->saddr; 312 *lport = ports[0]; 313 *raddr = &inside_iph->daddr; 314 *rport = ports[1]; 315 316 return 0; 317 } 318 319 static struct sock * 320 xt_socket_get_sock_v6(struct net *net, const u8 protocol, 321 const struct in6_addr *saddr, const struct in6_addr *daddr, 322 const __be16 sport, const __be16 dport, 323 const struct net_device *in) 324 { 325 switch (protocol) { 326 case IPPROTO_TCP: 327 return inet6_lookup(net, &tcp_hashinfo, 328 saddr, sport, daddr, dport, 329 in->ifindex); 330 case IPPROTO_UDP: 331 return udp6_lib_lookup(net, saddr, sport, daddr, dport, 332 in->ifindex); 333 } 334 335 return NULL; 336 } 337 338 static struct sock *xt_socket_lookup_slow_v6(const struct sk_buff *skb, 339 const struct net_device *indev) 340 { 341 __be16 uninitialized_var(dport), uninitialized_var(sport); 342 const struct in6_addr *daddr = NULL, *saddr = NULL; 343 struct ipv6hdr *iph = ipv6_hdr(skb); 344 int thoff = 0, tproto; 345 346 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); 347 if (tproto < 0) { 348 pr_debug("unable to find transport header in IPv6 packet, dropping\n"); 349 return NULL; 350 } 351 352 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) { 353 struct udphdr _hdr, *hp; 354 355 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); 356 if (hp == NULL) 357 return NULL; 358 359 saddr = &iph->saddr; 360 sport = hp->source; 361 daddr = &iph->daddr; 362 dport = hp->dest; 363 364 } else if (tproto == IPPROTO_ICMPV6) { 365 struct ipv6hdr ipv6_var; 366 367 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr, 368 &sport, &dport, &ipv6_var)) 369 return NULL; 370 } else { 371 return NULL; 372 } 373 374 return xt_socket_get_sock_v6(dev_net(skb->dev), tproto, saddr, daddr, 375 sport, dport, indev); 376 } 377 378 static bool 379 socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par) 380 { 381 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 382 struct sk_buff *pskb = (struct sk_buff *)skb; 383 struct sock *sk = skb->sk; 384 385 if (!sk) 386 sk = xt_socket_lookup_slow_v6(skb, par->in); 387 if (sk) { 388 bool wildcard; 389 bool transparent = true; 390 391 /* Ignore sockets listening on INADDR_ANY 392 * unless XT_SOCKET_NOWILDCARD is set 393 */ 394 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 395 sk_fullsock(sk) && 396 ipv6_addr_any(&sk->sk_v6_rcv_saddr)); 397 398 /* Ignore non-transparent sockets, 399 * if XT_SOCKET_TRANSPARENT is used 400 */ 401 if (info->flags & XT_SOCKET_TRANSPARENT) 402 transparent = xt_socket_sk_is_transparent(sk); 403 404 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard && 405 transparent) 406 pskb->mark = sk->sk_mark; 407 408 if (sk != skb->sk) 409 sock_gen_put(sk); 410 411 if (wildcard || !transparent) 412 sk = NULL; 413 } 414 415 return sk != NULL; 416 } 417 #endif 418 419 static int socket_mt_v1_check(const struct xt_mtchk_param *par) 420 { 421 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 422 423 if (info->flags & ~XT_SOCKET_FLAGS_V1) { 424 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1); 425 return -EINVAL; 426 } 427 return 0; 428 } 429 430 static int socket_mt_v2_check(const struct xt_mtchk_param *par) 431 { 432 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo; 433 434 if (info->flags & ~XT_SOCKET_FLAGS_V2) { 435 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2); 436 return -EINVAL; 437 } 438 return 0; 439 } 440 441 static int socket_mt_v3_check(const struct xt_mtchk_param *par) 442 { 443 const struct xt_socket_mtinfo3 *info = 444 (struct xt_socket_mtinfo3 *)par->matchinfo; 445 446 if (info->flags & ~XT_SOCKET_FLAGS_V3) { 447 pr_info("unknown flags 0x%x\n", 448 info->flags & ~XT_SOCKET_FLAGS_V3); 449 return -EINVAL; 450 } 451 return 0; 452 } 453 454 static struct xt_match socket_mt_reg[] __read_mostly = { 455 { 456 .name = "socket", 457 .revision = 0, 458 .family = NFPROTO_IPV4, 459 .match = socket_mt4_v0, 460 .hooks = (1 << NF_INET_PRE_ROUTING) | 461 (1 << NF_INET_LOCAL_IN), 462 .me = THIS_MODULE, 463 }, 464 { 465 .name = "socket", 466 .revision = 1, 467 .family = NFPROTO_IPV4, 468 .match = socket_mt4_v1_v2_v3, 469 .checkentry = socket_mt_v1_check, 470 .matchsize = sizeof(struct xt_socket_mtinfo1), 471 .hooks = (1 << NF_INET_PRE_ROUTING) | 472 (1 << NF_INET_LOCAL_IN), 473 .me = THIS_MODULE, 474 }, 475 #ifdef XT_SOCKET_HAVE_IPV6 476 { 477 .name = "socket", 478 .revision = 1, 479 .family = NFPROTO_IPV6, 480 .match = socket_mt6_v1_v2_v3, 481 .checkentry = socket_mt_v1_check, 482 .matchsize = sizeof(struct xt_socket_mtinfo1), 483 .hooks = (1 << NF_INET_PRE_ROUTING) | 484 (1 << NF_INET_LOCAL_IN), 485 .me = THIS_MODULE, 486 }, 487 #endif 488 { 489 .name = "socket", 490 .revision = 2, 491 .family = NFPROTO_IPV4, 492 .match = socket_mt4_v1_v2_v3, 493 .checkentry = socket_mt_v2_check, 494 .matchsize = sizeof(struct xt_socket_mtinfo1), 495 .hooks = (1 << NF_INET_PRE_ROUTING) | 496 (1 << NF_INET_LOCAL_IN), 497 .me = THIS_MODULE, 498 }, 499 #ifdef XT_SOCKET_HAVE_IPV6 500 { 501 .name = "socket", 502 .revision = 2, 503 .family = NFPROTO_IPV6, 504 .match = socket_mt6_v1_v2_v3, 505 .checkentry = socket_mt_v2_check, 506 .matchsize = sizeof(struct xt_socket_mtinfo1), 507 .hooks = (1 << NF_INET_PRE_ROUTING) | 508 (1 << NF_INET_LOCAL_IN), 509 .me = THIS_MODULE, 510 }, 511 #endif 512 { 513 .name = "socket", 514 .revision = 3, 515 .family = NFPROTO_IPV4, 516 .match = socket_mt4_v1_v2_v3, 517 .checkentry = socket_mt_v3_check, 518 .matchsize = sizeof(struct xt_socket_mtinfo1), 519 .hooks = (1 << NF_INET_PRE_ROUTING) | 520 (1 << NF_INET_LOCAL_IN), 521 .me = THIS_MODULE, 522 }, 523 #ifdef XT_SOCKET_HAVE_IPV6 524 { 525 .name = "socket", 526 .revision = 3, 527 .family = NFPROTO_IPV6, 528 .match = socket_mt6_v1_v2_v3, 529 .checkentry = socket_mt_v3_check, 530 .matchsize = sizeof(struct xt_socket_mtinfo1), 531 .hooks = (1 << NF_INET_PRE_ROUTING) | 532 (1 << NF_INET_LOCAL_IN), 533 .me = THIS_MODULE, 534 }, 535 #endif 536 }; 537 538 static int __init socket_mt_init(void) 539 { 540 nf_defrag_ipv4_enable(); 541 #ifdef XT_SOCKET_HAVE_IPV6 542 nf_defrag_ipv6_enable(); 543 #endif 544 545 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 546 } 547 548 static void __exit socket_mt_exit(void) 549 { 550 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 551 } 552 553 module_init(socket_mt_init); 554 module_exit(socket_mt_exit); 555 556 MODULE_LICENSE("GPL"); 557 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler"); 558 MODULE_DESCRIPTION("x_tables socket match module"); 559 MODULE_ALIAS("ipt_socket"); 560 MODULE_ALIAS("ip6t_socket"); 561