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 38static int 39extract_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 */ 114static struct sock * 115xt_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 132static 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 146static struct sock *xt_socket_lookup_slow_v4(struct net *net, 147 const struct sk_buff *skb, 148 const struct net_device *indev) 149{ 150 const struct iphdr *iph = ip_hdr(skb); 151 __be32 uninitialized_var(daddr), uninitialized_var(saddr); 152 __be16 uninitialized_var(dport), uninitialized_var(sport); 153 u8 uninitialized_var(protocol); 154#ifdef XT_SOCKET_HAVE_CONNTRACK 155 struct nf_conn const *ct; 156 enum ip_conntrack_info ctinfo; 157#endif 158 159 if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) { 160 struct udphdr _hdr, *hp; 161 162 hp = skb_header_pointer(skb, ip_hdrlen(skb), 163 sizeof(_hdr), &_hdr); 164 if (hp == NULL) 165 return NULL; 166 167 protocol = iph->protocol; 168 saddr = iph->saddr; 169 sport = hp->source; 170 daddr = iph->daddr; 171 dport = hp->dest; 172 173 } else if (iph->protocol == IPPROTO_ICMP) { 174 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr, 175 &sport, &dport)) 176 return NULL; 177 } else { 178 return NULL; 179 } 180 181#ifdef XT_SOCKET_HAVE_CONNTRACK 182 /* Do the lookup with the original socket address in 183 * case this is a reply packet of an established 184 * SNAT-ted connection. 185 */ 186 ct = nf_ct_get(skb, &ctinfo); 187 if (ct && !nf_ct_is_untracked(ct) && 188 ((iph->protocol != IPPROTO_ICMP && 189 ctinfo == IP_CT_ESTABLISHED_REPLY) || 190 (iph->protocol == IPPROTO_ICMP && 191 ctinfo == IP_CT_RELATED_REPLY)) && 192 (ct->status & IPS_SRC_NAT_DONE)) { 193 194 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip; 195 dport = (iph->protocol == IPPROTO_TCP) ? 196 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port : 197 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port; 198 } 199#endif 200 201 return xt_socket_get_sock_v4(net, protocol, saddr, daddr, 202 sport, dport, indev); 203} 204 205static bool 206socket_match(const struct sk_buff *skb, struct xt_action_param *par, 207 const struct xt_socket_mtinfo1 *info) 208{ 209 struct sk_buff *pskb = (struct sk_buff *)skb; 210 struct sock *sk = skb->sk; 211 212 if (!sk) 213 sk = xt_socket_lookup_slow_v4(par->net, skb, par->in); 214 if (sk) { 215 bool wildcard; 216 bool transparent = true; 217 218 /* Ignore sockets listening on INADDR_ANY, 219 * unless XT_SOCKET_NOWILDCARD is set 220 */ 221 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 222 sk_fullsock(sk) && 223 inet_sk(sk)->inet_rcv_saddr == 0); 224 225 /* Ignore non-transparent sockets, 226 * if XT_SOCKET_TRANSPARENT is used 227 */ 228 if (info->flags & XT_SOCKET_TRANSPARENT) 229 transparent = xt_socket_sk_is_transparent(sk); 230 231 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard && 232 transparent) 233 pskb->mark = sk->sk_mark; 234 235 if (sk != skb->sk) 236 sock_gen_put(sk); 237 238 if (wildcard || !transparent) 239 sk = NULL; 240 } 241 242 return sk != NULL; 243} 244 245static bool 246socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par) 247{ 248 static struct xt_socket_mtinfo1 xt_info_v0 = { 249 .flags = 0, 250 }; 251 252 return socket_match(skb, par, &xt_info_v0); 253} 254 255static bool 256socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par) 257{ 258 return socket_match(skb, par, par->matchinfo); 259} 260 261#ifdef XT_SOCKET_HAVE_IPV6 262 263static int 264extract_icmp6_fields(const struct sk_buff *skb, 265 unsigned int outside_hdrlen, 266 int *protocol, 267 const struct in6_addr **raddr, 268 const struct in6_addr **laddr, 269 __be16 *rport, 270 __be16 *lport, 271 struct ipv6hdr *ipv6_var) 272{ 273 const struct ipv6hdr *inside_iph; 274 struct icmp6hdr *icmph, _icmph; 275 __be16 *ports, _ports[2]; 276 u8 inside_nexthdr; 277 __be16 inside_fragoff; 278 int inside_hdrlen; 279 280 icmph = skb_header_pointer(skb, outside_hdrlen, 281 sizeof(_icmph), &_icmph); 282 if (icmph == NULL) 283 return 1; 284 285 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK) 286 return 1; 287 288 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), 289 sizeof(*ipv6_var), ipv6_var); 290 if (inside_iph == NULL) 291 return 1; 292 inside_nexthdr = inside_iph->nexthdr; 293 294 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + 295 sizeof(*ipv6_var), 296 &inside_nexthdr, &inside_fragoff); 297 if (inside_hdrlen < 0) 298 return 1; /* hjm: Packet has no/incomplete transport layer headers. */ 299 300 if (inside_nexthdr != IPPROTO_TCP && 301 inside_nexthdr != IPPROTO_UDP) 302 return 1; 303 304 ports = skb_header_pointer(skb, inside_hdrlen, 305 sizeof(_ports), &_ports); 306 if (ports == NULL) 307 return 1; 308 309 /* the inside IP packet is the one quoted from our side, thus 310 * its saddr is the local address */ 311 *protocol = inside_nexthdr; 312 *laddr = &inside_iph->saddr; 313 *lport = ports[0]; 314 *raddr = &inside_iph->daddr; 315 *rport = ports[1]; 316 317 return 0; 318} 319 320static struct sock * 321xt_socket_get_sock_v6(struct net *net, const u8 protocol, 322 const struct in6_addr *saddr, const struct in6_addr *daddr, 323 const __be16 sport, const __be16 dport, 324 const struct net_device *in) 325{ 326 switch (protocol) { 327 case IPPROTO_TCP: 328 return inet6_lookup(net, &tcp_hashinfo, 329 saddr, sport, daddr, dport, 330 in->ifindex); 331 case IPPROTO_UDP: 332 return udp6_lib_lookup(net, saddr, sport, daddr, dport, 333 in->ifindex); 334 } 335 336 return NULL; 337} 338 339static struct sock *xt_socket_lookup_slow_v6(struct net *net, 340 const struct sk_buff *skb, 341 const struct net_device *indev) 342{ 343 __be16 uninitialized_var(dport), uninitialized_var(sport); 344 const struct in6_addr *daddr = NULL, *saddr = NULL; 345 struct ipv6hdr *iph = ipv6_hdr(skb); 346 int thoff = 0, tproto; 347 348 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); 349 if (tproto < 0) { 350 pr_debug("unable to find transport header in IPv6 packet, dropping\n"); 351 return NULL; 352 } 353 354 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) { 355 struct udphdr _hdr, *hp; 356 357 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); 358 if (hp == NULL) 359 return NULL; 360 361 saddr = &iph->saddr; 362 sport = hp->source; 363 daddr = &iph->daddr; 364 dport = hp->dest; 365 366 } else if (tproto == IPPROTO_ICMPV6) { 367 struct ipv6hdr ipv6_var; 368 369 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr, 370 &sport, &dport, &ipv6_var)) 371 return NULL; 372 } else { 373 return NULL; 374 } 375 376 return xt_socket_get_sock_v6(net, tproto, saddr, daddr, 377 sport, dport, indev); 378} 379 380static bool 381socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par) 382{ 383 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 384 struct sk_buff *pskb = (struct sk_buff *)skb; 385 struct sock *sk = skb->sk; 386 387 if (!sk) 388 sk = xt_socket_lookup_slow_v6(par->net, skb, par->in); 389 if (sk) { 390 bool wildcard; 391 bool transparent = true; 392 393 /* Ignore sockets listening on INADDR_ANY 394 * unless XT_SOCKET_NOWILDCARD is set 395 */ 396 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 397 sk_fullsock(sk) && 398 ipv6_addr_any(&sk->sk_v6_rcv_saddr)); 399 400 /* Ignore non-transparent sockets, 401 * if XT_SOCKET_TRANSPARENT is used 402 */ 403 if (info->flags & XT_SOCKET_TRANSPARENT) 404 transparent = xt_socket_sk_is_transparent(sk); 405 406 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard && 407 transparent) 408 pskb->mark = sk->sk_mark; 409 410 if (sk != skb->sk) 411 sock_gen_put(sk); 412 413 if (wildcard || !transparent) 414 sk = NULL; 415 } 416 417 return sk != NULL; 418} 419#endif 420 421static int socket_mt_v1_check(const struct xt_mtchk_param *par) 422{ 423 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 424 425 if (info->flags & ~XT_SOCKET_FLAGS_V1) { 426 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1); 427 return -EINVAL; 428 } 429 return 0; 430} 431 432static int socket_mt_v2_check(const struct xt_mtchk_param *par) 433{ 434 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo; 435 436 if (info->flags & ~XT_SOCKET_FLAGS_V2) { 437 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2); 438 return -EINVAL; 439 } 440 return 0; 441} 442 443static int socket_mt_v3_check(const struct xt_mtchk_param *par) 444{ 445 const struct xt_socket_mtinfo3 *info = 446 (struct xt_socket_mtinfo3 *)par->matchinfo; 447 448 if (info->flags & ~XT_SOCKET_FLAGS_V3) { 449 pr_info("unknown flags 0x%x\n", 450 info->flags & ~XT_SOCKET_FLAGS_V3); 451 return -EINVAL; 452 } 453 return 0; 454} 455 456static struct xt_match socket_mt_reg[] __read_mostly = { 457 { 458 .name = "socket", 459 .revision = 0, 460 .family = NFPROTO_IPV4, 461 .match = socket_mt4_v0, 462 .hooks = (1 << NF_INET_PRE_ROUTING) | 463 (1 << NF_INET_LOCAL_IN), 464 .me = THIS_MODULE, 465 }, 466 { 467 .name = "socket", 468 .revision = 1, 469 .family = NFPROTO_IPV4, 470 .match = socket_mt4_v1_v2_v3, 471 .checkentry = socket_mt_v1_check, 472 .matchsize = sizeof(struct xt_socket_mtinfo1), 473 .hooks = (1 << NF_INET_PRE_ROUTING) | 474 (1 << NF_INET_LOCAL_IN), 475 .me = THIS_MODULE, 476 }, 477#ifdef XT_SOCKET_HAVE_IPV6 478 { 479 .name = "socket", 480 .revision = 1, 481 .family = NFPROTO_IPV6, 482 .match = socket_mt6_v1_v2_v3, 483 .checkentry = socket_mt_v1_check, 484 .matchsize = sizeof(struct xt_socket_mtinfo1), 485 .hooks = (1 << NF_INET_PRE_ROUTING) | 486 (1 << NF_INET_LOCAL_IN), 487 .me = THIS_MODULE, 488 }, 489#endif 490 { 491 .name = "socket", 492 .revision = 2, 493 .family = NFPROTO_IPV4, 494 .match = socket_mt4_v1_v2_v3, 495 .checkentry = socket_mt_v2_check, 496 .matchsize = sizeof(struct xt_socket_mtinfo1), 497 .hooks = (1 << NF_INET_PRE_ROUTING) | 498 (1 << NF_INET_LOCAL_IN), 499 .me = THIS_MODULE, 500 }, 501#ifdef XT_SOCKET_HAVE_IPV6 502 { 503 .name = "socket", 504 .revision = 2, 505 .family = NFPROTO_IPV6, 506 .match = socket_mt6_v1_v2_v3, 507 .checkentry = socket_mt_v2_check, 508 .matchsize = sizeof(struct xt_socket_mtinfo1), 509 .hooks = (1 << NF_INET_PRE_ROUTING) | 510 (1 << NF_INET_LOCAL_IN), 511 .me = THIS_MODULE, 512 }, 513#endif 514 { 515 .name = "socket", 516 .revision = 3, 517 .family = NFPROTO_IPV4, 518 .match = socket_mt4_v1_v2_v3, 519 .checkentry = socket_mt_v3_check, 520 .matchsize = sizeof(struct xt_socket_mtinfo1), 521 .hooks = (1 << NF_INET_PRE_ROUTING) | 522 (1 << NF_INET_LOCAL_IN), 523 .me = THIS_MODULE, 524 }, 525#ifdef XT_SOCKET_HAVE_IPV6 526 { 527 .name = "socket", 528 .revision = 3, 529 .family = NFPROTO_IPV6, 530 .match = socket_mt6_v1_v2_v3, 531 .checkentry = socket_mt_v3_check, 532 .matchsize = sizeof(struct xt_socket_mtinfo1), 533 .hooks = (1 << NF_INET_PRE_ROUTING) | 534 (1 << NF_INET_LOCAL_IN), 535 .me = THIS_MODULE, 536 }, 537#endif 538}; 539 540static int __init socket_mt_init(void) 541{ 542 nf_defrag_ipv4_enable(); 543#ifdef XT_SOCKET_HAVE_IPV6 544 nf_defrag_ipv6_enable(); 545#endif 546 547 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 548} 549 550static void __exit socket_mt_exit(void) 551{ 552 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 553} 554 555module_init(socket_mt_init); 556module_exit(socket_mt_exit); 557 558MODULE_LICENSE("GPL"); 559MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler"); 560MODULE_DESCRIPTION("x_tables socket match module"); 561MODULE_ALIAS("ipt_socket"); 562MODULE_ALIAS("ip6t_socket"); 563