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(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 204static bool 205socket_match(const struct sk_buff *skb, struct xt_action_param *par, 206 const struct xt_socket_mtinfo1 *info) 207{ 208 struct sock *sk = skb->sk; 209 210 if (!sk) 211 sk = xt_socket_lookup_slow_v4(skb, par->in); 212 if (sk) { 213 bool wildcard; 214 bool transparent = true; 215 216 /* Ignore sockets listening on INADDR_ANY, 217 * unless XT_SOCKET_NOWILDCARD is set 218 */ 219 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 220 sk_fullsock(sk) && 221 inet_sk(sk)->inet_rcv_saddr == 0); 222 223 /* Ignore non-transparent sockets, 224 * if XT_SOCKET_TRANSPARENT is used 225 */ 226 if (info->flags & XT_SOCKET_TRANSPARENT) 227 transparent = xt_socket_sk_is_transparent(sk); 228 229 if (sk != skb->sk) 230 sock_gen_put(sk); 231 232 if (wildcard || !transparent) 233 sk = NULL; 234 } 235 236 return sk != NULL; 237} 238 239static bool 240socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par) 241{ 242 static struct xt_socket_mtinfo1 xt_info_v0 = { 243 .flags = 0, 244 }; 245 246 return socket_match(skb, par, &xt_info_v0); 247} 248 249static bool 250socket_mt4_v1_v2(const struct sk_buff *skb, struct xt_action_param *par) 251{ 252 return socket_match(skb, par, par->matchinfo); 253} 254 255#ifdef XT_SOCKET_HAVE_IPV6 256 257static int 258extract_icmp6_fields(const struct sk_buff *skb, 259 unsigned int outside_hdrlen, 260 int *protocol, 261 const struct in6_addr **raddr, 262 const struct in6_addr **laddr, 263 __be16 *rport, 264 __be16 *lport, 265 struct ipv6hdr *ipv6_var) 266{ 267 const struct ipv6hdr *inside_iph; 268 struct icmp6hdr *icmph, _icmph; 269 __be16 *ports, _ports[2]; 270 u8 inside_nexthdr; 271 __be16 inside_fragoff; 272 int inside_hdrlen; 273 274 icmph = skb_header_pointer(skb, outside_hdrlen, 275 sizeof(_icmph), &_icmph); 276 if (icmph == NULL) 277 return 1; 278 279 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK) 280 return 1; 281 282 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), 283 sizeof(*ipv6_var), ipv6_var); 284 if (inside_iph == NULL) 285 return 1; 286 inside_nexthdr = inside_iph->nexthdr; 287 288 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + 289 sizeof(*ipv6_var), 290 &inside_nexthdr, &inside_fragoff); 291 if (inside_hdrlen < 0) 292 return 1; /* hjm: Packet has no/incomplete transport layer headers. */ 293 294 if (inside_nexthdr != IPPROTO_TCP && 295 inside_nexthdr != IPPROTO_UDP) 296 return 1; 297 298 ports = skb_header_pointer(skb, inside_hdrlen, 299 sizeof(_ports), &_ports); 300 if (ports == NULL) 301 return 1; 302 303 /* the inside IP packet is the one quoted from our side, thus 304 * its saddr is the local address */ 305 *protocol = inside_nexthdr; 306 *laddr = &inside_iph->saddr; 307 *lport = ports[0]; 308 *raddr = &inside_iph->daddr; 309 *rport = ports[1]; 310 311 return 0; 312} 313 314static struct sock * 315xt_socket_get_sock_v6(struct net *net, const u8 protocol, 316 const struct in6_addr *saddr, const struct in6_addr *daddr, 317 const __be16 sport, const __be16 dport, 318 const struct net_device *in) 319{ 320 switch (protocol) { 321 case IPPROTO_TCP: 322 return inet6_lookup(net, &tcp_hashinfo, 323 saddr, sport, daddr, dport, 324 in->ifindex); 325 case IPPROTO_UDP: 326 return udp6_lib_lookup(net, saddr, sport, daddr, dport, 327 in->ifindex); 328 } 329 330 return NULL; 331} 332 333static struct sock *xt_socket_lookup_slow_v6(const struct sk_buff *skb, 334 const struct net_device *indev) 335{ 336 __be16 uninitialized_var(dport), uninitialized_var(sport); 337 const struct in6_addr *daddr = NULL, *saddr = NULL; 338 struct ipv6hdr *iph = ipv6_hdr(skb); 339 int thoff = 0, tproto; 340 341 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); 342 if (tproto < 0) { 343 pr_debug("unable to find transport header in IPv6 packet, dropping\n"); 344 return NULL; 345 } 346 347 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) { 348 struct udphdr _hdr, *hp; 349 350 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); 351 if (hp == NULL) 352 return NULL; 353 354 saddr = &iph->saddr; 355 sport = hp->source; 356 daddr = &iph->daddr; 357 dport = hp->dest; 358 359 } else if (tproto == IPPROTO_ICMPV6) { 360 struct ipv6hdr ipv6_var; 361 362 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr, 363 &sport, &dport, &ipv6_var)) 364 return NULL; 365 } else { 366 return NULL; 367 } 368 369 return xt_socket_get_sock_v6(dev_net(skb->dev), tproto, saddr, daddr, 370 sport, dport, indev); 371} 372 373static bool 374socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par) 375{ 376 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 377 struct sock *sk = skb->sk; 378 379 if (!sk) 380 sk = xt_socket_lookup_slow_v6(skb, par->in); 381 if (sk) { 382 bool wildcard; 383 bool transparent = true; 384 385 /* Ignore sockets listening on INADDR_ANY 386 * unless XT_SOCKET_NOWILDCARD is set 387 */ 388 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 389 sk_fullsock(sk) && 390 ipv6_addr_any(&sk->sk_v6_rcv_saddr)); 391 392 /* Ignore non-transparent sockets, 393 * if XT_SOCKET_TRANSPARENT is used 394 */ 395 if (info->flags & XT_SOCKET_TRANSPARENT) 396 transparent = xt_socket_sk_is_transparent(sk); 397 398 if (sk != skb->sk) 399 sock_gen_put(sk); 400 401 if (wildcard || !transparent) 402 sk = NULL; 403 } 404 405 return sk != NULL; 406} 407#endif 408 409static int socket_mt_v1_check(const struct xt_mtchk_param *par) 410{ 411 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 412 413 if (info->flags & ~XT_SOCKET_FLAGS_V1) { 414 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1); 415 return -EINVAL; 416 } 417 return 0; 418} 419 420static int socket_mt_v2_check(const struct xt_mtchk_param *par) 421{ 422 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo; 423 424 if (info->flags & ~XT_SOCKET_FLAGS_V2) { 425 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2); 426 return -EINVAL; 427 } 428 return 0; 429} 430 431static struct xt_match socket_mt_reg[] __read_mostly = { 432 { 433 .name = "socket", 434 .revision = 0, 435 .family = NFPROTO_IPV4, 436 .match = socket_mt4_v0, 437 .hooks = (1 << NF_INET_PRE_ROUTING) | 438 (1 << NF_INET_LOCAL_IN), 439 .me = THIS_MODULE, 440 }, 441 { 442 .name = "socket", 443 .revision = 1, 444 .family = NFPROTO_IPV4, 445 .match = socket_mt4_v1_v2, 446 .checkentry = socket_mt_v1_check, 447 .matchsize = sizeof(struct xt_socket_mtinfo1), 448 .hooks = (1 << NF_INET_PRE_ROUTING) | 449 (1 << NF_INET_LOCAL_IN), 450 .me = THIS_MODULE, 451 }, 452#ifdef XT_SOCKET_HAVE_IPV6 453 { 454 .name = "socket", 455 .revision = 1, 456 .family = NFPROTO_IPV6, 457 .match = socket_mt6_v1_v2, 458 .checkentry = socket_mt_v1_check, 459 .matchsize = sizeof(struct xt_socket_mtinfo1), 460 .hooks = (1 << NF_INET_PRE_ROUTING) | 461 (1 << NF_INET_LOCAL_IN), 462 .me = THIS_MODULE, 463 }, 464#endif 465 { 466 .name = "socket", 467 .revision = 2, 468 .family = NFPROTO_IPV4, 469 .match = socket_mt4_v1_v2, 470 .checkentry = socket_mt_v2_check, 471 .matchsize = sizeof(struct xt_socket_mtinfo1), 472 .hooks = (1 << NF_INET_PRE_ROUTING) | 473 (1 << NF_INET_LOCAL_IN), 474 .me = THIS_MODULE, 475 }, 476#ifdef XT_SOCKET_HAVE_IPV6 477 { 478 .name = "socket", 479 .revision = 2, 480 .family = NFPROTO_IPV6, 481 .match = socket_mt6_v1_v2, 482 .checkentry = socket_mt_v2_check, 483 .matchsize = sizeof(struct xt_socket_mtinfo1), 484 .hooks = (1 << NF_INET_PRE_ROUTING) | 485 (1 << NF_INET_LOCAL_IN), 486 .me = THIS_MODULE, 487 }, 488#endif 489}; 490 491static int __init socket_mt_init(void) 492{ 493 nf_defrag_ipv4_enable(); 494#ifdef XT_SOCKET_HAVE_IPV6 495 nf_defrag_ipv6_enable(); 496#endif 497 498 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 499} 500 501static void __exit socket_mt_exit(void) 502{ 503 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 504} 505 506module_init(socket_mt_init); 507module_exit(socket_mt_exit); 508 509MODULE_LICENSE("GPL"); 510MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler"); 511MODULE_DESCRIPTION("x_tables socket match module"); 512MODULE_ALIAS("ipt_socket"); 513MODULE_ALIAS("ip6t_socket"); 514