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 void 39 xt_socket_put_sk(struct sock *sk) 40 { 41 if (sk->sk_state == TCP_TIME_WAIT) 42 inet_twsk_put(inet_twsk(sk)); 43 else 44 sock_put(sk); 45 } 46 47 static int 48 extract_icmp4_fields(const struct sk_buff *skb, 49 u8 *protocol, 50 __be32 *raddr, 51 __be32 *laddr, 52 __be16 *rport, 53 __be16 *lport) 54 { 55 unsigned int outside_hdrlen = ip_hdrlen(skb); 56 struct iphdr *inside_iph, _inside_iph; 57 struct icmphdr *icmph, _icmph; 58 __be16 *ports, _ports[2]; 59 60 icmph = skb_header_pointer(skb, outside_hdrlen, 61 sizeof(_icmph), &_icmph); 62 if (icmph == NULL) 63 return 1; 64 65 switch (icmph->type) { 66 case ICMP_DEST_UNREACH: 67 case ICMP_SOURCE_QUENCH: 68 case ICMP_REDIRECT: 69 case ICMP_TIME_EXCEEDED: 70 case ICMP_PARAMETERPROB: 71 break; 72 default: 73 return 1; 74 } 75 76 inside_iph = skb_header_pointer(skb, outside_hdrlen + 77 sizeof(struct icmphdr), 78 sizeof(_inside_iph), &_inside_iph); 79 if (inside_iph == NULL) 80 return 1; 81 82 if (inside_iph->protocol != IPPROTO_TCP && 83 inside_iph->protocol != IPPROTO_UDP) 84 return 1; 85 86 ports = skb_header_pointer(skb, outside_hdrlen + 87 sizeof(struct icmphdr) + 88 (inside_iph->ihl << 2), 89 sizeof(_ports), &_ports); 90 if (ports == NULL) 91 return 1; 92 93 /* the inside IP packet is the one quoted from our side, thus 94 * its saddr is the local address */ 95 *protocol = inside_iph->protocol; 96 *laddr = inside_iph->saddr; 97 *lport = ports[0]; 98 *raddr = inside_iph->daddr; 99 *rport = ports[1]; 100 101 return 0; 102 } 103 104 /* "socket" match based redirection (no specific rule) 105 * =================================================== 106 * 107 * There are connections with dynamic endpoints (e.g. FTP data 108 * connection) that the user is unable to add explicit rules 109 * for. These are taken care of by a generic "socket" rule. It is 110 * assumed that the proxy application is trusted to open such 111 * connections without explicit iptables rule (except of course the 112 * generic 'socket' rule). In this case the following sockets are 113 * matched in preference order: 114 * 115 * - match: if there's a fully established connection matching the 116 * _packet_ tuple 117 * 118 * - match: if there's a non-zero bound listener (possibly with a 119 * non-local address) We don't accept zero-bound listeners, since 120 * then local services could intercept traffic going through the 121 * box. 122 */ 123 static struct sock * 124 xt_socket_get_sock_v4(struct net *net, const u8 protocol, 125 const __be32 saddr, const __be32 daddr, 126 const __be16 sport, const __be16 dport, 127 const struct net_device *in) 128 { 129 switch (protocol) { 130 case IPPROTO_TCP: 131 return __inet_lookup(net, &tcp_hashinfo, 132 saddr, sport, daddr, dport, 133 in->ifindex); 134 case IPPROTO_UDP: 135 return udp4_lib_lookup(net, saddr, sport, daddr, dport, 136 in->ifindex); 137 } 138 return NULL; 139 } 140 141 static bool 142 socket_match(const struct sk_buff *skb, struct xt_action_param *par, 143 const struct xt_socket_mtinfo1 *info) 144 { 145 const struct iphdr *iph = ip_hdr(skb); 146 struct udphdr _hdr, *hp = NULL; 147 struct sock *sk = skb->sk; 148 __be32 uninitialized_var(daddr), uninitialized_var(saddr); 149 __be16 uninitialized_var(dport), uninitialized_var(sport); 150 u8 uninitialized_var(protocol); 151 #ifdef XT_SOCKET_HAVE_CONNTRACK 152 struct nf_conn const *ct; 153 enum ip_conntrack_info ctinfo; 154 #endif 155 156 if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) { 157 hp = skb_header_pointer(skb, ip_hdrlen(skb), 158 sizeof(_hdr), &_hdr); 159 if (hp == NULL) 160 return false; 161 162 protocol = iph->protocol; 163 saddr = iph->saddr; 164 sport = hp->source; 165 daddr = iph->daddr; 166 dport = hp->dest; 167 168 } else if (iph->protocol == IPPROTO_ICMP) { 169 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr, 170 &sport, &dport)) 171 return false; 172 } else { 173 return false; 174 } 175 176 #ifdef XT_SOCKET_HAVE_CONNTRACK 177 /* Do the lookup with the original socket address in case this is a 178 * reply packet of an established SNAT-ted connection. */ 179 180 ct = nf_ct_get(skb, &ctinfo); 181 if (ct && !nf_ct_is_untracked(ct) && 182 ((iph->protocol != IPPROTO_ICMP && 183 ctinfo == IP_CT_ESTABLISHED_REPLY) || 184 (iph->protocol == IPPROTO_ICMP && 185 ctinfo == IP_CT_RELATED_REPLY)) && 186 (ct->status & IPS_SRC_NAT_DONE)) { 187 188 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip; 189 dport = (iph->protocol == IPPROTO_TCP) ? 190 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port : 191 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port; 192 } 193 #endif 194 195 if (!sk) 196 sk = xt_socket_get_sock_v4(dev_net(skb->dev), protocol, 197 saddr, daddr, sport, dport, 198 par->in); 199 if (sk) { 200 bool wildcard; 201 bool transparent = true; 202 203 /* Ignore sockets listening on INADDR_ANY, 204 * unless XT_SOCKET_NOWILDCARD is set 205 */ 206 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 207 sk->sk_state != TCP_TIME_WAIT && 208 inet_sk(sk)->inet_rcv_saddr == 0); 209 210 /* Ignore non-transparent sockets, 211 if XT_SOCKET_TRANSPARENT is used */ 212 if (info->flags & XT_SOCKET_TRANSPARENT) 213 transparent = ((sk->sk_state != TCP_TIME_WAIT && 214 inet_sk(sk)->transparent) || 215 (sk->sk_state == TCP_TIME_WAIT && 216 inet_twsk(sk)->tw_transparent)); 217 218 if (sk != skb->sk) 219 xt_socket_put_sk(sk); 220 221 if (wildcard || !transparent) 222 sk = NULL; 223 } 224 225 pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n", 226 protocol, &saddr, ntohs(sport), 227 &daddr, ntohs(dport), 228 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk); 229 230 return (sk != NULL); 231 } 232 233 static bool 234 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par) 235 { 236 static struct xt_socket_mtinfo1 xt_info_v0 = { 237 .flags = 0, 238 }; 239 240 return socket_match(skb, par, &xt_info_v0); 241 } 242 243 static bool 244 socket_mt4_v1_v2(const struct sk_buff *skb, struct xt_action_param *par) 245 { 246 return socket_match(skb, par, par->matchinfo); 247 } 248 249 #ifdef XT_SOCKET_HAVE_IPV6 250 251 static int 252 extract_icmp6_fields(const struct sk_buff *skb, 253 unsigned int outside_hdrlen, 254 int *protocol, 255 struct in6_addr **raddr, 256 struct in6_addr **laddr, 257 __be16 *rport, 258 __be16 *lport) 259 { 260 struct ipv6hdr *inside_iph, _inside_iph; 261 struct icmp6hdr *icmph, _icmph; 262 __be16 *ports, _ports[2]; 263 u8 inside_nexthdr; 264 __be16 inside_fragoff; 265 int inside_hdrlen; 266 267 icmph = skb_header_pointer(skb, outside_hdrlen, 268 sizeof(_icmph), &_icmph); 269 if (icmph == NULL) 270 return 1; 271 272 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK) 273 return 1; 274 275 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), sizeof(_inside_iph), &_inside_iph); 276 if (inside_iph == NULL) 277 return 1; 278 inside_nexthdr = inside_iph->nexthdr; 279 280 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph), 281 &inside_nexthdr, &inside_fragoff); 282 if (inside_hdrlen < 0) 283 return 1; /* hjm: Packet has no/incomplete transport layer headers. */ 284 285 if (inside_nexthdr != IPPROTO_TCP && 286 inside_nexthdr != IPPROTO_UDP) 287 return 1; 288 289 ports = skb_header_pointer(skb, inside_hdrlen, 290 sizeof(_ports), &_ports); 291 if (ports == NULL) 292 return 1; 293 294 /* the inside IP packet is the one quoted from our side, thus 295 * its saddr is the local address */ 296 *protocol = inside_nexthdr; 297 *laddr = &inside_iph->saddr; 298 *lport = ports[0]; 299 *raddr = &inside_iph->daddr; 300 *rport = ports[1]; 301 302 return 0; 303 } 304 305 static struct sock * 306 xt_socket_get_sock_v6(struct net *net, const u8 protocol, 307 const struct in6_addr *saddr, const struct in6_addr *daddr, 308 const __be16 sport, const __be16 dport, 309 const struct net_device *in) 310 { 311 switch (protocol) { 312 case IPPROTO_TCP: 313 return inet6_lookup(net, &tcp_hashinfo, 314 saddr, sport, daddr, dport, 315 in->ifindex); 316 case IPPROTO_UDP: 317 return udp6_lib_lookup(net, saddr, sport, daddr, dport, 318 in->ifindex); 319 } 320 321 return NULL; 322 } 323 324 static bool 325 socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par) 326 { 327 struct ipv6hdr *iph = ipv6_hdr(skb); 328 struct udphdr _hdr, *hp = NULL; 329 struct sock *sk = skb->sk; 330 struct in6_addr *daddr = NULL, *saddr = NULL; 331 __be16 uninitialized_var(dport), uninitialized_var(sport); 332 int thoff = 0, uninitialized_var(tproto); 333 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 334 335 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); 336 if (tproto < 0) { 337 pr_debug("unable to find transport header in IPv6 packet, dropping\n"); 338 return NF_DROP; 339 } 340 341 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) { 342 hp = skb_header_pointer(skb, thoff, 343 sizeof(_hdr), &_hdr); 344 if (hp == NULL) 345 return false; 346 347 saddr = &iph->saddr; 348 sport = hp->source; 349 daddr = &iph->daddr; 350 dport = hp->dest; 351 352 } else if (tproto == IPPROTO_ICMPV6) { 353 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr, 354 &sport, &dport)) 355 return false; 356 } else { 357 return false; 358 } 359 360 if (!sk) 361 sk = xt_socket_get_sock_v6(dev_net(skb->dev), tproto, 362 saddr, daddr, sport, dport, 363 par->in); 364 if (sk) { 365 bool wildcard; 366 bool transparent = true; 367 368 /* Ignore sockets listening on INADDR_ANY 369 * unless XT_SOCKET_NOWILDCARD is set 370 */ 371 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 372 sk->sk_state != TCP_TIME_WAIT && 373 ipv6_addr_any(&inet6_sk(sk)->rcv_saddr)); 374 375 /* Ignore non-transparent sockets, 376 if XT_SOCKET_TRANSPARENT is used */ 377 if (info->flags & XT_SOCKET_TRANSPARENT) 378 transparent = ((sk->sk_state != TCP_TIME_WAIT && 379 inet_sk(sk)->transparent) || 380 (sk->sk_state == TCP_TIME_WAIT && 381 inet_twsk(sk)->tw_transparent)); 382 383 if (sk != skb->sk) 384 xt_socket_put_sk(sk); 385 386 if (wildcard || !transparent) 387 sk = NULL; 388 } 389 390 pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu " 391 "(orig %pI6:%hu) sock %p\n", 392 tproto, saddr, ntohs(sport), 393 daddr, ntohs(dport), 394 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk); 395 396 return (sk != NULL); 397 } 398 #endif 399 400 static int socket_mt_v1_check(const struct xt_mtchk_param *par) 401 { 402 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 403 404 if (info->flags & ~XT_SOCKET_FLAGS_V1) { 405 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1); 406 return -EINVAL; 407 } 408 return 0; 409 } 410 411 static int socket_mt_v2_check(const struct xt_mtchk_param *par) 412 { 413 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo; 414 415 if (info->flags & ~XT_SOCKET_FLAGS_V2) { 416 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2); 417 return -EINVAL; 418 } 419 return 0; 420 } 421 422 static struct xt_match socket_mt_reg[] __read_mostly = { 423 { 424 .name = "socket", 425 .revision = 0, 426 .family = NFPROTO_IPV4, 427 .match = socket_mt4_v0, 428 .hooks = (1 << NF_INET_PRE_ROUTING) | 429 (1 << NF_INET_LOCAL_IN), 430 .me = THIS_MODULE, 431 }, 432 { 433 .name = "socket", 434 .revision = 1, 435 .family = NFPROTO_IPV4, 436 .match = socket_mt4_v1_v2, 437 .checkentry = socket_mt_v1_check, 438 .matchsize = sizeof(struct xt_socket_mtinfo1), 439 .hooks = (1 << NF_INET_PRE_ROUTING) | 440 (1 << NF_INET_LOCAL_IN), 441 .me = THIS_MODULE, 442 }, 443 #ifdef XT_SOCKET_HAVE_IPV6 444 { 445 .name = "socket", 446 .revision = 1, 447 .family = NFPROTO_IPV6, 448 .match = socket_mt6_v1_v2, 449 .checkentry = socket_mt_v1_check, 450 .matchsize = sizeof(struct xt_socket_mtinfo1), 451 .hooks = (1 << NF_INET_PRE_ROUTING) | 452 (1 << NF_INET_LOCAL_IN), 453 .me = THIS_MODULE, 454 }, 455 #endif 456 { 457 .name = "socket", 458 .revision = 2, 459 .family = NFPROTO_IPV4, 460 .match = socket_mt4_v1_v2, 461 .checkentry = socket_mt_v2_check, 462 .matchsize = sizeof(struct xt_socket_mtinfo1), 463 .hooks = (1 << NF_INET_PRE_ROUTING) | 464 (1 << NF_INET_LOCAL_IN), 465 .me = THIS_MODULE, 466 }, 467 #ifdef XT_SOCKET_HAVE_IPV6 468 { 469 .name = "socket", 470 .revision = 2, 471 .family = NFPROTO_IPV6, 472 .match = socket_mt6_v1_v2, 473 .checkentry = socket_mt_v2_check, 474 .matchsize = sizeof(struct xt_socket_mtinfo1), 475 .hooks = (1 << NF_INET_PRE_ROUTING) | 476 (1 << NF_INET_LOCAL_IN), 477 .me = THIS_MODULE, 478 }, 479 #endif 480 }; 481 482 static int __init socket_mt_init(void) 483 { 484 nf_defrag_ipv4_enable(); 485 #ifdef XT_SOCKET_HAVE_IPV6 486 nf_defrag_ipv6_enable(); 487 #endif 488 489 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 490 } 491 492 static void __exit socket_mt_exit(void) 493 { 494 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 495 } 496 497 module_init(socket_mt_init); 498 module_exit(socket_mt_exit); 499 500 MODULE_LICENSE("GPL"); 501 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler"); 502 MODULE_DESCRIPTION("x_tables socket match module"); 503 MODULE_ALIAS("ipt_socket"); 504 MODULE_ALIAS("ip6t_socket"); 505