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 133 socket_match(const struct sk_buff *skb, struct xt_action_param *par, 134 const struct xt_socket_mtinfo1 *info) 135 { 136 const struct iphdr *iph = ip_hdr(skb); 137 struct udphdr _hdr, *hp = NULL; 138 struct sock *sk = skb->sk; 139 __be32 uninitialized_var(daddr), uninitialized_var(saddr); 140 __be16 uninitialized_var(dport), uninitialized_var(sport); 141 u8 uninitialized_var(protocol); 142 #ifdef XT_SOCKET_HAVE_CONNTRACK 143 struct nf_conn const *ct; 144 enum ip_conntrack_info ctinfo; 145 #endif 146 147 if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) { 148 hp = skb_header_pointer(skb, ip_hdrlen(skb), 149 sizeof(_hdr), &_hdr); 150 if (hp == NULL) 151 return false; 152 153 protocol = iph->protocol; 154 saddr = iph->saddr; 155 sport = hp->source; 156 daddr = iph->daddr; 157 dport = hp->dest; 158 159 } else if (iph->protocol == IPPROTO_ICMP) { 160 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr, 161 &sport, &dport)) 162 return false; 163 } else { 164 return false; 165 } 166 167 #ifdef XT_SOCKET_HAVE_CONNTRACK 168 /* Do the lookup with the original socket address in case this is a 169 * reply packet of an established SNAT-ted connection. */ 170 171 ct = nf_ct_get(skb, &ctinfo); 172 if (ct && !nf_ct_is_untracked(ct) && 173 ((iph->protocol != IPPROTO_ICMP && 174 ctinfo == IP_CT_ESTABLISHED_REPLY) || 175 (iph->protocol == IPPROTO_ICMP && 176 ctinfo == IP_CT_RELATED_REPLY)) && 177 (ct->status & IPS_SRC_NAT_DONE)) { 178 179 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip; 180 dport = (iph->protocol == IPPROTO_TCP) ? 181 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port : 182 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port; 183 } 184 #endif 185 186 if (!sk) 187 sk = xt_socket_get_sock_v4(dev_net(skb->dev), protocol, 188 saddr, daddr, sport, dport, 189 par->in); 190 if (sk) { 191 bool wildcard; 192 bool transparent = true; 193 194 /* Ignore sockets listening on INADDR_ANY, 195 * unless XT_SOCKET_NOWILDCARD is set 196 */ 197 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 198 sk->sk_state != TCP_TIME_WAIT && 199 inet_sk(sk)->inet_rcv_saddr == 0); 200 201 /* Ignore non-transparent sockets, 202 if XT_SOCKET_TRANSPARENT is used */ 203 if (info->flags & XT_SOCKET_TRANSPARENT) 204 transparent = ((sk->sk_state != TCP_TIME_WAIT && 205 inet_sk(sk)->transparent) || 206 (sk->sk_state == TCP_TIME_WAIT && 207 inet_twsk(sk)->tw_transparent)); 208 209 if (sk != skb->sk) 210 sock_gen_put(sk); 211 212 if (wildcard || !transparent) 213 sk = NULL; 214 } 215 216 pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n", 217 protocol, &saddr, ntohs(sport), 218 &daddr, ntohs(dport), 219 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk); 220 221 return (sk != NULL); 222 } 223 224 static bool 225 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par) 226 { 227 static struct xt_socket_mtinfo1 xt_info_v0 = { 228 .flags = 0, 229 }; 230 231 return socket_match(skb, par, &xt_info_v0); 232 } 233 234 static bool 235 socket_mt4_v1_v2(const struct sk_buff *skb, struct xt_action_param *par) 236 { 237 return socket_match(skb, par, par->matchinfo); 238 } 239 240 #ifdef XT_SOCKET_HAVE_IPV6 241 242 static int 243 extract_icmp6_fields(const struct sk_buff *skb, 244 unsigned int outside_hdrlen, 245 int *protocol, 246 const struct in6_addr **raddr, 247 const struct in6_addr **laddr, 248 __be16 *rport, 249 __be16 *lport, 250 struct ipv6hdr *ipv6_var) 251 { 252 const struct ipv6hdr *inside_iph; 253 struct icmp6hdr *icmph, _icmph; 254 __be16 *ports, _ports[2]; 255 u8 inside_nexthdr; 256 __be16 inside_fragoff; 257 int inside_hdrlen; 258 259 icmph = skb_header_pointer(skb, outside_hdrlen, 260 sizeof(_icmph), &_icmph); 261 if (icmph == NULL) 262 return 1; 263 264 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK) 265 return 1; 266 267 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), 268 sizeof(*ipv6_var), ipv6_var); 269 if (inside_iph == NULL) 270 return 1; 271 inside_nexthdr = inside_iph->nexthdr; 272 273 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + 274 sizeof(*ipv6_var), 275 &inside_nexthdr, &inside_fragoff); 276 if (inside_hdrlen < 0) 277 return 1; /* hjm: Packet has no/incomplete transport layer headers. */ 278 279 if (inside_nexthdr != IPPROTO_TCP && 280 inside_nexthdr != IPPROTO_UDP) 281 return 1; 282 283 ports = skb_header_pointer(skb, inside_hdrlen, 284 sizeof(_ports), &_ports); 285 if (ports == NULL) 286 return 1; 287 288 /* the inside IP packet is the one quoted from our side, thus 289 * its saddr is the local address */ 290 *protocol = inside_nexthdr; 291 *laddr = &inside_iph->saddr; 292 *lport = ports[0]; 293 *raddr = &inside_iph->daddr; 294 *rport = ports[1]; 295 296 return 0; 297 } 298 299 static struct sock * 300 xt_socket_get_sock_v6(struct net *net, const u8 protocol, 301 const struct in6_addr *saddr, const struct in6_addr *daddr, 302 const __be16 sport, const __be16 dport, 303 const struct net_device *in) 304 { 305 switch (protocol) { 306 case IPPROTO_TCP: 307 return inet6_lookup(net, &tcp_hashinfo, 308 saddr, sport, daddr, dport, 309 in->ifindex); 310 case IPPROTO_UDP: 311 return udp6_lib_lookup(net, saddr, sport, daddr, dport, 312 in->ifindex); 313 } 314 315 return NULL; 316 } 317 318 static bool 319 socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par) 320 { 321 struct ipv6hdr ipv6_var, *iph = ipv6_hdr(skb); 322 struct udphdr _hdr, *hp = NULL; 323 struct sock *sk = skb->sk; 324 const struct in6_addr *daddr = NULL, *saddr = NULL; 325 __be16 uninitialized_var(dport), uninitialized_var(sport); 326 int thoff = 0, uninitialized_var(tproto); 327 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 328 329 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); 330 if (tproto < 0) { 331 pr_debug("unable to find transport header in IPv6 packet, dropping\n"); 332 return NF_DROP; 333 } 334 335 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) { 336 hp = skb_header_pointer(skb, thoff, 337 sizeof(_hdr), &_hdr); 338 if (hp == NULL) 339 return false; 340 341 saddr = &iph->saddr; 342 sport = hp->source; 343 daddr = &iph->daddr; 344 dport = hp->dest; 345 346 } else if (tproto == IPPROTO_ICMPV6) { 347 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr, 348 &sport, &dport, &ipv6_var)) 349 return false; 350 } else { 351 return false; 352 } 353 354 if (!sk) 355 sk = xt_socket_get_sock_v6(dev_net(skb->dev), tproto, 356 saddr, daddr, sport, dport, 357 par->in); 358 if (sk) { 359 bool wildcard; 360 bool transparent = true; 361 362 /* Ignore sockets listening on INADDR_ANY 363 * unless XT_SOCKET_NOWILDCARD is set 364 */ 365 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 366 sk->sk_state != TCP_TIME_WAIT && 367 ipv6_addr_any(&sk->sk_v6_rcv_saddr)); 368 369 /* Ignore non-transparent sockets, 370 if XT_SOCKET_TRANSPARENT is used */ 371 if (info->flags & XT_SOCKET_TRANSPARENT) 372 transparent = ((sk->sk_state != TCP_TIME_WAIT && 373 inet_sk(sk)->transparent) || 374 (sk->sk_state == TCP_TIME_WAIT && 375 inet_twsk(sk)->tw_transparent)); 376 377 if (sk != skb->sk) 378 sock_gen_put(sk); 379 380 if (wildcard || !transparent) 381 sk = NULL; 382 } 383 384 pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu " 385 "(orig %pI6:%hu) sock %p\n", 386 tproto, saddr, ntohs(sport), 387 daddr, ntohs(dport), 388 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk); 389 390 return (sk != NULL); 391 } 392 #endif 393 394 static int socket_mt_v1_check(const struct xt_mtchk_param *par) 395 { 396 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 397 398 if (info->flags & ~XT_SOCKET_FLAGS_V1) { 399 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1); 400 return -EINVAL; 401 } 402 return 0; 403 } 404 405 static int socket_mt_v2_check(const struct xt_mtchk_param *par) 406 { 407 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo; 408 409 if (info->flags & ~XT_SOCKET_FLAGS_V2) { 410 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2); 411 return -EINVAL; 412 } 413 return 0; 414 } 415 416 static struct xt_match socket_mt_reg[] __read_mostly = { 417 { 418 .name = "socket", 419 .revision = 0, 420 .family = NFPROTO_IPV4, 421 .match = socket_mt4_v0, 422 .hooks = (1 << NF_INET_PRE_ROUTING) | 423 (1 << NF_INET_LOCAL_IN), 424 .me = THIS_MODULE, 425 }, 426 { 427 .name = "socket", 428 .revision = 1, 429 .family = NFPROTO_IPV4, 430 .match = socket_mt4_v1_v2, 431 .checkentry = socket_mt_v1_check, 432 .matchsize = sizeof(struct xt_socket_mtinfo1), 433 .hooks = (1 << NF_INET_PRE_ROUTING) | 434 (1 << NF_INET_LOCAL_IN), 435 .me = THIS_MODULE, 436 }, 437 #ifdef XT_SOCKET_HAVE_IPV6 438 { 439 .name = "socket", 440 .revision = 1, 441 .family = NFPROTO_IPV6, 442 .match = socket_mt6_v1_v2, 443 .checkentry = socket_mt_v1_check, 444 .matchsize = sizeof(struct xt_socket_mtinfo1), 445 .hooks = (1 << NF_INET_PRE_ROUTING) | 446 (1 << NF_INET_LOCAL_IN), 447 .me = THIS_MODULE, 448 }, 449 #endif 450 { 451 .name = "socket", 452 .revision = 2, 453 .family = NFPROTO_IPV4, 454 .match = socket_mt4_v1_v2, 455 .checkentry = socket_mt_v2_check, 456 .matchsize = sizeof(struct xt_socket_mtinfo1), 457 .hooks = (1 << NF_INET_PRE_ROUTING) | 458 (1 << NF_INET_LOCAL_IN), 459 .me = THIS_MODULE, 460 }, 461 #ifdef XT_SOCKET_HAVE_IPV6 462 { 463 .name = "socket", 464 .revision = 2, 465 .family = NFPROTO_IPV6, 466 .match = socket_mt6_v1_v2, 467 .checkentry = socket_mt_v2_check, 468 .matchsize = sizeof(struct xt_socket_mtinfo1), 469 .hooks = (1 << NF_INET_PRE_ROUTING) | 470 (1 << NF_INET_LOCAL_IN), 471 .me = THIS_MODULE, 472 }, 473 #endif 474 }; 475 476 static int __init socket_mt_init(void) 477 { 478 nf_defrag_ipv4_enable(); 479 #ifdef XT_SOCKET_HAVE_IPV6 480 nf_defrag_ipv6_enable(); 481 #endif 482 483 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 484 } 485 486 static void __exit socket_mt_exit(void) 487 { 488 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 489 } 490 491 module_init(socket_mt_init); 492 module_exit(socket_mt_exit); 493 494 MODULE_LICENSE("GPL"); 495 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler"); 496 MODULE_DESCRIPTION("x_tables socket match module"); 497 MODULE_ALIAS("ipt_socket"); 498 MODULE_ALIAS("ip6t_socket"); 499