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/nf_tproxy_core.h> 23 #include <net/netfilter/ipv4/nf_defrag_ipv4.h> 24 25 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) 26 #define XT_SOCKET_HAVE_IPV6 1 27 #include <linux/netfilter_ipv6/ip6_tables.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 static bool 105 socket_match(const struct sk_buff *skb, struct xt_action_param *par, 106 const struct xt_socket_mtinfo1 *info) 107 { 108 const struct iphdr *iph = ip_hdr(skb); 109 struct udphdr _hdr, *hp = NULL; 110 struct sock *sk = skb->sk; 111 __be32 uninitialized_var(daddr), uninitialized_var(saddr); 112 __be16 uninitialized_var(dport), uninitialized_var(sport); 113 u8 uninitialized_var(protocol); 114 #ifdef XT_SOCKET_HAVE_CONNTRACK 115 struct nf_conn const *ct; 116 enum ip_conntrack_info ctinfo; 117 #endif 118 119 if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) { 120 hp = skb_header_pointer(skb, ip_hdrlen(skb), 121 sizeof(_hdr), &_hdr); 122 if (hp == NULL) 123 return false; 124 125 protocol = iph->protocol; 126 saddr = iph->saddr; 127 sport = hp->source; 128 daddr = iph->daddr; 129 dport = hp->dest; 130 131 } else if (iph->protocol == IPPROTO_ICMP) { 132 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr, 133 &sport, &dport)) 134 return false; 135 } else { 136 return false; 137 } 138 139 #ifdef XT_SOCKET_HAVE_CONNTRACK 140 /* Do the lookup with the original socket address in case this is a 141 * reply packet of an established SNAT-ted connection. */ 142 143 ct = nf_ct_get(skb, &ctinfo); 144 if (ct && !nf_ct_is_untracked(ct) && 145 ((iph->protocol != IPPROTO_ICMP && 146 ctinfo == IP_CT_ESTABLISHED_REPLY) || 147 (iph->protocol == IPPROTO_ICMP && 148 ctinfo == IP_CT_RELATED_REPLY)) && 149 (ct->status & IPS_SRC_NAT_DONE)) { 150 151 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip; 152 dport = (iph->protocol == IPPROTO_TCP) ? 153 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port : 154 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port; 155 } 156 #endif 157 158 if (!sk) 159 sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol, 160 saddr, daddr, sport, dport, 161 par->in, NFT_LOOKUP_ANY); 162 if (sk) { 163 bool wildcard; 164 bool transparent = true; 165 166 /* Ignore sockets listening on INADDR_ANY, 167 * unless XT_SOCKET_NOWILDCARD is set 168 */ 169 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 170 sk->sk_state != TCP_TIME_WAIT && 171 inet_sk(sk)->inet_rcv_saddr == 0); 172 173 /* Ignore non-transparent sockets, 174 if XT_SOCKET_TRANSPARENT is used */ 175 if (info->flags & XT_SOCKET_TRANSPARENT) 176 transparent = ((sk->sk_state != TCP_TIME_WAIT && 177 inet_sk(sk)->transparent) || 178 (sk->sk_state == TCP_TIME_WAIT && 179 inet_twsk(sk)->tw_transparent)); 180 181 if (sk != skb->sk) 182 xt_socket_put_sk(sk); 183 184 if (wildcard || !transparent) 185 sk = NULL; 186 } 187 188 pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n", 189 protocol, &saddr, ntohs(sport), 190 &daddr, ntohs(dport), 191 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk); 192 193 return (sk != NULL); 194 } 195 196 static bool 197 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par) 198 { 199 static struct xt_socket_mtinfo1 xt_info_v0 = { 200 .flags = 0, 201 }; 202 203 return socket_match(skb, par, &xt_info_v0); 204 } 205 206 static bool 207 socket_mt4_v1_v2(const struct sk_buff *skb, struct xt_action_param *par) 208 { 209 return socket_match(skb, par, par->matchinfo); 210 } 211 212 #ifdef XT_SOCKET_HAVE_IPV6 213 214 static int 215 extract_icmp6_fields(const struct sk_buff *skb, 216 unsigned int outside_hdrlen, 217 int *protocol, 218 struct in6_addr **raddr, 219 struct in6_addr **laddr, 220 __be16 *rport, 221 __be16 *lport) 222 { 223 struct ipv6hdr *inside_iph, _inside_iph; 224 struct icmp6hdr *icmph, _icmph; 225 __be16 *ports, _ports[2]; 226 u8 inside_nexthdr; 227 __be16 inside_fragoff; 228 int inside_hdrlen; 229 230 icmph = skb_header_pointer(skb, outside_hdrlen, 231 sizeof(_icmph), &_icmph); 232 if (icmph == NULL) 233 return 1; 234 235 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK) 236 return 1; 237 238 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), sizeof(_inside_iph), &_inside_iph); 239 if (inside_iph == NULL) 240 return 1; 241 inside_nexthdr = inside_iph->nexthdr; 242 243 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph), 244 &inside_nexthdr, &inside_fragoff); 245 if (inside_hdrlen < 0) 246 return 1; /* hjm: Packet has no/incomplete transport layer headers. */ 247 248 if (inside_nexthdr != IPPROTO_TCP && 249 inside_nexthdr != IPPROTO_UDP) 250 return 1; 251 252 ports = skb_header_pointer(skb, inside_hdrlen, 253 sizeof(_ports), &_ports); 254 if (ports == NULL) 255 return 1; 256 257 /* the inside IP packet is the one quoted from our side, thus 258 * its saddr is the local address */ 259 *protocol = inside_nexthdr; 260 *laddr = &inside_iph->saddr; 261 *lport = ports[0]; 262 *raddr = &inside_iph->daddr; 263 *rport = ports[1]; 264 265 return 0; 266 } 267 268 static bool 269 socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par) 270 { 271 struct ipv6hdr *iph = ipv6_hdr(skb); 272 struct udphdr _hdr, *hp = NULL; 273 struct sock *sk = skb->sk; 274 struct in6_addr *daddr = NULL, *saddr = NULL; 275 __be16 uninitialized_var(dport), uninitialized_var(sport); 276 int thoff = 0, uninitialized_var(tproto); 277 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 278 279 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); 280 if (tproto < 0) { 281 pr_debug("unable to find transport header in IPv6 packet, dropping\n"); 282 return NF_DROP; 283 } 284 285 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) { 286 hp = skb_header_pointer(skb, thoff, 287 sizeof(_hdr), &_hdr); 288 if (hp == NULL) 289 return false; 290 291 saddr = &iph->saddr; 292 sport = hp->source; 293 daddr = &iph->daddr; 294 dport = hp->dest; 295 296 } else if (tproto == IPPROTO_ICMPV6) { 297 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr, 298 &sport, &dport)) 299 return false; 300 } else { 301 return false; 302 } 303 304 if (!sk) 305 sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto, 306 saddr, daddr, sport, dport, 307 par->in, NFT_LOOKUP_ANY); 308 if (sk) { 309 bool wildcard; 310 bool transparent = true; 311 312 /* Ignore sockets listening on INADDR_ANY 313 * unless XT_SOCKET_NOWILDCARD is set 314 */ 315 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 316 sk->sk_state != TCP_TIME_WAIT && 317 ipv6_addr_any(&inet6_sk(sk)->rcv_saddr)); 318 319 /* Ignore non-transparent sockets, 320 if XT_SOCKET_TRANSPARENT is used */ 321 if (info->flags & XT_SOCKET_TRANSPARENT) 322 transparent = ((sk->sk_state != TCP_TIME_WAIT && 323 inet_sk(sk)->transparent) || 324 (sk->sk_state == TCP_TIME_WAIT && 325 inet_twsk(sk)->tw_transparent)); 326 327 if (sk != skb->sk) 328 xt_socket_put_sk(sk); 329 330 if (wildcard || !transparent) 331 sk = NULL; 332 } 333 334 pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu " 335 "(orig %pI6:%hu) sock %p\n", 336 tproto, saddr, ntohs(sport), 337 daddr, ntohs(dport), 338 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk); 339 340 return (sk != NULL); 341 } 342 #endif 343 344 static int socket_mt_v1_check(const struct xt_mtchk_param *par) 345 { 346 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 347 348 if (info->flags & ~XT_SOCKET_FLAGS_V1) { 349 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1); 350 return -EINVAL; 351 } 352 return 0; 353 } 354 355 static int socket_mt_v2_check(const struct xt_mtchk_param *par) 356 { 357 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo; 358 359 if (info->flags & ~XT_SOCKET_FLAGS_V2) { 360 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2); 361 return -EINVAL; 362 } 363 return 0; 364 } 365 366 static struct xt_match socket_mt_reg[] __read_mostly = { 367 { 368 .name = "socket", 369 .revision = 0, 370 .family = NFPROTO_IPV4, 371 .match = socket_mt4_v0, 372 .hooks = (1 << NF_INET_PRE_ROUTING) | 373 (1 << NF_INET_LOCAL_IN), 374 .me = THIS_MODULE, 375 }, 376 { 377 .name = "socket", 378 .revision = 1, 379 .family = NFPROTO_IPV4, 380 .match = socket_mt4_v1_v2, 381 .checkentry = socket_mt_v1_check, 382 .matchsize = sizeof(struct xt_socket_mtinfo1), 383 .hooks = (1 << NF_INET_PRE_ROUTING) | 384 (1 << NF_INET_LOCAL_IN), 385 .me = THIS_MODULE, 386 }, 387 #ifdef XT_SOCKET_HAVE_IPV6 388 { 389 .name = "socket", 390 .revision = 1, 391 .family = NFPROTO_IPV6, 392 .match = socket_mt6_v1_v2, 393 .checkentry = socket_mt_v1_check, 394 .matchsize = sizeof(struct xt_socket_mtinfo1), 395 .hooks = (1 << NF_INET_PRE_ROUTING) | 396 (1 << NF_INET_LOCAL_IN), 397 .me = THIS_MODULE, 398 }, 399 #endif 400 { 401 .name = "socket", 402 .revision = 2, 403 .family = NFPROTO_IPV4, 404 .match = socket_mt4_v1_v2, 405 .checkentry = socket_mt_v2_check, 406 .matchsize = sizeof(struct xt_socket_mtinfo1), 407 .hooks = (1 << NF_INET_PRE_ROUTING) | 408 (1 << NF_INET_LOCAL_IN), 409 .me = THIS_MODULE, 410 }, 411 #ifdef XT_SOCKET_HAVE_IPV6 412 { 413 .name = "socket", 414 .revision = 2, 415 .family = NFPROTO_IPV6, 416 .match = socket_mt6_v1_v2, 417 .checkentry = socket_mt_v2_check, 418 .matchsize = sizeof(struct xt_socket_mtinfo1), 419 .hooks = (1 << NF_INET_PRE_ROUTING) | 420 (1 << NF_INET_LOCAL_IN), 421 .me = THIS_MODULE, 422 }, 423 #endif 424 }; 425 426 static int __init socket_mt_init(void) 427 { 428 nf_defrag_ipv4_enable(); 429 #ifdef XT_SOCKET_HAVE_IPV6 430 nf_defrag_ipv6_enable(); 431 #endif 432 433 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 434 } 435 436 static void __exit socket_mt_exit(void) 437 { 438 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 439 } 440 441 module_init(socket_mt_init); 442 module_exit(socket_mt_exit); 443 444 MODULE_LICENSE("GPL"); 445 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler"); 446 MODULE_DESCRIPTION("x_tables socket match module"); 447 MODULE_ALIAS("ipt_socket"); 448 MODULE_ALIAS("ip6t_socket"); 449