1/* 2 * Transparent proxy support for Linux/iptables 3 * 4 * Copyright (c) 2006-2010 BalaBit IT Ltd. 5 * Author: Balazs Scheidler, 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/ip.h> 16#include <net/checksum.h> 17#include <net/udp.h> 18#include <net/inet_sock.h> 19#include <linux/inetdevice.h> 20#include <linux/netfilter/x_tables.h> 21#include <linux/netfilter_ipv4/ip_tables.h> 22 23#include <net/netfilter/ipv4/nf_defrag_ipv4.h> 24 25#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) 26#define XT_TPROXY_HAVE_IPV6 1 27#include <net/if_inet6.h> 28#include <net/addrconf.h> 29#include <linux/netfilter_ipv6/ip6_tables.h> 30#include <net/netfilter/ipv6/nf_defrag_ipv6.h> 31#endif 32 33#include <net/netfilter/nf_tproxy_core.h> 34#include <linux/netfilter/xt_TPROXY.h> 35 36static bool tproxy_sk_is_transparent(struct sock *sk) 37{ 38 if (sk->sk_state != TCP_TIME_WAIT) { 39 if (inet_sk(sk)->transparent) 40 return true; 41 sock_put(sk); 42 } else { 43 if (inet_twsk(sk)->tw_transparent) 44 return true; 45 inet_twsk_put(inet_twsk(sk)); 46 } 47 return false; 48} 49 50static inline __be32 51tproxy_laddr4(struct sk_buff *skb, __be32 user_laddr, __be32 daddr) 52{ 53 struct in_device *indev; 54 __be32 laddr; 55 56 if (user_laddr) 57 return user_laddr; 58 59 laddr = 0; 60 rcu_read_lock(); 61 indev = __in_dev_get_rcu(skb->dev); 62 for_primary_ifa(indev) { 63 laddr = ifa->ifa_local; 64 break; 65 } endfor_ifa(indev); 66 rcu_read_unlock(); 67 68 return laddr ? laddr : daddr; 69} 70 71/** 72 * tproxy_handle_time_wait4 - handle IPv4 TCP TIME_WAIT reopen redirections 73 * @skb: The skb being processed. 74 * @laddr: IPv4 address to redirect to or zero. 75 * @lport: TCP port to redirect to or zero. 76 * @sk: The TIME_WAIT TCP socket found by the lookup. 77 * 78 * We have to handle SYN packets arriving to TIME_WAIT sockets 79 * differently: instead of reopening the connection we should rather 80 * redirect the new connection to the proxy if there's a listener 81 * socket present. 82 * 83 * tproxy_handle_time_wait4() consumes the socket reference passed in. 84 * 85 * Returns the listener socket if there's one, the TIME_WAIT socket if 86 * no such listener is found, or NULL if the TCP header is incomplete. 87 */ 88static struct sock * 89tproxy_handle_time_wait4(struct sk_buff *skb, __be32 laddr, __be16 lport, 90 struct sock *sk) 91{ 92 const struct iphdr *iph = ip_hdr(skb); 93 struct tcphdr _hdr, *hp; 94 95 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); 96 if (hp == NULL) { 97 inet_twsk_put(inet_twsk(sk)); 98 return NULL; 99 } 100 101 if (hp->syn && !hp->rst && !hp->ack && !hp->fin) { 102 /* SYN to a TIME_WAIT socket, we'd rather redirect it 103 * to a listener socket if there's one */ 104 struct sock *sk2; 105 106 sk2 = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, 107 iph->saddr, laddr ? laddr : iph->daddr, 108 hp->source, lport ? lport : hp->dest, 109 skb->dev, NFT_LOOKUP_LISTENER); 110 if (sk2) { 111 inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row); 112 inet_twsk_put(inet_twsk(sk)); 113 sk = sk2; 114 } 115 } 116 117 return sk; 118} 119 120static unsigned int 121tproxy_tg4(struct sk_buff *skb, __be32 laddr, __be16 lport, 122 u_int32_t mark_mask, u_int32_t mark_value) 123{ 124 const struct iphdr *iph = ip_hdr(skb); 125 struct udphdr _hdr, *hp; 126 struct sock *sk; 127 128 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); 129 if (hp == NULL) 130 return NF_DROP; 131 132 /* check if there's an ongoing connection on the packet 133 * addresses, this happens if the redirect already happened 134 * and the current packet belongs to an already established 135 * connection */ 136 sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, 137 iph->saddr, iph->daddr, 138 hp->source, hp->dest, 139 skb->dev, NFT_LOOKUP_ESTABLISHED); 140 141 laddr = tproxy_laddr4(skb, laddr, iph->daddr); 142 if (!lport) 143 lport = hp->dest; 144 145 /* UDP has no TCP_TIME_WAIT state, so we never enter here */ 146 if (sk && sk->sk_state == TCP_TIME_WAIT) 147 /* reopening a TIME_WAIT connection needs special handling */ 148 sk = tproxy_handle_time_wait4(skb, laddr, lport, sk); 149 else if (!sk) 150 /* no, there's no established connection, check if 151 * there's a listener on the redirected addr/port */ 152 sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, 153 iph->saddr, laddr, 154 hp->source, lport, 155 skb->dev, NFT_LOOKUP_LISTENER); 156 157 /* NOTE: assign_sock consumes our sk reference */ 158 if (sk && tproxy_sk_is_transparent(sk)) { 159 /* This should be in a separate target, but we don't do multiple 160 targets on the same rule yet */ 161 skb->mark = (skb->mark & ~mark_mask) ^ mark_value; 162 163 pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n", 164 iph->protocol, &iph->daddr, ntohs(hp->dest), 165 &laddr, ntohs(lport), skb->mark); 166 167 nf_tproxy_assign_sock(skb, sk); 168 return NF_ACCEPT; 169 } 170 171 pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n", 172 iph->protocol, &iph->saddr, ntohs(hp->source), 173 &iph->daddr, ntohs(hp->dest), skb->mark); 174 return NF_DROP; 175} 176 177static unsigned int 178tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par) 179{ 180 const struct xt_tproxy_target_info *tgi = par->targinfo; 181 182 return tproxy_tg4(skb, tgi->laddr, tgi->lport, tgi->mark_mask, tgi->mark_value); 183} 184 185static unsigned int 186tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par) 187{ 188 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; 189 190 return tproxy_tg4(skb, tgi->laddr.ip, tgi->lport, tgi->mark_mask, tgi->mark_value); 191} 192 193#ifdef XT_TPROXY_HAVE_IPV6 194 195static inline const struct in6_addr * 196tproxy_laddr6(struct sk_buff *skb, const struct in6_addr *user_laddr, 197 const struct in6_addr *daddr) 198{ 199 struct inet6_dev *indev; 200 struct inet6_ifaddr *ifa; 201 struct in6_addr *laddr; 202 203 if (!ipv6_addr_any(user_laddr)) 204 return user_laddr; 205 laddr = NULL; 206 207 rcu_read_lock(); 208 indev = __in6_dev_get(skb->dev); 209 if (indev) 210 list_for_each_entry(ifa, &indev->addr_list, if_list) { 211 if (ifa->flags & (IFA_F_TENTATIVE | IFA_F_DEPRECATED)) 212 continue; 213 214 laddr = &ifa->addr; 215 break; 216 } 217 rcu_read_unlock(); 218 219 return laddr ? laddr : daddr; 220} 221 222/** 223 * tproxy_handle_time_wait6 - handle IPv6 TCP TIME_WAIT reopen redirections 224 * @skb: The skb being processed. 225 * @tproto: Transport protocol. 226 * @thoff: Transport protocol header offset. 227 * @par: Iptables target parameters. 228 * @sk: The TIME_WAIT TCP socket found by the lookup. 229 * 230 * We have to handle SYN packets arriving to TIME_WAIT sockets 231 * differently: instead of reopening the connection we should rather 232 * redirect the new connection to the proxy if there's a listener 233 * socket present. 234 * 235 * tproxy_handle_time_wait6() consumes the socket reference passed in. 236 * 237 * Returns the listener socket if there's one, the TIME_WAIT socket if 238 * no such listener is found, or NULL if the TCP header is incomplete. 239 */ 240static struct sock * 241tproxy_handle_time_wait6(struct sk_buff *skb, int tproto, int thoff, 242 const struct xt_action_param *par, 243 struct sock *sk) 244{ 245 const struct ipv6hdr *iph = ipv6_hdr(skb); 246 struct tcphdr _hdr, *hp; 247 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; 248 249 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); 250 if (hp == NULL) { 251 inet_twsk_put(inet_twsk(sk)); 252 return NULL; 253 } 254 255 if (hp->syn && !hp->rst && !hp->ack && !hp->fin) { 256 /* SYN to a TIME_WAIT socket, we'd rather redirect it 257 * to a listener socket if there's one */ 258 struct sock *sk2; 259 260 sk2 = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto, 261 &iph->saddr, 262 tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr), 263 hp->source, 264 tgi->lport ? tgi->lport : hp->dest, 265 skb->dev, NFT_LOOKUP_LISTENER); 266 if (sk2) { 267 inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row); 268 inet_twsk_put(inet_twsk(sk)); 269 sk = sk2; 270 } 271 } 272 273 return sk; 274} 275 276static unsigned int 277tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par) 278{ 279 const struct ipv6hdr *iph = ipv6_hdr(skb); 280 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; 281 struct udphdr _hdr, *hp; 282 struct sock *sk; 283 const struct in6_addr *laddr; 284 __be16 lport; 285 int thoff = 0; 286 int tproto; 287 288 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); 289 if (tproto < 0) { 290 pr_debug("unable to find transport header in IPv6 packet, dropping\n"); 291 return NF_DROP; 292 } 293 294 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); 295 if (hp == NULL) { 296 pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n"); 297 return NF_DROP; 298 } 299 300 /* check if there's an ongoing connection on the packet 301 * addresses, this happens if the redirect already happened 302 * and the current packet belongs to an already established 303 * connection */ 304 sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto, 305 &iph->saddr, &iph->daddr, 306 hp->source, hp->dest, 307 par->in, NFT_LOOKUP_ESTABLISHED); 308 309 laddr = tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr); 310 lport = tgi->lport ? tgi->lport : hp->dest; 311 312 /* UDP has no TCP_TIME_WAIT state, so we never enter here */ 313 if (sk && sk->sk_state == TCP_TIME_WAIT) 314 /* reopening a TIME_WAIT connection needs special handling */ 315 sk = tproxy_handle_time_wait6(skb, tproto, thoff, par, sk); 316 else if (!sk) 317 /* no there's no established connection, check if 318 * there's a listener on the redirected addr/port */ 319 sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto, 320 &iph->saddr, laddr, 321 hp->source, lport, 322 par->in, NFT_LOOKUP_LISTENER); 323 324 /* NOTE: assign_sock consumes our sk reference */ 325 if (sk && tproxy_sk_is_transparent(sk)) { 326 /* This should be in a separate target, but we don't do multiple 327 targets on the same rule yet */ 328 skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value; 329 330 pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", 331 tproto, &iph->saddr, ntohs(hp->source), 332 laddr, ntohs(lport), skb->mark); 333 334 nf_tproxy_assign_sock(skb, sk); 335 return NF_ACCEPT; 336 } 337 338 pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", 339 tproto, &iph->saddr, ntohs(hp->source), 340 &iph->daddr, ntohs(hp->dest), skb->mark); 341 342 return NF_DROP; 343} 344 345static int tproxy_tg6_check(const struct xt_tgchk_param *par) 346{ 347 const struct ip6t_ip6 *i = par->entryinfo; 348 349 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) 350 && !(i->flags & IP6T_INV_PROTO)) 351 return 0; 352 353 pr_info("Can be used only in combination with " 354 "either -p tcp or -p udp\n"); 355 return -EINVAL; 356} 357#endif 358 359static int tproxy_tg4_check(const struct xt_tgchk_param *par) 360{ 361 const struct ipt_ip *i = par->entryinfo; 362 363 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) 364 && !(i->invflags & IPT_INV_PROTO)) 365 return 0; 366 367 pr_info("Can be used only in combination with " 368 "either -p tcp or -p udp\n"); 369 return -EINVAL; 370} 371 372static struct xt_target tproxy_tg_reg[] __read_mostly = { 373 { 374 .name = "TPROXY", 375 .family = NFPROTO_IPV4, 376 .table = "mangle", 377 .target = tproxy_tg4_v0, 378 .revision = 0, 379 .targetsize = sizeof(struct xt_tproxy_target_info), 380 .checkentry = tproxy_tg4_check, 381 .hooks = 1 << NF_INET_PRE_ROUTING, 382 .me = THIS_MODULE, 383 }, 384 { 385 .name = "TPROXY", 386 .family = NFPROTO_IPV4, 387 .table = "mangle", 388 .target = tproxy_tg4_v1, 389 .revision = 1, 390 .targetsize = sizeof(struct xt_tproxy_target_info_v1), 391 .checkentry = tproxy_tg4_check, 392 .hooks = 1 << NF_INET_PRE_ROUTING, 393 .me = THIS_MODULE, 394 }, 395#ifdef XT_TPROXY_HAVE_IPV6 396 { 397 .name = "TPROXY", 398 .family = NFPROTO_IPV6, 399 .table = "mangle", 400 .target = tproxy_tg6_v1, 401 .revision = 1, 402 .targetsize = sizeof(struct xt_tproxy_target_info_v1), 403 .checkentry = tproxy_tg6_check, 404 .hooks = 1 << NF_INET_PRE_ROUTING, 405 .me = THIS_MODULE, 406 }, 407#endif 408 409}; 410 411static int __init tproxy_tg_init(void) 412{ 413 nf_defrag_ipv4_enable(); 414#ifdef XT_TPROXY_HAVE_IPV6 415 nf_defrag_ipv6_enable(); 416#endif 417 418 return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); 419} 420 421static void __exit tproxy_tg_exit(void) 422{ 423 xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); 424} 425 426module_init(tproxy_tg_init); 427module_exit(tproxy_tg_exit); 428MODULE_LICENSE("GPL"); 429MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs"); 430MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module."); 431MODULE_ALIAS("ipt_TPROXY"); 432MODULE_ALIAS("ip6t_TPROXY"); 433