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/tcp.h> 19 #include <net/inet_sock.h> 20 #include <net/inet_hashtables.h> 21 #include <linux/inetdevice.h> 22 #include <linux/netfilter/x_tables.h> 23 #include <linux/netfilter_ipv4/ip_tables.h> 24 25 #include <net/netfilter/ipv4/nf_defrag_ipv4.h> 26 27 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) 28 #define XT_TPROXY_HAVE_IPV6 1 29 #include <net/if_inet6.h> 30 #include <net/addrconf.h> 31 #include <net/inet6_hashtables.h> 32 #include <linux/netfilter_ipv6/ip6_tables.h> 33 #include <net/netfilter/ipv6/nf_defrag_ipv6.h> 34 #endif 35 36 #include <net/netfilter/nf_tproxy.h> 37 #include <linux/netfilter/xt_TPROXY.h> 38 39 static unsigned int 40 tproxy_tg4(struct net *net, struct sk_buff *skb, __be32 laddr, __be16 lport, 41 u_int32_t mark_mask, u_int32_t mark_value) 42 { 43 const struct iphdr *iph = ip_hdr(skb); 44 struct udphdr _hdr, *hp; 45 struct sock *sk; 46 47 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); 48 if (hp == NULL) 49 return NF_DROP; 50 51 /* check if there's an ongoing connection on the packet 52 * addresses, this happens if the redirect already happened 53 * and the current packet belongs to an already established 54 * connection */ 55 sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol, 56 iph->saddr, iph->daddr, 57 hp->source, hp->dest, 58 skb->dev, NF_TPROXY_LOOKUP_ESTABLISHED); 59 60 laddr = nf_tproxy_laddr4(skb, laddr, iph->daddr); 61 if (!lport) 62 lport = hp->dest; 63 64 /* UDP has no TCP_TIME_WAIT state, so we never enter here */ 65 if (sk && sk->sk_state == TCP_TIME_WAIT) 66 /* reopening a TIME_WAIT connection needs special handling */ 67 sk = nf_tproxy_handle_time_wait4(net, skb, laddr, lport, sk); 68 else if (!sk) 69 /* no, there's no established connection, check if 70 * there's a listener on the redirected addr/port */ 71 sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol, 72 iph->saddr, laddr, 73 hp->source, lport, 74 skb->dev, NF_TPROXY_LOOKUP_LISTENER); 75 76 /* NOTE: assign_sock consumes our sk reference */ 77 if (sk && nf_tproxy_sk_is_transparent(sk)) { 78 /* This should be in a separate target, but we don't do multiple 79 targets on the same rule yet */ 80 skb->mark = (skb->mark & ~mark_mask) ^ mark_value; 81 82 pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n", 83 iph->protocol, &iph->daddr, ntohs(hp->dest), 84 &laddr, ntohs(lport), skb->mark); 85 86 nf_tproxy_assign_sock(skb, sk); 87 return NF_ACCEPT; 88 } 89 90 pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n", 91 iph->protocol, &iph->saddr, ntohs(hp->source), 92 &iph->daddr, ntohs(hp->dest), skb->mark); 93 return NF_DROP; 94 } 95 96 static unsigned int 97 tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par) 98 { 99 const struct xt_tproxy_target_info *tgi = par->targinfo; 100 101 return tproxy_tg4(xt_net(par), skb, tgi->laddr, tgi->lport, 102 tgi->mark_mask, tgi->mark_value); 103 } 104 105 static unsigned int 106 tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par) 107 { 108 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; 109 110 return tproxy_tg4(xt_net(par), skb, tgi->laddr.ip, tgi->lport, 111 tgi->mark_mask, tgi->mark_value); 112 } 113 114 #ifdef XT_TPROXY_HAVE_IPV6 115 116 static unsigned int 117 tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par) 118 { 119 const struct ipv6hdr *iph = ipv6_hdr(skb); 120 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; 121 struct udphdr _hdr, *hp; 122 struct sock *sk; 123 const struct in6_addr *laddr; 124 __be16 lport; 125 int thoff = 0; 126 int tproto; 127 128 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); 129 if (tproto < 0) { 130 pr_debug("unable to find transport header in IPv6 packet, dropping\n"); 131 return NF_DROP; 132 } 133 134 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); 135 if (hp == NULL) { 136 pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n"); 137 return NF_DROP; 138 } 139 140 /* check if there's an ongoing connection on the packet 141 * addresses, this happens if the redirect already happened 142 * and the current packet belongs to an already established 143 * connection */ 144 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, tproto, 145 &iph->saddr, &iph->daddr, 146 hp->source, hp->dest, 147 xt_in(par), NF_TPROXY_LOOKUP_ESTABLISHED); 148 149 laddr = nf_tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr); 150 lport = tgi->lport ? tgi->lport : hp->dest; 151 152 /* UDP has no TCP_TIME_WAIT state, so we never enter here */ 153 if (sk && sk->sk_state == TCP_TIME_WAIT) { 154 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; 155 /* reopening a TIME_WAIT connection needs special handling */ 156 sk = nf_tproxy_handle_time_wait6(skb, tproto, thoff, 157 xt_net(par), 158 &tgi->laddr.in6, 159 tgi->lport, 160 sk); 161 } 162 else if (!sk) 163 /* no there's no established connection, check if 164 * there's a listener on the redirected addr/port */ 165 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, 166 tproto, &iph->saddr, laddr, 167 hp->source, lport, 168 xt_in(par), NF_TPROXY_LOOKUP_LISTENER); 169 170 /* NOTE: assign_sock consumes our sk reference */ 171 if (sk && nf_tproxy_sk_is_transparent(sk)) { 172 /* This should be in a separate target, but we don't do multiple 173 targets on the same rule yet */ 174 skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value; 175 176 pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", 177 tproto, &iph->saddr, ntohs(hp->source), 178 laddr, ntohs(lport), skb->mark); 179 180 nf_tproxy_assign_sock(skb, sk); 181 return NF_ACCEPT; 182 } 183 184 pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", 185 tproto, &iph->saddr, ntohs(hp->source), 186 &iph->daddr, ntohs(hp->dest), skb->mark); 187 188 return NF_DROP; 189 } 190 191 static int tproxy_tg6_check(const struct xt_tgchk_param *par) 192 { 193 const struct ip6t_ip6 *i = par->entryinfo; 194 int err; 195 196 err = nf_defrag_ipv6_enable(par->net); 197 if (err) 198 return err; 199 200 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) && 201 !(i->invflags & IP6T_INV_PROTO)) 202 return 0; 203 204 pr_info_ratelimited("Can be used only with -p tcp or -p udp\n"); 205 return -EINVAL; 206 } 207 #endif 208 209 static int tproxy_tg4_check(const struct xt_tgchk_param *par) 210 { 211 const struct ipt_ip *i = par->entryinfo; 212 int err; 213 214 err = nf_defrag_ipv4_enable(par->net); 215 if (err) 216 return err; 217 218 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) 219 && !(i->invflags & IPT_INV_PROTO)) 220 return 0; 221 222 pr_info_ratelimited("Can be used only with -p tcp or -p udp\n"); 223 return -EINVAL; 224 } 225 226 static struct xt_target tproxy_tg_reg[] __read_mostly = { 227 { 228 .name = "TPROXY", 229 .family = NFPROTO_IPV4, 230 .table = "mangle", 231 .target = tproxy_tg4_v0, 232 .revision = 0, 233 .targetsize = sizeof(struct xt_tproxy_target_info), 234 .checkentry = tproxy_tg4_check, 235 .hooks = 1 << NF_INET_PRE_ROUTING, 236 .me = THIS_MODULE, 237 }, 238 { 239 .name = "TPROXY", 240 .family = NFPROTO_IPV4, 241 .table = "mangle", 242 .target = tproxy_tg4_v1, 243 .revision = 1, 244 .targetsize = sizeof(struct xt_tproxy_target_info_v1), 245 .checkentry = tproxy_tg4_check, 246 .hooks = 1 << NF_INET_PRE_ROUTING, 247 .me = THIS_MODULE, 248 }, 249 #ifdef XT_TPROXY_HAVE_IPV6 250 { 251 .name = "TPROXY", 252 .family = NFPROTO_IPV6, 253 .table = "mangle", 254 .target = tproxy_tg6_v1, 255 .revision = 1, 256 .targetsize = sizeof(struct xt_tproxy_target_info_v1), 257 .checkentry = tproxy_tg6_check, 258 .hooks = 1 << NF_INET_PRE_ROUTING, 259 .me = THIS_MODULE, 260 }, 261 #endif 262 263 }; 264 265 static int __init tproxy_tg_init(void) 266 { 267 return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); 268 } 269 270 static void __exit tproxy_tg_exit(void) 271 { 272 xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); 273 } 274 275 module_init(tproxy_tg_init); 276 module_exit(tproxy_tg_exit); 277 MODULE_LICENSE("GPL"); 278 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs"); 279 MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module."); 280 MODULE_ALIAS("ipt_TPROXY"); 281 MODULE_ALIAS("ip6t_TPROXY"); 282