1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Transparent proxy support for Linux/iptables 4 * 5 * Copyright (c) 2006-2010 BalaBit IT Ltd. 6 * Author: Balazs Scheidler, Krisztian Kovacs 7 */ 8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 9 #include <linux/module.h> 10 #include <linux/skbuff.h> 11 #include <linux/ip.h> 12 #include <net/checksum.h> 13 #include <net/udp.h> 14 #include <net/tcp.h> 15 #include <net/inet_sock.h> 16 #include <net/inet_hashtables.h> 17 #include <linux/inetdevice.h> 18 #include <linux/netfilter/x_tables.h> 19 #include <linux/netfilter_ipv4/ip_tables.h> 20 21 #include <net/netfilter/ipv4/nf_defrag_ipv4.h> 22 23 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) 24 #define XT_TPROXY_HAVE_IPV6 1 25 #include <net/if_inet6.h> 26 #include <net/addrconf.h> 27 #include <net/inet6_hashtables.h> 28 #include <linux/netfilter_ipv6/ip6_tables.h> 29 #include <net/netfilter/ipv6/nf_defrag_ipv6.h> 30 #endif 31 32 #include <net/netfilter/nf_tproxy.h> 33 #include <linux/netfilter/xt_TPROXY.h> 34 35 static unsigned int 36 tproxy_tg4(struct net *net, struct sk_buff *skb, __be32 laddr, __be16 lport, 37 u_int32_t mark_mask, u_int32_t mark_value) 38 { 39 const struct iphdr *iph = ip_hdr(skb); 40 struct udphdr _hdr, *hp; 41 struct sock *sk; 42 43 hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); 44 if (hp == NULL) 45 return NF_DROP; 46 47 /* check if there's an ongoing connection on the packet 48 * addresses, this happens if the redirect already happened 49 * and the current packet belongs to an already established 50 * connection */ 51 sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol, 52 iph->saddr, iph->daddr, 53 hp->source, hp->dest, 54 skb->dev, NF_TPROXY_LOOKUP_ESTABLISHED); 55 56 laddr = nf_tproxy_laddr4(skb, laddr, iph->daddr); 57 if (!lport) 58 lport = hp->dest; 59 60 /* UDP has no TCP_TIME_WAIT state, so we never enter here */ 61 if (sk && sk->sk_state == TCP_TIME_WAIT) 62 /* reopening a TIME_WAIT connection needs special handling */ 63 sk = nf_tproxy_handle_time_wait4(net, skb, laddr, lport, sk); 64 else if (!sk) 65 /* no, there's no established connection, check if 66 * there's a listener on the redirected addr/port */ 67 sk = nf_tproxy_get_sock_v4(net, skb, iph->protocol, 68 iph->saddr, laddr, 69 hp->source, lport, 70 skb->dev, NF_TPROXY_LOOKUP_LISTENER); 71 72 /* NOTE: assign_sock consumes our sk reference */ 73 if (sk && nf_tproxy_sk_is_transparent(sk)) { 74 /* This should be in a separate target, but we don't do multiple 75 targets on the same rule yet */ 76 skb->mark = (skb->mark & ~mark_mask) ^ mark_value; 77 78 pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n", 79 iph->protocol, &iph->daddr, ntohs(hp->dest), 80 &laddr, ntohs(lport), skb->mark); 81 82 nf_tproxy_assign_sock(skb, sk); 83 return NF_ACCEPT; 84 } 85 86 pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n", 87 iph->protocol, &iph->saddr, ntohs(hp->source), 88 &iph->daddr, ntohs(hp->dest), skb->mark); 89 return NF_DROP; 90 } 91 92 static unsigned int 93 tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par) 94 { 95 const struct xt_tproxy_target_info *tgi = par->targinfo; 96 97 return tproxy_tg4(xt_net(par), skb, tgi->laddr, tgi->lport, 98 tgi->mark_mask, tgi->mark_value); 99 } 100 101 static unsigned int 102 tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par) 103 { 104 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; 105 106 return tproxy_tg4(xt_net(par), skb, tgi->laddr.ip, tgi->lport, 107 tgi->mark_mask, tgi->mark_value); 108 } 109 110 #ifdef XT_TPROXY_HAVE_IPV6 111 112 static unsigned int 113 tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par) 114 { 115 const struct ipv6hdr *iph = ipv6_hdr(skb); 116 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; 117 struct udphdr _hdr, *hp; 118 struct sock *sk; 119 const struct in6_addr *laddr; 120 __be16 lport; 121 int thoff = 0; 122 int tproto; 123 124 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); 125 if (tproto < 0) { 126 pr_debug("unable to find transport header in IPv6 packet, dropping\n"); 127 return NF_DROP; 128 } 129 130 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); 131 if (hp == NULL) { 132 pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n"); 133 return NF_DROP; 134 } 135 136 /* check if there's an ongoing connection on the packet 137 * addresses, this happens if the redirect already happened 138 * and the current packet belongs to an already established 139 * connection */ 140 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, tproto, 141 &iph->saddr, &iph->daddr, 142 hp->source, hp->dest, 143 xt_in(par), NF_TPROXY_LOOKUP_ESTABLISHED); 144 145 laddr = nf_tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr); 146 lport = tgi->lport ? tgi->lport : hp->dest; 147 148 /* UDP has no TCP_TIME_WAIT state, so we never enter here */ 149 if (sk && sk->sk_state == TCP_TIME_WAIT) { 150 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; 151 /* reopening a TIME_WAIT connection needs special handling */ 152 sk = nf_tproxy_handle_time_wait6(skb, tproto, thoff, 153 xt_net(par), 154 &tgi->laddr.in6, 155 tgi->lport, 156 sk); 157 } 158 else if (!sk) 159 /* no there's no established connection, check if 160 * there's a listener on the redirected addr/port */ 161 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, 162 tproto, &iph->saddr, laddr, 163 hp->source, lport, 164 xt_in(par), NF_TPROXY_LOOKUP_LISTENER); 165 166 /* NOTE: assign_sock consumes our sk reference */ 167 if (sk && nf_tproxy_sk_is_transparent(sk)) { 168 /* This should be in a separate target, but we don't do multiple 169 targets on the same rule yet */ 170 skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value; 171 172 pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", 173 tproto, &iph->saddr, ntohs(hp->source), 174 laddr, ntohs(lport), skb->mark); 175 176 nf_tproxy_assign_sock(skb, sk); 177 return NF_ACCEPT; 178 } 179 180 pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", 181 tproto, &iph->saddr, ntohs(hp->source), 182 &iph->daddr, ntohs(hp->dest), skb->mark); 183 184 return NF_DROP; 185 } 186 187 static int tproxy_tg6_check(const struct xt_tgchk_param *par) 188 { 189 const struct ip6t_ip6 *i = par->entryinfo; 190 int err; 191 192 err = nf_defrag_ipv6_enable(par->net); 193 if (err) 194 return err; 195 196 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) && 197 !(i->invflags & IP6T_INV_PROTO)) 198 return 0; 199 200 pr_info_ratelimited("Can be used only with -p tcp or -p udp\n"); 201 return -EINVAL; 202 } 203 #endif 204 205 static int tproxy_tg4_check(const struct xt_tgchk_param *par) 206 { 207 const struct ipt_ip *i = par->entryinfo; 208 int err; 209 210 err = nf_defrag_ipv4_enable(par->net); 211 if (err) 212 return err; 213 214 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) 215 && !(i->invflags & IPT_INV_PROTO)) 216 return 0; 217 218 pr_info_ratelimited("Can be used only with -p tcp or -p udp\n"); 219 return -EINVAL; 220 } 221 222 static struct xt_target tproxy_tg_reg[] __read_mostly = { 223 { 224 .name = "TPROXY", 225 .family = NFPROTO_IPV4, 226 .table = "mangle", 227 .target = tproxy_tg4_v0, 228 .revision = 0, 229 .targetsize = sizeof(struct xt_tproxy_target_info), 230 .checkentry = tproxy_tg4_check, 231 .hooks = 1 << NF_INET_PRE_ROUTING, 232 .me = THIS_MODULE, 233 }, 234 { 235 .name = "TPROXY", 236 .family = NFPROTO_IPV4, 237 .table = "mangle", 238 .target = tproxy_tg4_v1, 239 .revision = 1, 240 .targetsize = sizeof(struct xt_tproxy_target_info_v1), 241 .checkentry = tproxy_tg4_check, 242 .hooks = 1 << NF_INET_PRE_ROUTING, 243 .me = THIS_MODULE, 244 }, 245 #ifdef XT_TPROXY_HAVE_IPV6 246 { 247 .name = "TPROXY", 248 .family = NFPROTO_IPV6, 249 .table = "mangle", 250 .target = tproxy_tg6_v1, 251 .revision = 1, 252 .targetsize = sizeof(struct xt_tproxy_target_info_v1), 253 .checkentry = tproxy_tg6_check, 254 .hooks = 1 << NF_INET_PRE_ROUTING, 255 .me = THIS_MODULE, 256 }, 257 #endif 258 259 }; 260 261 static int __init tproxy_tg_init(void) 262 { 263 return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); 264 } 265 266 static void __exit tproxy_tg_exit(void) 267 { 268 xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); 269 } 270 271 module_init(tproxy_tg_init); 272 module_exit(tproxy_tg_exit); 273 MODULE_LICENSE("GPL"); 274 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs"); 275 MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module."); 276 MODULE_ALIAS("ipt_TPROXY"); 277 MODULE_ALIAS("ip6t_TPROXY"); 278