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 nf_tproxy_assign_sock(skb, sk); 78 return NF_ACCEPT; 79 } 80 81 return NF_DROP; 82 } 83 84 static unsigned int 85 tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par) 86 { 87 const struct xt_tproxy_target_info *tgi = par->targinfo; 88 89 return tproxy_tg4(xt_net(par), skb, tgi->laddr, tgi->lport, 90 tgi->mark_mask, tgi->mark_value); 91 } 92 93 static unsigned int 94 tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par) 95 { 96 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; 97 98 return tproxy_tg4(xt_net(par), skb, tgi->laddr.ip, tgi->lport, 99 tgi->mark_mask, tgi->mark_value); 100 } 101 102 #ifdef XT_TPROXY_HAVE_IPV6 103 104 static unsigned int 105 tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par) 106 { 107 const struct ipv6hdr *iph = ipv6_hdr(skb); 108 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; 109 struct udphdr _hdr, *hp; 110 struct sock *sk; 111 const struct in6_addr *laddr; 112 __be16 lport; 113 int thoff = 0; 114 int tproto; 115 116 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); 117 if (tproto < 0) 118 return NF_DROP; 119 120 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); 121 if (!hp) 122 return NF_DROP; 123 124 /* check if there's an ongoing connection on the packet 125 * addresses, this happens if the redirect already happened 126 * and the current packet belongs to an already established 127 * connection */ 128 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, tproto, 129 &iph->saddr, &iph->daddr, 130 hp->source, hp->dest, 131 xt_in(par), NF_TPROXY_LOOKUP_ESTABLISHED); 132 133 laddr = nf_tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr); 134 lport = tgi->lport ? tgi->lport : hp->dest; 135 136 /* UDP has no TCP_TIME_WAIT state, so we never enter here */ 137 if (sk && sk->sk_state == TCP_TIME_WAIT) { 138 const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; 139 /* reopening a TIME_WAIT connection needs special handling */ 140 sk = nf_tproxy_handle_time_wait6(skb, tproto, thoff, 141 xt_net(par), 142 &tgi->laddr.in6, 143 tgi->lport, 144 sk); 145 } 146 else if (!sk) 147 /* no there's no established connection, check if 148 * there's a listener on the redirected addr/port */ 149 sk = nf_tproxy_get_sock_v6(xt_net(par), skb, thoff, 150 tproto, &iph->saddr, laddr, 151 hp->source, lport, 152 xt_in(par), NF_TPROXY_LOOKUP_LISTENER); 153 154 /* NOTE: assign_sock consumes our sk reference */ 155 if (sk && nf_tproxy_sk_is_transparent(sk)) { 156 /* This should be in a separate target, but we don't do multiple 157 targets on the same rule yet */ 158 skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value; 159 nf_tproxy_assign_sock(skb, sk); 160 return NF_ACCEPT; 161 } 162 163 return NF_DROP; 164 } 165 166 static int tproxy_tg6_check(const struct xt_tgchk_param *par) 167 { 168 const struct ip6t_ip6 *i = par->entryinfo; 169 int err; 170 171 err = nf_defrag_ipv6_enable(par->net); 172 if (err) 173 return err; 174 175 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) && 176 !(i->invflags & IP6T_INV_PROTO)) 177 return 0; 178 179 pr_info_ratelimited("Can be used only with -p tcp or -p udp\n"); 180 return -EINVAL; 181 } 182 183 static void tproxy_tg6_destroy(const struct xt_tgdtor_param *par) 184 { 185 nf_defrag_ipv6_disable(par->net); 186 } 187 #endif 188 189 static int tproxy_tg4_check(const struct xt_tgchk_param *par) 190 { 191 const struct ipt_ip *i = par->entryinfo; 192 int err; 193 194 err = nf_defrag_ipv4_enable(par->net); 195 if (err) 196 return err; 197 198 if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) 199 && !(i->invflags & IPT_INV_PROTO)) 200 return 0; 201 202 pr_info_ratelimited("Can be used only with -p tcp or -p udp\n"); 203 return -EINVAL; 204 } 205 206 static void tproxy_tg4_destroy(const struct xt_tgdtor_param *par) 207 { 208 nf_defrag_ipv4_disable(par->net); 209 } 210 211 static struct xt_target tproxy_tg_reg[] __read_mostly = { 212 { 213 .name = "TPROXY", 214 .family = NFPROTO_IPV4, 215 .table = "mangle", 216 .target = tproxy_tg4_v0, 217 .revision = 0, 218 .targetsize = sizeof(struct xt_tproxy_target_info), 219 .checkentry = tproxy_tg4_check, 220 .destroy = tproxy_tg4_destroy, 221 .hooks = 1 << NF_INET_PRE_ROUTING, 222 .me = THIS_MODULE, 223 }, 224 { 225 .name = "TPROXY", 226 .family = NFPROTO_IPV4, 227 .table = "mangle", 228 .target = tproxy_tg4_v1, 229 .revision = 1, 230 .targetsize = sizeof(struct xt_tproxy_target_info_v1), 231 .checkentry = tproxy_tg4_check, 232 .destroy = tproxy_tg4_destroy, 233 .hooks = 1 << NF_INET_PRE_ROUTING, 234 .me = THIS_MODULE, 235 }, 236 #ifdef XT_TPROXY_HAVE_IPV6 237 { 238 .name = "TPROXY", 239 .family = NFPROTO_IPV6, 240 .table = "mangle", 241 .target = tproxy_tg6_v1, 242 .revision = 1, 243 .targetsize = sizeof(struct xt_tproxy_target_info_v1), 244 .checkentry = tproxy_tg6_check, 245 .destroy = tproxy_tg6_destroy, 246 .hooks = 1 << NF_INET_PRE_ROUTING, 247 .me = THIS_MODULE, 248 }, 249 #endif 250 251 }; 252 253 static int __init tproxy_tg_init(void) 254 { 255 return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); 256 } 257 258 static void __exit tproxy_tg_exit(void) 259 { 260 xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); 261 } 262 263 module_init(tproxy_tg_init); 264 module_exit(tproxy_tg_exit); 265 MODULE_LICENSE("GPL"); 266 MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs"); 267 MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module."); 268 MODULE_ALIAS("ipt_TPROXY"); 269 MODULE_ALIAS("ip6t_TPROXY"); 270