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/ipv4/nf_defrag_ipv4.h> 23 24 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) 25 #include <linux/netfilter_ipv6/ip6_tables.h> 26 #include <net/inet6_hashtables.h> 27 #include <net/netfilter/ipv6/nf_defrag_ipv6.h> 28 #endif 29 30 #include <net/netfilter/nf_socket.h> 31 #include <linux/netfilter/xt_socket.h> 32 33 /* "socket" match based redirection (no specific rule) 34 * =================================================== 35 * 36 * There are connections with dynamic endpoints (e.g. FTP data 37 * connection) that the user is unable to add explicit rules 38 * for. These are taken care of by a generic "socket" rule. It is 39 * assumed that the proxy application is trusted to open such 40 * connections without explicit iptables rule (except of course the 41 * generic 'socket' rule). In this case the following sockets are 42 * matched in preference order: 43 * 44 * - match: if there's a fully established connection matching the 45 * _packet_ tuple 46 * 47 * - match: if there's a non-zero bound listener (possibly with a 48 * non-local address) We don't accept zero-bound listeners, since 49 * then local services could intercept traffic going through the 50 * box. 51 */ 52 static bool 53 socket_match(const struct sk_buff *skb, struct xt_action_param *par, 54 const struct xt_socket_mtinfo1 *info) 55 { 56 struct sk_buff *pskb = (struct sk_buff *)skb; 57 struct sock *sk = skb->sk; 58 59 if (!sk) 60 sk = nf_sk_lookup_slow_v4(xt_net(par), skb, xt_in(par)); 61 if (sk) { 62 bool wildcard; 63 bool transparent = true; 64 65 /* Ignore sockets listening on INADDR_ANY, 66 * unless XT_SOCKET_NOWILDCARD is set 67 */ 68 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 69 sk_fullsock(sk) && 70 inet_sk(sk)->inet_rcv_saddr == 0); 71 72 /* Ignore non-transparent sockets, 73 * if XT_SOCKET_TRANSPARENT is used 74 */ 75 if (info->flags & XT_SOCKET_TRANSPARENT) 76 transparent = nf_sk_is_transparent(sk); 77 78 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard && 79 transparent) 80 pskb->mark = sk->sk_mark; 81 82 if (sk != skb->sk) 83 sock_gen_put(sk); 84 85 if (wildcard || !transparent) 86 sk = NULL; 87 } 88 89 return sk != NULL; 90 } 91 92 static bool 93 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par) 94 { 95 static struct xt_socket_mtinfo1 xt_info_v0 = { 96 .flags = 0, 97 }; 98 99 return socket_match(skb, par, &xt_info_v0); 100 } 101 102 static bool 103 socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par) 104 { 105 return socket_match(skb, par, par->matchinfo); 106 } 107 108 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) 109 static bool 110 socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par) 111 { 112 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 113 struct sk_buff *pskb = (struct sk_buff *)skb; 114 struct sock *sk = skb->sk; 115 116 if (!sk) 117 sk = nf_sk_lookup_slow_v6(xt_net(par), skb, xt_in(par)); 118 if (sk) { 119 bool wildcard; 120 bool transparent = true; 121 122 /* Ignore sockets listening on INADDR_ANY 123 * unless XT_SOCKET_NOWILDCARD is set 124 */ 125 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) && 126 sk_fullsock(sk) && 127 ipv6_addr_any(&sk->sk_v6_rcv_saddr)); 128 129 /* Ignore non-transparent sockets, 130 * if XT_SOCKET_TRANSPARENT is used 131 */ 132 if (info->flags & XT_SOCKET_TRANSPARENT) 133 transparent = nf_sk_is_transparent(sk); 134 135 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard && 136 transparent) 137 pskb->mark = sk->sk_mark; 138 139 if (sk != skb->sk) 140 sock_gen_put(sk); 141 142 if (wildcard || !transparent) 143 sk = NULL; 144 } 145 146 return sk != NULL; 147 } 148 #endif 149 150 static int socket_mt_v1_check(const struct xt_mtchk_param *par) 151 { 152 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 153 154 if (info->flags & ~XT_SOCKET_FLAGS_V1) { 155 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1); 156 return -EINVAL; 157 } 158 return 0; 159 } 160 161 static int socket_mt_v2_check(const struct xt_mtchk_param *par) 162 { 163 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo; 164 165 if (info->flags & ~XT_SOCKET_FLAGS_V2) { 166 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2); 167 return -EINVAL; 168 } 169 return 0; 170 } 171 172 static int socket_mt_v3_check(const struct xt_mtchk_param *par) 173 { 174 const struct xt_socket_mtinfo3 *info = 175 (struct xt_socket_mtinfo3 *)par->matchinfo; 176 177 if (info->flags & ~XT_SOCKET_FLAGS_V3) { 178 pr_info("unknown flags 0x%x\n", 179 info->flags & ~XT_SOCKET_FLAGS_V3); 180 return -EINVAL; 181 } 182 return 0; 183 } 184 185 static struct xt_match socket_mt_reg[] __read_mostly = { 186 { 187 .name = "socket", 188 .revision = 0, 189 .family = NFPROTO_IPV4, 190 .match = socket_mt4_v0, 191 .hooks = (1 << NF_INET_PRE_ROUTING) | 192 (1 << NF_INET_LOCAL_IN), 193 .me = THIS_MODULE, 194 }, 195 { 196 .name = "socket", 197 .revision = 1, 198 .family = NFPROTO_IPV4, 199 .match = socket_mt4_v1_v2_v3, 200 .checkentry = socket_mt_v1_check, 201 .matchsize = sizeof(struct xt_socket_mtinfo1), 202 .hooks = (1 << NF_INET_PRE_ROUTING) | 203 (1 << NF_INET_LOCAL_IN), 204 .me = THIS_MODULE, 205 }, 206 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) 207 { 208 .name = "socket", 209 .revision = 1, 210 .family = NFPROTO_IPV6, 211 .match = socket_mt6_v1_v2_v3, 212 .checkentry = socket_mt_v1_check, 213 .matchsize = sizeof(struct xt_socket_mtinfo1), 214 .hooks = (1 << NF_INET_PRE_ROUTING) | 215 (1 << NF_INET_LOCAL_IN), 216 .me = THIS_MODULE, 217 }, 218 #endif 219 { 220 .name = "socket", 221 .revision = 2, 222 .family = NFPROTO_IPV4, 223 .match = socket_mt4_v1_v2_v3, 224 .checkentry = socket_mt_v2_check, 225 .matchsize = sizeof(struct xt_socket_mtinfo1), 226 .hooks = (1 << NF_INET_PRE_ROUTING) | 227 (1 << NF_INET_LOCAL_IN), 228 .me = THIS_MODULE, 229 }, 230 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) 231 { 232 .name = "socket", 233 .revision = 2, 234 .family = NFPROTO_IPV6, 235 .match = socket_mt6_v1_v2_v3, 236 .checkentry = socket_mt_v2_check, 237 .matchsize = sizeof(struct xt_socket_mtinfo1), 238 .hooks = (1 << NF_INET_PRE_ROUTING) | 239 (1 << NF_INET_LOCAL_IN), 240 .me = THIS_MODULE, 241 }, 242 #endif 243 { 244 .name = "socket", 245 .revision = 3, 246 .family = NFPROTO_IPV4, 247 .match = socket_mt4_v1_v2_v3, 248 .checkentry = socket_mt_v3_check, 249 .matchsize = sizeof(struct xt_socket_mtinfo1), 250 .hooks = (1 << NF_INET_PRE_ROUTING) | 251 (1 << NF_INET_LOCAL_IN), 252 .me = THIS_MODULE, 253 }, 254 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) 255 { 256 .name = "socket", 257 .revision = 3, 258 .family = NFPROTO_IPV6, 259 .match = socket_mt6_v1_v2_v3, 260 .checkentry = socket_mt_v3_check, 261 .matchsize = sizeof(struct xt_socket_mtinfo1), 262 .hooks = (1 << NF_INET_PRE_ROUTING) | 263 (1 << NF_INET_LOCAL_IN), 264 .me = THIS_MODULE, 265 }, 266 #endif 267 }; 268 269 static int __init socket_mt_init(void) 270 { 271 nf_defrag_ipv4_enable(); 272 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) 273 nf_defrag_ipv6_enable(); 274 #endif 275 276 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 277 } 278 279 static void __exit socket_mt_exit(void) 280 { 281 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); 282 } 283 284 module_init(socket_mt_init); 285 module_exit(socket_mt_exit); 286 287 MODULE_LICENSE("GPL"); 288 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler"); 289 MODULE_DESCRIPTION("x_tables socket match module"); 290 MODULE_ALIAS("ipt_socket"); 291 MODULE_ALIAS("ip6t_socket"); 292