net/netfilter/xt_socket.c

   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 && !net_eq(xt_net(par), sock_net(sk)))
  60                 sk = NULL;
  61
  62         if (!sk)
  63                 sk = nf_sk_lookup_slow_v4(xt_net(par), skb, xt_in(par));
  64
  65         if (sk) {
  66                 bool wildcard;
  67                 bool transparent = true;
  68
  69                 /* Ignore sockets listening on INADDR_ANY,
  70                  * unless XT_SOCKET_NOWILDCARD is set
  71                  */
  72                 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
  73                             sk_fullsock(sk) &&
  74                             inet_sk(sk)->inet_rcv_saddr == 0);
  75
  76                 /* Ignore non-transparent sockets,
  77                  * if XT_SOCKET_TRANSPARENT is used
  78                  */
  79                 if (info->flags & XT_SOCKET_TRANSPARENT)
  80                         transparent = inet_sk_transparent(sk);
  81
  82                 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
  83                     transparent && sk_fullsock(sk))
  84                         pskb->mark = sk->sk_mark;
  85
  86                 if (sk != skb->sk)
  87                         sock_gen_put(sk);
  88
  89                 if (wildcard || !transparent)
  90                         sk = NULL;
  91         }
  92
  93         return sk != NULL;
  94 }
  95
  96 static bool
  97 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
  98 {
  99         static struct xt_socket_mtinfo1 xt_info_v0 = {
 100                 .flags = 0,
 101         };
 102
 103         return socket_match(skb, par, &xt_info_v0);
 104 }
 105
 106 static bool
 107 socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
 108 {
 109         return socket_match(skb, par, par->matchinfo);
 110 }
 111
 112 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 113 static bool
 114 socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
 115 {
 116         const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 117         struct sk_buff *pskb = (struct sk_buff *)skb;
 118         struct sock *sk = skb->sk;
 119
 120         if (sk && !net_eq(xt_net(par), sock_net(sk)))
 121                 sk = NULL;
 122
 123         if (!sk)
 124                 sk = nf_sk_lookup_slow_v6(xt_net(par), skb, xt_in(par));
 125
 126         if (sk) {
 127                 bool wildcard;
 128                 bool transparent = true;
 129
 130                 /* Ignore sockets listening on INADDR_ANY
 131                  * unless XT_SOCKET_NOWILDCARD is set
 132                  */
 133                 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
 134                             sk_fullsock(sk) &&
 135                             ipv6_addr_any(&sk->sk_v6_rcv_saddr));
 136
 137                 /* Ignore non-transparent sockets,
 138                  * if XT_SOCKET_TRANSPARENT is used
 139                  */
 140                 if (info->flags & XT_SOCKET_TRANSPARENT)
 141                         transparent = inet_sk_transparent(sk);
 142
 143                 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
 144                     transparent && sk_fullsock(sk))
 145                         pskb->mark = sk->sk_mark;
 146
 147                 if (sk != skb->sk)
 148                         sock_gen_put(sk);
 149
 150                 if (wildcard || !transparent)
 151                         sk = NULL;
 152         }
 153
 154         return sk != NULL;
 155 }
 156 #endif
 157
 158 static int socket_mt_enable_defrag(struct net *net, int family)
 159 {
 160         switch (family) {
 161         case NFPROTO_IPV4:
 162                 return nf_defrag_ipv4_enable(net);
 163 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 164         case NFPROTO_IPV6:
 165                 return nf_defrag_ipv6_enable(net);
 166 #endif
 167         }
 168         WARN_ONCE(1, "Unknown family %d\n", family);
 169         return 0;
 170 }
 171
 172 static int socket_mt_v1_check(const struct xt_mtchk_param *par)
 173 {
 174         const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 175         int err;
 176
 177         err = socket_mt_enable_defrag(par->net, par->family);
 178         if (err)
 179                 return err;
 180
 181         if (info->flags & ~XT_SOCKET_FLAGS_V1) {
 182                 pr_info_ratelimited("unknown flags 0x%x\n",
 183                                     info->flags & ~XT_SOCKET_FLAGS_V1);
 184                 return -EINVAL;
 185         }
 186         return 0;
 187 }
 188
 189 static int socket_mt_v2_check(const struct xt_mtchk_param *par)
 190 {
 191         const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
 192         int err;
 193
 194         err = socket_mt_enable_defrag(par->net, par->family);
 195         if (err)
 196                 return err;
 197
 198         if (info->flags & ~XT_SOCKET_FLAGS_V2) {
 199                 pr_info_ratelimited("unknown flags 0x%x\n",
 200                                     info->flags & ~XT_SOCKET_FLAGS_V2);
 201                 return -EINVAL;
 202         }
 203         return 0;
 204 }
 205
 206 static int socket_mt_v3_check(const struct xt_mtchk_param *par)
 207 {
 208         const struct xt_socket_mtinfo3 *info =
 209                                     (struct xt_socket_mtinfo3 *)par->matchinfo;
 210         int err;
 211
 212         err = socket_mt_enable_defrag(par->net, par->family);
 213         if (err)
 214                 return err;
 215         if (info->flags & ~XT_SOCKET_FLAGS_V3) {
 216                 pr_info_ratelimited("unknown flags 0x%x\n",
 217                                     info->flags & ~XT_SOCKET_FLAGS_V3);
 218                 return -EINVAL;
 219         }
 220         return 0;
 221 }
 222
 223 static struct xt_match socket_mt_reg[] __read_mostly = {
 224         {
 225                 .name           = "socket",
 226                 .revision       = 0,
 227                 .family         = NFPROTO_IPV4,
 228                 .match          = socket_mt4_v0,
 229                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 230                                   (1 << NF_INET_LOCAL_IN),
 231                 .me             = THIS_MODULE,
 232         },
 233         {
 234                 .name           = "socket",
 235                 .revision       = 1,
 236                 .family         = NFPROTO_IPV4,
 237                 .match          = socket_mt4_v1_v2_v3,
 238                 .checkentry     = socket_mt_v1_check,
 239                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 240                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 241                                   (1 << NF_INET_LOCAL_IN),
 242                 .me             = THIS_MODULE,
 243         },
 244 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 245         {
 246                 .name           = "socket",
 247                 .revision       = 1,
 248                 .family         = NFPROTO_IPV6,
 249                 .match          = socket_mt6_v1_v2_v3,
 250                 .checkentry     = socket_mt_v1_check,
 251                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 252                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 253                                   (1 << NF_INET_LOCAL_IN),
 254                 .me             = THIS_MODULE,
 255         },
 256 #endif
 257         {
 258                 .name           = "socket",
 259                 .revision       = 2,
 260                 .family         = NFPROTO_IPV4,
 261                 .match          = socket_mt4_v1_v2_v3,
 262                 .checkentry     = socket_mt_v2_check,
 263                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 264                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 265                                   (1 << NF_INET_LOCAL_IN),
 266                 .me             = THIS_MODULE,
 267         },
 268 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 269         {
 270                 .name           = "socket",
 271                 .revision       = 2,
 272                 .family         = NFPROTO_IPV6,
 273                 .match          = socket_mt6_v1_v2_v3,
 274                 .checkentry     = socket_mt_v2_check,
 275                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 276                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 277                                   (1 << NF_INET_LOCAL_IN),
 278                 .me             = THIS_MODULE,
 279         },
 280 #endif
 281         {
 282                 .name           = "socket",
 283                 .revision       = 3,
 284                 .family         = NFPROTO_IPV4,
 285                 .match          = socket_mt4_v1_v2_v3,
 286                 .checkentry     = socket_mt_v3_check,
 287                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 288                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 289                                   (1 << NF_INET_LOCAL_IN),
 290                 .me             = THIS_MODULE,
 291         },
 292 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 293         {
 294                 .name           = "socket",
 295                 .revision       = 3,
 296                 .family         = NFPROTO_IPV6,
 297                 .match          = socket_mt6_v1_v2_v3,
 298                 .checkentry     = socket_mt_v3_check,
 299                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 300                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 301                                   (1 << NF_INET_LOCAL_IN),
 302                 .me             = THIS_MODULE,
 303         },
 304 #endif
 305 };
 306
 307 static int __init socket_mt_init(void)
 308 {
 309         return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 310 }
 311
 312 static void __exit socket_mt_exit(void)
 313 {
 314         xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 315 }
 316
 317 module_init(socket_mt_init);
 318 module_exit(socket_mt_exit);
 319
 320 MODULE_LICENSE("GPL");
 321 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
 322 MODULE_DESCRIPTION("x_tables socket match module");
 323 MODULE_ALIAS("ipt_socket");
 324 MODULE_ALIAS("ip6t_socket");