text: /*
   * Transparent proxy support for Linux/iptables
   *
   * Copyright (C) 2007-2008 BalaBit IT Ltd.
   * Author: Krisztian Kovacs
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   */
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  #include <linux/module.h>
  #include <linux/skbuff.h>
  #include <linux/netfilter/x_tables.h>
  #include <linux/netfilter_ipv4/ip_tables.h>
  #include <net/tcp.h>
  #include <net/udp.h>
  #include <net/icmp.h>
  #include <net/sock.h>
  #include <net/inet_sock.h>
  #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  
  #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
  #include <linux/netfilter_ipv6/ip6_tables.h>
  #include <net/inet6_hashtables.h>
  #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
  #endif
  
  #include <net/netfilter/nf_socket.h>
  #include <linux/netfilter/xt_socket.h>
  
  /* "socket" match based redirection (no specific rule)
   * ===================================================
   *
   * There are connections with dynamic endpoints (e.g. FTP data
   * connection) that the user is unable to add explicit rules
   * for. These are taken care of by a generic "socket" rule. It is
   * assumed that the proxy application is trusted to open such
   * connections without explicit iptables rule (except of course the
   * generic 'socket' rule). In this case the following sockets are
   * matched in preference order:
   *
   *   - match: if there's a fully established connection matching the
   *     _packet_ tuple
   *
   *   - match: if there's a non-zero bound listener (possibly with a
   *     non-local address) We don't accept zero-bound listeners, since
   *     then local services could intercept traffic going through the
   *     box.
   */
  static bool
  socket_match(const struct sk_buff *skb, struct xt_action_param *par,
  	     const struct xt_socket_mtinfo1 *info)
  {
  	struct sk_buff *pskb = (struct sk_buff *)skb;
  	struct sock *sk = skb->sk;
  
  	if (!sk)
  		sk = nf_sk_lookup_slow_v4(xt_net(par), skb, xt_in(par));
  	if (sk) {
  		bool wildcard;
  		bool transparent = true;
  
  		/* Ignore sockets listening on INADDR_ANY,
  		 * unless XT_SOCKET_NOWILDCARD is set
  		 */
  		wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
  			    sk_fullsock(sk) &&
  			    inet_sk(sk)->inet_rcv_saddr == 0);
  
  		/* Ignore non-transparent sockets,
  		 * if XT_SOCKET_TRANSPARENT is used
  		 */
  		if (info->flags & XT_SOCKET_TRANSPARENT)
  			transparent = nf_sk_is_transparent(sk);
  
  		if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
  		    transparent && sk_fullsock(sk))
  			pskb->mark = sk->sk_mark;
  
  		sock_gen_put(sk);
  
  		if (wildcard || !transparent)
  			sk = NULL;
  	}
  
  	return sk != NULL;
  }
  
  static bool
  socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
  {
  	static struct xt_socket_mtinfo1 xt_info_v0 = {
  		.flags = 0,
  	};
  
  	return socket_match(skb, par, &xt_info_v0);
  }
  
  static bool
  socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
  {
  	return socket_match(skb, par, par->matchinfo);
  }
  
  #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
  static bool
  socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
  {
  	const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
  	struct sk_buff *pskb = (struct sk_buff *)skb;
  	struct sock *sk = skb->sk;
  
  	if (!sk)
  		sk = nf_sk_lookup_slow_v6(xt_net(par), skb, xt_in(par));
  	if (sk) {
  		bool wildcard;
  		bool transparent = true;
  
  		/* Ignore sockets listening on INADDR_ANY
  		 * unless XT_SOCKET_NOWILDCARD is set
  		 */
  		wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
  			    sk_fullsock(sk) &&
  			    ipv6_addr_any(&sk->sk_v6_rcv_saddr));
  
  		/* Ignore non-transparent sockets,
  		 * if XT_SOCKET_TRANSPARENT is used
  		 */
  		if (info->flags & XT_SOCKET_TRANSPARENT)
  			transparent = nf_sk_is_transparent(sk);
  
  		if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
  		    transparent && sk_fullsock(sk))
  			pskb->mark = sk->sk_mark;
  
  		if (sk != skb->sk)
  			sock_gen_put(sk);
  
  		if (wildcard || !transparent)
  			sk = NULL;
  	}
  
  	return sk != NULL;
  }
  #endif
  
  static int socket_mt_enable_defrag(struct net *net, int family)
  {
  	switch (family) {
  	case NFPROTO_IPV4:
  		return nf_defrag_ipv4_enable(net);
  #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
  	case NFPROTO_IPV6:
  		return nf_defrag_ipv6_enable(net);
  #endif
  	}
  	WARN_ONCE(1, "Unknown family %d\n", family);
  	return 0;
  }
  
  static int socket_mt_v1_check(const struct xt_mtchk_param *par)
  {
  	const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
  	int err;
  
  	err = socket_mt_enable_defrag(par->net, par->family);
  	if (err)
  		return err;
  
  	if (info->flags & ~XT_SOCKET_FLAGS_V1) {
  		pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1);
  		return -EINVAL;
  	}
  	return 0;
  }
  
  static int socket_mt_v2_check(const struct xt_mtchk_param *par)
  {
  	const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
  	int err;
  
  	err = socket_mt_enable_defrag(par->net, par->family);
  	if (err)
  		return err;
  
  	if (info->flags & ~XT_SOCKET_FLAGS_V2) {
  		pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2);
  		return -EINVAL;
  	}
  	return 0;
  }
  
  static int socket_mt_v3_check(const struct xt_mtchk_param *par)
  {
  	const struct xt_socket_mtinfo3 *info =
  				    (struct xt_socket_mtinfo3 *)par->matchinfo;
  	int err;
  
  	err = socket_mt_enable_defrag(par->net, par->family);
  	if (err)
  		return err;
  	if (info->flags & ~XT_SOCKET_FLAGS_V3) {
  		pr_info("unknown flags 0x%x\n",
  			info->flags & ~XT_SOCKET_FLAGS_V3);
  		return -EINVAL;
  	}
  	return 0;
  }
  
  static struct xt_match socket_mt_reg[] __read_mostly = {
  	{
  		.name		= "socket",
  		.revision	= 0,
  		.family		= NFPROTO_IPV4,
  		.match		= socket_mt4_v0,
  		.hooks		= (1 << NF_INET_PRE_ROUTING) |
  				  (1 << NF_INET_LOCAL_IN),
  		.me		= THIS_MODULE,
  	},
  	{
  		.name		= "socket",
  		.revision	= 1,
  		.family		= NFPROTO_IPV4,
  		.match		= socket_mt4_v1_v2_v3,
  		.checkentry	= socket_mt_v1_check,
  		.matchsize	= sizeof(struct xt_socket_mtinfo1),
  		.hooks		= (1 << NF_INET_PRE_ROUTING) |
  				  (1 << NF_INET_LOCAL_IN),
  		.me		= THIS_MODULE,
  	},
  #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
  	{
  		.name		= "socket",
  		.revision	= 1,
  		.family		= NFPROTO_IPV6,
  		.match		= socket_mt6_v1_v2_v3,
  		.checkentry	= socket_mt_v1_check,
  		.matchsize	= sizeof(struct xt_socket_mtinfo1),
  		.hooks		= (1 << NF_INET_PRE_ROUTING) |
  				  (1 << NF_INET_LOCAL_IN),
  		.me		= THIS_MODULE,
  	},
  #endif
  	{
  		.name		= "socket",
  		.revision	= 2,
  		.family		= NFPROTO_IPV4,
  		.match		= socket_mt4_v1_v2_v3,
  		.checkentry	= socket_mt_v2_check,
  		.matchsize	= sizeof(struct xt_socket_mtinfo1),
  		.hooks		= (1 << NF_INET_PRE_ROUTING) |
  				  (1 << NF_INET_LOCAL_IN),
  		.me		= THIS_MODULE,
  	},
  #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
  	{
  		.name		= "socket",
  		.revision	= 2,
  		.family		= NFPROTO_IPV6,
  		.match		= socket_mt6_v1_v2_v3,
  		.checkentry	= socket_mt_v2_check,
  		.matchsize	= sizeof(struct xt_socket_mtinfo1),
  		.hooks		= (1 << NF_INET_PRE_ROUTING) |
  				  (1 << NF_INET_LOCAL_IN),
  		.me		= THIS_MODULE,
  	},
  #endif
  	{
  		.name		= "socket",
  		.revision	= 3,
  		.family		= NFPROTO_IPV4,
  		.match		= socket_mt4_v1_v2_v3,
  		.checkentry	= socket_mt_v3_check,
  		.matchsize	= sizeof(struct xt_socket_mtinfo1),
  		.hooks		= (1 << NF_INET_PRE_ROUTING) |
  				  (1 << NF_INET_LOCAL_IN),
  		.me		= THIS_MODULE,
  	},
  #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
  	{
  		.name		= "socket",
  		.revision	= 3,
  		.family		= NFPROTO_IPV6,
  		.match		= socket_mt6_v1_v2_v3,
  		.checkentry	= socket_mt_v3_check,
  		.matchsize	= sizeof(struct xt_socket_mtinfo1),
  		.hooks		= (1 << NF_INET_PRE_ROUTING) |
  				  (1 << NF_INET_LOCAL_IN),
  		.me		= THIS_MODULE,
  	},
  #endif
  };
  
  static int __init socket_mt_init(void)
  {
  	return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
  }
  
  static void __exit socket_mt_exit(void)
  {
  	xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
  }
  
  module_init(socket_mt_init);
  module_exit(socket_mt_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
  MODULE_DESCRIPTION("x_tables socket match module");
  MODULE_ALIAS("ipt_socket");
  MODULE_ALIAS("ip6t_socket");
  