net/netfilter/xt_socket.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Transparent proxy support for Linux/iptables
  *
  * Copyright (C) 2007-2008 BalaBit IT Ltd.
  * Author: Krisztian Kovacs
  */
 #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 && !net_eq(xt_net(par), sock_net(sk)))
 		sk = NULL;

 	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 = inet_sk_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;
 }

 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 && !net_eq(xt_net(par), sock_net(sk)))
 		sk = NULL;

 	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 = inet_sk_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_ratelimited("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_ratelimited("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_ratelimited("unknown flags 0x%x\n",
 				    info->flags & ~XT_SOCKET_FLAGS_V3);
 		return -EINVAL;
 	}
 	return 0;
 }

 static void socket_mt_destroy(const struct xt_mtdtor_param *par)
 {
 	if (par->family == NFPROTO_IPV4)
 		nf_defrag_ipv4_disable(par->net);
 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 	else if (par->family == NFPROTO_IPV6)
 		nf_defrag_ipv6_disable(par->net);
 #endif
 }

 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,
 		.destroy	= socket_mt_destroy,
 		.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),
 		.destroy	= socket_mt_destroy,
 		.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,
 		.destroy	= socket_mt_destroy,
 		.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,
 		.destroy	= socket_mt_destroy,
 		.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,
 		.destroy	= socket_mt_destroy,
 		.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,
 		.destroy	= socket_mt_destroy,
 		.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");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Transparent proxy support for Linux/iptables
	*
	* Copyright (C) 2007-2008 BalaBit IT Ltd.
	* Author: Krisztian Kovacs
	*/
	#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 && !net_eq(xt_net(par), sock_net(sk)))
	sk = NULL;

	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 = inet_sk_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;
	}

	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 && !net_eq(xt_net(par), sock_net(sk)))
	sk = NULL;

	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 = inet_sk_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_ratelimited("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_ratelimited("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_ratelimited("unknown flags 0x%x\n",
	info->flags & ~XT_SOCKET_FLAGS_V3);
	return -EINVAL;
	}
	return 0;
	}

	static void socket_mt_destroy(const struct xt_mtdtor_param *par)
	{
	if (par->family == NFPROTO_IPV4)
	nf_defrag_ipv4_disable(par->net);
	#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
	else if (par->family == NFPROTO_IPV6)
	nf_defrag_ipv6_disable(par->net);
	#endif
	}

	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,
	.destroy = socket_mt_destroy,
	.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),
	.destroy = socket_mt_destroy,
	.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,
	.destroy = socket_mt_destroy,
	.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,
	.destroy = socket_mt_destroy,
	.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,
	.destroy = socket_mt_destroy,
	.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,
	.destroy = socket_mt_destroy,
	.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");