// 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 boolsocket_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 boolsocket_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 boolsocket_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 boolsocket_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);	else if (par->family == NFPROTO_IPV6)		nf_defrag_ipv4_disable(par->net);} 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");