/* * 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)#define XT_SOCKET_HAVE_IPV6 1#include <linux/netfilter_ipv6/ip6_tables.h>#include <net/inet6_hashtables.h>#include <net/netfilter/ipv6/nf_defrag_ipv6.h>#endif #include <linux/netfilter/xt_socket.h> #if IS_ENABLED(CONFIG_NF_CONNTRACK)#define XT_SOCKET_HAVE_CONNTRACK 1#include <net/netfilter/nf_conntrack.h>#endif static intextract_icmp4_fields(const struct sk_buff *skb,		    u8 *protocol,		    __be32 *raddr,		    __be32 *laddr,		    __be16 *rport,		    __be16 *lport){	unsigned int outside_hdrlen = ip_hdrlen(skb);	struct iphdr *inside_iph, _inside_iph;	struct icmphdr *icmph, _icmph;	__be16 *ports, _ports[2]; 	icmph = skb_header_pointer(skb, outside_hdrlen,				   sizeof(_icmph), &_icmph);	if (icmph == NULL)		return 1; 	switch (icmph->type) {	case ICMP_DEST_UNREACH:	case ICMP_SOURCE_QUENCH:	case ICMP_REDIRECT:	case ICMP_TIME_EXCEEDED:	case ICMP_PARAMETERPROB:		break;	default:		return 1;	} 	inside_iph = skb_header_pointer(skb, outside_hdrlen +					sizeof(struct icmphdr),					sizeof(_inside_iph), &_inside_iph);	if (inside_iph == NULL)		return 1; 	if (inside_iph->protocol != IPPROTO_TCP &&	    inside_iph->protocol != IPPROTO_UDP)		return 1; 	ports = skb_header_pointer(skb, outside_hdrlen +				   sizeof(struct icmphdr) +				   (inside_iph->ihl << 2),				   sizeof(_ports), &_ports);	if (ports == NULL)		return 1; 	/* the inside IP packet is the one quoted from our side, thus	 * its saddr is the local address */	*protocol = inside_iph->protocol;	*laddr = inside_iph->saddr;	*lport = ports[0];	*raddr = inside_iph->daddr;	*rport = ports[1]; 	return 0;} /* "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 struct sock *xt_socket_get_sock_v4(struct net *net, struct sk_buff *skb, const int doff,		      const u8 protocol,		      const __be32 saddr, const __be32 daddr,		      const __be16 sport, const __be16 dport,		      const struct net_device *in){	switch (protocol) {	case IPPROTO_TCP:		return inet_lookup(net, &tcp_hashinfo, skb, doff,				   saddr, sport, daddr, dport,				   in->ifindex);	case IPPROTO_UDP:		return udp4_lib_lookup(net, saddr, sport, daddr, dport,				       in->ifindex);	}	return NULL;} static bool xt_socket_sk_is_transparent(struct sock *sk){	switch (sk->sk_state) {	case TCP_TIME_WAIT:		return inet_twsk(sk)->tw_transparent; 	case TCP_NEW_SYN_RECV:		return inet_rsk(inet_reqsk(sk))->no_srccheck; 	default:		return inet_sk(sk)->transparent;	}} static struct sock *xt_socket_lookup_slow_v4(struct net *net,					     const struct sk_buff *skb,					     const struct net_device *indev){	const struct iphdr *iph = ip_hdr(skb);	struct sk_buff *data_skb = NULL;	int doff = 0;	__be32 uninitialized_var(daddr), uninitialized_var(saddr);	__be16 uninitialized_var(dport), uninitialized_var(sport);	u8 uninitialized_var(protocol);#ifdef XT_SOCKET_HAVE_CONNTRACK	struct nf_conn const *ct;	enum ip_conntrack_info ctinfo;#endif 	if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {		struct udphdr _hdr, *hp; 		hp = skb_header_pointer(skb, ip_hdrlen(skb),					sizeof(_hdr), &_hdr);		if (hp == NULL)			return NULL; 		protocol = iph->protocol;		saddr = iph->saddr;		sport = hp->source;		daddr = iph->daddr;		dport = hp->dest;		data_skb = (struct sk_buff *)skb;		doff = iph->protocol == IPPROTO_TCP ?			ip_hdrlen(skb) + __tcp_hdrlen((struct tcphdr *)hp) :			ip_hdrlen(skb) + sizeof(*hp); 	} else if (iph->protocol == IPPROTO_ICMP) {		if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,					 &sport, &dport))			return NULL;	} else {		return NULL;	} #ifdef XT_SOCKET_HAVE_CONNTRACK	/* Do the lookup with the original socket address in	 * case this is a reply packet of an established	 * SNAT-ted connection.	 */	ct = nf_ct_get(skb, &ctinfo);	if (ct && !nf_ct_is_untracked(ct) &&	    ((iph->protocol != IPPROTO_ICMP &&	      ctinfo == IP_CT_ESTABLISHED_REPLY) ||	     (iph->protocol == IPPROTO_ICMP &&	      ctinfo == IP_CT_RELATED_REPLY)) &&	    (ct->status & IPS_SRC_NAT_DONE)) { 		daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;		dport = (iph->protocol == IPPROTO_TCP) ?			ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :			ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;	}#endif 	return xt_socket_get_sock_v4(net, data_skb, doff, protocol, saddr,				     daddr, sport, dport, indev);} 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)		sk = xt_socket_lookup_slow_v4(par->net, skb, par->in);	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 = xt_socket_sk_is_transparent(sk); 		if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&		    transparent)			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);} #ifdef XT_SOCKET_HAVE_IPV6 static intextract_icmp6_fields(const struct sk_buff *skb,		     unsigned int outside_hdrlen,		     int *protocol,		     const struct in6_addr **raddr,		     const struct in6_addr **laddr,		     __be16 *rport,		     __be16 *lport,		     struct ipv6hdr *ipv6_var){	const struct ipv6hdr *inside_iph;	struct icmp6hdr *icmph, _icmph;	__be16 *ports, _ports[2];	u8 inside_nexthdr;	__be16 inside_fragoff;	int inside_hdrlen; 	icmph = skb_header_pointer(skb, outside_hdrlen,				   sizeof(_icmph), &_icmph);	if (icmph == NULL)		return 1; 	if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)		return 1; 	inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph),					sizeof(*ipv6_var), ipv6_var);	if (inside_iph == NULL)		return 1;	inside_nexthdr = inside_iph->nexthdr; 	inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) +					      sizeof(*ipv6_var),					 &inside_nexthdr, &inside_fragoff);	if (inside_hdrlen < 0)		return 1; /* hjm: Packet has no/incomplete transport layer headers. */ 	if (inside_nexthdr != IPPROTO_TCP &&	    inside_nexthdr != IPPROTO_UDP)		return 1; 	ports = skb_header_pointer(skb, inside_hdrlen,				   sizeof(_ports), &_ports);	if (ports == NULL)		return 1; 	/* the inside IP packet is the one quoted from our side, thus	 * its saddr is the local address */	*protocol = inside_nexthdr;	*laddr = &inside_iph->saddr;	*lport = ports[0];	*raddr = &inside_iph->daddr;	*rport = ports[1]; 	return 0;} static struct sock *xt_socket_get_sock_v6(struct net *net, struct sk_buff *skb, int doff,		      const u8 protocol,		      const struct in6_addr *saddr, const struct in6_addr *daddr,		      const __be16 sport, const __be16 dport,		      const struct net_device *in){	switch (protocol) {	case IPPROTO_TCP:		return inet6_lookup(net, &tcp_hashinfo, skb, doff,				    saddr, sport, daddr, dport,				    in->ifindex);	case IPPROTO_UDP:		return udp6_lib_lookup(net, saddr, sport, daddr, dport,				       in->ifindex);	} 	return NULL;} static struct sock *xt_socket_lookup_slow_v6(struct net *net,					     const struct sk_buff *skb,					     const struct net_device *indev){	__be16 uninitialized_var(dport), uninitialized_var(sport);	const struct in6_addr *daddr = NULL, *saddr = NULL;	struct ipv6hdr *iph = ipv6_hdr(skb);	struct sk_buff *data_skb = NULL;	int doff = 0;	int thoff = 0, tproto; 	tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);	if (tproto < 0) {		pr_debug("unable to find transport header in IPv6 packet, dropping\n");		return NULL;	} 	if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {		struct udphdr _hdr, *hp; 		hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);		if (hp == NULL)			return NULL; 		saddr = &iph->saddr;		sport = hp->source;		daddr = &iph->daddr;		dport = hp->dest;		data_skb = (struct sk_buff *)skb;		doff = tproto == IPPROTO_TCP ?			thoff + __tcp_hdrlen((struct tcphdr *)hp) :			thoff + sizeof(*hp); 	} else if (tproto == IPPROTO_ICMPV6) {		struct ipv6hdr ipv6_var; 		if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,					 &sport, &dport, &ipv6_var))			return NULL;	} else {		return NULL;	} 	return xt_socket_get_sock_v6(net, data_skb, doff, tproto, saddr, daddr,				     sport, dport, indev);} 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)		sk = xt_socket_lookup_slow_v6(par->net, skb, par->in);	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 = xt_socket_sk_is_transparent(sk); 		if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&		    transparent)			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_v1_check(const struct xt_mtchk_param *par){	const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo; 	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; 	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; 	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,	},#ifdef XT_SOCKET_HAVE_IPV6	{		.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),

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