1 files changed, 605 insertions, 0 deletions

diff --git a/net/netfilter/xt_TPROXY.c b/net/netfilter/xt_TPROXY.c
new file mode 100644
index 000000000..cca96cec1
--- /dev/null
+++ b/net/netfilter/xt_TPROXY.c
@@ -0,0 +1,605 @@
+/*
+ * Transparent proxy support for Linux/iptables
+ *
+ * Copyright (c) 2006-2010 BalaBit IT Ltd.
+ * Author: Balazs Scheidler, 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/ip.h>
+#include <net/checksum.h>
+#include <net/udp.h>
+#include <net/tcp.h>
+#include <net/inet_sock.h>
+#include <net/inet_hashtables.h>
+#include <linux/inetdevice.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+
+#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
+
+#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
+#define XT_TPROXY_HAVE_IPV6 1
+#include <net/if_inet6.h>
+#include <net/addrconf.h>
+#include <net/inet6_hashtables.h>
+#include <linux/netfilter_ipv6/ip6_tables.h>
+#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
+#endif
+
+#include <linux/netfilter/xt_TPROXY.h>
+
+enum nf_tproxy_lookup_t {
+	 NFT_LOOKUP_LISTENER,
+	 NFT_LOOKUP_ESTABLISHED,
+};
+
+static bool tproxy_sk_is_transparent(struct sock *sk)
+{
+	switch (sk->sk_state) {
+	case TCP_TIME_WAIT:
+		if (inet_twsk(sk)->tw_transparent)
+			return true;
+		break;
+	case TCP_NEW_SYN_RECV:
+		if (inet_rsk(inet_reqsk(sk))->no_srccheck)
+			return true;
+		break;
+	default:
+		if (inet_sk(sk)->transparent)
+			return true;
+	}
+
+	sock_gen_put(sk);
+	return false;
+}
+
+static inline __be32
+tproxy_laddr4(struct sk_buff *skb, __be32 user_laddr, __be32 daddr)
+{
+	struct in_device *indev;
+	__be32 laddr;
+
+	if (user_laddr)
+		return user_laddr;
+
+	laddr = 0;
+	rcu_read_lock();
+	indev = __in_dev_get_rcu(skb->dev);
+	for_primary_ifa(indev) {
+		laddr = ifa->ifa_local;
+		break;
+	} endfor_ifa(indev);
+	rcu_read_unlock();
+
+	return laddr ? laddr : daddr;
+}
+
+/*
+ * This is used when the user wants to intercept a connection matching
+ * an explicit iptables rule. In this case the sockets are assumed
+ * matching in preference order:
+ *
+ *   - match: if there's a fully established connection matching the
+ *     _packet_ tuple, it is returned, assuming the redirection
+ *     already took place and we process a packet belonging to an
+ *     established connection
+ *
+ *   - match: if there's a listening socket matching the redirection
+ *     (e.g. on-port & on-ip of the connection), it is returned,
+ *     regardless if it was bound to 0.0.0.0 or an explicit
+ *     address. The reasoning is that if there's an explicit rule, it
+ *     does not really matter if the listener is bound to an interface
+ *     or to 0. The user already stated that he wants redirection
+ *     (since he added the rule).
+ *
+ * Please note that there's an overlap between what a TPROXY target
+ * and a socket match will match. Normally if you have both rules the
+ * "socket" match will be the first one, effectively all packets
+ * belonging to established connections going through that one.
+ */
+static inline struct sock *
+nf_tproxy_get_sock_v4(struct net *net, const u8 protocol,
+		      const __be32 saddr, const __be32 daddr,
+		      const __be16 sport, const __be16 dport,
+		      const struct net_device *in,
+		      const enum nf_tproxy_lookup_t lookup_type)
+{
+	struct sock *sk;
+
+	switch (protocol) {
+	case IPPROTO_TCP:
+		switch (lookup_type) {
+		case NFT_LOOKUP_LISTENER:
+			sk = inet_lookup_listener(net, &tcp_hashinfo,
+						    saddr, sport,
+						    daddr, dport,
+						    in->ifindex);
+
+			/* NOTE: we return listeners even if bound to
+			 * 0.0.0.0, those are filtered out in
+			 * xt_socket, since xt_TPROXY needs 0 bound
+			 * listeners too
+			 */
+			break;
+		case NFT_LOOKUP_ESTABLISHED:
+			sk = inet_lookup_established(net, &tcp_hashinfo,
+						    saddr, sport, daddr, dport,
+						    in->ifindex);
+			break;
+		default:
+			BUG();
+		}
+		break;
+	case IPPROTO_UDP:
+		sk = udp4_lib_lookup(net, saddr, sport, daddr, dport,
+				     in->ifindex);
+		if (sk) {
+			int connected = (sk->sk_state == TCP_ESTABLISHED);
+			int wildcard = (inet_sk(sk)->inet_rcv_saddr == 0);
+
+			/* NOTE: we return listeners even if bound to
+			 * 0.0.0.0, those are filtered out in
+			 * xt_socket, since xt_TPROXY needs 0 bound
+			 * listeners too
+			 */
+			if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
+			    (lookup_type == NFT_LOOKUP_LISTENER && connected)) {
+				sock_put(sk);
+				sk = NULL;
+			}
+		}
+		break;
+	default:
+		WARN_ON(1);
+		sk = NULL;
+	}
+
+	pr_debug("tproxy socket lookup: proto %u %08x:%u -> %08x:%u, lookup type: %d, sock %p\n",
+		 protocol, ntohl(saddr), ntohs(sport), ntohl(daddr), ntohs(dport), lookup_type, sk);
+
+	return sk;
+}
+
+#ifdef XT_TPROXY_HAVE_IPV6
+static inline struct sock *
+nf_tproxy_get_sock_v6(struct net *net, const u8 protocol,
+		      const struct in6_addr *saddr, const struct in6_addr *daddr,
+		      const __be16 sport, const __be16 dport,
+		      const struct net_device *in,
+		      const enum nf_tproxy_lookup_t lookup_type)
+{
+	struct sock *sk;
+
+	switch (protocol) {
+	case IPPROTO_TCP:
+		switch (lookup_type) {
+		case NFT_LOOKUP_LISTENER:
+			sk = inet6_lookup_listener(net, &tcp_hashinfo,
+						   saddr, sport,
+						   daddr, ntohs(dport),
+						   in->ifindex);
+
+			/* NOTE: we return listeners even if bound to
+			 * 0.0.0.0, those are filtered out in
+			 * xt_socket, since xt_TPROXY needs 0 bound
+			 * listeners too
+			 */
+			break;
+		case NFT_LOOKUP_ESTABLISHED:
+			sk = __inet6_lookup_established(net, &tcp_hashinfo,
+							saddr, sport, daddr, ntohs(dport),
+							in->ifindex);
+			break;
+		default:
+			BUG();
+		}
+		break;
+	case IPPROTO_UDP:
+		sk = udp6_lib_lookup(net, saddr, sport, daddr, dport,
+				     in->ifindex);
+		if (sk) {
+			int connected = (sk->sk_state == TCP_ESTABLISHED);
+			int wildcard = ipv6_addr_any(&sk->sk_v6_rcv_saddr);
+
+			/* NOTE: we return listeners even if bound to
+			 * 0.0.0.0, those are filtered out in
+			 * xt_socket, since xt_TPROXY needs 0 bound
+			 * listeners too
+			 */
+			if ((lookup_type == NFT_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
+			    (lookup_type == NFT_LOOKUP_LISTENER && connected)) {
+				sock_put(sk);
+				sk = NULL;
+			}
+		}
+		break;
+	default:
+		WARN_ON(1);
+		sk = NULL;
+	}
+
+	pr_debug("tproxy socket lookup: proto %u %pI6:%u -> %pI6:%u, lookup type: %d, sock %p\n",
+		 protocol, saddr, ntohs(sport), daddr, ntohs(dport), lookup_type, sk);
+
+	return sk;
+}
+#endif
+
+/**
+ * tproxy_handle_time_wait4 - handle IPv4 TCP TIME_WAIT reopen redirections
+ * @skb:	The skb being processed.
+ * @laddr:	IPv4 address to redirect to or zero.
+ * @lport:	TCP port to redirect to or zero.
+ * @sk:		The TIME_WAIT TCP socket found by the lookup.
+ *
+ * We have to handle SYN packets arriving to TIME_WAIT sockets
+ * differently: instead of reopening the connection we should rather
+ * redirect the new connection to the proxy if there's a listener
+ * socket present.
+ *
+ * tproxy_handle_time_wait4() consumes the socket reference passed in.
+ *
+ * Returns the listener socket if there's one, the TIME_WAIT socket if
+ * no such listener is found, or NULL if the TCP header is incomplete.
+ */
+static struct sock *
+tproxy_handle_time_wait4(struct sk_buff *skb, __be32 laddr, __be16 lport,
+			struct sock *sk)
+{
+	const struct iphdr *iph = ip_hdr(skb);
+	struct tcphdr _hdr, *hp;
+
+	hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
+	if (hp == NULL) {
+		inet_twsk_put(inet_twsk(sk));
+		return NULL;
+	}
+
+	if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
+		/* SYN to a TIME_WAIT socket, we'd rather redirect it
+		 * to a listener socket if there's one */
+		struct sock *sk2;
+
+		sk2 = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
+					    iph->saddr, laddr ? laddr : iph->daddr,
+					    hp->source, lport ? lport : hp->dest,
+					    skb->dev, NFT_LOOKUP_LISTENER);
+		if (sk2) {
+			inet_twsk_deschedule(inet_twsk(sk));
+			inet_twsk_put(inet_twsk(sk));
+			sk = sk2;
+		}
+	}
+
+	return sk;
+}
+
+/* assign a socket to the skb -- consumes sk */
+static void
+nf_tproxy_assign_sock(struct sk_buff *skb, struct sock *sk)
+{
+	skb_orphan(skb);
+	skb->sk = sk;
+	skb->destructor = sock_edemux;
+}
+
+static unsigned int
+tproxy_tg4(struct sk_buff *skb, __be32 laddr, __be16 lport,
+	   u_int32_t mark_mask, u_int32_t mark_value)
+{
+	const struct iphdr *iph = ip_hdr(skb);
+	struct udphdr _hdr, *hp;
+	struct sock *sk;
+
+	hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
+	if (hp == NULL)
+		return NF_DROP;
+
+	/* check if there's an ongoing connection on the packet
+	 * addresses, this happens if the redirect already happened
+	 * and the current packet belongs to an already established
+	 * connection */
+	sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
+				   iph->saddr, iph->daddr,
+				   hp->source, hp->dest,
+				   skb->dev, NFT_LOOKUP_ESTABLISHED);
+
+	laddr = tproxy_laddr4(skb, laddr, iph->daddr);
+	if (!lport)
+		lport = hp->dest;
+
+	/* UDP has no TCP_TIME_WAIT state, so we never enter here */
+	if (sk && sk->sk_state == TCP_TIME_WAIT)
+		/* reopening a TIME_WAIT connection needs special handling */
+		sk = tproxy_handle_time_wait4(skb, laddr, lport, sk);
+	else if (!sk)
+		/* no, there's no established connection, check if
+		 * there's a listener on the redirected addr/port */
+		sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
+					   iph->saddr, laddr,
+					   hp->source, lport,
+					   skb->dev, NFT_LOOKUP_LISTENER);
+
+	/* NOTE: assign_sock consumes our sk reference */
+	if (sk && tproxy_sk_is_transparent(sk)) {
+		/* This should be in a separate target, but we don't do multiple
+		   targets on the same rule yet */
+		skb->mark = (skb->mark & ~mark_mask) ^ mark_value;
+
+		pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
+			 iph->protocol, &iph->daddr, ntohs(hp->dest),
+			 &laddr, ntohs(lport), skb->mark);
+
+		nf_tproxy_assign_sock(skb, sk);
+		return NF_ACCEPT;
+	}
+
+	pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
+		 iph->protocol, &iph->saddr, ntohs(hp->source),
+		 &iph->daddr, ntohs(hp->dest), skb->mark);
+	return NF_DROP;
+}
+
+static unsigned int
+tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par)
+{
+	const struct xt_tproxy_target_info *tgi = par->targinfo;
+
+	return tproxy_tg4(skb, tgi->laddr, tgi->lport, tgi->mark_mask, tgi->mark_value);
+}
+
+static unsigned int
+tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par)
+{
+	const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
+
+	return tproxy_tg4(skb, tgi->laddr.ip, tgi->lport, tgi->mark_mask, tgi->mark_value);
+}
+
+#ifdef XT_TPROXY_HAVE_IPV6
+
+static inline const struct in6_addr *
+tproxy_laddr6(struct sk_buff *skb, const struct in6_addr *user_laddr,
+	      const struct in6_addr *daddr)
+{
+	struct inet6_dev *indev;
+	struct inet6_ifaddr *ifa;
+	struct in6_addr *laddr;
+
+	if (!ipv6_addr_any(user_laddr))
+		return user_laddr;
+	laddr = NULL;
+
+	rcu_read_lock();
+	indev = __in6_dev_get(skb->dev);
+	if (indev)
+		list_for_each_entry(ifa, &indev->addr_list, if_list) {
+			if (ifa->flags & (IFA_F_TENTATIVE | IFA_F_DEPRECATED))
+				continue;
+
+			laddr = &ifa->addr;
+			break;
+		}
+	rcu_read_unlock();
+
+	return laddr ? laddr : daddr;
+}
+
+/**
+ * tproxy_handle_time_wait6 - handle IPv6 TCP TIME_WAIT reopen redirections
+ * @skb:	The skb being processed.
+ * @tproto:	Transport protocol.
+ * @thoff:	Transport protocol header offset.
+ * @par:	Iptables target parameters.
+ * @sk:		The TIME_WAIT TCP socket found by the lookup.
+ *
+ * We have to handle SYN packets arriving to TIME_WAIT sockets
+ * differently: instead of reopening the connection we should rather
+ * redirect the new connection to the proxy if there's a listener
+ * socket present.
+ *
+ * tproxy_handle_time_wait6() consumes the socket reference passed in.
+ *
+ * Returns the listener socket if there's one, the TIME_WAIT socket if
+ * no such listener is found, or NULL if the TCP header is incomplete.
+ */
+static struct sock *
+tproxy_handle_time_wait6(struct sk_buff *skb, int tproto, int thoff,
+			 const struct xt_action_param *par,
+			 struct sock *sk)
+{
+	const struct ipv6hdr *iph = ipv6_hdr(skb);
+	struct tcphdr _hdr, *hp;
+	const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
+
+	hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
+	if (hp == NULL) {
+		inet_twsk_put(inet_twsk(sk));
+		return NULL;
+	}
+
+	if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
+		/* SYN to a TIME_WAIT socket, we'd rather redirect it
+		 * to a listener socket if there's one */
+		struct sock *sk2;
+
+		sk2 = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
+					    &iph->saddr,
+					    tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr),
+					    hp->source,
+					    tgi->lport ? tgi->lport : hp->dest,
+					    skb->dev, NFT_LOOKUP_LISTENER);
+		if (sk2) {
+			inet_twsk_deschedule(inet_twsk(sk));
+			inet_twsk_put(inet_twsk(sk));
+			sk = sk2;
+		}
+	}
+
+	return sk;
+}
+
+static unsigned int
+tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par)
+{
+	const struct ipv6hdr *iph = ipv6_hdr(skb);
+	const struct xt_tproxy_target_info_v1 *tgi = par->targinfo;
+	struct udphdr _hdr, *hp;
+	struct sock *sk;
+	const struct in6_addr *laddr;
+	__be16 lport;
+	int thoff = 0;
+	int 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 NF_DROP;
+	}
+
+	hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
+	if (hp == NULL) {
+		pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n");
+		return NF_DROP;
+	}
+
+	/* check if there's an ongoing connection on the packet
+	 * addresses, this happens if the redirect already happened
+	 * and the current packet belongs to an already established
+	 * connection */
+	sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
+				   &iph->saddr, &iph->daddr,
+				   hp->source, hp->dest,
+				   par->in, NFT_LOOKUP_ESTABLISHED);
+
+	laddr = tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr);
+	lport = tgi->lport ? tgi->lport : hp->dest;
+
+	/* UDP has no TCP_TIME_WAIT state, so we never enter here */
+	if (sk && sk->sk_state == TCP_TIME_WAIT)
+		/* reopening a TIME_WAIT connection needs special handling */
+		sk = tproxy_handle_time_wait6(skb, tproto, thoff, par, sk);
+	else if (!sk)
+		/* no there's no established connection, check if
+		 * there's a listener on the redirected addr/port */
+		sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
+					   &iph->saddr, laddr,
+					   hp->source, lport,
+					   par->in, NFT_LOOKUP_LISTENER);
+
+	/* NOTE: assign_sock consumes our sk reference */
+	if (sk && tproxy_sk_is_transparent(sk)) {
+		/* This should be in a separate target, but we don't do multiple
+		   targets on the same rule yet */
+		skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;
+
+		pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
+			 tproto, &iph->saddr, ntohs(hp->source),
+			 laddr, ntohs(lport), skb->mark);
+
+		nf_tproxy_assign_sock(skb, sk);
+		return NF_ACCEPT;
+	}
+
+	pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n",
+		 tproto, &iph->saddr, ntohs(hp->source),
+		 &iph->daddr, ntohs(hp->dest), skb->mark);
+
+	return NF_DROP;
+}
+
+static int tproxy_tg6_check(const struct xt_tgchk_param *par)
+{
+	const struct ip6t_ip6 *i = par->entryinfo;
+
+	if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) &&
+	    !(i->invflags & IP6T_INV_PROTO))
+		return 0;
+
+	pr_info("Can be used only in combination with "
+		"either -p tcp or -p udp\n");
+	return -EINVAL;
+}
+#endif
+
+static int tproxy_tg4_check(const struct xt_tgchk_param *par)
+{
+	const struct ipt_ip *i = par->entryinfo;
+
+	if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)
+	    && !(i->invflags & IPT_INV_PROTO))
+		return 0;
+
+	pr_info("Can be used only in combination with "
+		"either -p tcp or -p udp\n");
+	return -EINVAL;
+}
+
+static struct xt_target tproxy_tg_reg[] __read_mostly = {
+	{
+		.name		= "TPROXY",
+		.family		= NFPROTO_IPV4,
+		.table		= "mangle",
+		.target		= tproxy_tg4_v0,
+		.revision	= 0,
+		.targetsize	= sizeof(struct xt_tproxy_target_info),
+		.checkentry	= tproxy_tg4_check,
+		.hooks		= 1 << NF_INET_PRE_ROUTING,
+		.me		= THIS_MODULE,
+	},
+	{
+		.name		= "TPROXY",
+		.family		= NFPROTO_IPV4,
+		.table		= "mangle",
+		.target		= tproxy_tg4_v1,
+		.revision	= 1,
+		.targetsize	= sizeof(struct xt_tproxy_target_info_v1),
+		.checkentry	= tproxy_tg4_check,
+		.hooks		= 1 << NF_INET_PRE_ROUTING,
+		.me		= THIS_MODULE,
+	},
+#ifdef XT_TPROXY_HAVE_IPV6
+	{
+		.name		= "TPROXY",
+		.family		= NFPROTO_IPV6,
+		.table		= "mangle",
+		.target		= tproxy_tg6_v1,
+		.revision	= 1,
+		.targetsize	= sizeof(struct xt_tproxy_target_info_v1),
+		.checkentry	= tproxy_tg6_check,
+		.hooks		= 1 << NF_INET_PRE_ROUTING,
+		.me		= THIS_MODULE,
+	},
+#endif
+
+};
+
+static int __init tproxy_tg_init(void)
+{
+	nf_defrag_ipv4_enable();
+#ifdef XT_TPROXY_HAVE_IPV6
+	nf_defrag_ipv6_enable();
+#endif
+
+	return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
+}
+
+static void __exit tproxy_tg_exit(void)
+{
+	xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg));
+}
+
+module_init(tproxy_tg_init);
+module_exit(tproxy_tg_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
+MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");
+MODULE_ALIAS("ipt_TPROXY");
+MODULE_ALIAS("ip6t_TPROXY");