[v3,nf-next] netfilter: Add native tproxy support for nf_tables

Message ID 20180629143806.28835-1-ecklm94@gmail.com
State Changes Requested
Delegated to: Pablo Neira
Headers show
Series
  • [v3,nf-next] netfilter: Add native tproxy support for nf_tables
Related show

Commit Message

Máté Eckl June 29, 2018, 2:38 p.m.
v2:
 - address or port is now compulsory
 - nf_defrag_ipv{4,6}_enable called in init
 - nft_tproxy now selects NF_DEFRAG_IPV4/6
 - Add transport header presence test in ipv4 eval (in ipv6 it was
   already present)
 - Add check for the case when address is specified but the rule family
   is not set accordingly

v3:
 - Fix tproxy and context family compatibility test in init

-- 8< --
A great portion of the code is taken from xt_TPROXY.c

There are some changes compared to the iptables implementation:
 - tproxy statement is not terminal here

Signed-off-by: Máté Eckl <ecklm94@gmail.com>
---
 include/uapi/linux/netfilter/nf_tables.h |  16 ++
 net/netfilter/Kconfig                    |  10 +
 net/netfilter/Makefile                   |   1 +
 net/netfilter/nft_tproxy.c               | 331 +++++++++++++++++++++++
 4 files changed, 358 insertions(+)
 create mode 100644 net/netfilter/nft_tproxy.c

Comments

Pablo Neira Ayuso July 17, 2018, 3:59 p.m. | #1
On Fri, Jun 29, 2018 at 04:38:06PM +0200, Máté Eckl wrote:
> v2:
>  - address or port is now compulsory
>  - nf_defrag_ipv{4,6}_enable called in init
>  - nft_tproxy now selects NF_DEFRAG_IPV4/6
>  - Add transport header presence test in ipv4 eval (in ipv6 it was
>    already present)
>  - Add check for the case when address is specified but the rule family
>    is not set accordingly
> 
> v3:
>  - Fix tproxy and context family compatibility test in init
> 
> -- 8< --
> A great portion of the code is taken from xt_TPROXY.c
> 
> There are some changes compared to the iptables implementation:
>  - tproxy statement is not terminal here

Applied, thanks.
--
To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 89438e68dc03..e58d2b70dde7 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -1250,6 +1250,22 @@  enum nft_nat_attributes {
 };
 #define NFTA_NAT_MAX		(__NFTA_NAT_MAX - 1)
 
+/**
+ * enum nft_tproxy_attributes - nf_tables tproxy expression netlink attributes
+ *
+ * NFTA_TPROXY_FAMILY: Target address family (NLA_U32: nft_registers)
+ * NFTA_TPROXY_REG_ADDR: Target address register (NLA_U32: nft_registers)
+ * NFTA_TPROXY_REG_PORT: Target port register (NLA_U32: nft_registers)
+ */
+enum nft_tproxy_attributes {
+	NFTA_TPROXY_UNSPEC,
+	NFTA_TPROXY_FAMILY,
+	NFTA_TPROXY_REG_ADDR,
+	NFTA_TPROXY_REG_PORT,
+	__NFTA_TPROXY_MAX
+};
+#define NFTA_TPROXY_MAX		(__NFTA_TPROXY_MAX - 1)
+
 /**
  * enum nft_masq_attributes - nf_tables masquerade expression attributes
  *
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index aec182c22020..41861b8216da 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -631,6 +631,16 @@  config NFT_SOCKET
 	  This option allows matching for the presence or absence of a
 	  corresponding socket and its attributes.
 
+config NFT_TPROXY
+	tristate "Netfilter nf_tables tproxy support"
+	depends on IPV6 || IPV6=n
+	select NF_DEFRAG_IPV4
+	select NF_DEFRAG_IPV6 if NF_TABLES_IPV6
+	select NF_TPROXY_IPV4
+	select NF_TPROXY_IPV6 if NF_TABLES_IPV6
+	help
+	  This makes transparent proxy support available in nftables.
+
 if NF_TABLES_NETDEV
 
 config NF_DUP_NETDEV
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 44449389e527..2af51df46d71 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -104,6 +104,7 @@  obj-$(CONFIG_NFT_FIB_INET)	+= nft_fib_inet.o
 obj-$(CONFIG_NFT_FIB_NETDEV)	+= nft_fib_netdev.o
 obj-$(CONFIG_NF_OSF)		+= nf_osf.o
 obj-$(CONFIG_NFT_SOCKET)	+= nft_socket.o
+obj-$(CONFIG_NFT_TPROXY)	+= nft_tproxy.o
 
 # nf_tables netdev
 obj-$(CONFIG_NFT_DUP_NETDEV)	+= nft_dup_netdev.o
diff --git a/net/netfilter/nft_tproxy.c b/net/netfilter/nft_tproxy.c
new file mode 100644
index 000000000000..b3de90055a6a
--- /dev/null
+++ b/net/netfilter/nft_tproxy.c
@@ -0,0 +1,331 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/module.h>
+#include <linux/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables_core.h>
+#include <net/netfilter/nf_tproxy.h>
+#include <net/inet_sock.h>
+#include <net/tcp.h>
+#include <linux/if_ether.h>
+#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
+#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
+#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
+#endif
+
+struct nft_tproxy {
+	enum nft_registers      sreg_addr:8;
+	enum nft_registers      sreg_port:8;
+	u8			family;
+};
+
+static void nft_tproxy_eval_v4(const struct nft_expr *expr,
+			    struct nft_regs *regs,
+			    const struct nft_pktinfo *pkt)
+{
+	const struct nft_tproxy *priv = nft_expr_priv(expr);
+	struct sk_buff *skb = pkt->skb;
+	struct sock *sk = skb->sk;
+	const struct iphdr *iph = ip_hdr(skb);
+	struct udphdr _hdr, *hp;
+	__be32 taddr = 0;
+	__be16 tport = 0;
+
+	if (!pkt->tprot_set) {
+		regs->verdict.code = NFT_BREAK;
+		return;
+	}
+
+	hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
+	if (!hp) {
+		regs->verdict.code = NFT_BREAK;
+		return;
+	}
+
+	/* 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(nft_net(pkt), skb, hp, iph->protocol,
+				   iph->saddr, iph->daddr,
+				   hp->source, hp->dest,
+				   skb->dev, NF_TPROXY_LOOKUP_ESTABLISHED);
+
+	if (priv->sreg_addr)
+		taddr = regs->data[priv->sreg_addr];
+	taddr = nf_tproxy_laddr4(skb, taddr, iph->daddr);
+
+	if (priv->sreg_port)
+		tport = regs->data[priv->sreg_port];
+	if (!tport)
+		tport = 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 = nf_tproxy_handle_time_wait4(nft_net(pkt), skb, taddr, tport, 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(nft_net(pkt), skb, hp, iph->protocol,
+					   iph->saddr, taddr,
+					   hp->source, tport,
+					   skb->dev, NF_TPROXY_LOOKUP_LISTENER);
+
+	if (sk && nf_tproxy_sk_is_transparent(sk))
+		nf_tproxy_assign_sock(skb, sk);
+	else
+		regs->verdict.code = NFT_BREAK;
+}
+
+#if IS_ENABLED(CONFIG_NF_TPROXY_IPV6)
+static void nft_tproxy_eval_v6(const struct nft_expr *expr,
+			    struct nft_regs *regs,
+			    const struct nft_pktinfo *pkt)
+{
+	const struct nft_tproxy *priv = nft_expr_priv(expr);
+	struct sk_buff *skb = pkt->skb;
+	struct sock *sk = skb->sk;
+	const struct ipv6hdr *iph = ipv6_hdr(skb);
+	struct udphdr _hdr, *hp;
+	struct in6_addr taddr = {0};
+	__be16 tport = 0;
+	int thoff = 0;
+	int l4proto;
+
+	l4proto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
+	if (l4proto < 0) {
+		regs->verdict.code = NFT_BREAK;
+		return;
+	}
+
+	hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
+	if (hp == NULL) {
+		regs->verdict.code = NFT_BREAK;
+		return;
+	}
+
+	/* 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(nft_net(pkt), skb, thoff, hp, l4proto,
+				   &iph->saddr, &iph->daddr,
+				   hp->source, hp->dest,
+				   nft_in(pkt), NF_TPROXY_LOOKUP_ESTABLISHED);
+
+	if (priv->sreg_addr)
+		memcpy (&taddr, &regs->data[priv->sreg_addr], sizeof(taddr));
+	taddr = *nf_tproxy_laddr6(skb, &taddr, &iph->daddr);
+
+	if (priv->sreg_port)
+		tport = regs->data[priv->sreg_port];
+	if (!tport)
+		tport = 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 = nf_tproxy_handle_time_wait6(skb, l4proto, thoff,
+						 nft_net(pkt),
+						 &taddr,
+						 tport,
+						 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(nft_net(pkt), skb, thoff, hp,
+					   l4proto, &iph->saddr, &taddr,
+					   hp->source, tport,
+					   nft_in(pkt), NF_TPROXY_LOOKUP_LISTENER);
+
+	/* NOTE: assign_sock consumes our sk reference */
+	if (sk && nf_tproxy_sk_is_transparent(sk))
+		nf_tproxy_assign_sock(skb, sk);
+	else
+		regs->verdict.code = NFT_BREAK;
+}
+#endif
+
+static void nft_tproxy_eval(const struct nft_expr *expr,
+			    struct nft_regs *regs,
+			    const struct nft_pktinfo *pkt)
+{
+	const struct nft_tproxy *priv = nft_expr_priv(expr);
+
+	switch (nft_pf(pkt)) {
+	case NFPROTO_IPV4:
+		switch (priv->family) {
+		case NFPROTO_IPV4:
+		case NFPROTO_INET:
+			nft_tproxy_eval_v4(expr, regs, pkt);
+			break;
+		default:
+			regs->verdict.code = NFT_BREAK;
+			break;
+		}
+		break;
+#if IS_ENABLED(CONFIG_NF_TPROXY_IPV6)
+	case NFPROTO_IPV6:
+		switch (priv->family) {
+		case NFPROTO_IPV6:
+		case NFPROTO_INET:
+			nft_tproxy_eval_v6(expr, regs, pkt);
+			break;
+		default:
+			regs->verdict.code = NFT_BREAK;
+			break;
+		}
+		break;
+#endif
+	default:
+		regs->verdict.code = NFT_BREAK;
+	}
+}
+
+static const struct nla_policy nft_tproxy_policy[NFTA_TPROXY_MAX + 1] = {
+	[NFTA_TPROXY_FAMILY]   = { .type = NLA_U32 },
+	[NFTA_TPROXY_REG_ADDR] = { .type = NLA_U32 },
+	[NFTA_TPROXY_REG_PORT] = { .type = NLA_U32 },
+};
+
+static int nft_tproxy_init(const struct nft_ctx *ctx,
+			   const struct nft_expr *expr,
+			   const struct nlattr * const tb[])
+{
+	struct nft_tproxy *priv = nft_expr_priv(expr);
+	unsigned int alen = 0;
+	int err;
+
+	switch(ctx->family) {
+	case NFPROTO_IPV4:
+#if IS_ENABLED(CONFIG_NF_TPROXY_IPV6)
+	case NFPROTO_IPV6:
+#endif
+	case NFPROTO_INET:
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	if (!tb[NFTA_TPROXY_FAMILY] ||
+	    (!tb[NFTA_TPROXY_REG_ADDR] && !tb[NFTA_TPROXY_REG_PORT]))
+		return -EINVAL;
+
+	priv->family = ntohl(nla_get_be32(tb[NFTA_TPROXY_FAMILY]));
+	switch (ctx->family) {
+	case NFPROTO_IPV4:
+		if (priv->family != NFPROTO_IPV4)
+			return -EINVAL;
+		break;
+	case NFPROTO_IPV6:
+		if (priv->family != NFPROTO_IPV6)
+			return -EINVAL;
+		break;
+	}
+
+	if ((priv->family != NFPROTO_IPV4 && priv->family != NFPROTO_IPV6) &&
+	    tb[NFTA_TPROXY_REG_ADDR])
+		/* Address is specified but the rule family is not set accordingly */
+		return -EINVAL;
+
+	switch (priv->family) {
+	case NFPROTO_IPV4:
+		alen = FIELD_SIZEOF(union nf_inet_addr, in);
+		err = nf_defrag_ipv4_enable(ctx->net);
+		if (err)
+			return err;
+		break;
+#if IS_ENABLED(CONFIG_NF_TPROXY_IPV6)
+	case NFPROTO_IPV6:
+		alen = FIELD_SIZEOF(union nf_inet_addr, in6);
+		err = nf_defrag_ipv6_enable(ctx->net);
+		if (err)
+			return err;
+		break;
+#endif
+	case NFPROTO_INET:
+		/* No address is specified here */
+		err = nf_defrag_ipv4_enable(ctx->net);
+		if (err)
+			return err;
+		err = nf_defrag_ipv6_enable(ctx->net);
+		if (err)
+			return err;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	if (tb[NFTA_TPROXY_REG_ADDR]) {
+		priv->sreg_addr = nft_parse_register(tb[NFTA_TPROXY_REG_ADDR]);
+		err = nft_validate_register_load(priv->sreg_addr, alen);
+		if (err < 0)
+			return err;
+	}
+
+	if (tb[NFTA_TPROXY_REG_PORT]) {
+		priv->sreg_port = nft_parse_register(tb[NFTA_TPROXY_REG_PORT]);
+		err = nft_validate_register_load(priv->sreg_port, sizeof(u16));
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+
+static int nft_tproxy_dump(struct sk_buff *skb,
+			   const struct nft_expr *expr)
+{
+	const struct nft_tproxy *priv = nft_expr_priv(expr);
+
+	if(nla_put_be32(skb, NFTA_TPROXY_FAMILY, htonl(priv->family)))
+		return -1;
+
+	if (priv->sreg_addr) {
+		if (nft_dump_register(skb, NFTA_TPROXY_REG_ADDR, priv->sreg_addr))
+			return -1;
+	}
+
+	if (priv->sreg_port) {
+		if (nft_dump_register(skb, NFTA_TPROXY_REG_PORT, priv->sreg_port))
+			return -1;
+	}
+
+	return 0;
+}
+
+static struct nft_expr_type nft_tproxy_type;
+static const struct nft_expr_ops nft_tproxy_ops = {
+	.type		= &nft_tproxy_type,
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_tproxy)),
+	.eval		= nft_tproxy_eval,
+	.init		= nft_tproxy_init,
+	.dump		= nft_tproxy_dump,
+};
+
+static struct nft_expr_type nft_tproxy_type __read_mostly = {
+	.name		= "tproxy",
+	.ops		= &nft_tproxy_ops,
+	.policy		= nft_tproxy_policy,
+	.maxattr	= NFTA_TPROXY_MAX,
+	.owner		= THIS_MODULE,
+};
+
+static int __init nft_tproxy_module_init(void)
+{
+	return nft_register_expr(&nft_tproxy_type);
+}
+
+static void __exit nft_tproxy_module_exit(void)
+{
+	nft_unregister_expr(&nft_tproxy_type);
+}
+
+module_init(nft_tproxy_module_init);
+module_exit(nft_tproxy_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Máté Eckl");
+MODULE_DESCRIPTION("nf_tables tproxy support module");
+MODULE_ALIAS_NFT_EXPR("tproxy");