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Commit b96af92d authored by Fernando Fernandez Mancera's avatar Fernando Fernandez Mancera Committed by Pablo Neira Ayuso
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netfilter: nf_tables: implement Passive OS fingerprint module in nft_osf 



Add basic module functions into nft_osf.[ch] in order to implement OSF
module in nf_tables.

Signed-off-by: default avatarFernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent f9324952

include/uapi/linux/netfilter/nf_tables.h

+7 −0
Original line number Diff line number Diff line
@@ -1463,6 +1463,13 @@ enum nft_flowtable_hook_attributes { 
};

#define NFTA_FLOWTABLE_HOOK_MAX	(__NFTA_FLOWTABLE_HOOK_MAX - 1)



enum nft_osf_attributes {

	NFTA_OSF_UNSPEC,

	NFTA_OSF_DREG,

	__NFTA_OSF_MAX,

};

#define NFTA_OSF_MAX (__NFTA_OSF_MAX - 1)



/**

 * enum nft_device_attributes - nf_tables device netlink attributes

 *

net/netfilter/Kconfig

+7 −0
Original line number Diff line number Diff line
@@ -627,6 +627,13 @@ config NFT_SOCKET 
	  This option allows matching for the presence or absence of a

	  corresponding socket and its attributes.



config NFT_OSF

	tristate "Netfilter nf_tables passive OS fingerprint support"

	depends on NETFILTER_ADVANCED

	select NETFILTER_NETLINK_OSF

	help

	  This option allows matching packets from an specific OS.



if NF_TABLES_NETDEV



config NF_DUP_NETDEV

net/netfilter/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -110,6 +110,7 @@ obj-$(CONFIG_NFT_FIB) += nft_fib.o 
obj-$(CONFIG_NFT_FIB_INET)	+= nft_fib_inet.o

obj-$(CONFIG_NFT_FIB_NETDEV)	+= nft_fib_netdev.o

obj-$(CONFIG_NFT_SOCKET)	+= nft_socket.o

obj-$(CONFIG_NFT_OSF)		+= nft_osf.o



# nf_tables netdev

obj-$(CONFIG_NFT_DUP_NETDEV)	+= nft_dup_netdev.o

net/netfilter/nft_osf.c

0 → 100644
+106 −0
Original line number Diff line number Diff line 
#include <net/ip.h>

#include <net/tcp.h>



#include <net/netfilter/nf_tables.h>

#include <linux/netfilter/nf_osf.h>



#define OSF_GENRE_SIZE		32



struct nft_osf {

	enum nft_registers	dreg:8;

};



static const struct nla_policy nft_osf_policy[NFTA_OSF_MAX + 1] = {

	[NFTA_OSF_DREG]		= { .type = NLA_U32 },

};



static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,

			 const struct nft_pktinfo *pkt)

{

	struct nft_osf *priv = nft_expr_priv(expr);

	u32 *dest = &regs->data[priv->dreg];

	struct sk_buff *skb = pkt->skb;

	const struct tcphdr *tcp;

	struct tcphdr _tcph;

	const char *os_name;



	tcp = skb_header_pointer(skb, ip_hdrlen(skb),

				 sizeof(struct tcphdr), &_tcph);

	if (!tcp) {

		regs->verdict.code = NFT_BREAK;

		return;

	}

	if (!tcp->syn) {

		regs->verdict.code = NFT_BREAK;

		return;

	}



	os_name = nf_osf_find(skb, nf_osf_fingers);

	if (!os_name)

		strncpy((char *)dest, "unknown", IFNAMSIZ);

	else

		strncpy((char *)dest, os_name, IFNAMSIZ);

}



static int nft_osf_init(const struct nft_ctx *ctx,

			const struct nft_expr *expr,

			const struct nlattr * const tb[])

{

	struct nft_osf *priv = nft_expr_priv(expr);

	int err;



	priv->dreg = nft_parse_register(tb[NFTA_OSF_DREG]);

	err = nft_validate_register_store(ctx, priv->dreg, NULL,

					  NFTA_DATA_VALUE, OSF_GENRE_SIZE);

	if (err < 0)

		return err;



	return 0;

}



static int nft_osf_dump(struct sk_buff *skb, const struct nft_expr *expr)

{

	const struct nft_osf *priv = nft_expr_priv(expr);



	if (nft_dump_register(skb, NFTA_OSF_DREG, priv->dreg))

		goto nla_put_failure;



	return 0;



nla_put_failure:

	return -1;

}



static struct nft_expr_type nft_osf_type;

static const struct nft_expr_ops nft_osf_op = {

	.eval		= nft_osf_eval,

	.size		= NFT_EXPR_SIZE(sizeof(struct nft_osf)),

	.init		= nft_osf_init,

	.dump		= nft_osf_dump,

	.type		= &nft_osf_type,

};



static struct nft_expr_type nft_osf_type __read_mostly = {

	.ops		= &nft_osf_op,

	.name		= "osf",

	.owner		= THIS_MODULE,

	.policy		= nft_osf_policy,

	.maxattr	= NFTA_OSF_MAX,

};



static int __init nft_osf_module_init(void)

{

	return nft_register_expr(&nft_osf_type);

}



static void __exit nft_osf_module_exit(void)

{

	return nft_unregister_expr(&nft_osf_type);

}



module_init(nft_osf_module_init);

module_exit(nft_osf_module_exit);



MODULE_LICENSE("GPL");

MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");

MODULE_ALIAS_NFT_EXPR("osf");