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Commit bfb15f2a authored by Fernando Fernandez Mancera's avatar Fernando Fernandez Mancera Committed by Pablo Neira Ayuso
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netfilter: extract Passive OS fingerprint infrastructure from xt_osf 



Add nf_osf_ttl() and nf_osf_match() into nf_osf.c to prepare for
nf_tables support.

Signed-off-by: default avatarFernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 3f9c56a5

include/linux/netfilter/nf_osf.h

0 → 100644
+27 −0
Original line number Diff line number Diff line 
#include <uapi/linux/netfilter/nf_osf.h>



/* Initial window size option state machine: multiple of mss, mtu or

 * plain numeric value. Can also be made as plain numeric value which

 * is not a multiple of specified value.

 */

enum nf_osf_window_size_options {

	OSF_WSS_PLAIN   = 0,

	OSF_WSS_MSS,

	OSF_WSS_MTU,

	OSF_WSS_MODULO,

	OSF_WSS_MAX,

};



enum osf_fmatch_states {

	/* Packet does not match the fingerprint */

	FMATCH_WRONG = 0,

	/* Packet matches the fingerprint */

	FMATCH_OK,

	/* Options do not match the fingerprint, but header does */

	FMATCH_OPT_WRONG,

};



bool nf_osf_match(const struct sk_buff *skb, u_int8_t family,

		  int hooknum, struct net_device *in, struct net_device *out,

		  const struct nf_osf_info *info, struct net *net,

		  const struct list_head *nf_osf_fingers);

include/uapi/linux/netfilter/nf_osf.h

0 → 100644
+90 −0
Original line number Diff line number Diff line 
#ifndef _NF_OSF_H

#define _NF_OSF_H



#define MAXGENRELEN	32



#define NF_OSF_GENRE	(1 << 0)

#define NF_OSF_TTL	(1 << 1)

#define NF_OSF_LOG	(1 << 2)

#define NF_OSF_INVERT	(1 << 3)



#define NF_OSF_LOGLEVEL_ALL		0	/* log all matched fingerprints */

#define NF_OSF_LOGLEVEL_FIRST		1	/* log only the first matced fingerprint */

#define NF_OSF_LOGLEVEL_ALL_KNOWN	2	/* do not log unknown packets */



#define NF_OSF_TTL_TRUE			0	/* True ip and fingerprint TTL comparison */



/* Do not compare ip and fingerprint TTL at all */

#define NF_OSF_TTL_NOCHECK		2



/* Wildcard MSS (kind of).

 * It is used to implement a state machine for the different wildcard values

 * of the MSS and window sizes.

 */

struct nf_osf_wc {

	__u32	wc;

	__u32	val;

};



/* This struct represents IANA options

 * http://www.iana.org/assignments/tcp-parameters

 */

struct nf_osf_opt {

	__u16			kind, length;

	struct nf_osf_wc	wc;

};



struct nf_osf_info {

	char	genre[MAXGENRELEN];

	__u32	len;

	__u32	flags;

	__u32	loglevel;

	__u32	ttl;

};



struct nf_osf_user_finger {

	struct nf_osf_wc	wss;



	__u8	ttl, df;

	__u16	ss, mss;

	__u16	opt_num;



	char	genre[MAXGENRELEN];

	char	version[MAXGENRELEN];

	char	subtype[MAXGENRELEN];



	/* MAX_IPOPTLEN is maximum if all options are NOPs or EOLs */

	struct nf_osf_opt	opt[MAX_IPOPTLEN];

};



struct nf_osf_finger {

	struct rcu_head			rcu_head;

	struct list_head		finger_entry;

	struct nf_osf_user_finger	finger;

};



struct nf_osf_nlmsg {

	struct nf_osf_user_finger	f;

	struct iphdr			ip;

	struct tcphdr			tcp;

};



/* Defines for IANA option kinds */

enum iana_options {

	OSFOPT_EOL = 0,		/* End of options */

	OSFOPT_NOP,		/* NOP */

	OSFOPT_MSS,		/* Maximum segment size */

	OSFOPT_WSO,		/* Window scale option */

	OSFOPT_SACKP,		/* SACK permitted */

	OSFOPT_SACK,		/* SACK */

	OSFOPT_ECHO,

	OSFOPT_ECHOREPLY,

	OSFOPT_TS,		/* Timestamp option */

	OSFOPT_POCP,		/* Partial Order Connection Permitted */

	OSFOPT_POSP,		/* Partial Order Service Profile */



	/* Others are not used in the current OSF */

	OSFOPT_EMPTY = 255,

};



#endif /* _NF_OSF_H */

include/uapi/linux/netfilter/xt_osf.h

+17 −89
Original line number Diff line number Diff line
@@ -23,101 +23,29 @@ 
#include <linux/types.h>

#include <linux/ip.h>

#include <linux/tcp.h>

#include <linux/netfilter/nf_osf.h>



#define MAXGENRELEN		32

#define XT_OSF_GENRE		NF_OSF_GENRE

#define XT_OSF_INVERT		NF_OSF_INVERT



#define XT_OSF_GENRE		(1<<0)

#define	XT_OSF_TTL		(1<<1)

#define XT_OSF_LOG		(1<<2)

#define XT_OSF_INVERT		(1<<3)

#define XT_OSF_TTL		NF_OSF_TTL

#define XT_OSF_LOG		NF_OSF_LOG



#define XT_OSF_LOGLEVEL_ALL	0	/* log all matched fingerprints */

#define XT_OSF_LOGLEVEL_FIRST	1	/* log only the first matced fingerprint */

#define XT_OSF_LOGLEVEL_ALL_KNOWN	2 /* do not log unknown packets */

#define XT_OSF_LOGLEVEL_ALL		NF_OSF_LOGLEVEL_ALL

#define XT_OSF_LOGLEVEL_FIRST		NF_OSF_LOGLEVEL_FIRST

#define XT_OSF_LOGLEVEL_ALL_KNOWN	NF_OSF_LOGLEVEL_ALL_KNOWN



#define XT_OSF_TTL_TRUE		0	/* True ip and fingerprint TTL comparison */

#define XT_OSF_TTL_LESS		1	/* Check if ip TTL is less than fingerprint one */

#define XT_OSF_TTL_NOCHECK	2	/* Do not compare ip and fingerprint TTL at all */



struct xt_osf_info {

	char			genre[MAXGENRELEN];

	__u32			len;

	__u32			flags;

	__u32			loglevel;

	__u32			ttl;

};



/*

 * Wildcard MSS (kind of).

 * It is used to implement a state machine for the different wildcard values

 * of the MSS and window sizes.

 */

struct xt_osf_wc {

	__u32			wc;

	__u32			val;

};



/*

 * This struct represents IANA options

 * http://www.iana.org/assignments/tcp-parameters

 */

struct xt_osf_opt {

	__u16			kind, length;

	struct xt_osf_wc	wc;

};



struct xt_osf_user_finger {

	struct xt_osf_wc	wss;



	__u8			ttl, df;

	__u16			ss, mss;

	__u16			opt_num;

#define XT_OSF_TTL_TRUE		NF_OSF_TTL_TRUE

#define XT_OSF_TTL_NOCHECK	NF_OSF_TTL_NOCHECK



	char			genre[MAXGENRELEN];

	char			version[MAXGENRELEN];

	char			subtype[MAXGENRELEN];



	/* MAX_IPOPTLEN is maximum if all options are NOPs or EOLs */

	struct xt_osf_opt	opt[MAX_IPOPTLEN];

};



struct xt_osf_nlmsg {

	struct xt_osf_user_finger	f;

	struct iphdr		ip;

	struct tcphdr		tcp;

};



/* Defines for IANA option kinds */



enum iana_options {

	OSFOPT_EOL = 0,		/* End of options */

	OSFOPT_NOP, 		/* NOP */

	OSFOPT_MSS, 		/* Maximum segment size */

	OSFOPT_WSO, 		/* Window scale option */

	OSFOPT_SACKP,		/* SACK permitted */

	OSFOPT_SACK,		/* SACK */

	OSFOPT_ECHO,

	OSFOPT_ECHOREPLY,

	OSFOPT_TS,		/* Timestamp option */

	OSFOPT_POCP,		/* Partial Order Connection Permitted */

	OSFOPT_POSP,		/* Partial Order Service Profile */



	/* Others are not used in the current OSF */

	OSFOPT_EMPTY = 255,

};

#define XT_OSF_TTL_LESS	1	/* Check if ip TTL is less than fingerprint one */



/*

 * Initial window size option state machine: multiple of mss, mtu or

 * plain numeric value. Can also be made as plain numeric value which

 * is not a multiple of specified value.

 */

enum xt_osf_window_size_options {

	OSF_WSS_PLAIN	= 0,

	OSF_WSS_MSS,

	OSF_WSS_MTU,

	OSF_WSS_MODULO,

	OSF_WSS_MAX,

};

#define xt_osf_wc		nf_osf_wc

#define xt_osf_opt		nf_osf_opt

#define xt_osf_info		nf_osf_info

#define xt_osf_user_finger	nf_osf_user_finger

#define xt_osf_finger		nf_osf_finger

#define xt_osf_nlmsg		nf_osf_nlmsg



/*

 * Add/remove fingerprint from the kernel.

net/netfilter/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -444,6 +444,9 @@ config NETFILTER_SYNPROXY 


endif # NF_CONNTRACK



config NF_OSF

	tristate 'Passive OS fingerprint infrastructure'



config NF_TABLES

	select NETFILTER_NETLINK

	tristate "Netfilter nf_tables support"
@@ -1358,6 +1361,7 @@ config NETFILTER_XT_MATCH_NFACCT 
config NETFILTER_XT_MATCH_OSF

	tristate '"osf" Passive OS fingerprint match'

	depends on NETFILTER_ADVANCED && NETFILTER_NETLINK

	select NF_OSF

	help

	  This option selects the Passive OS Fingerprinting match module

	  that allows to passively match the remote operating system by

net/netfilter/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -101,6 +101,7 @@ obj-$(CONFIG_NFT_HASH) += nft_hash.o 
obj-$(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_NF_OSF)		+= nf_osf.o



# nf_tables netdev

obj-$(CONFIG_NFT_DUP_NETDEV)	+= nft_dup_netdev.o