Commit 06ff4aa2 authored by Pablo Neira Ayuso's avatar Pablo Neira Ayuso
Browse files

netfilter: nf_osf: add nf_osf_match_one() 



This new function allows us to check if there is TCP syn packet matching
with a given fingerprint that can be reused from the upcoming new
nf_osf_find() function.

Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent f102d66b

net/netfilter/nf_osf.c

+111 −96
Original line number Diff line number Diff line
@@ -21,15 +21,14 @@ 
#include <linux/netfilter/nf_osf.h>



static inline int nf_osf_ttl(const struct sk_buff *skb,

			     const struct nf_osf_info *info,

			     unsigned char f_ttl)

			     int ttl_check, unsigned char f_ttl)

{

	const struct iphdr *ip = ip_hdr(skb);



	if (info->flags & NF_OSF_TTL) {

		if (info->ttl == NF_OSF_TTL_TRUE)

	if (ttl_check != -1) {

		if (ttl_check == NF_OSF_TTL_TRUE)

			return ip->ttl == f_ttl;

		if (info->ttl == NF_OSF_TTL_NOCHECK)

		if (ttl_check == NF_OSF_TTL_NOCHECK)

			return 1;

		else if (ip->ttl <= f_ttl)

			return 1;
@@ -52,61 +51,25 @@ static inline int nf_osf_ttl(const struct sk_buff *skb, 
	return ip->ttl == f_ttl;

}



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)

static bool nf_osf_match_one(const struct sk_buff *skb,

			     const struct nf_osf_user_finger *f,

			     int ttl_check, u16 totlen, u16 window,

			     const unsigned char *optp,

			     unsigned int optsize)

{

	const unsigned char *optp = NULL, *_optp = NULL;

	unsigned int optsize = 0, check_WSS = 0;

	int fmatch = FMATCH_WRONG, fcount = 0;

	const struct iphdr *ip = ip_hdr(skb);

	const struct nf_osf_user_finger *f;

	unsigned char opts[MAX_IPOPTLEN];

	const struct nf_osf_finger *kf;

	u16 window, totlen, mss = 0;

	const struct tcphdr *tcp;

	struct tcphdr _tcph;

	bool df;



	tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);

	if (!tcp)

		return false;



	if (!tcp->syn)

		return false;



	totlen = ntohs(ip->tot_len);

	df = ntohs(ip->frag_off) & IP_DF;

	window = ntohs(tcp->window);



	if (tcp->doff * 4 > sizeof(struct tcphdr)) {

		optsize = tcp->doff * 4 - sizeof(struct tcphdr);



		_optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) +

				sizeof(struct tcphdr), optsize, opts);

	}



	list_for_each_entry_rcu(kf, &nf_osf_fingers[df], finger_entry) {

	unsigned int check_WSS = 0;

	int fmatch = FMATCH_WRONG;

	int foptsize, optnum;

	u16 mss = 0;



		f = &kf->finger;



		if (!(info->flags & NF_OSF_LOG) && strcmp(info->genre, f->genre))

			continue;



		optp = _optp;

		fmatch = FMATCH_WRONG;



		if (totlen != f->ss || !nf_osf_ttl(skb, info, f->ttl))

			continue;

	if (totlen != f->ss || !nf_osf_ttl(skb, ttl_check, f->ttl))

		return false;



	/*

	 * Should not happen if userspace parser was written correctly.

	 */

	if (f->wss.wc >= OSF_WSS_MAX)

			continue;

		return false;



	/* Check options */
@@ -117,7 +80,7 @@ nf_osf_match(const struct sk_buff *skb, u_int8_t family, 
	if (foptsize > MAX_IPOPTLEN ||

	    optsize > MAX_IPOPTLEN ||

	    optsize != foptsize)

			continue;

		return false;



	check_WSS = f->wss.wc;
@@ -183,9 +146,61 @@ nf_osf_match(const struct sk_buff *skb, u_int8_t family, 
		}

	}



		if (fmatch != FMATCH_OK)

	return fmatch == FMATCH_OK;

}



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)

{

	const unsigned char *optp = NULL, *_optp = NULL;

	const struct iphdr *ip = ip_hdr(skb);

	const struct nf_osf_user_finger *f;

	unsigned char opts[MAX_IPOPTLEN];

	const struct nf_osf_finger *kf;

	int fcount = 0, ttl_check;

	int fmatch = FMATCH_WRONG;

	unsigned int optsize = 0;

	const struct tcphdr *tcp;

	struct tcphdr _tcph;

	u16 window, totlen;

	bool df;



	tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);

	if (!tcp)

		return false;



	if (!tcp->syn)

		return false;



	totlen = ntohs(ip->tot_len);

	df = ntohs(ip->frag_off) & IP_DF;

	window = ntohs(tcp->window);



	if (tcp->doff * 4 > sizeof(struct tcphdr)) {

		optsize = tcp->doff * 4 - sizeof(struct tcphdr);



		_optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) +

				sizeof(struct tcphdr), optsize, opts);

	}



	ttl_check = (info->flags & NF_OSF_TTL) ? info->ttl : -1;



	list_for_each_entry_rcu(kf, &nf_osf_fingers[df], finger_entry) {



		f = &kf->finger;



		if (!(info->flags & NF_OSF_LOG) && strcmp(info->genre, f->genre))

			continue;



		if (!nf_osf_match_one(skb, f,

				      ttl_check, totlen, window, optp, optsize))

			continue;



		fmatch = FMATCH_OK;



		fcount++;



		if (info->flags & NF_OSF_LOG)