[deliverable/linux.git] / net / netfilter / xt_osf.c

/*
 * Copyright (c) 2003+ Evgeniy Polyakov <zbr@ioremap.net>
 *
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>

#include <linux/if.h>
#include <linux/inetdevice.h>
#include <linux/ip.h>
#include <linux/list.h>
#include <linux/rculist.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/tcp.h>

#include <net/ip.h>
#include <net/tcp.h>

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/x_tables.h>
#include <net/netfilter/nf_log.h>
#include <linux/netfilter/xt_osf.h>

struct xt_osf_finger {
	struct rcu_head			rcu_head;
	struct list_head		finger_entry;
	struct xt_osf_user_finger	finger;
};

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,
};

/*
 * Indexed by dont-fragment bit.
 * It is the only constant value in the fingerprint.
 */
static struct list_head xt_osf_fingers[2];

static const struct nla_policy xt_osf_policy[OSF_ATTR_MAX + 1] = {
	[OSF_ATTR_FINGER]	= { .len = sizeof(struct xt_osf_user_finger) },
};

static int xt_osf_add_callback(struct net *net, struct sock *ctnl,
			       struct sk_buff *skb, const struct nlmsghdr *nlh,
			       const struct nlattr * const osf_attrs[])
{
	struct xt_osf_user_finger *f;
	struct xt_osf_finger *kf = NULL, *sf;
	int err = 0;

	if (!osf_attrs[OSF_ATTR_FINGER])
		return -EINVAL;

	if (!(nlh->nlmsg_flags & NLM_F_CREATE))
		return -EINVAL;

	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);

	kf = kmalloc(sizeof(struct xt_osf_finger), GFP_KERNEL);
	if (!kf)
		return -ENOMEM;

	memcpy(&kf->finger, f, sizeof(struct xt_osf_user_finger));

	list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
		if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
			continue;

		kfree(kf);
		kf = NULL;

		if (nlh->nlmsg_flags & NLM_F_EXCL)
			err = -EEXIST;
		break;
	}

	/*
	 * We are protected by nfnl mutex.
	 */
	if (kf)
		list_add_tail_rcu(&kf->finger_entry, &xt_osf_fingers[!!f->df]);

	return err;
}

static int xt_osf_remove_callback(struct net *net, struct sock *ctnl,
				  struct sk_buff *skb,
				  const struct nlmsghdr *nlh,
				  const struct nlattr * const osf_attrs[])
{
	struct xt_osf_user_finger *f;
	struct xt_osf_finger *sf;
	int err = -ENOENT;

	if (!osf_attrs[OSF_ATTR_FINGER])
		return -EINVAL;

	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);

	list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
		if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
			continue;

		/*
		 * We are protected by nfnl mutex.
		 */
		list_del_rcu(&sf->finger_entry);
		kfree_rcu(sf, rcu_head);

		err = 0;
		break;
	}

	return err;
}

static const struct nfnl_callback xt_osf_nfnetlink_callbacks[OSF_MSG_MAX] = {
	[OSF_MSG_ADD]	= {
		.call		= xt_osf_add_callback,
		.attr_count	= OSF_ATTR_MAX,
		.policy		= xt_osf_policy,
	},
	[OSF_MSG_REMOVE]	= {
		.call		= xt_osf_remove_callback,
		.attr_count	= OSF_ATTR_MAX,
		.policy		= xt_osf_policy,
	},
};

static const struct nfnetlink_subsystem xt_osf_nfnetlink = {
	.name			= "osf",
	.subsys_id		= NFNL_SUBSYS_OSF,
	.cb_count		= OSF_MSG_MAX,
	.cb			= xt_osf_nfnetlink_callbacks,
};

static inline int xt_osf_ttl(const struct sk_buff *skb, const struct xt_osf_info *info,
			    unsigned char f_ttl)
{
	const struct iphdr *ip = ip_hdr(skb);

	if (info->flags & XT_OSF_TTL) {
		if (info->ttl == XT_OSF_TTL_TRUE)
			return ip->ttl == f_ttl;
		if (info->ttl == XT_OSF_TTL_NOCHECK)
			return 1;
		else if (ip->ttl <= f_ttl)
			return 1;
		else {
			struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
			int ret = 0;

			for_ifa(in_dev) {
				if (inet_ifa_match(ip->saddr, ifa)) {
					ret = (ip->ttl == f_ttl);
					break;
				}
			}
			endfor_ifa(in_dev);

			return ret;
		}
	}

	return ip->ttl == f_ttl;
}

static bool
xt_osf_match_packet(const struct sk_buff *skb, struct xt_action_param *p)
{
	const struct xt_osf_info *info = p->matchinfo;
	const struct iphdr *ip = ip_hdr(skb);
	const struct tcphdr *tcp;
	struct tcphdr _tcph;
	int fmatch = FMATCH_WRONG, fcount = 0;
	unsigned int optsize = 0, check_WSS = 0;
	u16 window, totlen, mss = 0;
	bool df;
	const unsigned char *optp = NULL, *_optp = NULL;
	unsigned char opts[MAX_IPOPTLEN];
	const struct xt_osf_finger *kf;
	const struct xt_osf_user_finger *f;
	struct net *net = p->net;

	if (!info)
		return false;

	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);
	}

	rcu_read_lock();
	list_for_each_entry_rcu(kf, &xt_osf_fingers[df], finger_entry) {
		int foptsize, optnum;

		f = &kf->finger;

		if (!(info->flags & XT_OSF_LOG) && strcmp(info->genre, f->genre))
			continue;

		optp = _optp;
		fmatch = FMATCH_WRONG;

		if (totlen != f->ss || !xt_osf_ttl(skb, info, f->ttl))
			continue;

		/*
		 * Should not happen if userspace parser was written correctly.
		 */
		if (f->wss.wc >= OSF_WSS_MAX)
			continue;

		/* Check options */

		foptsize = 0;
		for (optnum = 0; optnum < f->opt_num; ++optnum)
			foptsize += f->opt[optnum].length;

		if (foptsize > MAX_IPOPTLEN ||
		    optsize > MAX_IPOPTLEN ||
		    optsize != foptsize)
			continue;

		check_WSS = f->wss.wc;

		for (optnum = 0; optnum < f->opt_num; ++optnum) {
			if (f->opt[optnum].kind == (*optp)) {
				__u32 len = f->opt[optnum].length;
				const __u8 *optend = optp + len;

				fmatch = FMATCH_OK;

				switch (*optp) {
				case OSFOPT_MSS:
					mss = optp[3];
					mss <<= 8;
					mss |= optp[2];

					mss = ntohs((__force __be16)mss);
					break;
				case OSFOPT_TS:
					break;
				}

				optp = optend;
			} else
				fmatch = FMATCH_OPT_WRONG;

			if (fmatch != FMATCH_OK)
				break;
		}

		if (fmatch != FMATCH_OPT_WRONG) {
			fmatch = FMATCH_WRONG;

			switch (check_WSS) {
			case OSF_WSS_PLAIN:
				if (f->wss.val == 0 || window == f->wss.val)
					fmatch = FMATCH_OK;
				break;
			case OSF_WSS_MSS:
				/*
				 * Some smart modems decrease mangle MSS to
				 * SMART_MSS_2, so we check standard, decreased
				 * and the one provided in the fingerprint MSS
				 * values.
				 */
#define SMART_MSS_1	1460
#define SMART_MSS_2	1448
				if (window == f->wss.val * mss ||
				    window == f->wss.val * SMART_MSS_1 ||
				    window == f->wss.val * SMART_MSS_2)
					fmatch = FMATCH_OK;
				break;
			case OSF_WSS_MTU:
				if (window == f->wss.val * (mss + 40) ||
				    window == f->wss.val * (SMART_MSS_1 + 40) ||
				    window == f->wss.val * (SMART_MSS_2 + 40))
					fmatch = FMATCH_OK;
				break;
			case OSF_WSS_MODULO:
				if ((window % f->wss.val) == 0)
					fmatch = FMATCH_OK;
				break;
			}
		}

		if (fmatch != FMATCH_OK)
			continue;

		fcount++;

		if (info->flags & XT_OSF_LOG)
			nf_log_packet(net, p->family, p->hooknum, skb,
				      p->in, p->out, NULL,
				      "%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n",
				      f->genre, f->version, f->subtype,
				      &ip->saddr, ntohs(tcp->source),
				      &ip->daddr, ntohs(tcp->dest),
				      f->ttl - ip->ttl);

		if ((info->flags & XT_OSF_LOG) &&
		    info->loglevel == XT_OSF_LOGLEVEL_FIRST)
			break;
	}
	rcu_read_unlock();

	if (!fcount && (info->flags & XT_OSF_LOG))
		nf_log_packet(net, p->family, p->hooknum, skb, p->in,
			      p->out, NULL,
			"Remote OS is not known: %pI4:%u -> %pI4:%u\n",
				&ip->saddr, ntohs(tcp->source),
				&ip->daddr, ntohs(tcp->dest));

	if (fcount)
		fmatch = FMATCH_OK;

	return fmatch == FMATCH_OK;
}

static struct xt_match xt_osf_match = {
	.name 		= "osf",
	.revision	= 0,
	.family		= NFPROTO_IPV4,
	.proto		= IPPROTO_TCP,
	.hooks      	= (1 << NF_INET_LOCAL_IN) |
				(1 << NF_INET_PRE_ROUTING) |
				(1 << NF_INET_FORWARD),
	.match 		= xt_osf_match_packet,
	.matchsize	= sizeof(struct xt_osf_info),
	.me		= THIS_MODULE,
};

static int __init xt_osf_init(void)
{
	int err = -EINVAL;
	int i;

	for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i)
		INIT_LIST_HEAD(&xt_osf_fingers[i]);

	err = nfnetlink_subsys_register(&xt_osf_nfnetlink);
	if (err < 0) {
		pr_err("Failed to register OSF nsfnetlink helper (%d)\n", err);
		goto err_out_exit;
	}

	err = xt_register_match(&xt_osf_match);
	if (err) {
		pr_err("Failed to register OS fingerprint "
		       "matching module (%d)\n", err);
		goto err_out_remove;
	}

	return 0;

err_out_remove:
	nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
err_out_exit:
	return err;
}

static void __exit xt_osf_fini(void)
{
	struct xt_osf_finger *f;
	int i;

	nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
	xt_unregister_match(&xt_osf_match);

	rcu_read_lock();
	for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i) {

		list_for_each_entry_rcu(f, &xt_osf_fingers[i], finger_entry) {
			list_del_rcu(&f->finger_entry);
			kfree_rcu(f, rcu_head);
		}
	}
	rcu_read_unlock();

	rcu_barrier();
}

module_init(xt_osf_init);
module_exit(xt_osf_fini);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
MODULE_DESCRIPTION("Passive OS fingerprint matching.");
MODULE_ALIAS("ipt_osf");
MODULE_ALIAS("ip6t_osf");
MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_OSF);
Commit	Line	Data
11eeef41 EP	1	/*
	2	* Copyright (c) 2003+ Evgeniy Polyakov <zbr@ioremap.net>
	3	*
	4	*
	5	* This program is free software; you can redistribute it and/or modify
	6	* it under the terms of the GNU General Public License as published by
	7	* the Free Software Foundation; either version 2 of the License, or
	8	* (at your option) any later version.
	9	*
	10	* This program is distributed in the hope that it will be useful,
	11	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	13	* GNU General Public License for more details.
	14	*
	15	* You should have received a copy of the GNU General Public License
e664eabd	16	* along with this program; if not, see <http://www.gnu.org/licenses/>.
11eeef41	17	*/
8bee4bad	18	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11eeef41 EP	19	#include <linux/module.h>
	20	#include <linux/kernel.h>
	21
	22	#include <linux/if.h>
	23	#include <linux/inetdevice.h>
	24	#include <linux/ip.h>
	25	#include <linux/list.h>
	26	#include <linux/rculist.h>
	27	#include <linux/skbuff.h>
	28	#include <linux/slab.h>
	29	#include <linux/tcp.h>
	30
	31	#include <net/ip.h>
	32	#include <net/tcp.h>
	33
	34	#include <linux/netfilter/nfnetlink.h>
	35	#include <linux/netfilter/x_tables.h>
	36	#include <net/netfilter/nf_log.h>
	37	#include <linux/netfilter/xt_osf.h>
	38
	39	struct xt_osf_finger {
	40	struct rcu_head rcu_head;
	41	struct list_head finger_entry;
	42	struct xt_osf_user_finger finger;
	43	};
	44
	45	enum osf_fmatch_states {
	46	/* Packet does not match the fingerprint */
	47	FMATCH_WRONG = 0,
	48	/* Packet matches the fingerprint */
	49	FMATCH_OK,
	50	/* Options do not match the fingerprint, but header does */
	51	FMATCH_OPT_WRONG,
	52	};
	53
	54	/*
	55	* Indexed by dont-fragment bit.
	56	* It is the only constant value in the fingerprint.
	57	*/
	58	static struct list_head xt_osf_fingers[2];
	59
	60	static const struct nla_policy xt_osf_policy[OSF_ATTR_MAX + 1] = {
	61	[OSF_ATTR_FINGER] = { .len = sizeof(struct xt_osf_user_finger) },
	62	};
	63
7b8002a1 PNA	64	static int xt_osf_add_callback(struct net net, struct sock ctnl,
7b8002a1 PNA	65	struct sk_buff skb, const struct nlmsghdr nlh,
39938324	66	const struct nlattr * const osf_attrs[])
11eeef41 EP	67	{
	68	struct xt_osf_user_finger *f;
	69	struct xt_osf_finger kf = NULL, sf;
	70	int err = 0;
	71
	72	if (!osf_attrs[OSF_ATTR_FINGER])
	73	return -EINVAL;
	74
	75	if (!(nlh->nlmsg_flags & NLM_F_CREATE))
	76	return -EINVAL;
	77
	78	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
	79
	80	kf = kmalloc(sizeof(struct xt_osf_finger), GFP_KERNEL);
	81	if (!kf)
	82	return -ENOMEM;
	83
	84	memcpy(&kf->finger, f, sizeof(struct xt_osf_user_finger));
	85
	86	list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
	87	if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
	88	continue;
	89
	90	kfree(kf);
	91	kf = NULL;
	92
	93	if (nlh->nlmsg_flags & NLM_F_EXCL)
	94	err = -EEXIST;
	95	break;
	96	}
	97
	98	/*
	99	* We are protected by nfnl mutex.
	100	*/
	101	if (kf)
	102	list_add_tail_rcu(&kf->finger_entry, &xt_osf_fingers[!!f->df]);
	103
	104	return err;
	105	}
	106
7b8002a1 PNA	107	static int xt_osf_remove_callback(struct net net, struct sock ctnl,
7b8002a1 PNA	108	struct sk_buff *skb,
39938324 PM	109	const struct nlmsghdr *nlh,
39938324 PM	110	const struct nlattr * const osf_attrs[])
11eeef41 EP	111	{
	112	struct xt_osf_user_finger *f;
	113	struct xt_osf_finger *sf;
d667b9cf	114	int err = -ENOENT;
11eeef41 EP	115
	116	if (!osf_attrs[OSF_ATTR_FINGER])
	117	return -EINVAL;
	118
	119	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
	120
	121	list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
	122	if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
	123	continue;
	124
	125	/*
	126	* We are protected by nfnl mutex.
	127	*/
	128	list_del_rcu(&sf->finger_entry);
88b4a034	129	kfree_rcu(sf, rcu_head);
11eeef41 EP	130
	131	err = 0;
	132	break;
	133	}
	134
	135	return err;
	136	}
	137
	138	static const struct nfnl_callback xt_osf_nfnetlink_callbacks[OSF_MSG_MAX] = {
	139	[OSF_MSG_ADD] = {
	140	.call = xt_osf_add_callback,
	141	.attr_count = OSF_ATTR_MAX,
	142	.policy = xt_osf_policy,
	143	},
	144	[OSF_MSG_REMOVE] = {
	145	.call = xt_osf_remove_callback,
	146	.attr_count = OSF_ATTR_MAX,
	147	.policy = xt_osf_policy,
	148	},
	149	};
	150
	151	static const struct nfnetlink_subsystem xt_osf_nfnetlink = {
	152	.name = "osf",
	153	.subsys_id = NFNL_SUBSYS_OSF,
	154	.cb_count = OSF_MSG_MAX,
	155	.cb = xt_osf_nfnetlink_callbacks,
	156	};
	157
	158	static inline int xt_osf_ttl(const struct sk_buff skb, const struct xt_osf_info info,
	159	unsigned char f_ttl)
	160	{
	161	const struct iphdr *ip = ip_hdr(skb);
	162
	163	if (info->flags & XT_OSF_TTL) {
	164	if (info->ttl == XT_OSF_TTL_TRUE)
	165	return ip->ttl == f_ttl;
	166	if (info->ttl == XT_OSF_TTL_NOCHECK)
	167	return 1;
	168	else if (ip->ttl <= f_ttl)
	169	return 1;
	170	else {
	171	struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
	172	int ret = 0;
	173
	174	for_ifa(in_dev) {
	175	if (inet_ifa_match(ip->saddr, ifa)) {
	176	ret = (ip->ttl == f_ttl);
	177	break;
	178	}
	179	}
	180	endfor_ifa(in_dev);
	181
	182	return ret;
	183	}
	184	}
	185
	186	return ip->ttl == f_ttl;
	187	}
	188
4b560b44	189	static bool
62fc8051	190	xt_osf_match_packet(const struct sk_buff skb, struct xt_action_param p)
11eeef41 EP	191	{
	192	const struct xt_osf_info *info = p->matchinfo;
	193	const struct iphdr *ip = ip_hdr(skb);
	194	const struct tcphdr *tcp;
	195	struct tcphdr _tcph;
	196	int fmatch = FMATCH_WRONG, fcount = 0;
	197	unsigned int optsize = 0, check_WSS = 0;
	198	u16 window, totlen, mss = 0;
	199	bool df;
	200	const unsigned char optp = NULL, _optp = NULL;
	201	unsigned char opts[MAX_IPOPTLEN];
	202	const struct xt_osf_finger *kf;
	203	const struct xt_osf_user_finger *f;
686c9b50	204	struct net *net = p->net;
11eeef41 EP	205
	206	if (!info)
	207	return false;
	208
	209	tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
	210	if (!tcp)
	211	return false;
	212
	213	if (!tcp->syn)
	214	return false;
	215
	216	totlen = ntohs(ip->tot_len);
	217	df = ntohs(ip->frag_off) & IP_DF;
	218	window = ntohs(tcp->window);
	219
	220	if (tcp->doff * 4 > sizeof(struct tcphdr)) {
	221	optsize = tcp->doff * 4 - sizeof(struct tcphdr);
	222
	223	_optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) +
	224	sizeof(struct tcphdr), optsize, opts);
	225	}
	226
	227	rcu_read_lock();
	228	list_for_each_entry_rcu(kf, &xt_osf_fingers[df], finger_entry) {
372e2866 JP	229	int foptsize, optnum;
372e2866 JP	230
11eeef41 EP	231	f = &kf->finger;
	232
	233	if (!(info->flags & XT_OSF_LOG) && strcmp(info->genre, f->genre))
	234	continue;
	235
	236	optp = _optp;
	237	fmatch = FMATCH_WRONG;
	238
372e2866 JP	239	if (totlen != f->ss \|\| !xt_osf_ttl(skb, info, f->ttl))
372e2866 JP	240	continue;
11eeef41	241
372e2866 JP	242	/*
	243	* Should not happen if userspace parser was written correctly.
	244	*/
	245	if (f->wss.wc >= OSF_WSS_MAX)
	246	continue;
11eeef41	247
372e2866	248	/* Check options */
11eeef41	249
372e2866 JP	250	foptsize = 0;
	251	for (optnum = 0; optnum < f->opt_num; ++optnum)
	252	foptsize += f->opt[optnum].length;
11eeef41	253
372e2866 JP	254	if (foptsize > MAX_IPOPTLEN \|\|
	255	optsize > MAX_IPOPTLEN \|\|
	256	optsize != foptsize)
	257	continue;
11eeef41	258
372e2866	259	check_WSS = f->wss.wc;
11eeef41	260
372e2866 JP	261	for (optnum = 0; optnum < f->opt_num; ++optnum) {
	262	if (f->opt[optnum].kind == (*optp)) {
	263	__u32 len = f->opt[optnum].length;
	264	const __u8 *optend = optp + len;
11eeef41	265
372e2866	266	fmatch = FMATCH_OK;
11eeef41	267
372e2866 JP	268	switch (*optp) {
	269	case OSFOPT_MSS:
	270	mss = optp[3];
	271	mss <<= 8;
	272	mss \|= optp[2];
11eeef41	273
372e2866 JP	274	mss = ntohs((__force __be16)mss);
	275	break;
	276	case OSFOPT_TS:
372e2866 JP	277	break;
372e2866 JP	278	}
11eeef41	279
372e2866 JP	280	optp = optend;
	281	} else
	282	fmatch = FMATCH_OPT_WRONG;
11eeef41	283
372e2866 JP	284	if (fmatch != FMATCH_OK)
	285	break;
	286	}
11eeef41	287
372e2866 JP	288	if (fmatch != FMATCH_OPT_WRONG) {
372e2866 JP	289	fmatch = FMATCH_WRONG;
11eeef41	290
372e2866 JP	291	switch (check_WSS) {
	292	case OSF_WSS_PLAIN:
	293	if (f->wss.val == 0 \|\| window == f->wss.val)
	294	fmatch = FMATCH_OK;
	295	break;
	296	case OSF_WSS_MSS:
	297	/*
	298	* Some smart modems decrease mangle MSS to
	299	* SMART_MSS_2, so we check standard, decreased
	300	* and the one provided in the fingerprint MSS
	301	* values.
	302	*/
11eeef41 EP	303	#define SMART_MSS_1 1460
11eeef41 EP	304	#define SMART_MSS_2 1448
372e2866 JP	305	if (window == f->wss.val * mss \|\|
	306	window == f->wss.val * SMART_MSS_1 \|\|
	307	window == f->wss.val * SMART_MSS_2)
	308	fmatch = FMATCH_OK;
	309	break;
	310	case OSF_WSS_MTU:
	311	if (window == f->wss.val * (mss + 40) \|\|
	312	window == f->wss.val * (SMART_MSS_1 + 40) \|\|
	313	window == f->wss.val * (SMART_MSS_2 + 40))
	314	fmatch = FMATCH_OK;
	315	break;
	316	case OSF_WSS_MODULO:
	317	if ((window % f->wss.val) == 0)
	318	fmatch = FMATCH_OK;
	319	break;
11eeef41	320	}
372e2866	321	}
11eeef41	322
372e2866 JP	323	if (fmatch != FMATCH_OK)
372e2866 JP	324	continue;
11eeef41	325
372e2866	326	fcount++;
11eeef41	327
372e2866 JP	328	if (info->flags & XT_OSF_LOG)
	329	nf_log_packet(net, p->family, p->hooknum, skb,
	330	p->in, p->out, NULL,
	331	"%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n",
	332	f->genre, f->version, f->subtype,
	333	&ip->saddr, ntohs(tcp->source),
	334	&ip->daddr, ntohs(tcp->dest),
	335	f->ttl - ip->ttl);
11eeef41	336
372e2866 JP	337	if ((info->flags & XT_OSF_LOG) &&
	338	info->loglevel == XT_OSF_LOGLEVEL_FIRST)
	339	break;
11eeef41 EP	340	}
	341	rcu_read_unlock();
	342
	343	if (!fcount && (info->flags & XT_OSF_LOG))
30e0c6a6 G	344	nf_log_packet(net, p->family, p->hooknum, skb, p->in,
30e0c6a6 G	345	p->out, NULL,
7f635d0d	346	"Remote OS is not known: %pI4:%u -> %pI4:%u\n",
11eeef41 EP	347	&ip->saddr, ntohs(tcp->source),
	348	&ip->daddr, ntohs(tcp->dest));
	349
	350	if (fcount)
	351	fmatch = FMATCH_OK;
	352
	353	return fmatch == FMATCH_OK;
	354	}
	355
	356	static struct xt_match xt_osf_match = {
	357	.name = "osf",
	358	.revision = 0,
	359	.family = NFPROTO_IPV4,
	360	.proto = IPPROTO_TCP,
	361	.hooks = (1 << NF_INET_LOCAL_IN) \|
	362	(1 << NF_INET_PRE_ROUTING) \|
	363	(1 << NF_INET_FORWARD),
	364	.match = xt_osf_match_packet,
	365	.matchsize = sizeof(struct xt_osf_info),
	366	.me = THIS_MODULE,
	367	};
	368
	369	static int __init xt_osf_init(void)
	370	{
	371	int err = -EINVAL;
	372	int i;
	373
	374	for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i)
	375	INIT_LIST_HEAD(&xt_osf_fingers[i]);
	376
	377	err = nfnetlink_subsys_register(&xt_osf_nfnetlink);
	378	if (err < 0) {
8bee4bad	379	pr_err("Failed to register OSF nsfnetlink helper (%d)\n", err);
11eeef41 EP	380	goto err_out_exit;
	381	}
	382
	383	err = xt_register_match(&xt_osf_match);
	384	if (err) {
8bee4bad JE	385	pr_err("Failed to register OS fingerprint "
8bee4bad JE	386	"matching module (%d)\n", err);
11eeef41 EP	387	goto err_out_remove;
	388	}
	389
	390	return 0;
	391
	392	err_out_remove:
	393	nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
	394	err_out_exit:
	395	return err;
	396	}
	397
	398	static void __exit xt_osf_fini(void)
	399	{
	400	struct xt_osf_finger *f;
	401	int i;
	402
	403	nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
	404	xt_unregister_match(&xt_osf_match);
	405
	406	rcu_read_lock();
	407	for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i) {
	408
	409	list_for_each_entry_rcu(f, &xt_osf_fingers[i], finger_entry) {
	410	list_del_rcu(&f->finger_entry);
88b4a034	411	kfree_rcu(f, rcu_head);
11eeef41 EP	412	}
	413	}
	414	rcu_read_unlock();
	415
	416	rcu_barrier();
	417	}
	418
	419	module_init(xt_osf_init);
	420	module_exit(xt_osf_fini);
	421
	422	MODULE_LICENSE("GPL");
	423	MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
	424	MODULE_DESCRIPTION("Passive OS fingerprint matching.");
b8ddd9ea KT	425	MODULE_ALIAS("ipt_osf");
b8ddd9ea KT	426	MODULE_ALIAS("ip6t_osf");
11eeef41	427	MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_OSF);