[mirror_ubuntu-bionic-kernel.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/capability.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 netlink_ext_ack *extack)
{
	struct xt_osf_user_finger *f;
	struct xt_osf_finger *kf = NULL, *sf;
	int err = 0;

	if (!capable(CAP_NET_ADMIN))
		return -EPERM;

	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 netlink_ext_ack *extack)
{
	struct xt_osf_user_finger *f;
	struct xt_osf_finger *sf;
	int err = -ENOENT;

	if (!capable(CAP_NET_ADMIN))
		return -EPERM;

	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 = xt_net(p);

	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);
	}

	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, xt_family(p), xt_hooknum(p), skb,
				      xt_in(p), xt_out(p), 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;
	}

	if (!fcount && (info->flags & XT_OSF_LOG))
		nf_log_packet(net, xt_family(p), xt_hooknum(p), skb, xt_in(p),
			      xt_out(p), 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
916a2790	22	#include <linux/capability.h>
11eeef41 EP	23	#include <linux/if.h>
	24	#include <linux/inetdevice.h>
	25	#include <linux/ip.h>
	26	#include <linux/list.h>
	27	#include <linux/rculist.h>
	28	#include <linux/skbuff.h>
	29	#include <linux/slab.h>
	30	#include <linux/tcp.h>
	31
	32	#include <net/ip.h>
	33	#include <net/tcp.h>
	34
	35	#include <linux/netfilter/nfnetlink.h>
	36	#include <linux/netfilter/x_tables.h>
	37	#include <net/netfilter/nf_log.h>
	38	#include <linux/netfilter/xt_osf.h>
	39
	40	struct xt_osf_finger {
	41	struct rcu_head rcu_head;
	42	struct list_head finger_entry;
	43	struct xt_osf_user_finger finger;
	44	};
	45
	46	enum osf_fmatch_states {
	47	/* Packet does not match the fingerprint */
	48	FMATCH_WRONG = 0,
	49	/* Packet matches the fingerprint */
	50	FMATCH_OK,
	51	/* Options do not match the fingerprint, but header does */
	52	FMATCH_OPT_WRONG,
	53	};
	54
	55	/*
	56	* Indexed by dont-fragment bit.
	57	* It is the only constant value in the fingerprint.
	58	*/
	59	static struct list_head xt_osf_fingers[2];
	60
	61	static const struct nla_policy xt_osf_policy[OSF_ATTR_MAX + 1] = {
	62	[OSF_ATTR_FINGER] = { .len = sizeof(struct xt_osf_user_finger) },
	63	};
	64
7b8002a1 PNA	65	static int xt_osf_add_callback(struct net net, struct sock ctnl,
7b8002a1 PNA	66	struct sk_buff skb, const struct nlmsghdr nlh,
04ba724b PNA	67	const struct nlattr * const osf_attrs[],
04ba724b PNA	68	struct netlink_ext_ack *extack)
11eeef41 EP	69	{
	70	struct xt_osf_user_finger *f;
	71	struct xt_osf_finger kf = NULL, sf;
	72	int err = 0;
	73
916a2790 KC	74	if (!capable(CAP_NET_ADMIN))
	75	return -EPERM;
	76
11eeef41 EP	77	if (!osf_attrs[OSF_ATTR_FINGER])
	78	return -EINVAL;
	79
	80	if (!(nlh->nlmsg_flags & NLM_F_CREATE))
	81	return -EINVAL;
	82
	83	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
	84
	85	kf = kmalloc(sizeof(struct xt_osf_finger), GFP_KERNEL);
	86	if (!kf)
	87	return -ENOMEM;
	88
	89	memcpy(&kf->finger, f, sizeof(struct xt_osf_user_finger));
	90
	91	list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
	92	if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
	93	continue;
	94
	95	kfree(kf);
	96	kf = NULL;
	97
	98	if (nlh->nlmsg_flags & NLM_F_EXCL)
	99	err = -EEXIST;
	100	break;
	101	}
	102
	103	/*
	104	* We are protected by nfnl mutex.
	105	*/
	106	if (kf)
	107	list_add_tail_rcu(&kf->finger_entry, &xt_osf_fingers[!!f->df]);
	108
	109	return err;
	110	}
	111
7b8002a1 PNA	112	static int xt_osf_remove_callback(struct net net, struct sock ctnl,
7b8002a1 PNA	113	struct sk_buff *skb,
39938324	114	const struct nlmsghdr *nlh,
04ba724b PNA	115	const struct nlattr * const osf_attrs[],
04ba724b PNA	116	struct netlink_ext_ack *extack)
11eeef41 EP	117	{
	118	struct xt_osf_user_finger *f;
	119	struct xt_osf_finger *sf;
d667b9cf	120	int err = -ENOENT;
11eeef41	121
916a2790 KC	122	if (!capable(CAP_NET_ADMIN))
	123	return -EPERM;
	124
11eeef41 EP	125	if (!osf_attrs[OSF_ATTR_FINGER])
	126	return -EINVAL;
	127
	128	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
	129
	130	list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
	131	if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
	132	continue;
	133
	134	/*
	135	* We are protected by nfnl mutex.
	136	*/
	137	list_del_rcu(&sf->finger_entry);
88b4a034	138	kfree_rcu(sf, rcu_head);
11eeef41 EP	139
	140	err = 0;
	141	break;
	142	}
	143
	144	return err;
	145	}
	146
	147	static const struct nfnl_callback xt_osf_nfnetlink_callbacks[OSF_MSG_MAX] = {
	148	[OSF_MSG_ADD] = {
	149	.call = xt_osf_add_callback,
	150	.attr_count = OSF_ATTR_MAX,
	151	.policy = xt_osf_policy,
	152	},
	153	[OSF_MSG_REMOVE] = {
	154	.call = xt_osf_remove_callback,
	155	.attr_count = OSF_ATTR_MAX,
	156	.policy = xt_osf_policy,
	157	},
	158	};
	159
	160	static const struct nfnetlink_subsystem xt_osf_nfnetlink = {
	161	.name = "osf",
	162	.subsys_id = NFNL_SUBSYS_OSF,
	163	.cb_count = OSF_MSG_MAX,
	164	.cb = xt_osf_nfnetlink_callbacks,
	165	};
	166
	167	static inline int xt_osf_ttl(const struct sk_buff skb, const struct xt_osf_info info,
	168	unsigned char f_ttl)
	169	{
	170	const struct iphdr *ip = ip_hdr(skb);
	171
	172	if (info->flags & XT_OSF_TTL) {
	173	if (info->ttl == XT_OSF_TTL_TRUE)
	174	return ip->ttl == f_ttl;
	175	if (info->ttl == XT_OSF_TTL_NOCHECK)
	176	return 1;
	177	else if (ip->ttl <= f_ttl)
	178	return 1;
	179	else {
	180	struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
	181	int ret = 0;
	182
	183	for_ifa(in_dev) {
	184	if (inet_ifa_match(ip->saddr, ifa)) {
	185	ret = (ip->ttl == f_ttl);
	186	break;
	187	}
	188	}
	189	endfor_ifa(in_dev);
	190
	191	return ret;
	192	}
	193	}
	194
	195	return ip->ttl == f_ttl;
	196	}
	197
4b560b44	198	static bool
62fc8051	199	xt_osf_match_packet(const struct sk_buff skb, struct xt_action_param p)
11eeef41 EP	200	{
	201	const struct xt_osf_info *info = p->matchinfo;
	202	const struct iphdr *ip = ip_hdr(skb);
	203	const struct tcphdr *tcp;
	204	struct tcphdr _tcph;
	205	int fmatch = FMATCH_WRONG, fcount = 0;
	206	unsigned int optsize = 0, check_WSS = 0;
	207	u16 window, totlen, mss = 0;
	208	bool df;
	209	const unsigned char optp = NULL, _optp = NULL;
	210	unsigned char opts[MAX_IPOPTLEN];
	211	const struct xt_osf_finger *kf;
	212	const struct xt_osf_user_finger *f;
613dbd95	213	struct net *net = xt_net(p);
11eeef41 EP	214
	215	if (!info)
	216	return false;
	217
	218	tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
	219	if (!tcp)
	220	return false;
	221
	222	if (!tcp->syn)
	223	return false;
	224
	225	totlen = ntohs(ip->tot_len);
	226	df = ntohs(ip->frag_off) & IP_DF;
	227	window = ntohs(tcp->window);
	228
	229	if (tcp->doff * 4 > sizeof(struct tcphdr)) {
	230	optsize = tcp->doff * 4 - sizeof(struct tcphdr);
	231
	232	_optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) +
	233	sizeof(struct tcphdr), optsize, opts);
	234	}
	235
11eeef41	236	list_for_each_entry_rcu(kf, &xt_osf_fingers[df], finger_entry) {
372e2866 JP	237	int foptsize, optnum;
372e2866 JP	238
11eeef41 EP	239	f = &kf->finger;
	240
	241	if (!(info->flags & XT_OSF_LOG) && strcmp(info->genre, f->genre))
	242	continue;
	243
	244	optp = _optp;
	245	fmatch = FMATCH_WRONG;
	246
372e2866 JP	247	if (totlen != f->ss \|\| !xt_osf_ttl(skb, info, f->ttl))
372e2866 JP	248	continue;
11eeef41	249
372e2866 JP	250	/*
	251	* Should not happen if userspace parser was written correctly.
	252	*/
	253	if (f->wss.wc >= OSF_WSS_MAX)
	254	continue;
11eeef41	255
372e2866	256	/* Check options */
11eeef41	257
372e2866 JP	258	foptsize = 0;
	259	for (optnum = 0; optnum < f->opt_num; ++optnum)
	260	foptsize += f->opt[optnum].length;
11eeef41	261
372e2866 JP	262	if (foptsize > MAX_IPOPTLEN \|\|
	263	optsize > MAX_IPOPTLEN \|\|
	264	optsize != foptsize)
	265	continue;
11eeef41	266
372e2866	267	check_WSS = f->wss.wc;
11eeef41	268
372e2866 JP	269	for (optnum = 0; optnum < f->opt_num; ++optnum) {
	270	if (f->opt[optnum].kind == (*optp)) {
	271	__u32 len = f->opt[optnum].length;
	272	const __u8 *optend = optp + len;
11eeef41	273
372e2866	274	fmatch = FMATCH_OK;
11eeef41	275
372e2866 JP	276	switch (*optp) {
	277	case OSFOPT_MSS:
	278	mss = optp[3];
	279	mss <<= 8;
	280	mss \|= optp[2];
11eeef41	281
372e2866 JP	282	mss = ntohs((__force __be16)mss);
	283	break;
	284	case OSFOPT_TS:
372e2866 JP	285	break;
372e2866 JP	286	}
11eeef41	287
372e2866 JP	288	optp = optend;
	289	} else
	290	fmatch = FMATCH_OPT_WRONG;
11eeef41	291
372e2866 JP	292	if (fmatch != FMATCH_OK)
	293	break;
	294	}
11eeef41	295
372e2866 JP	296	if (fmatch != FMATCH_OPT_WRONG) {
372e2866 JP	297	fmatch = FMATCH_WRONG;
11eeef41	298
372e2866 JP	299	switch (check_WSS) {
	300	case OSF_WSS_PLAIN:
	301	if (f->wss.val == 0 \|\| window == f->wss.val)
	302	fmatch = FMATCH_OK;
	303	break;
	304	case OSF_WSS_MSS:
	305	/*
	306	* Some smart modems decrease mangle MSS to
	307	* SMART_MSS_2, so we check standard, decreased
	308	* and the one provided in the fingerprint MSS
	309	* values.
	310	*/
11eeef41 EP	311	#define SMART_MSS_1 1460
11eeef41 EP	312	#define SMART_MSS_2 1448
372e2866 JP	313	if (window == f->wss.val * mss \|\|
	314	window == f->wss.val * SMART_MSS_1 \|\|
	315	window == f->wss.val * SMART_MSS_2)
	316	fmatch = FMATCH_OK;
	317	break;
	318	case OSF_WSS_MTU:
	319	if (window == f->wss.val * (mss + 40) \|\|
	320	window == f->wss.val * (SMART_MSS_1 + 40) \|\|
	321	window == f->wss.val * (SMART_MSS_2 + 40))
	322	fmatch = FMATCH_OK;
	323	break;
	324	case OSF_WSS_MODULO:
	325	if ((window % f->wss.val) == 0)
	326	fmatch = FMATCH_OK;
	327	break;
11eeef41	328	}
372e2866	329	}
11eeef41	330
372e2866 JP	331	if (fmatch != FMATCH_OK)
372e2866 JP	332	continue;
11eeef41	333
372e2866	334	fcount++;
11eeef41	335
372e2866	336	if (info->flags & XT_OSF_LOG)
613dbd95 PNA	337	nf_log_packet(net, xt_family(p), xt_hooknum(p), skb,
613dbd95 PNA	338	xt_in(p), xt_out(p), NULL,
372e2866 JP	339	"%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n",
	340	f->genre, f->version, f->subtype,
	341	&ip->saddr, ntohs(tcp->source),
	342	&ip->daddr, ntohs(tcp->dest),
	343	f->ttl - ip->ttl);
11eeef41	344
372e2866 JP	345	if ((info->flags & XT_OSF_LOG) &&
	346	info->loglevel == XT_OSF_LOGLEVEL_FIRST)
	347	break;
11eeef41	348	}
11eeef41 EP	349
11eeef41 EP	350	if (!fcount && (info->flags & XT_OSF_LOG))
613dbd95 PNA	351	nf_log_packet(net, xt_family(p), xt_hooknum(p), skb, xt_in(p),
613dbd95 PNA	352	xt_out(p), NULL,
7f635d0d	353	"Remote OS is not known: %pI4:%u -> %pI4:%u\n",
11eeef41 EP	354	&ip->saddr, ntohs(tcp->source),
	355	&ip->daddr, ntohs(tcp->dest));
	356
	357	if (fcount)
	358	fmatch = FMATCH_OK;
	359
	360	return fmatch == FMATCH_OK;
	361	}
	362
	363	static struct xt_match xt_osf_match = {
	364	.name = "osf",
	365	.revision = 0,
	366	.family = NFPROTO_IPV4,
	367	.proto = IPPROTO_TCP,
	368	.hooks = (1 << NF_INET_LOCAL_IN) \|
	369	(1 << NF_INET_PRE_ROUTING) \|
	370	(1 << NF_INET_FORWARD),
	371	.match = xt_osf_match_packet,
	372	.matchsize = sizeof(struct xt_osf_info),
	373	.me = THIS_MODULE,
	374	};
	375
	376	static int __init xt_osf_init(void)
	377	{
	378	int err = -EINVAL;
	379	int i;
	380
	381	for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i)
	382	INIT_LIST_HEAD(&xt_osf_fingers[i]);
	383
	384	err = nfnetlink_subsys_register(&xt_osf_nfnetlink);
	385	if (err < 0) {
8bee4bad	386	pr_err("Failed to register OSF nsfnetlink helper (%d)\n", err);
11eeef41 EP	387	goto err_out_exit;
	388	}
	389
	390	err = xt_register_match(&xt_osf_match);
	391	if (err) {
8bee4bad JE	392	pr_err("Failed to register OS fingerprint "
8bee4bad JE	393	"matching module (%d)\n", err);
11eeef41 EP	394	goto err_out_remove;
	395	}
	396
	397	return 0;
	398
	399	err_out_remove:
	400	nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
	401	err_out_exit:
	402	return err;
	403	}
	404
	405	static void __exit xt_osf_fini(void)
	406	{
	407	struct xt_osf_finger *f;
	408	int i;
	409
	410	nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
	411	xt_unregister_match(&xt_osf_match);
	412
	413	rcu_read_lock();
	414	for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i) {
	415
	416	list_for_each_entry_rcu(f, &xt_osf_fingers[i], finger_entry) {
	417	list_del_rcu(&f->finger_entry);
88b4a034	418	kfree_rcu(f, rcu_head);
11eeef41 EP	419	}
	420	}
	421	rcu_read_unlock();
	422
	423	rcu_barrier();
	424	}
	425
	426	module_init(xt_osf_init);
	427	module_exit(xt_osf_fini);
	428
	429	MODULE_LICENSE("GPL");
	430	MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
	431	MODULE_DESCRIPTION("Passive OS fingerprint matching.");
b8ddd9ea KT	432	MODULE_ALIAS("ipt_osf");
b8ddd9ea KT	433	MODULE_ALIAS("ip6t_osf");
11eeef41	434	MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_OSF);