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/*
* 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>
/*
* 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 bool
xt_osf_match_packet(const struct sk_buff *skb, struct xt_action_param *p)
{
const struct xt_osf_info *info = p->matchinfo;
struct net *net = xt_net(p);
if (!info)
return false;
return nf_osf_match(skb, xt_family(p), xt_hooknum(p), xt_in(p),
xt_out(p), info, net, xt_osf_fingers);
}
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);
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