iptable_security.c

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/*
 * "security" table
 *
 * This is for use by Mandatory Access Control (MAC) security models,
 * which need to be able to manage security policy in separate context
 * to DAC.
 *
 * Based on iptable_mangle.c
 *
 * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
 * Copyright (C) 2000-2004 Netfilter Core Team <coreteam <at> netfilter.org>
 * Copyright (C) 2008 Red Hat, Inc., James Morris <jmorris <at> redhat.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/module.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/slab.h>
#include <net/ip.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("James Morris <jmorris <at> redhat.com>");
MODULE_DESCRIPTION("iptables security table, for MAC rules");

#define SECURITY_VALID_HOOKS    (1 << NF_INET_LOCAL_IN) | \
                (1 << NF_INET_FORWARD) | \
                (1 << NF_INET_LOCAL_OUT)

static const struct xt_table security_table = {
    .name       = "security",
    .valid_hooks    = SECURITY_VALID_HOOKS,
    .me     = THIS_MODULE,
    .af     = NFPROTO_IPV4,
    .priority   = NF_IP_PRI_SECURITY,
};

static unsigned int
iptable_security_hook(unsigned int hook, struct sk_buff *skb,
              const struct net_device *in,
              const struct net_device *out,
              int (*okfn)(struct sk_buff *))
{
    const struct net *net;

    if (hook == NF_INET_LOCAL_OUT &&
        (skb->len < sizeof(struct iphdr) ||
         ip_hdrlen(skb) < sizeof(struct iphdr)))
        /* Somebody is playing with raw sockets. */
        return NF_ACCEPT;

    net = dev_net((in != NULL) ? in : out);
    return ipt_do_table(skb, hook, in, out, net->ipv4.iptable_security);
}

static struct nf_hook_ops *sectbl_ops __read_mostly;

static int __net_init iptable_security_net_init(struct net *net)
{
    struct ipt_replace *repl;

    repl = ipt_alloc_initial_table(&security_table);
    if (repl == NULL)
        return -ENOMEM;
    net->ipv4.iptable_security =
        ipt_register_table(net, &security_table, repl);
    kfree(repl);
    return PTR_RET(net->ipv4.iptable_security);
}

static void __net_exit iptable_security_net_exit(struct net *net)
{
    ipt_unregister_table(net, net->ipv4.iptable_security);
}

static struct pernet_operations iptable_security_net_ops = {
    .init = iptable_security_net_init,
    .exit = iptable_security_net_exit,
};

static int __init iptable_security_init(void)
{
    int ret;

    ret = register_pernet_subsys(&iptable_security_net_ops);
        if (ret < 0)
        return ret;

    sectbl_ops = xt_hook_link(&security_table, iptable_security_hook);
    if (IS_ERR(sectbl_ops)) {
        ret = PTR_ERR(sectbl_ops);
        goto cleanup_table;
    }

    return ret;

cleanup_table:
    unregister_pernet_subsys(&iptable_security_net_ops);
    return ret;
}

static void __exit iptable_security_fini(void)
{
    xt_hook_unlink(&security_table, sectbl_ops);
    unregister_pernet_subsys(&iptable_security_net_ops);
}

module_init(iptable_security_init);
module_exit(iptable_security_fini);