xt_addrtype.c

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/*
 *  iptables module to match inet_addr_type() of an ip.
 *
 *  Copyright (c) 2004 Patrick McHardy <[email protected]>
 *  (C) 2007 Laszlo Attila Toth <[email protected]>
 *
 *  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.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/ip.h>
#include <net/route.h>

#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
#include <net/ipv6.h>
#include <net/ip6_route.h>
#include <net/ip6_fib.h>
#endif

#include <linux/netfilter/xt_addrtype.h>
#include <linux/netfilter/x_tables.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Patrick McHardy <[email protected]>");
MODULE_DESCRIPTION("Xtables: address type match");
MODULE_ALIAS("ipt_addrtype");
MODULE_ALIAS("ip6t_addrtype");

#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
static u32 match_lookup_rt6(struct net *net, const struct net_device *dev,
                const struct in6_addr *addr)
{
    const struct nf_afinfo *afinfo;
    struct flowi6 flow;
    struct rt6_info *rt;
    u32 ret;
    int route_err;

    memset(&flow, 0, sizeof(flow));
    flow.daddr = *addr;
    if (dev)
        flow.flowi6_oif = dev->ifindex;

    rcu_read_lock();

    afinfo = nf_get_afinfo(NFPROTO_IPV6);
    if (afinfo != NULL)
        route_err = afinfo->route(net, (struct dst_entry **)&rt,
                    flowi6_to_flowi(&flow), !!dev);
    else
        route_err = 1;

    rcu_read_unlock();

    if (route_err)
        return XT_ADDRTYPE_UNREACHABLE;

    if (rt->rt6i_flags & RTF_REJECT)
        ret = XT_ADDRTYPE_UNREACHABLE;
    else
        ret = 0;

    if (rt->rt6i_flags & RTF_LOCAL)
        ret |= XT_ADDRTYPE_LOCAL;
    if (rt->rt6i_flags & RTF_ANYCAST)
        ret |= XT_ADDRTYPE_ANYCAST;


    dst_release(&rt->dst);
    return ret;
}

static bool match_type6(struct net *net, const struct net_device *dev,
                const struct in6_addr *addr, u16 mask)
{
    int addr_type = ipv6_addr_type(addr);

    if ((mask & XT_ADDRTYPE_MULTICAST) &&
        !(addr_type & IPV6_ADDR_MULTICAST))
        return false;
    if ((mask & XT_ADDRTYPE_UNICAST) && !(addr_type & IPV6_ADDR_UNICAST))
        return false;
    if ((mask & XT_ADDRTYPE_UNSPEC) && addr_type != IPV6_ADDR_ANY)
        return false;

    if ((XT_ADDRTYPE_LOCAL | XT_ADDRTYPE_ANYCAST |
         XT_ADDRTYPE_UNREACHABLE) & mask)
        return !!(mask & match_lookup_rt6(net, dev, addr));
    return true;
}

static bool
addrtype_mt6(struct net *net, const struct net_device *dev,
    const struct sk_buff *skb, const struct xt_addrtype_info_v1 *info)
{
    const struct ipv6hdr *iph = ipv6_hdr(skb);
    bool ret = true;

    if (info->source)
        ret &= match_type6(net, dev, &iph->saddr, info->source) ^
               (info->flags & XT_ADDRTYPE_INVERT_SOURCE);
    if (ret && info->dest)
        ret &= match_type6(net, dev, &iph->daddr, info->dest) ^
               !!(info->flags & XT_ADDRTYPE_INVERT_DEST);
    return ret;
}
#endif

static inline bool match_type(struct net *net, const struct net_device *dev,
                  __be32 addr, u_int16_t mask)
{
    return !!(mask & (1 << inet_dev_addr_type(net, dev, addr)));
}

static bool
addrtype_mt_v0(const struct sk_buff *skb, struct xt_action_param *par)
{
    struct net *net = dev_net(par->in ? par->in : par->out);
    const struct xt_addrtype_info *info = par->matchinfo;
    const struct iphdr *iph = ip_hdr(skb);
    bool ret = true;

    if (info->source)
        ret &= match_type(net, NULL, iph->saddr, info->source) ^
               info->invert_source;
    if (info->dest)
        ret &= match_type(net, NULL, iph->daddr, info->dest) ^
               info->invert_dest;

    return ret;
}

static bool
addrtype_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
{
    struct net *net = dev_net(par->in ? par->in : par->out);
    const struct xt_addrtype_info_v1 *info = par->matchinfo;
    const struct iphdr *iph;
    const struct net_device *dev = NULL;
    bool ret = true;

    if (info->flags & XT_ADDRTYPE_LIMIT_IFACE_IN)
        dev = par->in;
    else if (info->flags & XT_ADDRTYPE_LIMIT_IFACE_OUT)
        dev = par->out;

#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
    if (par->family == NFPROTO_IPV6)
        return addrtype_mt6(net, dev, skb, info);
#endif
    iph = ip_hdr(skb);
    if (info->source)
        ret &= match_type(net, dev, iph->saddr, info->source) ^
               (info->flags & XT_ADDRTYPE_INVERT_SOURCE);
    if (ret && info->dest)
        ret &= match_type(net, dev, iph->daddr, info->dest) ^
               !!(info->flags & XT_ADDRTYPE_INVERT_DEST);
    return ret;
}

static int addrtype_mt_checkentry_v1(const struct xt_mtchk_param *par)
{
    struct xt_addrtype_info_v1 *info = par->matchinfo;

    if (info->flags & XT_ADDRTYPE_LIMIT_IFACE_IN &&
        info->flags & XT_ADDRTYPE_LIMIT_IFACE_OUT) {
        pr_info("both incoming and outgoing "
            "interface limitation cannot be selected\n");
        return -EINVAL;
    }

    if (par->hook_mask & ((1 << NF_INET_PRE_ROUTING) |
        (1 << NF_INET_LOCAL_IN)) &&
        info->flags & XT_ADDRTYPE_LIMIT_IFACE_OUT) {
        pr_info("output interface limitation "
            "not valid in PREROUTING and INPUT\n");
        return -EINVAL;
    }

    if (par->hook_mask & ((1 << NF_INET_POST_ROUTING) |
        (1 << NF_INET_LOCAL_OUT)) &&
        info->flags & XT_ADDRTYPE_LIMIT_IFACE_IN) {
        pr_info("input interface limitation "
            "not valid in POSTROUTING and OUTPUT\n");
        return -EINVAL;
    }

#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
    if (par->family == NFPROTO_IPV6) {
        if ((info->source | info->dest) & XT_ADDRTYPE_BLACKHOLE) {
            pr_err("ipv6 BLACKHOLE matching not supported\n");
            return -EINVAL;
        }
        if ((info->source | info->dest) >= XT_ADDRTYPE_PROHIBIT) {
            pr_err("ipv6 PROHIBT (THROW, NAT ..) matching not supported\n");
            return -EINVAL;
        }
        if ((info->source | info->dest) & XT_ADDRTYPE_BROADCAST) {
            pr_err("ipv6 does not support BROADCAST matching\n");
            return -EINVAL;
        }
    }
#endif
    return 0;
}

static struct xt_match addrtype_mt_reg[] __read_mostly = {
    {
        .name       = "addrtype",
        .family     = NFPROTO_IPV4,
        .match      = addrtype_mt_v0,
        .matchsize  = sizeof(struct xt_addrtype_info),
        .me     = THIS_MODULE
    },
    {
        .name       = "addrtype",
        .family     = NFPROTO_UNSPEC,
        .revision   = 1,
        .match      = addrtype_mt_v1,
        .checkentry = addrtype_mt_checkentry_v1,
        .matchsize  = sizeof(struct xt_addrtype_info_v1),
        .me     = THIS_MODULE
    }
};

static int __init addrtype_mt_init(void)
{
    return xt_register_matches(addrtype_mt_reg,
                   ARRAY_SIZE(addrtype_mt_reg));
}

static void __exit addrtype_mt_exit(void)
{
    xt_unregister_matches(addrtype_mt_reg, ARRAY_SIZE(addrtype_mt_reg));
}

module_init(addrtype_mt_init);
module_exit(addrtype_mt_exit);