linux/net/netfilter/xt_policy.c
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   1/* IP tables module for matching IPsec policy
   2 *
   3 * Copyright (c) 2004,2005 Patrick McHardy, <kaber@trash.net>
   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 version 2 as
   7 * published by the Free Software Foundation.
   8 */
   9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  10#include <linux/kernel.h>
  11#include <linux/module.h>
  12#include <linux/skbuff.h>
  13#include <linux/init.h>
  14#include <net/xfrm.h>
  15
  16#include <linux/netfilter.h>
  17#include <linux/netfilter/xt_policy.h>
  18#include <linux/netfilter/x_tables.h>
  19
  20MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  21MODULE_DESCRIPTION("Xtables: IPsec policy match");
  22MODULE_LICENSE("GPL");
  23
  24static inline bool
  25xt_addr_cmp(const union nf_inet_addr *a1, const union nf_inet_addr *m,
  26            const union nf_inet_addr *a2, unsigned short family)
  27{
  28        switch (family) {
  29        case NFPROTO_IPV4:
  30                return ((a1->ip ^ a2->ip) & m->ip) == 0;
  31        case NFPROTO_IPV6:
  32                return ipv6_masked_addr_cmp(&a1->in6, &m->in6, &a2->in6) == 0;
  33        }
  34        return false;
  35}
  36
  37static bool
  38match_xfrm_state(const struct xfrm_state *x, const struct xt_policy_elem *e,
  39                 unsigned short family)
  40{
  41#define MATCH_ADDR(x,y,z)       (!e->match.x ||                        \
  42                                 (xt_addr_cmp(&e->x, &e->y, (const union nf_inet_addr *)(z), family) \
  43                                  ^ e->invert.x))
  44#define MATCH(x,y)              (!e->match.x || ((e->x == (y)) ^ e->invert.x))
  45
  46        return MATCH_ADDR(saddr, smask, &x->props.saddr) &&
  47               MATCH_ADDR(daddr, dmask, &x->id.daddr) &&
  48               MATCH(proto, x->id.proto) &&
  49               MATCH(mode, x->props.mode) &&
  50               MATCH(spi, x->id.spi) &&
  51               MATCH(reqid, x->props.reqid);
  52}
  53
  54static int
  55match_policy_in(const struct sk_buff *skb, const struct xt_policy_info *info,
  56                unsigned short family)
  57{
  58        const struct xt_policy_elem *e;
  59        const struct sec_path *sp = skb->sp;
  60        int strict = info->flags & XT_POLICY_MATCH_STRICT;
  61        int i, pos;
  62
  63        if (sp == NULL)
  64                return -1;
  65        if (strict && info->len != sp->len)
  66                return 0;
  67
  68        for (i = sp->len - 1; i >= 0; i--) {
  69                pos = strict ? i - sp->len + 1 : 0;
  70                if (pos >= info->len)
  71                        return 0;
  72                e = &info->pol[pos];
  73
  74                if (match_xfrm_state(sp->xvec[i], e, family)) {
  75                        if (!strict)
  76                                return 1;
  77                } else if (strict)
  78                        return 0;
  79        }
  80
  81        return strict ? 1 : 0;
  82}
  83
  84static int
  85match_policy_out(const struct sk_buff *skb, const struct xt_policy_info *info,
  86                 unsigned short family)
  87{
  88        const struct xt_policy_elem *e;
  89        const struct dst_entry *dst = skb_dst(skb);
  90        int strict = info->flags & XT_POLICY_MATCH_STRICT;
  91        int i, pos;
  92
  93        if (dst->xfrm == NULL)
  94                return -1;
  95
  96        for (i = 0; dst && dst->xfrm; dst = dst->child, i++) {
  97                pos = strict ? i : 0;
  98                if (pos >= info->len)
  99                        return 0;
 100                e = &info->pol[pos];
 101
 102                if (match_xfrm_state(dst->xfrm, e, family)) {
 103                        if (!strict)
 104                                return 1;
 105                } else if (strict)
 106                        return 0;
 107        }
 108
 109        return strict ? i == info->len : 0;
 110}
 111
 112static bool
 113policy_mt(const struct sk_buff *skb, struct xt_action_param *par)
 114{
 115        const struct xt_policy_info *info = par->matchinfo;
 116        int ret;
 117
 118        if (info->flags & XT_POLICY_MATCH_IN)
 119                ret = match_policy_in(skb, info, par->family);
 120        else
 121                ret = match_policy_out(skb, info, par->family);
 122
 123        if (ret < 0)
 124                ret = info->flags & XT_POLICY_MATCH_NONE ? true : false;
 125        else if (info->flags & XT_POLICY_MATCH_NONE)
 126                ret = false;
 127
 128        return ret;
 129}
 130
 131static int policy_mt_check(const struct xt_mtchk_param *par)
 132{
 133        const struct xt_policy_info *info = par->matchinfo;
 134
 135        if (!(info->flags & (XT_POLICY_MATCH_IN|XT_POLICY_MATCH_OUT))) {
 136                pr_info("neither incoming nor outgoing policy selected\n");
 137                return -EINVAL;
 138        }
 139        if (par->hook_mask & ((1 << NF_INET_PRE_ROUTING) |
 140            (1 << NF_INET_LOCAL_IN)) && info->flags & XT_POLICY_MATCH_OUT) {
 141                pr_info("output policy not valid in PREROUTING and INPUT\n");
 142                return -EINVAL;
 143        }
 144        if (par->hook_mask & ((1 << NF_INET_POST_ROUTING) |
 145            (1 << NF_INET_LOCAL_OUT)) && info->flags & XT_POLICY_MATCH_IN) {
 146                pr_info("input policy not valid in POSTROUTING and OUTPUT\n");
 147                return -EINVAL;
 148        }
 149        if (info->len > XT_POLICY_MAX_ELEM) {
 150                pr_info("too many policy elements\n");
 151                return -EINVAL;
 152        }
 153        return 0;
 154}
 155
 156static struct xt_match policy_mt_reg[] __read_mostly = {
 157        {
 158                .name           = "policy",
 159                .family         = NFPROTO_IPV4,
 160                .checkentry     = policy_mt_check,
 161                .match          = policy_mt,
 162                .matchsize      = sizeof(struct xt_policy_info),
 163                .me             = THIS_MODULE,
 164        },
 165        {
 166                .name           = "policy",
 167                .family         = NFPROTO_IPV6,
 168                .checkentry     = policy_mt_check,
 169                .match          = policy_mt,
 170                .matchsize      = sizeof(struct xt_policy_info),
 171                .me             = THIS_MODULE,
 172        },
 173};
 174
 175static int __init policy_mt_init(void)
 176{
 177        return xt_register_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
 178}
 179
 180static void __exit policy_mt_exit(void)
 181{
 182        xt_unregister_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
 183}
 184
 185module_init(policy_mt_init);
 186module_exit(policy_mt_exit);
 187MODULE_ALIAS("ipt_policy");
 188MODULE_ALIAS("ip6t_policy");
 189
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