net/netfilter/xt_policy.c

   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
  20 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  21 MODULE_DESCRIPTION("Xtables: IPsec policy match");
  22 MODULE_LICENSE("GPL");
  23
  24 static inline bool
  25 xt_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
  37 static bool
  38 match_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
  54 static int
  55 match_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
  84 static int
  85 match_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
 112 static bool
 113 policy_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
 131 static 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
 156 static 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
 175 static int __init policy_mt_init(void)
 176 {
 177         return xt_register_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
 178 }
 179
 180 static void __exit policy_mt_exit(void)
 181 {
 182         xt_unregister_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
 183 }
 184
 185 module_init(policy_mt_init);
 186 module_exit(policy_mt_exit);
 187 MODULE_ALIAS("ipt_policy");
 188 MODULE_ALIAS("ip6t_policy");