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_sec_path(skb);
  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;
  97              dst = ((struct xfrm_dst *)dst)->child, i++) {
  98                 pos = strict ? i : 0;
  99                 if (pos >= info->len)
 100                         return 0;
 101                 e = &info->pol[pos];
 102
 103                 if (match_xfrm_state(dst->xfrm, e, family)) {
 104                         if (!strict)
 105                                 return 1;
 106                 } else if (strict)
 107                         return 0;
 108         }
 109
 110         return strict ? i == info->len : 0;
 111 }
 112
 113 static bool
 114 policy_mt(const struct sk_buff *skb, struct xt_action_param *par)
 115 {
 116         const struct xt_policy_info *info = par->matchinfo;
 117         int ret;
 118
 119         if (info->flags & XT_POLICY_MATCH_IN)
 120                 ret = match_policy_in(skb, info, xt_family(par));
 121         else
 122                 ret = match_policy_out(skb, info, xt_family(par));
 123
 124         if (ret < 0)
 125                 ret = info->flags & XT_POLICY_MATCH_NONE ? true : false;
 126         else if (info->flags & XT_POLICY_MATCH_NONE)
 127                 ret = false;
 128
 129         return ret;
 130 }
 131
 132 static int policy_mt_check(const struct xt_mtchk_param *par)
 133 {
 134         const struct xt_policy_info *info = par->matchinfo;
 135         const char *errmsg = "neither incoming nor outgoing policy selected";
 136
 137         if (!(info->flags & (XT_POLICY_MATCH_IN|XT_POLICY_MATCH_OUT)))
 138                 goto err;
 139
 140         if (par->hook_mask & ((1 << NF_INET_PRE_ROUTING) |
 141             (1 << NF_INET_LOCAL_IN)) && info->flags & XT_POLICY_MATCH_OUT) {
 142                 errmsg = "output policy not valid in PREROUTING and INPUT";
 143                 goto err;
 144         }
 145         if (par->hook_mask & ((1 << NF_INET_POST_ROUTING) |
 146             (1 << NF_INET_LOCAL_OUT)) && info->flags & XT_POLICY_MATCH_IN) {
 147                 errmsg = "input policy not valid in POSTROUTING and OUTPUT";
 148                 goto err;
 149         }
 150         if (info->len > XT_POLICY_MAX_ELEM) {
 151                 errmsg = "too many policy elements";
 152                 goto err;
 153         }
 154         return 0;
 155 err:
 156         pr_info_ratelimited("%s\n", errmsg);
 157         return -EINVAL;
 158 }
 159
 160 static struct xt_match policy_mt_reg[] __read_mostly = {
 161         {
 162                 .name           = "policy",
 163                 .family         = NFPROTO_IPV4,
 164                 .checkentry     = policy_mt_check,
 165                 .match          = policy_mt,
 166                 .matchsize      = sizeof(struct xt_policy_info),
 167                 .me             = THIS_MODULE,
 168         },
 169         {
 170                 .name           = "policy",
 171                 .family         = NFPROTO_IPV6,
 172                 .checkentry     = policy_mt_check,
 173                 .match          = policy_mt,
 174                 .matchsize      = sizeof(struct xt_policy_info),
 175                 .me             = THIS_MODULE,
 176         },
 177 };
 178
 179 static int __init policy_mt_init(void)
 180 {
 181         return xt_register_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
 182 }
 183
 184 static void __exit policy_mt_exit(void)
 185 {
 186         xt_unregister_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
 187 }
 188
 189 module_init(policy_mt_init);
 190 module_exit(policy_mt_exit);
 191 MODULE_ALIAS("ipt_policy");
 192 MODULE_ALIAS("ip6t_policy");