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
  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 AF_INET:
  30                 return ((a1->ip ^ a2->ip) & m->ip) == 0;
  31         case AF_INET6:
  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;
  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, const struct net_device *in,
 114           const struct net_device *out, const struct xt_match *match,
 115           const void *matchinfo, int offset, unsigned int protoff,
 116           bool *hotdrop)
 117 {
 118         const struct xt_policy_info *info = matchinfo;
 119         int ret;
 120
 121         if (info->flags & XT_POLICY_MATCH_IN)
 122                 ret = match_policy_in(skb, info, match->family);
 123         else
 124                 ret = match_policy_out(skb, info, match->family);
 125
 126         if (ret < 0)
 127                 ret = info->flags & XT_POLICY_MATCH_NONE ? true : false;
 128         else if (info->flags & XT_POLICY_MATCH_NONE)
 129                 ret = false;
 130
 131         return ret;
 132 }
 133
 134 static bool
 135 policy_mt_check(const char *tablename, const void *ip_void,
 136                 const struct xt_match *match, void *matchinfo,
 137                 unsigned int hook_mask)
 138 {
 139         const struct xt_policy_info *info = matchinfo;
 140
 141         if (!(info->flags & (XT_POLICY_MATCH_IN|XT_POLICY_MATCH_OUT))) {
 142                 printk(KERN_ERR "xt_policy: neither incoming nor "
 143                                 "outgoing policy selected\n");
 144                 return false;
 145         }
 146         if (hook_mask & (1 << NF_INET_PRE_ROUTING | 1 << NF_INET_LOCAL_IN)
 147             && info->flags & XT_POLICY_MATCH_OUT) {
 148                 printk(KERN_ERR "xt_policy: output policy not valid in "
 149                                 "PRE_ROUTING and INPUT\n");
 150                 return false;
 151         }
 152         if (hook_mask & (1 << NF_INET_POST_ROUTING | 1 << NF_INET_LOCAL_OUT)
 153             && info->flags & XT_POLICY_MATCH_IN) {
 154                 printk(KERN_ERR "xt_policy: input policy not valid in "
 155                                 "POST_ROUTING and OUTPUT\n");
 156                 return false;
 157         }
 158         if (info->len > XT_POLICY_MAX_ELEM) {
 159                 printk(KERN_ERR "xt_policy: too many policy elements\n");
 160                 return false;
 161         }
 162         return true;
 163 }
 164
 165 static struct xt_match policy_mt_reg[] __read_mostly = {
 166         {
 167                 .name           = "policy",
 168                 .family         = AF_INET,
 169                 .checkentry     = policy_mt_check,
 170                 .match          = policy_mt,
 171                 .matchsize      = sizeof(struct xt_policy_info),
 172                 .me             = THIS_MODULE,
 173         },
 174         {
 175                 .name           = "policy",
 176                 .family         = AF_INET6,
 177                 .checkentry     = policy_mt_check,
 178                 .match          = policy_mt,
 179                 .matchsize      = sizeof(struct xt_policy_info),
 180                 .me             = THIS_MODULE,
 181         },
 182 };
 183
 184 static int __init policy_mt_init(void)
 185 {
 186         return xt_register_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
 187 }
 188
 189 static void __exit policy_mt_exit(void)
 190 {
 191         xt_unregister_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
 192 }
 193
 194 module_init(policy_mt_init);
 195 module_exit(policy_mt_exit);
 196 MODULE_ALIAS("ipt_policy");
 197 MODULE_ALIAS("ip6t_policy");