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/config.h>
  12 #include <linux/module.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/init.h>
  15 #include <net/xfrm.h>
  16
  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 matching module");
  22 MODULE_LICENSE("GPL");
  23
  24 static inline int
  25 xt_addr_cmp(const union xt_policy_addr *a1, const union xt_policy_addr *m,
  26             const union xt_policy_addr *a2, unsigned short family)
  27 {
  28         switch (family) {
  29         case AF_INET:
  30                 return !((a1->a4.s_addr ^ a2->a4.s_addr) & m->a4.s_addr);
  31         case AF_INET6:
  32                 return !ipv6_masked_addr_cmp(&a1->a6, &m->a6, &a2->a6);
  33         }
  34         return 0;
  35 }
  36
  37 static inline int
  38 match_xfrm_state(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, 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, (union xt_policy_addr *)&x->props.saddr) &&
  47                MATCH_ADDR(daddr, dmask, (union xt_policy_addr *)&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         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         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 int match(const struct sk_buff *skb,
 113                  const struct net_device *in,
 114                  const struct net_device *out,
 115                  const struct xt_match *match,
 116                  const void *matchinfo,
 117                  int offset,
 118                  unsigned int protoff,
 119                  int *hotdrop)
 120 {
 121         const struct xt_policy_info *info = matchinfo;
 122         int ret;
 123
 124         if (info->flags & XT_POLICY_MATCH_IN)
 125                 ret = match_policy_in(skb, info, match->family);
 126         else
 127                 ret = match_policy_out(skb, info, match->family);
 128
 129         if (ret < 0)
 130                 ret = info->flags & XT_POLICY_MATCH_NONE ? 1 : 0;
 131         else if (info->flags & XT_POLICY_MATCH_NONE)
 132                 ret = 0;
 133
 134         return ret;
 135 }
 136
 137 static int checkentry(const char *tablename, const void *ip_void,
 138                       const struct xt_match *match,
 139                       void *matchinfo, unsigned int matchsize,
 140                       unsigned int hook_mask)
 141 {
 142         struct xt_policy_info *info = matchinfo;
 143
 144         if (!(info->flags & (XT_POLICY_MATCH_IN|XT_POLICY_MATCH_OUT))) {
 145                 printk(KERN_ERR "xt_policy: neither incoming nor "
 146                                 "outgoing policy selected\n");
 147                 return 0;
 148         }
 149         /* hook values are equal for IPv4 and IPv6 */
 150         if (hook_mask & (1 << NF_IP_PRE_ROUTING | 1 << NF_IP_LOCAL_IN)
 151             && info->flags & XT_POLICY_MATCH_OUT) {
 152                 printk(KERN_ERR "xt_policy: output policy not valid in "
 153                                 "PRE_ROUTING and INPUT\n");
 154                 return 0;
 155         }
 156         if (hook_mask & (1 << NF_IP_POST_ROUTING | 1 << NF_IP_LOCAL_OUT)
 157             && info->flags & XT_POLICY_MATCH_IN) {
 158                 printk(KERN_ERR "xt_policy: input policy not valid in "
 159                                 "POST_ROUTING and OUTPUT\n");
 160                 return 0;
 161         }
 162         if (info->len > XT_POLICY_MAX_ELEM) {
 163                 printk(KERN_ERR "xt_policy: too many policy elements\n");
 164                 return 0;
 165         }
 166         return 1;
 167 }
 168
 169 static struct xt_match policy_match = {
 170         .name           = "policy",
 171         .family         = AF_INET,
 172         .match          = match,
 173         .matchsize      = sizeof(struct xt_policy_info),
 174         .checkentry     = checkentry,
 175         .family         = AF_INET,
 176         .me             = THIS_MODULE,
 177 };
 178
 179 static struct xt_match policy6_match = {
 180         .name           = "policy",
 181         .family         = AF_INET6,
 182         .match          = match,
 183         .matchsize      = sizeof(struct xt_policy_info),
 184         .checkentry     = checkentry,
 185         .family         = AF_INET6,
 186         .me             = THIS_MODULE,
 187 };
 188
 189 static int __init init(void)
 190 {
 191         int ret;
 192
 193         ret = xt_register_match(&policy_match);
 194         if (ret)
 195                 return ret;
 196         ret = xt_register_match(&policy6_match);
 197         if (ret)
 198                 xt_unregister_match(&policy_match);
 199         return ret;
 200 }
 201
 202 static void __exit fini(void)
 203 {
 204         xt_unregister_match(&policy6_match);
 205         xt_unregister_match(&policy_match);
 206 }
 207
 208 module_init(init);
 209 module_exit(fini);
 210 MODULE_ALIAS("ipt_policy");
 211 MODULE_ALIAS("ip6t_policy");