net/ipv4/netfilter/ipt_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_ipv4.h>
  18 #include <linux/netfilter_ipv4/ip_tables.h>
  19 #include <linux/netfilter_ipv4/ipt_policy.h>
  20
  21 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  22 MODULE_DESCRIPTION("IPtables IPsec policy matching module");
  23 MODULE_LICENSE("GPL");
  24
  25
  26 static inline int
  27 match_xfrm_state(struct xfrm_state *x, const struct ipt_policy_elem *e)
  28 {
  29 #define MATCH(x,y)      (!e->match.x || ((e->x == (y)) ^ e->invert.x))
  30
  31         return MATCH(saddr, x->props.saddr.a4 & e->smask) &&
  32                MATCH(daddr, x->id.daddr.a4 & e->dmask) &&
  33                MATCH(proto, x->id.proto) &&
  34                MATCH(mode, x->props.mode) &&
  35                MATCH(spi, x->id.spi) &&
  36                MATCH(reqid, x->props.reqid);
  37 }
  38
  39 static int
  40 match_policy_in(const struct sk_buff *skb, const struct ipt_policy_info *info)
  41 {
  42         const struct ipt_policy_elem *e;
  43         struct sec_path *sp = skb->sp;
  44         int strict = info->flags & IPT_POLICY_MATCH_STRICT;
  45         int i, pos;
  46
  47         if (sp == NULL)
  48                 return -1;
  49         if (strict && info->len != sp->len)
  50                 return 0;
  51
  52         for (i = sp->len - 1; i >= 0; i--) {
  53                 pos = strict ? i - sp->len + 1 : 0;
  54                 if (pos >= info->len)
  55                         return 0;
  56                 e = &info->pol[pos];
  57
  58                 if (match_xfrm_state(sp->x[i].xvec, e)) {
  59                         if (!strict)
  60                                 return 1;
  61                 } else if (strict)
  62                         return 0;
  63         }
  64
  65         return strict ? 1 : 0;
  66 }
  67
  68 static int
  69 match_policy_out(const struct sk_buff *skb, const struct ipt_policy_info *info)
  70 {
  71         const struct ipt_policy_elem *e;
  72         struct dst_entry *dst = skb->dst;
  73         int strict = info->flags & IPT_POLICY_MATCH_STRICT;
  74         int i, pos;
  75
  76         if (dst->xfrm == NULL)
  77                 return -1;
  78
  79         for (i = 0; dst && dst->xfrm; dst = dst->child, i++) {
  80                 pos = strict ? i : 0;
  81                 if (pos >= info->len)
  82                         return 0;
  83                 e = &info->pol[pos];
  84
  85                 if (match_xfrm_state(dst->xfrm, e)) {
  86                         if (!strict)
  87                                 return 1;
  88                 } else if (strict)
  89                         return 0;
  90         }
  91
  92         return strict ? 1 : 0;
  93 }
  94
  95 static int match(const struct sk_buff *skb,
  96                  const struct net_device *in,
  97                  const struct net_device *out,
  98                  const void *matchinfo,
  99                  int offset,
 100                  unsigned int protoff,
 101                  int *hotdrop)
 102 {
 103         const struct ipt_policy_info *info = matchinfo;
 104         int ret;
 105
 106         if (info->flags & IPT_POLICY_MATCH_IN)
 107                 ret = match_policy_in(skb, info);
 108         else
 109                 ret = match_policy_out(skb, info);
 110
 111         if (ret < 0)
 112                 ret = info->flags & IPT_POLICY_MATCH_NONE ? 1 : 0;
 113         else if (info->flags & IPT_POLICY_MATCH_NONE)
 114                 ret = 0;
 115
 116         return ret;
 117 }
 118
 119 static int checkentry(const char *tablename, const void *ip_void,
 120                       void *matchinfo, unsigned int matchsize,
 121                       unsigned int hook_mask)
 122 {
 123         struct ipt_policy_info *info = matchinfo;
 124
 125         if (matchsize != IPT_ALIGN(sizeof(*info))) {
 126                 printk(KERN_ERR "ipt_policy: matchsize %u != %zu\n",
 127                        matchsize, IPT_ALIGN(sizeof(*info)));
 128                 return 0;
 129         }
 130         if (!(info->flags & (IPT_POLICY_MATCH_IN|IPT_POLICY_MATCH_OUT))) {
 131                 printk(KERN_ERR "ipt_policy: neither incoming nor "
 132                                 "outgoing policy selected\n");
 133                 return 0;
 134         }
 135         if (hook_mask & (1 << NF_IP_PRE_ROUTING | 1 << NF_IP_LOCAL_IN)
 136             && info->flags & IPT_POLICY_MATCH_OUT) {
 137                 printk(KERN_ERR "ipt_policy: output policy not valid in "
 138                                 "PRE_ROUTING and INPUT\n");
 139                 return 0;
 140         }
 141         if (hook_mask & (1 << NF_IP_POST_ROUTING | 1 << NF_IP_LOCAL_OUT)
 142             && info->flags & IPT_POLICY_MATCH_IN) {
 143                 printk(KERN_ERR "ipt_policy: input policy not valid in "
 144                                 "POST_ROUTING and OUTPUT\n");
 145                 return 0;
 146         }
 147         if (info->len > IPT_POLICY_MAX_ELEM) {
 148                 printk(KERN_ERR "ipt_policy: too many policy elements\n");
 149                 return 0;
 150         }
 151
 152         return 1;
 153 }
 154
 155 static struct ipt_match policy_match = {
 156         .name           = "policy",
 157         .match          = match,
 158         .checkentry     = checkentry,
 159         .me             = THIS_MODULE,
 160 };
 161
 162 static int __init init(void)
 163 {
 164         return ipt_register_match(&policy_match);
 165 }
 166
 167 static void __exit fini(void)
 168 {
 169         ipt_unregister_match(&policy_match);
 170 }
 171
 172 module_init(init);
 173 module_exit(fini);