net/ipv6/netfilter/ip6t_ipv6header.c

   1 /* ipv6header match - matches IPv6 packets based
   2    on whether they contain certain headers */
   3
   4 /* Original idea: Brad Chapman
   5  * Rewritten by: Andras Kis-Szabo <[email protected]> */
   6
   7 /* (C) 2001-2002 Andras Kis-Szabo <[email protected]>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/ipv6.h>
  17 #include <linux/types.h>
  18 #include <net/checksum.h>
  19 #include <net/ipv6.h>
  20
  21 #include <linux/netfilter/x_tables.h>
  22 #include <linux/netfilter_ipv6/ip6_tables.h>
  23 #include <linux/netfilter_ipv6/ip6t_ipv6header.h>
  24
  25 MODULE_LICENSE("GPL");
  26 MODULE_DESCRIPTION("Xtables: IPv6 header types match");
  27 MODULE_AUTHOR("Andras Kis-Szabo <[email protected]>");
  28
  29 static bool
  30 ipv6header_mt6(const struct sk_buff *skb, struct xt_action_param *par)
  31 {
  32         const struct ip6t_ipv6header_info *info = par->matchinfo;
  33         unsigned int temp;
  34         int len;
  35         u8 nexthdr;
  36         unsigned int ptr;
  37
  38         /* Make sure this isn't an evil packet */
  39
  40         /* type of the 1st exthdr */
  41         nexthdr = ipv6_hdr(skb)->nexthdr;
  42         /* pointer to the 1st exthdr */
  43         ptr = sizeof(struct ipv6hdr);
  44         /* available length */
  45         len = skb->len - ptr;
  46         temp = 0;
  47
  48         while (ip6t_ext_hdr(nexthdr)) {
  49                 const struct ipv6_opt_hdr *hp;
  50                 struct ipv6_opt_hdr _hdr;
  51                 int hdrlen;
  52
  53                 /* No more exthdr -> evaluate */
  54                 if (nexthdr == NEXTHDR_NONE) {
  55                         temp |= MASK_NONE;
  56                         break;
  57                 }
  58                 /* Is there enough space for the next ext header? */
  59                 if (len < (int)sizeof(struct ipv6_opt_hdr))
  60                         return false;
  61                 /* ESP -> evaluate */
  62                 if (nexthdr == NEXTHDR_ESP) {
  63                         temp |= MASK_ESP;
  64                         break;
  65                 }
  66
  67                 hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
  68                 if (!hp) {
  69                         par->hotdrop = true;
  70                         return false;
  71                 }
  72
  73                 /* Calculate the header length */
  74                 if (nexthdr == NEXTHDR_FRAGMENT)
  75                         hdrlen = 8;
  76                 else if (nexthdr == NEXTHDR_AUTH)
  77                         hdrlen = (hp->hdrlen + 2) << 2;
  78                 else
  79                         hdrlen = ipv6_optlen(hp);
  80
  81                 /* set the flag */
  82                 switch (nexthdr) {
  83                 case NEXTHDR_HOP:
  84                         temp |= MASK_HOPOPTS;
  85                         break;
  86                 case NEXTHDR_ROUTING:
  87                         temp |= MASK_ROUTING;
  88                         break;
  89                 case NEXTHDR_FRAGMENT:
  90                         temp |= MASK_FRAGMENT;
  91                         break;
  92                 case NEXTHDR_AUTH:
  93                         temp |= MASK_AH;
  94                         break;
  95                 case NEXTHDR_DEST:
  96                         temp |= MASK_DSTOPTS;
  97                         break;
  98                 default:
  99                         return false;
 100                 }
 101
 102                 nexthdr = hp->nexthdr;
 103                 len -= hdrlen;
 104                 ptr += hdrlen;
 105                 if (ptr > skb->len)
 106                         break;
 107         }
 108
 109         if (nexthdr != NEXTHDR_NONE && nexthdr != NEXTHDR_ESP)
 110                 temp |= MASK_PROTO;
 111
 112         if (info->modeflag)
 113                 return !((temp ^ info->matchflags ^ info->invflags)
 114                          & info->matchflags);
 115         else {
 116                 if (info->invflags)
 117                         return temp != info->matchflags;
 118                 else
 119                         return temp == info->matchflags;
 120         }
 121 }
 122
 123 static int ipv6header_mt6_check(const struct xt_mtchk_param *par)
 124 {
 125         const struct ip6t_ipv6header_info *info = par->matchinfo;
 126
 127         /* invflags is 0 or 0xff in hard mode */
 128         if ((!info->modeflag) && info->invflags != 0x00 &&
 129             info->invflags != 0xFF)
 130                 return -EINVAL;
 131
 132         return 0;
 133 }
 134
 135 static struct xt_match ipv6header_mt6_reg __read_mostly = {
 136         .name           = "ipv6header",
 137         .family         = NFPROTO_IPV6,
 138         .match          = ipv6header_mt6,
 139         .matchsize      = sizeof(struct ip6t_ipv6header_info),
 140         .checkentry     = ipv6header_mt6_check,
 141         .destroy        = NULL,
 142         .me             = THIS_MODULE,
 143 };
 144
 145 static int __init ipv6header_mt6_init(void)
 146 {
 147         return xt_register_match(&ipv6header_mt6_reg);
 148 }
 149
 150 static void __exit ipv6header_mt6_exit(void)
 151 {
 152         xt_unregister_match(&ipv6header_mt6_reg);
 153 }
 154
 155 module_init(ipv6header_mt6_init);
 156 module_exit(ipv6header_mt6_exit);