LXR linux/net/ipv6/netfilter/ip6t

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* ipv6header match - matches IPv6 packets based
   3   on whether they contain certain headers */
   4
   5/* Original idea: Brad Chapman
   6 * Rewritten by: Andras Kis-Szabo <kisza@sch.bme.hu> */
   7
   8/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
   9 */
  10
  11#include <linux/module.h>
  12#include <linux/skbuff.h>
  13#include <linux/ipv6.h>
  14#include <linux/types.h>
  15#include <net/checksum.h>
  16#include <net/ipv6.h>
  17
  18#include <linux/netfilter/x_tables.h>
  19#include <linux/netfilter_ipv6/ip6_tables.h>
  20#include <linux/netfilter_ipv6/ip6t_ipv6header.h>
  21
  22MODULE_LICENSE("GPL");
  23MODULE_DESCRIPTION("Xtables: IPv6 header types match");
  24MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  25
  26static bool
  27ipv6header_mt6(const struct sk_buff *skb, struct xt_action_param *par)
  28{
  29        const struct ip6t_ipv6header_info *info = par->matchinfo;
  30        unsigned int temp;
  31        int len;
  32        u8 nexthdr;
  33        unsigned int ptr;
  34
  35        /* Make sure this isn't an evil packet */
  36
  37        /* type of the 1st exthdr */
  38        nexthdr = ipv6_hdr(skb)->nexthdr;
  39        /* pointer to the 1st exthdr */
  40        ptr = sizeof(struct ipv6hdr);
  41        /* available length */
  42        len = skb->len - ptr;
  43        temp = 0;
  44
  45        while (ip6t_ext_hdr(nexthdr)) {
  46                const struct ipv6_opt_hdr *hp;
  47                struct ipv6_opt_hdr _hdr;
  48                int hdrlen;
  49
  50                /* No more exthdr -> evaluate */
  51                if (nexthdr == NEXTHDR_NONE) {
  52                        temp |= MASK_NONE;
  53                        break;
  54                }
  55                /* Is there enough space for the next ext header? */
  56                if (len < (int)sizeof(struct ipv6_opt_hdr))
  57                        return false;
  58                /* ESP -> evaluate */
  59                if (nexthdr == NEXTHDR_ESP) {
  60                        temp |= MASK_ESP;
  61                        break;
  62                }
  63
  64                hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
  65                if (!hp) {
  66                        par->hotdrop = true;
  67                        return false;
  68                }
  69
  70                /* Calculate the header length */
  71                if (nexthdr == NEXTHDR_FRAGMENT)
  72                        hdrlen = 8;
  73                else if (nexthdr == NEXTHDR_AUTH)
  74                        hdrlen = ipv6_authlen(hp);
  75                else
  76                        hdrlen = ipv6_optlen(hp);
  77
  78                /* set the flag */
  79                switch (nexthdr) {
  80                case NEXTHDR_HOP:
  81                        temp |= MASK_HOPOPTS;
  82                        break;
  83                case NEXTHDR_ROUTING:
  84                        temp |= MASK_ROUTING;
  85                        break;
  86                case NEXTHDR_FRAGMENT:
  87                        temp |= MASK_FRAGMENT;
  88                        break;
  89                case NEXTHDR_AUTH:
  90                        temp |= MASK_AH;
  91                        break;
  92                case NEXTHDR_DEST:
  93                        temp |= MASK_DSTOPTS;
  94                        break;
  95                default:
  96                        return false;
  97                }
  98
  99                nexthdr = hp->nexthdr;
 100                len -= hdrlen;
 101                ptr += hdrlen;
 102                if (ptr > skb->len)
 103                        break;
 104        }
 105
 106        if (nexthdr != NEXTHDR_NONE && nexthdr != NEXTHDR_ESP)
 107                temp |= MASK_PROTO;
 108
 109        if (info->modeflag)
 110                return !((temp ^ info->matchflags ^ info->invflags)
 111                         & info->matchflags);
 112        else {
 113                if (info->invflags)
 114                        return temp != info->matchflags;
 115                else
 116                        return temp == info->matchflags;
 117        }
 118}
 119
 120static int ipv6header_mt6_check(const struct xt_mtchk_param *par)
 121{
 122        const struct ip6t_ipv6header_info *info = par->matchinfo;
 123
 124        /* invflags is 0 or 0xff in hard mode */
 125        if ((!info->modeflag) && info->invflags != 0x00 &&
 126            info->invflags != 0xFF)
 127                return -EINVAL;
 128
 129        return 0;
 130}
 131
 132static struct xt_match ipv6header_mt6_reg __read_mostly = {
 133        .name           = "ipv6header",
 134        .family         = NFPROTO_IPV6,
 135        .match          = ipv6header_mt6,
 136        .matchsize      = sizeof(struct ip6t_ipv6header_info),
 137        .checkentry     = ipv6header_mt6_check,
 138        .destroy        = NULL,
 139        .me             = THIS_MODULE,
 140};
 141
 142static int __init ipv6header_mt6_init(void)
 143{
 144        return xt_register_match(&ipv6header_mt6_reg);
 145}
 146
 147static void __exit ipv6header_mt6_exit(void)
 148{
 149        xt_unregister_match(&ipv6header_mt6_reg);
 150}
 151
 152module_init(ipv6header_mt6_init);
 153module_exit(ipv6header_mt6_exit);
 154