net/ipv6/netfilter/ip6t_mh.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C)2006 USAGI/WIDE Project
   4  *
   5  * Author:
   6  *      Masahide NAKAMURA @USAGI <masahide.nakamura.cz@hitachi.com>
   7  *
   8  * Based on net/netfilter/xt_tcpudp.c
   9  */
  10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11 #include <linux/types.h>
  12 #include <linux/module.h>
  13 #include <net/ip.h>
  14 #include <linux/ipv6.h>
  15 #include <net/ipv6.h>
  16 #include <net/mip6.h>
  17
  18 #include <linux/netfilter/x_tables.h>
  19 #include <linux/netfilter_ipv6/ip6t_mh.h>
  20
  21 MODULE_DESCRIPTION("Xtables: IPv6 Mobility Header match");
  22 MODULE_LICENSE("GPL");
  23
  24 /* Returns 1 if the type is matched by the range, 0 otherwise */
  25 static inline bool
  26 type_match(u_int8_t min, u_int8_t max, u_int8_t type, bool invert)
  27 {
  28         return (type >= min && type <= max) ^ invert;
  29 }
  30
  31 static bool mh_mt6(const struct sk_buff *skb, struct xt_action_param *par)
  32 {
  33         struct ip6_mh _mh;
  34         const struct ip6_mh *mh;
  35         const struct ip6t_mh *mhinfo = par->matchinfo;
  36
  37         /* Must not be a fragment. */
  38         if (par->fragoff != 0)
  39                 return false;
  40
  41         mh = skb_header_pointer(skb, par->thoff, sizeof(_mh), &_mh);
  42         if (mh == NULL) {
  43                 /* We've been asked to examine this packet, and we
  44                    can't.  Hence, no choice but to drop. */
  45                 pr_debug("Dropping evil MH tinygram.\n");
  46                 par->hotdrop = true;
  47                 return false;
  48         }
  49
  50         if (mh->ip6mh_proto != IPPROTO_NONE) {
  51                 pr_debug("Dropping invalid MH Payload Proto: %u\n",
  52                          mh->ip6mh_proto);
  53                 par->hotdrop = true;
  54                 return false;
  55         }
  56
  57         return type_match(mhinfo->types[0], mhinfo->types[1], mh->ip6mh_type,
  58                           !!(mhinfo->invflags & IP6T_MH_INV_TYPE));
  59 }
  60
  61 static int mh_mt6_check(const struct xt_mtchk_param *par)
  62 {
  63         const struct ip6t_mh *mhinfo = par->matchinfo;
  64
  65         /* Must specify no unknown invflags */
  66         return (mhinfo->invflags & ~IP6T_MH_INV_MASK) ? -EINVAL : 0;
  67 }
  68
  69 static struct xt_match mh_mt6_reg __read_mostly = {
  70         .name           = "mh",
  71         .family         = NFPROTO_IPV6,
  72         .checkentry     = mh_mt6_check,
  73         .match          = mh_mt6,
  74         .matchsize      = sizeof(struct ip6t_mh),
  75         .proto          = IPPROTO_MH,
  76         .me             = THIS_MODULE,
  77 };
  78
  79 static int __init mh_mt6_init(void)
  80 {
  81         return xt_register_match(&mh_mt6_reg);
  82 }
  83
  84 static void __exit mh_mt6_exit(void)
  85 {
  86         xt_unregister_match(&mh_mt6_reg);
  87 }
  88
  89 module_init(mh_mt6_init);
  90 module_exit(mh_mt6_exit);