net/netfilter/xt_ipcomp.c

   1 /*  Kernel module to match IPComp parameters for IPv4 and IPv6
   2  *
   3  *  Copyright (C) 2013 WindRiver
   4  *
   5  *  Author:
   6  *  Fan Du <fan.du@windriver.com>
   7  *
   8  *  Based on:
   9  *  net/netfilter/xt_esp.c
  10  *
  11  *  This program is free software; you can redistribute it and/or
  12  *  modify it under the terms of the GNU General Public License
  13  *  as published by the Free Software Foundation; either version
  14  *  2 of the License, or (at your option) any later version.
  15  */
  16
  17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  18 #include <linux/in.h>
  19 #include <linux/module.h>
  20 #include <linux/skbuff.h>
  21 #include <linux/ip.h>
  22
  23 #include <linux/netfilter/xt_ipcomp.h>
  24 #include <linux/netfilter/x_tables.h>
  25
  26 MODULE_LICENSE("GPL");
  27 MODULE_AUTHOR("Fan Du <fan.du@windriver.com>");
  28 MODULE_DESCRIPTION("Xtables: IPv4/6 IPsec-IPComp SPI match");
  29 MODULE_ALIAS("ipt_ipcomp");
  30 MODULE_ALIAS("ip6t_ipcomp");
  31
  32 /* Returns 1 if the spi is matched by the range, 0 otherwise */
  33 static inline bool
  34 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
  35 {
  36         bool r;
  37         pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
  38                  invert ? '!' : ' ', min, spi, max);
  39         r = (spi >= min && spi <= max) ^ invert;
  40         pr_debug(" result %s\n", r ? "PASS" : "FAILED");
  41         return r;
  42 }
  43
  44 static bool comp_mt(const struct sk_buff *skb, struct xt_action_param *par)
  45 {
  46         struct ip_comp_hdr _comphdr;
  47         const struct ip_comp_hdr *chdr;
  48         const struct xt_ipcomp *compinfo = par->matchinfo;
  49
  50         /* Must not be a fragment. */
  51         if (par->fragoff != 0)
  52                 return false;
  53
  54         chdr = skb_header_pointer(skb, par->thoff, sizeof(_comphdr), &_comphdr);
  55         if (chdr == NULL) {
  56                 /* We've been asked to examine this packet, and we
  57                  * can't.  Hence, no choice but to drop.
  58                  */
  59                 pr_debug("Dropping evil IPComp tinygram.\n");
  60                 par->hotdrop = true;
  61                 return false;
  62         }
  63
  64         return spi_match(compinfo->spis[0], compinfo->spis[1],
  65                          ntohs(chdr->cpi),
  66                          !!(compinfo->invflags & XT_IPCOMP_INV_SPI));
  67 }
  68
  69 static int comp_mt_check(const struct xt_mtchk_param *par)
  70 {
  71         const struct xt_ipcomp *compinfo = par->matchinfo;
  72
  73         /* Must specify no unknown invflags */
  74         if (compinfo->invflags & ~XT_IPCOMP_INV_MASK) {
  75                 pr_info_ratelimited("unknown flags %X\n", compinfo->invflags);
  76                 return -EINVAL;
  77         }
  78         return 0;
  79 }
  80
  81 static struct xt_match comp_mt_reg[] __read_mostly = {
  82         {
  83                 .name           = "ipcomp",
  84                 .family         = NFPROTO_IPV4,
  85                 .match          = comp_mt,
  86                 .matchsize      = sizeof(struct xt_ipcomp),
  87                 .proto          = IPPROTO_COMP,
  88                 .checkentry     = comp_mt_check,
  89                 .me             = THIS_MODULE,
  90         },
  91         {
  92                 .name           = "ipcomp",
  93                 .family         = NFPROTO_IPV6,
  94                 .match          = comp_mt,
  95                 .matchsize      = sizeof(struct xt_ipcomp),
  96                 .proto          = IPPROTO_COMP,
  97                 .checkentry     = comp_mt_check,
  98                 .me             = THIS_MODULE,
  99         },
 100 };
 101
 102 static int __init comp_mt_init(void)
 103 {
 104         return xt_register_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
 105 }
 106
 107 static void __exit comp_mt_exit(void)
 108 {
 109         xt_unregister_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
 110 }
 111
 112 module_init(comp_mt_init);
 113 module_exit(comp_mt_exit);