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
  30 /* Returns 1 if the spi is matched by the range, 0 otherwise */
  31 static inline bool
  32 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
  33 {
  34         bool r;
  35         pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
  36                  invert ? '!' : ' ', min, spi, max);
  37         r = (spi >= min && spi <= max) ^ invert;
  38         pr_debug(" result %s\n", r ? "PASS" : "FAILED");
  39         return r;
  40 }
  41
  42 static bool comp_mt(const struct sk_buff *skb, struct xt_action_param *par)
  43 {
  44         struct ip_comp_hdr _comphdr;
  45         const struct ip_comp_hdr *chdr;
  46         const struct xt_ipcomp *compinfo = par->matchinfo;
  47
  48         /* Must not be a fragment. */
  49         if (par->fragoff != 0)
  50                 return false;
  51
  52         chdr = skb_header_pointer(skb, par->thoff, sizeof(_comphdr), &_comphdr);
  53         if (chdr == NULL) {
  54                 /* We've been asked to examine this packet, and we
  55                  * can't.  Hence, no choice but to drop.
  56                  */
  57                 pr_debug("Dropping evil IPComp tinygram.\n");
  58                 par->hotdrop = true;
  59                 return 0;
  60         }
  61
  62         return spi_match(compinfo->spis[0], compinfo->spis[1],
  63                          ntohs(chdr->cpi),
  64                          !!(compinfo->invflags & XT_IPCOMP_INV_SPI));
  65 }
  66
  67 static int comp_mt_check(const struct xt_mtchk_param *par)
  68 {
  69         const struct xt_ipcomp *compinfo = par->matchinfo;
  70
  71         /* Must specify no unknown invflags */
  72         if (compinfo->invflags & ~XT_IPCOMP_INV_MASK) {
  73                 pr_err("unknown flags %X\n", compinfo->invflags);
  74                 return -EINVAL;
  75         }
  76         return 0;
  77 }
  78
  79 static struct xt_match comp_mt_reg[] __read_mostly = {
  80         {
  81                 .name           = "ipcomp",
  82                 .family         = NFPROTO_IPV4,
  83                 .match          = comp_mt,
  84                 .matchsize      = sizeof(struct xt_ipcomp),
  85                 .proto          = IPPROTO_COMP,
  86                 .checkentry     = comp_mt_check,
  87                 .me             = THIS_MODULE,
  88         },
  89         {
  90                 .name           = "ipcomp",
  91                 .family         = NFPROTO_IPV6,
  92                 .match          = comp_mt,
  93                 .matchsize      = sizeof(struct xt_ipcomp),
  94                 .proto          = IPPROTO_COMP,
  95                 .checkentry     = comp_mt_check,
  96                 .me             = THIS_MODULE,
  97         },
  98 };
  99
 100 static int __init comp_mt_init(void)
 101 {
 102         return xt_register_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
 103 }
 104
 105 static void __exit comp_mt_exit(void)
 106 {
 107         xt_unregister_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
 108 }
 109
 110 module_init(comp_mt_init);
 111 module_exit(comp_mt_exit);