LXR linux/net/netfilter/xt

   1/* Kernel module to match ESP parameters. */
   2
   3/* (C) 1999-2000 Yon Uriarte <yon@astaro.de>
   4 *
   5 * This program is free software; you can redistribute it and/or modify
   6 * it under the terms of the GNU General Public License version 2 as
   7 * published by the Free Software Foundation.
   8 */
   9
  10#include <linux/module.h>
  11#include <linux/skbuff.h>
  12#include <linux/in.h>
  13#include <linux/ip.h>
  14
  15#include <linux/netfilter/xt_esp.h>
  16#include <linux/netfilter/x_tables.h>
  17
  18#include <linux/netfilter_ipv4/ip_tables.h>
  19#include <linux/netfilter_ipv6/ip6_tables.h>
  20
  21MODULE_LICENSE("GPL");
  22MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
  23MODULE_DESCRIPTION("Xtables: IPsec-ESP packet match");
  24MODULE_ALIAS("ipt_esp");
  25MODULE_ALIAS("ip6t_esp");
  26
  27#if 0
  28#define duprintf(format, args...) printk(format , ## args)
  29#else
  30#define duprintf(format, args...)
  31#endif
  32
  33/* Returns 1 if the spi is matched by the range, 0 otherwise */
  34static inline bool
  35spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
  36{
  37        bool r;
  38        duprintf("esp spi_match:%c 0x%x <= 0x%x <= 0x%x", invert ? '!' : ' ',
  39                 min, spi, max);
  40        r = (spi >= min && spi <= max) ^ invert;
  41        duprintf(" result %s\n", r ? "PASS" : "FAILED");
  42        return r;
  43}
  44
  45static bool esp_mt(const struct sk_buff *skb, const struct xt_match_param *par)
  46{
  47        const struct ip_esp_hdr *eh;
  48        struct ip_esp_hdr _esp;
  49        const struct xt_esp *espinfo = par->matchinfo;
  50
  51        /* Must not be a fragment. */
  52        if (par->fragoff != 0)
  53                return false;
  54
  55        eh = skb_header_pointer(skb, par->thoff, sizeof(_esp), &_esp);
  56        if (eh == NULL) {
  57                /* We've been asked to examine this packet, and we
  58                 * can't.  Hence, no choice but to drop.
  59                 */
  60                duprintf("Dropping evil ESP tinygram.\n");
  61                *par->hotdrop = true;
  62                return false;
  63        }
  64
  65        return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi),
  66                         !!(espinfo->invflags & XT_ESP_INV_SPI));
  67}
  68
  69static bool esp_mt_check(const struct xt_mtchk_param *par)
  70{
  71        const struct xt_esp *espinfo = par->matchinfo;
  72
  73        if (espinfo->invflags & ~XT_ESP_INV_MASK) {
  74                duprintf("xt_esp: unknown flags %X\n", espinfo->invflags);
  75                return false;
  76        }
  77
  78        return true;
  79}
  80
  81static struct xt_match esp_mt_reg[] __read_mostly = {
  82        {
  83                .name           = "esp",
  84                .family         = NFPROTO_IPV4,
  85                .checkentry     = esp_mt_check,
  86                .match          = esp_mt,
  87                .matchsize      = sizeof(struct xt_esp),
  88                .proto          = IPPROTO_ESP,
  89                .me             = THIS_MODULE,
  90        },
  91        {
  92                .name           = "esp",
  93                .family         = NFPROTO_IPV6,
  94                .checkentry     = esp_mt_check,
  95                .match          = esp_mt,
  96                .matchsize      = sizeof(struct xt_esp),
  97                .proto          = IPPROTO_ESP,
  98                .me             = THIS_MODULE,
  99        },
 100};
 101
 102static int __init esp_mt_init(void)
 103{
 104        return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
 105}
 106
 107static void __exit esp_mt_exit(void)
 108{
 109        xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
 110}
 111
 112module_init(esp_mt_init);
 113module_exit(esp_mt_exit);
 114