linux/net/netfilter/xt_esp.c
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   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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  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/* Returns 1 if the spi is matched by the range, 0 otherwise */
  28static inline bool
  29spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
  30{
  31        bool r;
  32        pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
  33                 invert ? '!' : ' ', min, spi, max);
  34        r = (spi >= min && spi <= max) ^ invert;
  35        pr_debug(" result %s\n", r ? "PASS" : "FAILED");
  36        return r;
  37}
  38
  39static bool esp_mt(const struct sk_buff *skb, struct xt_action_param *par)
  40{
  41        const struct ip_esp_hdr *eh;
  42        struct ip_esp_hdr _esp;
  43        const struct xt_esp *espinfo = par->matchinfo;
  44
  45        /* Must not be a fragment. */
  46        if (par->fragoff != 0)
  47                return false;
  48
  49        eh = skb_header_pointer(skb, par->thoff, sizeof(_esp), &_esp);
  50        if (eh == NULL) {
  51                /* We've been asked to examine this packet, and we
  52                 * can't.  Hence, no choice but to drop.
  53                 */
  54                pr_debug("Dropping evil ESP tinygram.\n");
  55                par->hotdrop = true;
  56                return false;
  57        }
  58
  59        return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi),
  60                         !!(espinfo->invflags & XT_ESP_INV_SPI));
  61}
  62
  63static int esp_mt_check(const struct xt_mtchk_param *par)
  64{
  65        const struct xt_esp *espinfo = par->matchinfo;
  66
  67        if (espinfo->invflags & ~XT_ESP_INV_MASK) {
  68                pr_debug("unknown flags %X\n", espinfo->invflags);
  69                return -EINVAL;
  70        }
  71
  72        return 0;
  73}
  74
  75static struct xt_match esp_mt_reg[] __read_mostly = {
  76        {
  77                .name           = "esp",
  78                .family         = NFPROTO_IPV4,
  79                .checkentry     = esp_mt_check,
  80                .match          = esp_mt,
  81                .matchsize      = sizeof(struct xt_esp),
  82                .proto          = IPPROTO_ESP,
  83                .me             = THIS_MODULE,
  84        },
  85        {
  86                .name           = "esp",
  87                .family         = NFPROTO_IPV6,
  88                .checkentry     = esp_mt_check,
  89                .match          = esp_mt,
  90                .matchsize      = sizeof(struct xt_esp),
  91                .proto          = IPPROTO_ESP,
  92                .me             = THIS_MODULE,
  93        },
  94};
  95
  96static int __init esp_mt_init(void)
  97{
  98        return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
  99}
 100
 101static void __exit esp_mt_exit(void)
 102{
 103        xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
 104}
 105
 106module_init(esp_mt_init);
 107module_exit(esp_mt_exit);
 108
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