net/netfilter/xt_esp.c

   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
  21 MODULE_LICENSE("GPL");
  22 MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
  23 MODULE_DESCRIPTION("Xtables: IPsec-ESP packet match");
  24 MODULE_ALIAS("ipt_esp");
  25 MODULE_ALIAS("ip6t_esp");
  26
  27 /* Returns 1 if the spi is matched by the range, 0 otherwise */
  28 static inline bool
  29 spi_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
  39 static 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
  63 static 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
  75 static 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
  96 static int __init esp_mt_init(void)
  97 {
  98         return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
  99 }
 100
 101 static void __exit esp_mt_exit(void)
 102 {
 103         xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
 104 }
 105
 106 module_init(esp_mt_init);
 107 module_exit(esp_mt_exit);