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
  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 #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 */
  34 static inline bool
  35 spi_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
  45 static 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
  69 /* Called when user tries to insert an entry of this type. */
  70 static bool
  71 esp_mt_check(const char *tablename, const void *ip_void,
  72              const struct xt_match *match, void *matchinfo,
  73              unsigned int hook_mask)
  74 {
  75         const struct xt_esp *espinfo = matchinfo;
  76
  77         if (espinfo->invflags & ~XT_ESP_INV_MASK) {
  78                 duprintf("xt_esp: unknown flags %X\n", espinfo->invflags);
  79                 return false;
  80         }
  81
  82         return true;
  83 }
  84
  85 static struct xt_match esp_mt_reg[] __read_mostly = {
  86         {
  87                 .name           = "esp",
  88                 .family         = NFPROTO_IPV4,
  89                 .checkentry     = esp_mt_check,
  90                 .match          = esp_mt,
  91                 .matchsize      = sizeof(struct xt_esp),
  92                 .proto          = IPPROTO_ESP,
  93                 .me             = THIS_MODULE,
  94         },
  95         {
  96                 .name           = "esp",
  97                 .family         = NFPROTO_IPV6,
  98                 .checkentry     = esp_mt_check,
  99                 .match          = esp_mt,
 100                 .matchsize      = sizeof(struct xt_esp),
 101                 .proto          = IPPROTO_ESP,
 102                 .me             = THIS_MODULE,
 103         },
 104 };
 105
 106 static int __init esp_mt_init(void)
 107 {
 108         return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
 109 }
 110
 111 static void __exit esp_mt_exit(void)
 112 {
 113         xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
 114 }
 115
 116 module_init(esp_mt_init);
 117 module_exit(esp_mt_exit);