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
  46 esp_mt(const struct sk_buff *skb, const struct net_device *in,
  47        const struct net_device *out, const struct xt_match *match,
  48        const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop)
  49 {
  50         const struct ip_esp_hdr *eh;
  51         struct ip_esp_hdr _esp;
  52         const struct xt_esp *espinfo = matchinfo;
  53
  54         /* Must not be a fragment. */
  55         if (offset)
  56                 return false;
  57
  58         eh = skb_header_pointer(skb, protoff, sizeof(_esp), &_esp);
  59         if (eh == NULL) {
  60                 /* We've been asked to examine this packet, and we
  61                  * can't.  Hence, no choice but to drop.
  62                  */
  63                 duprintf("Dropping evil ESP tinygram.\n");
  64                 *hotdrop = true;
  65                 return false;
  66         }
  67
  68         return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi),
  69                          !!(espinfo->invflags & XT_ESP_INV_SPI));
  70 }
  71
  72 /* Called when user tries to insert an entry of this type. */
  73 static bool
  74 esp_mt_check(const char *tablename, const void *ip_void,
  75              const struct xt_match *match, void *matchinfo,
  76              unsigned int hook_mask)
  77 {
  78         const struct xt_esp *espinfo = matchinfo;
  79
  80         if (espinfo->invflags & ~XT_ESP_INV_MASK) {
  81                 duprintf("xt_esp: unknown flags %X\n", espinfo->invflags);
  82                 return false;
  83         }
  84
  85         return true;
  86 }
  87
  88 static struct xt_match esp_mt_reg[] __read_mostly = {
  89         {
  90                 .name           = "esp",
  91                 .family         = AF_INET,
  92                 .checkentry     = esp_mt_check,
  93                 .match          = esp_mt,
  94                 .matchsize      = sizeof(struct xt_esp),
  95                 .proto          = IPPROTO_ESP,
  96                 .me             = THIS_MODULE,
  97         },
  98         {
  99                 .name           = "esp",
 100                 .family         = AF_INET6,
 101                 .checkentry     = esp_mt_check,
 102                 .match          = esp_mt,
 103                 .matchsize      = sizeof(struct xt_esp),
 104                 .proto          = IPPROTO_ESP,
 105                 .me             = THIS_MODULE,
 106         },
 107 };
 108
 109 static int __init esp_mt_init(void)
 110 {
 111         return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
 112 }
 113
 114 static void __exit esp_mt_exit(void)
 115 {
 116         xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
 117 }
 118
 119 module_init(esp_mt_init);
 120 module_exit(esp_mt_exit);