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("x_tables ESP SPI match module");
  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 int
  35 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert)
  36 {
  37         int r = 0;
  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 int
  46 match(const struct sk_buff *skb,
  47       const struct net_device *in,
  48       const struct net_device *out,
  49       const struct xt_match *match,
  50       const void *matchinfo,
  51       int offset,
  52       unsigned int protoff,
  53       int *hotdrop)
  54 {
  55         struct ip_esp_hdr _esp, *eh;
  56         const struct xt_esp *espinfo = matchinfo;
  57
  58         /* Must not be a fragment. */
  59         if (offset)
  60                 return 0;
  61
  62         eh = skb_header_pointer(skb, protoff, sizeof(_esp), &_esp);
  63         if (eh == NULL) {
  64                 /* We've been asked to examine this packet, and we
  65                  * can't.  Hence, no choice but to drop.
  66                  */
  67                 duprintf("Dropping evil ESP tinygram.\n");
  68                 *hotdrop = 1;
  69                 return 0;
  70         }
  71
  72         return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi),
  73                          !!(espinfo->invflags & XT_ESP_INV_SPI));
  74 }
  75
  76 /* Called when user tries to insert an entry of this type. */
  77 static int
  78 checkentry(const char *tablename,
  79            const void *ip_void,
  80            const struct xt_match *match,
  81            void *matchinfo,
  82            unsigned int hook_mask)
  83 {
  84         const struct xt_esp *espinfo = matchinfo;
  85
  86         if (espinfo->invflags & ~XT_ESP_INV_MASK) {
  87                 duprintf("xt_esp: unknown flags %X\n", espinfo->invflags);
  88                 return 0;
  89         }
  90
  91         return 1;
  92 }
  93
  94 static struct xt_match xt_esp_match[] = {
  95         {
  96                 .name           = "esp",
  97                 .family         = AF_INET,
  98                 .checkentry     = checkentry,
  99                 .match          = match,
 100                 .matchsize      = sizeof(struct xt_esp),
 101                 .proto          = IPPROTO_ESP,
 102                 .me             = THIS_MODULE,
 103         },
 104         {
 105                 .name           = "esp",
 106                 .family         = AF_INET6,
 107                 .checkentry     = checkentry,
 108                 .match          = match,
 109                 .matchsize      = sizeof(struct xt_esp),
 110                 .proto          = IPPROTO_ESP,
 111                 .me             = THIS_MODULE,
 112         },
 113 };
 114
 115 static int __init xt_esp_init(void)
 116 {
 117         return xt_register_matches(xt_esp_match, ARRAY_SIZE(xt_esp_match));
 118 }
 119
 120 static void __exit xt_esp_cleanup(void)
 121 {
 122         xt_unregister_matches(xt_esp_match, ARRAY_SIZE(xt_esp_match));
 123 }
 124
 125 module_init(xt_esp_init);
 126 module_exit(xt_esp_cleanup);