net/ipv4/netfilter/ipt_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/ip.h>
  13
  14 #include <linux/netfilter_ipv4/ipt_esp.h>
  15 #include <linux/netfilter_ipv4/ip_tables.h>
  16
  17 MODULE_LICENSE("GPL");
  18 MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
  19 MODULE_DESCRIPTION("iptables ESP SPI match module");
  20
  21 #ifdef DEBUG_CONNTRACK
  22 #define duprintf(format, args...) printk(format , ## args)
  23 #else
  24 #define duprintf(format, args...)
  25 #endif
  26
  27 /* Returns 1 if the spi is matched by the range, 0 otherwise */
  28 static inline int
  29 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert)
  30 {
  31         int r=0;
  32         duprintf("esp spi_match:%c 0x%x <= 0x%x <= 0x%x",invert? '!':' ',
  33                 min,spi,max);
  34         r=(spi >= min && spi <= max) ^ invert;
  35         duprintf(" result %s\n",r? "PASS" : "FAILED");
  36         return r;
  37 }
  38
  39 static int
  40 match(const struct sk_buff *skb,
  41       const struct net_device *in,
  42       const struct net_device *out,
  43       const struct xt_match *match,
  44       const void *matchinfo,
  45       int offset,
  46       unsigned int protoff,
  47       int *hotdrop)
  48 {
  49         struct ip_esp_hdr _esp, *eh;
  50         const struct ipt_esp *espinfo = matchinfo;
  51
  52         /* Must not be a fragment. */
  53         if (offset)
  54                 return 0;
  55
  56         eh = skb_header_pointer(skb, protoff,
  57                                 sizeof(_esp), &_esp);
  58         if (eh == NULL) {
  59                 /* We've been asked to examine this packet, and we
  60                  * can't.  Hence, no choice but to drop.
  61                  */
  62                 duprintf("Dropping evil ESP tinygram.\n");
  63                 *hotdrop = 1;
  64                 return 0;
  65         }
  66
  67         return spi_match(espinfo->spis[0], espinfo->spis[1],
  68                          ntohl(eh->spi),
  69                          !!(espinfo->invflags & IPT_ESP_INV_SPI));
  70 }
  71
  72 /* Called when user tries to insert an entry of this type. */
  73 static int
  74 checkentry(const char *tablename,
  75            const void *ip_void,
  76            const struct xt_match *match,
  77            void *matchinfo,
  78            unsigned int matchinfosize,
  79            unsigned int hook_mask)
  80 {
  81         const struct ipt_esp *espinfo = matchinfo;
  82
  83         /* Must specify no unknown invflags */
  84         if (espinfo->invflags & ~IPT_ESP_INV_MASK) {
  85                 duprintf("ipt_esp: unknown flags %X\n", espinfo->invflags);
  86                 return 0;
  87         }
  88         return 1;
  89 }
  90
  91 static struct ipt_match esp_match = {
  92         .name           = "esp",
  93         .match          = match,
  94         .matchsize      = sizeof(struct ipt_esp),
  95         .proto          = IPPROTO_ESP,
  96         .checkentry     = checkentry,
  97         .me             = THIS_MODULE,
  98 };
  99
 100 static int __init ipt_esp_init(void)
 101 {
 102         return ipt_register_match(&esp_match);
 103 }
 104
 105 static void __exit ipt_esp_fini(void)
 106 {
 107         ipt_unregister_match(&esp_match);
 108 }
 109
 110 module_init(ipt_esp_init);
 111 module_exit(ipt_esp_fini);