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 void *matchinfo,
  44       int offset,
  45       int *hotdrop)
  46 {
  47         struct ip_esp_hdr _esp, *eh;
  48         const struct ipt_esp *espinfo = matchinfo;
  49
  50         /* Must not be a fragment. */
  51         if (offset)
  52                 return 0;
  53
  54         eh = skb_header_pointer(skb, skb->nh.iph->ihl * 4,
  55                                 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                 *hotdrop = 1;
  62                 return 0;
  63         }
  64
  65         return spi_match(espinfo->spis[0], espinfo->spis[1],
  66                          ntohl(eh->spi),
  67                          !!(espinfo->invflags & IPT_ESP_INV_SPI));
  68 }
  69
  70 /* Called when user tries to insert an entry of this type. */
  71 static int
  72 checkentry(const char *tablename,
  73            const struct ipt_ip *ip,
  74            void *matchinfo,
  75            unsigned int matchinfosize,
  76            unsigned int hook_mask)
  77 {
  78         const struct ipt_esp *espinfo = matchinfo;
  79
  80         /* Must specify proto == ESP, and no unknown invflags */
  81         if (ip->proto != IPPROTO_ESP || (ip->invflags & IPT_INV_PROTO)) {
  82                 duprintf("ipt_esp: Protocol %u != %u\n", ip->proto,
  83                          IPPROTO_ESP);
  84                 return 0;
  85         }
  86         if (matchinfosize != IPT_ALIGN(sizeof(struct ipt_esp))) {
  87                 duprintf("ipt_esp: matchsize %u != %u\n",
  88                          matchinfosize, IPT_ALIGN(sizeof(struct ipt_esp)));
  89                 return 0;
  90         }
  91         if (espinfo->invflags & ~IPT_ESP_INV_MASK) {
  92                 duprintf("ipt_esp: unknown flags %X\n",
  93                          espinfo->invflags);
  94                 return 0;
  95         }
  96
  97         return 1;
  98 }
  99
 100 static struct ipt_match esp_match = {
 101         .name           = "esp",
 102         .match          = &match,
 103         .checkentry     = &checkentry,
 104         .me             = THIS_MODULE,
 105 };
 106
 107 static int __init init(void)
 108 {
 109         return ipt_register_match(&esp_match);
 110 }
 111
 112 static void __exit cleanup(void)
 113 {
 114         ipt_unregister_match(&esp_match);
 115 }
 116
 117 module_init(init);
 118 module_exit(cleanup);