net/ipv4/netfilter/ipt_ah.c

   1 /* Kernel module to match AH parameters. */
   2 /* (C) 1999-2000 Yon Uriarte <yon@astaro.de>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/skbuff.h>
  11 #include <linux/ip.h>
  12
  13 #include <linux/netfilter_ipv4/ipt_ah.h>
  14 #include <linux/netfilter_ipv4/ip_tables.h>
  15
  16 MODULE_LICENSE("GPL");
  17 MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
  18 MODULE_DESCRIPTION("iptables AH SPI match module");
  19
  20 #ifdef DEBUG_CONNTRACK
  21 #define duprintf(format, args...) printk(format , ## args)
  22 #else
  23 #define duprintf(format, args...)
  24 #endif
  25
  26 /* Returns 1 if the spi is matched by the range, 0 otherwise */
  27 static inline int
  28 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert)
  29 {
  30         int r=0;
  31         duprintf("ah spi_match:%c 0x%x <= 0x%x <= 0x%x",invert? '!':' ',
  32                 min,spi,max);
  33         r=(spi >= min && spi <= max) ^ invert;
  34         duprintf(" result %s\n",r? "PASS" : "FAILED");
  35         return r;
  36 }
  37
  38 static int
  39 match(const struct sk_buff *skb,
  40       const struct net_device *in,
  41       const struct net_device *out,
  42       const struct xt_match *match,
  43       const void *matchinfo,
  44       int offset,
  45       unsigned int protoff,
  46       int *hotdrop)
  47 {
  48         struct ip_auth_hdr _ahdr, *ah;
  49         const struct ipt_ah *ahinfo = matchinfo;
  50
  51         /* Must not be a fragment. */
  52         if (offset)
  53                 return 0;
  54
  55         ah = skb_header_pointer(skb, protoff,
  56                                 sizeof(_ahdr), &_ahdr);
  57         if (ah == NULL) {
  58                 /* We've been asked to examine this packet, and we
  59                  * can't.  Hence, no choice but to drop.
  60                  */
  61                 duprintf("Dropping evil AH tinygram.\n");
  62                 *hotdrop = 1;
  63                 return 0;
  64         }
  65
  66         return spi_match(ahinfo->spis[0], ahinfo->spis[1],
  67                          ntohl(ah->spi),
  68                          !!(ahinfo->invflags & IPT_AH_INV_SPI));
  69 }
  70
  71 /* Called when user tries to insert an entry of this type. */
  72 static int
  73 checkentry(const char *tablename,
  74            const void *ip_void,
  75            const struct xt_match *match,
  76            void *matchinfo,
  77            unsigned int hook_mask)
  78 {
  79         const struct ipt_ah *ahinfo = matchinfo;
  80
  81         /* Must specify no unknown invflags */
  82         if (ahinfo->invflags & ~IPT_AH_INV_MASK) {
  83                 duprintf("ipt_ah: unknown flags %X\n", ahinfo->invflags);
  84                 return 0;
  85         }
  86         return 1;
  87 }
  88
  89 static struct ipt_match ah_match = {
  90         .name           = "ah",
  91         .match          = match,
  92         .matchsize      = sizeof(struct ipt_ah),
  93         .proto          = IPPROTO_AH,
  94         .checkentry     = checkentry,
  95         .me             = THIS_MODULE,
  96 };
  97
  98 static int __init ipt_ah_init(void)
  99 {
 100         return ipt_register_match(&ah_match);
 101 }
 102
 103 static void __exit ipt_ah_fini(void)
 104 {
 105         ipt_unregister_match(&ah_match);
 106 }
 107
 108 module_init(ipt_ah_init);
 109 module_exit(ipt_ah_fini);