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 void *matchinfo,
  43       int offset,
  44       int *hotdrop)
  45 {
  46         struct ip_auth_hdr _ahdr, *ah;
  47         const struct ipt_ah *ahinfo = matchinfo;
  48
  49         /* Must not be a fragment. */
  50         if (offset)
  51                 return 0;
  52
  53         ah = skb_header_pointer(skb, skb->nh.iph->ihl * 4,
  54                                 sizeof(_ahdr), &_ahdr);
  55         if (ah == NULL) {
  56                 /* We've been asked to examine this packet, and we
  57                  * can't.  Hence, no choice but to drop.
  58                  */
  59                 duprintf("Dropping evil AH tinygram.\n");
  60                 *hotdrop = 1;
  61                 return 0;
  62         }
  63
  64         return spi_match(ahinfo->spis[0], ahinfo->spis[1],
  65                          ntohl(ah->spi),
  66                          !!(ahinfo->invflags & IPT_AH_INV_SPI));
  67 }
  68
  69 /* Called when user tries to insert an entry of this type. */
  70 static int
  71 checkentry(const char *tablename,
  72            const struct ipt_ip *ip,
  73            void *matchinfo,
  74            unsigned int matchinfosize,
  75            unsigned int hook_mask)
  76 {
  77         const struct ipt_ah *ahinfo = matchinfo;
  78
  79         /* Must specify proto == AH, and no unknown invflags */
  80         if (ip->proto != IPPROTO_AH || (ip->invflags & IPT_INV_PROTO)) {
  81                 duprintf("ipt_ah: Protocol %u != %u\n", ip->proto,
  82                          IPPROTO_AH);
  83                 return 0;
  84         }
  85         if (matchinfosize != IPT_ALIGN(sizeof(struct ipt_ah))) {
  86                 duprintf("ipt_ah: matchsize %u != %u\n",
  87                          matchinfosize, IPT_ALIGN(sizeof(struct ipt_ah)));
  88                 return 0;
  89         }
  90         if (ahinfo->invflags & ~IPT_AH_INV_MASK) {
  91                 duprintf("ipt_ah: unknown flags %X\n",
  92                          ahinfo->invflags);
  93                 return 0;
  94         }
  95
  96         return 1;
  97 }
  98
  99 static struct ipt_match ah_match = {
 100         .name           = "ah",
 101         .match          = &match,
 102         .checkentry     = &checkentry,
 103         .me             = THIS_MODULE,
 104 };
 105
 106 static int __init init(void)
 107 {
 108         return ipt_register_match(&ah_match);
 109 }
 110
 111 static void __exit cleanup(void)
 112 {
 113         ipt_unregister_match(&ah_match);
 114 }
 115
 116 module_init(init);
 117 module_exit(cleanup);