LXR linux/net/ipv4/netfilter/ipt

   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/in.h>
  10#include <linux/module.h>
  11#include <linux/skbuff.h>
  12#include <linux/ip.h>
  13
  14#include <linux/netfilter_ipv4/ipt_ah.h>
  15#include <linux/netfilter/x_tables.h>
  16
  17MODULE_LICENSE("GPL");
  18MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
  19MODULE_DESCRIPTION("Xtables: IPv4 IPsec-AH SPI match");
  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 */
  28static inline bool
  29spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
  30{
  31        bool r;
  32        duprintf("ah 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
  39static bool ah_mt(const struct sk_buff *skb, const struct xt_match_param *par)
  40{
  41        struct ip_auth_hdr _ahdr;
  42        const struct ip_auth_hdr *ah;
  43        const struct ipt_ah *ahinfo = par->matchinfo;
  44
  45        /* Must not be a fragment. */
  46        if (par->fragoff != 0)
  47                return false;
  48
  49        ah = skb_header_pointer(skb, par->thoff, sizeof(_ahdr), &_ahdr);
  50        if (ah == NULL) {
  51                /* We've been asked to examine this packet, and we
  52                 * can't.  Hence, no choice but to drop.
  53                 */
  54                duprintf("Dropping evil AH tinygram.\n");
  55                *par->hotdrop = true;
  56                return 0;
  57        }
  58
  59        return spi_match(ahinfo->spis[0], ahinfo->spis[1],
  60                         ntohl(ah->spi),
  61                         !!(ahinfo->invflags & IPT_AH_INV_SPI));
  62}
  63
  64static bool ah_mt_check(const struct xt_mtchk_param *par)
  65{
  66        const struct ipt_ah *ahinfo = par->matchinfo;
  67
  68        /* Must specify no unknown invflags */
  69        if (ahinfo->invflags & ~IPT_AH_INV_MASK) {
  70                duprintf("ipt_ah: unknown flags %X\n", ahinfo->invflags);
  71                return false;
  72        }
  73        return true;
  74}
  75
  76static struct xt_match ah_mt_reg __read_mostly = {
  77        .name           = "ah",
  78        .family         = NFPROTO_IPV4,
  79        .match          = ah_mt,
  80        .matchsize      = sizeof(struct ipt_ah),
  81        .proto          = IPPROTO_AH,
  82        .checkentry     = ah_mt_check,
  83        .me             = THIS_MODULE,
  84};
  85
  86static int __init ah_mt_init(void)
  87{
  88        return xt_register_match(&ah_mt_reg);
  89}
  90
  91static void __exit ah_mt_exit(void)
  92{
  93        xt_unregister_match(&ah_mt_reg);
  94}
  95
  96module_init(ah_mt_init);
  97module_exit(ah_mt_exit);
  98