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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   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/* Returns 1 if the spi is matched by the range, 0 otherwise */
  22static inline bool
  23spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
  24{
  25        bool r;
  26        pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
  27                 invert ? '!' : ' ', min, spi, max);
  28        r = (spi >= min && spi <= max) ^ invert;
  29        pr_debug(" result %s\n", r ? "PASS" : "FAILED");
  30        return r;
  31}
  32
  33static bool ah_mt(const struct sk_buff *skb, struct xt_action_param *par)
  34{
  35        struct ip_auth_hdr _ahdr;
  36        const struct ip_auth_hdr *ah;
  37        const struct ipt_ah *ahinfo = par->matchinfo;
  38
  39        /* Must not be a fragment. */
  40        if (par->fragoff != 0)
  41                return false;
  42
  43        ah = skb_header_pointer(skb, par->thoff, sizeof(_ahdr), &_ahdr);
  44        if (ah == NULL) {
  45                /* We've been asked to examine this packet, and we
  46                 * can't.  Hence, no choice but to drop.
  47                 */
  48                pr_debug("Dropping evil AH tinygram.\n");
  49                par->hotdrop = true;
  50                return false;
  51        }
  52
  53        return spi_match(ahinfo->spis[0], ahinfo->spis[1],
  54                         ntohl(ah->spi),
  55                         !!(ahinfo->invflags & IPT_AH_INV_SPI));
  56}
  57
  58static int ah_mt_check(const struct xt_mtchk_param *par)
  59{
  60        const struct ipt_ah *ahinfo = par->matchinfo;
  61
  62        /* Must specify no unknown invflags */
  63        if (ahinfo->invflags & ~IPT_AH_INV_MASK) {
  64                pr_debug("unknown flags %X\n", ahinfo->invflags);
  65                return -EINVAL;
  66        }
  67        return 0;
  68}
  69
  70static struct xt_match ah_mt_reg __read_mostly = {
  71        .name           = "ah",
  72        .family         = NFPROTO_IPV4,
  73        .match          = ah_mt,
  74        .matchsize      = sizeof(struct ipt_ah),
  75        .proto          = IPPROTO_AH,
  76        .checkentry     = ah_mt_check,
  77        .me             = THIS_MODULE,
  78};
  79
  80static int __init ah_mt_init(void)
  81{
  82        return xt_register_match(&ah_mt_reg);
  83}
  84
  85static void __exit ah_mt_exit(void)
  86{
  87        xt_unregister_match(&ah_mt_reg);
  88}
  89
  90module_init(ah_mt_init);
  91module_exit(ah_mt_exit);
  92