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/* Kernel module to match AH parameters. */
/* (C) 1999-2000 Yon Uriarte <yon@astaro.de>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/in.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/netfilter_ipv4/ipt_ah.h>
#include <linux/netfilter/x_tables.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
MODULE_DESCRIPTION("Xtables: IPv4 IPsec-AH SPI match");
/* Returns 1 if the spi is matched by the range, 0 otherwise */
static inline bool
spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
{
bool r;
pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
invert ? '!' : ' ', min, spi, max);
r = (spi >= min && spi <= max) ^ invert;
pr_debug(" result %s\n", r ? "PASS" : "FAILED");
return r;
}
static bool ah_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
struct ip_auth_hdr _ahdr;
const struct ip_auth_hdr *ah;
const struct ipt_ah *ahinfo = par->matchinfo;
/* Must not be a fragment. */
if (par->fragoff != 0)
return false;
ah = skb_header_pointer(skb, par->thoff, sizeof(_ahdr), &_ahdr);
if (ah == NULL) {
/* We've been asked to examine this packet, and we
* can't. Hence, no choice but to drop.
*/
pr_debug("Dropping evil AH tinygram.\n");
par->hotdrop = true;
return false;
}
return spi_match(ahinfo->spis[0], ahinfo->spis[1],
ntohl(ah->spi),
!!(ahinfo->invflags & IPT_AH_INV_SPI));
}
static int ah_mt_check(const struct xt_mtchk_param *par)
{
const struct ipt_ah *ahinfo = par->matchinfo;
/* Must specify no unknown invflags */
if (ahinfo->invflags & ~IPT_AH_INV_MASK) {
pr_debug("unknown flags %X\n", ahinfo->invflags);
return -EINVAL;
}
return 0;
}
static struct xt_match ah_mt_reg __read_mostly = {
.name = "ah",
.family = NFPROTO_IPV4,
.match = ah_mt,
.matchsize = sizeof(struct ipt_ah),
.proto = IPPROTO_AH,
.checkentry = ah_mt_check,
.me = THIS_MODULE,
};
static int __init ah_mt_init(void)
{
return xt_register_match(&ah_mt_reg);
}
static void __exit ah_mt_exit(void)
{
xt_unregister_match(&ah_mt_reg);
}
module_init(ah_mt_init);
module_exit(ah_mt_exit);
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