ip6t_ah.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/* Kernel module to match AH parameters. */
  3
  4/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
  5 */
  6#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  7#include <linux/module.h>
  8#include <linux/skbuff.h>
  9#include <linux/ip.h>
 10#include <linux/ipv6.h>
 11#include <linux/types.h>
 12#include <net/checksum.h>
 13#include <net/ipv6.h>
 14
 15#include <linux/netfilter/x_tables.h>
 16#include <linux/netfilter_ipv6/ip6_tables.h>
 17#include <linux/netfilter_ipv6/ip6t_ah.h>
 18
 19MODULE_LICENSE("GPL");
 20MODULE_DESCRIPTION("Xtables: IPv6 IPsec-AH match");
 21MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
 22
 23/* Returns 1 if the spi is matched by the range, 0 otherwise */
 24static inline bool
 25spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
 26{
 27	bool r;
 28
 29	pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
 30		 invert ? '!' : ' ', min, spi, max);
 31	r = (spi >= min && spi <= max) ^ invert;
 32	pr_debug(" result %s\n", r ? "PASS" : "FAILED");
 33	return r;
 34}
 35
 36static bool ah_mt6(const struct sk_buff *skb, struct xt_action_param *par)
 37{
 38	struct ip_auth_hdr _ah;
 39	const struct ip_auth_hdr *ah;
 40	const struct ip6t_ah *ahinfo = par->matchinfo;
 41	unsigned int ptr = 0;
 42	unsigned int hdrlen = 0;
 43	int err;
 44
 45	err = ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL, NULL);
 46	if (err < 0) {
 47		if (err != -ENOENT)
 48			par->hotdrop = true;
 49		return false;
 50	}
 51
 52	ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah);
 53	if (ah == NULL) {
 54		par->hotdrop = true;
 55		return false;
 56	}
 57
 58	hdrlen = ipv6_authlen(ah);
 59
 60	pr_debug("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen);
 61	pr_debug("RES %04X ", ah->reserved);
 62	pr_debug("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi));
 63
 64	pr_debug("IPv6 AH spi %02X ",
 65		 spi_match(ahinfo->spis[0], ahinfo->spis[1],
 66			   ntohl(ah->spi),
 67			   !!(ahinfo->invflags & IP6T_AH_INV_SPI)));
 68	pr_debug("len %02X %04X %02X ",
 69		 ahinfo->hdrlen, hdrlen,
 70		 (!ahinfo->hdrlen ||
 71		  (ahinfo->hdrlen == hdrlen) ^
 72		  !!(ahinfo->invflags & IP6T_AH_INV_LEN)));
 73	pr_debug("res %02X %04X %02X\n",
 74		 ahinfo->hdrres, ah->reserved,
 75		 !(ahinfo->hdrres && ah->reserved));
 76
 77	return spi_match(ahinfo->spis[0], ahinfo->spis[1],
 78			  ntohl(ah->spi),
 79			  !!(ahinfo->invflags & IP6T_AH_INV_SPI)) &&
 80		(!ahinfo->hdrlen ||
 81		 (ahinfo->hdrlen == hdrlen) ^
 82		 !!(ahinfo->invflags & IP6T_AH_INV_LEN)) &&
 83		!(ahinfo->hdrres && ah->reserved);
 84}
 85
 86static int ah_mt6_check(const struct xt_mtchk_param *par)
 87{
 88	const struct ip6t_ah *ahinfo = par->matchinfo;
 89
 90	if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
 91		pr_debug("unknown flags %X\n", ahinfo->invflags);
 92		return -EINVAL;
 93	}
 94	return 0;
 95}
 96
 97static struct xt_match ah_mt6_reg __read_mostly = {
 98	.name		= "ah",
 99	.family		= NFPROTO_IPV6,
100	.match		= ah_mt6,
101	.matchsize	= sizeof(struct ip6t_ah),
102	.checkentry	= ah_mt6_check,
103	.me		= THIS_MODULE,
104};
105
106static int __init ah_mt6_init(void)
107{
108	return xt_register_match(&ah_mt6_reg);
109}
110
111static void __exit ah_mt6_exit(void)
112{
113	xt_unregister_match(&ah_mt6_reg);
114}
115
116module_init(ah_mt6_init);
117module_exit(ah_mt6_exit);