ip6t_ah.c revision 9b4fce7a3508a9776534188b6065b206a9608ccf 
1/* Kernel module to match AH parameters. */
2
3/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 */
9
10#include <linux/module.h>
11#include <linux/skbuff.h>
12#include <linux/ip.h>
13#include <linux/ipv6.h>
14#include <linux/types.h>
15#include <net/checksum.h>
16#include <net/ipv6.h>
17
18#include <linux/netfilter/x_tables.h>
19#include <linux/netfilter_ipv6/ip6_tables.h>
20#include <linux/netfilter_ipv6/ip6t_ah.h>
21
22MODULE_LICENSE("GPL");
23MODULE_DESCRIPTION("Xtables: IPv6 IPsec-AH match");
24MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
25
26/* Returns 1 if the spi is matched by the range, 0 otherwise */
27static inline bool
28spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
29{
30	bool r;
31
32	pr_debug("ah spi_match:%c 0x%x <= 0x%x <= 0x%x",
33		 invert ? '!' : ' ', min, spi, max);
34	r = (spi >= min && spi <= max) ^ invert;
35	pr_debug(" result %s\n", r ? "PASS" : "FAILED");
36	return r;
37}
38
39static bool ah_mt6(const struct sk_buff *skb, const struct xt_match_param *par)
40{
41	struct ip_auth_hdr _ah;
42	const struct ip_auth_hdr *ah;
43	const struct ip6t_ah *ahinfo = par->matchinfo;
44	unsigned int ptr;
45	unsigned int hdrlen = 0;
46	int err;
47
48	err = ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL);
49	if (err < 0) {
50		if (err != -ENOENT)
51			*par->hotdrop = true;
52		return false;
53	}
54
55	ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah);
56	if (ah == NULL) {
57		*par->hotdrop = true;
58		return false;
59	}
60
61	hdrlen = (ah->hdrlen + 2) << 2;
62
63	pr_debug("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen);
64	pr_debug("RES %04X ", ah->reserved);
65	pr_debug("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi));
66
67	pr_debug("IPv6 AH spi %02X ",
68		 spi_match(ahinfo->spis[0], ahinfo->spis[1],
69			   ntohl(ah->spi),
70			   !!(ahinfo->invflags & IP6T_AH_INV_SPI)));
71	pr_debug("len %02X %04X %02X ",
72		 ahinfo->hdrlen, hdrlen,
73		 (!ahinfo->hdrlen ||
74		  (ahinfo->hdrlen == hdrlen) ^
75		  !!(ahinfo->invflags & IP6T_AH_INV_LEN)));
76	pr_debug("res %02X %04X %02X\n",
77		 ahinfo->hdrres, ah->reserved,
78		 !(ahinfo->hdrres && ah->reserved));
79
80	return (ah != NULL)
81	       &&
82	       spi_match(ahinfo->spis[0], ahinfo->spis[1],
83			 ntohl(ah->spi),
84			 !!(ahinfo->invflags & IP6T_AH_INV_SPI))
85	       &&
86	       (!ahinfo->hdrlen ||
87		(ahinfo->hdrlen == hdrlen) ^
88		!!(ahinfo->invflags & IP6T_AH_INV_LEN))
89	       &&
90	       !(ahinfo->hdrres && ah->reserved);
91}
92
93static bool ah_mt6_check(const struct xt_mtchk_param *par)
94{
95	const struct ip6t_ah *ahinfo = par->matchinfo;
96
97	if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
98		pr_debug("ip6t_ah: unknown flags %X\n", ahinfo->invflags);
99		return false;
100	}
101	return true;
102}
103
104static struct xt_match ah_mt6_reg __read_mostly = {
105	.name		= "ah",
106	.family		= NFPROTO_IPV6,
107	.match		= ah_mt6,
108	.matchsize	= sizeof(struct ip6t_ah),
109	.checkentry	= ah_mt6_check,
110	.me		= THIS_MODULE,
111};
112
113static int __init ah_mt6_init(void)
114{
115	return xt_register_match(&ah_mt6_reg);
116}
117
118static void __exit ah_mt6_exit(void)
119{
120	xt_unregister_match(&ah_mt6_reg);
121}
122
123module_init(ah_mt6_init);
124module_exit(ah_mt6_exit);
125