1/* Kernel module to match ESP parameters. */
2
3/* (C) 1999-2000 Yon Uriarte <yon@astaro.de>
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10#include <linux/module.h>
11#include <linux/skbuff.h>
12#include <linux/in.h>
13#include <linux/ip.h>
14
15#include <linux/netfilter/xt_esp.h>
16#include <linux/netfilter/x_tables.h>
17
18#include <linux/netfilter_ipv4/ip_tables.h>
19#include <linux/netfilter_ipv6/ip6_tables.h>
20
21MODULE_LICENSE("GPL");
22MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
23MODULE_DESCRIPTION("Xtables: IPsec-ESP packet match");
24MODULE_ALIAS("ipt_esp");
25MODULE_ALIAS("ip6t_esp");
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	pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
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 esp_mt(const struct sk_buff *skb, struct xt_action_param *par)
40{
41	const struct ip_esp_hdr *eh;
42	struct ip_esp_hdr _esp;
43	const struct xt_esp *espinfo = par->matchinfo;
44
45	/* Must not be a fragment. */
46	if (par->fragoff != 0)
47		return false;
48
49	eh = skb_header_pointer(skb, par->thoff, sizeof(_esp), &_esp);
50	if (eh == NULL) {
51		/* We've been asked to examine this packet, and we
52		 * can't.  Hence, no choice but to drop.
53		 */
54		pr_debug("Dropping evil ESP tinygram.\n");
55		par->hotdrop = true;
56		return false;
57	}
58
59	return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi),
60			 !!(espinfo->invflags & XT_ESP_INV_SPI));
61}
62
63static int esp_mt_check(const struct xt_mtchk_param *par)
64{
65	const struct xt_esp *espinfo = par->matchinfo;
66
67	if (espinfo->invflags & ~XT_ESP_INV_MASK) {
68		pr_debug("unknown flags %X\n", espinfo->invflags);
69		return -EINVAL;
70	}
71
72	return 0;
73}
74
75static struct xt_match esp_mt_reg[] __read_mostly = {
76	{
77		.name		= "esp",
78		.family		= NFPROTO_IPV4,
79		.checkentry	= esp_mt_check,
80		.match		= esp_mt,
81		.matchsize	= sizeof(struct xt_esp),
82		.proto		= IPPROTO_ESP,
83		.me		= THIS_MODULE,
84	},
85	{
86		.name		= "esp",
87		.family		= NFPROTO_IPV6,
88		.checkentry	= esp_mt_check,
89		.match		= esp_mt,
90		.matchsize	= sizeof(struct xt_esp),
91		.proto		= IPPROTO_ESP,
92		.me		= THIS_MODULE,
93	},
94};
95
96static int __init esp_mt_init(void)
97{
98	return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
99}
100
101static void __exit esp_mt_exit(void)
102{
103	xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
104}
105
106module_init(esp_mt_init);
107module_exit(esp_mt_exit);
108