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
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("x_tables ESP SPI match module");
24MODULE_ALIAS("ipt_esp");
25MODULE_ALIAS("ip6t_esp");
26
27#define duprintf(format, args...)
28
29/* Returns 1 if the spi is matched by the range, 0 otherwise */
30static inline int
31spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert)
32{
33	int r = 0;
34	duprintf("esp spi_match:%c 0x%x <= 0x%x <= 0x%x", invert ? '!' : ' ',
35		 min, spi, max);
36	r = (spi >= min && spi <= max) ^ invert;
37	duprintf(" result %s\n", r ? "PASS" : "FAILED");
38	return r;
39}
40
41static int
42match(const struct sk_buff *skb,
43      const struct net_device *in,
44      const struct net_device *out,
45      const struct xt_match *match,
46      const void *matchinfo,
47      int offset,
48      unsigned int protoff,
49      int *hotdrop)
50{
51	struct ip_esp_hdr _esp, *eh;
52	const struct xt_esp *espinfo = matchinfo;
53
54	/* Must not be a fragment. */
55	if (offset)
56		return 0;
57
58	eh = skb_header_pointer(skb, protoff, sizeof(_esp), &_esp);
59	if (eh == NULL) {
60		/* We've been asked to examine this packet, and we
61		 * can't.  Hence, no choice but to drop.
62		 */
63		duprintf("Dropping evil ESP tinygram.\n");
64		*hotdrop = 1;
65		return 0;
66	}
67
68	return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi),
69			 !!(espinfo->invflags & XT_ESP_INV_SPI));
70}
71
72/* Called when user tries to insert an entry of this type. */
73static int
74checkentry(const char *tablename,
75	   const void *ip_void,
76	   const struct xt_match *match,
77	   void *matchinfo,
78	   unsigned int hook_mask)
79{
80	const struct xt_esp *espinfo = matchinfo;
81
82	if (espinfo->invflags & ~XT_ESP_INV_MASK) {
83		duprintf("xt_esp: unknown flags %X\n", espinfo->invflags);
84		return 0;
85	}
86
87	return 1;
88}
89
90static struct xt_match xt_esp_match[] = {
91	{
92		.name		= "esp",
93		.family		= AF_INET,
94		.checkentry	= checkentry,
95		.match		= match,
96		.matchsize	= sizeof(struct xt_esp),
97		.proto		= IPPROTO_ESP,
98		.me		= THIS_MODULE,
99	},
100	{
101		.name		= "esp",
102		.family		= AF_INET6,
103		.checkentry	= checkentry,
104		.match		= match,
105		.matchsize	= sizeof(struct xt_esp),
106		.proto		= IPPROTO_ESP,
107		.me		= THIS_MODULE,
108	},
109};
110
111static int __init xt_esp_init(void)
112{
113	return xt_register_matches(xt_esp_match, ARRAY_SIZE(xt_esp_match));
114}
115
116static void __exit xt_esp_cleanup(void)
117{
118	xt_unregister_matches(xt_esp_match, ARRAY_SIZE(xt_esp_match));
119}
120
121module_init(xt_esp_init);
122module_exit(xt_esp_cleanup);
123