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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("Xtables: IPsec-ESP packet match");
24MODULE_ALIAS("ipt_esp");
25MODULE_ALIAS("ip6t_esp");
26
27#if 0
28#define duprintf(format, args...) printk(format , ## args)
29#else
30#define duprintf(format, args...)
31#endif
32
33/* Returns 1 if the spi is matched by the range, 0 otherwise */
34static inline bool
35spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
36{
37 bool r;
38 duprintf("esp spi_match:%c 0x%x <= 0x%x <= 0x%x", invert ? '!' : ' ',
39 min, spi, max);
40 r = (spi >= min && spi <= max) ^ invert;
41 duprintf(" result %s\n", r ? "PASS" : "FAILED");
42 return r;
43}
44
45static bool
46esp_mt(const struct sk_buff *skb, const struct net_device *in,
47 const struct net_device *out, const struct xt_match *match,
48 const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop)
49{
50 const struct ip_esp_hdr *eh;
51 struct ip_esp_hdr _esp;
52 const struct xt_esp *espinfo = matchinfo;
53
54 /* Must not be a fragment. */
55 if (offset)
56 return false;
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 = true;
65 return false;
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 bool
74esp_mt_check(const char *tablename, const void *ip_void,
75 const struct xt_match *match, void *matchinfo,
76 unsigned int hook_mask)
77{
78 const struct xt_esp *espinfo = matchinfo;
79
80 if (espinfo->invflags & ~XT_ESP_INV_MASK) {
81 duprintf("xt_esp: unknown flags %X\n", espinfo->invflags);
82 return false;
83 }
84
85 return true;
86}
87
88static struct xt_match esp_mt_reg[] __read_mostly = {
89 {
90 .name = "esp",
91 .family = AF_INET,
92 .checkentry = esp_mt_check,
93 .match = esp_mt,
94 .matchsize = sizeof(struct xt_esp),
95 .proto = IPPROTO_ESP,
96 .me = THIS_MODULE,
97 },
98 {
99 .name = "esp",
100 .family = AF_INET6,
101 .checkentry = esp_mt_check,
102 .match = esp_mt,
103 .matchsize = sizeof(struct xt_esp),
104 .proto = IPPROTO_ESP,
105 .me = THIS_MODULE,
106 },
107};
108
109static int __init esp_mt_init(void)
110{
111 return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
112}
113
114static void __exit esp_mt_exit(void)
115{
116 xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
117}
118
119module_init(esp_mt_init);
120module_exit(esp_mt_exit);