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
21 MODULE_LICENSE("GPL");
22 MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
23 MODULE_DESCRIPTION("Xtables: IPsec-ESP packet match");
24 MODULE_ALIAS("ipt_esp");
25 MODULE_ALIAS("ip6t_esp");
26
27 /* Returns 1 if the spi is matched by the range, 0 otherwise */
28 static inline bool
spi_match(u_int32_t min,u_int32_t max,u_int32_t spi,bool invert)29 spi_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
esp_mt(const struct sk_buff * skb,struct xt_action_param * par)39 static 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
esp_mt_check(const struct xt_mtchk_param * par)63 static 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
75 static 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
esp_mt_init(void)96 static int __init esp_mt_init(void)
97 {
98 return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
99 }
100
esp_mt_exit(void)101 static void __exit esp_mt_exit(void)
102 {
103 xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
104 }
105
106 module_init(esp_mt_init);
107 module_exit(esp_mt_exit);
108