1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Kernel module to match ESP parameters. */
3 
4 /* (C) 1999-2000 Yon Uriarte <yon@astaro.de>
5  */
6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7 #include <linux/module.h>
8 #include <linux/skbuff.h>
9 #include <linux/in.h>
10 #include <linux/ip.h>
11 
12 #include <linux/netfilter/xt_esp.h>
13 #include <linux/netfilter/x_tables.h>
14 
15 #include <linux/netfilter_ipv4/ip_tables.h>
16 #include <linux/netfilter_ipv6/ip6_tables.h>
17 
18 MODULE_LICENSE("GPL");
19 MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
20 MODULE_DESCRIPTION("Xtables: IPsec-ESP packet match");
21 MODULE_ALIAS("ipt_esp");
22 MODULE_ALIAS("ip6t_esp");
23 
24 /* Returns 1 if the spi is matched by the range, 0 otherwise */
25 static inline bool
spi_match(u_int32_t min,u_int32_t max,u_int32_t spi,bool invert)26 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
27 {
28 	bool r;
29 	pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
30 		 invert ? '!' : ' ', min, spi, max);
31 	r = (spi >= min && spi <= max) ^ invert;
32 	pr_debug(" result %s\n", r ? "PASS" : "FAILED");
33 	return r;
34 }
35 
esp_mt(const struct sk_buff * skb,struct xt_action_param * par)36 static bool esp_mt(const struct sk_buff *skb, struct xt_action_param *par)
37 {
38 	const struct ip_esp_hdr *eh;
39 	struct ip_esp_hdr _esp;
40 	const struct xt_esp *espinfo = par->matchinfo;
41 
42 	/* Must not be a fragment. */
43 	if (par->fragoff != 0)
44 		return false;
45 
46 	eh = skb_header_pointer(skb, par->thoff, sizeof(_esp), &_esp);
47 	if (eh == NULL) {
48 		/* We've been asked to examine this packet, and we
49 		 * can't.  Hence, no choice but to drop.
50 		 */
51 		pr_debug("Dropping evil ESP tinygram.\n");
52 		par->hotdrop = true;
53 		return false;
54 	}
55 
56 	return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi),
57 			 !!(espinfo->invflags & XT_ESP_INV_SPI));
58 }
59 
esp_mt_check(const struct xt_mtchk_param * par)60 static int esp_mt_check(const struct xt_mtchk_param *par)
61 {
62 	const struct xt_esp *espinfo = par->matchinfo;
63 
64 	if (espinfo->invflags & ~XT_ESP_INV_MASK) {
65 		pr_debug("unknown flags %X\n", espinfo->invflags);
66 		return -EINVAL;
67 	}
68 
69 	return 0;
70 }
71 
72 static struct xt_match esp_mt_reg[] __read_mostly = {
73 	{
74 		.name		= "esp",
75 		.family		= NFPROTO_IPV4,
76 		.checkentry	= esp_mt_check,
77 		.match		= esp_mt,
78 		.matchsize	= sizeof(struct xt_esp),
79 		.proto		= IPPROTO_ESP,
80 		.me		= THIS_MODULE,
81 	},
82 	{
83 		.name		= "esp",
84 		.family		= NFPROTO_IPV6,
85 		.checkentry	= esp_mt_check,
86 		.match		= esp_mt,
87 		.matchsize	= sizeof(struct xt_esp),
88 		.proto		= IPPROTO_ESP,
89 		.me		= THIS_MODULE,
90 	},
91 };
92 
esp_mt_init(void)93 static int __init esp_mt_init(void)
94 {
95 	return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
96 }
97 
esp_mt_exit(void)98 static void __exit esp_mt_exit(void)
99 {
100 	xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
101 }
102 
103 module_init(esp_mt_init);
104 module_exit(esp_mt_exit);
105