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 return (spi >= min && spi <= max) ^ invert;
29 }
30
esp_mt(const struct sk_buff * skb,struct xt_action_param * par)31 static bool esp_mt(const struct sk_buff *skb, struct xt_action_param *par)
32 {
33 const struct ip_esp_hdr *eh;
34 struct ip_esp_hdr _esp;
35 const struct xt_esp *espinfo = par->matchinfo;
36
37 /* Must not be a fragment. */
38 if (par->fragoff != 0)
39 return false;
40
41 eh = skb_header_pointer(skb, par->thoff, sizeof(_esp), &_esp);
42 if (eh == NULL) {
43 /* We've been asked to examine this packet, and we
44 * can't. Hence, no choice but to drop.
45 */
46 par->hotdrop = true;
47 return false;
48 }
49
50 return spi_match(espinfo->spis[0], espinfo->spis[1], ntohl(eh->spi),
51 !!(espinfo->invflags & XT_ESP_INV_SPI));
52 }
53
esp_mt_check(const struct xt_mtchk_param * par)54 static int esp_mt_check(const struct xt_mtchk_param *par)
55 {
56 const struct xt_esp *espinfo = par->matchinfo;
57
58 if (espinfo->invflags & ~XT_ESP_INV_MASK) {
59 pr_info_ratelimited("unknown flags %X\n", espinfo->invflags);
60 return -EINVAL;
61 }
62
63 return 0;
64 }
65
66 static struct xt_match esp_mt_reg[] __read_mostly = {
67 {
68 .name = "esp",
69 .family = NFPROTO_IPV4,
70 .checkentry = esp_mt_check,
71 .match = esp_mt,
72 .matchsize = sizeof(struct xt_esp),
73 .proto = IPPROTO_ESP,
74 .me = THIS_MODULE,
75 },
76 {
77 .name = "esp",
78 .family = NFPROTO_IPV6,
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
esp_mt_init(void)87 static int __init esp_mt_init(void)
88 {
89 return xt_register_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
90 }
91
esp_mt_exit(void)92 static void __exit esp_mt_exit(void)
93 {
94 xt_unregister_matches(esp_mt_reg, ARRAY_SIZE(esp_mt_reg));
95 }
96
97 module_init(esp_mt_init);
98 module_exit(esp_mt_exit);
99