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
