1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C)2006 USAGI/WIDE Project
4  *
5  * Author:
6  *	Masahide NAKAMURA @USAGI <masahide.nakamura.cz@hitachi.com>
7  *
8  * Based on net/netfilter/xt_tcpudp.c
9  */
10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11 #include <linux/types.h>
12 #include <linux/module.h>
13 #include <net/ip.h>
14 #include <linux/ipv6.h>
15 #include <net/ipv6.h>
16 #include <net/mip6.h>
17 
18 #include <linux/netfilter/x_tables.h>
19 #include <linux/netfilter_ipv6/ip6t_mh.h>
20 
21 MODULE_DESCRIPTION("Xtables: IPv6 Mobility Header match");
22 MODULE_LICENSE("GPL");
23 
24 /* Returns 1 if the type is matched by the range, 0 otherwise */
25 static inline bool
type_match(u_int8_t min,u_int8_t max,u_int8_t type,bool invert)26 type_match(u_int8_t min, u_int8_t max, u_int8_t type, bool invert)
27 {
28 	return (type >= min && type <= max) ^ invert;
29 }
30 
mh_mt6(const struct sk_buff * skb,struct xt_action_param * par)31 static bool mh_mt6(const struct sk_buff *skb, struct xt_action_param *par)
32 {
33 	struct ip6_mh _mh;
34 	const struct ip6_mh *mh;
35 	const struct ip6t_mh *mhinfo = par->matchinfo;
36 
37 	/* Must not be a fragment. */
38 	if (par->fragoff != 0)
39 		return false;
40 
41 	mh = skb_header_pointer(skb, par->thoff, sizeof(_mh), &_mh);
42 	if (mh == NULL) {
43 		/* We've been asked to examine this packet, and we
44 		   can't.  Hence, no choice but to drop. */
45 		pr_debug("Dropping evil MH tinygram.\n");
46 		par->hotdrop = true;
47 		return false;
48 	}
49 
50 	if (mh->ip6mh_proto != IPPROTO_NONE) {
51 		pr_debug("Dropping invalid MH Payload Proto: %u\n",
52 			 mh->ip6mh_proto);
53 		par->hotdrop = true;
54 		return false;
55 	}
56 
57 	return type_match(mhinfo->types[0], mhinfo->types[1], mh->ip6mh_type,
58 			  !!(mhinfo->invflags & IP6T_MH_INV_TYPE));
59 }
60 
mh_mt6_check(const struct xt_mtchk_param * par)61 static int mh_mt6_check(const struct xt_mtchk_param *par)
62 {
63 	const struct ip6t_mh *mhinfo = par->matchinfo;
64 
65 	/* Must specify no unknown invflags */
66 	return (mhinfo->invflags & ~IP6T_MH_INV_MASK) ? -EINVAL : 0;
67 }
68 
69 static struct xt_match mh_mt6_reg __read_mostly = {
70 	.name		= "mh",
71 	.family		= NFPROTO_IPV6,
72 	.checkentry	= mh_mt6_check,
73 	.match		= mh_mt6,
74 	.matchsize	= sizeof(struct ip6t_mh),
75 	.proto		= IPPROTO_MH,
76 	.me		= THIS_MODULE,
77 };
78 
mh_mt6_init(void)79 static int __init mh_mt6_init(void)
80 {
81 	return xt_register_match(&mh_mt6_reg);
82 }
83 
mh_mt6_exit(void)84 static void __exit mh_mt6_exit(void)
85 {
86 	xt_unregister_match(&mh_mt6_reg);
87 }
88 
89 module_init(mh_mt6_init);
90 module_exit(mh_mt6_exit);
91