1/*  Kernel module to match IPComp parameters for IPv4 and IPv6
2 *
3 *  Copyright (C) 2013 WindRiver
4 *
5 *  Author:
6 *  Fan Du <fan.du@windriver.com>
7 *
8 *  Based on:
9 *  net/netfilter/xt_esp.c
10 *
11 *  This program is free software; you can redistribute it and/or
12 *  modify it under the terms of the GNU General Public License
13 *  as published by the Free Software Foundation; either version
14 *  2 of the License, or (at your option) any later version.
15 */
16
17#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18#include <linux/in.h>
19#include <linux/module.h>
20#include <linux/skbuff.h>
21#include <linux/ip.h>
22
23#include <linux/netfilter/xt_ipcomp.h>
24#include <linux/netfilter/x_tables.h>
25
26MODULE_LICENSE("GPL");
27MODULE_AUTHOR("Fan Du <fan.du@windriver.com>");
28MODULE_DESCRIPTION("Xtables: IPv4/6 IPsec-IPComp SPI match");
29
30/* Returns 1 if the spi is matched by the range, 0 otherwise */
31static inline bool
32spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
33{
34	bool r;
35	pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
36		 invert ? '!' : ' ', min, spi, max);
37	r = (spi >= min && spi <= max) ^ invert;
38	pr_debug(" result %s\n", r ? "PASS" : "FAILED");
39	return r;
40}
41
42static bool comp_mt(const struct sk_buff *skb, struct xt_action_param *par)
43{
44	struct ip_comp_hdr _comphdr;
45	const struct ip_comp_hdr *chdr;
46	const struct xt_ipcomp *compinfo = par->matchinfo;
47
48	/* Must not be a fragment. */
49	if (par->fragoff != 0)
50		return false;
51
52	chdr = skb_header_pointer(skb, par->thoff, sizeof(_comphdr), &_comphdr);
53	if (chdr == NULL) {
54		/* We've been asked to examine this packet, and we
55		 * can't.  Hence, no choice but to drop.
56		 */
57		pr_debug("Dropping evil IPComp tinygram.\n");
58		par->hotdrop = true;
59		return 0;
60	}
61
62	return spi_match(compinfo->spis[0], compinfo->spis[1],
63			 ntohs(chdr->cpi),
64			 !!(compinfo->invflags & XT_IPCOMP_INV_SPI));
65}
66
67static int comp_mt_check(const struct xt_mtchk_param *par)
68{
69	const struct xt_ipcomp *compinfo = par->matchinfo;
70
71	/* Must specify no unknown invflags */
72	if (compinfo->invflags & ~XT_IPCOMP_INV_MASK) {
73		pr_err("unknown flags %X\n", compinfo->invflags);
74		return -EINVAL;
75	}
76	return 0;
77}
78
79static struct xt_match comp_mt_reg[] __read_mostly = {
80	{
81		.name		= "ipcomp",
82		.family		= NFPROTO_IPV4,
83		.match		= comp_mt,
84		.matchsize	= sizeof(struct xt_ipcomp),
85		.proto		= IPPROTO_COMP,
86		.checkentry	= comp_mt_check,
87		.me		= THIS_MODULE,
88	},
89	{
90		.name		= "ipcomp",
91		.family		= NFPROTO_IPV6,
92		.match		= comp_mt,
93		.matchsize	= sizeof(struct xt_ipcomp),
94		.proto		= IPPROTO_COMP,
95		.checkentry	= comp_mt_check,
96		.me		= THIS_MODULE,
97	},
98};
99
100static int __init comp_mt_init(void)
101{
102	return xt_register_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
103}
104
105static void __exit comp_mt_exit(void)
106{
107	xt_unregister_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
108}
109
110module_init(comp_mt_init);
111module_exit(comp_mt_exit);
112