1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*  Kernel module to match IPComp parameters for IPv4 and IPv6
3  *
4  *  Copyright (C) 2013 WindRiver
5  *
6  *  Author:
7  *  Fan Du <fan.du@windriver.com>
8  *
9  *  Based on:
10  *  net/netfilter/xt_esp.c
11  */
12 
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14 #include <linux/in.h>
15 #include <linux/module.h>
16 #include <linux/skbuff.h>
17 #include <linux/ip.h>
18 
19 #include <linux/netfilter/xt_ipcomp.h>
20 #include <linux/netfilter/x_tables.h>
21 
22 MODULE_LICENSE("GPL");
23 MODULE_AUTHOR("Fan Du <fan.du@windriver.com>");
24 MODULE_DESCRIPTION("Xtables: IPv4/6 IPsec-IPComp SPI match");
25 MODULE_ALIAS("ipt_ipcomp");
26 MODULE_ALIAS("ip6t_ipcomp");
27 
28 /* Returns 1 if the spi is matched by the range, 0 otherwise */
29 static inline bool
spi_match(u_int32_t min,u_int32_t max,u_int32_t spi,bool invert)30 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
31 {
32 	bool r;
33 	pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
34 		 invert ? '!' : ' ', min, spi, max);
35 	r = (spi >= min && spi <= max) ^ invert;
36 	pr_debug(" result %s\n", r ? "PASS" : "FAILED");
37 	return r;
38 }
39 
comp_mt(const struct sk_buff * skb,struct xt_action_param * par)40 static bool comp_mt(const struct sk_buff *skb, struct xt_action_param *par)
41 {
42 	struct ip_comp_hdr _comphdr;
43 	const struct ip_comp_hdr *chdr;
44 	const struct xt_ipcomp *compinfo = par->matchinfo;
45 
46 	/* Must not be a fragment. */
47 	if (par->fragoff != 0)
48 		return false;
49 
50 	chdr = skb_header_pointer(skb, par->thoff, sizeof(_comphdr), &_comphdr);
51 	if (chdr == NULL) {
52 		/* We've been asked to examine this packet, and we
53 		 * can't.  Hence, no choice but to drop.
54 		 */
55 		pr_debug("Dropping evil IPComp tinygram.\n");
56 		par->hotdrop = true;
57 		return false;
58 	}
59 
60 	return spi_match(compinfo->spis[0], compinfo->spis[1],
61 			 ntohs(chdr->cpi),
62 			 !!(compinfo->invflags & XT_IPCOMP_INV_SPI));
63 }
64 
comp_mt_check(const struct xt_mtchk_param * par)65 static int comp_mt_check(const struct xt_mtchk_param *par)
66 {
67 	const struct xt_ipcomp *compinfo = par->matchinfo;
68 
69 	/* Must specify no unknown invflags */
70 	if (compinfo->invflags & ~XT_IPCOMP_INV_MASK) {
71 		pr_info_ratelimited("unknown flags %X\n", compinfo->invflags);
72 		return -EINVAL;
73 	}
74 	return 0;
75 }
76 
77 static struct xt_match comp_mt_reg[] __read_mostly = {
78 	{
79 		.name		= "ipcomp",
80 		.family		= NFPROTO_IPV4,
81 		.match		= comp_mt,
82 		.matchsize	= sizeof(struct xt_ipcomp),
83 		.proto		= IPPROTO_COMP,
84 		.checkentry	= comp_mt_check,
85 		.me		= THIS_MODULE,
86 	},
87 	{
88 		.name		= "ipcomp",
89 		.family		= NFPROTO_IPV6,
90 		.match		= comp_mt,
91 		.matchsize	= sizeof(struct xt_ipcomp),
92 		.proto		= IPPROTO_COMP,
93 		.checkentry	= comp_mt_check,
94 		.me		= THIS_MODULE,
95 	},
96 };
97 
comp_mt_init(void)98 static int __init comp_mt_init(void)
99 {
100 	return xt_register_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
101 }
102 
comp_mt_exit(void)103 static void __exit comp_mt_exit(void)
104 {
105 	xt_unregister_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
106 }
107 
108 module_init(comp_mt_init);
109 module_exit(comp_mt_exit);
110