1/* IP tables module for matching IPsec policy
2 *
3 * Copyright (c) 2004,2005 Patrick McHardy, <kaber@trash.net>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 */
9
10#include <linux/kernel.h>
11#include <linux/module.h>
12#include <linux/skbuff.h>
13#include <linux/init.h>
14#include <net/xfrm.h>
15
16#include <linux/netfilter/xt_policy.h>
17#include <linux/netfilter/x_tables.h>
18
19MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
20MODULE_DESCRIPTION("Xtables IPsec policy matching module");
21MODULE_LICENSE("GPL");
22
23static inline int
24xt_addr_cmp(const union xt_policy_addr *a1, const union xt_policy_addr *m,
25	    const union xt_policy_addr *a2, unsigned short family)
26{
27	switch (family) {
28	case AF_INET:
29		return !((a1->a4.s_addr ^ a2->a4.s_addr) & m->a4.s_addr);
30	case AF_INET6:
31		return !ipv6_masked_addr_cmp(&a1->a6, &m->a6, &a2->a6);
32	}
33	return 0;
34}
35
36static inline int
37match_xfrm_state(struct xfrm_state *x, const struct xt_policy_elem *e,
38		 unsigned short family)
39{
40#define MATCH_ADDR(x,y,z)	(!e->match.x ||			       \
41				 (xt_addr_cmp(&e->x, &e->y, z, family) \
42				  ^ e->invert.x))
43#define MATCH(x,y)		(!e->match.x || ((e->x == (y)) ^ e->invert.x))
44
45	return MATCH_ADDR(saddr, smask, (union xt_policy_addr *)&x->props.saddr) &&
46	       MATCH_ADDR(daddr, dmask, (union xt_policy_addr *)&x->id.daddr) &&
47	       MATCH(proto, x->id.proto) &&
48	       MATCH(mode, x->props.mode) &&
49	       MATCH(spi, x->id.spi) &&
50	       MATCH(reqid, x->props.reqid);
51}
52
53static int
54match_policy_in(const struct sk_buff *skb, const struct xt_policy_info *info,
55		unsigned short family)
56{
57	const struct xt_policy_elem *e;
58	struct sec_path *sp = skb->sp;
59	int strict = info->flags & XT_POLICY_MATCH_STRICT;
60	int i, pos;
61
62	if (sp == NULL)
63		return -1;
64	if (strict && info->len != sp->len)
65		return 0;
66
67	for (i = sp->len - 1; i >= 0; i--) {
68		pos = strict ? i - sp->len + 1 : 0;
69		if (pos >= info->len)
70			return 0;
71		e = &info->pol[pos];
72
73		if (match_xfrm_state(sp->xvec[i], e, family)) {
74			if (!strict)
75				return 1;
76		} else if (strict)
77			return 0;
78	}
79
80	return strict ? 1 : 0;
81}
82
83static int
84match_policy_out(const struct sk_buff *skb, const struct xt_policy_info *info,
85		 unsigned short family)
86{
87	const struct xt_policy_elem *e;
88	struct dst_entry *dst = skb->dst;
89	int strict = info->flags & XT_POLICY_MATCH_STRICT;
90	int i, pos;
91
92	if (dst->xfrm == NULL)
93		return -1;
94
95	for (i = 0; dst && dst->xfrm; dst = dst->child, i++) {
96		pos = strict ? i : 0;
97		if (pos >= info->len)
98			return 0;
99		e = &info->pol[pos];
100
101		if (match_xfrm_state(dst->xfrm, e, family)) {
102			if (!strict)
103				return 1;
104		} else if (strict)
105			return 0;
106	}
107
108	return strict ? i == info->len : 0;
109}
110
111static int match(const struct sk_buff *skb,
112		 const struct net_device *in,
113		 const struct net_device *out,
114		 const struct xt_match *match,
115		 const void *matchinfo,
116		 int offset,
117		 unsigned int protoff,
118		 int *hotdrop)
119{
120	const struct xt_policy_info *info = matchinfo;
121	int ret;
122
123	if (info->flags & XT_POLICY_MATCH_IN)
124		ret = match_policy_in(skb, info, match->family);
125	else
126		ret = match_policy_out(skb, info, match->family);
127
128	if (ret < 0)
129		ret = info->flags & XT_POLICY_MATCH_NONE ? 1 : 0;
130	else if (info->flags & XT_POLICY_MATCH_NONE)
131		ret = 0;
132
133	return ret;
134}
135
136static int checkentry(const char *tablename, const void *ip_void,
137		      const struct xt_match *match,
138		      void *matchinfo, unsigned int hook_mask)
139{
140	struct xt_policy_info *info = matchinfo;
141
142	if (!(info->flags & (XT_POLICY_MATCH_IN|XT_POLICY_MATCH_OUT))) {
143		printk(KERN_ERR "xt_policy: neither incoming nor "
144				"outgoing policy selected\n");
145		return 0;
146	}
147	/* hook values are equal for IPv4 and IPv6 */
148	if (hook_mask & (1 << NF_IP_PRE_ROUTING | 1 << NF_IP_LOCAL_IN)
149	    && info->flags & XT_POLICY_MATCH_OUT) {
150		printk(KERN_ERR "xt_policy: output policy not valid in "
151				"PRE_ROUTING and INPUT\n");
152		return 0;
153	}
154	if (hook_mask & (1 << NF_IP_POST_ROUTING | 1 << NF_IP_LOCAL_OUT)
155	    && info->flags & XT_POLICY_MATCH_IN) {
156		printk(KERN_ERR "xt_policy: input policy not valid in "
157				"POST_ROUTING and OUTPUT\n");
158		return 0;
159	}
160	if (info->len > XT_POLICY_MAX_ELEM) {
161		printk(KERN_ERR "xt_policy: too many policy elements\n");
162		return 0;
163	}
164	return 1;
165}
166
167static struct xt_match xt_policy_match[] = {
168	{
169		.name		= "policy",
170		.family		= AF_INET,
171		.checkentry 	= checkentry,
172		.match		= match,
173		.matchsize	= sizeof(struct xt_policy_info),
174		.me		= THIS_MODULE,
175	},
176	{
177		.name		= "policy",
178		.family		= AF_INET6,
179		.checkentry	= checkentry,
180		.match		= match,
181		.matchsize	= sizeof(struct xt_policy_info),
182		.me		= THIS_MODULE,
183	},
184};
185
186static int __init init(void)
187{
188	return xt_register_matches(xt_policy_match,
189				   ARRAY_SIZE(xt_policy_match));
190}
191
192static void __exit fini(void)
193{
194	xt_unregister_matches(xt_policy_match, ARRAY_SIZE(xt_policy_match));
195}
196
197module_init(init);
198module_exit(fini);
199MODULE_ALIAS("ipt_policy");
200MODULE_ALIAS("ip6t_policy");
201