1 // SPDX-License-Identifier: GPL-2.0-only
2 /* IP tables module for matching IPsec policy
3  *
4  * Copyright (c) 2004,2005 Patrick McHardy, <kaber@trash.net>
5  */
6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7 #include <linux/kernel.h>
8 #include <linux/module.h>
9 #include <linux/skbuff.h>
10 #include <linux/init.h>
11 #include <net/xfrm.h>
12 
13 #include <linux/netfilter.h>
14 #include <linux/netfilter/xt_policy.h>
15 #include <linux/netfilter/x_tables.h>
16 
17 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
18 MODULE_DESCRIPTION("Xtables: IPsec policy match");
19 MODULE_LICENSE("GPL");
20 
21 static inline bool
xt_addr_cmp(const union nf_inet_addr * a1,const union nf_inet_addr * m,const union nf_inet_addr * a2,unsigned short family)22 xt_addr_cmp(const union nf_inet_addr *a1, const union nf_inet_addr *m,
23 	    const union nf_inet_addr *a2, unsigned short family)
24 {
25 	switch (family) {
26 	case NFPROTO_IPV4:
27 		return ((a1->ip ^ a2->ip) & m->ip) == 0;
28 	case NFPROTO_IPV6:
29 		return ipv6_masked_addr_cmp(&a1->in6, &m->in6, &a2->in6) == 0;
30 	}
31 	return false;
32 }
33 
34 static bool
match_xfrm_state(const struct xfrm_state * x,const struct xt_policy_elem * e,unsigned short family)35 match_xfrm_state(const struct xfrm_state *x, const struct xt_policy_elem *e,
36 		 unsigned short family)
37 {
38 #define MATCH_ADDR(x,y,z)	(!e->match.x ||			       \
39 				 (xt_addr_cmp(&e->x, &e->y, (const union nf_inet_addr *)(z), family) \
40 				  ^ e->invert.x))
41 #define MATCH(x,y)		(!e->match.x || ((e->x == (y)) ^ e->invert.x))
42 
43 	return MATCH_ADDR(saddr, smask, &x->props.saddr) &&
44 	       MATCH_ADDR(daddr, dmask, &x->id.daddr) &&
45 	       MATCH(proto, x->id.proto) &&
46 	       MATCH(mode, x->props.mode) &&
47 	       MATCH(spi, x->id.spi) &&
48 	       MATCH(reqid, x->props.reqid);
49 }
50 
51 static int
match_policy_in(const struct sk_buff * skb,const struct xt_policy_info * info,unsigned short family)52 match_policy_in(const struct sk_buff *skb, const struct xt_policy_info *info,
53 		unsigned short family)
54 {
55 	const struct xt_policy_elem *e;
56 	const struct sec_path *sp = skb_sec_path(skb);
57 	int strict = info->flags & XT_POLICY_MATCH_STRICT;
58 	int i, pos;
59 
60 	if (sp == NULL)
61 		return -1;
62 	if (strict && info->len != sp->len)
63 		return 0;
64 
65 	for (i = sp->len - 1; i >= 0; i--) {
66 		pos = strict ? i - sp->len + 1 : 0;
67 		if (pos >= info->len)
68 			return 0;
69 		e = &info->pol[pos];
70 
71 		if (match_xfrm_state(sp->xvec[i], e, family)) {
72 			if (!strict)
73 				return 1;
74 		} else if (strict)
75 			return 0;
76 	}
77 
78 	return strict ? 1 : 0;
79 }
80 
81 static int
match_policy_out(const struct sk_buff * skb,const struct xt_policy_info * info,unsigned short family)82 match_policy_out(const struct sk_buff *skb, const struct xt_policy_info *info,
83 		 unsigned short family)
84 {
85 	const struct xt_policy_elem *e;
86 	const struct dst_entry *dst = skb_dst(skb);
87 	int strict = info->flags & XT_POLICY_MATCH_STRICT;
88 	int i, pos;
89 
90 	if (dst->xfrm == NULL)
91 		return -1;
92 
93 	for (i = 0; dst && dst->xfrm;
94 	     dst = ((struct xfrm_dst *)dst)->child, i++) {
95 		pos = strict ? i : 0;
96 		if (pos >= info->len)
97 			return 0;
98 		e = &info->pol[pos];
99 
100 		if (match_xfrm_state(dst->xfrm, e, family)) {
101 			if (!strict)
102 				return 1;
103 		} else if (strict)
104 			return 0;
105 	}
106 
107 	return strict ? i == info->len : 0;
108 }
109 
110 static bool
policy_mt(const struct sk_buff * skb,struct xt_action_param * par)111 policy_mt(const struct sk_buff *skb, struct xt_action_param *par)
112 {
113 	const struct xt_policy_info *info = par->matchinfo;
114 	int ret;
115 
116 	if (info->flags & XT_POLICY_MATCH_IN)
117 		ret = match_policy_in(skb, info, xt_family(par));
118 	else
119 		ret = match_policy_out(skb, info, xt_family(par));
120 
121 	if (ret < 0)
122 		ret = info->flags & XT_POLICY_MATCH_NONE ? true : false;
123 	else if (info->flags & XT_POLICY_MATCH_NONE)
124 		ret = false;
125 
126 	return ret;
127 }
128 
policy_mt_check(const struct xt_mtchk_param * par)129 static int policy_mt_check(const struct xt_mtchk_param *par)
130 {
131 	const struct xt_policy_info *info = par->matchinfo;
132 	const char *errmsg = "neither incoming nor outgoing policy selected";
133 
134 	if (!(info->flags & (XT_POLICY_MATCH_IN|XT_POLICY_MATCH_OUT)))
135 		goto err;
136 
137 	if (par->hook_mask & ((1 << NF_INET_PRE_ROUTING) |
138 	    (1 << NF_INET_LOCAL_IN)) && info->flags & XT_POLICY_MATCH_OUT) {
139 		errmsg = "output policy not valid in PREROUTING and INPUT";
140 		goto err;
141 	}
142 	if (par->hook_mask & ((1 << NF_INET_POST_ROUTING) |
143 	    (1 << NF_INET_LOCAL_OUT)) && info->flags & XT_POLICY_MATCH_IN) {
144 		errmsg = "input policy not valid in POSTROUTING and OUTPUT";
145 		goto err;
146 	}
147 	if (info->len > XT_POLICY_MAX_ELEM) {
148 		errmsg = "too many policy elements";
149 		goto err;
150 	}
151 	return 0;
152 err:
153 	pr_info_ratelimited("%s\n", errmsg);
154 	return -EINVAL;
155 }
156 
157 static struct xt_match policy_mt_reg[] __read_mostly = {
158 	{
159 		.name		= "policy",
160 		.family		= NFPROTO_IPV4,
161 		.checkentry 	= policy_mt_check,
162 		.match		= policy_mt,
163 		.matchsize	= sizeof(struct xt_policy_info),
164 		.me		= THIS_MODULE,
165 	},
166 	{
167 		.name		= "policy",
168 		.family		= NFPROTO_IPV6,
169 		.checkentry	= policy_mt_check,
170 		.match		= policy_mt,
171 		.matchsize	= sizeof(struct xt_policy_info),
172 		.me		= THIS_MODULE,
173 	},
174 };
175 
policy_mt_init(void)176 static int __init policy_mt_init(void)
177 {
178 	return xt_register_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
179 }
180 
policy_mt_exit(void)181 static void __exit policy_mt_exit(void)
182 {
183 	xt_unregister_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
184 }
185 
186 module_init(policy_mt_init);
187 module_exit(policy_mt_exit);
188 MODULE_ALIAS("ipt_policy");
189 MODULE_ALIAS("ip6t_policy");
190