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