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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.h> |
17 | #include <linux/netfilter/xt_policy.h> |
18 | #include <linux/netfilter/x_tables.h> |
19 | |
20 | MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); |
21 | MODULE_DESCRIPTION("Xtables: IPsec policy match"); |
22 | MODULE_LICENSE("GPL"); |
23 | |
24 | static inline bool |
25 | xt_addr_cmp(const union nf_inet_addr *a1, const union nf_inet_addr *m, |
26 | const union nf_inet_addr *a2, unsigned short family) |
27 | { |
28 | switch (family) { |
29 | case NFPROTO_IPV4: |
30 | return ((a1->ip ^ a2->ip) & m->ip) == 0; |
31 | case NFPROTO_IPV6: |
32 | return ipv6_masked_addr_cmp(&a1->in6, &m->in6, &a2->in6) == 0; |
33 | } |
34 | return false; |
35 | } |
36 | |
37 | static bool |
38 | match_xfrm_state(const struct xfrm_state *x, const struct xt_policy_elem *e, |
39 | unsigned short family) |
40 | { |
41 | #define MATCH_ADDR(x,y,z) (!e->match.x || \ |
42 | (xt_addr_cmp(&e->x, &e->y, (const union nf_inet_addr *)(z), family) \ |
43 | ^ e->invert.x)) |
44 | #define MATCH(x,y) (!e->match.x || ((e->x == (y)) ^ e->invert.x)) |
45 | |
46 | return MATCH_ADDR(saddr, smask, &x->props.saddr) && |
47 | MATCH_ADDR(daddr, dmask, &x->id.daddr) && |
48 | MATCH(proto, x->id.proto) && |
49 | MATCH(mode, x->props.mode) && |
50 | MATCH(spi, x->id.spi) && |
51 | MATCH(reqid, x->props.reqid); |
52 | } |
53 | |
54 | static int |
55 | match_policy_in(const struct sk_buff *skb, const struct xt_policy_info *info, |
56 | unsigned short family) |
57 | { |
58 | const struct xt_policy_elem *e; |
59 | const struct sec_path *sp = skb->sp; |
60 | int strict = info->flags & XT_POLICY_MATCH_STRICT; |
61 | int i, pos; |
62 | |
63 | if (sp == NULL) |
64 | return -1; |
65 | if (strict && info->len != sp->len) |
66 | return 0; |
67 | |
68 | for (i = sp->len - 1; i >= 0; i--) { |
69 | pos = strict ? i - sp->len + 1 : 0; |
70 | if (pos >= info->len) |
71 | return 0; |
72 | e = &info->pol[pos]; |
73 | |
74 | if (match_xfrm_state(sp->xvec[i], e, family)) { |
75 | if (!strict) |
76 | return 1; |
77 | } else if (strict) |
78 | return 0; |
79 | } |
80 | |
81 | return strict ? 1 : 0; |
82 | } |
83 | |
84 | static int |
85 | match_policy_out(const struct sk_buff *skb, const struct xt_policy_info *info, |
86 | unsigned short family) |
87 | { |
88 | const struct xt_policy_elem *e; |
89 | const struct dst_entry *dst = skb_dst(skb); |
90 | int strict = info->flags & XT_POLICY_MATCH_STRICT; |
91 | int i, pos; |
92 | |
93 | if (dst->xfrm == NULL) |
94 | return -1; |
95 | |
96 | for (i = 0; dst && dst->xfrm; dst = dst->child, i++) { |
97 | pos = strict ? i : 0; |
98 | if (pos >= info->len) |
99 | return 0; |
100 | e = &info->pol[pos]; |
101 | |
102 | if (match_xfrm_state(dst->xfrm, e, family)) { |
103 | if (!strict) |
104 | return 1; |
105 | } else if (strict) |
106 | return 0; |
107 | } |
108 | |
109 | return strict ? i == info->len : 0; |
110 | } |
111 | |
112 | static bool |
113 | policy_mt(const struct sk_buff *skb, const struct xt_match_param *par) |
114 | { |
115 | const struct xt_policy_info *info = par->matchinfo; |
116 | int ret; |
117 | |
118 | if (info->flags & XT_POLICY_MATCH_IN) |
119 | ret = match_policy_in(skb, info, par->match->family); |
120 | else |
121 | ret = match_policy_out(skb, info, par->match->family); |
122 | |
123 | if (ret < 0) |
124 | ret = info->flags & XT_POLICY_MATCH_NONE ? true : false; |
125 | else if (info->flags & XT_POLICY_MATCH_NONE) |
126 | ret = false; |
127 | |
128 | return ret; |
129 | } |
130 | |
131 | static bool policy_mt_check(const struct xt_mtchk_param *par) |
132 | { |
133 | const struct xt_policy_info *info = par->matchinfo; |
134 | |
135 | if (!(info->flags & (XT_POLICY_MATCH_IN|XT_POLICY_MATCH_OUT))) { |
136 | printk(KERN_ERR "xt_policy: neither incoming nor " |
137 | "outgoing policy selected\n"); |
138 | return false; |
139 | } |
140 | if (par->hook_mask & ((1 << NF_INET_PRE_ROUTING) | |
141 | (1 << NF_INET_LOCAL_IN)) && info->flags & XT_POLICY_MATCH_OUT) { |
142 | printk(KERN_ERR "xt_policy: output policy not valid in " |
143 | "PRE_ROUTING and INPUT\n"); |
144 | return false; |
145 | } |
146 | if (par->hook_mask & ((1 << NF_INET_POST_ROUTING) | |
147 | (1 << NF_INET_LOCAL_OUT)) && info->flags & XT_POLICY_MATCH_IN) { |
148 | printk(KERN_ERR "xt_policy: input policy not valid in " |
149 | "POST_ROUTING and OUTPUT\n"); |
150 | return false; |
151 | } |
152 | if (info->len > XT_POLICY_MAX_ELEM) { |
153 | printk(KERN_ERR "xt_policy: too many policy elements\n"); |
154 | return false; |
155 | } |
156 | return true; |
157 | } |
158 | |
159 | static struct xt_match policy_mt_reg[] __read_mostly = { |
160 | { |
161 | .name = "policy", |
162 | .family = NFPROTO_IPV4, |
163 | .checkentry = policy_mt_check, |
164 | .match = policy_mt, |
165 | .matchsize = sizeof(struct xt_policy_info), |
166 | .me = THIS_MODULE, |
167 | }, |
168 | { |
169 | .name = "policy", |
170 | .family = NFPROTO_IPV6, |
171 | .checkentry = policy_mt_check, |
172 | .match = policy_mt, |
173 | .matchsize = sizeof(struct xt_policy_info), |
174 | .me = THIS_MODULE, |
175 | }, |
176 | }; |
177 | |
178 | static int __init policy_mt_init(void) |
179 | { |
180 | return xt_register_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg)); |
181 | } |
182 | |
183 | static void __exit policy_mt_exit(void) |
184 | { |
185 | xt_unregister_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg)); |
186 | } |
187 | |
188 | module_init(policy_mt_init); |
189 | module_exit(policy_mt_exit); |
190 | MODULE_ALIAS("ipt_policy"); |
191 | MODULE_ALIAS("ip6t_policy"); |
192 |
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