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 |
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: &a1->in6, m: &m->in6, a2: &a2->in6) == 0; |
30 | } |
31 | return false; |
32 | } |
33 | |
34 | static bool |
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 |
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(x: 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 |
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(x: 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 |
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, family: xt_family(par)); |
118 | else |
119 | ret = match_policy_out(skb, info, family: 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 | |
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 | |
176 | static int __init policy_mt_init(void) |
177 | { |
178 | return xt_register_matches(match: policy_mt_reg, ARRAY_SIZE(policy_mt_reg)); |
179 | } |
180 | |
181 | static void __exit policy_mt_exit(void) |
182 | { |
183 | xt_unregister_matches(match: 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 | |