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Linux/net/netfilter/xt_policy.c

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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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 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, struct xt_action_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->family);
120         else
121                 ret = match_policy_out(skb, info, par->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 int 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                 pr_info("neither incoming nor outgoing policy selected\n");
137                 return -EINVAL;
138         }
139         if (par->hook_mask & ((1 << NF_INET_PRE_ROUTING) |
140             (1 << NF_INET_LOCAL_IN)) && info->flags & XT_POLICY_MATCH_OUT) {
141                 pr_info("output policy not valid in PREROUTING and INPUT\n");
142                 return -EINVAL;
143         }
144         if (par->hook_mask & ((1 << NF_INET_POST_ROUTING) |
145             (1 << NF_INET_LOCAL_OUT)) && info->flags & XT_POLICY_MATCH_IN) {
146                 pr_info("input policy not valid in POSTROUTING and OUTPUT\n");
147                 return -EINVAL;
148         }
149         if (info->len > XT_POLICY_MAX_ELEM) {
150                 pr_info("too many policy elements\n");
151                 return -EINVAL;
152         }
153         return 0;
154 }
155 
156 static struct xt_match policy_mt_reg[] __read_mostly = {
157         {
158                 .name           = "policy",
159                 .family         = NFPROTO_IPV4,
160                 .checkentry     = policy_mt_check,
161                 .match          = policy_mt,
162                 .matchsize      = sizeof(struct xt_policy_info),
163                 .me             = THIS_MODULE,
164         },
165         {
166                 .name           = "policy",
167                 .family         = NFPROTO_IPV6,
168                 .checkentry     = policy_mt_check,
169                 .match          = policy_mt,
170                 .matchsize      = sizeof(struct xt_policy_info),
171                 .me             = THIS_MODULE,
172         },
173 };
174 
175 static int __init policy_mt_init(void)
176 {
177         return xt_register_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
178 }
179 
180 static void __exit policy_mt_exit(void)
181 {
182         xt_unregister_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
183 }
184 
185 module_init(policy_mt_init);
186 module_exit(policy_mt_exit);
187 MODULE_ALIAS("ipt_policy");
188 MODULE_ALIAS("ip6t_policy");
189 

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