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Linux/net/netfilter/xt_policy.c

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  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->in6, &m->in6, &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(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(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, 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 
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(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
179 }
180 
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 

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