net/netfilter/xt_policy.c

   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");