security/selinux/netif.c

   1 /*
   2  * Network interface table.
   3  *
   4  * Network interfaces (devices) do not have a security field, so we
   5  * maintain a table associating each interface with a SID.
   6  *
   7  * Author: James Morris <jmorris@redhat.com>
   8  *
   9  * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
  10  * Copyright (C) 2007 Hewlett-Packard Development Company, L.P.
  11  *                    Paul Moore <paul@paul-moore.com>
  12  *
  13  * This program is free software; you can redistribute it and/or modify
  14  * it under the terms of the GNU General Public License version 2,
  15  * as published by the Free Software Foundation.
  16  */
  17 #include <linux/init.h>
  18 #include <linux/types.h>
  19 #include <linux/slab.h>
  20 #include <linux/stddef.h>
  21 #include <linux/kernel.h>
  22 #include <linux/list.h>
  23 #include <linux/notifier.h>
  24 #include <linux/netdevice.h>
  25 #include <linux/rcupdate.h>
  26 #include <net/net_namespace.h>
  27
  28 #include "security.h"
  29 #include "objsec.h"
  30 #include "netif.h"
  31
  32 #define SEL_NETIF_HASH_SIZE     64
  33 #define SEL_NETIF_HASH_MAX      1024
  34
  35 struct sel_netif {
  36         struct list_head list;
  37         struct netif_security_struct nsec;
  38         struct rcu_head rcu_head;
  39 };
  40
  41 static u32 sel_netif_total;
  42 static LIST_HEAD(sel_netif_list);
  43 static DEFINE_SPINLOCK(sel_netif_lock);
  44 static struct list_head sel_netif_hash[SEL_NETIF_HASH_SIZE];
  45
  46 /**
  47  * sel_netif_hashfn - Hashing function for the interface table
  48  * @ns: the network namespace
  49  * @ifindex: the network interface
  50  *
  51  * Description:
  52  * This is the hashing function for the network interface table, it returns the
  53  * bucket number for the given interface.
  54  *
  55  */
  56 static inline u32 sel_netif_hashfn(const struct net *ns, int ifindex)
  57 {
  58         return (((uintptr_t)ns + ifindex) & (SEL_NETIF_HASH_SIZE - 1));
  59 }
  60
  61 /**
  62  * sel_netif_find - Search for an interface record
  63  * @ns: the network namespace
  64  * @ifindex: the network interface
  65  *
  66  * Description:
  67  * Search the network interface table and return the record matching @ifindex.
  68  * If an entry can not be found in the table return NULL.
  69  *
  70  */
  71 static inline struct sel_netif *sel_netif_find(const struct net *ns,
  72                                                int ifindex)
  73 {
  74         int idx = sel_netif_hashfn(ns, ifindex);
  75         struct sel_netif *netif;
  76
  77         list_for_each_entry_rcu(netif, &sel_netif_hash[idx], list)
  78                 if (net_eq(netif->nsec.ns, ns) &&
  79                     netif->nsec.ifindex == ifindex)
  80                         return netif;
  81
  82         return NULL;
  83 }
  84
  85 /**
  86  * sel_netif_insert - Insert a new interface into the table
  87  * @netif: the new interface record
  88  *
  89  * Description:
  90  * Add a new interface record to the network interface hash table.  Returns
  91  * zero on success, negative values on failure.
  92  *
  93  */
  94 static int sel_netif_insert(struct sel_netif *netif)
  95 {
  96         int idx;
  97
  98         if (sel_netif_total >= SEL_NETIF_HASH_MAX)
  99                 return -ENOSPC;
 100
 101         idx = sel_netif_hashfn(netif->nsec.ns, netif->nsec.ifindex);
 102         list_add_rcu(&netif->list, &sel_netif_hash[idx]);
 103         sel_netif_total++;
 104
 105         return 0;
 106 }
 107
 108 /**
 109  * sel_netif_destroy - Remove an interface record from the table
 110  * @netif: the existing interface record
 111  *
 112  * Description:
 113  * Remove an existing interface record from the network interface table.
 114  *
 115  */
 116 static void sel_netif_destroy(struct sel_netif *netif)
 117 {
 118         list_del_rcu(&netif->list);
 119         sel_netif_total--;
 120         kfree_rcu(netif, rcu_head);
 121 }
 122
 123 /**
 124  * sel_netif_sid_slow - Lookup the SID of a network interface using the policy
 125  * @ns: the network namespace
 126  * @ifindex: the network interface
 127  * @sid: interface SID
 128  *
 129  * Description:
 130  * This function determines the SID of a network interface by quering the
 131  * security policy.  The result is added to the network interface table to
 132  * speedup future queries.  Returns zero on success, negative values on
 133  * failure.
 134  *
 135  */
 136 static int sel_netif_sid_slow(struct net *ns, int ifindex, u32 *sid)
 137 {
 138         int ret;
 139         struct sel_netif *netif;
 140         struct sel_netif *new = NULL;
 141         struct net_device *dev;
 142
 143         /* NOTE: we always use init's network namespace since we don't
 144          * currently support containers */
 145
 146         dev = dev_get_by_index(ns, ifindex);
 147         if (unlikely(dev == NULL)) {
 148                 pr_warn("SELinux: failure in %s(), invalid network interface (%d)\n",
 149                         __func__, ifindex);
 150                 return -ENOENT;
 151         }
 152
 153         spin_lock_bh(&sel_netif_lock);
 154         netif = sel_netif_find(ns, ifindex);
 155         if (netif != NULL) {
 156                 *sid = netif->nsec.sid;
 157                 ret = 0;
 158                 goto out;
 159         }
 160         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 161         if (new == NULL) {
 162                 ret = -ENOMEM;
 163                 goto out;
 164         }
 165         ret = security_netif_sid(&selinux_state, dev->name, &new->nsec.sid);
 166         if (ret != 0)
 167                 goto out;
 168         new->nsec.ns = ns;
 169         new->nsec.ifindex = ifindex;
 170         ret = sel_netif_insert(new);
 171         if (ret != 0)
 172                 goto out;
 173         *sid = new->nsec.sid;
 174
 175 out:
 176         spin_unlock_bh(&sel_netif_lock);
 177         dev_put(dev);
 178         if (unlikely(ret)) {
 179                 pr_warn("SELinux: failure in %s(), unable to determine network interface label (%d)\n",
 180                         __func__, ifindex);
 181                 kfree(new);
 182         }
 183         return ret;
 184 }
 185
 186 /**
 187  * sel_netif_sid - Lookup the SID of a network interface
 188  * @ns: the network namespace
 189  * @ifindex: the network interface
 190  * @sid: interface SID
 191  *
 192  * Description:
 193  * This function determines the SID of a network interface using the fastest
 194  * method possible.  First the interface table is queried, but if an entry
 195  * can't be found then the policy is queried and the result is added to the
 196  * table to speedup future queries.  Returns zero on success, negative values
 197  * on failure.
 198  *
 199  */
 200 int sel_netif_sid(struct net *ns, int ifindex, u32 *sid)
 201 {
 202         struct sel_netif *netif;
 203
 204         rcu_read_lock();
 205         netif = sel_netif_find(ns, ifindex);
 206         if (likely(netif != NULL)) {
 207                 *sid = netif->nsec.sid;
 208                 rcu_read_unlock();
 209                 return 0;
 210         }
 211         rcu_read_unlock();
 212
 213         return sel_netif_sid_slow(ns, ifindex, sid);
 214 }
 215
 216 /**
 217  * sel_netif_kill - Remove an entry from the network interface table
 218  * @ns: the network namespace
 219  * @ifindex: the network interface
 220  *
 221  * Description:
 222  * This function removes the entry matching @ifindex from the network interface
 223  * table if it exists.
 224  *
 225  */
 226 static void sel_netif_kill(const struct net *ns, int ifindex)
 227 {
 228         struct sel_netif *netif;
 229
 230         rcu_read_lock();
 231         spin_lock_bh(&sel_netif_lock);
 232         netif = sel_netif_find(ns, ifindex);
 233         if (netif)
 234                 sel_netif_destroy(netif);
 235         spin_unlock_bh(&sel_netif_lock);
 236         rcu_read_unlock();
 237 }
 238
 239 /**
 240  * sel_netif_flush - Flush the entire network interface table
 241  *
 242  * Description:
 243  * Remove all entries from the network interface table.
 244  *
 245  */
 246 void sel_netif_flush(void)
 247 {
 248         int idx;
 249         struct sel_netif *netif;
 250
 251         spin_lock_bh(&sel_netif_lock);
 252         for (idx = 0; idx < SEL_NETIF_HASH_SIZE; idx++)
 253                 list_for_each_entry(netif, &sel_netif_hash[idx], list)
 254                         sel_netif_destroy(netif);
 255         spin_unlock_bh(&sel_netif_lock);
 256 }
 257
 258 static int sel_netif_netdev_notifier_handler(struct notifier_block *this,
 259                                              unsigned long event, void *ptr)
 260 {
 261         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 262
 263         if (event == NETDEV_DOWN)
 264                 sel_netif_kill(dev_net(dev), dev->ifindex);
 265
 266         return NOTIFY_DONE;
 267 }
 268
 269 static struct notifier_block sel_netif_netdev_notifier = {
 270         .notifier_call = sel_netif_netdev_notifier_handler,
 271 };
 272
 273 static __init int sel_netif_init(void)
 274 {
 275         int i;
 276
 277         if (!selinux_enabled)
 278                 return 0;
 279
 280         for (i = 0; i < SEL_NETIF_HASH_SIZE; i++)
 281                 INIT_LIST_HEAD(&sel_netif_hash[i]);
 282
 283         register_netdevice_notifier(&sel_netif_netdev_notifier);
 284
 285         return 0;
 286 }
 287
 288 __initcall(sel_netif_init);
 289