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.moore@hp.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/stddef.h>
  20 #include <linux/kernel.h>
  21 #include <linux/list.h>
  22 #include <linux/notifier.h>
  23 #include <linux/netdevice.h>
  24 #include <linux/rcupdate.h>
  25 #include <net/net_namespace.h>
  26
  27 #include "security.h"
  28 #include "objsec.h"
  29 #include "netif.h"
  30
  31 #define SEL_NETIF_HASH_SIZE     64
  32 #define SEL_NETIF_HASH_MAX      1024
  33
  34 struct sel_netif
  35 {
  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  * @ifindex: the network interface
  49  *
  50  * Description:
  51  * This is the hashing function for the network interface table, it returns the
  52  * bucket number for the given interface.
  53  *
  54  */
  55 static inline u32 sel_netif_hashfn(int ifindex)
  56 {
  57         return (ifindex & (SEL_NETIF_HASH_SIZE - 1));
  58 }
  59
  60 /**
  61  * sel_netif_find - Search for an interface record
  62  * @ifindex: the network interface
  63  *
  64  * Description:
  65  * Search the network interface table and return the record matching @ifindex.
  66  * If an entry can not be found in the table return NULL.
  67  *
  68  */
  69 static inline struct sel_netif *sel_netif_find(int ifindex)
  70 {
  71         int idx = sel_netif_hashfn(ifindex);
  72         struct sel_netif *netif;
  73
  74         list_for_each_entry_rcu(netif, &sel_netif_hash[idx], list)
  75                 /* all of the devices should normally fit in the hash, so we
  76                  * optimize for that case */
  77                 if (likely(netif->nsec.ifindex == ifindex))
  78                         return netif;
  79
  80         return NULL;
  81 }
  82
  83 /**
  84  * sel_netif_insert - Insert a new interface into the table
  85  * @netif: the new interface record
  86  *
  87  * Description:
  88  * Add a new interface record to the network interface hash table.  Returns
  89  * zero on success, negative values on failure.
  90  *
  91  */
  92 static int sel_netif_insert(struct sel_netif *netif)
  93 {
  94         int idx;
  95
  96         if (sel_netif_total >= SEL_NETIF_HASH_MAX)
  97                 return -ENOSPC;
  98
  99         idx = sel_netif_hashfn(netif->nsec.ifindex);
 100         list_add_rcu(&netif->list, &sel_netif_hash[idx]);
 101         sel_netif_total++;
 102
 103         return 0;
 104 }
 105
 106 /**
 107  * sel_netif_free - Frees an interface entry
 108  * @p: the entry's RCU field
 109  *
 110  * Description:
 111  * This function is designed to be used as a callback to the call_rcu()
 112  * function so that memory allocated to a hash table interface entry can be
 113  * released safely.
 114  *
 115  */
 116 static void sel_netif_free(struct rcu_head *p)
 117 {
 118         struct sel_netif *netif = container_of(p, struct sel_netif, rcu_head);
 119         kfree(netif);
 120 }
 121
 122 /**
 123  * sel_netif_destroy - Remove an interface record from the table
 124  * @netif: the existing interface record
 125  *
 126  * Description:
 127  * Remove an existing interface record from the network interface table.
 128  *
 129  */
 130 static void sel_netif_destroy(struct sel_netif *netif)
 131 {
 132         list_del_rcu(&netif->list);
 133         sel_netif_total--;
 134         call_rcu(&netif->rcu_head, sel_netif_free);
 135 }
 136
 137 /**
 138  * sel_netif_sid_slow - Lookup the SID of a network interface using the policy
 139  * @ifindex: the network interface
 140  * @sid: interface SID
 141  *
 142  * Description:
 143  * This function determines the SID of a network interface by quering the
 144  * security policy.  The result is added to the network interface table to
 145  * speedup future queries.  Returns zero on success, negative values on
 146  * failure.
 147  *
 148  */
 149 static int sel_netif_sid_slow(int ifindex, u32 *sid)
 150 {
 151         int ret;
 152         struct sel_netif *netif;
 153         struct sel_netif *new = NULL;
 154         struct net_device *dev;
 155
 156         /* NOTE: we always use init's network namespace since we don't
 157          * currently support containers */
 158
 159         dev = dev_get_by_index(&init_net, ifindex);
 160         if (dev == NULL)
 161                 return -ENOENT;
 162
 163         spin_lock_bh(&sel_netif_lock);
 164         netif = sel_netif_find(ifindex);
 165         if (netif != NULL) {
 166                 *sid = netif->nsec.sid;
 167                 ret = 0;
 168                 goto out;
 169         }
 170         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 171         if (new == NULL) {
 172                 ret = -ENOMEM;
 173                 goto out;
 174         }
 175         ret = security_netif_sid(dev->name, &new->nsec.sid);
 176         if (ret != 0)
 177                 goto out;
 178         new->nsec.ifindex = ifindex;
 179         ret = sel_netif_insert(new);
 180         if (ret != 0)
 181                 goto out;
 182         *sid = new->nsec.sid;
 183
 184 out:
 185         spin_unlock_bh(&sel_netif_lock);
 186         dev_put(dev);
 187         if (ret != 0)
 188                 kfree(new);
 189         return ret;
 190 }
 191
 192 /**
 193  * sel_netif_sid - Lookup the SID of a network interface
 194  * @ifindex: the network interface
 195  * @sid: interface SID
 196  *
 197  * Description:
 198  * This function determines the SID of a network interface using the fastest
 199  * method possible.  First the interface table is queried, but if an entry
 200  * can't be found then the policy is queried and the result is added to the
 201  * table to speedup future queries.  Returns zero on success, negative values
 202  * on failure.
 203  *
 204  */
 205 int sel_netif_sid(int ifindex, u32 *sid)
 206 {
 207         struct sel_netif *netif;
 208
 209         rcu_read_lock();
 210         netif = sel_netif_find(ifindex);
 211         if (likely(netif != NULL)) {
 212                 *sid = netif->nsec.sid;
 213                 rcu_read_unlock();
 214                 return 0;
 215         }
 216         rcu_read_unlock();
 217
 218         return sel_netif_sid_slow(ifindex, sid);
 219 }
 220
 221 /**
 222  * sel_netif_kill - Remove an entry from the network interface table
 223  * @ifindex: the network interface
 224  *
 225  * Description:
 226  * This function removes the entry matching @ifindex from the network interface
 227  * table if it exists.
 228  *
 229  */
 230 static void sel_netif_kill(int ifindex)
 231 {
 232         struct sel_netif *netif;
 233
 234         spin_lock_bh(&sel_netif_lock);
 235         netif = sel_netif_find(ifindex);
 236         if (netif)
 237                 sel_netif_destroy(netif);
 238         spin_unlock_bh(&sel_netif_lock);
 239 }
 240
 241 /**
 242  * sel_netif_flush - Flush the entire network interface table
 243  *
 244  * Description:
 245  * Remove all entries from the network interface table.
 246  *
 247  */
 248 static void sel_netif_flush(void)
 249 {
 250         int idx;
 251         struct sel_netif *netif;
 252
 253         spin_lock_bh(&sel_netif_lock);
 254         for (idx = 0; idx < SEL_NETIF_HASH_SIZE; idx++)
 255                 list_for_each_entry(netif, &sel_netif_hash[idx], list)
 256                         sel_netif_destroy(netif);
 257         spin_unlock_bh(&sel_netif_lock);
 258 }
 259
 260 static int sel_netif_avc_callback(u32 event, u32 ssid, u32 tsid,
 261                                   u16 class, u32 perms, u32 *retained)
 262 {
 263         if (event == AVC_CALLBACK_RESET) {
 264                 sel_netif_flush();
 265                 synchronize_net();
 266         }
 267         return 0;
 268 }
 269
 270 static int sel_netif_netdev_notifier_handler(struct notifier_block *this,
 271                                              unsigned long event, void *ptr)
 272 {
 273         struct net_device *dev = ptr;
 274
 275         if (dev->nd_net != &init_net)
 276                 return NOTIFY_DONE;
 277
 278         if (event == NETDEV_DOWN)
 279                 sel_netif_kill(dev->ifindex);
 280
 281         return NOTIFY_DONE;
 282 }
 283
 284 static struct notifier_block sel_netif_netdev_notifier = {
 285         .notifier_call = sel_netif_netdev_notifier_handler,
 286 };
 287
 288 static __init int sel_netif_init(void)
 289 {
 290         int i, err;
 291
 292         if (!selinux_enabled)
 293                 return 0;
 294
 295         for (i = 0; i < SEL_NETIF_HASH_SIZE; i++)
 296                 INIT_LIST_HEAD(&sel_netif_hash[i]);
 297
 298         register_netdevice_notifier(&sel_netif_netdev_notifier);
 299
 300         err = avc_add_callback(sel_netif_avc_callback, AVC_CALLBACK_RESET,
 301                                SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0);
 302         if (err)
 303                 panic("avc_add_callback() failed, error %d\n", err);
 304
 305         return err;
 306 }
 307
 308 __initcall(sel_netif_init);
 309