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  * @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_destroy - Remove an interface record from the table
 108  * @netif: the existing interface record
 109  *
 110  * Description:
 111  * Remove an existing interface record from the network interface table.
 112  *
 113  */
 114 static void sel_netif_destroy(struct sel_netif *netif)
 115 {
 116         list_del_rcu(&netif->list);
 117         sel_netif_total--;
 118         kfree_rcu(netif, rcu_head);
 119 }
 120
 121 /**
 122  * sel_netif_sid_slow - Lookup the SID of a network interface using the policy
 123  * @ifindex: the network interface
 124  * @sid: interface SID
 125  *
 126  * Description:
 127  * This function determines the SID of a network interface by quering the
 128  * security policy.  The result is added to the network interface table to
 129  * speedup future queries.  Returns zero on success, negative values on
 130  * failure.
 131  *
 132  */
 133 static int sel_netif_sid_slow(int ifindex, u32 *sid)
 134 {
 135         int ret;
 136         struct sel_netif *netif;
 137         struct sel_netif *new = NULL;
 138         struct net_device *dev;
 139
 140         /* NOTE: we always use init's network namespace since we don't
 141          * currently support containers */
 142
 143         dev = dev_get_by_index(&init_net, ifindex);
 144         if (unlikely(dev == NULL)) {
 145                 printk(KERN_WARNING
 146                        "SELinux: failure in sel_netif_sid_slow(),"
 147                        " invalid network interface (%d)\n", ifindex);
 148                 return -ENOENT;
 149         }
 150
 151         spin_lock_bh(&sel_netif_lock);
 152         netif = sel_netif_find(ifindex);
 153         if (netif != NULL) {
 154                 *sid = netif->nsec.sid;
 155                 ret = 0;
 156                 goto out;
 157         }
 158         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 159         if (new == NULL) {
 160                 ret = -ENOMEM;
 161                 goto out;
 162         }
 163         ret = security_netif_sid(dev->name, &new->nsec.sid);
 164         if (ret != 0)
 165                 goto out;
 166         new->nsec.ifindex = ifindex;
 167         ret = sel_netif_insert(new);
 168         if (ret != 0)
 169                 goto out;
 170         *sid = new->nsec.sid;
 171
 172 out:
 173         spin_unlock_bh(&sel_netif_lock);
 174         dev_put(dev);
 175         if (unlikely(ret)) {
 176                 printk(KERN_WARNING
 177                        "SELinux: failure in sel_netif_sid_slow(),"
 178                        " unable to determine network interface label (%d)\n",
 179                        ifindex);
 180                 kfree(new);
 181         }
 182         return ret;
 183 }
 184
 185 /**
 186  * sel_netif_sid - Lookup the SID of a network interface
 187  * @ifindex: the network interface
 188  * @sid: interface SID
 189  *
 190  * Description:
 191  * This function determines the SID of a network interface using the fastest
 192  * method possible.  First the interface table is queried, but if an entry
 193  * can't be found then the policy is queried and the result is added to the
 194  * table to speedup future queries.  Returns zero on success, negative values
 195  * on failure.
 196  *
 197  */
 198 int sel_netif_sid(int ifindex, u32 *sid)
 199 {
 200         struct sel_netif *netif;
 201
 202         rcu_read_lock();
 203         netif = sel_netif_find(ifindex);
 204         if (likely(netif != NULL)) {
 205                 *sid = netif->nsec.sid;
 206                 rcu_read_unlock();
 207                 return 0;
 208         }
 209         rcu_read_unlock();
 210
 211         return sel_netif_sid_slow(ifindex, sid);
 212 }
 213
 214 /**
 215  * sel_netif_kill - Remove an entry from the network interface table
 216  * @ifindex: the network interface
 217  *
 218  * Description:
 219  * This function removes the entry matching @ifindex from the network interface
 220  * table if it exists.
 221  *
 222  */
 223 static void sel_netif_kill(int ifindex)
 224 {
 225         struct sel_netif *netif;
 226
 227         rcu_read_lock();
 228         spin_lock_bh(&sel_netif_lock);
 229         netif = sel_netif_find(ifindex);
 230         if (netif)
 231                 sel_netif_destroy(netif);
 232         spin_unlock_bh(&sel_netif_lock);
 233         rcu_read_unlock();
 234 }
 235
 236 /**
 237  * sel_netif_flush - Flush the entire network interface table
 238  *
 239  * Description:
 240  * Remove all entries from the network interface table.
 241  *
 242  */
 243 static void sel_netif_flush(void)
 244 {
 245         int idx;
 246         struct sel_netif *netif;
 247
 248         spin_lock_bh(&sel_netif_lock);
 249         for (idx = 0; idx < SEL_NETIF_HASH_SIZE; idx++)
 250                 list_for_each_entry(netif, &sel_netif_hash[idx], list)
 251                         sel_netif_destroy(netif);
 252         spin_unlock_bh(&sel_netif_lock);
 253 }
 254
 255 static int sel_netif_avc_callback(u32 event)
 256 {
 257         if (event == AVC_CALLBACK_RESET) {
 258                 sel_netif_flush();
 259                 synchronize_net();
 260         }
 261         return 0;
 262 }
 263
 264 static int sel_netif_netdev_notifier_handler(struct notifier_block *this,
 265                                              unsigned long event, void *ptr)
 266 {
 267         struct net_device *dev = ptr;
 268
 269         if (dev_net(dev) != &init_net)
 270                 return NOTIFY_DONE;
 271
 272         if (event == NETDEV_DOWN)
 273                 sel_netif_kill(dev->ifindex);
 274
 275         return NOTIFY_DONE;
 276 }
 277
 278 static struct notifier_block sel_netif_netdev_notifier = {
 279         .notifier_call = sel_netif_netdev_notifier_handler,
 280 };
 281
 282 static __init int sel_netif_init(void)
 283 {
 284         int i, err;
 285
 286         if (!selinux_enabled)
 287                 return 0;
 288
 289         for (i = 0; i < SEL_NETIF_HASH_SIZE; i++)
 290                 INIT_LIST_HEAD(&sel_netif_hash[i]);
 291
 292         register_netdevice_notifier(&sel_netif_netdev_notifier);
 293
 294         err = avc_add_callback(sel_netif_avc_callback, AVC_CALLBACK_RESET);
 295         if (err)
 296                 panic("avc_add_callback() failed, error %d\n", err);
 297
 298         return err;
 299 }
 300
 301 __initcall(sel_netif_init);
 302