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/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_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 (unlikely(dev == NULL)) {
 161                 printk(KERN_WARNING
 162                        "SELinux: failure in sel_netif_sid_slow(),"
 163                        " invalid network interface (%d)\n", ifindex);
 164                 return -ENOENT;
 165         }
 166
 167         spin_lock_bh(&sel_netif_lock);
 168         netif = sel_netif_find(ifindex);
 169         if (netif != NULL) {
 170                 *sid = netif->nsec.sid;
 171                 ret = 0;
 172                 goto out;
 173         }
 174         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 175         if (new == NULL) {
 176                 ret = -ENOMEM;
 177                 goto out;
 178         }
 179         ret = security_netif_sid(dev->name, &new->nsec.sid);
 180         if (ret != 0)
 181                 goto out;
 182         new->nsec.ifindex = ifindex;
 183         ret = sel_netif_insert(new);
 184         if (ret != 0)
 185                 goto out;
 186         *sid = new->nsec.sid;
 187
 188 out:
 189         spin_unlock_bh(&sel_netif_lock);
 190         dev_put(dev);
 191         if (unlikely(ret)) {
 192                 printk(KERN_WARNING
 193                        "SELinux: failure in sel_netif_sid_slow(),"
 194                        " unable to determine network interface label (%d)\n",
 195                        ifindex);
 196                 kfree(new);
 197         }
 198         return ret;
 199 }
 200
 201 /**
 202  * sel_netif_sid - Lookup the SID of a network interface
 203  * @ifindex: the network interface
 204  * @sid: interface SID
 205  *
 206  * Description:
 207  * This function determines the SID of a network interface using the fastest
 208  * method possible.  First the interface table is queried, but if an entry
 209  * can't be found then the policy is queried and the result is added to the
 210  * table to speedup future queries.  Returns zero on success, negative values
 211  * on failure.
 212  *
 213  */
 214 int sel_netif_sid(int ifindex, u32 *sid)
 215 {
 216         struct sel_netif *netif;
 217
 218         rcu_read_lock();
 219         netif = sel_netif_find(ifindex);
 220         if (likely(netif != NULL)) {
 221                 *sid = netif->nsec.sid;
 222                 rcu_read_unlock();
 223                 return 0;
 224         }
 225         rcu_read_unlock();
 226
 227         return sel_netif_sid_slow(ifindex, sid);
 228 }
 229
 230 /**
 231  * sel_netif_kill - Remove an entry from the network interface table
 232  * @ifindex: the network interface
 233  *
 234  * Description:
 235  * This function removes the entry matching @ifindex from the network interface
 236  * table if it exists.
 237  *
 238  */
 239 static void sel_netif_kill(int ifindex)
 240 {
 241         struct sel_netif *netif;
 242
 243         rcu_read_lock();
 244         spin_lock_bh(&sel_netif_lock);
 245         netif = sel_netif_find(ifindex);
 246         if (netif)
 247                 sel_netif_destroy(netif);
 248         spin_unlock_bh(&sel_netif_lock);
 249         rcu_read_unlock();
 250 }
 251
 252 /**
 253  * sel_netif_flush - Flush the entire network interface table
 254  *
 255  * Description:
 256  * Remove all entries from the network interface table.
 257  *
 258  */
 259 static void sel_netif_flush(void)
 260 {
 261         int idx;
 262         struct sel_netif *netif;
 263
 264         spin_lock_bh(&sel_netif_lock);
 265         for (idx = 0; idx < SEL_NETIF_HASH_SIZE; idx++)
 266                 list_for_each_entry(netif, &sel_netif_hash[idx], list)
 267                         sel_netif_destroy(netif);
 268         spin_unlock_bh(&sel_netif_lock);
 269 }
 270
 271 static int sel_netif_avc_callback(u32 event, u32 ssid, u32 tsid,
 272                                   u16 class, u32 perms, u32 *retained)
 273 {
 274         if (event == AVC_CALLBACK_RESET) {
 275                 sel_netif_flush();
 276                 synchronize_net();
 277         }
 278         return 0;
 279 }
 280
 281 static int sel_netif_netdev_notifier_handler(struct notifier_block *this,
 282                                              unsigned long event, void *ptr)
 283 {
 284         struct net_device *dev = ptr;
 285
 286         if (dev_net(dev) != &init_net)
 287                 return NOTIFY_DONE;
 288
 289         if (event == NETDEV_DOWN)
 290                 sel_netif_kill(dev->ifindex);
 291
 292         return NOTIFY_DONE;
 293 }
 294
 295 static struct notifier_block sel_netif_netdev_notifier = {
 296         .notifier_call = sel_netif_netdev_notifier_handler,
 297 };
 298
 299 static __init int sel_netif_init(void)
 300 {
 301         int i, err;
 302
 303         if (!selinux_enabled)
 304                 return 0;
 305
 306         for (i = 0; i < SEL_NETIF_HASH_SIZE; i++)
 307                 INIT_LIST_HEAD(&sel_netif_hash[i]);
 308
 309         register_netdevice_notifier(&sel_netif_netdev_notifier);
 310
 311         err = avc_add_callback(sel_netif_avc_callback, AVC_CALLBACK_RESET,
 312                                SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0);
 313         if (err)
 314                 panic("avc_add_callback() failed, error %d\n", err);
 315
 316         return err;
 317 }
 318
 319 __initcall(sel_netif_init);
 320