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         struct list_head list;
  36         struct netif_security_struct nsec;
  37         struct rcu_head rcu_head;
  38 };
  39
  40 static u32 sel_netif_total;
  41 static LIST_HEAD(sel_netif_list);
  42 static DEFINE_SPINLOCK(sel_netif_lock);
  43 static struct list_head sel_netif_hash[SEL_NETIF_HASH_SIZE];
  44
  45 /**
  46  * sel_netif_hashfn - Hashing function for the interface table
  47  * @ifindex: the network interface
  48  *
  49  * Description:
  50  * This is the hashing function for the network interface table, it returns the
  51  * bucket number for the given interface.
  52  *
  53  */
  54 static inline u32 sel_netif_hashfn(int ifindex)
  55 {
  56         return (ifindex & (SEL_NETIF_HASH_SIZE - 1));
  57 }
  58
  59 /**
  60  * sel_netif_find - Search for an interface record
  61  * @ifindex: the network interface
  62  *
  63  * Description:
  64  * Search the network interface table and return the record matching @ifindex.
  65  * If an entry can not be found in the table return NULL.
  66  *
  67  */
  68 static inline struct sel_netif *sel_netif_find(int ifindex)
  69 {
  70         int idx = sel_netif_hashfn(ifindex);
  71         struct sel_netif *netif;
  72
  73         list_for_each_entry_rcu(netif, &sel_netif_hash[idx], list)
  74                 /* all of the devices should normally fit in the hash, so we
  75                  * optimize for that case */
  76                 if (likely(netif->nsec.ifindex == ifindex))
  77                         return netif;
  78
  79         return NULL;
  80 }
  81
  82 /**
  83  * sel_netif_insert - Insert a new interface into the table
  84  * @netif: the new interface record
  85  *
  86  * Description:
  87  * Add a new interface record to the network interface hash table.  Returns
  88  * zero on success, negative values on failure.
  89  *
  90  */
  91 static int sel_netif_insert(struct sel_netif *netif)
  92 {
  93         int idx;
  94
  95         if (sel_netif_total >= SEL_NETIF_HASH_MAX)
  96                 return -ENOSPC;
  97
  98         idx = sel_netif_hashfn(netif->nsec.ifindex);
  99         list_add_rcu(&netif->list, &sel_netif_hash[idx]);
 100         sel_netif_total++;
 101
 102         return 0;
 103 }
 104
 105 /**
 106  * sel_netif_free - Frees an interface entry
 107  * @p: the entry's RCU field
 108  *
 109  * Description:
 110  * This function is designed to be used as a callback to the call_rcu()
 111  * function so that memory allocated to a hash table interface entry can be
 112  * released safely.
 113  *
 114  */
 115 static void sel_netif_free(struct rcu_head *p)
 116 {
 117         struct sel_netif *netif = container_of(p, struct sel_netif, rcu_head);
 118         kfree(netif);
 119 }
 120
 121 /**
 122  * sel_netif_destroy - Remove an interface record from the table
 123  * @netif: the existing interface record
 124  *
 125  * Description:
 126  * Remove an existing interface record from the network interface table.
 127  *
 128  */
 129 static void sel_netif_destroy(struct sel_netif *netif)
 130 {
 131         list_del_rcu(&netif->list);
 132         sel_netif_total--;
 133         call_rcu(&netif->rcu_head, sel_netif_free);
 134 }
 135
 136 /**
 137  * sel_netif_sid_slow - Lookup the SID of a network interface using the policy
 138  * @ifindex: the network interface
 139  * @sid: interface SID
 140  *
 141  * Description:
 142  * This function determines the SID of a network interface by quering the
 143  * security policy.  The result is added to the network interface table to
 144  * speedup future queries.  Returns zero on success, negative values on
 145  * failure.
 146  *
 147  */
 148 static int sel_netif_sid_slow(int ifindex, u32 *sid)
 149 {
 150         int ret;
 151         struct sel_netif *netif;
 152         struct sel_netif *new = NULL;
 153         struct net_device *dev;
 154
 155         /* NOTE: we always use init's network namespace since we don't
 156          * currently support containers */
 157
 158         dev = dev_get_by_index(&init_net, ifindex);
 159         if (unlikely(dev == NULL)) {
 160                 printk(KERN_WARNING
 161                        "SELinux: failure in sel_netif_sid_slow(),"
 162                        " invalid network interface (%d)\n", ifindex);
 163                 return -ENOENT;
 164         }
 165
 166         spin_lock_bh(&sel_netif_lock);
 167         netif = sel_netif_find(ifindex);
 168         if (netif != NULL) {
 169                 *sid = netif->nsec.sid;
 170                 ret = 0;
 171                 goto out;
 172         }
 173         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 174         if (new == NULL) {
 175                 ret = -ENOMEM;
 176                 goto out;
 177         }
 178         ret = security_netif_sid(dev->name, &new->nsec.sid);
 179         if (ret != 0)
 180                 goto out;
 181         new->nsec.ifindex = ifindex;
 182         ret = sel_netif_insert(new);
 183         if (ret != 0)
 184                 goto out;
 185         *sid = new->nsec.sid;
 186
 187 out:
 188         spin_unlock_bh(&sel_netif_lock);
 189         dev_put(dev);
 190         if (unlikely(ret)) {
 191                 printk(KERN_WARNING
 192                        "SELinux: failure in sel_netif_sid_slow(),"
 193                        " unable to determine network interface label (%d)\n",
 194                        ifindex);
 195                 kfree(new);
 196         }
 197         return ret;
 198 }
 199
 200 /**
 201  * sel_netif_sid - Lookup the SID of a network interface
 202  * @ifindex: the network interface
 203  * @sid: interface SID
 204  *
 205  * Description:
 206  * This function determines the SID of a network interface using the fastest
 207  * method possible.  First the interface table is queried, but if an entry
 208  * can't be found then the policy is queried and the result is added to the
 209  * table to speedup future queries.  Returns zero on success, negative values
 210  * on failure.
 211  *
 212  */
 213 int sel_netif_sid(int ifindex, u32 *sid)
 214 {
 215         struct sel_netif *netif;
 216
 217         rcu_read_lock();
 218         netif = sel_netif_find(ifindex);
 219         if (likely(netif != NULL)) {
 220                 *sid = netif->nsec.sid;
 221                 rcu_read_unlock();
 222                 return 0;
 223         }
 224         rcu_read_unlock();
 225
 226         return sel_netif_sid_slow(ifindex, sid);
 227 }
 228
 229 /**
 230  * sel_netif_kill - Remove an entry from the network interface table
 231  * @ifindex: the network interface
 232  *
 233  * Description:
 234  * This function removes the entry matching @ifindex from the network interface
 235  * table if it exists.
 236  *
 237  */
 238 static void sel_netif_kill(int ifindex)
 239 {
 240         struct sel_netif *netif;
 241
 242         rcu_read_lock();
 243         spin_lock_bh(&sel_netif_lock);
 244         netif = sel_netif_find(ifindex);
 245         if (netif)
 246                 sel_netif_destroy(netif);
 247         spin_unlock_bh(&sel_netif_lock);
 248         rcu_read_unlock();
 249 }
 250
 251 /**
 252  * sel_netif_flush - Flush the entire network interface table
 253  *
 254  * Description:
 255  * Remove all entries from the network interface table.
 256  *
 257  */
 258 static void sel_netif_flush(void)
 259 {
 260         int idx;
 261         struct sel_netif *netif;
 262
 263         spin_lock_bh(&sel_netif_lock);
 264         for (idx = 0; idx < SEL_NETIF_HASH_SIZE; idx++)
 265                 list_for_each_entry(netif, &sel_netif_hash[idx], list)
 266                         sel_netif_destroy(netif);
 267         spin_unlock_bh(&sel_netif_lock);
 268 }
 269
 270 static int sel_netif_avc_callback(u32 event, u32 ssid, u32 tsid,
 271                                   u16 class, u32 perms, u32 *retained)
 272 {
 273         if (event == AVC_CALLBACK_RESET) {
 274                 sel_netif_flush();
 275                 synchronize_net();
 276         }
 277         return 0;
 278 }
 279
 280 static int sel_netif_netdev_notifier_handler(struct notifier_block *this,
 281                                              unsigned long event, void *ptr)
 282 {
 283         struct net_device *dev = ptr;
 284
 285         if (dev_net(dev) != &init_net)
 286                 return NOTIFY_DONE;
 287
 288         if (event == NETDEV_DOWN)
 289                 sel_netif_kill(dev->ifindex);
 290
 291         return NOTIFY_DONE;
 292 }
 293
 294 static struct notifier_block sel_netif_netdev_notifier = {
 295         .notifier_call = sel_netif_netdev_notifier_handler,
 296 };
 297
 298 static __init int sel_netif_init(void)
 299 {
 300         int i, err;
 301
 302         if (!selinux_enabled)
 303                 return 0;
 304
 305         for (i = 0; i < SEL_NETIF_HASH_SIZE; i++)
 306                 INIT_LIST_HEAD(&sel_netif_hash[i]);
 307
 308         register_netdevice_notifier(&sel_netif_netdev_notifier);
 309
 310         err = avc_add_callback(sel_netif_avc_callback, AVC_CALLBACK_RESET,
 311                                SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0);
 312         if (err)
 313                 panic("avc_add_callback() failed, error %d\n", err);
 314
 315         return err;
 316 }
 317
 318 __initcall(sel_netif_init);
 319