security/selinux/netif.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Network interface table.
   4  *
   5  * Network interfaces (devices) do not have a security field, so we
   6  * maintain a table associating each interface with a SID.
   7  *
   8  * Author: James Morris <jmorris@redhat.com>
   9  *
  10  * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
  11  * Copyright (C) 2007 Hewlett-Packard Development Company, L.P.
  12  *                    Paul Moore <paul@paul-moore.com>
  13  */
  14 #include <linux/init.h>
  15 #include <linux/types.h>
  16 #include <linux/slab.h>
  17 #include <linux/stddef.h>
  18 #include <linux/kernel.h>
  19 #include <linux/list.h>
  20 #include <linux/notifier.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/rcupdate.h>
  23 #include <net/net_namespace.h>
  24
  25 #include "security.h"
  26 #include "objsec.h"
  27 #include "netif.h"
  28
  29 #define SEL_NETIF_HASH_SIZE     64
  30 #define SEL_NETIF_HASH_MAX      1024
  31
  32 struct sel_netif {
  33         struct list_head list;
  34         struct netif_security_struct nsec;
  35         struct rcu_head rcu_head;
  36 };
  37
  38 static u32 sel_netif_total;
  39 static LIST_HEAD(sel_netif_list);
  40 static DEFINE_SPINLOCK(sel_netif_lock);
  41 static struct list_head sel_netif_hash[SEL_NETIF_HASH_SIZE];
  42
  43 /**
  44  * sel_netif_hashfn - Hashing function for the interface table
  45  * @ns: the network namespace
  46  * @ifindex: the network interface
  47  *
  48  * Description:
  49  * This is the hashing function for the network interface table, it returns the
  50  * bucket number for the given interface.
  51  *
  52  */
  53 static inline u32 sel_netif_hashfn(const struct net *ns, int ifindex)
  54 {
  55         return (((uintptr_t)ns + ifindex) & (SEL_NETIF_HASH_SIZE - 1));
  56 }
  57
  58 /**
  59  * sel_netif_find - Search for an interface record
  60  * @ns: the network namespace
  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(const struct net *ns,
  69                                                int ifindex)
  70 {
  71         int idx = sel_netif_hashfn(ns, ifindex);
  72         struct sel_netif *netif;
  73
  74         list_for_each_entry_rcu(netif, &sel_netif_hash[idx], list)
  75                 if (net_eq(netif->nsec.ns, ns) &&
  76                     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.ns, 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_destroy - Remove an interface record from the table
 107  * @netif: the existing interface record
 108  *
 109  * Description:
 110  * Remove an existing interface record from the network interface table.
 111  *
 112  */
 113 static void sel_netif_destroy(struct sel_netif *netif)
 114 {
 115         list_del_rcu(&netif->list);
 116         sel_netif_total--;
 117         kfree_rcu(netif, rcu_head);
 118 }
 119
 120 /**
 121  * sel_netif_sid_slow - Lookup the SID of a network interface using the policy
 122  * @ns: the network namespace
 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(struct net *ns, 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(ns, ifindex);
 144         if (unlikely(dev == NULL)) {
 145                 pr_warn("SELinux: failure in %s(), invalid network interface (%d)\n",
 146                         __func__, ifindex);
 147                 return -ENOENT;
 148         }
 149
 150         spin_lock_bh(&sel_netif_lock);
 151         netif = sel_netif_find(ns, ifindex);
 152         if (netif != NULL) {
 153                 *sid = netif->nsec.sid;
 154                 ret = 0;
 155                 goto out;
 156         }
 157         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 158         if (new == NULL) {
 159                 ret = -ENOMEM;
 160                 goto out;
 161         }
 162         ret = security_netif_sid(&selinux_state, dev->name, &new->nsec.sid);
 163         if (ret != 0)
 164                 goto out;
 165         new->nsec.ns = ns;
 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                 pr_warn("SELinux: failure in %s(), unable to determine network interface label (%d)\n",
 177                         __func__, ifindex);
 178                 kfree(new);
 179         }
 180         return ret;
 181 }
 182
 183 /**
 184  * sel_netif_sid - Lookup the SID of a network interface
 185  * @ns: the network namespace
 186  * @ifindex: the network interface
 187  * @sid: interface SID
 188  *
 189  * Description:
 190  * This function determines the SID of a network interface using the fastest
 191  * method possible.  First the interface table is queried, but if an entry
 192  * can't be found then the policy is queried and the result is added to the
 193  * table to speedup future queries.  Returns zero on success, negative values
 194  * on failure.
 195  *
 196  */
 197 int sel_netif_sid(struct net *ns, int ifindex, u32 *sid)
 198 {
 199         struct sel_netif *netif;
 200
 201         rcu_read_lock();
 202         netif = sel_netif_find(ns, ifindex);
 203         if (likely(netif != NULL)) {
 204                 *sid = netif->nsec.sid;
 205                 rcu_read_unlock();
 206                 return 0;
 207         }
 208         rcu_read_unlock();
 209
 210         return sel_netif_sid_slow(ns, ifindex, sid);
 211 }
 212
 213 /**
 214  * sel_netif_kill - Remove an entry from the network interface table
 215  * @ns: the network namespace
 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(const struct net *ns, 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(ns, 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 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_netdev_notifier_handler(struct notifier_block *this,
 256                                              unsigned long event, void *ptr)
 257 {
 258         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 259
 260         if (event == NETDEV_DOWN)
 261                 sel_netif_kill(dev_net(dev), dev->ifindex);
 262
 263         return NOTIFY_DONE;
 264 }
 265
 266 static struct notifier_block sel_netif_netdev_notifier = {
 267         .notifier_call = sel_netif_netdev_notifier_handler,
 268 };
 269
 270 static __init int sel_netif_init(void)
 271 {
 272         int i;
 273
 274         if (!selinux_enabled)
 275                 return 0;
 276
 277         for (i = 0; i < SEL_NETIF_HASH_SIZE; i++)
 278                 INIT_LIST_HEAD(&sel_netif_hash[i]);
 279
 280         register_netdevice_notifier(&sel_netif_netdev_notifier);
 281
 282         return 0;
 283 }
 284
 285 __initcall(sel_netif_init);
 286