security/selinux/netnode.c

   1 /*
   2  * Network node table
   3  *
   4  * SELinux must keep a mapping of network nodes to labels/SIDs.  This
   5  * mapping is maintained as part of the normal policy but a fast cache is
   6  * needed to reduce the lookup overhead since most of these queries happen on
   7  * a per-packet basis.
   8  *
   9  * Author: Paul Moore <paul.moore@hp.com>
  10  *
  11  * This code is heavily based on the "netif" concept originally developed by
  12  * James Morris <jmorris@redhat.com>
  13  *   (see security/selinux/netif.c for more information)
  14  *
  15  */
  16
  17 /*
  18  * (c) Copyright Hewlett-Packard Development Company, L.P., 2007
  19  *
  20  * This program is free software: you can redistribute it and/or modify
  21  * it under the terms of version 2 of the GNU General Public License as
  22  * published by the Free Software Foundation.
  23  *
  24  * This program is distributed in the hope that it will be useful,
  25  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  26  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  27  * GNU General Public License for more details.
  28  *
  29  */
  30
  31 #include <linux/types.h>
  32 #include <linux/rcupdate.h>
  33 #include <linux/list.h>
  34 #include <linux/slab.h>
  35 #include <linux/spinlock.h>
  36 #include <linux/in.h>
  37 #include <linux/in6.h>
  38 #include <linux/ip.h>
  39 #include <linux/ipv6.h>
  40 #include <net/ip.h>
  41 #include <net/ipv6.h>
  42
  43 #include "netnode.h"
  44 #include "objsec.h"
  45
  46 #define SEL_NETNODE_HASH_SIZE       256
  47 #define SEL_NETNODE_HASH_BKT_LIMIT   16
  48
  49 struct sel_netnode_bkt {
  50         unsigned int size;
  51         struct list_head list;
  52 };
  53
  54 struct sel_netnode {
  55         struct netnode_security_struct nsec;
  56
  57         struct list_head list;
  58         struct rcu_head rcu;
  59 };
  60
  61 /* NOTE: we are using a combined hash table for both IPv4 and IPv6, the reason
  62  * for this is that I suspect most users will not make heavy use of both
  63  * address families at the same time so one table will usually end up wasted,
  64  * if this becomes a problem we can always add a hash table for each address
  65  * family later */
  66
  67 static LIST_HEAD(sel_netnode_list);
  68 static DEFINE_SPINLOCK(sel_netnode_lock);
  69 static struct sel_netnode_bkt sel_netnode_hash[SEL_NETNODE_HASH_SIZE];
  70
  71 /**
  72  * sel_netnode_free - Frees a node entry
  73  * @p: the entry's RCU field
  74  *
  75  * Description:
  76  * This function is designed to be used as a callback to the call_rcu()
  77  * function so that memory allocated to a hash table node entry can be
  78  * released safely.
  79  *
  80  */
  81 static void sel_netnode_free(struct rcu_head *p)
  82 {
  83         struct sel_netnode *node = container_of(p, struct sel_netnode, rcu);
  84         kfree(node);
  85 }
  86
  87 /**
  88  * sel_netnode_hashfn_ipv4 - IPv4 hashing function for the node table
  89  * @addr: IPv4 address
  90  *
  91  * Description:
  92  * This is the IPv4 hashing function for the node interface table, it returns
  93  * the bucket number for the given IP address.
  94  *
  95  */
  96 static unsigned int sel_netnode_hashfn_ipv4(__be32 addr)
  97 {
  98         /* at some point we should determine if the mismatch in byte order
  99          * affects the hash function dramatically */
 100         return (addr & (SEL_NETNODE_HASH_SIZE - 1));
 101 }
 102
 103 /**
 104  * sel_netnode_hashfn_ipv6 - IPv6 hashing function for the node table
 105  * @addr: IPv6 address
 106  *
 107  * Description:
 108  * This is the IPv6 hashing function for the node interface table, it returns
 109  * the bucket number for the given IP address.
 110  *
 111  */
 112 static unsigned int sel_netnode_hashfn_ipv6(const struct in6_addr *addr)
 113 {
 114         /* just hash the least significant 32 bits to keep things fast (they
 115          * are the most likely to be different anyway), we can revisit this
 116          * later if needed */
 117         return (addr->s6_addr32[3] & (SEL_NETNODE_HASH_SIZE - 1));
 118 }
 119
 120 /**
 121  * sel_netnode_find - Search for a node record
 122  * @addr: IP address
 123  * @family: address family
 124  *
 125  * Description:
 126  * Search the network node table and return the record matching @addr.  If an
 127  * entry can not be found in the table return NULL.
 128  *
 129  */
 130 static struct sel_netnode *sel_netnode_find(const void *addr, u16 family)
 131 {
 132         unsigned int idx;
 133         struct sel_netnode *node;
 134
 135         switch (family) {
 136         case PF_INET:
 137                 idx = sel_netnode_hashfn_ipv4(*(__be32 *)addr);
 138                 break;
 139         case PF_INET6:
 140                 idx = sel_netnode_hashfn_ipv6(addr);
 141                 break;
 142         default:
 143                 BUG();
 144         }
 145
 146         list_for_each_entry_rcu(node, &sel_netnode_hash[idx].list, list)
 147                 if (node->nsec.family == family)
 148                         switch (family) {
 149                         case PF_INET:
 150                                 if (node->nsec.addr.ipv4 == *(__be32 *)addr)
 151                                         return node;
 152                                 break;
 153                         case PF_INET6:
 154                                 if (ipv6_addr_equal(&node->nsec.addr.ipv6,
 155                                                     addr))
 156                                         return node;
 157                                 break;
 158                         }
 159
 160         return NULL;
 161 }
 162
 163 /**
 164  * sel_netnode_insert - Insert a new node into the table
 165  * @node: the new node record
 166  *
 167  * Description:
 168  * Add a new node record to the network address hash table.
 169  *
 170  */
 171 static void sel_netnode_insert(struct sel_netnode *node)
 172 {
 173         unsigned int idx;
 174
 175         switch (node->nsec.family) {
 176         case PF_INET:
 177                 idx = sel_netnode_hashfn_ipv4(node->nsec.addr.ipv4);
 178                 break;
 179         case PF_INET6:
 180                 idx = sel_netnode_hashfn_ipv6(&node->nsec.addr.ipv6);
 181                 break;
 182         default:
 183                 BUG();
 184         }
 185
 186         INIT_RCU_HEAD(&node->rcu);
 187
 188         /* we need to impose a limit on the growth of the hash table so check
 189          * this bucket to make sure it is within the specified bounds */
 190         list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
 191         if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
 192                 struct sel_netnode *tail;
 193                 tail = list_entry(
 194                         rcu_dereference(sel_netnode_hash[idx].list.prev),
 195                         struct sel_netnode, list);
 196                 list_del_rcu(&tail->list);
 197                 call_rcu(&tail->rcu, sel_netnode_free);
 198         } else
 199                 sel_netnode_hash[idx].size++;
 200 }
 201
 202 /**
 203  * sel_netnode_sid_slow - Lookup the SID of a network address using the policy
 204  * @addr: the IP address
 205  * @family: the address family
 206  * @sid: node SID
 207  *
 208  * Description:
 209  * This function determines the SID of a network address by quering the
 210  * security policy.  The result is added to the network address table to
 211  * speedup future queries.  Returns zero on success, negative values on
 212  * failure.
 213  *
 214  */
 215 static int sel_netnode_sid_slow(void *addr, u16 family, u32 *sid)
 216 {
 217         int ret = -ENOMEM;
 218         struct sel_netnode *node;
 219         struct sel_netnode *new = NULL;
 220
 221         spin_lock_bh(&sel_netnode_lock);
 222         node = sel_netnode_find(addr, family);
 223         if (node != NULL) {
 224                 *sid = node->nsec.sid;
 225                 spin_unlock_bh(&sel_netnode_lock);
 226                 return 0;
 227         }
 228         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 229         if (new == NULL)
 230                 goto out;
 231         switch (family) {
 232         case PF_INET:
 233                 ret = security_node_sid(PF_INET,
 234                                         addr, sizeof(struct in_addr), sid);
 235                 new->nsec.addr.ipv4 = *(__be32 *)addr;
 236                 break;
 237         case PF_INET6:
 238                 ret = security_node_sid(PF_INET6,
 239                                         addr, sizeof(struct in6_addr), sid);
 240                 ipv6_addr_copy(&new->nsec.addr.ipv6, addr);
 241                 break;
 242         default:
 243                 BUG();
 244         }
 245         if (ret != 0)
 246                 goto out;
 247
 248         new->nsec.family = family;
 249         new->nsec.sid = *sid;
 250         sel_netnode_insert(new);
 251
 252 out:
 253         spin_unlock_bh(&sel_netnode_lock);
 254         if (unlikely(ret)) {
 255                 printk(KERN_WARNING
 256                        "SELinux: failure in sel_netnode_sid_slow(),"
 257                        " unable to determine network node label\n");
 258                 kfree(new);
 259         }
 260         return ret;
 261 }
 262
 263 /**
 264  * sel_netnode_sid - Lookup the SID of a network address
 265  * @addr: the IP address
 266  * @family: the address family
 267  * @sid: node SID
 268  *
 269  * Description:
 270  * This function determines the SID of a network address using the fastest
 271  * method possible.  First the address table is queried, but if an entry
 272  * can't be found then the policy is queried and the result is added to the
 273  * table to speedup future queries.  Returns zero on success, negative values
 274  * on failure.
 275  *
 276  */
 277 int sel_netnode_sid(void *addr, u16 family, u32 *sid)
 278 {
 279         struct sel_netnode *node;
 280
 281         rcu_read_lock();
 282         node = sel_netnode_find(addr, family);
 283         if (node != NULL) {
 284                 *sid = node->nsec.sid;
 285                 rcu_read_unlock();
 286                 return 0;
 287         }
 288         rcu_read_unlock();
 289
 290         return sel_netnode_sid_slow(addr, family, sid);
 291 }
 292
 293 /**
 294  * sel_netnode_flush - Flush the entire network address table
 295  *
 296  * Description:
 297  * Remove all entries from the network address table.
 298  *
 299  */
 300 static void sel_netnode_flush(void)
 301 {
 302         unsigned int idx;
 303         struct sel_netnode *node, *node_tmp;
 304
 305         spin_lock_bh(&sel_netnode_lock);
 306         for (idx = 0; idx < SEL_NETNODE_HASH_SIZE; idx++) {
 307                 list_for_each_entry_safe(node, node_tmp,
 308                                          &sel_netnode_hash[idx].list, list) {
 309                                 list_del_rcu(&node->list);
 310                                 call_rcu(&node->rcu, sel_netnode_free);
 311                 }
 312                 sel_netnode_hash[idx].size = 0;
 313         }
 314         spin_unlock_bh(&sel_netnode_lock);
 315 }
 316
 317 static int sel_netnode_avc_callback(u32 event, u32 ssid, u32 tsid,
 318                                     u16 class, u32 perms, u32 *retained)
 319 {
 320         if (event == AVC_CALLBACK_RESET) {
 321                 sel_netnode_flush();
 322                 synchronize_net();
 323         }
 324         return 0;
 325 }
 326
 327 static __init int sel_netnode_init(void)
 328 {
 329         int iter;
 330         int ret;
 331
 332         if (!selinux_enabled)
 333                 return 0;
 334
 335         for (iter = 0; iter < SEL_NETNODE_HASH_SIZE; iter++) {
 336                 INIT_LIST_HEAD(&sel_netnode_hash[iter].list);
 337                 sel_netnode_hash[iter].size = 0;
 338         }
 339
 340         ret = avc_add_callback(sel_netnode_avc_callback, AVC_CALLBACK_RESET,
 341                                SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0);
 342         if (ret != 0)
 343                 panic("avc_add_callback() failed, error %d\n", ret);
 344
 345         return ret;
 346 }
 347
 348 __initcall(sel_netnode_init);