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         /* we need to impose a limit on the growth of the hash table so check
 187          * this bucket to make sure it is within the specified bounds */
 188         list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
 189         if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
 190                 struct sel_netnode *tail;
 191                 tail = list_entry(
 192                         rcu_dereference(sel_netnode_hash[idx].list.prev),
 193                         struct sel_netnode, list);
 194                 list_del_rcu(&tail->list);
 195                 call_rcu(&tail->rcu, sel_netnode_free);
 196         } else
 197                 sel_netnode_hash[idx].size++;
 198 }
 199
 200 /**
 201  * sel_netnode_sid_slow - Lookup the SID of a network address using the policy
 202  * @addr: the IP address
 203  * @family: the address family
 204  * @sid: node SID
 205  *
 206  * Description:
 207  * This function determines the SID of a network address by quering the
 208  * security policy.  The result is added to the network address table to
 209  * speedup future queries.  Returns zero on success, negative values on
 210  * failure.
 211  *
 212  */
 213 static int sel_netnode_sid_slow(void *addr, u16 family, u32 *sid)
 214 {
 215         int ret = -ENOMEM;
 216         struct sel_netnode *node;
 217         struct sel_netnode *new = NULL;
 218
 219         spin_lock_bh(&sel_netnode_lock);
 220         node = sel_netnode_find(addr, family);
 221         if (node != NULL) {
 222                 *sid = node->nsec.sid;
 223                 spin_unlock_bh(&sel_netnode_lock);
 224                 return 0;
 225         }
 226         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 227         if (new == NULL)
 228                 goto out;
 229         switch (family) {
 230         case PF_INET:
 231                 ret = security_node_sid(PF_INET,
 232                                         addr, sizeof(struct in_addr), sid);
 233                 new->nsec.addr.ipv4 = *(__be32 *)addr;
 234                 break;
 235         case PF_INET6:
 236                 ret = security_node_sid(PF_INET6,
 237                                         addr, sizeof(struct in6_addr), sid);
 238                 ipv6_addr_copy(&new->nsec.addr.ipv6, addr);
 239                 break;
 240         default:
 241                 BUG();
 242         }
 243         if (ret != 0)
 244                 goto out;
 245
 246         new->nsec.family = family;
 247         new->nsec.sid = *sid;
 248         sel_netnode_insert(new);
 249
 250 out:
 251         spin_unlock_bh(&sel_netnode_lock);
 252         if (unlikely(ret)) {
 253                 printk(KERN_WARNING
 254                        "SELinux: failure in sel_netnode_sid_slow(),"
 255                        " unable to determine network node label\n");
 256                 kfree(new);
 257         }
 258         return ret;
 259 }
 260
 261 /**
 262  * sel_netnode_sid - Lookup the SID of a network address
 263  * @addr: the IP address
 264  * @family: the address family
 265  * @sid: node SID
 266  *
 267  * Description:
 268  * This function determines the SID of a network address using the fastest
 269  * method possible.  First the address table is queried, but if an entry
 270  * can't be found then the policy is queried and the result is added to the
 271  * table to speedup future queries.  Returns zero on success, negative values
 272  * on failure.
 273  *
 274  */
 275 int sel_netnode_sid(void *addr, u16 family, u32 *sid)
 276 {
 277         struct sel_netnode *node;
 278
 279         rcu_read_lock();
 280         node = sel_netnode_find(addr, family);
 281         if (node != NULL) {
 282                 *sid = node->nsec.sid;
 283                 rcu_read_unlock();
 284                 return 0;
 285         }
 286         rcu_read_unlock();
 287
 288         return sel_netnode_sid_slow(addr, family, sid);
 289 }
 290
 291 /**
 292  * sel_netnode_flush - Flush the entire network address table
 293  *
 294  * Description:
 295  * Remove all entries from the network address table.
 296  *
 297  */
 298 static void sel_netnode_flush(void)
 299 {
 300         unsigned int idx;
 301         struct sel_netnode *node, *node_tmp;
 302
 303         spin_lock_bh(&sel_netnode_lock);
 304         for (idx = 0; idx < SEL_NETNODE_HASH_SIZE; idx++) {
 305                 list_for_each_entry_safe(node, node_tmp,
 306                                          &sel_netnode_hash[idx].list, list) {
 307                                 list_del_rcu(&node->list);
 308                                 call_rcu(&node->rcu, sel_netnode_free);
 309                 }
 310                 sel_netnode_hash[idx].size = 0;
 311         }
 312         spin_unlock_bh(&sel_netnode_lock);
 313 }
 314
 315 static int sel_netnode_avc_callback(u32 event, u32 ssid, u32 tsid,
 316                                     u16 class, u32 perms, u32 *retained)
 317 {
 318         if (event == AVC_CALLBACK_RESET) {
 319                 sel_netnode_flush();
 320                 synchronize_net();
 321         }
 322         return 0;
 323 }
 324
 325 static __init int sel_netnode_init(void)
 326 {
 327         int iter;
 328         int ret;
 329
 330         if (!selinux_enabled)
 331                 return 0;
 332
 333         for (iter = 0; iter < SEL_NETNODE_HASH_SIZE; iter++) {
 334                 INIT_LIST_HEAD(&sel_netnode_hash[iter].list);
 335                 sel_netnode_hash[iter].size = 0;
 336         }
 337
 338         ret = avc_add_callback(sel_netnode_avc_callback, AVC_CALLBACK_RESET,
 339                                SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0);
 340         if (ret != 0)
 341                 panic("avc_add_callback() failed, error %d\n", ret);
 342
 343         return ret;
 344 }
 345
 346 __initcall(sel_netnode_init);