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