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@paul-moore.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_hashfn_ipv4 - IPv4 hashing function for the node table
  73  * @addr: IPv4 address
  74  *
  75  * Description:
  76  * This is the IPv4 hashing function for the node interface table, it returns
  77  * the bucket number for the given IP address.
  78  *
  79  */
  80 static unsigned int sel_netnode_hashfn_ipv4(__be32 addr)
  81 {
  82         /* at some point we should determine if the mismatch in byte order
  83          * affects the hash function dramatically */
  84         return (addr & (SEL_NETNODE_HASH_SIZE - 1));
  85 }
  86
  87 /**
  88  * sel_netnode_hashfn_ipv6 - IPv6 hashing function for the node table
  89  * @addr: IPv6 address
  90  *
  91  * Description:
  92  * This is the IPv6 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_ipv6(const struct in6_addr *addr)
  97 {
  98         /* just hash the least significant 32 bits to keep things fast (they
  99          * are the most likely to be different anyway), we can revisit this
 100          * later if needed */
 101         return (addr->s6_addr32[3] & (SEL_NETNODE_HASH_SIZE - 1));
 102 }
 103
 104 /**
 105  * sel_netnode_find - Search for a node record
 106  * @addr: IP address
 107  * @family: address family
 108  *
 109  * Description:
 110  * Search the network node table and return the record matching @addr.  If an
 111  * entry can not be found in the table return NULL.
 112  *
 113  */
 114 static struct sel_netnode *sel_netnode_find(const void *addr, u16 family)
 115 {
 116         unsigned int idx;
 117         struct sel_netnode *node;
 118
 119         switch (family) {
 120         case PF_INET:
 121                 idx = sel_netnode_hashfn_ipv4(*(__be32 *)addr);
 122                 break;
 123         case PF_INET6:
 124                 idx = sel_netnode_hashfn_ipv6(addr);
 125                 break;
 126         default:
 127                 BUG();
 128                 return NULL;
 129         }
 130
 131         list_for_each_entry_rcu(node, &sel_netnode_hash[idx].list, list)
 132                 if (node->nsec.family == family)
 133                         switch (family) {
 134                         case PF_INET:
 135                                 if (node->nsec.addr.ipv4 == *(__be32 *)addr)
 136                                         return node;
 137                                 break;
 138                         case PF_INET6:
 139                                 if (ipv6_addr_equal(&node->nsec.addr.ipv6,
 140                                                     addr))
 141                                         return node;
 142                                 break;
 143                         }
 144
 145         return NULL;
 146 }
 147
 148 /**
 149  * sel_netnode_insert - Insert a new node into the table
 150  * @node: the new node record
 151  *
 152  * Description:
 153  * Add a new node record to the network address hash table.
 154  *
 155  */
 156 static void sel_netnode_insert(struct sel_netnode *node)
 157 {
 158         unsigned int idx;
 159
 160         switch (node->nsec.family) {
 161         case PF_INET:
 162                 idx = sel_netnode_hashfn_ipv4(node->nsec.addr.ipv4);
 163                 break;
 164         case PF_INET6:
 165                 idx = sel_netnode_hashfn_ipv6(&node->nsec.addr.ipv6);
 166                 break;
 167         default:
 168                 BUG();
 169         }
 170
 171         /* we need to impose a limit on the growth of the hash table so check
 172          * this bucket to make sure it is within the specified bounds */
 173         list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
 174         if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
 175                 struct sel_netnode *tail;
 176                 tail = list_entry(
 177                         rcu_dereference(sel_netnode_hash[idx].list.prev),
 178                         struct sel_netnode, list);
 179                 list_del_rcu(&tail->list);
 180                 kfree_rcu(tail, rcu);
 181         } else
 182                 sel_netnode_hash[idx].size++;
 183 }
 184
 185 /**
 186  * sel_netnode_sid_slow - Lookup the SID of a network address using the policy
 187  * @addr: the IP address
 188  * @family: the address family
 189  * @sid: node SID
 190  *
 191  * Description:
 192  * This function determines the SID of a network address by quering the
 193  * security policy.  The result is added to the network address table to
 194  * speedup future queries.  Returns zero on success, negative values on
 195  * failure.
 196  *
 197  */
 198 static int sel_netnode_sid_slow(void *addr, u16 family, u32 *sid)
 199 {
 200         int ret = -ENOMEM;
 201         struct sel_netnode *node;
 202         struct sel_netnode *new = NULL;
 203
 204         spin_lock_bh(&sel_netnode_lock);
 205         node = sel_netnode_find(addr, family);
 206         if (node != NULL) {
 207                 *sid = node->nsec.sid;
 208                 spin_unlock_bh(&sel_netnode_lock);
 209                 return 0;
 210         }
 211         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 212         if (new == NULL)
 213                 goto out;
 214         switch (family) {
 215         case PF_INET:
 216                 ret = security_node_sid(PF_INET,
 217                                         addr, sizeof(struct in_addr), sid);
 218                 new->nsec.addr.ipv4 = *(__be32 *)addr;
 219                 break;
 220         case PF_INET6:
 221                 ret = security_node_sid(PF_INET6,
 222                                         addr, sizeof(struct in6_addr), sid);
 223                 ipv6_addr_copy(&new->nsec.addr.ipv6, addr);
 224                 break;
 225         default:
 226                 BUG();
 227         }
 228         if (ret != 0)
 229                 goto out;
 230
 231         new->nsec.family = family;
 232         new->nsec.sid = *sid;
 233         sel_netnode_insert(new);
 234
 235 out:
 236         spin_unlock_bh(&sel_netnode_lock);
 237         if (unlikely(ret)) {
 238                 printk(KERN_WARNING
 239                        "SELinux: failure in sel_netnode_sid_slow(),"
 240                        " unable to determine network node label\n");
 241                 kfree(new);
 242         }
 243         return ret;
 244 }
 245
 246 /**
 247  * sel_netnode_sid - Lookup the SID of a network address
 248  * @addr: the IP address
 249  * @family: the address family
 250  * @sid: node SID
 251  *
 252  * Description:
 253  * This function determines the SID of a network address using the fastest
 254  * method possible.  First the address table is queried, but if an entry
 255  * can't be found then the policy is queried and the result is added to the
 256  * table to speedup future queries.  Returns zero on success, negative values
 257  * on failure.
 258  *
 259  */
 260 int sel_netnode_sid(void *addr, u16 family, u32 *sid)
 261 {
 262         struct sel_netnode *node;
 263
 264         rcu_read_lock();
 265         node = sel_netnode_find(addr, family);
 266         if (node != NULL) {
 267                 *sid = node->nsec.sid;
 268                 rcu_read_unlock();
 269                 return 0;
 270         }
 271         rcu_read_unlock();
 272
 273         return sel_netnode_sid_slow(addr, family, sid);
 274 }
 275
 276 /**
 277  * sel_netnode_flush - Flush the entire network address table
 278  *
 279  * Description:
 280  * Remove all entries from the network address table.
 281  *
 282  */
 283 static void sel_netnode_flush(void)
 284 {
 285         unsigned int idx;
 286         struct sel_netnode *node, *node_tmp;
 287
 288         spin_lock_bh(&sel_netnode_lock);
 289         for (idx = 0; idx < SEL_NETNODE_HASH_SIZE; idx++) {
 290                 list_for_each_entry_safe(node, node_tmp,
 291                                          &sel_netnode_hash[idx].list, list) {
 292                                 list_del_rcu(&node->list);
 293                                 kfree_rcu(node, rcu);
 294                 }
 295                 sel_netnode_hash[idx].size = 0;
 296         }
 297         spin_unlock_bh(&sel_netnode_lock);
 298 }
 299
 300 static int sel_netnode_avc_callback(u32 event, u32 ssid, u32 tsid,
 301                                     u16 class, u32 perms, u32 *retained)
 302 {
 303         if (event == AVC_CALLBACK_RESET) {
 304                 sel_netnode_flush();
 305                 synchronize_net();
 306         }
 307         return 0;
 308 }
 309
 310 static __init int sel_netnode_init(void)
 311 {
 312         int iter;
 313         int ret;
 314
 315         if (!selinux_enabled)
 316                 return 0;
 317
 318         for (iter = 0; iter < SEL_NETNODE_HASH_SIZE; iter++) {
 319                 INIT_LIST_HEAD(&sel_netnode_hash[iter].list);
 320                 sel_netnode_hash[iter].size = 0;
 321         }
 322
 323         ret = avc_add_callback(sel_netnode_avc_callback, AVC_CALLBACK_RESET,
 324                                SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0);
 325         if (ret != 0)
 326                 panic("avc_add_callback() failed, error %d\n", ret);
 327
 328         return ret;
 329 }
 330
 331 __initcall(sel_netnode_init);