security/selinux/netnode.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Network node table
   4  *
   5  * SELinux must keep a mapping of network nodes to labels/SIDs.  This
   6  * mapping is maintained as part of the normal policy but a fast cache is
   7  * needed to reduce the lookup overhead since most of these queries happen on
   8  * a per-packet basis.
   9  *
  10  * Author: Paul Moore <paul@paul-moore.com>
  11  *
  12  * This code is heavily based on the "netif" concept originally developed by
  13  * James Morris <jmorris@redhat.com>
  14  *   (see security/selinux/netif.c for more information)
  15  */
  16
  17 /*
  18  * (c) Copyright Hewlett-Packard Development Company, L.P., 2007
  19  */
  20
  21 #include <linux/types.h>
  22 #include <linux/rcupdate.h>
  23 #include <linux/list.h>
  24 #include <linux/slab.h>
  25 #include <linux/spinlock.h>
  26 #include <linux/in.h>
  27 #include <linux/in6.h>
  28 #include <linux/ip.h>
  29 #include <linux/ipv6.h>
  30 #include <net/ip.h>
  31 #include <net/ipv6.h>
  32
  33 #include "netnode.h"
  34 #include "objsec.h"
  35
  36 #define SEL_NETNODE_HASH_SIZE       256
  37 #define SEL_NETNODE_HASH_BKT_LIMIT   16
  38
  39 struct sel_netnode_bkt {
  40         unsigned int size;
  41         struct list_head list;
  42 };
  43
  44 struct sel_netnode {
  45         struct netnode_security_struct nsec;
  46
  47         struct list_head list;
  48         struct rcu_head rcu;
  49 };
  50
  51 /* NOTE: we are using a combined hash table for both IPv4 and IPv6, the reason
  52  * for this is that I suspect most users will not make heavy use of both
  53  * address families at the same time so one table will usually end up wasted,
  54  * if this becomes a problem we can always add a hash table for each address
  55  * family later */
  56
  57 static LIST_HEAD(sel_netnode_list);
  58 static DEFINE_SPINLOCK(sel_netnode_lock);
  59 static struct sel_netnode_bkt sel_netnode_hash[SEL_NETNODE_HASH_SIZE];
  60
  61 /**
  62  * sel_netnode_hashfn_ipv4 - IPv4 hashing function for the node table
  63  * @addr: IPv4 address
  64  *
  65  * Description:
  66  * This is the IPv4 hashing function for the node interface table, it returns
  67  * the bucket number for the given IP address.
  68  *
  69  */
  70 static unsigned int sel_netnode_hashfn_ipv4(__be32 addr)
  71 {
  72         /* at some point we should determine if the mismatch in byte order
  73          * affects the hash function dramatically */
  74         return (addr & (SEL_NETNODE_HASH_SIZE - 1));
  75 }
  76
  77 /**
  78  * sel_netnode_hashfn_ipv6 - IPv6 hashing function for the node table
  79  * @addr: IPv6 address
  80  *
  81  * Description:
  82  * This is the IPv6 hashing function for the node interface table, it returns
  83  * the bucket number for the given IP address.
  84  *
  85  */
  86 static unsigned int sel_netnode_hashfn_ipv6(const struct in6_addr *addr)
  87 {
  88         /* just hash the least significant 32 bits to keep things fast (they
  89          * are the most likely to be different anyway), we can revisit this
  90          * later if needed */
  91         return (addr->s6_addr32[3] & (SEL_NETNODE_HASH_SIZE - 1));
  92 }
  93
  94 /**
  95  * sel_netnode_find - Search for a node record
  96  * @addr: IP address
  97  * @family: address family
  98  *
  99  * Description:
 100  * Search the network node table and return the record matching @addr.  If an
 101  * entry can not be found in the table return NULL.
 102  *
 103  */
 104 static struct sel_netnode *sel_netnode_find(const void *addr, u16 family)
 105 {
 106         unsigned int idx;
 107         struct sel_netnode *node;
 108
 109         switch (family) {
 110         case PF_INET:
 111                 idx = sel_netnode_hashfn_ipv4(*(__be32 *)addr);
 112                 break;
 113         case PF_INET6:
 114                 idx = sel_netnode_hashfn_ipv6(addr);
 115                 break;
 116         default:
 117                 BUG();
 118                 return NULL;
 119         }
 120
 121         list_for_each_entry_rcu(node, &sel_netnode_hash[idx].list, list)
 122                 if (node->nsec.family == family)
 123                         switch (family) {
 124                         case PF_INET:
 125                                 if (node->nsec.addr.ipv4 == *(__be32 *)addr)
 126                                         return node;
 127                                 break;
 128                         case PF_INET6:
 129                                 if (ipv6_addr_equal(&node->nsec.addr.ipv6,
 130                                                     addr))
 131                                         return node;
 132                                 break;
 133                         }
 134
 135         return NULL;
 136 }
 137
 138 /**
 139  * sel_netnode_insert - Insert a new node into the table
 140  * @node: the new node record
 141  *
 142  * Description:
 143  * Add a new node record to the network address hash table.
 144  *
 145  */
 146 static void sel_netnode_insert(struct sel_netnode *node)
 147 {
 148         unsigned int idx;
 149
 150         switch (node->nsec.family) {
 151         case PF_INET:
 152                 idx = sel_netnode_hashfn_ipv4(node->nsec.addr.ipv4);
 153                 break;
 154         case PF_INET6:
 155                 idx = sel_netnode_hashfn_ipv6(&node->nsec.addr.ipv6);
 156                 break;
 157         default:
 158                 BUG();
 159                 return;
 160         }
 161
 162         /* we need to impose a limit on the growth of the hash table so check
 163          * this bucket to make sure it is within the specified bounds */
 164         list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
 165         if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
 166                 struct sel_netnode *tail;
 167                 tail = list_entry(
 168                         rcu_dereference_protected(sel_netnode_hash[idx].list.prev,
 169                                                   lockdep_is_held(&sel_netnode_lock)),
 170                         struct sel_netnode, list);
 171                 list_del_rcu(&tail->list);
 172                 kfree_rcu(tail, rcu);
 173         } else
 174                 sel_netnode_hash[idx].size++;
 175 }
 176
 177 /**
 178  * sel_netnode_sid_slow - Lookup the SID of a network address using the policy
 179  * @addr: the IP address
 180  * @family: the address family
 181  * @sid: node SID
 182  *
 183  * Description:
 184  * This function determines the SID of a network address by quering the
 185  * security policy.  The result is added to the network address table to
 186  * speedup future queries.  Returns zero on success, negative values on
 187  * failure.
 188  *
 189  */
 190 static int sel_netnode_sid_slow(void *addr, u16 family, u32 *sid)
 191 {
 192         int ret;
 193         struct sel_netnode *node;
 194         struct sel_netnode *new;
 195
 196         spin_lock_bh(&sel_netnode_lock);
 197         node = sel_netnode_find(addr, family);
 198         if (node != NULL) {
 199                 *sid = node->nsec.sid;
 200                 spin_unlock_bh(&sel_netnode_lock);
 201                 return 0;
 202         }
 203
 204         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 205         switch (family) {
 206         case PF_INET:
 207                 ret = security_node_sid(&selinux_state, PF_INET,
 208                                         addr, sizeof(struct in_addr), sid);
 209                 if (new)
 210                         new->nsec.addr.ipv4 = *(__be32 *)addr;
 211                 break;
 212         case PF_INET6:
 213                 ret = security_node_sid(&selinux_state, PF_INET6,
 214                                         addr, sizeof(struct in6_addr), sid);
 215                 if (new)
 216                         new->nsec.addr.ipv6 = *(struct in6_addr *)addr;
 217                 break;
 218         default:
 219                 BUG();
 220                 ret = -EINVAL;
 221         }
 222         if (ret == 0 && new) {
 223                 new->nsec.family = family;
 224                 new->nsec.sid = *sid;
 225                 sel_netnode_insert(new);
 226         } else
 227                 kfree(new);
 228
 229         spin_unlock_bh(&sel_netnode_lock);
 230         if (unlikely(ret))
 231                 pr_warn("SELinux: failure in %s(), unable to determine network node label\n",
 232                         __func__);
 233         return ret;
 234 }
 235
 236 /**
 237  * sel_netnode_sid - Lookup the SID of a network address
 238  * @addr: the IP address
 239  * @family: the address family
 240  * @sid: node SID
 241  *
 242  * Description:
 243  * This function determines the SID of a network address using the fastest
 244  * method possible.  First the address table is queried, but if an entry
 245  * can't be found then the policy is queried and the result is added to the
 246  * table to speedup future queries.  Returns zero on success, negative values
 247  * on failure.
 248  *
 249  */
 250 int sel_netnode_sid(void *addr, u16 family, u32 *sid)
 251 {
 252         struct sel_netnode *node;
 253
 254         rcu_read_lock();
 255         node = sel_netnode_find(addr, family);
 256         if (node != NULL) {
 257                 *sid = node->nsec.sid;
 258                 rcu_read_unlock();
 259                 return 0;
 260         }
 261         rcu_read_unlock();
 262
 263         return sel_netnode_sid_slow(addr, family, sid);
 264 }
 265
 266 /**
 267  * sel_netnode_flush - Flush the entire network address table
 268  *
 269  * Description:
 270  * Remove all entries from the network address table.
 271  *
 272  */
 273 void sel_netnode_flush(void)
 274 {
 275         unsigned int idx;
 276         struct sel_netnode *node, *node_tmp;
 277
 278         spin_lock_bh(&sel_netnode_lock);
 279         for (idx = 0; idx < SEL_NETNODE_HASH_SIZE; idx++) {
 280                 list_for_each_entry_safe(node, node_tmp,
 281                                          &sel_netnode_hash[idx].list, list) {
 282                                 list_del_rcu(&node->list);
 283                                 kfree_rcu(node, rcu);
 284                 }
 285                 sel_netnode_hash[idx].size = 0;
 286         }
 287         spin_unlock_bh(&sel_netnode_lock);
 288 }
 289
 290 static __init int sel_netnode_init(void)
 291 {
 292         int iter;
 293
 294         if (!selinux_enabled_boot)
 295                 return 0;
 296
 297         for (iter = 0; iter < SEL_NETNODE_HASH_SIZE; iter++) {
 298                 INIT_LIST_HEAD(&sel_netnode_hash[iter].list);
 299                 sel_netnode_hash[iter].size = 0;
 300         }
 301
 302         return 0;
 303 }
 304
 305 __initcall(sel_netnode_init);