security/selinux/netport.c

   1 /*
   2  * Network port table
   3  *
   4  * SELinux must keep a mapping of network ports 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.
   7  *
   8  * Author: Paul Moore <paul.moore@hp.com>
   9  *
  10  * This code is heavily based on the "netif" concept originally developed by
  11  * James Morris <jmorris@redhat.com>
  12  *   (see security/selinux/netif.c for more information)
  13  *
  14  */
  15
  16 /*
  17  * (c) Copyright Hewlett-Packard Development Company, L.P., 2008
  18  *
  19  * This program is free software: you can redistribute it and/or modify
  20  * it under the terms of version 2 of the GNU General Public License as
  21  * published by the Free Software Foundation.
  22  *
  23  * This program is distributed in the hope that it will be useful,
  24  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  25  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  26  * GNU General Public License for more details.
  27  *
  28  */
  29
  30 #include <linux/types.h>
  31 #include <linux/rcupdate.h>
  32 #include <linux/list.h>
  33 #include <linux/spinlock.h>
  34 #include <linux/in.h>
  35 #include <linux/in6.h>
  36 #include <linux/ip.h>
  37 #include <linux/ipv6.h>
  38 #include <net/ip.h>
  39 #include <net/ipv6.h>
  40
  41 #include "netport.h"
  42 #include "objsec.h"
  43
  44 #define SEL_NETPORT_HASH_SIZE       256
  45 #define SEL_NETPORT_HASH_BKT_LIMIT   16
  46
  47 struct sel_netport_bkt {
  48         int size;
  49         struct list_head list;
  50 };
  51
  52 struct sel_netport {
  53         struct netport_security_struct psec;
  54
  55         struct list_head list;
  56         struct rcu_head rcu;
  57 };
  58
  59 /* NOTE: we are using a combined hash table for both IPv4 and IPv6, the reason
  60  * for this is that I suspect most users will not make heavy use of both
  61  * address families at the same time so one table will usually end up wasted,
  62  * if this becomes a problem we can always add a hash table for each address
  63  * family later */
  64
  65 static LIST_HEAD(sel_netport_list);
  66 static DEFINE_SPINLOCK(sel_netport_lock);
  67 static struct sel_netport_bkt sel_netport_hash[SEL_NETPORT_HASH_SIZE];
  68
  69 /**
  70  * sel_netport_free - Frees a port entry
  71  * @p: the entry's RCU field
  72  *
  73  * Description:
  74  * This function is designed to be used as a callback to the call_rcu()
  75  * function so that memory allocated to a hash table port entry can be
  76  * released safely.
  77  *
  78  */
  79 static void sel_netport_free(struct rcu_head *p)
  80 {
  81         struct sel_netport *port = container_of(p, struct sel_netport, rcu);
  82         kfree(port);
  83 }
  84
  85 /**
  86  * sel_netport_hashfn - Hashing function for the port table
  87  * @pnum: port number
  88  *
  89  * Description:
  90  * This is the hashing function for the port table, it returns the bucket
  91  * number for the given port.
  92  *
  93  */
  94 static unsigned int sel_netport_hashfn(u16 pnum)
  95 {
  96         return (pnum & (SEL_NETPORT_HASH_SIZE - 1));
  97 }
  98
  99 /**
 100  * sel_netport_find - Search for a port record
 101  * @protocol: protocol
 102  * @port: pnum
 103  *
 104  * Description:
 105  * Search the network port table and return the matching record.  If an entry
 106  * can not be found in the table return NULL.
 107  *
 108  */
 109 static struct sel_netport *sel_netport_find(u8 protocol, u16 pnum)
 110 {
 111         unsigned int idx;
 112         struct sel_netport *port;
 113
 114         idx = sel_netport_hashfn(pnum);
 115         list_for_each_entry_rcu(port, &sel_netport_hash[idx].list, list)
 116                 if (port->psec.port == pnum && port->psec.protocol == protocol)
 117                         return port;
 118
 119         return NULL;
 120 }
 121
 122 /**
 123  * sel_netport_insert - Insert a new port into the table
 124  * @port: the new port record
 125  *
 126  * Description:
 127  * Add a new port record to the network address hash table.
 128  *
 129  */
 130 static void sel_netport_insert(struct sel_netport *port)
 131 {
 132         unsigned int idx;
 133
 134         /* we need to impose a limit on the growth of the hash table so check
 135          * this bucket to make sure it is within the specified bounds */
 136         idx = sel_netport_hashfn(port->psec.port);
 137         list_add_rcu(&port->list, &sel_netport_hash[idx].list);
 138         if (sel_netport_hash[idx].size == SEL_NETPORT_HASH_BKT_LIMIT) {
 139                 struct sel_netport *tail;
 140                 tail = list_entry(
 141                         rcu_dereference(sel_netport_hash[idx].list.prev),
 142                         struct sel_netport, list);
 143                 list_del_rcu(&tail->list);
 144                 call_rcu(&tail->rcu, sel_netport_free);
 145         } else
 146                 sel_netport_hash[idx].size++;
 147 }
 148
 149 /**
 150  * sel_netport_sid_slow - Lookup the SID of a network address using the policy
 151  * @protocol: protocol
 152  * @pnum: port
 153  * @sid: port SID
 154  *
 155  * Description:
 156  * This function determines the SID of a network port by quering the security
 157  * policy.  The result is added to the network port table to speedup future
 158  * queries.  Returns zero on success, negative values on failure.
 159  *
 160  */
 161 static int sel_netport_sid_slow(u8 protocol, u16 pnum, u32 *sid)
 162 {
 163         int ret = -ENOMEM;
 164         struct sel_netport *port;
 165         struct sel_netport *new = NULL;
 166
 167         spin_lock_bh(&sel_netport_lock);
 168         port = sel_netport_find(protocol, pnum);
 169         if (port != NULL) {
 170                 *sid = port->psec.sid;
 171                 spin_unlock_bh(&sel_netport_lock);
 172                 return 0;
 173         }
 174         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 175         if (new == NULL)
 176                 goto out;
 177         ret = security_port_sid(protocol, pnum, sid);
 178         if (ret != 0)
 179                 goto out;
 180
 181         new->psec.port = pnum;
 182         new->psec.protocol = protocol;
 183         new->psec.sid = *sid;
 184         sel_netport_insert(new);
 185
 186 out:
 187         spin_unlock_bh(&sel_netport_lock);
 188         if (unlikely(ret)) {
 189                 printk(KERN_WARNING
 190                        "SELinux: failure in sel_netport_sid_slow(),"
 191                        " unable to determine network port label\n");
 192                 kfree(new);
 193         }
 194         return ret;
 195 }
 196
 197 /**
 198  * sel_netport_sid - Lookup the SID of a network port
 199  * @protocol: protocol
 200  * @pnum: port
 201  * @sid: port SID
 202  *
 203  * Description:
 204  * This function determines the SID of a network port using the fastest method
 205  * possible.  First the port table is queried, but if an entry can't be found
 206  * then the policy is queried and the result is added to the table to speedup
 207  * future queries.  Returns zero on success, negative values on failure.
 208  *
 209  */
 210 int sel_netport_sid(u8 protocol, u16 pnum, u32 *sid)
 211 {
 212         struct sel_netport *port;
 213
 214         rcu_read_lock();
 215         port = sel_netport_find(protocol, pnum);
 216         if (port != NULL) {
 217                 *sid = port->psec.sid;
 218                 rcu_read_unlock();
 219                 return 0;
 220         }
 221         rcu_read_unlock();
 222
 223         return sel_netport_sid_slow(protocol, pnum, sid);
 224 }
 225
 226 /**
 227  * sel_netport_flush - Flush the entire network port table
 228  *
 229  * Description:
 230  * Remove all entries from the network address table.
 231  *
 232  */
 233 static void sel_netport_flush(void)
 234 {
 235         unsigned int idx;
 236         struct sel_netport *port, *port_tmp;
 237
 238         spin_lock_bh(&sel_netport_lock);
 239         for (idx = 0; idx < SEL_NETPORT_HASH_SIZE; idx++) {
 240                 list_for_each_entry_safe(port, port_tmp,
 241                                          &sel_netport_hash[idx].list, list) {
 242                         list_del_rcu(&port->list);
 243                         call_rcu(&port->rcu, sel_netport_free);
 244                 }
 245                 sel_netport_hash[idx].size = 0;
 246         }
 247         spin_unlock_bh(&sel_netport_lock);
 248 }
 249
 250 static int sel_netport_avc_callback(u32 event, u32 ssid, u32 tsid,
 251                                     u16 class, u32 perms, u32 *retained)
 252 {
 253         if (event == AVC_CALLBACK_RESET) {
 254                 sel_netport_flush();
 255                 synchronize_net();
 256         }
 257         return 0;
 258 }
 259
 260 static __init int sel_netport_init(void)
 261 {
 262         int iter;
 263         int ret;
 264
 265         if (!selinux_enabled)
 266                 return 0;
 267
 268         for (iter = 0; iter < SEL_NETPORT_HASH_SIZE; iter++) {
 269                 INIT_LIST_HEAD(&sel_netport_hash[iter].list);
 270                 sel_netport_hash[iter].size = 0;
 271         }
 272
 273         ret = avc_add_callback(sel_netport_avc_callback, AVC_CALLBACK_RESET,
 274                                SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0);
 275         if (ret != 0)
 276                 panic("avc_add_callback() failed, error %d\n", ret);
 277
 278         return ret;
 279 }
 280
 281 __initcall(sel_netport_init);