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/slab.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 "netport.h"
  43 #include "objsec.h"
  44
  45 #define SEL_NETPORT_HASH_SIZE       256
  46 #define SEL_NETPORT_HASH_BKT_LIMIT   16
  47
  48 struct sel_netport_bkt {
  49         int size;
  50         struct list_head list;
  51 };
  52
  53 struct sel_netport {
  54         struct netport_security_struct psec;
  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_netport_list);
  67 static DEFINE_SPINLOCK(sel_netport_lock);
  68 static struct sel_netport_bkt sel_netport_hash[SEL_NETPORT_HASH_SIZE];
  69
  70 /**
  71  * sel_netport_free - Frees a port 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 port entry can be
  77  * released safely.
  78  *
  79  */
  80 static void sel_netport_free(struct rcu_head *p)
  81 {
  82         struct sel_netport *port = container_of(p, struct sel_netport, rcu);
  83         kfree(port);
  84 }
  85
  86 /**
  87  * sel_netport_hashfn - Hashing function for the port table
  88  * @pnum: port number
  89  *
  90  * Description:
  91  * This is the hashing function for the port table, it returns the bucket
  92  * number for the given port.
  93  *
  94  */
  95 static unsigned int sel_netport_hashfn(u16 pnum)
  96 {
  97         return (pnum & (SEL_NETPORT_HASH_SIZE - 1));
  98 }
  99
 100 /**
 101  * sel_netport_find - Search for a port record
 102  * @protocol: protocol
 103  * @port: pnum
 104  *
 105  * Description:
 106  * Search the network port table and return the matching record.  If an entry
 107  * can not be found in the table return NULL.
 108  *
 109  */
 110 static struct sel_netport *sel_netport_find(u8 protocol, u16 pnum)
 111 {
 112         unsigned int idx;
 113         struct sel_netport *port;
 114
 115         idx = sel_netport_hashfn(pnum);
 116         list_for_each_entry_rcu(port, &sel_netport_hash[idx].list, list)
 117                 if (port->psec.port == pnum && port->psec.protocol == protocol)
 118                         return port;
 119
 120         return NULL;
 121 }
 122
 123 /**
 124  * sel_netport_insert - Insert a new port into the table
 125  * @port: the new port record
 126  *
 127  * Description:
 128  * Add a new port record to the network address hash table.
 129  *
 130  */
 131 static void sel_netport_insert(struct sel_netport *port)
 132 {
 133         unsigned int idx;
 134
 135         /* we need to impose a limit on the growth of the hash table so check
 136          * this bucket to make sure it is within the specified bounds */
 137         idx = sel_netport_hashfn(port->psec.port);
 138         list_add_rcu(&port->list, &sel_netport_hash[idx].list);
 139         if (sel_netport_hash[idx].size == SEL_NETPORT_HASH_BKT_LIMIT) {
 140                 struct sel_netport *tail;
 141                 tail = list_entry(
 142                         rcu_dereference(sel_netport_hash[idx].list.prev),
 143                         struct sel_netport, list);
 144                 list_del_rcu(&tail->list);
 145                 call_rcu(&tail->rcu, sel_netport_free);
 146         } else
 147                 sel_netport_hash[idx].size++;
 148 }
 149
 150 /**
 151  * sel_netport_sid_slow - Lookup the SID of a network address using the policy
 152  * @protocol: protocol
 153  * @pnum: port
 154  * @sid: port SID
 155  *
 156  * Description:
 157  * This function determines the SID of a network port by quering the security
 158  * policy.  The result is added to the network port table to speedup future
 159  * queries.  Returns zero on success, negative values on failure.
 160  *
 161  */
 162 static int sel_netport_sid_slow(u8 protocol, u16 pnum, u32 *sid)
 163 {
 164         int ret = -ENOMEM;
 165         struct sel_netport *port;
 166         struct sel_netport *new = NULL;
 167
 168         spin_lock_bh(&sel_netport_lock);
 169         port = sel_netport_find(protocol, pnum);
 170         if (port != NULL) {
 171                 *sid = port->psec.sid;
 172                 spin_unlock_bh(&sel_netport_lock);
 173                 return 0;
 174         }
 175         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 176         if (new == NULL)
 177                 goto out;
 178         ret = security_port_sid(protocol, pnum, sid);
 179         if (ret != 0)
 180                 goto out;
 181
 182         new->psec.port = pnum;
 183         new->psec.protocol = protocol;
 184         new->psec.sid = *sid;
 185         sel_netport_insert(new);
 186
 187 out:
 188         spin_unlock_bh(&sel_netport_lock);
 189         if (unlikely(ret)) {
 190                 printk(KERN_WARNING
 191                        "SELinux: failure in sel_netport_sid_slow(),"
 192                        " unable to determine network port label\n");
 193                 kfree(new);
 194         }
 195         return ret;
 196 }
 197
 198 /**
 199  * sel_netport_sid - Lookup the SID of a network port
 200  * @protocol: protocol
 201  * @pnum: port
 202  * @sid: port SID
 203  *
 204  * Description:
 205  * This function determines the SID of a network port using the fastest method
 206  * possible.  First the port table is queried, but if an entry can't be found
 207  * then the policy is queried and the result is added to the table to speedup
 208  * future queries.  Returns zero on success, negative values on failure.
 209  *
 210  */
 211 int sel_netport_sid(u8 protocol, u16 pnum, u32 *sid)
 212 {
 213         struct sel_netport *port;
 214
 215         rcu_read_lock();
 216         port = sel_netport_find(protocol, pnum);
 217         if (port != NULL) {
 218                 *sid = port->psec.sid;
 219                 rcu_read_unlock();
 220                 return 0;
 221         }
 222         rcu_read_unlock();
 223
 224         return sel_netport_sid_slow(protocol, pnum, sid);
 225 }
 226
 227 /**
 228  * sel_netport_flush - Flush the entire network port table
 229  *
 230  * Description:
 231  * Remove all entries from the network address table.
 232  *
 233  */
 234 static void sel_netport_flush(void)
 235 {
 236         unsigned int idx;
 237         struct sel_netport *port, *port_tmp;
 238
 239         spin_lock_bh(&sel_netport_lock);
 240         for (idx = 0; idx < SEL_NETPORT_HASH_SIZE; idx++) {
 241                 list_for_each_entry_safe(port, port_tmp,
 242                                          &sel_netport_hash[idx].list, list) {
 243                         list_del_rcu(&port->list);
 244                         call_rcu(&port->rcu, sel_netport_free);
 245                 }
 246                 sel_netport_hash[idx].size = 0;
 247         }
 248         spin_unlock_bh(&sel_netport_lock);
 249 }
 250
 251 static int sel_netport_avc_callback(u32 event, u32 ssid, u32 tsid,
 252                                     u16 class, u32 perms, u32 *retained)
 253 {
 254         if (event == AVC_CALLBACK_RESET) {
 255                 sel_netport_flush();
 256                 synchronize_net();
 257         }
 258         return 0;
 259 }
 260
 261 static __init int sel_netport_init(void)
 262 {
 263         int iter;
 264         int ret;
 265
 266         if (!selinux_enabled)
 267                 return 0;
 268
 269         for (iter = 0; iter < SEL_NETPORT_HASH_SIZE; iter++) {
 270                 INIT_LIST_HEAD(&sel_netport_hash[iter].list);
 271                 sel_netport_hash[iter].size = 0;
 272         }
 273
 274         ret = avc_add_callback(sel_netport_avc_callback, AVC_CALLBACK_RESET,
 275                                SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0);
 276         if (ret != 0)
 277                 panic("avc_add_callback() failed, error %d\n", ret);
 278
 279         return ret;
 280 }
 281
 282 __initcall(sel_netport_init);