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_protected(
 143                                 sel_netport_hash[idx].list.prev,
 144                                 lockdep_is_held(&sel_netport_lock)),
 145                         struct sel_netport, list);
 146                 list_del_rcu(&tail->list);
 147                 call_rcu(&tail->rcu, sel_netport_free);
 148         } else
 149                 sel_netport_hash[idx].size++;
 150 }
 151
 152 /**
 153  * sel_netport_sid_slow - Lookup the SID of a network address using the policy
 154  * @protocol: protocol
 155  * @pnum: port
 156  * @sid: port SID
 157  *
 158  * Description:
 159  * This function determines the SID of a network port by quering the security
 160  * policy.  The result is added to the network port table to speedup future
 161  * queries.  Returns zero on success, negative values on failure.
 162  *
 163  */
 164 static int sel_netport_sid_slow(u8 protocol, u16 pnum, u32 *sid)
 165 {
 166         int ret = -ENOMEM;
 167         struct sel_netport *port;
 168         struct sel_netport *new = NULL;
 169
 170         spin_lock_bh(&sel_netport_lock);
 171         port = sel_netport_find(protocol, pnum);
 172         if (port != NULL) {
 173                 *sid = port->psec.sid;
 174                 spin_unlock_bh(&sel_netport_lock);
 175                 return 0;
 176         }
 177         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 178         if (new == NULL)
 179                 goto out;
 180         ret = security_port_sid(protocol, pnum, sid);
 181         if (ret != 0)
 182                 goto out;
 183
 184         new->psec.port = pnum;
 185         new->psec.protocol = protocol;
 186         new->psec.sid = *sid;
 187         sel_netport_insert(new);
 188
 189 out:
 190         spin_unlock_bh(&sel_netport_lock);
 191         if (unlikely(ret)) {
 192                 printk(KERN_WARNING
 193                        "SELinux: failure in sel_netport_sid_slow(),"
 194                        " unable to determine network port label\n");
 195                 kfree(new);
 196         }
 197         return ret;
 198 }
 199
 200 /**
 201  * sel_netport_sid - Lookup the SID of a network port
 202  * @protocol: protocol
 203  * @pnum: port
 204  * @sid: port SID
 205  *
 206  * Description:
 207  * This function determines the SID of a network port using the fastest method
 208  * possible.  First the port table is queried, but if an entry can't be found
 209  * then the policy is queried and the result is added to the table to speedup
 210  * future queries.  Returns zero on success, negative values on failure.
 211  *
 212  */
 213 int sel_netport_sid(u8 protocol, u16 pnum, u32 *sid)
 214 {
 215         struct sel_netport *port;
 216
 217         rcu_read_lock();
 218         port = sel_netport_find(protocol, pnum);
 219         if (port != NULL) {
 220                 *sid = port->psec.sid;
 221                 rcu_read_unlock();
 222                 return 0;
 223         }
 224         rcu_read_unlock();
 225
 226         return sel_netport_sid_slow(protocol, pnum, sid);
 227 }
 228
 229 /**
 230  * sel_netport_flush - Flush the entire network port table
 231  *
 232  * Description:
 233  * Remove all entries from the network address table.
 234  *
 235  */
 236 static void sel_netport_flush(void)
 237 {
 238         unsigned int idx;
 239         struct sel_netport *port, *port_tmp;
 240
 241         spin_lock_bh(&sel_netport_lock);
 242         for (idx = 0; idx < SEL_NETPORT_HASH_SIZE; idx++) {
 243                 list_for_each_entry_safe(port, port_tmp,
 244                                          &sel_netport_hash[idx].list, list) {
 245                         list_del_rcu(&port->list);
 246                         call_rcu(&port->rcu, sel_netport_free);
 247                 }
 248                 sel_netport_hash[idx].size = 0;
 249         }
 250         spin_unlock_bh(&sel_netport_lock);
 251 }
 252
 253 static int sel_netport_avc_callback(u32 event, u32 ssid, u32 tsid,
 254                                     u16 class, u32 perms, u32 *retained)
 255 {
 256         if (event == AVC_CALLBACK_RESET) {
 257                 sel_netport_flush();
 258                 synchronize_net();
 259         }
 260         return 0;
 261 }
 262
 263 static __init int sel_netport_init(void)
 264 {
 265         int iter;
 266         int ret;
 267
 268         if (!selinux_enabled)
 269                 return 0;
 270
 271         for (iter = 0; iter < SEL_NETPORT_HASH_SIZE; iter++) {
 272                 INIT_LIST_HEAD(&sel_netport_hash[iter].list);
 273                 sel_netport_hash[iter].size = 0;
 274         }
 275
 276         ret = avc_add_callback(sel_netport_avc_callback, AVC_CALLBACK_RESET,
 277                                SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0);
 278         if (ret != 0)
 279                 panic("avc_add_callback() failed, error %d\n", ret);
 280
 281         return ret;
 282 }
 283
 284 __initcall(sel_netport_init);