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@paul-moore.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_hashfn - Hashing function for the port table
  72  * @pnum: port number
  73  *
  74  * Description:
  75  * This is the hashing function for the port table, it returns the bucket
  76  * number for the given port.
  77  *
  78  */
  79 static unsigned int sel_netport_hashfn(u16 pnum)
  80 {
  81         return (pnum & (SEL_NETPORT_HASH_SIZE - 1));
  82 }
  83
  84 /**
  85  * sel_netport_find - Search for a port record
  86  * @protocol: protocol
  87  * @port: pnum
  88  *
  89  * Description:
  90  * Search the network port table and return the matching record.  If an entry
  91  * can not be found in the table return NULL.
  92  *
  93  */
  94 static struct sel_netport *sel_netport_find(u8 protocol, u16 pnum)
  95 {
  96         unsigned int idx;
  97         struct sel_netport *port;
  98
  99         idx = sel_netport_hashfn(pnum);
 100         list_for_each_entry_rcu(port, &sel_netport_hash[idx].list, list)
 101                 if (port->psec.port == pnum && port->psec.protocol == protocol)
 102                         return port;
 103
 104         return NULL;
 105 }
 106
 107 /**
 108  * sel_netport_insert - Insert a new port into the table
 109  * @port: the new port record
 110  *
 111  * Description:
 112  * Add a new port record to the network address hash table.
 113  *
 114  */
 115 static void sel_netport_insert(struct sel_netport *port)
 116 {
 117         unsigned int idx;
 118
 119         /* we need to impose a limit on the growth of the hash table so check
 120          * this bucket to make sure it is within the specified bounds */
 121         idx = sel_netport_hashfn(port->psec.port);
 122         list_add_rcu(&port->list, &sel_netport_hash[idx].list);
 123         if (sel_netport_hash[idx].size == SEL_NETPORT_HASH_BKT_LIMIT) {
 124                 struct sel_netport *tail;
 125                 tail = list_entry(
 126                         rcu_dereference(sel_netport_hash[idx].list.prev),
 127                         struct sel_netport, list);
 128                 list_del_rcu(&tail->list);
 129                 kfree_rcu(tail, rcu);
 130         } else
 131                 sel_netport_hash[idx].size++;
 132 }
 133
 134 /**
 135  * sel_netport_sid_slow - Lookup the SID of a network address using the policy
 136  * @protocol: protocol
 137  * @pnum: port
 138  * @sid: port SID
 139  *
 140  * Description:
 141  * This function determines the SID of a network port by quering the security
 142  * policy.  The result is added to the network port table to speedup future
 143  * queries.  Returns zero on success, negative values on failure.
 144  *
 145  */
 146 static int sel_netport_sid_slow(u8 protocol, u16 pnum, u32 *sid)
 147 {
 148         int ret = -ENOMEM;
 149         struct sel_netport *port;
 150         struct sel_netport *new = NULL;
 151
 152         spin_lock_bh(&sel_netport_lock);
 153         port = sel_netport_find(protocol, pnum);
 154         if (port != NULL) {
 155                 *sid = port->psec.sid;
 156                 spin_unlock_bh(&sel_netport_lock);
 157                 return 0;
 158         }
 159         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 160         if (new == NULL)
 161                 goto out;
 162         ret = security_port_sid(protocol, pnum, sid);
 163         if (ret != 0)
 164                 goto out;
 165
 166         new->psec.port = pnum;
 167         new->psec.protocol = protocol;
 168         new->psec.sid = *sid;
 169         sel_netport_insert(new);
 170
 171 out:
 172         spin_unlock_bh(&sel_netport_lock);
 173         if (unlikely(ret)) {
 174                 printk(KERN_WARNING
 175                        "SELinux: failure in sel_netport_sid_slow(),"
 176                        " unable to determine network port label\n");
 177                 kfree(new);
 178         }
 179         return ret;
 180 }
 181
 182 /**
 183  * sel_netport_sid - Lookup the SID of a network port
 184  * @protocol: protocol
 185  * @pnum: port
 186  * @sid: port SID
 187  *
 188  * Description:
 189  * This function determines the SID of a network port using the fastest method
 190  * possible.  First the port table is queried, but if an entry can't be found
 191  * then the policy is queried and the result is added to the table to speedup
 192  * future queries.  Returns zero on success, negative values on failure.
 193  *
 194  */
 195 int sel_netport_sid(u8 protocol, u16 pnum, u32 *sid)
 196 {
 197         struct sel_netport *port;
 198
 199         rcu_read_lock();
 200         port = sel_netport_find(protocol, pnum);
 201         if (port != NULL) {
 202                 *sid = port->psec.sid;
 203                 rcu_read_unlock();
 204                 return 0;
 205         }
 206         rcu_read_unlock();
 207
 208         return sel_netport_sid_slow(protocol, pnum, sid);
 209 }
 210
 211 /**
 212  * sel_netport_flush - Flush the entire network port table
 213  *
 214  * Description:
 215  * Remove all entries from the network address table.
 216  *
 217  */
 218 static void sel_netport_flush(void)
 219 {
 220         unsigned int idx;
 221         struct sel_netport *port, *port_tmp;
 222
 223         spin_lock_bh(&sel_netport_lock);
 224         for (idx = 0; idx < SEL_NETPORT_HASH_SIZE; idx++) {
 225                 list_for_each_entry_safe(port, port_tmp,
 226                                          &sel_netport_hash[idx].list, list) {
 227                         list_del_rcu(&port->list);
 228                         kfree_rcu(port, rcu);
 229                 }
 230                 sel_netport_hash[idx].size = 0;
 231         }
 232         spin_unlock_bh(&sel_netport_lock);
 233 }
 234
 235 static int sel_netport_avc_callback(u32 event, u32 ssid, u32 tsid,
 236                                     u16 class, u32 perms, u32 *retained)
 237 {
 238         if (event == AVC_CALLBACK_RESET) {
 239                 sel_netport_flush();
 240                 synchronize_net();
 241         }
 242         return 0;
 243 }
 244
 245 static __init int sel_netport_init(void)
 246 {
 247         int iter;
 248         int ret;
 249
 250         if (!selinux_enabled)
 251                 return 0;
 252
 253         for (iter = 0; iter < SEL_NETPORT_HASH_SIZE; iter++) {
 254                 INIT_LIST_HEAD(&sel_netport_hash[iter].list);
 255                 sel_netport_hash[iter].size = 0;
 256         }
 257
 258         ret = avc_add_callback(sel_netport_avc_callback, AVC_CALLBACK_RESET,
 259                                SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0);
 260         if (ret != 0)
 261                 panic("avc_add_callback() failed, error %d\n", ret);
 262
 263         return ret;
 264 }
 265
 266 __initcall(sel_netport_init);