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_protected(
 127                                 sel_netport_hash[idx].list.prev,
 128                                 lockdep_is_held(&sel_netport_lock)),
 129                         struct sel_netport, list);
 130                 list_del_rcu(&tail->list);
 131                 kfree_rcu(tail, rcu);
 132         } else
 133                 sel_netport_hash[idx].size++;
 134 }
 135
 136 /**
 137  * sel_netport_sid_slow - Lookup the SID of a network address using the policy
 138  * @protocol: protocol
 139  * @pnum: port
 140  * @sid: port SID
 141  *
 142  * Description:
 143  * This function determines the SID of a network port by quering the security
 144  * policy.  The result is added to the network port table to speedup future
 145  * queries.  Returns zero on success, negative values on failure.
 146  *
 147  */
 148 static int sel_netport_sid_slow(u8 protocol, u16 pnum, u32 *sid)
 149 {
 150         int ret = -ENOMEM;
 151         struct sel_netport *port;
 152         struct sel_netport *new = NULL;
 153
 154         spin_lock_bh(&sel_netport_lock);
 155         port = sel_netport_find(protocol, pnum);
 156         if (port != NULL) {
 157                 *sid = port->psec.sid;
 158                 spin_unlock_bh(&sel_netport_lock);
 159                 return 0;
 160         }
 161         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 162         if (new == NULL)
 163                 goto out;
 164         ret = security_port_sid(protocol, pnum, sid);
 165         if (ret != 0)
 166                 goto out;
 167
 168         new->psec.port = pnum;
 169         new->psec.protocol = protocol;
 170         new->psec.sid = *sid;
 171         sel_netport_insert(new);
 172
 173 out:
 174         spin_unlock_bh(&sel_netport_lock);
 175         if (unlikely(ret)) {
 176                 printk(KERN_WARNING
 177                        "SELinux: failure in sel_netport_sid_slow(),"
 178                        " unable to determine network port label\n");
 179                 kfree(new);
 180         }
 181         return ret;
 182 }
 183
 184 /**
 185  * sel_netport_sid - Lookup the SID of a network port
 186  * @protocol: protocol
 187  * @pnum: port
 188  * @sid: port SID
 189  *
 190  * Description:
 191  * This function determines the SID of a network port using the fastest method
 192  * possible.  First the port table is queried, but if an entry can't be found
 193  * then the policy is queried and the result is added to the table to speedup
 194  * future queries.  Returns zero on success, negative values on failure.
 195  *
 196  */
 197 int sel_netport_sid(u8 protocol, u16 pnum, u32 *sid)
 198 {
 199         struct sel_netport *port;
 200
 201         rcu_read_lock();
 202         port = sel_netport_find(protocol, pnum);
 203         if (port != NULL) {
 204                 *sid = port->psec.sid;
 205                 rcu_read_unlock();
 206                 return 0;
 207         }
 208         rcu_read_unlock();
 209
 210         return sel_netport_sid_slow(protocol, pnum, sid);
 211 }
 212
 213 /**
 214  * sel_netport_flush - Flush the entire network port table
 215  *
 216  * Description:
 217  * Remove all entries from the network address table.
 218  *
 219  */
 220 static void sel_netport_flush(void)
 221 {
 222         unsigned int idx;
 223         struct sel_netport *port, *port_tmp;
 224
 225         spin_lock_bh(&sel_netport_lock);
 226         for (idx = 0; idx < SEL_NETPORT_HASH_SIZE; idx++) {
 227                 list_for_each_entry_safe(port, port_tmp,
 228                                          &sel_netport_hash[idx].list, list) {
 229                         list_del_rcu(&port->list);
 230                         kfree_rcu(port, rcu);
 231                 }
 232                 sel_netport_hash[idx].size = 0;
 233         }
 234         spin_unlock_bh(&sel_netport_lock);
 235 }
 236
 237 static int sel_netport_avc_callback(u32 event)
 238 {
 239         if (event == AVC_CALLBACK_RESET) {
 240                 sel_netport_flush();
 241                 synchronize_net();
 242         }
 243         return 0;
 244 }
 245
 246 static __init int sel_netport_init(void)
 247 {
 248         int iter;
 249         int ret;
 250
 251         if (!selinux_enabled)
 252                 return 0;
 253
 254         for (iter = 0; iter < SEL_NETPORT_HASH_SIZE; iter++) {
 255                 INIT_LIST_HEAD(&sel_netport_hash[iter].list);
 256                 sel_netport_hash[iter].size = 0;
 257         }
 258
 259         ret = avc_add_callback(sel_netport_avc_callback, AVC_CALLBACK_RESET);
 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);