linux/security/selinux/netport.c
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   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
  47struct sel_netport_bkt {
  48        int size;
  49        struct list_head list;
  50};
  51
  52struct 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
  65static LIST_HEAD(sel_netport_list);
  66static DEFINE_SPINLOCK(sel_netport_lock);
  67static 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 */
  79static 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 */
  94static 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 */
 109static 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 */
 130static 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 */
 161static 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
 186out:
 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 */
 210int 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 */
 233static 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
 250static 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
 260static __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);
 282