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@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
  48struct sel_netport_bkt {
  49        int size;
  50        struct list_head list;
  51};
  52
  53struct 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
  66static LIST_HEAD(sel_netport_list);
  67static DEFINE_SPINLOCK(sel_netport_lock);
  68static 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 */
  79static 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 */
  94static 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 */
 115static 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 */
 148static 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
 173out:
 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 */
 197int 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 */
 220static 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
 237static 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
 246static __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);
 267
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