security/selinux/netport.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Network port table
   4  *
   5  * SELinux must keep a mapping of network ports to labels/SIDs.  This
   6  * mapping is maintained as part of the normal policy but a fast cache is
   7  * needed to reduce the lookup overhead.
   8  *
   9  * Author: Paul Moore <paul@paul-moore.com>
  10  *
  11  * This code is heavily based on the "netif" concept originally developed by
  12  * James Morris <jmorris@redhat.com>
  13  *   (see security/selinux/netif.c for more information)
  14  */
  15
  16 /*
  17  * (c) Copyright Hewlett-Packard Development Company, L.P., 2008
  18  */
  19
  20 #include <linux/types.h>
  21 #include <linux/rcupdate.h>
  22 #include <linux/list.h>
  23 #include <linux/slab.h>
  24 #include <linux/spinlock.h>
  25 #include <linux/in.h>
  26 #include <linux/in6.h>
  27 #include <linux/ip.h>
  28 #include <linux/ipv6.h>
  29 #include <net/ip.h>
  30 #include <net/ipv6.h>
  31
  32 #include "netport.h"
  33 #include "objsec.h"
  34
  35 #define SEL_NETPORT_HASH_SIZE       256
  36 #define SEL_NETPORT_HASH_BKT_LIMIT   16
  37
  38 struct sel_netport_bkt {
  39         int size;
  40         struct list_head list;
  41 };
  42
  43 struct sel_netport {
  44         struct netport_security_struct psec;
  45
  46         struct list_head list;
  47         struct rcu_head rcu;
  48 };
  49
  50 /* NOTE: we are using a combined hash table for both IPv4 and IPv6, the reason
  51  * for this is that I suspect most users will not make heavy use of both
  52  * address families at the same time so one table will usually end up wasted,
  53  * if this becomes a problem we can always add a hash table for each address
  54  * family later */
  55
  56 static DEFINE_SPINLOCK(sel_netport_lock);
  57 static struct sel_netport_bkt sel_netport_hash[SEL_NETPORT_HASH_SIZE];
  58
  59 /**
  60  * sel_netport_hashfn - Hashing function for the port table
  61  * @pnum: port number
  62  *
  63  * Description:
  64  * This is the hashing function for the port table, it returns the bucket
  65  * number for the given port.
  66  *
  67  */
  68 static unsigned int sel_netport_hashfn(u16 pnum)
  69 {
  70         return (pnum & (SEL_NETPORT_HASH_SIZE - 1));
  71 }
  72
  73 /**
  74  * sel_netport_find - Search for a port record
  75  * @protocol: protocol
  76  * @port: pnum
  77  *
  78  * Description:
  79  * Search the network port table and return the matching record.  If an entry
  80  * can not be found in the table return NULL.
  81  *
  82  */
  83 static struct sel_netport *sel_netport_find(u8 protocol, u16 pnum)
  84 {
  85         unsigned int idx;
  86         struct sel_netport *port;
  87
  88         idx = sel_netport_hashfn(pnum);
  89         list_for_each_entry_rcu(port, &sel_netport_hash[idx].list, list)
  90                 if (port->psec.port == pnum && port->psec.protocol == protocol)
  91                         return port;
  92
  93         return NULL;
  94 }
  95
  96 /**
  97  * sel_netport_insert - Insert a new port into the table
  98  * @port: the new port record
  99  *
 100  * Description:
 101  * Add a new port record to the network address hash table.
 102  *
 103  */
 104 static void sel_netport_insert(struct sel_netport *port)
 105 {
 106         unsigned int idx;
 107
 108         /* we need to impose a limit on the growth of the hash table so check
 109          * this bucket to make sure it is within the specified bounds */
 110         idx = sel_netport_hashfn(port->psec.port);
 111         list_add_rcu(&port->list, &sel_netport_hash[idx].list);
 112         if (sel_netport_hash[idx].size == SEL_NETPORT_HASH_BKT_LIMIT) {
 113                 struct sel_netport *tail;
 114                 tail = list_entry(
 115                         rcu_dereference_protected(
 116                                 sel_netport_hash[idx].list.prev,
 117                                 lockdep_is_held(&sel_netport_lock)),
 118                         struct sel_netport, list);
 119                 list_del_rcu(&tail->list);
 120                 kfree_rcu(tail, rcu);
 121         } else
 122                 sel_netport_hash[idx].size++;
 123 }
 124
 125 /**
 126  * sel_netport_sid_slow - Lookup the SID of a network address using the policy
 127  * @protocol: protocol
 128  * @pnum: port
 129  * @sid: port SID
 130  *
 131  * Description:
 132  * This function determines the SID of a network port by querying the security
 133  * policy.  The result is added to the network port table to speedup future
 134  * queries.  Returns zero on success, negative values on failure.
 135  *
 136  */
 137 static int sel_netport_sid_slow(u8 protocol, u16 pnum, u32 *sid)
 138 {
 139         int ret;
 140         struct sel_netport *port;
 141         struct sel_netport *new;
 142
 143         spin_lock_bh(&sel_netport_lock);
 144         port = sel_netport_find(protocol, pnum);
 145         if (port != NULL) {
 146                 *sid = port->psec.sid;
 147                 spin_unlock_bh(&sel_netport_lock);
 148                 return 0;
 149         }
 150
 151         ret = security_port_sid(&selinux_state, protocol, pnum, sid);
 152         if (ret != 0)
 153                 goto out;
 154         new = kzalloc(sizeof(*new), GFP_ATOMIC);
 155         if (new) {
 156                 new->psec.port = pnum;
 157                 new->psec.protocol = protocol;
 158                 new->psec.sid = *sid;
 159                 sel_netport_insert(new);
 160         }
 161
 162 out:
 163         spin_unlock_bh(&sel_netport_lock);
 164         if (unlikely(ret))
 165                 pr_warn("SELinux: failure in %s(), unable to determine network port label\n",
 166                         __func__);
 167         return ret;
 168 }
 169
 170 /**
 171  * sel_netport_sid - Lookup the SID of a network port
 172  * @protocol: protocol
 173  * @pnum: port
 174  * @sid: port SID
 175  *
 176  * Description:
 177  * This function determines the SID of a network port using the fastest method
 178  * possible.  First the port table is queried, but if an entry can't be found
 179  * then the policy is queried and the result is added to the table to speedup
 180  * future queries.  Returns zero on success, negative values on failure.
 181  *
 182  */
 183 int sel_netport_sid(u8 protocol, u16 pnum, u32 *sid)
 184 {
 185         struct sel_netport *port;
 186
 187         rcu_read_lock();
 188         port = sel_netport_find(protocol, pnum);
 189         if (port != NULL) {
 190                 *sid = port->psec.sid;
 191                 rcu_read_unlock();
 192                 return 0;
 193         }
 194         rcu_read_unlock();
 195
 196         return sel_netport_sid_slow(protocol, pnum, sid);
 197 }
 198
 199 /**
 200  * sel_netport_flush - Flush the entire network port table
 201  *
 202  * Description:
 203  * Remove all entries from the network address table.
 204  *
 205  */
 206 void sel_netport_flush(void)
 207 {
 208         unsigned int idx;
 209         struct sel_netport *port, *port_tmp;
 210
 211         spin_lock_bh(&sel_netport_lock);
 212         for (idx = 0; idx < SEL_NETPORT_HASH_SIZE; idx++) {
 213                 list_for_each_entry_safe(port, port_tmp,
 214                                          &sel_netport_hash[idx].list, list) {
 215                         list_del_rcu(&port->list);
 216                         kfree_rcu(port, rcu);
 217                 }
 218                 sel_netport_hash[idx].size = 0;
 219         }
 220         spin_unlock_bh(&sel_netport_lock);
 221 }
 222
 223 static __init int sel_netport_init(void)
 224 {
 225         int iter;
 226
 227         if (!selinux_enabled_boot)
 228                 return 0;
 229
 230         for (iter = 0; iter < SEL_NETPORT_HASH_SIZE; iter++) {
 231                 INIT_LIST_HEAD(&sel_netport_hash[iter].list);
 232                 sel_netport_hash[iter].size = 0;
 233         }
 234
 235         return 0;
 236 }
 237
 238 __initcall(sel_netport_init);