/*
   * Network port table
   *
   * SELinux must keep a mapping of network ports to labels/SIDs.  This
   * mapping is maintained as part of the normal policy but a fast cache is
   * needed to reduce the lookup overhead.
   *

   * Author: Paul Moore <paul@paul-moore.com>

   *
   * This code is heavily based on the "netif" concept originally developed by
   * James Morris <jmorris@redhat.com>
   *   (see security/selinux/netif.c for more information)
   *
   */
  
  /*
   * (c) Copyright Hewlett-Packard Development Company, L.P., 2008
   *
   * This program is free software: you can redistribute it and/or modify
   * it under the terms of version 2 of the GNU General Public License as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   */
  
  #include <linux/types.h>
  #include <linux/rcupdate.h>
  #include <linux/list.h>

  #include <linux/slab.h>

  #include <linux/spinlock.h>
  #include <linux/in.h>
  #include <linux/in6.h>
  #include <linux/ip.h>
  #include <linux/ipv6.h>
  #include <net/ip.h>
  #include <net/ipv6.h>

  
  #include "netport.h"
  #include "objsec.h"
  
  #define SEL_NETPORT_HASH_SIZE       256
  #define SEL_NETPORT_HASH_BKT_LIMIT   16
  
  struct sel_netport_bkt {
  	int size;
  	struct list_head list;
  };
  
  struct sel_netport {
  	struct netport_security_struct psec;
  
  	struct list_head list;
  	struct rcu_head rcu;
  };
  
  /* NOTE: we are using a combined hash table for both IPv4 and IPv6, the reason
   * for this is that I suspect most users will not make heavy use of both
   * address families at the same time so one table will usually end up wasted,
   * if this becomes a problem we can always add a hash table for each address
   * family later */
  
  static LIST_HEAD(sel_netport_list);
  static DEFINE_SPINLOCK(sel_netport_lock);
  static struct sel_netport_bkt sel_netport_hash[SEL_NETPORT_HASH_SIZE];
  
  /**

   * sel_netport_hashfn - Hashing function for the port table
   * @pnum: port number
   *
   * Description:
   * This is the hashing function for the port table, it returns the bucket
   * number for the given port.
   *
   */
  static unsigned int sel_netport_hashfn(u16 pnum)
  {
  	return (pnum & (SEL_NETPORT_HASH_SIZE - 1));
  }
  
  /**
   * sel_netport_find - Search for a port record
   * @protocol: protocol
   * @port: pnum
   *
   * Description:
   * Search the network port table and return the matching record.  If an entry
   * can not be found in the table return NULL.
   *
   */
  static struct sel_netport *sel_netport_find(u8 protocol, u16 pnum)
  {
  	unsigned int idx;
  	struct sel_netport *port;
  
  	idx = sel_netport_hashfn(pnum);
  	list_for_each_entry_rcu(port, &sel_netport_hash[idx].list, list)

  		if (port->psec.port == pnum && port->psec.protocol == protocol)

  			return port;
  
  	return NULL;
  }
  
  /**
   * sel_netport_insert - Insert a new port into the table
   * @port: the new port record
   *
   * Description:

   * Add a new port record to the network address hash table.

   *
   */

  static void sel_netport_insert(struct sel_netport *port)

  {
  	unsigned int idx;
  
  	/* we need to impose a limit on the growth of the hash table so check
  	 * this bucket to make sure it is within the specified bounds */
  	idx = sel_netport_hashfn(port->psec.port);
  	list_add_rcu(&port->list, &sel_netport_hash[idx].list);
  	if (sel_netport_hash[idx].size == SEL_NETPORT_HASH_BKT_LIMIT) {
  		struct sel_netport *tail;

  		tail = list_entry(

  			rcu_dereference_protected(
  				sel_netport_hash[idx].list.prev,
  				lockdep_is_held(&sel_netport_lock)),

  			struct sel_netport, list);
  		list_del_rcu(&tail->list);

  		kfree_rcu(tail, rcu);

  	} else
  		sel_netport_hash[idx].size++;

  }
  
  /**
   * sel_netport_sid_slow - Lookup the SID of a network address using the policy
   * @protocol: protocol
   * @pnum: port
   * @sid: port SID
   *
   * Description:
   * This function determines the SID of a network port by quering the security
   * policy.  The result is added to the network port table to speedup future
   * queries.  Returns zero on success, negative values on failure.
   *
   */
  static int sel_netport_sid_slow(u8 protocol, u16 pnum, u32 *sid)
  {

  	int ret = -ENOMEM;

  	struct sel_netport *port;
  	struct sel_netport *new = NULL;
  
  	spin_lock_bh(&sel_netport_lock);
  	port = sel_netport_find(protocol, pnum);
  	if (port != NULL) {
  		*sid = port->psec.sid;

  		spin_unlock_bh(&sel_netport_lock);
  		return 0;

  	}
  	new = kzalloc(sizeof(*new), GFP_ATOMIC);

  	if (new == NULL)

  		goto out;

  	ret = security_port_sid(protocol, pnum, sid);

  	if (ret != 0)
  		goto out;

  	new->psec.port = pnum;
  	new->psec.protocol = protocol;

  	new->psec.sid = *sid;
  	sel_netport_insert(new);

  
  out:
  	spin_unlock_bh(&sel_netport_lock);
  	if (unlikely(ret)) {
  		printk(KERN_WARNING
  		       "SELinux: failure in sel_netport_sid_slow(),"
  		       " unable to determine network port label
  ");
  		kfree(new);
  	}
  	return ret;
  }
  
  /**
   * sel_netport_sid - Lookup the SID of a network port
   * @protocol: protocol
   * @pnum: port
   * @sid: port SID
   *
   * Description:
   * This function determines the SID of a network port using the fastest method
   * possible.  First the port table is queried, but if an entry can't be found
   * then the policy is queried and the result is added to the table to speedup
   * future queries.  Returns zero on success, negative values on failure.
   *
   */
  int sel_netport_sid(u8 protocol, u16 pnum, u32 *sid)
  {
  	struct sel_netport *port;
  
  	rcu_read_lock();
  	port = sel_netport_find(protocol, pnum);
  	if (port != NULL) {
  		*sid = port->psec.sid;
  		rcu_read_unlock();
  		return 0;
  	}
  	rcu_read_unlock();
  
  	return sel_netport_sid_slow(protocol, pnum, sid);
  }
  
  /**
   * sel_netport_flush - Flush the entire network port table
   *
   * Description:
   * Remove all entries from the network address table.
   *
   */
  static void sel_netport_flush(void)
  {
  	unsigned int idx;

  	struct sel_netport *port, *port_tmp;

  
  	spin_lock_bh(&sel_netport_lock);
  	for (idx = 0; idx < SEL_NETPORT_HASH_SIZE; idx++) {

  		list_for_each_entry_safe(port, port_tmp,
  					 &sel_netport_hash[idx].list, list) {

  			list_del_rcu(&port->list);

  			kfree_rcu(port, rcu);

  		}
  		sel_netport_hash[idx].size = 0;
  	}
  	spin_unlock_bh(&sel_netport_lock);
  }
  
  static int sel_netport_avc_callback(u32 event, u32 ssid, u32 tsid,
  				    u16 class, u32 perms, u32 *retained)
  {
  	if (event == AVC_CALLBACK_RESET) {
  		sel_netport_flush();
  		synchronize_net();
  	}
  	return 0;
  }
  
  static __init int sel_netport_init(void)
  {
  	int iter;
  	int ret;
  
  	if (!selinux_enabled)
  		return 0;
  
  	for (iter = 0; iter < SEL_NETPORT_HASH_SIZE; iter++) {
  		INIT_LIST_HEAD(&sel_netport_hash[iter].list);
  		sel_netport_hash[iter].size = 0;
  	}
  
  	ret = avc_add_callback(sel_netport_avc_callback, AVC_CALLBACK_RESET,

  			       SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0);

  	if (ret != 0)
  		panic("avc_add_callback() failed, error %d
  ", ret);
  
  	return ret;
  }
  
  __initcall(sel_netport_init);