SELinux: add netport.[ch]

/*

 * 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.moore@hp.com>

 *

 */

/*

 * (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.

 *

 */

#ifndef _SELINUX_NETPORT_H

#define _SELINUX_NETPORT_H

int sel_netport_sid(u8 protocol, u16 pnum, u32 *sid);

#endif

/*

 * 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.moore@hp.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/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 <asm/bug.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_free - Frees a port entry

 * @p: the entry's RCU field

 *

 * Description:

 * This function is designed to be used as a callback to the call_rcu()

 * function so that memory allocated to a hash table port entry can be

 * released safely.

 *

 */

static void sel_netport_free(struct rcu_head *p)

{

	struct sel_netport *port = container_of(p, struct sel_netport, rcu);

	kfree(port);

}

/**

 * 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.  Returns zero on

 * success, negative values on failure.

 *

 */

static int 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(port->list.prev, struct sel_netport, list);

		list_del_rcu(port->list.prev);

		call_rcu(&tail->rcu, sel_netport_free);

	} else

		sel_netport_hash[idx].size++;

	return 0;

}

/**

 * 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;

	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;

		ret = 0;

		goto out;

	}

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

	if (new == NULL) {

		ret = -ENOMEM;

		goto out;

	}

	ret = security_port_sid(protocol, pnum, &new->psec.sid);

	if (ret != 0)

		goto out;

	new->psec.port = pnum;

	new->psec.protocol = protocol;

	ret = sel_netport_insert(new);

	if (ret != 0)

		goto out;

	*sid = new->psec.sid;

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\n");

		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;

	spin_lock_bh(&sel_netport_lock);

	for (idx = 0; idx < SEL_NETPORT_HASH_SIZE; idx++) {

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

			list_del_rcu(&port->list);

			call_rcu(&port->rcu, sel_netport_free);

		}

		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\n", ret);

	return ret;

}

__initcall(sel_netport_init);