/*
 * 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/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_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.
 *
 */
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(sel_netport_hash[idx].list.prev),
                        struct sel_netport, list);
                list_del_rcu(&tail->list);
                call_rcu(&tail->rcu, sel_netport_free);
        } 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\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, *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);
                        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);