netnode.c

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/*
 * Network node table
 *
 * SELinux must keep a mapping of network nodes to labels/SIDs.  This
 * mapping is maintained as part of the normal policy but a fast cache is
 * needed to reduce the lookup overhead since most of these queries happen on
 * a per-packet basis.
 *
 * Author: Paul Moore <[email protected]>
 *
 * This code is heavily based on the "netif" concept originally developed by
 * James Morris <[email protected]>
 *   (see security/selinux/netif.c for more information)
 *
 */

/*
 * (c) Copyright Hewlett-Packard Development Company, L.P., 2007
 *
 * 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 "netnode.h"
#include "objsec.h"

#define SEL_NETNODE_HASH_SIZE       256
#define SEL_NETNODE_HASH_BKT_LIMIT   16

struct sel_netnode_bkt {
    unsigned int size;
    struct list_head list;
};

struct sel_netnode {
    struct netnode_security_struct nsec;

    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_netnode_list);
static DEFINE_SPINLOCK(sel_netnode_lock);
static struct sel_netnode_bkt sel_netnode_hash[SEL_NETNODE_HASH_SIZE];

static unsigned int sel_netnode_hashfn_ipv4(__be32 addr)
{
    /* at some point we should determine if the mismatch in byte order
     * affects the hash function dramatically */
    return (addr & (SEL_NETNODE_HASH_SIZE - 1));
}

static unsigned int sel_netnode_hashfn_ipv6(const struct in6_addr *addr)
{
    /* just hash the least significant 32 bits to keep things fast (they
     * are the most likely to be different anyway), we can revisit this
     * later if needed */
    return (addr->s6_addr32[3] & (SEL_NETNODE_HASH_SIZE - 1));
}

static struct sel_netnode *sel_netnode_find(const void *addr, u16 family)
{
    unsigned int idx;
    struct sel_netnode *node;

    switch (family) {
    case PF_INET:
        idx = sel_netnode_hashfn_ipv4(*(__be32 *)addr);
        break;
    case PF_INET6:
        idx = sel_netnode_hashfn_ipv6(addr);
        break;
    default:
        BUG();
        return NULL;
    }

    list_for_each_entry_rcu(node, &sel_netnode_hash[idx].list, list)
        if (node->nsec.family == family)
            switch (family) {
            case PF_INET:
                if (node->nsec.addr.ipv4 == *(__be32 *)addr)
                    return node;
                break;
            case PF_INET6:
                if (ipv6_addr_equal(&node->nsec.addr.ipv6,
                            addr))
                    return node;
                break;
            }

    return NULL;
}

static void sel_netnode_insert(struct sel_netnode *node)
{
    unsigned int idx;

    switch (node->nsec.family) {
    case PF_INET:
        idx = sel_netnode_hashfn_ipv4(node->nsec.addr.ipv4);
        break;
    case PF_INET6:
        idx = sel_netnode_hashfn_ipv6(&node->nsec.addr.ipv6);
        break;
    default:
        BUG();
    }

    /* 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 */
    list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
    if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
        struct sel_netnode *tail;
        tail = list_entry(
            rcu_dereference_protected(sel_netnode_hash[idx].list.prev,
                          lockdep_is_held(&sel_netnode_lock)),
            struct sel_netnode, list);
        list_del_rcu(&tail->list);
        kfree_rcu(tail, rcu);
    } else
        sel_netnode_hash[idx].size++;
}

static int sel_netnode_sid_slow(void *addr, u16 family, u32 *sid)
{
    int ret = -ENOMEM;
    struct sel_netnode *node;
    struct sel_netnode *new = NULL;

    spin_lock_bh(&sel_netnode_lock);
    node = sel_netnode_find(addr, family);
    if (node != NULL) {
        *sid = node->nsec.sid;
        spin_unlock_bh(&sel_netnode_lock);
        return 0;
    }
    new = kzalloc(sizeof(*new), GFP_ATOMIC);
    if (new == NULL)
        goto out;
    switch (family) {
    case PF_INET:
        ret = security_node_sid(PF_INET,
                    addr, sizeof(struct in_addr), sid);
        new->nsec.addr.ipv4 = *(__be32 *)addr;
        break;
    case PF_INET6:
        ret = security_node_sid(PF_INET6,
                    addr, sizeof(struct in6_addr), sid);
        new->nsec.addr.ipv6 = *(struct in6_addr *)addr;
        break;
    default:
        BUG();
    }
    if (ret != 0)
        goto out;

    new->nsec.family = family;
    new->nsec.sid = *sid;
    sel_netnode_insert(new);

out:
    spin_unlock_bh(&sel_netnode_lock);
    if (unlikely(ret)) {
        printk(KERN_WARNING
               "SELinux: failure in sel_netnode_sid_slow(),"
               " unable to determine network node label\n");
        kfree(new);
    }
    return ret;
}

int sel_netnode_sid(void *addr, u16 family, u32 *sid)
{
    struct sel_netnode *node;

    rcu_read_lock();
    node = sel_netnode_find(addr, family);
    if (node != NULL) {
        *sid = node->nsec.sid;
        rcu_read_unlock();
        return 0;
    }
    rcu_read_unlock();

    return sel_netnode_sid_slow(addr, family, sid);
}

static void sel_netnode_flush(void)
{
    unsigned int idx;
    struct sel_netnode *node, *node_tmp;

    spin_lock_bh(&sel_netnode_lock);
    for (idx = 0; idx < SEL_NETNODE_HASH_SIZE; idx++) {
        list_for_each_entry_safe(node, node_tmp,
                     &sel_netnode_hash[idx].list, list) {
                list_del_rcu(&node->list);
                kfree_rcu(node, rcu);
        }
        sel_netnode_hash[idx].size = 0;
    }
    spin_unlock_bh(&sel_netnode_lock);
}

static int sel_netnode_avc_callback(u32 event)
{
    if (event == AVC_CALLBACK_RESET) {
        sel_netnode_flush();
        synchronize_net();
    }
    return 0;
}

static __init int sel_netnode_init(void)
{
    int iter;
    int ret;

    if (!selinux_enabled)
        return 0;

    for (iter = 0; iter < SEL_NETNODE_HASH_SIZE; iter++) {
        INIT_LIST_HEAD(&sel_netnode_hash[iter].list);
        sel_netnode_hash[iter].size = 0;
    }

    ret = avc_add_callback(sel_netnode_avc_callback, AVC_CALLBACK_RESET);
    if (ret != 0)
        panic("avc_add_callback() failed, error %d\n", ret);

    return ret;
}

__initcall(sel_netnode_init);