// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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 <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., 2007
 */

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

/**
 * sel_netnode_hashfn_ipv4 - IPv4 hashing function for the node table
 * @addr: IPv4 address
 *
 * Description:
 * This is the IPv4 hashing function for the node interface table, it returns
 * the bucket number for the given IP address.
 *
 */
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));
}

/**
 * sel_netnode_hashfn_ipv6 - IPv6 hashing function for the node table
 * @addr: IPv6 address
 *
 * Description:
 * This is the IPv6 hashing function for the node interface table, it returns
 * the bucket number for the given IP address.
 *
 */
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));
}

/**
 * sel_netnode_find - Search for a node record
 * @addr: IP address
 * @family: address family
 *
 * Description:
 * Search the network node table and return the record matching @addr.  If an
 * entry can not be found in the table return NULL.
 *
 */
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;
}

/**
 * sel_netnode_insert - Insert a new node into the table
 * @node: the new node record
 *
 * Description:
 * Add a new node record to the network address hash table.
 *
 */
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();
                return;
        }

        /* 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++;
}

/**
 * sel_netnode_sid_slow - Lookup the SID of a network address using the policy
 * @addr: the IP address
 * @family: the address family
 * @sid: node SID
 *
 * Description:
 * This function determines the SID of a network address by querying the
 * security policy.  The result is added to the network address table to
 * speedup future queries.  Returns zero on success, negative values on
 * failure.
 *
 */
static int sel_netnode_sid_slow(void *addr, u16 family, u32 *sid)
{
        int ret;
        struct sel_netnode *node;
        struct sel_netnode *new;

        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);
        switch (family) {
        case PF_INET:
                ret = security_node_sid(&selinux_state, PF_INET,
                                        addr, sizeof(struct in_addr), sid);
                if (new)
                        new->nsec.addr.ipv4 = *(__be32 *)addr;
                break;
        case PF_INET6:
                ret = security_node_sid(&selinux_state, PF_INET6,
                                        addr, sizeof(struct in6_addr), sid);
                if (new)
                        new->nsec.addr.ipv6 = *(struct in6_addr *)addr;
                break;
        default:
                BUG();
                ret = -EINVAL;
        }
        if (ret == 0 && new) {
                new->nsec.family = family;
                new->nsec.sid = *sid;
                sel_netnode_insert(new);
        } else
                kfree(new);

        spin_unlock_bh(&sel_netnode_lock);
        if (unlikely(ret))
                pr_warn("SELinux: failure in %s(), unable to determine network node label\n",
                        __func__);
        return ret;
}

/**
 * sel_netnode_sid - Lookup the SID of a network address
 * @addr: the IP address
 * @family: the address family
 * @sid: node SID
 *
 * Description:
 * This function determines the SID of a network address using the fastest
 * method possible.  First the address 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_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);
}

/**
 * sel_netnode_flush - Flush the entire network address table
 *
 * Description:
 * Remove all entries from the network address table.
 *
 */
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 __init int sel_netnode_init(void)
{
        int iter;

        if (!selinux_enabled_boot)
                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;
        }

        return 0;
}

__initcall(sel_netnode_init);