/* Basic authentication token and access key management

   *

   * Copyright (C) 2004-2008 Red Hat, Inc. All Rights Reserved.

   * Written by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version
   * 2 of the License, or (at your option) any later version.
   */
  
  #include <linux/module.h>
  #include <linux/init.h>

  #include <linux/poison.h>

  #include <linux/sched.h>
  #include <linux/slab.h>

  #include <linux/security.h>

  #include <linux/workqueue.h>

  #include <linux/random.h>

  #include <linux/err.h>

  #include <linux/user_namespace.h>

  #include "internal.h"

  struct kmem_cache *key_jar;

  struct rb_root		key_serial_tree; /* tree of keys indexed by serial */
  DEFINE_SPINLOCK(key_serial_lock);
  
  struct rb_root	key_user_tree; /* tree of quota records indexed by UID */
  DEFINE_SPINLOCK(key_user_lock);

  unsigned int key_quota_root_maxkeys = 200;	/* root's key count quota */
  unsigned int key_quota_root_maxbytes = 20000;	/* root's key space quota */
  unsigned int key_quota_maxkeys = 200;		/* general key count quota */
  unsigned int key_quota_maxbytes = 20000;	/* general key space quota */

  static LIST_HEAD(key_types_list);
  static DECLARE_RWSEM(key_types_sem);

  /* We serialise key instantiation and link */

  DEFINE_MUTEX(key_construction_mutex);

  #ifdef KEY_DEBUGGING
  void __key_check(const struct key *key)
  {
  	printk("__key_check: key %p {%08x} should be {%08x}
  ",
  	       key, key->magic, KEY_DEBUG_MAGIC);
  	BUG();
  }
  #endif

  /*

   * Get the key quota record for a user, allocating a new record if one doesn't
   * already exist.

   */

  struct key_user *key_user_lookup(uid_t uid, struct user_namespace *user_ns)

  {
  	struct key_user *candidate = NULL, *user;
  	struct rb_node *parent = NULL;
  	struct rb_node **p;

  try_again:

  	p = &key_user_tree.rb_node;
  	spin_lock(&key_user_lock);
  
  	/* search the tree for a user record with a matching UID */
  	while (*p) {
  		parent = *p;
  		user = rb_entry(parent, struct key_user, node);
  
  		if (uid < user->uid)
  			p = &(*p)->rb_left;
  		else if (uid > user->uid)
  			p = &(*p)->rb_right;

  		else if (user_ns < user->user_ns)
  			p = &(*p)->rb_left;
  		else if (user_ns > user->user_ns)
  			p = &(*p)->rb_right;

  		else
  			goto found;
  	}
  
  	/* if we get here, we failed to find a match in the tree */
  	if (!candidate) {
  		/* allocate a candidate user record if we don't already have
  		 * one */
  		spin_unlock(&key_user_lock);
  
  		user = NULL;
  		candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
  		if (unlikely(!candidate))
  			goto out;
  
  		/* the allocation may have scheduled, so we need to repeat the
  		 * search lest someone else added the record whilst we were
  		 * asleep */
  		goto try_again;
  	}
  
  	/* if we get here, then the user record still hadn't appeared on the
  	 * second pass - so we use the candidate record */
  	atomic_set(&candidate->usage, 1);
  	atomic_set(&candidate->nkeys, 0);
  	atomic_set(&candidate->nikeys, 0);
  	candidate->uid = uid;

  	candidate->user_ns = get_user_ns(user_ns);

  	candidate->qnkeys = 0;
  	candidate->qnbytes = 0;
  	spin_lock_init(&candidate->lock);

  	mutex_init(&candidate->cons_lock);

  
  	rb_link_node(&candidate->node, parent, p);
  	rb_insert_color(&candidate->node, &key_user_tree);
  	spin_unlock(&key_user_lock);
  	user = candidate;
  	goto out;
  
  	/* okay - we found a user record for this UID */

  found:

  	atomic_inc(&user->usage);
  	spin_unlock(&key_user_lock);

  	kfree(candidate);

  out:

  	return user;

  }

  /*

   * Dispose of a user structure

   */
  void key_user_put(struct key_user *user)
  {
  	if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
  		rb_erase(&user->node, &key_user_tree);
  		spin_unlock(&key_user_lock);

  		put_user_ns(user->user_ns);

  
  		kfree(user);
  	}

  }

  /*

   * Allocate a serial number for a key.  These are assigned randomly to avoid
   * security issues through covert channel problems.

   */
  static inline void key_alloc_serial(struct key *key)
  {
  	struct rb_node *parent, **p;
  	struct key *xkey;

  	/* propose a random serial number and look for a hole for it in the

  	 * serial number tree */

  	do {
  		get_random_bytes(&key->serial, sizeof(key->serial));
  
  		key->serial >>= 1; /* negative numbers are not permitted */
  	} while (key->serial < 3);
  
  	spin_lock(&key_serial_lock);

  attempt_insertion:

  	parent = NULL;
  	p = &key_serial_tree.rb_node;
  
  	while (*p) {
  		parent = *p;
  		xkey = rb_entry(parent, struct key, serial_node);
  
  		if (key->serial < xkey->serial)
  			p = &(*p)->rb_left;
  		else if (key->serial > xkey->serial)
  			p = &(*p)->rb_right;
  		else
  			goto serial_exists;
  	}

  
  	/* we've found a suitable hole - arrange for this key to occupy it */
  	rb_link_node(&key->serial_node, parent, p);
  	rb_insert_color(&key->serial_node, &key_serial_tree);
  
  	spin_unlock(&key_serial_lock);
  	return;

  
  	/* we found a key with the proposed serial number - walk the tree from
  	 * that point looking for the next unused serial number */

  serial_exists:

  	for (;;) {

  		key->serial++;

  		if (key->serial < 3) {
  			key->serial = 3;
  			goto attempt_insertion;
  		}

  
  		parent = rb_next(parent);
  		if (!parent)

  			goto attempt_insertion;

  
  		xkey = rb_entry(parent, struct key, serial_node);
  		if (key->serial < xkey->serial)

  			goto attempt_insertion;

  	}

  }

  /**
   * key_alloc - Allocate a key of the specified type.
   * @type: The type of key to allocate.
   * @desc: The key description to allow the key to be searched out.
   * @uid: The owner of the new key.
   * @gid: The group ID for the new key's group permissions.
   * @cred: The credentials specifying UID namespace.
   * @perm: The permissions mask of the new key.
   * @flags: Flags specifying quota properties.
   *
   * Allocate a key of the specified type with the attributes given.  The key is
   * returned in an uninstantiated state and the caller needs to instantiate the
   * key before returning.
   *
   * The user's key count quota is updated to reflect the creation of the key and
   * the user's key data quota has the default for the key type reserved.  The
   * instantiation function should amend this as necessary.  If insufficient
   * quota is available, -EDQUOT will be returned.
   *
   * The LSM security modules can prevent a key being created, in which case
   * -EACCES will be returned.
   *
   * Returns a pointer to the new key if successful and an error code otherwise.
   *
   * Note that the caller needs to ensure the key type isn't uninstantiated.
   * Internally this can be done by locking key_types_sem.  Externally, this can
   * be done by either never unregistering the key type, or making sure
   * key_alloc() calls don't race with module unloading.

   */
  struct key *key_alloc(struct key_type *type, const char *desc,

  		      uid_t uid, gid_t gid, const struct cred *cred,

  		      key_perm_t perm, unsigned long flags)

  {
  	struct key_user *user = NULL;
  	struct key *key;
  	size_t desclen, quotalen;

  	int ret;

  
  	key = ERR_PTR(-EINVAL);
  	if (!desc || !*desc)
  		goto error;

  	if (type->vet_description) {
  		ret = type->vet_description(desc);
  		if (ret < 0) {
  			key = ERR_PTR(ret);
  			goto error;
  		}
  	}

  	desclen = strlen(desc) + 1;
  	quotalen = desclen + type->def_datalen;
  
  	/* get hold of the key tracking for this user */

  	user = key_user_lookup(uid, cred->user->user_ns);

  	if (!user)
  		goto no_memory_1;
  
  	/* check that the user's quota permits allocation of another key and
  	 * its description */

  	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {

  		unsigned maxkeys = (uid == 0) ?
  			key_quota_root_maxkeys : key_quota_maxkeys;
  		unsigned maxbytes = (uid == 0) ?
  			key_quota_root_maxbytes : key_quota_maxbytes;

  		spin_lock(&user->lock);

  		if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {

  			if (user->qnkeys + 1 >= maxkeys ||
  			    user->qnbytes + quotalen >= maxbytes ||
  			    user->qnbytes + quotalen < user->qnbytes)

  				goto no_quota;
  		}

  
  		user->qnkeys++;
  		user->qnbytes += quotalen;
  		spin_unlock(&user->lock);
  	}
  
  	/* allocate and initialise the key and its description */

  	key = kmem_cache_alloc(key_jar, GFP_KERNEL);

  	if (!key)
  		goto no_memory_2;
  
  	if (desc) {

  		key->description = kmemdup(desc, desclen, GFP_KERNEL);

  		if (!key->description)
  			goto no_memory_3;

  	}
  
  	atomic_set(&key->usage, 1);

  	init_rwsem(&key->sem);

  	lockdep_set_class(&key->sem, &type->lock_class);

  	key->type = type;
  	key->user = user;
  	key->quotalen = quotalen;
  	key->datalen = type->def_datalen;
  	key->uid = uid;
  	key->gid = gid;
  	key->perm = perm;
  	key->flags = 0;
  	key->expiry = 0;
  	key->payload.data = NULL;

  	key->security = NULL;

  	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))

  		key->flags |= 1 << KEY_FLAG_IN_QUOTA;

  
  	memset(&key->type_data, 0, sizeof(key->type_data));
  
  #ifdef KEY_DEBUGGING
  	key->magic = KEY_DEBUG_MAGIC;
  #endif

  	/* let the security module know about the key */

  	ret = security_key_alloc(key, cred, flags);

  	if (ret < 0)
  		goto security_error;

  	/* publish the key by giving it a serial number */
  	atomic_inc(&user->nkeys);
  	key_alloc_serial(key);

  error:

  	return key;

  security_error:
  	kfree(key->description);

  	kmem_cache_free(key_jar, key);

  	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {

  		spin_lock(&user->lock);
  		user->qnkeys--;
  		user->qnbytes -= quotalen;
  		spin_unlock(&user->lock);
  	}
  	key_user_put(user);

  	key = ERR_PTR(ret);
  	goto error;
  
  no_memory_3:
  	kmem_cache_free(key_jar, key);
  no_memory_2:

  	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {

  		spin_lock(&user->lock);
  		user->qnkeys--;
  		user->qnbytes -= quotalen;
  		spin_unlock(&user->lock);
  	}
  	key_user_put(user);
  no_memory_1:

  	key = ERR_PTR(-ENOMEM);
  	goto error;

  no_quota:

  	spin_unlock(&user->lock);
  	key_user_put(user);
  	key = ERR_PTR(-EDQUOT);
  	goto error;

  }

  EXPORT_SYMBOL(key_alloc);

  /**
   * key_payload_reserve - Adjust data quota reservation for the key's payload
   * @key: The key to make the reservation for.
   * @datalen: The amount of data payload the caller now wants.
   *
   * Adjust the amount of the owning user's key data quota that a key reserves.
   * If the amount is increased, then -EDQUOT may be returned if there isn't
   * enough free quota available.
   *
   * If successful, 0 is returned.

   */
  int key_payload_reserve(struct key *key, size_t datalen)
  {

  	int delta = (int)datalen - key->datalen;

  	int ret = 0;
  
  	key_check(key);
  
  	/* contemplate the quota adjustment */

  	if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {

  		unsigned maxbytes = (key->user->uid == 0) ?
  			key_quota_root_maxbytes : key_quota_maxbytes;

  		spin_lock(&key->user->lock);
  
  		if (delta > 0 &&

  		    (key->user->qnbytes + delta >= maxbytes ||
  		     key->user->qnbytes + delta < key->user->qnbytes)) {

  			ret = -EDQUOT;
  		}
  		else {
  			key->user->qnbytes += delta;
  			key->quotalen += delta;
  		}
  		spin_unlock(&key->user->lock);
  	}
  
  	/* change the recorded data length if that didn't generate an error */
  	if (ret == 0)
  		key->datalen = datalen;
  
  	return ret;

  }

  EXPORT_SYMBOL(key_payload_reserve);

  /*

   * Instantiate a key and link it into the target keyring atomically.  Must be
   * called with the target keyring's semaphore writelocked.  The target key's
   * semaphore need not be locked as instantiation is serialised by
   * key_construction_mutex.

   */
  static int __key_instantiate_and_link(struct key *key,
  				      const void *data,
  				      size_t datalen,

  				      struct key *keyring,

  				      struct key *authkey,

  				      unsigned long *_prealloc)

  {
  	int ret, awaken;
  
  	key_check(key);
  	key_check(keyring);
  
  	awaken = 0;
  	ret = -EBUSY;

  	mutex_lock(&key_construction_mutex);

  
  	/* can't instantiate twice */

  	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {

  		/* instantiate the key */
  		ret = key->type->instantiate(key, data, datalen);
  
  		if (ret == 0) {
  			/* mark the key as being instantiated */

  			atomic_inc(&key->user->nikeys);

  			set_bit(KEY_FLAG_INSTANTIATED, &key->flags);

  			if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))

  				awaken = 1;

  
  			/* and link it into the destination keyring */
  			if (keyring)

  				__key_link(keyring, key, _prealloc);

  
  			/* disable the authorisation key */

  			if (authkey)
  				key_revoke(authkey);

  		}
  	}

  	mutex_unlock(&key_construction_mutex);

  
  	/* wake up anyone waiting for a key to be constructed */
  	if (awaken)

  		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);

  
  	return ret;

  }

  /**
   * key_instantiate_and_link - Instantiate a key and link it into the keyring.
   * @key: The key to instantiate.
   * @data: The data to use to instantiate the keyring.
   * @datalen: The length of @data.
   * @keyring: Keyring to create a link in on success (or NULL).
   * @authkey: The authorisation token permitting instantiation.
   *
   * Instantiate a key that's in the uninstantiated state using the provided data
   * and, if successful, link it in to the destination keyring if one is
   * supplied.
   *
   * If successful, 0 is returned, the authorisation token is revoked and anyone
   * waiting for the key is woken up.  If the key was already instantiated,
   * -EBUSY will be returned.

   */
  int key_instantiate_and_link(struct key *key,
  			     const void *data,
  			     size_t datalen,

  			     struct key *keyring,

  			     struct key *authkey)

  {

  	unsigned long prealloc;

  	int ret;

  	if (keyring) {
  		ret = __key_link_begin(keyring, key->type, key->description,
  				       &prealloc);
  		if (ret < 0)
  			return ret;
  	}

  	ret = __key_instantiate_and_link(key, data, datalen, keyring, authkey,
  					 &prealloc);

  
  	if (keyring)

  		__key_link_end(keyring, key->type, prealloc);

  
  	return ret;

  }

  
  EXPORT_SYMBOL(key_instantiate_and_link);

  /**

   * key_reject_and_link - Negatively instantiate a key and link it into the keyring.

   * @key: The key to instantiate.
   * @timeout: The timeout on the negative key.

   * @error: The error to return when the key is hit.

   * @keyring: Keyring to create a link in on success (or NULL).
   * @authkey: The authorisation token permitting instantiation.
   *
   * Negatively instantiate a key that's in the uninstantiated state and, if

   * successful, set its timeout and stored error and link it in to the
   * destination keyring if one is supplied.  The key and any links to the key
   * will be automatically garbage collected after the timeout expires.

   *
   * Negative keys are used to rate limit repeated request_key() calls by causing

   * them to return the stored error code (typically ENOKEY) until the negative
   * key expires.

   *
   * If successful, 0 is returned, the authorisation token is revoked and anyone
   * waiting for the key is woken up.  If the key was already instantiated,
   * -EBUSY will be returned.

   */

  int key_reject_and_link(struct key *key,

  			unsigned timeout,

  			unsigned error,

  			struct key *keyring,

  			struct key *authkey)

  {

  	unsigned long prealloc;

  	struct timespec now;

  	int ret, awaken, link_ret = 0;

  
  	key_check(key);
  	key_check(keyring);
  
  	awaken = 0;
  	ret = -EBUSY;
  
  	if (keyring)

  		link_ret = __key_link_begin(keyring, key->type,
  					    key->description, &prealloc);

  	mutex_lock(&key_construction_mutex);

  
  	/* can't instantiate twice */

  	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {

  		/* mark the key as being negatively instantiated */

  		atomic_inc(&key->user->nikeys);

  		set_bit(KEY_FLAG_NEGATIVE, &key->flags);
  		set_bit(KEY_FLAG_INSTANTIATED, &key->flags);

  		key->type_data.reject_error = -error;

  		now = current_kernel_time();
  		key->expiry = now.tv_sec + timeout;

  		key_schedule_gc(key->expiry + key_gc_delay);

  		if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))

  			awaken = 1;

  		ret = 0;
  
  		/* and link it into the destination keyring */

  		if (keyring && link_ret == 0)
  			__key_link(keyring, key, &prealloc);

  
  		/* disable the authorisation key */

  		if (authkey)
  			key_revoke(authkey);

  	}

  	mutex_unlock(&key_construction_mutex);

  
  	if (keyring)

  		__key_link_end(keyring, key->type, prealloc);

  
  	/* wake up anyone waiting for a key to be constructed */
  	if (awaken)

  		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);

  	return ret == 0 ? link_ret : ret;

  }

  EXPORT_SYMBOL(key_reject_and_link);

  /**
   * key_put - Discard a reference to a key.
   * @key: The key to discard a reference from.
   *
   * Discard a reference to a key, and when all the references are gone, we
   * schedule the cleanup task to come and pull it out of the tree in process
   * context at some later time.

   */
  void key_put(struct key *key)
  {
  	if (key) {
  		key_check(key);
  
  		if (atomic_dec_and_test(&key->usage))

  			queue_work(system_nrt_wq, &key_gc_work);

  	}

  }

  EXPORT_SYMBOL(key_put);

  /*

   * Find a key by its serial number.

   */
  struct key *key_lookup(key_serial_t id)
  {
  	struct rb_node *n;
  	struct key *key;
  
  	spin_lock(&key_serial_lock);
  
  	/* search the tree for the specified key */
  	n = key_serial_tree.rb_node;
  	while (n) {
  		key = rb_entry(n, struct key, serial_node);
  
  		if (id < key->serial)
  			n = n->rb_left;
  		else if (id > key->serial)
  			n = n->rb_right;
  		else
  			goto found;
  	}

  not_found:

  	key = ERR_PTR(-ENOKEY);
  	goto error;

  found:

  	/* pretend it doesn't exist if it is awaiting deletion */
  	if (atomic_read(&key->usage) == 0)

  		goto not_found;
  
  	/* this races with key_put(), but that doesn't matter since key_put()
  	 * doesn't actually change the key
  	 */
  	atomic_inc(&key->usage);

  error:

  	spin_unlock(&key_serial_lock);
  	return key;

  }

  /*

   * Find and lock the specified key type against removal.
   *
   * We return with the sem read-locked if successful.  If the type wasn't
   * available -ENOKEY is returned instead.

   */
  struct key_type *key_type_lookup(const char *type)
  {
  	struct key_type *ktype;
  
  	down_read(&key_types_sem);
  
  	/* look up the key type to see if it's one of the registered kernel
  	 * types */
  	list_for_each_entry(ktype, &key_types_list, link) {
  		if (strcmp(ktype->name, type) == 0)
  			goto found_kernel_type;
  	}
  
  	up_read(&key_types_sem);
  	ktype = ERR_PTR(-ENOKEY);

  found_kernel_type:

  	return ktype;

  }

  /*

   * Unlock a key type locked by key_type_lookup().

   */
  void key_type_put(struct key_type *ktype)
  {
  	up_read(&key_types_sem);

  }

  /*

   * Attempt to update an existing key.
   *
   * The key is given to us with an incremented refcount that we need to discard
   * if we get an error.

   */

  static inline key_ref_t __key_update(key_ref_t key_ref,
  				     const void *payload, size_t plen)

  {

  	struct key *key = key_ref_to_ptr(key_ref);

  	int ret;
  
  	/* need write permission on the key to update it */

  	ret = key_permission(key_ref, KEY_WRITE);
  	if (ret < 0)

  		goto error;
  
  	ret = -EEXIST;
  	if (!key->type->update)
  		goto error;
  
  	down_write(&key->sem);
  
  	ret = key->type->update(key, payload, plen);

  	if (ret == 0)

  		/* updating a negative key instantiates it */

  		clear_bit(KEY_FLAG_NEGATIVE, &key->flags);

  
  	up_write(&key->sem);
  
  	if (ret < 0)
  		goto error;

  out:
  	return key_ref;

  error:

  	key_put(key);

  	key_ref = ERR_PTR(ret);

  	goto out;

  }

  /**
   * key_create_or_update - Update or create and instantiate a key.
   * @keyring_ref: A pointer to the destination keyring with possession flag.
   * @type: The type of key.
   * @description: The searchable description for the key.
   * @payload: The data to use to instantiate or update the key.
   * @plen: The length of @payload.
   * @perm: The permissions mask for a new key.
   * @flags: The quota flags for a new key.
   *
   * Search the destination keyring for a key of the same description and if one
   * is found, update it, otherwise create and instantiate a new one and create a
   * link to it from that keyring.
   *
   * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
   * concocted.
   *
   * Returns a pointer to the new key if successful, -ENODEV if the key type
   * wasn't available, -ENOTDIR if the keyring wasn't a keyring, -EACCES if the
   * caller isn't permitted to modify the keyring or the LSM did not permit
   * creation of the key.
   *
   * On success, the possession flag from the keyring ref will be tacked on to
   * the key ref before it is returned.

   */

  key_ref_t key_create_or_update(key_ref_t keyring_ref,
  			       const char *type,
  			       const char *description,
  			       const void *payload,
  			       size_t plen,

  			       key_perm_t perm,

  			       unsigned long flags)

  {

  	unsigned long prealloc;

  	const struct cred *cred = current_cred();

  	struct key_type *ktype;

  	struct key *keyring, *key = NULL;

  	key_ref_t key_ref;

  	int ret;

  	/* look up the key type to see if it's one of the registered kernel
  	 * types */
  	ktype = key_type_lookup(type);
  	if (IS_ERR(ktype)) {

  		key_ref = ERR_PTR(-ENODEV);

  		goto error;
  	}

  	key_ref = ERR_PTR(-EINVAL);

  	if (!ktype->match || !ktype->instantiate)
  		goto error_2;

  	keyring = key_ref_to_ptr(keyring_ref);
  
  	key_check(keyring);

  	key_ref = ERR_PTR(-ENOTDIR);
  	if (keyring->type != &key_type_keyring)
  		goto error_2;

  	ret = __key_link_begin(keyring, ktype, description, &prealloc);
  	if (ret < 0)
  		goto error_2;

  
  	/* if we're going to allocate a new key, we're going to have
  	 * to modify the keyring */

  	ret = key_permission(keyring_ref, KEY_WRITE);
  	if (ret < 0) {
  		key_ref = ERR_PTR(ret);

  		goto error_3;

  	}

  	/* if it's possible to update this type of key, search for an existing
  	 * key of the same type and description in the destination keyring and
  	 * update that instead if possible

  	 */

  	if (ktype->update) {
  		key_ref = __keyring_search_one(keyring_ref, ktype, description,
  					       0);
  		if (!IS_ERR(key_ref))
  			goto found_matching_key;
  	}

  	/* if the client doesn't provide, decide on the permissions we want */
  	if (perm == KEY_PERM_UNDEF) {
  		perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
  		perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;

  		if (ktype->read)
  			perm |= KEY_POS_READ | KEY_USR_READ;

  		if (ktype == &key_type_keyring || ktype->update)
  			perm |= KEY_USR_WRITE;
  	}

  
  	/* allocate a new key */

  	key = key_alloc(ktype, description, cred->fsuid, cred->fsgid, cred,
  			perm, flags);

  	if (IS_ERR(key)) {

  		key_ref = ERR_CAST(key);

  		goto error_3;
  	}
  
  	/* instantiate it and link it into the target keyring */

  	ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL,
  					 &prealloc);

  	if (ret < 0) {
  		key_put(key);

  		key_ref = ERR_PTR(ret);
  		goto error_3;

  	}

  	key_ref = make_key_ref(key, is_key_possessed(keyring_ref));

   error_3:

  	__key_link_end(keyring, ktype, prealloc);

   error_2:
  	key_type_put(ktype);
   error:

  	return key_ref;

  
   found_matching_key:
  	/* we found a matching key, so we're going to try to update it
  	 * - we can drop the locks first as we have the key pinned
  	 */

  	__key_link_end(keyring, ktype, prealloc);

  	key_type_put(ktype);

  	key_ref = __key_update(key_ref, payload, plen);

  	goto error;

  }

  EXPORT_SYMBOL(key_create_or_update);

  /**
   * key_update - Update a key's contents.
   * @key_ref: The pointer (plus possession flag) to the key.
   * @payload: The data to be used to update the key.
   * @plen: The length of @payload.
   *
   * Attempt to update the contents of a key with the given payload data.  The
   * caller must be granted Write permission on the key.  Negative keys can be
   * instantiated by this method.
   *
   * Returns 0 on success, -EACCES if not permitted and -EOPNOTSUPP if the key
   * type does not support updating.  The key type may return other errors.

   */

  int key_update(key_ref_t key_ref, const void *payload, size_t plen)

  {

  	struct key *key = key_ref_to_ptr(key_ref);

  	int ret;
  
  	key_check(key);
  
  	/* the key must be writable */

  	ret = key_permission(key_ref, KEY_WRITE);
  	if (ret < 0)

  		goto error;
  
  	/* attempt to update it if supported */
  	ret = -EOPNOTSUPP;
  	if (key->type->update) {
  		down_write(&key->sem);

  		ret = key->type->update(key, payload, plen);

  		if (ret == 0)

  			/* updating a negative key instantiates it */

  			clear_bit(KEY_FLAG_NEGATIVE, &key->flags);

  
  		up_write(&key->sem);
  	}
  
   error:
  	return ret;

  }

  EXPORT_SYMBOL(key_update);

  /**
   * key_revoke - Revoke a key.
   * @key: The key to be revoked.
   *
   * Mark a key as being revoked and ask the type to free up its resources.  The
   * revocation timeout is set and the key and all its links will be
   * automatically garbage collected after key_gc_delay amount of time if they
   * are not manually dealt with first.

   */
  void key_revoke(struct key *key)
  {

  	struct timespec now;
  	time_t time;

  	key_check(key);

  	/* make sure no one's trying to change or use the key when we mark it
  	 * - we tell lockdep that we might nest because we might be revoking an
  	 *   authorisation key whilst holding the sem on a key we've just
  	 *   instantiated
  	 */
  	down_write_nested(&key->sem, 1);
  	if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
  	    key->type->revoke)

  		key->type->revoke(key);

  	/* set the death time to no more than the expiry time */
  	now = current_kernel_time();
  	time = now.tv_sec;
  	if (key->revoked_at == 0 || key->revoked_at > time) {
  		key->revoked_at = time;

  		key_schedule_gc(key->revoked_at + key_gc_delay);

  	}

  	up_write(&key->sem);

  }

  EXPORT_SYMBOL(key_revoke);

  /**
   * register_key_type - Register a type of key.
   * @ktype: The new key type.
   *
   * Register a new key type.
   *
   * Returns 0 on success or -EEXIST if a type of this name already exists.

   */
  int register_key_type(struct key_type *ktype)
  {
  	struct key_type *p;
  	int ret;

  	memset(&ktype->lock_class, 0, sizeof(ktype->lock_class));

  	ret = -EEXIST;
  	down_write(&key_types_sem);
  
  	/* disallow key types with the same name */
  	list_for_each_entry(p, &key_types_list, link) {
  		if (strcmp(p->name, ktype->name) == 0)
  			goto out;
  	}
  
  	/* store the type */
  	list_add(&ktype->link, &key_types_list);
  	ret = 0;

  out:

  	up_write(&key_types_sem);
  	return ret;

  }

  EXPORT_SYMBOL(register_key_type);

  /**
   * unregister_key_type - Unregister a type of key.
   * @ktype: The key type.
   *
   * Unregister a key type and mark all the extant keys of this type as dead.
   * Those keys of this type are then destroyed to get rid of their payloads and
   * they and their links will be garbage collected as soon as possible.

   */
  void unregister_key_type(struct key_type *ktype)
  {

  	down_write(&key_types_sem);

  	list_del_init(&ktype->link);

  	downgrade_write(&key_types_sem);
  	key_gc_keytype(ktype);
  	up_read(&key_types_sem);

  }

  EXPORT_SYMBOL(unregister_key_type);

  /*

   * Initialise the key management state.

   */
  void __init key_init(void)
  {
  	/* allocate a slab in which we can store keys */
  	key_jar = kmem_cache_create("key_jar", sizeof(struct key),

  			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);

  
  	/* add the special key types */
  	list_add_tail(&key_type_keyring.link, &key_types_list);
  	list_add_tail(&key_type_dead.link, &key_types_list);
  	list_add_tail(&key_type_user.link, &key_types_list);
  
  	/* record the root user tracking */
  	rb_link_node(&root_key_user.node,
  		     NULL,
  		     &key_user_tree.rb_node);
  
  	rb_insert_color(&root_key_user.node,
  			&key_user_tree);

  }