/* Userspace key control operations

   *

   * Copyright (C) 2004-5 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/sched.h>
  #include <linux/slab.h>
  #include <linux/syscalls.h>
  #include <linux/keyctl.h>
  #include <linux/fs.h>

  #include <linux/capability.h>

  #include <linux/string.h>

  #include <linux/err.h>

  #include <linux/vmalloc.h>

  #include <linux/security.h>

  #include <asm/uaccess.h>
  #include "internal.h"

  static int key_get_type_from_user(char *type,
  				  const char __user *_type,
  				  unsigned len)
  {
  	int ret;
  
  	ret = strncpy_from_user(type, _type, len);

  	if (ret < 0)

  		return ret;

  	if (ret == 0 || ret >= len)
  		return -EINVAL;

  	if (type[0] == '.')
  		return -EPERM;

  	type[len - 1] = '\0';

  	return 0;
  }

  /*

   * Extract the description of a new key from userspace and either add it as a
   * new key to the specified keyring or update a matching key in that keyring.
   *
   * The keyring must be writable so that we can attach the key to it.
   *
   * If successful, the new key's serial number is returned, otherwise an error
   * code is returned.

   */

  SYSCALL_DEFINE5(add_key, const char __user *, _type,
  		const char __user *, _description,
  		const void __user *, _payload,
  		size_t, plen,
  		key_serial_t, ringid)

  {

  	key_ref_t keyring_ref, key_ref;

  	char type[32], *description;
  	void *payload;

  	long ret;

  	bool vm;

  
  	ret = -EINVAL;

  	if (plen > 1024 * 1024 - 1)

  		goto error;
  
  	/* draw all the data into kernel space */

  	ret = key_get_type_from_user(type, _type, sizeof(type));

  	if (ret < 0)
  		goto error;

  	description = strndup_user(_description, PAGE_SIZE);
  	if (IS_ERR(description)) {
  		ret = PTR_ERR(description);

  		goto error;

  	}

  
  	/* pull the payload in if one was supplied */
  	payload = NULL;

  	vm = false;

  	if (_payload) {
  		ret = -ENOMEM;
  		payload = kmalloc(plen, GFP_KERNEL);

  		if (!payload) {
  			if (plen <= PAGE_SIZE)
  				goto error2;
  			vm = true;
  			payload = vmalloc(plen);
  			if (!payload)
  				goto error2;
  		}

  
  		ret = -EFAULT;
  		if (copy_from_user(payload, _payload, plen) != 0)
  			goto error3;
  	}
  
  	/* find the target keyring (which must be writable) */

  	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);

  	if (IS_ERR(keyring_ref)) {
  		ret = PTR_ERR(keyring_ref);

  		goto error3;
  	}
  
  	/* create or update the requested key and add it to the target
  	 * keyring */

  	key_ref = key_create_or_update(keyring_ref, type, description,

  				       payload, plen, KEY_PERM_UNDEF,
  				       KEY_ALLOC_IN_QUOTA);

  	if (!IS_ERR(key_ref)) {
  		ret = key_ref_to_ptr(key_ref)->serial;
  		key_ref_put(key_ref);

  	}
  	else {

  		ret = PTR_ERR(key_ref);

  	}

  	key_ref_put(keyring_ref);

   error3:

  	if (!vm)
  		kfree(payload);
  	else
  		vfree(payload);

   error2:
  	kfree(description);
   error:
  	return ret;

  }

  /*

   * Search the process keyrings and keyring trees linked from those for a
   * matching key.  Keyrings must have appropriate Search permission to be
   * searched.
   *
   * If a key is found, it will be attached to the destination keyring if there's
   * one specified and the serial number of the key will be returned.
   *
   * If no key is found, /sbin/request-key will be invoked if _callout_info is
   * non-NULL in an attempt to create a key.  The _callout_info string will be
   * passed to /sbin/request-key to aid with completing the request.  If the
   * _callout_info string is "" then it will be changed to "-".

   */

  SYSCALL_DEFINE4(request_key, const char __user *, _type,
  		const char __user *, _description,
  		const char __user *, _callout_info,
  		key_serial_t, destringid)

  {
  	struct key_type *ktype;

  	struct key *key;
  	key_ref_t dest_ref;

  	size_t callout_len;

  	char type[32], *description, *callout_info;

  	long ret;

  
  	/* pull the type into kernel space */

  	ret = key_get_type_from_user(type, _type, sizeof(type));

  	if (ret < 0)
  		goto error;

  	/* pull the description into kernel space */

  	description = strndup_user(_description, PAGE_SIZE);
  	if (IS_ERR(description)) {
  		ret = PTR_ERR(description);

  		goto error;

  	}

  
  	/* pull the callout info into kernel space */
  	callout_info = NULL;

  	callout_len = 0;

  	if (_callout_info) {

  		callout_info = strndup_user(_callout_info, PAGE_SIZE);
  		if (IS_ERR(callout_info)) {
  			ret = PTR_ERR(callout_info);

  			goto error2;

  		}

  		callout_len = strlen(callout_info);

  	}
  
  	/* get the destination keyring if specified */

  	dest_ref = NULL;

  	if (destringid) {

  		dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
  					   KEY_WRITE);

  		if (IS_ERR(dest_ref)) {
  			ret = PTR_ERR(dest_ref);

  			goto error3;
  		}
  	}
  
  	/* find the key type */
  	ktype = key_type_lookup(type);
  	if (IS_ERR(ktype)) {
  		ret = PTR_ERR(ktype);
  		goto error4;
  	}
  
  	/* do the search */

  	key = request_key_and_link(ktype, description, callout_info,
  				   callout_len, NULL, key_ref_to_ptr(dest_ref),

  				   KEY_ALLOC_IN_QUOTA);

  	if (IS_ERR(key)) {
  		ret = PTR_ERR(key);
  		goto error5;
  	}

  	/* wait for the key to finish being constructed */
  	ret = wait_for_key_construction(key, 1);
  	if (ret < 0)
  		goto error6;

  	ret = key->serial;

  error6:

   	key_put(key);

  error5:

  	key_type_put(ktype);

  error4:

  	key_ref_put(dest_ref);

  error3:

  	kfree(callout_info);

  error2:

  	kfree(description);

  error:

  	return ret;

  }

  /*

   * Get the ID of the specified process keyring.
   *
   * The requested keyring must have search permission to be found.
   *
   * If successful, the ID of the requested keyring will be returned.

   */
  long keyctl_get_keyring_ID(key_serial_t id, int create)
  {

  	key_ref_t key_ref;

  	unsigned long lflags;

  	long ret;

  	lflags = create ? KEY_LOOKUP_CREATE : 0;
  	key_ref = lookup_user_key(id, lflags, KEY_SEARCH);

  	if (IS_ERR(key_ref)) {
  		ret = PTR_ERR(key_ref);

  		goto error;
  	}

  	ret = key_ref_to_ptr(key_ref)->serial;
  	key_ref_put(key_ref);

  error:

  	return ret;

  }

  /*

   * Join a (named) session keyring.
   *
   * Create and join an anonymous session keyring or join a named session
   * keyring, creating it if necessary.  A named session keyring must have Search
   * permission for it to be joined.  Session keyrings without this permit will
   * be skipped over.
   *
   * If successful, the ID of the joined session keyring will be returned.

   */
  long keyctl_join_session_keyring(const char __user *_name)
  {
  	char *name;

  	long ret;

  
  	/* fetch the name from userspace */
  	name = NULL;
  	if (_name) {

  		name = strndup_user(_name, PAGE_SIZE);
  		if (IS_ERR(name)) {
  			ret = PTR_ERR(name);

  			goto error;

  		}

  	}
  
  	/* join the session */
  	ret = join_session_keyring(name);

  	kfree(name);

  error:

  	return ret;

  }

  /*

   * Update a key's data payload from the given data.
   *
   * The key must grant the caller Write permission and the key type must support
   * updating for this to work.  A negative key can be positively instantiated
   * with this call.
   *
   * If successful, 0 will be returned.  If the key type does not support
   * updating, then -EOPNOTSUPP will be returned.

   */
  long keyctl_update_key(key_serial_t id,
  		       const void __user *_payload,
  		       size_t plen)
  {

  	key_ref_t key_ref;

  	void *payload;
  	long ret;
  
  	ret = -EINVAL;
  	if (plen > PAGE_SIZE)
  		goto error;
  
  	/* pull the payload in if one was supplied */
  	payload = NULL;
  	if (_payload) {
  		ret = -ENOMEM;
  		payload = kmalloc(plen, GFP_KERNEL);
  		if (!payload)
  			goto error;
  
  		ret = -EFAULT;
  		if (copy_from_user(payload, _payload, plen) != 0)
  			goto error2;
  	}
  
  	/* find the target key (which must be writable) */

  	key_ref = lookup_user_key(id, 0, KEY_WRITE);

  	if (IS_ERR(key_ref)) {
  		ret = PTR_ERR(key_ref);

  		goto error2;
  	}
  
  	/* update the key */

  	ret = key_update(key_ref, payload, plen);

  	key_ref_put(key_ref);

  error2:

  	kfree(payload);

  error:

  	return ret;

  }

  /*

   * Revoke a key.
   *
   * The key must be grant the caller Write or Setattr permission for this to
   * work.  The key type should give up its quota claim when revoked.  The key
   * and any links to the key will be automatically garbage collected after a
   * certain amount of time (/proc/sys/kernel/keys/gc_delay).
   *
   * If successful, 0 is returned.

   */
  long keyctl_revoke_key(key_serial_t id)
  {

  	key_ref_t key_ref;

  	long ret;

  	key_ref = lookup_user_key(id, 0, KEY_WRITE);

  	if (IS_ERR(key_ref)) {
  		ret = PTR_ERR(key_ref);

  		if (ret != -EACCES)
  			goto error;
  		key_ref = lookup_user_key(id, 0, KEY_SETATTR);
  		if (IS_ERR(key_ref)) {
  			ret = PTR_ERR(key_ref);
  			goto error;
  		}

  	}

  	key_revoke(key_ref_to_ptr(key_ref));

  	ret = 0;

  	key_ref_put(key_ref);

  error:

  	return ret;

  }

  /*

   * Clear the specified keyring, creating an empty process keyring if one of the
   * special keyring IDs is used.
   *
   * The keyring must grant the caller Write permission for this to work.  If
   * successful, 0 will be returned.

   */
  long keyctl_keyring_clear(key_serial_t ringid)
  {

  	key_ref_t keyring_ref;

  	long ret;

  	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);

  	if (IS_ERR(keyring_ref)) {
  		ret = PTR_ERR(keyring_ref);

  		goto error;
  	}

  	ret = keyring_clear(key_ref_to_ptr(keyring_ref));

  	key_ref_put(keyring_ref);

  error:

  	return ret;

  }

  /*

   * Create a link from a keyring to a key if there's no matching key in the
   * keyring, otherwise replace the link to the matching key with a link to the
   * new key.
   *
   * The key must grant the caller Link permission and the the keyring must grant
   * the caller Write permission.  Furthermore, if an additional link is created,
   * the keyring's quota will be extended.
   *
   * If successful, 0 will be returned.

   */
  long keyctl_keyring_link(key_serial_t id, key_serial_t ringid)
  {

  	key_ref_t keyring_ref, key_ref;

  	long ret;

  	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);

  	if (IS_ERR(keyring_ref)) {
  		ret = PTR_ERR(keyring_ref);

  		goto error;
  	}

  	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_LINK);

  	if (IS_ERR(key_ref)) {
  		ret = PTR_ERR(key_ref);

  		goto error2;
  	}

  	ret = key_link(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));

  	key_ref_put(key_ref);

  error2:

  	key_ref_put(keyring_ref);

  error:

  	return ret;

  }

  /*

   * Unlink a key from a keyring.
   *
   * The keyring must grant the caller Write permission for this to work; the key
   * itself need not grant the caller anything.  If the last link to a key is
   * removed then that key will be scheduled for destruction.
   *
   * If successful, 0 will be returned.

   */
  long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
  {

  	key_ref_t keyring_ref, key_ref;

  	long ret;

  	keyring_ref = lookup_user_key(ringid, 0, KEY_WRITE);

  	if (IS_ERR(keyring_ref)) {
  		ret = PTR_ERR(keyring_ref);

  		goto error;
  	}

  	key_ref = lookup_user_key(id, KEY_LOOKUP_FOR_UNLINK, 0);

  	if (IS_ERR(key_ref)) {
  		ret = PTR_ERR(key_ref);

  		goto error2;
  	}

  	ret = key_unlink(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));

  	key_ref_put(key_ref);

  error2:

  	key_ref_put(keyring_ref);

  error:

  	return ret;

  }

  /*

   * Return a description of a key to userspace.
   *
   * The key must grant the caller View permission for this to work.
   *
   * If there's a buffer, we place up to buflen bytes of data into it formatted
   * in the following way:
   *

   *	type;uid;gid;perm;description<NUL>

   *
   * If successful, we return the amount of description available, irrespective
   * of how much we may have copied into the buffer.

   */
  long keyctl_describe_key(key_serial_t keyid,
  			 char __user *buffer,
  			 size_t buflen)
  {

  	struct key *key, *instkey;

  	key_ref_t key_ref;

  	char *tmpbuf;
  	long ret;

  	key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_VIEW);

  	if (IS_ERR(key_ref)) {

  		/* viewing a key under construction is permitted if we have the
  		 * authorisation token handy */

  		if (PTR_ERR(key_ref) == -EACCES) {

  			instkey = key_get_instantiation_authkey(keyid);
  			if (!IS_ERR(instkey)) {
  				key_put(instkey);

  				key_ref = lookup_user_key(keyid,

  							  KEY_LOOKUP_PARTIAL,
  							  0);

  				if (!IS_ERR(key_ref))

  					goto okay;
  			}
  		}

  		ret = PTR_ERR(key_ref);

  		goto error;
  	}

  okay:

  	/* calculate how much description we're going to return */
  	ret = -ENOMEM;
  	tmpbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
  	if (!tmpbuf)
  		goto error2;

  	key = key_ref_to_ptr(key_ref);

  	ret = snprintf(tmpbuf, PAGE_SIZE - 1,

  		       "%s;%d;%d;%08x;%s",

  		       key->type->name,
  		       key->uid,
  		       key->gid,
  		       key->perm,
  		       key->description ?: "");

  
  	/* include a NUL char at the end of the data */
  	if (ret > PAGE_SIZE - 1)
  		ret = PAGE_SIZE - 1;
  	tmpbuf[ret] = 0;
  	ret++;
  
  	/* consider returning the data */
  	if (buffer && buflen > 0) {
  		if (buflen > ret)
  			buflen = ret;
  
  		if (copy_to_user(buffer, tmpbuf, buflen) != 0)
  			ret = -EFAULT;
  	}
  
  	kfree(tmpbuf);

  error2:

  	key_ref_put(key_ref);

  error:

  	return ret;

  }

  /*

   * Search the specified keyring and any keyrings it links to for a matching
   * key.  Only keyrings that grant the caller Search permission will be searched
   * (this includes the starting keyring).  Only keys with Search permission can
   * be found.
   *
   * If successful, the found key will be linked to the destination keyring if
   * supplied and the key has Link permission, and the found key ID will be
   * returned.

   */
  long keyctl_keyring_search(key_serial_t ringid,
  			   const char __user *_type,
  			   const char __user *_description,
  			   key_serial_t destringid)
  {
  	struct key_type *ktype;

  	key_ref_t keyring_ref, key_ref, dest_ref;

  	char type[32], *description;

  	long ret;

  
  	/* pull the type and description into kernel space */

  	ret = key_get_type_from_user(type, _type, sizeof(type));

  	if (ret < 0)
  		goto error;

  	description = strndup_user(_description, PAGE_SIZE);
  	if (IS_ERR(description)) {
  		ret = PTR_ERR(description);

  		goto error;

  	}

  
  	/* get the keyring at which to begin the search */

  	keyring_ref = lookup_user_key(ringid, 0, KEY_SEARCH);

  	if (IS_ERR(keyring_ref)) {
  		ret = PTR_ERR(keyring_ref);

  		goto error2;
  	}
  
  	/* get the destination keyring if specified */

  	dest_ref = NULL;

  	if (destringid) {

  		dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
  					   KEY_WRITE);

  		if (IS_ERR(dest_ref)) {
  			ret = PTR_ERR(dest_ref);

  			goto error3;
  		}
  	}
  
  	/* find the key type */
  	ktype = key_type_lookup(type);
  	if (IS_ERR(ktype)) {
  		ret = PTR_ERR(ktype);
  		goto error4;
  	}
  
  	/* do the search */

  	key_ref = keyring_search(keyring_ref, ktype, description);
  	if (IS_ERR(key_ref)) {
  		ret = PTR_ERR(key_ref);

  
  		/* treat lack or presence of a negative key the same */
  		if (ret == -EAGAIN)
  			ret = -ENOKEY;
  		goto error5;
  	}
  
  	/* link the resulting key to the destination keyring if we can */

  	if (dest_ref) {

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

  			goto error6;

  		ret = key_link(key_ref_to_ptr(dest_ref), key_ref_to_ptr(key_ref));

  		if (ret < 0)
  			goto error6;
  	}

  	ret = key_ref_to_ptr(key_ref)->serial;

  error6:

  	key_ref_put(key_ref);

  error5:

  	key_type_put(ktype);

  error4:

  	key_ref_put(dest_ref);

  error3:

  	key_ref_put(keyring_ref);

  error2:

  	kfree(description);

  error:

  	return ret;

  }

  /*

   * Read a key's payload.
   *
   * The key must either grant the caller Read permission, or it must grant the
   * caller Search permission when searched for from the process keyrings.
   *
   * If successful, we place up to buflen bytes of data into the buffer, if one
   * is provided, and return the amount of data that is available in the key,
   * irrespective of how much we copied into the buffer.

   */
  long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
  {

  	struct key *key;
  	key_ref_t key_ref;

  	long ret;
  
  	/* find the key first */

  	key_ref = lookup_user_key(keyid, 0, 0);

  	if (IS_ERR(key_ref)) {
  		ret = -ENOKEY;
  		goto error;

  	}

  	key = key_ref_to_ptr(key_ref);
  
  	/* see if we can read it directly */

  	ret = key_permission(key_ref, KEY_READ);
  	if (ret == 0)

  		goto can_read_key;

  	if (ret != -EACCES)
  		goto error;

  
  	/* we can't; see if it's searchable from this process's keyrings
  	 * - we automatically take account of the fact that it may be
  	 *   dangling off an instantiation key
  	 */
  	if (!is_key_possessed(key_ref)) {
  		ret = -EACCES;
  		goto error2;
  	}

  
  	/* the key is probably readable - now try to read it */

  can_read_key:

  	ret = key_validate(key);
  	if (ret == 0) {
  		ret = -EOPNOTSUPP;
  		if (key->type->read) {
  			/* read the data with the semaphore held (since we
  			 * might sleep) */
  			down_read(&key->sem);
  			ret = key->type->read(key, buffer, buflen);
  			up_read(&key->sem);
  		}
  	}

  error2:

  	key_put(key);

  error:

  	return ret;

  }

  /*

   * Change the ownership of a key
   *
   * The key must grant the caller Setattr permission for this to work, though
   * the key need not be fully instantiated yet.  For the UID to be changed, or
   * for the GID to be changed to a group the caller is not a member of, the
   * caller must have sysadmin capability.  If either uid or gid is -1 then that
   * attribute is not changed.
   *
   * If the UID is to be changed, the new user must have sufficient quota to
   * accept the key.  The quota deduction will be removed from the old user to
   * the new user should the attribute be changed.
   *
   * If successful, 0 will be returned.

   */
  long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
  {

  	struct key_user *newowner, *zapowner = NULL;

  	struct key *key;

  	key_ref_t key_ref;

  	long ret;
  
  	ret = 0;
  	if (uid == (uid_t) -1 && gid == (gid_t) -1)
  		goto error;

  	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
  				  KEY_SETATTR);

  	if (IS_ERR(key_ref)) {
  		ret = PTR_ERR(key_ref);

  		goto error;
  	}

  	key = key_ref_to_ptr(key_ref);

  	/* make the changes with the locks held to prevent chown/chown races */
  	ret = -EACCES;
  	down_write(&key->sem);

  
  	if (!capable(CAP_SYS_ADMIN)) {
  		/* only the sysadmin can chown a key to some other UID */
  		if (uid != (uid_t) -1 && key->uid != uid)

  			goto error_put;

  
  		/* only the sysadmin can set the key's GID to a group other
  		 * than one of those that the current process subscribes to */
  		if (gid != (gid_t) -1 && gid != key->gid && !in_group_p(gid))

  			goto error_put;

  	}

  	/* change the UID */

  	if (uid != (uid_t) -1 && uid != key->uid) {

  		ret = -ENOMEM;

  		newowner = key_user_lookup(uid, current_user_ns());

  		if (!newowner)
  			goto error_put;
  
  		/* transfer the quota burden to the new user */
  		if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {

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

  			spin_lock(&newowner->lock);

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

  				goto quota_overrun;
  
  			newowner->qnkeys++;
  			newowner->qnbytes += key->quotalen;
  			spin_unlock(&newowner->lock);
  
  			spin_lock(&key->user->lock);
  			key->user->qnkeys--;
  			key->user->qnbytes -= key->quotalen;
  			spin_unlock(&key->user->lock);
  		}
  
  		atomic_dec(&key->user->nkeys);
  		atomic_inc(&newowner->nkeys);
  
  		if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
  			atomic_dec(&key->user->nikeys);
  			atomic_inc(&newowner->nikeys);
  		}
  
  		zapowner = key->user;
  		key->user = newowner;
  		key->uid = uid;

  	}
  
  	/* change the GID */
  	if (gid != (gid_t) -1)
  		key->gid = gid;
  
  	ret = 0;

  error_put:

  	up_write(&key->sem);
  	key_put(key);

  	if (zapowner)
  		key_user_put(zapowner);
  error:

  	return ret;

  quota_overrun:
  	spin_unlock(&newowner->lock);
  	zapowner = newowner;
  	ret = -EDQUOT;
  	goto error_put;

  }

  /*

   * Change the permission mask on a key.
   *
   * The key must grant the caller Setattr permission for this to work, though
   * the key need not be fully instantiated yet.  If the caller does not have
   * sysadmin capability, it may only change the permission on keys that it owns.

   */
  long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
  {
  	struct key *key;

  	key_ref_t key_ref;

  	long ret;
  
  	ret = -EINVAL;

  	if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))

  		goto error;

  	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
  				  KEY_SETATTR);

  	if (IS_ERR(key_ref)) {
  		ret = PTR_ERR(key_ref);

  		goto error;
  	}

  	key = key_ref_to_ptr(key_ref);

  	/* make the changes with the locks held to prevent chown/chmod races */

  	ret = -EACCES;
  	down_write(&key->sem);

  	/* if we're not the sysadmin, we can only change a key that we own */

  	if (capable(CAP_SYS_ADMIN) || key->uid == current_fsuid()) {

  		key->perm = perm;
  		ret = 0;
  	}

  	up_write(&key->sem);
  	key_put(key);

  error:

  	return ret;

  }

  /*

   * Get the destination keyring for instantiation and check that the caller has
   * Write permission on it.

   */
  static long get_instantiation_keyring(key_serial_t ringid,
  				      struct request_key_auth *rka,
  				      struct key **_dest_keyring)
  {
  	key_ref_t dkref;

  	*_dest_keyring = NULL;

  	/* just return a NULL pointer if we weren't asked to make a link */

  	if (ringid == 0)

  		return 0;

  
  	/* if a specific keyring is nominated by ID, then use that */
  	if (ringid > 0) {

  		dkref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);

  		if (IS_ERR(dkref))
  			return PTR_ERR(dkref);
  		*_dest_keyring = key_ref_to_ptr(dkref);
  		return 0;
  	}
  
  	if (ringid == KEY_SPEC_REQKEY_AUTH_KEY)
  		return -EINVAL;
  
  	/* otherwise specify the destination keyring recorded in the
  	 * authorisation key (any KEY_SPEC_*_KEYRING) */
  	if (ringid >= KEY_SPEC_REQUESTOR_KEYRING) {

  		*_dest_keyring = key_get(rka->dest_keyring);

  		return 0;
  	}
  
  	return -ENOKEY;
  }

  /*

   * Change the request_key authorisation key on the current process.

   */
  static int keyctl_change_reqkey_auth(struct key *key)
  {
  	struct cred *new;
  
  	new = prepare_creds();
  	if (!new)
  		return -ENOMEM;
  
  	key_put(new->request_key_auth);
  	new->request_key_auth = key_get(key);
  
  	return commit_creds(new);
  }

  /*

   * Copy the iovec data from userspace
   */
  static long copy_from_user_iovec(void *buffer, const struct iovec *iov,
  				 unsigned ioc)
  {
  	for (; ioc > 0; ioc--) {
  		if (copy_from_user(buffer, iov->iov_base, iov->iov_len) != 0)
  			return -EFAULT;
  		buffer += iov->iov_len;
  		iov++;
  	}
  	return 0;
  }
  
  /*

   * Instantiate a key with the specified payload and link the key into the
   * destination keyring if one is given.
   *
   * The caller must have the appropriate instantiation permit set for this to
   * work (see keyctl_assume_authority).  No other permissions are required.
   *
   * If successful, 0 will be returned.

   */

  long keyctl_instantiate_key_common(key_serial_t id,
  				   const struct iovec *payload_iov,
  				   unsigned ioc,
  				   size_t plen,
  				   key_serial_t ringid)

  {

  	const struct cred *cred = current_cred();

  	struct request_key_auth *rka;

  	struct key *instkey, *dest_keyring;

  	void *payload;
  	long ret;

  	bool vm = false;

  	kenter("%d,,%zu,%d", id, plen, ringid);

  	ret = -EINVAL;

  	if (plen > 1024 * 1024 - 1)

  		goto error;

  	/* the appropriate instantiation authorisation key must have been
  	 * assumed before calling this */
  	ret = -EPERM;

  	instkey = cred->request_key_auth;

  	if (!instkey)
  		goto error;
  
  	rka = instkey->payload.data;
  	if (rka->target_key->serial != id)
  		goto error;

  	/* pull the payload in if one was supplied */
  	payload = NULL;

  	if (payload_iov) {

  		ret = -ENOMEM;
  		payload = kmalloc(plen, GFP_KERNEL);

  		if (!payload) {
  			if (plen <= PAGE_SIZE)
  				goto error;
  			vm = true;
  			payload = vmalloc(plen);
  			if (!payload)
  				goto error;
  		}

  		ret = copy_from_user_iovec(payload, payload_iov, ioc);
  		if (ret < 0)

  			goto error2;
  	}

  	/* find the destination keyring amongst those belonging to the
  	 * requesting task */

  	ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
  	if (ret < 0)
  		goto error2;

  
  	/* instantiate the key and link it into a keyring */

  	ret = key_instantiate_and_link(rka->target_key, payload, plen,

  				       dest_keyring, instkey);

  	key_put(dest_keyring);

  
  	/* discard the assumed authority if it's just been disabled by
  	 * instantiation of the key */

  	if (ret == 0)
  		keyctl_change_reqkey_auth(NULL);

  
  error2:

  	if (!vm)
  		kfree(payload);
  	else
  		vfree(payload);

  error:

  	return ret;

  }

  /*

   * Instantiate a key with the specified payload and link the key into the
   * destination keyring if one is given.
   *
   * The caller must have the appropriate instantiation permit set for this to
   * work (see keyctl_assume_authority).  No other permissions are required.
   *
   * If successful, 0 will be returned.
   */
  long keyctl_instantiate_key(key_serial_t id,
  			    const void __user *_payload,
  			    size_t plen,
  			    key_serial_t ringid)
  {
  	if (_payload && plen) {
  		struct iovec iov[1] = {
  			[0].iov_base = (void __user *)_payload,
  			[0].iov_len  = plen
  		};
  
  		return keyctl_instantiate_key_common(id, iov, 1, plen, ringid);
  	}
  
  	return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
  }
  
  /*
   * Instantiate a key with the specified multipart payload and link the key into
   * the destination keyring if one is given.
   *
   * The caller must have the appropriate instantiation permit set for this to
   * work (see keyctl_assume_authority).  No other permissions are required.
   *
   * If successful, 0 will be returned.
   */
  long keyctl_instantiate_key_iov(key_serial_t id,
  				const struct iovec __user *_payload_iov,
  				unsigned ioc,
  				key_serial_t ringid)
  {
  	struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
  	long ret;
  
  	if (_payload_iov == 0 || ioc == 0)
  		goto no_payload;
  
  	ret = rw_copy_check_uvector(WRITE, _payload_iov, ioc,

  				    ARRAY_SIZE(iovstack), iovstack, &iov, 1);

  	if (ret < 0)
  		return ret;
  	if (ret == 0)
  		goto no_payload_free;
  
  	ret = keyctl_instantiate_key_common(id, iov, ioc, ret, ringid);
  
  	if (iov != iovstack)
  		kfree(iov);
  	return ret;
  
  no_payload_free:
  	if (iov != iovstack)
  		kfree(iov);
  no_payload:
  	return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
  }
  
  /*

   * Negatively instantiate the key with the given timeout (in seconds) and link
   * the key into the destination keyring if one is given.
   *
   * The caller must have the appropriate instantiation permit set for this to
   * work (see keyctl_assume_authority).  No other permissions are required.
   *
   * 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 -ENOKEY until the negative key expires.
   *
   * If successful, 0 will be returned.

   */
  long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
  {

  	return keyctl_reject_key(id, timeout, ENOKEY, ringid);
  }
  
  /*
   * Negatively instantiate the key with the given timeout (in seconds) and error
   * code and link the key into the destination keyring if one is given.
   *
   * The caller must have the appropriate instantiation permit set for this to
   * work (see keyctl_assume_authority).  No other permissions are required.
   *
   * 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 specified error code until the negative key expires.
   *
   * If successful, 0 will be returned.
   */
  long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
  		       key_serial_t ringid)
  {

  	const struct cred *cred = current_cred();

  	struct request_key_auth *rka;

  	struct key *instkey, *dest_keyring;

  	long ret;

  	kenter("%d,%u,%u,%d", id, timeout, error, ringid);
  
  	/* must be a valid error code and mustn't be a kernel special */
  	if (error <= 0 ||
  	    error >= MAX_ERRNO ||
  	    error == ERESTARTSYS ||
  	    error == ERESTARTNOINTR ||
  	    error == ERESTARTNOHAND ||
  	    error == ERESTART_RESTARTBLOCK)
  		return -EINVAL;

  	/* the appropriate instantiation authorisation key must have been
  	 * assumed before calling this */
  	ret = -EPERM;

  	instkey = cred->request_key_auth;

  	if (!instkey)

  		goto error;

  	rka = instkey->payload.data;

  	if (rka->target_key->serial != id)
  		goto error;

  	/* find the destination keyring if present (which must also be
  	 * writable) */

  	ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
  	if (ret < 0)
  		goto error;

  
  	/* instantiate the key and link it into a keyring */

  	ret = key_reject_and_link(rka->target_key, timeout, error,

  				  dest_keyring, instkey);

  	key_put(dest_keyring);

  
  	/* discard the assumed authority if it's just been disabled by
  	 * instantiation of the key */

  	if (ret == 0)
  		keyctl_change_reqkey_auth(NULL);

  
  error:

  	return ret;

  }

  /*

   * Read or set the default keyring in which request_key() will cache keys and
   * return the old setting.
   *
   * If a process keyring is specified then this will be created if it doesn't
   * yet exist.  The old setting will be returned if successful.

   */
  long keyctl_set_reqkey_keyring(int reqkey_defl)
  {

  	struct cred *new;
  	int ret, old_setting;
  
  	old_setting = current_cred_xxx(jit_keyring);
  
  	if (reqkey_defl == KEY_REQKEY_DEFL_NO_CHANGE)
  		return old_setting;
  
  	new = prepare_creds();
  	if (!new)
  		return -ENOMEM;

  
  	switch (reqkey_defl) {
  	case KEY_REQKEY_DEFL_THREAD_KEYRING:

  		ret = install_thread_keyring_to_cred(new);

  		if (ret < 0)

  			goto error;

  		goto set;
  
  	case KEY_REQKEY_DEFL_PROCESS_KEYRING:

  		ret = install_process_keyring_to_cred(new);
  		if (ret < 0) {
  			if (ret != -EEXIST)
  				goto error;
  			ret = 0;
  		}
  		goto set;

  
  	case KEY_REQKEY_DEFL_DEFAULT:
  	case KEY_REQKEY_DEFL_SESSION_KEYRING:
  	case KEY_REQKEY_DEFL_USER_KEYRING:
  	case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:

  	case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
  		goto set;

  
  	case KEY_REQKEY_DEFL_NO_CHANGE:

  	case KEY_REQKEY_DEFL_GROUP_KEYRING:
  	default:

  		ret = -EINVAL;
  		goto error;

  	}

  set:
  	new->jit_keyring = reqkey_defl;
  	commit_creds(new);
  	return old_setting;
  error:
  	abort_creds(new);

  	return ret;

  }

  /*

   * Set or clear the timeout on a key.
   *
   * Either the key must grant the caller Setattr permission or else the caller
   * must hold an instantiation authorisation token for the key.
   *
   * The timeout is either 0 to clear the timeout, or a number of seconds from
   * the current time.  The key and any links to the key will be automatically
   * garbage collected after the timeout expires.
   *
   * If successful, 0 is returned.

   */
  long keyctl_set_timeout(key_serial_t id, unsigned timeout)
  {
  	struct timespec now;

  	struct key *key, *instkey;

  	key_ref_t key_ref;
  	time_t expiry;
  	long ret;

  	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
  				  KEY_SETATTR);

  	if (IS_ERR(key_ref)) {

  		/* setting the timeout on a key under construction is permitted
  		 * if we have the authorisation token handy */
  		if (PTR_ERR(key_ref) == -EACCES) {
  			instkey = key_get_instantiation_authkey(id);
  			if (!IS_ERR(instkey)) {
  				key_put(instkey);
  				key_ref = lookup_user_key(id,
  							  KEY_LOOKUP_PARTIAL,
  							  0);
  				if (!IS_ERR(key_ref))
  					goto okay;
  			}
  		}

  		ret = PTR_ERR(key_ref);
  		goto error;
  	}

  okay:

  	key = key_ref_to_ptr(key_ref);
  
  	/* make the changes with the locks held to prevent races */
  	down_write(&key->sem);
  
  	expiry = 0;
  	if (timeout > 0) {
  		now = current_kernel_time();
  		expiry = now.tv_sec + timeout;
  	}
  
  	key->expiry = expiry;

  	key_schedule_gc(key->expiry + key_gc_delay);

  
  	up_write(&key->sem);
  	key_put(key);
  
  	ret = 0;
  error:
  	return ret;

  }

  /*

   * Assume (or clear) the authority to instantiate the specified key.
   *
   * This sets the authoritative token currently in force for key instantiation.
   * This must be done for a key to be instantiated.  It has the effect of making
   * available all the keys from the caller of the request_key() that created a
   * key to request_key() calls made by the caller of this function.
   *
   * The caller must have the instantiation key in their process keyrings with a
   * Search permission grant available to the caller.
   *
   * If the ID given is 0, then the setting will be cleared and 0 returned.
   *
   * If the ID given has a matching an authorisation key, then that key will be
   * set and its ID will be returned.  The authorisation key can be read to get
   * the callout information passed to request_key().

   */
  long keyctl_assume_authority(key_serial_t id)
  {
  	struct key *authkey;
  	long ret;
  
  	/* special key IDs aren't permitted */
  	ret = -EINVAL;
  	if (id < 0)
  		goto error;
  
  	/* we divest ourselves of authority if given an ID of 0 */
  	if (id == 0) {

  		ret = keyctl_change_reqkey_auth(NULL);

  		goto error;
  	}
  
  	/* attempt to assume the authority temporarily granted to us whilst we
  	 * instantiate the specified key
  	 * - the authorisation key must be in the current task's keyrings
  	 *   somewhere
  	 */
  	authkey = key_get_instantiation_authkey(id);
  	if (IS_ERR(authkey)) {
  		ret = PTR_ERR(authkey);
  		goto error;
  	}

  	ret = keyctl_change_reqkey_auth(authkey);
  	if (ret < 0)
  		goto error;
  	key_put(authkey);

  	ret = authkey->serial;

  error:
  	return ret;

  }

  /*

   * Get a key's the LSM security label.
   *
   * The key must grant the caller View permission for this to work.
   *
   * If there's a buffer, then up to buflen bytes of data will be placed into it.
   *
   * If successful, the amount of information available will be returned,
   * irrespective of how much was copied (including the terminal NUL).

   */
  long keyctl_get_security(key_serial_t keyid,
  			 char __user *buffer,
  			 size_t buflen)
  {
  	struct key *key, *instkey;
  	key_ref_t key_ref;
  	char *context;
  	long ret;

  	key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_VIEW);

  	if (IS_ERR(key_ref)) {
  		if (PTR_ERR(key_ref) != -EACCES)
  			return PTR_ERR(key_ref);
  
  		/* viewing a key under construction is also permitted if we
  		 * have the authorisation token handy */
  		instkey = key_get_instantiation_authkey(keyid);
  		if (IS_ERR(instkey))

  			return PTR_ERR(instkey);

  		key_put(instkey);

  		key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, 0);

  		if (IS_ERR(key_ref))
  			return PTR_ERR(key_ref);
  	}
  
  	key = key_ref_to_ptr(key_ref);
  	ret = security_key_getsecurity(key, &context);
  	if (ret == 0) {
  		/* if no information was returned, give userspace an empty
  		 * string */
  		ret = 1;
  		if (buffer && buflen > 0 &&
  		    copy_to_user(buffer, "", 1) != 0)
  			ret = -EFAULT;
  	} else if (ret > 0) {
  		/* return as much data as there's room for */
  		if (buffer && buflen > 0) {
  			if (buflen > ret)
  				buflen = ret;
  
  			if (copy_to_user(buffer, context, buflen) != 0)
  				ret = -EFAULT;
  		}
  
  		kfree(context);
  	}
  
  	key_ref_put(key_ref);
  	return ret;
  }

  /*

   * Attempt to install the calling process's session keyring on the process's
   * parent process.
   *
   * The keyring must exist and must grant the caller LINK permission, and the
   * parent process must be single-threaded and must have the same effective
   * ownership as this process and mustn't be SUID/SGID.
   *
   * The keyring will be emplaced on the parent when it next resumes userspace.
   *
   * If successful, 0 will be returned.

   */
  long keyctl_session_to_parent(void)
  {

  #ifdef TIF_NOTIFY_RESUME

  	struct task_struct *me, *parent;
  	const struct cred *mycred, *pcred;
  	struct cred *cred, *oldcred;
  	key_ref_t keyring_r;
  	int ret;
  
  	keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_LINK);
  	if (IS_ERR(keyring_r))
  		return PTR_ERR(keyring_r);
  
  	/* our parent is going to need a new cred struct, a new tgcred struct
  	 * and new security data, so we allocate them here to prevent ENOMEM in
  	 * our parent */
  	ret = -ENOMEM;
  	cred = cred_alloc_blank();
  	if (!cred)
  		goto error_keyring;
  
  	cred->tgcred->session_keyring = key_ref_to_ptr(keyring_r);
  	keyring_r = NULL;
  
  	me = current;

  	rcu_read_lock();

  	write_lock_irq(&tasklist_lock);
  
  	parent = me->real_parent;
  	ret = -EPERM;
  
  	/* the parent mustn't be init and mustn't be a kernel thread */
  	if (parent->pid <= 1 || !parent->mm)
  		goto not_permitted;
  
  	/* the parent must be single threaded */

  	if (!thread_group_empty(parent))

  		goto not_permitted;
  
  	/* the parent and the child must have different session keyrings or
  	 * there's no point */
  	mycred = current_cred();
  	pcred = __task_cred(parent);
  	if (mycred == pcred ||
  	    mycred->tgcred->session_keyring == pcred->tgcred->session_keyring)
  		goto already_same;
  
  	/* the parent must have the same effective ownership and mustn't be
  	 * SUID/SGID */

  	if (pcred->uid	!= mycred->euid	||

  	    pcred->euid	!= mycred->euid	||
  	    pcred->suid	!= mycred->euid	||

  	    pcred->gid	!= mycred->egid	||

  	    pcred->egid	!= mycred->egid	||
  	    pcred->sgid	!= mycred->egid)
  		goto not_permitted;
  
  	/* the keyrings must have the same UID */

  	if ((pcred->tgcred->session_keyring &&
  	     pcred->tgcred->session_keyring->uid != mycred->euid) ||

  	    mycred->tgcred->session_keyring->uid != mycred->euid)
  		goto not_permitted;

  	/* if there's an already pending keyring replacement, then we replace
  	 * that */
  	oldcred = parent->replacement_session_keyring;
  
  	/* the replacement session keyring is applied just prior to userspace
  	 * restarting */
  	parent->replacement_session_keyring = cred;
  	cred = NULL;
  	set_ti_thread_flag(task_thread_info(parent), TIF_NOTIFY_RESUME);
  
  	write_unlock_irq(&tasklist_lock);

  	rcu_read_unlock();

  	if (oldcred)
  		put_cred(oldcred);
  	return 0;
  
  already_same:
  	ret = 0;
  not_permitted:

  	write_unlock_irq(&tasklist_lock);

  	rcu_read_unlock();

  	put_cred(cred);
  	return ret;
  
  error_keyring:
  	key_ref_put(keyring_r);
  	return ret;

  
  #else /* !TIF_NOTIFY_RESUME */
  	/*
  	 * To be removed when TIF_NOTIFY_RESUME has been implemented on
  	 * m68k/xtensa
  	 */
  #warning TIF_NOTIFY_RESUME not implemented
  	return -EOPNOTSUPP;
  #endif /* !TIF_NOTIFY_RESUME */

  }

  /*

   * The key control system call

   */

  SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
  		unsigned long, arg4, unsigned long, arg5)

  {
  	switch (option) {
  	case KEYCTL_GET_KEYRING_ID:
  		return keyctl_get_keyring_ID((key_serial_t) arg2,
  					     (int) arg3);
  
  	case KEYCTL_JOIN_SESSION_KEYRING:
  		return keyctl_join_session_keyring((const char __user *) arg2);
  
  	case KEYCTL_UPDATE:
  		return keyctl_update_key((key_serial_t) arg2,
  					 (const void __user *) arg3,
  					 (size_t) arg4);
  
  	case KEYCTL_REVOKE:
  		return keyctl_revoke_key((key_serial_t) arg2);
  
  	case KEYCTL_DESCRIBE:
  		return keyctl_describe_key((key_serial_t) arg2,
  					   (char __user *) arg3,
  					   (unsigned) arg4);
  
  	case KEYCTL_CLEAR:
  		return keyctl_keyring_clear((key_serial_t) arg2);
  
  	case KEYCTL_LINK:
  		return keyctl_keyring_link((key_serial_t) arg2,
  					   (key_serial_t) arg3);
  
  	case KEYCTL_UNLINK:
  		return keyctl_keyring_unlink((key_serial_t) arg2,
  					     (key_serial_t) arg3);
  
  	case KEYCTL_SEARCH:
  		return keyctl_keyring_search((key_serial_t) arg2,
  					     (const char __user *) arg3,
  					     (const char __user *) arg4,
  					     (key_serial_t) arg5);
  
  	case KEYCTL_READ:
  		return keyctl_read_key((key_serial_t) arg2,
  				       (char __user *) arg3,
  				       (size_t) arg4);
  
  	case KEYCTL_CHOWN:
  		return keyctl_chown_key((key_serial_t) arg2,
  					(uid_t) arg3,
  					(gid_t) arg4);
  
  	case KEYCTL_SETPERM:
  		return keyctl_setperm_key((key_serial_t) arg2,
  					  (key_perm_t) arg3);
  
  	case KEYCTL_INSTANTIATE:
  		return keyctl_instantiate_key((key_serial_t) arg2,
  					      (const void __user *) arg3,
  					      (size_t) arg4,
  					      (key_serial_t) arg5);
  
  	case KEYCTL_NEGATE:
  		return keyctl_negate_key((key_serial_t) arg2,
  					 (unsigned) arg3,
  					 (key_serial_t) arg4);

  	case KEYCTL_SET_REQKEY_KEYRING:
  		return keyctl_set_reqkey_keyring(arg2);

  	case KEYCTL_SET_TIMEOUT:
  		return keyctl_set_timeout((key_serial_t) arg2,
  					  (unsigned) arg3);

  	case KEYCTL_ASSUME_AUTHORITY:
  		return keyctl_assume_authority((key_serial_t) arg2);

  	case KEYCTL_GET_SECURITY:
  		return keyctl_get_security((key_serial_t) arg2,

  					   (char __user *) arg3,

  					   (size_t) arg4);

  	case KEYCTL_SESSION_TO_PARENT:
  		return keyctl_session_to_parent();

  	case KEYCTL_REJECT:
  		return keyctl_reject_key((key_serial_t) arg2,
  					 (unsigned) arg3,
  					 (unsigned) arg4,
  					 (key_serial_t) arg5);

  	case KEYCTL_INSTANTIATE_IOV:
  		return keyctl_instantiate_key_iov(
  			(key_serial_t) arg2,
  			(const struct iovec __user *) arg3,
  			(unsigned) arg4,
  			(key_serial_t) arg5);

  	default:
  		return -EOPNOTSUPP;
  	}

  }