/* keyctl.c: userspace keyctl 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 -EFAULT;
  
  	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
   * - returns the new key's serial number
   * - implements add_key()
   */

  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, 1, 0, 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;
  
  } /* end sys_add_key() */
  
  /*****************************************************************************/
  /*
   * search the process keyrings for a matching key
   * - nested keyrings may also be searched if they have Search permission
   * - if a key is found, it will be attached to the destination keyring if
   *   there's one specified
   * - /sbin/request-key will be invoked if _callout_info is non-NULL
   *   - the _callout_info string will be passed to /sbin/request-key
   *   - if the _callout_info string is empty, it will be rendered as "-"
   * - implements request_key()
   */

  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, 1, 0, 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;
  	}

  	ret = key->serial;

   	key_put(key);

   error5:
  	key_type_put(ktype);
   error4:

  	key_ref_put(dest_ref);

   error3:
  	kfree(callout_info);
   error2:
  	kfree(description);
   error:
  	return ret;
  
  } /* end sys_request_key() */
  
  /*****************************************************************************/
  /*
   * get the ID of the specified process keyring
   * - the keyring must have search permission to be found
   * - implements keyctl(KEYCTL_GET_KEYRING_ID)
   */
  long keyctl_get_keyring_ID(key_serial_t id, int create)
  {

  	key_ref_t key_ref;

  	long ret;

  	key_ref = lookup_user_key(id, create, 0, 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;
  
  } /* end keyctl_get_keyring_ID() */
  
  /*****************************************************************************/
  /*
   * join the session keyring
   * - implements keyctl(KEYCTL_JOIN_SESSION_KEYRING)
   */
  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;
  
  } /* end keyctl_join_session_keyring() */
  
  /*****************************************************************************/
  /*
   * update a key's data payload
   * - the key must be writable
   * - implements keyctl(KEYCTL_UPDATE)
   */
  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, 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;
  
  } /* end keyctl_update_key() */
  
  /*****************************************************************************/
  /*
   * revoke a key
   * - the key must be writable
   * - implements keyctl(KEYCTL_REVOKE)
   */
  long keyctl_revoke_key(key_serial_t id)
  {

  	key_ref_t key_ref;

  	long ret;

  	key_ref = lookup_user_key(id, 0, 0, KEY_WRITE);

  	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;

  
  } /* end keyctl_revoke_key() */
  
  /*****************************************************************************/
  /*
   * clear the specified process keyring
   * - the keyring must be writable
   * - implements keyctl(KEYCTL_CLEAR)
   */
  long keyctl_keyring_clear(key_serial_t ringid)
  {

  	key_ref_t keyring_ref;

  	long ret;

  	keyring_ref = lookup_user_key(ringid, 1, 0, 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;
  
  } /* end keyctl_keyring_clear() */
  
  /*****************************************************************************/
  /*
   * link a key into a keyring
   * - the keyring must be writable
   * - the key must be linkable
   * - implements keyctl(KEYCTL_LINK)
   */
  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, 1, 0, KEY_WRITE);

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

  		goto error;
  	}

  	key_ref = lookup_user_key(id, 1, 0, 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;
  
  } /* end keyctl_keyring_link() */
  
  /*****************************************************************************/
  /*
   * unlink the first attachment of a key from a keyring
   * - the keyring must be writable
   * - we don't need any permissions on the key
   * - implements keyctl(KEYCTL_UNLINK)
   */
  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, 0, KEY_WRITE);

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

  		goto error;
  	}

  	key_ref = lookup_user_key(id, 0, 0, 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;
  
  } /* end keyctl_keyring_unlink() */
  
  /*****************************************************************************/
  /*
   * describe a user key
   * - the key must have view permission
   * - if there's a buffer, we place up to buflen bytes of data into it
   * - unless there's an error, we return the amount of description available,
   *   irrespective of how much we may have copied
   * - the description is formatted thus:
   *	type;uid;gid;perm;description<NUL>
   * - implements keyctl(KEYCTL_DESCRIBE)
   */
  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, 0, 1, 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,

  							  0, 1, 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_ref_to_ptr(key_ref)->type->name,
  		       key_ref_to_ptr(key_ref)->uid,
  		       key_ref_to_ptr(key_ref)->gid,
  		       key_ref_to_ptr(key_ref)->perm,
  		       key_ref_to_ptr(key_ref)->description ?
  		       key_ref_to_ptr(key_ref)->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;
  
  } /* end keyctl_describe_key() */
  
  /*****************************************************************************/
  /*
   * search the specified keyring for a matching key
   * - the start keyring must be searchable
   * - nested keyrings may also be searched if they are searchable
   * - only keys with search permission may be found
   * - if a key is found, it will be attached to the destination keyring if
   *   there's one specified
   * - implements keyctl(KEYCTL_SEARCH)
   */
  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, 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, 1, 0, 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;
  
  } /* end keyctl_keyring_search() */
  
  /*****************************************************************************/
  /*

   * read a user key's payload
   * - the keyring must be readable or the key must be searchable from the
   *   process's keyrings
   * - if there's a buffer, we place up to buflen bytes of data into it
   * - unless there's an error, we return the amount of data in the key,
   *   irrespective of how much we may have copied
   * - implements keyctl(KEYCTL_READ)
   */
  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, 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;
  
  } /* end keyctl_read_key() */
  
  /*****************************************************************************/
  /*
   * change the ownership of a key
   * - the keyring owned by the changer
   * - if the uid or gid is -1, then that parameter is not changed
   * - implements keyctl(KEYCTL_CHOWN)
   */
  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, 1, 1, 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;

  } /* end keyctl_chown_key() */
  
  /*****************************************************************************/
  /*
   * change the permission mask on a key
   * - the keyring owned by the changer
   * - implements keyctl(KEYCTL_SETPERM)
   */
  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, 1, 1, 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;
  
  } /* end keyctl_setperm_key() */

  /*
   * get the destination keyring for instantiation
   */
  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, 1, 0, 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 = 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);
  }

  /*****************************************************************************/
  /*
   * instantiate the key with the specified payload, and, if one is given, link
   * the key into the keyring
   */
  long keyctl_instantiate_key(key_serial_t id,
  			    const void __user *_payload,
  			    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) {
  		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 = -EFAULT;
  		if (copy_from_user(payload, _payload, plen) != 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;
  
  } /* end keyctl_instantiate_key() */
  
  /*****************************************************************************/
  /*
   * negatively instantiate the key with the given timeout (in seconds), and, if
   * one is given, link the key into the keyring
   */
  long keyctl_negate_key(key_serial_t id, unsigned timeout, 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,%d", id, timeout, ringid);

  	/* 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_negate_and_link(rka->target_key, timeout,

  				  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;
  
  } /* end keyctl_negate_key() */
  
  /*****************************************************************************/
  /*

   * set the default keyring in which request_key() will cache keys
   * - return the old setting
   */
  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 -EINVAL;

  } /* end keyctl_set_reqkey_keyring() */
  
  /*****************************************************************************/
  /*

   * set or clear the timeout for a key
   */
  long keyctl_set_timeout(key_serial_t id, unsigned timeout)
  {
  	struct timespec now;
  	struct key *key;
  	key_ref_t key_ref;
  	time_t expiry;
  	long ret;

  	key_ref = lookup_user_key(id, 1, 1, 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 races */
  	down_write(&key->sem);
  
  	expiry = 0;
  	if (timeout > 0) {
  		now = current_kernel_time();
  		expiry = now.tv_sec + timeout;
  	}
  
  	key->expiry = expiry;
  
  	up_write(&key->sem);
  	key_put(key);
  
  	ret = 0;
  error:
  	return ret;
  
  } /* end keyctl_set_timeout() */
  
  /*****************************************************************************/
  /*

   * assume the authority to instantiate the specified 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;
  
  } /* end keyctl_assume_authority() */

  /*
   * get the security label of a key
   * - the key must grant us view permission
   * - if there's a buffer, we place up to buflen bytes of data into it
   * - unless there's an error, we return the amount of information available,
   *   irrespective of how much we may have copied (including the terminal NUL)
   * - implements keyctl(KEYCTL_GET_SECURITY)
   */
  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, 0, 1, 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(key_ref);
  		key_put(instkey);

  		key_ref = lookup_user_key(keyid, 0, 1, 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;
  }

  /*****************************************************************************/
  /*

   * 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);

  	default:
  		return -EOPNOTSUPP;
  	}
  
  } /* end sys_keyctl() */