security/keys/request_key.c - kernel/msm-4.9 - Gitiles

 /* Request a key from userspace
  *
  * Copyright (C) 2004-2007 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.
  *
  * See Documentation/keys-request-key.txt
  */

 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/kmod.h>
 #include <linux/err.h>
 #include <linux/keyctl.h>
 #include "internal.h"

 /*
  * wait_on_bit() sleep function for uninterruptible waiting
  */
 static int key_wait_bit(void *flags)
 {
 	schedule();
 	return 0;
 }

 /*
  * wait_on_bit() sleep function for interruptible waiting
  */
 static int key_wait_bit_intr(void *flags)
 {
 	schedule();
 	return signal_pending(current) ? -ERESTARTSYS : 0;
 }

 /*
  * call to complete the construction of a key
  */
 void complete_request_key(struct key_construction *cons, int error)
 {
 	kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);

 	if (error < 0)
 		key_negate_and_link(cons->key, key_negative_timeout, NULL,
 				    cons->authkey);
 	else
 		key_revoke(cons->authkey);

 	key_put(cons->key);
 	key_put(cons->authkey);
 	kfree(cons);
 }
 EXPORT_SYMBOL(complete_request_key);

 /*
  * request userspace finish the construction of a key
  * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
  */
 static int call_sbin_request_key(struct key_construction *cons,
 				 const char *op,
 				 void *aux)
 {
 	struct task_struct *tsk = current;
 	key_serial_t prkey, sskey;
 	struct key *key = cons->key, *authkey = cons->authkey, *keyring;
 	char *argv[9], *envp[3], uid_str[12], gid_str[12];
 	char key_str[12], keyring_str[3][12];
 	char desc[20];
 	int ret, i;

 	kenter("{%d},{%d},%s", key->serial, authkey->serial, op);

 	/* allocate a new session keyring */
 	sprintf(desc, "_req.%u", key->serial);

 	keyring = keyring_alloc(desc, current->fsuid, current->fsgid, current,
 				KEY_ALLOC_QUOTA_OVERRUN, NULL);
 	if (IS_ERR(keyring)) {
 		ret = PTR_ERR(keyring);
 		goto error_alloc;
 	}

 	/* attach the auth key to the session keyring */
 	ret = __key_link(keyring, authkey);
 	if (ret < 0)
 		goto error_link;

 	/* record the UID and GID */
 	sprintf(uid_str, "%d", current->fsuid);
 	sprintf(gid_str, "%d", current->fsgid);

 	/* we say which key is under construction */
 	sprintf(key_str, "%d", key->serial);

 	/* we specify the process's default keyrings */
 	sprintf(keyring_str[0], "%d",
 		tsk->thread_keyring ? tsk->thread_keyring->serial : 0);

 	prkey = 0;
 	if (tsk->signal->process_keyring)
 		prkey = tsk->signal->process_keyring->serial;

 	sprintf(keyring_str[1], "%d", prkey);

 	if (tsk->signal->session_keyring) {
 		rcu_read_lock();
 		sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
 		rcu_read_unlock();
 	} else {
 		sskey = tsk->user->session_keyring->serial;
 	}

 	sprintf(keyring_str[2], "%d", sskey);

 	/* set up a minimal environment */
 	i = 0;
 	envp[i++] = "HOME=/";
 	envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
 	envp[i] = NULL;

 	/* set up the argument list */
 	i = 0;
 	argv[i++] = "/sbin/request-key";
 	argv[i++] = (char *) op;
 	argv[i++] = key_str;
 	argv[i++] = uid_str;
 	argv[i++] = gid_str;
 	argv[i++] = keyring_str[0];
 	argv[i++] = keyring_str[1];
 	argv[i++] = keyring_str[2];
 	argv[i] = NULL;

 	/* do it */
 	ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
 				       UMH_WAIT_PROC);
 	kdebug("usermode -> 0x%x", ret);
 	if (ret >= 0) {
 		/* ret is the exit/wait code */
 		if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
 		    key_validate(key) < 0)
 			ret = -ENOKEY;
 		else
 			/* ignore any errors from userspace if the key was
 			 * instantiated */
 			ret = 0;
 	}

 error_link:
 	key_put(keyring);

 error_alloc:
 	kleave(" = %d", ret);
 	complete_request_key(cons, ret);
 	return ret;
 }

 /*
  * call out to userspace for key construction
  * - we ignore program failure and go on key status instead
  */
 static int construct_key(struct key *key, const char *callout_info, void *aux)
 {
 	struct key_construction *cons;
 	request_key_actor_t actor;
 	struct key *authkey;
 	int ret;

 	kenter("%d,%s,%p", key->serial, callout_info, aux);

 	cons = kmalloc(sizeof(*cons), GFP_KERNEL);
 	if (!cons)
 		return -ENOMEM;

 	/* allocate an authorisation key */
 	authkey = request_key_auth_new(key, callout_info);
 	if (IS_ERR(authkey)) {
 		kfree(cons);
 		ret = PTR_ERR(authkey);
 		authkey = NULL;
 	} else {
 		cons->authkey = key_get(authkey);
 		cons->key = key_get(key);

 		/* make the call */
 		actor = call_sbin_request_key;
 		if (key->type->request_key)
 			actor = key->type->request_key;

 		ret = actor(cons, "create", aux);

 		/* check that the actor called complete_request_key() prior to
 		 * returning an error */
 		WARN_ON(ret < 0 &&
 			!test_bit(KEY_FLAG_REVOKED, &authkey->flags));
 		key_put(authkey);
 	}

 	kleave(" = %d", ret);
 	return ret;
 }

 /*
  * link a key to the appropriate destination keyring
  * - the caller must hold a write lock on the destination keyring
  */
 static void construct_key_make_link(struct key *key, struct key *dest_keyring)
 {
 	struct task_struct *tsk = current;
 	struct key *drop = NULL;

 	kenter("{%d},%p", key->serial, dest_keyring);

 	/* find the appropriate keyring */
 	if (!dest_keyring) {
 		switch (tsk->jit_keyring) {
 		case KEY_REQKEY_DEFL_DEFAULT:
 		case KEY_REQKEY_DEFL_THREAD_KEYRING:
 			dest_keyring = tsk->thread_keyring;
 			if (dest_keyring)
 				break;

 		case KEY_REQKEY_DEFL_PROCESS_KEYRING:
 			dest_keyring = tsk->signal->process_keyring;
 			if (dest_keyring)
 				break;

 		case KEY_REQKEY_DEFL_SESSION_KEYRING:
 			rcu_read_lock();
 			dest_keyring = key_get(
 				rcu_dereference(tsk->signal->session_keyring));
 			rcu_read_unlock();
 			drop = dest_keyring;

 			if (dest_keyring)
 				break;

 		case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
 			dest_keyring = tsk->user->session_keyring;
 			break;

 		case KEY_REQKEY_DEFL_USER_KEYRING:
 			dest_keyring = tsk->user->uid_keyring;
 			break;

 		case KEY_REQKEY_DEFL_GROUP_KEYRING:
 		default:
 			BUG();
 		}
 	}

 	/* and attach the key to it */
 	__key_link(dest_keyring, key);
 	key_put(drop);
 	kleave("");
 }

 /*
  * allocate a new key in under-construction state and attempt to link it in to
  * the requested place
  * - may return a key that's already under construction instead
  */
 static int construct_alloc_key(struct key_type *type,
 			       const char *description,
 			       struct key *dest_keyring,
 			       unsigned long flags,
 			       struct key_user *user,
 			       struct key **_key)
 {
 	struct key *key;
 	key_ref_t key_ref;

 	kenter("%s,%s,,,", type->name, description);

 	mutex_lock(&user->cons_lock);

 	key = key_alloc(type, description,
 			current->fsuid, current->fsgid, current, KEY_POS_ALL,
 			flags);
 	if (IS_ERR(key))
 		goto alloc_failed;

 	set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);

 	if (dest_keyring)
 		down_write(&dest_keyring->sem);

 	/* attach the key to the destination keyring under lock, but we do need
 	 * to do another check just in case someone beat us to it whilst we
 	 * waited for locks */
 	mutex_lock(&key_construction_mutex);

 	key_ref = search_process_keyrings(type, description, type->match,
 					  current);
 	if (!IS_ERR(key_ref))
 		goto key_already_present;

 	if (dest_keyring)
 		construct_key_make_link(key, dest_keyring);

 	mutex_unlock(&key_construction_mutex);
 	if (dest_keyring)
 		up_write(&dest_keyring->sem);
 	mutex_unlock(&user->cons_lock);
 	*_key = key;
 	kleave(" = 0 [%d]", key_serial(key));
 	return 0;

 key_already_present:
 	mutex_unlock(&key_construction_mutex);
 	if (dest_keyring)
 		up_write(&dest_keyring->sem);
 	mutex_unlock(&user->cons_lock);
 	key_put(key);
 	*_key = key = key_ref_to_ptr(key_ref);
 	kleave(" = -EINPROGRESS [%d]", key_serial(key));
 	return -EINPROGRESS;

 alloc_failed:
 	mutex_unlock(&user->cons_lock);
 	*_key = NULL;
 	kleave(" = %ld", PTR_ERR(key));
 	return PTR_ERR(key);
 }

 /*
  * commence key construction
  */
 static struct key *construct_key_and_link(struct key_type *type,
 					  const char *description,
 					  const char *callout_info,
 					  void *aux,
 					  struct key *dest_keyring,
 					  unsigned long flags)
 {
 	struct key_user *user;
 	struct key *key;
 	int ret;

 	user = key_user_lookup(current->fsuid);
 	if (!user)
 		return ERR_PTR(-ENOMEM);

 	ret = construct_alloc_key(type, description, dest_keyring, flags, user,
 				  &key);
 	key_user_put(user);

 	if (ret == 0) {
 		ret = construct_key(key, callout_info, aux);
 		if (ret < 0)
 			goto construction_failed;
 	}

 	return key;

 construction_failed:
 	key_negate_and_link(key, key_negative_timeout, NULL, NULL);
 	key_put(key);
 	return ERR_PTR(ret);
 }

 /*
  * request a key
  * - search the process's keyrings
  * - check the list of keys being created or updated
  * - call out to userspace for a key if supplementary info was provided
  * - cache the key in an appropriate keyring
  */
 struct key *request_key_and_link(struct key_type *type,
 				 const char *description,
 				 const char *callout_info,
 				 void *aux,
 				 struct key *dest_keyring,
 				 unsigned long flags)
 {
 	struct key *key;
 	key_ref_t key_ref;

 	kenter("%s,%s,%s,%p,%p,%lx",
 	       type->name, description, callout_info, aux,
 	       dest_keyring, flags);

 	/* search all the process keyrings for a key */
 	key_ref = search_process_keyrings(type, description, type->match,
 					  current);

 	if (!IS_ERR(key_ref)) {
 		key = key_ref_to_ptr(key_ref);
 	} else if (PTR_ERR(key_ref) != -EAGAIN) {
 		key = ERR_PTR(PTR_ERR(key_ref));
 	} else  {
 		/* the search failed, but the keyrings were searchable, so we
 		 * should consult userspace if we can */
 		key = ERR_PTR(-ENOKEY);
 		if (!callout_info)
 			goto error;

 		key = construct_key_and_link(type, description, callout_info,
 					     aux, dest_keyring, flags);
 	}

 error:
 	kleave(" = %p", key);
 	return key;
 }

 /*
  * wait for construction of a key to complete
  */
 int wait_for_key_construction(struct key *key, bool intr)
 {
 	int ret;

 	ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
 			  intr ? key_wait_bit_intr : key_wait_bit,
 			  intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
 	if (ret < 0)
 		return ret;
 	return key_validate(key);
 }
 EXPORT_SYMBOL(wait_for_key_construction);

 /*
  * request a key
  * - search the process's keyrings
  * - check the list of keys being created or updated
  * - call out to userspace for a key if supplementary info was provided
  * - waits uninterruptible for creation to complete
  */
 struct key *request_key(struct key_type *type,
 			const char *description,
 			const char *callout_info)
 {
 	struct key *key;
 	int ret;

 	key = request_key_and_link(type, description, callout_info, NULL,
 				   NULL, KEY_ALLOC_IN_QUOTA);
 	if (!IS_ERR(key)) {
 		ret = wait_for_key_construction(key, false);
 		if (ret < 0) {
 			key_put(key);
 			return ERR_PTR(ret);
 		}
 	}
 	return key;
 }
 EXPORT_SYMBOL(request_key);

 /*
  * request a key with auxiliary data for the upcaller
  * - search the process's keyrings
  * - check the list of keys being created or updated
  * - call out to userspace for a key if supplementary info was provided
  * - waits uninterruptible for creation to complete
  */
 struct key *request_key_with_auxdata(struct key_type *type,
 				     const char *description,
 				     const char *callout_info,
 				     void *aux)
 {
 	struct key *key;
 	int ret;

 	key = request_key_and_link(type, description, callout_info, aux,
 				   NULL, KEY_ALLOC_IN_QUOTA);
 	if (!IS_ERR(key)) {
 		ret = wait_for_key_construction(key, false);
 		if (ret < 0) {
 			key_put(key);
 			return ERR_PTR(ret);
 		}
 	}
 	return key;
 }
 EXPORT_SYMBOL(request_key_with_auxdata);

 /*
  * request a key (allow async construction)
  * - search the process's keyrings
  * - check the list of keys being created or updated
  * - call out to userspace for a key if supplementary info was provided
  */
 struct key *request_key_async(struct key_type *type,
 			      const char *description,
 			      const char *callout_info)
 {
 	return request_key_and_link(type, description, callout_info, NULL,
 				    NULL, KEY_ALLOC_IN_QUOTA);
 }
 EXPORT_SYMBOL(request_key_async);

 /*
  * request a key with auxiliary data for the upcaller (allow async construction)
  * - search the process's keyrings
  * - check the list of keys being created or updated
  * - call out to userspace for a key if supplementary info was provided
  */
 struct key *request_key_async_with_auxdata(struct key_type *type,
 					   const char *description,
 					   const char *callout_info,
 					   void *aux)
 {
 	return request_key_and_link(type, description, callout_info, aux,
 				    NULL, KEY_ALLOC_IN_QUOTA);
 }
 EXPORT_SYMBOL(request_key_async_with_auxdata);
	/* Request a key from userspace
	*
	* Copyright (C) 2004-2007 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.
	*
	* See Documentation/keys-request-key.txt
	*/

	#include <linux/module.h>
	#include <linux/sched.h>
	#include <linux/kmod.h>
	#include <linux/err.h>
	#include <linux/keyctl.h>
	#include "internal.h"

	/*
	* wait_on_bit() sleep function for uninterruptible waiting
	*/
	static int key_wait_bit(void *flags)
	{
	schedule();
	return 0;
	}

	/*
	* wait_on_bit() sleep function for interruptible waiting
	*/
	static int key_wait_bit_intr(void *flags)
	{
	schedule();
	return signal_pending(current) ? -ERESTARTSYS : 0;
	}

	/*
	* call to complete the construction of a key
	*/
	void complete_request_key(struct key_construction *cons, int error)
	{
	kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);

	if (error < 0)
	key_negate_and_link(cons->key, key_negative_timeout, NULL,
	cons->authkey);
	else
	key_revoke(cons->authkey);

	key_put(cons->key);
	key_put(cons->authkey);
	kfree(cons);
	}
	EXPORT_SYMBOL(complete_request_key);

	/*
	* request userspace finish the construction of a key
	* - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
	*/
	static int call_sbin_request_key(struct key_construction *cons,
	const char *op,
	void *aux)
	{
	struct task_struct *tsk = current;
	key_serial_t prkey, sskey;
	struct key key = cons->key, authkey = cons->authkey, *keyring;
	char argv[9], envp[3], uid_str[12], gid_str[12];
	char key_str[12], keyring_str[3][12];
	char desc[20];
	int ret, i;

	kenter("{%d},{%d},%s", key->serial, authkey->serial, op);

	/* allocate a new session keyring */
	sprintf(desc, "_req.%u", key->serial);

	keyring = keyring_alloc(desc, current->fsuid, current->fsgid, current,
	KEY_ALLOC_QUOTA_OVERRUN, NULL);
	if (IS_ERR(keyring)) {
	ret = PTR_ERR(keyring);
	goto error_alloc;
	}

	/* attach the auth key to the session keyring */
	ret = __key_link(keyring, authkey);
	if (ret < 0)
	goto error_link;

	/* record the UID and GID */
	sprintf(uid_str, "%d", current->fsuid);
	sprintf(gid_str, "%d", current->fsgid);

	/* we say which key is under construction */
	sprintf(key_str, "%d", key->serial);

	/* we specify the process's default keyrings */
	sprintf(keyring_str[0], "%d",
	tsk->thread_keyring ? tsk->thread_keyring->serial : 0);

	prkey = 0;
	if (tsk->signal->process_keyring)
	prkey = tsk->signal->process_keyring->serial;

	sprintf(keyring_str[1], "%d", prkey);

	if (tsk->signal->session_keyring) {
	rcu_read_lock();
	sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
	rcu_read_unlock();
	} else {
	sskey = tsk->user->session_keyring->serial;
	}

	sprintf(keyring_str[2], "%d", sskey);

	/* set up a minimal environment */
	i = 0;
	envp[i++] = "HOME=/";
	envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
	envp[i] = NULL;

	/* set up the argument list */
	i = 0;
	argv[i++] = "/sbin/request-key";
	argv[i++] = (char *) op;
	argv[i++] = key_str;
	argv[i++] = uid_str;
	argv[i++] = gid_str;
	argv[i++] = keyring_str[0];
	argv[i++] = keyring_str[1];
	argv[i++] = keyring_str[2];
	argv[i] = NULL;

	/* do it */
	ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
	UMH_WAIT_PROC);
	kdebug("usermode -> 0x%x", ret);
	if (ret >= 0) {
	/* ret is the exit/wait code */
	if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) \|\|
	key_validate(key) < 0)
	ret = -ENOKEY;
	else
	/* ignore any errors from userspace if the key was
	* instantiated */
	ret = 0;
	}

	error_link:
	key_put(keyring);

	error_alloc:
	kleave(" = %d", ret);
	complete_request_key(cons, ret);
	return ret;
	}

	/*
	* call out to userspace for key construction
	* - we ignore program failure and go on key status instead
	*/
	static int construct_key(struct key key, const char callout_info, void *aux)
	{
	struct key_construction *cons;
	request_key_actor_t actor;
	struct key *authkey;
	int ret;

	kenter("%d,%s,%p", key->serial, callout_info, aux);

	cons = kmalloc(sizeof(*cons), GFP_KERNEL);
	if (!cons)
	return -ENOMEM;

	/* allocate an authorisation key */
	authkey = request_key_auth_new(key, callout_info);
	if (IS_ERR(authkey)) {
	kfree(cons);
	ret = PTR_ERR(authkey);
	authkey = NULL;
	} else {
	cons->authkey = key_get(authkey);
	cons->key = key_get(key);

	/* make the call */
	actor = call_sbin_request_key;
	if (key->type->request_key)
	actor = key->type->request_key;

	ret = actor(cons, "create", aux);

	/* check that the actor called complete_request_key() prior to
	* returning an error */
	WARN_ON(ret < 0 &&
	!test_bit(KEY_FLAG_REVOKED, &authkey->flags));
	key_put(authkey);
	}

	kleave(" = %d", ret);
	return ret;
	}

	/*
	* link a key to the appropriate destination keyring
	* - the caller must hold a write lock on the destination keyring
	*/
	static void construct_key_make_link(struct key key, struct key dest_keyring)
	{
	struct task_struct *tsk = current;
	struct key *drop = NULL;

	kenter("{%d},%p", key->serial, dest_keyring);

	/* find the appropriate keyring */
	if (!dest_keyring) {
	switch (tsk->jit_keyring) {
	case KEY_REQKEY_DEFL_DEFAULT:
	case KEY_REQKEY_DEFL_THREAD_KEYRING:
	dest_keyring = tsk->thread_keyring;
	if (dest_keyring)
	break;

	case KEY_REQKEY_DEFL_PROCESS_KEYRING:
	dest_keyring = tsk->signal->process_keyring;
	if (dest_keyring)
	break;

	case KEY_REQKEY_DEFL_SESSION_KEYRING:
	rcu_read_lock();
	dest_keyring = key_get(
	rcu_dereference(tsk->signal->session_keyring));
	rcu_read_unlock();
	drop = dest_keyring;

	if (dest_keyring)
	break;

	case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
	dest_keyring = tsk->user->session_keyring;
	break;

	case KEY_REQKEY_DEFL_USER_KEYRING:
	dest_keyring = tsk->user->uid_keyring;
	break;

	case KEY_REQKEY_DEFL_GROUP_KEYRING:
	default:
	BUG();
	}
	}

	/* and attach the key to it */
	__key_link(dest_keyring, key);
	key_put(drop);
	kleave("");
	}

	/*
	* allocate a new key in under-construction state and attempt to link it in to
	* the requested place
	* - may return a key that's already under construction instead
	*/
	static int construct_alloc_key(struct key_type *type,
	const char *description,
	struct key *dest_keyring,
	unsigned long flags,
	struct key_user *user,
	struct key **_key)
	{
	struct key *key;
	key_ref_t key_ref;

	kenter("%s,%s,,,", type->name, description);

	mutex_lock(&user->cons_lock);

	key = key_alloc(type, description,
	current->fsuid, current->fsgid, current, KEY_POS_ALL,
	flags);
	if (IS_ERR(key))
	goto alloc_failed;

	set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);

	if (dest_keyring)
	down_write(&dest_keyring->sem);

	/* attach the key to the destination keyring under lock, but we do need
	* to do another check just in case someone beat us to it whilst we
	* waited for locks */
	mutex_lock(&key_construction_mutex);

	key_ref = search_process_keyrings(type, description, type->match,
	current);
	if (!IS_ERR(key_ref))
	goto key_already_present;

	if (dest_keyring)
	construct_key_make_link(key, dest_keyring);

	mutex_unlock(&key_construction_mutex);
	if (dest_keyring)
	up_write(&dest_keyring->sem);
	mutex_unlock(&user->cons_lock);
	*_key = key;
	kleave(" = 0 [%d]", key_serial(key));
	return 0;

	key_already_present:
	mutex_unlock(&key_construction_mutex);
	if (dest_keyring)
	up_write(&dest_keyring->sem);
	mutex_unlock(&user->cons_lock);
	key_put(key);
	*_key = key = key_ref_to_ptr(key_ref);
	kleave(" = -EINPROGRESS [%d]", key_serial(key));
	return -EINPROGRESS;

	alloc_failed:
	mutex_unlock(&user->cons_lock);
	*_key = NULL;
	kleave(" = %ld", PTR_ERR(key));
	return PTR_ERR(key);
	}

	/*
	* commence key construction
	*/
	static struct key construct_key_and_link(struct key_type type,
	const char *description,
	const char *callout_info,
	void *aux,
	struct key *dest_keyring,
	unsigned long flags)
	{
	struct key_user *user;
	struct key *key;
	int ret;

	user = key_user_lookup(current->fsuid);
	if (!user)
	return ERR_PTR(-ENOMEM);

	ret = construct_alloc_key(type, description, dest_keyring, flags, user,
	&key);
	key_user_put(user);

	if (ret == 0) {
	ret = construct_key(key, callout_info, aux);
	if (ret < 0)
	goto construction_failed;
	}

	return key;

	construction_failed:
	key_negate_and_link(key, key_negative_timeout, NULL, NULL);
	key_put(key);
	return ERR_PTR(ret);
	}

	/*
	* request a key
	* - search the process's keyrings
	* - check the list of keys being created or updated
	* - call out to userspace for a key if supplementary info was provided
	* - cache the key in an appropriate keyring
	*/
	struct key request_key_and_link(struct key_type type,
	const char *description,
	const char *callout_info,
	void *aux,
	struct key *dest_keyring,
	unsigned long flags)
	{
	struct key *key;
	key_ref_t key_ref;

	kenter("%s,%s,%s,%p,%p,%lx",
	type->name, description, callout_info, aux,
	dest_keyring, flags);

	/* search all the process keyrings for a key */
	key_ref = search_process_keyrings(type, description, type->match,
	current);

	if (!IS_ERR(key_ref)) {
	key = key_ref_to_ptr(key_ref);
	} else if (PTR_ERR(key_ref) != -EAGAIN) {
	key = ERR_PTR(PTR_ERR(key_ref));
	} else {
	/* the search failed, but the keyrings were searchable, so we
	* should consult userspace if we can */
	key = ERR_PTR(-ENOKEY);
	if (!callout_info)
	goto error;

	key = construct_key_and_link(type, description, callout_info,
	aux, dest_keyring, flags);
	}

	error:
	kleave(" = %p", key);
	return key;
	}

	/*
	* wait for construction of a key to complete
	*/
	int wait_for_key_construction(struct key *key, bool intr)
	{
	int ret;

	ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
	intr ? key_wait_bit_intr : key_wait_bit,
	intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
	if (ret < 0)
	return ret;
	return key_validate(key);
	}
	EXPORT_SYMBOL(wait_for_key_construction);

	/*
	* request a key
	* - search the process's keyrings
	* - check the list of keys being created or updated
	* - call out to userspace for a key if supplementary info was provided
	* - waits uninterruptible for creation to complete
	*/
	struct key request_key(struct key_type type,
	const char *description,
	const char *callout_info)
	{
	struct key *key;
	int ret;

	key = request_key_and_link(type, description, callout_info, NULL,
	NULL, KEY_ALLOC_IN_QUOTA);
	if (!IS_ERR(key)) {
	ret = wait_for_key_construction(key, false);
	if (ret < 0) {
	key_put(key);
	return ERR_PTR(ret);
	}
	}
	return key;
	}
	EXPORT_SYMBOL(request_key);

	/*
	* request a key with auxiliary data for the upcaller
	* - search the process's keyrings
	* - check the list of keys being created or updated
	* - call out to userspace for a key if supplementary info was provided
	* - waits uninterruptible for creation to complete
	*/
	struct key request_key_with_auxdata(struct key_type type,
	const char *description,
	const char *callout_info,
	void *aux)
	{
	struct key *key;
	int ret;

	key = request_key_and_link(type, description, callout_info, aux,
	NULL, KEY_ALLOC_IN_QUOTA);
	if (!IS_ERR(key)) {
	ret = wait_for_key_construction(key, false);
	if (ret < 0) {
	key_put(key);
	return ERR_PTR(ret);
	}
	}
	return key;
	}
	EXPORT_SYMBOL(request_key_with_auxdata);

	/*
	* request a key (allow async construction)
	* - search the process's keyrings
	* - check the list of keys being created or updated
	* - call out to userspace for a key if supplementary info was provided
	*/
	struct key request_key_async(struct key_type type,
	const char *description,
	const char *callout_info)
	{
	return request_key_and_link(type, description, callout_info, NULL,
	NULL, KEY_ALLOC_IN_QUOTA);
	}
	EXPORT_SYMBOL(request_key_async);

	/*
	* request a key with auxiliary data for the upcaller (allow async construction)
	* - search the process's keyrings
	* - check the list of keys being created or updated
	* - call out to userspace for a key if supplementary info was provided
	*/
	struct key request_key_async_with_auxdata(struct key_type type,
	const char *description,
	const char *callout_info,
	void *aux)
	{
	return request_key_and_link(type, description, callout_info, aux,
	NULL, KEY_ALLOC_IN_QUOTA);
	}
	EXPORT_SYMBOL(request_key_async_with_auxdata);