Work on post_share hook for files_encryption

New method in OCP\Share{}:: getUsersSharingFile()
Development shapshot

4 files changed, 430 insertions, 312 deletions

diff --git a/apps/files_encryption/hooks/hooks.php b/apps/files_encryption/hooks/hooks.php
index 8bdeee0937b..c6d4c16115a 100644
--- a/apps/files_encryption/hooks/hooks.php
+++ b/apps/files_encryption/hooks/hooks.php
@@ -166,14 +166,77 @@ class Hooks {
 	 */

 	public static function postShared( $params ) {

 		

-		// Delete existing catfile

-		Keymanager::deleteFileKey(  );

+		// NOTE: $params is an array with these keys:

+		// itemSource -> int, filecache file ID

+		// shareWith -> string, uid of user being shared to

+		// fileTarget -> path of file being shared

+		// uidOwner -> owner of the original file being shared

 		

-		// Generate new catfile and env keys

-		Crypt::multiKeyEncrypt( $plainContent, $publicKeys );

+		$view = new \OC_FilesystemView( '/' );

+		$userId = \OCP\User::getUser();

+		$util = new Util( $view, $userId );

+		

+		$shares = \OCP\Share::getUsersSharingFile( $params['fileTarget'] );

+		

+		$userIds = array();

+		

+		foreach ( $shares as $share ) {

+		

+			$util = new Util( $view, $share['userId'] );

+			

+			// Check that the user is encryption capable

+			if ( $util->ready() ) {

+		

+				// Construct array of just UIDs for Keymanager{}

+				$userIds[] = $share['userId'];

+			

+			} else {

+			

+				// Log warning; we can't do necessary setup here

+				// because we don't have the user passphrase

+				// TODO: Provide user feedback indicating that

+				// sharing failed

+				\OC_Log::write( 'Encryption library', 'File cannot be shared: user "'.$share['userId'].'" is not setup for encryption', \OC_Log::WARN );

+				

+			}

+		

+		}

+		

+		trigger_error("UIDS = ".var_export($userIds, 1));

+		

+		$userPubKeys = Keymanager::getPublicKeys( $view, $userIds );

+		

+// 		trigger_error("PUB KEYS = ".var_export($userPubKeys, 1));

+		

+		// TODO: Fetch path from Crypt{} getter

+		$plainContent = $view->file_get_contents( $userId . '/' . 'files'. '/' . $params['fileTarget'] );

+		

+		// Generate new catfile and share keys

+		if ( ! $encrypted = Crypt::multiKeyEncrypt( $plainContent, $userPubKeys ) ) {

+		

+			// If the re-encryption failed, don't risk deleting data

+			return false;

+			

+		}

+		

+		trigger_error("ENCRYPTED = ". var_export($encrypted, 1));

 		

 		// Save env keys to user folders

+		foreach ( $encrypted['keys'] as $key ) {

+		

+// 			Keymanager::setShareKey( $view, $params['fileTarget'], $userId, $key );

+		

+		}

 		

+		// Delete existing catfile

+		// Check if keyfile exists (it won't if file has been shared before)

+		// Do this last to ensure file is recoverable in case of error

+		if ( $util->isEncryptedPath( $params['fileTarget'] ) ) {

+			

+			// NOTE: This will trigger an error if keyfile isn't found

+// 			Keymanager::deleteFileKey( $params['fileTarget'] );

+		

+		}

 		

 	}

 	

diff --git a/apps/files_encryption/lib/keymanager.php b/apps/files_encryption/lib/keymanager.php
index 0d0380db6ec..3160572ba1b 100755
--- a/apps/files_encryption/lib/keymanager.php
+++ b/apps/files_encryption/lib/keymanager.php
@@ -1,267 +1,244 @@
-<?php
-
-/**
- * ownCloud
- *
- * @author Bjoern Schiessle
- * @copyright 2012 Bjoern Schiessle <schiessle@owncloud.com>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
- * License as published by the Free Software Foundation; either
- * version 3 of the License, or any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU AFFERO GENERAL PUBLIC LICENSE for more details.
- *
- * You should have received a copy of the GNU Affero General Public
- * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
- *
- */
-
-namespace OCA\Encryption;
-
-/**
- * @brief Class to manage storage and retrieval of encryption keys
- * @note Where a method requires a view object, it's root must be '/'
- */
-class Keymanager {
-		

-	/**
-	 * @brief retrieve the ENCRYPTED private key from a user
-	 * 
-	 * @return string private key or false
-	 * @note the key returned by this method must be decrypted before use
-	 */
-	public static function getPrivateKey( \OC_FilesystemView $view, $user ) {
-	
-		$path =  '/' . $user . '/' . 'files_encryption' . '/' . $user.'.private.key';
-		
-		$key = $view->file_get_contents( $path );
-		
-		return $key;
-	}
-
-	/**
-	 * @brief retrieve public key for a specified user
+<?php

+

+/**

+ * ownCloud

+ *

+ * @author Bjoern Schiessle

+ * @copyright 2012 Bjoern Schiessle <schiessle@owncloud.com>

+ *

+ * This library is free software; you can redistribute it and/or

+ * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE

+ * License as published by the Free Software Foundation; either

+ * version 3 of the License, or any later version.

+ *

+ * This library is distributed in the hope that it will be useful,

+ * but WITHOUT ANY WARRANTY; without even the implied warranty of

+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+ * GNU AFFERO GENERAL PUBLIC LICENSE for more details.

+ *

+ * You should have received a copy of the GNU Affero General Public

+ * License along with this library.  If not, see <http://www.gnu.org/licenses/>.

+ *

+ */

+

+namespace OCA\Encryption;

+

+/**

+ * @brief Class to manage storage and retrieval of encryption keys

+ * @note Where a method requires a view object, it's root must be '/'

+ */

+class Keymanager {

+		

+	/**

+	 * @brief retrieve the ENCRYPTED private key from a user

+	 * 

+	 * @return string private key or false

+	 * @note the key returned by this method must be decrypted before use

+	 */

+	public static function getPrivateKey( \OC_FilesystemView $view, $user ) {

+	

+		$path =  '/' . $user . '/' . 'files_encryption' . '/' . $user.'.private.key';

+		

+		$key = $view->file_get_contents( $path );

+		

+		return $key;

+	}

+

+	/**

+	 * @brief retrieve public key for a specified user

 	 * @param \OC_FilesystemView $view

 	 * @param $userId

-	 * @return string public key or false
-	 */
-	public static function getPublicKey( \OC_FilesystemView $view, $userId ) {
-		
-		return $view->file_get_contents( '/public-keys/' . '/' . $userId . '.public.key' );
-		
-	}
-	
-	/**
-	 * @brief retrieve both keys from a user (private and public)
+	 * @return string public key or false

+	 */

+	public static function getPublicKey( \OC_FilesystemView $view, $userId ) {

+		

+		return $view->file_get_contents( '/public-keys/' . '/' . $userId . '.public.key' );

+		

+	}

+	

+	/**

+	 * @brief Retrieve a user's public and private key

 	 * @param \OC_FilesystemView $view

 	 * @param $userId

-	 * @return array keys: privateKey, publicKey
-	 */
-	public static function getUserKeys( \OC_FilesystemView $view, $userId ) {
-	
-		return array(
-			'publicKey' => self::getPublicKey( $view, $userId )
-			, 'privateKey' => self::getPrivateKey( $view, $userId )
-		);
-	
-	}
-	
-	/**
-	 * @brief Retrieve public keys of all users with access to a file
-	 * @param string $path Path to file
-	 * @return array of public keys for the given file
-	 * @note Checks that the sharing app is enabled should be performed 
-	 * by client code, that isn't checked here
-	 */
-	public static function getPublicKeys( \OC_FilesystemView $view, $userId, $filePath ) {
-		
-		$path = ltrim( $path, '/' );
-		
-		$filepath = '/' . $userId . '/files/' . $filePath;
-		
-		// Check if sharing is enabled
-		if ( OC_App::isEnabled( 'files_sharing' ) ) {
-			
-
-		
-		} else {
-		
-			// check if it is a file owned by the user and not shared at all
-			$userview = new \OC_FilesystemView( '/'.$userId.'/files/' );
-			
-			if ( $userview->file_exists( $path ) ) {
-			
-				$users[] = $userId;
-				
-			}
-			
-		}
-		
-		$view = new \OC_FilesystemView( '/public-keys/' );
-		
-		$keylist = array();
-		
-		$count = 0;
-		
-		foreach ( $users as $user ) {
-		
-			$keylist['key'.++$count] = $view->file_get_contents( $user.'.public.key' );
-			
-		}
-		
-		return $keylist;
-		
-	}
-	
-	/**
-	 * @brief store file encryption key
-	 *
-	 * @param string $path relative path of the file, including filename
-	 * @param string $key
-	 * @return bool true/false
-	 * @note The keyfile is not encrypted here. Client code must 
-	 * asymmetrically encrypt the keyfile before passing it to this method
-	 */
-	public static function setFileKey( \OC_FilesystemView $view, $path, $userId, $catfile ) {
-		
-		$basePath = '/' . $userId . '/files_encryption/keyfiles';
-		
-		$targetPath = self::keySetPreparation( $view, $path, $basePath, $userId );
-		
-		if ( $view->is_dir( $basePath . '/' . $targetPath ) ) {
-		
-			
-		
-		} else {
-
-			// Save the keyfile in parallel directory
-			return $view->file_put_contents( $basePath . '/' . $targetPath . '.key', $catfile );
-		
-		}
-		
-	}
-	
-	/**
-	 * @brief retrieve keyfile for an encrypted file
+	 * @return array keys: privateKey, publicKey

+	 */

+	public static function getUserKeys( \OC_FilesystemView $view, $userId ) {

+	

+		return array(

+			'publicKey' => self::getPublicKey( $view, $userId )

+			, 'privateKey' => self::getPrivateKey( $view, $userId )

+		);

+	

+	}

+	

+	/**

+	 * @brief Retrieve public keys for given users

+	 * @param \OC_FilesystemView $view

+	 * @param array $userIds

+	 * @return array of public keys for the specified users

+	 */

+	public static function getPublicKeys( \OC_FilesystemView $view, $userIds ) {

+		

+		$i = 0;

+		$keys = array();

+		

+		foreach ( $userIds as $userId ) {

+		

+			$i++;

+			$keys[$userId] = self::getPublicKey( $view, $userId );

+		

+		}

+		

+		$keys['total'] = $i;

+		

+		return $keys;

+		

+	}

+	

+	/**

+	 * @brief store file encryption key

+	 *

+	 * @param string $path relative path of the file, including filename

+	 * @param string $key

+	 * @return bool true/false

+	 * @note The keyfile is not encrypted here. Client code must 

+	 * asymmetrically encrypt the keyfile before passing it to this method

+	 */

+	public static function setFileKey( \OC_FilesystemView $view, $path, $userId, $catfile ) {

+		

+		$basePath = '/' . $userId . '/files_encryption/keyfiles';

+		

+		$targetPath = self::keySetPreparation( $view, $path, $basePath, $userId );

+		

+		if ( $view->is_dir( $basePath . '/' . $targetPath ) ) {

+		

+			

+		

+		} else {

+

+			// Save the keyfile in parallel directory

+			return $view->file_put_contents( $basePath . '/' . $targetPath . '.key', $catfile );

+		

+		}

+		

+	}

+	

+	/**

+	 * @brief retrieve keyfile for an encrypted file

 	 * @param \OC_FilesystemView $view

 	 * @param $userId

 	 * @param $filePath

 	 * @internal param \OCA\Encryption\file $string name

 	 * @return string file key or false

-	 * @note The keyfile returned is asymmetrically encrypted. Decryption
-	 * of the keyfile must be performed by client code
-	 */
-	public static function getFileKey( \OC_FilesystemView $view, $userId, $filePath ) {
-		
-		$filePath_f = ltrim( $filePath, '/' );
-		
-		$catfilePath = '/' . $userId . '/files_encryption/keyfiles/' . $filePath_f . '.key';
-		
-		if ( $view->file_exists( $catfilePath ) ) {
-
-			return $view->file_get_contents( $catfilePath );
-			
-		} else {
-		
-			return false;
-			
-		}
-		
-	}
-	
-	/**
-	 * @brief Delete a keyfile
-	 *
+	 * @note The keyfile returned is asymmetrically encrypted. Decryption

+	 * of the keyfile must be performed by client code

+	 */

+	public static function getFileKey( \OC_FilesystemView $view, $userId, $filePath ) {

+		

+		$filePath_f = ltrim( $filePath, '/' );

+		

+		$catfilePath = '/' . $userId . '/files_encryption/keyfiles/' . $filePath_f . '.key';

+		

+		if ( $view->file_exists( $catfilePath ) ) {

+

+			return $view->file_get_contents( $catfilePath );

+			

+		} else {

+		

+			return false;

+			

+		}

+		

+	}

+	

+	/**

+	 * @brief Delete a keyfile

+	 *

 	 * @param OC_FilesystemView $view

 	 * @param string $userId username

 	 * @param string $path path of the file the key belongs to

 	 * @return bool Outcome of unlink operation

 	 * @note $path must be relative to data/user/files. e.g. mydoc.txt NOT

 	 *       /data/admin/files/mydoc.txt

-	 */
-	public static function deleteFileKey( \OC_FilesystemView $view, $userId, $path ) {
-		
-		$trimmed = ltrim( $path, '/' );
-		$keyPath =  '/' . $userId . '/files_encryption/keyfiles/' . $trimmed . '.key';
-		
-		// Unlink doesn't tell us if file was deleted (not found returns
-		// true), so we perform our own test
-		if ( $view->file_exists( $keyPath ) ) {
-		
-			return $view->unlink( $keyPath );
-			
-		} else {
-			
-			\OC_Log::write( 'Encryption library', 'Could not delete keyfile; does not exist: "' . $keyPath, \OC_Log::ERROR );
-			
-			return false;
-			
-		}
-		
-	}
-	
-	/**
-	 * @brief store private key from the user
-	 * @param string key
-	 * @return bool
-	 * @note Encryption of the private key must be performed by client code
-	 * as no encryption takes place here
-	 */
-	public static function setPrivateKey( $key ) {
-		
-		$user = \OCP\User::getUser();
-		
-		$view = new \OC_FilesystemView( '/' . $user . '/files_encryption' );
-		
-		\OC_FileProxy::$enabled = false;
-		
-		if ( !$view->file_exists( '' ) ) $view->mkdir( '' );
-		
-		return $view->file_put_contents( $user . '.private.key', $key );
-		
-		\OC_FileProxy::$enabled = true;
-		
-	}
-	
-	/**
-	 * @brief store private keys from the user
-	 *
-	 * @param string privatekey
-	 * @param string publickey
-	 * @return bool true/false
-	 */
-	public static function setUserKeys($privatekey, $publickey) {
-	
-		return ( self::setPrivateKey( $privatekey ) && self::setPublicKey( $publickey ) );
-	
-	}
-	
-	/**
-	 * @brief store public key of the user
-	 *
-	 * @param string key
-	 * @return bool true/false
-	 */
-	public static function setPublicKey( $key ) {
-		
-		$view = new \OC_FilesystemView( '/public-keys' );
-		
-		\OC_FileProxy::$enabled = false;
-		
-		if ( !$view->file_exists( '' ) ) $view->mkdir( '' );
-		
-		return $view->file_put_contents( \OCP\User::getUser() . '.public.key', $key );
-		
-		\OC_FileProxy::$enabled = true;
-		
-	}
-	
-	/**
+	 */

+	public static function deleteFileKey( \OC_FilesystemView $view, $userId, $path ) {

+		

+		$trimmed = ltrim( $path, '/' );

+		$keyPath =  '/' . $userId . '/files_encryption/keyfiles/' . $trimmed . '.key';

+		

+		// Unlink doesn't tell us if file was deleted (not found returns

+		// true), so we perform our own test

+		if ( $view->file_exists( $keyPath ) ) {

+		

+			return $view->unlink( $keyPath );

+			

+		} else {

+			

+			\OC_Log::write( 'Encryption library', 'Could not delete keyfile; does not exist: "' . $keyPath, \OC_Log::ERROR );

+			

+			return false;

+			

+		}

+		

+	}

+	

+	/**

+	 * @brief store private key from the user

+	 * @param string key

+	 * @return bool

+	 * @note Encryption of the private key must be performed by client code

+	 * as no encryption takes place here

+	 */

+	public static function setPrivateKey( $key ) {

+		

+		$user = \OCP\User::getUser();

+		

+		$view = new \OC_FilesystemView( '/' . $user . '/files_encryption' );

+		

+		\OC_FileProxy::$enabled = false;

+		

+		if ( !$view->file_exists( '' ) ) $view->mkdir( '' );

+		

+		return $view->file_put_contents( $user . '.private.key', $key );

+		

+		\OC_FileProxy::$enabled = true;

+		

+	}

+	

+	/**

+	 * @brief store private keys from the user

+	 *

+	 * @param string privatekey

+	 * @param string publickey

+	 * @return bool true/false

+	 */

+	public static function setUserKeys($privatekey, $publickey) {

+	

+		return ( self::setPrivateKey( $privatekey ) && self::setPublicKey( $publickey ) );

+	

+	}

+	

+	/**

+	 * @brief store public key of the user

+	 *

+	 * @param string key

+	 * @return bool true/false

+	 */

+	public static function setPublicKey( $key ) {

+		

+		$view = new \OC_FilesystemView( '/public-keys' );

+		

+		\OC_FileProxy::$enabled = false;

+		

+		if ( !$view->file_exists( '' ) ) $view->mkdir( '' );

+		

+		return $view->file_put_contents( \OCP\User::getUser() . '.public.key', $key );

+		

+		\OC_FileProxy::$enabled = true;

+		

+	}

+	

+	/**

 	 * @brief store file encryption key

 	 *

 	 * @param string $path relative path of the file, including filename

@@ -271,70 +248,70 @@ class Keymanager {
 	 * @return bool true/false

 	 * @note The keyfile is not encrypted here. Client code must

 	 * asymmetrically encrypt the keyfile before passing it to this method

-	 */
-	public static function setShareKey( \OC_FilesystemView $view, $path, $userId, $shareKey ) {
-		
-		$basePath = '/' . $userId . '/files_encryption/share-keys';
-		
-		$shareKeyPath = self::keySetPreparation( $view, $path, $basePath, $userId );
-		
-		return $view->file_put_contents( $basePath . '/' . $shareKeyPath . '.shareKey', $shareKey );
-		
+	 */

+	public static function setShareKey( \OC_FilesystemView $view, $path, $userId, $shareKey ) {

+		

+		$basePath = '/' . $userId . '/files_encryption/share-keys';

+		

+		$shareKeyPath = self::keySetPreparation( $view, $path, $basePath, $userId );

+		

+		return $view->file_put_contents( $basePath . '/' . $shareKeyPath . '.shareKey', $shareKey );

+		

 	}

 	

 	/**

 	 * @brief Make preparations to vars and filesystem for saving a keyfile

 	 */

 	public static function keySetPreparation( \OC_FilesystemView $view, $path, $basePath, $userId ) {

-		
-		$targetPath = ltrim( $path, '/' );
-		
-		$path_parts = pathinfo( $targetPath );
-		
-		// If the file resides within a subdirectory, create it
+		

+		$targetPath = ltrim( $path, '/' );

+		

+		$path_parts = pathinfo( $targetPath );

+		

+		// If the file resides within a subdirectory, create it

 		if ( 

 		isset( $path_parts['dirname'] )

 		&& ! $view->file_exists( $basePath . '/' . $path_parts['dirname'] ) 

-		) {
-		
-			$view->mkdir( $basePath . '/' . $path_parts['dirname'] );
-			
-		}
-		
+		) {

+		

+			$view->mkdir( $basePath . '/' . $path_parts['dirname'] );

+			

+		}

+		

 		return $targetPath;

 	

-	}
-	
-	/**
-	 * @brief change password of private encryption key
-	 *
-	 * @param string $oldpasswd old password
-	 * @param string $newpasswd new password
-	 * @return bool true/false
-	 */
-	public static function changePasswd($oldpasswd, $newpasswd) {
-		
-		if ( \OCP\User::checkPassword(\OCP\User::getUser(), $newpasswd) ) {
-			return Crypt::changekeypasscode($oldpasswd, $newpasswd);
-		}
-		return false;
-		
-	}
-	
-	/**
-	 * @brief Fetch the legacy encryption key from user files
-	 * @param string $login used to locate the legacy key
-	 * @param string $passphrase used to decrypt the legacy key
-	 * @return true / false
-	 *
-	 * if the key is left out, the default handeler will be used
-	 */
-	public function getLegacyKey() {
-		
-		$user = \OCP\User::getUser();
-		$view = new \OC_FilesystemView( '/' . $user );
-		return $view->file_get_contents( 'encryption.key' );
-		
-	}
-	
+	}

+	

+	/**

+	 * @brief change password of private encryption key

+	 *

+	 * @param string $oldpasswd old password

+	 * @param string $newpasswd new password

+	 * @return bool true/false

+	 */

+	public static function changePasswd($oldpasswd, $newpasswd) {

+		

+		if ( \OCP\User::checkPassword(\OCP\User::getUser(), $newpasswd) ) {

+			return Crypt::changekeypasscode($oldpasswd, $newpasswd);

+		}

+		return false;

+		

+	}

+	

+	/**

+	 * @brief Fetch the legacy encryption key from user files

+	 * @param string $login used to locate the legacy key

+	 * @param string $passphrase used to decrypt the legacy key

+	 * @return true / false

+	 *

+	 * if the key is left out, the default handeler will be used

+	 */

+	public function getLegacyKey() {

+		

+		$user = \OCP\User::getUser();

+		$view = new \OC_FilesystemView( '/' . $user );

+		return $view->file_get_contents( 'encryption.key' );

+		

+	}

+	

 }
\ No newline at end of file
diff --git a/apps/files_encryption/lib/proxy.php b/apps/files_encryption/lib/proxy.php
index 7ae36e34ce1..58b9bc0725b 100644
--- a/apps/files_encryption/lib/proxy.php
+++ b/apps/files_encryption/lib/proxy.php
@@ -95,7 +95,8 @@ class Proxy extends \OC_FileProxy {
 		
 		if ( self::shouldEncrypt( $path ) ) {
 		
-			if ( !is_resource( $data ) ) { //stream put contents should have been converted to fopen
+			// Stream put contents should have been converted to fopen
+			if ( !is_resource( $data ) ) {
 			
 				$userId = \OCP\USER::getUser();
 				
@@ -107,10 +108,33 @@ class Proxy extends \OC_FileProxy {
 				// Disable encryption proxy to prevent recursive calls
 				\OC_FileProxy::$enabled = false;
 				
-				// TODO: Check if file is shared, if so, use multiKeyEncrypt
+				$fileOwner = \OC\Files\Filesystem::getOwner( $path );
 				
-				// Encrypt plain data and fetch key
-				$encrypted = Crypt::keyEncryptKeyfile( $data, Keymanager::getPublicKey( $rootView, $userId ) );
+				// Check if the keyfile needs to be shared
+				if ( 
+					$fileOwner !== true
+					or $fileOwner !== $userId 
+				) {
+					
+					// Shared storage backend isn't loaded
+					
+					$users = \OCP\Share::getItemShared( 'file', $path, \OC_Share_backend_File::FORMAT_SHARED_STORAGE );
+// 					
+					trigger_error("SHARE USERS = ". var_export($users, 1));
+// 					
+// 					$publicKeys = Keymanager::getPublicKeys( $rootView, $users);
+// 					
+// 					// Encrypt plain data to multiple users
+// 					$encrypted = Crypt::multiKeyEncrypt( $data, $publicKeys );
+				
+				} else {
+				
+					$publicKey = Keymanager::getPublicKey( $rootView, $userId );
+				
+					// Encrypt plain data to a single user
+					$encrypted = Crypt::keyEncryptKeyfile( $data, $publicKey );
+				
+				}
 				
 				// Replace plain content with encrypted content by reference
 				$data = $encrypted['data'];
diff --git a/lib/public/share.php b/lib/public/share.php
index af2a538e252..936f85021c0 100644
--- a/lib/public/share.php
+++ b/lib/public/share.php
@@ -91,6 +91,60 @@ class Share {
 		}
 		return false;
 	}
+	
+	/**
+	* @brief Find which users can access a shared item
+	* @param string Item type
+	* @param int Format (optional) Format type must be defined by the backend
+	* @param int Number of items to return (optional) Returns all by default
+	* @return Return depends on format
+	*/
+	public static function getUsersSharingFile( $path ) {
+		
+		// Fetch all shares of this file path from DB
+		$query = \OC_DB::prepare( 
+			'SELECT 
+				share_type
+				, share_with
+				, permissions
+			FROM 
+				`*PREFIX*share` 
+			WHERE 
+				file_target = ?'
+			);
+			
+		$result = $query->execute( array( $path ) );
+		
+		if ( \OC_DB::isError( $result ) ) {
+		
+			\OC_Log::write( 'OCP\Share', \OC_DB::getErrorMessage($result) . ', path=' . $path, \OC_Log::ERROR );
+		
+		}
+		
+		$shares = array();
+		
+		while( $row = $result->fetchRow() ) {
+		
+			// Set helpful array keys
+			$shares[] = array( 
+				'userId' => $row['share_with']
+				, 'shareType' => $row['share_type']
+				, 'permissions' => $row['permissions']
+			);
+			
+		}
+		
+		if ( ! empty( $shares ) ) {
+		
+			return $shares;
+			
+		} else {
+		
+			return false;
+			
+		}
+	
+	}
 
 	/**
 	* @brief Get the items of item type shared with the current user