I want to use the Webservice Function for Upload a File for different user.I tried this with this example, Rest API and the simpleserver.php
Authentication with wsusername and wspassword.

$fileinfo = array(

    'contextid' => 0, 

    'component' => 'user', 

    'filearea' => 'draft', 

    'itemid' => 0, 

    'filepath' => '/',

    'filename' => 'sample.txt',

    'filecontent' => base64_encode("Hello World!"), 

    'contextlevel' => 'user',

    'instanceid' => $userid,

);

The Upload on files/externallib.php works and the file is on a temporary directory, but they exit (throw new moodle_exception('nofile'); ) - method upload

// Move file to filepool. if ($dir = $browser->get_file_info($context, $component, $filearea, $itemid, $filepath, '.'))
$dir is NULL

My output from the variables context, component, filearea, itemid and filepath

Context: object(context_user)#236 (5) {

["_id":protected]=> int(5)
["_contextlevel":protected]=> int(30)
["_instanceid":protected]=> string(1) "2"
["_path":protected]=> string(4) "/1/5"
["_depth":protected]=> string(1) "2" }

Component: string(4) "user"

Filearea: string(5) "draft"

Itemid: int(176260806)

Filepath: string(1) "/"

I found a Problem at the file lib/filebrowser/file_info_context_user.php
There is a check on Line 183

        // access control: only my files

        if ($this->user->id != $USER->id) {

            return null;

        } 

$this->user->id is the ID from the specified User (5) and $USER->id is the Webservice User.

I hope someone can fix it.
There are a lot of Forum Posts about this Error, but no one has a solution.
All Examples used the webservice/upload.php with a Token - and this is not possible for our project.