Download streamer isn't returning real files. Wrong Content-type or mime?

Question

A Python application is saying the zip files I am streaming via a PHP streamer aren't zip files. However, winrar opens them with no issues.

This is the headers it is sending:

Content-disposition: filename=example.zip
Content-type: application/zip; charset=binary

Do I need more/different headers?

Below is the code:

<?php
session_start();
if(!$_SESSION['directory']){
    print "Sorry, only logged in users can view downloads";
    exit;
};
?>
<?php

$hidden_file_directory = "download/".$_SESSION['directory']; //Name of the directory where all the sub directories and files exists
$file_path = $_GET['file']; //Get the file from URL variable
$real_file_path = realpath("$hidden_file_directory/$file_path"); //Set the file path w.r.t the download.php... It may be different for u
$filename = basename($real_file_path);

if(dirname($real_file_path) != getcwd() ."/". $hidden_file_directory)
    die("File does not exist.");

if(file_exists($real_file_path)) {
    $content_type = get_mime($real_file_path);
    header("Content-disposition: filename=$filename"); //Tell the filename to the browser
    header("Content-type: $content_type"); //Stream as a binary file! So it would force browser to download
    readfile($real_file_path); //Read and stream the file
}
else {
    echo "File does not exist.";
}


function get_mime($filename) {

    $mime_types = array(

        'txt' => 'text/plain',
        'htm' => 'text/html',
        'html' => 'text/html',
        'php' => 'text/html',
        'css' => 'text/css',
        'js' => 'application/javascript',
        'json' => 'application/json',
        'xml' => 'application/xml',
        'swf' => 'application/x-shockwave-flash',
        'flv' => 'video/x-flv',

        // images
        'png' => 'image/png',
        'jpe' => 'image/jpeg',
        'jpeg' => 'image/jpeg',
        'jpg' => 'image/jpeg',
        'gif' => 'image/gif',
        'bmp' => 'image/bmp',
        'ico' => 'image/vnd.microsoft.icon',
        'tiff' => 'image/tiff',
        'tif' => 'image/tiff',
        'svg' => 'image/svg+xml',
        'svgz' => 'image/svg+xml',

        // archives
        'zip' => 'application/zip',
        'rar' => 'application/x-rar-compressed',
        'exe' => 'application/x-msdownload',
        'msi' => 'application/x-msdownload',
        'cab' => 'application/vnd.ms-cab-compressed',

        // audio/video
        'mp3' => 'audio/mpeg',
        'qt' => 'video/quicktime',
        'mov' => 'video/quicktime',

        // adobe
        'pdf' => 'application/pdf',
        'psd' => 'image/vnd.adobe.photoshop',
        'ai' => 'application/postscript',
        'eps' => 'application/postscript',
        'ps' => 'application/postscript',

        // ms office
        'doc' => 'application/msword',
        'rtf' => 'application/rtf',
        'xls' => 'application/vnd.ms-excel',
        'ppt' => 'application/vnd.ms-powerpoint',

        // open office
        'odt' => 'application/vnd.oasis.opendocument.text',
        'ods' => 'application/vnd.oasis.opendocument.spreadsheet',
    );

    $ext = strtolower(array_pop(explode('.',$filename)));
    if (array_key_exists($ext, $mime_types)) {
        return $mime_types[$ext];
    }
    elseif (function_exists('finfo_open')) {
        $finfo = finfo_open(FILEINFO_MIME);
        $mimetype = finfo_file($finfo, $filename);
        finfo_close($finfo);
        return $mimetype;
    }
    else {
        return 'application/octet-stream';
    }
}


?>

Edit - I added:

if(dirname($real_file_path) != getcwd() ."/". $hidden_file_directory)
    die("File does not exist.");

When those who pointed out the insecurity. Hopefully this will be secure enough.

Answer 1

I've noticed that some browsers need the filename to be double quoted or they dont know what it is, perhaps python does the same. Try sending

 header("Content-disposition: filename=\"$filename\"");

Also are you sure it is infact application/zip and not application/x-zip-compressed?

On a side note: You are using the filename directly from the querystring. What if I send my filename as file=..\..\..\..\..\..\systemdir\config.xml? Perhaps you should add some checking. basename() like you use the next step might be a good idea.