<?php

/*
 * SCROTT IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * For more information, please refer to UNLICENSE
 */

require_once "class/user.class.php";
require_once "class/group.class.php";
require_once "class/mesg.class.php";

/*
 * This file is a proxy script for fetching resources from the /dynmic
 * directory.  This script enforces access-control on HTTP objects such
 * as images and flat files which are supplied by users.
 *
 * Example request:
 * https://yourdomain.com/scrott/df.php?d=heads&f=a4bf903a
 *
 * In cases of error or lack of access privilege, this script will
 * produce no output and fail silently.
 */

/*
 * Serve the resource at the given URI in response to the current
 * request.  When finished, this function will exit PHP and terminate
 * this script.
 */
function serveResource(string $uri, ?string $filename = NULL) : void
{
    $f = fopen($uri, "rb");

    /* no file */
    if (!$f)
        exit;

    /* enable client caching */
    header("Cache-Control: max-age=0");
    header("Pragma: cache");

    $hash = hash_file("sha256", $uri);

    /* validate client cache */
    if (isset($_SERVER['HTTP_IF_NONE_MATCH']) &&
            $_SERVER['HTTP_IF_NONE_MATCH'] == $hash)
    {
        header("HTTP/1.1 304 Not Modified");
        exit;
    }

    /* resource metadata */
    header("Content-Type: " . mime_content_type($uri));
    header("Content-Length: " . filesize($uri));
    header("ETag: " . $hash);

    if ($filename)
        header("Content-Disposition: attachment; filename=\"" . $filename . "\"");

    fpassthru($f);
    fclose($f);

    exit;
}

/*
 * Check the current user's permissions.  User must have access
 * rights for the file's object, unless that object is a user
 * object and $allowHeadUser is set to true.
 */
function checkPermissions(string $guid, bool $allowHeadUser = false) : bool
{
    if (!($user = user::getCurrent()))
        return false;

    $obj = new obj($guid);

    if ($allowHeadUser && $obj->objtype == "user")
        return true;

    return $user->canAccess($obj);
}

/*
 * Respond to users' requests for dynamic files
 */
function main(string $dir, string $guid) : void
{
    try
    {
        if (basename($guid) != $guid || $guid == "")
            return;

        if (!checkPermissions($guid, $dir == "heads"))
            return;

        switch ($dir)
        {
            case "heads":
                if (file_exists("dynmic/heads/" . $guid))
                    serveResource("dynmic/heads/" . $guid);
                else
                    serveResource("static/img/null.jpg");
                break;

            case "bgs":
                serveResource("dynmic/bgs/" . $guid);
                break;

            case "thumbs":
                serveResource("dynmic/thumbs/" . $guid);
                break;

            case "attach":
                $mesg = new mesg($guid);
                serveResource("dynmic/attach/" . $guid, $mesg->attachment);
                break;
        }
    }
    catch (Exception $e)
    {
        /* fail silently */
    }
}

main($_REQUEST['d'], $_REQUEST['f']);

?>