index.php

<?php
header('Content-Type: text/plain; charset=utf-8');

$config = require('config.php');

if(getBearerToken() !== $config['password']) {
    return;
}

try {
    // Undefined | Multiple Files | $_FILES Corruption Attack
    // If this request falls under any of them, treat it invalid.
    if (
        !isset($_FILES['upfile']['error']) ||
        is_array($_FILES['upfile']['error'])
    ) {
        throw new RuntimeException('Invalid parameters.');
    }

    // Check $_FILES['upfile']['error'] value.
    switch ($_FILES['upfile']['error']) {
        case UPLOAD_ERR_OK:
            break;
        case UPLOAD_ERR_NO_FILE:
            throw new RuntimeException('No file sent.');
        case UPLOAD_ERR_INI_SIZE:
        case UPLOAD_ERR_FORM_SIZE:
            throw new RuntimeException('Exceeded filesize limit.');
        default:
            throw new RuntimeException('Unknown errors.');
    }

    // You should also check filesize here.
    if ($_FILES['upfile']['size'] > 1000000) {
        throw new RuntimeException('Exceeded filesize limit.');
    }

    // DO NOT TRUST $_FILES['upfile']['mime'] VALUE !!
    // Check MIME Type by yourself.
    $finfo = new finfo(FILEINFO_MIME_TYPE);
    if (false === $ext = array_search(
        $finfo->file($_FILES['upfile']['tmp_name']),
        array(
            'jpg' => 'image/jpeg',
            'png' => 'image/png',
            'gif' => 'image/gif',
        ),
        true
    )) {
        throw new RuntimeException('Invalid file format.');
    }

    // You should name it uniquely.
    // DO NOT USE $_FILES['upfile']['name'] WITHOUT ANY VALIDATION !!
    // On this example, obtain safe unique name from its binary data.
    $filename = sprintf('./uploads/%s.%s', sha1_file($_FILES['upfile']['tmp_name']), $ext);

    if (!move_uploaded_file(
        $_FILES['upfile']['tmp_name'],
        $filename
    )) {
        throw new RuntimeException('Failed to move uploaded file.');
    }

    echo $_SERVER['REQUEST_SCHEME'] . '://' . $_SERVER['HTTP_HOST'] . substr($filename, 1);

} catch (RuntimeException $e) {
    echo $e->getMessage();
}

/**
 * Get hearder Authorization
 * */
function getAuthorizationHeader(): ?string {
    $headers = null;
    if (isset($_SERVER['Authorization'])) {
        $headers = trim($_SERVER["Authorization"]);
    }
    else if (isset($_SERVER['HTTP_AUTHORIZATION'])) { //Nginx or fast CGI
        $headers = trim($_SERVER["HTTP_AUTHORIZATION"]);
    }

    return $headers;
}

/**
 * get access token from header
 * */
function getBearerToken() {
    $headers = getAuthorizationHeader();
    // HEADER: Get the access token from the header
    if (!empty($headers)) {
        if (preg_match('/Bearer\s(\S+)/', $headers, $matches)) {
            return $matches[1];
        }
    }
    return null;
}