\Cake\Http\MiddlewareSecurityHeadersMiddleware

<?php
/**
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the LICENSE.txt
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @since         3.5.0
 * @license       http://www.opensource.org/licenses/mit-license.php MIT License
 */
namespace Cake\Http\Middleware;

use InvalidArgumentException;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;

/**
 * Handles common security headers in a convenient way
 */
class SecurityHeadersMiddleware
{
    /** @var string X-Content-Type-Option nosniff */
    const NOSNIFF = 'nosniff';

    /** @var string X-Download-Option noopen */
    const NOOPEN = 'noopen';

    /** @var string Referrer-Policy no-referrer */
    const NO_REFERRER = 'no-referrer';

    /** @var string Referrer-Policy no-referrer-when-downgrade */
    const NO_REFERRER_WHEN_DOWNGRADE = 'no-referrer-when-downgrade';

    /** @var string Referrer-Policy origin */
    const ORIGIN = 'origin';

    /** @var string Referrer-Policy origin-when-cross-origin */
    const ORIGIN_WHEN_CROSS_ORIGIN = 'origin-when-cross-origin';

    /** @var string Referrer-Policy same-origin */
    const SAME_ORIGIN = 'same-origin';

    /** @var string Referrer-Policy strict-origin */
    const STRICT_ORIGIN = 'strict-origin';

    /** @var string Referrer-Policy strict-origin-when-cross-origin */
    const STRICT_ORIGIN_WHEN_CROSS_ORIGIN = 'strict-origin-when-cross-origin';

    /** @var string Referrer-Policy unsafe-url */
    const UNSAFE_URL = 'unsafe-url';

    /** @var string X-Frame-Option deny */
    const DENY = 'deny';

    /** @var string X-Frame-Option sameorigin */
    const SAMEORIGIN = 'sameorigin';

    /** @var string X-Frame-Option allow-from */
    const ALLOW_FROM = 'allow-from';

    /** @var string X-XSS-Protection block, sets enabled with block */
    const XSS_BLOCK = 'block';

    /** @var string X-XSS-Protection enabled with block */
    const XSS_ENABLED_BLOCK = '1; mode=block';

    /** @var string X-XSS-Protection enabled */
    const XSS_ENABLED = '1';

    /** @var string X-XSS-Protection disabled */
    const XSS_DISABLED = '0';

    /** @var string X-Permitted-Cross-Domain-Policy all */
    const ALL = 'all';

    /** @var string X-Permitted-Cross-Domain-Policy none */
    const NONE = 'none';

    /** @var string X-Permitted-Cross-Domain-Policy master-only */
    const MASTER_ONLY = 'master-only';

    /** @var string X-Permitted-Cross-Domain-Policy by-content-type */
    const BY_CONTENT_TYPE = 'by-content-type';

    /** @var string X-Permitted-Cross-Domain-Policy by-ftp-filename */
    const BY_FTP_FILENAME = 'by-ftp-filename';

    /**
     * Security related headers to set
     *
     * @var array
     */
    protected $headers = [];

    /**
     * X-Content-Type-Options
     *
     * Sets the header value for it to 'nosniff'
     *
     * @link https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Content-Type-Options
     * @return $this
     */
    public function noSniff()
    {
        $this->headers['x-content-type-options'] = self::NOSNIFF;

        return $this;
    }

    /**
     * X-Download-Options
     *
     * Sets the header value for it to 'noopen'
     *
     * @link https://msdn.microsoft.com/en-us/library/jj542450(v=vs.85).aspx
     * @return $this
     */
    public function noOpen()
    {
        $this->headers['x-download-options'] = self::NOOPEN;

        return $this;
    }

    /**
     * Referrer-Policy
     *
     * @link https://w3c.github.io/webappsec-referrer-policy
     * @param string $policy Policy value. Available Value: 'no-referrer', 'no-referrer-when-downgrade', 'origin',
     *     'origin-when-cross-origin', 'same-origin', 'strict-origin', 'strict-origin-when-cross-origin', 'unsafe-url'
     * @return $this
     */
    public function setReferrerPolicy($policy = self::SAME_ORIGIN)
    {
        $available = [
            self::NO_REFERRER,
            self::NO_REFERRER_WHEN_DOWNGRADE,
            self::ORIGIN,
            self::ORIGIN_WHEN_CROSS_ORIGIN,
            self::SAME_ORIGIN,
            self::STRICT_ORIGIN,
            self::STRICT_ORIGIN_WHEN_CROSS_ORIGIN,
            self::UNSAFE_URL,
        ];

        $this->checkValues($policy, $available);
        $this->headers['referrer-policy'] = $policy;

        return $this;
    }

    /**
     * X-Frame-Options
     *
     * @link https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options
     * @param string $option Option value. Available Values: 'deny', 'sameorigin', 'allow-from <uri>'
     * @param string $url URL if mode is `allow-from`
     * @return $this
     */
    public function setXFrameOptions($option = self::SAMEORIGIN, $url = null)
    {
        $this->checkValues($option, [self::DENY, self::SAMEORIGIN, self::ALLOW_FROM]);

        if ($option === self::ALLOW_FROM) {
            if (empty($url)) {
                throw new InvalidArgumentException('The 2nd arg $url can not be empty when `allow-from` is used');
            }
            $option .= ' ' . $url;
        }

        $this->headers['x-frame-options'] = $option;

        return $this;
    }

    /**
     * X-XSS-Protection
     *
     * @link https://blogs.msdn.microsoft.com/ieinternals/2011/01/31/controlling-the-xss-filter
     * @param string $mode Mode value. Available Values: '1', '0', 'block'
     * @return $this
     */
    public function setXssProtection($mode = self::XSS_BLOCK)
    {
        $mode = (string)$mode;

        if ($mode === self::XSS_BLOCK) {
            $mode = self::XSS_ENABLED_BLOCK;
        }

        $this->checkValues($mode, [self::XSS_ENABLED, self::XSS_DISABLED, self::XSS_ENABLED_BLOCK]);
        $this->headers['x-xss-protection'] = $mode;

        return $this;
    }

    /**
     * X-Permitted-Cross-Domain-Policies
     *
     * @link https://www.adobe.com/devnet/adobe-media-server/articles/cross-domain-xml-for-streaming.html
     * @param string $policy Policy value. Available Values: 'all', 'none', 'master-only', 'by-content-type',
     *     'by-ftp-filename'
     * @return $this
     */
    public function setCrossDomainPolicy($policy = self::ALL)
    {
        $this->checkValues($policy, [
            self::ALL,
            self::NONE,
            self::MASTER_ONLY,
            self::BY_CONTENT_TYPE,
            self::BY_FTP_FILENAME,
        ]);
        $this->headers['x-permitted-cross-domain-policies'] = $policy;

        return $this;
    }

    /**
     * Convenience method to check if a value is in the list of allowed args
     *
     * @throws \InvalidArgumentException Thrown when a value is invalid.
     * @param string $value Value to check
     * @param array $allowed List of allowed values
     * @return void
     */
    protected function checkValues($value, array $allowed)
    {
        if (!in_array($value, $allowed)) {
            throw new InvalidArgumentException(sprintf(
                'Invalid arg `%s`, use one of these: %s',
                $value,
                implode(', ', $allowed)
            ));
        }
    }

    /**
     * Serve assets if the path matches one.
     *
     * @param \Psr\Http\Message\ServerRequestInterface $request The request.
     * @param \Psr\Http\Message\ResponseInterface $response The response.
     * @param callable $next Callback to invoke the next middleware.
     * @return \Psr\Http\Message\ResponseInterface A response
     */
    public function __invoke(ServerRequestInterface $request, ResponseInterface $response, $next)
    {
        $response = $next($request, $response);
        foreach ($this->headers as $header => $value) {
            $response = $response->withHeader($header, $value);
        }

        return $response;
    }
}