Sketch out EncryptedCookieMiddleware

Include support for Set-Cookie and cookie objects being encoded. Still
need lots of docs and tests.

src/Http/Middleware/EncryptedCookieMiddleware.php

@@ -0,0 +1,118 @@
+<?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 Cake\Http\Response;
+use Cake\Http\Cookie\CookieCollection;
+use Cake\Utility\CookieCryptTrait;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+
+/**
+ * Encrypt/Decrypt cookie data.
+ *
+ * This middleware layer will encrypt/decrypt the named cookies with the given key
+ * and cipher type. To support multiple keys/cipher types use this middleware multiple
+ * times.
+ *
+ * Cookies in request data will be decrypted, while cookies in response headers will
+ * be encrypted automatically. If the response is a Cake\Http\Response, the cookie
+ * data set with `withCookie()` and `cookie()`` will also be encrypted.
+ *
+ * The encryption types and padding are compatible with those used by CookieComponent
+ * for backwards compatibility.
+ */
+class EncryptedCookieMiddleware
+{
+    use CookieCryptTrait;
+
+    protected $cookieNames;
+    protected $key;
+    protected $cipherType;
+
+    public function __construct(array $cookieNames = [], $key, $cipherType = 'aes')
+    {
+        $this->cookieNames = $cookieNames;
+        $this->key = $key;
+        $this->cipherType = $cipherType;
+    }
+
+    /**
+     * @param \Psr\Http\Message\ServerRequestInterface $request The request.
+     * @param \Psr\Http\Message\ResponseInterface $response The response.
+     * @param callable $next The next middleware to call.
+     * @return \Psr\Http\Message\ResponseInterface A response.
+     */
+    public function __invoke(ServerRequestInterface $request, ResponseInterface $response, $next)
+    {
+        if ($request->getCookieParams()) {
+            $request = $this->decodeCookies($request);
+        }
+        $response = $next($request, $response);
+        if ($response->hasHeader('Set-Cookie')) {
+            $response = $this->encodeSetCookieHeader($response);
+        }
+        if ($response instanceof Response) {
+            $response = $this->encodeCookies($response);
+        }
+
+        return $response;
+    }
+
+    protected function _getCookieEncryptionKey()
+    {
+        return $this->key;
+    }
+
+    protected function decodeCookies(ServerRequestInterface $request)
+    {
+        $cookies = $request->getCookieParams();
+        foreach ($this->cookieNames as $name) {
+            if (isset($cookies[$name])) {
+                $cookies[$name] = $this->_decrypt($cookies[$name], $this->cipherType, $this->key);
+            }
+        }
+
+        return $request->withCookieParams($cookies);
+    }
+
+    protected function encodeCookies(Response $response)
+    {
+        $cookies = $response->getCookieCollection();
+        foreach ($cookies as $cookie) {
+            if (in_array($cookie->getName(), $this->cookieNames, true)) {
+                $value = $this->_encrypt($cookie->getValue(), $this->cipherType, $this->key);
+                $response = $response->withCookie($cookie->withValue($value));
+            }
+        }
+
+        return $response;
+    }
+
+    protected function encodeSetCookieHeader(ResponseInterface $response)
+    {
+        $cookies = CookieCollection::createFromHeader($response->getHeader('Set-Cookie'));
+        $header = [];
+        foreach ($cookies as $cookie) {
+            if (in_array($cookie->getName(), $this->cookieNames, true)) {
+                $value = $this->_encrypt($cookie->getValue(), $this->cipherType, $this->key);
+                $cookie = $cookie->withValue($value);
+            }
+            $header[] = $cookie->toHeaderValue();
+        }
+
+        return $request->withHeader('Set-Cookie', $header);
+    }
+}