Merge pull request #168 from pusher/wh-validation

Add pusher signature validation

Author: kn100

README.md

@@ -149,6 +149,17 @@ Using presence channels is similar to private channels, but you can specify extr
 $pusher->presence_auth('presence-my-channel','socket_id', 'user_id', 'user_info');
 ```
 
+## Webhooks
+
+This library provides a way of verifying that webhooks you receive from Pusher are actually genuine webhooks from Pusher. It also provides a structure for storing them. A helper method called `webhook` enables this. Pass in the headers and body of the request, and it'll return a Webhook object with your verified events. If the library was unable to validate the signature, an exception is thrown instead.
+
+```php
+$webhook = $pusher->webhook($request_headers, $request_body);
+$number_of_events = count($webhook->get_events());
+$time_recieved = $webhook->get_time_ms();
+```
+
+
 ### Presence example
 
 First set this variable in your JS app:

src/Pusher.php

@@ -143,7 +143,7 @@ public function __construct($auth_key, $secret, $app_id, $options = array(), $ho
 
         // ensure host doesn't have a scheme prefix
         $this->settings['host'] =
-        preg_replace('/http[s]?\:\/\//', '', $this->settings['host'], 1);
+            preg_replace('/http[s]?\:\/\//', '', $this->settings['host'], 1);
     }
 
     /**
@@ -398,9 +398,15 @@ private function ddn_domain()
      *
      * @return string
      */
-    public static function build_auth_query_string($auth_key, $auth_secret, $request_method, $request_path,
-    $query_params = array(), $auth_version = '1.0', $auth_timestamp = null)
-    {
+    public static function build_auth_query_string(
+        $auth_key,
+        $auth_secret,
+        $request_method,
+        $request_path,
+        $query_params = array(),
+        $auth_version = '1.0',
+        $auth_timestamp = null
+    ) {
         $params = array();
         $params['auth_key'] = $auth_key;
         $params['auth_timestamp'] = (is_null($auth_timestamp) ? time() : $auth_timestamp);
@@ -745,4 +751,43 @@ public function notify($interests, $data = array(), $debug = false)
 
         return false;
     }
+
+    /**
+     * Verify that a webhook actually came from Pusher, and marshals them into a Webhook object.
+     *
+     * @param array  $headers an array of headers from the request (for example, from getallheaders())
+     * @param string $body    the body of the request (for example, from file_get_contents('php://input'))
+     *
+     * @return Webhook object with the properties time_ms (an int) and events (an array of event objects)
+     */
+    public function webhook($headers, $body)
+    {
+        $this->ensure_valid_signature($headers, $body);
+        $decoded_json = json_decode($body);
+        $webhookobj = new Webhook($decoded_json->time_ms, $decoded_json->events);
+
+        return $webhookobj;
+    }
+
+    /**
+     * Verify that a given Pusher Signature is valid.
+     *
+     * @param array  $headers an array of headers from the request (for example, from getallheaders())
+     * @param string $body    the body of the request (for example, from file_get_contents('php://input'))
+     *
+     * @throws PusherException if signature is inccorrect.
+     */
+    public function ensure_valid_signature($headers, $body)
+    {
+        $x_pusher_key = $headers['X-Pusher-Key'];
+        $x_pusher_signature = $headers['X-Pusher-Signature'];
+        if ($x_pusher_key == $this->settings['auth_key']) {
+            $expected = hash_hmac('sha256', $body, $this->settings['secret']);
+            if ($expected === $x_pusher_signature) {
+                return;
+            }
+        }
+
+        throw new PusherException(sprintf('Received WebHook with invalid signature: got %s, expected %s.', $x_pusher_signature, $expected));
+    }
 }

src/Webhook.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace Pusher;
+
+class Webhook
+{
+    private $time_ms;
+    private $events = array();
+
+    public function __construct($time_ms, $events)
+    {
+        $this->time_ms = $time_ms;
+        $this->events = $events;
+    }
+
+    public function get_events()
+    {
+        return $this->events;
+    }
+
+    public function get_time_ms()
+    {
+        return $this->time_ms;
+    }
+}

tests/unit/webhookTest.php

@@ -0,0 +1,47 @@
+<?php
+
+class webhookTest extends PHPUnit_Framework_TestCase
+{
+    protected function setUp()
+    {
+        $this->pusher = new Pusher\Pusher('thisisaauthkey', 'thisisasecret', 1, true);
+        $this->auth_key = 'thisisaauthkey';
+    }
+
+    public function testValidWebhookSignature()
+    {
+        $signature = '40e0ad3b9aa49529322879e84de1aaaf18bde1efe839ca263d540cc865510d25';
+        $body = '{"hello":"world"}';
+        $headers = array(
+            'X-Pusher-Key'       => $this->auth_key,
+            'X-Pusher-Signature' => $signature,
+        );
+
+        $this->pusher->ensure_valid_signature($headers, $body);
+    }
+
+    /**
+     * @expectedException \Pusher\PusherException
+     */
+    public function testInvalidWebhookSignature()
+    {
+        $signature = 'potato';
+        $body = '{"hello":"world"}';
+        $headers = array(
+            'X-Pusher-Key'       => $this->auth_key,
+            'X-Pusher-Signature' => $signature,
+        );
+        $wrong_signature = $this->pusher->ensure_valid_signature($headers, $body);
+    }
+
+    public function testDecodeWebhook()
+    {
+        $headers_json = '{"X-Pusher-Key":"'.$this->auth_key.'","X-Pusher-Signature":"a19cab2af3ca1029257570395e78d5d675e9e700ca676d18a375a7083178df1c"}';
+        $body = '{"time_ms":1530710011901,"events":[{"name":"client_event","channel":"private-my-channel","event":"client-event","data":"Unencrypted","socket_id":"240621.35780774"}]}';
+        $headers = json_decode($headers_json, true);
+
+        $decodedWebhook = $this->pusher->webhook($headers, $body);
+        $this->assertEquals($decodedWebhook->get_time_ms(), 1530710011901);
+        $this->assertEquals(count($decodedWebhook->get_events()), 1);
+    }
+}