Add Mailgun->verifyWebhookSignature

src/Mailgun/Mailgun.php

@@ -20,8 +20,10 @@ class Mailgun{
 
     protected $workingDomain;
     protected $restClient;
+    protected $apiKey;
     
     public function __construct($apiKey = null, $apiEndpoint = "api.mailgun.net", $apiVersion = "v2", $ssl = true){
+	    $this->apiKey = $apiKey;
 	    $this->restClient = new RestClient($apiKey, $apiEndpoint, $apiVersion, $ssl);
     }
 
@@ -52,6 +54,31 @@ class Mailgun{
 	    }
 	}
 	
+	public function verifyWebhookSignature($postData = NULL) {
+		/*
+		 * This function checks the signature in a POST request to see if it is
+		 * authentic.
+		 *
+		 * Pass an array of parameters.  If you pass nothing, $_POST will be
+		 * used instead.
+		 *
+		 * If this function returns FALSE, you must not process the request.
+		 * You should reject the request with status code 403 Forbidden.
+		 */
+		if(is_null($postData)) {
+		    $postData = $_POST;
+		}
+		$hmac = hash_hmac('sha256', "{$postData["timestamp"]}{$postData["token"]}", $this->apiKey);
+		$sig = $postData['signature'];
+		if(function_exists('hash_equals')) {
+			// hash_equals is constant time, but will not be introduced until PHP 5.6
+			return hash_equals($hmac, $sig);
+		}
+		else {
+			return ($hmac == $sig);
+		}
+	}
+
 	public function post($endpointUrl, $postData = array(), $files = array()){
 		return $this->restClient->post($endpointUrl, $postData, $files);
 	}

tests/Mailgun/Tests/MailgunTest.php

@@ -13,6 +13,26 @@ class MailgunTest extends \Mailgun\Tests\MailgunTestCase
         $client = new Mailgun();
         $client->sendMessage("test.mailgun.com", "etss", 1);
     }
+
+    public function testVerifyWebhookGood() {
+        $client = new Mailgun('key-3ax6xnjp29jd6fds4gc373sgvjxteol0');
+        $postData = [
+            'timestamp' => '1403645220',
+            'token' => '5egbgr1vjgqxtrnp65xfznchgdccwh5d6i09vijqi3whgowmn6',
+            'signature' => '9cfc5c41582e51246e73c88d34db3af0a3a2692a76fbab81492842f000256d33',
+        ];
+        assert($client->verifyWebhookSignature($postData));
+    }
+
+    public function testVerifyWebhookBad() {
+        $client = new Mailgun('key-3ax6xnjp29jd6fds4gc373sgvjxteol0');
+        $postData = [
+            'timestamp' => '1403645220',
+            'token' => 'owyldpe6nxhmrn78epljl6bj0orrki1u3d2v5e6cnlmmuox8jr',
+            'signature' => '9cfc5c41582e51246e73c88d34db3af0a3a2692a76fbab81492842f000256d33',
+        ];
+        assert(!$client->verifyWebhookSignature($postData));
+    }
 }
 
 ?>