Add SMS support

Summary:
Provides a working SMS implementation with support for Twilio.

This version doesn't really retry if we get any gruff at all. Future versions should retry.

Test Plan: used bin/sms to send messages and look at them.

Reviewers: chad, epriestley

Reviewed By: epriestley

Subscribers: aurelijus, epriestley, Korvin

Maniphest Tasks: T920

Differential Revision: https://secure.phabricator.com/D8930

externals/twilio-php/Services/Twilio/RequestValidator.php

@@ -0,0 +1,36 @@
+<?php
+
+class Services_Twilio_RequestValidator
+{
+
+    protected $AuthToken;
+
+    function __construct($token)
+    {
+        $this->AuthToken = $token;
+    }
+    
+    public function computeSignature($url, $data = array())
+    {
+        // sort the array by keys
+        ksort($data);
+
+        // append them to the data string in order
+        // with no delimiters
+        foreach($data as $key => $value)
+            $url .= "$key$value";
+            
+        // This function calculates the HMAC hash of the data with the key
+        // passed in
+        // Note: hash_hmac requires PHP 5 >= 5.1.2 or PECL hash:1.1-1.5
+        // Or http://pear.php.net/package/Crypt_HMAC/
+        return base64_encode(hash_hmac("sha1", $url, $this->AuthToken, true));
+    }
+
+    public function validate($expectedSignature, $url, $data = array())
+    {
+        return $this->computeSignature($url, $data)
+            == $expectedSignature;
+    }
+
+}