Azure Notification Hubs REST API with PHP

I'm trying to create a SharedAccessSignature for the Azure Notifications Hubs API in PHP.

I keep getting the error "Invalid authorization token signature".

Anyone has an example of creating the SAS in PHP 5.4+? There is some documentation of the API on: http://msdn.microsoft.com/en-us/library/dn170477.aspx, but some people say that the implementation differs from the documentation.

This is my failing implementation:

private static function get_authentication_header()
    {
        $uri = "https://x.servicebus.windows.net/x";
        $expiry = time() + (60*60);
        $string = utf8_encode(urlencode($uri) . "\n" . $expiry);
        $keyname = "DefaultFullSharedAccessSignature";
        $key = base64_decode(static::HUB_KEY);
        $signature = base64_encode(hash_hmac('sha256', $string,  $key));
        $sas = 'SharedAccessSignature sig=' . $signature . '&se=' . $expiry . '&skn=' .      $keyname . '&sr=' . urlencode($uri);
        return $sas;
 }

Here is a simple wrapper to send notifications to Notification Hubs with PHP.

<?php

include 'Notification.php';

class NotificationHub {

    const API_VERSION = "?api-version=2013-10";

    private $endpoint;
    private $hubPath;
    private $sasKeyName;
    private $sasKeyValue;

    function __construct($connectionString, $hubPath) {
        $this->hubPath = $hubPath;

        $this->parseConnectionString($connectionString);
    }

    private function parseConnectionString($connectionString) {
        $parts = explode(";", $connectionString);
        if (sizeof($parts) != 3) {
            throw new Exception("Error parsing connection string: " . $connectionString);
        }

        foreach ($parts as $part) {
            if (strpos($part, "Endpoint") === 0) {
                $this->endpoint = "https" . substr($part, 11);
            } else if (strpos($part, "SharedAccessKeyName") === 0) {
                $this->sasKeyName = substr($part, 20);
            } else if (strpos($part, "SharedAccessKey") === 0) {
                $this->sasKeyValue = substr($part, 16);
            }
        }
    }

    private function generateSasToken($uri) {
        $targetUri = strtolower(rawurlencode(strtolower($uri)));

        $expires = time();
        $expiresInMins = 60;
        $expires = $expires + $expiresInMins * 60;
        $toSign = $targetUri . "\n" . $expires;

        $signature = rawurlencode(base64_encode(hash_hmac('sha256', $toSign, $this->sasKeyValue, TRUE)));

        $token = "SharedAccessSignature sr=" . $targetUri . "&sig="
                    . $signature . "&se=" . $expires . "&skn=" . $this->sasKeyName;

        return $token;
    }

    public function broadcastNotification($notification) {
        $this->sendNotification($notification, "");
    }

    public function sendNotification($notification, $tagsOrTagExpression) {
        echo $tagsOrTagExpression."<p>";

        if (is_array($tagsOrTagExpression)) {
            $tagExpression = implode(" || ", $tagsOrTagExpression);
        } else {
            $tagExpression = $tagsOrTagExpression;
        }

        # build uri
        $uri = $this->endpoint . $this->hubPath . "/messages" . NotificationHub::API_VERSION;

        echo $uri."<p>";

        $ch = curl_init($uri);

        if (in_array($notification->format, ["template", "apple", "gcm"])) {
            $contentType = "application/json";
        } else {
            $contentType = "application/xml";
        }

        $token = $this->generateSasToken($uri);

        $headers = [
            'Authorization: '.$token,
            'Content-Type: '.$contentType,
            'ServiceBusNotification-Format: '.$notification->format
        ];

        if ("" !== $tagExpression) {
            $headers[] = 'ServiceBusNotification-Tags: '.$tagExpression;
        }

        # add headers for other platforms
        if (is_array($notification->headers)) {
            $headers = array_merge($headers, $notification->headers);
        }

        curl_setopt_array($ch, array(
            CURLOPT_POST => TRUE,
            CURLOPT_RETURNTRANSFER => TRUE,
            CURLOPT_SSL_VERIFYPEER => FALSE,
            CURLOPT_HTTPHEADER => $headers,
            CURLOPT_POSTFIELDS => $notification->payload
        ));

        // Send the request
        $response = curl_exec($ch);

        // Check for errors
        if($response === FALSE){
            throw new Exception(curl_error($ch));
        }

        $info = curl_getinfo($ch);

        if ($info['http_code'] <> 201) {
            throw new Exception('Error sending notificaiton: '. $info['http_code'] . ' msg: ' . $response);
        }

        //print_r($info);

        //echo $response;
    } 
}

?>

I do not know if you wanted to send pushes or to do registration management. It is not hard to modify the above to do registration management as shown in the NH REST APIs (remember the order in the xml documents matters!): http://msdn.microsoft.com/en-us/library/dn223264.aspx.

Let me know if you still run into problems.

Elio