If you played with the pretty cool Amazon Web Services, you probably started off fetching a sample off the Developer’s Connection pages. At least, I did.

One cool sample for Simple Queue Service is the one by Justin@AWS. But (you saw it coming, I suppose), being anti-PEAR (for many reason, such as dependencies, weight, version conflicts, non-catchiness of the name, fructose intolerance, etc.), I just couldn’t leave the sample like that. Yes, this is me again reinventing the wheel.

The original library depended on two PEAR components:

• Crypt_HMAC, for authentication
• HTTP_Request, for HTTP calls

The Crypt_HMAC replacement

I replaced the Crypt_HMAC dependency by three potential routines: hash PECL, mhash, and Lance’s function (which you will never hear in a Numb3r’s episode, as it has nothing to do with a mathematician, but rather with a smart dude who posted a fully PHP HMAC code snippet in the PHP comments of the mhash() function).

The code goes as follow:

/**
 * HMAC function using hash PECL (http://ca.php.net/manual/en/book.hash.php)
 *
 * @author Tommy Lacroix
 * @param string $stringToSign
 * @return string	base64 encoded hmac
 * @internal
 */
private function hmac_hash($stringToSign) {
	return base64_encode(pack('H*',hash_hmac('sha1', $stringToSign, $this->secretKey)));
}	

/**
 * HMAC function using mhash (http://ca.php.net/manual/en/book.hash.php)
 *
 * @author Tommy Lacroix
 * @param string $stringToSign
 * @return string	base64 encoded hmac
 * @internal
 */
private function hmac_mhash($stringToSign) {
	return base64_encode(mhash(MHASH_SHA1, $stringToSign, $this->secretKey));
}

/**
 * HMAC function using Lance's function (http://ca.php.net/manual/en/function.mhash.php, see comments)
 *
 * @author Tommy Lacroix
 * @param string $stringToSign
 * @return string	base64 encoded hmac
 * @internal
 */
private function hmac_lance($stringToSign) {
    $b = 64;
	if (strlen($this->secretKey) > $b) {
		$key = pack("H*",sha1($this->secretKey));
	} else {
		$key = $this->secretKey;
	}
	$key  = str_pad($key, $b, chr(0x00));
	$ipad = str_pad('', $b, chr(0x36));
	$opad = str_pad('', $b, chr(0x5c));
	$k_ipad = $key ^ $ipad ;
	$k_opad = $key ^ $opad;

	return base64_encode(pack('H*', sha1($k_opad  . pack("H*",sha1($k_ipad . $stringToSign)))));
}

HTTP_Request replacement

I replaced the HTTP_Request dependency by two potential routines: cURL and URL wrappers.

The code goes as follow:

/**
 * Fetch with curl
 *
 * @author Tommy Lacroix
 * @param string 	$url
 * @param string 	$qs
 * @param bool		$post
 * @return array(output,httpCode)
 * @internal
 */
private function fetch_curl($url, $qs, $post) {
	$curl = curl_init();
	curl_setopt($curl, CURLOPT_RETURNTRANSFER, TRUE);
	curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, FALSE);
	curl_setopt($curl, CURLOPT_HEADER, false);
	curl_setopt($curl, CURLOPT_POST, $post);
	curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
	curl_setopt($curl, CURLOPT_FOLLOWLOCATION, false);
	curl_setopt($curl, CURLOPT_URL, $url . (!$post ? '?'.$qs : ''));
	if ($post) {
		curl_setopt($curl, CURLOPT_POSTFIELDS, $qs);
	}

	// Execute
	$output = array();
	$output[0] = curl_exec($curl);
	$output[1] = curl_getinfo($curl,CURLINFO_HTTP_CODE);

	// Close handle
	curl_close($curl);

	return $output;
}

/**
 * Fetch with urlwrappers
 *
 * @author Tommy Lacroix
 * @param string 	$url
 * @param string 	$qs
 * @param bool		$post
 * @return array(output,httpCode)
 * @internal
 */
private function fetch_urlwrappers($url, $qs, $post) {
	$output = array();

	if ($post) {
		$opts = array(
		  'http'=>array(
		    'method'=>"POST",
		    'header'=>"Content-type: application/x-www-form-urlencoded\r\n" .
		              "Content-length: " . strlen($qs),
		    'content'=>$qs
		  )
		);
		$context = stream_context_create($opts);
	} else {
		$opts = array(
		  'http'=>array(
		    'method'=>"GET"
		  )
		);
		$context = stream_context_create($opts);
		$url .= '?'.$qs;
	}

	$output[0] = '';
	$f = @fopen($url,'r',null,$context);
	if (!$f) {
		$output[0] = '';
		$output[1] = 404;
		return $output;
	}
	while (!feof($f)) {
		$output[0] .= fread($f,1024);
	}
	$meta_data = stream_get_meta_data($f);
	if (preg_match('/^HTTP\/1\.[01] ([0-9]{3})/',$meta_data['wrapper_data'][0],$m)) {
		$output[1] = $m[1];
	} else {
		$output[1] = false;
	}
	fclose($f);

	$output[2] = 'wrappers';

	return $output;
}

Detection and conclusion

Finally, the constructor includes a small detection mechanism that selects an HMAC and a fetching function:

/**
 * Constructor
 *
 * @author Justin@AWS
 * @author Tommy Lacroix
 * @param string $accessKey
 * @param string $secretKey
 * @param string $endpoint	http://queue.amazonaws.com
 * @param string $queueName	optional
 * @return SQSClient
 */
public function SQSClient($accessKey, $secretKey, $endpoint = 'http://queue.amazonaws.com', $queueName = '')
{
	.
	.
	.

	// Select fetch function
	// Call it with $this->{$this->fetchFunction}(...)
	if (function_exists('curl_init')) $this->fetchFunction = 'fetch_curl';
		else $this->fetchFunction = 'fetch_urlwrappers';

	// Select hash function
	// Call it with $this->{$this->hmacFunction}(...)
	if (function_exists('hash_hmac')) {
		$this->hmacFunction = 'hmac_hash';
	} else if (function_exists('mhash')) {
		$this->hmacFunction = 'hmac_mhash';
	} else if (class_exists('Crypt_HMAC')) {
		$this->hmacFunction = 'hmac_pear';
	} else {
		$this->hmacFunction = 'hmac_lance';
	}

	.
	.
	.
}

The complete modified sqsClient package can be downloaded below. The original Justin@AWS package is available here.

sqsClientPHP-2.1.zip (11k)

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