/Lib/Network/Http/HttpSocketOauth.php

<?php
/**
 * Extension to CakePHP core HttpSocket class that overrides the request method
 * and intercepts requests whose $request['auth']['method'] param is 'OAuth'.
 *
 * The correct OAuth Authorization header is determined from the request params
 * and then set in the $request['header']['Authorization'] param of the request
 * array before passing it back to HttpSocket::request() to send the request and
 * parse the response.
 *
 * So to trigger OAuth, add $request['auth']['method'] = 'OAuth' to your
 * request. In addition, you'll need to add your consumer key in the
 * $request['auth']['oauth_consumer_key'] and your consumer secret in the
 * $request['auth']['oauth_consumer_secret'] param. These are given to you by
 * the OAuth provider. And once you have them, $request['auth']['oauth_token']
 * and $request['auth']['oauth_token_secret'] params. Your OAuth provider may
 * require you to send additional params too. Include them in the
 * $request['auth'] array and they'll be passed on in the Authorization header
 * and considered when signing the request.
 *
 * @author Neil Crookes <neil@neilcrookes.com>
 * @link http://www.neilcrookes.com
 * @copyright (c) 2010 Neil Crookes
 * @license MIT License - http://www.opensource.org/licenses/mit-license.php
 */
App::uses('HttpSocket', 'Network/Http');
class HttpSocketOauth extends HttpSocket {

	/**
	 * Default OAuth parameters. These get merged into the $request['auth'] param.
	 *
	 * @var array
	 */
	public $defaults = array(
		'oauth_version' => '1.0',
		'oauth_signature_method' => 'HMAC-SHA1',
	);

	/**
	 * Overrides HttpSocket::request() to handle cases where
	 * $request['auth']['method'] is 'OAuth'.
	 *
	 * @param array $request As required by HttpSocket::request(). NOTE ONLY
	 *   THE ARRAY TYPE OF REQUEST IS SUPPORTED
	 * @return array
	 */
	public function request($request = array()) {

		// If the request does not need OAuth Authorization header, let the parent
		// deal with it.
		if (!isset($request['auth']['method']) || $request['auth']['method'] != 'OAuth') {
			return parent::request($request);
		}

		// Generate the OAuth Authorization Header content for this request from the
		// request data and add it into the request's Authorization Header. Note, we
		// don't just add the header directly in the request variable and return the
		// whole thing from the authorizationHeader() method because in some cases
		// we may not want the authorization header content in the request's
		// authorization header, for example, OAuth Echo as used by Twitpic and
		// Twitter includes an Authorization Header as required by twitter's verify
		// credentials API in the X-Verify-Credentials-Authorization header.
		$request['header']['Authorization'] = $this->authorizationHeader($request);

		// Now the Authorization header is built, fire the request off to the parent
		// HttpSocket class request method that we intercepted earlier.
		return parent::request($request);

	}

	/**
	 * Returns the OAuth Authorization Header string for a given request array.
	 *
	 * This method is called by request but can also be called directly, which is
	 * useful if you need to get the OAuth Authorization Header string, such as
	 * when integrating with a service that uses OAuth Echo (Authorization
	 * Delegation) e.g. Twitpic. In this case you send a normal unauthenticated
	 * request to the service e.g. Twitpic along with 2 extra headers:
	 * - X-Auth-Service-Provider - effectively, this is the realm that identity
	 *   delegation should be sent to - in the case of Twitter, just set this to
	 *   https://api.twitter.com/1/account/verify_credentials.json;
	 * - X-Verify-Credentials-Authorization - Consumer should create all the OAuth
	 *   parameters necessary so it could call
	 *   https://api.twitter.com/1/account/verify_credentials.json using OAuth in
	 *   the HTTP header (e.g. it should look like OAuth oauth_consumer_key="...",
	 *   oauth_token="...", oauth_signature_method="...", oauth_signature="...",
	 *   oauth_timestamp="...", oauth_nonce="...", oauth_version="...".
	 *
	 * @param array $request As required by HttpSocket::request(). NOTE ONLY
	 *   THE ARRAY TYPE OF REQUEST IS SUPPORTED
	 * @return String
	 */
	public function authorizationHeader($request) {

		$request['auth'] = array_merge($this->defaults, $request['auth']);

		// Nonce, or number used once is used to distinguish between different
		// requests to the OAuth provider
		if (!isset($request['auth']['oauth_nonce'])) {
			$request['auth']['oauth_nonce'] = md5(uniqid(rand(), true));
		}

		if (!isset($request['auth']['oauth_timestamp'])) {
			$request['auth']['oauth_timestamp'] = time();
		}

		// Now starts the process of signing the request. The signature is a hash of
		// a signature base string with the secret keys. The signature base string
		// is made up of the request http verb, the request uri and the request
		// params, and the secret keys are the consumer secret (for your
		// application) and the access token secret generated for the user by the
		// provider, e.g. twitter, when the user authorizes your app to access their
		// details.

		// Building the request uri, note we don't include the query string or
		// fragment. Standard ports must not be included but non standard ones must.
		$uriFormat = '%scheme://%host';
		if (isset($request['uri']['port']) && !in_array($request['uri']['port'], array(80, 443))) {
			$uriFormat .= ':' . $request['uri']['port'];
		}
		$uriFormat .= '/%path';
		$requestUrl = $this->_buildUri($request['uri'], $uriFormat);

		// OAuth reference states that the request params, i.e. oauth_ params, body
		// params and query string params need to be normalised, i.e. combined in a
		// single string, separated by '&' in the format name=value. But they also
		// need to be sorted by key, then by value. You can't just merge the auth,
		// body and query arrays together then do a ksort because there may be
		// parameters with the same name. Instead we've got to get them into an
		// array of array('name' => '<name>', 'value' => '<value>') elements, then
		// sort those elements.

		// Let's start with the auth params - however, we shouldn't include the auth
		// method (OAuth), and OAuth reference says not to include the realm or the
		// consumer or token secrets
		$requestParams = $this->assocToNumericNameValue(array_diff_key(
			$request['auth'],
			array_flip(array('realm', 'method', 'oauth_consumer_secret', 'oauth_token_secret'))
			));

		// Next add the body params if there are any and the content type header is
		// not set, or it's application/x-www-form-urlencoded
		if (isset($request['body']) && (!isset($request['header']['Content-Type']) || stristr($request['header']['Content-Type'], 'application/x-www-form-urlencoded'))) {
			$requestParams = array_merge($requestParams, $this->assocToNumericNameValue($request['body']));
		}

		// Finally the query params
		if (isset($request['uri']['query'])) {
			$requestParams = array_merge($requestParams, $this->assocToNumericNameValue($request['uri']['query']));
		}

		// Now we can sort them by name then value
		usort($requestParams, array($this, 'sortByNameThenByValue'));

		// Now we concatenate them together in name=value pairs separated by &
		$normalisedRequestParams = '';
		foreach ($requestParams as $k => $requestParam) {
			if ($k) {
				$normalisedRequestParams .= '&';
			}
			$normalisedRequestParams .= $requestParam['name'] . '=' . $this->parameterEncode($requestParam['value']);
		}

		// The signature base string consists of the request method (uppercased) and
		// concatenated with the request URL and normalised request parameters
		// string, both encoded, and separated by &
		$signatureBaseString = strtoupper($request['method']) . '&'
			. $this->parameterEncode($requestUrl) . '&'
			. $this->parameterEncode($normalisedRequestParams);

		// The signature base string is hashed with a key which is the consumer
		// secret (assigned to your application by the provider) and the token
		// secret (also known as the access token secret, if you've got it yet),
		// both encoded and separated by an &
		$key = '';
		if (isset($request['auth']['oauth_consumer_secret'])) {
			$key .= $this->parameterEncode($request['auth']['oauth_consumer_secret']);
		}
		$key .= '&';
		if (isset($request['auth']['oauth_token_secret'])) {
			$key .= $this->parameterEncode($request['auth']['oauth_token_secret']);
		}

		// Finally construct the signature according to the value of the
		// oauth_signature_method auth param in the request array.
		switch ($request['auth']['oauth_signature_method']) {
			case 'HMAC-SHA1':
			$request['auth']['oauth_signature'] = base64_encode(hash_hmac('sha1', $signatureBaseString, $key, true));
			break;
			default:
			// @todo implement the other 2 hashing methods
			break;
		}

		// Finally, we have all the Authorization header parameters so we can build
		// the header string.
		$authorizationHeader = 'OAuth';

		// We don't want to include the realm, method or secrets though
		$authorizationHeaderParams = array_diff_key(
			$request['auth'],
			array_flip(array('method', 'oauth_consumer_secret', 'oauth_token_secret', 'realm'))
		);

		// Add the Authorization header params to the Authorization header string,
		// properly encoded.
		$first = true;

		if (isset($request['auth']['realm'])) {
			$authorizationHeader .= ' realm="' . $request['auth']['realm'] . '"';
			$first = false;
		}

		foreach ($authorizationHeaderParams as $name => $value) {
			if (!$first) {
				$authorizationHeader .= ',';
			} else {
				$authorizationHeader .= ' ';
				$first = false;
			}
			$authorizationHeader .= $this->authorizationHeaderParamEncode($name, $value);
		}

		return $authorizationHeader;
	}

	/**
	 * Builds an Authorization header param string from the supplied name and
	 * value. See below for example:
	 *
	 * @param string $name E.g. 'oauth_signature_method'
	 * @param string $value E.g. 'HMAC-SHA1'
	 * @return string E.g. 'oauth_signature_method="HMAC-SHA1"'
	 */
	public function authorizationHeaderParamEncode($name, $value) {
		return $this->parameterEncode($name) . '="' . $this->parameterEncode($value) . '"';
	}

	/**
	 * Converts an associative array of name => value pairs to a numerically
	 * indexed array of array('name' => '<name>', 'value' => '<value>') elements.
	 *
	 * @param array $array Associative array
	 * @return array
	 */
	public function assocToNumericNameValue($array) {
		$return = array();
		foreach ($array as $name => $value) {
			$return[] = array(
				'name' => $name,
				'value' => $value,
			);
		}
		return $return;
	}

	/**
	 * User defined function to lexically sort an array of
	 * array('name' => '<name>', 'value' => '<value>') elements by the value of
	 * the name key, and if they're the same, then by the value of the value key.
	 *
	 * @param array $a Array with key for 'name' and one for 'value'
	 * @param array $b Array with key for 'name' and one for 'value'
	 * @return integer 1, 0 or -1 depending on whether a greater than b, less than
	 *  or the same.
	 */
	public function sortByNameThenByValue($a, $b) {
		if ($a['name'] == $b['name']) {
			if ($a['value'] == $b['value']) {
				return 0;
			}
			return ($a['value'] > $b['value']) ? 1 : -1;
		}
		return ($a['name'] > $b['name']) ? 1 : -1;
	}

	/**
	 * Encodes paramters as per the OAuth spec by utf 8 encoding the param (if it
	 * is not already utf 8 encoded) and then percent encoding it according to
	 * RFC3986
	 *
	 * @param string $param
	 * @return string
	 */
	public function parameterEncode($param) {
		$encoding = mb_detect_encoding($param);
		if ($encoding != 'UTF-8') {
			$param = mb_convert_encoding($param, 'UTF-8', $encoding);
		}
		$param = rawurlencode($param);
		$param = str_replace('%7E', '~', $param);
		return $param;
	}

}