HttpSocketOauth.php

<?php

App::uses('HttpSocket', 'Network/Http');

/**
 * 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
 */
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 $request As required by HttpSocket::request(). NOTE ONLY
     *   THE ARRAY TYPE OF REQUEST IS SUPPORTED
     * @return array
     */
    function request($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 $request As required by HttpSocket::request(). NOTE ONLY
     *   THE ARRAY TYPE OF REQUEST IS SUPPORTED
     * @return String
     */
    function authorizationHeader($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.
        $request['uri'] = $this->_parseUri($request['uri']);
        $uriFormat = '%scheme://%host';
        if (isset($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 $value E.g. 'HMAC-SHA1'
     * @return string E.g. 'oauth_signature_method="HMAC-SHA1"'
     */
    function authorizationHeaderParamEncode($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 $array Associative array
     * @return array
     */
    function assocToNumericNameValue($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 $b Array with key for 'name' and one for 'value'
     * @return integer 1, 0 or -1 depending on whether a greater than b, less than
     *  or the same.
     */
    function sortByNameThenByValue($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 $param
     * @return string
     */
    function parameterEncode($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;
    }

}