/chapter_9/oauth1-php-3legged/OAuth.php

<?php
/**
 * The MIT License
 * 
 * Copyright (c) 2008 OAuth.net
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 * 
 */

/**
 * Branched from version 587 of OAuth.php from the OAuth.net project. Major 
 * changes are limited to adding PHP 4 compatibility.
 *
 * Ryan Kennedy (rckenned@yahoo-inc.com)
 */

class OAuthConsumer {/*{{{*/
  var $key;
  var $secret;

  function OAuthConsumer($key, $secret, $callback_url=NULL) {/*{{{*/
    $this->key = $key;
    $this->secret = $secret;
    $this->callback_url = $callback_url;
  }/*}}}*/
}/*}}}*/

class OAuthToken {/*{{{*/
  // access tokens and request tokens
  var $key;
  var $secret;

  /**
   * key = the token
   * secret = the token secret
   */
  function OAuthToken($key, $secret) {/*{{{*/
    $this->key = $key;
    $this->secret = $secret;
  }/*}}}*/

  /**
   * generates the basic string serialization of a token that a server
   * would respond to request_token and access_token calls with
   */
  function to_string() {/*{{{*/
    return "oauth_token=" . OAuthUtil::urlencodeRFC3986($this->key) . 
        "&oauth_token_secret=" . OAuthUtil::urlencodeRFC3986($this->secret);
  }/*}}}*/

  function __toString() {/*{{{*/
    return $this->to_string();
  }/*}}}*/
}/*}}}*/

class OAuthSignatureMethod {/*{{{*/
  function check_signature(&$request, $consumer, $token, $signature) {
    $built = $this->build_signature($request, $consumer, $token);
    return $built == $signature;
  }
}/*}}}*/

class OAuthSignatureMethod_HMAC_SHA1 extends OAuthSignatureMethod {/*{{{*/
  function get_name() {/*{{{*/
    return "HMAC-SHA1";
  }/*}}}*/

  function build_signature($request, $consumer, $token) {/*{{{*/
    $base_string = $request->get_signature_base_string();
    $request->base_string = $base_string;

    $key_parts = array(
      $consumer->secret,
      ($token) ? $token->secret : ""
    );

    $key_parts = array_map(array('OAuthUtil','urlencodeRFC3986'), $key_parts);
    $key = implode('&', $key_parts);

    return base64_encode(hash_hmac('sha1', $base_string, $key, true));
  }/*}}}*/
}/*}}}*/

class OAuthSignatureMethod_PLAINTEXT extends OAuthSignatureMethod {/*{{{*/
  function get_name() {/*{{{*/
    return "PLAINTEXT";
  }/*}}}*/

  function build_signature($request, $consumer, $token) {/*{{{*/
    $sig = array(
      OAuthUtil::urlencodeRFC3986($consumer->secret)
    );

    if ($token) {
      array_push($sig, OAuthUtil::urlencodeRFC3986($token->secret));
    } else {
      array_push($sig, '');
    }

    $raw = implode("&", $sig);
    // for debug purposes
    $request->base_string = $raw;

    return $raw;
  }/*}}}*/
}/*}}}*/

class OAuthSignatureMethod_RSA_SHA1 extends OAuthSignatureMethod {/*{{{*/
  function get_name() {/*{{{*/
    return "RSA-SHA1";
  }/*}}}*/

  function fetch_public_cert(&$request) {/*{{{*/
    // not implemented yet, ideas are:
    // (1) do a lookup in a table of trusted certs keyed off of consumer
    // (2) fetch via http using a url provided by the requester
    // (3) some sort of specific discovery code based on request
    //
    // either way should return a string representation of the certificate
    trigger_error("fetch_public_cert not implemented", E_USER_ERROR);
    return NULL;
  }/*}}}*/

  function fetch_private_cert(&$request) {/*{{{*/
    // not implemented yet, ideas are:
    // (1) do a lookup in a table of trusted certs keyed off of consumer
    //
    // either way should return a string representation of the certificate
    trigger_error("fetch_private_cert not implemented", E_USER_ERROR);
    return NULL;
  }/*}}}*/

  function build_signature(&$request, $consumer, $token) {/*{{{*/
    $base_string = $request->get_signature_base_string();
  
    // Fetch the private key cert based on the request
    $cert = $this->fetch_private_cert($request);

    // Pull the private key ID from the certificate
    $privatekeyid = openssl_get_privatekey($cert);

    // Sign using the key
    $ok = openssl_sign($base_string, $signature, $privatekeyid);   

    // Release the key resource
    openssl_free_key($privatekeyid);
  
    return base64_encode($signature);
  } /*}}}*/

  function check_signature(&$request, $consumer, $token, $signature) {/*{{{*/
    $decoded_sig = base64_decode($signature);

    $base_string = $request->get_signature_base_string();
  
    // Fetch the public key cert based on the request
    $cert = $this->fetch_public_cert($request);

    // Pull the public key ID from the certificate
    $publickeyid = openssl_get_publickey($cert);

    // Check the computed signature against the one passed in the query
    $ok = openssl_verify($base_string, $decoded_sig, $publickeyid);   

    // Release the key resource
    openssl_free_key($publickeyid);
  
    return $ok == 1;
  } /*}}}*/
}/*}}}*/

class OAuthRequest {/*{{{*/
  var $parameters;
  var $http_method;
  var $http_url;
  // for debug purposes
  var $base_string;

  function OAuthRequest($http_method, $http_url, $parameters=array()) {/*{{{*/
    $this->parameters = $parameters;
    $this->http_method = $http_method;
    $this->http_url = $http_url;
  }/*}}}*/


  /**
   * attempt to build up a request from what was passed to the server
   */
  function from_request($http_method=NULL, $http_url=NULL, $parameters=NULL) {/*{{{*/
    $scheme = (!isset($_SERVER['HTTPS']) || $_SERVER['HTTPS'] != "on") ? 'http' : 'https';
    @$http_url or $http_url = $scheme . '://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
    @$http_method or $http_method = $_SERVER['REQUEST_METHOD'];
    
    $request_headers = OAuthRequest::get_headers();

    // let the library user override things however they'd like, if they know
    // which parameters to use then go for it, for example XMLRPC might want to
    // do this
    if ($parameters) {
      $req = new OAuthRequest($http_method, $http_url, $parameters);
    }
    // next check for the auth header, we need to do some extra stuff
    // if that is the case, namely suck in the parameters from GET or POST
    // so that we can include them in the signature
    else if (@substr($request_headers['Authorization'], 0, 5) == "OAuth") {
      $header_parameters = OAuthRequest::split_header($request_headers['Authorization']);
      if ($http_method == "GET") {
        $req_parameters = $_GET;
      } 
      else if ($http_method = "POST") {
        $req_parameters = $_POST;
      } 
      $parameters = array_merge($header_parameters, $req_parameters);
      $req = new OAuthRequest($http_method, $http_url, $parameters);
    }
    else if ($http_method == "GET") {
      $req = new OAuthRequest($http_method, $http_url, $_GET);
    }
    else if ($http_method == "POST") {
      $req = new OAuthRequest($http_method, $http_url, $_POST);
    }
    return $req;
  }/*}}}*/

  /**
   * pretty much a helper function to set up the request
   */
  function from_consumer_and_token($consumer, $token, $http_method, $http_url, $parameters=array()) {/*{{{*/
    static $version = '1.0';
    $defaults = array("oauth_version" => $version,
                      "oauth_nonce" => OAuthRequest::generate_nonce(),
                      "oauth_timestamp" => OAuthRequest::generate_timestamp(),
                      "oauth_consumer_key" => $consumer->key);
    $parameters = array_merge($defaults, $parameters);

    if ($token) {
      $parameters['oauth_token'] = $token->key;
    }
    $req = new OAuthRequest($http_method, $http_url, $parameters);
    return $req;
  }/*}}}*/

  function set_parameter($name, $value) {/*{{{*/
    $this->parameters[$name] = $value;
  }/*}}}*/

  function get_parameter($name) {/*{{{*/
    return $this->parameters[$name];
  }/*}}}*/

  function get_parameters() {/*{{{*/
    return $this->parameters;
  }/*}}}*/

  /**
   * Returns the normalized parameters of the request
   * 
   * This will be all (except oauth_signature) parameters,
   * sorted first by key, and if duplicate keys, then by
   * value.
   *
   * The returned string will be all the key=value pairs
   * concated by &.
   * 
   * @return string
   */
  function get_signable_parameters() {/*{{{*/
    // Include query parameters
    $url = parse_url($this->http_url);
    if(array_key_exists("query", $url)) {
        parse_str($url["query"], $query);

        foreach($query as $key => $value) {
            $this->set_parameter($key, $value);
        }
    }

    // Grab all parameters
    $params = $this->parameters;
		
    // Remove oauth_signature if present
    if (isset($params['oauth_signature'])) {
      unset($params['oauth_signature']);
    }
		
    // Urlencode both keys and values
    $keys = array_map(array('OAuthUtil', 'urlencodeRFC3986'), array_keys($params));
    $values = array_map(array('OAuthUtil', 'urlencodeRFC3986'), array_values($params));
    $params = array();
    for($i = 0; $i < count($keys); $i++) {
        $params[$keys[$i]] = $values[$i];
    }

    // Sort by keys (natsort)
    uksort($params, 'strnatcmp');

    // Generate key=value pairs
    $pairs = array();
    foreach ($params as $key=>$value ) {
      if (is_array($value)) {
        // If the value is an array, it's because there are multiple 
        // with the same key, sort them, then add all the pairs
        natsort($value);
        foreach ($value as $v2) {
          $pairs[] = $key . '=' . $v2;
        }
      } else {
        $pairs[] = $key . '=' . $value;
      }
    }
		
    // Return the pairs, concated with &
    return implode('&', $pairs);
  }/*}}}*/

  /**
   * Returns the base string of this request
   *
   * The base string defined as the method, the url
   * and the parameters (normalized), each urlencoded
   * and the concated with &.
   */
  function get_signature_base_string() {/*{{{*/
    $parts = array(
      $this->get_normalized_http_method(),
      $this->get_normalized_http_url(),
      $this->get_signable_parameters()
    );

    $parts = array_map(array('OAuthUtil', 'urlencodeRFC3986'), $parts);

    return implode('&', $parts);
  }/*}}}*/

  /**
   * just uppercases the http method
   */
  function get_normalized_http_method() {/*{{{*/
    return strtoupper($this->http_method);
  }/*}}}*/

  /**
   * parses the url and rebuilds it to be
   * scheme://host/path
   */
  function get_normalized_http_url() {/*{{{*/
    $parts = parse_url($this->http_url);

    // FIXME: port should handle according to http://groups.google.com/group/oauth/browse_thread/thread/1b203a51d9590226
    $port = (isset($parts['port']) && $parts['port'] != '80') ? ':' . $parts['port'] : '';
    $path = (isset($parts['path'])) ? $parts['path'] : '';

    return $parts['scheme'] . '://' . $parts['host'] . $port . $path;
  }/*}}}*/

  /**
   * builds a url usable for a GET request
   */
  function to_url() {/*{{{*/
    $out = $this->get_normalized_http_url() . "?";
    $out .= $this->to_postdata();
    return $out;
  }/*}}}*/

  /**
   * builds the data one would send in a POST request
   */
  function to_postdata() {/*{{{*/
    $total = array();
    foreach ($this->parameters as $k => $v) {
      $total[] = OAuthUtil::urlencodeRFC3986($k) . "=" . OAuthUtil::urlencodeRFC3986($v);
    }
    $out = implode("&", $total);
    return $out;
  }/*}}}*/

  /**
   * builds the Authorization: header
   */
  function to_header() {/*{{{*/
    $headerParams = array();
    foreach ($this->parameters as $k => $v) {
      if (substr($k, 0, 5) != "oauth") continue;
      $headerParams[] = OAuthUtil::urlencodeRFC3986($k) . '="' . OAuthUtil::urlencodeRFC3986($v) . '"';
    }
    return sprintf("Authorization: OAuth %s", implode(",", $headerParams));
  }/*}}}*/

  function __toString() {/*{{{*/
    return $this->to_url();
  }/*}}}*/


  function sign_request($signature_method, $consumer, $token) {/*{{{*/
    $this->set_parameter("oauth_signature_method", $signature_method->get_name());
    $signature = $this->build_signature($signature_method, $consumer, $token);
    $this->set_parameter("oauth_signature", $signature);
  }/*}}}*/

  function build_signature($signature_method, $consumer, $token) {/*{{{*/
    $signature = $signature_method->build_signature($this, $consumer, $token);
    return $signature;
  }/*}}}*/

  /**
   * util function: current timestamp
   */
  function generate_timestamp() {/*{{{*/
    return time();
  }/*}}}*/

  /**
   * util function: current nonce
   */
  function generate_nonce() {/*{{{*/
    $mt = microtime();
    $rand = mt_rand();

    return md5($mt . $rand); // md5s look nicer than numbers
  }/*}}}*/

  /**
   * util function for turning the Authorization: header into
   * parameters, has to do some unescaping
   */
  function split_header($header) {/*{{{*/
    // this should be a regex
    // error cases: commas in parameter values
    $parts = explode(",", $header);
    $out = array();
    foreach ($parts as $param) {
      $param = ltrim($param);
      // skip the "realm" param, nobody ever uses it anyway
      if (substr($param, 0, 5) != "oauth") continue;

      $param_parts = explode("=", $param);

      // rawurldecode() used because urldecode() will turn a "+" in the
      // value into a space
      $out[$param_parts[0]] = rawurldecode(substr($param_parts[1], 1, -1));
    }
    return $out;
  }/*}}}*/

  /**
   * helper to try to sort out headers for people who aren't running apache
   */
  function get_headers() {/*{{{*/
    if (function_exists('apache_request_headers')) {
      // we need this to get the actual Authorization: header
      // because apache tends to tell us it doesn't exist
      return apache_request_headers();
    }
    // otherwise we don't have apache and are just going to have to hope
    // that $_SERVER actually contains what we need
    $out = array();
    foreach ($_SERVER as $key => $value) {
      if (substr($key, 0, 5) == "HTTP_") {
        // this is chaos, basically it is just there to capitalize the first
        // letter of every word that is not an initial HTTP and strip HTTP
        // code from przemek
        $key = str_replace(" ", "-", ucwords(strtolower(str_replace("_", " ", substr($key, 5)))));
        $out[$key] = $value;
      }
    }
    return $out;
  }/*}}}*/
}/*}}}*/

class OAuthServer {/*{{{*/
  var $timestamp_threshold = 300; // in seconds, five minutes
  var $version = 1.0;             // hi blaine
  var $signature_methods = array();

  var $data_store;

  function OAuthServer($data_store) {/*{{{*/
    $this->data_store = $data_store;
  }/*}}}*/

  function add_signature_method($signature_method) {/*{{{*/
    $this->signature_methods[$signature_method->get_name()] = 
        $signature_method;
  }/*}}}*/
  
  // high level functions

  /**
   * process a request_token request
   * returns the request token on success
   */
  function fetch_request_token(&$request) {/*{{{*/
    $this->get_version($request);

    $consumer = $this->get_consumer($request);

    // no token required for the initial token request
    $token = NULL;

    $this->check_signature($request, $consumer, $token);

    $new_token = $this->data_store->new_request_token($consumer);

    return $new_token;
  }/*}}}*/

  /**
   * process an access_token request
   * returns the access token on success
   */
  function fetch_access_token(&$request) {/*{{{*/
    $this->get_version($request);

    $consumer = $this->get_consumer($request);

    // requires authorized request token
    $token = $this->get_token($request, $consumer, "request");

    $this->check_signature($request, $consumer, $token);

    $new_token = $this->data_store->new_access_token($token, $consumer);

    return $new_token;
  }/*}}}*/

  /**
   * verify an api call, checks all the parameters
   */
  function verify_request(&$request) {/*{{{*/
    $this->get_version($request);
    $consumer = $this->get_consumer($request);
    $token = $this->get_token($request, $consumer, "access");
    $this->check_signature($request, $consumer, $token);
    return array($consumer, $token);
  }/*}}}*/

  // Internals from here
  /**
   * version 1
   */
  function get_version(&$request) {/*{{{*/
    $version = $request->get_parameter("oauth_version");
    if (!$version) {
      $version = 1.0;
    }
    if ($version && $version != $this->version) {
      trigger_error("OAuth version '$version' not supported", E_USER_WARNING);
      return NULL;
    }
    return $version;
  }/*}}}*/

  /**
   * figure out the signature with some defaults
   */
  function get_signature_method(&$request) {/*{{{*/
    $signature_method =  
        @$request->get_parameter("oauth_signature_method");
    if (!$signature_method) {
      $signature_method = "PLAINTEXT";
    }
    if (!in_array($signature_method, 
                  array_keys($this->signature_methods))) {
      trigger_error("Signature method '$signature_method' not supported try one of the following: " . implode(", ", array_keys($this->signature_methods)), E_USER_WARNING);      
      return NULL;
    }
    return $this->signature_methods[$signature_method];
  }/*}}}*/

  /**
   * try to find the consumer for the provided request's consumer key
   */
  function get_consumer(&$request) {/*{{{*/
    $consumer_key = @$request->get_parameter("oauth_consumer_key");
    if (!$consumer_key) {
      trigger_error("Invalid consumer key", E_USER_WARNING);
      return NULL;
    }

    $consumer = $this->data_store->lookup_consumer($consumer_key);
    if (!$consumer) {
      trigger_error("Invalid consumer", E_USER_WARNING);
      return NULL;
    }

    return $consumer;
  }/*}}}*/

  /**
   * try to find the token for the provided request's token key
   */
  function get_token(&$request, $consumer, $token_type="access") {/*{{{*/
    $token_field = @$request->get_parameter('oauth_token');
    $token = $this->data_store->lookup_token(
      $consumer, $token_type, $token_field
    );
    if (!$token) {
      trigger_error("Invalid $token_type token: $token_field", E_USER_WARNING);
      return NULL;
    }
    return $token;
  }/*}}}*/

  /**
   * all-in-one function to check the signature on a request
   * should guess the signature method appropriately
   */
  function check_signature(&$request, $consumer, $token) {/*{{{*/
    // this should probably be in a different method
    $timestamp = @$request->get_parameter('oauth_timestamp');
    $nonce = @$request->get_parameter('oauth_nonce');

    $this->check_timestamp($timestamp);
    $this->check_nonce($consumer, $token, $nonce, $timestamp);

    $signature_method = $this->get_signature_method($request);

    $signature = $request->get_parameter('oauth_signature');    
    $valid_sig = $signature_method->check_signature(
      $request, 
      $consumer, 
      $token, 
      $signature
    );

    if (!$valid_sig) {
      trigger_error("Invalid signature", E_USER_WARNING);
      return NULL;
    }
  }/*}}}*/

  /**
   * check that the timestamp is new enough
   */
  function check_timestamp($timestamp) {/*{{{*/
    // verify that timestamp is recentish
    $now = time();
    if ($now - $timestamp > $this->timestamp_threshold) {
      trigger_error("Expired timestamp, yours $timestamp, ours $now", E_USER_WARNING);
      return NULL;
    }
  }/*}}}*/

  /**
   * check that the nonce is not repeated
   */
  function check_nonce($consumer, $token, $nonce, $timestamp) {/*{{{*/
    // verify that the nonce is uniqueish
    $found = $this->data_store->lookup_nonce($consumer, $token, $nonce, $timestamp);
    if ($found) {
      trigger_error("Nonce already used: $nonce", E_USER_WARNING);
      return NULL;
    }
  }/*}}}*/



}/*}}}*/

class OAuthDataStore {/*{{{*/
  function lookup_consumer($consumer_key) {/*{{{*/
    // implement me
  }/*}}}*/

  function lookup_token($consumer, $token_type, $token) {/*{{{*/
    // implement me
  }/*}}}*/

  function lookup_nonce($consumer, $token, $nonce, $timestamp) {/*{{{*/
    // implement me
  }/*}}}*/

  function fetch_request_token($consumer) {/*{{{*/
    // return a new token attached to this consumer
  }/*}}}*/

  function fetch_access_token($token, $consumer) {/*{{{*/
    // return a new access token attached to this consumer
    // for the user associated with this token if the request token
    // is authorized
    // should also invalidate the request token
  }/*}}}*/

}/*}}}*/


/*  A very naive dbm-based oauth storage
 */
class SimpleOAuthDataStore extends OAuthDataStore {/*{{{*/
  var $dbh;

  function SimpleOAuthDataStore($path = "oauth.gdbm") {/*{{{*/
    $this->dbh = dba_popen($path, 'c', 'gdbm');
  }/*}}}*/

  function __destruct() {/*{{{*/
    dba_close($this->dbh);
  }/*}}}*/

  function lookup_consumer($consumer_key) {/*{{{*/
    $rv = dba_fetch("consumer_$consumer_key", $this->dbh);
    if ($rv === FALSE) {
      return NULL;
    }
    $obj = unserialize($rv);
    if (!is_a($obj, "OAuthConsumer")) {
      return NULL;
    }
    return $obj;
  }/*}}}*/

  function lookup_token($consumer, $token_type, $token) {/*{{{*/
    $rv = dba_fetch("${token_type}_${token}", $this->dbh);
    if ($rv === FALSE) {
      return NULL;
    }
    $obj = unserialize($rv);
    if (!is_a($obj, "OAuthToken")) {
      return NULL;
    }
    return $obj;
  }/*}}}*/

  function lookup_nonce($consumer, $token, $nonce, $timestamp) {/*{{{*/
    if (dba_exists("nonce_$nonce", $this->dbh)) {
      return TRUE;
    } else {
      dba_insert("nonce_$nonce", "1", $this->dbh);
      return FALSE;
    }
  }/*}}}*/

  function new_token($consumer, $type="request") {/*{{{*/
    $key = md5(time());
    $secret = time() + time();
    $token = new OAuthToken($key, md5(md5($secret)));
    if (!dba_insert("${type}_$key", serialize($token), $this->dbh)) {
      trigger_error("doooom!", E_USER_WARNING);
      return NULL;
    }
    return $token;
  }/*}}}*/

  function new_request_token($consumer) {/*{{{*/
    return $this->new_token($consumer, "request");
  }/*}}}*/

  function new_access_token($token, $consumer) {/*{{{*/

    $token = $this->new_token($consumer, 'access');
    dba_delete("request_" . $token->key, $this->dbh);
    return $token;
  }/*}}}*/
}/*}}}*/

class OAuthUtil {/*{{{*/
  function urlencodeRFC3986($string) {/*{{{*/
    return str_replace('%7E', '~', rawurlencode($string));
  }/*}}}*/
    
  function urldecodeRFC3986($string) {/*{{{*/
    return rawurldecode($string);
  }/*}}}*/
}/*}}}*/

/**
 * Crib'd native implementation of hash_hmac() for SHA1 from the 
 * Fire Eagle PHP code:
 *
 * http://fireeagle.yahoo.net/developer/code/php
 */
if (!function_exists("hash_hmac")) {
    // Earlier versions of PHP5 are missing hash_hmac().  Here's a
    // pure-PHP version in case you're using one of them.
    function hash_hmac($algo, $data, $key) {
        // Thanks, Kellan: http://laughingmeme.org/code/hmacsha1.php.txt
        if ($algo != 'sha1') {
            error_log("Internal hash_hmac() can only do sha1, sorry");
            return NULL;
        }

        $blocksize = 64;
        $hashfunc = 'sha1';
        if (strlen($key)>$blocksize)
            $key = pack('H*', $hashfunc($key));
        $key = str_pad($key,$blocksize,chr(0x00));
        $ipad = str_repeat(chr(0x36),$blocksize);
        $opad = str_repeat(chr(0x5c),$blocksize);
        $hmac = pack(
                'H*',$hashfunc(
                    ($key^$opad).pack(
                                      'H*',$hashfunc(
                                          ($key^$ipad).$data
                                          )
                                     )
                    )
                );
        return $hmac;
    }
}

?>