<?php
/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/* Generic exception class
 */
class OAuthException extends Exception { // pass
}

class OAuthConsumer {
  public $key;
  public $secret;

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

  function __toString() {
    return "OAuthConsumer[key=$this->key,secret=$this->secret]";
  }
}

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

  /**
   * key = the token
   * secret = the token secret
   */
  function __construct($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 {

  public 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";
  }

  public 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 {

  public function get_name() {
    return "PLAINTEXT";
  }

  public 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 OAuthUtil::urlencodeRFC3986($raw);
  }
}

class OAuthSignatureMethod_RSA_SHA1 extends OAuthSignatureMethod {

  public function get_name() {
    return "RSA-SHA1";
  }

  protected 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
    throw Exception("fetch_public_cert not implemented");
  }

  protected 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
    throw Exception("fetch_private_cert not implemented");
  }

  public function build_signature(&$request, $consumer, $token) {
    $base_string = $request->get_signature_base_string();
    $request->base_string = $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);
  }

  public 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 {
  public $parameters;
  private $http_method;
  private $http_url;
  // for debug purposes
  public $base_string;
  public static $version = '1.0';

  function __construct($http_method, $http_url, $parameters = NULL) {
    @$parameters or $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
   */
  public static 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);
    } else {
      // collect request parameters from query string (GET) and post-data (POST) if appropriate (note: POST vars have priority)
      $req_parameters = $_GET;
      if ($http_method == "POST" && @$request_headers["Content-Type"] == "application/x-www-form-urlencoded") {
        $req_parameters = array_merge($req_parameters, $_POST);
      }

      // 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
      if (@substr($request_headers['Authorization'], 0, 5) == "OAuth") {
        $header_parameters = OAuthRequest::split_header($request_headers['Authorization']);
        $parameters = array_merge($req_parameters, $header_parameters);
        $req = new OAuthRequest($http_method, $http_url, $parameters);
      } else
        $req = new OAuthRequest($http_method, $http_url, $req_parameters);
    }

    return $req;
  }

  /**
   * pretty much a helper function to set up the request
   */
  public static function from_consumer_and_token($consumer, $token, $http_method, $http_url, $parameters = NULL) {
    @$parameters or $parameters = array();
    $defaults = array("oauth_version" => OAuthRequest::$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'] = $token->key;
    }
    return new OAuthRequest($http_method, $http_url, $parameters);
  }

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

  public function get_parameter($name) {
    return isset($this->parameters[$name]) ? $this->parameters[$name] : null;
  }

  public 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
   */
  public function get_signable_parameters() {
    // 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));
    $params = array_combine($keys, $values);

    // 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 &.
   */
  public 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
   */
  public function get_normalized_http_method() {
    return strtoupper($this->http_method);
  }

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

    $port = @$parts['port'];
    $scheme = $parts['scheme'];
    $host = $parts['host'];
    $path = @$parts['path'];

    $port or $port = ($scheme == 'https') ? '443' : '80';

    if (($scheme == 'https' && $port != '443') || ($scheme == 'http' && $port != '80')) {
      $host = "$host:$port";
    }
    return "$scheme://$host$path";
  }

  /**
   * builds a url usable for a GET request
   */
  public 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
   */
  public 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
   */
  public function to_header($realm = "") {
    $out = 'Authorization: OAuth realm="' . $realm . '"';
    $total = array();
    foreach ($this->parameters as $k => $v) {
      if (substr($k, 0, 5) != "oauth") continue;
      $out .= ',' . OAuthUtil::urlencodeRFC3986($k) . '="' . OAuthUtil::urlencodeRFC3986($v) . '"';
    }
    return $out;
  }

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

  public 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);
  }

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

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

  /**
   * util function: current nonce
   */
  private static 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
   */
  private static function split_header($header) {
    // remove 'OAuth ' at the start of a header
    $header = substr($header, 6);

    // 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
   */
  private static 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 {
  protected $timestamp_threshold = 300; // in seconds, five minutes
  protected $version = 1.0; // hi blaine
  protected $signature_methods = array();

  protected $data_store;

  function __construct($data_store) {
    $this->data_store = $data_store;
  }

  public 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
   */
  public 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
   */
  public 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
   */
  public 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
   */
  private function get_version(&$request) {
    $version = $request->get_parameter("oauth_version");
    if (! $version) {
      $version = 1.0;
    }
    if ($version && $version != $this->version) {
      throw new OAuthException("OAuth version '$version' not supported");
    }
    return $version;
  }

  /**
   * figure out the signature with some defaults
   */
  private 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($this->signature_methods))) {
      throw new OAuthException("Signature method '$signature_method' not supported try one of the following: " . implode(", ", array_keys($this->signature_methods)));
    }
    return $this->signature_methods[$signature_method];
  }

  /**
   * try to find the consumer for the provided request's consumer key
   */
  private function get_consumer(&$request) {
    $consumer_key = @$request->get_parameter("oauth_consumer_key");
    if (! $consumer_key) {
      throw new OAuthException("Invalid consumer key");
    }

    $consumer = $this->data_store->lookup_consumer($consumer_key);
    if (! $consumer) {
      throw new OAuthException("Invalid consumer");
    }

    return $consumer;
  }

  /**
   * try to find the token for the provided request's token key
   */
  private 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) {
      throw new OAuthException("Invalid $token_type token: $token_field");
    }
    return $token;
  }

  /**
   * all-in-one function to check the signature on a request
   * should guess the signature method appropriately
   */
  private 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) {
      throw new OAuthException("Invalid signature");
    }
  }

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

  /**
   * check that the nonce is not repeated
   */
  private 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) {
      throw new OAuthException("Nonce already used: $nonce");
    }
  }

}

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, $token_secret) {
    // 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 {
  private $dbh;

  function __construct($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 (! ($obj instanceof 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 (! ($obj instanceof 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)) {
      throw new OAuthException("doooom!");
    }
    return $token;
  }

  function new_request_token($consumer, $token_secret = null) {
    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 {

  public static function urlencodeRFC3986($string) {
    return str_replace('+', ' ', str_replace('%7E', '~', rawurlencode($string)));

  }

  // This decode function isn't taking into consideration the above
  // modifications to the encoding process. However, this method doesn't
  // seem to be used anywhere so leaving it as is.
  public static function urldecodeRFC3986($string) {
    return rawurldecode($string);
  }
}
