webservice/lib.php

   1 <?php
   2
   3 // This file is part of Moodle - http://moodle.org/
   4 //
   5 // Moodle is free software: you can redistribute it and/or modify
   6 // it under the terms of the GNU General Public License as published by
   7 // the Free Software Foundation, either version 3 of the License, or
   8 // (at your option) any later version.
   9 //
  10 // Moodle is distributed in the hope that it will be useful,
  11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 // GNU General Public License for more details.
  14 //
  15 // You should have received a copy of the GNU General Public License
  16 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  17
  18 /**
  19  * Web services utility functions and classes
  20  *
  21  * @package   webservice
  22  * @copyright 2009 Moodle Pty Ltd (http://moodle.com)
  23  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  24  */
  25
  26 require_once($CFG->libdir.'/externallib.php');
  27
  28 /**
  29  * Exception indicating access control problem in web service call
  30  * @author Petr Skoda (skodak)
  31  */
  32 class webservice_access_exception extends moodle_exception {
  33     /**
  34      * Constructor
  35      */
  36     function __construct($debuginfo) {
  37         parent::__construct('accessexception', 'webservice', '', null, $debuginfo);
  38     }
  39 }
  40
  41 /**
  42  * Is protocol enabled?
  43  * @param string $protocol name of WS protocol
  44  * @return bool
  45  */
  46 function webservice_protocol_is_enabled($protocol) {
  47     global $CFG;
  48
  49     if (empty($CFG->enablewebservices)) {
  50         return false;
  51     }
  52
  53     $active = explode(',', $CFG->webserviceprotocols);
  54
  55     return(in_array($protocol, $active));
  56 }
  57
  58 //=== WS classes ===
  59
  60 /**
  61  * Mandatory interface for all test client classes.
  62  * @author Petr Skoda (skodak)
  63  */
  64 interface webservice_test_client_interface {
  65     /**
  66      * Execute test client WS request
  67      * @param string $serverurl
  68      * @param string $function
  69      * @param array $params
  70      * @return mixed
  71      */
  72     public function simpletest($serverurl, $function, $params);
  73 }
  74
  75 /**
  76  * Mandatory interface for all web service protocol classes
  77  * @author Petr Skoda (skodak)
  78  */
  79 interface webservice_server_interface {
  80     /**
  81      * Process request from client.
  82      * @return void
  83      */
  84     public function run();
  85 }
  86
  87 /**
  88  * Abstract web service base class.
  89  * @author Petr Skoda (skodak)
  90  */
  91 abstract class webservice_server implements webservice_server_interface {
  92
  93     /** @property string $wsname name of the web server plugin */
  94     protected $wsname = null;
  95
  96     /** @property string $username name of local user */
  97     protected $username = null;
  98
  99     /** @property string $password password of the local user */
 100     protected $password = null;
 101
 102     /** @property int $userid the local user */
 103     protected $userid = null;
 104
 105     /** @property bool $simple true if simple auth used */
 106     protected $simple;
 107
 108     /** @property string $token authentication token*/
 109     protected $token = null;
 110
 111     /** @property object restricted context */
 112     protected $restricted_context;
 113
 114     /** @property int restrict call to one service id*/
 115     protected $restricted_serviceid = null;
 116
 117     /**
 118      * Authenticate user using username+password or token.
 119      * This function sets up $USER global.
 120      * It is safe to use has_capability() after this.
 121      * This method also verifies user is allowed to use this
 122      * server.
 123      * @return void
 124      */
 125     protected function authenticate_user() {
 126         global $CFG, $DB;
 127
 128         if (!NO_MOODLE_COOKIES) {
 129             throw new coding_exception('Cookies must be disabled in WS servers!');
 130         }
 131
 132         if ($this->simple) {
 133
 134             //we check that authentication plugin is enabled
 135             //it is only required by simple authentication
 136             if (!is_enabled_auth('webservice')) {
 137                 throw new webservice_access_exception(get_string('wsauthnotenabled', 'webservice'));
 138             }
 139
 140             if (!$auth = get_auth_plugin('webservice')) {
 141                 throw new webservice_access_exception(get_string('wsauthmissing', 'webservice'));
 142             }
 143
 144             $this->restricted_context = get_context_instance(CONTEXT_SYSTEM);
 145
 146             if (!$this->username) {
 147                 throw new webservice_access_exception(get_string('missingusername', 'webservice'));
 148             }
 149
 150             if (!$this->password) {
 151                 throw new webservice_access_exception(get_string('missingpassword', 'webservice'));
 152             }
 153
 154             if (!$auth->user_login_webservice($this->username, $this->password)) {
 155                 // log failed login attempts
 156                 add_to_log(1, 'webservice', get_string('simpleauthlog', 'webservice'), '' , get_string('failedtolog', 'webservice').": ".$this->username."/".$this->password." - ".getremoteaddr() , 0);
 157                 throw new webservice_access_exception(get_string('wrongusernamepassword', 'webservice'));
 158             }
 159
 160             $user = $DB->get_record('user', array('username'=>$this->username, 'mnethostid'=>$CFG->mnet_localhost_id, 'deleted'=>0), '*', MUST_EXIST);
 161
 162         } else {
 163             if (!$token = $DB->get_record('external_tokens', array('token'=>$this->token, 'tokentype'=>EXTERNAL_TOKEN_PERMANENT))) {
 164                 // log failed login attempts
 165                 add_to_log(1, 'webservice', get_string('tokenauthlog', 'webservice'), '' , get_string('failedtolog', 'webservice').": ".$this->token. " - ".getremoteaddr() , 0);
 166                 throw new webservice_access_exception(get_string('invalidtoken', 'webservice'));
 167             }
 168
 169             if ($token->validuntil and $token->validuntil < time()) {
 170                 throw new webservice_access_exception(get_string('invalidtimedtoken', 'webservice'));
 171             }
 172
 173             if ($token->iprestriction and !address_in_subnet(getremoteaddr(), $token->iprestriction)) {
 174                 add_to_log(1, 'webservice', get_string('tokenauthlog', 'webservice'), '' , get_string('failedtolog', 'webservice').": ".getremoteaddr() , 0);
 175                 throw new webservice_access_exception(get_string('invalidiptoken', 'webservice'));
 176             }
 177
 178             $this->restricted_context = get_context_instance_by_id($token->contextid);
 179             $this->restricted_serviceid = $token->externalserviceid;
 180
 181             $user = $DB->get_record('user', array('id'=>$token->userid, 'deleted'=>0), '*', MUST_EXIST);
 182
 183             // log token access
 184             $DB->set_field('external_tokens', 'lastaccess', time(), array('id'=>$token->id));
 185         }
 186
 187         // now fake user login, the session is completely empty too
 188         session_set_user($user);
 189         $this->userid = $user->id;
 190
 191         if (!has_capability("webservice/$this->wsname:use", $this->restricted_context)) {
 192             throw new webservice_access_exception(get_string('accessnotallowed', 'webservice'));
 193         }
 194
 195         external_api::set_context_restriction($this->restricted_context);
 196     }
 197 }
 198
 199 /**
 200  * Special abstraction of our srvices that allows
 201  * interaction with stock Zend ws servers.
 202  * @author Petr Skoda (skodak)
 203  */
 204 abstract class webservice_zend_server extends webservice_server {
 205
 206     /** @property string name of the zend server class : Zend_XmlRpc_Server, Zend_Soap_Server, Zend_Soap_AutoDiscover, ...*/
 207     protected $zend_class;
 208
 209     /** @property object Zend server instance */
 210     protected $zend_server;
 211
 212     /** @property string $service_class virtual web service class with all functions user name execute, created on the fly */
 213     protected $service_class;
 214
 215     /**
 216      * Contructor
 217      * @param bool $simple use simple authentication
 218      */
 219     public function __construct($simple, $zend_class) {
 220         $this->simple = $simple;
 221         $this->zend_class = $zend_class;
 222     }
 223
 224     /**
 225      * Process request from client.
 226      * @param bool $simple use simple authentication
 227      * @return void
 228      */
 229     public function run() {
 230         // we will probably need a lot of memory in some functions
 231         @raise_memory_limit('128M');
 232
 233         // set some longer timeout, this script is not sending any output,
 234         // this means we need to manually extend the timeout operations
 235         // that need longer time to finish
 236         external_api::set_timeout();
 237
 238         // now create the instance of zend server
 239         $this->init_zend_server();
 240
 241         // set up exception handler first, we want to sent them back in correct format that
 242         // the other system understands
 243         // we do not need to call the original default handler because this ws handler does everything
 244         set_exception_handler(array($this, 'exception_handler'));
 245
 246         // init all properties from the request data
 247         $this->parse_request();
 248
 249         // this sets up $USER and $SESSION and context restrictions
 250         $this->authenticate_user();
 251
 252         // make a list of all functions user is allowed to excecute
 253         $this->init_service_class();
 254
 255         // tell server what functions are available
 256         $this->zend_server->setClass($this->service_class);
 257
 258         //log the web service request
 259         add_to_log(1, 'webservice', '', '' , $this->zend_class." ".getremoteaddr() , 0, $this->userid);
 260
 261         // execute and return response, this sends some headers too
 262         $response = $this->zend_server->handle();
 263
 264 /*
 265         error_log(ob_get_clean());
 266         error_log($response);
 267 */
 268         // session cleanup
 269         $this->session_cleanup();
 270
 271         //finally send the result
 272         $this->send_headers();
 273         echo $response;
 274         die;
 275     }
 276
 277     /**
 278      * Load virtual class needed for Zend api
 279      * @return void
 280      */
 281     protected function init_service_class() {
 282         global $USER, $DB;
 283
 284         // first ofall get a complete list of services user is allowed to access
 285
 286         if ($this->restricted_serviceid) {
 287             $params = array('sid1'=>$this->restricted_serviceid, 'sid2'=>$this->restricted_serviceid);
 288             $wscond1 = 'AND s.id = :sid1';
 289             $wscond2 = 'AND s.id = :sid2';
 290         } else {
 291             $params = array();
 292             $wscond1 = '';
 293             $wscond2 = '';
 294         }
 295
 296         // now make sure the function is listed in at least one service user is allowed to use
 297         // allow access only if:
 298         //  1/ entry in the external_services_users table if required
 299         //  2/ validuntil not reached
 300         //  3/ has capability if specified in service desc
 301         //  4/ iprestriction
 302
 303         $sql = "SELECT s.*, NULL AS iprestriction
 304                   FROM {external_services} s
 305                   JOIN {external_services_functions} sf ON (sf.externalserviceid = s.id AND s.restrictedusers = 0)
 306                  WHERE s.enabled = 1 $wscond1
 307
 308                  UNION
 309
 310                 SELECT s.*, su.iprestriction
 311                   FROM {external_services} s
 312                   JOIN {external_services_functions} sf ON (sf.externalserviceid = s.id AND s.restrictedusers = 1)
 313                   JOIN {external_services_users} su ON (su.externalserviceid = s.id AND su.userid = :userid)
 314                  WHERE s.enabled = 1 AND su.validuntil IS NULL OR su.validuntil < :now $wscond2";
 315
 316         $params = array_merge($params, array('userid'=>$USER->id, 'now'=>time()));
 317
 318         $serviceids = array();
 319         $rs = $DB->get_recordset_sql($sql, $params);
 320
 321         // now make sure user may access at least one service
 322         $remoteaddr = getremoteaddr();
 323         $allowed = false;
 324         foreach ($rs as $service) {
 325             if (isset($serviceids[$service->id])) {
 326                 continue;
 327             }
 328             if ($service->requiredcapability and !has_capability($service->requiredcapability, $this->restricted_context)) {
 329                 continue; // cap required, sorry
 330             }
 331             if ($service->iprestriction and !address_in_subnet($remoteaddr, $service->iprestriction)) {
 332                 continue; // wrong request source ip, sorry
 333             }
 334             $serviceids[$service->id] = $service->id;
 335         }
 336         $rs->close();
 337
 338         // now get the list of all functions
 339         if ($serviceids) {
 340             list($serviceids, $params) = $DB->get_in_or_equal($serviceids);
 341             $sql = "SELECT f.*
 342                       FROM {external_functions} f
 343                      WHERE f.name IN (SELECT sf.functionname
 344                                         FROM {external_services_functions} sf
 345                                        WHERE sf.externalserviceid $serviceids)";
 346             $functions = $DB->get_records_sql($sql, $params);
 347         } else {
 348             $functions = array();
 349         }
 350
 351         // now make the virtual WS class with all the fuctions for this particular user
 352         $methods = '';
 353         foreach ($functions as $function) {
 354             $methods .= $this->get_virtual_method_code($function);
 355         }
 356
 357         // let's use unique class name, there might be problem in unit tests
 358         $classname = 'webservices_virtual_class_000000';
 359         while(class_exists($classname)) {
 360             $classname++;
 361         }
 362
 363         $code = '
 364 /**
 365  * Virtual class web services for user id '.$USER->id.' in context '.$this->restricted_context->id.'.
 366  */
 367 class '.$classname.' {
 368 '.$methods.'
 369 }
 370 ';
 371
 372         // load the virtual class definition into memory
 373         eval($code);
 374         $this->service_class = $classname;
 375     }
 376
 377     /**
 378      * returns virtual method code
 379      * @param object $function
 380      * @return string PHP code
 381      */
 382     protected function get_virtual_method_code($function) {
 383         global $CFG;
 384
 385         $function = external_function_info($function);
 386
 387         $params      = array();
 388         $params_desc = array();
 389         foreach ($function->parameters_desc->keys as $name=>$keydesc) {
 390             $params[]      = '$'.$name;
 391             $type = 'string';
 392             if ($keydesc instanceof external_value) {
 393                 switch($keydesc->type) {
 394                     case PARAM_BOOL: // 0 or 1 only for now
 395                     case PARAM_INT:
 396                         $type = 'int'; break;
 397                     case PARAM_FLOAT;
 398                         $type = 'double'; break;
 399                     default:
 400                         $type = 'string';
 401                 }
 402             } else if ($keydesc instanceof external_single_structure) {
 403                 $type = 'struct';
 404             } else if ($keydesc instanceof external_multiple_structure) {
 405                 $type = 'array';
 406             }
 407             $params_desc[] = '     * @param '.$type.' $'.$name.' '.$keydesc->desc;
 408         }
 409         $params      = implode(', ', $params);
 410         $params_desc = implode("\n", $params_desc);
 411
 412         $serviceclassmethodbody = $this->service_class_method_body($function, $params);
 413
 414         if (is_null($function->returns_desc)) {
 415             $return = '     * @return void';
 416         } else {
 417             $type = 'string';
 418             if ($function->returns_desc instanceof external_value) {
 419                 switch($function->returns_desc->type) {
 420                     case PARAM_BOOL: // 0 or 1 only for now
 421                     case PARAM_INT:
 422                         $type = 'int'; break;
 423                     case PARAM_FLOAT;
 424                         $type = 'double'; break;
 425                     default:
 426                         $type = 'string';
 427                 }
 428             } else if ($function->returns_desc instanceof external_single_structure) {
 429                 $type = 'struct';
 430             } else if ($function->returns_desc instanceof external_multiple_structure) {
 431                 $type = 'array';
 432             }
 433             $return = '     * @return '.$type.' '.$function->returns_desc->desc;
 434         }
 435
 436         // now crate the virtual method that calls the ext implementation
 437
 438         $code = '
 439     /**
 440      * '.$function->description.'
 441      *
 442 '.$params_desc.'
 443 '.$return.'
 444      */
 445     public function '.$function->name.'('.$params.') {
 446 '.$serviceclassmethodbody.'
 447     }
 448 ';
 449         return $code;
 450     }
 451
 452     /**
 453      * You can override this function in your child class to add extra code into the dynamically
 454      * created service class. For example it is used in the amf server to cast types of parameters and to
 455      * cast the return value to the types as specified in the return value description.
 456      * @param unknown_type $function
 457      * @param unknown_type $params
 458      * @return string body of the method for $function ie. everything within the {} of the method declaration.
 459      */
 460     protected function service_class_method_body($function, $params){
 461         return '        return '.$function->classname.'::'.$function->methodname.'('.$params.');';
 462     }
 463
 464     /**
 465      * Set up zend service class
 466      * @return void
 467      */
 468     protected function init_zend_server() {
 469         $this->zend_server = new $this->zend_class();
 470     }
 471
 472     /**
 473      * This method parses the $_REQUEST superglobal and looks for
 474      * the following information:
 475      *  1/ user authentication - username+password or token (wsusername, wspassword and wstoken parameters)
 476      *
 477      * @return void
 478      */
 479     protected function parse_request() {
 480         if ($this->simple) {
 481             //note: some clients have problems with entity encoding :-(
 482             if (isset($_REQUEST['wsusername'])) {
 483                 $this->username = $_REQUEST['wsusername'];
 484             }
 485             if (isset($_REQUEST['wspassword'])) {
 486                 $this->password = $_REQUEST['wspassword'];
 487             }
 488         } else {
 489             if (isset($_REQUEST['wstoken'])) {
 490                 $this->token = $_REQUEST['wstoken'];
 491             }
 492         }
 493     }
 494
 495     /**
 496      * Internal implementation - sending of page headers.
 497      * @return void
 498      */
 499     protected function send_headers() {
 500         header('Cache-Control: private, must-revalidate, pre-check=0, post-check=0, max-age=0');
 501         header('Expires: '. gmdate('D, d M Y H:i:s', 0) .' GMT');
 502         header('Pragma: no-cache');
 503         header('Accept-Ranges: none');
 504     }
 505
 506     /**
 507      * Specialised exception handler, we can not use the standard one because
 508      * it can not just print html to output.
 509      *
 510      * @param exception $ex
 511      * @return void does not return
 512      */
 513     public function exception_handler($ex) {
 514         // detect active db transactions, rollback and log as error
 515         abort_all_db_transactions();
 516
 517         // some hacks might need a cleanup hook
 518         $this->session_cleanup($ex);
 519
 520         // now let the plugin send the exception to client
 521         $this->send_error($ex);
 522
 523         // not much else we can do now, add some logging later
 524         exit(1);
 525     }
 526
 527     /**
 528      * Send the error information to the WS client
 529      * formatted as XML document.
 530      * @param exception $ex
 531      * @return void
 532      */
 533     protected function send_error($ex=null) {
 534         $this->send_headers();
 535         echo $this->zend_server->fault($ex);
 536     }
 537
 538     /**
 539      * Future hook needed for emulated sessions.
 540      * @param exception $exception null means normal termination, $exception received when WS call failed
 541      * @return void
 542      */
 543     protected function session_cleanup($exception=null) {
 544         if ($this->simple) {
 545             // nothing needs to be done, there is no persistent session
 546         } else {
 547             // close emulated session if used
 548         }
 549     }
 550
 551 }
 552
 553 /**
 554  * Web Service server base class, this class handles both
 555  * simple and token authentication.
 556  * @author Petr Skoda (skodak)
 557  */
 558 abstract class webservice_base_server extends webservice_server {
 559
 560     /** @property array $parameters the function parameters - the real values submitted in the request */
 561     protected $parameters = null;
 562
 563     /** @property string $functionname the name of the function that is executed */
 564     protected $functionname = null;
 565
 566     /** @property object $function full function description */
 567     protected $function = null;
 568
 569     /** @property mixed $returns function return value */
 570     protected $returns = null;
 571
 572     /**
 573      * Contructor
 574      * @param bool $simple use simple authentication
 575      */
 576     public function __construct($simple) {
 577         $this->simple = $simple;
 578     }
 579
 580     /**
 581      * This method parses the request input, it needs to get:
 582      *  1/ user authentication - username+password or token
 583      *  2/ function name
 584      *  3/ function parameters
 585      *
 586      * @return void
 587      */
 588     abstract protected function parse_request();
 589
 590     /**
 591      * Send the result of function call to the WS client.
 592      * @return void
 593      */
 594     abstract protected function send_response();
 595
 596     /**
 597      * Send the error information to the WS client.
 598      * @param exception $ex
 599      * @return void
 600      */
 601     abstract protected function send_error($ex=null);
 602
 603     /**
 604      * Process request from client.
 605      * @return void
 606      */
 607     public function run() {
 608         // we will probably need a lot of memory in some functions
 609         @raise_memory_limit('128M');
 610
 611         // set some longer timeout, this script is not sending any output,
 612         // this means we need to manually extend the timeout operations
 613         // that need longer time to finish
 614         external_api::set_timeout();
 615
 616         // set up exception handler first, we want to sent them back in correct format that
 617         // the other system understands
 618         // we do not need to call the original default handler because this ws handler does everything
 619         set_exception_handler(array($this, 'exception_handler'));
 620
 621         // init all properties from the request data
 622         $this->parse_request();
 623
 624         // authenticate user, this has to be done after the request parsing
 625         // this also sets up $USER and $SESSION
 626         $this->authenticate_user();
 627
 628         // find all needed function info and make sure user may actually execute the function
 629         $this->load_function_info();
 630
 631         //log the web service request
 632         add_to_log(1, 'webservice', $this->functionname, '' , getremoteaddr() , 0, $this->userid);
 633
 634         // finally, execute the function - any errors are catched by the default exception handler
 635         $this->execute();
 636
 637         // send the results back in correct format
 638         $this->send_response();
 639
 640         // session cleanup
 641         $this->session_cleanup();
 642
 643         die;
 644     }
 645
 646     /**
 647      * Specialised exception handler, we can not use the standard one because
 648      * it can not just print html to output.
 649      *
 650      * @param exception $ex
 651      * @return void does not return
 652      */
 653     public function exception_handler($ex) {
 654         // detect active db transactions, rollback and log as error
 655         abort_all_db_transactions();
 656
 657         // some hacks might need a cleanup hook
 658         $this->session_cleanup($ex);
 659
 660         // now let the plugin send the exception to client
 661         $this->send_error($ex);
 662
 663         // not much else we can do now, add some logging later
 664         exit(1);
 665     }
 666
 667     /**
 668      * Future hook needed for emulated sessions.
 669      * @param exception $exception null means normal termination, $exception received when WS call failed
 670      * @return void
 671      */
 672     protected function session_cleanup($exception=null) {
 673         if ($this->simple) {
 674             // nothing needs to be done, there is no persistent session
 675         } else {
 676             // close emulated session if used
 677         }
 678     }
 679
 680     /**
 681      * Fetches the function description from database,
 682      * verifies user is allowed to use this function and
 683      * loads all paremeters and return descriptions.
 684      * @return void
 685      */
 686     protected function load_function_info() {
 687         global $DB, $USER, $CFG;
 688
 689         if (empty($this->functionname)) {
 690             throw new invalid_parameter_exception('Missing function name');
 691         }
 692
 693         // function must exist
 694         $function = external_function_info($this->functionname);
 695
 696         if ($this->restricted_serviceid) {
 697             $params = array('sid1'=>$this->restricted_serviceid, 'sid2'=>$this->restricted_serviceid);
 698             $wscond1 = 'AND s.id = :sid1';
 699             $wscond2 = 'AND s.id = :sid2';
 700         } else {
 701             $params = array();
 702             $wscond1 = '';
 703             $wscond2 = '';
 704         }
 705
 706         // now let's verify access control
 707
 708         // now make sure the function is listed in at least one service user is allowed to use
 709         // allow access only if:
 710         //  1/ entry in the external_services_users table if required
 711         //  2/ validuntil not reached
 712         //  3/ has capability if specified in service desc
 713         //  4/ iprestriction
 714
 715         $sql = "SELECT s.*, NULL AS iprestriction
 716                   FROM {external_services} s
 717                   JOIN {external_services_functions} sf ON (sf.externalserviceid = s.id AND s.restrictedusers = 0 AND sf.functionname = :name1)
 718                  WHERE s.enabled = 1 $wscond1
 719
 720                  UNION
 721
 722                 SELECT s.*, su.iprestriction
 723                   FROM {external_services} s
 724                   JOIN {external_services_functions} sf ON (sf.externalserviceid = s.id AND s.restrictedusers = 1 AND sf.functionname = :name2)
 725                   JOIN {external_services_users} su ON (su.externalserviceid = s.id AND su.userid = :userid)
 726                  WHERE s.enabled = 1 AND su.validuntil IS NULL OR su.validuntil < :now $wscond2";
 727         $params = array_merge($params, array('userid'=>$USER->id, 'name1'=>$function->name, 'name2'=>$function->name, 'now'=>time()));
 728
 729         $rs = $DB->get_recordset_sql($sql, $params);
 730         // now make sure user may access at least one service
 731         $remoteaddr = getremoteaddr();
 732         $allowed = false;
 733         foreach ($rs as $service) {
 734             if ($service->requiredcapability and !has_capability($service->requiredcapability, $this->restricted_context)) {
 735                 continue; // cap required, sorry
 736             }
 737             if ($service->iprestriction and !address_in_subnet($remoteaddr, $service->iprestriction)) {
 738                 continue; // wrong request source ip, sorry
 739             }
 740             $allowed = true;
 741             break; // one service is enough, no need to continue
 742         }
 743         $rs->close();
 744         if (!$allowed) {
 745             throw new webservice_access_exception('Access to external function not allowed');
 746         }
 747
 748         // we have all we need now
 749         $this->function = $function;
 750     }
 751
 752     /**
 753      * Execute previously loaded function using parameters parsed from the request data.
 754      * @return void
 755      */
 756     protected function execute() {
 757         // validate params, this also sorts the params properly, we need the correct order in the next part
 758         $params = call_user_func(array($this->function->classname, 'validate_parameters'), $this->function->parameters_desc, $this->parameters);
 759
 760         // execute - yay!
 761         $this->returns = call_user_func_array(array($this->function->classname, $this->function->methodname), array_values($params));
 762     }
 763 }
 764
 765