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<?php
 /**
 * Handle linkback() response from Twitter.
 */
 
 if (!array_key_exists('AuthState', $_REQUEST) || empty($_REQUEST['AuthState'])) {
 throw new SimpleSAML_Error_BadRequest('Missing state parameter on twitter linkback endpoint.');
 }
 $stateID = $_REQUEST['AuthState'];
 
 // sanitize the input
 $sid = SimpleSAML_Utilities::parseStateID($stateID);
 if (!is_null($sid['url'])) {
 SimpleSAML_Utilities::checkURLAllowed($sid['url']);
 }
 
 $state = SimpleSAML_Auth_State::loadState($stateID, sspmod_authtwitter_Auth_Source_Twitter::STAGE_INIT);
 
 /* Find authentication source. */
 if (!array_key_exists(sspmod_authtwitter_Auth_Source_Twitter::AUTHID, $state)) {
 throw new SimpleSAML_Error_BadRequest('No data in state for ' . sspmod_authtwitter_Auth_Source_Twitter::AUTHID);
 }
 $sourceId = $state[sspmod_authtwitter_Auth_Source_Twitter::AUTHID];
 
 $source = SimpleSAML_Auth_Source::getById($sourceId);
 if ($source === NULL) {
 throw new SimpleSAML_Error_BadRequest('Could not find authentication source with id ' . var_export($sourceId, TRUE));
 }
 
 try {
 if (array_key_exists('denied', $_REQUEST)) {
 throw new SimpleSAML_Error_UserAborted();
 }
 
 $source->finalStep($state);
 } catch (SimpleSAML_Error_Exception $e) {
 SimpleSAML_Auth_State::throwException($state, $e);
 } catch (Exception $e) {
 SimpleSAML_Auth_State::throwException($state, new SimpleSAML_Error_AuthSource($sourceId, 'Error on authtwitter linkback endpoint.', $e));
 }
 
 SimpleSAML_Auth_Source::completeAuth($state);
 
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