moved api.php to web_services.php as it is more descriptive

git-svn-id: http://code.elgg.org/elgg/trunk@7459 36083f99-b078-4883-b0ff-0f9b5a30f544

1 files changed, 1404 insertions, 0 deletions

diff --git a/engine/lib/web_services.php b/engine/lib/web_services.php
new file mode 100644
index 000000000..b9c87843e
--- /dev/null
+++ b/engine/lib/web_services.php
@@ -0,0 +1,1404 @@
+<?php
+/**
+ * Elgg web services API
+ * Functions and objects for exposing custom web services.
+ *
+ * @package    Elgg.Core
+ * @subpackage WebServicesAPI
+ */
+
+// Primary Services API Server functions
+
+/**
+ * A global array holding API methods.
+ * The structure of this is
+ * 	$API_METHODS = array (
+ * 		$method => array (
+ * 			"description" => "Some human readable description"
+ * 			"function" = 'my_function_callback'
+ * 			"parameters" = array (
+ * 				"variable" = array ( // the order should be the same as the function callback
+ * 					type => 'int' | 'bool' | 'float' | 'string'
+ * 					required => true (default) | false
+ *					default => value // optional
+ * 				)
+ * 			)
+ * 			"call_method" = 'GET' | 'POST'
+ * 			"require_api_auth" => true | false (default)
+ * 			"require_user_auth" => true | false (default)
+ * 		)
+ *  )
+ */
+$API_METHODS = array();
+
+/**
+ * Expose a function as a services api call.
+ *
+ * Limitations: Currently cannot expose functions which expect objects.
+ * It also cannot handle arrays of bools or arrays of arrays.
+ * Also, input will be filtered to protect against XSS attacks through the API.
+ *
+ * @param string $method            The api name to expose - for example "myapi.dosomething"
+ * @param string $function          Your function callback.
+ * @param array  $parameters        (optional) List of parameters in the same order as in
+ *                                  your function. Default values may be set for parameters which
+ *                                  allow REST api users flexibility in what parameters are passed.
+ *                                  Generally, optional parameters should be after required
+ *                                  parameters.
+ *
+ *                                  This array should be in the format
+ *                                    "variable" = array (
+ *                                  					type => 'int' | 'bool' | 'float' | 'string' | 'array'
+ *                                  					required => true (default) | false
+ *                                  					default => value (optional)
+ *                                  	 )
+ * @param string $description       (optional) human readable description of the function.
+ * @param string $call_method       (optional) Define what http method must be used for
+ *                                  this function. Default: GET
+ * @param bool   $require_api_auth  (optional) (default is false) Does this method
+ *                                  require API authorization? (example: API key)
+ * @param bool   $require_user_auth (optional) (default is false) Does this method
+ *                                  require user authorization?
+ *
+ * @return bool
+ */
+function expose_function($method, $function, array $parameters = NULL, $description = "",
+$call_method = "GET", $require_api_auth = false, $require_user_auth = false) {
+
+	global $API_METHODS;
+
+	if (($method == "") || ($function == "")) {
+		$msg = elgg_echo('InvalidParameterException:APIMethodOrFunctionNotSet');
+		throw new InvalidParameterException($msg);
+	}
+
+	// does not check whether this method has already been exposed - good idea?
+	$API_METHODS[$method] = array();
+
+	$API_METHODS[$method]["description"] = $description;
+
+	// does not check whether callable - done in execute_method()
+	$API_METHODS[$method]["function"] = $function;
+
+	if ($parameters != NULL) {
+		if (!is_array($parameters)) {
+			$msg = elgg_echo('InvalidParameterException:APIParametersArrayStructure', array($method));
+			throw new InvalidParameterException($msg);
+		}
+
+		// catch common mistake of not setting up param array correctly
+		$first = current($parameters);
+		if (!is_array($first)) {
+			$msg = elgg_echo('InvalidParameterException:APIParametersArrayStructure', array($method));
+			throw new InvalidParameterException($msg);
+		}
+	}
+
+	if ($parameters != NULL) {
+		// ensure the required flag is set correctly in default case for each parameter
+		foreach ($parameters as $key => $value) {
+			// check if 'required' was specified - if not, make it true
+			if (!array_key_exists('required', $value)) {
+				$parameters[$key]['required'] = true;
+			}
+		}
+
+		$API_METHODS[$method]["parameters"] = $parameters;
+	}
+
+	$call_method = strtoupper($call_method);
+	switch ($call_method) {
+		case 'POST' :
+			$API_METHODS[$method]["call_method"] = 'POST';
+			break;
+		case 'GET' :
+			$API_METHODS[$method]["call_method"] = 'GET';
+			break;
+		default :
+			$msg = elgg_echo('InvalidParameterException:UnrecognisedHttpMethod',
+			array($call_method, $method));
+
+			throw new InvalidParameterException($msg);
+	}
+
+	$API_METHODS[$method]["require_api_auth"] = $require_api_auth;
+
+	$API_METHODS[$method]["require_user_auth"] = $require_user_auth;
+
+	return true;
+}
+
+/**
+ * Unregister an API method
+ *
+ * @param string $method The api name that was exposed
+ *
+ * @since 1.7.0
+ *
+ * @return void
+ */
+function unexpose_function($method) {
+	global $API_METHODS;
+
+	if (isset($API_METHODS[$method])) {
+		unset($API_METHODS[$method]);
+	}
+}
+
+/**
+ * Check that the method call has the proper API and user authentication
+ *
+ * @param string $method The api name that was exposed
+ *
+ * @return true or throws an exception
+ * @throws APIException
+ * @since 1.7.0
+ */
+function authenticate_method($method) {
+	global $API_METHODS;
+
+	// method must be exposed
+	if (!isset($API_METHODS[$method])) {
+		throw new APIException(elgg_echo('APIException:MethodCallNotImplemented', array($method)));
+	}
+
+	// make sure that POST variables are available if needed
+	// @todo this may not be needed anymore due to adding %{QUERY_STRING} in .htaccess in 1.7.2
+	if (get_call_method() === 'POST' && empty($_POST)) {
+		include_post_data();
+	}
+
+	// check API authentication if required
+	if ($API_METHODS[$method]["require_api_auth"] == true) {
+		$api_pam = new ElggPAM('api');
+		if ($api_pam->authenticate() !== true) {
+			throw new APIException(elgg_echo('APIException:APIAuthenticationFailed'));
+		}
+	}
+
+	$user_pam = new ElggPAM('user');
+	$user_auth_result = $user_pam->authenticate();
+
+	// check if user authentication is required
+	if ($API_METHODS[$method]["require_user_auth"] == true) {
+		if ($user_auth_result == false) {
+			throw new APIException($user_pam->getFailureMessage());
+		}
+	}
+
+	return true;
+}
+
+/**
+ * Executes a method.
+ * A method is a function which you have previously exposed using expose_function.
+ *
+ * @param string $method Method, e.g. "foo.bar"
+ *
+ * @return GenericResult The result of the execution.
+ * @throws APIException, CallException
+ */
+function execute_method($method) {
+	global $API_METHODS, $CONFIG;
+
+	// method must be exposed
+	if (!isset($API_METHODS[$method])) {
+		$msg = elgg_echo('APIException:MethodCallNotImplemented', array($method));
+		throw new APIException($msg);
+	}
+
+	// function must be callable
+	if (!(isset($API_METHODS[$method]["function"]))
+	|| !(is_callable($API_METHODS[$method]["function"]))) {
+
+		$msg = elgg_echo('APIException:FunctionDoesNotExist', array($method));
+		throw new APIException($msg);
+	}
+
+	// check http call method
+	if (strcmp(get_call_method(), $API_METHODS[$method]["call_method"]) != 0) {
+		$msg = elgg_echo('CallException:InvalidCallMethod', array($method,
+		$API_METHODS[$method]["call_method"]));
+
+		throw new CallException($msg);
+	}
+
+	$parameters = get_parameters_for_method($method);
+
+	if (verify_parameters($method, $parameters) == false) {
+		// if verify_parameters fails, it throws exception which is not caught here
+	}
+
+	$serialised_parameters = serialise_parameters($method, $parameters);
+
+	// Execute function: Construct function and calling parameters
+	$function = $API_METHODS[$method]["function"];
+	$serialised_parameters = trim($serialised_parameters, ", ");
+
+	$result = eval("return $function($serialised_parameters);");
+
+	// Sanity check result
+	// If this function returns an api result itself, just return it
+	if ($result instanceof GenericResult) {
+		return $result;
+	}
+
+	if ($result === false) {
+		$msg = elgg_echo('APIException:FunctionParseError', array($function, $serialised_parameters));
+		throw new APIException($msg);
+	}
+
+	if ($result === NULL) {
+		// If no value
+		$msg = elgg_echo('APIException:FunctionNoReturn', array($function, $serialised_parameters));
+		throw new APIException($msg);
+	}
+
+	// Otherwise assume that the call was successful and return it as a success object.
+	return SuccessResult::getInstance($result);
+}
+
+/**
+ * Get the request method.
+ *
+ * @return string HTTP request method
+ */
+function get_call_method() {
+	return $_SERVER['REQUEST_METHOD'];
+}
+
+/**
+ * This function analyses all expected parameters for a given method
+ *
+ * This function sanitizes the input parameters and returns them in
+ * an associated array.
+ *
+ * @param string $method The method
+ *
+ * @return array containing parameters as key => value
+ */
+function get_parameters_for_method($method) {
+	global $API_METHODS;
+
+	$sanitised = array();
+
+	// if there are parameters, sanitize them
+	if (isset($API_METHODS[$method]['parameters'])) {
+		foreach ($API_METHODS[$method]['parameters'] as $k => $v) {
+			$param = get_input($k); // Make things go through the sanitiser
+			if ($param !== '') {
+				$sanitised[$k] = $param;
+			} else {
+				// parameter wasn't passed so check for default
+				if (isset($v['default'])) {
+					$sanitised[$k] = $v['default'];
+				}
+			}
+		}
+	}
+
+	return $sanitised;
+}
+
+/**
+ * Get POST data
+ * Since this is called through a handler, we need to manually get the post data
+ *
+ * @return POST data as string encoded as multipart/form-data
+ */
+function get_post_data() {
+
+	$postdata = file_get_contents('php://input');
+
+	return $postdata;
+}
+
+/**
+ * This fixes the post parameters that are munged due to page handler
+ *
+ * @since 1.7.0
+ *
+ * @return void
+ */
+function include_post_data() {
+
+	$postdata = get_post_data();
+
+	if (isset($postdata)) {
+		$query_arr = elgg_parse_str($postdata);
+
+		// grrrr... magic quotes is turned on so we need to strip slashes
+		if (ini_get_bool('magic_quotes_gpc')) {
+			if (function_exists('stripslashes_deep')) {
+				// defined in input.php to handle magic quotes
+				$query_arr = stripslashes_deep($query_arr);
+			}
+		}
+
+		if (is_array($query_arr)) {
+			foreach ($query_arr as $name => $val) {
+				set_input($name, $val);
+			}
+		}
+
+	}
+}
+
+/**
+ * Verify that the required parameters are present
+ *
+ * @param string $method     Method name
+ * @param array  $parameters List of expected parameters
+ *
+ * @return true on success or exception
+ * @throws APIException
+ * @since 1.7.0
+ */
+function verify_parameters($method, $parameters) {
+	global $API_METHODS;
+
+	// are there any parameters for this method
+	if (!(isset($API_METHODS[$method]["parameters"]))) {
+		return true; // no so return
+	}
+
+	// check that the parameters were registered correctly and all required ones are there
+	foreach ($API_METHODS[$method]['parameters'] as $key => $value) {
+		// this tests the expose structure: must be array to describe parameter and type must be defined
+		if (!is_array($value) || !isset($value['type'])) {
+
+			$msg = elgg_echo('APIException:InvalidParameter', array($key, $method));
+			throw new APIException($msg);
+		}
+
+		// Check that the variable is present in the request if required
+		if ($value['required'] && !array_key_exists($key, $parameters)) {
+			$msg = elgg_echo('APIException:MissingParameterInMethod', array($key, $method));
+			throw new APIException($msg);
+		}
+	}
+
+	return true;
+}
+
+/**
+ * Serialize an array of parameters for an API method call
+ *
+ * @param string $method     API method name
+ * @param array  $parameters Array of parameters
+ *
+ * @return string or exception
+ * @throws APIException
+ * @since 1.7.0
+ */
+function serialise_parameters($method, $parameters) {
+	global $API_METHODS;
+
+	// are there any parameters for this method
+	if (!(isset($API_METHODS[$method]["parameters"]))) {
+		return ''; // if not, return
+	}
+
+	$serialised_parameters = "";
+	foreach ($API_METHODS[$method]['parameters'] as $key => $value) {
+
+		// avoid warning on parameters that are not required and not present
+		if (!isset($parameters[$key])) {
+			continue;
+		}
+
+		// Set variables casting to type.
+		switch (strtolower($value['type']))
+		{
+			case 'int':
+			case 'integer' :
+				$serialised_parameters .= "," . (int)trim($parameters[$key]);
+				break;
+			case 'bool':
+			case 'boolean':
+				// change word false to boolean false
+				if (strcasecmp(trim($parameters[$key]), "false") == 0) {
+					$serialised_parameters .= ',false';
+				} else if ($parameters[$key] == 0) {
+					$serialised_parameters .= ',false';
+				} else {
+					$serialised_parameters .= ',true';
+				}
+
+				break;
+			case 'string':
+				$serialised_parameters .= ",'" . addcslashes(trim($parameters[$key]), "'") . "'";
+				break;
+			case 'float':
+				$serialised_parameters .= "," . (float)trim($parameters[$key]);
+				break;
+			case 'array':
+				// we can handle an array of strings, maybe ints, definitely not booleans or other arrays
+				if (!is_array($parameters[$key])) {
+					$msg = elgg_echo('APIException:ParameterNotArray', array($key));
+					throw new APIException($msg);
+				}
+
+				$array = "array(";
+
+				foreach ($parameters[$key] as $k => $v) {
+					$k = sanitise_string($k);
+					$v = sanitise_string($v);
+
+					$array .= "'$k'=>'$v',";
+				}
+
+				$array = trim($array, ",");
+
+				$array .= ")";
+				$array = ",$array";
+
+				$serialised_parameters .= $array;
+				break;
+			default:
+				$msg = elgg_echo('APIException:UnrecognisedTypeCast', array($value['type'], $key, $method));
+				throw new APIException($msg);
+		}
+	}
+
+	return $serialised_parameters;
+}
+
+// API authorization handlers /////////////////////////////////////////////////////////////////////
+
+/**
+ * PAM: Confirm that the call includes a valid API key
+ *
+ * @return true if good API key - otherwise throws exception
+ *
+ * @return mixed
+ * @throws APIException
+ * @since 1.7.0
+ */
+function api_auth_key() {
+	global $CONFIG;
+
+	// check that an API key is present
+	$api_key = get_input('api_key');
+	if ($api_key == "") {
+		throw new APIException(elgg_echo('APIException:MissingAPIKey'));
+	}
+
+	// check that it is active
+	$api_user = get_api_user($CONFIG->site_id, $api_key);
+	if (!$api_user) {
+		// key is not active or does not exist
+		throw new APIException(elgg_echo('APIException:BadAPIKey'));
+	}
+
+	// can be used for keeping stats
+	// plugin can also return false to fail this authentication method
+	return elgg_trigger_plugin_hook('api_key', 'use', $api_key, true);
+}
+
+
+/**
+ * PAM: Confirm the HMAC signature
+ *
+ * @return true if success - otherwise throws exception
+ *
+ * @throws SecurityException
+ * @since 1.7.0
+ */
+function api_auth_hmac() {
+	global $CONFIG;
+
+	// Get api header
+	$api_header = get_and_validate_api_headers();
+
+	// Pull API user details
+	$api_user = get_api_user($CONFIG->site_id, $api_header->api_key);
+
+	if (!$api_user) {
+		throw new SecurityException(elgg_echo('SecurityException:InvalidAPIKey'),
+		ErrorResult::$RESULT_FAIL_APIKEY_INVALID);
+	}
+
+	// Get the secret key
+	$secret_key = $api_user->secret;
+
+	// get the query string
+	$query = substr($_SERVER['REQUEST_URI'], strpos($_SERVER['REQUEST_URI'], '?') + 1);
+
+	// calculate expected HMAC
+	$hmac = calculate_hmac(	$api_header->hmac_algo,
+							$api_header->time,
+							$api_header->nonce,
+							$api_header->api_key,
+							$secret_key,
+							$query,
+							$api_header->method == 'POST' ? $api_header->posthash : "");
+
+
+	if ($api_header->hmac !== $hmac) {
+		throw new SecurityException("HMAC is invalid.  {$api_header->hmac} != [calc]$hmac");
+	}
+
+	// Now make sure this is not a replay
+	if (cache_hmac_check_replay($hmac)) {
+		throw new SecurityException(elgg_echo('SecurityException:DupePacket'));
+	}
+
+	// Validate post data
+	if ($api_header->method == "POST") {
+		$postdata = get_post_data();
+		$calculated_posthash = calculate_posthash($postdata, $api_header->posthash_algo);
+
+		if (strcmp($api_header->posthash, $calculated_posthash) != 0) {
+			$msg = elgg_echo('SecurityException:InvalidPostHash',
+			array($calculated_posthash, $api_header->posthash));
+
+			throw new SecurityException($msg);
+		}
+	}
+
+	return true;
+}
+
+// HMAC /////////////////////////////////////////////////////////////////////
+
+/**
+ * This function looks at the super-global variable $_SERVER and extracts the various
+ * header variables needed for the HMAC PAM
+ *
+ * @return stdClass Containing all the values.
+ * @throws APIException Detailing any error.
+ */
+function get_and_validate_api_headers() {
+	$result = new stdClass;
+
+	$result->method = get_call_method();
+	// Only allow these methods
+	if (($result->method != "GET") && ($result->method != "POST")) {
+		throw new APIException(elgg_echo('APIException:NotGetOrPost'));
+	}
+
+	$result->api_key = $_SERVER['HTTP_X_ELGG_APIKEY'];
+	if ($result->api_key == "") {
+		throw new APIException(elgg_echo('APIException:MissingAPIKey'));
+	}
+
+	$result->hmac = $_SERVER['HTTP_X_ELGG_HMAC'];
+	if ($result->hmac == "") {
+		throw new APIException(elgg_echo('APIException:MissingHmac'));
+	}
+
+	$result->hmac_algo = $_SERVER['HTTP_X_ELGG_HMAC_ALGO'];
+	if ($result->hmac_algo == "") {
+		throw new APIException(elgg_echo('APIException:MissingHmacAlgo'));
+	}
+
+	$result->time = $_SERVER['HTTP_X_ELGG_TIME'];
+	if ($result->time == "") {
+		throw new APIException(elgg_echo('APIException:MissingTime'));
+	}
+
+	// Must have been sent within 25 hour period.
+	// 25 hours is more than enough to handle server clock drift.
+	// This values determines how long the HMAC cache needs to store previous
+	// signatures. Heavy use of HMAC is better handled with a shorter sig lifetime.
+	// See cache_hmac_check_replay()
+	if (($result->time < (time() - 90000)) || ($result->time > (time() + 90000))) {
+		throw new APIException(elgg_echo('APIException:TemporalDrift'));
+	}
+
+	$result->nonce = $_SERVER['HTTP_X_ELGG_NONCE'];
+	if ($result->nonce == "") {
+		throw new APIException(elgg_echo('APIException:MissingNonce'));
+	}
+
+	if ($result->method == "POST") {
+		$result->posthash = $_SERVER['HTTP_X_ELGG_POSTHASH'];
+		if ($result->posthash == "") {
+			throw new APIException(elgg_echo('APIException:MissingPOSTHash'));
+		}
+
+		$result->posthash_algo = $_SERVER['HTTP_X_ELGG_POSTHASH_ALGO'];
+		if ($result->posthash_algo == "") {
+			throw new APIException(elgg_echo('APIException:MissingPOSTAlgo'));
+		}
+
+		$result->content_type = $_SERVER['CONTENT_TYPE'];
+		if ($result->content_type == "") {
+			throw new APIException(elgg_echo('APIException:MissingContentType'));
+		}
+	}
+
+	return $result;
+}
+
+/**
+ * Map various algorithms to their PHP equivs.
+ * This also gives us an easy way to disable algorithms.
+ *
+ * @param string $algo The algorithm
+ *
+ * @return string The php algorithm
+ * @throws APIException if an algorithm is not supported.
+ */
+function map_api_hash($algo) {
+	$algo = strtolower(sanitise_string($algo));
+	$supported_algos = array(
+		"md5" => "md5",	// @todo Consider phasing this out
+		"sha" => "sha1", // alias for sha1
+		"sha1" => "sha1",
+		"sha256" => "sha256"
+	);
+
+	if (array_key_exists($algo, $supported_algos)) {
+		return $supported_algos[$algo];
+	}
+
+	throw new APIException(elgg_echo('APIException:AlgorithmNotSupported', array($algo)));
+}
+
+/**
+ * Calculate the HMAC for the http request.
+ * This function signs an api request using the information provided. The signature returned
+ * has been base64 encoded and then url encoded.
+ *
+ * @param string $algo          The HMAC algorithm used
+ * @param string $time          String representation of unix time
+ * @param string $nonce         Nonce
+ * @param string $api_key       Your api key
+ * @param string $secret_key    Your private key
+ * @param string $get_variables URLEncoded string representation of the get variable parameters,
+ *                              eg "method=user&guid=2"
+ * @param string $post_hash     Optional sha1 hash of the post data.
+ *
+ * @return string The HMAC signature
+ */
+function calculate_hmac($algo, $time, $nonce, $api_key, $secret_key,
+$get_variables, $post_hash = "") {
+
+	global $CONFIG;
+
+	elgg_log("HMAC Parts: $algo, $time, $api_key, $secret_key, $get_variables, $post_hash");
+
+	$ctx = hash_init(map_api_hash($algo), HASH_HMAC, $secret_key);
+
+	hash_update($ctx, trim($time));
+	hash_update($ctx, trim($nonce));
+	hash_update($ctx, trim($api_key));
+	hash_update($ctx, trim($get_variables));
+	if (trim($post_hash) != "") {
+		hash_update($ctx, trim($post_hash));
+	}
+
+	return urlencode(base64_encode(hash_final($ctx, true)));
+}
+
+/**
+ * Calculate a hash for some post data.
+ *
+ * @todo Work out how to handle really large bits of data.
+ *
+ * @param string $postdata The post data.
+ * @param string $algo     The algorithm used.
+ *
+ * @return string The hash.
+ */
+function calculate_posthash($postdata, $algo) {
+	$ctx = hash_init(map_api_hash($algo));
+
+	hash_update($ctx, $postdata);
+
+	return hash_final($ctx);
+}
+
+/**
+ * This function will do two things. Firstly it verifies that a HMAC signature
+ * hasn't been seen before, and secondly it will add the given hmac to the cache.
+ *
+ * @param string $hmac The hmac string.
+ *
+ * @return bool True if replay detected, false if not.
+ */
+function cache_hmac_check_replay($hmac) {
+	// cache lifetime is 25 hours (this should be related to the time drift
+	// allowed in get_and_validate_headers
+	$cache = new ElggHMACCache(90000);
+
+	if (!$cache->load($hmac)) {
+		$cache->save($hmac, $hmac);
+
+		return false;
+	}
+
+	return true;
+}
+
+// API key functions /////////////////////////////////////////////////////////////////////
+
+/**
+ * Generate a new API user for a site, returning a new keypair on success.
+ *
+ * @param int $site_guid The GUID of the site. (default is current site)
+ *
+ * @return stdClass object or false
+ */
+function create_api_user($site_guid) {
+	global $CONFIG;
+
+	if (!isset($site_guid)) {
+		$site_guid = $CONFIG->site_id;
+	}
+
+	$site_guid = (int)$site_guid;
+
+	$public = sha1(rand() . $site_guid . microtime());
+	$secret = sha1(rand() . $site_guid . microtime() . $public);
+
+	$insert = insert_data("INSERT into {$CONFIG->dbprefix}api_users
+		(site_guid, api_key, secret) values
+		($site_guid, '$public', '$secret')");
+
+	if ($insert) {
+		return get_api_user($site_guid, $public);
+	}
+
+	return false;
+}
+
+/**
+ * Find an API User's details based on the provided public api key.
+ * These users are not users in the traditional sense.
+ *
+ * @param int    $site_guid The GUID of the site.
+ * @param string $api_key   The API Key
+ *
+ * @return mixed stdClass representing the database row or false.
+ */
+function get_api_user($site_guid, $api_key) {
+	global $CONFIG;
+
+	$api_key = sanitise_string($api_key);
+	$site_guid = (int)$site_guid;
+
+	$query = "SELECT * from {$CONFIG->dbprefix}api_users"
+	. " where api_key='$api_key' and site_guid=$site_guid and active=1";
+
+	return get_data_row($query);
+}
+
+/**
+ * Revoke an api user key.
+ *
+ * @param int    $site_guid The GUID of the site.
+ * @param string $api_key   The API Key (public).
+ *
+ * @return bool
+ */
+function remove_api_user($site_guid, $api_key) {
+	global $CONFIG;
+
+	$keypair = get_api_user($site_guid, $api_key);
+	if ($keypair) {
+		return delete_data("DELETE from {$CONFIG->dbprefix}api_users where id={$keypair->id}");
+	}
+
+	return false;
+}
+
+
+// User Authorization functions
+
+/**
+ * Check the user token
+ * This examines whether an authentication token is present and returns true if
+ * it is present and is valid. The user gets logged in so with the current
+ * session code of Elgg, that user will be logged out of all other sessions.
+ *
+ * @return bool
+ */
+function pam_auth_usertoken() {
+	global $CONFIG;
+
+	$token = get_input('auth_token');
+	if (!$token) {
+		return false;
+	}
+
+	$validated_userid = validate_user_token($token, $CONFIG->site_id);
+
+	if ($validated_userid) {
+		$u = get_entity($validated_userid);
+
+		// Could we get the user?
+		if (!$u) {
+			return false;
+		}
+
+		// Not an elgg user
+		if ((!$u instanceof ElggUser)) {
+			return false;
+		}
+
+		// User is banned
+		if ($u->isBanned()) {
+			return false;
+		}
+
+		// Fail if we couldn't log the user in
+		if (!login($u)) {
+			return false;
+		}
+
+		return true;
+	}
+
+	return false;
+}
+
+/**
+ * See if the user has a valid login sesson
+ *
+ * @return bool
+ */
+function pam_auth_session() {
+	return isloggedin();
+}
+
+// user token functions
+
+/**
+ * Obtain a token for a user.
+ *
+ * @param string $username The username
+ * @param int    $expire   Minutes until token expires (default is 60 minutes)
+ *
+ * @return bool
+ */
+function create_user_token($username, $expire = 60) {
+	global $CONFIG;
+
+	$site_guid = $CONFIG->site_id;
+	$user = get_user_by_username($username);
+	$time = time();
+	$time += 60 * $expire;
+	$token = md5(rand() . microtime() . $username . $time . $site_guid);
+
+	if (!$user) {
+		return false;
+	}
+
+	if (insert_data("INSERT into {$CONFIG->dbprefix}users_apisessions
+				(user_guid, site_guid, token, expires) values
+				({$user->guid}, $site_guid, '$token', '$time')
+				on duplicate key update token='$token', expires='$time'")) {
+		return $token;
+	}
+
+	return false;
+}
+
+/**
+ * Get all tokens attached to a user
+ *
+ * @param int $user_guid The user GUID
+ * @param int $site_guid The ID of the site (default is current site)
+ *
+ * @return false if none available or array of stdClass objects
+ * 		(see users_apisessions schema for available variables in objects)
+ * @since 1.7.0
+ */
+function get_user_tokens($user_guid, $site_guid) {
+	global $CONFIG;
+
+	if (!isset($site_guid)) {
+		$site_guid = $CONFIG->site_id;
+	}
+
+	$site_guid = (int)$site_guid;
+	$user_guid = (int)$user_guid;
+
+	$tokens = get_data("SELECT * from {$CONFIG->dbprefix}users_apisessions
+		where user_guid=$user_guid and site_guid=$site_guid");
+
+	return $tokens;
+}
+
+/**
+ * Validate a token against a given site.
+ *
+ * A token registered with one site can not be used from a
+ * different apikey(site), so be aware of this during development.
+ *
+ * @param string $token     The Token.
+ * @param int    $site_guid The ID of the site (default is current site)
+ *
+ * @return mixed The user id attached to the token if not expired or false.
+ */
+function validate_user_token($token, $site_guid) {
+	global $CONFIG;
+
+	if (!isset($site_guid)) {
+		$site_guid = $CONFIG->site_id;
+	}
+
+	$site_guid = (int)$site_guid;
+	$token = sanitise_string($token);
+
+	$time = time();
+
+	$user = get_data_row("SELECT * from {$CONFIG->dbprefix}users_apisessions
+		where token='$token' and site_guid=$site_guid and $time < expires");
+
+	if ($user) {
+		return $user->user_guid;
+	}
+
+	return false;
+}
+
+/**
+ * Remove user token
+ *
+ * @param string $token     The toekn
+ * @param int    $site_guid The ID of the site (default is current site)
+ *
+ * @return bool
+ * @since 1.7.0
+ */
+function remove_user_token($token, $site_guid) {
+	global $CONFIG;
+
+	if (!isset($site_guid)) {
+		$site_guid = $CONFIG->site_id;
+	}
+
+	$site_guid = (int)$site_guid;
+	$token = sanitise_string($token);
+
+	return delete_data("DELETE from {$CONFIG->dbprefix}users_apisessions
+		where site_guid=$site_guid and token='$token'");
+}
+
+/**
+ * Remove expired tokens
+ *
+ * @return bool
+ * @since 1.7.0
+ */
+function remove_expired_user_tokens() {
+	global $CONFIG;
+
+	$site_guid = $CONFIG->site_id;
+
+	$time = time();
+
+	return delete_data("DELETE from {$CONFIG->dbprefix}users_apisessions
+		where site_guid=$site_guid and expires < $time");
+}
+
+// Client api functions
+
+/**
+ * Utility function to serialise a header array into its text representation.
+ *
+ * @param array $headers The array of headers "key" => "value"
+ *
+ * @return string
+ */
+function serialise_api_headers(array $headers) {
+	$headers_str = "";
+
+	foreach ($headers as $k => $v) {
+		$headers_str .= trim($k) . ": " . trim($v) . "\r\n";
+	}
+
+	return trim($headers_str);
+}
+
+/**
+ * Send a raw API call to an elgg api endpoint.
+ *
+ * @param array  $keys         The api keys.
+ * @param string $url          URL of the endpoint.
+ * @param array  $call         Associated array of "variable" => "value"
+ * @param string $method       GET or POST
+ * @param string $post_data    The post data
+ * @param string $content_type The content type
+ *
+ * @return string
+ */
+function send_api_call(array $keys, $url, array $call, $method = 'GET', $post_data = '',
+$content_type = 'application/octet-stream') {
+
+	global $CONFIG;
+
+	$headers = array();
+	$encoded_params = array();
+
+	$method = strtoupper($method);
+	switch (strtoupper($method)) {
+		case 'GET' :
+		case 'POST' :
+			break;
+		default:
+			$msg = elgg_echo('NotImplementedException:CallMethodNotImplemented', array($method));
+			throw new NotImplementedException($msg);
+	}
+
+	// Time
+	$time = time();
+
+	// Nonce
+	$nonce = uniqid('');
+
+	// URL encode all the parameters
+	foreach ($call as $k => $v) {
+		$encoded_params[] = urlencode($k) . '=' . urlencode($v);
+	}
+
+	$params = implode('&', $encoded_params);
+
+	// Put together the query string
+	$url = $url . "?" . $params;
+
+	// Construct headers
+	$posthash = "";
+	if ($method == 'POST') {
+		$posthash = calculate_posthash($post_data, 'md5');
+	}
+
+	if ((isset($keys['public'])) && (isset($keys['private']))) {
+		$headers['X-Elgg-apikey'] = $keys['public'];
+		$headers['X-Elgg-time'] = $time;
+		$headers['X-Elgg-nonce'] = $nonce;
+		$headers['X-Elgg-hmac-algo'] = 'sha1';
+		$headers['X-Elgg-hmac'] = calculate_hmac('sha1',
+			$time,
+			$nonce,
+			$keys['public'],
+			$keys['private'],
+			$params,
+			$posthash
+		);
+	}
+	if ($method == 'POST') {
+		$headers['X-Elgg-posthash'] = $posthash;
+		$headers['X-Elgg-posthash-algo'] = 'md5';
+
+		$headers['Content-type'] = $content_type;
+		$headers['Content-Length'] = strlen($post_data);
+	}
+
+	// Opt array
+	$http_opts = array(
+		'method' => $method,
+		'header' => serialise_api_headers($headers)
+	);
+	if ($method == 'POST') {
+		$http_opts['content'] = $post_data;
+	}
+
+	$opts = array('http' => $http_opts);
+
+	// Send context
+	$context = stream_context_create($opts);
+
+	// Send the query and get the result and decode.
+	elgg_log("APICALL: $url");
+	$results = file_get_contents($url, false, $context);
+
+	return $results;
+}
+
+/**
+ * Send a GET call
+ *
+ * @param string $url  URL of the endpoint.
+ * @param array  $call Associated array of "variable" => "value"
+ * @param array  $keys The keys dependant on chosen authentication method
+ *
+ * @return string
+ */
+function send_api_get_call($url, array $call, array $keys) {
+	return send_api_call($keys, $url, $call);
+}
+
+/**
+ * Send a GET call
+ *
+ * @param string $url          URL of the endpoint.
+ * @param array  $call         Associated array of "variable" => "value"
+ * @param array  $keys         The keys dependant on chosen authentication method
+ * @param string $post_data    The post data
+ * @param string $content_type The content type
+ *
+ * @return string
+ */
+function send_api_post_call($url, array $call, array $keys, $post_data,
+$content_type = 'application/octet-stream') {
+
+	return send_api_call($keys, $url, $call, 'POST', $post_data, $content_type);
+}
+
+/**
+ * Return a key array suitable for the API client using the standard
+ * authentication method based on api-keys and secret keys.
+ *
+ * @param string $secret_key Your secret key
+ * @param string $api_key    Your api key
+ *
+ * @return array
+ */
+function get_standard_api_key_array($secret_key, $api_key) {
+	return array('public' => $api_key, 'private' => $secret_key);
+}
+
+// System functions
+
+/**
+ * Simple api to return a list of all api's installed on the system.
+ *
+ * @return array
+ */
+function list_all_apis() {
+	global $API_METHODS;
+
+	// sort first
+	ksort($API_METHODS);
+
+	return $API_METHODS;
+}
+
+/**
+ * The auth.gettoken API.
+ * This API call lets a user log in, returning an authentication token which can be used
+ * to authenticate a user for a period of time. It is passed in future calls as the parameter
+ * auth_token.
+ *
+ * @param string $username Username
+ * @param string $password Clear text password
+ *
+ * @return string Token string or exception
+ * @throws SecurityException
+ */
+function auth_gettoken($username, $password) {
+	if (authenticate($username, $password)) {
+		$token = create_user_token($username);
+		if ($token) {
+			return $token;
+		}
+	}
+
+	throw new SecurityException(elgg_echo('SecurityException:authenticationfailed'));
+}
+
+// Error handler functions
+
+/** Define a global array of errors */
+$ERRORS = array();
+
+/**
+ * API PHP Error handler function.
+ * This function acts as a wrapper to catch and report PHP error messages.
+ *
+ * @see http://uk3.php.net/set-error-handler
+ *
+ * @param int    $errno    Error number
+ * @param string $errmsg   Human readable message
+ * @param string $filename Filename
+ * @param int    $linenum  Line number
+ * @param array  $vars     Vars
+ *
+ * @return void
+ */
+function _php_api_error_handler($errno, $errmsg, $filename, $linenum, $vars) {
+	global $ERRORS;
+
+	$error = date("Y-m-d H:i:s (T)") . ": \"" . $errmsg . "\" in file "
+	. $filename . " (line " . $linenum . ")";
+
+	switch ($errno) {
+		case E_USER_ERROR:
+			error_log("ERROR: " . $error);
+			$ERRORS[] = "ERROR: " . $error;
+
+			// Since this is a fatal error, we want to stop any further execution but do so gracefully.
+			throw new Exception("ERROR: " . $error);
+			break;
+
+		case E_WARNING :
+		case E_USER_WARNING :
+			error_log("WARNING: " . $error);
+			$ERRORS[] = "WARNING: " . $error;
+			break;
+
+		default:
+			error_log("DEBUG: " . $error);
+			$ERRORS[] = "DEBUG: " . $error;
+	}
+}
+
+/**
+ * API PHP Exception handler.
+ * This is a generic exception handler for PHP exceptions. This will catch any
+ * uncaught exception, end API execution and return the result to the requestor
+ * as an ErrorResult in the requested format.
+ *
+ * @param Exception $exception Exception
+ *
+ * @return void
+ */
+function _php_api_exception_handler($exception) {
+
+	error_log("*** FATAL EXCEPTION (API) *** : " . $exception);
+
+	$code   = $exception->getCode() == 0 ? ErrorResult::$RESULT_FAIL : $exception->getCode();
+	$result = new ErrorResult($exception->getMessage(), $code, NULL);
+
+	echo elgg_view_page($exception->getMessage(), elgg_view("api/output", array("result" => $result)));
+}
+
+
+// Services handler
+
+/**
+ * Services handler - turns request over to the registered handler
+ * If no handler is found, this returns a 404 error
+ *
+ * @param string $handler Handler name
+ * @param array  $request Request string
+ *
+ * @return void
+ */
+function service_handler($handler, $request) {
+	global $CONFIG;
+
+	elgg_set_context('api');
+
+	$request = explode('/', $request);
+
+	// after the handler, the first identifier is response format
+	// ex) http://example.org/services/api/rest/xml/?method=test
+	$reponse_format = array_shift($request);
+	// Which view - xml, json, ...
+	if ($reponse_format) {
+		elgg_set_viewtype($reponse_format);
+	} else {
+		// default to xml
+		elgg_set_viewtype("xml");
+	}
+
+	if (!isset($CONFIG->servicehandler) || empty($handler)) {
+		// no handlers set or bad url
+		header("HTTP/1.0 404 Not Found");
+		exit;
+	} else if (isset($CONFIG->servicehandler[$handler])
+	&& is_callable($CONFIG->servicehandler[$handler])) {
+
+		$function = $CONFIG->servicehandler[$handler];
+		$function($request, $handler);
+	} else {
+		// no handler for this web service
+		header("HTTP/1.0 404 Not Found");
+		exit;
+	}
+}
+
+/**
+ * Registers a web services handler
+ *
+ * @param string $handler  Web services type
+ * @param string $function Your function name
+ *
+ * @return bool Depending on success
+ * @since 1.7.0
+ */
+function register_service_handler($handler, $function) {
+	global $CONFIG;
+	if (!isset($CONFIG->servicehandler)) {
+		$CONFIG->servicehandler = array();
+	}
+	if (is_callable($function)) {
+		$CONFIG->servicehandler[$handler] = $function;
+		return true;
+	}
+
+	return false;
+}
+
+/**
+ * Remove a web service
+ * To replace a web service handler, register the desired handler over the old on
+ * with register_service_handler().
+ *
+ * @param string $handler web services type
+ *
+ * @return 1.7.0
+ */
+function unregister_service_handler($handler) {
+	global $CONFIG;
+	if (isset($CONFIG->servicehandler) && isset($CONFIG->servicehandler[$handler])) {
+		unset($CONFIG->servicehandler[$handler]);
+	}
+}
+
+// REST handler
+
+/**
+ * REST API handler
+ *
+ * @return void
+ */
+function rest_handler() {
+	global $CONFIG;
+
+	require $CONFIG->path . "services/api/rest_api.php";
+}
+
+// Initialisation
+
+/**
+ * Unit tests for API
+ *
+ * @param sting  $hook   unit_test
+ * @param string $type   system
+ * @param mixed  $value  Array of tests
+ * @param mixed  $params Params
+ *
+ * @return array
+ */
+function api_unit_test($hook, $type, $value, $params) {
+	global $CONFIG;
+	$value[] = $CONFIG->path . 'engine/tests/services/api.php';
+	return $value;
+}
+
+/**
+ * Initialise the API subsystem.
+ *
+ * @return void
+ */
+function api_init() {
+	// Register a page handler, so we can have nice URLs
+	register_service_handler('rest', 'rest_handler');
+
+	elgg_register_plugin_hook_handler('unit_test', 'system', 'api_unit_test');
+
+	// expose the list of api methods
+	expose_function("system.api.list", "list_all_apis", NULL,
+	elgg_echo("system.api.list"), "GET", false, false);
+
+	// The authentication token api
+	expose_function("auth.gettoken",
+					"auth_gettoken", array(
+											'username' => array ('type' => 'string'),
+											'password' => array ('type' => 'string'),
+											),
+					elgg_echo('auth.gettoken'),
+					'POST',
+					false,
+					false);
+}
+
+
+elgg_register_event_handler('init', 'system', 'api_init');