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<?php
namespace SMW\Utils;
/**
* Serialize/encode a data element with a hmac hash to verify that the output are
* in fact the same as the input data, minimizing an attack vector on injecting
* malicious content when retrieving the data from en external systems (like
* a cache).
*
* The shared secret key to generate the HMAC is by default MediaWiki's
* $wgSecretKey.
*
* @license GNU GPL v2+
* @since 3.0
*
* @author mwjames
*/
class HmacSerializer {
/**
* @since 3.0
*
* @param mixed $data
* @param string $key
* @param string $algo = 'md5'
*
* @return string|boolean
*/
public static function encode( $data, $key = null, $algo = 'md5' ) {
if ( $key === null ) {
$key = $GLOBALS['wgSecretKey'];
}
$data = json_encode( $data );
$hash = hash_hmac( $algo, $data, $key );
if ( $hash !== false ) {
return json_encode( [ 'hmac' => $hash, 'data' => $data ] );
}
return false;
}
/**
* @since 3.0
*
* @param mixed $data
* @param string $key
* @param string $algo = 'md5'
*
* @return string|boolean
*/
public static function decode( $data, $key = null, $algo = 'md5' ) {
if ( $key === null ) {
$key = $GLOBALS['wgSecretKey'];
}
if ( !is_string( $data ) ) {
return false;
}
$hash = '';
$data = json_decode( $data, true );
// Timing attack safe string comparison
if ( isset( $data['hmac'] ) && hash_equals( hash_hmac( $algo, $data['data'], $key ), $data['hmac'] ) ) {
return json_decode( $data['data'], true );
}
return false;
}
/**
* @since 3.0
*
* @param mixed $data
* @param string $key
* @param string $algo = 'md5'
*
* @return string|boolean
*/
public static function serialize( $data, $key = null, $algo = 'md5' ) {
if ( $key === null ) {
$key = $GLOBALS['wgSecretKey'];
}
$data = serialize( $data );
$hash = hash_hmac( $algo, $data, $key );
if ( $hash !== false ) {
return "$hash|$data";
}
return false;
}
/**
* @since 3.0
*
* @param string $data
* @param string $key
* @param string $algo = 'md5'
*
* @return mixed|boolean
*/
public static function unserialize( $data, $key = null, $algo = 'md5' ) {
if ( $key === null ) {
$key = $GLOBALS['wgSecretKey'];
}
if ( !is_string( $data ) ) {
return false;
}
$hash = '';
if ( strpos( $data, '|' ) !== false ) {
list( $hash, $data ) = explode( '|', $data, 2 );
}
// Timing attack safe string comparison
if ( hash_equals( hash_hmac( $algo, $data, $key ), $hash ) ) {
return unserialize( $data );
}
return false;
}
/**
* @since 3.0
*
* @param mixed $data
* @param string $key
* @param string $algo = 'md5'
*
* @return string|boolean
*/
public static function compress( $data, $key = null, $algo = 'md5' ) {
if ( $key === null ) {
$key = $GLOBALS['wgSecretKey'];
}
$key = $key . 'compress';
return gzcompress( self::serialize( $data, $key, $algo ), 9 );
}
/**
* @since 3.0
*
* @param string $data
* @param string $key
* @param string $algo = 'md5'
*
* @return mixed|boolean
*/
public static function uncompress( $data, $key = null, $algo = 'md5' ) {
if ( $key === null ) {
$key = $GLOBALS['wgSecretKey'];
}
$key = $key . 'compress';
return self::unserialize( @gzuncompress( $data ), $key, $algo );
}
}
|
