includes/TemplateParser.php

   1 <?php
   2 use MediaWiki\MediaWikiServices;
   3
   4 /**
   5  * Handles compiling Mustache templates into PHP rendering functions
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along
  18  * with this program; if not, write to the Free Software Foundation, Inc.,
  19  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  20  * http://www.gnu.org/copyleft/gpl.html
  21  *
  22  * @file
  23  * @since 1.25
  24  */
  25 class TemplateParser {
  26         /**
  27          * @var string The path to the Mustache templates
  28          */
  29         protected $templateDir;
  30
  31         /**
  32          * @var callable[] Array of cached rendering functions
  33          */
  34         protected $renderers;
  35
  36         /**
  37          * @var bool Always compile template files
  38          */
  39         protected $forceRecompile = false;
  40
  41         /**
  42          * @param string $templateDir
  43          * @param bool $forceRecompile
  44          */
  45         public function __construct( $templateDir = null, $forceRecompile = false ) {
  46                 $this->templateDir = $templateDir ?: __DIR__ . '/templates';
  47                 $this->forceRecompile = $forceRecompile;
  48         }
  49
  50         /**
  51          * Constructs the location of the the source Mustache template
  52          * @param string $templateName The name of the template
  53          * @return string
  54          * @throws UnexpectedValueException If $templateName attempts upwards directory traversal
  55          */
  56         protected function getTemplateFilename( $templateName ) {
  57                 // Prevent path traversal. Based on Language::isValidCode().
  58                 // This is for paranoia. The $templateName should never come from
  59                 // untrusted input.
  60                 if (
  61                         strcspn( $templateName, ":/\\\000&<>'\"%" ) !== strlen( $templateName )
  62                 ) {
  63                         throw new UnexpectedValueException( "Malformed \$templateName: $templateName" );
  64                 }
  65
  66                 return "{$this->templateDir}/{$templateName}.mustache";
  67         }
  68
  69         /**
  70          * Returns a given template function if found, otherwise throws an exception.
  71          * @param string $templateName The name of the template (without file suffix)
  72          * @return callable
  73          * @throws RuntimeException
  74          */
  75         protected function getTemplate( $templateName ) {
  76                 // If a renderer has already been defined for this template, reuse it
  77                 if ( isset( $this->renderers[$templateName] ) &&
  78                         is_callable( $this->renderers[$templateName] )
  79                 ) {
  80                         return $this->renderers[$templateName];
  81                 }
  82
  83                 $filename = $this->getTemplateFilename( $templateName );
  84
  85                 if ( !file_exists( $filename ) ) {
  86                         throw new RuntimeException( "Could not locate template: {$filename}" );
  87                 }
  88
  89                 // Read the template file
  90                 $fileContents = file_get_contents( $filename );
  91
  92                 // Generate a quick hash for cache invalidation
  93                 $fastHash = md5( $fileContents );
  94
  95                 // Fetch a secret key for building a keyed hash of the PHP code
  96                 $config = MediaWikiServices::getInstance()->getMainConfig();
  97                 $secretKey = $config->get( 'SecretKey' );
  98
  99                 if ( $secretKey ) {
 100                         // See if the compiled PHP code is stored in cache.
 101                         $cache = ObjectCache::getLocalServerInstance( CACHE_ANYTHING );
 102                         $key = $cache->makeKey( 'template', $templateName, $fastHash );
 103                         $code = $this->forceRecompile ? null : $cache->get( $key );
 104
 105                         if ( $code ) {
 106                                 // Verify the integrity of the cached PHP code
 107                                 $keyedHash = substr( $code, 0, 64 );
 108                                 $code = substr( $code, 64 );
 109                                 if ( $keyedHash !== hash_hmac( 'sha256', $code, $secretKey ) ) {
 110                                         // If the integrity check fails, don't use the cached code
 111                                         // We'll update the invalid cache below
 112                                         $code = null;
 113                                 }
 114                         }
 115                         if ( !$code ) {
 116                                 $code = $this->compileForEval( $fileContents, $filename );
 117
 118                                 // Prefix the cached code with a keyed hash (64 hex chars) as an integrity check
 119                                 $cache->set( $key, hash_hmac( 'sha256', $code, $secretKey ) . $code );
 120                         }
 121                 // If there is no secret key available, don't use cache
 122                 } else {
 123                         $code = $this->compileForEval( $fileContents, $filename );
 124                 }
 125
 126                 $renderer = eval( $code );
 127                 if ( !is_callable( $renderer ) ) {
 128                         throw new RuntimeException( "Requested template, {$templateName}, is not callable" );
 129                 }
 130                 $this->renderers[$templateName] = $renderer;
 131                 return $renderer;
 132         }
 133
 134         /**
 135          * Wrapper for compile() function that verifies successful compilation and strips
 136          * out the '<?php' part so that the code is ready for eval()
 137          * @param string $fileContents Mustache code
 138          * @param string $filename Name of the template
 139          * @return string PHP code (without '<?php')
 140          * @throws RuntimeException
 141          */
 142         protected function compileForEval( $fileContents, $filename ) {
 143                 // Compile the template into PHP code
 144                 $code = $this->compile( $fileContents );
 145
 146                 if ( !$code ) {
 147                         throw new RuntimeException( "Could not compile template: {$filename}" );
 148                 }
 149
 150                 // Strip the "<?php" added by lightncandy so that it can be eval()ed
 151                 if ( substr( $code, 0, 5 ) === '<?php' ) {
 152                         $code = substr( $code, 5 );
 153                 }
 154
 155                 return $code;
 156         }
 157
 158         /**
 159          * Compile the Mustache code into PHP code using LightnCandy
 160          * @param string $code Mustache code
 161          * @return string PHP code (with '<?php')
 162          * @throws RuntimeException
 163          */
 164         protected function compile( $code ) {
 165                 if ( !class_exists( 'LightnCandy' ) ) {
 166                         throw new RuntimeException( 'LightnCandy class not defined' );
 167                 }
 168                 return LightnCandy::compile(
 169                         $code,
 170                         [
 171                                 // Do not add more flags here without discussion.
 172                                 // If you do add more flags, be sure to update unit tests as well.
 173                                 'flags' => LightnCandy::FLAG_ERROR_EXCEPTION,
 174                                 'basedir' => $this->templateDir,
 175                                 'fileext' => '.mustache',
 176                         ]
 177                 );
 178         }
 179
 180         /**
 181          * Returns HTML for a given template by calling the template function with the given args
 182          *
 183          * @code
 184          *     echo $templateParser->processTemplate(
 185          *         'ExampleTemplate',
 186          *         [
 187          *             'username' => $user->getName(),
 188          *             'message' => 'Hello!'
 189          *         ]
 190          *     );
 191          * @endcode
 192          * @param string $templateName The name of the template
 193          * @param mixed $args
 194          * @param array $scopes
 195          * @return string
 196          */
 197         public function processTemplate( $templateName, $args, array $scopes = [] ) {
 198                 $template = $this->getTemplate( $templateName );
 199                 return call_user_func( $template, $args, $scopes );
 200         }
 201 }