includes/json/FormatJson.php

   1 <?php
   2 /**
   3  * Wrapper for json_encode and json_decode.
   4  *
   5  * This program 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 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program 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 along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  */
  22
  23 /**
  24  * JSON formatter wrapper class
  25  */
  26 class FormatJson {
  27         /**
  28          * Skip escaping most characters above U+007F for readability and compactness.
  29          * This encoding option saves 3 to 8 bytes (uncompressed) for each such character;
  30          * however, it could break compatibility with systems that incorrectly handle UTF-8.
  31          *
  32          * @since 1.22
  33          */
  34         const UTF8_OK = 1;
  35
  36         /**
  37          * Skip escaping the characters '<', '>', and '&', which have special meanings in
  38          * HTML and XML.
  39          *
  40          * @warning Do not use this option for JSON that could end up in inline scripts.
  41          * - HTML5, §4.3.1.2 Restrictions for contents of script elements
  42          * - XML 1.0 (5th Ed.), §2.4 Character Data and Markup
  43          *
  44          * @since 1.22
  45          */
  46         const XMLMETA_OK = 2;
  47
  48         /**
  49          * Skip escaping as many characters as reasonably possible.
  50          *
  51          * @warning When generating inline script blocks, use FormatJson::UTF8_OK instead.
  52          *
  53          * @since 1.22
  54          */
  55         const ALL_OK = 3;
  56
  57         /**
  58          * If set, treat json objects '{...}' as associative arrays. Without this option,
  59          * json objects will be converted to stdClass.
  60          * The value is set to 1 to be backward compatible with 'true' that was used before.
  61          *
  62          * @since 1.24
  63          */
  64         const FORCE_ASSOC = 0x100;
  65
  66         /**
  67          * If set, attempts to fix invalid json.
  68          *
  69          * @since 1.24
  70          */
  71         const TRY_FIXING = 0x200;
  72
  73         /**
  74          * If set, strip comments from input before parsing as JSON.
  75          *
  76          * @since 1.25
  77          */
  78         const STRIP_COMMENTS = 0x400;
  79
  80         /**
  81          * Characters problematic in JavaScript.
  82          *
  83          * @note These are listed in ECMA-262 (5.1 Ed.), §7.3 Line Terminators along with U+000A (LF)
  84          *       and U+000D (CR). However, PHP already escapes LF and CR according to RFC 4627.
  85          */
  86         private static $badChars = [
  87                 "\u{2028}", // U+2028 LINE SEPARATOR
  88                 "\u{2029}", // U+2029 PARAGRAPH SEPARATOR
  89         ];
  90
  91         /**
  92          * Escape sequences for characters listed in FormatJson::$badChars.
  93          */
  94         private static $badCharsEscaped = [
  95                 '\u2028', // U+2028 LINE SEPARATOR
  96                 '\u2029', // U+2029 PARAGRAPH SEPARATOR
  97         ];
  98
  99         /**
 100          * Returns the JSON representation of a value.
 101          *
 102          * @note Empty arrays are encoded as numeric arrays, not as objects, so cast any associative
 103          *       array that might be empty to an object before encoding it.
 104          *
 105          * @note In pre-1.22 versions of MediaWiki, using this function for generating inline script
 106          *       blocks may result in an XSS vulnerability, and quite likely will in XML documents
 107          *       (cf. FormatJson::XMLMETA_OK). Use Xml::encodeJsVar() instead in such cases.
 108          *
 109          * @param mixed $value The value to encode. Can be any type except a resource.
 110          * @param string|bool $pretty If a string, add non-significant whitespace to improve
 111          *   readability, using that string for indentation. If true, use the default indent
 112          *   string (four spaces).
 113          * @param int $escaping Bitfield consisting of _OK class constants
 114          * @return string|false String if successful; false upon failure
 115          */
 116         public static function encode( $value, $pretty = false, $escaping = 0 ) {
 117                 if ( !is_string( $pretty ) ) {
 118                         $pretty = $pretty ? '    ' : false;
 119                 }
 120
 121                 // PHP escapes '/' to prevent breaking out of inline script blocks using '</script>',
 122                 // which is hardly useful when '<' and '>' are escaped (and inadequate), and such
 123                 // escaping negatively impacts the human readability of URLs and similar strings.
 124                 $options = JSON_UNESCAPED_SLASHES;
 125                 $options |= $pretty !== false ? JSON_PRETTY_PRINT : 0;
 126                 $options |= ( $escaping & self::UTF8_OK ) ? JSON_UNESCAPED_UNICODE : 0;
 127                 $options |= ( $escaping & self::XMLMETA_OK ) ? 0 : ( JSON_HEX_TAG | JSON_HEX_AMP );
 128                 $json = json_encode( $value, $options );
 129                 if ( $json === false ) {
 130                         return false;
 131                 }
 132
 133                 if ( $pretty !== false ) {
 134                         if ( $pretty !== '    ' ) {
 135                                 // Change the four-space indent to a tab indent
 136                                 $json = str_replace( "\n    ", "\n\t", $json );
 137                                 while ( strpos( $json, "\t    " ) !== false ) {
 138                                         $json = str_replace( "\t    ", "\t\t", $json );
 139                                 }
 140
 141                                 if ( $pretty !== "\t" ) {
 142                                         // Change the tab indent to the provided indent
 143                                         $json = str_replace( "\t", $pretty, $json );
 144                                 }
 145                         }
 146                 }
 147                 if ( $escaping & self::UTF8_OK ) {
 148                         $json = str_replace( self::$badChars, self::$badCharsEscaped, $json );
 149                 }
 150
 151                 return $json;
 152         }
 153
 154         /**
 155          * Decodes a JSON string. It is recommended to use FormatJson::parse(),
 156          * which returns more comprehensive result in case of an error, and has
 157          * more parsing options.
 158          *
 159          * @param string $value The JSON string being decoded
 160          * @param bool $assoc When true, returned objects will be converted into associative arrays.
 161          *
 162          * @return mixed The value encoded in JSON in appropriate PHP type.
 163          * `null` is returned if $value represented `null`, if $value could not be decoded,
 164          * or if the encoded data was deeper than the recursion limit.
 165          * Use FormatJson::parse() to distinguish between types of `null` and to get proper error code.
 166          */
 167         public static function decode( $value, $assoc = false ) {
 168                 return json_decode( $value, $assoc );
 169         }
 170
 171         /**
 172          * Decodes a JSON string.
 173          * Unlike FormatJson::decode(), if $value represents null value, it will be
 174          * properly decoded as valid.
 175          *
 176          * @param string $value The JSON string being decoded
 177          * @param int $options A bit field that allows FORCE_ASSOC, TRY_FIXING,
 178          * STRIP_COMMENTS
 179          * @return Status If valid JSON, the value is available in $result->getValue()
 180          */
 181         public static function parse( $value, $options = 0 ) {
 182                 if ( $options & self::STRIP_COMMENTS ) {
 183                         $value = self::stripComments( $value );
 184                 }
 185                 $assoc = ( $options & self::FORCE_ASSOC ) !== 0;
 186                 $result = json_decode( $value, $assoc );
 187                 $code = json_last_error();
 188
 189                 if ( $code === JSON_ERROR_SYNTAX && ( $options & self::TRY_FIXING ) !== 0 ) {
 190                         // The most common error is the trailing comma in a list or an object.
 191                         // We cannot simply replace /,\s*[}\]]/ because it could be inside a string value.
 192                         // But we could use the fact that JSON does not allow multi-line string values,
 193                         // And remove trailing commas if they are et the end of a line.
 194                         // JSON only allows 4 control characters: [ \t\r\n].  So we must not use '\s' for matching.
 195                         // Regex match   ,]<any non-quote chars>\n   or   ,\n]   with optional spaces/tabs.
 196                         $count = 0;
 197                         $value =
 198                                 preg_replace( '/,([ \t]*[}\]][^"\r\n]*([\r\n]|$)|[ \t]*[\r\n][ \t\r\n]*[}\]])/', '$1',
 199                                         $value, -1, $count );
 200                         if ( $count > 0 ) {
 201                                 $result = json_decode( $value, $assoc );
 202                                 if ( JSON_ERROR_NONE === json_last_error() ) {
 203                                         // Report warning
 204                                         $st = Status::newGood( $result );
 205                                         $st->warning( wfMessage( 'json-warn-trailing-comma' )->numParams( $count ) );
 206                                         return $st;
 207                                 }
 208                         }
 209                 }
 210
 211                 switch ( $code ) {
 212                         case JSON_ERROR_NONE:
 213                                 return Status::newGood( $result );
 214                         default:
 215                                 return Status::newFatal( wfMessage( 'json-error-unknown' )->numParams( $code ) );
 216                         case JSON_ERROR_DEPTH:
 217                                 $msg = 'json-error-depth';
 218                                 break;
 219                         case JSON_ERROR_STATE_MISMATCH:
 220                                 $msg = 'json-error-state-mismatch';
 221                                 break;
 222                         case JSON_ERROR_CTRL_CHAR:
 223                                 $msg = 'json-error-ctrl-char';
 224                                 break;
 225                         case JSON_ERROR_SYNTAX:
 226                                 $msg = 'json-error-syntax';
 227                                 break;
 228                         case JSON_ERROR_UTF8:
 229                                 $msg = 'json-error-utf8';
 230                                 break;
 231                         case JSON_ERROR_RECURSION:
 232                                 $msg = 'json-error-recursion';
 233                                 break;
 234                         case JSON_ERROR_INF_OR_NAN:
 235                                 $msg = 'json-error-inf-or-nan';
 236                                 break;
 237                         case JSON_ERROR_UNSUPPORTED_TYPE:
 238                                 $msg = 'json-error-unsupported-type';
 239                                 break;
 240                 }
 241                 return Status::newFatal( $msg );
 242         }
 243
 244         /**
 245          * Remove multiline and single line comments from an otherwise valid JSON
 246          * input string. This can be used as a preprocessor for to allow JSON
 247          * formatted configuration files to contain comments.
 248          *
 249          * @param string $json
 250          * @return string JSON with comments removed
 251          */
 252         public static function stripComments( $json ) {
 253                 // Ensure we have a string
 254                 $str = (string)$json;
 255                 $buffer = '';
 256                 $maxLen = strlen( $str );
 257                 $mark = 0;
 258
 259                 $inString = false;
 260                 $inComment = false;
 261                 $multiline = false;
 262
 263                 for ( $idx = 0; $idx < $maxLen; $idx++ ) {
 264                         switch ( $str[$idx] ) {
 265                                 case '"':
 266                                         $lookBehind = ( $idx - 1 >= 0 ) ? $str[$idx - 1] : '';
 267                                         if ( !$inComment && $lookBehind !== '\\' ) {
 268                                                 // Either started or ended a string
 269                                                 $inString = !$inString;
 270                                         }
 271                                         break;
 272
 273                                 case '/':
 274                                         $lookAhead = ( $idx + 1 < $maxLen ) ? $str[$idx + 1] : '';
 275                                         $lookBehind = ( $idx - 1 >= 0 ) ? $str[$idx - 1] : '';
 276                                         if ( $inString ) {
 277                                                 continue;
 278
 279                                         } elseif ( !$inComment &&
 280                                                 ( $lookAhead === '/' || $lookAhead === '*' )
 281                                         ) {
 282                                                 // Transition into a comment
 283                                                 // Add characters seen to buffer
 284                                                 $buffer .= substr( $str, $mark, $idx - $mark );
 285                                                 // Consume the look ahead character
 286                                                 $idx++;
 287                                                 // Track state
 288                                                 $inComment = true;
 289                                                 $multiline = $lookAhead === '*';
 290
 291                                         } elseif ( $multiline && $lookBehind === '*' ) {
 292                                                 // Found the end of the current comment
 293                                                 $mark = $idx + 1;
 294                                                 $inComment = false;
 295                                                 $multiline = false;
 296                                         }
 297                                         break;
 298
 299                                 case "\n":
 300                                         if ( $inComment && !$multiline ) {
 301                                                 // Found the end of the current comment
 302                                                 $mark = $idx + 1;
 303                                                 $inComment = false;
 304                                         }
 305                                         break;
 306                         }
 307                 }
 308                 if ( $inComment ) {
 309                         // Comment ends with input
 310                         // Technically we should check to ensure that we aren't in
 311                         // a multiline comment that hasn't been properly ended, but this
 312                         // is a strip filter, not a validating parser.
 313                         $mark = $maxLen;
 314                 }
 315                 // Add final chunk to buffer before returning
 316                 return $buffer . substr( $str, $mark, $maxLen - $mark );
 317         }
 318 }