File indexing completed on 2024-12-22 05:36:21

 <?php
 
 /**
  * A UTF-8 specific character encoder that handles cleaning and transforming.
  * @note All functions in this class should be static.
  */
 class HTMLPurifier_Encoder
 {
 
     /**
      * Constructor throws fatal error if you attempt to instantiate class
      */
     private function __construct()
     {
         trigger_error('Cannot instantiate encoder, call methods statically', E_USER_ERROR);
     }
 
     /**
      * Error-handler that mutes errors, alternative to shut-up operator.
      */
     public static function muteErrorHandler()
     {
     }
 
     /**
      * iconv wrapper which mutes errors, but doesn't work around bugs.
      * @param string $in Input encoding
      * @param string $out Output encoding
      * @param string $text The text to convert
      * @return string
      */
     public static function unsafeIconv($in, $out, $text)
     {
         set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler'));
         $r = iconv($in, $out, $text);
         restore_error_handler();
         return $r;
     }
 
     /**
      * iconv wrapper which mutes errors and works around bugs.
      * @param string $in Input encoding
      * @param string $out Output encoding
      * @param string $text The text to convert
      * @param int $max_chunk_size
      * @return string
      */
     public static function iconv($in, $out, $text, $max_chunk_size = 8000)
     {
         $code = self::testIconvTruncateBug();
         if ($code == self::ICONV_OK) {
             return self::unsafeIconv($in, $out, $text);
         } elseif ($code == self::ICONV_TRUNCATES) {
             // we can only work around this if the input character set
             // is utf-8
             if ($in == 'utf-8') {
                 if ($max_chunk_size < 4) {
                     trigger_error('max_chunk_size is too small', E_USER_WARNING);
                     return false;
                 }
                 // split into 8000 byte chunks, but be careful to handle
                 // multibyte boundaries properly
                 if (($c = strlen($text)) <= $max_chunk_size) {
                     return self::unsafeIconv($in, $out, $text);
                 }
                 $r = '';
                 $i = 0;
                 while (true) {
                     if ($i + $max_chunk_size >= $c) {
                         $r .= self::unsafeIconv($in, $out, substr($text, $i));
                         break;
                     }
                     // wibble the boundary
                     if (0x80 != (0xC0 & ord($text[$i + $max_chunk_size]))) {
                         $chunk_size = $max_chunk_size;
                     } elseif (0x80 != (0xC0 & ord($text[$i + $max_chunk_size - 1]))) {
                         $chunk_size = $max_chunk_size - 1;
                     } elseif (0x80 != (0xC0 & ord($text[$i + $max_chunk_size - 2]))) {
                         $chunk_size = $max_chunk_size - 2;
                     } elseif (0x80 != (0xC0 & ord($text[$i + $max_chunk_size - 3]))) {
                         $chunk_size = $max_chunk_size - 3;
                     } else {
                         return false; // rather confusing UTF-8...
                     }
                     $chunk = substr($text, $i, $chunk_size); // substr doesn't mind overlong lengths
                     $r .= self::unsafeIconv($in, $out, $chunk);
                     $i += $chunk_size;
                 }
                 return $r;
             } else {
                 return false;
             }
         } else {
             return false;
         }
     }
 
     /**
      * Cleans a UTF-8 string for well-formedness and SGML validity
      *
      * It will parse according to UTF-8 and return a valid UTF8 string, with
      * non-SGML codepoints excluded.
      *
      * Specifically, it will permit:
      * \x{9}\x{A}\x{D}\x{20}-\x{7E}\x{A0}-\x{D7FF}\x{E000}-\x{FFFD}\x{10000}-\x{10FFFF}
      * Source: https://www.w3.org/TR/REC-xml/#NT-Char
      * Arguably this function should be modernized to the HTML5 set
      * of allowed characters:
      * https://www.w3.org/TR/html5/syntax.html#preprocessing-the-input-stream
      * which simultaneously expand and restrict the set of allowed characters.
      *
      * @param string $str The string to clean
      * @param bool $force_php
      * @return string
      *
      * @note Just for reference, the non-SGML code points are 0 to 31 and
      *       127 to 159, inclusive.  However, we allow code points 9, 10
      *       and 13, which are the tab, line feed and carriage return
      *       respectively. 128 and above the code points map to multibyte
      *       UTF-8 representations.
      *
      * @note Fallback code adapted from utf8ToUnicode by Henri Sivonen and
      *       hsivonen@iki.fi at <http://iki.fi/hsivonen/php-utf8/> under the
      *       LGPL license.  Notes on what changed are inside, but in general,
      *       the original code transformed UTF-8 text into an array of integer
      *       Unicode codepoints. Understandably, transforming that back to
      *       a string would be somewhat expensive, so the function was modded to
      *       directly operate on the string.  However, this discourages code
      *       reuse, and the logic enumerated here would be useful for any
      *       function that needs to be able to understand UTF-8 characters.
      *       As of right now, only smart lossless character encoding converters
      *       would need that, and I'm probably not going to implement them.
      */
     public static function cleanUTF8($str, $force_php = false)
     {
         // UTF-8 validity is checked since PHP 4.3.5
         // This is an optimization: if the string is already valid UTF-8, no
         // need to do PHP stuff. 99% of the time, this will be the case.
         if (preg_match(
             '/^[\x{9}\x{A}\x{D}\x{20}-\x{7E}\x{A0}-\x{D7FF}\x{E000}-\x{FFFD}\x{10000}-\x{10FFFF}]*$/Du',
             $str
         )) {
             return $str;
         }
 
         $mState = 0; // cached expected number of octets after the current octet
                      // until the beginning of the next UTF8 character sequence
         $mUcs4  = 0; // cached Unicode character
         $mBytes = 1; // cached expected number of octets in the current sequence
 
         // original code involved an $out that was an array of Unicode
         // codepoints.  Instead of having to convert back into UTF-8, we've
         // decided to directly append valid UTF-8 characters onto a string
         // $out once they're done.  $char accumulates raw bytes, while $mUcs4
         // turns into the Unicode code point, so there's some redundancy.
 
         $out = '';
         $char = '';
 
         $len = strlen($str);
         for ($i = 0; $i < $len; $i++) {
             $in = ord($str{$i});
             $char .= $str[$i]; // append byte to char
             if (0 == $mState) {
                 // When mState is zero we expect either a US-ASCII character
                 // or a multi-octet sequence.
                 if (0 == (0x80 & ($in))) {
                     // US-ASCII, pass straight through.
                     if (($in <= 31 || $in == 127) &&
                         !($in == 9 || $in == 13 || $in == 10) // save \r\t\n
                     ) {
                         // control characters, remove
                     } else {
                         $out .= $char;
                     }
                     // reset
                     $char = '';
                     $mBytes = 1;
                 } elseif (0xC0 == (0xE0 & ($in))) {
                     // First octet of 2 octet sequence
                     $mUcs4 = ($in);
                     $mUcs4 = ($mUcs4 & 0x1F) << 6;
                     $mState = 1;
                     $mBytes = 2;
                 } elseif (0xE0 == (0xF0 & ($in))) {
                     // First octet of 3 octet sequence
                     $mUcs4 = ($in);
                     $mUcs4 = ($mUcs4 & 0x0F) << 12;
                     $mState = 2;
                     $mBytes = 3;
                 } elseif (0xF0 == (0xF8 & ($in))) {
                     // First octet of 4 octet sequence
                     $mUcs4 = ($in);
                     $mUcs4 = ($mUcs4 & 0x07) << 18;
                     $mState = 3;
                     $mBytes = 4;
                 } elseif (0xF8 == (0xFC & ($in))) {
                     // First octet of 5 octet sequence.
                     //
                     // This is illegal because the encoded codepoint must be
                     // either:
                     // (a) not the shortest form or
                     // (b) outside the Unicode range of 0-0x10FFFF.
                     // Rather than trying to resynchronize, we will carry on
                     // until the end of the sequence and let the later error
                     // handling code catch it.
                     $mUcs4 = ($in);
                     $mUcs4 = ($mUcs4 & 0x03) << 24;
                     $mState = 4;
                     $mBytes = 5;
                 } elseif (0xFC == (0xFE & ($in))) {
                     // First octet of 6 octet sequence, see comments for 5
                     // octet sequence.
                     $mUcs4 = ($in);
                     $mUcs4 = ($mUcs4 & 1) << 30;
                     $mState = 5;
                     $mBytes = 6;
                 } else {
                     // Current octet is neither in the US-ASCII range nor a
                     // legal first octet of a multi-octet sequence.
                     $mState = 0;
                     $mUcs4  = 0;
                     $mBytes = 1;
                     $char = '';
                 }
             } else {
                 // When mState is non-zero, we expect a continuation of the
                 // multi-octet sequence
                 if (0x80 == (0xC0 & ($in))) {
                     // Legal continuation.
                     $shift = ($mState - 1) * 6;
                     $tmp = $in;
                     $tmp = ($tmp & 0x0000003F) << $shift;
                     $mUcs4 |= $tmp;
 
                     if (0 == --$mState) {
                         // End of the multi-octet sequence. mUcs4 now contains
                         // the final Unicode codepoint to be output
 
                         // Check for illegal sequences and codepoints.
 
                         // From Unicode 3.1, non-shortest form is illegal
                         if (((2 == $mBytes) && ($mUcs4 < 0x0080)) ||
                             ((3 == $mBytes) && ($mUcs4 < 0x0800)) ||
                             ((4 == $mBytes) && ($mUcs4 < 0x10000)) ||
                             (4 < $mBytes) ||
                             // From Unicode 3.2, surrogate characters = illegal
                             (($mUcs4 & 0xFFFFF800) == 0xD800) ||
                             // Codepoints outside the Unicode range are illegal
                             ($mUcs4 > 0x10FFFF)
                         ) {
 
                         } elseif (0xFEFF != $mUcs4 && // omit BOM
                             // check for valid Char unicode codepoints
                             (
                                 0x9 == $mUcs4 ||
                                 0xA == $mUcs4 ||
                                 0xD == $mUcs4 ||
                                 (0x20 <= $mUcs4 && 0x7E >= $mUcs4) ||
                                 // 7F-9F is not strictly prohibited by XML,
                                 // but it is non-SGML, and thus we don't allow it
                                 (0xA0 <= $mUcs4 && 0xD7FF >= $mUcs4) ||
                                 (0xE000 <= $mUcs4 && 0xFFFD >= $mUcs4) ||
                                 (0x10000 <= $mUcs4 && 0x10FFFF >= $mUcs4)
                             )
                         ) {
                             $out .= $char;
                         }
                         // initialize UTF8 cache (reset)
                         $mState = 0;
                         $mUcs4  = 0;
                         $mBytes = 1;
                         $char = '';
                     }
                 } else {
                     // ((0xC0 & (*in) != 0x80) && (mState != 0))
                     // Incomplete multi-octet sequence.
                     // used to result in complete fail, but we'll reset
                     $mState = 0;
                     $mUcs4  = 0;
                     $mBytes = 1;
                     $char ='';
                 }
             }
         }
         return $out;
     }
 
     /**
      * Translates a Unicode codepoint into its corresponding UTF-8 character.
      * @note Based on Feyd's function at
      *       <http://forums.devnetwork.net/viewtopic.php?p=191404#191404>,
      *       which is in public domain.
      * @note While we're going to do code point parsing anyway, a good
      *       optimization would be to refuse to translate code points that
      *       are non-SGML characters.  However, this could lead to duplication.
      * @note This is very similar to the unichr function in
      *       maintenance/generate-entity-file.php (although this is superior,
      *       due to its sanity checks).
      */
 
     // +----------+----------+----------+----------+
     // | 33222222 | 22221111 | 111111   |          |
     // | 10987654 | 32109876 | 54321098 | 76543210 | bit
     // +----------+----------+----------+----------+
     // |          |          |          | 0xxxxxxx | 1 byte 0x00000000..0x0000007F
     // |          |          | 110yyyyy | 10xxxxxx | 2 byte 0x00000080..0x000007FF
     // |          | 1110zzzz | 10yyyyyy | 10xxxxxx | 3 byte 0x00000800..0x0000FFFF
     // | 11110www | 10wwzzzz | 10yyyyyy | 10xxxxxx | 4 byte 0x00010000..0x0010FFFF
     // +----------+----------+----------+----------+
     // | 00000000 | 00011111 | 11111111 | 11111111 | Theoretical upper limit of legal scalars: 2097151 (0x001FFFFF)
     // | 00000000 | 00010000 | 11111111 | 11111111 | Defined upper limit of legal scalar codes
     // +----------+----------+----------+----------+
 
     public static function unichr($code)
     {
         if ($code > 1114111 or $code < 0 or
           ($code >= 55296 and $code <= 57343) ) {
             // bits are set outside the "valid" range as defined
             // by UNICODE 4.1.0
             return '';
         }
 
         $x = $y = $z = $w = 0;
         if ($code < 128) {
             // regular ASCII character
             $x = $code;
         } else {
             // set up bits for UTF-8
             $x = ($code & 63) | 128;
             if ($code < 2048) {
                 $y = (($code & 2047) >> 6) | 192;
             } else {
                 $y = (($code & 4032) >> 6) | 128;
                 if ($code < 65536) {
                     $z = (($code >> 12) & 15) | 224;
                 } else {
                     $z = (($code >> 12) & 63) | 128;
                     $w = (($code >> 18) & 7)  | 240;
                 }
             }
         }
         // set up the actual character
         $ret = '';
         if ($w) {
             $ret .= chr($w);
         }
         if ($z) {
             $ret .= chr($z);
         }
         if ($y) {
             $ret .= chr($y);
         }
         $ret .= chr($x);
 
         return $ret;
     }
 
     /**
      * @return bool
      */
     public static function iconvAvailable()
     {
         static $iconv = null;
         if ($iconv === null) {
             $iconv = function_exists('iconv') && self::testIconvTruncateBug() != self::ICONV_UNUSABLE;
         }
         return $iconv;
     }
 
     /**
      * Convert a string to UTF-8 based on configuration.
      * @param string $str The string to convert
      * @param HTMLPurifier_Config $config
      * @param HTMLPurifier_Context $context
      * @return string
      */
     public static function convertToUTF8($str, $config, $context)
     {
         $encoding = $config->get('Core.Encoding');
         if ($encoding === 'utf-8') {
             return $str;
         }
         static $iconv = null;
         if ($iconv === null) {
             $iconv = self::iconvAvailable();
         }
         if ($iconv && !$config->get('Test.ForceNoIconv')) {
             // unaffected by bugs, since UTF-8 support all characters
             $str = self::unsafeIconv($encoding, 'utf-8//IGNORE', $str);
             if ($str === false) {
                 // $encoding is not a valid encoding
                 trigger_error('Invalid encoding ' . $encoding, E_USER_ERROR);
                 return '';
             }
             // If the string is bjorked by Shift_JIS or a similar encoding
             // that doesn't support all of ASCII, convert the naughty
             // characters to their true byte-wise ASCII/UTF-8 equivalents.
             $str = strtr($str, self::testEncodingSupportsASCII($encoding));
             return $str;
         } elseif ($encoding === 'iso-8859-1') {
             $str = utf8_encode($str);
             return $str;
         }
         $bug = HTMLPurifier_Encoder::testIconvTruncateBug();
         if ($bug == self::ICONV_OK) {
             trigger_error('Encoding not supported, please install iconv', E_USER_ERROR);
         } else {
             trigger_error(
                 'You have a buggy version of iconv, see https://bugs.php.net/bug.php?id=48147 ' .
                 'and http://sourceware.org/bugzilla/show_bug.cgi?id=13541',
                 E_USER_ERROR
             );
         }
     }
 
     /**
      * Converts a string from UTF-8 based on configuration.
      * @param string $str The string to convert
      * @param HTMLPurifier_Config $config
      * @param HTMLPurifier_Context $context
      * @return string
      * @note Currently, this is a lossy conversion, with unexpressable
      *       characters being omitted.
      */
     public static function convertFromUTF8($str, $config, $context)
     {
         $encoding = $config->get('Core.Encoding');
         if ($escape = $config->get('Core.EscapeNonASCIICharacters')) {
             $str = self::convertToASCIIDumbLossless($str);
         }
         if ($encoding === 'utf-8') {
             return $str;
         }
         static $iconv = null;
         if ($iconv === null) {
             $iconv = self::iconvAvailable();
         }
         if ($iconv && !$config->get('Test.ForceNoIconv')) {
             // Undo our previous fix in convertToUTF8, otherwise iconv will barf
             $ascii_fix = self::testEncodingSupportsASCII($encoding);
             if (!$escape && !empty($ascii_fix)) {
                 $clear_fix = array();
                 foreach ($ascii_fix as $utf8 => $native) {
                     $clear_fix[$utf8] = '';
                 }
                 $str = strtr($str, $clear_fix);
             }
             $str = strtr($str, array_flip($ascii_fix));
             // Normal stuff
             $str = self::iconv('utf-8', $encoding . '//IGNORE', $str);
             return $str;
         } elseif ($encoding === 'iso-8859-1') {
             $str = utf8_decode($str);
             return $str;
         }
         trigger_error('Encoding not supported', E_USER_ERROR);
         // You might be tempted to assume that the ASCII representation
         // might be OK, however, this is *not* universally true over all
         // encodings.  So we take the conservative route here, rather
         // than forcibly turn on %Core.EscapeNonASCIICharacters
     }
 
     /**
      * Lossless (character-wise) conversion of HTML to ASCII
      * @param string $str UTF-8 string to be converted to ASCII
      * @return string ASCII encoded string with non-ASCII character entity-ized
      * @warning Adapted from MediaWiki, claiming fair use: this is a common
      *       algorithm. If you disagree with this license fudgery,
      *       implement it yourself.
      * @note Uses decimal numeric entities since they are best supported.
      * @note This is a DUMB function: it has no concept of keeping
      *       character entities that the projected character encoding
      *       can allow. We could possibly implement a smart version
      *       but that would require it to also know which Unicode
      *       codepoints the charset supported (not an easy task).
      * @note Sort of with cleanUTF8() but it assumes that $str is
      *       well-formed UTF-8
      */
     public static function convertToASCIIDumbLossless($str)
     {
         $bytesleft = 0;
         $result = '';
         $working = 0;
         $len = strlen($str);
         for ($i = 0; $i < $len; $i++) {
             $bytevalue = ord($str[$i]);
             if ($bytevalue <= 0x7F) { //0xxx xxxx
                 $result .= chr($bytevalue);
                 $bytesleft = 0;
             } elseif ($bytevalue <= 0xBF) { //10xx xxxx
                 $working = $working << 6;
                 $working += ($bytevalue & 0x3F);
                 $bytesleft--;
                 if ($bytesleft <= 0) {
                     $result .= "&#" . $working . ";";
                 }
             } elseif ($bytevalue <= 0xDF) { //110x xxxx
                 $working = $bytevalue & 0x1F;
                 $bytesleft = 1;
             } elseif ($bytevalue <= 0xEF) { //1110 xxxx
                 $working = $bytevalue & 0x0F;
                 $bytesleft = 2;
             } else { //1111 0xxx
                 $working = $bytevalue & 0x07;
                 $bytesleft = 3;
             }
         }
         return $result;
     }
 
     /** No bugs detected in iconv. */
     const ICONV_OK = 0;
 
     /** Iconv truncates output if converting from UTF-8 to another
      *  character set with //IGNORE, and a non-encodable character is found */
     const ICONV_TRUNCATES = 1;
 
     /** Iconv does not support //IGNORE, making it unusable for
      *  transcoding purposes */
     const ICONV_UNUSABLE = 2;
 
     /**
      * glibc iconv has a known bug where it doesn't handle the magic
      * //IGNORE stanza correctly.  In particular, rather than ignore
      * characters, it will return an EILSEQ after consuming some number
      * of characters, and expect you to restart iconv as if it were
      * an E2BIG.  Old versions of PHP did not respect the errno, and
      * returned the fragment, so as a result you would see iconv
      * mysteriously truncating output. We can work around this by
      * manually chopping our input into segments of about 8000
      * characters, as long as PHP ignores the error code.  If PHP starts
      * paying attention to the error code, iconv becomes unusable.
      *
      * @return int Error code indicating severity of bug.
      */
     public static function testIconvTruncateBug()
     {
         static $code = null;
         if ($code === null) {
             // better not use iconv, otherwise infinite loop!
             $r = self::unsafeIconv('utf-8', 'ascii//IGNORE', "\xCE\xB1" . str_repeat('a', 9000));
             if ($r === false) {
                 $code = self::ICONV_UNUSABLE;
             } elseif (($c = strlen($r)) < 9000) {
                 $code = self::ICONV_TRUNCATES;
             } elseif ($c > 9000) {
                 trigger_error(
                     'Your copy of iconv is extremely buggy. Please notify HTML Purifier maintainers: ' .
                     'include your iconv version as per phpversion()',
                     E_USER_ERROR
                 );
             } else {
                 $code = self::ICONV_OK;
             }
         }
         return $code;
     }
 
     /**
      * This expensive function tests whether or not a given character
      * encoding supports ASCII. 7/8-bit encodings like Shift_JIS will
      * fail this test, and require special processing. Variable width
      * encodings shouldn't ever fail.
      *
      * @param string $encoding Encoding name to test, as per iconv format
      * @param bool $bypass Whether or not to bypass the precompiled arrays.
      * @return Array of UTF-8 characters to their corresponding ASCII,
      *      which can be used to "undo" any overzealous iconv action.
      */
     public static function testEncodingSupportsASCII($encoding, $bypass = false)
     {
         // All calls to iconv here are unsafe, proof by case analysis:
         // If ICONV_OK, no difference.
         // If ICONV_TRUNCATE, all calls involve one character inputs,
         // so bug is not triggered.
         // If ICONV_UNUSABLE, this call is irrelevant
         static $encodings = array();
         if (!$bypass) {
             if (isset($encodings[$encoding])) {
                 return $encodings[$encoding];
             }
             $lenc = strtolower($encoding);
             switch ($lenc) {
                 case 'shift_jis':
                     return array("\xC2\xA5" => '\\', "\xE2\x80\xBE" => '~');
                 case 'johab':
                     return array("\xE2\x82\xA9" => '\\');
             }
             if (strpos($lenc, 'iso-8859-') === 0) {
                 return array();
             }
         }
         $ret = array();
         if (self::unsafeIconv('UTF-8', $encoding, 'a') === false) {
             return false;
         }
         for ($i = 0x20; $i <= 0x7E; $i++) { // all printable ASCII chars
             $c = chr($i); // UTF-8 char
             $r = self::unsafeIconv('UTF-8', "$encoding//IGNORE", $c); // initial conversion
             if ($r === '' ||
                 // This line is needed for iconv implementations that do not
                 // omit characters that do not exist in the target character set
                 ($r === $c && self::unsafeIconv($encoding, 'UTF-8//IGNORE', $r) !== $c)
             ) {
                 // Reverse engineer: what's the UTF-8 equiv of this byte
                 // sequence? This assumes that there's no variable width
                 // encoding that doesn't support ASCII.
                 $ret[self::unsafeIconv($encoding, 'UTF-8//IGNORE', $c)] = $c;
             }
         }
         $encodings[$encoding] = $ret;
         return $ret;
     }
 }
 
 // vim: et sw=4 sts=4