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