mirror of
https://github.com/ezyang/htmlpurifier.git
synced 2024-12-23 08:51:53 +00:00
541 lines
23 KiB
PHP
541 lines
23 KiB
PHP
<?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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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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* iconv wrapper which mutes errors, but doesn't work around bugs.
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*/
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public static function unsafeIconv($in, $out, $text) {
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set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler'));
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$r = iconv($in, $out, $text);
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restore_error_handler();
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return $r;
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}
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/**
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* iconv wrapper which mutes errors and works around bugs.
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*/
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public static function iconv($in, $out, $text, $max_chunk_size = 8000) {
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$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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* @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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* Once again, PHP 6 should solve all our problems.
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*/
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public static function cleanUTF8($str, $force_php = false) {
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// UTF-8 validity is checked since PHP 4.3.5
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// This is an optimization: if the string is already valid UTF-8, no
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// need to do PHP stuff. 99% of the time, this will be the case.
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// The regexp matches the XML char production, as well as well as excluding
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// non-SGML codepoints U+007F to U+009F
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if (preg_match('/^[\x{9}\x{A}\x{D}\x{20}-\x{7E}\x{A0}-\x{D7FF}\x{E000}-\x{FFFD}\x{10000}-\x{10FFFF}]*$/Du', $str)) {
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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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// 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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(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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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) $ret .= chr($w);
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if($z) $ret .= chr($z);
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if($y) $ret .= chr($y);
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$ret .= chr($x);
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return $ret;
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}
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public static function iconvAvailable() {
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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 $iconv;
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}
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/**
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* Converts a string to UTF-8 based on configuration.
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*/
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public static function convertToUTF8($str, $config, $context) {
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$encoding = $config->get('Core.Encoding');
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if ($encoding === 'utf-8') return $str;
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static $iconv = null;
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if ($iconv === null) $iconv = self::iconvAvailable();
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if ($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') {
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$str = utf8_encode($str);
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return $str;
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}
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trigger_error('Encoding not supported, please install iconv', E_USER_ERROR);
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}
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/**
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* Converts a string from UTF-8 based on configuration.
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* @note Currently, this is a lossy conversion, with unexpressable
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* characters being omitted.
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*/
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public static function convertFromUTF8($str, $config, $context) {
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$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') return $str;
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static $iconv = null;
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if ($iconv === null) $iconv = self::iconvAvailable();
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if ($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) $clear_fix[$utf8] = '';
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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') {
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$str = utf8_decode($str);
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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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* Lossless (character-wise) conversion of HTML to ASCII
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* @param $str UTF-8 string to be converted to ASCII
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* @returns 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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$bytesleft = 0;
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$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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/** No bugs detected in iconv. */
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const ICONV_OK = 0;
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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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/** 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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* 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
|
|
* 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.
|
|
*
|
|
* @returns 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
|