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<?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