wp-includes/Requests/IDNAEncoder.php

   1 <?php
   2
   3 /**
   4  * IDNA URL encoder
   5  *
   6  * Note: Not fully compliant, as nameprep does nothing yet.
   7  *
   8  * @package Requests
   9  * @subpackage Utilities
  10  * @see https://tools.ietf.org/html/rfc3490 IDNA specification
  11  * @see https://tools.ietf.org/html/rfc3492 Punycode/Bootstrap specification
  12  */
  13 class Requests_IDNAEncoder {
  14         /**
  15          * ACE prefix used for IDNA
  16          *
  17          * @see https://tools.ietf.org/html/rfc3490#section-5
  18          * @var string
  19          */
  20         const ACE_PREFIX = 'xn--';
  21
  22         /**#@+
  23          * Bootstrap constant for Punycode
  24          *
  25          * @see https://tools.ietf.org/html/rfc3492#section-5
  26          * @var int
  27          */
  28         const BOOTSTRAP_BASE         = 36;
  29         const BOOTSTRAP_TMIN         = 1;
  30         const BOOTSTRAP_TMAX         = 26;
  31         const BOOTSTRAP_SKEW         = 38;
  32         const BOOTSTRAP_DAMP         = 700;
  33         const BOOTSTRAP_INITIAL_BIAS = 72;
  34         const BOOTSTRAP_INITIAL_N    = 128;
  35         /**#@-*/
  36
  37         /**
  38          * Encode a hostname using Punycode
  39          *
  40          * @param string $string Hostname
  41          * @return string Punycode-encoded hostname
  42          */
  43         public static function encode($string) {
  44                 $parts = explode('.', $string);
  45                 foreach ($parts as &$part) {
  46                         $part = self::to_ascii($part);
  47                 }
  48                 return implode('.', $parts);
  49         }
  50
  51         /**
  52          * Convert a UTF-8 string to an ASCII string using Punycode
  53          *
  54          * @throws Requests_Exception Provided string longer than 64 ASCII characters (`idna.provided_too_long`)
  55          * @throws Requests_Exception Prepared string longer than 64 ASCII characters (`idna.prepared_too_long`)
  56          * @throws Requests_Exception Provided string already begins with xn-- (`idna.provided_is_prefixed`)
  57          * @throws Requests_Exception Encoded string longer than 64 ASCII characters (`idna.encoded_too_long`)
  58          *
  59          * @param string $string ASCII or UTF-8 string (max length 64 characters)
  60          * @return string ASCII string
  61          */
  62         public static function to_ascii($string) {
  63                 // Step 1: Check if the string is already ASCII
  64                 if (self::is_ascii($string)) {
  65                         // Skip to step 7
  66                         if (strlen($string) < 64) {
  67                                 return $string;
  68                         }
  69
  70                         throw new Requests_Exception('Provided string is too long', 'idna.provided_too_long', $string);
  71                 }
  72
  73                 // Step 2: nameprep
  74                 $string = self::nameprep($string);
  75
  76                 // Step 3: UseSTD3ASCIIRules is false, continue
  77                 // Step 4: Check if it's ASCII now
  78                 if (self::is_ascii($string)) {
  79                         // Skip to step 7
  80                         if (strlen($string) < 64) {
  81                                 return $string;
  82                         }
  83
  84                         throw new Requests_Exception('Prepared string is too long', 'idna.prepared_too_long', $string);
  85                 }
  86
  87                 // Step 5: Check ACE prefix
  88                 if (strpos($string, self::ACE_PREFIX) === 0) {
  89                         throw new Requests_Exception('Provided string begins with ACE prefix', 'idna.provided_is_prefixed', $string);
  90                 }
  91
  92                 // Step 6: Encode with Punycode
  93                 $string = self::punycode_encode($string);
  94
  95                 // Step 7: Prepend ACE prefix
  96                 $string = self::ACE_PREFIX . $string;
  97
  98                 // Step 8: Check size
  99                 if (strlen($string) < 64) {
 100                         return $string;
 101                 }
 102
 103                 throw new Requests_Exception('Encoded string is too long', 'idna.encoded_too_long', $string);
 104         }
 105
 106         /**
 107          * Check whether a given string contains only ASCII characters
 108          *
 109          * @internal (Testing found regex was the fastest implementation)
 110          *
 111          * @param string $string
 112          * @return bool Is the string ASCII-only?
 113          */
 114         protected static function is_ascii($string) {
 115                 return (preg_match('/(?:[^\x00-\x7F])/', $string) !== 1);
 116         }
 117
 118         /**
 119          * Prepare a string for use as an IDNA name
 120          *
 121          * @todo Implement this based on RFC 3491 and the newer 5891
 122          * @param string $string
 123          * @return string Prepared string
 124          */
 125         protected static function nameprep($string) {
 126                 return $string;
 127         }
 128
 129         /**
 130          * Convert a UTF-8 string to a UCS-4 codepoint array
 131          *
 132          * Based on Requests_IRI::replace_invalid_with_pct_encoding()
 133          *
 134          * @throws Requests_Exception Invalid UTF-8 codepoint (`idna.invalidcodepoint`)
 135          * @param string $input
 136          * @return array Unicode code points
 137          */
 138         protected static function utf8_to_codepoints($input) {
 139                 $codepoints = array();
 140
 141                 // Get number of bytes
 142                 $strlen = strlen($input);
 143
 144                 for ($position = 0; $position < $strlen; $position++) {
 145                         $value = ord($input[$position]);
 146
 147                         // One byte sequence:
 148                         if ((~$value & 0x80) === 0x80) {
 149                                 $character = $value;
 150                                 $length = 1;
 151                                 $remaining = 0;
 152                         }
 153                         // Two byte sequence:
 154                         elseif (($value & 0xE0) === 0xC0) {
 155                                 $character = ($value & 0x1F) << 6;
 156                                 $length = 2;
 157                                 $remaining = 1;
 158                         }
 159                         // Three byte sequence:
 160                         elseif (($value & 0xF0) === 0xE0) {
 161                                 $character = ($value & 0x0F) << 12;
 162                                 $length = 3;
 163                                 $remaining = 2;
 164                         }
 165                         // Four byte sequence:
 166                         elseif (($value & 0xF8) === 0xF0) {
 167                                 $character = ($value & 0x07) << 18;
 168                                 $length = 4;
 169                                 $remaining = 3;
 170                         }
 171                         // Invalid byte:
 172                         else {
 173                                 throw new Requests_Exception('Invalid Unicode codepoint', 'idna.invalidcodepoint', $value);
 174                         }
 175
 176                         if ($remaining > 0) {
 177                                 if ($position + $length > $strlen) {
 178                                         throw new Requests_Exception('Invalid Unicode codepoint', 'idna.invalidcodepoint', $character);
 179                                 }
 180                                 for ($position++; $remaining > 0; $position++) {
 181                                         $value = ord($input[$position]);
 182
 183                                         // If it is invalid, count the sequence as invalid and reprocess the current byte:
 184                                         if (($value & 0xC0) !== 0x80) {
 185                                                 throw new Requests_Exception('Invalid Unicode codepoint', 'idna.invalidcodepoint', $character);
 186                                         }
 187
 188                                         $character |= ($value & 0x3F) << (--$remaining * 6);
 189                                 }
 190                                 $position--;
 191                         }
 192
 193                         if (
 194                                 // Non-shortest form sequences are invalid
 195                                    $length > 1 && $character <= 0x7F
 196                                 || $length > 2 && $character <= 0x7FF
 197                                 || $length > 3 && $character <= 0xFFFF
 198                                 // Outside of range of ucschar codepoints
 199                                 // Noncharacters
 200                                 || ($character & 0xFFFE) === 0xFFFE
 201                                 || $character >= 0xFDD0 && $character <= 0xFDEF
 202                                 || (
 203                                         // Everything else not in ucschar
 204                                            $character > 0xD7FF && $character < 0xF900
 205                                         || $character < 0x20
 206                                         || $character > 0x7E && $character < 0xA0
 207                                         || $character > 0xEFFFD
 208                                 )
 209                         ) {
 210                                 throw new Requests_Exception('Invalid Unicode codepoint', 'idna.invalidcodepoint', $character);
 211                         }
 212
 213                         $codepoints[] = $character;
 214                 }
 215
 216                 return $codepoints;
 217         }
 218
 219         /**
 220          * RFC3492-compliant encoder
 221          *
 222          * @internal Pseudo-code from Section 6.3 is commented with "#" next to relevant code
 223          * @throws Requests_Exception On character outside of the domain (never happens with Punycode) (`idna.character_outside_domain`)
 224          *
 225          * @param string $input UTF-8 encoded string to encode
 226          * @return string Punycode-encoded string
 227          */
 228         public static function punycode_encode($input) {
 229                 $output = '';
 230 #               let n = initial_n
 231                 $n = self::BOOTSTRAP_INITIAL_N;
 232 #               let delta = 0
 233                 $delta = 0;
 234 #               let bias = initial_bias
 235                 $bias = self::BOOTSTRAP_INITIAL_BIAS;
 236 #               let h = b = the number of basic code points in the input
 237                 $h = $b = 0; // see loop
 238 #               copy them to the output in order
 239                 $codepoints = self::utf8_to_codepoints($input);
 240                 $extended = array();
 241
 242                 foreach ($codepoints as $char) {
 243                         if ($char < 128) {
 244                                 // Character is valid ASCII
 245                                 // TODO: this should also check if it's valid for a URL
 246                                 $output .= chr($char);
 247                                 $h++;
 248                         }
 249                         // Check if the character is non-ASCII, but below initial n
 250                         // This never occurs for Punycode, so ignore in coverage
 251                         // @codeCoverageIgnoreStart
 252                         elseif ($char < $n) {
 253                                 throw new Requests_Exception('Invalid character', 'idna.character_outside_domain', $char);
 254                         }
 255                         // @codeCoverageIgnoreEnd
 256                         else {
 257                                 $extended[$char] = true;
 258                         }
 259                 }
 260                 $extended = array_keys($extended);
 261                 sort($extended);
 262                 $b = $h;
 263 #               [copy them] followed by a delimiter if b > 0
 264                 if (strlen($output) > 0) {
 265                         $output .= '-';
 266                 }
 267 #               {if the input contains a non-basic code point < n then fail}
 268 #               while h < length(input) do begin
 269                 while ($h < count($codepoints)) {
 270 #                       let m = the minimum code point >= n in the input
 271                         $m = array_shift($extended);
 272                         //printf('next code point to insert is %s' . PHP_EOL, dechex($m));
 273 #                       let delta = delta + (m - n) * (h + 1), fail on overflow
 274                         $delta += ($m - $n) * ($h + 1);
 275 #                       let n = m
 276                         $n = $m;
 277 #                       for each code point c in the input (in order) do begin
 278                         for ($num = 0; $num < count($codepoints); $num++) {
 279                                 $c = $codepoints[$num];
 280 #                               if c < n then increment delta, fail on overflow
 281                                 if ($c < $n) {
 282                                         $delta++;
 283                                 }
 284 #                               if c == n then begin
 285                                 elseif ($c === $n) {
 286 #                                       let q = delta
 287                                         $q = $delta;
 288 #                                       for k = base to infinity in steps of base do begin
 289                                         for ($k = self::BOOTSTRAP_BASE; ; $k += self::BOOTSTRAP_BASE) {
 290 #                                               let t = tmin if k <= bias {+ tmin}, or
 291 #                                                               tmax if k >= bias + tmax, or k - bias otherwise
 292                                                 if ($k <= ($bias + self::BOOTSTRAP_TMIN)) {
 293                                                         $t = self::BOOTSTRAP_TMIN;
 294                                                 }
 295                                                 elseif ($k >= ($bias + self::BOOTSTRAP_TMAX)) {
 296                                                         $t = self::BOOTSTRAP_TMAX;
 297                                                 }
 298                                                 else {
 299                                                         $t = $k - $bias;
 300                                                 }
 301 #                                               if q < t then break
 302                                                 if ($q < $t) {
 303                                                         break;
 304                                                 }
 305 #                                               output the code point for digit t + ((q - t) mod (base - t))
 306                                                 $digit = $t + (($q - $t) % (self::BOOTSTRAP_BASE - $t));
 307                                                 $output .= self::digit_to_char($digit);
 308 #                                               let q = (q - t) div (base - t)
 309                                                 $q = floor(($q - $t) / (self::BOOTSTRAP_BASE - $t));
 310 #                                       end
 311                                         }
 312 #                                       output the code point for digit q
 313                                         $output .= self::digit_to_char($q);
 314 #                                       let bias = adapt(delta, h + 1, test h equals b?)
 315                                         $bias = self::adapt($delta, $h + 1, $h === $b);
 316 #                                       let delta = 0
 317                                         $delta = 0;
 318 #                                       increment h
 319                                         $h++;
 320 #                               end
 321                                 }
 322 #                       end
 323                         }
 324 #                       increment delta and n
 325                         $delta++;
 326                         $n++;
 327 #               end
 328                 }
 329
 330                 return $output;
 331         }
 332
 333         /**
 334          * Convert a digit to its respective character
 335          *
 336          * @see https://tools.ietf.org/html/rfc3492#section-5
 337          * @throws Requests_Exception On invalid digit (`idna.invalid_digit`)
 338          *
 339          * @param int $digit Digit in the range 0-35
 340          * @return string Single character corresponding to digit
 341          */
 342         protected static function digit_to_char($digit) {
 343                 // @codeCoverageIgnoreStart
 344                 // As far as I know, this never happens, but still good to be sure.
 345                 if ($digit < 0 || $digit > 35) {
 346                         throw new Requests_Exception(sprintf('Invalid digit %d', $digit), 'idna.invalid_digit', $digit);
 347                 }
 348                 // @codeCoverageIgnoreEnd
 349                 $digits = 'abcdefghijklmnopqrstuvwxyz0123456789';
 350                 return substr($digits, $digit, 1);
 351         }
 352
 353         /**
 354          * Adapt the bias
 355          *
 356          * @see https://tools.ietf.org/html/rfc3492#section-6.1
 357          * @param int $delta
 358          * @param int $numpoints
 359          * @param bool $firsttime
 360          * @return int New bias
 361          */
 362         protected static function adapt($delta, $numpoints, $firsttime) {
 363 #       function adapt(delta,numpoints,firsttime):
 364 #               if firsttime then let delta = delta div damp
 365                 if ($firsttime) {
 366                         $delta = floor($delta / self::BOOTSTRAP_DAMP);
 367                 }
 368 #               else let delta = delta div 2
 369                 else {
 370                         $delta = floor($delta / 2);
 371                 }
 372 #               let delta = delta + (delta div numpoints)
 373                 $delta += floor($delta / $numpoints);
 374 #               let k = 0
 375                 $k = 0;
 376 #               while delta > ((base - tmin) * tmax) div 2 do begin
 377                 $max = floor(((self::BOOTSTRAP_BASE - self::BOOTSTRAP_TMIN) * self::BOOTSTRAP_TMAX) / 2);
 378                 while ($delta > $max) {
 379 #                       let delta = delta div (base - tmin)
 380                         $delta = floor($delta / (self::BOOTSTRAP_BASE - self::BOOTSTRAP_TMIN));
 381 #                       let k = k + base
 382                         $k += self::BOOTSTRAP_BASE;
 383 #               end
 384                 }
 385 #               return k + (((base - tmin + 1) * delta) div (delta + skew))
 386                 return $k + floor(((self::BOOTSTRAP_BASE - self::BOOTSTRAP_TMIN + 1) * $delta) / ($delta + self::BOOTSTRAP_SKEW));
 387         }
 388 }