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   1  <?php
   2  
   3  namespace WpOrg\Requests;
   4  
   5  use WpOrg\Requests\Exception;
   6  use WpOrg\Requests\Exception\InvalidArgument;
   7  use WpOrg\Requests\Utility\InputValidator;
   8  
   9  /**
  10   * IDNA URL encoder
  11   *
  12   * Note: Not fully compliant, as nameprep does nothing yet.
  13   *
  14   * @package Requests\Utilities
  15   *
  16   * @link https://tools.ietf.org/html/rfc3490 IDNA specification
  17   * @link https://tools.ietf.org/html/rfc3492 Punycode/Bootstrap specification
  18   */
  19  class IdnaEncoder {
  20      /**
  21       * ACE prefix used for IDNA
  22       *
  23       * @link https://tools.ietf.org/html/rfc3490#section-5
  24       * @var string
  25       */
  26      const ACE_PREFIX = 'xn--';
  27  
  28      /**
  29       * Maximum length of a IDNA URL in ASCII.
  30       *
  31       * @see \WpOrg\Requests\IdnaEncoder::to_ascii()
  32       *
  33       * @since 2.0.0
  34       *
  35       * @var int
  36       */
  37      const MAX_LENGTH = 64;
  38  
  39      /**#@+
  40       * Bootstrap constant for Punycode
  41       *
  42       * @link https://tools.ietf.org/html/rfc3492#section-5
  43       * @var int
  44       */
  45      const BOOTSTRAP_BASE         = 36;
  46      const BOOTSTRAP_TMIN         = 1;
  47      const BOOTSTRAP_TMAX         = 26;
  48      const BOOTSTRAP_SKEW         = 38;
  49      const BOOTSTRAP_DAMP         = 700;
  50      const BOOTSTRAP_INITIAL_BIAS = 72;
  51      const BOOTSTRAP_INITIAL_N    = 128;
  52      /**#@-*/
  53  
  54      /**
  55       * Encode a hostname using Punycode
  56       *
  57       * @param string|Stringable $hostname Hostname
  58       * @return string Punycode-encoded hostname
  59       * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed argument is not a string or a stringable object.
  60       */
  61  	public static function encode($hostname) {
  62          if (InputValidator::is_string_or_stringable($hostname) === false) {
  63              throw InvalidArgument::create(1, '$hostname', 'string|Stringable', gettype($hostname));
  64          }
  65  
  66          $parts = explode('.', $hostname);
  67          foreach ($parts as &$part) {
  68              $part = self::to_ascii($part);
  69          }
  70  
  71          return implode('.', $parts);
  72      }
  73  
  74      /**
  75       * Convert a UTF-8 text string to an ASCII string using Punycode
  76       *
  77       * @param string $text ASCII or UTF-8 string (max length 64 characters)
  78       * @return string ASCII string
  79       *
  80       * @throws \WpOrg\Requests\Exception Provided string longer than 64 ASCII characters (`idna.provided_too_long`)
  81       * @throws \WpOrg\Requests\Exception Prepared string longer than 64 ASCII characters (`idna.prepared_too_long`)
  82       * @throws \WpOrg\Requests\Exception Provided string already begins with xn-- (`idna.provided_is_prefixed`)
  83       * @throws \WpOrg\Requests\Exception Encoded string longer than 64 ASCII characters (`idna.encoded_too_long`)
  84       */
  85  	public static function to_ascii($text) {
  86          // Step 1: Check if the text is already ASCII
  87          if (self::is_ascii($text)) {
  88              // Skip to step 7
  89              if (strlen($text) < self::MAX_LENGTH) {
  90                  return $text;
  91              }
  92  
  93              throw new Exception('Provided string is too long', 'idna.provided_too_long', $text);
  94          }
  95  
  96          // Step 2: nameprep
  97          $text = self::nameprep($text);
  98  
  99          // Step 3: UseSTD3ASCIIRules is false, continue
 100          // Step 4: Check if it's ASCII now
 101          if (self::is_ascii($text)) {
 102              // Skip to step 7
 103              /*
 104               * As the `nameprep()` method returns the original string, this code will never be reached until
 105               * that method is properly implemented.
 106               */
 107              // @codeCoverageIgnoreStart
 108              if (strlen($text) < self::MAX_LENGTH) {
 109                  return $text;
 110              }
 111  
 112              throw new Exception('Prepared string is too long', 'idna.prepared_too_long', $text);
 113              // @codeCoverageIgnoreEnd
 114          }
 115  
 116          // Step 5: Check ACE prefix
 117          if (strpos($text, self::ACE_PREFIX) === 0) {
 118              throw new Exception('Provided string begins with ACE prefix', 'idna.provided_is_prefixed', $text);
 119          }
 120  
 121          // Step 6: Encode with Punycode
 122          $text = self::punycode_encode($text);
 123  
 124          // Step 7: Prepend ACE prefix
 125          $text = self::ACE_PREFIX . $text;
 126  
 127          // Step 8: Check size
 128          if (strlen($text) < self::MAX_LENGTH) {
 129              return $text;
 130          }
 131  
 132          throw new Exception('Encoded string is too long', 'idna.encoded_too_long', $text);
 133      }
 134  
 135      /**
 136       * Check whether a given text string contains only ASCII characters
 137       *
 138       * @internal (Testing found regex was the fastest implementation)
 139       *
 140       * @param string $text Text to examine.
 141       * @return bool Is the text string ASCII-only?
 142       */
 143  	protected static function is_ascii($text) {
 144          return (preg_match('/(?:[^\x00-\x7F])/', $text) !== 1);
 145      }
 146  
 147      /**
 148       * Prepare a text string for use as an IDNA name
 149       *
 150       * @todo Implement this based on RFC 3491 and the newer 5891
 151       * @param string $text Text to prepare.
 152       * @return string Prepared string
 153       */
 154  	protected static function nameprep($text) {
 155          return $text;
 156      }
 157  
 158      /**
 159       * Convert a UTF-8 string to a UCS-4 codepoint array
 160       *
 161       * Based on \WpOrg\Requests\Iri::replace_invalid_with_pct_encoding()
 162       *
 163       * @param string $input Text to convert.
 164       * @return array Unicode code points
 165       *
 166       * @throws \WpOrg\Requests\Exception Invalid UTF-8 codepoint (`idna.invalidcodepoint`)
 167       */
 168  	protected static function utf8_to_codepoints($input) {
 169          $codepoints = [];
 170  
 171          // Get number of bytes
 172          $strlen = strlen($input);
 173  
 174          // phpcs:ignore Generic.CodeAnalysis.JumbledIncrementer -- This is a deliberate choice.
 175          for ($position = 0; $position < $strlen; $position++) {
 176              $value = ord($input[$position]);
 177  
 178              if ((~$value & 0x80) === 0x80) {            // One byte sequence:
 179                  $character = $value;
 180                  $length    = 1;
 181                  $remaining = 0;
 182              } elseif (($value & 0xE0) === 0xC0) {       // Two byte sequence:
 183                  $character = ($value & 0x1F) << 6;
 184                  $length    = 2;
 185                  $remaining = 1;
 186              } elseif (($value & 0xF0) === 0xE0) {       // Three byte sequence:
 187                  $character = ($value & 0x0F) << 12;
 188                  $length    = 3;
 189                  $remaining = 2;
 190              } elseif (($value & 0xF8) === 0xF0) {       // Four byte sequence:
 191                  $character = ($value & 0x07) << 18;
 192                  $length    = 4;
 193                  $remaining = 3;
 194              } else {                                    // Invalid byte:
 195                  throw new Exception('Invalid Unicode codepoint', 'idna.invalidcodepoint', $value);
 196              }
 197  
 198              if ($remaining > 0) {
 199                  if ($position + $length > $strlen) {
 200                      throw new Exception('Invalid Unicode codepoint', 'idna.invalidcodepoint', $character);
 201                  }
 202  
 203                  for ($position++; $remaining > 0; $position++) {
 204                      $value = ord($input[$position]);
 205  
 206                      // If it is invalid, count the sequence as invalid and reprocess the current byte:
 207                      if (($value & 0xC0) !== 0x80) {
 208                          throw new Exception('Invalid Unicode codepoint', 'idna.invalidcodepoint', $character);
 209                      }
 210  
 211                      --$remaining;
 212                      $character |= ($value & 0x3F) << ($remaining * 6);
 213                  }
 214  
 215                  $position--;
 216              }
 217  
 218              if (// Non-shortest form sequences are invalid
 219                  $length > 1 && $character <= 0x7F
 220                  || $length > 2 && $character <= 0x7FF
 221                  || $length > 3 && $character <= 0xFFFF
 222                  // Outside of range of ucschar codepoints
 223                  // Noncharacters
 224                  || ($character & 0xFFFE) === 0xFFFE
 225                  || $character >= 0xFDD0 && $character <= 0xFDEF
 226                  || (
 227                      // Everything else not in ucschar
 228                      $character > 0xD7FF && $character < 0xF900
 229                      || $character < 0x20
 230                      || $character > 0x7E && $character < 0xA0
 231                      || $character > 0xEFFFD
 232                  )
 233              ) {
 234                  throw new Exception('Invalid Unicode codepoint', 'idna.invalidcodepoint', $character);
 235              }
 236  
 237              $codepoints[] = $character;
 238          }
 239  
 240          return $codepoints;
 241      }
 242  
 243      /**
 244       * RFC3492-compliant encoder
 245       *
 246       * @internal Pseudo-code from Section 6.3 is commented with "#" next to relevant code
 247       *
 248       * @param string $input UTF-8 encoded string to encode
 249       * @return string Punycode-encoded string
 250       *
 251       * @throws \WpOrg\Requests\Exception On character outside of the domain (never happens with Punycode) (`idna.character_outside_domain`)
 252       */
 253  	public static function punycode_encode($input) {
 254          $output = '';
 255          // let n = initial_n
 256          $n = self::BOOTSTRAP_INITIAL_N;
 257          // let delta = 0
 258          $delta = 0;
 259          // let bias = initial_bias
 260          $bias = self::BOOTSTRAP_INITIAL_BIAS;
 261          // let h = b = the number of basic code points in the input
 262          $h = 0;
 263          $b = 0; // see loop
 264          // copy them to the output in order
 265          $codepoints = self::utf8_to_codepoints($input);
 266          $extended   = [];
 267  
 268          foreach ($codepoints as $char) {
 269              if ($char < 128) {
 270                  // Character is valid ASCII
 271                  // TODO: this should also check if it's valid for a URL
 272                  $output .= chr($char);
 273                  $h++;
 274  
 275                  // Check if the character is non-ASCII, but below initial n
 276                  // This never occurs for Punycode, so ignore in coverage
 277                  // @codeCoverageIgnoreStart
 278              } elseif ($char < $n) {
 279                  throw new Exception('Invalid character', 'idna.character_outside_domain', $char);
 280                  // @codeCoverageIgnoreEnd
 281              } else {
 282                  $extended[$char] = true;
 283              }
 284          }
 285  
 286          $extended = array_keys($extended);
 287          sort($extended);
 288          $b = $h;
 289          // [copy them] followed by a delimiter if b > 0
 290          if (strlen($output) > 0) {
 291              $output .= '-';
 292          }
 293  
 294          // {if the input contains a non-basic code point < n then fail}
 295          // while h < length(input) do begin
 296          $codepointcount = count($codepoints);
 297          while ($h < $codepointcount) {
 298              // let m = the minimum code point >= n in the input
 299              $m = array_shift($extended);
 300              //printf('next code point to insert is %s' . PHP_EOL, dechex($m));
 301              // let delta = delta + (m - n) * (h + 1), fail on overflow
 302              $delta += ($m - $n) * ($h + 1);
 303              // let n = m
 304              $n = $m;
 305              // for each code point c in the input (in order) do begin
 306              for ($num = 0; $num < $codepointcount; $num++) {
 307                  $c = $codepoints[$num];
 308                  // if c < n then increment delta, fail on overflow
 309                  if ($c < $n) {
 310                      $delta++;
 311                  } elseif ($c === $n) { // if c == n then begin
 312                      // let q = delta
 313                      $q = $delta;
 314                      // for k = base to infinity in steps of base do begin
 315                      for ($k = self::BOOTSTRAP_BASE; ; $k += self::BOOTSTRAP_BASE) {
 316                          // let t = tmin if k <= bias {+ tmin}, or
 317                          //     tmax if k >= bias + tmax, or k - bias otherwise
 318                          if ($k <= ($bias + self::BOOTSTRAP_TMIN)) {
 319                              $t = self::BOOTSTRAP_TMIN;
 320                          } elseif ($k >= ($bias + self::BOOTSTRAP_TMAX)) {
 321                              $t = self::BOOTSTRAP_TMAX;
 322                          } else {
 323                              $t = $k - $bias;
 324                          }
 325  
 326                          // if q < t then break
 327                          if ($q < $t) {
 328                              break;
 329                          }
 330  
 331                          // output the code point for digit t + ((q - t) mod (base - t))
 332                          $digit   = (int) ($t + (($q - $t) % (self::BOOTSTRAP_BASE - $t)));
 333                          $output .= self::digit_to_char($digit);
 334                          // let q = (q - t) div (base - t)
 335                          $q = (int) floor(($q - $t) / (self::BOOTSTRAP_BASE - $t));
 336                      } // end
 337                      // output the code point for digit q
 338                      $output .= self::digit_to_char($q);
 339                      // let bias = adapt(delta, h + 1, test h equals b?)
 340                      $bias = self::adapt($delta, $h + 1, $h === $b);
 341                      // let delta = 0
 342                      $delta = 0;
 343                      // increment h
 344                      $h++;
 345                  } // end
 346              } // end
 347              // increment delta and n
 348              $delta++;
 349              $n++;
 350          } // end
 351  
 352          return $output;
 353      }
 354  
 355      /**
 356       * Convert a digit to its respective character
 357       *
 358       * @link https://tools.ietf.org/html/rfc3492#section-5
 359       *
 360       * @param int $digit Digit in the range 0-35
 361       * @return string Single character corresponding to digit
 362       *
 363       * @throws \WpOrg\Requests\Exception On invalid digit (`idna.invalid_digit`)
 364       */
 365  	protected static function digit_to_char($digit) {
 366          // @codeCoverageIgnoreStart
 367          // As far as I know, this never happens, but still good to be sure.
 368          if ($digit < 0 || $digit > 35) {
 369              throw new Exception(sprintf('Invalid digit %d', $digit), 'idna.invalid_digit', $digit);
 370          }
 371  
 372          // @codeCoverageIgnoreEnd
 373          $digits = 'abcdefghijklmnopqrstuvwxyz0123456789';
 374          return substr($digits, $digit, 1);
 375      }
 376  
 377      /**
 378       * Adapt the bias
 379       *
 380       * @link https://tools.ietf.org/html/rfc3492#section-6.1
 381       * @param int $delta
 382       * @param int $numpoints
 383       * @param bool $firsttime
 384       * @return int|float New bias
 385       *
 386       * function adapt(delta,numpoints,firsttime):
 387       */
 388  	protected static function adapt($delta, $numpoints, $firsttime) {
 389          // if firsttime then let delta = delta div damp
 390          if ($firsttime) {
 391              $delta = floor($delta / self::BOOTSTRAP_DAMP);
 392          } else {
 393              // else let delta = delta div 2
 394              $delta = floor($delta / 2);
 395          }
 396  
 397          // let delta = delta + (delta div numpoints)
 398          $delta += floor($delta / $numpoints);
 399          // let k = 0
 400          $k = 0;
 401          // while delta > ((base - tmin) * tmax) div 2 do begin
 402          $max = floor(((self::BOOTSTRAP_BASE - self::BOOTSTRAP_TMIN) * self::BOOTSTRAP_TMAX) / 2);
 403          while ($delta > $max) {
 404              // let delta = delta div (base - tmin)
 405              $delta = floor($delta / (self::BOOTSTRAP_BASE - self::BOOTSTRAP_TMIN));
 406              // let k = k + base
 407              $k += self::BOOTSTRAP_BASE;
 408          } // end
 409          // return k + (((base - tmin + 1) * delta) div (delta + skew))
 410          return $k + floor(((self::BOOTSTRAP_BASE - self::BOOTSTRAP_TMIN + 1) * $delta) / ($delta + self::BOOTSTRAP_SKEW));
 411      }
 412  }