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   1  <?php
   2  /*
   3   * This file is part of the PHPASN1 library.
   4   *
   5   * Copyright © Friedrich Große <[email protected]>
   6   *
   7   * For the full copyright and license information, please view the LICENSE
   8   * file that was distributed with this source code.
   9   */
  10  
  11  namespace FG\ASN1;
  12  
  13  use FG\ASN1\Exception\ParserException;
  14  
  15  /**
  16   * Class ExplicitlyTaggedObject decorate an inner object with an additional tag that gives information about
  17   * its context specific meaning.
  18   *
  19   * Explanation taken from A Layman's Guide to a Subset of ASN.1, BER, and DER:
  20   * >>> An RSA Laboratories Technical Note
  21   * >>> Burton S. Kaliski Jr.
  22   * >>> Revised November 1, 1993
  23   *
  24   * [...]
  25   * Explicitly tagged types are derived from other types by adding an outer tag to the underlying type.
  26   * In effect, explicitly tagged types are structured types consisting of one component, the underlying type.
  27   * Explicit tagging is denoted by the ASN.1 keywords [class number] EXPLICIT (see Section 5.2).
  28   * [...]
  29   *
  30   * @see http://luca.ntop.org/Teaching/Appunti/asn1.html
  31   */
  32  class ExplicitlyTaggedObject extends ASNObject
  33  {
  34      /** @var \FG\ASN1\ASNObject[] */
  35      private $decoratedObjects;
  36      private $tag;
  37  
  38      /**
  39       * @param int $tag
  40       * @param \FG\ASN1\ASNObject $objects,...
  41       */
  42      public function __construct($tag, /* HH_FIXME[4858]: variadic + strict */ ...$objects)
  43      {
  44          $this->tag = $tag;
  45          $this->decoratedObjects = $objects;
  46      }
  47  
  48      protected function calculateContentLength()
  49      {
  50          $length = 0;
  51          foreach ($this->decoratedObjects as $object) {
  52              $length += $object->getObjectLength();
  53          }
  54  
  55          return $length;
  56      }
  57  
  58      protected function getEncodedValue()
  59      {
  60          $encoded = '';
  61          foreach ($this->decoratedObjects as $object) {
  62              $encoded .= $object->getBinary();
  63          }
  64  
  65          return $encoded;
  66      }
  67  
  68      public function getContent()
  69      {
  70          return $this->decoratedObjects;
  71      }
  72  
  73      public function __toString()
  74      {
  75          switch ($length = count($this->decoratedObjects)) {
  76          case 0:
  77              return "Context specific empty object with tag [{$this->tag}]";
  78          case 1:
  79              $decoratedType = Identifier::getShortName($this->decoratedObjects[0]->getType());
  80              return "Context specific $decoratedType with tag [{$this->tag}]";
  81          default:
  82              return "$length context specific objects with tag [{$this->tag}]";
  83          }
  84      }
  85  
  86      public function getType()
  87      {
  88          return ord($this->getIdentifier());
  89      }
  90  
  91      public function getIdentifier()
  92      {
  93          $identifier = Identifier::create(Identifier::CLASS_CONTEXT_SPECIFIC, true, $this->tag);
  94  
  95          return is_int($identifier) ? chr($identifier) : $identifier;
  96      }
  97  
  98      public function getTag()
  99      {
 100          return $this->tag;
 101      }
 102  
 103      public static function fromBinary(&$binaryData, &$offsetIndex = 0)
 104      {
 105          $identifier = self::parseBinaryIdentifier($binaryData, $offsetIndex);
 106          $firstIdentifierOctet = ord($identifier);
 107          assert(Identifier::isContextSpecificClass($firstIdentifierOctet), 'identifier octet should indicate context specific class');
 108          assert(Identifier::isConstructed($firstIdentifierOctet), 'identifier octet should indicate constructed object');
 109          $tag = Identifier::getTagNumber($identifier);
 110  
 111          $totalContentLength = self::parseContentLength($binaryData, $offsetIndex);
 112          $remainingContentLength = $totalContentLength;
 113  
 114          $offsetIndexOfDecoratedObject = $offsetIndex;
 115          $decoratedObjects = [];
 116  
 117          while ($remainingContentLength > 0) {
 118              $nextObject = ASNObject::fromBinary($binaryData, $offsetIndex);
 119              $remainingContentLength -= $nextObject->getObjectLength();
 120              $decoratedObjects[] = $nextObject;
 121          }
 122  
 123          if ($remainingContentLength != 0) {
 124              throw new ParserException("Context-Specific explicitly tagged object [$tag] starting at offset $offsetIndexOfDecoratedObject specifies a length of $totalContentLength octets but $remainingContentLength remain after parsing the content", $offsetIndexOfDecoratedObject);
 125          }
 126  
 127          $parsedObject = new self($tag, ...$decoratedObjects);
 128          $parsedObject->setContentLength($totalContentLength);
 129          return $parsedObject;
 130      }
 131  }