132 lines
4.2 KiB
PHP
132 lines
4.2 KiB
PHP
<?php
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/*
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* This file is part of the PHPASN1 library.
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*
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* Copyright © Friedrich Große <friedrich.grosse@gmail.com>
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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namespace FG\ASN1;
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use FG\ASN1\Exception\ParserException;
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/**
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* Class ExplicitlyTaggedObject decorate an inner object with an additional tag that gives information about
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* its context specific meaning.
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*
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* Explanation taken from A Layman's Guide to a Subset of ASN.1, BER, and DER:
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* >>> An RSA Laboratories Technical Note
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* >>> Burton S. Kaliski Jr.
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* >>> Revised November 1, 1993
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*
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* [...]
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* Explicitly tagged types are derived from other types by adding an outer tag to the underlying type.
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* In effect, explicitly tagged types are structured types consisting of one component, the underlying type.
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* Explicit tagging is denoted by the ASN.1 keywords [class number] EXPLICIT (see Section 5.2).
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* [...]
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*
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* @see http://luca.ntop.org/Teaching/Appunti/asn1.html
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*/
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class ExplicitlyTaggedObject extends ASNObject
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{
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/** @var \FG\ASN1\ASNObject[] */
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private $decoratedObjects;
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private $tag;
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/**
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* @param int $tag
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* @param \FG\ASN1\ASNObject $objects,...
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*/
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public function __construct($tag, /* HH_FIXME[4858]: variadic + strict */ ...$objects)
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{
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$this->tag = $tag;
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$this->decoratedObjects = $objects;
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}
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protected function calculateContentLength()
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{
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$length = 0;
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foreach ($this->decoratedObjects as $object) {
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$length += $object->getObjectLength();
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}
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return $length;
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}
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protected function getEncodedValue()
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{
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$encoded = '';
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foreach ($this->decoratedObjects as $object) {
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$encoded .= $object->getBinary();
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}
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return $encoded;
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}
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public function getContent()
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{
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return $this->decoratedObjects;
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}
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public function __toString()
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{
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switch ($length = count($this->decoratedObjects)) {
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case 0:
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return "Context specific empty object with tag [{$this->tag}]";
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case 1:
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$decoratedType = Identifier::getShortName($this->decoratedObjects[0]->getType());
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return "Context specific $decoratedType with tag [{$this->tag}]";
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default:
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return "$length context specific objects with tag [{$this->tag}]";
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}
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}
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public function getType()
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{
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return ord($this->getIdentifier());
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}
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public function getIdentifier()
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{
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$identifier = Identifier::create(Identifier::CLASS_CONTEXT_SPECIFIC, true, $this->tag);
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return is_int($identifier) ? chr($identifier) : $identifier;
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}
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public function getTag()
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{
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return $this->tag;
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}
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public static function fromBinary(&$binaryData, &$offsetIndex = 0)
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{
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$identifier = self::parseBinaryIdentifier($binaryData, $offsetIndex);
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$firstIdentifierOctet = ord($identifier);
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assert(Identifier::isContextSpecificClass($firstIdentifierOctet), 'identifier octet should indicate context specific class');
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assert(Identifier::isConstructed($firstIdentifierOctet), 'identifier octet should indicate constructed object');
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$tag = Identifier::getTagNumber($identifier);
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$totalContentLength = self::parseContentLength($binaryData, $offsetIndex);
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$remainingContentLength = $totalContentLength;
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$offsetIndexOfDecoratedObject = $offsetIndex;
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$decoratedObjects = [];
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while ($remainingContentLength > 0) {
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$nextObject = ASNObject::fromBinary($binaryData, $offsetIndex);
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$remainingContentLength -= $nextObject->getObjectLength();
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$decoratedObjects[] = $nextObject;
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}
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if ($remainingContentLength != 0) {
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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", $offsetIndexOfDecoratedObject);
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}
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$parsedObject = new self($tag, ...$decoratedObjects);
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$parsedObject->setContentLength($totalContentLength);
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return $parsedObject;
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}
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}
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