<?php
declare(strict_types=1);
namespace PhpMyAdmin\WebAuthn;
use Webmozart\Assert\Assert;
use function ord;
use function unpack;
use const INF;
use const NAN;
/**
* Concise Binary Object Representation (CBOR) decoder.
*
* This is not a general purpose CBOR decoder and only implements the CTAP2 canonical CBOR encoding form.
*
* @see https://www.rfc-editor.org/rfc/rfc7049
* @see https://fidoalliance.org/specs/fido-v2.0-ps-20190130/fido-client-to-authenticator-protocol-v2.0-ps-20190130.html#message-encoding
*/
final class CBORDecoder
{
/**
* @return mixed
*
* @throws WebAuthnException
*/
public function decode(DataStream $stream)
{
return $this->wellFormed($stream);
}
/**
* @see https://www.rfc-editor.org/rfc/rfc7049#appendix-C
*
* @return mixed
*
* @throws WebAuthnException
*/
private function wellFormed(DataStream $stream)
{
// process initial bytes
$initialByte = ord($stream->take(1));
$majorType = $initialByte >> 5;
$value = $additionalInformation = $initialByte & 0x1f;
switch ($additionalInformation) {
case 24:
if ($majorType !== 7) {
$value = ord($stream->take(1));
}
break;
case 25:
if ($majorType !== 7) {
$unpackedValue = unpack('n', $stream->take(2));
Assert::isArray($unpackedValue);
Assert::keyExists($unpackedValue, 1);
Assert::integer($unpackedValue[1]);
$value = $unpackedValue[1];
}
break;
case 26:
if ($majorType !== 7) {
$unpackedValue = unpack('N', $stream->take(4));
Assert::isArray($unpackedValue);
Assert::keyExists($unpackedValue, 1);
Assert::integer($unpackedValue[1]);
$value = $unpackedValue[1];
}
break;
case 27:
if ($majorType !== 7) {
$unpackedValue = unpack('J', $stream->take(8));
Assert::isArray($unpackedValue);
Assert::keyExists($unpackedValue, 1);
Assert::integer($unpackedValue[1]);
$value = $unpackedValue[1];
}
break;
case 28:
case 29:
case 30:
case 31:
throw new WebAuthnException();
}
// process content
switch ($majorType) {
case 0:
return $this->getUnsignedInteger($value);
case 1:
return $this->getNegativeInteger($value);
case 2:
return $this->getByteString($stream, $value);
case 3:
return $this->getTextString($stream, $value);
case 4:
return $this->getList($stream, $value);
case 5:
return $this->getMap($stream, $value);
case 6:
return $this->getTag($stream);
case 7:
return $this->getFloatNumberOrSimpleValue($stream, $value, $additionalInformation);
default:
throw new WebAuthnException();
}
}
private function getUnsignedInteger(int $value): int
{
return $value;
}
private function getNegativeInteger(int $value): int
{
return -1 - $value;
}
/**
* @throws WebAuthnException
*/
private function getByteString(DataStream $stream, int $value): string
{
return $stream->take($value);
}
/**
* @throws WebAuthnException
*/
private function getTextString(DataStream $stream, int $value): string
{
return $stream->take($value);
}
/**
* @psalm-return list<mixed>
*
* @throws WebAuthnException
*/
private function getList(DataStream $stream, int $value): array
{
$list = [];
for ($i = 0; $i < $value; $i++) {
/** @psalm-suppress MixedAssignment */
$list[] = $this->wellFormed($stream);
}
return $list;
}
/**
* @psalm-return array<array-key, mixed>
*
* @throws WebAuthnException
*/
private function getMap(DataStream $stream, int $value): array
{
$map = [];
for ($i = 0; $i < $value; $i++) {
/** @psalm-suppress MixedAssignment, MixedArrayOffset */
$map[$this->wellFormed($stream)] = $this->wellFormed($stream);
}
return $map;
}
/**
* @return mixed
*
* @throws WebAuthnException
*/
private function getTag(DataStream $stream)
{
// 1 embedded data item
return $this->wellFormed($stream);
}
/**
* @return mixed
*
* @throws WebAuthnException
*/
private function getFloatNumberOrSimpleValue(DataStream $stream, int $value, int $additionalInformation)
{
switch ($additionalInformation) {
case 20:
return true;
case 21:
return false;
case 22:
return null;
case 24:
// simple value
return ord($stream->take(1));
case 25:
return $this->getHalfFloat($stream);
case 26:
return $this->getSingleFloat($stream);
case 27:
return $this->getDoubleFloat($stream);
case 31:
// "break" stop code for indefinite-length items
throw new WebAuthnException();
default:
return $value;
}
}
/**
* IEEE 754 Half-Precision Float (16 bits follow)
*
* @see https://www.rfc-editor.org/rfc/rfc7049#appendix-D
*
* @throws WebAuthnException
*/
private function getHalfFloat(DataStream $stream): float
{
$value = unpack('n', $stream->take(2));
Assert::isArray($value);
Assert::keyExists($value, 1);
Assert::integer($value[1]);
$half = $value[1];
$exp = ($half >> 10) & 0x1f;
$mant = $half & 0x3ff;
if ($exp === 0) {
$val = $mant * (2 ** -24);
} elseif ($exp !== 31) {
$val = ($mant + 1024) * (2 ** ($exp - 25));
} else {
$val = $mant === 0 ? INF : NAN;
}
return $half & 0x8000 ? -$val : $val;
}
/**
* IEEE 754 Single-Precision Float (32 bits follow)
*
* @throws WebAuthnException
*/
private function getSingleFloat(DataStream $stream): float
{
$value = unpack('G', $stream->take(4));
Assert::isArray($value);
Assert::keyExists($value, 1);
Assert::float($value[1]);
return $value[1];
}
/**
* IEEE 754 Double-Precision Float (64 bits follow)
*
* @throws WebAuthnException
*/
private function getDoubleFloat(DataStream $stream): float
{
$value = unpack('E', $stream->take(8));
Assert::isArray($value);
Assert::keyExists($value, 1);
Assert::float($value[1]);
return $value[1];
}
}