blob: 338cd45c3223b5ab3184a215cf70b028d6ba7b22 [file] [log] [blame]
<?php
namespace lbuchs\WebAuthn\Attestation\Format;
use lbuchs\WebAuthn\Attestation\AuthenticatorData;
use lbuchs\WebAuthn\WebAuthnException;
use lbuchs\WebAuthn\Binary\ByteBuffer;
class Tpm extends FormatBase {
private $_TPM_GENERATED_VALUE = "\xFF\x54\x43\x47";
private $_TPM_ST_ATTEST_CERTIFY = "\x80\x17";
private $_alg;
private $_signature;
private $_pubArea;
private $_x5c;
/**
* @var ByteBuffer
*/
private $_certInfo;
public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
parent::__construct($AttestionObject, $authenticatorData);
// check packed data
$attStmt = $this->_attestationObject['attStmt'];
if (!\array_key_exists('ver', $attStmt) || $attStmt['ver'] !== '2.0') {
throw new WebAuthnException('invalid tpm version: ' . $attStmt['ver'], WebAuthnException::INVALID_DATA);
}
if (!\array_key_exists('alg', $attStmt) || $this->_getCoseAlgorithm($attStmt['alg']) === null) {
throw new WebAuthnException('unsupported alg: ' . $attStmt['alg'], WebAuthnException::INVALID_DATA);
}
if (!\array_key_exists('sig', $attStmt) || !\is_object($attStmt['sig']) || !($attStmt['sig'] instanceof ByteBuffer)) {
throw new WebAuthnException('signature not found', WebAuthnException::INVALID_DATA);
}
if (!\array_key_exists('certInfo', $attStmt) || !\is_object($attStmt['certInfo']) || !($attStmt['certInfo'] instanceof ByteBuffer)) {
throw new WebAuthnException('certInfo not found', WebAuthnException::INVALID_DATA);
}
if (!\array_key_exists('pubArea', $attStmt) || !\is_object($attStmt['pubArea']) || !($attStmt['pubArea'] instanceof ByteBuffer)) {
throw new WebAuthnException('pubArea not found', WebAuthnException::INVALID_DATA);
}
$this->_alg = $attStmt['alg'];
$this->_signature = $attStmt['sig']->getBinaryString();
$this->_certInfo = $attStmt['certInfo'];
$this->_pubArea = $attStmt['pubArea'];
// certificate for validation
if (\array_key_exists('x5c', $attStmt) && \is_array($attStmt['x5c']) && \count($attStmt['x5c']) > 0) {
// The attestation certificate attestnCert MUST be the first element in the array
$attestnCert = array_shift($attStmt['x5c']);
if (!($attestnCert instanceof ByteBuffer)) {
throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
}
$this->_x5c = $attestnCert->getBinaryString();
// certificate chain
foreach ($attStmt['x5c'] as $chain) {
if ($chain instanceof ByteBuffer) {
$this->_x5c_chain[] = $chain->getBinaryString();
}
}
} else {
throw new WebAuthnException('no x5c certificate found', WebAuthnException::INVALID_DATA);
}
}
/*
* returns the key certificate in PEM format
* @return string|null
*/
public function getCertificatePem() {
if (!$this->_x5c) {
return null;
}
return $this->_createCertificatePem($this->_x5c);
}
/**
* @param string $clientDataHash
*/
public function validateAttestation($clientDataHash) {
return $this->_validateOverX5c($clientDataHash);
}
/**
* validates the certificate against root certificates
* @param array $rootCas
* @return boolean
* @throws WebAuthnException
*/
public function validateRootCertificate($rootCas) {
if (!$this->_x5c) {
return false;
}
$chainC = $this->_createX5cChainFile();
if ($chainC) {
$rootCas[] = $chainC;
}
$v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas);
if ($v === -1) {
throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED);
}
return $v;
}
/**
* validate if x5c is present
* @param string $clientDataHash
* @return bool
* @throws WebAuthnException
*/
protected function _validateOverX5c($clientDataHash) {
$publicKey = \openssl_pkey_get_public($this->getCertificatePem());
if ($publicKey === false) {
throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY);
}
// Concatenate authenticatorData and clientDataHash to form attToBeSigned.
$attToBeSigned = $this->_authenticatorData->getBinary();
$attToBeSigned .= $clientDataHash;
// Validate that certInfo is valid:
// Verify that magic is set to TPM_GENERATED_VALUE.
if ($this->_certInfo->getBytes(0, 4) !== $this->_TPM_GENERATED_VALUE) {
throw new WebAuthnException('tpm magic not TPM_GENERATED_VALUE', WebAuthnException::INVALID_DATA);
}
// Verify that type is set to TPM_ST_ATTEST_CERTIFY.
if ($this->_certInfo->getBytes(4, 2) !== $this->_TPM_ST_ATTEST_CERTIFY) {
throw new WebAuthnException('tpm type not TPM_ST_ATTEST_CERTIFY', WebAuthnException::INVALID_DATA);
}
$offset = 6;
$qualifiedSigner = $this->_tpmReadLengthPrefixed($this->_certInfo, $offset);
$extraData = $this->_tpmReadLengthPrefixed($this->_certInfo, $offset);
$coseAlg = $this->_getCoseAlgorithm($this->_alg);
// Verify that extraData is set to the hash of attToBeSigned using the hash algorithm employed in "alg".
if ($extraData->getBinaryString() !== \hash($coseAlg->hash, $attToBeSigned, true)) {
throw new WebAuthnException('certInfo:extraData not hash of attToBeSigned', WebAuthnException::INVALID_DATA);
}
// Verify the sig is a valid signature over certInfo using the attestation
// public key in aikCert with the algorithm specified in alg.
return \openssl_verify($this->_certInfo->getBinaryString(), $this->_signature, $publicKey, $coseAlg->openssl) === 1;
}
/**
* returns next part of ByteBuffer
* @param ByteBuffer $buffer
* @param int $offset
* @return ByteBuffer
*/
protected function _tpmReadLengthPrefixed(ByteBuffer $buffer, &$offset) {
$len = $buffer->getUint16Val($offset);
$data = $buffer->getBytes($offset + 2, $len);
$offset += (2 + $len);
return new ByteBuffer($data);
}
}