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@lbuchs @BenjaminHae
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<?php
namespace lbuchs\WebAuthn\Attestation\Format;
use lbuchs\WebAuthn\Attestation\AuthenticatorData;
use lbuchs\WebAuthn\WebAuthnException;
use lbuchs\WebAuthn\Binary\ByteBuffer;
class U2f extends FormatBase {
private $_alg = -7;
private $_signature;
private $_x5c;
public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
parent::__construct($AttestionObject, $authenticatorData);
// check u2f data
$attStmt = $this->_attestationObject['attStmt'];
if (\array_key_exists('alg', $attStmt) && $attStmt['alg'] !== $this->_alg) {
throw new WebAuthnException('u2f only accepts algorithm -7 ("ES256"), but got ' . $attStmt['alg'], WebAuthnException::INVALID_DATA);
}
if (!\array_key_exists('sig', $attStmt) || !\is_object($attStmt['sig']) || !($attStmt['sig'] instanceof ByteBuffer)) {
throw new WebAuthnException('no signature found', WebAuthnException::INVALID_DATA);
}
if (!\array_key_exists('x5c', $attStmt) || !\is_array($attStmt['x5c']) || \count($attStmt['x5c']) !== 1) {
throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
}
if (!\is_object($attStmt['x5c'][0]) || !($attStmt['x5c'][0] instanceof ByteBuffer)) {
throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
}
$this->_signature = $attStmt['sig']->getBinaryString();
$this->_x5c = $attStmt['x5c'][0]->getBinaryString();
}
/*
* returns the key certificate in PEM format
* @return string
*/
public function getCertificatePem() {
$pem = '-----BEGIN CERTIFICATE-----' . "\n";
$pem .= \chunk_split(\base64_encode($this->_x5c), 64, "\n");
$pem .= '-----END CERTIFICATE-----' . "\n";
return $pem;
}
/**
* @param string $clientDataHash
*/
public function validateAttestation($clientDataHash) {
$publicKey = \openssl_pkey_get_public($this->getCertificatePem());
if ($publicKey === false) {
throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY);
}
// Let verificationData be the concatenation of (0x00 || rpIdHash || clientDataHash || credentialId || publicKeyU2F)
$dataToVerify = "\x00";
$dataToVerify .= $this->_authenticatorData->getRpIdHash();
$dataToVerify .= $clientDataHash;
$dataToVerify .= $this->_authenticatorData->getCredentialId();
$dataToVerify .= $this->_authenticatorData->getPublicKeyU2F();
$coseAlgorithm = $this->_getCoseAlgorithm($this->_alg);
// check certificate
return \openssl_verify($dataToVerify, $this->_signature, $publicKey, $coseAlgorithm->openssl) === 1;
}
/**
* validates the certificate against root certificates
* @param array $rootCas
* @return boolean
* @throws WebAuthnException
*/
public function validateRootCertificate($rootCas) {
$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;
}
}
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