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<?php
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namespace lbuchs\WebAuthn\Attestation\Format;
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use lbuchs\WebAuthn\Attestation\AuthenticatorData;
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use lbuchs\WebAuthn\WebAuthnException;
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use lbuchs\WebAuthn\Binary\ByteBuffer;
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class U2f extends FormatBase {
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private $_alg = -7;
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private $_signature;
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private $_x5c;
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public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
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parent::__construct($AttestionObject, $authenticatorData);
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// check u2f data
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$attStmt = $this->_attestationObject['attStmt'];
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if (\array_key_exists('alg', $attStmt) && $attStmt['alg'] !== $this->_alg) {
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throw new WebAuthnException('u2f only accepts algorithm -7 ("ES256"), but got ' . $attStmt['alg'], WebAuthnException::INVALID_DATA);
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}
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if (!\array_key_exists('sig', $attStmt) || !\is_object($attStmt['sig']) || !($attStmt['sig'] instanceof ByteBuffer)) {
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throw new WebAuthnException('no signature found', WebAuthnException::INVALID_DATA);
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}
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if (!\array_key_exists('x5c', $attStmt) || !\is_array($attStmt['x5c']) || \count($attStmt['x5c']) !== 1) {
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throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
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}
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if (!\is_object($attStmt['x5c'][0]) || !($attStmt['x5c'][0] instanceof ByteBuffer)) {
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throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
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}
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$this->_signature = $attStmt['sig']->getBinaryString();
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$this->_x5c = $attStmt['x5c'][0]->getBinaryString();
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}
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/*
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* returns the key certificate in PEM format
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* @return string
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*/
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public function getCertificatePem() {
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$pem = '-----BEGIN CERTIFICATE-----' . "\n";
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$pem .= \chunk_split(\base64_encode($this->_x5c), 64, "\n");
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$pem .= '-----END CERTIFICATE-----' . "\n";
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return $pem;
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}
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/**
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* @param string $clientDataHash
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*/
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public function validateAttestation($clientDataHash) {
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$publicKey = \openssl_pkey_get_public($this->getCertificatePem());
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if ($publicKey === false) {
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throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY);
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}
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// Let verificationData be the concatenation of (0x00 || rpIdHash || clientDataHash || credentialId || publicKeyU2F)
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$dataToVerify = "\x00";
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$dataToVerify .= $this->_authenticatorData->getRpIdHash();
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$dataToVerify .= $clientDataHash;
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$dataToVerify .= $this->_authenticatorData->getCredentialId();
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$dataToVerify .= $this->_authenticatorData->getPublicKeyU2F();
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$coseAlgorithm = $this->_getCoseAlgorithm($this->_alg);
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// check certificate
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return \openssl_verify($dataToVerify, $this->_signature, $publicKey, $coseAlgorithm->openssl) === 1;
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}
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/**
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* validates the certificate against root certificates
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* @param array $rootCas
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* @return boolean
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* @throws WebAuthnException
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*/
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public function validateRootCertificate($rootCas) {
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$chainC = $this->_createX5cChainFile();
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if ($chainC) {
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$rootCas[] = $chainC;
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}
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$v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas);
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if ($v === -1) {
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throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED);
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}
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return $v;
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}
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}
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