blob: ba0db52515e56208612c9c66379b581207f4641a [file] [log] [blame]
<?php
namespace lbuchs\WebAuthn\Attestation\Format;
use lbuchs\WebAuthn\Attestation\AuthenticatorData;
use lbuchs\WebAuthn\WebAuthnException;
use lbuchs\WebAuthn\Binary\ByteBuffer;
class AndroidSafetyNet extends FormatBase {
private $_signature;
private $_signedValue;
private $_x5c;
private $_payload;
public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
parent::__construct($AttestionObject, $authenticatorData);
// check data
$attStmt = $this->_attestationObject['attStmt'];
if (!\array_key_exists('ver', $attStmt) || !$attStmt['ver']) {
throw new WebAuthnException('invalid Android Safety Net Format', WebAuthnException::INVALID_DATA);
}
if (!\array_key_exists('response', $attStmt) || !($attStmt['response'] instanceof ByteBuffer)) {
throw new WebAuthnException('invalid Android Safety Net Format', WebAuthnException::INVALID_DATA);
}
$response = $attStmt['response']->getBinaryString();
// Response is a JWS [RFC7515] object in Compact Serialization.
// JWSs have three segments separated by two period ('.') characters
$parts = \explode('.', $response);
unset ($response);
if (\count($parts) !== 3) {
throw new WebAuthnException('invalid JWS data', WebAuthnException::INVALID_DATA);
}
$header = $this->_base64url_decode($parts[0]);
$payload = $this->_base64url_decode($parts[1]);
$this->_signature = $this->_base64url_decode($parts[2]);
$this->_signedValue = $parts[0] . '.' . $parts[1];
unset ($parts);
$header = \json_decode($header);
$payload = \json_decode($payload);
if (!($header instanceof \stdClass)) {
throw new WebAuthnException('invalid JWS header', WebAuthnException::INVALID_DATA);
}
if (!($payload instanceof \stdClass)) {
throw new WebAuthnException('invalid JWS payload', WebAuthnException::INVALID_DATA);
}
if (!isset($header->x5c) || !is_array($header->x5c) || count($header->x5c) === 0) {
throw new WebAuthnException('No X.509 signature in JWS Header', WebAuthnException::INVALID_DATA);
}
// algorithm
if (!\in_array($header->alg, array('RS256', 'ES256'))) {
throw new WebAuthnException('invalid JWS algorithm ' . $header->alg, WebAuthnException::INVALID_DATA);
}
$this->_x5c = \base64_decode($header->x5c[0]);
$this->_payload = $payload;
if (count($header->x5c) > 1) {
for ($i=1; $i<count($header->x5c); $i++) {
$this->_x5c_chain[] = \base64_decode($header->x5c[$i]);
}
unset ($i);
}
}
/**
* ctsProfileMatch: A stricter verdict of device integrity.
* If the value of ctsProfileMatch is true, then the profile of the device running your app matches
* the profile of a device that has passed Android compatibility testing and
* has been approved as a Google-certified Android device.
* @return bool
*/
public function ctsProfileMatch() {
return isset($this->_payload->ctsProfileMatch) ? !!$this->_payload->ctsProfileMatch : false;
}
/*
* returns the key certificate in PEM format
* @return string
*/
public function getCertificatePem() {
return $this->_createCertificatePem($this->_x5c);
}
/**
* @param string $clientDataHash
*/
public function validateAttestation($clientDataHash) {
$publicKey = \openssl_pkey_get_public($this->getCertificatePem());
// Verify that the nonce in the response is identical to the Base64 encoding
// of the SHA-256 hash of the concatenation of authenticatorData and clientDataHash.
if (empty($this->_payload->nonce) || $this->_payload->nonce !== \base64_encode(\hash('SHA256', $this->_authenticatorData->getBinary() . $clientDataHash, true))) {
throw new WebAuthnException('invalid nonce in JWS payload', WebAuthnException::INVALID_DATA);
}
// Verify that attestationCert is issued to the hostname "attest.android.com"
$certInfo = \openssl_x509_parse($this->getCertificatePem());
if (!\is_array($certInfo) || ($certInfo['subject']['CN'] ?? '') !== 'attest.android.com') {
throw new WebAuthnException('invalid certificate CN in JWS (' . ($certInfo['subject']['CN'] ?? '-'). ')', WebAuthnException::INVALID_DATA);
}
// Verify that the basicIntegrity attribute in the payload of response is true.
if (empty($this->_payload->basicIntegrity)) {
throw new WebAuthnException('invalid basicIntegrity in payload', WebAuthnException::INVALID_DATA);
}
// check certificate
return \openssl_verify($this->_signedValue, $this->_signature, $publicKey, OPENSSL_ALGO_SHA256) === 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;
}
/**
* decode base64 url
* @param string $data
* @return string
*/
private function _base64url_decode($data) {
return \base64_decode(\strtr($data, '-_', '+/') . \str_repeat('=', 3 - (3 + \strlen($data)) % 4));
}
}