141 lines
5.2 KiB
PHP
141 lines
5.2 KiB
PHP
<?php
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namespace WebAuthn\Attestation\Format;
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use WebAuthn\WebAuthnException;
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use WebAuthn\Binary\ByteBuffer;
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class AndroidSafetyNet extends FormatBase {
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private $_signature;
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private $_signedValue;
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private $_x5c;
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private $_payload;
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public function __construct($AttestionObject, \WebAuthn\Attestation\AuthenticatorData $authenticatorData) {
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parent::__construct($AttestionObject, $authenticatorData);
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// check data
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$attStmt = $this->_attestationObject['attStmt'];
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if (!\array_key_exists('ver', $attStmt) || !$attStmt['ver']) {
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throw new WebAuthnException('invalid Android Safety Net Format', WebAuthnException::INVALID_DATA);
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}
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if (!\array_key_exists('response', $attStmt) || !($attStmt['response'] instanceof ByteBuffer)) {
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throw new WebAuthnException('invalid Android Safety Net Format', WebAuthnException::INVALID_DATA);
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}
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$response = $attStmt['response']->getBinaryString();
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// Response is a JWS [RFC7515] object in Compact Serialization.
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// JWSs have three segments separated by two period ('.') characters
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$parts = \explode('.', $response);
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unset ($response);
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if (\count($parts) !== 3) {
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throw new WebAuthnException('invalid JWS data', WebAuthnException::INVALID_DATA);
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}
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$header = $this->_base64url_decode($parts[0]);
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$payload = $this->_base64url_decode($parts[1]);
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$this->_signature = $this->_base64url_decode($parts[2]);
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$this->_signedValue = $parts[0] . '.' . $parts[1];
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unset ($parts);
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$header = \json_decode($header);
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$payload = \json_decode($payload);
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if (!($header instanceof \stdClass)) {
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throw new WebAuthnException('invalid JWS header', WebAuthnException::INVALID_DATA);
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}
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if (!($payload instanceof \stdClass)) {
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throw new WebAuthnException('invalid JWS payload', WebAuthnException::INVALID_DATA);
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}
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if (!$header->x5c || !is_array($header->x5c) || count($header->x5c) === 0) {
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throw new WebAuthnException('No X.509 signature in JWS Header', WebAuthnException::INVALID_DATA);
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}
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// algorithm
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if (!\in_array($header->alg, array('RS256', 'ES256'))) {
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throw new WebAuthnException('invalid JWS algorithm ' . $header->alg, WebAuthnException::INVALID_DATA);
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}
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$this->_x5c = \base64_decode($header->x5c[0]);
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$this->_payload = $payload;
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if (count($header->x5c) > 1) {
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for ($i=1; $i<count($header->x5c); $i++) {
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$this->_x5c_chain[] = \base64_decode($header->x5c[$i]);
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}
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unset ($i);
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}
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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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return $this->_createCertificatePem($this->_x5c);
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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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// Verify that the nonce in the response is identical to the Base64 encoding
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// of the SHA-256 hash of the concatenation of authenticatorData and clientDataHash.
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if (!$this->_payload->nonce || $this->_payload->nonce !== \base64_encode(\hash('SHA256', $this->_authenticatorData->getBinary() . $clientDataHash, true))) {
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throw new WebAuthnException('invalid nonce in JWS payload', WebAuthnException::INVALID_DATA);
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}
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// Verify that attestationCert is issued to the hostname "attest.android.com"
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$certInfo = \openssl_x509_parse($this->getCertificatePem());
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if (!\is_array($certInfo) || !$certInfo['subject'] || $certInfo['subject']['CN'] !== 'attest.android.com') {
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throw new WebAuthnException('invalid certificate CN in JWS (' . $certInfo['subject']['CN']. ')', WebAuthnException::INVALID_DATA);
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}
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// Verify that the ctsProfileMatch attribute in the payload of response is true.
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if (!$this->_payload->ctsProfileMatch) {
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throw new WebAuthnException('invalid ctsProfileMatch in payload', WebAuthnException::INVALID_DATA);
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}
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// check certificate
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return \openssl_verify($this->_signedValue, $this->_signature, $publicKey, OPENSSL_ALGO_SHA256) === 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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* decode base64 url
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* @param string $data
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* @return string
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*/
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private function _base64url_decode($data) {
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return \base64_decode(\strtr($data, '-_', '+/') . \str_repeat('=', 3 - (3 + \strlen($data)) % 4));
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}
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}
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