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   1  <?php
   2  
   3  namespace lbuchs\WebAuthn\Attestation\Format;
   4  use lbuchs\WebAuthn\Attestation\AuthenticatorData;
   5  use lbuchs\WebAuthn\WebAuthnException;
   6  use lbuchs\WebAuthn\Binary\ByteBuffer;
   7  
   8  class AndroidKey extends FormatBase {
   9      private $_alg;
  10      private $_signature;
  11      private $_x5c;
  12  
  13      public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
  14          parent::__construct($AttestionObject, $authenticatorData);
  15  
  16          // check u2f data
  17          $attStmt = $this->_attestationObject['attStmt'];
  18  
  19          if (!\array_key_exists('alg', $attStmt) || $this->_getCoseAlgorithm($attStmt['alg']) === null) {
  20              throw new WebAuthnException('unsupported alg: ' . $attStmt['alg'], WebAuthnException::INVALID_DATA);
  21          }
  22  
  23          if (!\array_key_exists('sig', $attStmt) || !\is_object($attStmt['sig']) || !($attStmt['sig'] instanceof ByteBuffer)) {
  24              throw new WebAuthnException('no signature found', WebAuthnException::INVALID_DATA);
  25          }
  26  
  27          if (!\array_key_exists('x5c', $attStmt) || !\is_array($attStmt['x5c']) || \count($attStmt['x5c']) < 1) {
  28              throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
  29          }
  30  
  31          if (!\is_object($attStmt['x5c'][0]) || !($attStmt['x5c'][0] instanceof ByteBuffer)) {
  32              throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
  33          }
  34  
  35          $this->_alg = $attStmt['alg'];
  36          $this->_signature = $attStmt['sig']->getBinaryString();
  37          $this->_x5c = $attStmt['x5c'][0]->getBinaryString();
  38  
  39          if (count($attStmt['x5c']) > 1) {
  40              for ($i=1; $i<count($attStmt['x5c']); $i++) {
  41                  $this->_x5c_chain[] = $attStmt['x5c'][$i]->getBinaryString();
  42              }
  43              unset ($i);
  44          }
  45      }
  46  
  47  
  48      /*
  49       * returns the key certificate in PEM format
  50       * @return string
  51       */
  52      public function getCertificatePem() {
  53          return $this->_createCertificatePem($this->_x5c);
  54      }
  55  
  56      /**
  57       * @param string $clientDataHash
  58       */
  59      public function validateAttestation($clientDataHash) {
  60          $publicKey = \openssl_pkey_get_public($this->getCertificatePem());
  61  
  62          if ($publicKey === false) {
  63              throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY);
  64          }
  65  
  66          // Verify that sig is a valid signature over the concatenation of authenticatorData and clientDataHash
  67          // using the attestation public key in attestnCert with the algorithm specified in alg.
  68          $dataToVerify = $this->_authenticatorData->getBinary();
  69          $dataToVerify .= $clientDataHash;
  70  
  71          $coseAlgorithm = $this->_getCoseAlgorithm($this->_alg);
  72  
  73          // check certificate
  74          return \openssl_verify($dataToVerify, $this->_signature, $publicKey, $coseAlgorithm->openssl) === 1;
  75      }
  76  
  77      /**
  78       * validates the certificate against root certificates
  79       * @param array $rootCas
  80       * @return boolean
  81       * @throws WebAuthnException
  82       */
  83      public function validateRootCertificate($rootCas) {
  84          $chainC = $this->_createX5cChainFile();
  85          if ($chainC) {
  86              $rootCas[] = $chainC;
  87          }
  88  
  89          $v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas);
  90          if ($v === -1) {
  91              throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED);
  92          }
  93          return $v;
  94      }
  95  }
  96