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   1  <?php
   2  
   3  
   4  namespace lbuchs\WebAuthn\Attestation\Format;
   5  use lbuchs\WebAuthn\Attestation\AuthenticatorData;
   6  use lbuchs\WebAuthn\WebAuthnException;
   7  use lbuchs\WebAuthn\Binary\ByteBuffer;
   8  
   9  class Packed extends FormatBase {
  10      private $_alg;
  11      private $_signature;
  12      private $_x5c;
  13  
  14      public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
  15          parent::__construct($AttestionObject, $authenticatorData);
  16  
  17          // check packed data
  18          $attStmt = $this->_attestationObject['attStmt'];
  19  
  20          if (!\array_key_exists('alg', $attStmt) || $this->_getCoseAlgorithm($attStmt['alg']) === null) {
  21              throw new WebAuthnException('unsupported alg: ' . $attStmt['alg'], WebAuthnException::INVALID_DATA);
  22          }
  23  
  24          if (!\array_key_exists('sig', $attStmt) || !\is_object($attStmt['sig']) || !($attStmt['sig'] instanceof ByteBuffer)) {
  25              throw new WebAuthnException('no signature found', WebAuthnException::INVALID_DATA);
  26          }
  27  
  28          $this->_alg = $attStmt['alg'];
  29          $this->_signature = $attStmt['sig']->getBinaryString();
  30  
  31          // certificate for validation
  32          if (\array_key_exists('x5c', $attStmt) && \is_array($attStmt['x5c']) && \count($attStmt['x5c']) > 0) {
  33  
  34              // The attestation certificate attestnCert MUST be the first element in the array
  35              $attestnCert = array_shift($attStmt['x5c']);
  36  
  37              if (!($attestnCert instanceof ByteBuffer)) {
  38                  throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
  39              }
  40  
  41              $this->_x5c = $attestnCert->getBinaryString();
  42  
  43              // certificate chain
  44              foreach ($attStmt['x5c'] as $chain) {
  45                  if ($chain instanceof ByteBuffer) {
  46                      $this->_x5c_chain[] = $chain->getBinaryString();
  47                  }
  48              }
  49          }
  50      }
  51  
  52  
  53      /*
  54       * returns the key certificate in PEM format
  55       * @return string|null
  56       */
  57      public function getCertificatePem() {
  58          if (!$this->_x5c) {
  59              return null;
  60          }
  61          return $this->_createCertificatePem($this->_x5c);
  62      }
  63  
  64      /**
  65       * @param string $clientDataHash
  66       */
  67      public function validateAttestation($clientDataHash) {
  68          if ($this->_x5c) {
  69              return $this->_validateOverX5c($clientDataHash);
  70          } else {
  71              return $this->_validateSelfAttestation($clientDataHash);
  72          }
  73      }
  74  
  75      /**
  76       * validates the certificate against root certificates
  77       * @param array $rootCas
  78       * @return boolean
  79       * @throws WebAuthnException
  80       */
  81      public function validateRootCertificate($rootCas) {
  82          if (!$this->_x5c) {
  83              return false;
  84          }
  85  
  86          $chainC = $this->_createX5cChainFile();
  87          if ($chainC) {
  88              $rootCas[] = $chainC;
  89          }
  90  
  91          $v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas);
  92          if ($v === -1) {
  93              throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED);
  94          }
  95          return $v;
  96      }
  97  
  98      /**
  99       * validate if x5c is present
 100       * @param string $clientDataHash
 101       * @return bool
 102       * @throws WebAuthnException
 103       */
 104      protected function _validateOverX5c($clientDataHash) {
 105          $publicKey = \openssl_pkey_get_public($this->getCertificatePem());
 106  
 107          if ($publicKey === false) {
 108              throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY);
 109          }
 110  
 111          // Verify that sig is a valid signature over the concatenation of authenticatorData and clientDataHash
 112          // using the attestation public key in attestnCert with the algorithm specified in alg.
 113          $dataToVerify = $this->_authenticatorData->getBinary();
 114          $dataToVerify .= $clientDataHash;
 115  
 116          $coseAlgorithm = $this->_getCoseAlgorithm($this->_alg);
 117  
 118          // check certificate
 119          return \openssl_verify($dataToVerify, $this->_signature, $publicKey, $coseAlgorithm->openssl) === 1;
 120      }
 121  
 122      /**
 123       * validate if self attestation is in use
 124       * @param string $clientDataHash
 125       * @return bool
 126       */
 127      protected function _validateSelfAttestation($clientDataHash) {
 128          // Verify that sig is a valid signature over the concatenation of authenticatorData and clientDataHash
 129          // using the credential public key with alg.
 130          $dataToVerify = $this->_authenticatorData->getBinary();
 131          $dataToVerify .= $clientDataHash;
 132  
 133          $publicKey = $this->_authenticatorData->getPublicKeyPem();
 134  
 135          // check certificate
 136          return \openssl_verify($dataToVerify, $this->_signature, $publicKey, OPENSSL_ALGO_SHA256) === 1;
 137      }
 138  }
 139