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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 U2f extends FormatBase {
  10      private $_alg = -7;
  11      private $_signature;
  12      private $_x5c;
  13  
  14      public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {
  15          parent::__construct($AttestionObject, $authenticatorData);
  16  
  17          // check u2f data
  18          $attStmt = $this->_attestationObject['attStmt'];
  19  
  20          if (\array_key_exists('alg', $attStmt) && $attStmt['alg'] !== $this->_alg) {
  21              throw new WebAuthnException('u2f only accepts algorithm -7 ("ES256"), but got ' . $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          if (!\array_key_exists('x5c', $attStmt) || !\is_array($attStmt['x5c']) || \count($attStmt['x5c']) !== 1) {
  29              throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
  30          }
  31  
  32          if (!\is_object($attStmt['x5c'][0]) || !($attStmt['x5c'][0] instanceof ByteBuffer)) {
  33              throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);
  34          }
  35  
  36          $this->_signature = $attStmt['sig']->getBinaryString();
  37          $this->_x5c = $attStmt['x5c'][0]->getBinaryString();
  38      }
  39  
  40  
  41      /*
  42       * returns the key certificate in PEM format
  43       * @return string
  44       */
  45      public function getCertificatePem() {
  46          $pem = '-----BEGIN CERTIFICATE-----' . "\n";
  47          $pem .= \chunk_split(\base64_encode($this->_x5c), 64, "\n");
  48          $pem .= '-----END CERTIFICATE-----' . "\n";
  49          return $pem;
  50      }
  51  
  52      /**
  53       * @param string $clientDataHash
  54       */
  55      public function validateAttestation($clientDataHash) {
  56          $publicKey = \openssl_pkey_get_public($this->getCertificatePem());
  57  
  58          if ($publicKey === false) {
  59              throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY);
  60          }
  61  
  62          // Let verificationData be the concatenation of (0x00 || rpIdHash || clientDataHash || credentialId || publicKeyU2F)
  63          $dataToVerify = "\x00";
  64          $dataToVerify .= $this->_authenticatorData->getRpIdHash();
  65          $dataToVerify .= $clientDataHash;
  66          $dataToVerify .= $this->_authenticatorData->getCredentialId();
  67          $dataToVerify .= $this->_authenticatorData->getPublicKeyU2F();
  68  
  69          $coseAlgorithm = $this->_getCoseAlgorithm($this->_alg);
  70  
  71          // check certificate
  72          return \openssl_verify($dataToVerify, $this->_signature, $publicKey, $coseAlgorithm->openssl) === 1;
  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          $chainC = $this->_createX5cChainFile();
  83          if ($chainC) {
  84              $rootCas[] = $chainC;
  85          }
  86  
  87          $v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas);
  88          if ($v === -1) {
  89              throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED);
  90          }
  91          return $v;
  92      }
  93  }