Copybara bot | be50d49 | 2023-11-30 00:16:42 +0100 | [diff] [blame^] | 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 Apple extends FormatBase { |
| 10 | private $_x5c; |
| 11 | |
| 12 | public function __construct($AttestionObject, AuthenticatorData $authenticatorData) { |
| 13 | parent::__construct($AttestionObject, $authenticatorData); |
| 14 | |
| 15 | // check packed data |
| 16 | $attStmt = $this->_attestationObject['attStmt']; |
| 17 | |
| 18 | |
| 19 | // certificate for validation |
| 20 | if (\array_key_exists('x5c', $attStmt) && \is_array($attStmt['x5c']) && \count($attStmt['x5c']) > 0) { |
| 21 | |
| 22 | // The attestation certificate attestnCert MUST be the first element in the array |
| 23 | $attestnCert = array_shift($attStmt['x5c']); |
| 24 | |
| 25 | if (!($attestnCert instanceof ByteBuffer)) { |
| 26 | throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA); |
| 27 | } |
| 28 | |
| 29 | $this->_x5c = $attestnCert->getBinaryString(); |
| 30 | |
| 31 | // certificate chain |
| 32 | foreach ($attStmt['x5c'] as $chain) { |
| 33 | if ($chain instanceof ByteBuffer) { |
| 34 | $this->_x5c_chain[] = $chain->getBinaryString(); |
| 35 | } |
| 36 | } |
| 37 | } else { |
| 38 | throw new WebAuthnException('invalid Apple attestation statement: missing x5c', WebAuthnException::INVALID_DATA); |
| 39 | } |
| 40 | } |
| 41 | |
| 42 | |
| 43 | /* |
| 44 | * returns the key certificate in PEM format |
| 45 | * @return string|null |
| 46 | */ |
| 47 | public function getCertificatePem() { |
| 48 | return $this->_createCertificatePem($this->_x5c); |
| 49 | } |
| 50 | |
| 51 | /** |
| 52 | * @param string $clientDataHash |
| 53 | */ |
| 54 | public function validateAttestation($clientDataHash) { |
| 55 | return $this->_validateOverX5c($clientDataHash); |
| 56 | } |
| 57 | |
| 58 | /** |
| 59 | * validates the certificate against root certificates |
| 60 | * @param array $rootCas |
| 61 | * @return boolean |
| 62 | * @throws WebAuthnException |
| 63 | */ |
| 64 | public function validateRootCertificate($rootCas) { |
| 65 | $chainC = $this->_createX5cChainFile(); |
| 66 | if ($chainC) { |
| 67 | $rootCas[] = $chainC; |
| 68 | } |
| 69 | |
| 70 | $v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas); |
| 71 | if ($v === -1) { |
| 72 | throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED); |
| 73 | } |
| 74 | return $v; |
| 75 | } |
| 76 | |
| 77 | /** |
| 78 | * validate if x5c is present |
| 79 | * @param string $clientDataHash |
| 80 | * @return bool |
| 81 | * @throws WebAuthnException |
| 82 | */ |
| 83 | protected function _validateOverX5c($clientDataHash) { |
| 84 | $publicKey = \openssl_pkey_get_public($this->getCertificatePem()); |
| 85 | |
| 86 | if ($publicKey === false) { |
| 87 | throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY); |
| 88 | } |
| 89 | |
| 90 | // Concatenate authenticatorData and clientDataHash to form nonceToHash. |
| 91 | $nonceToHash = $this->_authenticatorData->getBinary(); |
| 92 | $nonceToHash .= $clientDataHash; |
| 93 | |
| 94 | // Perform SHA-256 hash of nonceToHash to produce nonce |
| 95 | $nonce = hash('SHA256', $nonceToHash, true); |
| 96 | |
| 97 | $credCert = openssl_x509_read($this->getCertificatePem()); |
| 98 | if ($credCert === false) { |
| 99 | throw new WebAuthnException('invalid x5c certificate: ' . \openssl_error_string(), WebAuthnException::INVALID_DATA); |
| 100 | } |
| 101 | |
| 102 | $keyData = openssl_pkey_get_details(openssl_pkey_get_public($credCert)); |
| 103 | $key = is_array($keyData) && array_key_exists('key', $keyData) ? $keyData['key'] : null; |
| 104 | |
| 105 | |
| 106 | // Verify that nonce equals the value of the extension with OID ( 1.2.840.113635.100.8.2 ) in credCert. |
| 107 | $parsedCredCert = openssl_x509_parse($credCert); |
| 108 | $nonceExtension = $parsedCredCert['extensions']['1.2.840.113635.100.8.2'] ?? ''; |
| 109 | |
| 110 | // nonce padded by ASN.1 string: 30 24 A1 22 04 20 |
| 111 | // 30 — type tag indicating sequence |
| 112 | // 24 — 36 byte following |
| 113 | // A1 — Enumerated [1] |
| 114 | // 22 — 34 byte following |
| 115 | // 04 — type tag indicating octet string |
| 116 | // 20 — 32 byte following |
| 117 | |
| 118 | $asn1Padding = "\x30\x24\xA1\x22\x04\x20"; |
| 119 | if (substr($nonceExtension, 0, strlen($asn1Padding)) === $asn1Padding) { |
| 120 | $nonceExtension = substr($nonceExtension, strlen($asn1Padding)); |
| 121 | } |
| 122 | |
| 123 | if ($nonceExtension !== $nonce) { |
| 124 | throw new WebAuthnException('nonce doesn\'t equal the value of the extension with OID 1.2.840.113635.100.8.2', WebAuthnException::INVALID_DATA); |
| 125 | } |
| 126 | |
| 127 | // Verify that the credential public key equals the Subject Public Key of credCert. |
| 128 | $authKeyData = openssl_pkey_get_details(openssl_pkey_get_public($this->_authenticatorData->getPublicKeyPem())); |
| 129 | $authKey = is_array($authKeyData) && array_key_exists('key', $authKeyData) ? $authKeyData['key'] : null; |
| 130 | |
| 131 | if ($key === null || $key !== $authKey) { |
| 132 | throw new WebAuthnException('credential public key doesn\'t equal the Subject Public Key of credCert', WebAuthnException::INVALID_DATA); |
| 133 | } |
| 134 | |
| 135 | return true; |
| 136 | } |
| 137 | |
| 138 | } |
| 139 | |