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<?php

namespace lbuchs\WebAuthn\Attestation\Format;

use lbuchs\WebAuthn\Attestation\AuthenticatorData;

use lbuchs\WebAuthn\WebAuthnException;

use lbuchs\WebAuthn\Binary\ByteBuffer;

class Tpm extends FormatBase {

    private $_TPM_GENERATED_VALUE = "\xFF\x54\x43\x47";

    private $_TPM_ST_ATTEST_CERTIFY = "\x80\x17";

    private $_alg;

    private $_signature;

    private $_pubArea;

    private $_x5c;

    /**

     * @var ByteBuffer

     */

    private $_certInfo;

    public function __construct($AttestionObject, AuthenticatorData $authenticatorData) {

        parent::__construct($AttestionObject, $authenticatorData);

        // check packed data

        $attStmt = $this->_attestationObject['attStmt'];

        if (!\array_key_exists('ver', $attStmt) || $attStmt['ver'] !== '2.0') {

            throw new WebAuthnException('invalid tpm version: ' . $attStmt['ver'], WebAuthnException::INVALID_DATA);

        }

        if (!\array_key_exists('alg', $attStmt) || $this->_getCoseAlgorithm($attStmt['alg']) === null) {

            throw new WebAuthnException('unsupported alg: ' . $attStmt['alg'], WebAuthnException::INVALID_DATA);

        }

        if (!\array_key_exists('sig', $attStmt) || !\is_object($attStmt['sig']) || !($attStmt['sig'] instanceof ByteBuffer)) {

            throw new WebAuthnException('signature not found', WebAuthnException::INVALID_DATA);

        }

        if (!\array_key_exists('certInfo', $attStmt) || !\is_object($attStmt['certInfo']) || !($attStmt['certInfo'] instanceof ByteBuffer)) {

            throw new WebAuthnException('certInfo not found', WebAuthnException::INVALID_DATA);

        }

        if (!\array_key_exists('pubArea', $attStmt) || !\is_object($attStmt['pubArea']) || !($attStmt['pubArea'] instanceof ByteBuffer)) {

            throw new WebAuthnException('pubArea not found', WebAuthnException::INVALID_DATA);

        }

        $this->_alg = $attStmt['alg'];

        $this->_signature = $attStmt['sig']->getBinaryString();

        $this->_certInfo = $attStmt['certInfo'];

        $this->_pubArea = $attStmt['pubArea'];

        // certificate for validation

        if (\array_key_exists('x5c', $attStmt) && \is_array($attStmt['x5c']) && \count($attStmt['x5c']) > 0) {

            // The attestation certificate attestnCert MUST be the first element in the array

            $attestnCert = array_shift($attStmt['x5c']);

            if (!($attestnCert instanceof ByteBuffer)) {

                throw new WebAuthnException('invalid x5c certificate', WebAuthnException::INVALID_DATA);

            }

            $this->_x5c = $attestnCert->getBinaryString();

            // certificate chain

            foreach ($attStmt['x5c'] as $chain) {

                if ($chain instanceof ByteBuffer) {

                    $this->_x5c_chain[] = $chain->getBinaryString();

                }

            }

        } else {

            throw new WebAuthnException('no x5c certificate found', WebAuthnException::INVALID_DATA);

        }

    }

    /*

     * returns the key certificate in PEM format

     * @return string|null

     */

    public function getCertificatePem() {

        if (!$this->_x5c) {

            return null;

        }

        return $this->_createCertificatePem($this->_x5c);

    }

    /**

     * @param string $clientDataHash

     */

    public function validateAttestation($clientDataHash) {

        return $this->_validateOverX5c($clientDataHash);

    }

    /**

     * validates the certificate against root certificates

     * @param array $rootCas

     * @return boolean

     * @throws WebAuthnException

     */

    public function validateRootCertificate($rootCas) {

        if (!$this->_x5c) {

            return false;

        }

        $chainC = $this->_createX5cChainFile();

        if ($chainC) {

            $rootCas[] = $chainC;

        }

        $v = \openssl_x509_checkpurpose($this->getCertificatePem(), -1, $rootCas);

        if ($v === -1) {

            throw new WebAuthnException('error on validating root certificate: ' . \openssl_error_string(), WebAuthnException::CERTIFICATE_NOT_TRUSTED);

        }

        return $v;

    }

    /**

     * validate if x5c is present

     * @param string $clientDataHash

     * @return bool

     * @throws WebAuthnException

     */

    protected function _validateOverX5c($clientDataHash) {

        $publicKey = \openssl_pkey_get_public($this->getCertificatePem());

        if ($publicKey === false) {

            throw new WebAuthnException('invalid public key: ' . \openssl_error_string(), WebAuthnException::INVALID_PUBLIC_KEY);

        }

        // Concatenate authenticatorData and clientDataHash to form attToBeSigned.

        $attToBeSigned = $this->_authenticatorData->getBinary();

        $attToBeSigned .= $clientDataHash;

        // Validate that certInfo is valid:

        // Verify that magic is set to TPM_GENERATED_VALUE.

        if ($this->_certInfo->getBytes(0, 4) !== $this->_TPM_GENERATED_VALUE) {

            throw new WebAuthnException('tpm magic not TPM_GENERATED_VALUE', WebAuthnException::INVALID_DATA);

        }

        // Verify that type is set to TPM_ST_ATTEST_CERTIFY.

        if ($this->_certInfo->getBytes(4, 2) !== $this->_TPM_ST_ATTEST_CERTIFY) {

            throw new WebAuthnException('tpm type not TPM_ST_ATTEST_CERTIFY', WebAuthnException::INVALID_DATA);

        }

        $offset = 6;

        $qualifiedSigner = $this->_tpmReadLengthPrefixed($this->_certInfo, $offset);

        $extraData = $this->_tpmReadLengthPrefixed($this->_certInfo, $offset);

        $coseAlg = $this->_getCoseAlgorithm($this->_alg);

        // Verify that extraData is set to the hash of attToBeSigned using the hash algorithm employed in "alg".

        if ($extraData->getBinaryString() !== \hash($coseAlg->hash, $attToBeSigned, true)) {

            throw new WebAuthnException('certInfo:extraData not hash of attToBeSigned', WebAuthnException::INVALID_DATA);

        }

        // Verify the sig is a valid signature over certInfo using the attestation

        // public key in aikCert with the algorithm specified in alg.

        return \openssl_verify($this->_certInfo->getBinaryString(), $this->_signature, $publicKey, $coseAlg->openssl) === 1;

    }

    /**

     * returns next part of ByteBuffer

     * @param ByteBuffer $buffer

     * @param int $offset

     * @return ByteBuffer

     */

    protected function _tpmReadLengthPrefixed(ByteBuffer $buffer, &$offset) {

        $len = $buffer->getUint16Val($offset);

        $data = $buffer->getBytes($offset + 2, $len);

        $offset += (2 + $len);

        return new ByteBuffer($data);

    }

}