TPM

untested

Attestation/AttestationObject.php

@@ -36,12 +36,13 @@ class AttestationObject {
         }
 
         switch ($enc['fmt']) {
+            case 'android-key': $this->_attestationFormat = new Format\AndroidKey($enc, $this->_authenticatorData); break;
+            case 'android-safetynet': $this->_attestationFormat = new Format\AndroidSafetyNet($enc, $this->_authenticatorData); break;
             case 'fido-u2f': $this->_attestationFormat = new Format\U2f($enc, $this->_authenticatorData); break;
             case 'none': $this->_attestationFormat = new Format\None($enc, $this->_authenticatorData); break;
             case 'packed': $this->_attestationFormat = new Format\Packed($enc, $this->_authenticatorData); break;
-            case 'android-key': $this->_attestationFormat = new Format\AndroidKey($enc, $this->_authenticatorData); break;
-            case 'android-safetynet': $this->_attestationFormat = new Format\AndroidSafetyNet($enc, $this->_authenticatorData); break;
-            default: throw new WebAuthnException('invalid atttestation format: ' . $enc['fmt'], WebAuthnException::INVALID_DATA);
+            case 'tpm': $this->_attestationFormat = new Format\Tpm($enc, $this->_authenticatorData); break;
+            default: throw new WebAuthnException('invalid attestation format: ' . $enc['fmt'], WebAuthnException::INVALID_DATA);
         }
     }
 

Attestation/Format/Packed.php

@@ -47,7 +47,6 @@ class Packed extends FormatBase {
                         $this->_x5c_chain[] = $chain->getBinaryString();
                     }
                 }
-                unset ($i);
             }
         }
     }

Attestation/Format/Tpm.php

+<?php
+
+
+namespace WebAuthn\Attestation\Format;
+use WebAuthn\WebAuthnException;
+use WebAuthn\Binary\ByteBuffer;
+
+class Tpm extends FormatBase {
+    private static $_ES256 = -7; // ES256
+    private static $_RS256 = -257; // RS256
+
+    private $_TPM_GENERATED_VALUE = "\xFF\x54\x43\x47";
+    private $_TPM_ST_ATTEST_CERTIFY = "\x80\x17";
+
+    /**
+     * @var ByteBuffer
+     */
+    private $_certInfo;
+
+    private $_signature;
+    private $_pubArea;
+    private $_x5c;
+
+    public function __construct($AttestionObject, \WebAuthn\Attestation\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', $attStmt) || ($attStmt['alg'] !== self::$_ES256 && $attStmt['alg'] !== self::$_RS256)) { // SHA256
+            throw new WebAuthnException('only ES256/RS256 acceptable but got: ' . $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->_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 = $attestnCert->getBinaryString();
+
+            // certificate chain
+            if (count($attStmt['x5c']) > 1) {
+                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, $offset);
+
+        // Verify that extraData is set to the hash of attToBeSigned using the hash algorithm employed in "alg".
+        if ($extraData->getBinaryString() !== hash('SHA256', $attToBeSigned, true)) {
+            throw new WebAuthnException('certInfo:extraData not hash of attToBeSigned', WebAuthnException::INVALID_DATA);
+        }
+
+        // Verify the sig is a valid signature over certInfo using the attestation
+        // public key in aikCert with the algorithm specified in alg.
+        return \openssl_verify($this->_certInfo, $this->_signature, $publicKey, OPENSSL_ALGO_SHA256) === 1;
+    }
+
+
+    protected function _tpmReadLengthPrefixed(ByteBuffer $buffer, &$offset) {
+        $len = $buffer->getUint16Val($offset);
+        $data = $buffer->getBytes($offset + 2, $len);
+        $offset += (2 + $len);
+
+        return new ByteBuffer($data);
+    }
+
+}
+

WebAuthn.php

@@ -11,6 +11,7 @@ require_once 'Attestation/Format/None.php';
 require_once 'Attestation/Format/AndroidKey.php';
 require_once 'Attestation/Format/AndroidSafetyNet.php';
 require_once 'Attestation/Format/Packed.php';
+require_once 'Attestation/Format/Tpm.php';
 require_once 'Attestation/Format/U2f.php';
 require_once 'CBOR/CborDecoder.php';