TpmAttestationVerifier::verify() - Code Metrics - Inspection of "Fix test failure caused by PHPUnit update" - madwizard-org/webauthn-server - Measure and Improve Code Quality continuously with Scrutinizer

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Pull Request — master (#18)

unknown

created 2022-08-26 09:08 UTC

TpmAttestationVerifier::verify() A

↳ Parent: TpmAttestationVerifier

Complexity

Conditions	5
Paths	5

Size

Total Lines	34
Code Lines	11

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	8
CRAP Score	5.9256

Importance

Changes	1
Bugs	0	Features	0

Metric	Value
cc	5
eloc	11
c	1
b	0
f	0
nc	5
nop	3
dl	0
loc	34
ccs	8
cts	12
cp	0.6667
crap	5.9256
rs	9.6111

<?php

namespace MadWizard\WebAuthn\Attestation\Verifier;

use MadWizard\WebAuthn\Attestation\AttestationType;
use MadWizard\WebAuthn\Attestation\AuthenticatorData;
use MadWizard\WebAuthn\Attestation\Fido\FidoAaguidExtension;
use MadWizard\WebAuthn\Attestation\Registry\AttestationFormatInterface;
use MadWizard\WebAuthn\Attestation\Registry\BuiltInAttestationFormat;
use MadWizard\WebAuthn\Attestation\Statement\AttestationStatementInterface;
use MadWizard\WebAuthn\Attestation\Statement\TpmAttestationStatement;
use MadWizard\WebAuthn\Attestation\Tpm\TpmEccParameters;
use MadWizard\WebAuthn\Attestation\Tpm\TpmPublic;
use MadWizard\WebAuthn\Attestation\Tpm\TpmRsaParameters;
use MadWizard\WebAuthn\Attestation\TrustPath\CertificateTrustPath;
use MadWizard\WebAuthn\Crypto\CoseHash;
use MadWizard\WebAuthn\Crypto\Ec2Key;
use MadWizard\WebAuthn\Crypto\RsaKey;
use MadWizard\WebAuthn\Exception\UnsupportedException;
use MadWizard\WebAuthn\Exception\VerificationException;
use MadWizard\WebAuthn\Exception\WebAuthnException;
use MadWizard\WebAuthn\Format\ByteBuffer;
use MadWizard\WebAuthn\Pki\CertificateDetails;
use MadWizard\WebAuthn\Pki\CertificateDetailsInterface;

final class TpmAttestationVerifier implements AttestationVerifierInterface
{
    public const OID_TCG_AT_TPM_MANUFACTURER = '2.23.133.2.1';

    public const OID_TCG_AT_TPM_MODEL = '2.23.133.2.2';

    public const OID_TCG_AT_TPM_VERSION = '2.23.133.2.3';

    public const OID_TCG_KP_AIK_CERTIFICATE = '2.23.133.8.3';

    public function verify(AttestationStatementInterface $attStmt, AuthenticatorData $authenticatorData, string $clientDataHash): VerificationResult
    {
        // Verification procedure from https://www.w3.org/TR/webauthn/#tpm-attestation
        if (!($attStmt instanceof TpmAttestationStatement)) {
            throw new VerificationException('Expecting TpmAttestationStatement.');
        }

        // Verify that attStmt is valid CBOR conforming to the syntax defined above and perform CBOR decoding on it to
        // extract the contained fields.
        // -> this is done in TpmAttestationStatement

        // Verify that the public key specified by the parameters and unique fields of pubArea is identical to the
        // credentialPublicKey in the attestedCredentialData in authenticatorData.
        if (!$this->checkTpmPublicKeyMatchesAuthenticatorData($attStmt->getPubArea(), $authenticatorData)) {
            throw new VerificationException('Public key in pubArea does not match the key in authenticatorData');
        }

        // Concatenate authenticatorData and clientDataHash to form attToBeSigned.
        $attToBeSigned = $authenticatorData->getRaw()->getBinaryString() . $clientDataHash;

        //Validate that certInfo is valid:
        if (!$this->checkCertInfo($attStmt, $attStmt->getAlgorithm(), $attToBeSigned)) {
            throw new VerificationException('TPM certInfo is not valid.');
        }

        // If x5c is present, this indicates that the attestation type is not ECDAA. In this case:
        $x5c = $attStmt->getCertificates();
        if ($x5c !== null) {
            return  $this->verifyX5C($x5c, $attStmt->getSignature(), $attStmt->getAlgorithm(), $attStmt->getRawCertInfo(), $authenticatorData);
        }

        // Either x5c or ECDAA is set, but only x5c is supported by this library. So if we reach this the statement
        // is unsupported.
        throw new UnsupportedException('ECDAA is not supported by this library and is removed in later WebAuthn specifications.');
    }

    private function verifyX5c(array $x5c, ByteBuffer $signature, int $signatureAlgorithm, ByteBuffer $rawCertInfo, AuthenticatorData $authenticatorData): VerificationResult
    {
        // Verify the sig is a valid signature over certInfo using the attestation public key in aikCert with the
        // algorithm specified in alg.

        if (!isset($x5c[0])) {
            throw new VerificationException('Empty X5C in attestation.');
        }
        try {
            $cert = CertificateDetails::fromCertificate($x5c[0]);

            $valid = $cert->verifySignature($rawCertInfo->getBinaryString(), $signature->getBinaryString(), $signatureAlgorithm);
        } catch (WebAuthnException $e) {
            throw new VerificationException('Failed to process attestation certificate.', 0, $e);
        }

        if (!$valid) {
            throw new VerificationException('Attestation signature is invalid.');
        }

        // Verify that aikCert meets the requirements in §8.3.1 TPM attestation statement certificate requirements.
        $this->checkCertRequirements($cert);

        // If aikCert contains an extension with OID 1 3 6 1 4 1 45724 1 1 4 (id-fido-gen-ce-aaguid) verify that the
        // value of this extension matches the aaguid in authenticatorData.
        FidoAaguidExtension::checkAaguidExtension($cert, $authenticatorData->getAaguid());

        // If successful, return attestation type AttCA and attestation trust path x5c.
        return new VerificationResult(AttestationType::ATT_CA, new CertificateTrustPath(...$x5c));
    }

    private function checkTpmPublicKeyMatchesAuthenticatorData(TpmPublic $pubArea, AuthenticatorData $authData): bool
    {
        $key = $authData->getKey();
        $params = $pubArea->getParameters();
        if ($params instanceof TpmRsaParameters) {
            if (!($key instanceof RsaKey)) {
                return false;
            }

            if (!$params->getExponentAsBuffer()->equals($key->getExponent())) {
                return false;
            }

            if (!$pubArea->getUnique()->equals($key->getModulus())) {
                return false;
            }

            return true;
        }
        if ($params instanceof TpmEccParameters) {
            if (!($key instanceof Ec2Key)) {
                return false;
            }

            if (!$pubArea->getUnique()->equals($key->getUncompressedCoordinates())) {
                return false;
            }

            // TODO: CHECK CURVE ID
            throw new UnsupportedException('Not implemented yet');
            //return true;
        }
        throw new VerificationException('Unsupported TPM parameters type');
    }

    private function checkCertInfo(TpmAttestationStatement $attStmt, int $algorithm, string $attToBeSigned): bool
    {
        $certInfo = $attStmt->getCertInfo();
        $pubArea = $attStmt->getPubArea();

        $hash = new CoseHash($algorithm);

        // Verify that magic is set to TPM_GENERATED_VALUE.
        // Verify that type is set to TPM_ST_ATTEST_CERTIFY.
        // -> both done by TpmAttest class.

        // Verify that extraData is set to the hash of attToBeSigned using the hash algorithm employed in "alg".
        if (!\hash_equals($certInfo->getExtraData()->getBinaryString(), $hash->hash($attToBeSigned))) {
            return false;
        }

        // Verify that attested contains a TPMS_CERTIFY_INFO structure as specified in [TPMv2-Part2] section 10.12.3,
        // whose name field contains a valid Name for pubArea, as computed using the algorithm in the nameAlg field of
        // pubArea using the procedure specified in [TPMv2-Part1] section 16.
        if (!$pubArea->isValidPubInfoName($certInfo->getAttName())) {
            return false;
        }

        // Note that the remaining fields in the "Standard Attestation Structure" [TPMv2-Part1] section 31.2, i.e.,
        // qualifiedSigner, clockInfo and firmwareVersion are ignored. These fields MAY be used as an input to risk engines.
        // -> not used here
        return true;
    }

    private function checkCertRequirements(CertificateDetailsInterface $cert): void
    {
        // 8.3.1. TPM Attestation Statement Certificate Requirement

        // Version MUST be set to 3.
        $version = $cert->getCertificateVersion();
        if ($version !== CertificateDetails::VERSION_3) {
            throw new VerificationException(sprintf('Attestation certificate version value is %s but should be %s (version 3).', $version ?? 'null', CertificateDetails::VERSION_3));
        }

        // Subject field MUST be set to empty.
        if ($cert->getSubject() !== '') {
            throw new VerificationException('Subject of attestation certificate should be empty.');
        }

        // The Subject Alternative Name extension MUST be set as defined in [TPMv2-EK-Profile] section 3.2.9.
        $tpmManufacturer = $cert->getSubjectAlternateNameDN(self::OID_TCG_AT_TPM_MANUFACTURER);
        $cert->getSubjectAlternateNameDN(self::OID_TCG_AT_TPM_MODEL);
        $tpmVersion = $cert->getSubjectAlternateNameDN(self::OID_TCG_AT_TPM_VERSION);

        // Syntax is id:AABBCCDDEE where AABCCDDEE is the 4 byte manufacturer ID in hex.
        if (!preg_match('~^id:[0-9A-Fa-f]{8}$~', $tpmManufacturer, $match)) {
            throw new VerificationException('Invalid TPM manufacturer attribute in subjectAlternateName of attestation certificate.');
        }

        if (!preg_match('~^id:[0-9A-Fa-f]{2,}$~', $tpmVersion, $match)) {
            throw new VerificationException('Invalid TPM version attribute in subjectAlternateName of attestation certificate.');
        }

        // The Extended Key Usage extension MUST contain the "joint-iso-itu-t(2) internationalorganizations(23) 133 tcg-kp(8) tcg-kp-AIKCertificate(3)" OID.
        if (!$cert->extendedKeyUsageContains(self::OID_TCG_KP_AIK_CERTIFICATE)) {
            throw new VerificationException('Extended key usage of attestation certificate should contain tcg-kp-AIKCertificate.');
        }

        // The Basic Constraints extension MUST have the CA component set to false.
        if ($cert->isCA() !== false) {
            throw new VerificationException('Attestation certificate should not the CA basic constraint set to false.');
        }

        // An Authority Information Access (AIA) extension with entry id-ad-ocsp and a CRL Distribution Point extension
        // [RFC5280] are both OPTIONAL as the status of many attestation certificates is available through metadata services.
        // See, for example, the FIDO Metadata Service [FIDOMetadataService].
        // -> not handled here.
    }

    public function getSupportedFormat(): AttestationFormatInterface
    {
        return new BuiltInAttestationFormat(
            TpmAttestationStatement::FORMAT_ID,
            TpmAttestationStatement::class,
            $this
        );
    }
}


1		<?php
2
3		namespace MadWizard\WebAuthn\Attestation\Verifier;
4
5		use MadWizard\WebAuthn\Attestation\AttestationType;
6		use MadWizard\WebAuthn\Attestation\AuthenticatorData;
7		use MadWizard\WebAuthn\Attestation\Fido\FidoAaguidExtension;
8		use MadWizard\WebAuthn\Attestation\Registry\AttestationFormatInterface;
9		use MadWizard\WebAuthn\Attestation\Registry\BuiltInAttestationFormat;
10		use MadWizard\WebAuthn\Attestation\Statement\AttestationStatementInterface;
11		use MadWizard\WebAuthn\Attestation\Statement\TpmAttestationStatement;
12		use MadWizard\WebAuthn\Attestation\Tpm\TpmEccParameters;
13		use MadWizard\WebAuthn\Attestation\Tpm\TpmPublic;
14		use MadWizard\WebAuthn\Attestation\Tpm\TpmRsaParameters;
15		use MadWizard\WebAuthn\Attestation\TrustPath\CertificateTrustPath;
16		use MadWizard\WebAuthn\Crypto\CoseHash;
17		use MadWizard\WebAuthn\Crypto\Ec2Key;
18		use MadWizard\WebAuthn\Crypto\RsaKey;
19		use MadWizard\WebAuthn\Exception\UnsupportedException;
20		use MadWizard\WebAuthn\Exception\VerificationException;
21		use MadWizard\WebAuthn\Exception\WebAuthnException;
22		use MadWizard\WebAuthn\Format\ByteBuffer;
23		use MadWizard\WebAuthn\Pki\CertificateDetails;
24		use MadWizard\WebAuthn\Pki\CertificateDetailsInterface;
25
26		final class TpmAttestationVerifier implements AttestationVerifierInterface
27		{
28		public const OID_TCG_AT_TPM_MANUFACTURER = '2.23.133.2.1';
29
30		public const OID_TCG_AT_TPM_MODEL = '2.23.133.2.2';
31
32		public const OID_TCG_AT_TPM_VERSION = '2.23.133.2.3';
33
34		public const OID_TCG_KP_AIK_CERTIFICATE = '2.23.133.8.3';
35
36	1	public function verify(AttestationStatementInterface $attStmt, AuthenticatorData $authenticatorData, string $clientDataHash): VerificationResult
37		{
38		// Verification procedure from https://www.w3.org/TR/webauthn/#tpm-attestation
39	1	if (!($attStmt instanceof TpmAttestationStatement)) {
40		throw new VerificationException('Expecting TpmAttestationStatement.');
41		}
42
43		// Verify that attStmt is valid CBOR conforming to the syntax defined above and perform CBOR decoding on it to
44		// extract the contained fields.
45		// -> this is done in TpmAttestationStatement
46
47		// Verify that the public key specified by the parameters and unique fields of pubArea is identical to the
48		// credentialPublicKey in the attestedCredentialData in authenticatorData.
49	1	if (!$this->checkTpmPublicKeyMatchesAuthenticatorData($attStmt->getPubArea(), $authenticatorData)) {
50		throw new VerificationException('Public key in pubArea does not match the key in authenticatorData');
51		}
52
53		// Concatenate authenticatorData and clientDataHash to form attToBeSigned.
54	1	$attToBeSigned = $authenticatorData->getRaw()->getBinaryString() . $clientDataHash;
55
56		//Validate that certInfo is valid:
57	1	if (!$this->checkCertInfo($attStmt, $attStmt->getAlgorithm(), $attToBeSigned)) {
58		throw new VerificationException('TPM certInfo is not valid.');
59		}
60
61		// If x5c is present, this indicates that the attestation type is not ECDAA. In this case:
62	1	$x5c = $attStmt->getCertificates();
63	1	if ($x5c !== null) {
64	1	return $this->verifyX5C($x5c, $attStmt->getSignature(), $attStmt->getAlgorithm(), $attStmt->getRawCertInfo(), $authenticatorData);
65		}
66
67		// Either x5c or ECDAA is set, but only x5c is supported by this library. So if we reach this the statement
68		// is unsupported.
69		throw new UnsupportedException('ECDAA is not supported by this library and is removed in later WebAuthn specifications.');
70		}
71
72	1	private function verifyX5c(array $x5c, ByteBuffer $signature, int $signatureAlgorithm, ByteBuffer $rawCertInfo, AuthenticatorData $authenticatorData): VerificationResult
73		{
74		// Verify the sig is a valid signature over certInfo using the attestation public key in aikCert with the
75		// algorithm specified in alg.
76
77	1	if (!isset($x5c[0])) {
78		throw new VerificationException('Empty X5C in attestation.');
79		}
80		try {
81	1	$cert = CertificateDetails::fromCertificate($x5c[0]);
82
83	1	$valid = $cert->verifySignature($rawCertInfo->getBinaryString(), $signature->getBinaryString(), $signatureAlgorithm);
84		} catch (WebAuthnException $e) {
85		throw new VerificationException('Failed to process attestation certificate.', 0, $e);
86		}
87
88	1	if (!$valid) {
89		throw new VerificationException('Attestation signature is invalid.');
90		}
91
92		// Verify that aikCert meets the requirements in §8.3.1 TPM attestation statement certificate requirements.
93	1	$this->checkCertRequirements($cert);
94
95		// If aikCert contains an extension with OID 1 3 6 1 4 1 45724 1 1 4 (id-fido-gen-ce-aaguid) verify that the
96		// value of this extension matches the aaguid in authenticatorData.
97	1	FidoAaguidExtension::checkAaguidExtension($cert, $authenticatorData->getAaguid());
98
99		// If successful, return attestation type AttCA and attestation trust path x5c.
100	1	return new VerificationResult(AttestationType::ATT_CA, new CertificateTrustPath(...$x5c));
101		}
102
103	1	private function checkTpmPublicKeyMatchesAuthenticatorData(TpmPublic $pubArea, AuthenticatorData $authData): bool
104		{
105	1	$key = $authData->getKey();
106	1	$params = $pubArea->getParameters();
107	1	if ($params instanceof TpmRsaParameters) {
108	1	if (!($key instanceof RsaKey)) {
109		return false;
110		}
111
112	1	if (!$params->getExponentAsBuffer()->equals($key->getExponent())) {
113		return false;
114		}
115
116	1	if (!$pubArea->getUnique()->equals($key->getModulus())) {
117		return false;
118		}
119
120	1	return true;
121		}
122		if ($params instanceof TpmEccParameters) {
123		if (!($key instanceof Ec2Key)) {
124		return false;
125		}
126
127		if (!$pubArea->getUnique()->equals($key->getUncompressedCoordinates())) {
128		return false;
129		}
130
131		// TODO: CHECK CURVE ID
132		throw new UnsupportedException('Not implemented yet');
133		//return true;
134		}
135		throw new VerificationException('Unsupported TPM parameters type');
136		}
137
138	1	private function checkCertInfo(TpmAttestationStatement $attStmt, int $algorithm, string $attToBeSigned): bool
139		{
140	1	$certInfo = $attStmt->getCertInfo();
141	1	$pubArea = $attStmt->getPubArea();
142
143	1	$hash = new CoseHash($algorithm);
144
145		// Verify that magic is set to TPM_GENERATED_VALUE.
146		// Verify that type is set to TPM_ST_ATTEST_CERTIFY.
147		// -> both done by TpmAttest class.
148
149		// Verify that extraData is set to the hash of attToBeSigned using the hash algorithm employed in "alg".
150	1	if (!\hash_equals($certInfo->getExtraData()->getBinaryString(), $hash->hash($attToBeSigned))) {
151		return false;
152		}
153
154		// Verify that attested contains a TPMS_CERTIFY_INFO structure as specified in [TPMv2-Part2] section 10.12.3,
155		// whose name field contains a valid Name for pubArea, as computed using the algorithm in the nameAlg field of
156		// pubArea using the procedure specified in [TPMv2-Part1] section 16.
157	1	if (!$pubArea->isValidPubInfoName($certInfo->getAttName())) {
158		return false;
159		}
160
161		// Note that the remaining fields in the "Standard Attestation Structure" [TPMv2-Part1] section 31.2, i.e.,
162		// qualifiedSigner, clockInfo and firmwareVersion are ignored. These fields MAY be used as an input to risk engines.
163		// -> not used here
164	1	return true;
165		}
166
167	1	private function checkCertRequirements(CertificateDetailsInterface $cert): void
168		{
169		// 8.3.1. TPM Attestation Statement Certificate Requirement
170
171		// Version MUST be set to 3.
172	1	$version = $cert->getCertificateVersion();
173	1	if ($version !== CertificateDetails::VERSION_3) {
174		throw new VerificationException(sprintf('Attestation certificate version value is %s but should be %s (version 3).', $version ?? 'null', CertificateDetails::VERSION_3));
175		}
176
177		// Subject field MUST be set to empty.
178	1	if ($cert->getSubject() !== '') {
179		throw new VerificationException('Subject of attestation certificate should be empty.');
180		}
181
182		// The Subject Alternative Name extension MUST be set as defined in [TPMv2-EK-Profile] section 3.2.9.
183	1	$tpmManufacturer = $cert->getSubjectAlternateNameDN(self::OID_TCG_AT_TPM_MANUFACTURER);
184	1	$cert->getSubjectAlternateNameDN(self::OID_TCG_AT_TPM_MODEL);
185	1	$tpmVersion = $cert->getSubjectAlternateNameDN(self::OID_TCG_AT_TPM_VERSION);
186
187		// Syntax is id:AABBCCDDEE where AABCCDDEE is the 4 byte manufacturer ID in hex.
188	1	if (!preg_match('~^id:[0-9A-Fa-f]{8}$~', $tpmManufacturer, $match)) {
189		throw new VerificationException('Invalid TPM manufacturer attribute in subjectAlternateName of attestation certificate.');
190		}
191
192	1	if (!preg_match('~^id:[0-9A-Fa-f]{2,}$~', $tpmVersion, $match)) {
193		throw new VerificationException('Invalid TPM version attribute in subjectAlternateName of attestation certificate.');
194		}
195
196		// The Extended Key Usage extension MUST contain the "joint-iso-itu-t(2) internationalorganizations(23) 133 tcg-kp(8) tcg-kp-AIKCertificate(3)" OID.
197	1	if (!$cert->extendedKeyUsageContains(self::OID_TCG_KP_AIK_CERTIFICATE)) {
198		throw new VerificationException('Extended key usage of attestation certificate should contain tcg-kp-AIKCertificate.');
199		}
200
201		// The Basic Constraints extension MUST have the CA component set to false.
202	1	if ($cert->isCA() !== false) {
203		throw new VerificationException('Attestation certificate should not the CA basic constraint set to false.');
204		}
205
206		// An Authority Information Access (AIA) extension with entry id-ad-ocsp and a CRL Distribution Point extension
207		// [RFC5280] are both OPTIONAL as the status of many attestation certificates is available through metadata services.
208		// See, for example, the FIDO Metadata Service [FIDOMetadataService].
209		// -> not handled here.
210	1	}
211
212	19	public function getSupportedFormat(): AttestationFormatInterface
213		{
214	19	return new BuiltInAttestationFormat(
215	19	TpmAttestationStatement::FORMAT_ID,
216	19	TpmAttestationStatement::class,
217		$this
218		);
219		}
220		}
221

madwizard-org / webauthn-server

Pull Request — master (#18)

TpmAttestationVerifier::verify() A

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