blob: e4f38e0ee6a8efc794141171d14b9903603c6841 [file] [log] [blame]
Copybara botbe50d492023-11-30 00:16:42 +01001<?php
2
3
4namespace lbuchs\WebAuthn\Attestation\Format;
5use lbuchs\WebAuthn\Attestation\AuthenticatorData;
6use lbuchs\WebAuthn\WebAuthnException;
7use lbuchs\WebAuthn\Binary\ByteBuffer;
8
9class 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