/
webauthn.js
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/
webauthn.js
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/**
* @description MeshCentral WebAuthn module
* @version v0.0.1
*/
// This code is based on a portion of the webauthn module at: https://www.npmjs.com/package/webauthn
"use strict"
const crypto = require('crypto');
const cbor = require('cbor');
//const iso_3166_1 = require('iso-3166-1')
//const Certificate = null; //require('@fidm/x509')
module.exports.CreateWebAuthnModule = function () {
var obj = {};
obj.generateRegistrationChallenge = function (rpName, user) {
return {
rp: { name: rpName },
user: user,
challenge: crypto.randomBytes(64).toString('base64'),
pubKeyCredParams: [{ type: 'public-key', alg: -7 }],
timeout: 60000,
attestation: 'none'
};
}
obj.verifyAuthenticatorAttestationResponse = function (webauthnResponse) {
const attestationBuffer = Buffer.from(webauthnResponse.attestationObject, 'base64');
const ctapMakeCredResp = cbor.decodeAllSync(attestationBuffer)[0];
const authrDataStruct = parseMakeCredAuthData(ctapMakeCredResp.authData);
//console.log('***CTAP_RESPONSE', ctapMakeCredResp)
//console.log('***AUTHR_DATA_STRUCT', authrDataStruct)
const response = { 'verified': false };
if ((ctapMakeCredResp.fmt === 'none') || (ctapMakeCredResp.fmt === 'fido-u2f') || (ctapMakeCredResp.fmt === 'packed')) {
if (!(authrDataStruct.flags & 0x01)) { throw new Error('User was NOT presented during authentication!'); } // U2F_USER_PRESENTED
const publicKey = COSEECDHAtoPKCS(authrDataStruct.COSEPublicKey);
response.verified = true;
if (response.verified) {
response.authrInfo = {
fmt: 'none',
publicKey: ASN1toPEM(publicKey),
counter: authrDataStruct.counter,
keyId: authrDataStruct.credID.toString('base64')
};
}
}
/*
else if (ctapMakeCredResp.fmt === 'fido-u2f') {
if (!(authrDataStruct.flags & 0x01)) // U2F_USER_PRESENTED
throw new Error('User was NOT presented during authentication!');
const clientDataHash = hash(webauthnResponse.clientDataJSON)
const reservedByte = Buffer.from([0x00]);
const publicKey = COSEECDHAtoPKCS(authrDataStruct.COSEPublicKey)
const signatureBase = Buffer.concat([reservedByte, authrDataStruct.rpIdHash, clientDataHash, authrDataStruct.credID, publicKey]);
const PEMCertificate = ASN1toPEM(ctapMakeCredResp.attStmt.x5c[0]);
const signature = ctapMakeCredResp.attStmt.sig;
response.verified = verifySignature(signature, signatureBase, PEMCertificate)
if (response.verified) {
response.authrInfo = {
fmt: 'fido-u2f',
publicKey: ASN1toPEM(publicKey),
counter: authrDataStruct.counter,
keyId: authrDataStruct.credID.toString('base64')
}
}
} else if (ctapMakeCredResp.fmt === 'packed' && ctapMakeCredResp.attStmt.hasOwnProperty('x5c')) {
if (!(authrDataStruct.flags & 0x01)) // U2F_USER_PRESENTED
throw new Error('User was NOT presented durring authentication!');
const clientDataHash = hash(webauthnResponse.clientDataJSON)
const publicKey = COSEECDHAtoPKCS(authrDataStruct.COSEPublicKey)
const signatureBase = Buffer.concat([ctapMakeCredResp.authData, clientDataHash]);
const PEMCertificate = ASN1toPEM(ctapMakeCredResp.attStmt.x5c[0]);
const signature = ctapMakeCredResp.attStmt.sig;
const pem = Certificate.fromPEM(PEMCertificate);
// Getting requirements from https://www.w3.org/TR/webauthn/#packed-attestation
const aaguid_ext = pem.getExtension('1.3.6.1.4.1.45724.1.1.4')
response.verified = // Verify that sig is a valid signature over the concatenation of authenticatorData
// and clientDataHash using the attestation public key in attestnCert with the algorithm specified in alg.
verifySignature(signature, signatureBase, PEMCertificate) &&
// version must be 3 (which is indicated by an ASN.1 INTEGER with value 2)
pem.version == 3 &&
// ISO 3166 valid country
typeof iso_3166_1.whereAlpha2(pem.subject.countryName) !== 'undefined' &&
// Legal name of the Authenticator vendor (UTF8String)
pem.subject.organizationName &&
// Literal string “Authenticator Attestation” (UTF8String)
pem.subject.organizationalUnitName === 'Authenticator Attestation' &&
// A UTF8String of the vendor’s choosing
pem.subject.commonName &&
// The Basic Constraints extension MUST have the CA component set to false
!pem.extensions.isCA &&
// If attestnCert 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.
// The extension MUST NOT be marked as critical.
(aaguid_ext != null ?
(authrDataStruct.hasOwnProperty('aaguid') ?
!aaguid_ext.critical && aaguid_ext.value.slice(2).equals(authrDataStruct.aaguid) : false)
: true);
if (response.verified) {
response.authrInfo = {
fmt: 'fido-u2f',
publicKey: publicKey,
counter: authrDataStruct.counter,
keyId: authrDataStruct.credID.toString('base64')
}
}
// Self signed
} else if (ctapMakeCredResp.fmt === 'packed') {
if (!(authrDataStruct.flags & 0x01)) // U2F_USER_PRESENTED
throw new Error('User was NOT presented durring authentication!');
const clientDataHash = hash(webauthnResponse.clientDataJSON)
const publicKey = COSEECDHAtoPKCS(authrDataStruct.COSEPublicKey)
const signatureBase = Buffer.concat([ctapMakeCredResp.authData, clientDataHash]);
const PEMCertificate = ASN1toPEM(publicKey);
const { attStmt: { sig: signature, alg } } = ctapMakeCredResp
response.verified = // Verify that sig is a valid signature over the concatenation of authenticatorData
// and clientDataHash using the attestation public key in attestnCert with the algorithm specified in alg.
verifySignature(signature, signatureBase, PEMCertificate) && alg === -7
if (response.verified) {
response.authrInfo = {
fmt: 'fido-u2f',
publicKey: ASN1toPEM(publicKey),
counter: authrDataStruct.counter,
keyId: authrDataStruct.credID.toString('base64')
}
}
} else if (ctapMakeCredResp.fmt === 'android-safetynet') {
console.log("Android safetynet request\n")
console.log(ctapMakeCredResp)
const authrDataStruct = parseMakeCredAuthData(ctapMakeCredResp.authData);
console.log('AUTH_DATA', authrDataStruct)
//console.log('CLIENT_DATA_JSON ', webauthnResponse.clientDataJSON)
const publicKey = COSEECDHAtoPKCS(authrDataStruct.COSEPublicKey)
let [header, payload, signature] = ctapMakeCredResp.attStmt.response.toString('utf8').split('.')
const signatureBase = Buffer.from([header, payload].join('.'))
header = JSON.parse(header)
payload = JSON.parse(payload)
console.log('JWS HEADER', header)
console.log('JWS PAYLOAD', payload)
console.log('JWS SIGNATURE', signature)
const PEMCertificate = ASN1toPEM(Buffer.from(header.x5c[0], 'base64'))
const pem = Certificate.fromPEM(PEMCertificate)
console.log('PEM', pem)
response.verified = // Verify that sig is a valid signature over the concatenation of authenticatorData
// and clientDataHash using the attestation public key in attestnCert with the algorithm specified in alg.
verifySignature(signature, signatureBase, PEMCertificate) &&
// version must be 3 (which is indicated by an ASN.1 INTEGER with value 2)
pem.version == 3 &&
pem.subject.commonName === 'attest.android.com'
if (response.verified) {
response.authrInfo = {
fmt: 'fido-u2f',
publicKey: ASN1toPEM(publicKey),
counter: authrDataStruct.counter,
keyId: authrDataStruct.credID.toString('base64')
}
}
console.log('RESPONSE', response)
} */
else {
throw new Error(`Unsupported attestation format: ${ctapMakeCredResp.fmt}`);
}
return response;
}
obj.verifyAuthenticatorAssertionResponse = function (webauthnResponse, authr) {
const response = { 'verified': false }
if (['fido-u2f'].includes(authr.fmt)) {
const authrDataStruct = parseGetAssertAuthData(webauthnResponse.authenticatorData);
if (!(authrDataStruct.flags & 0x01)) { throw new Error('User was not presented durring authentication!'); } // U2F_USER_PRESENTED
response.counter = authrDataStruct.counter;
response.verified = verifySignature(webauthnResponse.signature, Buffer.concat([authrDataStruct.rpIdHash, authrDataStruct.flagsBuf, authrDataStruct.counterBuf, hash(webauthnResponse.clientDataJSON)]), authr.publicKey);
}
return response;
}
function hash(data) { return crypto.createHash('sha256').update(data).digest() }
function verifySignature(signature, data, publicKey) { return crypto.createVerify('SHA256').update(data).verify(publicKey, signature); }
function parseGetAssertAuthData(buffer) {
const rpIdHash = buffer.slice(0, 32);
buffer = buffer.slice(32);
const flagsBuf = buffer.slice(0, 1);
buffer = buffer.slice(1);
const flags = flagsBuf[0];
const counterBuf = buffer.slice(0, 4);
buffer = buffer.slice(4);
const counter = counterBuf.readUInt32BE(0);
return { rpIdHash, flagsBuf, flags, counter, counterBuf };
}
function parseMakeCredAuthData(buffer) {
const rpIdHash = buffer.slice(0, 32);
buffer = buffer.slice(32);
const flagsBuf = buffer.slice(0, 1);
buffer = buffer.slice(1);
const flags = flagsBuf[0];
const counterBuf = buffer.slice(0, 4);
buffer = buffer.slice(4);
const counter = counterBuf.readUInt32BE(0);
const aaguid = buffer.slice(0, 16);
buffer = buffer.slice(16);
const credIDLenBuf = buffer.slice(0, 2);
buffer = buffer.slice(2);
const credIDLen = credIDLenBuf.readUInt16BE(0);
const credID = buffer.slice(0, credIDLen);
buffer = buffer.slice(credIDLen);
const COSEPublicKey = buffer;
return { rpIdHash, flagsBuf, flags, counter, counterBuf, aaguid, credID, COSEPublicKey };
}
function COSEECDHAtoPKCS(COSEPublicKey) {
const coseStruct = cbor.decodeAllSync(COSEPublicKey)[0];
return Buffer.concat([Buffer.from([0x04]), coseStruct.get(-2), coseStruct.get(-3)]);
}
function ASN1toPEM(pkBuffer) {
if (!Buffer.isBuffer(pkBuffer)) { throw new Error("ASN1toPEM: pkBuffer must be Buffer."); }
let type;
if (pkBuffer.length == 65 && pkBuffer[0] == 0x04) { pkBuffer = Buffer.concat([Buffer.from("3059301306072a8648ce3d020106082a8648ce3d030107034200", "hex"), pkBuffer]); type = 'PUBLIC KEY'; } else { type = 'CERTIFICATE'; }
const b64cert = pkBuffer.toString('base64');
let PEMKey = '';
for (let i = 0; i < Math.ceil(b64cert.length / 64); i++) { const start = 64 * i; PEMKey += b64cert.substr(start, 64) + '\n'; }
PEMKey = `-----BEGIN ${type}-----\n` + PEMKey + `-----END ${type}-----\n`;
return PEMKey;
}
return obj;
}