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var bufferEqual = require('buffer-equal-constant-time');
var Buffer = require('safe-buffer').Buffer;
var crypto = require('crypto');
var formatEcdsa = require('ecdsa-sig-formatter');
var util = require('util');
var MSG_INVALID_ALGORITHM = '"%s" is not a valid algorithm.\n Supported algorithms are:\n "HS256", "HS384", "HS512", "RS256", "RS384", "RS512", "PS256", "PS384", "PS512", "ES256", "ES384", "ES512" and "none".'
var MSG_INVALID_SECRET = 'secret must be a string or buffer';
var MSG_INVALID_VERIFIER_KEY = 'key must be a string or a buffer';
var MSG_INVALID_SIGNER_KEY = 'key must be a string, a buffer or an object';
var supportsKeyObjects = typeof crypto.createPublicKey === 'function';
if (supportsKeyObjects) {
MSG_INVALID_VERIFIER_KEY += ' or a KeyObject';
MSG_INVALID_SECRET += 'or a KeyObject';
}
function checkIsPublicKey(key) {
if (Buffer.isBuffer(key)) {
return;
}
if (typeof key === 'string') {
return;
}
if (!supportsKeyObjects) {
throw typeError(MSG_INVALID_VERIFIER_KEY);
}
if (typeof key !== 'object') {
throw typeError(MSG_INVALID_VERIFIER_KEY);
}
if (typeof key.type !== 'string') {
throw typeError(MSG_INVALID_VERIFIER_KEY);
}
if (typeof key.asymmetricKeyType !== 'string') {
throw typeError(MSG_INVALID_VERIFIER_KEY);
}
if (typeof key.export !== 'function') {
throw typeError(MSG_INVALID_VERIFIER_KEY);
}
};
function checkIsPrivateKey(key) {
if (Buffer.isBuffer(key)) {
return;
}
if (typeof key === 'string') {
return;
}
if (typeof key === 'object') {
return;
}
throw typeError(MSG_INVALID_SIGNER_KEY);
};
function checkIsSecretKey(key) {
if (Buffer.isBuffer(key)) {
return;
}
if (typeof key === 'string') {
return key;
}
if (!supportsKeyObjects) {
throw typeError(MSG_INVALID_SECRET);
}
if (typeof key !== 'object') {
throw typeError(MSG_INVALID_SECRET);
}
if (key.type !== 'secret') {
throw typeError(MSG_INVALID_SECRET);
}
if (typeof key.export !== 'function') {
throw typeError(MSG_INVALID_SECRET);
}
}
function fromBase64(base64) {
return base64
.replace(/=/g, '')
.replace(/\+/g, '-')
.replace(/\//g, '_');
}
function toBase64(base64url) {
base64url = base64url.toString();
var padding = 4 - base64url.length % 4;
if (padding !== 4) {
for (var i = 0; i < padding; ++i) {
base64url += '=';
}
}
return base64url
.replace(/\-/g, '+')
.replace(/_/g, '/');
}
function typeError(template) {
var args = [].slice.call(arguments, 1);
var errMsg = util.format.bind(util, template).apply(null, args);
return new TypeError(errMsg);
}
function bufferOrString(obj) {
return Buffer.isBuffer(obj) || typeof obj === 'string';
}
function normalizeInput(thing) {
if (!bufferOrString(thing))
thing = JSON.stringify(thing);
return thing;
}
function createHmacSigner(bits) {
return function sign(thing, secret) {
checkIsSecretKey(secret);
thing = normalizeInput(thing);
var hmac = crypto.createHmac('sha' + bits, secret);
var sig = (hmac.update(thing), hmac.digest('base64'))
return fromBase64(sig);
}
}
function createHmacVerifier(bits) {
return function verify(thing, signature, secret) {
var computedSig = createHmacSigner(bits)(thing, secret);
return bufferEqual(Buffer.from(signature), Buffer.from(computedSig));
}
}
function createKeySigner(bits) {
return function sign(thing, privateKey) {
checkIsPrivateKey(privateKey);
thing = normalizeInput(thing);
// Even though we are specifying "RSA" here, this works with ECDSA
// keys as well.
var signer = crypto.createSign('RSA-SHA' + bits);
var sig = (signer.update(thing), signer.sign(privateKey, 'base64'));
return fromBase64(sig);
}
}
function createKeyVerifier(bits) {
return function verify(thing, signature, publicKey) {
checkIsPublicKey(publicKey);
thing = normalizeInput(thing);
signature = toBase64(signature);
var verifier = crypto.createVerify('RSA-SHA' + bits);
verifier.update(thing);
return verifier.verify(publicKey, signature, 'base64');
}
}
function createPSSKeySigner(bits) {
return function sign(thing, privateKey) {
checkIsPrivateKey(privateKey);
thing = normalizeInput(thing);
var signer = crypto.createSign('RSA-SHA' + bits);
var sig = (signer.update(thing), signer.sign({
key: privateKey,
padding: crypto.constants.RSA_PKCS1_PSS_PADDING,
saltLength: crypto.constants.RSA_PSS_SALTLEN_DIGEST
}, 'base64'));
return fromBase64(sig);
}
}
function createPSSKeyVerifier(bits) {
return function verify(thing, signature, publicKey) {
checkIsPublicKey(publicKey);
thing = normalizeInput(thing);
signature = toBase64(signature);
var verifier = crypto.createVerify('RSA-SHA' + bits);
verifier.update(thing);
return verifier.verify({
key: publicKey,
padding: crypto.constants.RSA_PKCS1_PSS_PADDING,
saltLength: crypto.constants.RSA_PSS_SALTLEN_DIGEST
}, signature, 'base64');
}
}
function createECDSASigner(bits) {
var inner = createKeySigner(bits);
return function sign() {
var signature = inner.apply(null, arguments);
signature = formatEcdsa.derToJose(signature, 'ES' + bits);
return signature;
};
}
function createECDSAVerifer(bits) {
var inner = createKeyVerifier(bits);
return function verify(thing, signature, publicKey) {
signature = formatEcdsa.joseToDer(signature, 'ES' + bits).toString('base64');
var result = inner(thing, signature, publicKey);
return result;
};
}
function createNoneSigner() {
return function sign() {
return '';
}
}
function createNoneVerifier() {
return function verify(thing, signature) {
return signature === '';
}
}
module.exports = function jwa(algorithm) {
var signerFactories = {
hs: createHmacSigner,
rs: createKeySigner,
ps: createPSSKeySigner,
es: createECDSASigner,
none: createNoneSigner,
}
var verifierFactories = {
hs: createHmacVerifier,
rs: createKeyVerifier,
ps: createPSSKeyVerifier,
es: createECDSAVerifer,
none: createNoneVerifier,
}
var match = algorithm.match(/^(RS|PS|ES|HS)(256|384|512)$|^(none)$/i);
if (!match)
throw typeError(MSG_INVALID_ALGORITHM, algorithm);
var algo = (match[1] || match[3]).toLowerCase();
var bits = match[2];
return {
sign: signerFactories[algo](bits),
verify: verifierFactories[algo](bits),
}
};
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