/**
* Module dependencies.
*/
var crypto = require('crypto');
/**
* Sign the given `val` with `secret`.
*
* @param {String} val
* @param {String|NodeJS.ArrayBufferView|crypto.KeyObject} secret
* @return {String}
* @api private
*/
exports.sign = function(val, secret){
if ('string' != typeof val) throw new TypeError("Cookie value must be provided as a string.");
if (null == secret) throw new TypeError("Secret key must be provided.");
return val + '.' + crypto
.createHmac('sha256', secret)
.update(val)
.digest('base64')
.replace(/\=+$/, '');
};
/**
* Unsign and decode the given `input` with `secret`,
* returning `false` if the signature is invalid.
*
* @param {String} input
* @param {String|NodeJS.ArrayBufferView|crypto.KeyObject} secret
* @return {String|Boolean}
* @api private
*/
exports.unsign = function(input, secret){
if ('string' != typeof input) throw new TypeError("Signed cookie string must be provided.");
if (null == secret) throw new TypeError("Secret key must be provided.");
var tentativeValue = input.slice(0, input.lastIndexOf('.')),
expectedInput = exports.sign(tentativeValue, secret),
expectedBuffer = Buffer.from(expectedInput),
inputBuffer = Buffer.from(input);
return (
expectedBuffer.length === inputBuffer.length &&
crypto.timingSafeEqual(expectedBuffer, inputBuffer)
) ? tentativeValue : false;
};