"use strict";

let crypto = require("crypto");

let projectRoot = require("path").dirname(require.main.filename).replace(/[\/\\]node_modules[\/\\].*/g, ""); // eslint-disable-line no-useless-escape

/**

* A basic encryption/decryption script/API for resting data for Node.js users.

* @class

*/

class basic256 {

constructor() {

try {

var savedKeys = require(`${projectRoot}/.basic256rc.js`);

} catch (e) {

throw new Error("An error happened while loading the key");

}

this.ALGORITHM = "AES-256-CBC";

this.HMAC_ALGORITHM = "SHA256";

this.KEY = savedKeys.key; // Use the automated script.

this.HMAC_KEY = savedKeys.hmac_key; // Use the automated script.

}

encrypt(plain_text) {

if (!plain_text || typeof (plain_text) !== "string") throw new Error("Plain text was not found.");

var IV = Buffer.from(tools.randomValueHex(16)); // ensure that the IV (initialization vector) is random

var encryptor, cipher_text, hmac;

encryptor = crypto.createCipheriv(this.ALGORITHM, this.KEY, IV);

encryptor.setEncoding("hex");

encryptor.write(plain_text);

encryptor.end();

cipher_text = encryptor.read();

hmac = crypto.createHmac(this.HMAC_ALGORITHM, this.HMAC_KEY);

hmac.update(cipher_text);

hmac.update(IV.toString("hex")); // ensure that both the IV and the cipher-text is protected by the HMAC

// The IV isn't a secret so it can be stored along side everything else

return cipher_text + "$" + IV.toString("hex") + "$" + hmac.digest("hex");

}

decrypt(cipher_text) {

if (!cipher_text || typeof (cipher_text) !== "string" || !cipher_text.match(/\$/g)) throw new Error("A valid cipher text was not found.");

var cipher_blob = cipher_text.split("$");

if (cipher_blob.length !== 3) throw new Error("Cipher text is broken.");

var ct = cipher_blob[0];

var IV = Buffer.from(cipher_blob[1], "hex");

var hmac = cipher_blob[2];

var chmac, decryptor;

chmac = crypto.createHmac(this.HMAC_ALGORITHM, this.HMAC_KEY);

chmac.update(ct);

chmac.update(IV.toString("hex"));

if (!tools.constant_time_compare(chmac.digest("hex"), hmac)) {

throw new Error("Encrypted Blob has been tampered with.");

}

decryptor = crypto.createDecipheriv(this.ALGORITHM, this.KEY, IV);

var decryptedText = decryptor.update(ct, "hex", "utf-8");

return decryptedText + decryptor.final("utf-8");

}

}

class tools {

static constant_time_compare(val1, val2) {

var sentinel;

if (val1.length !== val2.length) {

return false;

}

for (var i = 0; i <= (val1.length - 1); i++) {

sentinel |= val1.charCodeAt(i) ^ val2.charCodeAt(i);

}

return sentinel === 0;

}

static randomValueHex(len) {

return crypto.randomBytes(Math.ceil(len / 2))

.toString("hex") // convert to hexadecimal format

.slice(0, len); // return required number of characters

}

}

module.exports = basic256;