offline-token-generator/index.js

Offline Token Generator

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var aes_js_1 = require("aes-js");
var js_sha512_1 = require("js-sha512");
var OfflineTokenGenerator = /** @class */ (function () {
    function OfflineTokenGenerator(key, aesBits, ttl, tolerance, timeGen) {
        if (ttl === void 0) { ttl = 5; }
        if (tolerance === void 0) { tolerance = 0; }
        if (timeGen === void 0) { timeGen = {
            getTime: function () {
                return new Date().getTime();
            }
        }; }
        this.key = key;
        this.aesBits = aesBits;
        this.ttl = ttl;
        this.tolerance = tolerance;
        this.timeGen = timeGen;
        if (tolerance < 0) {
            throw new Error("tolerance must be >= 0");
        }
        if (ttl < 1) {
            throw new Error("ttl must be >= 1");
        }
        if (aesBits != 128
            && aesBits != 192
            && aesBits != 256) {
            throw new Error("aesBits must be 128 or 192 or 256");
        }
    }
    OfflineTokenGenerator.prototype.getCurrentTime = function (tol) {
        if (tol > this.tolerance) {
            return -1;
        }
        var t = Math.floor(this.timeGen.getTime() / 1000);
        t -= (t % this.ttl);
        while (tol > 0) {
            t -= this.ttl;
            tol--;
        }
        return t;
    };
    OfflineTokenGenerator.prototype.getKey = function (tol) {
        var t = this.getCurrentTime(tol);
        if (t == -1) {
            return null;
        }
        var hash = js_sha512_1.sha384.digest(t + "//" + this.key + "//" + this.aesBits + "//" + this.ttl + "//" + this.tolerance);
        return [hash.slice(0, this.aesBits / 8), hash.slice(32, 48)];
    };
    OfflineTokenGenerator.prototype.generate = function (value) {
        var envelope = [
            Math.random(),
            value
        ];
        var hash = this.getKey(0);
        var aesPass = hash[0];
        var aesIV = hash[1];
        var content = JSON.stringify(envelope);
        var padding = '';
        while ((content.length + padding.length) % 16 > 0) {
            padding += ' ';
        }
        content = content + padding;
        return aes_js_1.utils.hex.fromBytes(new aes_js_1.ModeOfOperation.cbc(aesPass, aesIV).encrypt(aes_js_1.utils.utf8.toBytes(content)));
    };
    OfflineTokenGenerator.prototype.doRead = function (tol, crypto) {
        var hash = this.getKey(tol);
        if (hash == null) {
            return null;
        }
        var aesPass = hash[0];
        var aesIV = hash[1];
        try {
            return JSON.parse(aes_js_1.utils.utf8.fromBytes(new aes_js_1.ModeOfOperation.cbc(aesPass, aesIV).decrypt(aes_js_1.utils.hex.toBytes(crypto))));
        }
        catch (e) {
            return this.doRead(tol + 1, crypto);
        }
    };
    OfflineTokenGenerator.prototype.read = function (crypto) {
        var json = this.doRead(0, crypto);
        if (json == null) {
            throw new Error("Expired token!");
        }
        return json[1];
    };
    return OfflineTokenGenerator;
}());
exports.OfflineTokenGenerator = OfflineTokenGenerator;
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