nextcloud / passman-webextension

window.OTP = (function () {

    function dec2hex(s) {

        return (s < 15.5 ? '0' : '') + Math.round(s).toString(16);

    }

    function hex2dec(s) {

        return parseInt(s, 16);

    }

    function base32tohex(base32) {

        if (!base32) {

            return;

        }

        var base32chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";

        var bits = "";

        var hex = "";

        var i;

        for (i = 0; i < base32.length; i++) {

            var val = base32chars.indexOf(base32.charAt(i).toUpperCase());

            bits += leftpad(val.toString(2), 5, '0');

        }

        for (i = 0; i + 4 <= bits.length; i += 4) {

            var chunk = bits.substr(i, 4);

            hex = hex + parseInt(chunk, 2).toString(16);

        }

        return hex;

    }

    function leftpad(str, len, pad) {

        if (len + 1 >= str.length) {

            str = Array(len + 1 - str.length).join(pad) + str;

        }

        return str;

    }

    var _OTP = {

        secret: '',

        getOTP:  function () {

            if (!this.secret) {

                return;

            }

            var key = base32tohex(this.secret);

            var epoch = Math.round(new Date().getTime() / 1000.0);

            var time = leftpad(dec2hex(Math.floor(epoch / 30)), 16, '0');

            /** global: jsSHA */

            var hmac = hmacObj.getHMAC(key, 'HEX', 'SHA-1', "HEX");

            var offset = hex2dec(hmac.substring(hmac.length - 1));

            var otp = (hex2dec(hmac.substr(offset * 2, 8)) & hex2dec('7fffffff')) + '';

            otp = (otp).substr(otp.length - 6, 6);

            return otp;

        }

    };

    return _OTP;

}());