60 lines
2.1 KiB
JavaScript
60 lines
2.1 KiB
JavaScript
import { decode } from "./base32decoder.js";
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import jsSHA from "jssha";
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("use bigint");
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/**
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* get HOTP based on counter
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* @param {BigInt} counter BigInt counter of HOTP
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* @param {string} secret base32 encoded string
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* @param {number} [digits=6] number of digits in OTP token
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* @param {string} [hashType='SHA-1'] type of hash (more in jsSHA documentation)
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* @returns HOTP string
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*/
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export function getHOTP(counter, secret, digits = 6, hashType = "SHA-1") {
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//Stage 1: Prepare data
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const rawDataCounter = new DataView(new ArrayBuffer(8));
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rawDataCounter.setUint32(4, counter);
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const bCounter = new Uint8Array(rawDataCounter.buffer);
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const bSecret = new Uint8Array(
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decode(secret)
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.match(/.{1,2}/g)
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.map((chunk) => parseInt(chunk, 16)),
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); //confirmed
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//Stage 2: Hash data
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const jssha = new jsSHA(hashType, "UINT8ARRAY");
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jssha.setHMACKey(bSecret, "UINT8ARRAY");
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jssha.update(bCounter);
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const hmacResult = jssha.getHMAC("UINT8ARRAY"); //confirmed
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//Stage 3: Dynamic truncate
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const offsetB = hmacResult[19] & 0xf;
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const P = hmacResult.slice(offsetB, offsetB + 4);
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P[0] = P[0] & 0x7f;
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//Stage 4: Format string
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let res = (
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new DataView(P.buffer).getInt32(0) % Math.pow(10, digits)
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).toString();
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while (res.length < digits) res = "0" + res;
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return res;
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}
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/**
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* get OTP based on current time
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* @param {string} secret base32 encoded string
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* @param {number} [digits=6] digits in OTP
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* @param {number} [time=Date.now()] time for counter (default unix time epoch)
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* @param {number} [fetchTime=30] period of token in seconds
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* @param {number} [timeOffset=0] time offset for token in seconds
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* @param {string} [hashType='SHA-1'] type of hash (more in jsSHA documentation)
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* @returns TOTP string
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*/
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export function getTOTP(
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secret,
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digits = 6,
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time = Date.now(),
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fetchTime = 30,
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timeOffset = 0,
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hashType = "SHA-1",
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) {
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const unixTime = Math.round((time / 1000n + timeOffset) / fetchTime);
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return getHOTP(BigInt(unixTime), secret, digits, hashType);
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}
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