53 lines
2.0 KiB
JavaScript
53 lines
2.0 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(decode(secret).match(/.{1,2}/g).map(chunk => parseInt(chunk, 16))); //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 = (new DataView(P.buffer).getInt32(0) % Math.pow(10, digits)).toString()
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while(res.length < digits)
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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(secret, digits = 6, time = Date.now(), fetchTime = 30, timeOffset = 0, hashType = 'SHA-1')
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{
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const unixTime = Math.round((time / 1000 + timeOffset) / fetchTime)
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return getHOTP(BigInt(unixTime), secret, digits)
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} |