Created
August 23, 2019 19:58
-
-
Save juliancantillo/0edd4b3c50ec894fa53819c519882978 to your computer and use it in GitHub Desktop.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
import JsSHA from 'jssha'; | |
export default function getToken(key, period = 30, otp_length = 6) { | |
let epoch, time, shaObj, hmac, offset, otp; | |
key = base32tohex(key); | |
epoch = Math.round(Date.now() / 1000.0); | |
time = leftpad(dec2hex(Math.floor(epoch / period)), 16, '0'); | |
shaObj = new JsSHA('SHA-1', 'HEX'); | |
shaObj.setHMACKey(key, 'HEX'); | |
shaObj.update(time); | |
hmac = shaObj.getHMAC('HEX'); | |
offset = hex2dec(hmac.substring(hmac.length - 1)); | |
otp = (hex2dec(hmac.substr(offset * 2, 8)) & hex2dec('7fffffff')) + ''; | |
otp = otp.substr(otp.length - otp_length, otp_length); | |
return otp; | |
} | |
function hex2dec(s) { | |
return parseInt(s, 16); | |
} | |
function dec2hex(s) { | |
return (s < 15.5 ? '0' : '') + Math.round(s).toString(16); | |
} | |
function base32tohex(base32) { | |
let base32chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567', | |
bits = '', | |
hex = ''; | |
for(let i = 0; i < base32.length; i++) { | |
let val = base32chars.indexOf(base32.charAt(i).toUpperCase()); | |
bits += leftpad(val.toString(2), 5, '0'); | |
} | |
for(let i = 0; i + 4 <= bits.length; i += 4) { | |
let 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; | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment