me.whitmarbut.mfa.TOTP.java Source code

Introduction

Here is the source code for me.whitmarbut.mfa.TOTP.java

Source

package me.whitmarbut.mfa;

/**
 * @copyright 2014 Whit Marbut
 * Licensed under Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International.
 * Full text of the license may be found here http://creativecommons.org/licenses/by-nc-sa/4.0/deed.en_US
 */
import org.apache.commons.codec.binary.Base32;

import java.lang.StringBuilder;
import java.nio.ByteBuffer;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

public class TOTP {

    public static void main(String[] args) throws InvalidKeyException, NoSuchAlgorithmException {
        TOTP token_gen = new TOTP();
        String str = "";
        System.out.println("\nYour token: " + token_gen.getToken(str));
    }

    public String getToken(String key) {
        byte[] priv_key = getSecretBytes(key);
        byte[] hmac;
        try {
            hmac = getHmac(getTimestamp(), priv_key);
        } catch (Exception ex) {
            return null;
        }
        return getToken(hmac);
    }

    private byte[] getSecretBytes(String secret) {
        secret = secret.toUpperCase();
        Base32 b32 = new Base32();
        return b32.decode(secret);
    }

    private byte[] getHmac(int timestamp, byte[] key) throws NoSuchAlgorithmException, InvalidKeyException {
        SecretKeySpec key_spec = new SecretKeySpec(key, "HmacSHA1");
        Mac mac = Mac.getInstance("HmacSHA1");
        mac.init(key_spec);
        byte[] bin_timestamp = ByteBuffer.allocate(4).putInt(timestamp).array();

        ByteBuffer bbuff = ByteBuffer.allocate(8);
        bbuff.putInt(0); //Left pad 4 bytes to make a 64 bit int
        bbuff.putInt(timestamp);

        return mac.doFinal(bbuff.array());
    }

    private int getTimestamp() {
        return (int) Math.floor((System.currentTimeMillis() / 1000) / 30);
    }

    private String getToken(byte[] hmac) {
        int offset = hmac[19] & 0xf;

        Integer token = (int) ((((hmac[offset] & 0x7f) << 24) | ((hmac[offset + 1] & 0xff) << 16)
                | ((hmac[offset + 2] & 0xff) << 8) | (hmac[offset + 3] & 0xff)) % (Math.pow(10, 6)));
        String token_str = token.toString();
        if (token_str.length() < 6) {
            int to_add = 6 - token_str.length();
            for (int i = 0; i < to_add; i++) {
                token_str = "0" + token_str;
            }
        }

        return token_str;
    }
}