Discussion : Hashing algorithm other than SHA-1

[OlivierJaquemet]

Were you able to successfully use hashing algorithm other than SHA-1 with any application ?
I could not...

I have tested the following application and I could not make it work :

On Android :

• andOTP - Android OTP Authenticator 0.6.3.1-play
• FreeOTP Authenticator 1.5
• Google Authenticator 5.0
  (Though its documentation clearly states it is not supported https://github.com/google/google-authenticator/wiki/Key-Uri-Format#algorithm)
• Microsoft Authenticator 6.2002.0898

On Windows :

• KeePassXC 2.5.3-Win64-portable
  it is supposed to be supported since Support for RFC-compliant TOTP hashes keepassxreboot/keepassxc#2972, there is a configuration for it but the do not match java-totp generation
  

Do you known any application supporting hashing algorithm other than SHA-1 ?

[Stexxen]

I think their are 2 problems here.

App makers are not clear on whether they support SHA-256/512 and I personally I think the getDigitsFromHash function in the DefaultCodeGenerator has an error for SHA-256/512.

I used oathtool to verify the results, and I also couldn't make it work. (SHA-1 matched, SHA-256/512 did not)
I eventually replaced it with the below which I took from the similiar aerogear function, this then matched the oathttool for all hash types.

  private String getDigitsFromHash(byte[] hash) {
    // put selected bytes into result int
    int offset = hash[hash.length - 1] & 0xf;

    int binary = ((hash[offset] & 0x7f) << 24) |
                         ((hash[offset + 1] & 0xff) << 16) |
                         ((hash[offset + 2] & 0xff) << 8) |
                         (hash[offset + 3] & 0xff);

    return String.format("%0" + digits + "d", binary % (int) Math.pow(10, digits));
  }

Back to your first question, apps that I have verified working with at SHA-256 after this change are

Android

• Oracle Mobile Authenticator
• Auth0 Guardian
• Sophos Authenticator
• FreeOTP Authenticator

iOS

• Oracle Mobile Authenticator
• IBM Verify
• Sophos Authenticator
• FreeOTP Authenticator

And apps that appear to not support SHA-256

• Google Authenticator
• Microsoft Authenticator
• LastPass Authenticator
• Duo Mobile
• Authy
• 2FAS Auth

And what I found most annoying is that these apps fail silently back to SHA-1, without erroring. So we've had to put a warning on our setup pages to not use them.

[samdjstevens]

Thanks for raising the issue @OlivierJaquemet and for your investigation/fix @Stexxen !

Will try and get some unit tests in place for all the different hash types and make a fix if needed as soon as I can.

[Stexxen]

I have this small test for SHA-256 if its any help?
oathtool result

~ % oathtool --totp=sha256 --now="2019-09-04 21:12:16 UTC" --digits=6 --base32 W3C5B3WKR4AUKFVWYU2WNMYB756OAKWY
272978
~ % oathtool --totp=sha256 --now="2019-09-04 21:12:16 UTC" --digits=8 --base32 W3C5B3WKR4AUKFVWYU2WNMYB756OAKWY
76272978

and the Test Case

  @Test
  public void testSHA256Result() {
    // 2019-09-04 21:12:16 UTC
    int time = 1567631536;
    long currentBucket = Math.floorDiv(time, 30);

    CodeGenerator g = new DefaultCodeGenerator(HashingAlgorithm.SHA256);
    String code = g.generate("W3C5B3WKR4AUKFVWYU2WNMYB756OAKWY", currentBucket);
    assertEquals("272978", code);

    g = new DefaultCodeGenerator(HashingAlgorithm.SHA256, 8);
    code = g.generate("W3C5B3WKR4AUKFVWYU2WNMYB756OAKWY", currentBucket);
    assertEquals("76272978", code);
}

[OlivierJaquemet]

Awesome work @Stexxen, thank you !

Thank you @samdjstevens for taking the time to maintain your project. If I can help, do not hesitate to ask.

[samdjstevens]

I've just pushed a fix for this to master with some unit tests that should hopefuly ensure it's working for all hashing algorithms. Please do have a look over if you can, and if all good I will publish v1.7 shortly.

Thanks!

[Stexxen]

Ahhh that's the problem was it. My binary maths was just not up to the challenge of working out what was wrong...

Thanks for fixing 👍

[samdjstevens]

Just released v1.6.1 to maven central with this fix

[OlivierJaquemet]

Great work. Version 1.6.1 tested and approved. :)
Other hashing algorithm are working perfectly fine with FreeOTP, andOTP and KeePassXC 👍🏻
Thanks again.