How to generate a QR Code for Google Authenticator that correctly shows Issuer displayed above the OTP?

Question

Warning: sharing your TOTP seed with third-parties breaks the very basic assumption of multi-factor authentication that the TOTP seed is secret.

So, I'm aware of the documentation on this, found here: Google Authenticator Key URI Format

When I follow this example from that page:

otpauth://totp/Example:[email protected]?secret=JBSWY3DPEHPK3PXP&issuer=Example

And I 'splice' it into a Google Charts URL, thus:

https://www.google.com/chart?chs=200x200&chld=M|0&cht=qr&chl=otpauth://totp/Example:[email protected]?secret=JBSWY3DPEHPK3PXP&issuer=Example

It will display a valid QR code, and if I scan it with my Google Authenticator app on my phone, it will begin to generate valid OTPs.

However, in the display on the phone, for the entry created by the QR code, I get the OTP, and under it, I get 'Example:[email protected]'. What I want, is to have 'Example' displayed above the OTP, and '[email protected]' displayed below the OTP. I can't help but notice that's the way all the professionally produced apps do it. For example, Google, Wordpress, Amazon, etc. The company name is above the OTP, and the username is displayed below the OTP. Yes, this is purely a cosmetic issue, but I want to get it right.

Can anyone offer me a clue?

Solution 1

Warning: sharing your TOTP seed with third-parties breaks the very basic assumption of multi-factor authentication that the TOTP seed is secret.

Just figured this out.

As it turns out, I needed to encode all the special characters in the 'oauth', i.e., '$', '%', '=', etc.

So, using the same Google Charts URL as before, but encoding those characters, like this:

https://www.google.com/chart?chs=200x200&chld=M|0&cht=qr&chl=otpauth://totp/Example%3Aalice%40google.com%3Fsecret%3DJBSWY3DPEHPK3PXP%26issuer%3DExample

And it works correctly.

Solution 2

The responses recommending usage of Google Charts are absolutely terrible from information security point of view. That's essentially sharing the TOTP secret as well as your username ([email protected]) and issuer (Example) with a third-party company with no legal obligation to keep them secret, and doing that over a GET request! Doing so you violate not only every single assumption underlying multi-factor authentication but also most likely your organisation's information security policy. It nullifies any value added by MFA since the only factor that protects you from compromising your account in case of password breach is itself breached.

Just use any QR code generator as long as it's processing your data locally.

NEVER USE ONLINE QR GENERATORS FOR MFA SECRETS

On Linux I'd recommend the python-qrcode library that can print your QR code using UTF-8 characters on the console.

pip install qrcode

Then:

qr "otpauth://totp/Example:[email protected]?secret=JBSWY3DPEHPK3PXP&issuer=Example"

Solution 3

I use a different way using a local qrencode installation:

qrencode -o- -d 300 -s 10 "otpauth://totp/YOUR_IDENTIFICATION?secret=YOUR_SECRET" | display

In this way I can rebuild my lost authentication key library from what I had on my laptop.

If you are worried about the SECRET showing up in the bash history you can read the secret in hidden mode and use it:

read -p "Write your secre here (no output expected): " -s YOUR_SECRET
qrencode -o- -d 300 -s 10 "otpauth://totp/YOUR_IDENTIFICATION?secret=$YOUR_SECRET" | display

In this way, when you close the bash session, no trace of your secrets will available.

Solution 4

Just want to note, newer versions for Google Authenticator will use the issuer parameter, documented here:

https://github.com/google/google-authenticator/wiki/Key-Uri-Format#issuer

e.g:

https://chart.googleapis.com/chart?chs=200x200&cht=qr&chl=otpauth%3A//totp/User%2540Realm%3Fsecret%3DKO5DE2YD3Q2ZXEOO%26issuer%3DIssuer%2520Name&choe=UTF-8

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Comments

[chx]

Take heed of David Thomas' answer below (which truly should be a comment here) to include issuer and also of gist.github.com/ragusa87/f9d82ca631df0d4d32a0 this script.

[Ber]

This is much safer than using online generators.

[masukomi]

downvoted because while this may solve the problem, this violates the whole point of adding an additional security layer by then sharing your secrets with unknown parties. No-one should do this.

[Daniel Hallgren]

Except this approach shows up in plain text via the command history in the Terminal.

[Christopher Smit]

This post inspired me to create a php library for this. Can be found here - github.com/MincDev/php-otpauth.git.

[pgr]

@DanielHallgren you are right. An easy way to avoid this is to start the command with a space.