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From "Michael Jumper (JIRA)" <>
Subject [jira] [Commented] (GUACAMOLE-96) Two factor authentication with Google Authenticator
Date Fri, 02 Sep 2016 06:44:20 GMT


Michael Jumper commented on GUACAMOLE-96:

I am not completely sure how the authentication extensions work, but how I understand it is
that guacamole will query them one by one untill one of them returns a UserContext, is that

Not quite.

All extensions will be queried, in filename order, until one of them returns an *AuthenticatedUser*.

That AuthenticatedUser is then passed to getUserContext() of *all* extensions, and each extension
can thus either (a) return a UserContext of its own or (b) throw an exception to override
the authentication result. If no exceptions are thrown, the union of all returned UserContexts
is exposed to the user, with each UserContext defining a unique set of data and associated

If an extension's getUserContext() throws a GuacamoleInsufficientCredentialsException (or
anything else that extends GuacamoleUnauthorizedException), the authentication result is vetoed,
and authentication fails. For MFA, an extension could:

# Not implement authenticateUser(), thus relying on any other extension to provide the first
authentication factor
# Check the values within the AuthenticatedUser to see if the additional authentication code
was provided
# Lacking the code, throw a GuacamoleInsufficientCredentialsException requesting that code,
thus invalidating the pending authentication result
# Once the user provides the code, that code along with all previously-submitted credentials
is resubmitted.


> Two factor authentication with Google Authenticator
> ---------------------------------------------------
>                 Key: GUACAMOLE-96
>                 URL:
>             Project: Guacamole
>          Issue Type: New Feature
>          Components: guacamole-client
>            Reporter: L.J. van Ruiten
>            Priority: Trivial
> We have a few critical systems that are accessible through Guacamole and we have had
some clients requesting a safer way to login. Two factor authentication is probably the best
and easiest way to improve on the current username/password login, and I can imagine that
this is something that other companies using Guacamole would also be interesting in this feature.
> I already did some tinkering myself and I found that Google Auhtenticator is simple to
use, does not require any configuration (like you would with SMS codes) easy to implement
and the "client" side of the authentication (the part that generates the codes) is easily
integrated into existing apps.
> So far I have got Google Authenticator "kinda working". What I did is:
> - Started with guacamole-auth-jdbc as base
> - Added a secret key to a user account that is randomly generated upon creation. Also
added a boolean field to indicate wether TFA is required for loggin in.
> - Used the GuacamoleInsufficientCredentialsException to redirect the user the a second
screen asking for a TFA code after loggin in with the username and password.
> However as said before this only "kinda works" because:
> I have only gotten the TFA enable button to appear in the user's managing page, so it
can only be enabled by administrators and that's also where I put the secret key shows up,
so users can't find it themself.
> For as far as I could find the previous point cannot be done with just the guacamole-ext
api. Even with the new API that enables you to insert HTML parts, you would also need an API
endpoint to provide the secret key or ideally generate a QR code that Google Auhtenticator
can read to bind a device to the account (I would like it to appear in the user's preference
> So in summary if other people are interested I would be willing to contribute this, but
I would need some directions and I have a few questions:
> - Am I right that it is currently not possible to add an API endpoint just using guacamole-ext
to provide the QR codes?
> - What would be the way to implement this? Personally I thought that adding these options
to the user's page would be the easiest.
> - Is this a feature you would like me to work on and contribute?

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