[keycloak-dev] Kerberos, login with different user

Thu Oct 1 06:04:38 EDT 2015

On 1 October 2015 at 11:42, Marek Posolda <mposolda at redhat.com> wrote:

> On 01/10/15 10:59, Stian Thorgersen wrote:
>
>
>
> On 1 October 2015 at 10:26, Marek Posolda <mposolda at redhat.com> wrote:
>
>> On 01/10/15 09:13, Stian Thorgersen wrote:
>>
>> I don't like the query param approach as it requires somehow adding the
>> query param to specify what authenticators to skip. This would have to be
>> added to applications themselves and with Keycloak the whole idea is that
>> applications shouldn't have to worry about authentication semantics.
>>
>> I thing that some applications care about how was user authenticated :-\
>>
>
> Maybe, but that's not the case in this use-case. In this case we simply
> want to use another user than the automatically logged-in user. So
> skip_auth_mech just becomes a work around/hack rather than a proper solution
>
>
>>
>>
>> For example when application wants to reuse Kerberos credential from the
>> SPNEGO authentication to call some other thirdparty kerberos-secured
>> service, it needs a way to "force" keycloak to authenticate with Kerberos.
>> Hence it can skip other authenticators and leave just Kerberos.
>>
>> Similar case is, when application wants to reuse Facebook access token -
>> in this case application wants to enforce login with Facebook. For this
>> case, we already have kc_idp_hint parameter, which also requires support on
>> the application side . Isn't it similar to the query parameter
>> skip_auth_mechanisms ?
>>
>
> Those situations are much more advanced than this use-case. In those case
> you'd have to have some form of a additional authenticators. For example if
> an app needs Facebook token they would need the user to authenticate with
> Facebook whether or not the user is already authenticated. This becomes
> quite tricky, especially if the user is already logged-in and logs in with
> FB as another user. But, that's not what this use case is about and we
> haven't had a request for this, so no need to consider it now.
>
>
>>
>> I might be wrong, but maybe some Keycloak users don't care too much about
>> SSO. The added value for them is provisioning of users and the fact, that
>> they don't need to implement Facebook or Kerberos authentication, but
>> Keycloak implements it for them. So they may want some control on the
>> application side how is user authenticated.
>>
>
> SSO or not, it's still the same concept of moving authentication semantics
> away from apps to the authentication server.
>
> TBH I am still not seeing why kc_idp_hint parameter support is ok, but
> skip_auth_mech is not. In both cases, it's the application which wants to
> control the behaviour somehow. Skip_auth_mech can be used to skip some
> mechanism, but also to enforce login with some mechanism (skip all other
> mechanisms besides the one required).
>

I'm not a big fan of kc_idp_hint either ;)

"skip_auth_mech" would be a horrible way to enforce a specific auth
mechanism. What if you add another mechanism? What if user is already
logged-in? It's just not something that should be added without thinking
about the corner cases. Then there are also similar things baked into OIDC
to consider (acr, amr, id_token_hint, etc..).

As we have loads of things to do and skip_auth_mech is not something that
anyone has requested, except for in this use-case. Where I'm arguing that
it's a bad way to do it. We shouldn't add it now as it's a work
around/hackish solution that we haven't fully considered.

>
>
>
>
>>
>> We need a generic mechanism to be able to skip any authenticators that
>> automatically log in a user. Currently this is only Kerberos, but in the
>> future we could add more, including an option to automatically route to
>> external IdPs.
>>
>> For external IdPs, we already have "Authenticate by Default" switch on
>> identity providers. We also have kc_idp_hint parameter as I mentioned above.
>>
>>
>> Ignoring implementation semantics for now, but taking Kerberos as the
>> example authenticator I can see some options (in the example below replace
>> 'Kerberos' with any other authentication method that can automatically
>> login a user):
>>
>> * If a user that was logged in using Kerberos logs out the user should
>> not just be automatically logged-in again for the current browser session.
>> Instead the user should be displayed with a regular username/password
>> field, but also with an option to login with Kerberos
>> * A variant on the above where if a user has logged-out from Kerberos the
>> user would be displayed with a "Is this you?" when login, if the user
>> selects yes the Kerberos authenticator would continue, if not the regular
>> username/password form would be displayed
>>
>> +1 to support "Is this you" screen. However maybe this should be
>> configurable as some deployments may not want to display the screen, but
>> want to relogin automatically.
>>
>> Classic example is redhat.com. When I have kerberos ticket, I can never
>> see the login screen on saml.redhat.com . If we enforce adding "Is this
>> you", some employees may complain "Hey, why there is another splash screen
>> I need to click. Why I am not logged automatically" etc. But maybe I am
>> wrong here. Maybe good opportunity to ask IT guys on the call today as they
>> have experience with the real world scenarios ;-)
>>
>
> I don't see why it's a problem that the splash screen is displayed. The
> user has decided to log out from the Kerberos session so it makes no sense
> whatsoever to automatically log the user in again. That's basically
> disabling the log out.
>
> I imagine I have 10 tabs opened in my browser. I want to close the tab
> with mojo.redhat.com and before that, I automatically click on "logout" .
> After few minutes, I want again to do something different for example in
> calendar. redhat.com and now I will see the splash screen when I want to
> relogin.
>
> For me, splash screen is not an issue. Not sure about all other
> employees...
>
> Maybe we can add splash screen automatically and add support for a flag to
> not display splash screen just when someone requests it. Again, I can be
> wrong, but I bet this request will come earlier or later :-)
>

Really? I just don't see that as a problem. 99.999% of the time the user
won't see any splash screen as they will just login and that's that. For
the times when someone logs out I just can't see it being a huge problem
that they get a "is this you" prompt.

If someone is really that bothered about the splash screen let them tell us
and we can add an option, but there's no point in filling the admin console
up with all sorts of unused toggles.

>
>
> Marek
>
>
>
>>
>>
>> Conclusion of my point of view: Add variable support for "Is this you"
>> screen and in addition have the support for skip_auth_mechanism Michael
>> implemented.
>>
>
> If we add is this you screen, then skip_auth_mechanism is not required for
> this use case and hence we should not add it unless specifically requested
>
>
>>
>>
>> Marek
>>
>> * Implement account switcher - where a user can login to multiple
>> accounts at a time and select which account to use
>>
>> Other ideas? Points for ideas that requires no hacks in applications ;)
>>
>> On 30 September 2015 at 15:39, Michael Gerber < <gerbermichi at me.com>
>> gerbermichi at me.com> wrote:
>>
>>> Hi all,
>>>
>>> I would like to use kerberos as my standard authentication mechanism,
>>> but I also want to have the possibility to log in as an admin over the
>>> login form.
>>> Therefore, I want to skip the kerberos authenticator after a successful
>>> logout.
>>> https://issues.jboss.org/browse/KEYCLOAK-1727
>>>
>>> How would you solve this problem?
>>>
>>> I've got two solutions, one sets a logout session cookie after a logout
>>> and then skips the kerberos authentication and another which allows users
>>> to skip any kind of alternative authenticators with a query parameter.
>>>
>>> Logout Session Cookie
>>>
>>> https://github.com/gerbermichi/keycloak/commit/f804d9e13573cb666cf6d2eff1407978c9e5e854
>>>
>>> Query Param
>>>
>>> https://github.com/gerbermichi/keycloak/commit/abd3bd87f5aa4c28914da677653268c0f44fe6cc
>>>
>>> Michael
>>>
>>> _______________________________________________
>>> keycloak-dev mailing list
>>> keycloak-dev at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/keycloak-dev
>>>
>>
>>
>>
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>>
>>
>
>
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