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Keycloak - how to handle multiple work contexts

I have an application where single user can work in contexts of multiple companies. We call such a connection (user<->company) a permit. Every one of this permits can have different sets of permissions/roles. We want user to login just once and then he can simply change permits within application without need to enter password again.
Till now we had only one application and kept this whole permission model in our own DB. Unfortunately now we have to support second application which should inherit those permits. I was wondering wether is possible to move that model to keycloak so we don't have to replicate it to every single db and keep it in sync manually.
I have searched keycloak documentation regarding this topic but have found no information att all, which seems quite odd, because I don't think we are the first one working with multiple context application.
So now I'm asking is it possible to configure our model in keycloak and if so, how to do it? Eventually are there different options? I guess that I can provided that model as a claim with json structure but that doesn't feel right to me. I was thinking about custom IDP which could provide such claims based on DB so there no spelling errors and less repetition but I feel there should be a better way.

You could try to write your own Keycloak provider (SPI). There is a built in mechanism that allows you to expose REST endpoint on the Keycloak: https://github.com/keycloak/keycloak/tree/master/examples/providers/domain-extension
That REST could be called with authorized context only for example by passing Access-Token (Authorization header with Bearer value). On the provider level (through implementation of: org.keycloak.services.resource.RealmResourceProviderFactory and org.keycloak.services.resource.RealmResourceProvider) you have access to user's Keycloak session and object UserModel like in the following code:
AuthenticationManager.AuthResult authResult = new AppAuthManager().authenticateBearerToken(keycloakSession, keycloakSession.getContext().getRealm());
UserModel userModel = authResult.getUser();
UserModel class has methods for getting and setting attributes, so some information that indicates the current permit/company ID can be stored there. You can use REST methods exposed on the Keycloak to modify the model within the 'session' (represented by Access-Token).
The Github example shows also how to use another Keycloak provider (ex. built-in JPA provider) from you custom provider's level, so using that approach you could try to connect to the database with your permits/company informations. Of course the datasource representing you database should also be registered as Keycloak datasource.

Expose Web Services to third party applications?

I've been asked in tech discussions how do we write an application to use internally in the firm, and also expose it as an API to third party clients?
I am assuming this is in context of Web Services. I am thinking, won't the third party simply call the end point and consume the response?
Clearly, that answer is raw, and I am missing the point.
Is there a known approach, or any Frameworks to do this?
What are the considerations here? And how do we address them?

You would write and expose the RESTful services for internal and external users same way however when you do it for external clients then you have to careful about some of the following points
Security - If your API is secured then how are we going to achieve this ? We can leverage external identity providers to secure our APIs like (Azure AD, Auth0 (https://auth0.com))
Limit call rate - If you want to cap number of call from external Users ? e.g. free tier would only allow 100 req/min etc .
Sign up process - For external users you need to take care how do they have to sign up to your services (acquire token) to access your services.
Scaleable - Your APIs should be scaleable.
HATEOAS - This is very important REST principal. IF you follow this pattern your external users can explore your API in a better way by just following links (https://en.wikipedia.org/wiki/HATEOAS).
Open API Your API should be very well documented and Open API (swagger) is very much a standard now (https://swagger.io/specification/)
You can do all these tasks by your self or you can use Any API manager to do that.

One concrete way to achieve this is with a REST API secured using Json Web Tokens (JWT). On each REST endpoint, you can specify the roles that are allowed to call that endpoint.
For your use case, you could achieve this with a "system" role for internal callers, and unauthorized (i.e. no role) for external callers.
A framework you can use to achieve this is MicroProfile JWT, which might look something like this:
#Path("/rank")
#ApplicationScoped
public class RankingService {
#GET
#Path("/{playerId}")
public long getRank(#PathParam("playerId") String id) {
// get the ranking info for a player
// anyone is allowed to do this
}
#POST
#RolesAllowed({ "system" })
#Path("/{playerId}")
public void recordGame(#PathParam("playerId") String id,
#QueryParam("place") int place,
#HeaderParam("Authorization") String token) {
// update player ranking information
// only internal users are allowed to update ranks!
}
}
Here is a link to a talk that I gave at conference that walks through securing a REST endpoint using MicroProfile JWT.

Implementing Collaborative Authentication in Java Web Application

I've a requirement to build a Java based web application where a resource should be available only when all the authorized users of that resource are logged in. Also, if any authorized user logs out, the resource should no longer be available to any of them.
The resource could be of any type(html pages, pdf documents, spread sheets etc.,)
Is there any existing authentication standards/protocols that supports this type of requirement or I've to build this from scratch?

the resource should be available only when all the authorized users of that resource are logged in. Also, if any authorized user logs out, the resource should no longer be available to any of them.
Once you have given access to the resource to an user, this user will be able to download / take screenshots / save / record the resource, no matter if it's a PDF document, an image, an audio file. I don't know the context and the goal of what you're trying to build, but you should know that it will be insecure in any case.
Even putting this consideration aside, you'll need a real-time solution. Once the user has loaded the page containing the resource, you need to be able to hide or deny modification rights to him. This means you have to use something like WebSockets or Ajax Polling on the client side to have the frontend know when your server considers that not all the required users are online, and that the access to the resource should be "denied". But once more since this is client-side code it can easily be changed or altered, the requests it is sending can easily be blocked by the user, so it is once again inherently insecure.
I'd suggest giving a little bit of context here and describing what is the problem you're trying to solve, because most likely there's a more reasonable solution to solve it.
If what you need to do is to deny modification rights if not all the "resource owners" are online, it is more easily doable since the modifications will happen on the server side. In this case, a solution using WebSockets could quite easily be implemented but I don't know a library or framework that does such a thing. Most likely you will have to build it yourself.

If you're not constrained to use a specific web framework, feel free to try the following filter based implementation for jersey. Note that you still need to add a fair amount of custom code for handling the logic of "Collective authentication" as jersey only provides the basic tools required for this, and it doesn't explicitly implement the whole concept. Here's how you could do it, on a high level:
class AuthorizationProvider {
public void authenticate(ContainerRequestContext requestContext) {
// Here you would need to query your database to get the Collection of Users belonging
// to the "Collective" Role. You would then check if they are all logged in.
// A really abstract version would look like this, assuming you've already queried the DB
// and have a reference to the above mentioned Collection.
if (collectiveUsers.size == collectiveUsers.stream().filter(User::isLoggedIn).count()) {
return true;
}
return false;
}
}
class AuthorizationRequestFilter implements ContainerRequestFilter {
private final AuthorizationProvider authorizationProvider;
#Override
public void filter(ContainerRequestContext requestContext) {
if (authorizationProvider.authenticate(requestContext)) {
// serve whatever it is you want to serve if all required users are logged in
} else {
// otherwise reject the request
requestContext.abortWith(Response
.status(Response.Status.UNAUTHORIZED)
.entity("Resource available only after collective login")
.build());
}
}
}
#ApplicationPath("/")
class MyApplication extends ResourceConfig {
public MyApplication() {
// Register the filter
register(AuthorizationRequestFilter.class);
}
}
Apart from this, you would also need to handle the Login part.
You would assign these specific users the Collective role, and you would mark them as logged in, whenever they successfully pass through login authentication.
If all the above conditions are met, you should be able to successfully serve your "Collective only" page, only when all "Collective" users are logged in.
This also covers the part where if either one of these users logs out, you store the state in your database (mark the Collective user with isLoggedIn = false). So from this point on, whenever somebody requests the page, it will return Unauthorized.
Conversely, you can also attempt to implement SSE (Server sent events) to actively update the frontend part, if somebody logs out. With this, the page will actively be disabled even if somebody has already managed to get it previously.
Container request filter source and example, for reference, jersey docs

Custom PermissionEvaluator for authorizing resource access for each REST Resource

I have implemented a REST application with some complicated authorization requirements.
Here's a summary
My customers purchase a proxy device called Collector that enables their home automation control to be centralized. My customers also purchase multiple home automation devices (let's call them HADevices) that report their metrics through the collector to my REST application.
An admin(who is my customer service rep), with role ROLE_ADMIN, should be able to look at any data from any Collector or HADevice. A customer, with role ROLE_USER role, should only be able to view data about the Collector or an HADevice that s/he owns.
The Collector, with role ROLE_COLLECTOR is the only role authorized to insert data i.e. create or update a resource in my REST service. Let's call this url /deviceMetrics (POST). A Collector can insert metrics for any HADevice associated with the customer. HADevices have no role and do not interact with my REST application. A Collector can only insert records to HADevices that have the same customer as the Collector.
I am using spring security 4.0 for authentication and #Secured annotation for authorization. However, I find that my code is cluttered with repetitive permission validations which take up a majority of my logic. The basic insertions and retrievals are pretty straightforward.
I want to use a PermissionEvaluator to centralize Access Control. I have to secure the following urls
GET /collectors/{id}/deviceMetrics - I retrieve the user from the
Principal and verify that the Collector with id={id} in my spring
data repository belongs to the Principal and if not I send a 403
GET/hadevices/{id}/deviceMetrics - I retrieve the user from the
Principal and verify that the HADevice with id={id} in my spring data
repository belongs to the Principal and if not I send a 403.
POST /collectors/{id}/deviceMetrics - I retrieve the Collector uniqueId
from the Principal and make sure that the Collector's id matches the
{id} in the URL
POST /hadevice/{id}/deviceMetrics - I retrieve the
Collector uniqueId from the Principal and the associated Customer. I
also pull the Customer associated with HADevice with id={id} and
compare the two. If they are unequal, I send a 403.
My application is littered with such complex authorization requirements for each REST resource, and I want to use a custom org.springframework.security.access.PermissionEvaluator, specifically by implementing the following method.
boolean hasPermission(Authentication authentication, Serializable targetId, String targetType, Object permission)
I'm planning to use a combination of targetType and request.getUrl() to get a specialized Evaluator for each url and resource.
Is there a better way to do this?

Your question is quite broad, but I think you can get away with quite simple logic for most cases.
GET /collectors/{id}/deviceMetrics
Given that you have a DeviceMetrics class with suitable properties, you can annotate your data repository with something like:
#PostAuthorize("hasRole('ROLE_ADMIN') or (hasRole('ROLE_USER') and returnObject.collector.owner = authentication.name)")
public DeviceMetrics getDeviceMetrics(long deviceId);
(This assumes that DeviceMetrics class has a property collector which has a property owner which is the username.)
That doesn't need a PermissionEvaluator at all. Maybe you need one for more complex cases:
POST /collectors/{id}/deviceMetrics
#PreAuthorize("hasRole('ROLE_COLLECTOR') and hasPermission(#collectorId, 'com.example.Collector', 'WRITE')")
public void saveDeviceMetrics(long collectorId, DeviceMetrics deviceMetrics);
You only need one PermissionEvaluator since you get all the information you need as method arguments.

For those who are wondering what my solution looks like, I borrowed from this example.
It's old and it's based on xml configuration which I am not particularly fond of. But the idea is to create a Map and initialize the custom PermissionValidator and to store the authorization logic in the Permission interface implementations.
The biggest pain point was injecting an autowired HashMap of tuples, but that's an implementation detail that reasonably experienced spring users can figure out.

Designing RESTful login service

I went through a similar question here. But I am yet not clear over concepts. Here is my scenario...
My client (a mobile device app) has a login screen to enter username, password. After submission, he should see the list of books in the database plus the list of books subscribed by that user.
I am having a /LoginService which accepts username, password & checks a mysql database for credential validation. Only after authorization....I have a /BookService ; GET on which returns all the books in database.
Should I use GET, POST or PUT on my loginservice ? Since a login request is a read-only operation, I should use GET - but this sounds stupid for browser(as the submitted data is visible).
What are accesstokens (mentioned in the linked answer above), and how to generate them using Java ? I am using Jersey for development. Are they a secure way of authorization ?
Thanks !

As far as I understand you are trying to implement stetefull communication between client and server. So you login with first request and then use some kind of token to make further requests.
Generally I can recommend you to have stateless communication. This means, that you authenticate and authorize each request. In this scenario you don't need LoginRestService. Important points here are:
Client can provide userName and password through HTTP Headers (non-standard, something like UserName: user and Password: secret).
At the server side you can use
Use AOP: just wrap you BooksService with AuthAdvice (which you should write yourself). In advise you access somehow (with Jersey functionality) HTTP request, take correspondent headers from it, authenticate and authorize user (that you load from DB), put user in ThreadLocal (so that it would be available to the rest of your app) if needed and just invoke correspondent method or throw exception if something wrong with credentials.
Use Jersey functionality: (sorry I'm not very familliar with Jersey, I'm using CXF, but conceptually it should be the same) just create some kind of AuthHendler and put it in request pre-processing pipeline. In this handler you need tho make exactly the same as in AuthAdvice
Now each of your request would be authenticated and authorized when it reaches BooksService. Generally stateless implementation is much better for scalability.
If you want to go statefull way, than you can just use HttpSession. LoginService.login() should be POST request because you actually making some side-effects at the server. Service will perform authentication of your user according to provided username and password and put loaded User object to session. At this point, the server side session is created and client has session ID in the cookies. So further requests should automatically send it to the server. In order to authorize requests to BooksService you still need some kind of Advice of Handler (see stateless solution). The only difference: this time user is taken from the HttpSession (you should check that you are logged in!).
Update: And use HTTPS! :)

I've got nothing to dispute in Easy Angel's answer, but got the impression you'd like some additional comment on the concepts too.
The problem is clearer if you think in terms of resources rather than services. Think of your proposed login as generating a new authorization resource, rather than querying a login service. Then you see that POST makes perfect sense.
The authorization token would be a key for your user into the session object (as explained in EA's answer). You'd probably want to generate it by concatenating some information that uniquely identifies that user and hashing it. I certainly agree that a stateless authentication method would be preferable, if you're aiming to get all the benefits of REST.

Use what is available in HTTP: HTTP AUTH over SSL.
Protect all your resources with HTTP AUTH and the browser will take care of providing a login for the user.
If you need session information on top of that, use cookies or a session parameter.
Cookies were made for exactly these kinds of purposes and usually work well.