There are established and popular protocols for identity providers to provide a client with properties about the logged in user.
For example in OpenID Connect (OIDC) the client can request access to certain scopes and then read claims about the authenticated user. The use case is the usage of centrally maintained user data, like name, department, e-mail etc.
I'm looking for way for the client to write custom properties about the authenticated user back into the identity provider.
Use cases:
a client application needs to save some app-specific preferences about the user and
a client application enables to user to edit some existing properties that are relevant for other client applications, too
(Yes, it would be trivial to design my own REST-like endpoint for this, but I'm looking for an open standard, in order to make it easier for clients.)
Have a look at System for Cross-domain Identity Management, aka SCIM. This is an out-of-the-box Rest API that an IDP should provide, and which should also enable you to save custom attributes against users.
Typically it is called by back end components, which use the client credentials grant to get a separate token with which to call the SCIM endpoint.
I'm looking for guidance and/or best practices in implementing step-up authentication. The generic scenario is as follows: user logs in to web app using some identity provider, user then goes to some specific area of web site which needs to be protected by additional MFA, for example OTP. All functionality for the website is via REST API, authenticating with JWT bearer token.
The best description of the flow I found is from Auth0 here. Basically, user acquires the access token with scope which is just enough to access APIs that do not require additional protection. When there is a need to access secure API the authorization handler on backend would check if the token has the scope indicating that the user has completed the additional MFA check, otherwise it's just HTTP 401.
Some sources, including the one from Auth0, suggest using amr claim as an indication of passed MFA check. That means that identity provider must be able to return this claim in response to access token request with acr_values parameter.
Now, the detail that is bugging me: should the frontend know in advance the list of API that might require MFA and request the elevated permissions beforehand, or should frontend treat the HTTP 401 response from backend as a signal to request elevated permissions and try again?
Should identity provider generate relatively additional short-lived token to access restricted APIs? Then, if frontend has 2 tokens it must definitely know which token to use with which API endpoint. Or maybe identity provider can re-issue the access token with normal lifespan but elevated permissions? Sounds less secure then the first approach.
Finally, do I understand the whole process right or not? Is there some well documented and time-tested flow at all?
CLIENTS
Clients can be made aware of authentication strength via ID tokens. Note that a client should never read access tokens - ideally they should use an opaque / reference token format. Most commonly the acr claim from the ID token is used.
This can be a little ugly and a better option can sometimes be to ask the API, eg 'can I make a payment'? The client sends an access token and gets a JSON response tailored to what the UI needs. The API's job is to serve the client after all.
APIs
APIs receive JWT access tokens containing scopes and claims. Often this occurs after an API gateway swaps an opaque token for a JWT.
The usual technique is that some logic in the Authorization Server omits high privilege ones, eg a payment scope or claim, unless strong authentication was used.
It is worth mentioning plain old API error responses here. Requests with an insufficient scope typically return 403, though a useful JSON error code in an error object can be useful for giving the client a more precise reason.
STEP UP
As you indicate, this involves the client running a new code flow, with different scope / claims and potentially also with an acr_values parameter. The Curity MFA Approaches article has some notes on this.
It should not be overused. The classic use case is for payments in banking scenarios. If the initial sign in / delegation used a password, the step up request might ask for a second factor, eg a PIN, but should not re-prompt for the password.
CLIENTS AND ACCESS TOKENS
It is awkward for a client to use multiple access tokens. If the original one had scope read then the stepped up one could use scope read write payment and completely replace the original one.
In this case you do not want the high privilege scope to hang around for long. This is yet another reason to use short lived access tokens (~ 15 minutes).
Interestingly also, different scopes the user has consented to can have different times to live, so that refreshed access tokens drop the payment scope.
ADVANCED EXAMPLE
Out of interest, here is an interesting but complicated article on payment workflows in Open Banking. A second OIDC redirect is used to get a payment scope after normal authentication but also to record consent in an audited manner. In a normal app this would be overkill however.
For the past 10+ days I've read an watched ALL the content I could find on understanding OAuth2 and OpenID Connect, only to find that many people disagree on the implementation, which really confuses me.
To my understanding, all the articles and examples I found assume you want access to eg. google calendar, profile info or emails if you eg. login with google, but I do NOT need to access other than my own API's - I only want to use Google, Facebook etc for logging in, and getting an id which I can link to my user in my own database - nothing more than that.
I'll try illustrate my use case and use that as an example.
A note on the diagram: the Authentication service could probably be built into the API Gateway - not that i matters for this example, since this is not about "where to do it", but "how to do it the best way" possible, for an architecture such as mine, where it's used for my own API's / Microservices, and not accessing Google, Facebook etc. external API's
If you can understand what I'm trying to illustrate with this diagram above, please tell me if I've misunderstood this.
The most basic requirements for this architecture you see here are:
Users can login with Google, Facebook, etc.
The same login will be used for all micro-services
OpenId user will have a linked account in the database
User access is defined in my own db, based on groups, roles and permissions
I do not intend to use external API's after the user is authenticated and logged in. No need for ever accessing a users calendar, email etc. so I really just need the authentication part and nothing else (proof of successful login). All user access is defined in my own database.
So a few fundamental questions comes to mind.
First of all, is OpenID Connect even the right tool for the job for authentication only (I'll have no use for authorization, since I will not need read/write access to google / facebook API's other than getting the ID from authenticating)?
People generally do not agree on whether to use the ID or Access token for accessing your own API's. As far as I understand the ID token is for the client (user-agent) only, and the access token is for eg. accessing google calendar, emails etc.... External API's of the OpenID Provider... but since I'll only be accessing my own API's, do I event need the access token or the ID token - what is the correct way to protect your own API's?
If the ID token is really just for the client, so it can show eg. currently logged in user, without going to the DB, I have 0 use for it, since I'll probably query the user from from the db and store it in redux for my react frontend app.
Dilemma: To store user details, groups, roles and permission inside JWT or not for API authorization?
By only storing the user identifier in the token, it means that I always allow authenticated users that has a valid token, to call endpoints BEFORE authorization and first then determine access based on the db query result and the permissions in my own database.
By storing more data about the user inside the JWT, it means that in some cases, I'd be able to do the authorization / access (group, role, permission) check before hitting the API - only possible with user info, groups, roles and permission stored inside a JWT issued upon login. In some cases it would not be possible due to eg. the CMS content access permissions being on a per-node level. But still it would mean a little better performance.
As you can see on the diagram I'm sending all API requests through the gateway, which will (in itself or with an authentication service) translate the opaque access token into some JWT with an identifier, so I can identify the user in the graph database - and then verify if the user has the required groups, roles and permissions - not from an external API, but from my own database like you see on the diagram.
This seems like a lot of work on every request, even if the services can share the JWT in case multiple services should need to cross call each other.
The advantage of always looking up the user, and his permissions in the db, is naturally that the moment the user access levels change, he is denied/granted access immediately and it will always be in sync. If I store the user details, groups, roles and permission inside a JWT and persist that in the client localstorage, I guess it could pose a security issue right, and it would be pretty hard to update the user info, groups, roles and permissions inside that JWT?
One big advantage of storing user access levels and info inside the JWT is of course that in many cases I'd be able to block the user from calling certain API's, instead of having to determine access after a db lookup.
So the whole token translation thing means increased security at the cost of performance, but is is generally recommended and worth it? Or is it safe enough to store user info and groups, roles, permissions inside the JWT?
If yes, do I store all that information from my own DB in the ID Token, Access token or a 3rd token - what token is sent to the API and determines if the user should be granted access to a given resource based on his permissions in the db? Do I really need an access token if I don't need to interact with the ID providers API? Or do I store and append all my groups, roles, permissions inside the ID token (that doesn't seem clean to me) issued by OpenID connect, and call the API and authorize my own API endpoints using that, even if some say you should never use the ID token to access an API? Or do I create a new JWT to store all the info fetched from my database, which is to be used for deciding if the user can access a given resource / API endpoint?
Please do not just link to general specs or general info, since I've already read it all - I just failed to understand how to apply all that info to my actual use case (the diagram above). Try to please be as concrete as possible.
Made another attempt to try and simply the flow:
The following answer does only apply for a OpenID Connect authentication flow with a 3rd party IDP (like Google). It does not apply for an architecture where you host your own IDP.
(There are some API gateways (e.g Tyk or Kong) which support OpenID Connect out of the box.)
You can use JWTs (ID token) to secure your APIs. However, this has one disadvantage. JWTs cannot be revoked easily.
I would not recommend this. Instead you should implement an OAuth2 authorization server which issues access tokens for your API. (In this case, you have two OAuth2 flows. One for authentication and one for authorization. The ID and access token from the IDP are used only for authentication.)
The following picture shows a setup where the API gateway and authentication/authorization server are two separate services. (As mentioned above, the authentication/authorization can also be done by the API gateway.)
The authentication flow (Authorization Code Grant) calls are marked blue. The authorization flow (Implicit Grant) calls are marked green.
1: Your web app is loaded from the app server.
2a: The user clicks on your login button, your web app builds the authorization URL and opens it. (See: Authorization Request)
2b: Because the user hasn't authenticated and has no valid session with your authorization server, the URL he wanted to access is stored and your authorization server responds with a redirect to its login page.
3: The login page is loaded from your authorization server.
4a: The user clicks on "Login with ...".
4b: Your authorization server builds the IDP authorization URL and responds with a redirect to it. (See: Authentication Request)
5a: The IDP authorization URL is opend.
5b: Because the user hasn't authenticated and has no valid session with the IDP, the URL he wanted to access is stored and the IDP responds with a redirect to its login page.
6: The login page is loaded from the IDP.
7a: The user fills in his credentials and clicks on the login button.
7b: The IDP checks the credentials, creates a new session and responds with a redirect to the stored URL.
8a: The IDP authorization URL is opend again.
(The approval steps are ignored here for simplicity.)
8b: The IDP creates an authorization and responds with a redirect to the callback URL of your authorization server. (See: Authentication Response)
9a: The callback URL is opened.
9b: Your authorization server extracts the authorization code from the callback URL.
10a: Your authorization server calls the IDP's token endpoint, gets an ID and access token and validates the data in the ID token. (See: Token Request)
(10b: Your authorization server calls the IDP's user info endpoint if some needed claims aren't available in the ID token.)
11a/b: Your authorization server queries/creates the user in your service/DB, creates a new session and responds with a redirect to the stored URL.
12a: The authorization URL is opend again.
(The approval steps are ignored here for simplicity.)
12b/+13a/b: Your authorization server creates/gets the authorization (creates access token) and responds with a redirect to the callback URL of your web app. (See: Access Token Response)
14a: The callback URL is opened.
14b: Your web app extracts the access token from the callback URL.
15: Your web app makes an API call.
16/17/18: The API gateway checks the access token, exchanges the access token with an JWT (which contains user infos, ...) and forwards the call.
A setup where the authorization server calls the API gateway is also possible. In this case, after the authorization is done, the authorization server passes the access token and JWT to the API gateway. Here, however, everytime the user infos change the authorization server has to "inform" the API gateway.
This is a very long question. But I believe most can be summarised by answering below,
To my understanding, all the articles and examples I found assume you want access to eg. google calendar, profile info or emails if you eg. login with google,
You do not necessarily use Access token (ID token in some occasions) to access the services offered by token issuer.You can consume tokens by your own APIs. What these Identity Providers (synonym to Authorization server, or IDP in shorthand) is to hold identities of end users. For example, typical internet have a Facebook account. With OAuth and OpenID Connect, the same user get the ability to consume your API or any OAuth/OIDC accepted service. This reduce user profile creation for end users.
In corporate domain, OAuth and OIDC serves the same purpose. Having a single Azure AD account lets you to consume MS Word as well as Azure AD's OIDC will issue tokens which can be used to Authorise against an in-house API or an third party ERP product (used in organization) which support OIDC based authentication. Hope it's clear now
A note on the diagram is that the Authentication service could probably be built into the API Gateway - not sure if that would be better?
If you are planning to implement an API gateway, think twice. If things are small scale and if you think you can maintain it, then go ahead. But consider about API managers which could provide most of your required functionalities. I welcome you to read this article about WSO2 API manger and understand its capabilities (No I'm not working for them).
For example, that API manager has built in authentication handling mechanism for OAuth and OIDC. It can handle API authentication with simple set of configurations. With such solution you get rid of the requirement of implement everything.
What if you can't use an API manager and has to do it yourself
OpenID Connect is for authentication. Your application can validate the id token and authenticate end user. To access APIs through API Gateway, I think you should utilise Access token.
To validate the access token, you can use introspection endpoint of the identity provider. And to get user information, you can use user-info endpoint.
Once access token is validated, API gateway could create a session for a limited time (ideally to be less or equal to access token lifetime). Consequent requests should come with this session to accept by API gateway. Alternatively, you can still use validated access token. Since you validated it at the first call, you may cache for a certain time period thus avoiding round trips to validations.
To validate user details, permission and other grants, well you must wither bind user to a session or else associate user to access token from API gateway at token validation. I'm also not super clear about this as I have no idea on how your DB logic works.
First Appreciate your patience in writing a very valuable question in this forum
we too have same situation and problem
I want to go through ,as images are blocked in our company in detail
Was trying to draw paralles to similar one quoted in the book
Advance API In Practise - Prabath Siriwerdena [ page 269]Federating access to API's Chapter. Definitely worth reading of his works
API GW should invoke Token Exchange OAUTH2.0 Profile to IDP [ provided the IDP should support TOken Exchange profile for OAUTH 2.0
The Absence of API Gateway , will result in quite bespoke development
for Access Control for each API Check
you land up in having this check at each of the api or microservice [ either as library which does work for you as a reusable code]
definitely will become a choking point.]
I am using Identity Server 4 for authenticate user from a single application page. For the need of the project, I have to use the resource owner password flow.
Identity Server and my application work fine together. Identity Server give an Access Token and I can use this token to access some API that we own.
However, I was asking myself about the Access Token, users and socpes. For now my setup is this one.
I have an API that require the scope API-1.
I have a client (my SPA) where I defined the scope API-1
And I have a user.
In this configuration, it is the client who own the right to access the API, not the user. And I'm wondering how to give this scope to the user and not anymore to the client.
Stupidly, I'm wondering if user can own the scope and not the client. Maybe I've miss or misunderstood something, so please teach me.
In the Resource Owner Password Flow your client will always need to have permission to the scope that your resource is protected by. This does not mean that you cannot protect your API based on claims related to the user however.
If in your API for example you need different permissions based on the user accessing the API look to use the claims information as part of your authorization. In the Resource Owner Password Flow example at http://docs.identityserver.io/en/release/quickstarts/2_resource_owner_passwords.html you will see that it mentions this at the foot of the page, see the two paragraphs as follows:
When you send the token to the identity API endpoint, you will notice one small but important difference compared to the client credentials grant. The access token will now contain a sub claim which uniquely identifies the user. This “sub” claim can be seen by examining the content variable after the call to the API and also will be displayed on the screen by the console application.
The presence (or absence) of the sub claim let’s the API distinguish between calls on behalf of clients and calls on behalf of users.
I recently learned how OIDC provides user identity on top of OAuth 2, and also managed to create an OIDC login to my webapp. However, when it comes to the authorization part, it is unclear how the application should know what scopes to request for the API?
For example, certain endpoints should be protected with the 'admin' scope, as well as respective UI elements should be hidden from non-admin users. The enforcement part I can implement easily, but when the user logs in, the app needs to know if the user is an admin or not - i.e whether or not to request the 'admin' scope / show the admin-related UI parts.
Is there any standard way of representing app-specific details in the user profile that comes from the IDP? What disturbs me most is that such information - to my knowledge - cannot be added to user profiles that come from e.g Google/Twitter/Facebook, so one needs either a) an extra layer (IdentityServer/OpenAM/etc), or b) extra user profile data in the webapp's DB.
My first thought was to add custom claims by doing a) - but when it comes to integrating with existing IDPs, it might not be possible to adjust all the user profiles (e.g large corporate databases), so I am assuming the app itself should be flexible enough to translate existing user profile data to 'admin/not-admin'.
Is there a better solution?
In my opinion it's not a good practice to base your authorization on the claims returned by your identity providers.
This responsibility should be delegated to the UMA server. It's up to him to decide or not to grant a request access to a protected resource.
For example, image that we have the following scenario :
Context : An e-commerce enterprise has internally developed a tool used by his marketing team, to retrieve information about his most loyal clients.
The application has been developed in WPF and interact with a RESTFUL API to retrieve the clients.
Only this application and users that belong to the marketing group are authorized to retrieve the list.
Problem : How the application can access to the protected operation ?
workflow
Solution : the workflow is made of three big steps :
Identity token : retrieve an identity token with implicit grant-type. The token is returned to the client in a callback parameter
RPT token : the identity and access token (valid for the scopes uma_authorization & uma_protection) are passed in the request to retrieve the RPT one.
When it is received by the WPF application, the token is passed in the Authorization header to retrieve the loyal clients. Both parameters are required by the authorization policy.
Check RPT token : the token is checked against the introspection endpoint, this endpoint is offered by the UMA server.
As you can see internal policies are used by the UMA server to grant / or not access to the resource.
Authorization policy is out of scope of the UMA specification, you have to define it yourself :'(.
I have developed a product (open-source) to easily manage authorization policies. If you are interested you can test the demo here :
http://lokit.westus.cloudapp.azure.com/Demo
Note : If you are not satisfied about claims returned by external identity providers, you can always enrich them (read the use case : "assign role to resource owner" in the documentation)