I know that the access token obtained from OAuth2.0 can be used to access protected resources.
OpenID Connect issues ID token and access token after authentication. And the spec says that the access token can be used to access userinfo endpoint to get additional user information.
One thing I'm not able to understand is, is there any difference between the access token obtained in #1 vs #2. If there is no difference then do we need OAuth2.0, if we implement OIDC.
You tend to just implement both OIDC and OAuth 2.0 together as a combined flow, by plugging in an Open Id Connect security library.
Eg For a mobile app it is common to plug in AppAuth Libraries, which would give you this behaviour:
An OAuth 2.0 authorization redirect using response_type=code
The Open Id Connect part is initiated by including scope=openid
You then get an authorization code (OAuth 2.0)
You then swap the authorization code for tokens
You get an access token (the OAuth 2.0 part)
You also get an id token (the OIDC part)
In practical terms OIDC introduces some standardisation that makes developing UI flows and dealing with access tokens in APIs easier, eg:
Metadata endpoint, to tell us where all the other endpoints live
JWKS endpoint, from which we can get the access token's public key
Typically in my own code I do not use the id token much at all. However, it is best practice to receive one, so that libraries such as AppAuth can make extra verification checks against received tokens.
If it helps, my Message Workflow Blog Post summarises some messages and use of endpoints.
This access tokens have different audiences ("aud" claim): the OAuth 2.0 access token is intended for resource server (i.e. API), and OIDC access token is intended for identity server itself.
As for me, they cannot be used interchangebly, but some examples (e.g. IdentityServer4) do that without checking the "aud" claim.
PS. The single access token can be used for both purposes if both audiences are included:
Each principal intended to process the JWT MUST identify itself with a
value in the audience claim.<...> In the general case, the "aud" value
is an array of case-sensitive strings, each containing a StringOrURI
value.
JWT doc
Related
I am missing some understanding of OAuth2 access_token hope someone can explain or guide me to what I am missing.
I am using Microsoft Azure AD as an authentication provider for my application, I used the returned id_token after successful authentication to extend it with some additional data custom to my application (to facilitate authorization).
I am doing this throw JWT.sign, I decode the data from id_token and add data then I sign it using a secret key saved at the server.
My question is, can I do the same for access_token? When I tried to do so, I get unauthorized.
Am I doing something wrong? Or this is not possible? And why is this happening, I don't find any request made to MS to validated my new signed access_token.
You should never change tokens issued - this is not a correct thing to do. But your point about using domain specific claims is totally valid - all real world systems need these for their authorization.
OPTION 1
Some specialist providers can reach out at time of token issuance and contact your APIs, to get domain specific data to include in tokens. See this Curity article for how that works. I don't think Azure AD supports this though.
PRIVACY
It is best to avoid revealing sensitive data in readable tokens returned to internet clients. If you include name, email etc in ID tokens or access tokens this may be flagged up in PEN tests, since it is Personally Identifiable Information and revealing it can conflict with regulations such as GDPR.
Curity recommends protecting access tokens by issuing them in an opaque reference token format - via the phantom token pattern.
OPTION 2
An option that would work fir Azure AD is to adopt the following approaches:
Look up extra domain specific claims in your API when an access token is first received, then cache results for further API requests with the same access token. See this Azure AD Code Sample class of mine for some code that builds a custom ClaimsPrincipal. Note that the API continues to validate the JWT on every request.
If the UI needs extra domain specific claims then serve them from your API, which can return both OAuth User Info and domain specific data from its ClaimsPrincipal to the UI. See this API controller class for how that looks. Personally I always do this and never read ID tokens in UIs - which should also never read access tokens.
Applications interacting with Azure AD, receive ID tokens after authenticating the users. The applications use access tokens and refresh tokens while interacting with APIs.
The id_token is a JSON Web Token (JWT) which has user profile
attributes in the form of claims. The ID Token is consumed by the
application and used to get user information like the user's name,
email.
The Access Token on the otherhand is a credential that can be
used by an application to access an API.
So if you need application to access api, there the access token is used and you may follow the suggestion steps provided by Tiny Wang
Similar to id tokens, access tokens are also signed, but they are not
encrypted. As per IETF OAuth (RFC 6749) standard specification ,
access token can have different formats and structures for each
services whereas, id token should be JWT format.
To validate an id_token or an access_token, your app has to validate
both the token's signature and the claims. To validate access tokens,
your app should also validate the issuer, the audience, and the
signing tokens.
So in production application, you should get id token by specifying
“id_token+code” or “id_token+token” as response_type to verify
whether the authentication is correctly succeeded. It means it uses
the id_token for authentication and “code” to exchange access_token
to access the resource for authorization.
In short id_token is used to identify the authenticated user, and the
access token is used to prove access rights to protected resources.
Refer this for the information regarding access token and id token.
I am confused about the use of OAuth 2.0 as an Authorization method and OpenID Connect as an Authentication method.
Based on my knowledge OAuth 2.0 is only an Authorization method. In other words, this is the process to request an ACCESS_TOKEN and RECEIVE this ACCESS_TOKEN, like depicted in the image below in yellow ellipse: (simplified)
Before an OAuth 2.0 Client retrieves an ACCESS_TOKEN from an Authorization Server this Server should verify if the User allows it and this is an Authentication Process that OAuth 2.0 does not care about.
When OpenID Connect is included in the mix it allows for an Authentication Method as well, but in my knowledge OpenID Connect just adds a "Claim" in the JWT Token that holds information about user that is using the service, like: email, name and others.
My questions are:
Why not ignore OpenID Connect and just add more "claims" in OAuth
2.0 to get information about users?
Is my description of the flows correct?
OpenID Connect does not merely "add a claim in JWT Token" but:
it introduces a completely new token (id_token) with radically different
semantics than the OAuth 2.0 access_token and a standardized format that is understood by the Client as opposed to the access_token which is opaque to the Client
it "twists" the role of the Client, now becoming the "audience" (or: intended recipient) of a token (i.e. the id_token) whilst the audience of the access_token is still a remote entity (aka. Resource Server) and the Client is only the "presenter" of the latter
The 2nd item is the primary source of confusion between OAuth 2.0 and OpenID Connect.
I don't know if your method will work or not but you're totally free to roll your own authentication. After all, that's what Facebook, GitHub and many others did by customizing oauth2. There ended up being so many oauth2 "authentication" methods that it was never plug and play if you wanted to change your provider. I believe that's why OpenID connect was introduced--a common way of connecting and reasoning about authentication while building on the established oauth2 pattern for authorization. Use OpenID connect or don't...but if you don't you'll be reinventing the wheel.
#sdoxee answers explains thing correctly. But I am adding bit more information for OP's understanding.
These days many identity providers (eg:- Azure AD) issue JWT based access tokens. These JWT access tokens do contain claims about end user as well as JWT related validation details (eg:- Token expiration). Here is the link for Azure AD OAuth 2 success response which highlights access token to be a JWT. Also, see JWT claims to see how they explain the claims. Samples are given below,
family_name : User’s last name or surname. The application can display this value.
given_name : User’s first name. The application can display this value.
One could think of building authentication on claims present in access token, but this is not sticking with protocol. And mostly claims and user information will be implementer specific. Also, by protocol definition, these two tokens (id and access) have two different audiences.
ID token is for client, for validation and for authentication.
Access token is for OAuth 2 protected endpoint.
Again, as #sdoxee highlight, use the correct protocol at correct place. Having claims in access token does not necessarily mean you should use them for authentication.
Can someone tells me the difference in OAuth2, Auth0, JWT in a concise way and when to use either one and which one is much better?
OAuth2.0 is the name of the protocol you can use to get tokens that can be used to perform an action on behalf of the user. Now these tokens can be used to access some 3rd party API or your own Service.
For example, if you wanted to access someones emails on Outlook for an app you're building, OAuth2.0 allows you to get an Access token (issued by Microsoft) on the end user's behalf (they have to sign in to the identity provider) that can be used in a bearer request (just an HTTP request w/ the Access token).
Highly recommend skimming the RFC to read about the different scenarios OAuth2.0 can be used, the example here is just one case.
JWT (JSON Web token) is the standard format of a token used by many identity providers. Those Access tokens above may come in this format. Here's a small site you can use to decode JWT tokens (try hitting the example token).
Auth0 is a private company that works in the Identity space.
I have very little experience with Oauth 2.0 and am trying to better understand how the system works. Are access tokens tied to a user/device/session? For example, can I migrate an access token granted for one app and use it in another app? How will the server/API know? I believe most APIs have apps request using an app_ID, is there any other data that goes into a request for a token?
Thanks!
The OAuth 2.0 protocol framework is designed to allow for different types of access tokens but the only access token that has been standardized so far is the so-called "Bearer" token, so I'm assuming your question is about that.
A Bearer token is opaque to the Client which means that it is just an "identifier" or "string" that the Client passes on to the Resource Server to get access to protected resources. This also means that it is not specifically tied to a device/session or Client. In fact anyone who gets a hold of the Bearer token can actually use it to get access to the protected resources. This is one of the known drawbacks of Bearer tokens but it makes it very easy to implement them. It relies on a secure HTTPs channel for confidentiality.
The previous paragraph describes how to use a Bearer token. The process that the Client has to go through to obtain such a token, may include presenting a Client identifier and a Client secret to the Authorization Server indeed. But the Resource Server (aka. Server or API) does not know or care how the Client obtained the Bearer token.
There are token extensions of OAuth 2.0 under development that would require the Client to proof that it is the rightful owner of the token. Such tokens are called "Proof of Possession" Tokens and may be useful in environments that have higher security requirements. See: http://www.thread-safe.com/2015/01/proof-of-possession-putting-pieces.html
I am working on a mobile application that uses an api built with ASP.NET web api framework. We decided to use ACS alongside a custm STS as a mechanism to secure the api.
We are using a custom STS because we need to authenticate users against our own identity store.
The information flow is as follows:
Mobile app calls the custom STS with user credentials.
User is authenticated against our own identity store.
Once user is authenticated an authorization code is retrieved from ACS and used to retrieve an SWT access token.
Token is returned to mobile app.
Mobile app embeds access token in authorization header and fires request to API
HTTP module in API validates the access token and data is returned if the token is valid.
Everything is done over SSL as we are using oAuth 2.0.
The problem with oAUth 2.0 is that it is at risk from man-in-the-middle attack as the SWT token issued by ACS is a raw token and not encrypted in any way. It is however, signed using a 256bit symmetric key.
We are using swt tokens because we are using an http based approach and the token fits nicely into the auth header of an http request.
Microsoft have provided some ACS security guidelines in the following post:
http://msdn.microsoft.com/en-us/library/windowsazure/gg185962.aspx
we currently implement 2 of these as we check the issuer and the audience i.e that the token was issued by our trusted issuer (ACS) and that the token was issued for the correct audience (our api).
our scenario is based on the following article:
http://msdn.microsoft.com/en-us/library/hh446531.aspx
as such WIF is not used to handle incoming tokens. WIF is only used in claims processing.
given the above mentioned scenario is there anything else that we could be doing to improve the implementation we have to secure our rest based api?
any and all comments/criticism/suggestions welcome.
Thank you.
I think you're already taking the correct approach. The most important thing is to verify if the token is signed by ACS. Never share your ACS secret key with anyone else. If they don't know the key, they cannot forge the signature.
Also do not store confidential information in the token (such as password, credit card number, etc.). You should expect the token may be obtained by someone else, but no one can forge a token with the correct signature.