I have a rest API service that enables API calls for some resources.
The API calls can be done from an API server using a secret, or from a web client using a bearer token.
In order to get to the web client flow, a URL must be generated by the API server call:
https://www.someapi.com/somelink
The response will be a link with a token I call "action token". This token is passed with the link, for example:
https://www.somepage.com/?action_token=somejwttoken
By entering the link, the action token will be exchanged with an access token, that enables a client to access some pre-defined resources.
I wonder if there is a best practice for such flow.
ONE TIME TOKENS
If using tokens in URLs you should also ensure that:
The token has a one time use
The token is short lived
The token is not guessable - eg make it a UUID
The final access token returned has limited privileges and also a short lifetime
The one time action token may then be available in the browser history or server logs, so be aware of that. Make the actual swap for the proper token a JSON to JSON POST operation, after the page has loaded.
Typically each action token issued would also be stored by the API in a database along with its expiry time, then used to verify links later.
This type of URL solution is sometimes used in operations such as verify email or to enable magic links, where users can quickly access limited data.
OAUTH FLOWS
One time tokens should not be overused and they are of course no substitute for signing the user in properly via OpenID Connect standards, then running an authenticated user session.
SCOPES AND API TO API FLOWS
A more secure option may be to forward JWTs from the original client to downstream APIs, as described in Scopes Best Practices. This enables user context to flow securely and also simplifies code. This may eliminate or reduce the need for any token exchange operations.
I am not clear on what exactly I should do with the id token from Google after the initial verification.
I'm developing on expo/react native and get the id token locally. Then, I send it to my server and verify it using google client libraries. Once it's verified what should I do with it?
Ideally I could use it to protect my api routes (express) but id tokens expire after 1 hour and I'm not sure how to refresh them with the client library. So, I don't know how I would do this.
Is that the intended use for id tokens? Should I instead be signing my own jwt and sending that back to the client? Then, the client could send that in the auth header of each request to a protected routes.
Google says:
After you have verified the token, check if the user is already in your user database. If so, establish an authenticated session for the user. If the user isn't yet in your user database, create a new user record from the information in the ID token payload, and establish a session for the user. You can prompt the user for any additional profile information you require when you detect a newly created user in your app.
https://developers.google.com/identity/sign-in/ios/backend-auth
Do I use the id token to "establish a session for the user"?
Yes, the ID-token is only used to create the local session, perhaps also create a local entry in your local database if that is used.
The ID token also have a very short lifetime, like 5 minutes in some systems. So it has no long-term use.
The ID token is intended to authenticate the user. It gives you information about the authenticated user, it should not be used to allow access to your endpoints. Access tokens or sessions are intended to do so. So in your case, you should do exactly as your gut feeling tells you - create a session for the user basing on the data you got in the ID token.
If you have your own Authorization Server you can use the ID token to issue an access token and return the token to the frontend app, then use the access token to access your backends. Have a look at OAuth flows if you would want to go this way.
Per Google's docs it would seem refresh tokens are only necessary for offline applications (applications that may run into an expired access token when the user isn't around).
Access tokens periodically expire. You can refresh an access token
without prompting the user for permission (including when the user is
not present) if you requested offline access to the scopes associated
with the token.
...
Requesting offline access is a requirement for any application that
needs to access a Google API when the user is not present. For
example, an app that performs backup services or executes actions at
predetermined times needs to be able to refresh its access token when
the user is not present. The default style of access is called online.
However, a description of refresh tokens in general and this question in particular both seem to imply that refresh tokens are needed anytime you want to request a new access token.
I think I would agree with Google's explanation and not use refresh tokens. My experience with OIDC providers has been that refresh works as follows:
User requests protected resource from client server
Client server determines access token has expired.
Client server redirects user to OP auth endpoint
OP authenticates user without interaction due to cookies stored on user's browser with OP's domain.
Client server finishes the request.
The user might see a few redirects but other than that the re-authentication went by without any interaction from them. Given this, is it necessary to bother with refresh tokens if the user will always be present at the application?
My biggest concern with using refresh tokens for online apps is that it takes away transparency from the user.
Refresh tokens facilitate long term access and should be stored safely. But they also don't provide a natural way to "sign out", and (most importantly) it becomes completely opaque how, when and from where your data is accessed, as the often used scope name offline_access suggests.
OIDC offers a front channel mechanism prompt=none that largely leads to the same effect (i.e. new tokens), and without needing intermediate redirects if the re-authentication is performed inside an iframe.
Hence in my opinion you and Google are right and the answer must be: No, don't use refresh tokens if the user is present.
No, it is not necessary to bother with refresh tokens if the user will always be present at the application. The reasoning is largely the OP describes.
But there are reasons why one may still want a refresh token:
as the OP mentions the user might see a few redirects and both the UI expert and the branding guy on your team will hate this
when an access token expires in the middle of an HTML Form POST action, the redirect may have lost the context/POST-data on return; you may want to minimize this or you'll have to take appropriate (complex) POST-data-save actions
if your access token expiry is really short, the redirects create a lot of overhead and nuisance; you may not be able to control access token expiry when dealing a Providers in a different domain and when dealing with multiple Providers it will vary across them
when refreshing the access token with a redirect your application now depends on the Provider keeping an SSO session; not all Providers may do this and if they do they may do it in different ways: the SSO session duration may vary between them and the authentication method may vary; as an example: a Provider that doesn't keep an SSO session but does use 2-factor authentication will have large impact on the user experience
Imagine a scenario where you want to use the access token to update user information in almost real-time from the user info endpoint but the access token expiry is relatively short. Either you'll have to perform a lot of redirects with the nuisance as described, or you can use a refresh token.
Refresh token is essentialy a credential reference, that your client can exchange for access token, when there is no active user session.
For example if you want to periodicaly sync issues from Github with your inhouse system.
It is often misused like some kind of session. It is essential to diffirentiate those things. And scope name offline_access is there for a reason.
So in simple cases - you just rely on OP session and get new token with authorize/token endpoints combo. You should not be prompted to provide credentials as long as session is alive and consent is given for that particular app.
If you need to do some backgound stuff - ask for refresh token also.
As for question: no.
EDIT(More in-depth explanation):
if we are talking about web there are two main cases:
Client that can securely store secrets like usual web app with server page rendering and clients, that cant store secrets, like SPA apps. From that perspective there are two main flows (omitting hybrid to not over-complicate): Authorization Code Flow and Implicit Flow respectively.
Authorization Code Flow
On first request your app checks it own session(client session) and if there is none - redirects to external OP(OpenID Connect provider) authorize url. OP authenticates user according to requirements expressed in request, gathers consent and other stuff and returns authorization code. Then client asks token endpoint with it and receives access_token/id_token pair with optional refresh token if user granted offline access consent. This is important, because user can deny it for your app. After this client can request userInfo endpoint to get all user claims that were granted during consent. Those claims represent user identity and do not contain stuff like authentication method, acr etc. Those claims present in id_token alongside with expiration for example. After that client starts it own session and have option to set its lifetime equal to id_token lifetime or use it own to provide smooth UX for example. At this point you can discard access_token and id_token at all if you don't need access to other APIs(like all scopes in access_token are specific to OP and subject). If you need access to some API you can store access_token and use it for access. It becomes invalid - redirect to OP for new one. Expiration can be more lax here, because of more secure environment on server. So even 1hr is an option. No refresh tokens used at all.
Implicit Flow
In this case your lets say Angular app redirects to OP, gets its id_token and optional access_token from authorize endpoint directly and uses it to access some APIs. On every request expiration is checked an if needed, client sends request to OP in hidden iFrame, so there won't be any visible redirects as long as OP session is alive. There are some great libs for that like openid-client.js. No refresh is allowed here at all.
It is important to differentiate client session from OP session, token lifetime and session lifetime.
To address some specific needs there is Hybrid Flow. It can be used to get authorization code and id_token for your session in one request. No chit chat over network.
So when you think about refresh token just check your needs and map them to a spec :) And if you need it anyway - store it as secure as you can.
Refresh tokens are useful for applications that keep access tokens in a server session. For example if a web application doesn't call a protected service using JavaScript XHR, but calls its backend and the backend calls the service. In this scenario, it's easier to get a new access token whenever it's needed than asking a user for a new one.
In JavaScript applications running in browsers, refresh tokens cannot be used, because you need a client secret to get an access token from the /token endpoint and you cannot keep the secret safe in such applications.
The process for getting new access tokens you described can be improved - an application may ask for a new access token just before the current one expires, so the user doesn't get redirected to the OAuth2 server, but the application calls the /auth endpoint with prompt=none parameter in an iframe.
I am facing a custom implementation of OpenId Connect. But (there is always a but) I have some doubts:
I understand the process of obtainning an acces_token an a id_token, except the step when the OP provides an authorization_code to the client. If it is done by a redirect (using the redirect uri)
HTTP/1.1 302 Found
Location: https://client.example.org/cb?
code=SplxlOBeZQQYbYS6WxSbIA
&state=af0ifjsldkj
The end-user is able to see that authorization code? It does not expire? Imagine we catch it and we use later (some days later) Is it a security hole? Should the state be expired in the Token Endpoint?
The flow continues and we got at the client the Access_token and the id_token in the client.
How the Access_token should be used on the OP side ? It should be stored in a database? Or be self containing of the information required to validate it ?What would you recommend?
And in the client-side , both tokens should be sent in every request?
And the last doubt, if we have an Access_token the existence of an id_token is for representing authorization and authentication in separated tokens?
Extra doubts:
I know the process to obtain an access token but I have doubts of how the OP ,once generated and sent, it validates the access_token that comes with every request
How the OP knows an access token is valid? As far as I know, the OP should say that an access_token is valid/invalid. There should be some way to check it right? How it gets to know that a token represents a valid authenticated user if it is not stored in DB?
Is it a bad idea to store access_token in a cookie? Because sometimes we call to some webservices and we want to send access_token as parameter. Or there is another workaroundsolution?
How the access token should be stored in the Client , for example, in ASP.NET, in the session?
Thanks very much to all of you, I will give upvote and mark as answer as soon as you give me the explanations.
Thanks!
The end-user is able to see that authorization code?
Yes. Although, even if the authorization code can be seen, the token request requires that the client's secret be sent as well (which the browser does not see)
it does not expires? Imagine we catch it and we use later (some days later) It is a security hole? Should the state be expired in the Token Endpoint?
The spec says that the authorization code should expire. See https://www.rfc-editor.org/rfc/rfc6749#section-4.1.2.
How the Access_token should be used on the OP side ? It should be stored in a database? Or be self containing of the information required to validate it ?What would you recommend?
The access token should be stored on the OP if you want to be able to revoke the tokens. If you don't, the token will be in JWT format (self-contained)...but you should store it if you want to be able to revoke it whether it's a JWT or not.
And in the client-side , both tokens should be sent in every request?
No, just the access token.
And the last doubt, if we have an Access_token the existance of an id_token is for representing authorization and authentication in separeted tokens?
Yes, they are separate tokens for different purposes. Access token is for authorization and Id token is self contained and used to communicate to the client that the user is authenticated.
How the OP knows an access token is valid? As far as i know, the OP should say that an access_token is valid/invalid. There should be some way to check it right? How it gets to know that a token represents a valid authenticated user if it is not stored in DB?
see How to validate an OAuth 2.0 access token for a resource server? about thoughts on how the resource server should validate the access token before letting the request from the client go through.
It´s a bad idea to store access_token in a cookie? because sometimes we call to some webservices and we want to send access_token as parameter. Or there is another workaroundsolution?
I'm assuming you're using the authorization code grant flow (...from your questions). If that's the case, the reason why an authorization code is, first of all, passed back from the OP rather than the access token is so that the access token can stay hidden on the server side--away from the browser itself. With the authorization code grant flow, the access token should stay out of the browser. If you're wanting to send api requests to the resource server directly from the browser, then look into the oauth2 implicit flow (https://www.rfc-editor.org/rfc/rfc6749#section-4.2).
How the access token should be stored in the Client , for example, in ASP.NET, in the session?
In the OpenID Connect flavour of OAuth2, the access token is for offline_access (i.e. outside of an authenticated "session"). The access token could be used during the session of the user but it might be better to store the refresh token in the database so that your client app can request new access tokens whenever it needs to and as long as the refresh token is valid...even when the user's authentication is expired. The access token should be short-lived so storing it in the database is an option but not necessary.
In OpenID Connect an access token has an expiry time. For authorization code flow, this is typically short (eg 20 minutes) after which you use the refresh token to request a new access token.
The ID token also has an expiry time. My question is what is the intent of this?
Any ID token expiry time less than the expiry time of the refresh token will mean you will eventually have an expired ID token, but a valid access token.
So are you meant to:
give your ID token an expiry longer than the refresh token expiry, or
set it to the same expiry as the access token and take some action (what?) when it expires, or
just consume the ID token in your client on receipt, then ignore the expiry time after that?
The OpenID Connect specification just says that when validating an ID token,
"The current time MUST be before the time represented by the exp Claim."
which (possibly) supports the third option above.
EDIT
As OpenID Connect builds on OAuth2 the answer to the supplementary question below can be found in the OAuth2 specification which says,
expires_in
RECOMMENDED. The lifetime in seconds of the access token.
A related question is when you exchange an authorization code for the tokens, the same specification says you might get a response such as:
{
"access_token": "SlAV32hkKG",
"token_type": "Bearer",
"refresh_token": "8xLOxBtZp8",
"expires_in": 3600,
"id_token": "eyJhbG[...]"
}
But what does "expires_in" relate to in this case? The access token, the refresh token or the ID token?
(For information, IdentityServer3 sets this to the access token expiry time).
I'm answering my own question as have discovered that some of the assumptions behind my question were wrong, so easier to clarify here, rather than re-write the question.
An ID token is meant for proving to a Client that the user has authenticated, and who they are as a result.
When a Client receives an ID token, it will generally do something like convert it to a ClaimsIdentity, and persist this, eg using a cookie.
The ID token has to be un-expired at this point of use (which it should be, since it has just been issued). But after this it is not used again, so it does not matter if it expires while the user still has an active session. The Client has the authentication information it needs, and in turn can choose its own policy for how long the session lasts before the user has to log in again.
My wrong assumption when asking the question was that an ID token and access token should be used together, and therefore both needed to have valid expiry dates. This is wrong for various reasons:
ID tokens are only for authenticating to a Client (as described above).
Access tokens have nothing to do with Clients. They are for access to resources and a Client only handles them if it in turn needs to call an resource.
Something like a standalone MVC or WebForms application only needs an ID token. If it isn't calling an external resource, there is nothing to grant access to, so no access token.
I had to dig into this for my own reasons and wrote it up, so I'll post what I learned here...
First, I'll answer the question at the risk of stating the obvious: The ID token cannot be trusted and its content must be ignored if the current time is greater than the expired time. The questioner's answer states that the after the initial authentication of the user, the ID Token isn't used again. However, since the ID Token is signed by the identity provider, it certainly could be useful at any time to give a way of reliably determining who the user is to other services that an app might be using. Using a simple user ID or email address isn't reliable because it can be easily spoofed (anyone can send an email address or user ID), but since an OIDC ID Token is signed by the Authorization server (which also usually has the benefit of being a third party) it cannot be spoofed and is a much more reliable authentication mechanism.
For example, a mobile app may want to be able to tell a backend service who the user is that is using the app and it may need to do so after the brief period following the initial authentication, at which time the ID Token is expired, and thus, cannot be used to reliably authenticate the user.
Therefore, just like the access token (used for authorization - specifying what permissions the user has) can be refreshed, can you refresh the ID Token (used for authentication - specifying who the user is)? According to the OIDC specification, the answer isn't obvious. In OIDC/OAuth there are three "flows" for getting tokens, The Authorization Code flow, the Implicit flow, and the Hybrid flow (which I'll skip below because it's a variant of the other two).
For the implicit flow in OIDC/OAuth you request the ID Token at the authorization endpoint by redirecting the user in the browser to the Authorization endpoint and including id_token as the value of the response_type request parameter. An Implicit Flow Successful Authentication Response is REQUIRED to include the id_token.
For the Authentication Code flow, the client specifies code as the value of the response_type request parameter when redirecting the user to the authorization endpoint. A successful response includes an authorization code. The client client makes a request to the token endpoint with the authorization code and, according to OIDC Core Section 3.1.3.3 Successful Token Response the response MUST include an ID Token.
So for either flow, that's how you initially get the ID Token, but how do you refresh it? OIDC Section 12: Using Refresh Tokens has the following statement about the Refresh Token Response:
Upon successful validation of the Refresh Token, the response body is the Token Response of Section 3.1.3.3 except that it might not contain an id_token.
It might not contain an ID Token and since there is no way specified to force it to include the ID token, you must assume that the response will not contain the ID Token. So technically there is no specified way to "refresh" an ID Token using a refresh token. Therefore, the only way to get a new ID Token is to re-authorize/authenticate the user by redirecting the user to the authorization endpoint and starting the implicit flow or authentication code flow as described above. The OIDC specification does add a prompt request parameter to the authorization request so the client can request that the authorization server not prompt the user with any UI, but the the redirect still has to happen.
If I understand correctly, according to this and the OpenID Connect Core 1.0 spec, the ID token itself can be stored in cookies as a mechanism to persist sessions, and sent with every authentication-requiring request to the Client. The Client can then verify the ID token either locally or through the Provider's verifier endpoint (if provided, like Google does). If the token is expired, it should make another auth request, except this time with prompt=none in the URL parameter. Also make sure to send the expired ID token in the id_token_hint parameter, otherwise the Provider may return an error.
So, it does seem natural for the ID Token to expire, but prompt=none ensures the new ID token can be obtained smoothly with no user intervention (unless of course the user is logged out of that OpenID).
It is the same intent: you can't use the id_token after it is expired. The main difference is that an id_token is a data structure and you won't need to call any servers or endpoints, as the information is encoded in the token itself. A regular access_token is usually an opaque artifact (like a GUID).
The consumer of the id_token must always verify the (time) validity of it.
I'm not 100% familiar with IS, but I would guess it is a convenience field. You should always check the exp claim.
Expiration is just one of the validations. id_tokens are also digitally signed and that is also a validation you must perform.
Refreshing a token means that you can use it again for requesting something from the authorization server (in this case the OP - the OpenID-Connect Provider) EVEN WHEN THE USER IS NOT LOGGED IN. You typically allow this for limited resources only, and only after the user has logged in and been authenticated at least once. The refresh tokens themselves should be also limited in time.
In OIDC implicit flow you call the Authorization endpoint,
and receive the ID token in the response along with all the scopes and in them all the claims info.
Subsequent calls to an API are meant to be done with code flow.
Implicit flow is meant to enable a javascript only or browser only app. Not an app that is interacting with a server.
So even if there was a way to "refresh" this token, you should not - security wise - allow it to live too long. It will be stolen and reused by unauthorized users impersonating the id. You should force a new login for that.
In code flow you call the OP's Authorization endpoint, and receive an Authorization code (also called an authorization token, or authcode for short). This should expire similar to the id_token that you received in implicit flow, for the same reasons and cannot and should not be renewed.
Your UI or app then call the OP's Token endpoint, and receives (sometimes after the user's further consent through a UI to allow use of their owned resources on the OP's server) both:
An id_token, for authentication - which should never be used again in server calls, except as a hint during logout, when its expiration is not important anymore, and so, for the reasons above should be let to expire, and never be refreshed.
An access_token - which later on, when calling an API, can be given to the OP's UserInfo endpoint. That will return the claims, and the API can authorize accordingly.
You can refresh this access_token, since it only tells the API what claims the user has, and what resources (by scopes and each scope's claims) the user agreed to give you. As explained above this is for allowing access even after the user is not logged in anymore. Of course you never wish to allow the id_token to be refreshed, because you don't want to allow impersonation without logging in.
I wanted to post this answer as a comment but since I haven't been very active on StackOverflow, I guess I'm posting it as an alternate answer.
You also use id_token as the id_token_hint when attempting to log the user out of a session http://openid.net/specs/openid-connect-session-1_0.html. I honestly don't think that it really matters if the id_token is expired at this point since you're only concerned about logging out a particular user.
TLDR;
Validate the ID token before trusting what it says.
More Details
What is intent of ID token expiry time in OpenID Connect?
The intent is to allow the client to validate the ID token, and the client must validate the ID token before operations that use the ID token's information.
From the OpenID Implicit Flow spec:
If any of the validation procedures defined in this document fail, any operations requiring the information that failed to correctly validate MUST be aborted and the information that failed to validate MUST NOT be used.
To corroborate that, Google's OpenID Connect documentation says this about ID token validation:
One thing that makes ID tokens useful is that fact that you can pass them around different components of your app. These components can use an ID token as a lightweight authentication mechanism authenticating the app and the user. But before you can use the information in the ID token or rely on it as an assertion that the user has authenticated, you must validate it.
So, if our client application is going to take some action based on the content of the ID token, then we must again validate the ID token.
Just share my journey. It's June, 2021. I'm writing this because I've stumbled into 3rd-party authentication business. I'm a veteran programmer but novice to security. In other words, all standards, spec, and terminologies are strangers, anybody can beat me in this field. Forgive me for not going by all the terms.
Cut to chase, I'm writing an Angular/Node app, so UI=Angular, API (API server)=Node/Express. Instead of creating my own Username/Password authentication, I'm turning to 3rd-party authentication, let them validate the genuineness of what the users claim they are. Here are two important guidebooks for me:
Angular Authentication With JSON Web Tokens (JWT): The Complete Guide
Eiji's Authenticate with a backend server
Combining No. 1 and angularx-social-login, I have the UI hooked up with Google, then attach idToken to API, vola! Following No. 2 using local library API can validate idToken, great!
Wait, idToken has exp expires in 1-hour. How do I refresh it?
My understanding is all I need is Google's authentication, I don't care what standard and version they use, but like others I just trust their authentication. Authentication is basically verify who they claim they are. Authorization is access control for what/where users can do/goto. The internal access control (allow users to do what) is not exposed to Google they have no idea of it. So accessToken should be out of the picture. Right?
I've spent days studying on how to refresh idToken now concluded Google does not recommend it nor angularx-social-login offers a way. In No. 2, Eiji has stated clearly:
Hence, solution for my situation is
use Google's authentication.
creates an own session management/timeout-rules at API after initial validation of idToken to mitigate exp.
preferably add this session data into cookie with res.cookie("SESSIONID", myOwnID, {httpOnly:true, secure:true});
For better protection, Eiji also recommends Cross Account Protection. Hope this will help someone!