I'm building a REST API and using AWS Cognito's user pools for authentication. I've got a "get_token" endpoint that returns the JWT access and refresh tokens to the user, which they use to authenticate access to the other REST endpoints provided by the API.
The access token has an expiration timeout. If the user of my API is an application program, what are the best practices for the application to handle when the access token expires? Does the application have to remember the username/password and re-authenticate to continue? Is using the refresh token to get a new access token and use that going forward the best approach?
Is there any documentation, suggestions anyone can point out that might help me out?
Cognito provides 3 types of tokens, id, access and refresh tokens when you login. The way this usually works is that you send either of the first two (depends on whether you want to be sending user payload information to your backend) to your backend via an Authorization header and verify the token there.
Your id and access tokens usually have a shorter expiration time compared to the refresh token. What you should do is, when the id (or access) token expire, you should use the refresh token to generate a new id (or access) token. When the refresh token expires that means that you can no longer generate new id/access tokens from it. In this case, the user (or app) must login again.
Please don't mark as duplicate I came through a lot of questions like this but still I didn't get the point of refresh token. Some of the reason they said are:
If an attacker gets the access token it will expiry soon
But where I am confused is if the attacker was able to get the access token why they wouldn't be able to get the refresh token (both of them needed to access token by JS to sent request so they needed to store in local storage)
If the attacker gets the refresh token we can block it in server.
But we can also block the access token in server right. (with DB)
Note I am not talking about OAuth refresh token, because as per the answers I read,
The idea of refresh tokens is that if an access token is compromised,
because it is short-lived, the attacker has a limited window in which
to abuse it.
Refresh tokens, if compromised, are useless because the attacker
requires the client id and secret in addition to the refresh token in
order to gain an access token.
So it makes sense here but what about JWT?
Typically the access token gets sent with every request, and to your API.
Typically a refresh token only gets sent once, immediately expires after use and only goes to your authentication server. All these measures generally reduce risk.
JWT and OAuth2 can be used together, and it's highly recommended to use OAuth2 instead of trying to write something from scratch.
I talk a bit more about the pitfalls in my article: https://evertpot.com/jwt-is-a-bad-default/
The refresh token allows the client to make a call and ask for a new access token. For setups where the access token does have a certain expiry, the refresh token will typically have an expiry which is later than the access token itself. Here is a typical workflow using access and refresh tokens:
The client authenticates to the server via 1FA or 2FA
The server responds with an access token having an expiry in 5 minutes, along with a refresh token which expires a minute later
The client then uses the access token as needed.
When authentication fails using the current access token, under the hood the client will take the refresh token and hit the server to get a new access token. We then go to step #2 above and recycle.
Note that for certain instances, the refresh token is not needed. One example would be sites like Stack Overflow, which uses token which never expire. Another example would be certain high security sites such as banking sites. In these cases, the site might force you to reauthorize via 1FA/2FA in order to keep the session going.
One way in which an update of the authentication token can be carried out through another and without exposing it to client applications (avoiding its use in a malicious way), is to store it in a cache system such as REDIS and in the When the request token has expired, check in storage if the user has a refresh token that allows him to regenerate the authentication. This could be implemented within the same middleware that validates the token that accompanies the request or in an endpoint intended for this purpose.
Im playing around and creating a custom access token system using JWT. I have already created a system for signing and validating JWT access tokens.
However, I find it hard to obtain information about what claims a refresh token should consist of.
Should i create refresh tokens identical to the access token - with a longer expiratiom time so that the same function that validates access tokens can be used to validate the refresh token?
A refresh token is typically an opaque value that is only used by clients to refresh access tokens. The flow works like this:
Web or mobile client implements OpenID Connect to authenticate users and get tokens - prompting the user to consent in some cases
An Authorization Server (AS) issues the tokens and stores details of this 'delegation' in a database - tokens are a pointer to this state
Client sends access tokens to APIs until a 401 expired response is received
Client then tries to refresh the access token by sending the refresh token to the Authorixation Server, which then looks up claim details from the stored state
I would make sure you get these responsibilities right - in particular avoid building your own AS and use a free one provided by experts, such as Curity Community Edition. Many security solutions will then be easier to develop.
I've been developing my first REST API to serve as the back-end for a mobile application. I'm pulling info from different resources, and am a little confused when it comes to the token implementation (I'm using JWT).
The access token is used to ensure that the requester has access to the resource that is being called. My understanding is that I will then encode the user details in the ID Token, such that the relevant information can be returned. The refresh token is used as a security mechanism, to keep the user authenticated after the short-lived ID and access tokens expire.
The access token seems a little redundant, and maybe it is an interchangeable term for ID token? Can I just remove that part from my authentication scheme?
In the proposed scheme access and ID tokens are used interchangeably and do not provide any value over the other. All information provided in the access token can be stored in the ID token, or vice versa. The entire authentication scheme will then simply consist of an access token (containing both info on access permissions, and user info), and a refresh token (ensuring that users don't need to login again every t minutes).
Why do you need both a "code" and a "token" in the Facebook OAuth2 authentication flow as described here: https://developers.facebook.com/docs/authentication/ ?
If you look at the OAuth dialog reference (https://developers.facebook.com/docs/reference/dialogs/oauth/), it seems like you only ever use the token to fetch information about the user, and if you specify the response_type parameter as token or code,token, then you get the token on the first time.
Why do you need to get a "code" and then use the code to get a "token" as opposed to getting the token directly?
I guess I'm misunderstanding something basic about how OAuth works, but it seems you avoid the request to https://graph.facebook.com/oauth/access_token entirely if you get the token the first time with the dialog.
Let us take a simple example to differentiate authentication code vs access token.
You as a user want to try a new Facebook app called Highjack.
So you click on the application and the Highjack app asks you to log into your Facebook account. When you are done, Facebook generates an authentication code for you.
This code is then passed to the Highjack server which uses its own FB client id, FB secret and your authentication code to get an access token.
In the above example the authentication code is confirming you as a user is a valid FB user. But the second steps says "you as a FB user is giving access to the Highjack app for certain resources".
If the Highjack app wanted implicit grant (i.e direct access token), then the access token would be visible to you also since it is being exchanged with the browser. This means you can now call all Facebook APIs on behalf of Highjack using the access token. (You can only use the access token to get your personal information but Facebook has no way of knowing who is calling their APIs.)
Since we have 2 parties (You and Highjack) authenticating with Facebook we have this 2 fold mechanism.
Borrowed shamelessly from Salesforce Documentation:
Authorization Code
An authorization code is a short-lived token representing the user's access grant, created by the authorization server and passed to the client application via the browser. The client application sends the authorization code to the authorization server to obtain an access token and, optionally, a refresh token.
Access Token
The access token is used by the client to make authenticated requests on behalf of the end user. It has a longer lifetime than the authorization code, typically on the order of minutes or hours. When the access token expires, attempts to use it will fail, and a new access token must be obtained via a refresh token.
From the OAuth 2.0 Spec:
The authorization code provides a few important security benefits
such as the ability to authenticate the client, and the transmission
of the access token directly to the client without passing it through
the resource owner's user-agent, potentially exposing it to others,
including the resource owner.
So, basically - the main reason is to limit the # of actors getting the access token.
"token" response is intended primarily for clients that live in the browser (e.g.: JavaScript client).
Answer) You need/want both the code and token for extra security.
According to Nate Barbettini we want the extra step of exchanging the authentication code for the access token, because the authentication code can be used in the front channel (less secure), and the access token can be used in the back channel (more secure).
Thus, the security benefit is that the access token isn't exposed to the browser, and thus cannot be intercepted/grabbed from a browser. We trust the web server more, which communicates via back channels. The access token, which is secret, can then remain on the web server, and not be exposed to the browser (i.e. front channels).
For more information, watch this fantastic video:
OAuth 2.0 and OpenID Connect (in plain English)
https://youtu.be/996OiexHze0?t=26m30s (Start 26 mins)
If you look at the flow of Authorization Code OAuth type, yes, there are actuary two steps:
<user_session_id, client_id> => authorization_code
<client_id, redirect_uri, authorization_code, client_secret> => access_token, refresh_token
In step1: the user tells the OAuth Server that "I want to auth this client (client_id) to access my resource. Here is my authentication (user_session_id or what else)"
In step2: the client (client_id) tells the OAuth server that "I've got the user the authorization (authorization_code), please give me an access token for later access. And this is my authentication (client_id & client_secret)"
You see, if we omit step 2, then there is no guarantee for client authentication. Any client can invoke step1 with a different client_id and get an access token for that client_id instead of its own. That's why we need step2.
If you really want to combine step1 and step2, you can do something like this:
<client_id, redirect_uri, client_secret> => access_token, refresh_token
We use this approach in our Open API Platform, and we haven't find any security problem yet.
BTW, there is actually an Implicit Grant type, that is:
<client_id, redirect_uri> => access_token, refresh_token
It is generally applicable to client only application which have no server backend. In that case, the OAuth server must ensure that the redirect URI belongs to that client (same with the register redirect_uri, for example).
The mix-up came because the user on behalf of himself and not the client app authenticate against the authorization server (i.e. facebook).
Its much simple to secure the client app (with https) then the user-agent (browser).
Here is the original formulation from IETF-oauth (https://datatracker.ietf.org/doc/html/draft-ietf-oauth-v2-threatmodel-08#section-3.4):
3.4. Authorization Code
An authorization code represents the intermediate result of a
successful end-user authorization process and is used by the client
to obtain access and refresh token. Authorization codes are sent to
the client's redirection URI instead of tokens for two purposes.
Browser-based flows expose protocol parameters to potential
attackers via URI query parameters (HTTP referrer), the browser
cache, or log file entries and could be replayed. In order to
reduce this threat, short-lived authorization codes are passed
instead of tokens and exchanged for tokens over a more secure
direct connection between client and authorization server.
It is much simpler to authenticate clients during the direct
request between client and authorization server than in the
context of the indirect authorization request. The latter would
require digital signatures.
Theoretically,
Access Tokens cannot tell us if the user has authenticated but auth code does.
Auth code should not be used to gain access to an API but access token should be.
If you have a single page application or mobile application with no or minimum backend, your application may want to access user's FB data directly at frontend. Hence the access token is provided.
In another case, you may want a user to register/login to your app using some external auth service provider like Facebook, Google etc. In this case, your frontend will send the auth code to the backend that can be used to get access token from Facebook at serverside. Now your server becomes enabled to access user's FB data from the server.
Basically, as an extension of Lix's answer, the access code route allows a Resource Owner (i.e. the Facebook User) to revoke authorization for their User Agent (i.e. their browser), e.g. by logging off, without revoking authorization for an offline Client (i.e. Your Application).
If this is not important, then there is no need to use the access code route.
Furthermore, the access code is provided to ensure that the Token provided to a server is actually registered to the Resource Owner (i.e. the Facebook User), and not the User Agent (or a Man-in-the-Middle).
This seems similar to the question of either choosing the implicit vs authorization code grant flow. In fact, here is what looks like an opposite view point?!.
Also, as Drew mentioned,
When the access token expires, attempts to use it will fail, and a new access token must be obtained via a refresh token.
another piece is the refresh token, but I don't see that being explained too well in the FB Docs. If I'm correct, the implicit grant (the direct token) should be really short lived, but that is to-be-enforced and FB.js seems to hide a lot of that (this one I have not looked as deep into).
If I'm correct, the code%20token is an optimization allowing both the User Agent to have a token and allowing for the server to initiate the token exchange process in a single request (as anything over Network IO is considered expensive, especially to a User Agent).
In OAuth 2.0 with facebook, the overall concept is simple as follows.
Step 1. Obtain "Authorization Code" by a GET request
request URI: https://www.facebook.com/dialog/oauth
Params:
response_type=code
client_id={add your "App id" got by registering app}
redirect_uri={add redirect uri defined at the registration of app}
scope={add the scope needed in your app}
Headers: None
Step 2. Obtain the "Access Token" by sending the authorization code as a POST request
URI: https://graph.facebook.com/oauth/access_token
Params:
grant_type=authorization_code
client_id=<add your "App id" got by registering app>
redirect_uri=<add redirect uri defined at the registration of app>
code=<obtained authorization code from previous step>
Headers:
Authorization:Basic encode <App Id:App Secret> with base64
Content-Type:application/json
Step 3. Use the access token got from above step and retrieve user resources
It’s because the access token is given to an AUTHENTICATED client (third-party app) using a shared secret that only FB and the client knows. The only way that the user could directly request the access token is by knowing the shared secret, which would make the secret public and could lead to a man-in-the-middle attack. Further, while FB can guarantee a secure connection to the user, FB can’t guarantee the handoff of the token to the client is secure. However, FB (and OAuth2) does require a secure connection between the client and FB. The access token is tied to the client public ID (usually hashed), which means only the original client application can use it to request the token because the secret is sent along with the authorization code to get the access token.
You recieve a token when the user logs in. But you might want to change the token when you are performing other actions. EG posting as your app/page or posting as a user with offline_access.