I am trying to understand this access_token, refresh_token feature. And this is what I understood:
-- LOGIN:
CREATES access_token;
CREATES refresh_token, sends to DB;
SENDS refresh_token + access_token to client;
access_token expired:
API automatically CREATES a new access_token, using refresh_token;
refresh_token expired: API DENIES all requests, forcing the client to login again.
And i heard that you need to save the refresh_token on a 'sessions' table of database, or smth like it. But i can't understant why, since the client will/may send the refresh_token on all requests. Making it useless to save to DB.
I don't know if i got anything wrong, i hope you can help me out!
What is a little bit awkward (or unclear) in your example - which system creates access and refresh tokens, and sends them to the customers?
Based on the description, I would conclude that this is the identity provider - the client authenticated themselves and got those tokens as a result.
Now when the client calls an API (on a resource provider), they have to include the access token with each request. The resource provider would take the access token and validate it. If the access token is not valid, the API just have to return "access denied".
The client has to use the refresh token to get the new access token from the identity provider and repeat the call to the API on the resource provider.
This would be the typical usage of the flow.
The other common use case is to allow a backend system to do api calls on behalf of the client - in those cases, the backend system has both access token and refresh token; so it can maintain the logged in state even if the client is not around.
It might be that your example is some kind of hybrid solution - both customer and the backend do some calls to IDP.
I am playing around with IBM Cloud Functions (OpenWhisk) and trying to setup authentication through OAuth with Facebook as the provider. I have setup an app with Facebook, I am able to successfully connect with this and fetch my token and I am able to verify this by fetching basic profile information (name and userID).
My problems starts when I enable OAuth in the IBM Cloud Functions API. I get a HTTP code 500 back from the call with very little information about what actually went wrong.
{"code":500, "message":"Oops. Something went wrong. Check your URI and try again."}
The only thing that is stated in the dashboard is:
You can control access to your API through the OAuth 2.0 standard. First require an end user to log in via IBM Cloud App ID, Facebook, GitHub, or Google. Then include the corresponding OAuth token in the Authorization header of each API request. The authenticity of the token will be validated with the specified token provider. If the token is invalid, the request will be rejected and response code 401 will be returned.
With this information I got that I need pass the token with the Authorization header. My best guess is that the call fails somewhere when the token is being validated.
I am using Vue and Vue-axios to perform the API call. My current call looks like this:
this.$http.get(API_URL+"?user_id="+localStorage.user_id,{headers :{'authorization':localStorage.token}}).then((response) => {
console.log(response);
});
I have tried adding bearer/Bearer or token/Token in front of the token (some posts I read indicated that you should do this), but this had no impact on the response.
If I disable the OAuth authentication from the Cloud Functions side, the code above works and correctly retrieves the data (with or without the header option).
From the Chrome Dev tools it looks to me like the token is added correctly to the request, since the request headers have the Authorization header with the token.
I am not that familiar with OAuth or IBM Cloud Functions, so the problem might have a very easy fix. However, I am unable to find documentation which clearly shows me how I am supposed set this up. I am also unable to find any logs or more information about what actually fails here. Am I missing something obvious here?
Kjetil
I am working on putting an application together that uses PayPal's REST APIs, starting with the invoicing API.
I am used to getting an Access Token and a Refresh Token with other implementations of OAuth 2.0 (ie, Google, MS, etc), but it seems PayPal has done away with Refresh Tokens in this instance.
Could I get some clarification? When the original access token expires, should I just request a new one? Or should I be receiving a refresh token as well and refreshing the Access Token using that?
Thanks!
Referenece: Access token validity and expiration
As the document mentioned, you should request a token and reuse it until it expires. Don't request a new token per session (and actually you will still get a same one before the one expires). It means that you should only request a new token when you meet a HTTP 401 response, and replace the old token with the new one.
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.
I want to authenticate native devise by oauth2 access token, which was obtained using client side flow (http://developers.facebook.com/docs/authentication/)
Currently I just call one of the protected method using this token and handle AccessDenied error. May be there is build in method that validates token?
Here is ruby sample with OAuth2 gem:
begin
response = JSON.parse(token.get('/me'))
rescue OAuth2::AccessDenied
render :json => { errors: {"" => ["Invalid oauth2 token"]}}
else
...
end
If I understand your question, you're asking how to handle when a valid access token becomes invalid, for example, if a user removes your app. According to this Facebook blog post: https://developers.facebook.com/blog/post/500/, there is no absolute way except for firing an API call, which you surmised. Guess we are all out of luck.
P.S. That blog post has good details on other scenarios a valid access token might expire.
as far as I know, there is no publicly available method / api that we can validate token.
The closest that I know is the access token linter that Facebook has provided.