Say you have a Facebook app which uses an external API to fetch relevant data for the user using this app. The API needs the user's access_token to retrieve this relevant data. Since the API is a separate service, it needs to be provided with a Facebook access_token to retrieve the relevant data (it cannot get the access_token of the logged in user because it runs on a separate domain than the one the user is logged into).
One way of giving the access_token to the API is by making an HTTP request (sync or async, doesn't matter).
The question is, what can somebody do if it intercepts this access_token (because, obviously, it can be intercepted in an HTTP request)? Is it somehow protected by unauthorized use or it can be used by anyone to query the Facebook API on whatever that individual wants?
Related
I am using FB js SDK to allow logging in on my platform. A user permits the needed access and I save his ID in my DB. The data is sent to my server via AJAX. Since the login is with FB, I can identify the user only by his ID.
Now, lets say I know someones FB ID and I know he has an account on my platform. In runtime, I can place his ID in the auth request and obtain a legit session of that user. How could that be avoided?
First of all, those are App Scoped IDs, it is very unlikely that someone would know the ID of a user who authorized your App, because it´s not the "real" ID.
That being said, you can (and should) send the User Token to the server and confirm the ID by calling the /me endpoint with that Token. You should also use appsecret_proof for API calls, more information can be found in the docs: https://developers.facebook.com/docs/graph-api/securing-requests
I implement some facebook related stuff and accessing graph api for that pourposes. But for implement Integration testing I need a simple strategy to get access_token. So I create test user for that. How could I get access_token only with server side involved, without including browser in the chain. Ideally I just need to exchange login/password to the token.
Correct workflow loooks like this:
According the correct answer, there is special tests users provided by facebook.
To to be able to tests system properly you need to do the following flow
Get application access token
Request application's tests user's via "GET /{app_id}/accounts/test-users"
Parse response and extract access_tokens for each user from that response.
You can't exchange the login/password for an Access Token, but you can create test users programmatically. Have a look here:
https://developers.facebook.com/docs/graph-api/reference/v2.0/test-user
https://developers.facebook.com/docs/graph-api/reference/v2.0/app/accounts/test-users
How to get an access token with the right permissions for a test User
https://developers.facebook.com/docs/graph-api/reference/v2.0/user/permissions/
Short answer: You can´t.
Server side you can only get an App Access Token, Page Access Token or extend an existing Access Token.
So it depends on what you need to achieve, if you just want to get public stuff from a Facebook Page, even an App Access Token may be good enough. But you cannot create User Access Tokens server side.
It may be possible with real test users created via the Graph API itself though, see Tobis answer for links about that. But it is definitely not possible with username/password.
We have a website where the only way to login and authenticate yourself with the site is with Facebook (this was not my choice). The first time you login with Facebook, an account gets automatically created for you.
We now want to create an iPhone application for our site and also a public API for others to use our service.
This question is about how to authenticate with our website from the app/API and is broken into 2 parts:
What is the correct way to handle REST authentication from an API to a website which only uses Facebook OAuth as an authentication method?
I have read and researched a lot about standard methods of authentication for REST API. We can't use such methods as Basic Auth over HTTPS, as there are no credentials for a user as such. Something like this seems to be only for authenticating applications using the API.
Currently, the best way I can think is you hit an /authorize end-point on our API, it redirects to Facebook OAuth, then redirects back to the site and provides a 'token' which the user of the API can use to authenticate subsequent requests.
For an official application that we create, we wouldn't necessarily need to use the public API in the same way. What would be the best way then to talk to our website and authenticate users?
I understand (I think) how to authenticate 3rd-party applications that are using our API, using API (public) keys and secret (private) keys. However, when it comes to authenticating the user who is using the app, I am getting rather confused about how to go about it when the only way we have to authenticate a user is Facebook.
I feel like I'm missing something very obvious, or don't fully understand how public REST APIs should work, so any advice and help would be greatly appreciated.
UPDATE: see below
I've been thinking hard about this question too. It's not entirely clear to me yet but here's the route I am thinking of going. I am creating a REST API an my users only auth with Facebook connect.
On the CLIENT:
Use the Facebook API to login and get an OAUTH2 code.
Exchange this code for an access token.
In every call to my custom API I'll include the Facebook user id and the access token.
On the API (for every method that requires user authentication):
Make a request to the /me Facebook graph using the access token from above.
Verify that the Facebook user id returned matches the user id passed to my API from above.
If the access token has expired additional communication is required.
I have yet to test this. How does it sound?
--- Update: July 27th, 2014 to answer question ---
I only use the above exchange once upon login. Once I determine which user is logging in, I create my own access token, and that token is used from that point going forward. So the new flow looks like this...
On the CLIENT:
Use the Facebook API to login and get an OAUTH2 code.
Exchange this code for an access token.
Request an access token from my API, including the Facebook token as a parameter
On the API
Receive access token request.
Make a request to the /me Facebook graph using the facebook access token
Verify that the Facebook user exists and match to a user in my database
Create my own access token, save it and return it to the client to be used from this point forward
This is my implementation using JWTs (JSON Web Tokens), basically similar to Chris' updated answer. I have used Facebook JS SDK and JWT.
Here's my implementation.
Client: Use Facebook JS SDK to log in and get the access token.
Client: Request JWT from my API by calling /verify-access-token endpoint.
MyAPI: Receives access token, verify it by calling /me endpoint of Facebook API.
MyAPI: If access token is valid, finds the user from database, logs in the user if exist. Create a JWT with required fields as payload, set an expiry, sign with the secret key and send back to the client.
Client: Stores the JWT in local storage.
Client: Sends the token (the JWT from step 5) along with the request for the next API call.
MyAPI: validate the token with the secret key, if token is valid, exchange the token for a new one, send it back to the client along with the API response. (No external API calls for verification of the token here after) [if the token is invalid/expired request client to authenticate again and repeat from 1]
Client Replaces the stored token with the new one and use it for the next API call. Once the token expiry is met, the token expires revoking access to API.
Every token is used once.
Read more answers about security and JWT
How secure is JWT
If you can decode JWT how are they secure?
JSON Web Tokens (JWT) as user identification and authentication tokens
I am trying to answer the same question and have been going through a lot of reading recently...
I won't have "the" answer but things are getting a little clearer for me. Have you read the comments in the article you mentioned? I found them really interesting and helpful.
As a result, and in the light of how things have evolved since the first article has been written, here's what I think I'll do:
HTTPS everywhere — this allows you to forget about HMAC, signing, nonce, ...
Use OAuth2:
When authentication requests come from my own apps/website, use this 'trick' (or a variation of it) described in a reply to the article mentioned before.
In my case, I have two types of users: those with classic login/password credentials and those who have signed up with Facebook Connect.
So I'd provide a regular login form with a "Login with Facebook" button. If the user logs in with his "classic" credentials, I'd just send these to my OAuth2 endpoint with a grant_type=password.
If he chooses to log in via Facebook, I think that would be a two-steps process:
First, use Facebook iOS SDK to open an FBSession
When that's done and the app is given back control, there should be a way to get a Facebook ID for that user. I'd send this ID alone to my OAuth2 endpoint with an extension grant understood by my server as "using an FB User ID".
Please note that I am still heavily researching on all this stuff, so that might not be a perfect answer... maybe not even a correct one! But I think that would make for a good starting point.
The idea of using an "extension grant" for the Facebook authentication might involve having to register it to do things properly? I'm not quite sure.
Anyway, I hope I was able to help you even a bit, and that at least it can start a discussion to find the best solution to this problem :)
Update
The Facebook login is not a solution as pointed in the comments: anybody could send an arbitrary user ID and log in as this user on the API.
What about doing it like this:
Show a login form with a "Facebook login" button
If this login method is chosen, act kinda like the Facebook SDK: open a web page from your authentication server, which will initiate the Facebook login.
Once the user has logged in, Facebook will use your redirect URL to confirm; make that URL point to another endpoint of your authentication server (possibly with an extra parameter indicating the call came from an app?)
When the authentication endpoint is hit, the authentication can securely identify the user, retain its FB User ID/FB Session and return an access token to your app using a custom URL scheme, just like the Facebook SDK would do
Looks better?
I receive an access token when a client allows my application on his facebook account. Based on that access token and an url I can print all his friends. I have a question: does this access token appears all the time the user logs in his application? i am asking this because the second time the user logs in in my application where i have a web browser the friend list doesn't pop up because the response from the site does not contain an access token anymore. where am i wrong? how can i check after the user accepts my app that he is online or loged in - if i want to prints his friends.
First thing: sounds like you want to add the scope offline_access because what you are trying to do is really leveraging the FB authentication mechanism.
Also: It is probably easiest to use the FB Connect button and the JavaScript Client API, unless you intend on using the graph or REST API from a back-end server.
If you ARE intending to use back-end API integration read this paragraph:
I have found it helps to ensure that you are using a proper authenticate URL (I use www.facebook.com/dialog/oauth but others have worked in the past..). Just don't use an authorize only URL, or users will be forced to grant permissions repeatedly (never really understood that 'feature'). Next redirect the user to the URL with a request token, and keep your request secret on the server side (or well encrypted if on the client side). After login, you receive the callback with an OAuth Verifier. Access verification URL graph.facebook.com/oauth/access_token with the Verifier and you will receive the OAuth Access Token. Save that token, as well as the user id.
As for checking that the current user is logged in, and/or has authorized your app and/or has friends using your app:
Have a look at FB Connect API:
http://developers.facebook.com/docs/guides/web/#login
call FB.init first, and then when you call FB.getLoginStatus, you will get an OAuth Token if the current user is logged in to FB and has previously authorized your app (either via the Connect Button or OAuth flow):
$wnd.FB.getLoginStatus(function(response) {
if (response.session)
var authToken = encodeURIComponent(response.session.access_token);
});
When executed in conjunction with the authenticate flow mentioned, users that have already authorized your application will get the same OAuth Access Token returned from previous calls, that you can use with the JS Client, Graph, or REST APIs.
I feel like every second question i ask here is relating to Facebook Connect - that says a lot about their API. Anyway, that's politics, i digress..
I'm trying to pull back user details from the Graph API for use in my application (which is an FBML external website - JavaScript SDK for authentication).
I have requested the following permissions from the user: (using the regular dialog)
publish_stream
email
This works, and allows me to post to the user's wall, and grab their email from the Graph API.
But when i do a HTTP GET Request to the following URL:
https://graph.facebook.com/uid?access_token=oat (where uid = the user id of the user i'm attempting to grab details for, and oat = the OAuth token i have).
All that comes back in the JSON is the User ID (which i already have, since im putting it in the URL), and the email.
Why can i not get things like first name, last name, locale, etc?
Am i using the wrong URL? Is my OAuth token wrong?
I'm getting the OAuth token from here:
https://graph.facebook.com/oauth/access_token?type=client_cred&client_id=myappid&client_secret=myappsecret
UPDATE:
It looks like the issue is my OAuth token.
Because when i go to the docs: http://developers.facebook.com/docs/api
And use the sample OAuth Token for the user im trying to retrieve, it gets all the details.
Anyone know what is wrong with my OAuth token call?
So, i was using the wrong URL for the OAuth Exchange. It needed to be this:
https://graph.facebook.com/oauth/exchange_sessions?type=client_cred&client_id=myappid&client_secrete=myappsecret&sessions=userseshid
The URL that i WAS using was as per the doco, the above one that works is nowhere to be found.
I'm at the point with FBC that i no longer care about the how, if it works, be thankful that it does even that and move on.
EDIT:
Also, i was wondering why the Graph API calls would "stop" working for no reason.
The answer is i needed to compare the Session Key used to obtain the OAuth token, with the Session Key currently in the cookies. If they are different, i needed to get a new OAuth token.
The session key used for any OAuth token is part of the actual OAuth token:
aaa|bbbb|cccc
Where bbbb is the session key. So i just compare that before doing any Graph API calls.