We have a simple setup: An authorization server based on OAuth 2.0, which currently only supports the client_credentials grant type. Then we have an API, the resource server, which is protected by requiring an access token from our OAuth server.
All use-cases for our API so far, have been pure machine-to-machine communcation, where it's simply our customers servers running batch jobs.
Today I had a meeting with a new customer. They have an SPA that seemingly does not have its own backend server. It uses AWS for authenticating, and seems to return a JWT, but from what I can tell, they make a lot of API calls directly to publicly available services, and then the logic is all performed in the SPA.
We ideally would've liked them to simply register a single OAuth client with us, so that when users make a request that needs one of our APIs, the request is first routed to their server, which performs the lookup, and then uses their client's credentials to contact our server. But they would prefer to not have to set up a backend. In this case I'm kind of at a loss for how we sensibly let them integrate with our system. They would prefer to send their user's JWT to our system, but I don't think they understand that we would need their key to verify the user's signature in that case, and we don't want to have to create new APIs simply for this purpose.
Would very much appreciate any advice on this issue - thanks very much in advance for any help.
We ideally would've liked them to simply register a single OAuth
client with us, so that when users make a request that needs one of
our APIs, the request is first routed to their server, which performs
the lookup, and then uses their client's credentials to contact our
server.
Your recommended approach is the right way of doing it with Client Credentials Grant.
They would prefer to send their user's JWT to our system, but I don't
think they understand that we would need their key to verify the
user's signature in that case, and we don't want to have to create new
APIs simply for this purpose.
If the previous approach doesn't work, I'm afraid that this is the only way of doing it. You will need to implement a Proxy to validate the JWT (You should be able to get their public key to verify the signature). You can do this in AWS itself, using AWS API Gateway + Lambda to verify the JWT to and forward the request to your existing backend with Client Credentials Grant where you don't need to pay anything upfront.
Related
I've an API that uses OAuth authentication (hydra) to authenticated requests that are
coming from the user browser.
I would also like to send requests to the same API's also from another backend (NodeJS).
I'm a bit confused what is the best way to do it.
The current Authentication mechanism uses a refresh token (1h).
I was thinking about creating another client for the backend in hydra, but it seems strange that also the backend will use the same method with the refresh token like the browser (never saw this before).
Any help with how to address this issue will be appreciated.
So... there are several concepts you might need to take into consideration here...
Since its conception the OAuth 2.0 family of standards distinguishes between private (trusted) and public (potentially vulnerable to attacks) clients. The client you've got running in the browser falls in the latter category, and thus most experienced OAuth devs out there would argue that it's not OK to use refresh tokens for this client. For you backend service (even if it is a simple backend-for-frontend) written in node, that's a completely different story - there it's OK to use and store refresh tokens.
If however your node.js backend is working "outside" an active customer session, i.e. tries to access customer data even when no customer is actively interacting with the frontend, you might also want to consider the machine-to-machine flow provided by OAuth 2.0 - the Client Credentials Flow.
I'm trying to accomplish the following scenario.
I have and API at the moment and one web app. I have also create a new oauth client on my auth server (keycloak), which follows the implicit grant. I also used jwks on my nodejs api to do the token verification.
Now I want to create an SDK that will target the same API.
The questions is how do I get the SDK to retrieve an access token from the auth server. The first thought is that I will have to create a new client oauth client on the authserver and then use the client credential flow to get the access token. However, I dont know what should the behaviour of my API be like. At the moment it used jwks against a single audience. How should it be configured to verify access tokens from multiple clients (potentially thousand of them)
If you want multiple clients to call your API they should all use the same audience, and your first level of security will work.
The audience in access tokens represents the API(s) the token can be used against.
You will then need to use something else to authorize API requests, depending on the type of client and what they are allowed to do.
Configure each type of client in your auth server so that you are in control and know who is calling the API.
You may have 1000 clients but only 4 levels of privilege - in which case only configuring 4 OAuth clients may make sense.
One OAuth option you can use is give different clients different scopes. Scopes can represent high level privileges.
If a particular client calls an addOrder operation but does not have an Orders scope you could return a 403 response.
Often though API authorization needs to go beyond OAuth checks and apply custom rules based on the end user privileges.
If you can provide more info on your scenario I could provide a more complete answer.
I have a web application which uses OAuth 2.0 to talk to a third-party service. I want both my server and my web app to talk to the authorized service on behalf of the user. I go through the normal authorization steps of doing the redirect, getting the auth code, exchanging it for the access token, all that jazz. Once complete, my server has the access token and can talk to the service. However, I'd like the web app to talk to the service as well so I don't have to route everything through my server.
Can I send the access token to the web app so I can achieve this? Or, is the access token supposed to be kept confidential between my service and the service, never being disclosed to the user, just just like the client secret is?
I've tried to find an answer for this in the spec and various blog posts, but haven't found a definitive answer either way. I know there is an implied auth method for client-side apps which don't involve a server-side component at all. Therefor my initial guess is that I can send the token to the client. I would like to verify this though.
The token is considered very sensitive information because it allows access to the service. Anyone could issue requests if they had this token.
This is why the token is passed in the Authorization Header, this is why it's highly recommended you make all calls over https, to protect the headers and body information. This is also why it is recommended that the tokens have s short life span so that if one is indeed compromised, it doesn't last for long.
Yes, you can share this token between your own applications and it should work, provided the receiver of the token does not store the IP addresses of the callers as well or has some other check mechanisms in place.
The ideal situation however would be for you to issue a different set of ClientID and Client Secret to each application which requires access.
Don't forget that this is the way the applications identify themselves to the receiver side and it might be important for reporting and analysis purposes.
I'm developing the restful web app that using some popular web framework on the backend, say (rails, sinatra, flask, express.js). Ideally, I want to develop client side with Backbone.js. How do I let only my javascript client side interact with those API calls? I don't want those API calls to be public and be called by curl or simply by entering the link on browser.
As a first principle, if your API is consumed by your JS client, you have to assume, that it is public: A simple JS debugger puts an attacker into a position, where he can send a byte-for-byte identical request from a tool of his choice.
That said, if I read your question correctly, this is not, what you want to avoid: What you really don't want to happen is, that your API is consumed (on a regular basis) without your JS client being involved. Here are some ideas on how to if not enforce, then at least encourage using your client:
I am sure, your API has some sort of authentication field (e.g. Hash computed on the client). If not, take a look at This SO question. Make sure you use a salt (or even API key) that is given to your JS client on a session basis (a.o.t. hardcoded). This way, an unauthorized consumer of your API is forced into much more work.
On loading the JS client, remember some HTTP headers (user agent comes to mind) and the IP address and ask for reauthentication if they change, employing blacklists for the usual suspects. This forces an attacker to do his homework more thoroughly again.
On the server side, remember the last few API calls, and before allowing another one, check if business logic allows for the new one right now: This denies an attacker the ability to concentrate many of his sessions into one session with your server: In combination with the other measures, this will make an abuser easy detectable.
I might not have said that with the necessary clarity: I consider it impossible to make it completely impossible for an abuser to consume your service, but you can make it so hard, it might not be worth the hassle.
You should implement some sort of authentication system. One good way to handle this is to define some expected header variables. For example, you can have an auth/login API call that returns a session token. Subsequent calls to your API will expect a session token to be set in an HTTP header variable with a specific name like 'your-api-token'.
Alternatively many systems create access tokens or keys that are expected (like youtube, facebook or twitter) using some sort of api account system. In those cases, your client would have to store these in some manner in the client.
Then it's simply a matter of adding a check for the session into your REST framework and throwing an exception. If at all possible the status code (to be restful) would be a 401 error.
There's an open standard now called "JSON Web Token",
see https://jwt.io/ & https://en.wikipedia.org/wiki/JSON_Web_Token
JSON Web Token (JWT) is a JSON-based open standard (RFC 7519) for
creating tokens that assert some number of claims. For example, a
server could generate a token that has the claim "logged in as admin"
and provide that to a client. The client could then use that token to
prove that they are logged in as admin. The tokens are signed by the
server's key, so the server is able to verify that the token is
legitimate. The tokens are designed to be compact, URL-safe and usable
especially in web browser single sign-on (SSO) context. JWT claims can
be typically used to pass identity of authenticated users between an
identity provider and a service provider, or any other type of claims
as required by business processes.[1][2] The tokens can also be
authenticated and encrypted.[3][4]
Set a SESSION var on the server when the client first loads your index.html (or backbone.js etc.)
Check this var on the server-side on every API call.
P.S. this is not a "security" solution!!! This is just to ease the load on your server so people don't abuse it or "hotlink" your API from other websites and apps.
Excuse me #MarkAmery and Eugene, but that is incorrect.
Your js+html (client) app running in the browser CAN be set up to exclude unauthorized direct calls to the API as follows:
First step: Set up the API to require authentication. The client must first authenticate itself via the server (or some other security server) for example asking the human user to provide the correct password.
Before authentication the calls to the API are not accepted.
During authentication a "token" is returned.
After authentication only API calls with the authentication "token" will be accepted.
Of course at this stage only authorized users who have the password can access the API, although if they are programmers debugging the app, they can access it directly for testing purposes.
Second step: Now set up an extra security API, that is to be called within a short limit of time after the client js+html app was initially requested from the server. This "callback" will tell the server that the client was downloaded successfully. Restrict your REST API calls to work only if the client was requested recently and successfully.
Now in order to use your API they must first download the client and actually run it in a browser. Only after successfully receiving the callback, and then user entry within a short frame of time, will the API accept calls.
So you do not have to worry that this may be an unauthorized user without credentials.
(The title of the question, 'How do I secure REST API calls', and from most of what you say, that is your major concern, and not the literal question of HOW your API is called, but rather BY WHOM, correct?)
Here's what I do:
Secure the API with an HTTP Header with calls such as X-APITOKEN:
Use session variables in PHP. Have a login system in place and save the user token in session variables.
Call JS code with Ajax to PHP and use the session variable with curl to call the API. That way, if the session variable is not set, it won't call and the PHP code contains the Access Token to the API.
We are building a rest service and we want to use OAauth 2 for authorization. The current draft (v2-16 from May 19th) describes four grant types. They are mechanisms or flows for obtaining authorization (an access token).
Authorization Code
Implicit Grant
Resource Owner Credentials
Client Credentials
It seems we need to support all four of them, since they serve different purposes. The first two (and possibly the last one) can be used from third-party apps that need access to the API. The authorization code is the standard way to authorize a web application that is lucky enough to reside on a secure server, while the implicit grant flow would be the choice for a client application that can’t quite keep its credentials confidential (e.g. mobile/desktop application, JavaScript client, etc.).
We want to use the third mechanism ourselves to provide a better user experience on mobile devices – instead of taking the user to a login dialog in a web browser and so on, the user will simply enter his or her username and password directly in the application and login.
We also want to use the Client Credentials grant type to obtain an access token that can be used to view public data, not associated with any user. In this case this is not so much authorization, but rather something similar to an API key that we use to give access only to applications that have registered with us, giving us an option to revoke access if needed.
So my questions are:
Do you think I have understood the purpose of the different grant types correctly?
How can you keep your client credentials confidential? In both the third and fourth case, we need to have the client id and client secret somewhere on the client, which doesn't sound like a good idea.
Even if you use the implicit grant type and you don’t expose your client secret, what stops another application from impersonating your app using the same authorization mechanism and your client id?
To summarize, we want to be able to use the client credentials and resource owner credentials flow from a client application. Both of these flows require you to store the client secret somehow, but the client is a mobile or JavaScript application, so these could easily be stolen.
I'm facing similar issues, and am also relatively new to OAuth. I've implemented "Resource Owner Password Credentials" in our API for our official mobile app to use -- the web flows just seem like they'd be so horrible to use on a mobile platform, and once the user installs an app and trusts that it's our official app, they should feel comfortable typing username/password directly into the app.
The problem is, as you point out, there is no way for my API server to securely verify the client_id of the app. If I include a client_secret in the app code/package, then it's exposed to anyone who installs the app, so requiring a client_secret wouldn't make the process any more secure. So basically, any other app can impersonate my app by copying the client_id.
Just to direct answers at each of your points:
I keep re-reading different drafts of the spec to see if anything's changed, and am focused mostly on the Resource Owner Password Credentials section, but I think you're correct on these. Client Credentials(4) I think could also be used by an in-house or third-party service that might need access to more than just "public" information, like maybe you have analytics or something that need to get information across all users.
I don't think you can keep anything confidential on the client.
Nothing stops someone else from using your client id. This is my issue too. Once your code leaves the server and is either installed as an app or is running as Javascript in a browser, you can't assume anything is secret.
For our website, we had a similar issue to what you describe with the Client Credentials flow. What I ended up doing is moving the authentication to the server side. The user can authenticate using our web app, but the OAuth token to our API is stored on the server side, and associated with the user's web session. All API requests that the Javascript code makes are actually AJAX calls to the web server. So the browser isn't directly authenticated with the API, but instead has an authenticated web session.
It seems like your use-case for Client Credentials is different, in that you're talking about third-party apps, and are only serving public data through this method. I think your concerns are valid (anyone can steal and use anyone else's API key), but if you only require a free registration to get an API key, I don't see why anyone would really want to steal one.
You could monitor/analyze the usage of each API key to try to detect abuse, at which point you could invalidate one API key and give the legitimate user a new one. This might be the best option, but it's in no way secure.
You could also use a Refresh Token-like scheme for this if you wanted to lock it up a bit tighter, although I don't know how much you would really gain. If you expired the Javascript-exposed api tokens once a day and required the third-party to do some sort of server-side refresh using a (secret) refresh token, then stolen api tokens would never be good for more than a day. Might encourage potential token thieves to just register instead. But sort of a pain for everyone else, so not sure if this is worth it.