I have an application that uses react to authenticate. With the Okta library, it by default stores the id token and access token in the local storage. I then grab the access token to make an .net api call that is protected by role authorization.
I'm having difficulty understand the issue with XSS attack. My understanding is that they can inject javascript code to do something with the access token. They are only able to get their own access token by logging in normally. Why is it an issue if they are doing something with their own access token? In addition, can't the access token be found in the network call, so it's not really hidden to begin with?
Can anyone provide me with an example or explain the gaps in my logic? Thanks!
My understanding is that the access token here will be stored in the browser (I'm not super clear on the differences between cookies and local storage but correct me if I'm wrong). When you do that .NET API call the browser knows to pass along the access token. The issue is that websites can include arbitrary JavaScript that runs on your browser, i.e. that arbitrary JavaScript can execute HTTPS requests from your browser using your access token.
In this way, the malicious agent wouldn't be creating their own access token, but instead using yours in arbitrary ways that might give them access to whatever private data you have stored behind your .NET API.
The avoid this, we limit the domains that can access our APIs. Typically, you might see APIs only allow requests from the same domain name. For example: if you API is accessible at mywebsite.com/api then it would only allow API requests from mywebsite.com.
edit:
Forgot to answer the "isn't the access token not hidden because it's included in a public HTTPS request" question. There's a couple of potential solutions here. On websites that use TLS (i.e. you're accessing with HTTPS), you know the public key of the website you're intending to send data to. You can use that public key to encrypt your access token and only the website will be able to decrypt it (with their private key). This way, your access token is kept secret between you and the .NET API.
In an XSS attack there is nothing that prevents the attacker from reading values in local storage. Unless there are countermeasures such as CSP to prevent exfiltration, an XSS attack can be used to steal access tokens.
When cookies have the HttpOnly flag set they are not accessible by script. The browser will attach them on relevant requests as intended.
When requests are encrypted using HTTPS the headers will be encrypted and thus hidden.
Related
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.
I need some advice regarding using session tokens to authenticate users. I am building an AngularJS app which uses an API to tie in with the backend. I am only building the front end, not the backend. The documentation states that all calls to the API have a session token attached in the body of the request (POST).
I would like to know about the security of storing this token in localStorage. That is where I am storing it now and retrieving and attaching it to each API request. After login, the server sends the session token in the body and I save it from there.
There is no documentation about an x-access-token header that should be sent with the request made to the server. It is not being checked server side. What are the implications of this? I feel that it is susceptible to attacks without this added layer of security.
My main concern is the security of this setup. I want to know what the best setup is to make sure this app is as secure as possible and recommend changes to the way the backend is setup to facilitate this.
Thanks!
As you tell, you are only working on the UI part and not the backend. It is up to the backend team to ensure headers are properly evaluated and security is enforced (btw request headers do not belong to request body). Just put the token into the x-access-token header as they tell.
Storing the token inside the localStorage gives you a little more control over the cookie: You will not accidentally send it to unnecessary URLs. However, older browsers do not support it - you may need to use a shim for that.
In a case of SPA, you may consider not storing the token at all: It could be fetched each time your application is accessed and then stored within a service in angularjs, but it depends how your fetch/login operation is implemented (is it always interactive, how long does it take, etc).
I would suggest use $cookies rather than localstorage. As localstorage does not support some legacy browser.
I am using cookies to store token in my project
It is common to authenticate to web services using an authorization header which contains a secret token. And since the security of this mechanism depends on the token to be secret care should be taken that this token is not leaked.
There are countless tutorials on the web which explains how such an authorization header can be set using angular and least the ones that I have actually read use an $http interceptor and now one discusses that the token is not leaked.
There are some public and some private APIs out there which can be talked to cross domain thanks to CORS. And obviously I do not want to send my internal authorization tokens on any of those requests.
Some other techniques come to mind such as setting the token manually only on each and every request, but that means lots of duplicate code. The $http server could be wrapped in an $authenticatedHttp service so that it is always appearent from the object used whether it is the authenticated service or the normal one. However the $http service has so many methods to be wrapped.
Is there a better solution?
UPDATE
From the answers I have the impression that my question was not understood. I try it with a more concrete example:
I have a private web page. People have to login with username/password and let's say for simplicity's sake that we use HTTP basic auth, so username/password are bas64 encoded and are transmitted on every request in the HTTP header "Authorization". So far there is no problem.
But there is this great&free weather widget. I can retrieve the current weather information in JSON format from https://myWhateverWeatherService.tld/weather.json. After the login to my private web service I also retrieve the weather information (CORS allows me to do this).
The problem is that even though myWhateverWeatherService.tld does not require any authentication at all, angular's $http service will still append the Authorization header. And I don't trust the guys at myWhateverWeatherService.tld. Maybe they just set up the service so they can steal Authorization token and do lot's of nasty stuff with them.
I need some reliable way to deal with that. I already thought about checking the url with some regex in the interceptor. This is possible, but it is also not to difficult to forget about a certain case that my regex will miss.
The token is always sent through the wire, I guess that is the most vulnerable part of it.
Since the token must always be present on the http header itself, the only way to make the request more secure is to encrypt the whole request, and for that you should use SSL.
If you are concerned about the safety of storing the token on the client machine, you can keep it only on the browser´s memory, without persisting it on a localstorage or something like that. So every time the user closes the browser and open it again, s/he must log in.
I've read almost every answer on SO and some blog postings, but I can't figure out one simple thing. In a simple token authentication scheme where the server generates a token and sends it back to the user after verifying credentials, how does the client store and then resend that token in each request? I have seen both cookie examples and header examples. I would like to use the HTTP Headers if possible, but I can't figure out the mechanics of how to send the token to the client, where it will sit, and then have it sent back in the header upon requesting a REST resource.
I am using Jersey/Guice with AngularJS on the front end. Here are the resources I started with:
http://porterhead.blogspot.co.uk/2013/01/writing-rest-services-in-java-part-6.html
Session management : How to generate Authentication token for REST service ? (Jersey)
It depends on your needs. You can use HTTP basic or digest auth, if it is appropriate for you. If not, then if you don't need a permanent storage, you can store credentials in memory. If you need a permanent storage, then you can store them in localstorage, or any other client side storage, but aware, that they are considered not secure.
Anyways I think if your client or service is compromised somehow with xss, then you lost, and it does not matter what else you do about it. Otherwise you can send the credentials in plain text securely as long as you use HTTPS with proper settings. (But that's just an opinion, I am not a security expert, at least not in this topic.) So I think you should concentrate on not being xss vulnerable. For example you should use the proper headers and filter the input against js injection (and by firefox data URI injection). And use TextNode in your client instead of innerHTML wherever it is possible.
For example if you are using Javascript you can store the token in localstorage like window.localStorage["token_id"] on the client side.
I have an Angular application (SPA) that communicates with a REST API server and I'm interested in finding out the best method to store an access token that is returned from an API server so that the Angular client can use it to authenticate future requests to the API. For security reasons, I would like to store it as a browser session variable so that the token is not persisted after the browser is closed.
I'm implementing a slightly customized version of OAuth 2.0 using the Resource Owner Password grant. The Angular application provides a form for the user to enter their username and password. These credentials are then sent to the API in exchange for an access token which must then be sent as a header (Authorization: Bearer %Token%) for all outbound requests to the API so that it can authorize requests to other routes.
I'm fairly new to the realm of Angular, but the workflow I would like to implement as far as handling these tokens is summarized as follows.
1) The client makes a request to the API providing it with user credentials.
2) If this request is successful, the token is stored somewhere (where is the question)
3) Intercept HTTP requests. If token is set, pass it along as a header to API
4) Token is destroyed when the browser/tab is closed.
I know Angular offers $window.sessionStorage, which appears to be what I am looking for, but I am concerned by the potential for it not to work on all browsers according to various resources I've read. This is an enterprise grade application and must be compatible across a broad range of browsers (IE, Chrome, Firefox). Can I safely use this with the confidence that it will be stable?
The alternatives, from what I understand, are either $window.localStorage or cookies ($cookies, $cookieStore). This would not be an ideal solution for me since I don't want this data to persist, but if this is more reliable I'll have to sacrifice efficiency for compatibility. I was also thinking it might be possible to simply set it as a value on the $rootScope and reference it this way, but I'm not sure if this is feasible.
I hope that all made sense. Any help / suggestions would be greatly appreciated.
Thanks!
If you are looking for something that will definitely not persist then I would simply keep the token in memory and not rely on the browser for storage. However storing inside rootScope would not be best practice.
I would recommend that you wrap your server access code in an Angular Service if you have not done so already. You can then encapsulate your token within that Service at runtime (e.g. as a property) without worrying about having to access it when calling from other parts of your application.
Angular Services are singleton so your "server service" will be a global instance that can be accessed using normal dependency injection.
$window.sessionStorage is the way to go unless you're targeting very old browsers.
According to www.w3schools.com sessionStorage is supported from IE 8.0, Chrome 4.0, Firefox 3.5, and Safari 4.0.