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When my users are authenticated they receive an authentication token, I need to use this authentication token to authorize some asp.net WebAPI calls. To do this I need to add the token to the head of that call, so I need the token accessible from the users browser. I think that storing the token in a cookie isn't the safest way, so what is the safest way to store that token and still accessible in my javascript to make API call's?

  • I think using a SSL certificates should do your job, there publications here explaining their usages and what they do: rfc-base.org/rfc-6101.html. – Rio Hazuki Feb 3 '15 at 10:29
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    In what way will SSL help secure a token stored on the client? – James Feb 3 '15 at 10:30
  • ceur-ws.org/Vol-313/paper9.pdf please read this.. If your trying to implement something against best practice that is not generic. Then your will have problems later down the line supporting your client. – Rio Hazuki Feb 3 '15 at 10:33
  • Session cookie. Don't overthink it, these things were made for a reason. – Andrew Hoffman Oct 21 '15 at 0:02
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    "I think that..." When the rest of the world relies on cookies for storing such tokens, maybe you should explain your thinking so we might all be better informed and have a chance of coming up with a solution which addresses your concerns? – symcbean Jul 30 '16 at 22:26
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There are two ways you can save authentication information in the browser:

  1. Cookies
  2. HTML5 Web Storage

In each case, you have to trust that browsers are implemented correctly, and that Website A can't somehow access the authentication information for Website B. In that sense, both storage mechanisms are equally secure. Problems can arise in terms of how you use them though.

If you use cookies:

  • The browser will automatically send the authentication information with every request to the API. This can be convenient so long as you know it's happening.
  • You have to remember that CSRF is a thing, and deal with it.

If you use HTML5 Web Storage:

  • You have to write Javascript that manages exactly when and what authentication information is sent.

The big difference people care about is that with cookies, you have to worry about CSRF. To handle CSRF properly, you usually need an additional "synchronizer token".

All-in-one web frameworks (like Grails, Rails, probably asp.net) usually provide an easy way to enable CSRF protection, and automatically add synchronizer token stuff in your UI. But if you're writing a UI using a client-side-only web framework (like AngularJS or BackboneJS), you're going to have to write some Javascript to manage the synchronizer token. So in that case you might as well just go with the HTML5 Web Storage approach and only worry about one token.

Some other differences are discussed here.

edit a google search reveals this for asp.net - they call the synchronizer token a "request verification token".

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The safest way to store your access token is to simply not store it client-side at all.

How does that work? Well at the point of generating the access token, generate some other cryptographically secure PRNG (which you map to the access token on the server), map this to the users session ID and return this to the client instead.

This will reduce the attack area because what you are now returning is a token tied to a session, and both would be required in order to authorize the token. When the session expires so does the token, naturally, and the user would be forced to re-authenticate thus generating a new access token.

It's still not 100% secure, however, you need to weigh up the possibility of something like that happening within a users session. Based on that, you can then tweak your session/token expiry times to suit, although you also need to be weary of usability - you don't want to be expiring sessions after 5 minutes as having to log back in constantly can be tedious (or maybe you can, depends on the type of application).

  • Thanks for your awnser, but I need to include the token in the header of my AJAX API call so I need the full token accessible in my javascript. – jfamvg Feb 3 '15 at 12:11
  • @jfamvg I'm not suggesting you don't store a token on the client, I'm saying don't store the private access token there. Generate a public token and send that instead. – James Feb 3 '15 at 15:43
  • I have to send the literal token to the WebAPI, so I need to make an additional call to the server to get the token form the private token to send that to my WebAPI. – jfamvg Feb 3 '15 at 16:03
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    I don't understand the distinction between a public and private token. In OAuth a token is a token. If you can use it to make a request to WebAPI then what protection are you offering here? Are you assuming there is some information in the token that needs to be protected? If you are using Katana's OAuth provider, it handles that by encrypting the claims that make up the token. – Ed Greaves Jun 14 '16 at 16:00
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    @LazarLjubenović well that all depends on how that token is generated, when using services like OAuth etc. then yes you can pretty much guarentee the token coming back is safe to be stored on the client (to an extent). – James Nov 6 '18 at 15:54
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ARMOR is designed specifically to meet this requirement. The Anti-forgery token can be stored anywhere on the UI that you see fit. The library comes equipped with a custom JavaScript component that extracts the token from the UI and automatically includes it in AJAX headers.

Here is a tutorial on the subject, and here is the GitHub repo.

1

Alex's blog must be informative.

A server dies every time someone implements OAuth in a single page is web app. Stop the genocide! Use a server side proxy! Act now!

https://github.com/alexbilbie/alexbilbie.github.com/blob/master/_posts/2014-11-11-oauth-and-javascript.md

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    The proposed solution in that article seems unhelpful. Assuming the attacker has access to a user's client state (tokens, cookies, etc.) then the attacker can simply send the same request to the proxy server: GET /ajax/resource/123 HTTP/1.1 Cookie: <encrypted cookie with tokens> Host: example.com. If he means "use cookies instead of local storage", he should say so more clearly. – BudgieInWA Nov 18 '15 at 2:40
  • That article does not make sense. How will the proposed proxy server differentiate between the "real user" and the "attacker"? All http requests can be faked. CSRF just needs one-extra http call to obtain csrf token. Only solution to author's problem can be captcha and rate-limiting. Please explain if I am wrong. – cnvzmxcvmcx Aug 7 '16 at 17:56
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You need to send the token to server in every requset. So it doesn't matter you store it in cookie or html 5 storage. Both are secure storages and eveyone who has access the client machine has access to the token too anyway.

But I recommend do not use the submitted token in cookie on your server to prevent CSRF attack. I think it is good idea to manually include the token in every request you make whenever required.

Using cookie also makes the request header bigger which is not appropriate.

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    This is conflicting. How can you include a token in every request and at the same time not include it in the Cookie: HTTP header? Well, you could make your own X-Something: header, but that is probably worse since you need to maintain the code for the storage of the content of the header. – grochmal Dec 16 '16 at 1:33
  • You are right grochmal. It is possible for my web apps as I always just invoke api call through ajax request. So my method can not be implemented in other senarios. – Mohammad Nikravan Dec 16 '16 at 9:18

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