The Good and the Bad of OAuth 2.0 Authorization Implementations

http://john-sheehan.com/post/41653656681/the-good-and-the-bad-of-oauth-2-0-authorization

by goronbjorn • 13 years ago

71 18 13 years ago

I always felt that implementing OAuth authorization was much too complicated. I used to think it was because I'm an idiot, but seeing so many people have trouble with the same thing makes me doubt myself.

I've used Mozilla Persona and THAT was straightforward. I can't help but feel that Person is what OAuth should have been. Secure, simple login for my grandmother, and easy to implement and integrate for Joe Coder.

jarcoal• 13 years ago

I felt the same way until I started writing the HTTP requests myself.

This was one situation where using a library really slowed me down and hurt my understanding of what was going on.

peter_l_downs3• 13 years ago

If you decide not to support the HMAC stuff, writing a server implementation for OAuth 2.0 isn't really that bad. Something I've been confused about since day one is the need for refresh token. If an attacker is able to sniff the auth token, wouldn't they be able to sniff the refresh token, too?

alanctgardner2• 13 years ago

I've been wondering this as well. Maybe it protects against replay attacks? They're certainly a bit frustrating.

johns3• 13 years ago

My understanding, and it may be wrong, is that if an attack walks off with your data, then wouldn't be able to refresh the access token you have on hand without the client ID and secret and so the extent to which they could compromise the authorized accounts is limited in time.

mikeknoop• 13 years ago

What's worse is when OAuth providers force the refresh tokens to be refreshed! Many OAuth providers are now requiring user-action (ie. re-walk through the oauth popup) every x months to get new refresh tokens.

johns3• 13 years ago

OAuth 1.0a is far too complex. OAuth 2.0 for the simple and common cases is not that bad since there's no signature to generate.

Most of the issues from OAuth 2 stem from a fluid spec that wasn't finalized until recently. Now that that's done hopefully the situation will stabilize and once you learn how to use one (I also recommend making the requests directly yourself and not using a library) you'll easily be able to use all the others without having to search out all the quirks I wrote about in this post.

peter_l_downs3• 13 years ago

Something to be aware of is that as of the last time I checked (a month or two ago) most of these providers do not implement the finalized 2.0 specification [0]. I was lucky enough to have to write an implementation recently, and using Google's and Facebook's docs as a reference often led to confusion.

[0] http://tools.ietf.org/html/rfc6749

socalnate1• 13 years ago

I love that the first comment on this is from Mike Krieger, one of the founders of Instagram trying to fix the "bad."

The idea that a guy who just made $100 million is reading hackernews on a Sunday night, and immediately tries to address a product issue he stumbles upon makes me happy.

dwolchon• 13 years ago

I had the same thought. Awesome.

conradev• 13 years ago

Also interesting is that Google will soon not require a client_secret parameter for installed applications[1], as it is impossible to keep secret. This is technically legal according to the spec, which states that "the client MAY omit the parameter if the client secret is an empty string"[2].

[1] https://groups.google.com/d/msg/oauth2-dev/HnFJJOvMfmA/JzZ8J...

[2] http://tools.ietf.org/html/rfc6749

ecesena• 13 years ago

[related] This year at CCS conference: San-Tsai Sun and Konstantin Beznosov, The Devil is in the (Implementation) Details: An Empirical Analysis of OAuth SSO Systems http://css.csail.mit.edu/6.858/2012/readings/oauth-sso.pdf

peter_l_downs3• 13 years ago

Thanks for posting this! Great overview of potential implementation flaws. From the article:

    In some RPs, access
    tokens are appended as query parameters to the RP's sign-in
    endpoint (i.e., the URI that issues the authenticated session
    cookie), which reveals the tokens in the browser's history
    and server logs.

The official spec only supports including the access token in a URL-encoded body of a POST request, or as part of an Authorization header [0]. This is one of the biggest differences between the official spec and most current (not up to spec) implementations.

Also disappointing^H^H^H^H^H^H^H^H^H^H^H^H^H interesting:

    Surprisingly, our evaluation shows that only 21% of RPs em-
    ploy SSL to protect SSO sessions, even though about half of
    tested RPs have protected their traditional login forms with
    SSL.

The relevant part of the specifcation [1]:

     Always use TLS (https):  Clients MUST always use TLS [RFC5246]
     (https) or equivalent transport security when making requests with
     bearer tokens.  Failing to do so exposes the token to numerous
     attacks that could give attackers unintended access.

[0]: http://tools.ietf.org/html/rfc6750#section-2 [1]: http://tools.ietf.org/html/rfc6750#section-5.3

eksith• 13 years ago

It's interesting that people who harp on about avoiding a single point of failure would gleefully go along with a single login option. Mind you, these are the same folks who insist you shouldn't use one password everywhere. But one login (which may still have one password) is totally OK.

Very interesting.

flyinRyan• 13 years ago

I must be missing something here. If someone hacks an oauth provider (e.g. Facebook, Google, etc.) and gets my password there does that not mean they can then log into any service that supports oauth as me at that point? Probably even if I have purposely avoided ever using oauth for anything?

How is this different from the vulnerability of using the same password everywhere?

csears• 13 years ago

Using the same password everywhere means a hacker only has to break the weakest of any service you use to get at all your accounts. Using oauth or any single-sign-on system allows you to put all your eggs in one (potentially) more trusted basket.

Your scenario certainly is a legitimate concern, but it depends on how the other services implement account linking. If you create a non-oauth account and then sign in with Facebook, some services will allow you to link the accounts based on your email address matching, others won't.

Of course in the case of Google, if someone hacked your account, they would probably also have access to your Gmail and could reset passwords from any other service. So the risk isn't significantly different.

As a general rule, I only use oauth SSO on sites that I trust less or care about less than my oath provider.

The Good and the Bad of OAuth 2.0 Authorization Implementations

Related Stories