Skip to main content

OAuth “dance” - server side flow

Getting some inspiration from this dialog about OAuth 1.0 I thought it would be nice to have something similar for OAuth 2.0


The Actors

 

The R.O. shows intent

Alice (R.O.): hey, Bob , I would like you to be able to access the profile pictures from my Facebook account so you can print for me a nice photo album.
Bob (client): no problem, I know how we can do it. All I need is you getting me an Authorization Code from Facebook.

The R.O. obtain an authorization code


Alice (R.O.): hey Mark, www.printondemand.biz wants an Authorization Code
Mark (server):
are you sure you want to give this code to www.printondemand.biz?
this will allow it to get all profile pictures from your profile.
Alice (R.O.):
yes it is ok.
Mark (server): ok I am sending you over to www.printondemand.biz

The R.O. is redirected to the client

Alice (R.O.): hey Bob here we go, this is the Authorization Code
Bob (client): thanks

The client exchange the Authorization Code for an
Access Token

Bob (client): hey Mark, I would like to trade my Authorization Code for an Access Token
Mark (server): hey Bob here we go

The client access the protected resource

Bob (client): hey Mark, give me the profile pictures, here is the
Access Token
Mark (server): here you are


Comments

Popular posts from this blog

Billion Laugh Attack in https://sites.google.com

tl;dr https://sites.google.com suffered from a Billion Laugh Attack vulnerability that made the containerized environment to crash with a single invocation.
Introduction Few months ago I applied for a talk at a security conference titled Soyouwanna be a Bug Bounty Hunter but it was rejected :(. The reason behind it is that I have been on/off in the bug bounty business for a while as you can see here:
Funny. Found in a forgotten drawer from the time I was a bug hunter :p #facebook#bug#bountypic.twitter.com/Tt4saGZVLI — Antonio Sanso (@asanso) November 30, 2018 and I would have liked to share some of the things I have learned during these years (not necessary technical advises only). You can find a couple of these advises here:


Rule #1 of any bug hunter is to have a good RSS feed list
and here


The rule #2 of any bug hunter is to DO NOT be to fussy with 'food' specifically with "left over"
Today's rule is: The rule #3 of any bug hunter is DO LOOK at the old stuff

and…

OpenSSL Key Recovery Attack on DH small subgroups (CVE-2016-0701)

Usual Mandatory Disclaimer: IANAC (I am not a cryptographer) so I might likely end up writing a bunch of mistakes in this blog post...

tl;dr The OpenSSL 1.0.2 releases suffer from a Key Recovery Attack on DH small subgroups. This issue got assigned CVE-2016-0701 with a severity of High and OpenSSL 1.0.2 users should upgrade to 1.0.2f. If an application is using DH configured with parameters based on primes that are not "safe" or not Lim-Lee (as the one in RFC 5114) and either Static DH ciphersuites are used or DHE ciphersuites with the default OpenSSL configuration (in particular SSL_OP_SINGLE_DH_USE is not set) then is vulnerable to this attack.  It is believed that many popular applications (e.g. Apache mod_ssl) do set the  SSL_OP_SINGLE_DH_USE option and would therefore not be at risk (for DHE ciphersuites), they still might be for Static DH ciphersuites.
Introduction So if you are still here it means you wanna know more. And here is the thing. In my last blog post I was …

Top 10 OAuth 2 Implementation Vulnerabilities

Some time ago I posted a blogpost abut  Top 5 OAuth 2 Implementation Vulnerabilities.
This week I have extended the list while presenting Top X OAuth 2 Hacks at OWASP Switzerland.

This blog post (like the presentation) is just a collection of interesting attack OAuth related.

#10 The Postman Always Rings Twice  I have introduced this 'attack' in last year post . This is for provider implementer, it is not extremely severe but, hey, is better to follow the spec. Specifically

The client MUST NOT use the authorization code  more than once.  If an authorization code is used more than once, the authorization server MUST deny the request and SHOULD revoke (when possible) all tokens previously issued based on that authorization code.

It turned out that even Facebook and Googledid it wrong... :)

#9 Match Point To all OAuth Providers be sure to follow section 4.1.3 of the spec in particular

...if the "redirect_uri" parameter was included in the initial authorization requ…