Skip to main content

Cross Site Request Forgery in Github

As usually I always try to blog about my "security finding".
The main reasons are basically two:

  • I think is really good to share knowledge in this area. 
  • Sometimes I do use my blog posts as a place to store information that I can always access in the future.
Unluckily though I am a really lazy blogger and sometimes I just do not blog :S
The really good news is that the last vulnerability I found is in github.
I already blogged about how good and responsive is the Github security team. And I am now even more impressed by their efficency.
The reason why this is a really good news is that in this case I can do both : 1) find a vulnerability 2) being lazy and not trying to describe the vulnerability I found, this because the github team is already describing the vulnerability in their wall of fame :)
Hurray.

Comments

Popular posts from this blog

Slack SAML authentication bypass

tl;dr  I found a severe issue in the Slack's SAML implementation that allowed me to bypass the authentication. This has now been solved by Slack.
Introduction IMHO the rule #1 of any bug hunter (note I do not consider myself one of them since I do this really sporadically) is to have a good RSS feed list.  In the course of the last years I built a pretty decent one and I try to follow other security experts trying to "steal" some useful tricks. There are many experts in different fields of the security panorama and too many to quote them here (maybe another post). But one of the leading expert (that I follow) on SAML is by far Ioannis Kakavas. Indeed he was able in the last years to find serious vulnerability in the SAML implementation of Microsoft and Github. Usually I am more an "OAuth guy" but since both, SAML and OAuth, are nothing else that grandchildren of Kerberos learning SAML has been in my todo list for long time. The Github incident gave me the final…

Cross-origin brute-forcing of Github SAML and 2FA recovery codes

Yesterday while reading my Twitter stream I found this interesting article about  downloading GitHub SSO bypass codes. Same as Yasin Soliman I was invited to a Github pre-release of the organisation SAML single sign-on (SSO) private program. And same as him I found an issue in the same endpoint. So I thought to write a quick blog post about it. Github already published a tl;dr about this,



 I will try to fill the blanks here.

As mentioned by Yasin, Github offers an endpoint where privileged users can recover bypass codes. These recovery codes were accessible for download as plaintext and had the content-type as text/plain, something like:



What immediately caught my attention was that the format of the code forms (with some exceptions) a valid JavaScript file with lines in the format of XXXXX-XXXXX, ten hex digits separated by a hyphen. This is interpreted in JavaScript as the subtraction of two variables! This remember an old blog post of mine where I could possibly exfiltrate informa…

Critical vulnerability in JSON Web Encryption (JWE) - RFC 7516

tl;dr if you are using go-jose, node-jose, jose2go, Nimbus JOSE+JWT or jose4j with ECDH-ES please update to the latest version. RFC 7516 aka JSON Web Encryption (JWE) hence many software libraries implementing this specification used to suffer from a classic Invalid Curve Attack. This would allow an attacker to completely recover the secret key of a party using JWE with Key Agreement with Elliptic Curve Diffie-Hellman Ephemeral Static (ECDH-ES), where the sender could extract receiver’s private key.

Premise
In this blog post I assume you are already knowledgeable about elliptic curves and their use in cryptography. If not Nick Sullivan's A (Relatively Easy To Understand) Primer on Elliptic Curve Cryptography or Andrea Corbellini's series Elliptic Curve Cryptography: finite fields and discrete logarithms are great starting points. Then if you further want to climb the elliptic learning curve including the related attacks you might also want to visit https://safecurves.cr.yp.to…