Skip to main content

Google Chrome Potential leak of sensitive information to malicious extensions (CVE-2016-1658)


Last Google Chrome release for Chrome 50.0.2661.75 contains the fix for a security low bug I found (CVE-2016-1658).
When first I found this bug I was under the impression it could be an UXSS. Quickly after I reported I started to realize that this wasn't as exploitable though.
The issue per se was extremely easy to reproduce:

  • Create an HTML file that looks like and save it (e.g. chrome.html)

<h1>Hi</h1> 
<script> alert(document.domain)</script>
  • Now supposing the file is saved under (in MacOS) /Users/xxx/Downloads/chrome.html open the file from hard disk in this way:

     file://mail.google.com/Users/xxx/Downloads/chrome.html

     Note: mail.google.com is arbitrary . This can be any domain (hence is universal) 

  • Observe the document.domain alerted is mail.google.com!


  •  Observe the cookies transported are the one associated with *.google.com domain :


Now this looked really weird to me and I reported as an UXSS. Pretty quickly though was cleat that the file: URL has a unique origin hence:
  • doesn't gain access to things that it frames
  • doesn't gain access to cookies on the hostname it asserts (even if the Cookie extensions shows it!!)
  • The cookies are NOT even transmitted over the wire!
On top it looks like hostnames are a legitimate part of file: URL (spec wise)!
So no UXSS :(
Said that the Google Chrome Team thought that there is still something weird going on (at least with the extensions). Indeed was clear that UX and Extensions API got confused when file: URLs have hostnames. Now I am not a big expert of Chrome codebase but the reason behind it seemed to be that stuff outside of WebKit used GURL::GetOrigin() to get the security origin rather than SecurityOrigin. This is not the case anymore and fixed in  Chrome 50.0.2661.75.
So as Mathias Karlsson said some time ago do not shout hello before you cross the pond :)



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…

Bug bounty left over (and rant) Part III (Google and Twitter)

tl;dr in this blog post I am going to talk about some bug bounty left over with a little rant.

Here you can find bug bounty left over part I and II
Here you can find bug bounty rant part I and II
Introduction In one of my previous post I was saying that: 

"The rule #1 of any bug hunter... is to have a good RSS feed list."
Well well well allow me in this post to state rule #2 (IMHO)

"The rule #2 of any bug hunter is to DO NOT be to fussy with 'food' specifically with left over"

aka even if the most experience bug hunter was there (and it definitely was my case here, given the fact we are talking about no one less than filedescriptor) do not assume that all the vulnerabilities have been found! So if you want some examples here we go.
Part I - GoogleI have the privilege to receive from time to time Google Vulnerability Research Grant. One of the last I received had many target options to choose from, but one in particular caught my attention, namely Google Issue T…

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 …