Skip to main content

Are your github's data safe?

Sure they are, if you do not user Firefox (even the last  version) or if you do not use iOs 6.1 or some older version of IE they are really safe :)
In the last few days I got the pleasure to be in touch with the github security guys.
I must admit I am really impressed about how security is important for Github and how much serious they take it (they embrace and leverage all the new security features supported by modern browsers, Content Security Policy included ).
Moreover they are really fast on reply and really friendly so kudos to them.
From the other hand I was a bit surprised on how the "handled" a couple of issues I did report.
Now the fact I did not get a bounty doesn't play any role on my opinion (apparently both issues I reported were well known by them).
The thing that does surprise me instead is the fact that even that those are well known issues are not yet fixed (if ever).
But no more words just fact...

The first issue I reported is the following.

The .patch selector in github.com is vulnerable to XSS indeed if a patch contains javascript this is not correctly sanitized. Live example in here.

Now I do appreciate that

a) nosniff is present
b) the content type is text/plain

but older browsers do ignore those and execute the javascript. One example is Safari for iPhone (that is actually not too old) and obviously older version of IE.
Now we are really talking about stealing cookies on a really sensitive domain right ? (always IMHO) :)
But apparently this is not enough and that output will continue to be not sanatized.

So this brings us to issue #2

Step to reproduce
- Create a new public repo e.g. (https://github.com/asanso/test)
- add a configuration config.txt file and put username and password
user="foobar"
password="supersecret"
- commit and push
- verify anybody can see https://github.com/asanso/test/blob/master/config.txt
- verify anybody can see https://raw.githubusercontent.com/asanso/test/master/config.txt
- change the permission of https://github.com/asanso/test to private
- verify nobody apart asanso can see https://github.com/asanso/test/blob/master/config.txt
-  verify nobody apart asanso can see https://raw.githubusercontent.com/asanso/test/master/config.txt

Create html and make the victim asanso visit the page

<script src="https://github.com/asanso/test/raw/master/config.txt">
<script>alert(user+'\n'+password)


This extrafiliates the credentials to an attacker... 

Now, true, this will work only in Firefox since doesn't have any support for nosniff .
But isn't Firefox still one of the most used browser or am I missing something :) ?
Moreover Firefox will probably fix this issue sooner or later but what until then ?
Said that,  I just (without any irony) want to reiterate : "Great stuff Github security" (they are seriously good!!)


 

Comments

Popular posts from this blog

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 bl

The Curious Case of WebCrypto Diffie-Hellman on Firefox - Small Subgroups Key Recovery Attack on DH

tl;dr Mozilla Firefox prior to version 72 suffers from Small Subgroups Key Recovery Attack on DH in the WebCrypto 's API. The Firefox's team fixed the issue r emoving completely support for DH over finite fields (that is not in the WebCrypto standard). If you find this interesting read further below. Premise In this blog post I assume you are already knowledgeable about Diffie-Hellman over finite fields and related attacks. If not I recommend to read any cryptography book that covers public key cryptography. Here is a really cool simple explanation by David Wong : I found a cooler way to explain Diffie-Hellman :D pic.twitter.com/DlPvGwZbto — David Wong (@cryptodavidw) January 4, 2020 If you want more details about Small Subgroups Key Recovery Attack on DH I covered some background in one of my previous post ( OpenSSL Key Recovery Attack on DH small subgroups (CVE-2016-0701) ). There is also an academic pape r where we examine the issue with some more rigors.

All your Paypal OAuth tokens belong to me - localhost for the win

tl;dr   I was able to hijack the OAuth tokens of EVERY Paypal OAuth application with a really simple trick. Introduction If you have been following this blog you might have got tired of how many times  I have stressed out the importance of the redirect_uri parameter in the OAuth flow. This simple parameter might be source of many headaches for any maintainer of OAuth installations being it a client or a server. Accepting the risk of repeating myself here is two simple suggestions that may help you stay away from troubles (you can always skip this part and going directly to the Paypal Vulnerability section): If you are building an OAuth client,   Thou shall register a redirect_uri as much as specific as you can i.e. if your OAuth client callback is https://yourouauthclient.com/oauth/oauthprovider/callback then DO register https://yourouauthclient.com/oauth/oauthprovider/callback   NOT JUST h ttps://yourouauthclient.com/ or https://yourouauthclient.com/oauth If