Into the symmetry

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 So you wanna 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 #bounty pic.twitter.com/Tt4saGZVLI — Antonio Sanso (@asanso) November 30, 2018 and I would have liked to share some of the things I have learned during th e se 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...

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 - Google I 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...

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...

tl;dr Firefox and Java suffered from a moderate vulnerability affecting the elliptic curve point addition algorithm that uses mixed Jacobian-affine coordinates where it can yield a result POINT_AT_INFINITY when it should not. Introduction Few months ago I was working on a vulnerability affecting the internet standard JWE (slides here ) and I got a stroke of luck . Yuppieeee  Basically I was constructing the malicious JWEs needed for the Demo Attack . When something weird happened :S You can try and share with me the surprise I had, the gist is here If you try to execute this class with Java 1.7 you basically have Exception in thread "main" java.lang.IllegalStateException     at sun.security.ec.ECDHKeyAgreement.deriveKey(Native Method)     at sun.security.ec.ECDHKeyAgreement.engineGenerateSecret(ECDHKeyAgreement.java:130)     at javax.crypto.KeyAgreement.generateSecret(KeyAgreement.java:586)     at orig...

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 ...

Note this is going to be a quick post. This year, at Enigma 2017 Conference , Facebook introduced a way to move Account Recovery beyond Email and the "Secret" Question . After the presentation the moved operationally and presented the first integration partner : Github . These days I have seen a lot of press around this and both Facebook and Github open sourced their implementation and s pecification (also presented at F8 ). Well it turned out that Facebook side was susceptible to Cross Site Request Forgery. Really simple explanation: The attacker start the integration with Github and stop the flow at the right moment.  The create an attacker page as https://github.com/asanso/asanso.github.io/blob/master/facebook/test_fb.html <html> <img src="https://www.facebook.com/recovery/delegated/save/?fr=OkpK%2FnF9oZk%3D& relay_token=AfFdhnFYiPWXlcS17dG19Tz4sJT%2B%2FzBorBbDwEKgNMvxUHRIqMAnmmEGrGZlMheUfJdNHv40xyraKOfj64fR7ZgZ8HNNmincyRiHdu6Nju...

tl;dr   Facebook Groups offers the option to upload files directly from the Dropbox account. This integration is done using the OAuth 2.0 protocol and suffered from a variant of the classic OAuth CSRF (defined by Egor Homakov as the the Most Common OAuth2 Vulnerability ),  see video below: Introduction  Facebook Groups offers the option to upload files directly from the Dropbox account: This will allow to surf via browser the Dropbox account  and post a specific file to the group.  This integration is done using a variant of the OAuth 2.0 protocol seen in this blog many many times . But once more, OAuth is an access delegation protocol standardized under the IETF umbrella . A typical OAuth flow would look like: From “OAuth 2 In Action” by Justin Richer and Antonio Sanso, Copyrights 2017 Usually the client initiates the OAuth flow in the following way: From “OAuth 2 In Action” by Justin Richer and Antonio Sa...

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://s...