• Attacking a co-hosted VM: A hacker, a hammer and two memory modules - Oct 4, 2017

  • Row-hammer is hardware bug that can cause bit-flips in physical RAM. Mark Seaborn and Thomas Dullien were the first to exploit the DRAM row-hammer bug to gain kernel privileges. Kaveh Razavi et al. pushed the exploitation of row-hammer bugs to the next level. They abused an OS feature - memory de-duplication - to surgically flip bits in a controlled way. They succeeded in flipping bits in memory loaded sensitive files (e.g. authorized_keys) assuming they know their contents. By weakening RSA moduli in authorized_keys file, they were able to generate corresponding private keys and authenticate on a co-hosted victim VM.

  • The macabre dance of memory chunks - Sep 16, 2017

  • In this post, we want to share some notes on how to exploit heap-based overflow vulnerabilities by corrupting the size of memory chunks. Please note that we do not present here original content but only want to share with the community two detailed write-up. The first one exploits a basic heap-based overflow by enlarging the size of memory chunks. The second one shrinks their sizes in order to turn a NULL byte off-by-one error – present in a hardened binary (all memory corruption mitigations are enabled) – into remote code execution.

  • Hackers do the Haka - Nov 23, 2015

  • Haka is an open source network security oriented language that allows writing security rules and protocol dissectors. In this first part of a two-part series, we will focus on writing security rules.

  • Playing with signals: An overview on sigreturn oriented programming - Jan 3, 2015

  • Back to last GreHack edition, Herbert Bos has presented a novel technique to exploit stack-based overflows more reliably on Linux. We review hereafter this new exploitation technique and provide an exploit along with the vulnerable server. Even if this technique is portable to multiple platforms, we will focus on a 64-bit Linux OS in this blog post.