Security | DMA | Hacking

It is possible to break Kernel Address Space Layout Randomization (KASLR) on modern operating systems running on modern x86 CPU's. One possible way of doing this is to time certain operations when using the Transactional Synchronization Extensions (TSX) instruction set. TSX makes it possible for unprivileged user mode programs to detect whether certain virtual memory pages are mapped or unmapped in kernel mode. It is also possible to detect whether a kernel page is executable or not. It has been known since at least 2014 that timing attacks against KASLR, using TSX, is possible. This was discussed by Rafal Wojtczuk from Bromium Labs in the blog post TSX improves timing attacks against KASLR . The technique was popularized and presented at Black Hat US-16 by Yeongjin, Sangho, and Taesoo from Georgia Institute of Technology. Their presentation and white paper is found on the Black Hat site. Example code for Linux was published on Github after the talk. Since no example code was pub

I this post I will show how it's possible to disable Windows 10 Virtualization Based Security (VBS), Credential and Device Guard, by corrupting in-memory structures prior to operating system boot. For this attack to succeed the target computer must not be protected by a pre-boot authentication password. Auto-booting Bitlocker with TPM and/or Network unlock will work. The target computer is also required to have Direct Memory Access (DMA) capable ports and a BIOS which will allow DMA before operating system boot. The Target Intel NUC Skull Canyon with a Skylake i7 CPU. 32GB RAM. M.2 SSD. Windows 10 Enterprise version 1607. The NUC have two options for DMA. The obvious choice is the USB-C port at the back which is capable of Thunderbolt 3. Thunderbolt is however secure by default on the NUC - which is unfortunate for us. The Thunderbolt to PCI-Express adapters I use also doesn't seem to be working prior to OS boot even in the less secure Thunderbolt Legacy Mode. The second option