![]() ![]() This has also been talked in at least one presentation, and, if accepted, a future SyScan 2015 talk from a friend of mine will also cover this technique. This has been covered in a few papers and presentations.Īnother related possibility is to disable SMEP Enforcement on a per-page basis - taking a user-mode page and marking it as a kernel page by making the required changes in the page level translation mapping entries. One possibility is to disable SMEP Enforcement in the CR4 register through Return-Oriented Programming, or ROP, if stack control is possible. However, with Supervisor Mode Execution Prevention (SMEP), also called Intel OS Guard, this technique is no longer reliable - a direct user-mode address cannot be used, and other techniques must be employed instead. Editing the tagWND structure or the HAL Dispatch Table are two very common vectors, as are many others. Relying on a user-mode address is an easy way not to worry about the kernel address space, and to have full control of the code within a process. ![]() ![]() The typical write-what-where kernel-mode exploit technique usually relies on either modifying some key kernel-mode data structure, which is easy to do locally on Windows thanks to poor Kernel Address Space Layout Randomization (KASLR), or on redirecting execution to a controlled user-mode address, which will now run with Ring 0 rights. ![]()
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