Indirector: High-Precision Branch Target Injection Attacks Exploiting the Indirect Branch Predictor

This paper introduces novel high-precision Branch Target Injection (BTI) attacks, leveraging the intricate structures of the Indirect Branch Predictor (IBP) and the Branch Target Buffer (BTB) in high-end Intel CPUs. It presents, for the first time, a comprehensive picture of the IBP and the BTB within the most recent Intel processors, revealing their size, structure, and the precise functions governing index and tag hashing. Additionally, this study reveals new details into the inner workings of Intel's hardware defenses, such as IBPB, IBRS, and STIBP, including previously unknown holes in their coverage. Leveraging insights from reverse engineering efforts, this research develops highly precise Branch Target Injection (BTI) attacks to breach security boundaries across diverse scenarios, including cross-process and cross-privilege scenarios and uses the IBP and the BTB to break Address Space Layout Randomization (ASLR).