Researchers at UCSD have identified a new method to conduct Spectre-like side-channel attacks on high-end Intel CPUs, such as Raptor Lake and Alder Lake processors. This technique, called Director, leverages speculative execution features in Intel CPUs to manipulate a program’s control flow and potentially leak sensitive data.
The attack was tested on various Intel CPUs, including Raptor Lake, Alder Lake, and Skylake, with the potential to impact flagship CPUs from the past decade with minor adjustments. Intel has not released any microcode fixes for Director, and instead, recommends using the IBPB (Indirect Branch Predictor Barrier) mitigation strategy introduced in 2018. However, concerns about the performance impact of IBPB have been raised, prompting the need for hardware or software patches to address potential vulnerabilities.
Speculative execution, a performance-enhancing technique utilized by CPUs like Raptor Lake and Alder Lake, involves predicting and executing future instructions before confirming their necessity. Previous speculative execution attacks, such as Spectre and Collapse, have focused on components like the Branch Target Buffer and the Return Stack Buffer.
The new attack targets the Indirect Branch Predictor, an overlooked component of speculative execution that predicts the target address of indirect branches. By reverse engineering the IBP structure in modern Intel processors, researchers were able to identify vulnerabilities that could bypass existing defenses and compromise CPU security.
The research aimed to uncover the intricate details of the IBP and BTB units responsible for predicting branch instruction addresses in modern CPUs. By analyzing prediction mechanisms and Intel’s mitigation measures, the researchers developed injection attacks that effectively target branch prediction mechanisms in Intel CPUs.
One potential exploit involves manipulating the IBP and BTB to hijack a program’s control flow, enabling an attacker to jump to arbitrary locations and potentially extract sensitive information. This attack requires the adversary to run on the same CPU core as the victim but is more efficient than other state-of-the-art target injection attacks.
In conclusion, the discovery of the Director attack highlights the ongoing challenges in mitigating side-channel attacks on modern CPUs. Addressing vulnerabilities in speculative execution features like the Indirect Branch Predictor is crucial for enhancing CPU security and protecting against potential data leaks.
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https://www.darkreading.com/endpoint-security/intel-cpus-spectre-like-indirector-attack-leaks-data