In a recent study conducted by security researchers, a new side-channel attack was discovered that can potentially compromise the security of modern Intel CPU variants, including Raptor Lake and Alder Lake. The attack, referred to as Indirector, takes advantage of vulnerabilities in the indirect branch predictor (IBP) and branch target buffer (BTB) to bypass existing defenses and extract sensitive information from processors.
The IBP plays a crucial role in modern CPUs by predicting the destination addresses of indirect branches, which are control flow instructions with destination addresses calculated at runtime, making them difficult to predict accurately. Attacks using Branch Target Injection (BTI) have been a topic of extensive research since the unveiling of the Spectre and Meltdown attacks in 2018.
The Indirector attack, developed by researchers at the University of California, San Diego, leverages weaknesses in Intel CPUs to execute precise targeted branch injection attacks. By using a custom tool called iBranch Locator, attackers can locate indirect branches and perform IBP and BTB injections to execute speculative code and extract sensitive data via a side-channel attack.
The attack tool enables two high-precision attacks: IBP Injection Attack and BTB Injection Attack, which can bypass existing defenses and compromise system security in scenarios involving cross-process and cross-privilege situations. While Intel has implemented several mitigations to protect against such attacks, including Indirect Branch Restricted Speculation (IBRS) and Single Thread Indirect Branch Predictors (STIBP), the defenses were found to be inadequate in some cases.
Despite the presence of these defense mechanisms, the research paper highlighted potential attack surfaces, detailing the interaction between the indirect branch predictor and branch target buffer in the latest Intel processor families. The paper also discussed mitigation mechanisms in Intel CPUs and demonstrated the effectiveness of the iBranch Locator tool in locating indirect branches without prior queries, leading to successful breaking of address space layout randomization.
To address the vulnerabilities exposed by the Indirector attack, the researchers recommended more aggressive use of the indirect branch prediction barrier (IBPB) and suggested incorporating finer-grained branch prediction unit (BPU) isolation into security domains in future CPU designs. Additional mitigation strategies included enhancing BPU design with complex tags, encryption, and randomization.
The researchers disclosed their findings to Intel in February 2024, prompting the company to inform other affected hardware and software vendors about the vulnerability. The study emphasized the importance of continuous scrutiny of hardware components and urged chipmakers to enhance their designs continually to combat potential threats.
Overall, the discovery of the Indirector attack highlights the ongoing challenge of securing modern CPU variants against sophisticated attacks and underscores the necessity for robust defense mechanisms and proactive measures by hardware manufacturers to safeguard sensitive data and system integrity.
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https://thecyberexpress.com/indirector-cpu-vulnerability-intel-chips/