Intel CPU’s found to be vulnerable to new ‘SGAxe’ and ‘CrossTalk’ Side-Channel Attacks

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Intel CPU’s found to be vulnerable to new ‘SGAxe’ and ‘CrossTalk’ Side-Channel Attacks that can leak sensitive information

Cybersecurity experts have discovered 2 news flaws that can be exploited against Intel processors to leak sensitive information from the CPU’s trusted execution environments (TEE). The two flaws are SGAxe and CrossTalk, according to the experts the first flaw is found to be an evolution of the previously uncovered CacheOut attack (CVE-2020-0549). The flaw allows an attacker to retrieve the contents from the CPU’s L1 Cache. About the second one namely CrossTalk it enables attacker-controlled code executing on one CPU core to target SGX enclaves running on a completely different core, and determine the enclave’s private keys.

By using the extended attack against the Intel-provided and signed architectural SGX enclaves, we retrieve the secret attestation key used for cryptographically proving the genuinity of enclaves over the network, allowing us to pass fake enclaves as genuine

a group of academics from the University of Michigan said.

What is an SGAxe Attack?

SGAxe is an evolution of CacheOut, specifically targeting SGX enclaves. We show that despite extensive efforts done by Intel in order to mitigate SGX side channels, an attacker can still breach the confidentiality of SGX enclaves even when all side-channel countermeasures are enabled. That exploit, as a result, results in a transient execution attack that can recover SGX cryptographic keys from a fully updated Intel machine, which is trusted by Intel’s attestation server.

In a nutshell, we use CacheOut to recover the sealing keys from within the address space of Intel’s production quoting enclave. Finally, we use the recovered sealing keys in order to decrypt the long term storage of the quoting enclave, obtaining the machines EPID attestation keys. With the machine’s production attestation keys compromised, any secrets provided by [the]server are immediately readable by the client’s untrusted host application, while all outputs allegedly produced by enclaves running on the client cannot be trusted for correctness. This effectively renders SGX-based DRM applications useless, as any provisioned secret can be trivially recovered.

the researchers stated

Vulnerability in Intel SGAxe

[Image source: cacheoutattack]

Although, Intel fixed the SGAxe vulnerability via a microcode update to OEM vendors and subsequently via BIOS updates to end-users. You can read the paper presented by cacheoutattack[.]com on SGAxe from here

What is the CrossTalk attack?

CrossTalk execution enables attackers to leak sensitive information also across cores on many Intel CPUs, bypassing all the existing intra-core mitigations against prior speculative (or transient) execution attacks such Spectre, Meltdown, etc. Until now, all the attacks assumed that attacker and victim were sharing the same core so that placing mutually untrusting code on different cores would thwart such attacks. Instead, we present a new transient execution vulnerability, which Intel refers to as “Special Register Buffer Data Sampling” or SRBDS (CVE-2020-0543), enabling attacker-controlled code executing on one CPU core to leak sensitive data from victim software executing on a different core.

Intel has implemented its mitigation for the SRBDS vulnerability in a microcode update distributed to software vendors on Tuesday, June 9, 2020, or earlier. The mitigation locks the entire memory bus before updating the staging buffer and only unlocks it after clearing its content. This strategy ensures no information is exposed to off core requests issued from other CPU cores.

Intel Vulnerability

[Image Source: vusec.net]

Due to the considerable performance overhead of locking the entire system’s memory bus, Intel only applied the mitigation to harden a small number of security-critical instructions, specifically RDRAND, RDSEED, and EGETKEY (a leaf of the ENCLU instruction). This means that output from any other instruction (e.g., RDMSR) that issues off core requests can be still leaked across CPU cores.

You can also read the paper presented by vusec.net from here

However, Intel has fixed the flaws in its processors and also suggest its users update the latest firmware on their system to avoid the flaw to be exploited. To stay updated on Tech and cybersecurity news subscribe to our newsletter from here

 

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