AMD 微码签名验证漏洞
文章讨论了AMD SEV-SNP漏洞及其修复方法。用户需更新SEV固件和BIOS以支持 attestation，并通过验证TCB值确认修复。然而，若攻击者控制hypervisor和微代码，VM如何确保验证未被欺骗仍存疑。 2025-2-6 03:38:0 Author: seclists.org(查看原文) 阅读量:10 收藏
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From: Jacob Bachmeyer <jcb62281 () gmail com>
Date: Wed, 5 Feb 2025 21:22:21 -0600
On 2/4/25 04:10, Solar Designer wrote:

On Wed, Jan 22, 2025 at 07:52:48AM -0800, Tavis Ormandy wrote:

[...]

AMD SEV-SNP users can verify the fix by confirming TCB values for SNP in
their attestation reports (can be observed from a VM, consult AMD's
security bulletin for further details).

[...]

The corresponding AMD security bulletin is:

https://www.amd.com/en/resources/product-security/bulletin/amd-sb-3019.html


[...] Additionally, an SEV firmware update
is required for some platforms to support SEV-SNP attestation. Updating
the system BIOS image and rebooting the platform will enable attestation
of the mitigation. A confidential guest can verify the mitigation has
been enabled on the target platform through the SEV-SNP attestation
report.


[*raises hand*]
If an attacker is able to control the hypervisor (necessary to load rogue microcode) and the processor microcode, how can the VM trust that it is actually verifying that attestation and not being sent down a "oh yes it is exactly what you want it to be" garden path?
Do the instructions necessary to obtain and verify that attestation not use microcode at all? 


-- Jacob

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文章来源: https://seclists.org/oss-sec/2025/q1/107
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