CVE-2024-35875

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

x86/coco: Require seeding RNG with RDRAND on CoCo systems

There are few uses of CoCo that don't rely on working cryptography and

hence a working RNG. Unfortunately, the CoCo threat model means that the

VM host cannot be trusted and may actively work against guests to

extract secrets or manipulate computation. Since a malicious host can

modify or observe nearly all inputs to guests, the only remaining source

of entropy for CoCo guests is RDRAND.

If RDRAND is broken -- due to CPU hardware fault -- the RNG as a whole

is meant to gracefully continue on gathering entropy from other sources,

but since there aren't other sources on CoCo, this is catastrophic.

This is mostly a concern at boot time when initially seeding the RNG, as

after that the consequences of a broken RDRAND are much more

theoretical.

So, try at boot to seed the RNG using 256 bits of RDRAND output. If this

fails, panic(). This will also trigger if the s

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References