Google Chrome OS and TPM features

Posted by Ken Y-N on March 16th, 2010 at 04:25pm

I’ve been searching around Google’s code repository for Chrome OS trying to find a few hints as to what they might be thinking of doing regarding the Trusted Platform Module, and I’ve had a few interesting hits:

Issue 313: Connman must encrypt credentials when it writes them to disk

Connman is the module that controls all the connectivity-related stuff, and comment 5 notes:

As such, this is pretty much subsumed in work on connman.  We need the TPM
working so that we can use a key that’s only available once the system’s successfully
booted.

So, connectivity passwords will only be available on a clean verified boot. Seems a sensible move to me, and one of these things that the TPM is good for. Issue 518 also covers the same feature.

Issue 564: New server to support TPM challenge/response

The heading is about the sum total of the information available – this seems to suggest that remote attestation will be a key part of Chrome security, although since usually a server initiates attestation, I’m not sure why the client needs to know the server beforehand.

Issue 1584: Add TPM NVRAM read/write calls to verified boot reference code for rollback prevention

This is an interesting one – preventing the reloading of an older version of the operating system, for reasons such as exploiting a known bug. Comment 5 says:

Chromium OS will not support verified boot rollback protection because that is a firmware (BIOS) level feature. Google Chrome OS (the official os) will be for specific hardware platforms which include custom firmware that will use the TPM for rollback protection.  We will publish docs on this in the near future.

I’m looking forward to these documents! The only problem with rollback prevention is if the upgrade causes a new problem on your device and you need to roll back the upgrade to kick your device back into life. I wonder if such a use case is in scope?

Furthermore, Issue 1859 adds a little more information:

If firmware A and B are both valid, and both have a higher key index than the
one stored in TPM NVRAM, the key index in TPM NVRAM is updated to min(A, B)
index.

I’ll keep watching their issues database and see what pops up in the future.

Tags: chrome, chromium, google

Under TPM Tags: chrome, chromium, google