Yesterday I pushed out to various of my venues a Google notice regarding a security vulnerability relating to a long list of Chrome OS based devices (that is, “CrOS” on Chromebooks and Chromeboxes). That notice (which is titled more like a firmware upgrade advisory than a security warning per se) is at:
While that page is generally very well written, it is still quite technical in its language. Unfortunately, while I thought it was important yesterday to disseminate it as quickly as possible, I was not in a position to write any significant additional commentary to accompany those postings at that time.
Today my inbox is filled with concerned queries from Chromebook and Chromebox users regarding this issue, who found that Google page to be relatively opaque.
Does this bug apply to us? Should we rush to upgrade? What happens if something goes wrong? Should our school be concerned — we’ve got lots of students using Chromebooks, what should we do? Help!
Here’s the executive summary — perhaps the way that Google should have said it: DON’T PANIC! — especially if you have strong passwords. Most of you don’t really have to worry much about this one. But please do keep reading, especially and definitely if you’re a corporate user or someone else in a particularly high security environment.
This is not a large-scale attack vulnerability, where millions of devices can be easily compromised. In fact, even in worst case scenarios, the attack is computationally “expensive” — meaning that much more “targeted” attacks, e.g., against perceived “high-value” individuals, would be the focus.
Google has already take steps in their routine Chrome OS updates to mitigate some aspects of this problem and to make it an even less practical attack from the standpoint of most individual users, though the vulnerability cannot be completely closed via this approach for everyone.
The underlying problem is a flaw in the firmware (the programming) of a specific chip in these devices, called a TPM. Google didn’t expand that acronym in their notice, so I will — it stands for Trusted Platform Module.
The TPM is a crucial part of the cryptographic system that protects the data on Chrome OS devices. It’s sort of the “roach motel” of security chips — certain important crypto key data gets in there but can’t get out (yet can still be utilized appropriately by the system).
The TPM firmware flaw in question makes the possibility of “brute force” guessing of internal crypto keys more practical in a targeted sense, but again, not at large scale. And in fact, if you have a weak password, that’s a far greater vulnerability for most users than this TPM bug ever would have been. Google’s mitigations of this problem already provide good protection for most individual users with strong passwords.
C’mon, switch to a strong password already! You’ll sleep better.
It’s really in high security corporate environments and similar situations where the TPM flaw is of more concern, particularly where individual users may be reasonably expected to be targets of security attacks.
Where firms or other organizations are using their own crypto certificates via the TPM to allow corporate or other access (or use “Verified Access” for enterprise-managed authentication) the TPM bug is definitely worthy of quite serious consideration at least.
Ordinary users can upgrade their TPM firmware if they wish (in enterprise-managed environments, you will likely need administrative permission to perform this). The procedure uses the “powerwash” function of the devices, as explained on the Google page.
But as also noted there, this is not a risk-free procedure. Powerwash wipes all user data from the device, and devices can fail to boot if things go wrong during the process. There are usually ways to recover even from that eventuality, but you probably don’t want to be in that position if you can reasonably avoid it.
For the record, I am personally not upgrading the TPM firmware on the Chrome OS devices that I use or manage at this time. They all have decent passwords, and especially for remote users I won’t risk the powerwash sequence for now.
I am of course monitoring the situation and will re-evaluate as necessary. Google is working on a way to update the TPM firmware without a powerwash — if that comes to pass it will significantly change the equation. And of course if I had to use any of these devices in an environment where TPM-based crypto certificates were required, I’d consider a powerwash for TPM firmware upgrade to be a mandatory prerequisite.
In the meantime, be aware of the situation, think about it, but once again, don’t panic!