Monday, November 9, 2015

Google, where is the confidentiality in Chrome OS?

Ask an information security expert what the three cornerstones of information security are, and s/he should tell you, Confidentiality, Integrity, and Availability. Google will tell you that Chromebooks are some of the most secure consumer computers available today. How well do they really do?


ChromeOS and the hardware specification that Google put out for Chromebooks (specifically around firmware changes) have done a decent job of improving the Integrity of the system. Kernel signing and OS signing (a cryptographic signature on the binary files) goes a long way to stopping malicious root kits.

Of course it also goes a long way to preventing people from messing with the system too. But that would be flexibility, which isn't an underlying principle of information security. Besides, Google gave us developer mode to allow for flexibility. So, you can mess with the system if you want to.

But, what about the application software? Well, that is all managed through the Google Play app store. If Google is managing the ChromeOS app store as well as they are the Android app store, then the integrity of the system has fallen back to be on-par with any other operating system as far as end-user application security goes. And since, by far, the majority of 21st century malicious software is targeting the user at the application layer, not the OS layer, Google has largely missed the boat.

Want to fix this? Take a look at how Apple does things with their app store. Every app is rigorously tested and questioned. Application functionality is tested by Apple's own quality assurance staff and bad applications are rejected. The need for access to system resources (even non-traditional resources like your address book) are questioned and must be justified with actual needs of the application before it gets approved.

Does Google do this? I don't actually know. But I do know that on my Google Phone applications are given a lot more access to things that it makes no sense they should need.

Integrity score: marginally above average.


Google may argue that they have provided availability too because your system is tied to your Google account and your files get written there if you lose access to your Chromebook for some reason. As long as the Chromebook can work entirely offline, it does provide availability.

It also provides Google with a guaranteed source of valuable information about you that they can use to direct ads that target you specifically. In case you didn't know, advertisers pay a premium for targeted advertisings. Of course, those ads are also what pays for all the google services.

Mind you, the exact same thing is true for Windows users that have a OneDrive account, Apple users that have a iCloud account, and anyone who has bothered to set-up and religiously use any of the plethora of cloud storage providers (Dropbox,, SugarSync, and a host more).

Availability score: average.


But, those ads are not what pays for the Chromebook. We, the consumers, pay for our Chromebooks. And, at least some of us, expect to have a high degree of that last tenant of information security: confidentiality. This, Google throws completely out the window. The problem is, information is not secure unless there is a balance of all three.

Google has taken away all the confidentiality. Oh sure, they will say they keep your data private. Except they don't. Their deep content inspection tools dig through it and figure things out about you.  Then they share what they learned with advertisers in the form of targeting ads. Except those things they learned about you they wouldn't know if they had proper confidentiality. Just because it isn't a human looking through your private documents doesn't mean it isn't a loss of confidentiality.

And, while people in the USA are stuck with all sorts of laws that required companies to reveal data on request (sometimes with a court order, sometimes with a warrant, sometimes accompanied by a gag order), may of us don't live in the USA and shouldn't have our data exposed to their laws when we aren't in that country. We have our own mandatory disclosure laws. Yet everyone is stuck with their data being exposed to a foreign government's scrutiny whether they consider this important or not.

Confidentiality score: below average.


Sadly, Google could very easily fix this. And should have fixed it from the start. Google has had plenty of time to fix it and yet still haven't. In only requires 2 modifications to ChromeOS using existing and available software:

  1. Bring back local user authentication. Linux has it built in and ChromeOS is Linux at the core.
  2. Implement client side file encryption. These exists this wonderful tool available for Linux (and Windows and OS X and a bunch of other operating systems) called encfs (encrypted filesystem).
Hopefully everyone knows about local user authentication since every modern desktop operating system except for ChromeOS had it built in and uses it by default. So, I won't go into detail about it.

On the other hand, some people may not be aware of EncFS, which stands for Encrypted Filesystem. It works in conjunction with another strange thing called FUSE (which stands for filesystem in user space). Together this pair of tools do something really useful for confidentiality of data. They let you read and write files in one directory just like you normally would but they store those files in an encrypted form in another directory.

Why is this so good? Well, it means that your files are not available for deep content inspection by Google. So Google will probably never implement this too. It also means that if the files you store on your Google Drive slip out to the whole world (like say you accidentally choose to make them public) nobody else can see them because they don't have the encryption key.

At first glance, this does look to be a problem because it means you can't access your files except from your Chromebook. Except, of course, as was said earlier, EncFS is available on pretty much all of the common operating systems in use today.

It wouldn't be all that difficult for a decent programmer to implement an EncFS plugin for Chrome (the web browser) that would do the file decryption client side and encrypt it before sending it back to Google for long term storage.

Admittedly this last part takes a bit of effort but Google should probably make the use of client side encryption optional anyway. Encryption is one of those trade-offs between two of the principles of information security. You give up availability to get more confidentiality.


In my opinion, Google has violated their motto. Or at least the motto they used to have, "Do no evil". Google, if you read this realize that I consider your actions evil.

I have been looking at Chromebooks for a long time and I've been wanting one for years. I will not buy one so long as I must use a Google account in order to use it.

P.S. It would also make my Google account considerably less secure since my password is a 32 character randomly generated password. It should be as difficult to guess as brute force cracking AES256 encryption. I can't memorize it. So, to use a Chromebook I would need to considerably reduce the security of my Google account. And, no, two-factor authentication the google way is not an option because I regularly run the battery down to zero on my cell phone.

Chrome OS and Chromebooks may have made a marginal improvement in the integrity of the core operating system but it was done at the near complete expense of confidentiality and with a loss of flexibility.


If you really want to impress me, Google, take a note from they way Apple manages the shared keychain access across device and use per-device PKI (like PGP or SMIME), to transfer the encryption key between ChromeOS and Chrome browsers installed on all my other systems so that I don't have to worry about losing the key as long as I remember the passphrase I use to lock it. You could even do a proper secure key escrow with that.

And, in the name of flexibility, give me a way to put my own validation key into the firmware of the Chromebook (alongside yours) so I can install my own, custom, OS without having the scary developer mode warning show up. But please do it in a way that hobbyists and small open source developers can reasonably afford to make use it.

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