Encrypting Volumes in OS X Mountain Lion

Encrypting a volume in OS X Mountain Lion couldn’t be easier. In this article, we will look at three ways to encrypt OS X Lion volumes. The reason there are three ways is that booted volumes and non-booted volumes have different methods for enabling encryption. The third way to enable encryption on a volume is to do so through

Encrypting Attached Storage

For non-boot volumes, just control-click or right-click on them and then click on Encrypt “VOLUMENAME” where the name of the volume is in quotes.

Encrypting a Volume in Mountain Lion

When prompted, provide an encryption password for the volume, verify that password and if you so choose, provide a hint.

Setting an Encryption Password For a Volume in Mountain Lion

Once the encryption process has begun, the entry previously clicked on says Encrypting “VOLUMENAME” where the name of the volume is in quotes.

Viewing the Encryption Status in Mountain Lion

Before you can encrypt a volume from the command line you must first convert it to CoreStorage if it isn’t already. As volumes on external disks aren’t likely to be CoreStorage, let’s check using diskutil along with corestorage and then list:

diskutil corestorage list

Assuming your volume was already formatted with a non-corestorage format and isn’t listed, locate the volume and document the disk identifier (in this case disk2s3). Then, run diskutil corestorage along with the convert verb and the disk, as follows (no need to run this command if it’s already listed):

sudo diskutil corestorage convert disk2s3

The output should look similar to the following:

Started CoreStorage operation on disk2s3 Reco
Resizing disk to fit Core Storage headers
Creating Core Storage Logical Volume Group
Attempting to unmount disk2s3
Switching disk2s3 to Core Storage
Waiting for Logical Volume to appear
Mounting Logical Volume
Core Storage LVG UUID: 19D34AAA-498A-44FC-99A5-3E719D3DB6FB
Core Storage PV UUID: 2639E13A-250D-4510-889A-3EEB3B7F065C
Core Storage LV UUID: 4CC5881F-88B3-42DD-B540-24AA63952E31
Core Storage disk: disk4
Finished CoreStorage operation on disk2s3 Reco

Once converted, the LV UUID (LV is short for Logical Volume) can be used to encrypt the logical volume using a password of crowbar to unlock it:

sudo diskutil corestorage encryptvolume 4CC5881F-88B3-42DD-B540-24AA63952E31 -passphrase crowbar

The output is similar to the following:

Started CoreStorage operation on disk4 Reco
Scheduling encryption of Core Storage Logical Volume
Core Storage LV UUID: 4CC5881F-88B3-42DD-B540-24AA63952E31
Finished CoreStorage operation on disk4 Reco

According to the size, this process can take some time. Monitor the progress using the corestorage list option:

diskutil corestorage list

In all of these commands, replace core storage w/ cs for less typing. I’ll use the shortened version as I go. I know that we rarely change passwords, but sometimes it needs to happen. If it needs to happen on a core storage encrypted volume, this can be done from the command line or a script. To do so, use diskutil cs with the changevolumepassphrase option. We’ll use -oldpassphrase to provide the old password and -newpassphrase to provide the new passphrase.

diskutil cs changeVolumePassphrase FC6D57CD-15FC-4A9A-B9D7-F7CF26312E00 -oldpassphrase crowbar -newpassphrase hedeservedit

I continue to get prompted when I send the -newpassphrase, so I’ve taken to using stdin , using -stdinpassphrase. Once encrypted there will occasionally come a time for decrypting, or removing the encryption, from a volume. It’s worth noting that neither encrypting or decrypting requires erasing. To decrypt, use the decryptVolume verb, again with the -passphrase option:

diskutil cs decryptvolume 4CC5881F-88B3-42DD-B540-24AA63952E31 -passphrase crowbar

FileVault 2: Encrypting Boot Volumes

Boot volumes are configured a bit differently. This is namely because the boot volume requires FileVault 2, which unifies usernames and passwords with the encryption so that users enter one username and password rather than unlocking drives. To configure FileVault 2, open the Security & Privacy System Preference pane and then click on the FileVault tab. Click on the lock to make changes and then provide the password for an administrative account of the system. Then, click on “Turn On FileVault…”

Enable FileVault In Mountain Lion

Enable FileVault In Mountain Lion

When prompted with the Recovery Key, document it and then click on

Documenting the FileVault 2 Recovery Key

Documenting the FileVault 2 Recovery Key

Choose whether to restore the recovery key with Apple. If you will be storing the key with Apple then provide the AppleID. Otherwise, simply click the bullet for “Do not store the recovery key with Apple” and then click on the Continue button.

Dealing With Recovery Keys in FileVault 2

Dealing With Recovery Keys in FileVault 2

When prompted, click on Restart to reboot and be prompted for the first account that can unlock the FileVaulted system.

Rebooting To Start FileVault 2 Encryption

Rebooting To Start FileVault 2 Encryption

Once encrypted, the FileVault tab in the Security & Privacy System Preference pane shows the encryption status, or percent during encryption.

Use the Enable Users… button to enable additional accounts to unlock the volume (note: by default accounts cannot login until their account has been added here).

Allowing Users To Boot The Computer

Allowing Users To Boot The Computer

That’s it. Managing FileVault 2 using the System Preferences is about as easy as it can get. But for those who require mass management, Apple has provided a tool called fdesetup for that as well.

Using fdesetup with FileVault 2

FileVault 2 now comes with a nifty configuration utility called fdesetup. To use fdesetup to encrypt the boot volume, first check FileVault’s status by entering the fdesetup command along with the –status option (wait, no — required any more!):

fdesetup status

As with most other commands, read the help page before starting to use just in case there are any changes to it between the writing of this article and when you kick off your automated encryption. Done using the help verb:

fdesetup help

After confirming FileVault is off, enable FileVault with the enable option, as follows:

sudo fdesetup enable

Unless additional parameters are specified, an interactive session prompts for the primary user’s short name and password. Once enabled, a Recovery key is returned by the fdesetup command. You can also cancel this by just hitting Control-C so we can look at more complicated iterations of the command. It should be recorded or otherwise stored, something easily done by mounting in a script (e.g. a write-only share in a script for key escrowing). If more complicated measures are needed, of course check out Cauliflower Vest at code.google.com. As fdesetup is in its first version, I find it amusing that it’s actually 1.3 as indicated using:

fdesetup version

Now, if you run fdesetup and you’ve deployed a master keychain then you’re going to have a little more work to do; namely point the -keychain command at the actual keychain. For example:

sudo fdesetup enable -keychain /Library//Keychains/FileVaultMaster.keychain

To define a certificate:

sudo fdesetup enable -certificate /temp/filename.cer

Adding additional users other than the one who enabled fdesetup is a bit different than the first:

sudo fdesetup add -usertoadd robin

To remove users, just remove them with a remove verb followed by the -user option and the username:

sudo fdesetup remove -user robin

The remove and add options also offer using the -uuid rather than the username. Let’s look at Robin’s uid :

dscl . read /Users/robin GeneratedUID | cut -c 15-50

Yes, I used cut. If you have a problem with that then take your judgmental fuc… Nevermind. Take that GUID and plug it in as the uuid using the -uuid option. For example, to do so with the remove verb:

sudo fdesetup remove -uuid 31E609D5-39CF-4A42-9F24-CFA2B36F5532

Or for good measure, we can basically replicate -user w/ -uuid for a nice stupid human trick:

sudo fdesetup remove -uuid `dscl . read /Users/robin GeneratedUID | cut -c 15-50`

All of the fdesetup commands can be run interactively or using options to define the variables otherwise provided in the interactive prompt. These are defined well in the man page. Finally, let’s look at -defer. Using -defer, you can run the fdesetup tool at the next login, write the key to a plist and then grab it with a script of some sort later. At logout, the user will get prompted for a

sudo fdesetup enable -defer /temp/fdesetupescrow.plist

Or define users concurrently (continuing to use the robin test user):

sudo fdesetup enable -user robin -defer /temp/fdesetupescrow.plist

FileVault accounts can also use accounts from Directory Services automatically. These need to synchronize with the Directory Service routinely as data is cached. To do so:

sudo fdesetup sync

This is really just scratching the surface of what you can do with fdesetup. The definitive source for which is the man page as well as a nicely done article by Rich Trouton (who I think I will start calling Trouty-mouth after having watched the Glee episode where one of the girls says that).

Encrypting Time Machine Backups

The last full disk encryption to discuss is Time Machine. To encrypt Time Machine backups, use Time Machine’s System Preference pane. The reason for this being that doing so automatically maintains mounting information in the Operating System, rather than potentially having an encrypted drive’s password get lost or not entered and therefore not have backups run.

To enable disk encryption for Time Machine destinations, open the Time Machine System Preference pane and click on Select Backup Disk… From the backup disk selection screen, choose your backup target and then check the box for “Encrypt backups”. Then, click on Use Disk.

Encrypting Time Machine Volumes

Encrypting Time Machine Target Volumes

At the overlay screen, provide a backup password twice and if you would like, a hint as to what that password is. When you are satisfied with your passwords, click on the Encrypt Disk button.

Configuring The Password For A Time Machine Backup

Configuring The Password For Encrypted Time Machine Backups

Now, there are a couple of things to know here. 1. Don’t forget that password. 2. If you use an institutional FileVault Key then still don’t forget that password as it will not work. 3. Don’t forget that password…

Conclusion

Encrypting data in OS X can take on other forms as well. The keychains encrypt passwords and other objects. Additionally, you can still create encrypted dmgs and many file types have built in encryption as well. But the gist is that Apple encrypts a lot. They also sandbox a lot and with the addition of gatekeeper are code signing a lot. But encrypting volumes and disks is mostly about physical security, which these types of encryption provide a substantial solution for.

While all this security might seem like a lot, it’s been in Apple’s DNA for a long time and really security is about layers and the Mac Systems Administrator batbelt needs a lot of items to allow us to adapt to the changing landscape of security threats. OS X is becoming a little more like iOS as can be expected and so I would suspect that encryption will become more and more transparent as time goes on. Overall, the options allow encrypting every piece of data that goes anywhere near a system. The mechanisms with which data is now encrypted are secure, as is the data at rest. Once data is decrypted, features like Gatekeeper and the application layer firewall supplement traditional network encryption to keep well secured.

5 Comments

  • July 30, 2012 - 3:03 am | Permalink

    Now this really is a good tutorial. I just have the problem, that I try to use a pre-created Master Password/keychain and the fdesetup always says it couldn’t create the institutional user. Any advice?

    • August 1, 2012 - 4:28 pm | Permalink

      Permissions on the keychain? Can you create it with fdesetup?

  • July 30, 2012 - 11:50 pm | Permalink

    Just had issues with my keychain file, this is solved by now.

  • Dezza
    August 29, 2012 - 2:00 am | Permalink

    Hi,

    Thanks for (all of) your awesome tutorials. They provide great examples of the many underpinnings of our chosen OS… :)

    I’m wondering how encrypting a Server’s harddrives should be done. For example, I have a MacBook Pro 3,1 running ML Server, with data held on external FireWire and USB drives. System data is on the internal main drive. All bound systems use FileVault and users’ home folders are also FileVault encrypted – but I’ve noted the Network Home Space is not (and individual files can easily be accessed by an Administrator).

    As this system auto starts/shuts down, is it possible (reasonable?) to encrypt any/all of those drives? And (if it’s not too much to ask) – is it possible to keep users Network Home Space in a FileVault style ‘sparse’ bundle?

    Thank you very much for your efforts and allowing your brain to be picked.
    :) :)

    • September 21, 2012 - 6:54 pm | Permalink

      I wouldn’t keep users data in a bundle. If you’re using FileVault in Lion or Mountain Lion then it encrypts the entire boot disk. To encrypt additional disks, just right-click on them and click Encrypt. Neither of these will allow you to boot the system in an unattended manner, but if you’re already using FileVault then you’re not doing so anyway. Using FileVault on clients and servers, provided all volumes are encrypted should keep all data encrypted.

      Hope this helps!

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