Archive for January 31, 2015

FileVault 2 deferred enablement in Yosemite

January 31, 2015 Leave a comment

One of the requirements when enabling an account for FileVault 2 is that the account’s own password must be provided in order for the account to be enabled. This is because the account’s password is used to generate a unique derived key via PBKDF2. This key is necessary for the account to unlock FileVault 2’s encryption, so the account’s password must be provided in order to enable an account.

Apple recognized that there would be situations where Mac admins would need to set up FileVault 2 for a person where the admin would not have the password for that person’s user account. To avoid the immediate need to enter a password, fdesetup has a -defer flag in Mountain Lion, Mavericks and Yosemite that can be used with fdesetup‘s enable verb to delay enabling FileVault 2 until after the current (or next) user logs out. With the -defer flag, the user will be prompted for their password at their next logout or restart. The recovery key information is not generated until the user password is obtained, so the -defer option requires a file location where this information will be written to as a plist file.

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The property list file will be created as a root-only readable file and contain information similar to what’s show below.

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Note: For security reasons, the plist file with the recovery key information should not stay on the encrypted system. Please copy it to a safe location and then securely delete this plist file from the encrypted system.

Run the following command with root privileges to defer enabling FileVault 2 and specify the account you want:

fdesetup enable -user username -defer /path/to/filename.plist

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If there is no user account specified with the -user option, then the current logged-in user will be enabled for FileVault 2. If there is no user specified and no users are logged in when the command is run, then the next user that logs in will be chosen and enabled.

If you don’t want to specify the account, run the following command with root privileges:

fdesetup enable -defer /path/to/filename.plist

Screen Shot 2015-01-31 at 2.24.49 PM

On logout, the user will be prompted to enter their account password.

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Once entered, FileVault 2 will be enabled and the recovery information plist file will be created. Once the enabling process is complete, the Mac will restart.

Screen Shot 2015-01-31 at 10.57.20 AM

An important thing to keep in mind about the –defer option is that it enables one single user account at the time of turning on FileVault 2 encryption. The –defer option does not enable multiple user accounts and cannot be used to enable accounts once FileVault 2 encryption has been turned on.

In Yosemite, Apple added new options for fdesetup‘s -defer flag. These new options now allow Mac admins to set a deferred enablement with the following options:

  1. Enforce FileVault 2 enablement at logout
  2. Enforce FileVault 2 enablement at login
  3. Enforce FileVault 2 enablement at both login and logout

For more information, see below the jump.

Read more…

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