Disk Utility Bug in macOS High Sierra Exposes Passwords of Encrypted APFS Volumes in Plain Text [Updated]

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Brazilian software developer Matheus Mariano appears to have discovered a significant Disk Utility bug that exposes the passwords of encrypted Apple File System volumes in plain text on macOS High Sierra.

disk utility password prompt

MacRumors confirmed our test password "dontdisplaythis" appeared as the hint

Mariano added a new encrypted APFS volume to a container, set a password and hint, and unmounted and remounted the container in order to force a password prompt for demonstration purposes. Then, he clicked the "Show Hint" button, which revealed the full password in plain text rather than the hint.

A second video with English system language is embedded below

MacRumors reproduced this behavior on a 2016 MacBook Pro running macOS High Sierra, including versions 10.13 and 10.13.1 beta. German software developer Felix Schwarz also shared a video of the issue on Twitter today.
The issue currently only affects Macs with SSD storage due to Apple File System compatibility, but APFS will eventually support machines with Fusion Drives as well. Schwarz believes users who haven't specified a password hint, or haven't used Disk Utility whatsoever, are probably not affected.

For clarity, this appears to be a bug within Disk Utility itself. When creating an encrypted APFS volume in Terminal with the diskutil command line utility, the actual hint is shown, rather than the password.

Mariano said he has reported the vulnerability to Apple. The company did not immediately respond to our request for a comment on the matter, but we'll update this article if we hear back.

Update: Apple has addressed this bug by releasing a macOS High Sierra 10.13 Supplemental Update, available from the Updates tab in the Mac App Store. Apple has also shared a support document outlining steps to back up, erase, and restore the encrypted APFS volume upon updating.

The bug has also been fixed in the base version of macOS High Sierra for those who have yet to install the full software update.

Tag: APFS
Related Forum: macOS High Sierra

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Top Rated Comments

masotime Avatar
masotime
89 months ago
Apple seriously needs to start hiring better QA engineers....
Score: 49 Votes (Like | Disagree)
IPPlanMan Avatar
IPPlanMan
89 months ago
But we need to have animated emoji faces...
Score: 26 Votes (Like | Disagree)
MasterMac Avatar
MasterMac
89 months ago
Does showing the password itself as the hint count as a password hint? ;)
Score: 23 Votes (Like | Disagree)
Frosties Avatar
Frosties
89 months ago
Thank you for the laugh. Great alpha software.
Score: 20 Votes (Like | Disagree)
smaffei Avatar
smaffei
89 months ago
Apple seriously needs to start hiring better QA engineers....
Yes, there some HUGE problems with Apple QA these days.

iOS 11 is riddled with obvious bugs. I just got one about 10 minutes ago. Was just deleting a few voicemails (swipe delete) and the Phone App crashed. Then there is a very reproducible Messages bug where the keyboard obscures the last few messages and you can't get to them. Real rinky-dink stuff that should be caught.

I'm starting to think that Apple is relying too much on the Beta process to collect bugs instead of having robust internal QA.
Score: 18 Votes (Like | Disagree)
RMo Avatar
RMo
89 months ago
To be clear, the linked Twitter thread ('https://twitter.com/felix_schwarz/status/915851372217683970/video/1') suggests that this is a Disk Utility bug, where if you create a password-protected volume in Disk Utility it inadvertently sets the hint to the password itself. It's not a bug that allows the password itself to be uncovered via other means, which is what I originally thought this meant and which was surprising to me since the only way to do that should be computationally expensive brute-force methods (the data itself is encrypted with the password; it's not just artificially protected by one, and it shouldn't be possible to "reverse lookup" the password by any true means).
Score: 17 Votes (Like | Disagree)
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