broken passphrase / reveal active passphrase on open LUKS [SOLVED]

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confrused
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broken passphrase / reveal active passphrase on open LUKS [SOLVED]

Post by confrused » Sat Dec 09, 2017 5:44 pm

My LUKS encrypted volume on an external drive is open and accessible in Linux Mint because I choose "Remember forever". However, it seems likely that *I* have not 'remembered forever' because I am unable to unlock it after I shutdown LM and then boot into Ubuntu. My question is, how can I find out what the passphrase is? It seems that should be possible since I have access to it in LM, I am hoping.
Last edited by confrused on Tue Dec 12, 2017 10:33 pm, edited 1 time in total.

Mute Ant
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Re: broken passphrase / reveal active passphrase on open LUKS

Post by Mute Ant » Sat Dec 09, 2017 10:26 pm

LUKS itself uses the pass-phrase you enter, adds 'salt' and mashes it up thousands of times, to slow down automated guessing. That result applied to the 'wrapped-master-key' regenerates the 'unwrapped-master-key' needed to unscramble the data. None of that is supposed to be reversible and I am assuming it isn't... you can't use a 'cold' LUKS without an acceptable pass-phrase.

With a 'warm' LUKS, the master key is in RAM somewhere, but not the pass-phrase.

I would consider it a very dodgy implementation if the pass-phrase can be reverse-engineered from what's stored by 'Remember Forever', but I have never gone looking. It is your Mint desktop doing the remembering, so...
A: Which version of Mint are you using? 17, 17.1, 17.2 ... 18.3
B: Which desktop has remembered the pass-phrase? KDE, Cinnamon, MATE or XFCE?
2018-10-13 Google designs 3-phase feed-forward to improve 2-phased governors with no sense of direction.

confrused
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Re: broken passphrase / reveal active passphrase on open LUKS

Post by confrused » Sun Dec 10, 2017 3:12 pm

LM 18.2 Cinnamon 64-bit
3.4.6
4.8.0-53-generic

Mute Ant
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Re: broken passphrase / reveal active passphrase on open LUKS

Post by Mute Ant » Sun Dec 10, 2017 6:50 pm

If you boot and log in to the Mint that has remembered the LUKS passphrase, then start the program seahorse it can show you the original passphrase.

[guess]The passphrase is remembered in the file ~/.local/share/keyrings/user.keystore encrypted using your login password.[/guess]
2018-10-13 Google designs 3-phase feed-forward to improve 2-phased governors with no sense of direction.

confrused
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Re: broken passphrase / reveal active passphrase on open LUKS

Post by confrused » Mon Dec 11, 2017 11:51 am

Seahorse did it. Thank you !

Mute Ant
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Re: broken passphrase / reveal active passphrase on open LUKS

Post by Mute Ant » Mon Dec 11, 2017 5:50 pm

Hurrah! If you edit the title of your original post to include Solved other readers will find it, and other members won't try to answer it.
2018-10-13 Google designs 3-phase feed-forward to improve 2-phased governors with no sense of direction.

confrused
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Re: broken passphrase / reveal active passphrase on open LUKS

Post by confrused » Tue Dec 12, 2017 7:38 pm

Yes, I would like to do that! I can edit my title above for this reply, but how do I edit the original title?

Mute Ant
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Re: broken passphrase / reveal active passphrase on open LUKS

Post by Mute Ant » Tue Dec 12, 2017 8:05 pm

2018-10-13 Google designs 3-phase feed-forward to improve 2-phased governors with no sense of direction.

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