cannot export file if drive is already unlocked

[sssoleileraaa]

Description

When the drive is already unlocked, the return code is USB_BAD_PASSPHRASE and the file is not copied to the usb drive.

Steps to Repro

1. From the Qubes menu in the upper-lefthand corner, hover over sd-export-usb and select sd-export-usb: Files
2. Select your thumb drive folder, enter in your luks passphrase with the default selection to keep the device unlocked
3. run qvm-open-in-vm sd-export-usb archive.sd-export from sd-svs and see that you get back USB_BAD_PASSPHRASE

[sssoleileraaa]

Another way to Repro

1. From the Qubes menu in the upper-lefthand corner, hover over sd-export-usb and select sd-export-usb: Files
2. Select your thumb drive folder, enter in your luks passphrase with the Forget password immediately option selected
3. Run qvm-open-in-vm sd-export-usb archive.sd-export from sd-svs

Expected
Either:

1. You get back USB_DRIVE_UNLOCKED during the preflight checks to indicate to the client that it doesn't need to request the user's passphrase, then the client provides the export without an encryption_key and the export is successful.
2. We just always ask the user for their passphrase and the export is successful

Actual
You get back USB_BAD_PASSPHRASE and the export is not successful

[sssoleileraaa]

Sounds like this has been repro'd but keeping label so in case someone wants to repro this less-than-ideal fix:

Unplug usb device, plug back in, try again. I don't think this will work if you say to remember the passphrase forever though.

[redshiftzero]

I tried to reproduce this before attempting a fix but it seems like this is resolved on master. To repro I unlocked my export drive manually in sd-export-usb prior to clicking export in the client. The export still occurred successfully.

Looking at the code, this if statement should handle the case where the drive has already been unlocked: https://github.com/freedomofpress/securedrop-export/blob/master/securedrop_export/export.py#L247

If you agree @creviera, I think we can close this one

[sssoleileraaa]

I still see this bug by running through the steps here: #12 (comment) except instead of seeing USB_BAD_PASSPHRASE you see ERROR_GENERIC now.

[sssoleileraaa]

i think the way to prevent this is to check if the drive is already unlocked and then skip the luksOpen step and later the unmount+luksClose step