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I have an Ubuntu VPS running at a remote host. The disk is not encrypted but I have a specific directory that is encrypted for which I must provide a password via an SSH session (not stored anywhere on the VPS) to "unlock" it so that the services can run on this VPS and serve the content decrypted.

Assuming the bad admin cannot login to the system like I do via SSH. Can the bad admin read the encrypted directory's decrypted content while running and/or can the bad admin gain access to the in-memory key for the encrypted directory?

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Yes

Your situation violates three of the Ten Immutable Laws of Security, namely:

Law #2: If a bad guy can alter the operating system on your computer, it’s not your computer anymore

Law #3: If a bad guy has unrestricted physical access to your computer, it’s not your computer anymore

Law #6: A computer is only as secure as the administrator is trustworthy

With enough effort the admin definitely can dump the memory and extract either the key or decrypted data while the VPS is running and the directory is decrypted. Alternatively, (since the disk is not encrypted) the rogue admin could modify the SSH server binary to log the password in cleartext.

What can you do?

The only way to be absolutely sure would be to host your own server. Or you could look into Confidential Computing VMs. However, I am not sure how foolproof these are, so proceed at your own risk.

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  • Thank you I will look at the Confidential Computing VMs, but I am sure it will open a whole new can of questions which I will post separately. Jan 11 at 9:42

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