linux-kernel - Re: [RFD] Common userspace tool for fscypto

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Message-ID: <87d9b3aa-684d-856a-0dcd-f960923f2484@nod.at>
Date:   Tue, 29 Nov 2016 22:59:28 +0100
From:   Richard Weinberger <richard@....at>
To:     Joe Richey <joerichey@...gle.com>
Cc:     Michael Halcrow <mhalcrow@...gle.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>, kzak@...hat.com,
        Theodore Ts'o <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Eric Biggers <ebiggers@...gle.com>,
        David Gstir <david@...ma-star.at>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        linux-f2fs-devel@...ts.sourceforge.net,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFD] Common userspace tool for fscypto

Joe,

On 29.11.2016 22:42, Joe Richey wrote:
> Hi Richard,
> 
> I'm Joe Richey, and I work on Mike's team. We've been playing around
> with a few design
> ideas regarding a tool for managing filesystem encryption. After going
> though some iterations
> with Ted, we have a fairly good idea about where to head design wise,
> and I'm working on a
> design document for it. It's a bit preliminary at this point, but I
> can share it if you want.
> 
> Our goal is to have a finished doc by end of Q4 and then get your and
> Jaegeuk's feedback.

Thanks for your quick response!
I hoped you had already some code, but having a decent design document
is also nice. I'm eager to read it.

Do you also plan to address d/page cache related issues?
i.e. when two users are logged into the system user rw
is able to see decrypted file names and contents in /home/dags/
if user dags installs a key and accessed a file.

Or files in /home/dags/ are still readable even after
user dags purged the key.

The tool could play games with CLONE_NEWNS to hide directories.
To provide a correct "logout" we could expose shrink_dcache_parent()
to usespace such that the emerging tool can purge the key and flush
the dcache on the encrypted directory. But I fear exposing shrink_dcache_parent()
is not a good idea. :-)

Just some random ideas...

Thanks,
//richard