linux-kernel - Re: overlayfs vs. fscrypt

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Message-ID: <3369831.hnip8tpcNh@blindfold>
Date:   Wed, 13 Mar 2019 16:30:03 +0100
From:   Richard Weinberger <richard@....at>
To:     Theodore Ts'o <tytso@....edu>
Cc:     Amir Goldstein <amir73il@...il.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-fscrypt@...r.kernel.org,
        overlayfs <linux-unionfs@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Paul Lawrence <paullawrence@...gle.com>, david@...ma-star.at
Subject: Re: overlayfs vs. fscrypt

Am Mittwoch, 13. März 2019, 16:16:33 CET schrieb Theodore Ts'o:
> So before we talk about how to make things work from a technical
> perspective, we should consider what the use case happens to be, and
> what are the security requirements.  *Why* are we trying to use the
> combination of overlayfs and fscrypt, and what are the security
> properties we are trying to provide to someone who is relying on this
> combination?

Well, as stated, on (deeply) embedded systems overlayfs is common.
You have a lowerdir with read-only files and an read-write upper dir.
Of course both lower and upper directory need to be encrypted.
In my case ubifs+fscrypt, sometimes also combined with an encrypted+authenticated
squashfs.

Thanks,
//richard