linux-ext4 - Re: [PATCH] fsverity: mark builtin signatures as deprecated

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Date:   Sat, 17 Dec 2022 02:04:02 +0000
From:   Luca Boccassi <bluca@...ian.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     linux-fscrypt@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-btrfs@...r.kernel.org, linux-integrity@...r.kernel.org,
        Jes Sorensen <jsorensen@...a.com>,
        Victor Hsieh <victorhsieh@...gle.com>
Subject: Re: [PATCH] fsverity: mark builtin signatures as deprecated

On Fri, 16 Dec 2022 at 20:55, Eric Biggers <ebiggers@...nel.org> wrote:
>
> On Thu, Dec 08, 2022 at 09:37:29PM +0000, Luca Boccassi wrote:
> >
> > The second question is easy: because the kernel is the right place for
> > our use case to do this verification and enforcement, exactly like dm-
> > verity does.
>
> Well, dm-verity's in-kernel signature verification support is a fairly new
> feature.  Most users of dm-verity don't use it, and will not be using it.

I'm not sure what you mean by "most users" - systemd has support for
dm-verity signatures all over the place, libcryptsetup/veritysetup
supports them, and even libmount has native first-class mount options
for them.

> > Userspace is largely untrusted, or much lower trust anyway.
>
> Yes, which means the kernel is highly trusted.  Which is why parsing complex
> binary formats, X.509 and PKCS#7, in C code in the kernel is not a great idea...

Maybe, but it's there and it's used for multiple purposes and
userspace relies on it. If you want to add a new alternative and
optional formats I don't think it would be a problem, I certainly
wouldn't mind.

Kind regards,
Luca Boccassi