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Date: Fri, 1 May 2020 18:15:04 -0600
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: Eric Biggers <ebiggers@...nel.org>
Cc: David Howells <dhowells@...hat.com>, keyrings@...r.kernel.org,
Andy Lutomirski <luto@...nel.org>, Greg KH <gregkh@...uxfoundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>, kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH] security/keys: rewrite big_key crypto to use Zinc
On Fri, May 1, 2020 at 6:14 PM Eric Biggers <ebiggers@...nel.org> wrote:
>
> On Fri, May 01, 2020 at 06:06:17PM -0600, Jason A. Donenfeld wrote:
> > Hey Eric,
> >
> > Thanks for the review.
> >
> > I'll add `select CONFIG` as you suggested. I agree about trying to
> > move as much as possible out of crypto and into lib/crypto. Breaking
> > those dependency cycles won't be easy but perhaps it'll be possible to
> > chip away at that gradually. (I'd also lib a
> > lib/crypto/arch/{arch}/..., but I guess that's a separate discussion.)
> >
> > I'll also change -EINVAL to -EBADMSG. Nice catch.
> >
> > Regarding the buffer zeroing... are you sure? These buffers are
> > already being copied into filesystem caches and all sorts of places
> > over which we have zero control. At that point, does it matter? Or do
> > you argue that because it's still technically key material, we should
> > zero out both the plaintext and ciphertext everywhere we can, and
> > hopefully at some point the places where we can't will go away? IOW,
> > I'm fine doing that, but would like to learn your explicit reasoning
> > before.
>
> It's true that the buffer zeroing doesn't matter in big_key_preparse() because
> the buffer only holds the encrypted key (which is what the shmem file will
> contain). But in big_key_read(), the buffer holds the decrypted key. So it's
> at least needed there. Having it in both places for consistency might be a good
> idea.
Alright. v2 coming your way shortly.
Jason
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