Re: [PATCH 0/2] crypto: remove MD4 generic shash

From: ronnie sahlberg <ronniesahlberg@gmail.com>
To: Denis Kenzior <denkenz@gmail.com>
Cc: Ard Biesheuvel <ardb@kernel.org>,
	Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Eric Biggers <ebiggers@kernel.org>,
	linux-cifs <linux-cifs@vger.kernel.org>,
	Steve French <sfrench@samba.org>,
	David Howells <dhowells@redhat.com>,
	keyrings@vger.kernel.org
Subject: Re: [PATCH 0/2] crypto: remove MD4 generic shash
Date: Thu, 19 Aug 2021 07:11:23 +1000	[thread overview]
Message-ID: <CAN05THSFpf+1BQ+yL9rjd=6_JWCxBMO8AyDMnhdVW9uVwBAMcg@mail.gmail.com> (raw)
In-Reply-To: <24606605-71ae-f918-b71a-480be7d68e43@gmail.com>

On Thu, Aug 19, 2021 at 2:23 AM Denis Kenzior <denkenz@gmail.com> wrote:
>
> Hi Ard,
>
> >>   The previous ARC4 removal
> >> already caused some headaches [0].
> >
> > This is the first time this has been reported on an upstream kernel list.
> >
> > As you know, I went out of my way to ensure that this removal would
> > happen as smoothly as possible, which is why I contributed code to
> > both iwd and libell beforehand, and worked with distros to ensure that
> > the updated versions would land before the removal of ARC4 from the
> > kernel.
> >
> > It is unfortunate that one of the distros failed to take that into
> > account for the backport of a newer kernel to an older distro release,
> > but I don't think it is fair to blame that on the process.
>
> Please don't misunderstand, I don't blame you at all.  I was in favor of ARC4
> removal since the kernel AF_ALG implementation was broken and the ell
> implementation had to work around that.  And you went the extra mile to make
> sure the migration was smooth.  The reported bug is still a fairly minor
> inconvenience in the grand scheme of things.
>
> But, I'm not in favor of doing the same for MD4...
>
> >
> >>   Please note that iwd does use MD4 for MSCHAP
> >> and MSCHAPv2 based 802.1X authentication.
> >>
> >
> > Thanks for reporting that.
> >
> > So what is your timeline for retaining MD4 support in iwd? You are
> > aware that it has been broken since 1991, right? Please, consider
> > having a deprecation path, so we can at least agree on *some* point in
> > time (in 6 months, in 6 years, etc) where we can start culling this
> > junk.
> >
>
> That is not something that iwd has any control over though?  We have to support
> it for as long as there are  organizations using TTLS + MD5 or PEAPv0.  There
> are still surprisingly many today.

The same situation exist for cifs. The cifs client depends on md4 in
order to authenticate to Windows/Azure/Samba/... cifs servers.
And like you we have no control of the servers.

Our solution will likely be to fork the md4 code and put a private
copy in our module.
Maybe you need to do the same.

--
ronnie

>
> Regards,
> -Denis