From: bfields@fieldses.org (J. Bruce Fields)
To: David Howells <dhowells@redhat.com>
Cc: herbert@gondor.apana.org.au, davem@davemloft.net,
trond.myklebust@hammerspace.com, linux-crypto@vger.kernel.org,
linux-nfs@vger.kernel.org, linux-afs@vger.kernel.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: gssapi, crypto and afs/rxrpc
Date: Mon, 19 Oct 2020 14:07:14 -0400 [thread overview]
Message-ID: <20201019180714.GA6692@fieldses.org> (raw)
In-Reply-To: <1444464.1602865106@warthog.procyon.org.uk>
On Fri, Oct 16, 2020 at 05:18:26PM +0100, David Howells wrote:
> Hi Herbert, Dave, Trond,
>
> I've written basic gssapi-derived security support for AF_RXRPC:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=rxrpc-rxgk
>
> I've borrowed some bits from net/sunrpc/auth_gss/ but there's a lot in there
> that is quite specific to the sunrpc module that makes it hard to use for
> rxrpc (dprintk, struct xdr_buf).
>
> Further, I've implemented some more enctypes that aren't supported yet by
> gssapi (AES with sha256/sha384 and Camellia), and that requires some changes
> to the handling as AES with sha384 has a 24-byte checksum size and a 24-byte
> calculated key size for Kc and Ki but a 32-byte Ke.
>
> Should I pull the core out and try to make it common? If so, should I move it
> to crypto/ or lib/, or perhaps put it in net/gssapi/?
>
> There are two components to it:
>
> (1) Key derivation steps.
>
> My thought is to use xdr_netobj or something similar for to communicate
> between the steps (though I'd prefer to change .data to be a void* rather
> than u8*).
>
> (2) Encryption/checksumming.
>
> My thought is to make this interface use scattergather lists[*] since
> that's what the crypto encryption API requires (though not the hash API).
>
> If I do this, should I create a "kerberos" crypto API for the data wrapping
> functions? I'm not sure that it quite matches the existing APIs because the
> size of the input data will likely not match the size of the output data and
> it's "one shot" as it needs to deal with a checksum.
>
> Or I can just keep my implementation separate inside net/rxrpc/.
I'd love to share whatever we can, though I'm not really sure what's
involved. Certainly some careful testing at least.
It's been about 15 years since I really worked on that code. I remember
struggling with struct xdr_buf. The client and server support
zero-copy, so requests and replies are represented by a combination of a
couple of linear buffers plus an array of pages. My memory is that the
(undocumented) meanings of the fields of the xdr_buf were different for
request and replies and for server and client, and getting them right
took some trial and error.
--b.
prev parent reply other threads:[~2020-10-19 18:07 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-16 16:18 gssapi, crypto and afs/rxrpc David Howells
2020-10-19 3:14 ` Herbert Xu
2020-10-19 18:07 ` J. Bruce Fields [this message]
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