netdev - Re: [PATCH RFC 4/5] net/tls: Add support for PF

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Date:   Thu, 28 Apr 2022 21:54:01 +0000
From:   Chuck Lever III <chuck.lever@...cle.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     netdev <netdev@...r.kernel.org>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "ak@...pesta-tech.com" <ak@...pesta-tech.com>,
        "borisp@...dia.com" <borisp@...dia.com>,
        "simo@...hat.com" <simo@...hat.com>
Subject: Re: [PATCH RFC 4/5] net/tls: Add support for PF_TLSH (a TLS handshake
 listener)



> On Apr 28, 2022, at 5:08 PM, Jakub Kicinski <kuba@...nel.org> wrote:
> 
> On Thu, 28 Apr 2022 01:29:10 +0000 Chuck Lever III wrote:
>>> Is it possible to instead create a fd-passing-like structured message
>>> which could carry the fd and all the relevant context (what goes 
>>> via the getsockopt() now)?
>>> 
>>> The user space agent can open such upcall socket, then bind to
>>> whatever entity it wants to talk to on the kernel side and read
>>> the notifications via recv()?  
>> 
>> We considered this kind of design. A reasonable place to start there
>> would be to fabricate new NETLINK messages to do this. I don't see
>> much benefit over what is done now, it's just a different isomer of
>> syntactic sugar, but it could be considered.
>> 
>> The issue is how the connected socket is materialized in user space.
>> accept(2) is the historical way to instantiate an already connected
>> socket in a process's file table, and seems like a natural fit. When
>> the handshake agent is done with the handshake, it closes the socket.
>> This invokes the tlsh_release() function which can check 
> 
> Actually - is that strictly necessary? It seems reasonable for NFS to
> check that it got TLS, since that's what it explicitly asks for per
> standard. But it may not always be the goal. In large data center
> networks there can be a policy the user space agent consults to choose
> what security to install. It may end up doing the auth but not enable
> crypto if confidentiality is deemed unnecessary.

> Obviously you may not have those requirements but if we can cover them
> without extra complexity it'd be great.

We can be flexible about how/where handshake success is checked.

However, using a simple close(2) to signal that the handshake
has completed does not communicate whether the handshake was
indeed successful. We will need a (richer) return/error code
from the handshake agent for that use case.


>> whether the IV implantation was successful.
> 
> I'm used to IV meaning Initialization Vector in context of crypto,
> what does "IV implementation" stand for?

Implantation, not implementation. The handshake agent implants
the initialization vector in the socket before it closes it.


--
Chuck Lever