Re: how to use the ktls

From: Benjamin Kaduk <>
Date: Sun, 12 Jan 2020 20:23:10 -0800
On Thu, Jan 09, 2020 at 10:53:38PM +0000, Rick Macklem wrote:
> John Baldwin wrote:
> >On 1/7/20 3:02 PM, Rick Macklem wrote:
> >> Hi,
> >>
> >> Now that I've completed NFSv4.2 I'm on to the next project, which is making NFS
> >> work over TLS.
> >> Of course, I know absolutely nothing about TLS, which will make this an interesting
> >> exercise for me.
> >> I did find simple server code in the OpenSSL doc. which at least gives me a starting
> >> point for the initialization stuff.
> >> As I understand it, this initialization must be done in userspace?
> >>
> >> Then somehow, the ktls takes over and does the encryption of the
> >> data being sent on the socket via sosend_generic(). Does that sound right?
> >>
> >> So, how does the kernel know the stuff that the initialization phase (handshake)
> >> figures out, or is it magic I don't have to worry about?
> >>
> >> Don't waste much time replying to this. A few quick hints will keep me going for
> >> now. (From what I've seen sofar, this TLS stuff isn't simple. And I thought Kerberos
> >> was a pain.;-)
> >>
> >> Thanks in advance for any hints, rick
> >
> >Hmmm, this might be a fair bit of work indeed.
> If it was easy,  it wouldn't be fun;-) FreeBSD13 is a ways off and if it doesn't make that, oh well..
> >Right now KTLS only works for transmit (though I have some WIP for receive).
> Hopefully your WIP will make progress someday, or I might be able to work on it.
> >KTLS does assumes that the initial handshake and key negotiation is handled by
> >OpenSSL.  OpenSSL uses custom setockopt() calls to tell the kernel which
> >session keys to use.
> Yea, I figured I'd need a daemon like the gssd for this. The krpc makes it a little
> more fun, since it handles TCP connections in the kernel.
> >I think what you would want to do is use something like OpenSSL_connect() in
> >userspace, and then check to see if KTLS "worked".
> Thanks (and for the code below). I found the simple server code in the OpenSSL doc,
> but the client code gets a web page and is quite involved.
> >If it did, you can tell
> >the kernel it can write to the socket directly, otherwise you will have to
> >bounce data back out to userspace to run it through SSL_write() and have
> >userspace do SSL_read() and then feed data into the kernel.
> I don't think bouncing the data up/down to/from userland would work well.
> I'd say "if it can't be done in the kernel, too bad". The above could be used for
> a NULL RPC to see it is working, for the client.

So you're saying that we'd only support rpc-over-tls as an NFS client and
not as a server, at least until the WIP for ktls read appears?

Received on Mon Jan 13 2020 - 03:23:17 UTC

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