Re: [nfsv4] questions w.r.t RPC-over-TLS draft

Hi Rick

----- Original Message -----
> From: "Rick Macklem" <rmacklem@uoguelph.ca>
> To: "NFSv4" <nfsv4@ietf.org>
> Sent: Monday, January 20, 2020 3:26:09 AM
> Subject: Re: [nfsv4] questions w.r.t RPC-over-TLS draft

> I wrote:
>>Hi,
>>
>>I've started implementing RPC-over-TLS for NFS and have run into a couple
>>of questions related to the draft (#4, I haven't downloaded #5).
>>
>>1 - Given this description...
>>   The flavor value of the verifier received in the reply message from
>>   the server MUST be AUTH_NONE.  The bytes of the verifier's string
>>   encode the fixed ASCII characters "STARTTLS".
>>
>>Is the verifier coded as:
>>A:   verifier length: 8
>>      bytes STARTTLS
>>OR
>>B:   verifier length: 12
>>      string length: 8
>>      bytes STARTTLS
>>
>>ie. Is there supposed to be a string length as coded by xdr_string() in the
>>verifier? (It is the words "verifier string" the above that I find confusing.)
>>
>>Then there is this sentence...
>>   AUTH_ERROR.  If the client sends a STARTTLS after it has sent other
>>   non-encrypted RPC traffic or after a TLS session has already been
>>   negotiated, the server MUST silently discard it.
>>
>>Does "other non-encrypted RPC traffic" refer specifically to traffic between
>>the NULL RPC with AUTH_TLS and the STARTTLS or does it refer to non-NULL RPC
>>>traffic or??
> I am also confused about what "sends a STARTTLS" actually means?
> (I'll admit I know nothing about TLS and can only find STARTTLS mentioned w.r.t.
> an SMTP email command.)

STARTTLS is a protocol specific signal that a client send to the server to start
TLS handshake. If I read spec correctly, then for RPC it's an operation NULL
with auth flavor AUTH_TLS and empty verifier. Server responds with verifier
that has body "STARTTLS" encoded as opaque bytes.

This is at least what our implementation does.

Regards,
   Tigran. 

> 
> Does this mean that the 8 bytes STARTTLS goes on the wire immediately after
> a NULL RPC with AUTH_TLS or does it mean the 8 bytes STARTTLS goes in a
> TCP RPC message (an 8byte message as indicated by the RPC over TCP record
> mark, which would normally be too small) or does "sends a STARTTLS" just saying
> that the TLS handshake should come immediately after the NULL RPC with AUTH_TLS?
> 
> Thanks for any clarification of this, rick
> 
> 
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