Subject: RE: SCVP Change Proposal (was: Signing Untrusted SCVP?)

From: "Trevor Freeman" <[email-masked]>
Date: Wed, 7 Apr 2004 17:33:25 -0700

The proposal is allowing cached responses and the presence or absence of
the nonce indicates to the server if cached signed responses are
acceptable.
Trevor

-----Original Message-----
From: Michael Myers [mailto:[email-masked]] 
Sent: Wednesday, April 07, 2004 4:09 PM
To: Trevor Freeman; Dave Engberg; Santosh Chokhani; [email-masked]
Subject: RE: SCVP Change Proposal (was: Signing Untrusted SCVP?)

Dave asked about signing DPD responses.  Why are we talking
about nonces?

Mike

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]On Behalf Of Trevor Freeman
Sent: Wednesday, April 07, 2004 3:25 PM
To: Dave Engberg; Santosh Chokhani; [email-masked]
Subject: RE: SCVP Change Proposal (was: Signing Untrusted SCVP?)

Hi Dave,
That is almost the proposed change. The presence of the nonce
will
indicate the request for a unique response, and I have added a
wantBack.

3.5 requestNonce

The OPTIONAL requestNonce item contains a request identifier
generated
by the SCVP client.  If the client includes a requestNonce value
in the
request, it is expressing a preference the SCVP server SHOULD
return a
specific response. If the server returns a specific response it
MUST
include the requestNonce from the request in the response, but
MAY
return a cached success response which MUST NOT have a
requestNonce. If
the client includes a requestNonce and also sets a wantBack of
id-swb-unique-resp-required, the client is indicating that the
SCVP
server MUST return either a specific response including the
requestNonce
or an error.  The client SHOULD include a requestNonce item in
every
request to prevent an attacker from acting as a
man-in-the-middle by
replaying old responses from the server.  The requestNonce value
SHOULD
change with every request sent by the client. The client MUST
NOT
include the wantBack of id-swb-unique-resp-required without a
requestNonce, and a server receiving such a request SHOULD
return an
invalidRequest error

Trevor

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]
On Behalf Of Dave Engberg
Sent: Wednesday, April 07, 2004 9:11 AM
To: Santosh Chokhani; [email-masked]
Subject: SCVP Change Proposal (was: Signing Untrusted SCVP?)

Thanks, Santosh.  Here's a specific list of changes to SCVP
Draft 13
that would allow the use of signatures to be optional on pure
DPD
lookups, and permit server caching of signed responses when
mutually
acceptable by server and client security policies.  Rather than
defining
a new request extension to signal a desire for a fresh
signature, this
proposal uses the request nonce.  I assume there would be
agreement that
any client who sends a nonce would not want an unsigned or
cached
response in return, but I wouldn't have any problem with
defining a
separate new extension if that makes the intent more clear.

The section 3 changes are separate from section 4, and either
could be
adopted independently.

In Section 3, replace:

  If a
  server is responding to an unsigned request or a signed
request, it
  MUST use a signed response or an unsigned error response.

With:

  If a server is responding to an unsigned request or a signed
request,
  it MUST use a signed response or an unsigned error response if
either
  of the following is true:

    - The request wantBack includes one or more of the
following:

        * id-swb-pkc-public-key-info
        * id-swb-pkc-cert-status
        * id-swb-ac-cert-status

    - The request includes a requestNonce

  If neither is true, a server responding to an unsigned request
or
  signed request MAY use a signed response, an unsigned
response, or
  an unsigned error response.

In Section 4, replace:

      requestRef            RequestReference,

With:

      requestRef        [0] RequestReference OPTIONAL,

In Section 4.5, replace:

  The requestRef allows the SCVP server to identify the request
that

With:

  The OPTIONAL requestRef item allows the SCVP server to
identify
  the request that ...

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]
On Behalf Of Santosh Chokhani
Sent: Wednesday, April 07, 2004 8:32 AM
To: [email-masked]
Subject: RE: Signing Untrusted SCVP?

Given the limited value of signature, DPD response signature by
the
server should be optional and signature verification by the
client
should be optional.

The question we should answer is that is there any benefit to
adding an
option for the client to request a signature and then should the
DPD
server be forced to sign the response

---

From: "Michael Myers" <[email-masked]>
Date: Wed, 7 Apr 2004 18:30:40 -0700

Trevor,

Please define "specific response" as used below in the proposed
amendment to section 3.5.  Nowhere does this term appear in -13
of SCVP.

Mike

-----Original Message-----
From: Trevor Freeman [mailto:[email-masked]]
Sent: Wednesday, April 07, 2004 5:33 PM

The proposal is allowing cached responses and the presence or
absence of
the nonce indicates to the server if cached signed responses are
acceptable.
Trevor

-----Original Message-----
From: Michael Myers [mailto:[email-masked]]
Sent: Wednesday, April 07, 2004 4:09 PM

Mike

-----Original Message-----

Hi Dave,

3.5 requestNonce

The OPTIONAL requestNonce item contains a request identifier
generated by the SCVP client.  If the client includes a
requestNonce value in the request, it is expressing a
preference the SCVP server SHOULD return a specific response.
If the server returns a specific response it MUST include
the requestNonce from the request in the response, but MAY
return a cached success response which MUST NOT have a
requestNonce. If the client includes a requestNonce and
also sets a wantBack of id-swb-unique-resp-required, the
client is indicating that the SCVP server MUST return either
a specific response including the requestNonce or an error.
The client SHOULD include a requestNonce item in every request
to prevent an attacker from acting as a man-in-the-middle
by replaying old responses from the server.  The requestNonce
value
SHOULD change with every request sent by the client. The client
MUST
NOT include the wantBack of id-swb-unique-resp-required without
a
requestNonce, and a server receiving such a request SHOULD
return an invalidRequest error

Trevor

---

From: David Engberg <[email-masked]>
Date: Thu, 08 Apr 2004 07:46:14 -0400

Mike's right that my proposal was to allow unsigned responses for pure 
DPD (see my proposed change to Section 3, below), and also to permit 
caching for responses by making the RequestReference optional (Section 4).