RE: [dss] XML time-stamp processing text for time-stamp profile

[Carlos González-Cadenas <gonzalezcarlos@netfocus.es>]

Dear all,

BTW with the XML timestamp definition in the core, have you considered to
protect the TSA's signing certificate (as 3161 mandates for CMS timestamps)
to avoid certificate replacement attacks?. I would include that in the
<ds:SignedInfo>/<ds:Reference> (lines 1879-1882)

<ds:SignedInfo>/<ds:Reference> [Required]
There MUST be a single <ds:Reference> element whose URI attribute references
the <ds:Object> containing the enveloped <TstInfo> element, and whose Type
attribute is equal to
urn:oasis:names:tc:dss:1.0:core:schema:XMLTimeStampToken.

Kind regards,

Carlos


Carlos González-Cadenas
Chief Security Officer

netfocus
Diagonal 188-198 Planta 2
08018 Barcelona
tel: 902 303 393
fax: 902 303 394
gonzalezcarlos@netfocus.es
www.netfocus.es 
-----Mensaje original-----
De: Juan Carlos Cruellas [mailto:cruellas@ac.upc.edu] 
Enviado el: domingo, 14 de mayo de 2006 20:19
Para: 'OASIS DSS TC'
Asunto: [dss] XML time-stamp processing text for time-stamp profile

Dear all,

Please find attached a proposal for details on text to be included 
within the time-stamp profile dealing with the basic processing for XML 
time-stamp for both SignRequest and VerifyRequest. I have taken the 
document of the profile, emptied all the sections and add what I think 
there should be the two new sections in order to facilitate the editor 
their inclusion in the final document. Nevertheless, I also copy below 
the text for facilitating comments in emails.

New section 3.3 (section 3 corresponds to profile of Signing Protocol. 
The text gives details on how the server should proceed for generating a 
XML time-stamp.
-------
3.3 Processing for XML time-stamps
If the <dss:SignatureType> content is 
“oasis:names:tc:dss:1.0:core:schema:XMLTimeStampToken” or when this 
element is not present and the server decides to generate a XML 
time-stamp, it MUST follow the rules established in the core for 
generating digital signatures (section 3.3 of [DSSCore]) with the 
changes mentioned below.
The server MUST perform the following steps between steps 2 and 3 of 
[DSSCore] section 3.3.1:
2.a Generate a dss:TSTInfo element as defined in [DSSCore] section 5.1.2 
with the suitable contents, and envelope it within a new ds:Object.
2.b Generate a new ds:Reference element referencing (explicitly or 
implicitly) the aforementioned ds:Object enveloping the TSTInfo. Set its 
“Type” attribute to 
“urn:oasis:names:tc:dss:1.0:core:schema:XMLTimeStampToken”.
2.c Insert this ds:Reference element within the ds:SignedInfo and the 
ds:Object element within the resulting ds:Signature element as mandated 
by [XMLSig]
----------------


New section 4.3. Section 4 corresponds to Verifying Protocol. The text 
gives details on how the server should proceed for verifying a XML 
time-stamp.


------------------
4.3 Processing for XML time-stamps
When receiving a dss:VerifyRequest requesting a XML time-stamp token 
verification the server MUST proceed as follows:
1.	Extract the dss:TimeStamp element from the dss:SignatureObject
element.
2.	Proceed as indicated in section 4.3.2.2 steps 2 to 6 (both included)

of [DSSCore]. This ensures that the arrived signature is a XML 
time-stamp as defined in [DSSCore] section 5.1.2 and that it envelopes 
and signs the corresponding dss:TSTInfo element.
3.	Proceed as indicated in section 4.3 steps 2 to 4 (both included) of 
[DSSCore] for each of the rest of ds:Reference elements within the 
ds:SignedInfo element. This will allow the server to retrieve the 
time-stamped documents from the corresponding ds:Reference elements, to 
extract them from the request, to validate their digests, to verify the 
signature value, and to generate the corresponding result value.

------------------

REMAINING ISSUE: Steps 2 to 4 in 4.3 contains details on how the server 
should proceed in case the ds:Signature (which is now a time-stamp) is 
an enveloped signature.... should we then clarify in the text of the 
time-stamp profile that this will not be possible ever for this kind of 
signatures?



Regards

Juan Carlos.