Re: [lamps] Review comment from the AD

Jim:

The CA that issued the certificate to the TSA should revoke that certificate if the TSA is compromised.  So, I think that the revocation checking on the TSA certification path is enough.

Russ

> On Sep 27, 2017, at 6:04 PM, Jim Schaad <ietf@augustcellars.com> wrote:
> 
> Yes, but if the time-stamp authority has been compromised, then it is no
> longer a good authority.  So perhaps some extra guidance is needed about
> doing two checks or something.
> 
> Jim
> 
> 
> 
>> -----Original Message-----
>> From: Russ Housley [mailto:housley@vigilsec.com]
>> Sent: Wednesday, September 27, 2017 11:56 AM
>> To: Jim Schaad <ietf@augustcellars.com>
>> Cc: SPASM <spasm@ietf.org>
>> Subject: Re: [lamps] Review comment from the AD
>> 
>> I think this text was supposed to say that SigningTime is the clock value
> of the
>> signer, which might be very wrong.  One might rely on a time-stamp
>> authority [RFC3161], if there is a valid attribute from one in the
> message.
>> Otherwise, the time that the message arrived in your mailbox is the best
>> guess that you have.
>> 
>> Russ
>> 
>> 
>>> On Sep 27, 2017, at 2:40 PM, Jim Schaad <ietf@augustcellars.com> wrote:
>>> 
>>> I have one review comment from EKR on rfc5750bis that I am not sure
>>> what to do with.
>>> 
>>> The following paragraph from Section 6 - Security Considerations
>>> 
>>> When determining the time for a certificate validity check, agents
>>>  have to be careful to use a reliable time.  Unless it is from a
>>>  trusted agent, this time MUST NOT be the SigningTime attribute found
>>>  in an S/MIME message.  For most sending agents, the SigningTime
>>>  attribute could be deliberately set to direct the receiving agent to
>>>  check a CRL that could have out-of-date revocation status for a
>>>  certificate, or cause an improper result when checking the Validity
>>>  field of a certificate.
>>> 
>>> The problem is two-fold:
>>> 1. Should the definition of trusted agent be expanded to be more
>>> clear, and 2. Should that sentence just be deleted because, even if it
>>> is a trusted agent, a compromised key is going to be able to lie about
> the
>> time anyway.
>>> 
>>> My memory was that this text was supposed to deal with things like
>>> time-stamp agents where the time was significant, but it could be wrong.
>>> 
>>> Jim
>>> 
>>> 
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> 
> 
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