Re: [lamps] Revocation Request Format?

[Tim Hollebeek <[e-mail]>]

One thing I would consider doing if I found myself in this situation is to take a fresh, signed OCSP response along with some text like REVOKE THIS CERTIFICATE and sign it with the private key for the certificate in question.

 

Haven’t done a full security analysis of the pros/cons but I thought I’d throw it out there.  It has some nice information about exactly which certificate and exactly when I made the request, and that it was made by someone with access to the private key.

 

It seems like a better idea than abusing a CSR for an unintended purpose.  Abusing signed messages for purposes they weren’t designed for usually ends badly.

 

-Tim

 

From: Spasm [mailto:[e-mail]] On Behalf Of Ryan Sleevi
Sent: Friday, March 2, 2018 9:08 AM
To: Phillip Hallam-Baker <[e-mail]>
Cc: SPASM <[e-mail]>
Subject: Re: [lamps] Revocation Request Format?

 

It seems signing a new CSR has been a common practice as proof of possession.

 

There's one segment of users that want to have a time-constrained request (that is, incorporating a challenge/response), while another would prefer that you can generate the 'request to revoke' at the same time you request the cert, so that you can use this token for situations such as loss of private key (but not loss of revocation token)

 

It doesn't seem like there needs to be a bespoke format here, considering that the industry is still working through its use cases, and any signed data is sufficient.

 

Further, it may do harm to try and standardize that. Consider the ROBOT attack ( https://robotattack.org/ ), which presented a signing oracle with TLS private keys. Prematurely constraining revocation requests to a particular format might otherwise preclude reasonable demonstration of private key compromise.

 

So I don't think there's anything for LAMPS to do here - we have ample available technology (running code that already works) and we have not yet ascertained industry needs in any meaningful way (no rough consensus for something new)

 

On Fri, Mar 2, 2018 at 9:24 AM, Phillip Hallam-Baker <[e-mail] <mailto:[e-mail]> > wrote:

Do we have a PKIX revocation request format?

 

I am asking because of a detail in the Trustico situation in which a file of 23K private keys was emailed to a CA to request revocation.

 

At the point, the circumstances of that situation are not clear. But I can see a scenario in which it is entirely plausible that a CA reseller would have access to large numbers of TLS private keys and that is when they are either hosting or managing the Web sites.

 

The management interfaces that allow Web sites to be wheeled around a data center have become very sophisticated of late with virtualization and much of that infrastructure is 'secret sauce'.

 

What might appear to be a five racks of 100 separate machines is likely visible in the management console as one single entity.


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