Subject: [Trans] [trans] #146 (gossip): SCT Feedback doesn't account for privacy-sensitive EE certs

From: "trans issue tracker" <[email-masked]>
Date: Wed, 09 Dec 2015 22:04:04 -0000

#146: SCT Feedback doesn't account for privacy-sensitive EE certs

 I think [https://tools.ietf.org/html/draft-ietf-trans-
 gossip-01#section-7.1.3 Section 7.1.3 of Gossip]'s requirement that "the
 'x509_chain' element MUST contain at least the leaf certificate" would
 leak private information in some cases. SCT Feedback should probably be
 extended to handle [https://tools.ietf.org/html/draft-ietf-trans-
 rfc6962-bis-11#section-4.2 name redaction] and
 [https://tools.ietf.org/html/draft-ietf-trans-rfc6962-bis-11#section-4.3
 name-constrained intermediate CAs].

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-------------------------+-------------------------------------------------
 Reporter:               |      Owner:  draft-ietf-trans-threat-
  [email-masked]   |  [email-masked]
     Type:  defect       |     Status:  new
 Priority:  major        |  Milestone:
Component:  gossip       |    Version:
 Severity:  -            |   Keywords:
-------------------------+-------------------------------------------------

Ticket URL: <https://trac.tools.ietf.org/wg/trans/trac/ticket/146>
trans <https://tools.ietf.org/trans/>

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From: "trans issue tracker" <[email-masked]>
Date: Fri, 11 Dec 2015 15:29:23 -0000

Comment (by [email-masked]):

 What cases would it leak in?

 Note that 7.1.3 is talking about what is sent back to the server the
 certificate allegedly came from in the first place...

 Severity:  -            |  Resolution:
 Keywords:               |

Ticket URL: <https://trac.tools.ietf.org/wg/trans/trac/ticket/146#comment:1>
trans <https://tools.ietf.org/trans/>

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From: "trans issue tracker" <[email-masked]>
Date: Fri, 11 Dec 2015 17:04:15 -0000

Comment (by [email-masked]):

 No, I agree.  Not because the server doesn't know about the certificate,
 but because the server is expected to share that exact same data with
 Auditors (either pushing the data or making available for polling.)

 So I'm wondering: should clients not post redacted certificates to the
 servers they came from.... or should servers be expected to hide their
 redacted certificates from auditors?

 I lean towards the latter.
 a) If a server was attacked, their should get the details of that attack,
 not have it hidden by an attacker who chose to get a redacted SCT
 b) the server wants to keep the data private, they can do the extra work

Ticket URL: <https://trac.tools.ietf.org/wg/trans/trac/ticket/146#comment:2>
trans <https://tools.ietf.org/trans/>