On 17/01/17 15:34, Paul Wouters wrote:
<snip>
So I think there might be a different perception here of the goal of
CT. I think you are looking at a 100% catch-before-it-happens
scenario. While the document is only about "exposing rogue parties".
<snip>
So personally, I would like to know that ACME-style issued certificates
would start being accepted within a few minutes. At least for those
sites that did not have a certificate before. If we are talking about
renewing, then it should be able to properly submit new entries to log
before actually activating the new certs, so some latency wouldn't matter.
Forking the thread to propose an idea:
Let a domain owner specify (perhaps via an extension to the proposed
Expect-CT HTTP header?) the minimum age of each SCT that TLS clients may
accept when establishing TLS connections to servers within that domain
space. (I'm imagining that minimum SCT ages would typically be measured
in days, rather than weeks or months).
This mechanism would transform CT from a detection system to a
prevention system. Well, sort of. Since each cert for that domain
space would have to be publicly logged some number of days in advance of
it being used, the legitimate domain owner would have a window of
opportunity to detect a misissued cert (and request that it be revoked)
before an attacker could actually use it for their nefarious purposes.
Of course, the downside of this mechanism is that it's a footgun. If a
domain owner forgets to obtain a cert and to publicly log it
sufficiently far in advance, there will be a period of time during which
they can't serve a compliant cert to TLS clients, even if they have a
correctly issued cert ready to go.
Any comments?
--
Rob Stradling
Senior Research & Development Scientist
COMODO - Creating Trust Online
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