Re:Let's Encrypt Has Issued a Billion Certificates
by tialaramex on Thursday February 27, 2020 @03:44PM
(#22437611)
If the certificate wasn't submitted to an otherwise trustworthy CT log server then there's no way to provide an SCT ("Signed Certificate Timestamp") for a qualified CT log server. Some browsers (including Chrome and Safari) expect to be shown qualified SCTs for certificates issued after a certain date.
The SCT is signed by the log, so if you want them to lie you'd need to control enough logs to get enough qualified SCTs. Bad news, for Chrome that means it must include a Google log, which means now you're asking Google to conspire against themselves.
For now you could sidestep this by issuing bogus certificates with back-dated issuance dates. But that will stop working once those dates are too long ago for a certificate to still be valid. I think that happens some point later this year or in 2021 maybe? If you show Chrome (perhaps other browsers but I've read the code in Chrome) a certificate in which the lifespan (between NotBefore and NotAfter) exceeds the maximum permissible lifespan at that issuance date, it treats the certificate as invalid anyway.
The SCT is signed by the log, so if you want them to lie you'd need to control enough logs to get enough qualified SCTs. Bad news, for Chrome that means it must include a Google log, which means now you're asking Google to conspire against themselves.
For now you could sidestep this by issuing bogus certificates with back-dated issuance dates. But that will stop working once those dates are too long ago for a certificate to still be valid. I think that happens some point later this year or in 2021 maybe? If you show Chrome (perhaps other browsers but I've read the code in Chrome) a certificate in which the lifespan (between NotBefore and NotAfter) exceeds the maximum permissible lifespan at that issuance date, it treats the certificate as invalid anyway.