Re: [Acme] Fixing the TLS-SNI challenge type

[Martin Thomson <[e-mail]>]

The confidentiality point was a minor one, certainly, but it would
represent an improvement.

TLS-SNI is a protocol already, but it's more complicated than it needs
to be.  Certificate generation is a pretty big lift compared to the
other challenges.


On Fri, Jan 12, 2018 at 2:29 PM, Jonathan Rudenberg
<[e-mail]> wrote:
>
>> On Jan 11, 2018, at 22:26, Martin Thomson <[e-mail]> wrote:
>>
>> If you are using a new protocol, all of the concerns Peter have come
>> into play.  If you are there, why wouldn't you do the challenge
>> validation within the new protocol rather than using the certificate
>> (which is sent in the clear in current TLS versions).  That might be
>> easier to implement than generating the self-signed certificate…
>
> I don’t think an entirely new protocol makes sense. In order to do the TLS/SNI/ALPN handshake a certificate is already sent in the ServerHello, so there’s no reason not to use it to transport the authorization token. Generating a self-signed certificate is trivial, and I’m not aware of any relevant security concerns around fetching the authorization in the clear (the dns-01 and http-01 challenge types are plaintext as well).