Re: [TLS] cross-domain cache sharing and 0rtt

[Martin Thomson <[e-mail]>]

On 4 January 2017 at 15:29, Ilari Liusvaara <[e-mail]> wrote:
>> Naively, if s1 and s2 share cert and private key, and ignore the SNI, it
>> seems like redirecting a full handshake would work.  But I didn't think
>> about it very hard.
>
> Actually, I think it would work if you merely have cross-valid
> selected certs. No need to share private key or even ignore SNI.

That's almost ignoring SNI.  You are X but will accept a connection
for Y.  It's certainly true that you don't need to share keys, you
share valid credentials and are willing to use them.

Either way, your point is well made.  How servers identify themselves
is bound up in how they expect to be identified, which is often
ambiguous intentionally.

For example, it's common to have a single deployment configuration
across an entire cluster and to rely on SNI alone for picking a
certificate.  That way you simplify management and don't have to look
at IP addresses or anything like that.