> On 13 Jan 2017, at 15:45, Nick Coghlan <ncogh...@gmail.com> wrote:
>
> So the essential stack would look like:
>
> TLSConfig[uration?]: implementation independent, settings only
> TLSClientContext: ABC to combine settings with a specific TLS implementation
> TLSServerContext: ABC to combine settings with a specific TLS implementation
> TLSSocket: ABC to combine a context with a network socket
> TLSBuffer: ABC to combine a context with a pair of data buffers
>
> And then TLSPolicy would be a potential future implementation
> independent addition that could be used to constrain acceptable TLS
> configurations.
If we were going this way, I’d want to add one extra caveat: I think I’d want
the Contexts to become immutable.
The logic for the SNI callback would then become: you are called with the
Context that created the socket/buffer, and you return a Configuration object
that contains any changes you want to make, and the Context applies them if it
can (or errors out if it cannot). A new Context is created. This relegates
Context to the role of “socket/buffer factory”. The advantage of this is that
we have vastly reduced the moving parts: a Context can ensure that, once
initiated, the Policy that belongs to it will not change under its feet. It
also allows the Context to refuse to change settings that a given concrete
implementation cannot change in the SNI callback.
Essentially, the logic in the callback would be:
def sni_callback(buffer, hostname, context):
# This creates a writable copy of the configuration: it does not
# mutate the original.
configuration = context.configuration
configuration.certificates = certs_for_hostname(hostname)
configuration.inner_protocols = [NextProtocol.H2, NextProtocol.HTTP1]
return configuration
This would almost certainly make Context implementation easier, as there is no
longer a requirement to monitor your configuration and support live-updates.
Cory
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