On 04/06/15 13:19, Simone Bordet wrote:
Hi,
On Wed, Jun 3, 2015 at 8:23 AM, Xuelei Fan <xuelei....@oracle.com> wrote:
Per section 4, RFC 7301:
"... The
"application_layer_protocol_negotiation" ServerHello extension is
intended to be definitive for the connection (until the connection is
renegotiated) and is sent in plaintext to permit network elements to
provide differentiated service for the connection when the TCP or UDP
port number is not definitive for the application-layer protocol to
be used in the connection. By placing ownership of protocol
selection on the server, ALPN facilitates scenarios in which
certificate selection or connection rerouting may be based on the
negotiated protocol."
Per my understanding, application protocol should be negotiated before
cipher suite and protocol version negotiated.
This is not possible for HTTP/2.
Application protocol negotiation MUST happen *after* the TLS protocol
and the TLS cipher are negotiated.
What do you mean by "after"? As far as TLS is concerned, all of this
negotiation happens in one negotiation. The client proposes a list of
ciphers and application protocols. The server chooses a cipher
and application protocol and sends back its choices.
The HTTP/2 RFC specifically warns against splitting this negotiation
with the example that a client could propose a mandatory TLS 1.2 cipher,
but which is black-listed by HTTP/2. If (internally) the server chooses
that cipher first,
without knowing the application protocol is going to be HTTP/2
then you end up with a non-compliant connection that will probably have
to be closed for reason of insufficient security.
- Michael
And the connection may be
rerouted (even to different machines) for further operation. The
requested application protocols list should be the only information for
the selection of a suitable application protocol.
Not sure what you exactly mean here, but you can't pick the HTTP/2
protocol unless you have the TLS protocol and TLS cipher available.
So *only* the list of protocol sent by the client is not enough for
HTTP/2, we would need additional contextual information.
What a HTTP/2 aware load balancer written in Java that offloads TLS
would need to do is to negotiate the TLS protocol, negotiate the TLS
cipher, *then* negotiate the application protocol (whether "h2" or
"http/1.1"), and with the last information pick a backend server,
typically forwarding clear text bytes to the backend.
Thanks !
