Re: [TLS] Application state binding with TLS session state

At Fri, 7 Sep 2007 12:36:24 +0300,
<Pasi.Eronen@nokia.com> wrote:
> 
> Binding of application state to TLS session applies not only 
> to 4507bis, but ordinary TLS session resumption as well.
> 
> Current TLS implementations usually have some kind of APIs that 
> allow applications to store application-specific data in the TLS 
> session cache entry (e.g., SSL_SESSION_set_ex_data() in OpenSSL 
> and SSLSession.putValue() in Java JSSE), but this is not really
> mentioned anywhere in the TLS RFCs.
> 
> As long as this is purely a local implementation detail, maybe 
> it even doesn't need to be mentioned in protocol standards...
> But if some application protocols would start assuming that
> this feature exists (in a way that has to be implemented in TLS
> layer, and can't be implemented by the application calling TLS),
> then things become more complicated...

Pasi's assessment looks right to me as well.

- This can only be used for soft state, because neither client or
  server is required to offer/accept resumption.
- This doesn't affect the wire protocol at all for ordinary resumption.
- RFC 4507 resumption does affect the wire protocol in the sense
  that the tickets change, but since they're opaque the client
  does not need to understand the ticket, so it should be 
  interoperable in either case.
- No stack support is actually required with ordinary resumption 
  because the app can simply store its own data keyed by the
  session ID.
- Stack support is required with 4507-style resumption, because
  the data has to be stored in the ticket.

-Ekr

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