Re: [TLS] [Emu] Fwd: Benjamin Kaduk's Discuss on draft-ietf-emu-eap-tls13-13: (with DISCUSS and COMMENT)

[Benjamin Kaduk <[e-mail]>]

On Mon, Feb 01, 2021 at 06:21:16AM +0000, Peter Gutmann wrote:
> Alan DeKok <[e-mail]> writes:
> 
> >OpenSSL has a feature SSL_MODE_AUTO_RETRY which makes it process TLS messages
> >*after* the Finished message. i.e. the Session Ticket, etc. When an
> >application calls SSL_Read(), all of the TLS data is processed, instead of
> >just the "TLS finished" message. They've made this the default, because most
> >applications get it wrong.
> 
> Asking as the author of a TLS library that has always done this, why would you
> stop immediately after the Finished and leave metadata messages sitting unread
> in the input stream?  Was it just some arbitrary implementation decision, or
> is there a technical reason for it?

I expect (but did not attempt to validate) that this was SSLeay-vintage logic
involving only reading a single record from the wire per call to
SSL_read().  If that record was a handshake record and not application
data, well, then the SSL_read() didn't do something useful and so the
special "try again" code was returned and the application was supposed to
call SSL_read() again.

There's no technical reason that I'm aware of.

-Ben