Re: [TLS] TLS Protocol Version

[Martin Rex <mrex at sap.com>]

Blumenthal, Uri - 0662 - MITLL wrote:
> 
> Is it the only viable solution???

I am open to suggestions and improvements.

It is the best one that _I_ have found in the SSLv3/TLSv1.0
ServerHello PDU (there are not that much elements to choose from).

Since this signal is security relevant, *I* strongly prefer
that old servers are extremely unlikely to create this value by accident.


> 
> I am concerned of "overloading" fields and assigning an additional
> meaning to them that they did not have. Not a clean design or
> programming practice, and prone to causing people or code used
> to the "old" meaning to stumble.

In principle, I tend to agree.

However, we are actually changing several past revisions of a protocol
in a significant and purposely non-interoperable fashion -- because
that interoperability turned out to be a security problem.

I will try to provide sufficiently clear guidance to implementors
what this particular change means -- and only code which implements
the fix will ever be confronted with this changed semantics that
should _only_ be visible in the network transfer encoding.

It is really just method to compress an extra bit of information
representing a protocal change orthogonal to existing protocol
versions into the network transfer encoding of the
server_version element in the ServerHello PDU.

-Martin