[TLS] record-level version number in ClientHello

[Manuel Pégourié-Gonnard <[e-mail]>]

[changing the subject line this it has nothing to do with RFC 7366]

On 01/11/2014 22:58, Christian Kahlo wrote:
>> IIRC, I found out that it doesn't like 03 00 as the record-level
>> version number in the ClientHello. I was able to connect by setting the
>> minimum version of my test client to TLS 1.0, which upped the record-
>> level version number of the ClientHello to 03 01.
> 
> Yes, SSLv3 is explicitly unsupported. As there is no handshake back-
> ward compatibility with SSLv3 "03 00" is forbidden at the record level.
> 
I certainly agree about not supporting SSLv3 at all, but I'm not convinced
rejecting record-level 03 00 this is the best thing to do . In practice this
mostly means rejecting clients that want to interoperate with old servers.

My interpretation of the last paragraph of RFC 5246 E.1 below

   TLS clients that wish to negotiate with older servers MAY send any
   value {03,XX} as the record layer version number.  Typical values
   would be {03,00}, the lowest version number supported by the client,
   and the value of ClientHello.client_version.  No single value will
   guarantee interoperability with all old servers, but this is a
   complex topic beyond the scope of this document.

is life is already complicated enough for clients, and servers should help them
by accepting any half-sensible value here (it's always time to be stricter later).

Just my opinion.

Manuel.