Re: [TLS] Open issue: Record Version Numbers

[Eric Rescorla <ekr@xxxxxxxxxxxxxxxxxxxx>]

Eric Rescorla <ekr@xxxxxxxxxxxxxxxxxxxx> writes:

> Yngve Petterson has pointed out [0] that there is some confusion
> in how to interpret what version numbers ought to appear in
> the ClientHello record in TLS handshakes. The issue is that
> there are two numbers:
>
> - the record version number
> - the client hello version number
>
> The text is quite clear that the second of these should be the
> highest version you support. However, the text for the secodn
> reads:

I had it pointed out to me in private that these are contradictory.
This should read:

  The text is quite clear that the second of these should be the
  highest version you support. However, the text for the first
  reads:


>    "TLS clients who wish
>    to negotiate with SSL 3.0 servers should send client hello messages
>    using the SSL 3.0 record format and client hello structure, sending
>    {3, 1} for the version field to note that they support TLS 1.0".	
>
> I read this text as saying that if you are a client who supports TLS 1.0
> and SSLv3, you should in general send the following values:
>
> - record version number           {3, 0} (SSLv3)
> - client hello version number     {3, 1} (TLSv1)
>
> If the server decides to accept TLS 1.0, it should respond with the
> following values:
>
> - record version number           {3, 1} (TLSv1)
> - client hello version number     {3, 1} (TLSv1)
>
> Pettersen reports that in some cases this causes errors because servers
> (inexplicably) use the record version in the negotiation.  However, I
> think at the end of the day, that's a clear implementation error
> and the spec should just clarify that the above behavior is what's
> expected.

-Ekr

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