Re: [TLS] TLS 1.2 draft (issue #25 about SSLv2 Hello)

You could say that the random length MUST be between 16 and 32
bytes, and add that it SHOULD be 32 bytes.

Mike

Pasi.Eronen@nokia.com wrote:
>> Cleaned up backward compatibility text [issue 25]
> 
> This text (in E.2) still needs some cleaning. Currently
> it says:
> 
>    challenge_length
>        The length in bytes of the client's challenge to the server to
>        authenticate itself. Historically, permissible values are between
>        16 and 32 bytes inclusive. When using the SSLv2 backward
>        compatible handshake the client MUST use a 32-byte challenge.
> [...]
>    challenge
>        Corresponds to ClientHello.random. If the challenge length is
>        less than 32, the TLS server will pad the data with leading
>        (note: not trailing) zero bytes to make it 32 bytes long.
> 
> Which is not exactly consistent: if the challenge length MUST be 32
> bytes, it can't be less than 32 bytes.
> 
> It was also noted that for historical and/or compatibility reasons,
> many existing browsers (e.g. Opera, IE6, FireFox 1.5) use 16-byte
> challenges:
> 
> http://www1.ietf.org/mail-archive/web/tls/current/msg00985.html
> 
> My proposal (in the mail linked above) was to to change this to "The
> length of the challenge field in bytes; MUST be between 16 and 32
> (inclusive)."
> 
> Comments? (At the very least, the text needs to be internally
> consistent. Preferably it should also promote real-world
> interoperability and reflect what implementations are expected to do.)
> 
> Best regards,
> Pasi

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