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Re: [TLS] Protocol version for inappropriate_fallback alerts

Florian Weimer <fweimer@redhat.com> Tue, 11 November 2014 17:16 UTC

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Date: Tue, 11 Nov 2014 18:13:29 +0100
From: Florian Weimer <fweimer@redhat.com>
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To: Bodo Moeller <bmoeller@acm.org>, "tls@ietf.org" <tls@ietf.org>
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Subject: Re: [TLS] Protocol version for inappropriate_fallback alerts
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On 11/11/2014 04:52 PM, Bodo Moeller wrote:
> Florian Weimer <fweimer@redhat.com <mailto:fweimer@redhat.com>>:
>
>     Section 3 still does not mention which version to put into the
>     inappropriate_fallback alert message.
>
>
> Good point; it can't hurt to be completely explicit about this.
>
> Proposed new wording:
>
>     o If TLS_FALLBACK_SCSV appears in ClientHello.cipher_suites and the
>     highest protocol version supported by the server is higher than the
>     version indicated in ClientHello.client_version, the server MUST
>     respond with a fatal inappropriate_fallback alert *(unless it
>     responds with a fatal protocol_version alert because the version
>     indicated in ClientHello.client_version is unsupported). The record
>     layer version number MUST be set to ClientHello.cipher_suites for
>     this alert (as it would for the Server Hello message if the server
>     was continuing the handshake)*.

The final ClientHello.cipher_suites should be ClientHello.client_version.

-- 
Florian Weimer / Red Hat Product Security

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