Subject: [TLS] [Editorial Errata Reported] RFC8446 (6820)

From: RFC Errata System <[email-masked]>
Date: Fri, 21 Jan 2022 05:14:19 -0800 (PST)

The following errata report has been submitted for RFC8446,
"The Transport Layer Security (TLS) Protocol Version 1.3".

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You may review the report below and at:
https://www.rfc-editor.org/errata/eid6820

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Type: Editorial
Reported by: Leander Schwarz <[email-masked]>

Section: 6.2

Original Text
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unsupported_extension:  Sent by endpoints receiving any handshake
      message containing an extension known to be prohibited for
      inclusion in the given handshake message, or including any
      extensions in a ServerHello or Certificate not first offered in
      the corresponding ClientHello or CertificateRequest. 

Corrected Text
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unsupported_extension:  Sent by endpoints receiving any handshake
      message containing an extension in a ServerHello or Certificate
      not first offered in the corresponding ClientHello or 
      CertificateRequest.

Notes
-----
The definition of the unsupported_extension alert in section 6.2 contradicts the statements in section 4.2:

        If an implementation receives an extension
        which it recognizes and which is not specified for the message in
        which it appears, it MUST abort the handshake with an
   "illegal_parameter" alert.

While this might not be inconsistent due to the "abort the handshake with an X alert" specification at the beginning of section 6.2, it might lead to confusion. (see https://mailarchive.ietf.org/arch/msg/tls/hGOGWZRMg718mWqOZ06LwjV9360/).

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-------------
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RFC8446 (draft-ietf-tls-tls13-28)
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Title               : The Transport Layer Security (TLS) Protocol Version 1.3
Publication Date    : August 2018
Author(s)           : E. Rescorla
Category            : PROPOSED STANDARD
Source              : Transport Layer Security
Area                : Security
Stream              : IETF
Verifying Party     : IESG