[TLS] [Technical Errata Reported] RFC5705 (4395)

RFC Errata System <rfc-editor@rfc-editor.org> Tue, 16 June 2015 20:06 UTC

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Date: Tue, 16 Jun 2015 13:04:07 -0700 (PDT)
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Subject: [TLS] [Technical Errata Reported] RFC5705 (4395)
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The following errata report has been submitted for RFC5705,
"Keying Material Exporters for Transport Layer Security (TLS)".

--------------------------------------
You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=5705&eid=4395

--------------------------------------
Type: Technical
Reported by: Rick van Rein <rick@openfortress.nl>;

Section: 4

Original Text
-------------
   If no context is provided, it then computes:

           PRF(SecurityParameters.master_secret, label,
               SecurityParameters.client_random +
               SecurityParameters.server_random
               )[length]

   If context is provided, it computes:

           PRF(SecurityParameters.master_secret, label,
               SecurityParameters.client_random +
               SecurityParameters.server_random +
               context_value_length + context_value
               )[length]


Corrected Text
--------------
   If no context is provided, it then computes:

           PRF(SecurityParameters.master_secret, label,
               SecurityParameters.client_random +
               SecurityParameters.server_random
               )[0..length-1]

   If context is provided, it computes:

           PRF(SecurityParameters.master_secret, label,
               SecurityParameters.client_random +
               SecurityParameters.server_random +
               context_value_length + context_value
               )[0..length-1]


Notes
-----
The current notation is not in line with that of RFC 5246, where the [0..N-1] notation is used on a PRF outcome in Sections 7.4.9 and 8.1 and similar [A..B] notation is also used elsewhere.  This makes me believe that the current text is technically wrong, and not in line with the intentions stated informally below it,

   The output is a pseudorandom bit string of length bytes generated
   from the master_secret.

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--------------------------------------
RFC5705 (draft-ietf-tls-extractor-07)
--------------------------------------
Title               : Keying Material Exporters for Transport Layer Security (TLS)
Publication Date    : March 2010
Author(s)           : E. Rescorla
Category            : PROPOSED STANDARD
Source              : Transport Layer Security
Area                : Security
Stream              : IETF
Verifying Party     : IESG