[IPFIX] [Technical Errata Reported] RFC7011 (7413)

RFC Errata System <rfc-editor@rfc-editor.org> Sun, 02 April 2023 23:17 UTC

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Subject: [IPFIX] [Technical Errata Reported] RFC7011 (7413)
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The following errata report has been submitted for RFC7011,
"Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information".

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You may review the report below and at:
https://www.rfc-editor.org/errata/eid7413

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Type: Technical
Reported by: Michael Duggan <mwd@cert.org>

Section: 3.4.1

Original Text
-------------
Field Count

      Number of fields in this Template Record.

Corrected Text
--------------
Field Count

      Number of fields in this Template Record.  The Field Count MUST NOT be zero.

The sum of the Field Lengths of the Field Specifiers of a Template Record MUST NOT be zero.

Notes
-----
If the size of data record corresponding to a template can ever be zero, then  the only valid size for such a data set is the size of the set header.  For normal cases any size greater than that of the set header is a valid size, since records are read from a set until the number of octets remaining is less than the smallest possible record size for that set.  If a record size can be zero, then any number of bytes past the header cannot be padding (is not smaller than the smallest record), and a conforming implementation might return an infinite number of zero-sized records.  As this could cause a denial of service situation, rejecting templates that define zero-sized records seems to be the simplest solution.

Similar text may be necessary for Option Template records, though the fact that the scope count MUST be non-zero may negate the necessity.

Other possible fixes:
* Require all Field Specifiers to have a non-zero Field Length.  This may be an even simpler solution, but I can envision uses for zero-sized data elements, especially for elements that MAY be of variable length.
* Require a conforming implementation to reject or ignore data sets for zero-sized templates.

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RFC7011 (draft-ietf-ipfix-protocol-rfc5101bis-10)
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Title               : Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information
Publication Date    : September 2013
Author(s)           : B. Claise, Ed., B. Trammell, Ed., P. Aitken
Category            : INTERNET STANDARD
Source              : IP Flow Information Export
Area                : Operations and Management
Stream              : IETF
Verifying Party     : IESG