Design Considerations for Metadata Insertion
RFC 8165

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Internet Engineering Task Force (IETF)                         T. Hardie
Request for Comments: 8165                                      May 2017
Category: Informational
ISSN: 2070-1721

              Design Considerations for Metadata Insertion

Abstract

   The IAB published RFC 7624 in response to several revelations of
   pervasive attacks on Internet communications.  This document
   considers the implications of protocol designs that associate
   metadata with encrypted flows.  In particular, it asserts that
   designs that share metadata only by explicit actions at the host are
   preferable to designs in which middleboxes insert metadata.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc8165.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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RFC 8165      Design Considerations for Metadata Insertion      May 2017

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................2
   3. Design Pattern ..................................................2
   4. Advice ..........................................................3
   5. Deployment Considerations .......................................4
   6. IANA Considerations .............................................5
   7. Security Considerations .........................................5
   8. References ......................................................6
      8.1. Normative References .......................................6
      8.2. Informative References .....................................6
   Acknowledgements ...................................................7
   Author's Address ...................................................7

1.  Introduction

   To minimize the risks associated with pervasive surveillance, it is
   necessary for the Internet technical community to address the
   vulnerabilities exploited in the attacks documented in [RFC7258] and
   the threats described in [RFC7624].  The goal of this document is to
   address a common design pattern that emerges from the increase in
   encryption: explicit association of metadata that would previously
   have been inferred from the plaintext protocol.

2.  Terminology

   This document makes extensive use of standard security and privacy
   terminology; see [RFC4949] and [RFC6973].  Readers should be familiar
   with the terms defined in [RFC6973], including "Eavesdropper",
   "Observer", "Initiator", "Intermediary", "Recipient", "Attack" (in a
   privacy context), "Correlation", "Fingerprint", "Traffic Analysis",
   and "Identifiability" (and related terms).  Readers should also be
   familiar with terms that are specific to the attacks discussed in
   [RFC7624], including "Pervasive Attack", "Passive Pervasive Attack",
   "Active Pervasive Attack", "Observation", "Inference", and
   "Collaborator".

3.  Design Pattern

   One of the core mitigations for the loss of confidentiality in the
   presence of pervasive surveillance is data minimization, which limits
   the amount of data disclosed to those elements absolutely required to
   complete the relevant protocol exchange.  When data minimization is
   in effect, some information that was previously available may be
   removed from specific protocol exchanges.  The information may be
   removed explicitly (for example, by a browser suppressing cookies

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RFC 8165      Design Considerations for Metadata Insertion      May 2017

   during private modes) or by other means.  As noted in [RFC7624], some
   topologies that aggregate or alter the network path also act to