Security Area Working Group                                M. Richardson
Internet-Draft                                  Sandelman Software Works
Updates: 4949 (if approved)                                   J. Hoyland
Intended status: Informational                           Cloudflare Ltd.
Expires: 16 June 2025                                   13 December 2024


                  A taxonomy of eavesdropping attacks
                draft-richardson-saag-onpath-attacker-04

Abstract

   The terms on-path attacker and MITM Attack have been used in a
   variety of ways, sometimes interchangeably, and sometimes meaning
   different things.

   Increasingly people have become uncomfortable with the gendered term
   "Man" in the middle and have sought alternatives.

   This document offers an update on terminology for network attacks,
   retaining some acronyms terms while redefining the expansion, and
   clarifying the different kinds of attacks.  Consistent terminology is
   important in describing what kinds of attacks a particular protocol
   defends against, and which kinds the protocol does not.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 16 June 2025.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://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 Revised BSD License text as
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Three kinds of attack . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Active On-Path Attacker, or Meddler in the Middle
           (MITM)  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Passive On-Path attack  . . . . . . . . . . . . . . . . .   4
     2.3.  Passive On-Path attack with bypass  . . . . . . . . . . .   5
     2.4.  Passive Off-path attacker . . . . . . . . . . . . . . . .   5
   3.  Existing uses of the terms  . . . . . . . . . . . . . . . . .   6
     3.1.  IETF QUIC terms . . . . . . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Changelog . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Appendix A.  Monster in the Middle  . . . . . . . . . . . . . . .   7
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   A number of terms have been used to describe attacks against
   networks.

   In the [dolevyao] paper, the attacker is assumed to be able to:

   *  view messages as they are transmitted

   *  selectively delete messages

   *  selectively insert or modify messages

   Some authors refer to such an attacker as an "on-path" attacker
   [reference], or a "Man-in-the-Middle" [reference].





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   Despite a broad consensus on what is meant by a MITM attack, there is
   less agreement on the how to describe its variants.  The term
   "passive attacker" has been used in many cases to describe situations
   where the attacker can only observe messages, but can not intercept,
   modify or delete any messages.

   Another variant is the case where an eavesdropper is not on the
   network path between the actual correspondants, and thus cannot drop
   messages, they may be able to inject packets faster than the
   correspondants, and thus beat legitimate packets in a race.

   As summarised, there are three broad variations of the MITM attacker:

   1.  An on-path attacker that can view, delete and modify messages.
       This is the Dolev-Yao attack.

   2.  An off-path attacker that can view messages and insert new
       messages.

   3.  An off-path attacker that can only view messages.

2.  Three kinds of attack

   The attacks are numbered in this section as no consensus on naming
   the attacks yet.  In the diagrams below, the sender is named "Alice",
   and the recipient is named "Bob", as is typical in many cryptographic
   protocols [alicebob], as first introduced by [digisign].

   Alice and Bob were named as expansions of "A" and "B", which would
   otherwise be very abstract concepts of the two end points.

   The attacker has historically been named "Mallory", but this document
   proposes that the expansion be named "Meddler"

   (Artwork only available as ASCII-ART: see
   https://www.ietf.org/archive/id/draft-richardson-saag-onpath-
   attacker-04.html)

                   Figure 1: Alice communicating with Bob

2.1.  Active On-Path Attacker, or Meddler in the Middle (MITM)

   In this attack, the attacker is involved with the forwarding of the
   packets.  A firewall or network router is ideally placed for this
   attack.






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      .-------.      ╭─────────╮      .-----.
      | Alice |──────│ Meddler │─────>| Bob |
      '-------'      ╰─────────╯      '-----'

                         Figure 2: On Path Attacker

   In this case the Meddler can:

   *  view all packets

   *  selectively forward or drop any packet

   *  modify any packets that is forwarded

   *  insert additional packets

2.2.  Passive On-Path attack

   In this attack, the attacker is not involved with the forwarding of
   the packets.  The attacker receives a copy of packets that are sent
   along the path.  This could be from, for instance, a mirror port or
   SPAN [span].  Alternatively, a copy of traffic may be obtained via
   passive (optical) tap [fibertap].  This kind of attack is often
   associated with Pervasive Monitoring [RFC7258].

      .-------.                       .-----.
      | Alice |──────────────────────>| Bob |
      '-------'           |           '-----'
                          |
                          v
                     ╭─────────╮
                     │ Meddler │
                     ╰─────────╯

                      Figure 3: Passive On-Path attack

   In this the meddler can:

   *  view all packets

   Note that they have no way to inject new packets, and this attack may
   occur seconds to decades after the data was exchanged.









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2.3.  Passive On-Path attack with bypass

   In some cases, the Meddler is be able to send messages to Bob via
   another route.  Due to some other factor (such as shorter or higher
   cost routing), these messages arrive at Bob prior to the original
   message from Alice.

      .-------.                 ╭──╮       .-----.
      | Alice |──────────────╮  │  │   ╭──>| Bob |
      '-------'     |        │  │  │   │   '-----'
                    |        │  │  ╰───╯      ^
                    v        │  │             │
               ╭─────────╮   ╰──╯             │
               │ Meddler │────────────────────╯
               ╰─────────╯

                Figure 4: Passive On-Path attack with bypass

   In that the Meddler can:

   *  view all packets

   *  insert additional/copied packets into the stream

   But the Meddler is unable to drop or modify the original packets.
   Bob however, may be unable to distinguish packets from Alice vs
   packets sent from the Meddler that purport to be from Alice.

   To be effective or useful, this type of attack needs to occur in real
   time.

2.4.  Passive Off-path attacker

   The third kind of attack is one in which the Meddler can not see any
   packets from Alice.  This is usually what is meant by an "off-path"
   attack.  The meddler can forge packets purporting to be from Alice,
   but can never see Alice's actual packets.

      .-------.                           .-----.
      | Alice |──────────────────────────>| Bob |
      '-------'                           '-----'
                                             ^
                                             │
               ╭─────────╮                   │
               │ Meddler │───────────────────╯
               ╰─────────╯

                    Figure 5: Passive Off-path attacker



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   In this the Meddler can:

   *  insert additional packets

3.  Existing uses of the terms

3.1.  IETF QUIC terms

   [quic] ended up the following taxonomy:

   on-path:  [Dolev-Yao] MITM, Active On-Path attacker

   Limited on-path (cannot delete):  Active Off-Path attacker

   Off-path:  Passive Off-Path attacker

4.  Security Considerations

   This document introduces a set of terminology that will be used in
   many Security Considerations sections.

5.  IANA Considerations

   This document makes no IANA requests.

6.  Acknowledgements

   The SAAG mailing list.

7.  Changelog

8.  References

8.1.  Normative References

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
              <https://www.rfc-editor.org/rfc/rfc4949>.

8.2.  Informative References

   [alicebob] "Alice and Bob", 2020,
              <https://en.wikipedia.org/wiki/Alice_and_Bob>.

   [alliteration]
              "Council of Attackers", 2020,
              <https://mailarchive.ietf.org/arch/msg/saag/
              R0uevzT0Vz9uqqaxiu98GtK1rks/>.



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   [digisign] Rivest, R. L., Shamir, A., and L. Adleman, "A method for
              obtaining digital signatures and public-key
              cryptosystems", February 1978,
              <https://doi.org/10.1145/359340.359342>.

   [dolevyao] "On the Security of Public Key Protocols", 1983,
              <https://www.cs.huji.ac.il/~dolev/pubs/dolev-yao-ieee-
              01056650.pdf>.

   [fibertap] "Fiber Tap", 2020,
              <https://en.wikipedia.org/wiki/Room_641A>.

   [malory]   "Man-in-the-Middle", 2020,
              <https://mailarchive.ietf.org/arch/msg/saag/b26jvEz4NRHSm-
              Xva6Lv5-L8QIA/>.

   [quic]     "QUIC terms for attacks", 2020,
              <https://mailarchive.ietf.org/arch/msg/saag/
              wTtDYlRAADMmgqd6Vhm8rFybr_g/>.

   [RFC7258]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
              Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
              2014, <https://www.rfc-editor.org/rfc/rfc7258>.

   [span]     "Port Mirroring", 2020,
              <https://en.wikipedia.org/wiki/Port_mirroring>.

Appendix A.  Monster in the Middle

   As a special case for the MITM, if the Meddler steals cookies
   (whether they are HTTP Cookies, IKE nonces, or TCP SYN Cookies), then
   this kind of attack is a Monster in The Middle.  This is otherwise
   known as a: nom-nom-nom-nom attack.


















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Contributors

   Eric Rescola
   Email: ekr@rtfm.com


   Lou Berger
   Email: lberger@labn.net


   Alan DeKok
   Email: aland@deployingradius.com


   Christian Huitema
   Email: huitema@huitema.net


Authors' Addresses

   Michael Richardson
   Sandelman Software Works
   Email: mcr+ietf@sandelman.ca


   Jonathan Hoyland
   Cloudflare Ltd.
   Email: jhoyland@cloudflare.com






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