Internet DRAFT - draft-ietf-ipsecme-implicit-iv
draft-ietf-ipsecme-implicit-iv
IPSECME D. Migault
Internet-Draft Ericsson
Intended status: Standards Track T. Guggemos
Expires: April 23, 2020 LMU Munich
Y. Nir
Dell EMC
October 21, 2019
Implicit IV for Counter-based Ciphers in Encapsulating Security Payload
(ESP)
draft-ietf-ipsecme-implicit-iv-11
Abstract
Encapsulating Security Payload (ESP) sends an initialization vector
(IV) in each packet. The size of IV depends on the applied
transform, being usually 8 or 16 octets for the transforms defined by
the time this document is written. Some algorithms such as AES-GCM,
AES-CCM and ChaCha20-Poly1305 when used with IPsec, take the IV to
generate a nonce that is used as an input parameter for encrypting
and decrypting. This IV must be unique but can be predictable. As a
result, the value provided in the ESP Sequence Number (SN) can be
used instead to generate the nonce. This avoids sending the IV
itself, and saves in the case of AES-GCM, AES-CCM and
ChaCha20-Poly1305 8 octets per packet. This document describes how
to do this.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 23, 2020.
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Copyright Notice
Copyright (c) 2019 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
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Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Implicit IV . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. IKEv2 Initiator Behavior . . . . . . . . . . . . . . . . . . 4
6. IKEv2 Responder Behavior . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 6
10.2. Informational References . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Requirements notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described BCP 14
[RFC2119], [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Introduction
Counter-based AES modes of operation such as AES-CCM ([RFC4309]), and
AES-GCM ([RFC4106]) require the specification of an nonce for each
ESP packet. The same applies for ChaCha20-Poly1305 ([RFC7634]).
Currently this nonce is generated thanks to the Initialization Vector
(IV) provided in each ESP packet ([RFC4303]). This practice is
designated in this document as "explicit IV".
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In some contexts, such as IoT, it may be preferable to avoid carrying
the extra bytes associated to the IV and instead generate it locally
on each peer. The local generation of the IV is designated in this
document as "implicit IV".
The size of this IV depends on the specific algorithm, but all of the
algorithms mentioned above take an 8-octet IV.
This document defines how to compute the IV locally when it is
implicit. It also specifies how peers agree with the Internet Key
Exchange version 2 (IKEv2 - [RFC7296]) on using an implicit IV versus
an explicit IV.
This document limits its scope to the algorithms mentioned above.
Other algorithms with similar properties may later be defined to use
similar mechanisms.
This document does not consider AES-CBC ([RFC3602]) as AES-CBC
requires the IV to be unpredictable. Deriving it directly from the
packet counter as described below is insecure as mentioned in
Security Consideration of [RFC3602] and has led to real world chosen
plain-text attack such as BEAST [BEAST].
This document does not consider AES-CTR [RFC3686] as it focuses on
the recommended AEAD suites provided in [RFC8221].
3. Terminology
o IoT: Internet of Things.
o IV: Initialization Vector.
o IIV: Implicit Initialization Vector.
o Nonce: a fixed-size octet string used only once. In our case, the
nonce takes the IV as input and is provided as an input parameter
for encryption/decryption.
4. Implicit IV
With the algorithms listed in Section 2, the 8-byte IV MUST NOT
repeat for a given key. The binding between an ESP packet and its IV
is provided using the Sequence Number or the Extended Sequence
Number. Figure 1 and Figure 2 represent the IV with a regular 4-byte
Sequence Number and with an 8-byte Extended Sequence Number
respectively.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Implicit IV with a 4 byte Sequence Number
o Sequence Number: the 4 byte Sequence Number carried in the ESP
packet.
o Zero: a 4 byte array with all bits set to zero.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended |
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Implicit IV with an 8-byte Extended Sequence Number
o Extended Sequence Number: the 8-byte Extended Sequence Number of
the Security Association. The 4 byte low order bytes are carried
in the ESP packet.
This document solely defines the IV generation of the algorithms
defined in [RFC4106] for AES-GCM, [RFC4309] for AES-CCM and [RFC7634]
for ChaCha20-Poly1305. All other aspects and parameters of those
algorithms are unchanged, and are used as defined in their respective
specifications.
5. IKEv2 Initiator Behavior
An initiator supporting this feature SHOULD propose implicit IV (IIV)
algorithms in the Transform Type 1 (Encryption Algorithm)
Substructure of the Proposal Substructure inside the Security
Association Payload (SA Payload) in the IKEv2 Exchange. To
facilitate backward compatibility with non-supporting peers the
initiator SHOULD also include those same algorithms with explicit IV
as separate transforms.
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6. IKEv2 Responder Behavior
The rules of SA Payload processing require that responder picks its
algorithms from the proposal sent by the initiator, thus this will
ensure that the responder will never send an SA payload containing
the IIV transform to an initiator that did not propose it.
7. Security Considerations
Nonce generation for these algorithms has not been explicitly
defined. It has been left to the implementation as long as certain
security requirements are met. Typically, for AES-GCM, AES-CCM and
ChaCha20-Poly1305, the IV is not allowed to be repeated for one
particular key. This document provides an explicit and normative way
to generate IVs. The mechanism described in this document meets the
IV security requirements of all relevant algorithms.
As the IV must not repeat for one SA when Counter-Mode ciphers are
used, implicit IV as described in this document MUST NOT be used in
setups with the chance that the Sequence Number overlaps for one SA.
The sender's counter and the receiver's counter MUST be reset (by
establishing a new SA and thus a new key) prior to the transmission
of the 2^32nd packet for an SA that uses a non extended Sequence
Number (respectively the 2^64nd packet for an SA that uses an
Extended Sequence Number). This prevents sequence number overlaps
for the mundane point-to-point case. Multicast as described in
[RFC5374], [RFC6407] and [I-D.yeung-g-ikev2] is a prominent example,
where many senders share one secret and thus one SA. As such,
Implicit IV may only be used with Multicast if some mechanisms are
employed that prevent Sequence Number to overlap for one SA,
otherwise Implicit IV MUST NOT be used with Multicast.
This document defines three new encryption transforms that use
implicit IV. Unlike most encryption transforms defined to date,
which can be used for both ESP and IKEv2, these transforms are
defined for ESP only and cannot be used in IKEv2. The reason is that
IKEv2 messages don't contain a unique per-message value that can be
used for IV generation. The Message-ID field in IKEv2 header is
similar to the SN field in ESP header, but recent IKEv2 extensions
([RFC6311], [RFC7383]) do allow it to repeat, so there is not an easy
way to derive unique IV from IKEv2 header fields.
8. IANA Considerations
The IANA has updated the "Internet Key Exchange Version 2 (IKEv2)
Parameters" [RFC7296] by adding new code points to the "Transform
Type Values"/"Transform Type 1 - Encryption Algorithm Transform IDs"
registry [IANA]:
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- ENCR_AES_CCM_8_IIV: 29
- ENCR_AES_GCM_16_IIV: 30
- ENCR_CHACHA20_POLY1305_IIV: 31
These algorithms should be added with this document as ESP Reference
and "Not Allowed" for IKEv2 Reference.
9. Acknowledgements
We would like to thank Valery Smyslov, Eric Vyncke, Alexey Melnikov,
Adam Roach, Magnus Nystrom (security directorate), as well as our
three Security ADs Eric Rescorla, Benjamin Kaduk and Roman Danyliw
for their valuable comments. We also would like to thank David
Schinazi for its implementation, as well as the ipseceme chairs Tero
Kivinen and David Waltermire for moving this work forward.
NOTE TO THE EDITOR Eric has a accent on E and Magnus has double
points on o.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3602] Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher
Algorithm and Its Use with IPsec", RFC 3602,
DOI 10.17487/RFC3602, September 2003,
<https://www.rfc-editor.org/info/rfc3602>.
[RFC3686] Housley, R., "Using Advanced Encryption Standard (AES)
Counter Mode With IPsec Encapsulating Security Payload
(ESP)", RFC 3686, DOI 10.17487/RFC3686, January 2004,
<https://www.rfc-editor.org/info/rfc3686>.
[RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode
(GCM) in IPsec Encapsulating Security Payload (ESP)",
RFC 4106, DOI 10.17487/RFC4106, June 2005,
<https://www.rfc-editor.org/info/rfc4106>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, DOI 10.17487/RFC4303, December 2005,
<https://www.rfc-editor.org/info/rfc4303>.
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[RFC4309] Housley, R., "Using Advanced Encryption Standard (AES) CCM
Mode with IPsec Encapsulating Security Payload (ESP)",
RFC 4309, DOI 10.17487/RFC4309, December 2005,
<https://www.rfc-editor.org/info/rfc4309>.
[RFC5374] Weis, B., Gross, G., and D. Ignjatic, "Multicast
Extensions to the Security Architecture for the Internet
Protocol", RFC 5374, DOI 10.17487/RFC5374, November 2008,
<https://www.rfc-editor.org/info/rfc5374>.
[RFC6311] Singh, R., Ed., Kalyani, G., Nir, Y., Sheffer, Y., and D.
Zhang, "Protocol Support for High Availability of IKEv2/
IPsec", RFC 6311, DOI 10.17487/RFC6311, July 2011,
<https://www.rfc-editor.org/info/rfc6311>.
[RFC6407] Weis, B., Rowles, S., and T. Hardjono, "The Group Domain
of Interpretation", RFC 6407, DOI 10.17487/RFC6407,
October 2011, <https://www.rfc-editor.org/info/rfc6407>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <https://www.rfc-editor.org/info/rfc7296>.
[RFC7383] Smyslov, V., "Internet Key Exchange Protocol Version 2
(IKEv2) Message Fragmentation", RFC 7383,
DOI 10.17487/RFC7383, November 2014,
<https://www.rfc-editor.org/info/rfc7383>.
[RFC7634] Nir, Y., "ChaCha20, Poly1305, and Their Use in the
Internet Key Exchange Protocol (IKE) and IPsec", RFC 7634,
DOI 10.17487/RFC7634, August 2015,
<https://www.rfc-editor.org/info/rfc7634>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8221] Wouters, P., Migault, D., Mattsson, J., Nir, Y., and T.
Kivinen, "Cryptographic Algorithm Implementation
Requirements and Usage Guidance for Encapsulating Security
Payload (ESP) and Authentication Header (AH)", RFC 8221,
DOI 10.17487/RFC8221, October 2017,
<https://www.rfc-editor.org/info/rfc8221>.
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10.2. Informational References
[BEAST] Thai, T. and J. Juliano, "Here Come The xor Ninjas", ,
May 2011, <https://www.researchgate.net/
publication/266529975_Here_Come_The_Ninjas>.
[I-D.yeung-g-ikev2]
Weis, B. and V. Smyslov, "Group Key Management using
IKEv2", draft-yeung-g-ikev2-16 (work in progress), July
2019.
[IANA] "IANA IKEv2 Parameter - Type 1 - Encryption Algorithm
Transform IDs", <https://www.iana.org/assignments/ikev2-
parameters/ikev2-parameters.xhtml#ikev2-parameters-5>.
Authors' Addresses
Daniel Migault
Ericsson
8275 Trans Canada Route
Saint Laurent, QC H4S 0B6
Canada
Email: daniel.migault@ericsson.com
Tobias Guggemos
LMU Munich
Oettingenstr. 67
80538 Munich, Bavaria
Germany
Email: guggemos@mnm-team.org
URI: http://mnm-team.org/~guggemos
Yoav Nir
Dell EMC
9 Andrei Sakharov St
Haifa 3190500
Israel
Email: ynir.ietf@gmail.com
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