Internet DRAFT - draft-mglt-ipsecme-implicit-iv
draft-mglt-ipsecme-implicit-iv
IPSECME D. Migault, Ed.
Internet-Draft Ericsson
Intended status: Standards Track T. Guggemos, Ed.
Expires: December 22, 2017 LMU Munich
Y. Nir
Dell EMC
June 20, 2017
Implicit IV for Counter-based Ciphers in IPsec
draft-mglt-ipsecme-implicit-iv-04
Abstract
IPsec ESP sends an initialization vector (IV) or nonce in each
packet, adding 8 or 16 octets. Some algorithms such as AES-GCM, AES-
CCM, AES-CTR and ChaCha20-Poly1305 require a unique nonce but do not
require an unpredictable nonce. When using such algorithms the
packet counter value can be used to generate a nonce, saving 8 octets
per packet. This document describes how to do this.
Status of This Memo
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This Internet-Draft will expire on December 22, 2017.
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Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Implicit IV . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Initiator Behavior . . . . . . . . . . . . . . . . . . . . . 4
6. Responder Behavior . . . . . . . . . . . . . . . . . . . . . 4
7. Security Consideration . . . . . . . . . . . . . . . . . . . 4
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informational References . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Requirements notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Introduction
Counter-based AES modes of operation such as AES-CTR ([RFC3686]),
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 sent in each
ESP packet ([RFC4303]). This practice is designated in this document
as "explicit nonce".
In some context, 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 nonce is designated in
this document as "implicit IV".
The size of this nonce depends on the specific algorithm, but all of
the algorithms mentioned above take an 8-octet nonce.
This document defines how to compute the nonce 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.
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This document limits its scope to the algorithms mentioned above.
Other algorithms with similar properties may later be defined to use
this extension.
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].
3. Terminology
o IoT: Internet of Things.
o IV: Initialization Vector.
o Nonce: a fixed-size octet string used only once. This is similar
to IV, except that in common usage there is no implication of non-
predictability.
4. Implicit IV
With the algorithms listed in Section 2, the 8 byte nonce MUST NOT
repeat. The binding between a ESP packet and its nonce 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.
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.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
5. Initiator Behavior
An initiator supporting this feature SHOULD propose implicit IV for
all relevant algorithms. To facilitate backward compatibility with
non-supporting peers the initiator SHOULD also include those same
algorithms without IIV. This may require extra transforms.
6. Responder Behavior
The rules of SA payload processing ensure that the responder will
never send an SA payload containing the IIV indicator to an initiator
that does not support IIV.
7. Security Consideration
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. 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 SPI 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 SPI.
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 SPI. Section 3.5 of [RFC6407] explains how
repetition MAY BE prevented by using a prefix for each group member,
which could be prefixed to the Sequence Number. Otherwise, Implicit
IV MUST NOT be used in multicast scenarios.
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8. IANA Considerations
AES-CTR, AES-CCM, AES-GCM and ChaCha20-Poly1305 are likely to
implement the implicit IV described in this document. This section
limits assignment of new code points to the recommended suites
provided in [I-D.ietf-ipsecme-rfc4307bis] and
[I-D.ietf-ipsecme-rfc7321bis], thus the new Transform Type 1 -
Encryption Algorithm Transform IDs are as defined below:
- ENCR_AES-CCM_8_IIV
- ENCR_AES-GCM_16_IIV
- ENCR_CHACHA20-POLY1305_IIV
9. References
9.1. Normative References
[I-D.ietf-ipsecme-rfc4307bis]
Nir, Y., Kivinen, T., Wouters, P., and D. Migault,
"Algorithm Implementation Requirements and Usage Guidance
for IKEv2", draft-ietf-ipsecme-rfc4307bis-18 (work in
progress), March 2017.
[I-D.ietf-ipsecme-rfc7321bis]
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)", draft-ietf-
ipsecme-rfc7321bis-06 (work in progress), June 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://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,
<http://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,
<http://www.rfc-editor.org/info/rfc3686>.
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[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,
<http://www.rfc-editor.org/info/rfc4106>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, DOI 10.17487/RFC4303, December 2005,
<http://www.rfc-editor.org/info/rfc4303>.
[RFC4309] Housley, R., "Using Advanced Encryption Standard (AES) CCM
Mode with IPsec Encapsulating Security Payload (ESP)",
RFC 4309, DOI 10.17487/RFC4309, December 2005,
<http://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,
<http://www.rfc-editor.org/info/rfc5374>.
[RFC6407] Weis, B., Rowles, S., and T. Hardjono, "The Group Domain
of Interpretation", RFC 6407, DOI 10.17487/RFC6407,
October 2011, <http://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, <http://www.rfc-editor.org/info/rfc7296>.
[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,
<http://www.rfc-editor.org/info/rfc7634>.
9.2. 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., Nir, Y., and V. Smyslov, "Group Key Management
using IKEv2", draft-yeung-g-ikev2-11 (work in progress),
March 2017.
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Authors' Addresses
Daniel Migault (editor)
Ericsson
8400 boulevard Decarie
Montreal, QC H4P 2N2
Canada
Email: daniel.migault@ericsson.com
Tobias Guggemos (editor)
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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