NETWORK WORKING GROUP N. Williams
Internet-Draft Sun
Expires: August 26, 2006 February 22, 2006
Better-Than-Nothing-Security: An Unauthenticated Mode of IPsec
draft-ietf-btns-core-00.txt
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Abstract
This document specifies how to use the Internet Key Exchange (IKE)
protocols, such as IKEv1 and IKEv2, to setup "unauthenticated"
security associations (SAs) for use with the IPsec Encapsulating
Security Payload (ESP) and the IPsec Authentication Header (AH). No
IKE extensions are needed, but Peer Authorization Database (PAD) and
Security Policy Database (SPD) extensions are specified.
Unauthenticated IPsec is herein referred to by its popular acronym,
"BTNS" (Better Than Nothing Security).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . . . 3
2. BTNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . 5
4. Normative . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . 7
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1. Introduction
Here we describe how to establish unauthenticated IPsec SAs using
IKEv1 [RFC2408] [RFC2409] or IKEv2 [RFC4306] and unauthenticated
public keys. No new on-the-wire protocol elements are added to IKE
or IKEv2.
The [RFC4301] processing model is assumed.
This document does not define an opportunistic BTNS mode of IPsec
whereby nodes may fallback on unprotected IP when their peers do not
support IKE or IKEv2, nor does it describe "leap-of-faith" modes, or
"connection latching."
See [I-D.ietf-btns-prob-and-applic] for the applicability and uses of
BTNS.
1.1. Conventions used in this document
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].
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2. BTNS
The IPsec processing model, IKE and IKEv2 are hereby modified as
follows:
o A new ID type is added, 'PUBLICKEY'; IDs of this type have public
keys as values. This ID type is not used on the wire.
o A BTNS-specific PAD entry. This entry is intended to be the last
entry in the PAD when BTNS is enabled. A peer that matches no
other PAD entries is to be "authenticated" by verifying that the
signature in its AUTH (or SIG) payload in the IKEv2 (or v1)
exchange with the public key from the peer's CERT payload. The
peer's ID MUST then be coerced to be of 'PUBLICKEY' type with the
peer's public key as its value.
o A new flag for SPD entries: 'BTNS_OK'. Traffic to/from peers that
match the BTNS PAD entry will only match SPD entries that have the
BTNS_OK flag set. The SPD may be searched done by address or by
ID (of typ PUBLICKEY, of course, for BTNS peers), as per the IPsec
processing model [RFC4301]; searching by ID in this case requires
creation of SPD entries that are bound to public key values (this
could be used to build "leap-of-faith" behaviour, for example).
Nodes MUST reject IKE_SA proposals from peers that match non-BTNS PAD
entries but fail to authenticated properly.
Nodes wishing to be treated as BTNS nodes by their peers SHOULD use
CERT payloads generated for the purpose (i.e., ephemeral, non-pre-
shared self-signed certificates or bare RSA public keys).
Note that nodes may unwittingly match peers' BTNS PAD entries and be
authenticated as BTNS nodes, as long as they do not match any non-
BTNS PAD entries.
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3. Security Considerations
Unauthenticated security association negotiation is subject to MITM
attacks and should be used with care. Where security infrastructures
are lacking this may indeed be better than nothing.
Use with applications that bind authentication at higher network
layers to secure channels at lower layers may provide one secure way
to use unauthenticated IPsec, but this is not specified herein.
[...]
4. Normative
[I-D.ietf-btns-prob-and-applic]
Touch, J., "Problem and Applicability Statement for Better
Than Nothing Security (BTNS)",
draft-ietf-btns-prob-and-applic-00 (work in progress),
July 2005.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2408] Maughan, D., Schneider, M., and M. Schertler, "Internet
Security Association and Key Management Protocol
(ISAKMP)", RFC 2408, November 1998.
[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, November 1998.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
RFC 4306, December 2005.
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Author's Address
Nicolas Williams
Sun Microsystems
5300 Riata Trace Ct
Austin, TX 78727
US
Email: Nicolas.Williams@sun.com
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