Network Working Group F. Xia
Internet-Draft Huawei
Expires: December 22, 2008 S. Krishnan
Ericsson Research
W. Haddad
Qualcomm
J-M. Combes
Orange Labs R&D
Chunqiang. Li
Huawei
June 20, 2008
Distributing a Symmetric Neighbor Discovery Key Using SEND
draft-xia-csi-symmetric-key-00.txt
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Abstract
In this document, a method for provisioning a shared key from the
router to the host is defined to protect Neighbor Discovery(ND)
signaling between the router and the host. The host sends a Router
Solicitation(RS) message with ND Shared Key Request Option to the
router. The router encrypts a ND shared key using the host's SEcure
Neighbor Discovery(SEND) public key and sends it back to the host
through a Router Advertisement(RA) message. The host decrypts the ND
shared key using the matching private key. The Neighbor Discovery
shared key is then used for protecting the following Neighbor
Discovery signaling between the router and the host. The Router
Solicitation and Router Advertisement message exchanges are required
to have SEND security.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Operation Description . . . . . . . . . . . . . . . . . . . . 4
3.1. Sending Router Solicitations . . . . . . . . . . . . . . . 4
3.2. Receiving Router Solicitations and Sending Router
Advertisements . . . . . . . . . . . . . . . . . . . . . . 4
3.3. Receiving Router Advertisements . . . . . . . . . . . . . 5
3.4. ND operation secured by a shared key . . . . . . . . . . . 5
3.5. Key Generation and Lifetime . . . . . . . . . . . . . . . 6
4. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. ND Shared Key Request Option . . . . . . . . . . . . . . . 6
4.2. ND Shared Key Reply Option . . . . . . . . . . . . . . . . 7
4.3. Neighbor Discovery Authenticator Option . . . . . . . . . 8
5. IANA consideration . . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . . 10
8.2. Informative references . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . . . 13
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1. Introduction
IPv6 nodes use Neighbor Discovery(ND) protocol [RFC4861] to discover
other nodes on the link, to determine their link-layer addresses, to
find routers, and to maintain reachability information about the
paths to active neighbors. [RFC3971] specifies security mechanisms
for ND, that is, Secure Neighbor Discovery (SEND) protocol in which
Cryptographically Generated Addresses (CGA) [RFC3972] are used.
The construction and verification of the RSA Signature option in SEND
operation is computationally expensive. In the ND context, however,
hosts typically only have to perform a few signature operations as
they enter a link, a few operations as they find a new on-link peer
with which to communicate, or Neighbor Unreachability Detection with
existing neighbors. Routers are required to perform a larger number
of operations, particularly when the frequency of router
advertisements is high due to mobility requirements. Scalability
issue arises when hundreds , even thousands of hosts attach to a
router.
In the same way, IPv6 over Low-Power Wireless Personal Area Networks
(6LoWPANs) have similar constraints. It is recommended that ND
signalling exchanges occur between the 6lowpan host and the PAN
coordinator, which is a router in [I-D.chakrabarti-6lowpan-ipv6-nd].
Another point is 6lowpan hosts may not be able to do asymmetric
cryptography all the time because of power/computing consumption.
In this document, a lightweight mechanism is defined by which a
shared key for securing ND exchanges between the host and the router
is provisioned on the host by the router. The mechanism described in
the document utilizes SEND [RFC3971] public/private key pair to
encrypt/decrypt a ND shared key sent from the router to the host.
Once the ND shared key is provisioned, all ND exchanges occurring
between the host and the router are protected by Message
Authentication Codes (MAC) which generally requires much less
computational operation. This main idea of the document is in line
with [I-D.ietf-mipshop-handover-key] in which shared handover key is
used for protecting handover signaling between a mobile node and an
access router.
The solution is based on and compatible with SEND operation.
2. Terminology
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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The terminology and messages in this document are based on the
definitions in [RFC3971], in addition to the ones defined below.
ND shared key : A key is shared between a router and a host, and
used to protect ND signaling between the router and the host.
3. Operation Description
3.1. Sending Router Solicitations
According to SEND [RFC3971], the CGA option MUST be present in Router
Solicitation(RS) messages unless they are sent with the unspecified
source address. In this document, RS message with a CGA source
address is used for a ND shared key request.
The host MUST send a RS containing a ND Shared Key Request Option
defined in Section 4.1 with the SEND's public key. A CGA for the
host MUST be the source address of the packet, and the host MUST
include the SEND CGA Option and SEND Signature Option with the
packet, as specified in [RFC3971]. The SEND signature covers all
fields in the RS, including the 128 bit source and destination
addresses and ICMP checksum as described in [RFC3971], except for the
Signature Option itself. The host also sets the authentication
Algorithm Type (AT) field in the ND Shared Key Request Option to the
host's preferred authentication algorithm. The SEND Nonce MUST also
be included for anti-replay protection.
3.2. Receiving Router Solicitations and Sending Router Advertisements
When the router receives a RS from the host protected with SEND and
including a ND Shared Key Request Option, the router MUST first
validate the RS using SEND as described in [RFC3971]. If the RS can
not be validated, the router MUST NOT include a ND Shared Key Reply
Option Section 4.2 in the reply.
If the RS is validated, the router MUST then determine whether the
CGA is already associated with a ND shared key. If the CGA is
associated with an existing key, the router MUST return the existing
key to the host. If the CGA does not have a ND shared key, the
router MUST construct a ND shared key as described in Section 3.5.
The router MUST encrypt the key with the host's SEND public key. The
router MUST insert the encrypted ND shared key into a ND Shared Key
Reply Option and MUST attach the option to the RA. The lifetime of
the key MUST also be included in the ND Shared Key Reply Option. The
router SHOULD set the AT field of the ND Shared Key Option to the
MN's preferred algorithm type indicated in the AT field of the ND
Shared Key Request Option, if it is supported; otherwise, the router
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MUST select an authentication algorithm which is of equivalent
strength or stronger and set the field to that. The router MUST also
include the SEND nonce from the RS for anti- replay protection. The
router MUST use the CGA constructed from its certified key as the
source address for the RA and include a SEND CGA Option and a SEND
Signature Option with the SEND signature of the message. The SEND
signature covers all fields in the RA, including the 128 bit source
and destination addresses and ICMP checksum as described in
[RFC3971], except for the Signature Option itself. The RA is then
unicast back to the host. The ND shared key MUST be stored by the
router for future use, indexed by the host's CGA, and the
authentication AT and a lifetime MUST be recorded with the key.
3.3. Receiving Router Advertisements
Upon receipt of one or more RA secured with SEND and having the ND
Shared Key Reply Option, the host MUST first validate the RA as
described in [RFC3971]. Normally the host will have obtained the
router's certification path to validate an RA prior to sending the RS
and the host MUST check to ensure that the key used to sign the RA is
the router's certified public key. If the host does not have the
router's certification path cached, it MUST use the SEND
Certification Path Solicitation (CPS) / Certification Path
Advertisement (CPA) messages to obtain the certification path to
validate the key. If the message is not signed by a certified key ,
the message MUST be dropped.
The host MUST use it's private key to decrypt the ND shared key. The
host MUST use the returned authentication AT indicated in the RA.
The host MUST index the ND shared keys with the router's CGA, and the
algorithm type and the lifetime are also stored.
When the host moves from a router to another router, it is possible
that the new router has no any idea about the ND Shared Key which is
provided by the old one. A solution is that the host erases the ND
shared key and re-use CGA after a certain number of NS
retransmissions.
3.4. ND operation secured by a shared key
When the host sends Neighbor Solicitation (NS), Neighbor
Advertisement (NA), Router Solicitation(RS) to the router, the host
SHOULD check if there is a ND shared key for the router. The host
SHOULD utilize the shared key and the corresponding authentication
algorithm type to generate an authenticator for the message if a ND
shared key exists; otherwise, the host behaves according to[RFC3971],
or requests a ND shared key using the procedure defined in this
document. The authenticator is conveyed in Neighbor Discovery
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Authenticator Option defined in Section 4.3.
When the router sends Neighbor Solicitation (NS), Neighbor
Advertisement (NA), Router Solicitation(RS), Redirect, Router
Advertisement(RA) to the host, the router SHOULD check if there is a
ND shared key for the host. The router SHOULD utilize the shared key
and the corresponding authentication algorithm to generate an
authenticator for the message if a ND shared key exists;
otherwise,the router behaves according to [RFC3971]. The
authenticator is conveyed in Neighbor Discovery Authenticator Option
defined in Section 4.3.
3.5. Key Generation and Lifetime
The router MUST randomly generate a key having sufficient strength to
match the authentication algorithm. Some authentication algorithms
specify a required key size. The router MUST generate a unique key
along with a lifetime for each CGA public key of a host.
Before the lifetime expires, the host SHOULD apply for a new ND
shared key using the procedure defined in this document. Once the ND
shared key expires, the host and the router SHOULD discard the key.
4. Message Formats
4.1. ND Shared Key Request Option
The ND Shared Key Request Option is a IPv6 Neighbor Discovery
[RFC4861] option in TLV format. The ND Shared Key Request Option is
included in the RS message along with the SEND CGA Option, RSA
Signature Option, and Nonce Option.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | AT | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fields:
Type: To be assigned by IANA.
Length: The length of the option in units of 8 octets,
including the Type and Length fields. The value 0
is invalid. The receiver MUST discard a message
that contains this value.
AT: authentication Algorithm Type
1 HMAC_SHA1
2 HMAC_SHA256
3 MD5
Reserved: A 40-bit field reserved for future use.
4.2. ND Shared Key Reply Option
ND Shared Key Reply Option is a IPv6 Neighbor Discovery [RFC4861]
option in TLV format. The Reply Option is included in the RA message
along with the SEND CGA Option, RSA Signature Option, and Nonce
Option.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | AT | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key Lifetime | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
. .
. Encrypted ND Shared Key .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fields:
Type: To be assigned by IANA.
Length: The length of the option in units of 8 octets,
including the Type and Length fields. The value 0
is invalid. The receiver MUST discard a message
that contains this value.
AT: authentication Algorithm Type
1 HMAC_SHA1
2 HMAC_SHA256
3 MD5
Reserved: A 8-bit field reserved for future use. The value
MUST be initialized to zero by the sender and MUST
be ignored by the receiver.
Key Lifetime:
lifetime of the ND shared key, in seconds.
Encrypted ND Shared Key:
The shared key, encrypted with the host's
ND shared key encryption public key, using the
RSAES-PKCS1-v1_5 format [RFC3447].
4.3. Neighbor Discovery Authenticator Option
This option MUST be present all ND signaling between the host and the
router. This option specifies how to compute and verify a MAC using
the established ND shared key.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Authenticator .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fields:
Type: To be assigned by IANA.
Length: The length of the option in units of 8 octets,
including the Type and Length fields. The value 0
is invalid. The receiver MUST discard a message
that contains this value.
Reserved: A 8-bit field reserved for future use. The value
MUST be initialized to zero by the sender and MUST
be ignored by the receiver.
Authenticator:
cryptographic value which can be used to determine
that the message in question comes from the right
authority
Rules for calculating the Authenticator value are the following:
ND Data = host's source address | router's address | ICMP Data
Authenticator = First (96, Algorithm( ND Shared Key, ND Data))
The algorithm type for authenticator is negotiated between the host
and the router through ND Shared Key Request Option and ND Shared Key
Reply Option.
5. IANA consideration
Three new IPv6 Neighbor Discovery options, the ND Shared Key Request
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Option, ND Shared Key Reply Option, and Neighbor Discovery
Authenticator Option, are defined, and require IPv6 Neighbor
Discovery option type codes from IANA.
6. Security Considerations
This document describes a shared key provisioning protocol for the
Neighbor Discovery protocol. The key provisioning protocol utilizes
a public key of SEND. General security considerations involving CGAs
apply to the protocol described in this document, see [RFC4861] for a
discussion of security considerations around CGAs.
7. Acknowledgements
Jean-Michel Combes is partly funded by MobiSEND, a research project
supported by the French 'National Research Agency' (ANR).
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, March 2005.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC5121] Patil, B., Xia, F., Sarikaya, B., Choi, JH., and S.
Madanapalli, "Transmission of IPv6 via the IPv6
Convergence Sublayer over IEEE 802.16 Networks", RFC 5121,
February 2008.
[RFC3314] Wasserman, M., "Recommendations for IPv6 in Third
Generation Partnership Project (3GPP) Standards",
RFC 3314, September 2002.
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8.2. Informative references
[I-D.ietf-mipshop-handover-key]
Kempf, J., "Distributing a Symmetric FMIPv6 Handover Key
using SEND", draft-ietf-mipshop-handover-key-03 (work in
progress), October 2007.
[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications
Version 2.1", RFC 3447, February 2003.
[I-D.chakrabarti-6lowpan-ipv6-nd]
Chakrabarti, S. and E. Nordmark, "LowPan Neighbor
Discovery Extensions",
draft-chakrabarti-6lowpan-ipv6-nd-04 (work in progress),
November 2007.
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Authors' Addresses
Frank Xia
Huawei
1700 Alma Dr. Suite 500
Plano, TX 75075
Phone: +1 972-509-5599
Email: xiayangsong@huawei.com
Suresh Krishnan
Ericsson Research
8400 Decarie Blvd.
Town of Mount Royal, QC Canada
Phone: +1 514 345 7900
Email: Suresh.Krishnan@ericsson.com
Wassim Haddad
Qualcomm
Phone:
Email: whaddad@qualcomm.com
Jean-Michel Combes
Orange Labs R&D
38 rue du General Leclerc
Issy-les-Moulineaux Cedex 9, France 92794
Phone:
Email: jeanmichel.combes@gmail.com
Chunqiang Li
Huawei
No.91 BaiXia Rd.
Nanjing, China 210001
Phone:
Email: li.chunqiang@huawei.com
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