Internet DRAFT - draft-sarikaya-6lowpan-cgand
draft-sarikaya-6lowpan-cgand
Network Working Group B. Sarikaya, Ed.
Internet-Draft F. Xia
Intended status: Standards Track Huawei USA
Expires: November 1, 2012 G. Zaverucha, Ed.
RIM
April 30, 2012
Lightweight Secure Neighbor Discovery for Low-power and Lossy Networks
draft-sarikaya-6lowpan-cgand-03
Abstract
This document defines lightweight secure neighbor discovery for low-
power and lossy networks. The nodes generate a Cryptographically
Generated Address, register the Cryptographically Generated Address
with a default router and periodically refresh the registration.
Modifications to 6lowpan Neighbor Discovery protocol are described
for secure neighbor discovery for low-power and lossy networks.
Cryptographically generated address and digital signatures are
calculated using elliptic curve cryptography, so that the
cryptographic operations are suitable for low power devices.
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 November 1, 2012.
Copyright Notice
Copyright (c) 2012 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
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
4. New Options . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. CGA Parameters and Digital Signature Option . . . . . . . 4
4.2. Digital Signature Option . . . . . . . . . . . . . . . . . 6
4.3. Calculation of the Digital Signature and CGA Using ECC . . 7
5. Protocol Interactions . . . . . . . . . . . . . . . . . . . . 8
5.1. Packet Sizes . . . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . . 10
9.2. Informative references . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
Neighbor discovery for IPv6 [RFC4861] and stateless address
autoconfiguration [RFC4862], together referred to as neighbor
discovery protocols (NDP), are defined for regular hosts operating
with wired/wireless links. These protocols are not suitable and
require optimizations for resource constrained, low power hosts
operating with lossy wireless links. Neighbor discovery
optimizations for 6lowpan networks include simple optimizations such
as a host address registration feature using the address registration
option which is sent in unicast Neighbor Solicitation (NS) and
Neighbor Advertisement (NA) messages [I-D.ietf-6lowpan-nd].
Neighbor discovery protocols (NDP) are not secure especially when
physical security on the link is not assured and vulnerable to
attacks defined in [RFC3756]. Secure neighbor discovery protocol
(SEND) is defined to secure NDP [RFC3971]. Cryptographically
generated addresses (CGA) are used in SEND [RFC3972]. SEND mandates
the use of the RSA signature algorithm which is computationally heavy
and not suitable to use for low-power and resource constrained nodes.
The use of an RSA public key and signature leads to long message
sizes not suitable to use in low-bit rate, short range, asymmetric
and non-transitive links such as IEEE 802.15.4.
In this document we extend the 6lowpan neighbor discovery protocol
with cryptographically generated addresses. The nodes generate CGAs
and register them with the default router. CGA generation is based
on elliptic curve cryptography (ECC)and signature is calculated using
elliptic curve digital signature algorithm (ECDSA) known to be
lightweight, leading to much smaller packet sizes. The resulting
protocol is called Lightweight Secure Neighbor Discovery Protocol
(LSEND).
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].
The terminology in this document is based on the definitions in
[RFC3971], [RFC3972] in addition to the ones specified in
[I-D.ietf-6lowpan-nd].
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3. Problem Statement
In this section we state requirements of a secure neighbor discovery
protocol for low-power and lossy networks.
The protocol MUST be based on the Neighbor Discovery Optimization for
Low-power and Lossy Networks protocol defined in
[I-D.ietf-6lowpan-nd] due to the host-initiated interactions to allow
for sleeping hosts, elimination of multicast-based address resolution
for hosts, etc.
New options to be added to neighbor solicitation messages MUST lead
to small packet sizes. Smaller packet sizes facilitate low-power
transmission by resource constrained nodes on lossy links.
CGA generation, signature and key hash calculation MUST avoid the use
of SHA-1 which is known to have security flaws. In this document, we
use SHA-2 instead of SHA-1 and thus avoid SHA-1's flaws.
Public key and signature sizes MUST be minimized and signature
calculation MUST be lightweight. In this document we adopt ECC and
ECDSA with the P-256 curve in order to meet this requirement.
4. New Options
4.1. CGA Parameters and Digital Signature Option
This option contains both CGA parameters and the digital signature.
A summary of the CGA Parameters and Digital Signature Option format
is shown below.
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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 | Pad Length | Sig. Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. CGA Parameters .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Digital Signature .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Padding .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
TBA1 for CGA Parameters and Digital Signature
Length
The length of the option (including the Type, Length, Pad Length,
Signature Length, CGA Parameters, Digital Signature and Padding
fields) in units of 8 octets.
Pad Length
The length of the Padding field.
Sig Length
The length of the Digital Signature field.
CGA Parameters
The CGA Parameters field is variable-length containing the CGA
Parameters data structure described in Section 4 of [RFC3972].
Digital Signature
The Digital Signature field is a variable length field containing
a Elliptic Curve Digital Signature Algorithm (ECDSA) signature
(with SHA-256 and P-256 curve of [FIPS-186-3]). Digital signature
is constructed as explained in Section 4.3.
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Padding
The Padding field contains a variable-length field making the CGA
Parameters and Digital Signature Option length a multiple of 8.
4.2. Digital Signature Option
This option contains the digital signature.
A summary of the Digital Signature Option format is shown below.
Note that this option has the same format as RSA Signature Option
defined in [RFC3971]. The differences are that Digital Signature
field carries an ECDSA signature not an RSA signature, and in
calculating Key Hash field SHA-2 is used instead of SHA-1.
In the sequence of octets to be signed using the sender's private key
includes 128-bit CGA Message Type tag. In LSEND, CGA Message Type
tag of 0xE8C47FB7FD2BB885DAB2D31A0F2808B4 MUST be used.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Key Hash |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Digital Signature .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Padding .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
TBA2 for Digital Signature
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Length
The length of the option (including the Type, Length, Reserved,
Key Hash, Digital Signature and Padding fields) in units of 8
octets.
Key Hash
The Key Hash field is a 128-bit field containing the most
significant (leftmost) 128 bits of a SHA-2 hash of the public key
used for constructing the signature. This is the same as in
[RFC3971] except for SHA-1 which has been replaced by SHA-2.
Digital Signature
Same as in Section 4.1.
Padding
The Padding field contains a variable-length field containing as
many bytes long as remain after the end of the signature.
4.3. Calculation of the Digital Signature and CGA Using ECC
Due to the use of Elliptic Curve Cryptography, the following
modifications are needed to [RFC3971] and [RFC3972].
The digital signature is constructed by using the sender's private
key over the same sequence of octets specified in Section 5.2 of
[RFC3971] up to all neighbor discovery protocol options preceding the
Digital Signature option containing the ECC-based signature. The
signature value is computed using the ECDSA signature algorithm as
defined in [SEC1] and hash function SHA-256.
Public Key is the most important parameter in CGA Parameters defined
in Section 4.1. Public Key MUST be DER-encoded ASN.1 structure of
the type SubjectPublicKeyInfo formatted as ECC Public Key. The
AlgorithmIdentifier, contained in ASN.1 structure of type
SubjectPublicKeyInfo, MUST be the (unrestricted) id- ecPublicKey
algorithm identifier, which is OID 1.2.840.10045.2.1, and the
subjectPublicKey MUST be formatted as an ECC Public Key, specified in
Section 2.2 of [RFC5480].
Note that the ECC key lengths are determined by the namedCurves
parameter stored in ECParameters field of the AlgorithmIdentifier.
The named curve to use is secp256r1 corresponding to P-256 which is
OID 1.2.840.10045.3.1.7 [SEC2].
ECC Public Key could be in uncompressed form or in compressed form
where the first octet of the OCTET STRING is 0x04 and 0x02 or 0x03,
respectively. Point compression using secp256r1 reduces the key size
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by 32 octets. In LSEND, point compression MUST be supported.
5. Protocol Interactions
Lightweight Secure Neighbor Discovery for Low-power and Lossy
Networks (LSEND for LLN) modifies Neighbor Discovery Optimization for
Low-power and Lossy Networks [I-D.ietf-6lowpan-nd] as explained in
this section. Protocol interactions are shown in Figure 1.
6LoWPAN Border Routers (6LBR) send router advertisements (RA).
6LoWPAN Nodes (6LN, or simply "nodes") receive these RAs and generate
their own cryptographically generated addresses using elliptic curve
cryptography as explained in Section 4.3. The node sends a neighbor
solicitation (NS) message with the address registration option (ARO)
to 6LBR. Such a NS is called an address registration NS.
An LSEND for LLN node MUST send an address registration NS message
after adding CGA Parameters and Digital Signature Option defined in
Section 4.1. Source address MUST be set to its crypotographically
generated address. An LSEND for LLN node MUST set the Owner
Interface Identifier field (EUI-64) in ARO to the rightmost 64 bits
of its crypotographically generated address. The Subnet Prefix field
of CGA Parameters MUST be set to the leftmost 64 bits of its
crypotographically generated address. The Public Key field of CGA
Parameters MUST be set to the node's ECC Public Key.
6LBR receives the address registration NS. 6LBR then verifies the
source address as described in Section 5.1.2. of [RFC3971] using the
claimed source address and CGA Parameters field in the message.
After successfully verifying the address 6LBR next does a
cryptographic check of the signature included in the Digital
Signature field in the message. If all checks succeed then 6LBR
performs a duplicate address detection procedure on the address. If
that also succeeds 6LBR registers the CGA in the neighbor cache. 6LBR
also caches the node's public key.
6LBR sends an address registration neighbor advertisement (NA) as a
reply to confirm the node's registration. Status is set to 0 to
indicate success. This completes initial address registration. The
address registration needs to be refreshed after the neighbor cache
entry times out.
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6LN 6LBR
| |
|<-----------------------RA-------------------------------|
| |
|---------------NS with ARO and CGA Option--------------->|
| |
|<-----------------------NA with ARO----------------------|
| |
|---------------NS with ARO and Digital Signature Option->|
| |
|<-----------------------NA with ARO----------------------|
| |
|---------------NS with ARO and Digital Signature Option->|
| |
|<-----------------------NA with ARO----------------------|
Figure 1: Lightweight SEND for LLN Protocol
In order to refresh the neighbor cache entry, an LSEND for LLN node
MUST send an address registration NS message after adding the Digital
Signature Option defined in Section 4.2. The Key Hash field is a
hash of the node's public key and MUST be set as described in
Section 4.2. The Digital Signature field MUST be set as described in
Section 4.2.
6LBR receives the address registration refresh NS. 6LBR uses the key
hash field in Digital Signature Option to find the node's public key
from the neighbor cache. 6LBR verifies the digital signature in the
NS. In case of successful verification, 6LBR sends back an address
registration neighbor advertisement (NA) to the node and sets the
status to 0 indicating successful refreshment of the CGA of the node.
Similar refresh NS and NA exchanges happen afterwards as shown in
Figure 1.
5.1. Packet Sizes
An original address registration NS message that contains a 40 byte
header and ARO is 16 octets. DER-encoded ECC Public Key for P-256
curve is 88 octets long uncompressed and 88-32=56 octets with point
compression. Digital Signature field when using ECDSA for P-256
curve is 72 octets long without padding bytes for a DER encoding of
the ASN.1 type "ECDSA-sig-value" [ANSIX9.62].
CGA Parameters and Digital Signature Option's CGA Parameters include
16 octet modifier, 8 octet prefix obtained from the router
advertisement message sent from 6LBR, 1 octet collision count and 56
octet Public Key. Digital Signature is 72 octets. The option is 160
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octets with Padding of 7 octets. The total message size of an
original LSEND address registration NS message is 216 octets and such
a message can be encapsulated into three 802.15.4 frames.
An address registration refresh NS message contains an ARO which is
16 octets and the digital signature option containing 16 octet key
hash and 71 octet signature and 5 octet Padding. The message is 152
octets long with the header. Such a message could be encapsulated in
two 802.15.4 frames.
6. Security Considerations
The same considerations regarding the threats to the Local Link Not
Covered (as in [RFC3971]) apply.
The threats discussed in Section 9.2 of [RFC3971] are countered by
the protocol described in this document as well.
As to the attacks to the protocol itself, denial of service attacks
that involve producing a very high number of packets are deemed
unlikely because of the assumptions on the node capabilities in low-
power and lossy networks.
7. IANA considerations
This document defines two new options to be used in neighbor
discovery protocol messages and new type values for CGA Parameters
and Digital Signature Option (TBA1) and Digital Signature Option
(TBA2) need to be assigned by IANA.
This document defines 0xE8C47FB7FD2BB885DAB2D31A0F2808B4 for LSEND
CGA Message Type Tag.
8. Acknowledgements
TBD.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC3756] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor
Discovery (ND) Trust Models and Threats", RFC 3756,
May 2004.
[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.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
[RFC5480] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
"Elliptic Curve Cryptography Subject Public Key
Information", RFC 5480, March 2009.
[I-D.ietf-6lowpan-nd]
Shelby, Z., Chakrabarti, S., and E. Nordmark, "Neighbor
Discovery Optimization for Low Power and Lossy Networks
(6LoWPAN)", draft-ietf-6lowpan-nd-18 (work in progress),
October 2011.
[SEC1] "Standards for Efficient Crtptography Group. SEC 1:
Elliptic Curve Cryptography Version 2.0", May 2009.
[ANSIX9.62]
"American National Standards Institute (ANSI), ANS X9.62-
2005: The Elliptic Curve Digital Signature Algorithm
(ECDSA)", November 2005.
9.2. Informative references
[SEC2] "Standards for Efficient Crtptography Group. SEC 2:
Recommended Elliptic Curve Domain Parameters Version
2.0", January 2010.
[FIPS-186-3]
"National Institute of Standards and Technology, "Digital
Signature Standard"", June 2009.
[NIST-ST] "National Institute of Standards and Technology, "NIST
Comments on Cryptanalytic Attackts on SHA-1"",
January 2009,
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<http://csrc.nist.gov/groups/ST/hash/statement.html>.
[I-D.cheneau-csi-ecc-sig-agility]
Cheneau, T., Laurent, M., Shen, S., and M. Vanderveen,
"ECC public key and signature support in Cryptographically
Generated Addresses (CGA) and in the Secure Neighbor
Discovery (SEND)", draft-cheneau-csi-ecc-sig-agility-02
(work in progress), June 2010.
[I-D.cheneau-csi-send-sig-agility]
Cheneau, T., Laurent, M., Shen, S., and M. Vanderveen,
"Signature Algorithm Agility in the Secure Neighbor
Discovery (SEND) Protocol",
draft-cheneau-csi-send-sig-agility-02 (work in progress),
June 2010.
Authors' Addresses
Behcet Sarikaya (editor)
Huawei USA
1700 Alma Dr. Suite 500
Plano, TX 75075
Phone: +1 972-509-5599
Email: sarikaya@ieee.org
Frank Xia
Huawei USA
1700 Alma Dr. Suite 500
Plano, TX 75075
Phone: +1 972-509-5599
Email: xiayangsong@huawei.com
Greg Zaverucha (editor)
RIM
5520 Explorer Drive, 4th Floor
Missisauga, ON, Canada L4W 5L1
Phone:
Email: gzaverucha@rim.com
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