Integrity Protection for Control Messages in NHDP and OLSRv2
draft-herberg-manet-nhdp-olsrv2-sec-00
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| Authors | Thomas H. Clausen , Christopher Dearlove , Ulrich Herberg | ||
| Last updated | 2013-02-18 | ||
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draft-herberg-manet-nhdp-olsrv2-sec-00
Mobile Ad hoc Networking (MANET) T. Clausen
Internet-Draft LIX, Ecole Polytechnique
Updates: RFC6130 (if approved) C. Dearlove
Intended status: Standards Track BAE Systems ATC
Expires: August 22, 2013 U. Herberg
Fujitsu Laboratories of America
February 18, 2013
Integrity Protection for Control Messages in NHDP and OLSRv2
draft-herberg-manet-nhdp-olsrv2-sec-00
Abstract
This document specifies integrity and replay protection for required
implementation in the MANET Neighborhood Discovery Protocol (NHDP)
and the Optimized Link State Routing Protocol version 2 (OLSRv2).
This document specifies how an integrity check value (ICV) and a
timestamp may be included as TLVs (defined in [RFC6622bis]) in NHDP's
and OLSRv2's control messages, countering a number of security
threats to NHDP and to OLSRv2. The ICV TLV uses a SHA-256 based HMAC
and a single shared secret key. The timestamp TLV is based on POSIX
time, assuming router synchronization. The mechanism in this
specification can also be used for other MANET protocols using
RFC5444.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 22, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Applicability Statement . . . . . . . . . . . . . . . . . . . 4
4. Protocol Overview and Functioning . . . . . . . . . . . . . . 5
5. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Message Generation and Processing . . . . . . . . . . . . . . 7
6.1. Message Content . . . . . . . . . . . . . . . . . . . . . 7
6.2. Message Generation . . . . . . . . . . . . . . . . . . . . 8
6.3. Message Processing . . . . . . . . . . . . . . . . . . . . 8
6.3.1. Invalidating a Message Based on Integrity Check . . . 9
6.3.2. Invalidating a Message Based on Timestamp . . . . . . 9
7. Provisioning of Routers . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9.1. Alleviated Attacks . . . . . . . . . . . . . . . . . . . . 10
9.1.1. Identity Spoofing . . . . . . . . . . . . . . . . . . 10
9.1.2. Link Spoofing . . . . . . . . . . . . . . . . . . . . 10
9.1.3. Replay Attack . . . . . . . . . . . . . . . . . . . . 10
9.2. Limitations . . . . . . . . . . . . . . . . . . . . . . . 11
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . . 11
10.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
This specification defines a framework of security mechanisms that
must be included in conforming implementations of the mobile ad hoc
network (MANET) protocols Neighborhood Discovery Protocol (NHDP)
[RFC6130] and the Optimized Link State Routing Protocol version 2
(OLSRv2) [OLSRv2]. A deployment of these protocols may however
choose to employ alternative(s) to these mechanisms, in particular it
may choose to protect packets rather than messages, it may choose to
use an alternative integrity check value (ICV) with preferred
properties, or it may use an alternative timestamp. A deployment may
choose to use no such security mechanisms, but this is not
recommended.
The mechanisms specified are the use of an ICV for protection of the
protocols' control messages, and the use of timestamps in those
messages to prevent replay attacks. Both use the TLV mechanism
specified in [RFC5444] to add this information to the messages.
These ICV and timestamp TLVs are defined in [RFC6622bis]. Different
ICV TLVs are used for HELLO messages in NHDP and TC messages in
OLSRv2, the former also protecting the source address of the IP
datagram that contains the HELLO message, because the IP datagram
source address is used by NHDP to determine the address of a neighbor
interface, and is not necessarily otherwise contained in the HELLO
message.
The mechanism specified in this document must insert itself between
NHDP's and OLSRv2's message processing/generation and the [RFC5444]
packet parsing/generation, as illustrated in Figure 1.
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| |
Incoming | /|\ Outgoing
packet \|/ | packet
| |
+--------------------------------+
| |
| RFC5444 packet |
| parsing / generation |
| |
+--------------------------------+
| |
Messages | /|\ Messages with
\|/ | added TLVs
| |
D +--------------------------------+
R /__________________ | |
O \ Messages | This specification |
P (failed check) | |
+--------------------------------+
| |
Messages | /|\ Messages
(passed check) \|/ |
| |
+--------------------------------+
| |
| NHDP/OLSRv2 message |
| processing / generation |
| |
+--------------------------------+
Figure 1: Relationship with RFC5444 and NHDP/OLSRv2
2. Terminology
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 in
[RFC2119].
Additionally, this document uses the terminology of [RFC5444],
[RFC6130], [OLSRv2], and [RFC6622bis].
3. Applicability Statement
[RFC6130] and [OLSRv2] enable extensions to recognize additional
reasons for rejecting a message as "badly formed and therefore
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invalid for processing", and mention security as an explicit example.
This framework's applicability to provide that functionality is
determined by its characteristics, which are that it:
o Specifies a security framework that is required to be included in
conforming implementations of [RFC6130] and [OLSRv2].
o Specifies an association of ICVs with messages, and for using
missing or invalid ICVs as such an "additional reason" for
rejecting a message as "badly formed and therefore invalid for
processing".
o Specifies ICV TLVs, defined in [RFC6622bis], using a SHA-256 based
HMAC applied to the appropriate message contents (and for HELLO
messages also including the IP datagram source address) to
implement the required association.
o Specifies a TIMESTAMP TLV, defined in [RFC6622bis], to provide
message replay protection.
o Assumes that a router which is able to generate correct integrity
checks is considered trusted.
This framework does NOT:
o Specify how to distribute cryptographic material (shared secret
key).
o Specify how to detect compromised routers with valid keys.
o Specify how to handle (revoke) compromised routers with valid
keys.
4. Protocol Overview and Functioning
The framework specified in this document provides the following
functionalities that may be used in the messages owned by [RFC6130]
and [OLSRv2]:
o Generation of an ICV TLV (as defined in [RFC6622bis]) for
inclusion in an outgoing message.
o Generation of a TIMESTAMP TLV (as defined in [RFC6622bis]) for
inclusion in an outgoing message.
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o Verification of an ICV TLV contained in a message, in order to
determine if this message MUST be rejected as "badly formed and
therefore invalid for processing" [RFC6130] [OLSRv2].
o Verification of a TIMESTAMP TLV (as defined in [RFC6622bis])
contained in a message, in order to determine if this message MUST
be rejected as "badly formed and therefore invalid for processing"
[RFC6130] [OLSRv2].
Specific cases of the ICV and TIMESTAMP TLVs that MUST be implemented
in conforming implementations of NHDP and OLSRv2 are specified in
this document, referenced from [RFC6622bis].
ICV Packet TLVs may be used by a deployment of the multiplexing
process defined in [RFC5444], either as well as, or instead of, the
protection of the NHDP and OLSRv2 messages. (Note that in the case
of NHDP, the packet protection is equally good, and also protects the
packet header. In the case of OLSRv2, the packet protection has
different properties than the message protection, especially for some
possible forms of ICV. When packets contain more than one message,
the packet protection has lower overheads in space and computation
time.)
When a router generates a message on a MANET interface, this
framework:
o Specifies how to calculate an integrity check value for the
message.
o Specifies how to include that integrity check value using an ICV
Message TLV.
The ICV algorithm whose implementation is REQUIRED by this framework
is an HMAC [RFC2104] using the SHA-256 hash function [RFC4634] and a
single secret key shared by all routers.
[RFC6130] and [OLSRv2] allow for rejecting incoming messages prior to
processing by NHDP or OLSRv2. This framework specifies that a
message MUST be rejected if the ICV Message TLV is absent, or its
value cannot be verified.
5. Parameters
This following router parameters is specified for use by the two
protocols; the first is required only by NHDP, but may be visible to
OLSRv2, the second is required only by OLSRv2:
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o MAX_HELLO_TIMESTAMP_DIFF - The maximum age that a HELLO message to
be validated may have. If the current POSIX time of the router
validating the HELLO message, minus the timestamp indicated in the
TIMESTAMP TLV of the HELLO message, is greater than
MAX_HELLO_TIMESTAMP_DIFF, the HELLO message MUST be silently
discarded.
o MAX_TC_TIMESTAMP_DIFF - The maximum age that a TC message to be
validated may have. If the current POSIX time of the router
validating the TC message, minus the timestamp indicated in the
TIMESTAMP TLV of the TC message, is greater than
MAX_TC_TIMESTAMP_DIFF, the TC message MUST be silently discarded.
The following constraints apply to these parameters:
o MAX_HELLO_TIMESTAMP_DIFF > 0
o MAX_HELLO_TIMESTAMP_DIFF < REFRESH_INTERVAL
o MAX_TC_TIMESTAMP_DIFF > 0
o MAX_TC_TIMESTAMP_DIFF < T_HOLD_TIME
The second and fourth of those constraints assume ideal
synchronization. These bounds MAY be relaxed to allow for expected
timing differences between routers (between neighboring routers for
MAX_HELLO_TIMESTAMP_DIFF). However it should also be noted that, in
the ideal case, the parameters SHOULD be significantly less than
those bounds.
6. Message Generation and Processing
This section specifies the modifications how messages are generated
and processed in [RFC6130] and [OLSRv2] when using this framework.
6.1. Message Content
Messages MUST have the content specified in [RFC6130] and [OLSRv2]
respectively. In addition, in order to conform to this
specification, each message MUST contain:
o One ICV Message TLV (as specified in [RFC6622bis]), generated
according to Section 6.2, with:
* For TC messages:
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+ type-extension := 1
* For HELLO messages:
+ type-extension := 2
* hash-function := 3 (SHA-256)
* cryptographic-function := 3 (HMAC)
o One TIMESTAMP TLV (as specified in [RFC6622bis]), with:
* type-extension := 1
6.2. Message Generation
After message generation (Section 11.1 of [RFC6130] and Section 16.1.
of [OLSRv2]) and before message transmission (Section 11.2 of
[RFC6130] and Section 16.2 of [OLSRv2]), the additional TLVs
specified in Section 6.1 MUST (unless already present) be added to an
outgoing message when using this framework.
The following processing steps MUST be performed in this case:
1. <msg-hop-count> and <msg-hop-limit>, if present, are temporarily
set to 0.
2. A TLV of type TIMESTAMP, as specified in Section 6.1, is added to
the Message TLV block. The message size is updated accordingly.
3. A TLV of type ICV, as specified in [RFC6622bis], is added to the
Message TLV block. The message size is updated accordingly.
4. <msg-hop-count> and <msg-hop-limit>, if present, are restored to
their previous values.
6.3. Message Processing
Both [RFC6130] and [OLSRv2] specify that:
"On receiving a ... message, a router MUST first check if the
message is invalid for processing by this router"
[RFC6130] and [OLSRv2] proceed to give a number of conditions that,
each, will lead to a rejection of the message as "badly formed and
therefore invalid for processing". This document adds the following
conditions to that list, each of which, if true, MUST cause NHDP or
OLSRv2 (as appropriate) to consider the message as invalid for
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processing when using this framework:
o The Message TLV block of the message does not contain exactly one
TIMESTAMP TLV and exactly one ICV TLV, each with the type
extension, and in the former case hash function and cryptographic
function, specified in Section 6.1. (The message may contain
additional ICV and/or TIMESTAMP TLVs, but with different
parameters.)
o Validation of the ICV TLV in the Message TLV block of the message
fails, according to Section 6.3.1.
o Validation of the TIMESTAMP TLV in the Message TLV block of the
message fails, according to Section 6.3.2.
6.3.1. Invalidating a Message Based on Integrity Check
Consider the ICV Message TLV identified as described in Section 6.2:
1. The identified ICV Message TLV is removed from the message, and
the message size is updated accordingly.
2. The message's <msg-hop-count> and <msg-hop-limit> fields are
temporarily set to 0.
3. Calculate the integrity check value for the parameters specified
in Section 6.1, as specified in [RFC6622bis].
4. If this message check value differs from the value of <ICV-data>
in the ICV Message TLV, then the message validation fails.
5. Otherwise, the message validation succeeds. The message's <msg-
hop-count> and <msg-hop-limit> fields are restored to their
previous value, and if required (as it MUST be if the message is
forwarded) the ICV Message TLV is returned to the message, whose
size is updated accordingly. (Alternatively, the original
received message may be used.)
6.3.2. Invalidating a Message Based on Timestamp
Consider the TIMESTAMP Message TLV identified as described in
Section 6.2:
1. If the current POSIX time minus the value of that TIMESTAMP TLV
is greater than MAX_HELLO_TIMESTAMP_DIFF (for a HELLO message) or
MAX_TC_TIMESTAMP_DIFF (for a TC message) then the message
validation fails.
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2. Otherwise the message validation succeeds.
7. Provisioning of Routers
Before a router is able to generate ICVs or validate messages, it
MUST acquire the single shared secret key that is to be used by all
routers that are to participate in the network. This specification
does not define how a router acquires this secret key.
8. IANA Considerations
This document has no actions for IANA.
9. Security Considerations
This document specifies a security framework for use with NHDP and
OLSRv2 that allows for alleviating several security threats.
9.1. Alleviated Attacks
This section briefly summarizes security threats that are alleviated
by the framework presented in this document.
9.1.1. Identity Spoofing
As only routers possessing the shared secret key are able to add a
valid ICV TLV to a message, identity spoofing is countered.
9.1.2. Link Spoofing
Link spoofing is countered by the framework specified in this
document, using the same argument as in Section 9.1.1.
9.1.3. Replay Attack
Replay attacks are partly counteracted by the framework specified in
this document, but this depends on synchronized clocks of all routers
in the MANET. An attacker that records messages to replay them later
can only do so in the selected time interval after the timestamp that
is contained in message. As an attacker cannot modify the content of
this timestamp (as it is protected by the identity check value), an
attacker cannot replay messages after this time. Within this time
interval it is still possible to perform replay attacks, however the
limits on the time interval are specified so that this will have a
limited effect on the operation of the protocol.
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9.2. Limitations
If no synchronized clocks are available in the MANET, replay attacks
cannot be countered by the framework provided by this document. An
alternative version of the TIMESTAMP TLV defined in [RFC6622bis],
with a monotonic sequence number, may have some partial value in this
case, but will necessitate adding state to record observed message
sequence number information.
The framework provided by this document does not avoid or detect
security attacks by routers possessing the shared secret key that is
used to generate integrity check values for messages.
This framework relies on an out-of-band protocol or mechanism for
distributing the shared secret key (and if an alternative integrity
check value is used, any additional cryptographic parameters).
This framework does not provide a key revocation mechanism.
10. References
10.1. Normative References
[OLSRv2] Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg,
"The Optimized Link State Routing Protocol version 2",
draft-ietf-manet-olsrv2-17 (work in progress),
October 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
"Generalized MANET Packet/Message Format", RFC 5444,
February 2009.
[RFC6130] Clausen, T., Dean, J., and C. Dearlove, "Mobile Ad Hoc
Network (MANET) Neighborhood Discovery Protocol (NHDP)",
RFC 6130, April 2011.
[RFC6622bis]
Herberg, U., Clausen, T., and C. Dearlove, "Integrity
Check Value and Timestamp TLV Definitions for Mobile Ad
Hoc Networks (MANETs)", Internet
Draft draft-herberg-manet-rfc6622-bis-00, February 2013.
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10.2. Informative References
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104.
[RFC4634] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and HMAC-SHA)", RFC 4634.
Authors' Addresses
Thomas Heide Clausen
LIX, Ecole Polytechnique
91128 Palaiseau Cedex,
France
Phone: +33 6 6058 9349
Email: T.Clausen@computer.org
URI: http://www.thomasclausen.org/
Christopher Dearlove
BAE Systems ATC
Phone: +44 1245 242194
Email: chris.dearlove@baesystems.com
URI: http://www.baesystems.com/
Ulrich Herberg
Fujitsu Laboratories of America
1240 E. Arques Ave.
Sunnyvale, CA, 94085,
USA
Email: ulrich@herberg.name
URI: http://www.herberg.name/
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