Mobile Ad hoc Networking (MANET) U. Herberg Internet-Draft Fujitsu Laboratories of America Updates: 6130, xxxx (if approved) C. Dearlove Intended status: Standards Track BAE Systems ATC Expires: January 3, 2014 T. Clausen LIX, Ecole Polytechnique July 2, 2013 Integrity Protection for Control Messages in NHDP and OLSRv2 draft-ietf-manet-nhdp-olsrv2-sec-03 Abstract This document specifies integrity and replay protection for the MANET Neighborhood Discovery Protocol (NHDP) and the Optimized Link State Routing Protocol version 2 (OLSRv2). This protection is achieved by using an HMAC-SHA-256 Integrity Check Value (ICV) TLV and a timestamp TLV based on POSIX time. The mechanism in this specification can also be used for other protocols that use the generalized packet/message format described in RFC 5444. This document updates RFC 6130 and RFC xxxx by mandating the implementation of this integrity and replay protection in NHDP and OLSRv2. 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 working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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 January 3, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the Herberg, et al. Expires January 3, 2014 [Page 1] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 document authors. All rights reserved. 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 to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Applicability Statement . . . . . . . . . . . . . . . . . . . 4 4. Protocol Overview and Functioning . . . . . . . . . . . . . . 6 5. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. Message Generation and Processing . . . . . . . . . . . . . . 8 6.1. Message Content . . . . . . . . . . . . . . . . . . . . . 8 6.2. Message Generation . . . . . . . . . . . . . . . . . . . . 9 6.3. Message Processing . . . . . . . . . . . . . . . . . . . . 10 6.3.1. Validating a Message Based on Timestamp . . . . . . . 11 6.3.2. Validating a Message Based on Integrity Check . . . . 11 7. Provisioning of Routers . . . . . . . . . . . . . . . . . . . 12 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 9.1. Alleviated Attacks . . . . . . . . . . . . . . . . . . . . 12 9.1.1. Identity Spoofing . . . . . . . . . . . . . . . . . . 12 9.1.2. Link Spoofing . . . . . . . . . . . . . . . . . . . . 12 9.1.3. Replay Attack . . . . . . . . . . . . . . . . . . . . 12 9.2. Limitations . . . . . . . . . . . . . . . . . . . . . . . 13 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 11.1. Normative References . . . . . . . . . . . . . . . . . . . 13 11.2. Informative References . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Herberg, et al. Expires January 3, 2014 [Page 2] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 1. Introduction [RFC Editor note: Please replace "xxxx" throughout this document with the RFC number assigned to [OLSRv2], and remove this note.] This specification updates [RFC6130] and [OLSRv2] by defining a framework of security mechanisms (for integrity and replay protection) that must be included in conforming implementations of those protocols (the Neighborhood Discovery Protocol, NHDP, and the Optimized Link State Routing Protocol version 2, OLSRv2). A deployment of these protocols may 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, and/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. This is 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, while OLSRv2's TC message is forwarded in a new packet, and thus has no single IP datagram source address. The mechanism specified in this document is placed in the packet/ message processing flow as indicated in Figure 1. It exists between the packet parsing/generation function of [RFC5444], and the message processing/generation function of NHDP and OLSRv2. Herberg, et al. Expires January 3, 2014 [Page 3] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 | | 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 and notation 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 Herberg, et al. Expires January 3, 2014 [Page 4] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 invalid for processing", and mention security (integrity protection) as an explicit example. This document specifies a framework that provides this functionality. Implementations of [RFC6130] and [OLSRv2] MUST include this framework, and deployments of [RFC6130] and [OLSRv2] SHOULD use this framework, except for when a different security mechanism is more appropriate. The applicability of this framework 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 protocol messages, and specifies how to use a missing or invalid ICV as an reason to reject a message as "badly formed and therefore invalid for processing". o Specifies the implementation of an ICV Message TLV, 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). Deployments of [RFC6130] and [OLSRv2] using this framework SHOULD use an HMAC/ SHA-256 ICV TLV, but MAY use different algorithms if more appropriate in a deployment. An implementation MAY also use more than one ICV TLV in a message, as long as they each use a different algorithm to calculate the ICV. o Specifies the implementation of a TIMESTAMP Message TLV, defined in [RFC6622bis], to provide message replay protection. Deployments of [RFC6130] and [OLSRv2] using this framework SHOULD use a POSIX time based timestamp, if the clocks in all routers in the network can be synchronized with sufficient precision. o Assumes that a router that is able to generate correct integrity check values is considered trusted. This framework does not: o Specify which key identifiers are to be used in a MANET in which the routers share more than one secret key. (Such keys will be differentiated using the field defined in an ICV TLV in [RFC6622bis].) o Specify how to distribute cryptographic material (shared secret key(s)). Herberg, et al. Expires January 3, 2014 [Page 5] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 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 for use with messages owned by [RFC6130] and [OLSRv2]: o Generation of ICV Message TLVs (as defined in [RFC6622bis]) for inclusion in an outgoing message. An implementation of [RFC6130] and [OLSRv2] MAY use more than one ICV TLV in a message, even with the same type extension, but these ICV TLVs MUST each use a different algorithm to calculate the ICV, e.g., with different hash and/or cryptographic functions when using type extension 1 or 2. An implementation of [RFC6130] and [OLSRv2] MUST at least be able to generate an ICV TLV using HMAC/SHA-256 and one or more secret keys shared by all routers. o Generation of TIMESTAMP Message TLVs (as defined in [RFC6622bis]) for inclusion in an outgoing message. An implementation of [RFC6130] and [OLSRv2] MAY use more than one ICV TLV in a message, but not with the same type extension. An implementation of [RFC6130] and [OLSRv2] that is able to synchronize the clocks in all routers in the network with sufficient precision, MUST at least be able to generate a TIMESTAMP TLV using POSIX time. o Verification of ICV Message TLVs contained in a message, in order to determine if this message MUST be rejected as "badly formed and therefore invalid for processing" [RFC6130] [OLSRv2]. An implementation of [RFC6130] and [OLSRv2] MUST at least be able to verify an ICV TLV using HMAC/SHA-256 and one or more secret keys shared by all routers. o Verification of TIMESTAMP Message TLVs (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]. An implementation of [RFC6130] and [OLSRv2] that is able to synchronize the clocks in all routers in the network with sufficient precision, MUST at least be able to verify a TIMESTAMP TLV using POSIX time. ICV Packet TLVs (as defined in [RFC6622bis]) 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 Herberg, et al. Expires January 3, 2014 [Page 6] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 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 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. [RFC6130] and [OLSRv2] allow for rejecting incoming messages prior to processing by NHDP or OLSRv2. This framework, when used, specifies that a message MUST be rejected if the ICV Message TLV is absent, or its value cannot be verified. Note that this means that routers whose implementation of NHDP and/or OLSRv2 does not include this specification will be ignored by routers using this framework, and these two sets of routers will, by design, form disjoint MANETs. (The unsecured MANET will retain some information about the secured MANET, but be unable to use it, not having any recognized symmetric links with the secured MANET.) 5. Parameters This following router parameters are 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: 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: Herberg, et al. Expires January 3, 2014 [Page 7] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 o MAX_HELLO_TIMESTAMP_DIFF > 0 o MAX_TC_TIMESTAMP_DIFF > 0 These bounds are however insufficient, MAX_HELLO_TIMESTAMP_DIFF and MAX_TC_TIMESTAMP_DIFF MUST be least as great as the maximum expected "age" of a message (i.e., the time difference between a message has been sent by a router and received by all intended destinations). For HELLO messages this needs only cover a single hop, but TC messages may have been forwarded a number of times. In particular for TC messages, if using jitter as specified in [OLSRv2] and [RFC5148], the largest contribution the age may be a delay of up to F_MAXJITTER per hop (except the final hop) that the message has traveled. Other factors in the delay of both message types, per hop, may include the link-layer that is used in the MANET, and CPU and memory resources of routers (e.g., queuing delays, and delays for processing ICVs). An implementation MAY set lower and/or upper bounds on these parameters, if so, then these MUST allow values meeting these requirements. An implementation MAY make its value of MAX_TC_TIMESTAMP_DIFF dependent on the number of hops that a TC message has traveled. The above constraints assume ideal time synchronization of the clock in all routers in the network. The parameters MAX_HELLO_TIMESTAMP_DIFF and MAX_TC_TIMESTAMP_DIFF (and any constraints on them) MAY be increased to allow for expected timing differences between routers (between neighboring routers for MAX_HELLO_TIMESTAMP_DIFF, allowing for greater separation, but usually not per hop, for MAX_TC_TIMESTAMP_DIFF). Note that excessively large values of these parameters defeats their objectives, so these parameters SHOULD be as large as is required, but not significantly larger. 6. Message Generation and Processing This section specifies how messages are generated and processed by [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 framework, each message MUST contain: o At least one ICV Message TLV (as specified in [RFC6622bis]), generated according to Section 6.2. Implementations of [RFC6130] Herberg, et al. Expires January 3, 2014 [Page 8] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 and [OLSRv2] MUST support the following version of the ICV TLV, but other versions MAY be used instead, or in addition, in a deployment, if more appropriate: * For TC messages: + type-extension := 1 * For HELLO messages: + type-extension := 2 * hash-function := 3 (SHA-256) * cryptographic-function := 3 (HMAC) The ICV Value MAY be truncated as specified in [RFC6622bis]; the selection of an appropriate length MAY be administratively configured. A message MAY contain several ICV Message TLVs. o At least one TIMESTAMP Message TLV (as specified in [RFC6622bis]), generated according to Section 6.2. Implementations of [RFC6130] and [OLSRv2] using this framework MUST support the following version of the TIMESTAMP TLV, but other versions MAY be used instead, or in addition, in a deployment, if more appropriate: * 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 (when using a single timestamp version and a single ICV algorithm) MUST be performed for a cryptographic algorithm that is used for generating an ICV for a message: 1. All ICV TLVs (if any) are temporarily removed from the message. Any temporarily removed ICV TLVs MUST be stored, in order to be reinserted into the message in step 5. The message size and Message TLV Block size are updated accordingly. 2. and , if present, are temporarily set to 0. Herberg, et al. Expires January 3, 2014 [Page 9] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 3. A TLV of type TIMESTAMP, as specified in Section 6.1, is added to the Message TLV Block. The message size and Message TLV block size are updated accordingly. 4. A TLV of type ICV, as specified in Section 6.1, is added to the Message TLV Block. The message size and Message TLV block size are updated accordingly. 5. All ICV TLVs that were temporary removed in step 1, are restored. The message size and Message TLV Block size are updated accordingly. 6. and , if present, are restored to their previous values. An implementation MAY add either alternative TIMESTAMP and/or ICV TLVs, or more than one TIMESTAMP and/or ICV TLVs. All TIMESTAMP TLVs MUST be inserted before adding ICV TLVs. 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". When using a single timestamp version, and a single ICV algorithm, 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 processing when using this framework: 1. The Message TLV Block of the message does not contain exactly one TIMESTAMP TLV of the selected version. This version specification includes the type extension. (The Message TLV Block may also contain TIMESTAMP TLVs of other versions.) 2. The Message TLV block does not contain exactly one ICV TLV using the selected algorithm and key identifier. This algorithm specification includes the type extension, and for type extensions 1 and 2, the hash function and cryptographic function. (The Message TLV Block may also contain ICV TLVs using other algorithms and key identifiers.) 3. Validation of the identified (in step 1) TIMESTAMP TLV in the Message TLV block of the message fails, as according to Herberg, et al. Expires January 3, 2014 [Page 10] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 Section 6.3.1. 4. Validation of the identified (in step 2) ICV TLV in the Message TLV block of the message fails, as according to Section 6.3.2. An implementation MAY check the existence of, and verify, either alternative TIMESTAMP and/or ICV TLVs, or more than one TIMESTAMP and/or ICV TLVs. 6.3.1. Validating a Message Based on Timestamp For a TIMESTAMP Message TLV with type extension 1 (POSIX time) 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. 2. Otherwise, the message validation succeeds. If a deployment chooses to use a different type extension from 1, appropriate measures MUST be taken to verify freshness of the message. 6.3.2. Validating a Message Based on Integrity Check For an ICV Message TLV identified as described in Section 6.2: 1. All ICV Message TLVs (including the identified ICV Message TLV) are temporarily removed from the message, and the message size and Message TLV block size are updated accordingly. 2. The message's and fields are temporarily set to 0. 3. Calculate the integrity check value for the parameters specified in the identified ICV Message TLV, as specified in [RFC6622bis]. 4. If this integrity check value differs from the value of in the ICV Message TLV, then the message validation fails. If the has been truncated (as specified in [RFC6622bis], the integrity check value calculated in the previous step MUST be truncated to the TLV length of the ICV Message TLV before comparing it with the . 5. Otherwise, the message validation succeeds. The message's and fields are restored to their Herberg, et al. Expires January 3, 2014 [Page 11] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 previous value, and the ICV Message TLVs are returned to the message, whose size is updated accordingly. 7. Provisioning of Routers Before a router using this framework is able to generate ICVs or validate messages, it MUST acquire the shared secret key(s) to be used by all routers that are to participate in the network. This specification does not define how a router acquires secret keys. Once a router has acquired suitable key(s) it MAY be configured to use, or not use, this framework. 8. IANA Considerations This document has no actions for IANA. [This section may be removed by the RFC Editor.] 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 selected shared secret key are able to add a valid ICV TLV to a message, identity spoofing, where an attacker falsely claims an identity of a valid router, is countered. 9.1.2. Link Spoofing Link spoofing, where an attacker falsely represents the existence of a non-existent link, or otherwise misrepresents a link's state, 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 countered by the framework specified in this document, but this depends on synchronized clocks of all routers Herberg, et al. Expires January 3, 2014 [Page 12] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 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. 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(s) (and if an alternative integrity check value is used, any additional cryptographic parameters). This framework does not provide a key revocation mechanism. 10. Acknowledgments The authors would like to gratefully acknowledge the following people: Henning Rogge (Frauenhofer FKIE). 11. References 11.1. Normative References [OLSRv2] Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg, "The Optimized Link State Routing Protocol version 2", work in progress draft-ietf-manet-olsrv2-19, March 2013. [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, Herberg, et al. Expires January 3, 2014 [Page 13] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 "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)", work in progress draft-ietf-manet-rfc6622-bis-02, April 2013. 11.2. Informative References [RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter Considerations in Mobile Ad Hoc Networks (MANETs)", RFC 5148, February 2008. Authors' Addresses Ulrich Herberg Fujitsu Laboratories of America 1240 E. Arques Ave. Sunnyvale, CA, 94085, USA Email: ulrich@herberg.name URI: http://www.herberg.name/ Christopher Dearlove BAE Systems Advanced Technology Centre West Hanningfield Road Great Baddow, Chelmsford United Kingdom Phone: +44 1245 242194 Email: chris.dearlove@baesystems.com URI: http://www.baesystems.com/ Herberg, et al. Expires January 3, 2014 [Page 14] Internet-Draft Integrity Protection for NHDP and OLSRv2 July 2013 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/ Herberg, et al. Expires January 3, 2014 [Page 15]