draft-ietf-roll-security-threats-06.txt   draft-ietf-roll-security-threats-07.txt 
Routing Over Low-Power and Lossy Networks T. Tsao Routing Over Low-Power and Lossy Networks T. Tsao
Internet-Draft R. Alexander Internet-Draft R. Alexander
Intended status: Informational Cooper Power Systems Intended status: Informational Cooper Power Systems
Expires: June 18, 2014 M. Dohler Expires: December 12, 2014 M. Dohler
CTTC CTTC
V. Daza V. Daza
A. Lozano A. Lozano
Universitat Pompeu Fabra Universitat Pompeu Fabra
M. Richardson M. Richardson
Sandelman Software Works Sandelman Software Works
December 15, 2013 June 10, 2014
A Security Threat Analysis for Routing Protocol for Low-power and lossy A Security Threat Analysis for Routing Protocol for Low-power and lossy
networks (RPL) networks (RPL)
draft-ietf-roll-security-threats-06 draft-ietf-roll-security-threats-07
Abstract Abstract
This document presents a security threat analysis for the Routing This document presents a security threat analysis for the Routing
Protocol for Low-power and lossy networks (RPL, ROLL). The Protocol for Low-power and lossy networks (RPL, ROLL). The
development builds upon previous work on routing security and adapts development builds upon previous work on routing security and adapts
the assessments to the issues and constraints specific to low-power the assessments to the issues and constraints specific to low-power
and lossy networks. A systematic approach is used in defining and and lossy networks. A systematic approach is used in defining and
evaluating the security threats. Applicable countermeasures are evaluating the security threats. Applicable countermeasures are
application specific and are addressed in relevant applicability application specific and are addressed in relevant applicability
skipping to change at page 2, line 10 skipping to change at page 2, line 10
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 18, 2014. This Internet-Draft will expire on December 12, 2014.
Copyright Notice Copyright Notice
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document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Relationship to other documents . . . . . . . . . . . . . . . 4
3. Considerations on RPL Security . . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Routing Assets and Points of Access . . . . . . . . . . . 5 4. Considerations on RPL Security . . . . . . . . . . . . . . . 5
3.2. The ISO 7498-2 Security Reference Model . . . . . . . . . 7 4.1. Routing Assets and Points of Access . . . . . . . . . . . 5
3.3. Issues Specific to or Amplified in LLNs . . . . . . . . . 9 4.2. The ISO 7498-2 Security Reference Model . . . . . . . . . 7
3.4. RPL Security Objectives . . . . . . . . . . . . . . . . . 11 4.3. Issues Specific to or Amplified in LLNs . . . . . . . . . 9
4. Threat Sources . . . . . . . . . . . . . . . . . . . . . . . 12 4.4. RPL Security Objectives . . . . . . . . . . . . . . . . . 11
5. Threats and Attacks . . . . . . . . . . . . . . . . . . . . . 12 5. Threat Sources . . . . . . . . . . . . . . . . . . . . . . . 12
5.1. Threats due to failures to Authenticate . . . . . . . . . 13 6. Threats and Attacks . . . . . . . . . . . . . . . . . . . . . 13
5.1.1. Node Impersonation . . . . . . . . . . . . . . . . . 13 6.1. Threats due to failures to Authenticate . . . . . . . . . 13
5.1.2. Dummy Node . . . . . . . . . . . . . . . . . . . . . 13 6.1.1. Node Impersonation . . . . . . . . . . . . . . . . . 13
5.1.3. Node Resource Spam . . . . . . . . . . . . . . . . . 13 6.1.2. Dummy Node . . . . . . . . . . . . . . . . . . . . . 14
5.2. Threats and Attacks on Confidentiality . . . . . . . . . 13 6.1.3. Node Resource Spam . . . . . . . . . . . . . . . . . 14
5.2.1. Routing Exchange Exposure . . . . . . . . . . . . . . 14 6.2. Threats and Attacks on Confidentiality . . . . . . . . . 14
5.2.2. Routing Information (Routes and Network Topology) 6.2.1. Routing Exchange Exposure . . . . . . . . . . . . . . 14
6.2.2. Routing Information (Routes and Network Topology)
Exposure . . . . . . . . . . . . . . . . . . . . . . 14 Exposure . . . . . . . . . . . . . . . . . . . . . . 14
5.3. Threats and Attacks on Integrity . . . . . . . . . . . . 15 6.3. Threats and Attacks on Integrity . . . . . . . . . . . . 15
5.3.1. Routing Information Manipulation . . . . . . . . . . 15 6.3.1. Routing Information Manipulation . . . . . . . . . . 15
5.3.2. Node Identity Misappropriation . . . . . . . . . . . 16 6.3.2. Node Identity Misappropriation . . . . . . . . . . . 16
5.4. Threats and Attacks on Availability . . . . . . . . . . . 16 6.4. Threats and Attacks on Availability . . . . . . . . . . . 17
5.4.1. Routing Exchange Interference or Disruption . . . . . 16 6.4.1. Routing Exchange Interference or Disruption . . . . . 17
5.4.2. Network Traffic Forwarding Disruption . . . . . . . . 16 6.4.2. Network Traffic Forwarding Disruption . . . . . . . . 17
5.4.3. Communications Resource Disruption . . . . . . . . . 18 6.4.3. Communications Resource Disruption . . . . . . . . . 18
5.4.4. Node Resource Exhaustion . . . . . . . . . . . . . . 18 6.4.4. Node Resource Exhaustion . . . . . . . . . . . . . . 19
6. Countermeasures . . . . . . . . . . . . . . . . . . . . . . . 19 7. Countermeasures . . . . . . . . . . . . . . . . . . . . . . . 20
6.1. Confidentiality Attack Countermeasures . . . . . . . . . 19 7.1. Confidentiality Attack Countermeasures . . . . . . . . . 20
6.1.1. Countering Deliberate Exposure Attacks . . . . . . . 19 7.1.1. Countering Deliberate Exposure Attacks . . . . . . . 20
6.1.2. Countering Passive Wiretapping Attacks . . . . . . . 20 7.1.2. Countering Passive Wiretapping Attacks . . . . . . . 21
6.1.3. Countering Traffic Analysis . . . . . . . . . . . . . 21 7.1.3. Countering Traffic Analysis . . . . . . . . . . . . . 21
6.1.4. Countering Remote Device Access Attacks . . . . . . . 22 7.1.4. Countering Remote Device Access Attacks . . . . . . . 22
6.2. Integrity Attack Countermeasures . . . . . . . . . . . . 22 7.2. Integrity Attack Countermeasures . . . . . . . . . . . . 22
6.2.1. Countering Unauthorized Modification Attacks . . . . 22 7.2.1. Countering Unauthorized Modification Attacks . . . . 23
6.2.2. Countering Overclaiming and Misclaiming Attacks . . . 23 7.2.2. Countering Overclaiming and Misclaiming Attacks . . . 23
6.2.3. Countering Identity (including Sybil) Attacks . . . . 23 7.2.3. Countering Identity (including Sybil) Attacks . . . . 24
6.2.4. Countering Routing Information Replay Attacks . . . . 23 7.2.4. Countering Routing Information Replay Attacks . . . . 24
6.2.5. Countering Byzantine Routing Information Attacks . . 24 7.2.5. Countering Byzantine Routing Information Attacks . . 25
6.3. Availability Attack Countermeasures . . . . . . . . . . . 25 7.3. Availability Attack Countermeasures . . . . . . . . . . . 25
6.3.1. Countering HELLO Flood Attacks and ACK Spoofing 7.3.1. Countering HELLO Flood Attacks and ACK Spoofing
Attacks . . . . . . . . . . . . . . . . . . . . . . . 25 Attacks . . . . . . . . . . . . . . . . . . . . . . . 26
6.3.2. Countering Overload Attacks . . . . . . . . . . . . . 26 7.3.2. Countering Overload Attacks . . . . . . . . . . . . . 26
6.3.3. Countering Selective Forwarding Attacks . . . . . . . 27 7.3.3. Countering Selective Forwarding Attacks . . . . . . . 28
6.3.4. Countering Sinkhole Attacks . . . . . . . . . . . . . 28 7.3.4. Countering Sinkhole Attacks . . . . . . . . . . . . . 29
6.3.5. Countering Wormhole Attacks . . . . . . . . . . . . . 29 7.3.5. Countering Wormhole Attacks . . . . . . . . . . . . . 30
7. RPL Security Features . . . . . . . . . . . . . . . . . . . . 29 8. RPL Security Features . . . . . . . . . . . . . . . . . . . . 30
7.1. Confidentiality Features . . . . . . . . . . . . . . . . 30 8.1. Confidentiality Features . . . . . . . . . . . . . . . . 31
7.2. Integrity Features . . . . . . . . . . . . . . . . . . . 31 8.2. Integrity Features . . . . . . . . . . . . . . . . . . . 32
7.3. Availability Features . . . . . . . . . . . . . . . . . . 32 8.3. Availability Features . . . . . . . . . . . . . . . . . . 33
7.4. Key Management . . . . . . . . . . . . . . . . . . . . . 32 8.4. Key Management . . . . . . . . . . . . . . . . . . . . . 33
7.5. Consideration on Matching Application Domain Needs . . . 33 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33
7.5.1. Mechanisms and Operations . . . . . . . . . . . . . . 33 10. Security Considerations . . . . . . . . . . . . . . . . . . . 34
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 34
9. Security Considerations . . . . . . . . . . . . . . . . . . . 34 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 34 12.1. Normative References . . . . . . . . . . . . . . . . . . 34
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 34 12.2. Informative References . . . . . . . . . . . . . . . . . 35
11.1. Normative References . . . . . . . . . . . . . . . . . . 35
11.2. Informative References . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39
1. Introduction 1. Introduction
In recent times, networked electronic devices have found an In recent times, networked electronic devices have found an
increasing number of applications in various fields. Yet, for increasing number of applications in various fields. Yet, for
reasons ranging from operational application to economics, these reasons ranging from operational application to economics, these
wired and wireless devices are often supplied with minimum physical wired and wireless devices are often supplied with minimum physical
resources; the constraints include those on computational resources resources; the constraints include those on computational resources
(RAM, clock speed, storage), communication resources (duty cycle, (RAM, clock speed, storage), communication resources (duty cycle,
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address their potential networking challenges. Securing the address their potential networking challenges. Securing the
establishment and maintenance of network connectivity among these establishment and maintenance of network connectivity among these
deployed devices becomes one of these key challenges. deployed devices becomes one of these key challenges.
This document presents a threat analysis for securing the Routing This document presents a threat analysis for securing the Routing
Protocol for LLNs (RPL). The process requires two steps. First, the Protocol for LLNs (RPL). The process requires two steps. First, the
analysis will be used to identify pertinent security issues. The analysis will be used to identify pertinent security issues. The
second step is to identify necessary countermeasures to secure RPL. second step is to identify necessary countermeasures to secure RPL.
As there are multiple ways to solve the problem and the specific As there are multiple ways to solve the problem and the specific
tradeoffs are deployment specific, the specific countermeasure to be tradeoffs are deployment specific, the specific countermeasure to be
used is detailed in applicatbility statements. used is detailed in applicability statements.
This document uses [IS07498-2] model, which includes Authentication, This document uses [IS07498-2] model, which describes Authentication,
Access Control, Data Confidentiality, Data Integrity, and Non- Access Control, Data Confidentiality, Data Integrity, and Non-
Repudiation but to which Availability is added. Repudiation security services and to which Availability is added.
All of this document concerns itself with securing the control plane All of this document concerns itself with securing the control plane
traffic. As such it does not address authorization or authentication traffic. As such it does not address authorization or authentication
of application traffic, nor does it deal with multicast traffic of application traffic. RPL uses multicast as part of it's protocol,
controls. Mechanisms used to secure RPL traffic SHOULD be leveraged and therefore mechanisms which RPL uses to secure this traffic MAY be
to secure other protocols. applicable to MPL control traffic as well: the important part is that
the threats are similiar.
2. Terminology 2. Relationship to other documents
ROLL has specified a set of routing protocols for Lossy and Low-
resource Networks (LLN) [RFC6550]. A number of applicability texts
describes a subset of these protocols and the conditions which make
the subset the correct choice. The text recommends and motivates the
accompanying parameter value ranges. Multiple applicability domains
are recognized including: Building and Home, and Advanced Metering
Infrastructure. The applicability domains distinguish themselves in
the way they are operated, their performance requirements, and the
most probable network structures. Each applicability statement
identifies the distinguishing properties according to a common set of
subjects described in as many sections.
The common set of security threats are herein are referred to by the
applicability statements, and that series of documents describes the
preferred security settings and solutions within the applicability
statement conditions. This applicability statements may recommend
more light weight security solutions and specify the conditions under
which these solutions are appropriate.
3. Terminology
This document adopts the terminology defined in [RFC6550], in This document adopts the terminology defined in [RFC6550], in
[RFC4949], and in [I-D.ietf-roll-terminology]. [RFC4949], and in [I-D.ietf-roll-terminology].
The terms control plane and forwarding plane are used consistently The terms control plane and forwarding plane are used consistently
with section 1 of [RFC6192]. with section 1 of [RFC6192].
3. Considerations on RPL Security 4. Considerations on RPL Security
Routing security, in essence, ensures that the routing protocol Routing security, in essence, ensures that the routing protocol
operates correctly. It entails implementing measures to ensure operates correctly. It entails implementing measures to ensure
controlled state changes on devices and network elements, both based controlled state changes on devices and network elements, both based
on external inputs (received via communications) or internal inputs on external inputs (received via communications) or internal inputs
(physical security of device itself and parameters maintained by the (physical security of device itself and parameters maintained by the
device, including, e.g., clock). State changes would thereby involve device, including, e.g., clock). State changes would thereby involve
not only authorization of injector's actions, authentication of not only authorization of injector's actions, authentication of
injectors, and potentially confidentiality of routing data, but also injectors, and potentially confidentiality of routing data, but also
proper order of state changes through timeliness, since seriously proper order of state changes through timeliness, since seriously
delayed state changes, such as commands or updates of routing tables, delayed state changes, such as commands or updates of routing tables,
may negatively impact system operation. A security assesment can may negatively impact system operation. A security assessment can
therefore begin with a focus on the assets [RFC4949] that may be the therefore begin with a focus on the assets [RFC4949] that may be the
target of the state changes and the access points in terms of target of the state changes and the access points in terms of
interfaces and protocol exchanges through which such changes may interfaces and protocol exchanges through which such changes may
occur. In the case of routing security the focus is directed towards occur. In the case of routing security, the focus is directed
the elements associated with the establishment and maintenance of towards the elements associated with the establishment and
network connectivity. maintenance of network connectivity.
This section sets the stage for the development of the analysis by This section sets the stage for the development of the analysis by
applying the systematic approach proposed in [Myagmar2005] to the applying the systematic approach proposed in [Myagmar2005] to the
routing security, while also drawing references from other reviews routing security, while also drawing references from other reviews
and assessments found in the literature, particularly, [RFC4593] and and assessments found in the literature, particularly, [RFC4593] and
[Karlof2003]. The subsequent subsections begin with a focus on the [Karlof2003]. The subsequent subsections begin with a focus on the
elements of a generic routing process that is used to establish elements of a generic routing process that is used to establish
routing assets and points of access to the routing functionality. routing assets and points of access to the routing functionality.
Next, the [ISO.7498-2.1988] security model is briefly described. Next, the [ISO.7498-2.1988] security model is briefly described.
Then, consideration is given to issues specific to or amplified in Then, consideration is given to issues specific to or amplified in
LLNs. This section concludes with the formulation of a set of LLNs. This section concludes with the formulation of a set of
security objectives for RPL. security objectives for RPL.
3.1. Routing Assets and Points of Access 4.1. Routing Assets and Points of Access
An asset is an important system resource (including information, An asset is an important system resource (including information,
process, or physical resource), the access to, corruption or loss of process, or physical resource), the access to, corruption or loss of
which adversely affects the system. In the control plane context, an which adversely affects the system. In the control plane context, an
asset is information about the network, processes used to manage and asset is information about the network, processes used to manage and
manipulate this data, and the physical devices on which this data is manipulate this data, and the physical devices on which this data is
stored and manipulated. The corruption or loss of these assets may stored and manipulated. The corruption or loss of these assets may
adversely impact the control plane of the network. Within the same adversely impact the control plane of the network. Within the same
context, a point of access is an interface or protocol that context, a point of access is an interface or protocol that
facilitates interaction between control plane components. facilitates interaction between control plane assets. Identifying
Identifying these assets and points of access will provide a basis these assets and points of access will provide a basis for
for enumerating the attack surface of the control plane. enumerating the attack surface of the control plane.
A level-0 data flow diagram [Yourdon1979] is used here to identify A level-0 data flow diagram [Yourdon1979] is used here to identify
the assets and points of access within a generic routing process. the assets and points of access within a generic routing process.
The use of a data flow diagram allows for a clear and concise model The use of a data flow diagram allows for a clear and concise model
of the way in which routing nodes interact and process information, of the way in which routing nodes interact and process information,
and hence provides a context for threats and attacks. The goal of and hence provides a context for threats and attacks. The goal of
the model is to be as detailed as possible so that corresponding the model is to be as detailed as possible so that corresponding
assets, points of access, and process in an individual routing assets, points of access, and process in an individual routing
protocol can be readily identified. protocol can be readily identified.
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A focus on the above list of assets and points of access enables a A focus on the above list of assets and points of access enables a
more directed assessment of routing security; for example, it is more directed assessment of routing security; for example, it is
readily understood that some routing attacks are in the form of readily understood that some routing attacks are in the form of
attempts to misrepresent routing topology. Indeed, the intention of attempts to misrepresent routing topology. Indeed, the intention of
the security threat analysis is to be comprehensive. Hence, some of the security threat analysis is to be comprehensive. Hence, some of
the discussion which follows is associated with assets and points of the discussion which follows is associated with assets and points of
access that are not directly related to routing protocol design but access that are not directly related to routing protocol design but
nonetheless provided for reference since they do have direct nonetheless provided for reference since they do have direct
consequences on the security of routing. consequences on the security of routing.
3.2. The ISO 7498-2 Security Reference Model 4.2. The ISO 7498-2 Security Reference Model
At the conceptual level, security within an information system in At the conceptual level, security within an information system in
general and applied to RPL in particular is concerned with the general and applied to RPL; in particular is concerned with the
primary issues of authentication, access control, data primary issues of authentication, access control, data
confidentiality, data integrity, and non-repudiation. In the context confidentiality, data integrity, and non-repudiation. In the context
of RPL of RPL
Authentication Authentication
Authentication involves the mutual authentication of the Authentication involves the mutual authentication of the
routing peers prior to exchanging route information (i.e., peer routing peers prior to exchanging route information (i.e., peer
authentication) as well as ensuring that the source of the authentication) as well as ensuring that the source of the
route data is from the peer (i.e., data origin authentication). route data is from the peer (i.e., data origin authentication).
[RFC5548] points out that LLNs can be drained by [RFC5548] points out that LLNs can be drained by
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apply to maintaining efficient and correct operation of routing apply to maintaining efficient and correct operation of routing
and neighbor discovery exchanges (including needed information) and neighbor discovery exchanges (including needed information)
and forwarding services so as not to impair or limit the and forwarding services so as not to impair or limit the
network's central traffic flow function network's central traffic flow function
It should be emphasized here that for RPL security the above It should be emphasized here that for RPL security the above
requirements must be complemented by the proper security policies and requirements must be complemented by the proper security policies and
enforcement mechanisms to ensure that security objectives are met by enforcement mechanisms to ensure that security objectives are met by
a given RPL implementation. a given RPL implementation.
3.3. Issues Specific to or Amplified in LLNs 4.3. Issues Specific to or Amplified in LLNs
The work [RFC5548], [RFC5673], [RFC5826], and [RFC5867] have The requirements work detailed in Urban Requirements ([RFC5548]),
identified specific issues and constraints of routing in LLNs for the Industrial Requirements ([RFC5673]), Home Automation ([RFC5826], and
urban, industrial, home automation, and building automation Building Automation ([RFC5867]) have identified specific issues and
application domains, respectively. The following is a list of constraints of routing in LLNs. The following is a list of
observations and evaluation of their impact on routing security observations from those requirements and evaluation of their impact
considerations. on routing security considerations.
Limited energy, memory, and processing node resources Limited energy, memory, and processing node resources
As a consequence of these constraints, there is an even more As a consequence of these constraints, there is an even more
critical need than usual for a careful study of trade-offs on critical need than usual for a careful study of trade-offs on
which and what level of security services are to be afforded which and what level of security services are to be afforded
during the system design process. The chosen security during the system design process. The chosen security
mechanisms also needs to work within these constraints. mechanisms also needs to work within these constraints.
Synchronization of security states with sleepy nodes is yet Synchronization of security states with sleepy nodes is yet
another issue. another issue.
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The above list considers how an LLN's physical constraints, size, The above list considers how an LLN's physical constraints, size,
operations, and variety of application areas may impact security. operations, and variety of application areas may impact security.
However, it is the combinations of these factors that particularly However, it is the combinations of these factors that particularly
stress the security concerns. For instance, securing routing for a stress the security concerns. For instance, securing routing for a
large number of autonomous devices that are left in unattended large number of autonomous devices that are left in unattended
locations with limited physical security presents challenges that are locations with limited physical security presents challenges that are
not found in the common circumstance of administered networked not found in the common circumstance of administered networked
routers. The following subsection sets up the security objectives routers. The following subsection sets up the security objectives
for the routing protocol designed by the ROLL WG. for the routing protocol designed by the ROLL WG.
3.4. RPL Security Objectives 4.4. RPL Security Objectives
This subsection applies the ISO 7498-2 model to routing assets and This subsection applies the ISO 7498-2 model to routing assets and
access points, taking into account the LLN issues, to develop a set access points, taking into account the LLN issues, to develop a set
of RPL security objectives. of RPL security objectives.
Since the fundamental function of a routing protocol is to build Since the fundamental function of a routing protocol is to build
routes for forwarding packets, it is essential to ensure that: routes for forwarding packets, it is essential to ensure that:
o routing/topology information iintegrity remains intact during o routing/topology information integrity remains intact during
transfer and in storage; transfer and in storage;
o routing/topology information is used by authorized entities; o routing/topology information is used by authorized entities;
o routing/topology information is available when needed. o routing/topology information is available when needed.
In conjunction, it is necessary to be assured that In conjunction, it is necessary to be assured that
o authorized peers authenticate themselves during the routing o authorized peers authenticate themselves during the routing
neighbor discovery process; neighbor discovery process;
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confidentiality, of stored information, as well as the integrity of confidentiality, of stored information, as well as the integrity of
routing and route generation processes. routing and route generation processes.
Each individual system's use and environment will dictate how the Each individual system's use and environment will dictate how the
above objectives are applied, including the choices of security above objectives are applied, including the choices of security
services as well as the strengths of the mechanisms that must be services as well as the strengths of the mechanisms that must be
implemented. The next two sections take a closer look at how the RPL implemented. The next two sections take a closer look at how the RPL
security objectives may be compromised and how those potential security objectives may be compromised and how those potential
compromises can be countered. compromises can be countered.
4. Threat Sources 5. Threat Sources
[RFC4593] provides a detailed review of the threat sources: outsiders [RFC4593] provides a detailed review of the threat sources: outsiders
and byzantine. RPL has the same threat sources. and byzantine. RPL has the same threat sources.
5. Threats and Attacks 6. Threats and Attacks
This section outlines general categories of threats under the ISO This section outlines general categories of threats under the ISO
7498-2 model and highlights the specific attacks in each of these 7498-2 model and highlights the specific attacks in each of these
categories for RPL. As defined in [RFC4949], a threat is "a categories for RPL. As defined in [RFC4949], a threat is "a
potential for violation of security, which exists when there is a potential for violation of security, which exists when there is a
circumstance, capability, action, or event that could breach security circumstance, capability, action, or event that could breach security
and cause harm." and cause harm."
An attack is "an assault on system security that derives from an An attack is "an assault on system security that derives from an
intelligent threat, i.e., an intelligent act that is a deliberate intelligent threat, i.e., an intelligent act that is a deliberate
attempt (especially in the sense of a method or technique) to evade attempt (especially in the sense of a method or technique) to evade
security services and violate the security policy of a system." security services and violate the security policy of a system."
The subsequent subsections consider the threats and the attacks that The subsequent subsections consider the threats and the attacks that
can cause security breaches under the ISO 7498-2 model to the routing can cause security breaches under the ISO 7498-2 model to the routing
assets and via the routing points of access identified in assets and via the routing points of access identified in
Section 3.1. The assessment steps through the security concerns of Section 4.1. The assessment steps through the security concerns of
each routing asset and looks at the attacks that can exploit routing each routing asset and looks at the attacks that can exploit routing
points of access. The threats and attacks identified are based on points of access. The threats and attacks identified are based on
the routing model analysis and associated review of the existing the routing model analysis and associated review of the existing
literature. The source of the attacks is assumed to be from either literature. The source of the attacks is assumed to be from either
inside or outside attackers. The capability these attackes may be inside or outside attackers. While some attackers inside the network
limited to node-equivalent, but also to more sophisticated computing will be using compromised nodes, and therefore are only able to do
platforms. what an ordinary node can ("node-equivalent"), other attacks may not
limited in memory, CPU, power consumption or long term storage.
Moore's law favours the attacker with access to the latest
capabilities, while the defenders will remain in place for years to
decades.
5.1. Threats due to failures to Authenticate 6.1. Threats due to failures to Authenticate
5.1.1. Node Impersonation An attacker can assert an arbitrary identity, including the identity
of another node is said to be able to assert "any" identity.
If an attacker can join a network with any identify, then it may be 6.1.1. Node Impersonation
If an attacker can join a network using any identity, then it may be
able to assume the role of a legitimate (and existing node). It may able to assume the role of a legitimate (and existing node). It may
be able to report false readings (in metering applications), or be able to report false readings (in metering applications), or
provide inappropriate control messages (in control systems involving provide inappropriate control messages (in control systems involving
actuators) if the security of the application is leveraged from the actuators) if the security of the application is implied by the
security of the routing system. security of the routing system.
In other systems where there is separate application layer security, Even in systems where there application layer security, the ability
the ability to impersonate a node would permit an attacker to direct to impersonate a node would permit an attacker to direct traffic to
traffic to itself, which facilitates on-path attacks including itself. This may permit various on-path attacks which would
replaying, delaying, or duplicating control messages. otherwise be difficult, such replaying, delaying, or duplicating
(application) control messages.
5.1.2. Dummy Node 6.1.2. Dummy Node
If an attacker can join a network with any identify, then it can If an attacker can join a network with any identify, then it can
pretend to be a legitimate node, receiving any service legitimate pretend to be a legitimate node, receiving any service legitimate
nodes receive. It may also be able to report false readings (in nodes receive. It may also be able to report false readings (in
metering applications), or provide inappropriate authorizations (in metering applications), or provide inappropriate authorizations (in
control systems involving actuators), or perform any other attacks control systems involving actuators), or perform any other attacks
that are facilitated by being able to direct traffic towards itself. that are facilitated by being able to direct traffic towards itself.
5.1.3. Node Resource Spam 6.1.3. Node Resource Spam
If an attacker can join a network with any identify, then it can If an attacker can join a network with any identify, then it can
continously do so, draining down the resources of the network to continously do so with new (random) identities. This act may drain
store identity and routing information, potentionally forcing down the resources of the network (battery, ram, bandwidth). This
legitimate nodes of the network. may cause legitimate nodes of the network to be unable to
communicate.
5.2. Threats and Attacks on Confidentiality 6.2. Threats and Attacks on Confidentiality
The assessment in Section 3.2 indicates that there are threat actions
The assessment in Section 4.2 indicates that there are attacks
against the confidentiality of routing information at all points of against the confidentiality of routing information at all points of
access. This threat results in disclosure, as described in access. This threat results in disclosure, as described in
Section 3.1.2 of [RFC4593], and it involves a disclosure of routing Section 3.1.2 of [RFC4593], and may involve a disclosure of routing
information. information.
5.2.1. Routing Exchange Exposure 6.2.1. Routing Exchange Exposure
Routing exchanges include both routing information as well as Routing exchanges include both routing information as well as
information associated with the establishment and maintenance of information associated with the establishment and maintenance of
neighbor state information. As indicated in Section 3.1, the neighbor state information. As indicated in Section 4.1, the
associated routing information assets may also include device associated routing information assets may also include device
specific resource information, such as memory, remaining power, etc., specific resource information, such as available memory, remaining
that may be metrics of the routing protocol. power, etc., that may be metrics of the routing protocol.
The routing exchanges will contain reachability information, which The routing exchanges will contain reachability information, which
would identify the relative importance of different nodes in the would identify the relative importance of different nodes in the
network. Nodes higher up in the DODAG, to which more streams of network. Nodes higher up in the DODAG, to which more streams of
information flow, would be more interesting targets for other information flow, would be more interesting targets for other
attacks, and routing exchange exposures can identify them. attacks, and routing exchange exposures can identify them.
5.2.2. Routing Information (Routes and Network Topology) Exposure 6.2.2. Routing Information (Routes and Network Topology) Exposure
Routes (which may be maintained in the form of the protocol Routes (which may be maintained in the form of the protocol
forwarding table) and neighbor topology information are the products forwarding table) and neighbor topology information are the products
of the routing process that are stored within the node device of the routing process that are stored within the node device
databases. databases.
The exposure of this information will allow attachers to gain direct The exposure of this information will allow attackers to gain direct
access to the configuration and connectivity of the network thereby access to the configuration and connectivity of the network thereby
exposing routing to targeted attacks on key nodes or links. Since exposing routing to targeted attacks on key nodes or links. Since
routes and neighbor topology information is stored within the node routes and neighbor topology information is stored within the node
device, threats or attacks on the confidentiality of the information device, attacks on the confidentiality of the information will apply
will apply to the physical device including specified and unspecified to the physical device including specified and unspecified internal
internal and external interfaces. and external interfaces.
The forms of attack that allow unauthorized access or disclosure of The forms of attack that allow unauthorized access or disclosure of
the routing information (other than occurring through explicit node the routing information will include:
exchanges) will include:
o Physical device compromise; o Physical device compromise;
o Remote device access attacks (including those occurring through o Remote device access attacks (including those occurring through
remote network management or software/field upgrade interfaces). remote network management or software/field upgrade interfaces).
Both of these attack vectors are considered a device specific issue, Both of these attack vectors are considered a device specific issue,
and are out of scope for RPL to defend against. In some and are out of scope for RPL to defend against. In some
applications, physical device compromise may be a real threat and it applications, physical device compromise may be a real threat and it
may be necessary to provide for other devices to react quickly to may be necessary to provide for other devices to securely detect a
exclude a compromised device. compromised device and react quickly to exclude it.
5.3. Threats and Attacks on Integrity 6.3. Threats and Attacks on Integrity
The assessment in Section 3.2 indicates that information and identity The assessment in Section 4.2 indicates that information and identity
assets are exposed to integrity threats from all points of access. assets are exposed to integrity threats from all points of access.
In other words, the integrity threat space is defined by the In other words, the integrity threat space is defined by the
potential for exploitation introduced by access to assets available potential for exploitation introduced by access to assets available
through routing exchanges and the on-device storage. through routing exchanges and the on-device storage.
5.3.1. Routing Information Manipulation 6.3.1. Routing Information Manipulation
Manipulation of routing information that range from neighbor states Manipulation of routing information that range from neighbor states
to derived routes will allow unauthorized sources to influence the to derived routes will allow unauthorized sources to influence the
operation and convergence of the routing protocols and ultimately operation and convergence of the routing protocols and ultimately
impact the forwarding decisions made in the network. impact the forwarding decisions made in the network.
Manipulation of topology and reachability information will allow Manipulation of topology and reachability information will allow
unauthorized sources to influence the nodes with which routing unauthorized sources to influence the nodes with which routing
information is exchanged and updated. The consequence of information is exchanged and updated. The consequence of
manipulating routing exchanges can thus lead to sub-optimality and manipulating routing exchanges can thus lead to sub-optimality and
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A sub-optimal network may use too much power and/or may congest some A sub-optimal network may use too much power and/or may congest some
routes leading to premature failure of a node, and a denial of routes leading to premature failure of a node, and a denial of
service on the entire network. service on the entire network.
In addition, being able to attract network traffic can make a In addition, being able to attract network traffic can make a
blackhole attack more damaging. blackhole attack more damaging.
The forms of attack that allow manipulation to compromise the content The forms of attack that allow manipulation to compromise the content
and validity of routing information include and validity of routing information include
o Falsification, including overclaiming and misclaiming; o Falsification, including overclaiming and misclaiming (claiming
routes to devices which the device can not in fact reach);
o Routing information replay; o Routing information replay;
o Byzantine (internal) attacks that permit corruption of routing o Byzantine (internal) attacks that permit corruption of routing
information in the node even where the node continues to be a information in the node even where the node continues to be a
validated entity within the network (see, for example, [RFC4593] validated entity within the network (see, for example, [RFC4593]
for further discussions on Byzantine attacks); for further discussions on Byzantine attacks);
o Physical device compromise or remote device access attacks. o Physical device compromise or remote device access attacks.
5.3.2. Node Identity Misappropriation 6.3.2. Node Identity Misappropriation
Falsification or misappropriation of node identity between routing Falsification or misappropriation of node identity between routing
participants opens the door for other attacks; it can also cause participants opens the door for other attacks; it can also cause
incorrect routing relationships to form and/or topologies to emerge. incorrect routing relationships to form and/or topologies to emerge.
Routing attacks may also be mounted through less sophisticated node Routing attacks may also be mounted through less sophisticated node
identity misappropriation in which the valid information broadcast or identity misappropriation in which the valid information broadcast or
exchanged by a node is replayed without modification. The receipt of exchanged by a node is replayed without modification. The receipt of
seemingly valid information that is however no longer current can seemingly valid information that is however no longer current can
result in routing disruption, and instability (including failure to result in routing disruption, and instability (including failure to
converge). Without measures to authenticate the routing participants converge). Without measures to authenticate the routing participants
and to ensure the freshness and validity of the received information and to ensure the freshness and validity of the received information
the protocol operation can be compromised. The forms of attack that the protocol operation can be compromised. The forms of attack that
misuse node identity include misuse node identity include
o Identity attacks, including Sybil attacks in which a malicious o Identity attacks, including Sybil attacks (see [Sybil2002]) in
node illegitimately assumes multiple identities; which a malicious node illegitimately assumes multiple identities;
o Routing information replay. o Routing information replay.
5.4. Threats and Attacks on Availability 6.4. Threats and Attacks on Availability
The assessment in Section 3.2 indicates that the process and The assessment in Section 4.2 indicates that the process and
resources assets are exposed to threats against availability; attacks resources assets are exposed to threats against availability; attacks
in this category may exploit directly or indirectly information in this category may exploit directly or indirectly information
exchange or forwarding (see [RFC4732] for a general discussion). exchange or forwarding (see [RFC4732] for a general discussion).
5.4.1. Routing Exchange Interference or Disruption 6.4.1. Routing Exchange Interference or Disruption
Interference is the threat action and disruption is threat Interference is the threat action and disruption is threat
consequence that allows attackers to influence the operation and consequence that allows attackers to influence the operation and
convergence of the routing protocols by impeding the routing convergence of the routing protocols by impeding the routing
information exchange. information exchange.
The forms of attack that allow interference or disruption of routing The forms of attack that allow interference or disruption of routing
exchange include: exchange include:
o Routing information replay; o Routing information replay;
o ACK spoofing; o ACK spoofing;
o Overload attacks. (Section 6.3.2) o Overload attacks. (Section 7.3.2)
In addition, attacks may also be directly conducted at the physical In addition, attacks may also be directly conducted at the physical
layer in the form of jamming or interfering. layer in the form of jamming or interfering.
5.4.2. Network Traffic Forwarding Disruption 6.4.2. Network Traffic Forwarding Disruption
The disruption of the network traffic forwarding capability will The disruption of the network traffic forwarding capability will
undermine the central function of network routers and the ability to undermine the central function of network routers and the ability to
handle user traffic. This affects the availability of the network handle user traffic. This affects the availability of the network
because of the potential to impair the primary capability of the because of the potential to impair the primary capability of the
network. network.
In addition to physical layer obstructions, the forms of attack that In addition to physical layer obstructions, the forms of attack that
allows disruption of network traffic forwarding include [Karlof2003] allows disruption of network traffic forwarding include [Karlof2003]
o Selective forwarding attacks; o Selective forwarding attacks;
|Node_1|--(msg1|msg2|msg3)-->|Attacker|--(msg1|msg3)-->|Node_2| |Node_1|--(msg1|msg2|msg3)-->|Attacker|--(msg1|msg3)-->|Node_2|
Figure 2: Selective Forwarding Figure 2: Selective forwarding example
o Wormhole attacks; o Wormhole attacks;
|Node_1|-------------Unreachable---------x|Node_2| |Node_1|-------------Unreachable---------x|Node_2|
| ^ | ^
| Private Link | | Private Link |
'-->|Attacker_1|===========>|Attacker_2|--' '-->|Attacker_1|===========>|Attacker_2|--'
Figure 3: Wormhole Attacks Figure 3: Wormhole Attacks
o Sinkhole attacks. o Sinkhole attacks.
|Node_1| |Node_4| |Node_1| |Node_4|
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\ V V \ V V
|Node_2|-->|Attacker|--Not Forwarded---x|Node_5| |Node_2|-->|Attacker|--Not Forwarded---x|Node_5|
^ ^ \ ^ ^ \
| | \ Falsify as | | \ Falsify as
| | \Good Link | | \Good Link
/ | To Node_5 / | To Node_5
,-------' | ,-------' |
| | | |
|Node_3| |Node_i| |Node_3| |Node_i|
Figure 4: Selective Forwarding, Wormhole, and Sinkhole Attacks Figure 4: sinkhole attack example
These attacks are generally done to both control plane and forwarding These attacks are generally done to both control plane and forwarding
plane traffic. A system that prevents control plane traffic (RPL plane traffic. A system that prevents control plane traffic (RPL
messages) from being diverted in these ways will also prevent actual messages) from being diverted in these ways will also prevent actual
data from being diverted. data from being diverted.
5.4.3. Communications Resource Disruption 6.4.3. Communications Resource Disruption
Attacks mounted against the communication channel resource assets Attacks mounted against the communication channel resource assets
needed by the routing protocol can be used as a means of disrupting needed by the routing protocol can be used as a means of disrupting
its operation. However, while various forms of Denial of Service its operation. However, while various forms of Denial of Service
(DoS) attacks on the underlying transport subsystem will affect (DoS) attacks on the underlying transport subsystem will affect
routing protocol exchanges and operation (for example physical layer routing protocol exchanges and operation (for example physical layer
RF jamming in a wireless network or link layer attacks), these RF jamming in a wireless network or link layer attacks), these
attacks cannot be countered by the routing protocol. As such, the attacks cannot be countered by the routing protocol. As such, the
threats to the underlying transport network that supports routing is threats to the underlying transport network that supports routing is
considered beyond the scope of the current document. Nonetheless, considered beyond the scope of the current document. Nonetheless,
attacks on the subsystem will affect routing operation and so must be attacks on the subsystem will affect routing operation and so must be
directly addressed within the underlying subsystem and its directly addressed within the underlying subsystem and its
implemented protocol layers. implemented protocol layers.
5.4.4. Node Resource Exhaustion 6.4.4. Node Resource Exhaustion
A potential threat consequence can arise from attempts to overload A potential threat consequence can arise from attempts to overload
the node resource asset by initiating exchanges that can lead to the the node resource asset by initiating exchanges that can lead to the
exhaustion of processing, memory, or energy resources. The exhaustion of processing, memory, or energy resources. The
establishment and maintenance of routing neighbors opens the routing establishment and maintenance of routing neighbors opens the routing
process to engagement and potential acceptance of multiple process to engagement and potential acceptance of multiple
neighboring peers. Association information must be stored for each neighboring peers. Association information must be stored for each
peer entity and for the wireless network operation provisions made to peer entity and for the wireless network operation provisions made to
periodically update and reassess the associations. An introduced periodically update and reassess the associations. An introduced
proliferation of apparent routing peers can therefore have a negative proliferation of apparent routing peers can therefore have a negative
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Node resources may also be unduly consumed by attackers attempting Node resources may also be unduly consumed by attackers attempting
uncontrolled topology peering or routing exchanges, routing replays, uncontrolled topology peering or routing exchanges, routing replays,
or the generating of other data traffic floods. Beyond the or the generating of other data traffic floods. Beyond the
disruption of communications channel resources, these consequences disruption of communications channel resources, these consequences
may be able to exhaust node resources only where the engagements are may be able to exhaust node resources only where the engagements are
able to proceed with the peer routing entities. Routing operation able to proceed with the peer routing entities. Routing operation
and network forwarding functions can thus be adversely impacted by and network forwarding functions can thus be adversely impacted by
node resources exhaustion that stems from attacks that include: node resources exhaustion that stems from attacks that include:
o Identity (including Sybil) attacks; o Identity (including Sybil) attacks (see [Sybil2002]);
o Routing information replay attacks; o Routing information replay attacks;
o HELLO-type flood attacks; o HELLO-type flood attacks;
o Overload attacks. (Section 6.3.2) o Overload attacks. (Section 7.3.2)
6. Countermeasures 7. Countermeasures
By recognizing the characteristics of LLNs that may impact routing, By recognizing the characteristics of LLNs that may impact routing,
this analysis provides the basis for understanding the capabilities this analysis provides the basis for understanding the capabilities
within RPL used to deter the identified attacks and mitigate the within RPL used to deter the identified attacks and mitigate the
threats. The following subsections consider such countermeasures by threats. The following subsections consider such countermeasures by
grouping the attacks according to the classification of the ISO grouping the attacks according to the classification of the ISO
7498-2 model so that associations with the necessary security 7498-2 model so that associations with the necessary security
services are more readily visible. services are more readily visible.
6.1. Confidentiality Attack Countermeasures 7.1. Confidentiality Attack Countermeasures
Attacks to disclosure routing information may be mounted at the level Attacks to disclosure routing information may be mounted at the level
of the routing information assets, at the points of access associated of the routing information assets, at the points of access associated
with routing exchanges between nodes, or through device interface with routing exchanges between nodes, or through device interface
access. To gain access to routing/topology information, the attacker access. To gain access to routing/topology information, the attacker
may rely on a compromised node that deliberately exposes the may rely on a compromised node that deliberately exposes the
information during the routing exchange process, may rely on passive information during the routing exchange process, may rely on passive
wiretapping or traffic analysis, or may attempt access through a wiretapping or traffic analysis, or may attempt access through a
component or device interface of a tampered routing node. component or device interface of a tampered routing node.
6.1.1. Countering Deliberate Exposure Attacks 7.1.1. Countering Deliberate Exposure Attacks
A deliberate exposure attack is one in which an entity that is party A deliberate exposure attack is one in which an entity that is party
to the routing process or topology exchange allows the routing/ to the routing process or topology exchange allows the routing/
topology information or generated route information to be exposed to topology information or generated route information to be exposed to
an unauthorized entity. an unauthorized entity.
For instance, due to mis-configuration or inappropriate enabling of a For instance, due to mis-configuration or inappropriate enabling of a
diagnostic interface, an entity might be copying ("bridging") traffic diagnostic interface, an entity might be copying ("bridging") traffic
from a secured ESSID/PAN to an unsecured interface. from a secured ESSID/PAN to an unsecured interface.
A prerequisite to countering this attack is to ensure that the A prerequisite to countering this attack is to ensure that the
communicating nodes are authenticated prior to data encryption communicating nodes are authenticated prior to data encryption
applied in the routing exchange. Authentication ensures that the applied in the routing exchange. Authentication ensures that the
nodes are who they claim to be even though it does not provide an nodes are who they claim to be even though it does not provide an
indication of whether the node has been compromised. indication of whether the node has been compromised.
To mitigate the risk of deliberate exposure, the process that To mitigate the risk of deliberate exposure, the process that
communicating nodes use to establish session keys must be peer-to- communicating nodes use to establish session keys must be peer-to-
peer (i.e., between the routing initiating and responding nodes). peer (i.e., between the routing initiating and responding nodes).
This helps ensure that neither node is exchaning routing information This helps ensure that neither node is exchanging routing information
with another peer without the knowledge of both communicating peers. with another peer without the knowledge of both communicating peers.
For a deliberate exposure attack to succeed, the comprised node will For a deliberate exposure attack to succeed, the comprised node will
need to be more overt and take independent actions in order to need to be more overt and take independent actions in order to
disclose the routing information to 3rd party. disclose the routing information to 3rd party.
Note that the same measures which apply to securing routing/topology Note that the same measures which apply to securing routing/topology
exchanges between operational nodes must also extend to field tools exchanges between operational nodes must also extend to field tools
and other devices used in a deployed network where such devices can and other devices used in a deployed network where such devices can
be configured to participate in routing exchanges. be configured to participate in routing exchanges.
6.1.2. Countering Passive Wiretapping Attacks 7.1.2. Countering Passive Wiretapping Attacks
A passive wiretap attack seeks to breach routing confidentiality A passive wiretap attack seeks to breach routing confidentiality
through passive, direct analysis and processing of the information through passive, direct analysis and processing of the information
exchanges between nodes. exchanges between nodes.
Passive wiretap attacks can be directly countered through the use of Passive wiretap attacks can be directly countered through the use of
data encryption for all routing exchanges. Only when a validated and data encryption for all routing exchanges. Only when a validated and
authenticated node association is completed will routing exchange be authenticated node association is completed will routing exchange be
allowed to proceed using established session keys and an agreed allowed to proceed using established session keys and an agreed
encryption algorithm. The mandatory to implement CCM mode AES-128 encryption algorithm. The mandatory to implement CCM mode AES-128
method, is described in [RFC3610], and is believed to be secure method, is described in [RFC3610], and is believed to be secure
against a brute force attack by even the most well equiped adversary. against a brute force attack by even the most well-equiped adversary.
The significant challenge for RPL is in the provisioning of the key, The significant challenge for RPL is in the provisioning of the key,
which in some modes of RFC6550 is used network-wide. RFC6550 does which in some modes of RFC6550 is used network-wide. RFC6550 does
not solve this problem, and it is the subject of significant future not solve this problem, and it is the subject of significant future
work: see, for instance: [AceCharterProposal], [SolaceProposal], work: see, for instance: [AceCharterProposal], [SolaceProposal],
[SmartObjectSecurityWorkshop]. [SmartObjectSecurityWorkshop].
A number of deployments, such as [ZigBeeIP] specify no layer-3/RPL A number of deployments, such as [ZigBeeIP] specify no layer-3/RPL
encryption or authentication and rely upon similiar security at encryption or authentication and rely upon similiar security at
layer-2. These networks are immune to outside wiretapping attacks, layer-2. These networks are immune to outside wiretapping attacks,
but are particularly vulnerable to passive (and active) attacks but are particularly vulnerable to passive (and active) attacks
through compromises of nodes. through compromises of nodes.
Section 10.9 of [RFC6550] specifies AES-128 in CCM mode with a 32-bit Section 10.9 of [RFC6550] specifies AES-128 in CCM mode with a 32-bit
MAC. MAC.
Section 5.6 Zigbee IP [ZigBeeIP] specifies use of CCM, with PANA and Section 5.6 Zigbee IP [ZigBeeIP] specifies use of CCM, with PANA and
EAP-TLS for key management. EAP-TLS for key management.
6.1.3. Countering Traffic Analysis 7.1.3. Countering Traffic Analysis
Traffic analysis provides an indirect means of subverting Traffic analysis provides an indirect means of subverting
confidentiality and gaining access to routing information by allowing confidentiality and gaining access to routing information by allowing
an attacker to indirectly map the connectivity or flow patterns an attacker to indirectly map the connectivity or flow patterns
(including link-load) of the network from which other attacks can be (including link-load) of the network from which other attacks can be
mounted. The traffic analysis attack on an LLN, especially one mounted. The traffic analysis attack on an LLN, especially one
founded on shared medium, is passive and relies on the ability to founded on shared medium, is passive and relies on the ability to
read the immutable source/destination layer-2 and/or layer-3 routing read the immutable source/destination layer-2 and/or layer-3 routing
information that must remain unencrypted to permit network routing. information that must remain unencrypted to permit network routing.
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destinations through the generation of arbitrary traffic flows; the destinations through the generation of arbitrary traffic flows; the
drawback of course would be the consequent overhead and energy drawback of course would be the consequent overhead and energy
expenditure. expenditure.
The only means of fully countering a traffic analysis attack is The only means of fully countering a traffic analysis attack is
through the use of tunneling (encapsulation) where encryption is through the use of tunneling (encapsulation) where encryption is
applied across the entirety of the original packet source/destination applied across the entirety of the original packet source/destination
addresses. Deployments which use layer-2 security that includes addresses. Deployments which use layer-2 security that includes
encryption already do this for all traffic. encryption already do this for all traffic.
6.1.4. Countering Remote Device Access Attacks 7.1.4. Countering Remote Device Access Attacks
Where LLN nodes are deployed in the field, measures are introduced to Where LLN nodes are deployed in the field, measures are introduced to
allow for remote retrieval of routing data and for software or field allow for remote retrieval of routing data and for software or field
upgrades. These paths create the potential for a device to be upgrades. These paths create the potential for a device to be
remotely accessed across the network or through a provided field remotely accessed across the network or through a provided field
tool. In the case of network management a node can be directly tool. In the case of network management a node can be directly
requested to provide routing tables and neighbor information. requested to provide routing tables and neighbor information.
To ensure confidentiality of the node routing information against To ensure confidentiality of the node routing information against
attacks through remote access, any local or remote device requesting attacks through remote access, any local or remote device requesting
routing information must be authenticated, and must be authorized for routing information must be authenticated, and must be authorized for
that access. Since remote access is not invoked as part of a routing that access. Since remote access is not invoked as part of a routing
protocol security of routing information stored on the node against protocol, security of routing information stored on the node against
remote access will not be addressable as part of the routing remote access will not be addressable as part of the routing
protocol. protocol.
6.2. Integrity Attack Countermeasures 7.2. Integrity Attack Countermeasures
Integrity attack countermeasures address routing information Integrity attack countermeasures address routing information
manipulation, as well as node identity and routing information manipulation, as well as node identity and routing information
misuse. Manipulation can occur in the form of falsification attack misuse. Manipulation can occur in the form of falsification attack
and physical compromise. To be effective, the following development and physical compromise. To be effective, the following development
considers the two aspects of falsification, namely, the unauthorized considers the two aspects of falsification, namely, the unauthorized
modifications and the overclaiming and misclaiming content. The modifications and the overclaiming and misclaiming content. The
countering of physical compromise was considered in the previous countering of physical compromise was considered in the previous
section and is not repeated here. With regard to misuse, there are section and is not repeated here. With regard to misuse, there are
two types of attacks to be deterred, identity attacks and replay two types of attacks to be deterred, identity attacks and replay
attacks. attacks.
6.2.1. Countering Unauthorized Modification Attacks 7.2.1. Countering Unauthorized Modification Attacks
Unauthorized modifications may occur in the form of altering the Unauthorized modifications may occur in the form of altering the
message being transferred or the data stored. Therefore, it is message being transferred or the data stored. Therefore, it is
necessary to ensure that only authorized nodes can change the portion necessary to ensure that only authorized nodes can change the portion
of the information that is allowed to be mutable, while the integrity of the information that is allowed to be mutable, while the integrity
of the rest of the information is protected, e.g., through well- of the rest of the information is protected, e.g., through well-
studied cryptographic mechanisms. studied cryptographic mechanisms.
Unauthorized modifications may also occur in the form of insertion or Unauthorized modifications may also occur in the form of insertion or
deletion of messages during protocol changes. Therefore, the deletion of messages during protocol changes. Therefore, the
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studied cryptographic mechanisms. studied cryptographic mechanisms.
Unauthorized modifications may also occur in the form of insertion or Unauthorized modifications may also occur in the form of insertion or
deletion of messages during protocol changes. Therefore, the deletion of messages during protocol changes. Therefore, the
protocol needs to ensure the integrity of the sequence of the protocol needs to ensure the integrity of the sequence of the
exchange sequence. exchange sequence.
The countermeasure to unauthorized modifications needs to: The countermeasure to unauthorized modifications needs to:
o implement access control on storage; o implement access control on storage;
o provide data integrity service to transferred messages and stored o provide data integrity service to transferred messages and stored
data; data;
o include sequence number under integrity protection. o include sequence number under integrity protection.
6.2.2. Countering Overclaiming and Misclaiming Attacks 7.2.2. Countering Overclaiming and Misclaiming Attacks
Both overclaiming and misclaiming aim to introduce false routes or Both overclaiming and misclaiming aim to introduce false routes or a
topology that would not be generated by the network otherwise, while false topology that would not occur otherwise, while there are not
there are not necessarily unauthorized modifications to the routing necessarily unauthorized modifications to the routing messages or
messages or information. In order to counter overclaiming, the information. In order to counter overclaiming, the capability to
capability to determine unreasonable routes or topology is required. determine unreasonable routes or topology is required.
The counter to overclaiming and misclaiming may employ: The counter to overclaiming and misclaiming may employ:
o comparison with historical routing/topology data; o comparison with historical routing/topology data;
o designs which restrict realizable network topologies. o designs which restrict realizable network topologies.
RPL includes no specific mechanisms in the protocol to counter RPL includes no specific mechanisms in the protocol to counter
overlaims. An implementation could have specific heuristics overclaims or misclaims. An implementation could have specific
implemented locally. heuristics implemented locally.
6.2.3. Countering Identity (including Sybil) Attacks 7.2.3. Countering Identity (including Sybil) Attacks
Identity attacks, sometimes simply called spoofing, seek to gain or Identity attacks, sometimes simply called spoofing, seek to gain or
damage assets whose access is controlled through identity. In damage assets whose access is controlled through identity. In
routing, an identity attacker can illegitimately participate in routing, an identity attacker can illegitimately participate in
routing exchanges, distribute false routing information, or cause an routing exchanges, distribute false routing information, or cause an
invalid outcome of a routing process. invalid outcome of a routing process.
A perpetrator of Sybil attacks assumes multiple identities. The A perpetrator of Sybil attacks assumes multiple identities. The
result is not only an amplification of the damage to routing, but result is not only an amplification of the damage to routing, but
extension to new areas, e.g., where geographic distribution is extension to new areas, e.g., where geographic distribution is
explicitly or implicitly an asset to an application running on the explicitly or implicitly an asset to an application running on the
LLN, for example, the LBR in a P2MP or MP2P LLN. LLN, for example, the LBR in a P2MP or MP2P LLN.
RPL includes specific public key based authentication at layer-3 that RPL includes specific public key based authentication at layer-3 that
provide for authorization. Many deployments use layer-2 security provide for authorization. Many deployments use layer-2 security
that includes admission controls at layer-2 using mechanisms such as that includes admission controls at layer-2 using mechanisms such as
PANA. PANA.
6.2.4. Countering Routing Information Replay Attacks 7.2.4. Countering Routing Information Replay Attacks
In many routing protocols, message replay can result in false In many routing protocols, message replay can result in false
topology and/or routes. This is often counted with some kind of topology and/or routes. This is often counted with some kind of
counter to ensure the freshness of the message. Replay of a current, counter to ensure the freshness of the message. Replay of a current,
literal RPL message are in general idempotent to the topology. An literal RPL message are in general idempotent to the topology. An
older (lower DODAGVersionNumber) message, if replayed would be older (lower DODAGVersionNumber) message, if replayed would be
rejected as being stale. The trickle algorithm further dampens the rejected as being stale. The trickle algorithm further dampens the
affect of any such replay, as if the message was current, then it effect of any such replay, as if the message was current, then it
would contain the same information as before, and it would cause no would contain the same information as before, and it would cause no
network changes. network changes.
Replays may well occur in some radio technologies (not very likely, Replays may well occur in some radio technologies (not very likely,
802.15.4) as a result of echos or reflections, and so some replays 802.15.4) as a result of echos or reflections, and so some replays
must be assumed to occur naturally. must be assumed to occur naturally.
Note that for there to be no affect at all, the replay must be done Note that for there to be no affect at all, the replay must be done
with the same apparent power for all nodes receiving the replay. A with the same apparent power for all nodes receiving the replay. A
change in apparent power might change the metrics through changes to change in apparent power might change the metrics through changes to
the ETX and therefore might affect the routing even though the the ETX and therefore might affect the routing even though the
contents of the packet were never changed. Any replay which appears contents of the packet were never changed. Any replay which appears
to be different should be analyzed as a Selective Forwarding Attack, to be different should be analyzed as a Selective Forwarding Attack,
Sinkhole Attack or Wormhole Attack. Sinkhole Attack or Wormhole Attack.
6.2.5. Countering Byzantine Routing Information Attacks 7.2.5. Countering Byzantine Routing Information Attacks
Where a node is captured or compromised but continues to operate for Where a node is captured or compromised but continues to operate for
a period with valid network security credentials, the potential a period with valid network security credentials, the potential
exists for routing information to be manipulated. This compromise of exists for routing information to be manipulated. This compromise of
the routing information could thus exist in spite of security the routing information could thus exist in spite of security
countermeasures that operate between the peer routing devices. countermeasures that operate between the peer routing devices.
Consistent with the end-to-end principle of communications, such an Consistent with the end-to-end principle of communications, such an
attack can only be fully addressed through measures operating attack can only be fully addressed through measures operating
directly between the routing entities themselves or by means of directly between the routing entities themselves or by means of
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performing routing information validation. S-RIP [Wan2004] is an performing routing information validation. S-RIP [Wan2004] is an
example of the implementation of this type of dedicated routing example of the implementation of this type of dedicated routing
protocol security where the correctness of aggregate distance vector protocol security where the correctness of aggregate distance vector
information can only be validated by initiating confirmation information can only be validated by initiating confirmation
exchanges directly between nodes that are not routing neighbors. exchanges directly between nodes that are not routing neighbors.
RPL does not provide any direct mechanisms like S-RIP. It does RPL does not provide any direct mechanisms like S-RIP. It does
listen to multiple parents, and may switch parents if it begins to listen to multiple parents, and may switch parents if it begins to
suspect that it is being lied to. suspect that it is being lied to.
6.3. Availability Attack Countermeasures 7.3. Availability Attack Countermeasures
As alluded to before, availability requires that routing information As alluded to before, availability requires that routing information
exchanges and forwarding mechanisms be available when needed so as to exchanges and forwarding mechanisms be available when needed so as to
guarantee proper functioning of the network. This may, e.g., include guarantee proper functioning of the network. This may, e.g., include
the correct operation of routing information and neighbor state the correct operation of routing information and neighbor state
information exchanges, among others. We will highlight the key information exchanges, among others. We will highlight the key
features of the security threats along with typical countermeasures features of the security threats along with typical countermeasures
to prevent or at least mitigate them. We will also note that an to prevent or at least mitigate them. We will also note that an
availability attack may be facilitated by an identity attack as well availability attack may be facilitated by an identity attack as well
as a replay attack, as was addressed in Section 6.2.3 and as a replay attack, as was addressed in Section 7.2.3 and
Section 6.2.4, respectively. Section 7.2.4, respectively.
6.3.1. Countering HELLO Flood Attacks and ACK Spoofing Attacks 7.3.1. Countering HELLO Flood Attacks and ACK Spoofing Attacks
HELLO Flood [Karlof2003],[I-D.suhopark-hello-wsn] and ACK Spoofing HELLO Flood [Karlof2003],[I-D.suhopark-hello-wsn] and ACK Spoofing
attacks are different but highly related forms of attacking an LLN. attacks are different but highly related forms of attacking an LLN.
They essentially lead nodes to believe that suitable routes are They essentially lead nodes to believe that suitable routes are
available even though they are not and hence constitute a serious available even though they are not and hence constitute a serious
availability attack. availability attack.
A HELLO attack mounted against RPL would involve sending out (or A HELLO attack mounted against RPL would involve sending out (or
replaying) DIO messages by the attacker. Lower power LLN nodes might replaying) DIO messages by the attacker. Lower power LLN nodes might
then attempt to join the DODAG at a lower rank than they would then attempt to join the DODAG at a lower rank than they would
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and this involves, in general, sending a number of messages between and this involves, in general, sending a number of messages between
nodes which are believed to be adjacent. nodes which are believed to be adjacent.
[I-D.kelsey-intarea-mesh-link-establishment] is one such protocol. [I-D.kelsey-intarea-mesh-link-establishment] is one such protocol.
In order to join the DODAG, a DAO message is sent upwards. In RPL In order to join the DODAG, a DAO message is sent upwards. In RPL
the DAO is acknowledged by the DAO-ACK message. This clearly checks the DAO is acknowledged by the DAO-ACK message. This clearly checks
bidirectionality at the control plane. bidirectionality at the control plane.
As discussed in section 5.1, [I-D.suhopark-hello-wsn] a receiver with As discussed in section 5.1, [I-D.suhopark-hello-wsn] a receiver with
a sensitive receiver could well hear the DAOs, and even send DAO-ACKs a sensitive receiver could well hear the DAOs, and even send DAO-ACKs
as well. Such a node is a form of WormHole attack. as well. Such a node is a form of wormhole attack.
These attacks are also all easily defended against using either These attacks are also all easily defended against using either
layer-2 or layer-3 authentication. Such an attack could only be made layer-2 or layer-3 authentication. Such an attack could only be made
against a completely open network (such as might be used for against a completely open network (such as might be used for
provisioning new nodes), or by a compromised node. provisioning new nodes), or by a compromised node.
6.3.2. Countering Overload Attacks 7.3.2. Countering Overload Attacks
Overload attacks are a form of DoS attack in that a malicious node Overload attacks are a form of DoS attack in that a malicious node
overloads the network with irrelevant traffic, thereby draining the overloads the network with irrelevant traffic, thereby draining the
nodes' energy store more quickly, when the nodes rely on batteries or nodes' energy store more quickly, when the nodes rely on batteries or
energy scavenging. It thus significantly shortens the lifetime of energy scavenging. It thus significantly shortens the lifetime of
networks of energy-constrained nodes and constitutes another serious networks of energy-constrained nodes and constitutes another serious
availability attack. availability attack.
With energy being one of the most precious assets of LLNs, targeting With energy being one of the most precious assets of LLNs, targeting
its availability is a fairly obvious attack. Another way of its availability is a fairly obvious attack. Another way of
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encrypt messages need to be cautious of cryptographic processing encrypt messages need to be cautious of cryptographic processing
usage when validating signatures and encrypting messages. Where usage when validating signatures and encrypting messages. Where
feasible, certificates should be validated prior to use of the feasible, certificates should be validated prior to use of the
associated keys to counter potential resource overloading attacks. associated keys to counter potential resource overloading attacks.
The associated design decision needs to also consider that the The associated design decision needs to also consider that the
validation process requires resources and thus itself could be validation process requires resources and thus itself could be
exploited for attacks. Alternatively, resource management limits can exploited for attacks. Alternatively, resource management limits can
be placed on routing security processing events (see the comment in be placed on routing security processing events (see the comment in
Section 6, paragraph 4, of [RFC5751]). Section 6, paragraph 4, of [RFC5751]).
6.3.3. Countering Selective Forwarding Attacks 7.3.3. Countering Selective Forwarding Attacks
Selective forwarding attacks are a form of DoS attack which impacts Selective forwarding attacks are a form of DoS attack which impacts
the availability of the generated routing paths. the availability of the generated routing paths.
A selective forwarding attack may be done by a node involved with the A selective forwarding attack may be done by a node involved with the
routing process, or it may be done by what otherwise appears to be a routing process, or it may be done by what otherwise appears to be a
passive antenna or other RF feature or device, but is in fact an passive antenna or other RF feature or device, but is in fact an
active (and selective) device. An RF antenna/repeater which is not active (and selective) device. An RF antenna/repeater which is not
selective, is not a threat. selective, is not a threat.
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a particular routing path due to a malicious selective forwarding a particular routing path due to a malicious selective forwarding
attack, there will be another route which successfully delivers the attack, there will be another route which successfully delivers the
data. Such a method is inherently suboptimal from an energy data. Such a method is inherently suboptimal from an energy
consumption point of view; it is also suboptimal from a network consumption point of view; it is also suboptimal from a network
utilization perspective. The second method basically involves a utilization perspective. The second method basically involves a
constantly changing routing topology in that next-hop routers are constantly changing routing topology in that next-hop routers are
chosen from a dynamic set in the hope that the number of malicious chosen from a dynamic set in the hope that the number of malicious
nodes in this set is negligible. A routing protocol that allows for nodes in this set is negligible. A routing protocol that allows for
disjoint routing paths may also be useful. disjoint routing paths may also be useful.
6.3.4. Countering Sinkhole Attacks 7.3.4. Countering Sinkhole Attacks
In sinkhole attacks, the malicious node manages to attract a lot of In sinkhole attacks, the malicious node manages to attract a lot of
traffic mainly by advertising the availability of high-quality links traffic mainly by advertising the availability of high-quality links
even though there are none [Karlof2003]. It hence constitutes a even though there are none [Karlof2003]. It hence constitutes a
serious attack on availability. serious attack on availability.
The malicious node creates a sinkhole by attracting a large amount The malicious node creates a sinkhole by attracting a large amount
of, if not all, traffic from surrounding neighbors by advertising in of, if not all, traffic from surrounding neighbors by advertising in
and outwards links of superior quality. Affected nodes hence eagerly and outwards links of superior quality. Affected nodes hence eagerly
route their traffic via the malicious node which, if coupled with route their traffic via the malicious node which, if coupled with
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solving triangulation equations from radio delay calculations, such solving triangulation equations from radio delay calculations, such
calculations could in theory be subverted by a sinkhole that calculations could in theory be subverted by a sinkhole that
transmitted at precisely the right power in a node to node fashion. transmitted at precisely the right power in a node to node fashion.
While geographic knowledge could help assure that traffic always went While geographic knowledge could help assure that traffic always went
in the physical direction desired, it would not assure that the in the physical direction desired, it would not assure that the
traffic was taking the most efficient route, as the lowest cost real traffic was taking the most efficient route, as the lowest cost real
route might be match the physical topology; such as when different route might be match the physical topology; such as when different
parts of an LLN are connected by high-speed wired networks. parts of an LLN are connected by high-speed wired networks.
6.3.5. Countering Wormhole Attacks 7.3.5. Countering Wormhole Attacks
In wormhole attacks at least two malicious nodes claim to have a In wormhole attacks at least two malicious nodes claim to have a
short path between themselves [Karlof2003]. This changes the short path between themselves [Karlof2003]. This changes the
availability of certain routing paths and hence constitutes a serious availability of certain routing paths and hence constitutes a serious
security breach. security breach.
Essentially, two malicious insider nodes use another, more powerful, Essentially, two malicious insider nodes use another, more powerful,
transmitter to communicate with each other and thereby distort the transmitter to communicate with each other and thereby distort the
would-be-agreed routing path. This distortion could involve would-be-agreed routing path. This distortion could involve
shortcutting and hence paralyzing a large part of the network; it shortcutting and hence paralyzing a large part of the network; it
could also involve tunneling the information to another region of the could also involve tunneling the information to another region of the
network where there are, e.g., more malicious nodes available to aid network where there are, e.g., more malicious nodes available to aid
the intrusion or where messages are replayed, etc. the intrusion or where messages are replayed, etc.
In conjunction with selective forwarding, wormhole attacks can create In conjunction with selective forwarding, wormhole attacks can create
race conditions which impact topology maintenance, routing protocols race conditions which impact topology maintenance, routing protocols
as well as any security suits built on "time of check" and "time of as well as any security suits built on "time of check" and "time of
use". use".
A pure Wormhole attack is nearly impossible to detect. A wormhole A pure wormhole attack is nearly impossible to detect. A wormhole
which is used in order to subsequently mount another kind of attack which is used in order to subsequently mount another kind of attack
would be defeated by defeating the other attack. A perfect wormhole, would be defeated by defeating the other attack. A perfect wormhole,
in which there is nothing adverse that occurs to the traffic, would in which there is nothing adverse that occurs to the traffic, would
be difficult to call an attack. The worst thing that a benign be difficult to call an attack. The worst thing that a benign
wormhole can do in such a situation is to cease to operate (become wormhole can do in such a situation is to cease to operate (become
unstable), causing the network to have to recalculate routes. unstable), causing the network to have to recalculate routes.
A highly unstable wormhole is no different than a radio opaque (i.e. A highly unstable wormhole is no different than a radio opaque (i.e.
metal) door that opens and closes a lot. RPL includes hystersis in metal) door that opens and closes a lot. RPL includes hysteresis in
its objective functions [RFC6719] in an attempt to deal with frequent its objective functions [RFC6719] in an attempt to deal with frequent
changes to the ETX between nodes. changes to the ETX between nodes.
7. RPL Security Features 8. RPL Security Features
The assessments and analysis in Section 6 examined all areas of
The assessments and analysis in Section 5 examined all areas of
threats and attacks that could impact routing, and the threats and attacks that could impact routing, and the
countermeasures presented in Section 6 were reached without confining countermeasures presented in Section 7 were reached without confining
the consideration to means only available to routing. This section the consideration to means only available to routing. This section
puts the results into perspective and provides a framework for puts the results into perspective; dealing with those threats which
addressing the derived set of security objectives that must be met by are endemnic to this field, those which have been mitigated through
the routing protocol(s) specified by the RPL Working Group. It bears RPL protocol design, and those which require specific decisions to be
emphasizing that the target here is a generic, universal form of the made as part of provisioning a network.
protocol(s) specified and the normative keywords are mainly to convey
the relative level of importance or urgency of the features
specified.
In this view, 'MUST' is used to define the requirements that are The first part of this section, Section 8.1 to Section 8.3, is a
specific to the routing protocol and that are essential for an LLN description of RPL security features that address specific threats.
routing protocol to ensure that routing operation can be maintained. The second part of this section, Section 8.4, discusses issues of
Adherence to MUST requirements is needed to directly counter attacks provisioning of security aspects that may impact routing but that
that can affect the routing operation (such as those that can impact also require considerations beyond the routing protocol, as well as
maintained or derived routing/forwarding tables). 'SHOULD' is used potential approaches.
to define requirements that counter indirect routing attacks where
such attacks do not of themselves affect routing but can assist an
attacker in focusing its attack resources to impact network operation
(such as DoS targeting of key forwarding nodes). 'MAY' covers
optional requirements that can further enhance security by increasing
the space over which an attacker must operate or the resources that
must be applied. While in support of routing security, where
appropriate, these requirements may also be addressed beyond the
network routing protocol at other system communications layers.
The first part of this section, Section 7.1 to Section 7.3, is a RPL employs multicast and so these alternative communications modes
prescription of RPL security features of measures that can be MUST be secured with the same routing security services specified in
addressed as part of the routing protocol itself. As routing is one this section. Furthermore, irrespective of the modes of
component of an LLN system, the actual strength of the security communication, nodes MUST provide adequate physical tamper resistance
services afforded to it should be made to conform to each system's commensurate with the particular application domain environment to
security policy; how a design may address the needs of the urban, ensure the confidentiality, integrity, and availability of stored
industrial, home automation, and building automation application routing information.
domains also needs to be considered. The second part of this
section, Section 7.4 and Section 7.5, discusses system security
aspects that may impact routing but that also require considerations
beyond the routing protocol, as well as potential approaches.
If an LLN employs multicast and/or anycast, these alternative 8.1. Confidentiality Features
communications modes MUST be secured with the same routing security
services specified in this section. Furthermore, irrespective of the
modes of communication, nodes MUST provide adequate physical tamper
resistance commensurate with the particular application domain
environment to ensure the confidentiality, integrity, and
availability of stored routing information.
7.1. Confidentiality Features
With regard to confidentiality, protecting the routing/topology With regard to confidentiality, protecting the routing/topology
information from unauthorized disclosure is not directly essential to information from unauthorized disclosure is not directly essential to
maintaining the routing function. Breaches of confidentiality may maintaining the routing function. Breaches of confidentiality may
lead to other attacks or the focusing of an attacker's resources (see lead to other attacks or the focusing of an attacker's resources (see
Section 5.2) but does not of itself directly undermine the operation Section 6.2) but does not of itself directly undermine the operation
of the routing function. However, to protect against, and reduce of the routing function. However, to protect against, and reduce
consequences from other more direct attacks, routing information consequences from other more direct attacks, routing information
should be protected. Thus, a secured RPL protocol: should be protected. Thus, to secure RPL:
o MUST implement payload encryption;
o MAY provide tunneling; o implement payload encryption using layer-3 mechanisms described in
[RFC6550];
o MAY provide load balancing. o or: implement layer-2 confidentiality;
Where confidentiality is incorporated into the routing exchanges, Where confidentiality is incorporated into the routing exchanges,
encryption algorithms and key lengths need to be specified in encryption algorithms and key lengths need to be specified in
accordance with the level of protection dictated by the routing accordance with the level of protection dictated by the routing
protocol and the associated application domain transport network. In protocol and the associated application domain transport network.
terms of the life time of the keys, the opportunity to periodically For most networks, this means use of AES128 in CCM mode, but this
change the encryption key increases the offered level of security for needs to be specified clearly in the applicability statement.
any given implementation. However, where strong cryptography is
employed, physical, procedural, and logical data access protection In terms of the life time of the keys, the opportunity to
considerations may have more significant impact on cryptoperiod periodically change the encryption key increases the offered level of
selection than algorithm and key size factors. Nevertheless, in security for any given implementation. However, where strong
general, shorter cryptoperiods, during which a single key is applied, cryptography is employed, physical, procedural, and logical data
will enhance security. access protection considerations may have more significant impact on
cryptoperiod selection than algorithm and key size factors.
Nevertheless, in general, shorter cryptoperiods, during which a
single key is applied, will enhance security.
Given the mandatory protocol requirement to implement routing node Given the mandatory protocol requirement to implement routing node
authentication as part of routing integrity (see Section 7.2), key authentication as part of routing integrity (see Section 8.2), key
exchanges may be coordinated as part of the integrity verification exchanges may be coordinated as part of the integrity verification
process. This provides an opportunity to increase the frequency of process. This provides an opportunity to increase the frequency of
key exchange and shorten the cryptoperiod as a complement to the key key exchange and shorten the cryptoperiod as a complement to the key
length and encryption algorithm required for a given application length and encryption algorithm required for a given application
domain. For LLNs, the coordination of confidentiality key management domain.
with the implementation of node device authentication can thus reduce
the overhead associated with supporting data confidentiality. If a
new ciphering key is concurrently generated or updated in conjunction
with the mandatory authentication exchange occurring with each
routing peer association, signaling exchange overhead can be reduced.
7.2. Integrity Features 8.2. Integrity Features
The integrity of routing information provides the basis for ensuring The integrity of routing information provides the basis for ensuring
that the function of the routing protocol is achieved and maintained. that the function of the routing protocol is achieved and maintained.
To protect integrity, RPL must either run using only the Secure To protect integrity, RPL must either run using only the Secure
versions of the messages, or must run over a layer-2 that uses versions of the messages, or must run over a layer-2 that uses
channel binding between node identity and transmissions. (i.e.: a channel binding between node identity and transmissions.
layer-2 which has an identical network-wide transmission key can not
defend against many attacks)
While logging is critical, it is often impossible. Some layer-2 security mechanisms use a single key for the entire
network, and these networks can not provide significant amount of
integrity protection, as any node that has that key may impersonate
any other node. This mode of operation is likely acceptable when an
entire deployment is under the control of a single administrative
entity.
7.3. Availability Features Other layer-2 security mechanisms form a unique session key for every
pair of nodes that needs to communicate; this is often called a per-
link key. Such networks can provide a strong degree of origin
authentication and integrity on unicast messages.
However, some RPL messages are broadcast, and even when per-node
layer-2 security mechanisms are used, the integrity and origin
authentication of broadcast messages can not be as securely known.
RPL has two specific messages which are broadcast: the DODAG
Information Object (DIO), and the DODAG Information Solicitation
(DIS). The purpose of the DIS is to cause potential parents to reply
with a DIO, so the integrity of the DIS is not of great concern. The
DIS may also be unicast.
The DIO is a critical piece of routing and carries many critical
parameters. RPL provides for assymetric authentication at layer-3 of
the DIO, and this may be waranteed in some deployments. A node
could, if it felt that the DIO that it had received was suspicious,
send a unicast DIS message to the node in question, and that node
would reply with a unicast DIS. Those messages could be protected
with the per-link key.
8.3. Availability Features
Availability of routing information is linked to system and network Availability of routing information is linked to system and network
availability which in the case of LLNs require a broader security availability which in the case of LLNs require a broader security
view beyond the requirements of the routing entities (see view beyond the requirements of the routing entities. Where
Section 7.5). Where availability of the network is compromised, availability of the network is compromised, routing information
routing information availability will be accordingly affected. availability will be accordingly affected. However, to specifically
However, to specifically assist in protecting routing availability: assist in protecting routing availability:
o MAY restrict neighborhood cardinality; o MAY restrict neighborhood cardinality;
o MAY use multiple paths; o MAY use multiple paths;
o MAY use multiple destinations; o MAY use multiple destinations;
o MAY choose randomly if multiple paths are available; o MAY choose randomly if multiple paths are available;
o MAY set quotas to limit transmit or receive volume; o MAY set quotas to limit transmit or receive volume;
o MAY use geographic information for flow control. o MAY use geographic information for flow control.
7.4. Key Management 8.4. Key Management
The functioning of the routing security services requires keys and The functioning of the routing security services requires keys and
credentials. Therefore, even though not directly a RPL security credentials. Therefore, even though not directly a RPL security
requirement, an LLN MUST have a process for initial key and requirement, an LLN MUST have a process for initial key and
credential configuration, as well as secure storage within the credential configuration, as well as secure storage within the
associated devices. Anti-tampering SHOULD be a consideration in associated devices. Anti-tampering SHOULD be a consideration in
physical design. Beyond initial credential configuration, an LLN is physical design. Beyond initial credential configuration, an LLN is
also encouraged to have automatic procedures for the revocation and also encouraged to have automatic procedures for the revocation and
replacement of the maintained security credentials. replacement of the maintained security credentials.
While RPL has secure modes, but some modes are impractical without While RPL has secure modes, but some modes are impractical without
use of public key cryptography believed to be too expensive by many. use of public key cryptography believed to be too expensive by many.
RPL layer-3 security will often depend upon existing LLN layer-2 RPL layer-3 security will often depend upon existing LLN layer-2
security mechanisms, which provides for node authentication, but security mechanisms, which provides for node authentication, but
little in the way of node authorization. little in the way of node authorization.
7.5. Consideration on Matching Application Domain Needs 9. IANA Considerations
Providing security within an LLN requires considerations that extend
beyond routing security to the broader LLN application domain
security implementation. In other words, as routing is one component
of an LLN system, the actual strength of the implemented security
algorithms for the routing protocol MUST be made to conform to the
system's target level of security. The development so far takes into
account collectively the impacts of the issues gathered from
[RFC5548], [RFC5673], [RFC5826], and [RFC5867]. The following two
subsections first consider from an architectural perspective how the
security design of a RPL protocol may be made to adapt to the four
application domains, and then examine mechanisms and protocol
operations issues.
7.5.1. Mechanisms and Operations
Figure 5 provides an overview of the larger context of system
security and the relationship between RPL requirements and measures
and those that relate to the LLN system.
Security Services for
RPL-Addressable
Security Requirements
| |
+---+ +---+
Node_i | | Node_j
_____v___ ___v_____
Specify Security / \ / \ Specify Security
Requirements | Routing | | Routing | Requirements
+---------| Protocol| | Protocol|---------+
| | Entity | | Entity | |
| \_________/ \_________/ |
| | | |
|RPL-Specified | | RPL-Specified|
---Interface | | Interface---
| ...................................... |
| : | | : |
| : +-----+----+ +----+-----+ : |
| : |Transport/| |Transport/| : |
____v___ : +>|Network | |Network |<+ : ___v____
/ \ : | +-----+----+ +----+-----+ | : / \
| |-:-+ | | +-:-| |
|Security| : +-----+----+ +----+-----+ : |Security|
+->|Services|-:-->| Link | | Link |<--:-|Services|<-+
| |Entity | : +-----+----+ +----+-----+ : |Entity | |
| | |-:-+ | | +-:-| | |
| \________/ : | +-----+----+ +----+-----+ | : \________/ |
| : +>| Physical | | Physical |<+ : |
Application : +-----+----+ +----+-----+ : Application
Domain User : | | : Domain User
Configuration : |__Comm. Channel_| : Configuration
: :
...Protocol Stack.....................
Figure 5: LLN Device Security Model
8. IANA Considerations
This memo includes no request to IANA. This memo includes no request to IANA.
9. Security Considerations 10. Security Considerations
The analysis presented in this document provides security analysis The analysis presented in this document provides security analysis
and design guidelines with a scope limited to RPL. Security services and design guidelines with a scope limited to RPL. Security services
are identified as requirements for securing RPL. The specific are identified as requirements for securing RPL. The specific
mechanisms to be used to deal with each threat is specified in link- mechanisms to be used to deal with each threat is specified in link-
layer and deployment specific applicability statements. layer and deployment specific applicability statements.
10. Acknowledgments 11. Acknowledgments
The authors would like to acknowledge the review and comments from The authors would like to acknowledge the review and comments from
Rene Struik and JP Vasseur. The authors would also like to Rene Struik and JP Vasseur. The authors would also like to
acknowledge the guidance and input provided by the RPL Chairs, David acknowledge the guidance and input provided by the RPL Chairs, David
Culler, and JP Vasseur, and the Area Director Adrian Farrel. Culler, and JP Vasseur, and the Area Director Adrian Farrel.
This document started out as a combined threat and solutions This document started out as a combined threat and solutions
document. As a result of security review, the document was split up document. As a result of security review, the document was split up
by RPL co-Chair Michael Richardson and security Area Director Sean by RPL co-Chair Michael Richardson and security Area Director Sean
Turner as it went through the IETF publication process. The Turner as it went through the IETF publication process. The
solutions to the threads are application and layer-2 specific, and solutions to the threats are application and layer-2 specific, and
have therefore been moved to the relevant applicability statements. have therefore been moved to the relevant applicability statements.
Ines Robles kept track of the many issues that were raised during the Ines Robles and Robert Craigie kept track of the many issues that
development of this document were raised during the development of this document
11. References 12. References
11.1. Normative References
12.1. Normative References
[I-D.ietf-roll-terminology] [I-D.ietf-roll-terminology]
Vasseur, J., "Terminology in Low power And Lossy Vasseur, J., "Terminology in Low power And Lossy
Networks", draft-ietf-roll-terminology-04 (work in Networks", draft-ietf-roll-terminology-04 (work in
progress), September 2010. progress), September 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4107] Bellovin, S. and R. Housley, "Guidelines for Cryptographic [RFC4107] Bellovin, S. and R. Housley, "Guidelines for Cryptographic
skipping to change at page 35, line 32 skipping to change at page 35, line 17
Alexander, "RPL: IPv6 Routing Protocol for Low-Power and Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
Lossy Networks", RFC 6550, March 2012. Lossy Networks", RFC 6550, March 2012.
[RFC6719] Gnawali, O. and P. Levis, "The Minimum Rank with [RFC6719] Gnawali, O. and P. Levis, "The Minimum Rank with
Hysteresis Objective Function", RFC 6719, September 2012. Hysteresis Objective Function", RFC 6719, September 2012.
[ZigBeeIP] [ZigBeeIP]
ZigBee Public Document 15-002r00, "ZigBee IP ZigBee Public Document 15-002r00, "ZigBee IP
Specification", 2013. Specification", 2013.
11.2. Informative References 12.2. Informative References
[AceCharterProposal] [AceCharterProposal]
Kepeng, L., Ed., "Authentication and Authorization for Li, Kepeng., Ed., "Authentication and Authorization for
Constrained Environment Charter (work-in-progress)", Constrained Environment Charter (work-in-progress)",
December 2013, <http://www.ietf.org/mail-archive/web/ace/ December 2013, <http://trac.tools.ietf.org/wg/core/trac/
current/msg00007.html>. wiki/ACE_charter>.
[FIPS197] , "Federal Information Processing Standards Publication [FIPS197] , "Federal Information Processing Standards Publication
197: Advanced Encryption Standard (AES)", US National 197: Advanced Encryption Standard (AES)", US National
Institute of Standards and Technology, Nov. 26 2001. Institute of Standards and Technology, Nov. 26 2001.
[Huang2003] [Huang2003]
Huang, Q., Cukier, J., Kobayashi, H., Liu, B., and J. Huang, Q., Cukier, J., Kobayashi, H., Liu, B., and J.
Zhang, "Fast Authenticated Key Establishment Protocols for Zhang, "Fast Authenticated Key Establishment Protocols for
Self-Organizing Sensor Networks", in Proceedings of the Self-Organizing Sensor Networks", in Proceedings of the
2nd ACM International Conference on Wireless Sensor 2nd ACM International Conference on Wireless Sensor
skipping to change at page 36, line 36 skipping to change at page 36, line 19
[ISO.7498-2.1988] [ISO.7498-2.1988]
International Organization for Standardization, International Organization for Standardization,
"Information Processing Systems - Open Systems "Information Processing Systems - Open Systems
Interconnection Reference Model - Security Architecture", Interconnection Reference Model - Security Architecture",
ISO Standard 7498-2, 1988. ISO Standard 7498-2, 1988.
[Karlof2003] [Karlof2003]
Karlof, C. and D. Wagner, "Secure routing in wireless Karlof, C. and D. Wagner, "Secure routing in wireless
sensor networks: attacks and countermeasures", Elsevier sensor networks: attacks and countermeasures", Elsevier
AdHoc Networks Journal, Special Issue on Sensor Network AdHoc Networks Journal, Special Issue on Sensor Network
Applications and Protocols, 1(2):293-315, September 2003. Applications and Protocols, 1(2):293-315, September 2003,
<http://nest.cs.berkeley.edu/papers/sensor-route-
security.pdf>.
[Kasumi3gpp] [Kasumi3gpp]
, "3GPP TS 35.202 Specification of the 3GPP , "3GPP TS 35.202 Specification of the 3GPP
confidentiality and integrity algorithms; Document 2: confidentiality and integrity algorithms; Document 2:
Kasumi specification", 3GPP TSG SA3, 2009. Kasumi specification", 3GPP TSG SA3, 2009.
[Messerges2003] [Messerges2003]
Messerges, T., Cukier, J., Kevenaar, T., Puhl, L., Struik, Messerges, T., Cukier, J., Kevenaar, T., Puhl, L., Struik,
R., and E. Callaway, "Low-Power Security for Wireless R., and E. Callaway, "Low-Power Security for Wireless
Sensor Networks", in Proceedings of the 1st ACM Workshop Sensor Networks", in Proceedings of the 1st ACM Workshop
skipping to change at page 38, line 49 skipping to change at page 38, line 33
[SmartObjectSecurityWorkshop] [SmartObjectSecurityWorkshop]
Klausen, T., Ed., "Workshop on Smart Object Security", Klausen, T., Ed., "Workshop on Smart Object Security",
March 2012, <http://www.lix.polytechnique.fr/hipercom/ March 2012, <http://www.lix.polytechnique.fr/hipercom/
SmartObjectSecurity>. SmartObjectSecurity>.
[SolaceProposal] [SolaceProposal]
Bormann, C., Ed., "Notes from the SOLACE ad-hoc at IETF85 Bormann, C., Ed., "Notes from the SOLACE ad-hoc at IETF85
(work-in-progress)", November 2012, <http://www.ietf.org/ (work-in-progress)", November 2012, <http://www.ietf.org/
mail-archive/web/solace/current/msg00015.html>. mail-archive/web/solace/current/msg00015.html>.
[Sybil2002]
Douceur, J., "The Sybil Attack", First International
Workshop on Peer-to-Peer Systems , March 2002.
[Szcze2008] [Szcze2008]
Szczechowiak1, P., Oliveira, L., Scott, M., Collier, M., Szczechowiak1, P., Oliveira, L., Scott, M., Collier, M.,
and R. Dahab, "NanoECC: testing the limits of elliptic and R. Dahab, "NanoECC: testing the limits of elliptic
curve cryptography in sensor networks", pp. 324-328, 2008, curve cryptography in sensor networks", pp. 324-328, 2008,
<http://www.ic.unicamp.br/~leob/publications/ewsn/ <http://www.ic.unicamp.br/~leob/publications/ewsn/
NanoECC.pdf>. NanoECC.pdf>.
[Wan2004] Wan, T., Kranakis, E., and PC. van Oorschot, "S-RIP: A [Wan2004] Wan, T., Kranakis, E., and PC. van Oorschot, "S-RIP: A
Secure Distance Vector Routing Protocol", in Proceedings Secure Distance Vector Routing Protocol", in Proceedings
of the 2nd International Conference on Applied of the 2nd International Conference on Applied
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