Internet Engineering Task Force T. Mizrahi
Internet-Draft MARVELL
Intended status: Informational E. Grossman, Ed.
Expires: October 25, 2018 DOLBY
A. Hacker
MISTIQ
S. Das
Applied Communication Sciences
J. Dowdell
Airbus Defence and Space
H. Austad
Cisco Systems
K. Stanton
INTEL
N. Finn
HUAWEI
April 23, 2018
Deterministic Networking (DetNet) Security Considerations
draft-ietf-detnet-security-02
Abstract
A deterministic network is one that can carry data flows for real-
time applications with extremely low data loss rates and bounded
latency. Deterministic networks have been successfully deployed in
real-time operational technology (OT) applications for some years
(for example [ARINC664P7]). However, such networks are typically
isolated from external access, and thus the security threat from
external attackers is low. IETF Deterministic Networking (DetNet)
specifies a set of technologies that enable creation of deterministic
networks on IP-based networks of potentially wide area (on the scale
of a corporate network) potentially bringing the OT network into
contact with Information Technology (IT) traffic and security threats
that lie outside of a tightly controlled and bounded area (such as
the internals of an aircraft). These DetNet technologies have not
previously been deployed together on a wide area IP-based network,
and thus can present security considerations that may be new to IP-
based wide area network designers. This draft, intended for use by
DetNet network designers, provides insight into these security
considerations. In addition, this draft collects all security-
related statements from the various DetNet drafts (Architecture, Use
Cases, etc) into a single location Section 7.
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Status of This Memo
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provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 25, 2018.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Security Threats . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Threat Model . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Threat Analysis . . . . . . . . . . . . . . . . . . . . . 7
3.2.1. Delay . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2.1.1. Delay Attack . . . . . . . . . . . . . . . . . . 7
3.2.2. DetNet Flow Modification or Spoofing . . . . . . . . 7
3.2.3. Resource Segmentation or Slicing . . . . . . . . . . 7
3.2.3.1. Inter-segment Attack . . . . . . . . . . . . . . 7
3.2.4. Packet Replication and Elimination . . . . . . . . . 8
3.2.4.1. Replication: Increased Attack Surface . . . . . . 8
3.2.4.2. Replication-related Header Manipulation . . . . . 8
3.2.5. Path Choice . . . . . . . . . . . . . . . . . . . . . 8
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3.2.5.1. Path Manipulation . . . . . . . . . . . . . . . . 8
3.2.5.2. Path Choice: Increased Attack Surface . . . . . . 9
3.2.6. Control Plane . . . . . . . . . . . . . . . . . . . . 9
3.2.6.1. Control or Signaling Packet Modification . . . . 9
3.2.6.2. Control or Signaling Packet Injection . . . . . . 9
3.2.7. Scheduling or Shaping . . . . . . . . . . . . . . . . 9
3.2.7.1. Reconnaissance . . . . . . . . . . . . . . . . . 9
3.2.8. Time Synchronization Mechanisms . . . . . . . . . . . 9
3.3. Threat Summary . . . . . . . . . . . . . . . . . . . . . 9
4. Security Threat Impacts . . . . . . . . . . . . . . . . . . . 10
4.1. Delay-Attacks . . . . . . . . . . . . . . . . . . . . . . 13
4.1.1. Data Plane Delay Attacks . . . . . . . . . . . . . . 13
4.1.2. Control Plane Delay Attacks . . . . . . . . . . . . . 13
4.2. Flow Modification and Spoofing . . . . . . . . . . . . . 14
4.2.1. Flow Modification . . . . . . . . . . . . . . . . . . 14
4.2.2. Spoofing . . . . . . . . . . . . . . . . . . . . . . 14
4.2.2.1. Dataplane Spoofing . . . . . . . . . . . . . . . 14
4.2.2.2. Control Plane Spoofing . . . . . . . . . . . . . 14
4.3. Segmentation attacks (injection) . . . . . . . . . . . . 15
4.3.1. Data Plane Segmentation . . . . . . . . . . . . . . . 15
4.3.2. Control Plane segmentation . . . . . . . . . . . . . 15
4.4. Replication and Elimination . . . . . . . . . . . . . . . 15
4.4.1. Increased Attack Surface . . . . . . . . . . . . . . 15
4.4.2. Header Manipulation at Elimination Bridges . . . . . 15
4.5. Control or Signaling Packet Modification . . . . . . . . 16
4.6. Control or Signaling Packet Injection . . . . . . . . . . 16
4.7. Reconnaissance . . . . . . . . . . . . . . . . . . . . . 16
4.8. Attacks on Time Sync Mechanisms . . . . . . . . . . . . . 16
4.9. Attacks on Path Choice . . . . . . . . . . . . . . . . . 16
5. Security Threat Mitigation . . . . . . . . . . . . . . . . . 16
5.1. Path Redundancy . . . . . . . . . . . . . . . . . . . . . 16
5.2. Integrity Protection . . . . . . . . . . . . . . . . . . 17
5.3. DetNet Node Authentication . . . . . . . . . . . . . . . 17
5.4. Encryption . . . . . . . . . . . . . . . . . . . . . . . 17
5.5. Control and Signaling Message Protection . . . . . . . . 18
5.6. Dynamic Performance Analytics . . . . . . . . . . . . . . 18
5.7. Mitigation Summary . . . . . . . . . . . . . . . . . . . 18
6. Association of Attacks to Use Cases . . . . . . . . . . . . . 20
6.1. Use Cases by Common Themes . . . . . . . . . . . . . . . 20
6.1.1. Network Layer - AVB/TSN Ethernet . . . . . . . . . . 20
6.1.2. Central Administration . . . . . . . . . . . . . . . 21
6.1.3. Hot Swap . . . . . . . . . . . . . . . . . . . . . . 21
6.1.4. Data Flow Information Models . . . . . . . . . . . . 22
6.1.5. L2 and L3 Integration . . . . . . . . . . . . . . . . 22
6.1.6. End-to-End Delivery . . . . . . . . . . . . . . . . . 22
6.1.7. Proprietary Deterministic Ethernet Networks . . . . . 23
6.1.8. Replacement for Proprietary Fieldbuses . . . . . . . 23
6.1.9. Deterministic vs Best-Effort Traffic . . . . . . . . 23
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6.1.10. Deterministic Flows . . . . . . . . . . . . . . . . . 24
6.1.11. Unused Reserved Bandwidth . . . . . . . . . . . . . . 24
6.1.12. Interoperability . . . . . . . . . . . . . . . . . . 24
6.1.13. Cost Reductions . . . . . . . . . . . . . . . . . . . 25
6.1.14. Insufficiently Secure Devices . . . . . . . . . . . . 25
6.1.15. DetNet Network Size . . . . . . . . . . . . . . . . . 25
6.1.16. Multiple Hops . . . . . . . . . . . . . . . . . . . . 26
6.1.17. Level of Service . . . . . . . . . . . . . . . . . . 26
6.1.18. Bounded Latency . . . . . . . . . . . . . . . . . . . 27
6.1.19. Low Latency . . . . . . . . . . . . . . . . . . . . . 27
6.1.20. Symmetrical Path Delays . . . . . . . . . . . . . . . 27
6.1.21. Reliability and Availability . . . . . . . . . . . . 27
6.1.22. Redundant Paths . . . . . . . . . . . . . . . . . . . 28
6.1.23. Security Measures . . . . . . . . . . . . . . . . . . 28
6.2. Attack Types by Use Case Common Theme . . . . . . . . . . 28
7. Appendix A: DetNet Draft Security-Related Statements . . . . 30
7.1. Architecture (draft 8) . . . . . . . . . . . . . . . . . 31
7.1.1. Fault Mitigation (sec 4.5) . . . . . . . . . . . . . 31
7.1.2. Security Considerations (sec 7) . . . . . . . . . . . 31
7.2. Data Plane Alternatives (draft 4) . . . . . . . . . . . . 32
7.2.1. Security Considerations (sec 7) . . . . . . . . . . . 32
7.3. Problem Statement (draft 5) . . . . . . . . . . . . . . . 32
7.3.1. Security Considerations (sec 5) . . . . . . . . . . . 32
7.4. Use Cases (draft 11) . . . . . . . . . . . . . . . . . . 33
7.4.1. (Utility Networks) Security Current Practices and
Limitations (sec 3.2.1) . . . . . . . . . . . . . . . 33
7.4.2. (Utility Networks) Security Trends in Utility
Networks (sec 3.3.3) . . . . . . . . . . . . . . . . 34
7.4.3. (BAS) Security Considerations (sec 4.2.4) . . . . . . 36
7.4.4. (6TiSCH) Security Considerations (sec 5.3.3) . . . . 36
7.4.5. (Cellular radio) Security Considerations (sec 6.1.5) 36
7.4.6. (Industrial M2M) Communication Today (sec 7.2) . . . 37
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37
9. Security Considerations . . . . . . . . . . . . . . . . . . . 37
10. Informative References . . . . . . . . . . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38
1. Introduction
Security is of particularly high importance in DetNet networks
because many of the use cases which are enabled by DetNet
[I-D.ietf-detnet-use-cases] include control of physical devices
(power grid components, industrial controls, building controls) which
can have high operational costs for failure, and present potentially
attractive targets for cyber-attackers.
This situation is even more acute given that one of the goals of
DetNet is to provide a "converged network", i.e. one that includes
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both IT traffic and OT traffic, thus exposing potentially sensitive
OT devices to attack in ways that were not previously common (usually
because they were under a separate control system or otherwise
isolated from the IT network). Security considerations for OT
networks is not a new area, and there are many OT networks today that
are connected to wide area networks or the Internet; this draft
focuses on the issues that are specific to the DetNet technologies
and use cases.
The DetNet technologies include ways to:
o Reserve data plane resources for DetNet flows in some or all of
the intermediate nodes (e.g. bridges or routers) along the path of
the flow
o Provide explicit routes for DetNet flows that do not rapidly
change with the network topology
o Distribute data from DetNet flow packets over time and/or space to
ensure delivery of each packet's data' in spite of the loss of a
path
This draft includes sections on threat modeling and analysis, threat
impact and mitigation, and the association of attacks with use cases
based on the Use Case Common Themes section of the DetNet Use Cases
draft [I-D.ietf-detnet-use-cases].
This draft also provides context for the DetNet security
considerations by collecting into one place Section 7 the various
remarks about security from the various DetNet drafts (Use Cases,
Architecture, etc). This text is duplicated here primarily because
the DetNet working group has elected not to produce a Requirements
draft and thus collectively these statements are as close as we have
to "DetNet Security Requirements".
2. Abbreviations
IT Information technology (the application of computers to
store, study, retrieve, transmit, and manipulate data or information,
often in the context of a business or other enterprise - Wikipedia).
OT Operational Technology (the hardware and software
dedicated to detecting or causing changes in physical processes
through direct monitoring and/or control of physical devices such as
valves, pumps, etc. - Wikipedia)
MITM Man in the Middle
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SN Sequence Number
STRIDE Addresses risk and severity associated with threat
categories: Spoofing identity, Tampering with data, Repudiation,
Information disclosure, Denial of service, Elevation of privilege.
DREAD Compares and prioritizes risk represented by these threat
categories: Damage potential, Reproducibility, Exploitability, how
many Affected users, Discoverability.
PTP Precision Time Protocol [IEEE1588]
3. Security Threats
This section presents a threat model, and analyzes the possible
threats in a DetNet-enabled network.
We distinguish control plane threats from data plane threats. The
attack surface may be the same, but the types of attacks as well as
the motivation behind them, are different. For example, a delay
attack is more relevant to data plane than to control plane. There
is also a difference in terms of security solutions: the way you
secure the data plane is often different than the way you secure the
control plane.
3.1. Threat Model
The threat model used in this memo is based on the threat model of
Section 3.1 of [RFC7384]. This model classifies attackers based on
two criteria:
o Internal vs. external: internal attackers either have access to a
trusted segment of the network or possess the encryption or
authentication keys. External attackers, on the other hand, do
not have the keys and have access only to the encrypted or
authenticated traffic.
o Man in the Middle (MITM) vs. packet injector: MITM attackers are
located in a position that allows interception and modification of
in-flight protocol packets, whereas a traffic injector can only
attack by generating protocol packets.
Care has also been taken to adhere to Section 5 of [RFC3552], both
with respect to what attacks are considered out-of-scope for this
document, but also what is considered to be the most common threats
(explored furhter in Section 3.2. Most of the direct threats to
DetNet are Active attacks, but it is highly suggested that DetNet
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application developers take appropriate measures to protect the
content of the streams from passive attacks.
DetNet-Service, one of the service scenarios described in
[I-D.varga-detnet-service-model], is the case where a service
connects DetNet networking islands, i.e. two or more otherwise
independent DetNet network domains are connected via a link that is
not intrinsically part of either network. This implies that there
could be DetNet traffic flowing over a non-DetNet link, which may
provide an attacker with an advantageous opportunity to tamper with
DetNet traffic. The security properties of non-DetNet links are
outside of the scope of DetNet Security, but it should be noted that
use of non-DetNet services to interconnect DetNet networks merits
security analysis to ensure the integrity of the DetNet networks
involved.
3.2. Threat Analysis
3.2.1. Delay
3.2.1.1. Delay Attack
An attacker can maliciously delay DetNet data flow traffic. By
delaying the traffic, the attacker can compromise the service of
applications that are sensitive to high delays or to high delay
variation.
3.2.2. DetNet Flow Modification or Spoofing
An attacker can modify some header fields of en route packets in a
way that causes the DetNet flow identification mechanisms to
misclassify the flow. Alternatively, the attacker can inject traffic
that is tailored to appear as if it belongs to a legitimate DetNet
flow. The potential consequence is that the DetNet flow resource
allocation cannot guarantee the performance that is expected when the
flow identification works correctly.
3.2.3. Resource Segmentation or Slicing
3.2.3.1. Inter-segment Attack
An attacker can inject traffic, consuming network device resources,
thereby affecting DetNet flows. This can be performed using non-
DetNet traffic that affects DetNet traffic, or by using DetNet
traffic from one DetNet flow that affects traffic from different
DetNet flows.
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3.2.4. Packet Replication and Elimination
3.2.4.1. Replication: Increased Attack Surface
Redundancy is intended to increase the robustness and survivability
of DetNet flows, and replication over multiple paths can potentially
mitigate an attack that is limited to a single path. However, the
fact that packets are replicated over multiple paths increases the
attack surface of the network, i.e., there are more points in the
network that may be subject to attacks.
3.2.4.2. Replication-related Header Manipulation
An attacker can manipulate the replication-related header fields
(R-TAG). This capability opens the door for various types of
attacks. For example:
o Forward both replicas - malicious change of a packet SN (Sequence
Number) can cause both replicas of the packet to be forwarded.
Note that this attack has a similar outcome to a replay attack.
o Eliminate both replicas - SN manipulation can be used to cause
both replicas to be eliminated. In this case an attacker that has
access to a single path can cause packets from other paths to be
dropped, thus compromising some of the advantage of path
redundancy.
o Flow hijacking - an attacker can hijack a DetNet flow with access
to a single path by systematically replacing the SNs on the given
path with higher SN values. For example, an attacker can replace
every SN value S with a higher value S+C, where C is a constant
integer. Thus, the attacker creates a false illusion that the
attacked path has the lowest delay, causing all packets from other
paths to be eliminated. Once the flow is hijacked the attacker
can either replace en route packets with malicious packets, or
simply injecting errors, causing the packets to be dropped at
their destination.
3.2.5. Path Choice
3.2.5.1. Path Manipulation
An attacker can maliciously change, add, or remove a path, thereby
affecting the corresponding DetNet flows that use the path.
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3.2.5.2. Path Choice: Increased Attack Surface
One of the possible consequences of a path manipulation attack is an
increased attack surface. Thus, when the attack described in the
previous subsection is implemented, it may increase the potential of
other attacks to be performed.
3.2.6. Control Plane
3.2.6.1. Control or Signaling Packet Modification
An attacker can maliciously modify en route control packets in order
to disrupt or manipulate the DetNet path/resource allocation.
3.2.6.2. Control or Signaling Packet Injection
An attacker can maliciously inject control packets in order to
disrupt or manipulate the DetNet path/resource allocation.
3.2.7. Scheduling or Shaping
3.2.7.1. Reconnaissance
A passive eavesdropper can identify DetNet flows and then gather
information about en route DetNet flows, e.g., the number of DetNet
flows, their bandwidths, and their schedules. The gathered
information can later be used to invoke other attacks on some or all
of the flows.
Note that in some cases DetNet flows may be identified based on an
explicit DetNet header, but in some cases the flow identification may
be based on fields from the L3/L4 headers. If L3/L4 headers are
involved, for purposes of this draft we assume they are encrypted
and/or integrity-protected from external attackers.
3.2.8. Time Synchronization Mechanisms
An attacker can use any of the attacks described in [RFC7384] to
attack the synchronization protocol, thus affecting the DetNet
service.
3.3. Threat Summary
A summary of the attacks that were discussed in this section is
presented in Figure 1. For each attack, the table specifies the type
of attackers that may invoke the attack. In the context of this
summary, the distinction between internal and external attacks is
under the assumption that a corresponding security mechanism is being
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used, and that the corresponding network equipment takes part in this
mechanism.
+-----------------------------------------+----+----+----+----+
| Attack | Attacker Type |
| +---------+---------+
| |Internal |External |
| |MITM|Inj.|MITM|Inj.|
+-----------------------------------------+----+----+----+----+
|Delay attack | + | | + | |
+-----------------------------------------+----+----+----+----+
|DetNet Flow Modification or Spoofing | + | + | | |
+-----------------------------------------+----+----+----+----+
|Inter-segment Attack | + | + | | |
+-----------------------------------------+----+----+----+----+
|Replication: Increased Attack Surface | + | + | + | + |
+-----------------------------------------+----+----+----+----+
|Replication-related Header Manipulation | + | | | |
+-----------------------------------------+----+----+----+----+
|Path Manipulation | + | + | | |
+-----------------------------------------+----+----+----+----+
|Path Choice: Increased Attack Surface | + | + | + | + |
+-----------------------------------------+----+----+----+----+
|Control or Signaling Packet Modification | + | | | |
+-----------------------------------------+----+----+----+----+
|Control or Signaling Packet Injection | | + | | |
+-----------------------------------------+----+----+----+----+
|Reconnaissance | + | | + | |
+-----------------------------------------+----+----+----+----+
|Attacks on Time Sync Mechanisms | + | + | + | + |
+-----------------------------------------+----+----+----+----+
Figure 1: Threat Analysis Summary
4. Security Threat Impacts
This section describes and rates the impact of the attacks described
in Section 3. In this section, the impacts as described assume that
the associated mitigation is not present or has failed. Mitigations
are discussed in Section 5.
In computer security, the impact (or consequence) of an incident can
be measured in loss of confidentiality, integrity or availability of
information.
DetNet raises these stakes significantly for OT applications,
particularly those which may have been designed to run in an OT-only
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environment and thus may not have been designed for security in an IT
environment with its associated devices, services and protocols.
The severity of various components of the impact of a successful
vulnerability exploit to use cases by industry is available in more
detail in [I-D.ietf-detnet-use-cases]. Each of the use cases in the
DetNet Use Cases draft is represented in the table below, including
Pro Audio, Electrical Utilities, Industrial M2M (split into two
areas, M2M Data Gathering and M2M Control Loop), and others.
Components of Impact (left column) include Criticality of Failure,
Effects of Failure, Recovery, and DetNet Functional Dependence.
Criticality of failure summarizes the seriousness of the impact. The
impact of a resulting failure can affect many different metrics that
vary greatly in scope and severity. In order to reduce the number of
variables, only the following were included: Financial, Health and
Safety, People well being, Affect on a single organization, and
affect on multiple organizations. Recovery outlines how long it
would take for an affected use case to get back to its pre-failure
state (Recovery time objective, RTO), and how much of the original
service would be lost in between the time of service failure and
recovery to original state (Recovery Point Objective, RPO). DetNet
dependence maps how much the following DetNet service objectives
contribute to impact of failure: Time dependency, data integrity,
source node integrity, availability, latency/jitter.
The scale of the Impact mappings is low, medium, and high. In some
use cases there may be a multitude of specific applications in which
DetNet is used. For simplicity this section attempts to average the
varied impacts of different applications. This section does not
address the overall risk of a certain impact which would require the
likelihood of a failure happening.
In practice any such ratings will vary from case to case; the ratings
shown here are given as examples.
Table, Part One (of Two)
+------------------+-----------------------------------------+-----+
| | Pro A | Util | Bldg |Wire- | Cell |M2M |M2M |
| | | | | less | |Data |Ctrl |
+------------------+-----------------------------------------+-----+
| Criticality | Med | Hi | Low | Med | Med | Med | Med |
+------------------+-----------------------------------------+-----+
| Effects
+------------------+-----------------------------------------+-----+
| Financial | Med | Hi | Med | Med | Low | Med | Med |
+------------------+-----------------------------------------+-----+
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| Health/Safety | Med | Hi | Hi | Med | Med | Med | Med |
+------------------+-----------------------------------------+-----+
| People WB | Med | Hi | Hi | Low | Hi | Low | Low |
+------------------+-----------------------------------------+-----+
| Effect 1 org | Hi | Hi | Med | Hi | Med | Med | Med |
+------------------+-----------------------------------------+-----+
| Effect >1 org | Med | Hi | Low | Med | Med | Med | Med |
+------------------+-----------------------------------------+-----+
|Recovery
+------------------+-----------------------------------------+-----+
| Recov Time Obj | Med | Hi | Med | Hi | Hi | Hi | Hi |
+------------------+-----------------------------------------+-----+
| Recov Point Obj | Med | Hi | Low | Med | Low | Hi | Hi |
+------------------+-----------------------------------------+-----+
|DetNet Dependence
+------------------+-----------------------------------------+-----+
| Time Dependency | Hi | Hi | Low | Hi | Med | Low | Hi |
+------------------+-----------------------------------------+-----+
| Latency/Jitter | Hi | Hi | Med | Med | Low | Low | Hi |
+------------------+-----------------------------------------+-----+
| Data Integrity | Hi | Hi | Med | Hi | Low | Hi | Low |
+------------------+-----------------------------------------+-----+
| Src Node Integ | Hi | Hi | Med | Hi | Med | Hi | Hi |
+------------------+-----------------------------------------+-----+
| Availability | Hi | Hi | Med | Hi | Low | Hi | Hi |
+------------------+-----------------------------------------+-----+
Table, Part Two (of Two)
+------------------+--------------------------+
| | Mining | Block | Network |
| | | Chain | Slicing |
+------------------+--------------------------+
| Criticality | Hi | Med | Hi |
+------------------+--------------------------+
| Effects
+------------------+--------------------------+
| Financial | Hi | Hi | Hi |
+------------------+--------------------------+
| Health/Safety | Hi | Low | Med |
+------------------+--------------------------+
| People WB | Hi | Low | Med |
+------------------+--------------------------+
| Effect 1 org | Hi | Hi | Hi |
+------------------+--------------------------+
| Effect >1 org | Hi | Low | Hi |
+------------------+--------------------------+
|Recovery
+------------------+--------------------------+
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| Recov Time Obj | Hi | Low | Hi |
+------------------+--------------------------+
| Recov Point Obj | Hi | Low | Hi |
+------------------+--------------------------+
|DetNet Dependence
+------------------+--------------------------+
| Time Dependency | Hi | Low | Hi |
+------------------+--------------------------+
| Latency/Jitter | Hi | Low | Hi |
+------------------+--------------------------+
| Data Integrity | Hi | Hi | Hi |
+------------------+--------------------------+
| Src Node Integ | Hi | Hi | Hi |
+------------------+--------------------------+
| Availability | Hi | Hi | Hi |
+------------------+--------------------------+
Figure 2: Impact of Attacks by Use Case Industry
The rest of this section will cover impact of the different groups in
more detail.
4.1. Delay-Attacks
4.1.1. Data Plane Delay Attacks
Severely delayed messages in a DetNet link can result in the same
behavior as dropped messages in ordinary networks as the services
attached to the stream has strict deterministic requirements.
For a single path scenario, disruption is a real possibility, whereas
in a multipath scenario, large delays or instabilities in one stream
can lead to increased buffer and CPU resources on the elimination
bridge.
4.1.2. Control Plane Delay Attacks
In and of itself, this is not directly a threat to the DetNet
service, but the effects of delaying control messages can have quite
adverse effects later.
o Delayed tear-down can lead to resource leakage, which in turn can
result in failure to allocate new streams finally giving rise to a
denial of service attack.
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o Failure to deliver, or severely delaying, signalling messages
adding an end-point to a multicast-group will prevent the new EP
from receiving expected frames thus disrupting expected behavior.
o Delaying messages removing an EP from a group can lead to loss of
privacy as the EP will continue to receive messages even after it
is supposedly removed.
4.2. Flow Modification and Spoofing
4.2.1. Flow Modification
ToDo.
4.2.2. Spoofing
4.2.2.1. Dataplane Spoofing
Spoofing dataplane messages can result in increased resource
consumptions on the bridges throughout the network as it will
increase buffer usage and CPU utilization. This can lead to resource
exhaustion and/or increased delay.
If the attacker manages to create valid headers, the false messages
can be forwarded through the network, using part of the allocated
bandwidth. This in turn can cause legitimate messages to be dropped
when the budget has been exhausted.
Finally, the endpoint will have to deal with invalid messages being
delivered to the endpoint instead of (or in addition to) a valid
message.
4.2.2.2. Control Plane Spoofing
A successful control plane spoofing-attack will potentionally have
adverse effects. It can do virtually anything from:
o modifying existing streams by changing the available bandwidth
o add or remove endpoints from a stream
o drop streams completly
o falsely create new streams (exhaust the systems resources, or to
enable streams outside the Network engineer's control)
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4.3. Segmentation attacks (injection)
4.3.1. Data Plane Segmentation
Injection of false messages in a DetNet stream could lead to
exhaustion of the available bandwidth for a stream if the bridges
accounts false messages to the stream's budget.
In a multipath scenario, injected messages will cause increased CPU
utilization in elimination bridges. If enough paths are subject to
malicious injection, the legitimate messages can be dropped.
Likewise it can cause an increase in buffer usage. In total, it will
consume more resources in the bridges than normal, giving rise to a
resource exhaustion attack on the bridges.
If a stream is interrupted, the end application will be affected by
what is now a non-deterministic stream.
4.3.2. Control Plane segmentation
A successful Control Plane segmentation attack control messages to be
interpreted by nodes in the network, unbeknownst to the central
controller or the network engineer. This has the potential to create
o new streams (exhausting resources)
o drop existing (denial of service)
o add/remove end-stations to a multicast group (loss of privacy)
o modify the stream attributes (affecting available bandwidth
4.4. Replication and Elimination
The Replication and Elimination is relevant only to Data Plane
messages as Signalling is not subject to multipath routing.
4.4.1. Increased Attack Surface
Covered briefly in Section 4.3
4.4.2. Header Manipulation at Elimination Bridges
Covered briefly in Section 4.3
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4.5. Control or Signaling Packet Modification
ToDo.
4.6. Control or Signaling Packet Injection
ToDo.
4.7. Reconnaissance
Of all the attacks, this is one of the most difficult to detect and
counter. Often, an attacker will start out by observing the traffic
going through the network and use the knowledge gathered in this
phase to mount future attacks.
The attacker can, at their leisure, observe over time all aspects of
the messaging and signalling, learning the intent and purpose of all
traffic flows. At some later date, possibly at an important time in
an operational context, the attacker can launch a multi-faceted
attack, possibly in conjunction with some demand for ransom.
The flow-id in the header of the data plane-messages gives an
attacker a very reliable identifier for DetNet traffic, and this
traffic has a high probability of going to lucrative targets.
4.8. Attacks on Time Sync Mechanisms
ToDo.
4.9. Attacks on Path Choice
This is covered in part in Section 4.3, and as with Replication and
Elimination (Section 4.4, this is relevant for DataPlane messages.
5. Security Threat Mitigation
This section describes a set of measures that can be taken to
mitigate the attacks described in Section 3. These mitigations
should be viewed as a toolset that includes several different and
diverse tools. Each application or system will typically use a
subset of these tools, based on a system-specific threat analysis.
5.1. Path Redundancy
Description
A DetNet flow that can be forwarded simultaneously over multiple
paths. Path replication and elimination
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[I-D.ietf-detnet-architecture] provides resiliency to dropped or
delayed packets. This redundancy improves the robustness to
failures and to man-in-the-middle attacks.
Related attacks
Path redundancy can be used to mitigate various man-in-the-middle
attacks, including attacks described in Section 3.2.1,
Section 3.2.2, Section 3.2.3, and Section 3.2.8.
5.2. Integrity Protection
Description
An integrity protection mechanism, such as a Hash-based Message
Authentication Code (HMAC) can be used to mitigate modification
attacks. Integrity protection can be used on the data plane
header, to prevent its modification and tampering. Integrity
protection in the control plane is discussed in Section 5.5.
Related attacks
Integrity protection mitigates attacks related to modification and
tampering, including the attacks described in Section 3.2.2 and
Section 3.2.4.
5.3. DetNet Node Authentication
Description
Source authentication verifies the authenticity of DetNet sources,
allowing to mitigate spoofing attacks. Note that while integrity
protection (Section 5.2) prevents intermediate nodes from
modifying information, authentication verfies the source of the
information.
Related attacks
DetNet node authentication is used to mitigate attacks related to
spoofing, including the attacks of Section 3.2.2, and
Section 3.2.4.
5.4. Encryption
Description
DetNet flows can be forwarded in encrypted form.
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Related attacks
While confidentiality is not considered an important goal with
respect to DetNet, encryption can be used to mitigate recon
attacks (Section 3.2.7).
5.5. Control and Signaling Message Protection
Description
Control and sigaling messages can be protected using
authentication and integrity protection mechanisms.
Related attacks
These mechanisms can be used to mitigate various attacks on the
control plane, as described in Section 3.2.6, Section 3.2.8 and
Section 3.2.5.
5.6. Dynamic Performance Analytics
Description
Information about the network performance can be gathered in real-
time in order to detect anomalies and unusual behavior that may be
the symptom of a security attack. The gathered information can be
based, for example, on per-flow counters, bandwidth measurement,
and monitoring of packet arrival times. Unusual behavior or
potentially malicious nodes can be reported to a management
system, or can be used as a trigger for taking corrective actions.
The information can be tracked by DetNet end systems and transit
nodes, and exported to a management system, for example using
NETCONF.
Related attacks
Performance analytics can be used to mitigate various attacks,
including the ones described in Section 3.2.1, Section 3.2.3, and
Section 3.2.8.
5.7. Mitigation Summary
The following table maps the attacks of Section 3 to the impacts of
Section 4, and to the mitigations of the current section. Each row
specifies an attack, the impact of this attack if it is successfully
implemented, and possible mitigation methods.
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+----------------------+---------------------+---------------------+
| Attack | Impact | Mitigations |
+----------------------+---------------------+---------------------+
|Delay Attack |-Non-deterministic |-Path redundancy |
| | delay |-Performance |
| |-Data disruption | analytics |
| |-Increased resource | |
| | consumption | |
+----------------------+---------------------+---------------------+
|Reconnaissance |-Enabler for other |-Encryption |
| | attacks | |
+----------------------+---------------------+---------------------+
|DetNet Flow Modificat-|-Increased resource |-Path redundancy |
|ion or Spoofing | consumption |-Integrity protection|
| |-Data disruption |-DetNet Node |
| | | authentication |
+----------------------+---------------------+---------------------+
|Inter-Segment Attack |-Increased resource |-Path redundancy |
| | consumption |-Performance |
| |-Data disruption | analytics |
+----------------------+---------------------+---------------------+
|Replication: Increased|-All impacts of other|-Integrity protection|
|attack surface | attacks |-DetNet Node |
| | | authentication |
+----------------------+---------------------+---------------------+
|Replication-related |-Non-deterministic |-Integrity protection|
|Header Manipulation | delay |-DetNet Node |
| |-Data disruption | authentication |
+----------------------+---------------------+---------------------+
|Path Manipulation |-Enabler for other |-Control message |
| | attacks | protection |
+----------------------+---------------------+---------------------+
|Path Choice: Increased|-All impacts of other|-Control message |
|Attack Surface | attacks | protection |
+----------------------+---------------------+---------------------+
|Control or Signaling |-Increased resource |-Control message |
|Packet Modification | consumption | protection |
| |-Non-deterministic | |
| | delay | |
| |-Data disruption | |
+----------------------+---------------------+---------------------+
|Control or Signaling |-Increased resource |-Control message |
|Packet Injection | consumption | protection |
| |-Non-deterministic | |
| | delay | |
| |-Data disruption | |
+----------------------+---------------------+---------------------+
|Attacks on Time Sync |-Non-deterministic |-Path redundancy |
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|Mechanisms | delay |-Control message |
| |-Increased resource | protection |
| | consumption |-Performance |
| |-Data disruption | analytics |
+----------------------+---------------------+---------------------+
Figure 3: Mapping Attacks to Impact and Mitigations
6. Association of Attacks to Use Cases
Different attacks can have different impact and/or mitigation
depending on the use case, so we would like to make this association
in our analysis. However since there is a potentially unbounded list
of use cases, we categorize the attacks with respect to the common
themes of the use cases as identified in the Use Case Common Themes
section of the DetNet Use Cases draft [I-D.ietf-detnet-use-cases].
See also Figure 2 for a mapping of the impact of attacks per use case
by industry.
6.1. Use Cases by Common Themes
In this section we review each theme and discuss the attacks that are
applicable to that theme, as well as anything specific about the
impact and mitigations for that attack with respect to that theme.
The table Figure 5 then provides a summary of the attacks that are
applicable to each theme.
6.1.1. Network Layer - AVB/TSN Ethernet
DetNet is expected to run over various transmission mediums, with
Ethernet being explicitly supported. Attacks such as Delay or
Reconnaissance might be implemented differently on a different
transmission medium, however the impact on the DetNet as a whole
would be essentially the same. We thus conclude that all attacks and
impacts that would be applicable to DetNet over Ethernet (i.e. all
those named in this draft) would also be applicable to DetNet over
other transmission mediums.
With respect to mitigations, some methods are specific to the
Ethernet medium, for example time-aware scheduling using 802.1Qbv can
protect against excessive use of bandwidth at the ingress - for other
mediums, other mitigations would have to be implemented to provide
analogous protection.
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6.1.2. Central Administration
A DetNet network is expected to be controlled by a centralized
network configuration and control system (CNC). Such a system may be
in a single central location, or it may be distributed across
multiple control entities that function together as a unified control
system for the network.
In this draft we distinguish between attacks on the DetNet Control
plane vs. Data plane. But is an attack affecting control plane
packets synonymous with an attack on the CNC itself? For purposes of
this draft let us consider an attack on the CNC itself to be out of
scope, and consider all attacks named in this draft which are
relevant to control plane packets to be relevant to this theme,
including Path Manipulation, Path Choice, Control Packet Modification
or Injection, Reconaissance and Attacks on Time Sync Mechanisms.
6.1.3. Hot Swap
A DetNet network is not expected to be "plug and play" - it is
expected that there is some centralized network configuration and
control system. However, the ability to "hot swap" components (e.g.
due to malfunction) is similar enough to "plug and play" that this
kind of behavior may be expected in DetNet networks, depending on the
implementation.
An attack surface related to Hot Swap is that the DetNet network must
at least consider input at runtime from devices that were not part of
the initial configuration of the network. Even a "perfect" (or
"hitless") replacement of a device at runtime would not necessarily
be ideal, since presumably one would want to distinguish it from the
original for OAM purposes (e.g. to report hot swap of a failed
device).
This implies that an attack such as Flow Modification, Spoofing or
Inter-segment (which could introduce packets from a "new" device
(i.e. one heretofore unknown on the network) could be used to exploit
the need to consider such packets (as opposed to rejecting them out
of hand as one would do if one did not have to consider introduction
of a new device).
Similarly if the network was designed to support runtime replacement
of a clock device, then presence (or apparent presence) and thus
consideration of packets from a new such device could affect the
network, or the time sync of the network, for example by initiating a
new Best Master Clock selection process. Thus attacks on time sync
should be considered when designing hot swap type functionality.
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6.1.4. Data Flow Information Models
Data Flow Information Models specific to DetNet networks are to be
specified by DetNet. Thus they are "new" and thus potentially
present a new attack surface. Does the threat take advantage of any
aspect of our new Data Flow Info Models?
This is TBD, thus there are no specific entries in our table, however
that does not imply that there could be no relevant attacks.
6.1.5. L2 and L3 Integration
A DetNet network integrates Layer 2 (bridged) networks (e.g. AVB/TSN
LAN) and Layer 3 (routed) networks via the use of well-known
protocols such as IPv6, MPLS-PW, and Ethernet. Presumably security
considerations applicable directly to those individual protocols is
not specific to DetNet, and thus out of scope for this draft.
However enabling DetNet to coordinate Layer 2 and Layer 3 behavior
will require some additions to existing protocols (see draft-dt-
detnet-dp-alt) and any such new work can introduce new attack
surfaces.
This is TBD, thus there are no specific entries in our table, however
that does not imply that there could be no relevant attacks.
6.1.6. End-to-End Delivery
Packets sent over DetNet are guaranteed not to be dropped by the
network due to congestion. (Packets may however be dropped for
intended reasons, e.g. per security measures).
A Data plane attack may force packets to be dropped, for example a
"long" Delay or Replication/Elimination or Flow Modification attack.
The same result might be obtained by a Control plane attack, e.g.
Path Manipulation or Signaling Packet Modification.
It may be that such attacks are limited to Internal MITM attackers,
but other possibilities should be considered.
An attack may also cause packets that should not be delivered to be
delivered, such as by forcing packets from one (e.g. replicated) path
to be preferred over another path when they should not be
(Replication attack), or by Flow Modification, or by Path Choice or
Packet Injection. A Time Sync attack could cause a system that was
expecting certain packets at certain times to accept unintended
packets based on compromised system time or time windowing in the
scheduler.
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6.1.7. Proprietary Deterministic Ethernet Networks
There are many proprietary non-interoperable deterministic Ethernet-
based networks currently available; DetNet is intended to provide an
open-standards-based alternative to such networks. In cases where a
DetNet intersects with remnants of such networks or their protocols,
such as by protocol emulation or access to such a network via a
gateway, new attack surfaces can be opened.
For example an Inter-Segment or Control plane attack such as Path
Manipulation, Path Choice or Control Packet Modification/Injection
could be used to exploit commands specific to such a protocol, or
that are interpreted differently by the different protocols or
gateway.
6.1.8. Replacement for Proprietary Fieldbuses
There are many proprietary "field buses" used in today's industrial
and other industries; DetNet is intended to provide an open-
standards-based alternative to such buses. In cases where a DetNet
intersects with such fieldbuses or their protocols, such as by
protocol emulation or access via a gateway, new attack surfaces can
be opened.
For example an Inter-Segment or Control plane attack such as Path
Manipulation, Path Choice or Control Packet Modification/Injection
could be used to exploit commands specific to such a protocol, or
that are interpreted differently by the different protocols or
gateway.
6.1.9. Deterministic vs Best-Effort Traffic
DetNet is intended to support coexistence of time-sensitive
operational (OT, deterministic) traffic and information (IT, "best
effort") traffic on the same ("unified") network.
The presence of IT traffic on a network carrying OT traffic has long
been considered insecure design [reference needed here]. With
DetNet, this coexistance will become more common, and mitigations
will need to be established. The fact that the IT traffic on a
DetNet is limited to a corporate controlled network makes this a less
difficult problem compared to being exposed to the open Internet,
however this aspect of DetNet security should not be underestimated.
Most of the themes described in this draft address OT (reserved)
streams - this item is intended to address issues related to IT
traffic on a DetNet.
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An Inter-segment attack can flood the network with IT-type traffic
with the intent of disrupting handling of IT traffic, and/or the goal
of interfering with OT traffic. Presumably if the stream reservation
and isolation of the DetNet is well-designed (better-designed than
the attack) then interference with OT traffic should not result from
an attack that floods the network with IT traffic.
However the DetNet's handling of IT traffic may not (by design) be as
resilient to DOS attack, and thus designers must be otherwise
prepared to mitigate DOS attacks on IT traffic in a DetNet.
6.1.10. Deterministic Flows
Reserved bandwidth data flows (deterministic flows) must provide the
allocated bandwidth, and must be isolated from each other.
A Spoofing or Inter-segment attack which adds packet traffic to a
bandwidth-reserved stream could cause that stream to occupy more
bandwidth than it is allocated, resulting in interference with other
deterministic flows.
A Flow Modification or Spoofing or Header Manipulation or Control
Packet Modification attack could cause packets from one flow to be
directed to another flow, thus breaching isolation between the flows.
6.1.11. Unused Reserved Bandwidth
If bandwidth reservations are made for a stream but the associated
bandwidth is not used at any point in time, that bandwidth is made
available on the network for best-effort traffic. If the owner of
the reserved stream then starts transmitting again, the bandwidth is
no longer available for best-effort traffic, on a moment-to-moment
basis. (Such "temporarily available" bandwidth is not available for
time-sensitive traffic, which must have its own reservation).
An Inter-segment attack could flood the network with IT traffic,
interfering with the intended IT traffic.
A Flow Modification or Spoofing or Control Packet Modification or
Injection attack could cause extra bandwidth to be reserved by a new
or existing stream, thus making it unavailable for use by best-effort
traffic.
6.1.12. Interoperability
The DetNet network specifications are intended to enable an ecosystem
in which multiple vendors can create interoperable products, thus
promoting device diversity and potentially higher numbers of each
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device manufactured. Does the threat take advantage of differences
in implementation of "interoperable" products made by different
vendors?
This is TBD, thus there are no specific entries in our table, however
that does not imply that there could be no relevant attacks.
6.1.13. Cost Reductions
The DetNet network specifications are intended to enable an ecosystem
in which multiple vendors can create interoperable products, thus
promoting higher numbers of each device manufactured, promoting cost
reduction and cost competition among vendors. Does the threat take
advantage of "low cost" HW or SW components or other "cost-related
shortcuts" that might be present in devices?
This is TBD, thus there are no specific entries in our table, however
that does not imply that there could be no relevant attacks.
6.1.14. Insufficiently Secure Devices
The DetNet network specifications are intended to enable an ecosystem
in which multiple vendors can create interoperable products, thus
promoting device diversity and potentially higher numbers of each
device manufactured. Does the threat attack "naivete" of SW, for
example SW that was not designed to be sufficiently secure (or secure
at all) but is deployed on a DetNet network that is intended to be
highly secure? (For example IoT exploits like the Mirai video-camera
botnet ([MIRAI]).
This is TBD, thus there are no specific entries in our table, however
that does not imply that there could be no relevant attacks.
6.1.15. DetNet Network Size
DetNet networks range in size from very small, e.g. inside a single
industrial machine, to very large, for example a Utility Grid network
spanning a whole country.
The size of the network might be related to how the attack is
introduced into the network, for example if the entire network is
local, there is a threat that power can be cut to the entire network.
If the network is large, perhaps only a part of the network is
attacked.
A Delay attack might be as relevant to a small network as to a large
network, although the amount of delay might be different.
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Attacks sourced from IT traffic might be more likely in large
networks, since more people might have access to the network.
Similarly Path Manipulation, Path Choice and Time Sync attacks seem
more likely relevant to large networks.
6.1.16. Multiple Hops
Large DetNet networks (e.g. a Utility Grid network) may involve many
"hops" over various kinds of links for example radio repeaters,
microwave links, fiber optic links, etc..
An attack that takes advantage of flaws (or even normal operation) in
the device drivers for the various links (through internal knowledge
of how the individual driver or firmware operates, perhaps like the
Stuxnet attack) could take proportionately greater advantage of this
topology. We don't currently have an attack like this defined; we
have only "protocol" (time or packet) based attacks. Perhaps we need
to define an attack like this? Or is that out of scope for DetNet?
It is also possible that this DetNet topology will not be in as
common use as other more homogeneous topologies so there may be more
opportunity for attackers to exploit software and/or protocol flaws
in the implementations which have not been wrung out by extensive
use, particularly in the case of early adopters.
Of the attacks we have defined, the ones identified above as relevant
to "large" networks seem to be most relevant.
6.1.17. Level of Service
A DetNet is expected to provide means to configure the network that
include querying network path latency, requesting bounded latency for
a given stream, requesting worst case maximum and/or minimum latency
for a given path or stream, and so on. It is an expected case that
the network cannot provide a given requested service level. In such
cases the network control system should reply that the requested
service level is not available (as opposed to accepting the parameter
but then not delivering the desired behavior).
Control plane attacks such as Signaling Packet Modification and
Injection could be used to modify or create control traffic that
could interfere with the process of a user requesting a level of
service and/or the network's reply.
Reconnaissance could be used to characterize flows and perhaps target
specific flows for attack via the Control plane as noted above.
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6.1.18. Bounded Latency
DetNet provides the expectation of guaranteed bounded latency.
Delay attacks can cause packets to miss their agreed-upon latency
boundaries.
Time Sync attacks can corrupt the system's time reference, resulting
in missed latency deadlines (with respect to the "correct" time
reference).
6.1.19. Low Latency
Applications may require "extremely low latency" however depending on
the application these may mean very different latency values; for
example "low latency" across a Utility grid network is on a different
time scale than "low latency" in a motor control loop in a small
machine. The intent is that the mechanisms for specifying desired
latency include wide ranges, and that architecturally there is
nothing to prevent arbitrarily low latencies from being implemented
in a given network.
Attacks on the Control plane (as described in the Level of Service
theme) and Delay and Time attacks (as described in the Bounded
Latency theme) both apply here.
6.1.20. Symmetrical Path Delays
Some applications would like to specify that the transit delay time
values be equal for both the transmit and return paths.
Delay attacks can cause path delays to differ.
Time Sync attacks can corrupt the system's time reference, resulting
in differing path delays (with respect to the "correct" time
reference).
6.1.21. Reliability and Availability
DetNet based systems are expected to be implemented with essentially
arbitrarily high availability (for example 99.9999% up time, or even
12 nines). The intent is that the DetNet designs should not make any
assumptions about the level of reliability and availability that may
be required of a given system, and should define parameters for
communicating these kinds of metrics within the network.
Any attack on the system, of any type, can affect its overall
reliability and availability, thus in our table we have marked every
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attack. Since every DetNet depends to a greater or lesser degree on
reliability and availability, this essentially means that all
networks have to mitigate all attacks, which to a greater or lesser
degree defeats the purpose of associating attacks with use cases. It
also underscores the difficulty of designing "extremely high
reliability" networks. I hope that in future drafts we can say
something more useful here.
6.1.22. Redundant Paths
DetNet based systems are expected to be implemented with essentially
arbitrarily high reliability/availability. A strategy used by DetNet
for providing such extraordinarily high levels of reliability is to
provide redundant paths that can be seamlessly switched between, all
the while maintaining the required performance of that system.
Replication-related attacks are by definition applicable here.
Control plane attacks can also interfere with the configuration of
redundant paths.
6.1.23. Security Measures
A DetNet network must be made secure against devices failures,
attackers, misbehaving devices, and so on. Does the threat affect
such security measures themselves, e.g. by attacking SW designed to
protect against device failure?
This is TBD, thus there are no specific entries in our table, however
that does not imply that there could be no relevant attacks.
6.2. Attack Types by Use Case Common Theme
The following table lists the attacks of Section 3, assigning a
number to each type of attack. That number is then used as a short
form identifier for the attack in Figure 5.
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+--+----------------------------------------+----------------------+
| | Attack | Section |
+--+----------------------------------------+----------------------+
| 1|Delay Attack | Section 3.2.1 |
+--+----------------------------------------+----------------------+
| 2|DetNet Flow Modification or Spoofing | Section 3.2.2 |
+--+----------------------------------------+----------------------+
| 3|Inter-Segment Attack | Section 3.2.3 |
+--+----------------------------------------+----------------------+
| 4|Replication: Increased attack surface | Section 3.2.4.1 |
+--+----------------------------------------+----------------------+
| 5|Replication-related Header Manipulation | Section 3.2.4.2 |
+--+----------------------------------------+----------------------+
| 6|Path Manipulation | Section 3.2.5.1 |
+--+----------------------------------------+----------------------+
| 7|Path Choice: Increased Attack Surface | Section 3.2.5.2 |
+--+----------------------------------------+----------------------+
| 8|Control or Signaling Packet Modification| Section 3.2.6.1 |
+--+----------------------------------------+----------------------+
| 9|Control or Signaling Packet Injection | Section 3.2.6.2 |
+--+----------------------------------------+----------------------+
|10|Reconnaissance | Section 3.2.7 |
+--+----------------------------------------+----------------------+
|11|Attacks on Time Sync Mechanisms | Section 3.2.8 |
+--+----------------------------------------+----------------------+
Figure 4: List of Attacks
The following table maps the use case themes presented in this memo
to the attacks of Figure 4. Each row specifies a theme, and the
attacks relevant to this theme are marked with a '+'.
+----------------------------+--------------------------------+
| Theme | Attack |
| +--+--+--+--+--+--+--+--+--+--+--+
| | 1| 2| 3| 4| 5| 6| 7| 8| 9|10|11|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Network Layer - AVB/TSN Eth.| +| +| +| +| +| +| +| +| +| +| +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Central Administration | | | | | | +| +| +| +| +| +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Hot Swap | | +| +| | | | | | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Data Flow Information Models| | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|L2 and L3 Integration | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
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|End-to-end Delivery | +| +| +| +| +| +| +| +| +| | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Proprietary Deterministic | | | +| | | +| +| +| +| | |
|Ethernet Networks | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Replacement for Proprietary | | | +| | | +| +| +| +| | |
|Fieldbuses | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Deterministic vs. Best- | | | +| | | | | | | | |
|Effort Traffic | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Deterministic Flows | | +| +| | +| +| | +| | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Unused Reserved Bandwidth | | +| +| | | | | +| +| | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Interoperability | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Cost Reductions | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Insufficiently Secure | | | | | | | | | | | |
|Devices | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|DetNet Network Size | +| | | | | +| +| | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Multiple Hops | +| +| | | | +| +| | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Level of Service | | | | | | | | +| +| +| |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Bounded Latency | +| | | | | | | | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Low Latency | +| | | | | | | +| +| +| +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Symmetric Path Delays | +| | | | | | | | | | +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Reliability and Availability| +| +| +| +| +| +| +| +| +| +| +|
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Redundant Paths | | | | +| +| | | +| +| | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
|Security Measures | | | | | | | | | | | |
+----------------------------+--+--+--+--+--+--+--+--+--+--+--+
Figure 5: Mapping Between Themes and Attacks
7. Appendix A: DetNet Draft Security-Related Statements
This section collects the various statements in the currently
existing DetNet Working Group drafts. For each draft, the section
name and number of the quoted section is shown. The text shown here
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is the work of the original draft authors, quoted verbatim from the
drafts. The intention is to explicitly quote all relevant text, not
to summarize it.
7.1. Architecture (draft 8)
7.1.1. Fault Mitigation (sec 4.5)
One key to building robust real-time systems is to reduce the
infinite variety of possible failures to a number that can be
analyzed with reasonable confidence. DetNet aids in the process by
providing filters and policers to detect DetNet packets received on
the wrong interface, or at the wrong time, or in too great a volume,
and to then take actions such as discarding the offending packet,
shutting down the offending DetNet flow, or shutting down the
offending interface.
It is also essential that filters and service remarking be employed
at the network edge to prevent non-DetNet packets from being mistaken
for DetNet packets, and thus impinging on the resources allocated to
DetNet packets.
There exist techniques, at present and/or in various stages of
standardization, that can perform these fault mitigation tasks that
deliver a high probability that misbehaving systems will have zero
impact on well-behaved DetNet flows, except of course, for the
receiving interface(s) immediately downstream of the misbehaving
device. Examples of such techniques include traffic policing
functions (e.g. [RFC2475]) and separating flows into per-flow rate-
limited queues.
7.1.2. Security Considerations (sec 7)
Security in the context of Deterministic Networking has an added
dimension; the time of delivery of a packet can be just as important
as the contents of the packet, itself. A man-in-the-middle attack,
for example, can impose, and then systematically adjust, additional
delays into a link, and thus disrupt or subvert a real-time
application without having to crack any encryption methods employed.
See [RFC7384] for an exploration of this issue in a related context.
Furthermore, in a control system where millions of dollars of
equipment, or even human lives, can be lost if the DetNet QoS is not
delivered, one must consider not only simple equipment failures,
where the box or wire instantly becomes perfectly silent, but bizarre
errors such as can be caused by software failures. Because there is
essential no limit to the kinds of failures that can occur,
protecting against realistic equipment failures is indistinguishable,
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in most cases, from protecting against malicious behavior, whether
accidental or intentional.
Security must cover:
o Protection of the signaling protocol
o Authentication and authorization of the controlling nodes
o Identification and shaping of the flows
7.2. Data Plane Alternatives (draft 4)
7.2.1. Security Considerations (sec 7)
This document does not add any new security considerations beyond
what the referenced technologies already have.
7.3. Problem Statement (draft 5)
7.3.1. Security Considerations (sec 5)
Security in the context of Deterministic Networking has an added
dimension; the time of delivery of a packet can be just as important
as the contents of the packet, itself. A man-in-the-middle attack,
for example, can impose, and then systematically adjust, additional
delays into a link, and thus disrupt or subvert a real-time
application without having to crack any encryption methods employed.
See [RFC7384] for an exploration of this issue in a related context.
Typical control networks today rely on complete physical isolation to
prevent rogue access to network resources. DetNet enables the
virtualization of those networks over a converged IT/OT
infrastructure. Doing so, DetNet introduces an additional risk that
flows interact and interfere with one another as they share physical
resources such as Ethernet trunks and radio spectrum. The
requirement is that there is no possible data leak from and into a
deterministic flow, and in a more general fashion there is no
possible influence whatsoever from the outside on a deterministic
flow. The expectation is that physical resources are effectively
associated with a given flow at a given point of time. In that
model, Time Sharing of physical resources becomes transparent to the
individual flows which have no clue whether the resources are used by
other flows at other times.
Security must cover:
o Protection of the signaling protocol
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o Authentication and authorization of the controlling nodes
o Identification and shaping of the flows
o Isolation of flows from leakage and other influences from any
activity sharing physical resources
7.4. Use Cases (draft 11)
7.4.1. (Utility Networks) Security Current Practices and Limitations
(sec 3.2.1)
Grid monitoring and control devices are already targets for cyber
attacks, and legacy telecommunications protocols have many intrinsic
network-related vulnerabilities. For example, DNP3, Modbus,
PROFIBUS/PROFINET, and other protocols are designed around a common
paradigm of request and respond. Each protocol is designed for a
master device such as an HMI (Human Machine Interface) system to send
commands to subordinate slave devices to retrieve data (reading
inputs) or control (writing to outputs). Because many of these
protocols lack authentication, encryption, or other basic security
measures, they are prone to network-based attacks, allowing a
malicious actor or attacker to utilize the request-and-respond system
as a mechanism for command-and-control like functionality. Specific
security concerns common to most industrial control, including
utility telecommunication protocols include the following:
o Network or transport errors (e.g. malformed packets or excessive
latency) can cause protocol failure.
o Protocol commands may be available that are capable of forcing
slave devices into inoperable states, including powering-off
devices, forcing them into a listen-only state, disabling
alarming.
o Protocol commands may be available that are capable of restarting
communications and otherwise interrupting processes.
o Protocol commands may be available that are capable of clearing,
erasing, or resetting diagnostic information such as counters and
diagnostic registers.
o Protocol commands may be available that are capable of requesting
sensitive information about the controllers, their configurations,
or other need-to-know information.
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o Most protocols are application layer protocols transported over
TCP; therefore it is easy to transport commands over non-standard
ports or inject commands into authorized traffic flows.
o Protocol commands may be available that are capable of
broadcasting messages to many devices at once (i.e. a potential
DoS).
o Protocol commands may be available to query the device network to
obtain defined points and their values (i.e. a configuration
scan).
o Protocol commands may be available that will list all available
function codes (i.e. a function scan).
o These inherent vulnerabilities, along with increasing connectivity
between IT an OT networks, make network-based attacks very
feasible.
o Simple injection of malicious protocol commands provides control
over the target process. Altering legitimate protocol traffic can
also alter information about a process and disrupt the legitimate
controls that are in place over that process. A man-in-the-middle
attack could provide both control over a process and
misrepresentation of data back to operator consoles.
7.4.2. (Utility Networks) Security Trends in Utility Networks (sec
3.3.3)
Although advanced telecommunications networks can assist in
transforming the energy industry by playing a critical role in
maintaining high levels of reliability, performance, and
manageability, they also introduce the need for an integrated
security infrastructure. Many of the technologies being deployed to
support smart grid projects such as smart meters and sensors can
increase the vulnerability of the grid to attack. Top security
concerns for utilities migrating to an intelligent smart grid
telecommunications platform center on the following trends:
o Integration of distributed energy resources
o Proliferation of digital devices to enable management, automation,
protection, and control
o Regulatory mandates to comply with standards for critical
infrastructure protection
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o Migration to new systems for outage management, distribution
automation, condition-based maintenance, load forecasting, and
smart metering
o Demand for new levels of customer service and energy management
This development of a diverse set of networks to support the
integration of microgrids, open-access energy competition, and the
use of network-controlled devices is driving the need for a converged
security infrastructure for all participants in the smart grid,
including utilities, energy service providers, large commercial and
industrial, as well as residential customers. Securing the assets of
electric power delivery systems (from the control center to the
substation, to the feeders and down to customer meters) requires an
end-to-end security infrastructure that protects the myriad of
telecommunications assets used to operate, monitor, and control power
flow and measurement.
"Cyber security" refers to all the security issues in automation and
telecommunications that affect any functions related to the operation
of the electric power systems. Specifically, it involves the
concepts of:
o Integrity : data cannot be altered undetectably
o Authenticity : the telecommunications parties involved must be
validated as genuine
o Authorization : only requests and commands from the authorized
users can be accepted by the system
o Confidentiality : data must not be accessible to any
unauthenticated users
When designing and deploying new smart grid devices and
telecommunications systems, it is imperative to understand the
various impacts of these new components under a variety of attack
situations on the power grid. Consequences of a cyber attack on the
grid telecommunications network can be catastrophic. This is why
security for smart grid is not just an ad hoc feature or product,
it's a complete framework integrating both physical and Cyber
security requirements and covering the entire smart grid networks
from generation to distribution. Security has therefore become one
of the main foundations of the utility telecom network architecture
and must be considered at every layer with a defense-in-depth
approach. Migrating to IP based protocols is key to address these
challenges for two reasons:
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o IP enables a rich set of features and capabilities to enhance the
security posture
o IP is based on open standards, which allows interoperability
between different vendors and products, driving down the costs
associated with implementing security solutions in OT networks.
Securing OT (Operation technology) telecommunications over packet-
switched IP networks follow the same principles that are foundational
for securing the IT infrastructure, i.e., consideration must be given
to enforcing electronic access control for both person-to-machine and
machine-to-machine communications, and providing the appropriate
levels of data privacy, device and platform integrity, and threat
detection and mitigation.
7.4.3. (BAS) Security Considerations (sec 4.2.4)
When BAS field networks were developed it was assumed that the field
networks would always be physically isolated from external networks
and therefore security was not a concern. In today's world many BASs
are managed remotely and are thus connected to shared IP networks and
so security is definitely a concern, yet security features are not
available in the majority of BAS field network deployments .
The management network, being an IP-based network, has the protocols
available to enable network security, but in practice many BAS
systems do not implement even the available security features such as
device authentication or encryption for data in transit.
7.4.4. (6TiSCH) Security Considerations (sec 5.3.3)
On top of the classical requirements for protection of control
signaling, it must be noted that 6TiSCH networks operate on limited
resources that can be depleted rapidly in a DoS attack on the system,
for instance by placing a rogue device in the network, or by
obtaining management control and setting up unexpected additional
paths.
7.4.5. (Cellular radio) Security Considerations (sec 6.1.5)
Establishing time-sensitive streams in the network entails reserving
networking resources for long periods of time. It is important that
these reservation requests be authenticated to prevent malicious
reservation attempts from hostile nodes (or accidental
misconfiguration). This is particularly important in the case where
the reservation requests span administrative domains. Furthermore,
the reservation information itself should be digitally signed to
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reduce the risk of a legitimate node pushing a stale or hostile
configuration into another networking node.
Note: This is considered important for the security policy of the
network, but does not affect the core DetNet architecture and design.
7.4.6. (Industrial M2M) Communication Today (sec 7.2)
Industrial network scenarios require advanced security solutions.
Many of the current industrial production networks are physically
separated. Preventing critical flows from be leaked outside a domain
is handled today by filtering policies that are typically enforced in
firewalls.
8. IANA Considerations
This memo includes no requests from IANA.
9. Security Considerations
The security considerations of DetNet networks are presented
throughout this document.
10. Informative References
[ARINC664P7]
ARINC, "ARINC 664 Aircraft Data Network, Part 7, Avionics
Full-Duplex Switched Ethernet Network", 2009.
[I-D.ietf-detnet-architecture]
Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", draft-ietf-
detnet-architecture-04 (work in progress), October 2017.
[I-D.ietf-detnet-use-cases]
Grossman, E., "Deterministic Networking Use Cases", draft-
ietf-detnet-use-cases-15 (work in progress), April 2018.
[I-D.varga-detnet-service-model]
Varga, B. and J. Farkas, "DetNet Service Model", draft-
varga-detnet-service-model-02 (work in progress), May
2017.
[IEEE1588]
IEEE, "IEEE 1588 Standard for a Precision Clock
Synchronization Protocol for Networked Measurement and
Control Systems Version 2", 2008.
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[MIRAI] krebsonsecurity.com, "https://krebsonsecurity.com/2016/10/
hacked-cameras-dvrs-powered-todays-massive-internet-
outage/", 2016.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<https://www.rfc-editor.org/info/rfc3552>.
[RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in
Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
October 2014, <https://www.rfc-editor.org/info/rfc7384>.
Authors' Addresses
Tal Mizrahi
Marvell
Email: talmi@marvell.com
Ethan Grossman (editor)
Dolby Laboratories, Inc.
1275 Market Street
San Francisco, CA 94103
USA
Phone: +1 415 645 4726
Email: ethan.grossman@dolby.com
URI: http://www.dolby.com
Andrew J. Hacker
MistIQ Technologies, Inc
Harrisburg, PA
USA
Email: ajhacker@mistiqtech.com
URI: http://www.mistiqtech.com
Subir Das
Applied Communication Sciences
150 Mount Airy Road, Basking Ridge
New Jersey, 07920
USA
Email: sdas@appcomsci.com
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John Dowdell
Airbus Defence and Space
Celtic Springs
Newport NP10 8FZ
United Kingdom
Email: john.dowdell.ietf@gmail.com
Henrik Austad
Cisco Systems
Philip Pedersens vei 1
Lysaker 1366
Norway
Email: henrik@austad.us
Kevin Stanton
Intel
Email: kevin.b.stanton@intel.com
Norman Finn
Huawei
Email: norman.finn@mail01.huawei.com
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