--- 1/draft-ietf-detnet-security-12.txt 2020-12-11 16:13:12.389256278 -0800 +++ 2/draft-ietf-detnet-security-13.txt 2020-12-11 16:13:12.509259337 -0800 @@ -1,203 +1,206 @@ Internet Engineering Task Force E. Grossman, Ed. Internet-Draft DOLBY Intended status: Informational T. Mizrahi -Expires: April 5, 2021 HUAWEI +Expires: June 14, 2021 HUAWEI A. Hacker MISTIQ - October 2, 2020 + December 11, 2020 Deterministic Networking (DetNet) Security Considerations - draft-ietf-detnet-security-12 + draft-ietf-detnet-security-13 Abstract A DetNet (deterministic network) provides specific performance guarantees to its data flows, such as extremely low data loss rates - and bounded latency. As a result, securing a DetNet requires that in - addition to the best practice security measures taken for any - mission-critical network, additional security measures may be needed - to secure the intended operation of these novel service properties. + and bounded latency (including bounded latency variation, i.e. + "jitter"). As a result, securing a DetNet requires that in addition + to the best practice security measures taken for any mission-critical + network, additional security measures may be needed to secure the + intended operation of these novel service properties. This document addresses DetNet-specific security considerations from the perspectives of both the DetNet system-level designer and component designer. System considerations include a threat model, taxonomy of relevant attacks, and associations of threats versus use cases and service properties. Component-level considerations include - ingress filtering and packet arrival time violation detection. This - document also addresses DetNet security considerations specific to - the IP and MPLS data plane technologies thereby complementing the - Security Considerations sections of the various DetNet Data Plane - (and other) DetNet documents. + ingress filtering and packet arrival time violation detection. + + This document also addresses security considerations specific to the + IP and MPLS data plane technologies, thereby complementing the + Security Considerations sections of those documents. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - - This Internet-Draft will expire on April 5, 2021. + This Internet-Draft will expire on June 14, 2021. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Abbreviations and Terminology . . . . . . . . . . . . . . . . 6 - 3. Security Considerations for DetNet Component Design . . . . . 6 + 3. Security Considerations for DetNet Component Design . . . . . 7 3.1. Resource Allocation . . . . . . . . . . . . . . . . . . . 7 - 3.2. Explicit Routes . . . . . . . . . . . . . . . . . . . . . 7 + 3.2. Explicit Routes . . . . . . . . . . . . . . . . . . . . . 8 3.3. Redundant Path Support . . . . . . . . . . . . . . . . . 8 3.4. Timing (or other) Violation Reporting . . . . . . . . . . 9 4. DetNet Security Considerations Compared With DiffServ - Security Considerations . . . . . . . . . . . . . . . . . . . 9 - 5. Security Threats . . . . . . . . . . . . . . . . . . . . . . 10 + Security Considerations . . . . . . . . . . . . . . . . . . . 10 + 5. Security Threats . . . . . . . . . . . . . . . . . . . . . . 11 5.1. Threat Model . . . . . . . . . . . . . . . . . . . . . . 11 5.2. Threat Analysis . . . . . . . . . . . . . . . . . . . . . 12 5.2.1. Delay . . . . . . . . . . . . . . . . . . . . . . . . 12 5.2.2. DetNet Flow Modification or Spoofing . . . . . . . . 12 5.2.3. Resource Segmentation (Inter-segment Attack) . . . . 12 - 5.2.4. Packet Replication and Elimination . . . . . . . . . 12 - 5.2.4.1. Replication: Increased Attack Surface . . . . . . 12 - 5.2.4.2. Replication-related Header Manipulation . . . . . 12 - 5.2.5. Controller Plane . . . . . . . . . . . . . . . . . . 13 - 5.2.5.1. Path Choice Manipulation . . . . . . . . . . . . 13 + 5.2.4. Packet Replication and Elimination . . . . . . . . . 13 + 5.2.4.1. Replication: Increased Attack Surface . . . . . . 13 + 5.2.4.2. Replication-related Header Manipulation . . . . . 13 + 5.2.5. Controller Plane . . . . . . . . . . . . . . . . . . 14 + 5.2.5.1. Path Choice Manipulation . . . . . . . . . . . . 14 5.2.5.2. Compromised Controller . . . . . . . . . . . . . 14 5.2.6. Reconnaissance . . . . . . . . . . . . . . . . . . . 14 - 5.2.7. Time Synchronization Mechanisms . . . . . . . . . . . 14 - 5.3. Threat Summary . . . . . . . . . . . . . . . . . . . . . 14 - 6. Security Threat Impacts . . . . . . . . . . . . . . . . . . . 15 - 6.1. Delay-Attacks . . . . . . . . . . . . . . . . . . . . . . 18 - 6.1.1. Data Plane Delay Attacks . . . . . . . . . . . . . . 18 - 6.1.2. Controller Plane Delay Attacks . . . . . . . . . . . 19 - 6.2. Flow Modification and Spoofing . . . . . . . . . . . . . 19 - 6.2.1. Flow Modification . . . . . . . . . . . . . . . . . . 19 - 6.2.2. Spoofing . . . . . . . . . . . . . . . . . . . . . . 19 - 6.2.2.1. Dataplane Spoofing . . . . . . . . . . . . . . . 19 - 6.2.2.2. Controller Plane Spoofing . . . . . . . . . . . . 20 - 6.3. Segmentation Attacks (injection) . . . . . . . . . . . . 20 - 6.3.1. Data Plane Segmentation . . . . . . . . . . . . . . . 20 - 6.3.2. Controller Plane Segmentation . . . . . . . . . . . . 20 - 6.4. Replication and Elimination . . . . . . . . . . . . . . . 21 - 6.4.1. Increased Attack Surface . . . . . . . . . . . . . . 21 - 6.4.2. Header Manipulation at Elimination Routers . . . . . 21 - 6.5. Control or Signaling Packet Modification . . . . . . . . 21 - 6.6. Control or Signaling Packet Injection . . . . . . . . . . 21 - 6.7. Reconnaissance . . . . . . . . . . . . . . . . . . . . . 21 - 6.8. Attacks on Time Sync Mechanisms . . . . . . . . . . . . . 22 - 6.9. Attacks on Path Choice . . . . . . . . . . . . . . . . . 22 - 7. Security Threat Mitigation . . . . . . . . . . . . . . . . . 22 - 7.1. Path Redundancy . . . . . . . . . . . . . . . . . . . . . 22 - 7.2. Integrity Protection . . . . . . . . . . . . . . . . . . 22 - 7.3. DetNet Node Authentication . . . . . . . . . . . . . . . 23 - 7.4. Dummy Traffic Insertion . . . . . . . . . . . . . . . . . 24 - 7.5. Encryption . . . . . . . . . . . . . . . . . . . . . . . 24 - 7.5.1. Encryption Considerations for DetNet . . . . . . . . 24 - 7.6. Control and Signaling Message Protection . . . . . . . . 25 - 7.7. Dynamic Performance Analytics . . . . . . . . . . . . . . 26 - 7.8. Mitigation Summary . . . . . . . . . . . . . . . . . . . 27 - 8. Association of Attacks to Use Cases . . . . . . . . . . . . . 28 - 8.1. Association of Attacks to Use Case Common Themes . . . . 28 - 8.1.1. Sub-Network Layer . . . . . . . . . . . . . . . . . . 28 - 8.1.2. Central Administration . . . . . . . . . . . . . . . 29 - 8.1.3. Hot Swap . . . . . . . . . . . . . . . . . . . . . . 29 - 8.1.4. Data Flow Information Models . . . . . . . . . . . . 30 - 8.1.5. L2 and L3 Integration . . . . . . . . . . . . . . . . 30 - 8.1.6. End-to-End Delivery . . . . . . . . . . . . . . . . . 30 + 5.2.7. Time Synchronization Mechanisms . . . . . . . . . . . 15 + 5.3. Threat Summary . . . . . . . . . . . . . . . . . . . . . 15 + 6. Security Threat Impacts . . . . . . . . . . . . . . . . . . . 16 + 6.1. Delay-Attacks . . . . . . . . . . . . . . . . . . . . . . 19 + 6.1.1. Data Plane Delay Attacks . . . . . . . . . . . . . . 19 + 6.1.2. Controller Plane Delay Attacks . . . . . . . . . . . 20 + 6.2. Flow Modification and Spoofing . . . . . . . . . . . . . 20 + 6.2.1. Flow Modification . . . . . . . . . . . . . . . . . . 20 + 6.2.2. Spoofing . . . . . . . . . . . . . . . . . . . . . . 20 + 6.2.2.1. Dataplane Spoofing . . . . . . . . . . . . . . . 20 + 6.2.2.2. Controller Plane Spoofing . . . . . . . . . . . . 21 + 6.3. Segmentation Attacks (injection) . . . . . . . . . . . . 21 + 6.3.1. Data Plane Segmentation . . . . . . . . . . . . . . . 21 + 6.3.2. Controller Plane Segmentation . . . . . . . . . . . . 21 + 6.4. Replication and Elimination . . . . . . . . . . . . . . . 22 + 6.4.1. Increased Attack Surface . . . . . . . . . . . . . . 22 + 6.4.2. Header Manipulation at Elimination Routers . . . . . 22 + 6.5. Control or Signaling Packet Modification . . . . . . . . 22 + 6.6. Control or Signaling Packet Injection . . . . . . . . . . 22 + 6.7. Reconnaissance . . . . . . . . . . . . . . . . . . . . . 22 + 6.8. Attacks on Time Synchronization Mechanisms . . . . . . . 23 + 6.9. Attacks on Path Choice . . . . . . . . . . . . . . . . . 23 + 7. Security Threat Mitigation . . . . . . . . . . . . . . . . . 23 + 7.1. Path Redundancy . . . . . . . . . . . . . . . . . . . . . 23 + 7.2. Integrity Protection . . . . . . . . . . . . . . . . . . 24 + 7.3. DetNet Node Authentication . . . . . . . . . . . . . . . 25 + 7.4. Dummy Traffic Insertion . . . . . . . . . . . . . . . . . 26 + 7.5. Encryption . . . . . . . . . . . . . . . . . . . . . . . 26 + 7.5.1. Encryption Considerations for DetNet . . . . . . . . 27 + 7.6. Control and Signaling Message Protection . . . . . . . . 28 + 7.7. Dynamic Performance Analytics . . . . . . . . . . . . . . 28 + 7.8. Mitigation Summary . . . . . . . . . . . . . . . . . . . 30 + 8. Association of Attacks to Use Cases . . . . . . . . . . . . . 32 + 8.1. Association of Attacks to Use Case Common Themes . . . . 32 + 8.1.1. Sub-Network Layer . . . . . . . . . . . . . . . . . . 32 + 8.1.2. Central Administration . . . . . . . . . . . . . . . 33 + 8.1.3. Hot Swap . . . . . . . . . . . . . . . . . . . . . . 33 + 8.1.4. Data Flow Information Models . . . . . . . . . . . . 34 + 8.1.5. L2 and L3 Integration . . . . . . . . . . . . . . . . 34 + 8.1.6. End-to-End Delivery . . . . . . . . . . . . . . . . . 34 8.1.7. Replacement for Proprietary Fieldbuses and Ethernet- - based Networks . . . . . . . . . . . . . . . . . . . 31 - 8.1.8. Deterministic vs Best-Effort Traffic . . . . . . . . 31 - 8.1.9. Deterministic Flows . . . . . . . . . . . . . . . . . 32 - 8.1.10. Unused Reserved Bandwidth . . . . . . . . . . . . . . 32 - 8.1.11. Interoperability . . . . . . . . . . . . . . . . . . 32 - 8.1.12. Cost Reductions . . . . . . . . . . . . . . . . . . . 32 - 8.1.13. Insufficiently Secure Devices . . . . . . . . . . . . 33 - 8.1.14. DetNet Network Size . . . . . . . . . . . . . . . . . 33 - 8.1.15. Multiple Hops . . . . . . . . . . . . . . . . . . . . 34 - 8.1.16. Level of Service . . . . . . . . . . . . . . . . . . 34 - 8.1.17. Bounded Latency . . . . . . . . . . . . . . . . . . . 34 - 8.1.18. Low Latency . . . . . . . . . . . . . . . . . . . . . 35 - 8.1.19. Bounded Jitter (Latency Variation) . . . . . . . . . 35 - 8.1.20. Symmetrical Path Delays . . . . . . . . . . . . . . . 35 - 8.1.21. Reliability and Availability . . . . . . . . . . . . 35 - 8.1.22. Redundant Paths . . . . . . . . . . . . . . . . . . . 36 - 8.1.23. Security Measures . . . . . . . . . . . . . . . . . . 36 - 8.2. Summary of Attack Types per Use Case Common Theme . . . . 36 - 8.3. Security Considerations for OAM Traffic . . . . . . . . . 39 - 9. DetNet Technology-Specific Threats . . . . . . . . . . . . . 39 - 9.1. IP . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 - 9.2. MPLS . . . . . . . . . . . . . . . . . . . . . . . . . . 41 - 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42 - 11. Security Considerations . . . . . . . . . . . . . . . . . . . 42 - 12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 42 - 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 42 - 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 43 - 14.1. Normative References . . . . . . . . . . . . . . . . . . 43 - 14.2. Informative References . . . . . . . . . . . . . . . . . 44 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 47 + based Networks . . . . . . . . . . . . . . . . . . . 35 + 8.1.8. Deterministic vs Best-Effort Traffic . . . . . . . . 35 + 8.1.9. Deterministic Flows . . . . . . . . . . . . . . . . . 36 + 8.1.10. Unused Reserved Bandwidth . . . . . . . . . . . . . . 36 + 8.1.11. Interoperability . . . . . . . . . . . . . . . . . . 36 + 8.1.12. Cost Reductions . . . . . . . . . . . . . . . . . . . 37 + 8.1.13. Insufficiently Secure Components . . . . . . . . . . 37 + 8.1.14. DetNet Network Size . . . . . . . . . . . . . . . . . 37 + 8.1.15. Multiple Hops . . . . . . . . . . . . . . . . . . . . 38 + 8.1.16. Level of Service . . . . . . . . . . . . . . . . . . 38 + 8.1.17. Bounded Latency . . . . . . . . . . . . . . . . . . . 39 + 8.1.18. Low Latency . . . . . . . . . . . . . . . . . . . . . 39 + 8.1.19. Bounded Jitter (Latency Variation) . . . . . . . . . 39 + 8.1.20. Symmetrical Path Delays . . . . . . . . . . . . . . . 39 + 8.1.21. Reliability and Availability . . . . . . . . . . . . 40 + 8.1.22. Redundant Paths . . . . . . . . . . . . . . . . . . . 40 + 8.1.23. Security Measures . . . . . . . . . . . . . . . . . . 40 + 8.2. Summary of Attack Types per Use Case Common Theme . . . . 41 + 8.3. Security Considerations for OAM Traffic . . . . . . . . . 43 + 9. DetNet Technology-Specific Threats . . . . . . . . . . . . . 43 + 9.1. IP . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 + 9.2. MPLS . . . . . . . . . . . . . . . . . . . . . . . . . . 45 + 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46 + 11. Security Considerations . . . . . . . . . . . . . . . . . . . 46 + 12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 46 + 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 46 + 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 47 + 14.1. Normative References . . . . . . . . . . . . . . . . . . 47 + 14.2. Informative References . . . . . . . . . . . . . . . . . 48 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 52 1. Introduction - 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. - However, such networks are typically isolated from external access, - and thus the security threat from external attackers is low. IETF - Deterministic Networking (DetNet, [RFC8655]) 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). + A DetNet is one that can carry data flows for real-time applications + with extremely low data loss rates and bounded latency. The bounds + on latency defined by DetNet + ([I-D.ietf-detnet-flow-information-model]) include both worst case + latency (Maximum Latency, Section 5.9.2) and worst case jitter + (Maximum Latency Variation, Section 5.9.3). Deterministic networks + have been successfully deployed in real-time Operational Technology + (OT) applications for some years, however such networks are typically + isolated from external access, and thus the security threat from + external attackers is low. IETF Deterministic Networking (DetNet, + [RFC8655]) specifies a set of technologies that enable creation of + deterministic flows 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 document provides insight into such system-level - security considerations. In addition, designers of DetNet components - (such as routers) face new security-related challenges in providing - DetNet services, for example maintaining reliable isolation between - traffic flows in an environment where IT traffic co-mingles with - critical reserved-bandwidth OT traffic; this document also examines - security implications internal to DetNet components. + These DetNet (OT-type) technologies may not have previously been + deployed on a wide area IP-based network that also carries IT + traffic, and thus can present security considerations that may be new + to IP-based wide area network designers; this document provides + insight into such system-level security considerations. In addition, + designers of DetNet components (such as routers) face new security- + related challenges in providing DetNet services, for example + maintaining reliable isolation between traffic flows in an + environment where IT traffic co-mingles with critical reserved- + bandwidth OT traffic; this document also examines security + implications internal to DetNet components. - Security is of particularly high importance in DetNet networks - because many of the use cases which are enabled by DetNet [RFC8578] - 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. + Security is of particularly high importance in DetNet because many of + the use cases which are enabled by DetNet [RFC8578] include control + of physical devices (power grid devices, 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 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, for example [ARINC664P7]). Security considerations for OT networks are not a new area, and there are many OT networks today that are connected to wide area networks or the Internet; this document focuses on the issues that are specific to @@ -209,78 +212,98 @@ and controller plane; this is the assumed starting point for the considerations discussed herein. Such assumptions also depend on the network components themselves upholding the security-related properties that are to be assumed by DetNet system-level designers; for example, the assumption that network traffic associated with a given flow can never affect traffic associated with a different flow is only true if the underlying components make it so. Such properties, which may represent new challenges to component designers, are also considered herein. - In this context we view the network design and management aspects of - network security as being primarily concerned with denial-of service - prevention by ensuring that DetNet traffic goes where it's supposed - to and that an external attacker can't inject traffic that disrupts - the DetNet's delivery timing assurance. The time-specific aspects of - DetNet security presented here take up where the design and + In this context we view the "traditional" (i.e. non-time-sensitive) + network design and management aspects of network security as being + primarily concerned with denial-of service prevention, i.e. they must + ensure that DetNet traffic goes where it's supposed to and that an + external attacker can't inject traffic that disrupts the delivery + timing assurance of the DetNet. The time-specific aspects of DetNet + security presented here take up where those "traditional" design and management aspects leave off. - The exact security requirements for any given DetNet network are - necessarily specific to the use cases handled by that network. Thus - the reader is assumed to be familiar with the specific security - requirements of their use cases, for example those outlined in the - DetNet Use Cases [RFC8578] and the Security Considerations sections - of the DetNet documents applicable to the network technologies in - use, for example [I-D.ietf-detnet-ip]). A general introduction to - the DetNet architecture can be found in [RFC8655] and it is also - recommended to be familiar with the DetNet Data Plane - [I-D.ietf-detnet-data-plane-framework] and Flow Information Model + However note that "traditional" methods for mitigating (among all the + others) denial-of service attack (such as throttling) can only be + effectively used in a DetNet when their use does not compromise the + required time-sensitive or behavioral properties required for the OT + flows on the network. For example, a "retry" protocol is typically + not going to be compatible with a low-latency (worst-case maximum + latency) requirement, however if in a specific use case and + implementation such a retry protocol is able to meet the timing + constraints, then it may well be used in that context. Similarly if + common security protocols such as TLS/DTLS or IPsec are to be used, + it must be verified that their implementations are able to meet the + timing and behavioral requirements of the time-sensitive network as + implemented for the given use case. An example of "behavioral + properties" might be that dropping of more than a specific number of + packets in a row is not acceptable according to the service level + agreement. + + The exact security requirements for any given DetNet are necessarily + specific to the use cases handled by that network. Thus the reader + is assumed to be familiar with the specific security requirements of + their use cases, for example those outlined in the DetNet Use Cases + [RFC8578] and the Security Considerations sections of the DetNet + documents applicable to the network technologies in use, for example + [RFC8939]). Readers can find a general introduction to the DetNet + Architecture in [RFC8655], the DetNet Data Plane in [RFC8938], and + the Flow Information Model in [I-D.ietf-detnet-flow-information-model]. The DetNet technologies include ways to: o Assign data plane resources for DetNet flows in some or all of the intermediate nodes (routers) along the path of the flow o Provide explicit routes for DetNet flows that do not dynamically change with the network topology in ways that affect the quality of service received by the affected flow(s) 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 + ensure delivery of the data in each packet in spite of the loss of + a path. This document includes sections considering DetNet component design as well as system design. The latter includes 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 [RFC8578]). The structure of the threat model and threat analysis sections were originally derived from [RFC7384], which also considers time-related security considerations in IP networks. 2. Abbreviations and Terminology - 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 - [IT_DEF]). + 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 - [IT_DEF]). - 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. - [OT_DEF]) + 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. - [OT_DEF]) - Component A component of a DetNet system - used here to refer - to any hardware or software element of a DetNet network which - implements DetNet-specific functionality, for example all or part of - a router, switch, or end system. + Component: A component of a DetNet system - used here to refer to any + hardware or software element of a DetNet which implements DetNet- + specific functionality, for example all or part of a router, switch, + or end system. + + Device: Used here to refer to a physical entity controlled by the + DetNet, for example a motor. Resource Segmentation Used as a more general form for Network Segmentation (the act or practice of splitting a computer network into subnetworks, each being a network segment - [RS_DEF]) 3. Security Considerations for DetNet Component Design As noted above, DetNet provides resource allocation, explicit routes and redundant path support. Each of these has associated security implications, which are discussed in this section, in the context of @@ -299,43 +322,42 @@ different manufacturer. From a security standpoint, this is a critical assumption, for example when designing against DOS attacks. It is the responsibility of the component designer to ensure that this condition is met; this implies protection against excess traffic from adjacent flows, and against compromises to the resource allocation/deallocation process, for example through the use of traffic shaping and policing. As an example, consider the implementation of Flow Aggregation for - DetNet flows (as discussed in - [I-D.ietf-detnet-data-plane-framework]). In this example say there + DetNet flows (as discussed in [RFC8938]). In this example say there are N flows that are to be aggregated, thus the bandwidth resources of the aggregate flow must be sufficient to contain the sum of the bandwidth reservation for the N flows. However if one of those flows - were to consume more than its individually allocated BW, this could - cause starvation of the other flows. Thus simply providing and + were to consume more than its individually allocated bandwidth, this + could cause starvation of the other flows. Thus simply providing and enforcing the calculated aggregate bandwidth may not be a complete solution - the bandwidth for each individual flow must still be guaranteed, for example via ingress policing of each flow (i.e. before it is aggregated). Alternatively, if by some other means each flow to be aggregated can be trusted not to exceed its allocated bandwidth, the same goal can be achieved. 3.2. Explicit Routes - The DetNet-specific purpose for constraining the network's ability to - re-route OT traffic is to maintain the specified service parameters - (such as upper and lower latency boundaries) for a given flow. For - example if the network were to re-route a flow (or some part of a - flow) based exclusively on statistical path usage metrics, or due to - malicious activity, it is possible that the new path would have a - latency that is outside the required latency bounds which were + The DetNet-specific purpose for constraining the ability of the + DetNet to re-route OT traffic is to maintain the specified service + parameters (such as upper and lower latency boundaries) for a given + flow. For example if the network were to re-route a flow (or some + part of a flow) based exclusively on statistical path usage metrics, + or due to malicious activity, it is possible that the new path would + have a latency that is outside the required latency bounds which were designed into the original TE-designed path, thereby violating the quality of service for the affected flow (or part of that flow). However, it is acceptable for the network to re-route OT traffic in such a way as to maintain the specified latency bounds (and any other specified service properties) for any reason, for example in response to a runtime component or path failure. From a security standpoint, the system designer relies on the premise that the packets will be delivered with the specified latency boundaries; thus any component that is involved in controlling or implementing any change of the @@ -360,56 +382,58 @@ component designer to ensure that the relevant PREOF operations are executed reliably and securely, to avoid potentially catastrophic situations for the operational technology relying on them. However, note that not all PREOF operations are necessarily implemented in every network; for example a packet re-ordering function may not be necessary if the packets are either not required to be in order, or if the ordering is performed in some other part of the network. - Ideally a redundant path could be specified from end to end of the - flow's path, however given that this is not always possible (as - described in [RFC8655]) the system designer will need to consider the - resulting end-to-end reliability and security resulting from any - given arrangment of network segments along the path, each of which - provides its individual PREOF implementation and thus its individual - level of reliabiilty and security. + Ideally a redundant path for a flow could be specified from end to + end, however given that this is not always possible (as described in + [RFC8655]) the system designer will need to consider the resulting + end-to-end reliability and security resulting from any given + arrangment of network segments along the path, each of which provides + its individual PREOF implementation and thus its individual level of + reliabiilty and security. At the data plane the implementation of PREOF depends on the correct assignment and interpretation of packet sequence numbers, as well as the actions taken based on them, such as elimination (including elimination of packets with spurious sequence numbers). Thus the integrity of these values must be maintained by the component as they - are assigned by the DetNet Data Plane's Service sub-layer, and + are assigned by the DetNet Data Plane Service sub-layer, and transported by the Forwarding sub-layer. This is no different than the integrity of the values in any header used by the DetNet (or any - other) data plane, and is not unique to redundant paths. From the + other) data plane, and is not unique to redundant paths. The + integrity protection of header values is technology-dependent; for + example, in Layer 2 networks the integrity of the header fields can + be protected by using MACsec [IEEE802.1AE-2018]. Similary, from the sequence number injection perspective, it is no different from any other protocols that use sequence numbers. 3.4. Timing (or other) Violation Reporting Another fundamental assumption of a secure DetNet is that in any case in which an incoming packet arrives with any timing or bandwidth violation, something can be done about it which doesn't cause damage to the system. For example having the network shut down a link if a packet arrives outside of its prescribed time window may serve the - attacker better than it serves the network. That means that the - component's data plane must be able to detect and act on a variety of + attacker better than it serves the network. That means that the data + plane of the component must be able to detect and act on a variety of such violations, at least alerting the controller plane. Any action apart from that needs to be carefully considered in the context of the specific system. Some possible violations that warrant detection include cases where a packet arrives: o Outside of its prescribed time window - o Within its time window but with a compromised time stamp that makes it appear that it is not within its window o Exceeding the reserved flow bandwidth Logging of such issues is unlikely to be adequate, since a delay in response to the situation could result in material damage, for example to mechanical devices controlled by the network. Given that the data plane component probably has no knowledge of the use case of the network, or its applications and end systems, it would seem @@ -409,91 +433,90 @@ o Exceeding the reserved flow bandwidth Logging of such issues is unlikely to be adequate, since a delay in response to the situation could result in material damage, for example to mechanical devices controlled by the network. Given that the data plane component probably has no knowledge of the use case of the network, or its applications and end systems, it would seem useful for a data plane component to allow the system designer to configure its actions in the face of such violations. - Possible direct actions that may be taken at the data plane include - dropping the packet and/or shutting down the link; however if any - such actions are configured to be taken, the system designer must - ensure that such actions do not compromise the continued safe - operation of the system. For example, the controller plane should + Some possible direct actions that may be taken at the data plane + include traffic policing and shaping functions (e.g., those described + in [RFC2475]), separating flows into per-flow rate-limited queues, + and potentially applying active queue management [RFC7567]. However + if those (or any other) actions are to be taken, the system designer + must ensure that the results of such actions do not compromise the + continued safe operation of the system. For example, the network + (i.e. the controller plane and data plane working together) must mitigate in a timely fashion any potential adverse effect on mechanical devices controlled by the network. 4. DetNet Security Considerations Compared With DiffServ Security Considerations DetNet is designed to be compatible with DiffServ [RFC2474] as applied to IT traffic in the DetNet. DetNet also incorporates the use of the 6-bit value of the DSCP field of the TOS field of the IP header for flow identification for OT traffic, however the DetNet interpretation of the DSCP value for OT traffic is not equivalent to the PHB selection behavior as defined by DiffServ. Thus security consideration for DetNet have some aspects in common with DiffServ, in fact overlapping 100% with respect to IP IT traffic. Security considerations for these aspects are part of the existing literature on IP network security, specifically the Security - sections of [RFC2474] and [RFC2475]. However DetNet also introduces - timing and other considerations which are not present in DiffServ, so - the DiffServ security considerations are necessary but not sufficient - for DetNet. + Considerations sections of [RFC2474] and [RFC2475]. However DetNet + also introduces timing and other considerations which are not present + in DiffServ, so the DiffServ security considerations are necessary + but not sufficient for DetNet. - In the case of DetNet OT traffic, the DSCP value, although - interpreted differently than in DiffServ, does contribute to - determination of the service provided to the packet. Thus in DetNet - there are similar consequences to DiffServ for lack of detection of, - or incorrect handling of, packets with mismarked DSCP values, and - thus many of the points made in the DiffServ draft Security - discussions are also relevant to DetNet OT traffic, though perhaps in - modified form. For example, in DetNet the effect of an undetected or - incorrectly handled maliciously mismarked DSCP field in an OT packet - is not identical to affecting that packet's PHB, since DetNet does - not use the PHB concept for OT traffic, but nonetheless the service - provided to the packet could be affected, so mitigation measures - analogous to those prescribed by DiffServ would be appropriate for - DetNet. For example, mismarked DSCP values should not cause failure - of network nodes, and any internal link that cannot be adequately - secured against modification of DSCP values should be treated as a - boundary link (and hence any arriving traffic on that link is treated - as if it were entering the domain at an ingress node). The remarks + In the case of DetNet OT traffic, the DSCP value is interpreted + differently than in DiffServ and contribute to determination of the + service provided to the packet. In DetNet, there are similar + consequences to DiffServ for lack of detection of, or incorrect + handling of, packets with mismarked DSCP values, and many of the + points made in the DiffServ Security discussions ([RFC2475] Sec. 6.1 + , [RFC2474] Sec. 7 and [RFC6274] Sec 3.3.2.1) are also relevant to + DetNet OT traffic, though perhaps in modified form. For example, in + DetNet the effect of an undetected or incorrectly handled maliciously + mismarked DSCP field in an OT packet is not identical to affecting + the PHB of that packet, since DetNet does not use the PHB concept for + OT traffic; but nonetheless the service provided to the packet could + be affected, so mitigation measures analogous to those prescribed by + DiffServ would be appropriate for DetNet. For example, mismarked + DSCP values should not cause failure of network nodes. The remarks in [RFC2474] regarding IPsec and Tunnelling Interactions are also relevant (though this is not to say that other sections are less relevant). 5. Security Threats This section presents a threat model, and analyzes the possible threats in a DetNet-enabled network. The threats considered in this section are independent of any specific technologies used to implement the DetNet; Section 9 considers attacks that are associated - with the DetNet technologies encompassed by - [I-D.ietf-detnet-data-plane-framework]. + with the DetNet technologies encompassed by [RFC8938]. We distinguish controller 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 controller 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 controller plane. 5.1. Threat Model - The threat model used in this memo employs organizational elements of - the threat models of [RFC7384] and [RFC7835] . This model classifies - attackers based on two criteria: + The threat model used in this document employs organizational + elements of the threat models of [RFC7384] and [RFC7835]. 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 On-path vs. off-path: on-path attackers are located in a position that allows interception and modification of in-flight protocol packets, whereas off-path attackers can only attack by generating @@ -505,30 +528,29 @@ (explored further in Section 5.2, Threat Analysis). Most of the direct threats to DetNet are active attacks (i.e. attacks that modify DetNet traffic), but it is highly suggested that DetNet application developers take appropriate measures to protect the content of the DetNet flows from passive attacks (i.e. attacks that observe but do not modify DetNet traffic) for example through the use of TLS or DTLS. 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. + connects DetNet islands, i.e. two or more otherwise independent + DetNets 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 DetNets merits security analysis to ensure the integrity + of the networks involved. 5.2. Threat Analysis 5.2.1. Delay 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. The delay may be constant or modulated. @@ -616,120 +638,122 @@ 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. 5.2.5.2. Compromised Controller An attacker can subvert a controller, or enable a compromised controller to falsely represent itself as a controller so that the network nodes believe it to be authorized to instruct them. - Presence of compromised nodes in a DetNet is not a "new" threat that + Presence of compromised nodes in a DetNet is not a new threat that arises as a result of determinism or time sensitivity; the same techniques used to prevent or mitigate against compromised nodes in any network are equally applicable in the DetNet case. However this underscores the requirement for careful system security design in a DetNet, given that the effects of even one bad actor on the network can be potentially catastrophic. Security concerns specific to any given controller plane technology used in DetNet will be addressed by the DetNet documents associated with that technology. 5.2.6. 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, their schedules, or other temporal properties. 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 the purposes of this document we assume they are + DetNet flows are typically uniquely identified by their 6-tuple, i.e. + fields within the IP header, however in some implementations the flow + ID may also be augmented by additional per-flow attributes known to + the system, e.g. above the IP-layer. For the purpose of this + document we assume any such additional fields used for flow ID are encrypted and/or integrity-protected from external attackers. 5.2.7. Time Synchronization Mechanisms An attacker can use any of the attacks described in [RFC7384] to attack the synchronization protocol, thus affecting the DetNet service. 5.3. 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 used, and that the corresponding network equipment takes part in this mechanism. - +-----------------------------------------+----+----+----+----+ + +-------------------------------------------+----+-----+----+-----+ | Attack | Attacker Type | - | +---------+---------+ + | +----------+----------+ | |Internal |External | | |On-P|Off-P|On-P|Off-P| - +-----------------------------------------+----+----+----+----+ + +-------------------------------------------+----+-----+----+-----+ |Delay attack | + | + | + | + | - +-----------------------------------------+----+----+----+----+ + +-------------------------------------------+----+-----+----+-----+ |DetNet Flow Modification or Spoofing | + | + | | | - +-----------------------------------------+----+----+----+----+ - |Inter-segment Attack | + | + | | | - +-----------------------------------------+----+----+----+----+ + +-------------------------------------------+----+-----+----+-----+ + |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 | | + | | | - +-----------------------------------------+----+----+----+----+ + +-------------------------------------------+----+-----+----+-----+ + |Control or Signaling Packet Injection | + | + | | | + +-------------------------------------------+----+-----+----+-----+ |Reconnaissance | + | | + | | - +-----------------------------------------+----+----+----+----+ - |Attacks on Time Sync Mechanisms | + | + | + | + | - +-----------------------------------------+----+----+----+----+ + +-------------------------------------------+----+-----+----+-----+ + |Attacks on Time Synchronization Mechanisms | + | + | + | + | + +-------------------------------------------+----+-----+----+-----+ Figure 1: Threat Analysis Summary 6. Security Threat Impacts This section describes and rates the impact of the attacks described in Section 5, Security Threats. In this section, the impacts as described assume that the associated mitigation is not present or has failed. Mitigations are discussed in Section 7, Security Threat Mitigation. In computer security, the impact (or consequence) of an incident can be measured in loss of confidentiality, integrity or availability of information. In the case of time sensitive networks, the impact of a network exploit can also include failure or malfunction of mechanical and/or other OT systems. DetNet raises these stakes significantly for OT applications, particularly those which may have been designed to run in an OT-only environment and thus may not have been designed for security in an IT - environment with its associated devices, services and protocols. + environment with its associated components, 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 the DetNet Use Cases [RFC8578]. Each of these use cases 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. + The extent of impact of a successful vulnerability exploit varies + considerably by use case and by industry; additional insights + regarding the individual use cases is available from [RFC8578], + DetNet Use Cases. Each of those use cases is represented in + Figure 2, 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, + Aspects 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 (People WB), 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 @@ -842,22 +866,22 @@ DetNet flow have strict deterministic requirements. For a single path scenario, disruption is a real possibility, whereas in a multipath scenario, large delays or instabilities in one DetNet flow can lead to increased buffer and processor resources at the eliminating router. A data-plane delay attack on a system controlling substantial moving devices, for example in industrial automation, can cause physical damage. For example, if the network promises a bounded latency of - 2ms for a flow, yet the machine receives it with 5ms latency, the - machine's control loop can become unstable. + 2ms for a flow, yet the machine receives it with 5ms latency, control + loop of the machine can become unstable. 6.1.2. Controller 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 DetNet flows, finally giving rise to a denial of service attack. @@ -903,30 +927,30 @@ adverse effects. It can do virtually anything from: o modifying existing DetNet flows by changing the available bandwidth o add or remove endpoints from a DetNet flow o drop DetNet flows completely o falsely create new DetNet flows (exhaust the systems resources, or - to enable DetNet flows that are outside the Network Engineer's - control) + to enable DetNet flows that are outside the control of the Network + Engineer) 6.3. Segmentation Attacks (injection) 6.3.1. Data Plane Segmentation Injection of false messages in a DetNet flow could lead to exhaustion of the available bandwidth for that flow if the routers attribute - these false messages to that flow's budget. + these false messages to the resource budget of that flow. In a multipath scenario, injected messages will cause increased processor utilization in elimination routers. 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 routers than normal, giving rise to a resource exhaustion attack on the routers. If a DetNet flow is interrupted, the end application will be affected by what is now a non-deterministic flow. @@ -986,39 +1010,46 @@ 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. Applications which are ported from a private OT network to the higher visibility DetNet environment may need to be adapted to limit distinctive flow properties that could make them susceptible to reconnaissance. -6.8. Attacks on Time Sync Mechanisms +6.8. Attacks on Time Synchronization Mechanisms - Attacks on time sync mechanisms are addressed in [RFC7384]. + Attacks on time synchronization mechanisms are addressed in + [RFC7384]. 6.9. Attacks on Path Choice This is covered in part in Section 6.3, Segmentation Attacks, and as with Replication and Elimination (Section 6.4), this is relevant for DataPlane messages. 7. Security Threat Mitigation This section describes a set of measures that can be taken to mitigate the attacks described in Section 5, Security Threats. 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. + Some of the technology-specific security considerations and + mitigation approaches are further discussed in the DETNET data plane + solution documents, such as [RFC8939], [RFC8938], + [I-D.ietf-detnet-mpls-over-udp-ip], and + [I-D.ietf-detnet-ip-over-mpls]. + 7.1. Path Redundancy Description A DetNet flow that can be forwarded simultaneously over multiple paths. Path replication and elimination [RFC8655] provides resiliency to dropped or delayed packets. This redundancy improves the robustness to failures and to on-path attacks. Note: At the time of this writing, PREOF is not defined for the IP data plane. @@ -1032,66 +1063,102 @@ source of an on-path attacker. A delay modulation attack could result in extensively exercising parts of the code that wouldn't normally be extensively exercised and thus might expose flaws in the system that might otherwise not be exposed. 7.2. Integrity Protection Description - An integrity protection mechanism, such as a hash-based Message - Authentication Code (MAC) can be used to mitigate modification - attacks on IP packets. Such MAC usage needs to be part of a - security association that is established and managed by a security - association protocol (such as IKEv2 for IPsec security - associations). Integrity protection in the controller plane is - discussed in Section 7.6. - Packet Sequence Number Integrity Considerations + Integrity Protection in the scope of DetNet is the ability to + detect if a header has been modified (either maliciously or by + chance) and propagate a warning to a responsible monitoring agent. + An integrity protection mechanism is designed to counteract header + modification attacks where a Message Authentication Code (MAC) is + the most common. The MAC can be distributed either in-line + (included in the same packet) or via a side channel. Due to the + nature of DetNet traffic. Note: a sideband approach may yield too + high overhead and complexity and should only be used as a very + last resort if in-line approaches are not viable. + + There are different levels of security available for integrity + protection, ranging from the basic ability to detect if a header + has been corrupted in transit (no malicious attack) to stopping a + skilled and determined attacker capable of both subtly modifying + fields in the headers as well as updating an unsigned MAC. Common + for all are the 2 steps that need to be performed in both ends. + The first is computing the checksum or MAC. The corresponding + verification step must perform the same steps before comparing the + provided with the computed value. Only then can the receiver be + reasonably sure that the header is authentic. + The most basic protection mechanism consists of computing a simple + checksum of the header fields and provide it to the next entity in + the packets path for verification. Using a MAC combined with a + secret key provides the best protection against modification and + replication attacks (see Section 5.2.2 and Section 5.2.4). This + MAC usage needs to be part of a security association that is + established and managed by a security association protocol (such + as IKEv2 for IPsec security associations). Integrity protection + in the controller plane is discussed in Section 7.6. The secret + key, regardless of MAC used, must be protected from falling into + the hands of unauthorized users. + + DetNet system- and/or component- level designers need to be aware + of these distinctions and enforce appropriate integrity protection + mechanisms as needed based on a threat analysis. Note that adding + integrity protection mechanisms may introduce latency, thus many + of the same considerations in Section 7.5.1 also apply here. + + Packet Sequence Number Integrity Considerations The use of PREOF in a DetNet implementation implies the use of a sequence number for each packet. There is a trust relationship - between the device that adds the sequence number and the device - that removes the sequence number. The sequence number may be end- - to-end source to destination, or may be added/deleted by network - edge devices. The adder and remover(s) have the trust - relationship because they are the ones that ensure that the - sequence numbers are not modifiable. Between those two points, - there may or may not be replication and elimination functions. - The elimination functions must be able to see the sequence - numbers. Therefore any encryption that is done between adders and - removers must not obscure the sequence number. If the sequence - removers and the eliminators are in the same physical device, it - may be possible to obscure the sequence number, however that is a - layer violation, and is not recommended practice. Note: At the - time of this writing, PREOF is not defined for the IP data plane. + between the component that adds the sequence number and the + component that removes the sequence number. The sequence number + may be end-to-end source to destination, or may be added/deleted + by network edge components. The adder and remover(s) have the + trust relationship because they are the ones that ensure that the + sequence numbers are not modifiable. Thus, sequence numbers can + be protected by using encryption, or by a MAC without using + encryption. Between the adder and remover there may or may not be + replication and elimination functions. The elimination functions + must be able to see the sequence numbers. Therefore, if + encryption is done between adders and removers it must not obscure + the sequence number. If the sequence removers and the eliminators + are in the same physical component, it may be possible to obscure + the sequence number, however that is a layer violation, and is not + recommended practice. Note: At the time of this writing, PREOF is + not defined for the IP data plane. Related attacks Integrity protection mitigates attacks related to modification and tampering, including the attacks described in Section 5.2.2 and Section 5.2.4. 7.3. DetNet Node Authentication Description Authentication verifies the identity of DetNet nodes (including - DetNet Controller Plane nodes), enabling mitigation of spoofing - attacks. Note that while integrity protection (Section 7.2) + DetNet Controller Plane nodes), and this enables mitigation of + spoofing attacks. While integrity protection ( Section 7.2) prevents intermediate nodes from modifying information, - authentication (such as provided by IPsec or MACsec) can provide - traffic origin verification, i.e. to verify that each packet in a - DetNet flow is from a trusted source. + authentication (such as IPsec [RFC4301] or MACsec + [IEEE802.1AE-2018]) can provide traffic origin verification, i.e. + to verify that each packet in a DetNet flow is from a known + source. Related attacks + DetNet node authentication is used to mitigate attacks related to spoofing, including the attacks of Section 5.2.2, and Section 5.2.4. 7.4. Dummy Traffic Insertion Description With some queueing methods such as [IEEE802.1Qch-2017] it is possible to introduce dummy traffic in order to regularize the @@ -1094,46 +1161,59 @@ Description With some queueing methods such as [IEEE802.1Qch-2017] it is possible to introduce dummy traffic in order to regularize the timing of packet transmission. Related attacks Removing distinctive temporal properties of individual packets or flows can be used to mitigate against reconnaissance attacks - Section 5.2.6. + Section 5.2.6. For example, dummy traffic can be used to + synthetically maintain constant traffic rate even when no user + data is transmitted, thus making it difficult to collect + information about the times at which users are active, and the + times at which DETNET flows are added or removed. 7.5. Encryption Description - DetNet flows can in principle be forwarded in encrypted form at - the DetNet layer, however, regarding encryption of IP headers see - Section 9. + Reconnaissance attacks (Section 5.2.6) can be mitigated by using + encryption. Specific encryption protocols will depend on the + lower layers that DetNet is forwarded over. For example, IP flows + may be forwarded over IPsec [RFC4301], and Ethernet flows may be + secured using MACsec [IEEE802.1AE-2018]. DetNet nodes do not have any need to inspect the payload of any DetNet packets, making them data-agnostic. This means that end- - to- end encryption at the application layer is an acceptable way - to protect user data. + to-end encryption at the application layer is an acceptable way to + protect user data. - Encryption can also be applied at the subnet layer, for example - for Ethernet using MACSec, as noted in Section 9. + Note that reconnaissance is a threat that is not specific to + DetNet flows, and therefore reconnaissance mitigation will + typically be analyzed and addressed by a network operator + regardless of whether DetNet flows are deployed. Thus, encryption + requirements will typically not be defined in DetNet technology- + specific specifications, but considerations of using DetNet in + encrypted environments will be discussed in these specifications. + For example, Section 5.1.2.3. of [RFC8939] discusses flow + identification of DetNet flows running over IPsec. Related attacks - Encryption can be used to mitigate recon attacks (Section 5.2.6). - However, for a DetNet network to give differentiated quality of - service on a flow-by-flow basis, the network must be able to - identify the flows individually. This implies that in a recon - attack the attacker may also be able to track individual flows to - learn more about the system. + As noted above, encryption can be used to mitigate reconnaissance + attacks ( Section 5.2.6). However, for a DetNet to provide + differentiated quality of service on a flow-by-flow basis, the + network must be able to identify the flows individually. This + implies that in a reconnaissance attack the attacker may also be + able to track individual flows to learn more about the system. 7.5.1. Encryption Considerations for DetNet Any compute time which is required for encryption and decryption processing ('crypto') must be included in the flow latency calculations. Thus, crypto algorithms used in a DetNet must have bounded worst-case execution times, and these values must be used in the latency calculations. Some crypto algorithms are symmetric in encode/decode time (such as @@ -1143,26 +1223,30 @@ timing implications of crypto for DetNet; it is assumed that integrity considerations are covered elsewhere in the literature. Asymmetrical crypto is typically not used in networks on a packet-by- packet basis due to its computational cost. For example, if only endpoint checks or checks at a small number of intermediate points are required, asymmetric crypto can be used to authenticate distribution or exchange of a secret symmetric crypto key; a successful check based on that key will provide traffic origin verification, as long as the key is kept secret by the participants. - TLS and IKE (for IPsec) are examples of this for endpoint checks. + TLS (v1.3 [RFC8446], in particular section 4.1 "Key exchange") and + IKEv2 [RFC6071]) are examples of this for endpoint checks. - However, if secret symmetrical keys are used for this purpose the key + However, if secret symmetric keys are used for this purpose the key must be given to all relays, which increases the probability of a - secret key being leaked. Also, if any relay is compromised or - misbehaving it may inject traffic into the flow. + secret key being leaked. Also, if any relay is compromised or faulty + then it may inject traffic into the flow. Group key management + protocols can be used to automate management of such symmetric keys; + for an example in the context of IPsec, see + [I-D.ietf-ipsecme-g-ikev2]. Alternatively, asymmetric crypto can provide traffic origin verification at every intermediate node. For example, a DetNet flow can be associated with an (asymmetric) keypair, such that the private key is available to the source of the flow and the public key is distributed with the flow information, allowing verification at every node for every packet. However, this is more computationally expensive. In either case, origin verification also requires replay detection as @@ -1171,68 +1255,141 @@ forwarding resources. If crypto keys are to be regenerated over the duration of the flow then the time required to accomplish this must be accounted for in the latency calculations. 7.6. Control and Signaling Message Protection Description - Control and sigaling messages can be protected using - authentication and integrity protection mechanisms. + Control and signaling messages can be protected through the use of + any or all of encryption, authentication, and integrity protection + mechanisms. Related attacks These mechanisms can be used to mitigate various attacks on the controller plane, as described in Section 5.2.5, Section 5.2.7 and Section 5.2.5.1. 7.7. Dynamic Performance Analytics Description - The expectation is that the network will have a way to monitor to - detect if timing guarantees are not being met, and a way to alert - the controller plane in that event. 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 - YANG. + Incorporating Dynamic Performance Analytics ("DPA") implies that + the DetNet design includes a performance monitoring system to + validate that timing guarantees are being met and to detect timing + violations or other anomalies that may be the symptom of a + security attack or system malfunction. If this monitoring system + detects unexpected behavior, it must then cause action to be + initiated to address the situation in an appropriate and timely + manner, either at the data plane or controller plane, or both in + concert. - If the monitoring or reporting mechanism itself is attacked or - subverted, this can result in malfunction of the network. The - design of the monitoring system needs to take this into account - based on the specifics of the monitoring or reporting system being - considered. + The overall DPA system can thus be decomposed into the "detection" + and "notification" functions. Although the time-specific DPA + performance indicators and their implementation will likely be + specific to a given DetNet, and as such are nascent technology at + the time of this writing, DPA is commonly used in existing + networks so we can make some observations on how such a system + might be implemented for a DetNet, given that it would need to be + adapted to address the time-specific performance indicators. + + Detection Mechanisms + + Measurement of timing performance can be done via "passive" or + "active" monitoring, as discussed below. + + Examples of passive monitoring strategies include + + * Monitoring of queue and buffer levels, e.g. via Active Queue + Management (e.g. [RFC7567] + + * Monitoring of per-flow counters + + * Measurement of link statistics such as traffic volume, + bandwidth, and QoS + + * Detection of dropped packets + + * Use of commercially available Network Monitoring tools + + Examples of active monitoring include + + * In-band timing measurements (such as packet arrival times) e.g. + by timestamping and packet inspection + + * Use of OAM. For DetNet-specific OAM considerations see + [I-D.ietf-detnet-ip-oam], [I-D.ietf-detnet-mpls-oam]. Note: At + the time of this writing, specifics of DPA have not been + developed for the DetNet OAM, but could be a subject for future + investigation + + * For OAM for Ethernet specifically, see also Connectivity Fault + Management (CFM, [IEEE802.1Q]) which defines protocols and + practices for OAM for paths through 802.1 bridges and LANs + + * Out-of-band detection. following the data path or parts of a + data path, for example Bidirectional Forwarding Detection (BFD, + e.g. [RFC5880]) + + Note that for some measurements (e.g. packet delay) it may be + necessary to make and reconcile measurements from more than one + physical location (e.g. a source and destination), possibly in + both directions, in order to arrive at a given performance + indicator value. + + Notification Mechanisms + + Making DPA measurement results available at the right place(s) and + time(s) to effect timely response can be challenging. Two + notification mechanisms that are in general use are Netconf/YANG + Notifications (e.g. [RFC5880]) and the proprietary local + telemetry interfaces provided with components from some vendors. + + At the time of this writing YANG Notifications are not addressed + by the DetNet YANG drafts, however this may be a topic for future + work. It is possible that some of the passive mechanisms could be + covered by notifications from non-DetNet-specific YANG modules; + for example if there is OAM or other performance monitoring that + can monitor delay bounds then that could have its own associated + YANG model which could be relevant to DetNet, for example some + "threshold" values for timing measurement notifications. + + At the time of this writing there is an IETF Working Group for + network/performance monitoring (IP Performance Measurement, ippm). + See also previous work by the completed Remote Network Monitoring + Working Group (rmonmib). See also [RFC6632], An Overview of the + IETF Network Management Standards. + + Vendor-specific local telemetry may be available on some + commercially available systems, whereby the system can be + programmed (via a proprietary dedicated port and API) to monitor + and report on specific conditions, based on both passive and + active measurements. Related attacks Performance analytics can be used to mitigate various attacks, including the ones described in Section 5.2.1 (Delay Attack), Section 5.2.3 (Resource Segmentation Attack), and Section 5.2.7 - (Time Sync Attack). + (Time Synchronization Attack). For example, in the case of data plane delay attacks, one possible mitigation is to timestamp the data at the source, and timestamp it again at the destination, and if the resulting latency exceeds - the promised bound, discard that data and warn the operator (and/ - or enter a fail-safe mode). Note that DetNet specifies packet - sequence numbering, however it does not specify use of packet - timestamps, although they may be used by the underlying transport - (for example TSN) to provide the service. + the promised bound, take appropriate action. Note that DetNet + specifies packet sequence numbering, however it does not specify + use of packet timestamps, although they may be used by the + underlying transport (for example TSN, [IEEE802.1BA]) to provide + the service. 7.8. Mitigation Summary The following table maps the attacks of Section 5, Security Threats, to the impacts of Section 6, Security Threat Impacts, 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. +----------------------+---------------------+---------------------+ @@ -1276,23 +1433,23 @@ | |-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 | - |Mechanisms | delay |-Control message | - | |-Increased resource | protection | + |Attacks on Time |-Non-deterministic |-Path redundancy | + |Synchronization | delay |-Control message | + |Mechanisms |-Increased resource | protection | | | consumption |-Performance | | |-Data disruption | analytics | +----------------------+---------------------+---------------------+ Figure 3: Mapping Attacks to Impact and Mitigations 8. 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 @@ -1333,104 +1490,118 @@ A DetNet network can be controlled by a centralized network configuration and control system. 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. All attacks named in this document which are relevant to controller plane packets (and the controller itself) are relevant to this theme, including Path Manipulation, Path Choice, Control Packet Modification - or Injection, Reconaissance and Attacks on Time Sync Mechanisms. + or Injection, Reconaissance and Attacks on Time Synchronization + Mechanisms. 8.1.3. 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). + at least consider input at runtime from components that were not part + of the initial configuration of the network. Even a "perfect" (or + "hitless") replacement of a component 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 component). 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 + Inter-segment (which could introduce packets from a "new" component, + 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). + of a new component). + + To mitigate this situation, deployments should provide a method for + dynamic and secure registration of new components, and (possibly + manual) deregistration of retired components. This would avoid the + situation in which the network must accommodate potentially insecure + packet flows from unknown components. 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 (see - [RFC7384]). + of a clock component, then presence (or apparent presence) and thus + consideration of packets from a new such component could affect the + network, or the time synchronization of the network, for example by + initiating a new Best Master Clock selection process. These types of + attacks should therefore be considered when designing hot swap type + functionality (see [RFC7384]). 8.1.4. Data Flow Information Models - Data Flow YANG models specific to DetNet networks are specified by - DetNet, and thus are 'new' and thus potentially present a new attack - surface. + DetNet specifies new YANG models which may present new attack + surfaces. Per IETF guidelines, security considerations for any YANG + model are expected to be part of the YANG model specification, as + described in [IETF_YANG_SEC]. 8.1.5. 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 IP, MPLS Pseudowire, and Ethernet. + LAN) and Layer 3 (routed) networks (e.g. IP) via the use of well- + known protocols such as IP, MPLS Pseudowire, and Ethernet. Various + DetNet drafts address many specific aspects of Layer 2 and Layer 3 + integration within a DetNet, and these are not individually + referenced here; security considerations for those aspects are + covered within those drafts or within the related subsections of the + present document. - There are no specific entries in the mapping table Figure 4, however - that does not imply that there could be no relevant attacks related - to L2-L3 integration. + Please note that although there are no entries in the L2 and L3 + Integration line of the Mapping Between Themes and Attacks table + Figure 4, this does not imply that there could be no relevant attacks + related to L2-L3 integration. 8.1.6. End-to-End Delivery Packets sent over DetNet are not to be dropped by the network due to congestion. (Packets may however intentionally 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 controller plane attack, e.g. Path Manipulation or Signaling Packet Modification. It may be that such attacks are limited to Internal on-path 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. + Packet Injection. A Time Synchronization 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. 8.1.7. Replacement for Proprietary Fieldbuses and Ethernet-based Networks - There are many proprietary "field buses" used in today's industrial - and other industries, as well as proprietary non-interoperable - deterministic Ethernet-based networks. DetNet is intended to provide - an open-standards-based alternative to such buses/networks. In cases - where a DetNet intersects with such fieldbuses/networks or their - protocols, such as by protocol emulation or access via a gateway, new - attack surfaces can be opened. + There are many proprietary "field buses" used in Industrial and other + industries, as well as proprietary non-interoperable deterministic + Ethernet-based networks. DetNet is intended to provide an open- + standards-based alternative to such buses/networks. In cases where a + DetNet intersects with such fieldbuses/networks 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 Controller 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. 8.1.8. Deterministic vs Best-Effort Traffic Most of the themes described in this document address OT (reserved) @@ -1448,24 +1619,33 @@ open Internet, however this aspect of DetNet security should not be underestimated. 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 DetNet flow 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 + However the handling of IT traffic by the DetNet 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. + The network design as a whole also needs to consider possible + application-level dependencies of "OT"-type applications on services + provided by the "IT part" of the network; for example, does the OT + application depend on IT network services such as DNS or OAM? If + such dependencies exist, how are malicious packet flows handled? + Such considerations are typically outside the scope of DetNet proper, + but nonetheless need to be addressed in the overall DetNet network + design for a given use case. + 8.1.9. 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 DetNet flow could cause that flow to occupy more bandwidth than it was allocated, resulting in interference with other DetNet flows. @@ -1479,83 +1659,88 @@ associated bandwidth is not used at any point in time, that bandwidth is made available on the network for best-effort traffic. However, note that security considerations for best-effort traffic on a DetNet network is out of scope of the present document, provided that such an attack does not affect performance for DetNet OT traffic. 8.1.11. 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 - device manufactured. + promoting component diversity and potentially higher numbers of each + component manufactured. + + The security mechanisms and protocols that are discussed in this + document also require interoperability. It is expected that DETNET + network specifications that define security measures and protocols + will be defined in a way that allows interoperability. Given that the DetNet specifications are unambiguously written and that the implementations are accurate, then this should not in and of itself cause a security concern; however, in the real world, it could be. The network operator can mitigate this through sufficient interoperability testing. 8.1.12. 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. + promoting higher numbers of each component manufactured, promoting + cost reduction and cost competition among vendors. This envisioned breadth of DetNet-enabled products is in general a positive factor, however implementation flaws in any individual component can present an attack surface. In addition, implementation differences between components from different vendors can result in attack surfaces (resulting from their interaction) which may not exist in any individual component. Network operators can mitigate such concerns through sufficient product and interoperability testing. -8.1.13. Insufficiently Secure Devices +8.1.13. Insufficiently Secure Components 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. However this raises the possibility that a + promoting component diversity and potentially higher numbers of each + component manufactured. However this raises the possibility that a vendor might repurpose for DetNet applications a hardware or software component that was originally designed for operation in an isolated OT network, and thus may not have been designed to be sufficiently - secure, or secure at all. Deployment of such a device on a DetNet + secure, or secure at all. Deployment of such a component on a DetNet network that is intended to be highly secure may present an attack surface. The DetNet network operator may need to take specific actions to - protect such devices, such as implementing a dedicated security layer - around the device. + protect such components, such as implementing a dedicated security + layer around the component. 8.1.14. 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. Attacks sourced from IT traffic might be more likely in large networks, since more people might have access to the network, presenting a larger attack surface. Similarly Path Manipulation, - Path Choice and Time Sync attacks seem more likely relevant to large - networks. + Path Choice and Time Synchronization attacks seem more likely + relevant to large networks. 8.1.15. 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) could take @@ -1578,36 +1763,36 @@ latency for a given path or DetNet flow, 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). Controller 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. + service and/or the reply from the network. Reconnaissance could be used to characterize flows and perhaps target specific flows for attack via the controller plane as noted in Section 6.7. 8.1.17. 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). + Time Synchronization attacks can corrupt the time reference of the + system, resulting in missed latency deadlines (with respect to the + "correct" time reference). 8.1.18. 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 @@ -1627,100 +1812,106 @@ the jitter specification. 8.1.20. 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 materially differ between paths. - Time Sync attacks can corrupt the system's time reference, resulting - in path delays that may be perceived to be different (with respect to - the "correct" time reference) even if they are not materially - different. + Time Synchronization attacks can corrupt the time reference of the + system, resulting in path delays that may be perceived to be + different (with respect to the "correct" time reference) even if they + are not materially different. 8.1.21. 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 the mapping table Figure 4 we have marked every 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. + In practice, network designers can adopt a risk-based approach, in + which only those attacks are mitigated whose potential cost is higher + than the cost of mitigation. + 8.1.22. 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. Controller plane attacks can also interfere with the configuration of redundant paths. 8.1.23. Security Measures - A DetNet network must be made secure against devices failures, - attackers, misbehaving component, and so on. If the security - mechanisms protecting the DetNet are attacked or subverted, this can - result in malfunction of the network. The design of the security - system itself needs to take this into account based on the specifics - of the security system being considered. The general topic of - protection of security mechanisms is not unique to DetNet; it is - identical to the case of securing any security mechanism for any - network. The text of this document addresses these concerns to the - extent that they are relevant to DetNet. + A DetNet network must be made sufficiently secure against problematic + component or traffic behavior, whether malicious or incidental, and + whether affecting a single component or multiple components. If any + of the security mechanisms which protect the DetNet from such + problems are attacked or subverted, this can result in malfunction of + the network. Thus the design of the security system itself needs to + be robust against attacks. + + The general topic of protection of security mechanisms is not unique + to DetNet; it is identical to the case of securing any security + mechanism for any network. This document addresses these concerns + only to the extent that they are unique to DetNet. 8.2. Summary of Attack Types per Use Case Common Theme The List of Attacks table Figure 4 lists the attacks of Section 5, Security Threats, assigning a number to each type of attack. That number is then used as a short form identifier for the attack in Figure 5, Mapping Between Themes and Attacks. - +----+----------------------------------------+ + +----+-------------------------------------------+ | | Attack | - +----+----------------------------------------+ + +----+-------------------------------------------+ | 1 |Delay Attack | - +----+----------------------------------------+ + +----+-------------------------------------------+ | 2 |DetNet Flow Modification or Spoofing | - +----+----------------------------------------+ + +----+-------------------------------------------+ | 3 |Inter-Segment Attack | - +----+----------------------------------------+ + +----+-------------------------------------------+ | 4 |Replication: Increased attack surface | - +----+----------------------------------------+ + +----+-------------------------------------------+ | 5 |Replication-related Header Manipulation | - +----+----------------------------------------+ + +----+-------------------------------------------+ | 6 |Path Manipulation | - +----+----------------------------------------+ + +----+-------------------------------------------+ | 7 |Path Choice: Increased Attack Surface | - +----+----------------------------------------+ + +----+-------------------------------------------+ | 8 |Control or Signaling Packet Modification| - +----+----------------------------------------+ + +----+-------------------------------------------+ | 9 |Control or Signaling Packet Injection | - +----+----------------------------------------+ + +----+-------------------------------------------+ | 10 |Reconnaissance | - +----+----------------------------------------+ - | 11 |Attacks on Time Sync Mechanisms | - +--+----------------------------------------+ + +----+-------------------------------------------+ + | 11 |Attacks on Time Synchronization Mechanisms | + +----+-------------------------------------------+ Figure 4: List of Attacks The Mapping Between Themes and Attacks table Figure 5 maps the use case themes of [RFC8578] (as also enumerated in this document) to the attacks of Figure 4. Each row specifies a theme, and the attacks relevant to this theme are marked with a '+'. The row items which have no threats associated with them are included in the table for completeness of the list of Use Case Common Themes, and do not have DetNet-specific threats associated with them. @@ -1753,21 +1944,21 @@ +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ |Deterministic Flows | | +| +| | +| +| | +| | | | +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ |Unused Reserved Bandwidth | | +| +| | | | | +| +| | | +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ |Interoperability | | | | | | | | | | | | +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ |Cost Reductions | | | | | | | | | | | | +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ |Insufficiently Secure | | | | | | | | | | | | - |Devices | | | | | | | | | | | | + |Components | | | | | | | | | | | | +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ |DetNet Network Size | +| | | | | +| +| | | | +| +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ |Multiple Hops | +| +| | | | +| +| | | | +| +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ |Level of Service | | | | | | | | +| +| +| | +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ |Bounded Latency | +| | | | | | | | | | +| +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ |Low Latency | +| | | | | | | +| +| +| +| @@ -1820,40 +2011,43 @@ specifically related to the IP- and MPLS-specific aspects of DetNet implementations. The primary security considerations for the data plane specifically are to maintain the integrity of the data and the delivery of the associated DetNet service traversing the DetNet network. The primary relevant differences between IP and MPLS implementations are in flow identification and OAM methodologies. - As noted in [RFC8655], DetNet operates at the IP layer - ([I-D.ietf-detnet-ip]) and delivers service over sub-layer - technologies such as MPLS ([I-D.ietf-detnet-mpls]) and IEEE 802.1 - Time-Sensitive Networking (TSN) ([I-D.ietf-detnet-ip-over-tsn]). - Application flows can be protected through whatever means are - provided by the layer and sub-layer technologies. For example, - technology-specific encryption may be used, such as that provided by - IPSec [RFC4301] for IP flows and/or by an underlying sub-net using - MACSec [IEEE802.1AE-2018] for IP over Ethernet (Layer-2) flows. + As noted in [RFC8655], DetNet operates at the IP layer ( [RFC8939]) + and delivers service over sub-layer technologies such as MPLS + ([RFC8938]) and IEEE 802.1 Time-Sensitive Networking (TSN) + ([I-D.ietf-detnet-ip-over-tsn]). Application flows can be protected + through whatever means are provided by the layer and sub-layer + technologies. For example, technology-specific encryption may be + used, for example for IP flows, IPSec [RFC4301]. For IP over + Ethernet (Layer 2) flows using an underlying sub-net, MACSec + [IEEE802.1AE-2018] may be appropriate. For some use cases packet + integrity protection without encryption may be sufficient. - However, if the DetNet nodes cannot decrypt IPsec traffic, IPSec may - not be a valid option; this is because the DetNet IP Data Plane - identifies flows via a 6-tuple that consists of two IP addresses, the - transport protocol ID, two transport protocol port numbers and the - DSCP in the IP header. When IPsec is used, the transport header is - encrypted and the next protocol ID is an IPsec protocol, usually ESP, - and not a transport protocol (e.g., neither TCP nor UDP, etc.) - leaving only three components of the 6-tuple, which are the two IP - addresses and the DSCP, which are in general not sufficient to - identify a DetNet flow. + However, if the DetNet nodes cannot decrypt IPsec traffic, then + DetNet flow identification for encrypted IP traffic flows must be + performed in a different way than it would be for unencrypted IP + DetNet flows. The DetNet IP Data Plane identifies unencrypted flows + via a 6-tuple that consists of two IP addresses, the transport + protocol ID, two transport protocol port numbers and the DSCP in the + IP header. When IPsec is used, the transport header is encrypted and + the next protocol ID is an IPsec protocol, usually ESP, and not a + transport protocol, leaving only three components of the 6-tuple, + which are the two IP addresses and the DSCP. Identification of + DetNet flows over IPsec is further discussed in Section 5.1.2.3. of + [RFC8939]. Sections below discuss threats specific to IP and MPLS in more detail. 9.1. IP The IP protocol has a long history of security considerations and architectural protection mechanisms. From a data plane perspective DetNet does not add or modify any IP header information, so the carriage of DetNet traffic over an IP data plane does not introduce @@ -1876,22 +2070,22 @@ Another way to look at DetNet IP security is to consider it in the light of VPN security; as an industry we have a lot of experience with VPNs running through networks with other VPNs, it is well known how to secure the network for that. However for a DetNet we have the additional subtlety that any possible interaction of one packet with another can have a potentially deleterious effect on the time properties of the flows. So the network must provide sufficient isolation between flows, for example by protecting the forwarding bandwidth and related resources so that they are available to detnet - traffic, by whatever means are appropriate for that network's data - plane, for example through the use of queueing mechanisms. + traffic, by whatever means are appropriate for the data plane of that + network, for example through the use of queueing mechanisms. In a VPN, bandwidth is generally guaranteed over a period of time, whereas in DetNet it is not aggregated over time. This implies that any VPN-type protection mechanism must also maintain the DetNet timing constraints. 9.2. MPLS An MPLS network carrying DetNet traffic is expected to be a "well- managed" network. Given that this is the case, it is difficult for @@ -1910,21 +2104,21 @@ operation of DetNet over some types of MPLS network. [RFC5921] introduces to MPLS new Operations, Administration, and Maintenance (OAM) capabilities, a transport-oriented path protection mechanism, and strong emphasis on static provisioning supported by network management systems. The operation of DetNet over an MPLS network is modeled on the operation of multi-segment pseudowires (MS-PW). Thus for guidance on securing the DetNet elements of DetNet over MPLS the reader is - referred to the MS-PW security mechanisms as defined in [RFC4447], + referred to the MS-PW security mechanisms as defined in [RFC8077], [RFC3931], [RFC3985], [RFC6073], and [RFC6478]. Having attended to the conventional aspects of network security it is necessary to attend to the dynamic aspects. The closest experience that the IETF has with securing protocols that are sensitive to manipulation of delay are the two way time transfer protocols (TWTT), which are NTP [RFC5905] and Precision Time Protocol [IEEE1588]. The security requirements for these are described in [RFC7384]. One particular problem that has been observed in operational tests of @@ -1932,21 +2126,21 @@ synchronized flows to beat and cause a sudden phase hit to one of the flows. This can be mitigated by the careful use of a scheduling system in the underlying packet transport. Further consideration of protection against dynamic attacks is work in progress. New work on MPLS security may also be applicable, for example [I-D.ietf-mpls-opportunistic-encrypt]. 10. IANA Considerations - This memo includes no requests from IANA. + This document includes no requests from IANA. 11. Security Considerations The security considerations of DetNet networks are presented throughout this document. 12. Privacy Considerations Privacy in the context of DetNet is maintained by the base technologies specific to the DetNet and user traffic. For example @@ -1954,86 +2148,111 @@ transport protocol-provided methods e.g. TLS and DTLS. MPLS typically uses L2/L3 VPNs combined with the previously mentioned privacy methods. 13. Contributors The Editor would like to recognize the contributions of the following individuals to this draft. Subir Das (Applied Communication Sciences) - 150 Mount Airy Road, Basking Ridge - New Jersey, 07920, USA + 150 Mount Airy Road, Basking Ridge, New Jersey, 07920, USA email sdas@appcomsci.com John Dowdell (Airbus Defence and Space) Celtic Springs, Newport, NP10 8FZ, United Kingdom email john.dowdell.ietf@gmail.com Henrik Austad (SINTEF Digital) Klaebuveien 153, Trondheim, 7037, Norway email henrik@austad.us - Norman Finn + Norman Finn (Huawei) + 3101 Rio Way, Spring Valley, California 91977, USA email nfinn@nfinnconsulting.com - Stewart Bryant - Futurewei Technologies + Stewart Bryant (Futurewei Technologies) + email: stewart.bryant@gmail.com - David Black - Dell EMC + David Black (Dell EMC) 176 South Street, Hopkinton, MA 01748, USA email: david.black@dell.com - Carsten Bormann + Carsten Bormann (Universitat Bremen TZI) + Postfach 330440, D-28359 Bremen, Germany + email: cabo@tzi.org 14. References 14.1. Normative References - [I-D.ietf-detnet-ip] - Varga, B., Farkas, J., Berger, L., Fedyk, D., and S. - Bryant, "DetNet Data Plane: IP", draft-ietf-detnet-ip-07 - (work in progress), July 2020. - - [I-D.ietf-detnet-mpls] - Varga, B., Farkas, J., Berger, L., Malis, A., Bryant, S., - and J. Korhonen, "DetNet Data Plane: MPLS", draft-ietf- - detnet-mpls-12 (work in progress), September 2020. - [RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas, "Deterministic Networking Architecture", RFC 8655, DOI 10.17487/RFC8655, October 2019, . + [RFC8938] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S. + Bryant, "Deterministic Networking (DetNet) Data Plane + Framework", RFC 8938, DOI 10.17487/RFC8938, November 2020, + . + + [RFC8939] Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S. + Bryant, "Deterministic Networking (DetNet) Data Plane: + IP", RFC 8939, DOI 10.17487/RFC8939, November 2020, + . + 14.2. Informative References [ARINC664P7] ARINC, "ARINC 664 Aircraft Data Network, Part 7, Avionics Full-Duplex Switched Ethernet Network", 2009. - [I-D.ietf-detnet-data-plane-framework] - Varga, B., Farkas, J., Berger, L., Malis, A., and S. - Bryant, "DetNet Data Plane Framework", draft-ietf-detnet- - data-plane-framework-06 (work in progress), May 2020. - [I-D.ietf-detnet-flow-information-model] Varga, B., Farkas, J., Cummings, R., Jiang, Y., and D. Fedyk, "DetNet Flow Information Model", draft-ietf-detnet- - flow-information-model-10 (work in progress), May 2020. + flow-information-model-12 (work in progress), December + 2020. + + [I-D.ietf-detnet-ip-oam] + Mirsky, G., Chen, M., and D. Black, "Operations, + Administration and Maintenance (OAM) for Deterministic + Networks (DetNet) with IP Data Plane", draft-ietf-detnet- + ip-oam-00 (work in progress), September 2020. + + [I-D.ietf-detnet-ip-over-mpls] + Varga, B., Berger, L., Fedyk, D., Bryant, S., and J. + Korhonen, "DetNet Data Plane: IP over MPLS", draft-ietf- + detnet-ip-over-mpls-09 (work in progress), October 2020. [I-D.ietf-detnet-ip-over-tsn] Varga, B., Farkas, J., Malis, A., and S. Bryant, "DetNet Data Plane: IP over IEEE 802.1 Time Sensitive Networking - (TSN)", draft-ietf-detnet-ip-over-tsn-03 (work in - progress), June 2020. + (TSN)", draft-ietf-detnet-ip-over-tsn-04 (work in + progress), November 2020. + + [I-D.ietf-detnet-mpls-oam] + Mirsky, G. and M. Chen, "Operations, Administration and + Maintenance (OAM) for Deterministic Networks (DetNet) with + MPLS Data Plane", draft-ietf-detnet-mpls-oam-01 (work in + progress), July 2020. + + [I-D.ietf-detnet-mpls-over-udp-ip] + Varga, B., Farkas, J., Berger, L., Malis, A., and S. + Bryant, "DetNet Data Plane: MPLS over UDP/IP", draft-ietf- + detnet-mpls-over-udp-ip-07 (work in progress), October + 2020. + + [I-D.ietf-ipsecme-g-ikev2] + Smyslov, V. and B. Weis, "Group Key Management using + IKEv2", draft-ietf-ipsecme-g-ikev2-01 (work in progress), + July 2020. [I-D.ietf-mpls-opportunistic-encrypt] Farrel, A. and S. Farrell, "Opportunistic Security in MPLS Networks", draft-ietf-mpls-opportunistic-encrypt-03 (work in progress), March 2017. [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. @@ -2041,32 +2260,49 @@ [IEEE1588] IEEE, "IEEE 1588 Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems Version 2", 2008. [IEEE802.1AE-2018] IEEE Standards Association, "IEEE Std 802.1AE-2018 MAC Security (MACsec)", 2018, . + [IEEE802.1BA] + IEEE Standards Association, "IEEE Standard for Local and + Metropolitan Area Networks -- Audio Video Bridging (AVB) + Systems", 2011, + . + + [IEEE802.1Q] + IEEE Standards Association, "IEEE Standard for Local and + metropolitan area networks--Bridges and Bridged Networks - + Annex J - Connectivity Fault Management", 2014, + . + [IEEE802.1Qbv-2015] IEEE Standards Association, "IEEE Standard for Local and metropolitan area networks -- Bridges and Bridged Networks - Amendment 25: Enhancements for Scheduled Traffic", 2015, . [IEEE802.1Qch-2017] IEEE Standards Association, "IEEE Standard for Local and metropolitan area networks--Bridges and Bridged Networks-- Amendment 29: Cyclic Queuing and Forwarding", 2017, . + [IETF_YANG_SEC] + IETF, "YANG Module Security Considerations", 2018, + . + [IT_DEF] Wikipedia, "IT Definition", 2020, . [OT_DEF] Wikipedia, "OT Definition", 2020, . [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI 10.17487/RFC2474, December 1998, @@ -2089,64 +2325,90 @@ [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, DOI 10.17487/RFC3985, March 2005, . [RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, December 2005, . - [RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and - G. Heron, "Pseudowire Setup and Maintenance Using the - Label Distribution Protocol (LDP)", RFC 4447, - DOI 10.17487/RFC4447, April 2006, - . + [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection + (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, + . [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, "Network Time Protocol Version 4: Protocol and Algorithms Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, . [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010, . [RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau, L., and L. Berger, "A Framework for MPLS in Transport Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010, . + [RFC6071] Frankel, S. and S. Krishnan, "IP Security (IPsec) and + Internet Key Exchange (IKE) Document Roadmap", RFC 6071, + DOI 10.17487/RFC6071, February 2011, + . + [RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M., and M. Aissaoui, "Segmented Pseudowire", RFC 6073, DOI 10.17487/RFC6073, January 2011, . + [RFC6274] Gont, F., "Security Assessment of the Internet Protocol + Version 4", RFC 6274, DOI 10.17487/RFC6274, July 2011, + . + [RFC6478] Martini, L., Swallow, G., Heron, G., and M. Bocci, "Pseudowire Status for Static Pseudowires", RFC 6478, DOI 10.17487/RFC6478, May 2012, . + [RFC6632] Ersue, M., Ed. and B. Claise, "An Overview of the IETF + Network Management Standards", RFC 6632, + DOI 10.17487/RFC6632, June 2012, + . + [RFC6941] Fang, L., Ed., Niven-Jenkins, B., Ed., Mansfield, S., Ed., and R. Graveman, Ed., "MPLS Transport Profile (MPLS-TP) Security Framework", RFC 6941, DOI 10.17487/RFC6941, April 2013, . [RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384, October 2014, . + [RFC7567] Baker, F., Ed. and G. Fairhurst, Ed., "IETF + Recommendations Regarding Active Queue Management", + BCP 197, RFC 7567, DOI 10.17487/RFC7567, July 2015, + . + [RFC7835] Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID Separation Protocol (LISP) Threat Analysis", RFC 7835, DOI 10.17487/RFC7835, April 2016, . + [RFC8077] Martini, L., Ed. and G. Heron, Ed., "Pseudowire Setup and + Maintenance Using the Label Distribution Protocol (LDP)", + STD 84, RFC 8077, DOI 10.17487/RFC8077, February 2017, + . + + [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol + Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, + . + [RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases", RFC 8578, DOI 10.17487/RFC8578, May 2019, . [RS_DEF] Wikipedia, "RS Definition", 2020, . Authors' Addresses Ethan Grossman (editor)