COINRG I. Fink Internet-Draft K. Wehrle Intended status: Informational RWTH Aachen University Expires: September 12, 2021 March 11, 2021 Enhancing Security and Privacy with In-Network Computing draft-fink-coin-sec-priv-02 Abstract With the growing interconnection of devices, cyber security and data protection are of increasing importance. This is especially the case regarding cyber-physical systems due to their close entanglement with the physical world. Misbehavior and information leakage can lead to financial and physical damage and endanger human lives and well- being. Thus, hard security and privacy requirements are necessary to be met. Furthermore, a thorough investigation of incidents is essential for ultimate protection. Computing in the Network (COIN) allows the processing of traffic and data directly in the network and at line-rate. Thus, COIN presents a promising solution for efficiently providing security and privacy mechanisms as well as event analysis. This document discusses select mechanisms to demonstrate how COIN concepts can be applied to counter existing shortcomings of cyber security and data privacy. 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 September 12, 2021. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. Fink & Wehrle Expires September 12, 2021 [Page 1] Internet-Draft Enhancing Security and Privacy March 2021 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Protection Mechanisms . . . . . . . . . . . . . . . . . . . . 3 2.1. Encryption and Integrity Checks . . . . . . . . . . . . . 4 2.2. Authorization and Authentication . . . . . . . . . . . . 4 2.3. Behavioral and Enterprise Policies . . . . . . . . . . . 5 2.4. In-Network Vulnerability Patches . . . . . . . . . . . . 6 2.5. Anonymization . . . . . . . . . . . . . . . . . . . . . . 7 3. Intrusion and Anomaly Detection . . . . . . . . . . . . . . . 7 3.1. Intrusion Detection . . . . . . . . . . . . . . . . . . . 7 3.2. Dead Man's Switch . . . . . . . . . . . . . . . . . . . . 8 4. Incident Investigation . . . . . . . . . . . . . . . . . . . 8 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 9 8. Informative References . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction With the ongoing digitalization, previously isolated devices and systems are increasingly connected to the Internet, concerning all aspects of life. In particular, in the context of Cyber-Physical Systems (CPS) and the (Industrial) Internet of Things, machines and infrastructure are equipped with additional sensors and CPUs to allow for automatization and higher processing efficiency. The entanglement of the sensors with the physical world leads to high sensitivity of the transmitted and collected data. Consequently, digitalization expands the attack surface and the possible impacts of cyber attacks, increasing the importance of proper protection mechanisms. Devices in CPS are often resource-constrained and do not offer the possibility to implement elaborate security mechanisms. Furthermore, legacy devices and communication protocols are often still used in industrial networks but were not designed to face the security and Fink & Wehrle Expires September 12, 2021 [Page 2] Internet-Draft Enhancing Security and Privacy March 2021 privacy challenges the new interconnection brings. Thus, communication and access are often unprotected. Upgrading legacy devices with protection mechanisms is an effortful and expensive procedure. A promising approach for retrofitting security is the deployment of suitable mechanisms within the network. To date, this is mainly realized using middle-boxes, leading to overhead and the need for additional hardware. One general and widespread security component is Intrusion Detection Systems (IDS) to detect and, ideally, prevent undesired events in a network. However, IDS are usually implemented in software, again running on middle boxes or edge devices in the same network. Thus, their reaction time is limited as well as their information gain, which is usually addressed by deploying additional IDS components. Last, the after-treatment of incidents in networks is critical to detect exploited vulnerabilities and prevent future attacks. Network forensics serves to retrace and comprehend the origin and course of malicious events. However, to provide high performance, the underlying monitoring of network traffic requires dedicated networking devices, leading to high costs in traditional networks. One common problem is that software solutions often require the deployment of additional hardware and lead to performance overhead, which is especially unfavorable in the context of time-sensitive applications, e.g., in industry. Existing high-performance solutions, e.g., running on traditional networking devices, require dedicated and costly hardware. Computing in the Network (COIN) covers these shortfalls by using programmable networking devices to conduct dynamic and custom processing of network packets at line-rate. Thus, security-related functions and packet inspection can be implemented and applied centrally in the network, e.g., at a programmable switch. This draft explores the opportunities of COIN for improving security and privacy as follows: we first describe feasible mechanisms for preventing attacks and intrusion in the first place. Then, we present which mechanisms we can implement with COIN for detecting intrusion and undesired behavior when it has already taken place. Last, we explore how COIN can improve network forensics for analyzing and following up incidents, preventing future attacks. 2. Protection Mechanisms The common ground for providing security and data privacy is to protect against unauthorized access. That protection is primarily provided by deploying the basic security mechanisms encryption, Fink & Wehrle Expires September 12, 2021 [Page 3] Internet-Draft Enhancing Security and Privacy March 2021 integrity checking, authentication, and authorization. Those are especially often missing in resource-constrained environments. [RFC7744] thoroughly discusses the need for authentication and authorization in resource-restrained environments. [RFC8576] presents security and privacy risks and challenges specific to the IoT. In the following, we describe how COIN can help to retrofit suitable mechanisms. 2.1. Encryption and Integrity Checks Encryption is critical to preserve confidentiality when transmitting data. Integrity checks prevent undetected manipulation, which can remain unnoticed even despite encryption, e.g., in case of flipped bits. Due to resource-constraints, many devices in CPS do not provide encryption or calculation of check-sums. Complex cryptography is not supported by current programmable switches either. However, this might change in the future, which would allow retrofitting encryption and integrity checks at networking devices. Concretely, using COIN with suitable hardware, data could be encrypted and supplemented with a check-sum directly at the first networking device passed by the respective data packet. The packet is then forwarded through the network or Internet to its designated destination. Decryption and integrity checks can be executed at the last networking device before the destination. Alternatively, this can be implemented at the destination if supported by the respective device. This approach does not require deployment or forwarding to additional middle-boxes. Thus, no additional attack surface or processing overhead is introduced, which is essential for time-sensitive processes as often at hand in the industry. Overall, COIN has the potential to help maintain confidentiality and integrity efficiently, and thus the availability of resource- constrained or legacy devices. Questions to clarify are if and at which costs hardware for enabling cryptographic calculations could and should be embedded in future generations of programmable networking devices. 2.2. Authorization and Authentication Authorization and authentication mechanisms are needed to avoid unauthorized access to devices and their manipulation in the first place. With COIN, networking devices can flexibly decide whether to forward packets, thus enforce authorization and authentication checks. Fink & Wehrle Expires September 12, 2021 [Page 4] Internet-Draft Enhancing Security and Privacy March 2021 One possibility for authorization is to conduct a handshake between the sender and networking device before starting the communication with the industrial device. If not feasible in the networking hardware, the respective calculations can be conducted in the control plane. In the case of success, the sender is added to a list of authorized communication partners. The decision is then enforced by the networking device. Since authorization is only needed when starting or refreshing a connection, the necessity and overhead for consulting the control plane are limited. The sender can append a secret token for authentication to packets directed to a specific device. The last networking device in line can extract the token, authenticate the sender, and forward the packet in case of success or drop it otherwise. One possibility to avoid eavesdropping the token is the use of hash chains. Secure reinitialization can again be done using the control plane, which usually has the resources for conducting encrypted communication. In the case of unsuccessful authorization or authentication, networking devices can inform the network administrator about possible intrusion of the system. Undesired traffic can emerge even from authorized and authenticated devices. A solution is to add policy-based access control, on which we elaborate in the next subsection. 2.3. Behavioral and Enterprise Policies Control processes can include communication between various parties. Even despite authorization and authentication mechanisms, undesired behavior can occur. For instance, malicious third-party software might be installed at the approved device. Regarding communication between two legacy devices, authentication might not be possible at all. An effective way to exclude malicious behavior nevertheless is policy-based access control. [RFC8520] proposes the Manufacturer Usage Description (MUD), a standard for defining the communication behavior of IoT devices, which use specific communication patterns. The definition is primarily based on domain names, ports, and protocols (e.g., TCP and UDP). Further characteristics as the TLS usage [I-D.draft-ietf-opsawg-mud-tls-04] or the required bandwidth of a device [I-D.draft-lear-opsawg-mud-bw-profile-01] can help to define connections more narrowly. By defining the typical behavior, we can exclude deviating communication, including undesired behavior. Likewise to IoT devices, industrial devices usually serve a specific purpose. Thus, Fink & Wehrle Expires September 12, 2021 [Page 5] Internet-Draft Enhancing Security and Privacy March 2021 the application of MUD or similar policies is possible in industrial scenarios as well. The problem that remains to date is the efficient enforcement of such policies through fine-granular and flexible traffic filtering. While middle-boxes increase costs and processing overhead, primary SDN approaches as OpenFlow allow only filtering based on match-action rules regarding fixed protocol header fields. Evaluation of traffic statistics for, e.g., limiting the bandwidth, requires consultation of the remote controller. This leads to latency overheads, which are not acceptable in time-sensitive scenarios. In contrast, the COIN paradigm allows flexible filtering even concerning the content of packets and connection metadata. Furthermore, traffic filtering can be executed by programmable networking devices at line-rate. Going one step further, not only network communication behavior of devices can be defined in policies. As [KANG] shows, COIN can be used to consider additional (contextual) parameters, e.g., the time of day or activity of other devices in the network. Furthermore, companies can define advanced policies to, e.g., authorize specific users or subnets. While the presented policies aim to restrict communication to its designated purpose, we can use access control to explicitly address individual devices' security vulnerabilities as described next. 2.4. In-Network Vulnerability Patches Resource-constrained devices are typically hard to update. Thus, device vulnerabilities often cannot be fixed after deployment. As a remedy and special case of policies, rules can be defined to describe known attacks' signatures. By enforcing these rules at programmable networking devices, e.g., by dropping matching traffic, COIN offers an efficient way to avoid exploitation of device vulnerabilities. Further advantages are the potentially easy and extensive roll-out of such "in-network patches" in the form of (automatic) software updates of the networking device. Future research is needed to evaluate the potential and benefits of in-network patches compared to traditional security measures, e.g., firewalls, and provide proof of concepts using existing devices and vulnerabilities. Besides presented security mechanisms, data protection mechanisms are required to preserve business secrets and the privacy of individuals. Fink & Wehrle Expires September 12, 2021 [Page 6] Internet-Draft Enhancing Security and Privacy March 2021 We show in the following subsection how COIN can contribute to data anonymization. 2.5. Anonymization Due to its interconnection with the physical world, the generation of sensitive data is inherent to CPS. Smart infrastructure leads to the collection of sensitive user data. In industrial networks, information about confidential processes is gathered. Such data is increasingly shared with other entities to increase production efficiency or enable automatic processing. Despite the benefits of data exchange, manufacturers and individuals, might not want to share sensitive information. Again, deployment of privacy mechanisms is usually not possible at resource-constrained or legacy devices. COIN has the potential to flexibly apply privacy mechanisms at line-rate. Data can be pseudonymized at networking devices by, e.g., extracting and replacing specific values. Furthermore, elaborate anonymization techniques can be implemented in the network by sensibly decreasing the data accuracy. For example, concepts like k-Anonymity can be applied by aggregating the values of multiple packets before forwarding the result. Noise addition can be implemented by adding a random number to values. Similarly, the state-of-the-art technique differential privacy can be implemented by adding noise to responses to statistical requests. Even though the COIN paradigm shows the potential to deploy described privacy mechanisms within the network, research is needed to clarify the proposed concepts' feasibility. 3. Intrusion and Anomaly Detection Ideally, attacks are prevented from the outset. However, in the case of incidents, fast detection is critical for limiting damage. Deployment of sensors, e.g., in industrial control systems, can help to monitor the system state and detect anomalies. This can be used in combination with COIN to detect intrusion and to provide advanced safety measures, as described in the following. 3.1. Intrusion Detection Data of sensors or monitored communication behavior can be compared against expected patterns to detect intrusion. Even if intrusion prevention is deployed and connections are allowed when taken individually, subtle attacks might still be possible. For example, a series of values might be out of line if put into context even though Fink & Wehrle Expires September 12, 2021 [Page 7] Internet-Draft Enhancing Security and Privacy March 2021 the individual values are unobtrusive. Anomaly detection can be used to detect such abnormalities and notify the network administrator for further assessment. While anomaly detection is usually outsourced to middle-boxes or external servers, COIN provides the possibility to detect anomalies at-line rate, e.g., by maintaining statistics about traffic flows. This decreases costs and latency, which is valuable for a prompt reaction. Another advantage is that one central networking device can monitor traffic from multiple devices. In contrast, multiple distributed middle boxes are usually needed to achieve the same information gain. Besides intrusion, anomalies can also imply safety risks. In the following, we pick up the potential of COIN to support safety. 3.2. Dead Man's Switch [I-D.draft-irtf-coinrg-use-cases-00] addresses the potential of COIN for improving industrial safety. Detection of an anomaly in the sensor data or operational flow can be used to automatically trigger an emergency shutdown of a system or single system components if the data indicates an actual hazard. Apart from that, other safety measures like warning systems or isolation of areas can be implemented. While we do not aim at replacing traditional dead man's switches, we see the potential of COIN to accelerate the detection of failures. Thus, COIN can valuably complement existing safety measures. 4. Incident Investigation After detecting an incident, it is essential to conduct Network Forensics to investigate the origin and spreading of the related activity. The results of this analysis can be used to allow for consistent recovery, to adapt protection mechanisms, and prevent similar events in the future. For enabling potential investigation, traffic records are constantly collected for each flow in a network, which requires dedicated hardware in large networks. Furthermore, it might be preferable to exclude traffic, e.g., from specific subnets, from the analysis. Dynamic and fine-granular traffic filtering is not possible with traditional networking devices, leading to storage and processing overhead. With COIN, networking devices can be programmed to create flow records without significant overhead when forwarding a packet. Furthermore, record generation can be done more flexibly, e.g., by applying fine-granular traffic filtering. Also, header fields of particular interest can be efficiently extracted. Therefore, COIN Fink & Wehrle Expires September 12, 2021 [Page 8] Internet-Draft Enhancing Security and Privacy March 2021 can considerably decrease the load and increase the efficiency of network forensics. This leads, in turn, to a better understanding of attacks and security. 5. Security Considerations When implementing security and privacy measures in networking devices, their security and failure resistance is critical. Related research questions to clarify in the future are stated in [I-D.draft-kutscher-coinrg-dir-02]. 6. IANA Considerations N/A 7. Conclusion COIN has the potential to improve and retrofit security and privacy, especially with regard to resource-restrained and legacy devices. First, COIN can provide intrusion prevention mechanisms like authentication and efficient enforcement of (context-based) policies. Easily deployable in-network patches of device vulnerabilities could further improve security. Encryption and integrity checks are limited by the current hardware but might be realizable in the future. Second, COIN allows examining packet contents at networking devices, which can help implement fast and comprehensive anomaly and intrusion detection. Last, COIN can contribute to an efficient and targeted incident analysis. Investigation of the feasibility of the presented mechanisms is subject to future research. 8. Informative References [I-D.draft-ietf-opsawg-mud-tls-04] Reddy, T., Wing, D., and B. Anderson, "Manufacturer Usage Description (MUD) (D)TLS Profiles for IoT Devices", draft- ietf-opsawg-mud-tls-04 (work in progress), January 2021. [I-D.draft-irtf-coinrg-use-cases-00] Kunze, I., Wehrle, K., Trossen, D., and M. Montpetit, "Use Cases for In-Network Computing", draft-irtf-coinrg-use- cases-00 (work in progress), February 2021. Fink & Wehrle Expires September 12, 2021 [Page 9] Internet-Draft Enhancing Security and Privacy March 2021 [I-D.draft-kutscher-coinrg-dir-02] Kutscher, D., Karkkainen, T., and J. Ott, "Directions for Computing in the Network", draft-kutscher-coinrg-dir-02 (work in progress), July 2020. [I-D.draft-lear-opsawg-mud-bw-profile-01] Lear, E. and O. Friel, "Bandwidth Profiling Extensions for MUD", draft-lear-opsawg-mud-bw-profile-01 (work in progress), July 2019. [KANG] Kang, Q., Morrison, A., Tang, Y., Chen, A., and X. Luo, "Programmable In-Network Security for Context-aware BYOD Policies", In Proceedings of the 29th USENIX Security Symposium (USENIX Security 20), August 2020, . [RFC7744] Seitz, L., Ed., Gerdes, S., Ed., Selander, G., Mani, M., and S. Kumar, "Use Cases for Authentication and Authorization in Constrained Environments", RFC 7744, DOI 10.17487/RFC7744, January 2016, . [RFC8520] Lear, E., Droms, R., and D. Romascanu, "Manufacturer Usage Description Specification", RFC 8520, DOI 10.17487/RFC8520, March 2019, . [RFC8576] Garcia-Morchon, O., Kumar, S., and M. Sethi, "Internet of Things (IoT) Security: State of the Art and Challenges", RFC 8576, DOI 10.17487/RFC8576, April 2019, . Authors' Addresses Ina Berenice Fink RWTH Aachen University Ahornstr. 55 Aachen D-52062 Germany Phone: +49-241-80-21419 Email: fink@comsys.rwth-aachen.de Fink & Wehrle Expires September 12, 2021 [Page 10] Internet-Draft Enhancing Security and Privacy March 2021 Klaus Wehrle RWTH Aachen University Ahornstr. 55 Aachen D-52062 Germany Phone: +49-241-80-21401 Email: wehrle@comsys.rwth-aachen.de Fink & Wehrle Expires September 12, 2021 [Page 11]