Internet Engineering Task Force (IETF) S. Hares Request for Comments: 8241 Huawei Category: Informational D. Migault ISSN: 2070-1721 J. Halpern Ericsson September 2017 Interface to the Routing System (I2RS) Security-Related Requirements
AbstractThis document presents security-related requirements for the Interface to the Routing System (I2RS) protocol, which provides a new interface to the routing system described in the I2RS architecture document (RFC 7921). The I2RS protocol is implemented by reusing portions of existing IETF protocols and adding new features to them. One such reuse is of the security features of a secure transport (e.g., Transport Layer Security (TLS), Secure SHell (SSH) Protocol, Datagram TLS (DTLS)) such as encryption, message integrity, mutual peer authentication, and anti-replay protection. The new I2RS features to consider from a security perspective are as follows: a priority mechanism to handle multi-headed write transactions, an opaque secondary identifier that identifies an application using the I2RS client, and an extremely constrained read-only non-secure transport. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 7841. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8241.
Copyright Notice Copyright (c) 2017 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. 1. Introduction ....................................................3 2. Terminology and Concepts ........................................4 2.1. Requirements Language ......................................4 2.2. Security Terminology .......................................4 2.3. I2RS-Specific Terminology ..................................5 2.4. Concepts ...................................................5 3. Security Features and Protocols: Reused and New .................6 3.1. Security Protocols Reused by the I2RS Protocol .............6 3.2. New Features Related to Security ...........................7 3.3. I2RS Protocol Security Requirements vs. IETF Management Protocols .......................................8 4. Security-Related Requirements ..................................10 4.1. I2RS Peer (Agent and Client) Identity Authentication ......10 4.2. Identity Validation before Role-Based Message Actions .....11 4.3. Peer Identity, Priority, and Client Redundancy ............12 4.4. Multi-Channel Transport: Secure and Non-Secure ............13 4.5. Management Protocol Security ..............................15 4.6. Role-Based Data Model Security ............................16 4.7. Security of the Environment ...............................17 5. IANA Considerations ............................................17 6. Security Considerations ........................................17 7. References .....................................................18 7.1. Normative References ......................................18 7.2. Informative References ....................................18 Acknowledgements ..................................................20 Authors' Addresses ................................................20
RFC7921] describes the architecture of this interface, and this document assumes the reader is familiar with this architecture and its definitions. The I2RS interface is instantiated by the I2RS protocol connecting an I2RS client and an I2RS agent associated with a routing system. The I2RS protocol is implemented by reusing portions of existing IETF protocols and adding new features to them. As a reuse protocol, it can be considered a higher-layer protocol because it can be instantiated in multiple management protocols (e.g., NETCONF [RFC6241] or RESTCONF [RFC8040]) operating over a secure transport. These protocols are what provide its security. This document is part of a suite of documents outlining requirements for the I2RS protocol, which also includes the following: o "An Architecture for the Interface to the Routing System" [RFC7921] o "I2RS Ephemeral State Requirements" [RFC8242] o "Interface to the Routing System (I2RS) Traceability: Framework and Information Model" (which discusses traceability) [RFC7923] o "Requirements for Subscription to YANG Datastores" (which highlights the publication/subscription requirements) [RFC7922] Since the I2RS "higher-layer" protocol changes the interface to the routing systems, it is important that implementers understand the new security requirements for the environment the I2RS protocol operates in. A summary of the I2RS protocol security environment is found in the I2RS architecture [RFC7921]. I2RS reuses the secure transport protocols (TLS, SSH, DTLS) that support encryption, message integrity, peer authentication, and key distribution protocols. Optionally, implementers may utilize Authentication, Authorization, and Accounting (AAA) protocols (Radius over TLS or Diameter over TLS) to securely distribute identity information. Section 2 highlights some of the terminology and concepts that the reader is required to be familiar with.
Section 3 provides an overview of security features and protocols being reused (Section 3.1), lists the new security features being required (Section 3.2), and explores how existing and new security features and protocols would be paired with existing IETF management protocols (Section 3.3). The new features I2RS extends to these protocols are a priority mechanism to handle multi-headed writes, an opaque secondary identifier to allow traceability of an application utilizing a specific I2RS client to communicate with an I2RS agent, and non- secure transport constrained to be used only for read-only data, which may include publicly available data (e.g., public BGP events, public telemetry information, web service availability) and some legacy data. Section 4 provides the I2RS protocol security requirements of several security features. Protocols designed to be I2RS higher-layer protocols need to fulfill these security requirements. RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. RFC4949] and [RFC7921]. Specifically, this document reuses the following terms from [RFC4949]: o access control o authentication o data confidentiality o data integrity o data privacy o identity o identifier o mutual authentication o role o role-based access control o security audit trail o trust
[RFC7922] describes traceability for the I2RS interface and the I2RS protocol. Traceability is not equivalent to a security audit trail or simple logging of information. A security audit trail may utilize traceability information. RFC7258]. This document uses the following concepts from the I2RS architecture [RFC7921] listed below with their respective section numbers from said RFC: o I2RS client, agent, and protocol (Section 2) o I2RS higher-layer protocol (Section 7.2)
o scope: read, notification, identity, and write (Section 2) o identity and secondary identity (Section 2) o roles or security rules (Section 2) o routing system/subsystem (Section 2) o I2RS assumed security environment (Section 4) o I2RS identity and authentication (Section 4.1) o scope of Authorization in I2RS client and agent (Section 4.2) o client redundancy with a single client identity (Section 4.3), o restrictions on I2RS in personal devices (Section 4.4) o communication channels and I2RS higher-layer protocol (Section 7.2) o active communication versus connectivity (Section 7.5) o multi-headed control (Section 7.8) o transaction, message, multi-message atomicity (Section 7.9) RFC8095], the secure transport protocols that support peer authentication, confidentiality, data integrity, and replay protection are the following: 1. TLS [RFC5246] over TCP or Stream Control Transmission Protocol (SCTP) 2. DTLS over UDP with replay detection and an anti-DoS stateless cookie mechanism required for the I2RS protocol and the DTLS options of record-size negotiation and conveyance of the Don't Fragment (DF) bit are set for IPv4, or no fragmentation extension headers for IPv6 to be optional in deployments are allowed by the I2RS protocol
3. HTTP over TLS (over TCP or SCTP) 4. HTTP over DTLS (with the requirements and optional features specified above in item 2) As detailed in Section 3.3, the following protocols would need to be extended to provide confidentiality, data integrity, peer authentication, and key distribution and to run over a secure transport (TLS or DTLS): o IP Flow Information Export (IPFIX) over SCTP, TCP, or UDP o Forwarding and Control Element Separation (ForCES) Transport Mapping Layer (TML) over SCTP The specific type of key management protocols an I2RS secure transport uses depends on the transport. Key management protocols utilized for the I2RS protocols SHOULD support automatic rotation. An I2RS implementer may use AAA protocols over secure transport to distribute the identities for the I2RS client, I2RS agent, and role- authorization information. Two AAA protocols are as follows: Diameter [RFC6733] and Radius [RFC2865]. To provide I2RS peer identities with the best security, the AAA protocols MUST be run over a secure transport (Diameter over secure transport (TLS over TCP) [RFC6733]), Radius over a secure transport (TLS) [RFC6614]). RFC7921] provides the concept of each I2RS client having a priority. The I2RS client with the highest priority will have its write succeed. This document specifies requirements for this new concept of priority (see Section 4.3). The opaque secondary identifier identifies an application that uses communication from the I2RS client to I2RS agent to manage the routing system. The secondary identifier is opaque to the I2RS protocol. In order to protect personal privacy, the secondary identifier should not contain identifiable personal information.
The last new feature related to I2RS security is the ability to allow nonconfidential data to be transferred over a non-secure transport. It is expected that most I2RS data models will describe information that will be transferred with confidentiality. Therefore, any model that transfers data over a non-secure transport is marked. The use of a non-secure transport is optional, and an implementer SHOULD create knobs that allow data marked as nonconfidential to be sent over a secure transport. Nonconfidential data can only be data with read-scope or notification-scope transmission of events. Nonconfidential data cannot have write-scope or notification-scope configuration. Examples of nonconfidential data would be the telemetry information that is publicly known (e.g., BGP route-views data or website status data) or some legacy data (e.g., interface) that cannot be transported using secure transport. The IETF I2RS data models MUST indicate (in the model) the specific data that is nonconfidential. Most I2RS data models will expect that the information described in the model will be transferred with confidentiality. Figure 1 provides a partial list of the candidate management protocols. It also lists the secure transports each protocol supports. The column on the right of the table indicates whether or not the transport protocol will need I2RS security extensions.
Management I2RS Security Protocol Transport Protocol Extensions ========= ===================== ================= NETCONF TLS over TCP (*1) None required (*2) RESTCONF HTTP over TLS with None required (*2) X.509v3 certificates, certificate validation, mutual authentication: 1) authenticated server identity, 2) authenticated client identity (*1) ForCES TML over SCTP Needs an extension to (*1) TML to run TML over TLS over SCTP, or DTLS with options for replay protection and anti-DoS stateless cookie mechanism. (DTLS record size negotiation and conveyance of DF bits are optional). The IPsec mechanism is not sufficient for I2RS traveling over multiple hops (router + link) (*2) IPFIX SCTP, TCP, UDP Needs an extension TLS or DTLS for to support TLS or DTLS with secure client (*1) options for replay protection and anti-DoS stateless cookie mechanism. (DTLS record size negotiation and conveyance of DF bits are optional) *1 - Key management protocols MUST support appropriate key rotation. *2 - Identity and role authorization distributed by Diameter or Radius MUST use Diameter over TLS or Radius over TLS. Figure 1: Candidate Management Protocols and Their Secure Transports
Section 4.1) o Peer Identity validation before role-based message actions (Section 4.2) o peer identity and client redundancy (Section 4.3) o multi-channel transport requirements: Secure transport and non- secure Transport (Section 4.4) o management protocol security requirements (Section 4.5) o role-based security (Section 4.6) o security environment (Section 4.7) The I2RS protocol depends upon a secure transport layer for peer authentication, data integrity, confidentiality, and replay protection. The optional non-secure transport can only be used for a restricted set of data available publicly (events or information) or a select set of legacy data. Data passed over the non-secure transport channel MUST NOT contain any data that identifies a person.
Explanation: These requirements are for I2RS peer (I2RS agent and client) authentication. A secure transport (e.g., TLS) will authenticate based on these identities, but these identities are for the I2RS management layer. A AAA protocol distributing I2RS identity information SHOULD transport its information over a secure transport.
Section 7.8 of [RFC7921]). The I2RS deployment using multiple clients SHOULD coordinate this multi-headed control of I2RS agents by I2RS clients so no conflict occurs in the write scope. However, in the case of conflict on a write-scope variable, the error resolution mechanisms defined by the I2RS architecture multi-headed control (Section 7.8 of [RFC7921]) allow the I2RS agent to deterministically choose one I2RS client. The I2RS client with highest priority is given permission to write the variable, and the second client receives an error message. A single I2RS client may be associated with multiple applications with different tasks (e.g., weekly configurations or emergency configurations). The secondary identity is an opaque value that the I2RS client passes to the I2RS agent so that this opaque value can be placed in the tracing file or event stream to identify the application using the communication from I2RS client to agent. The I2RS client is trusted to simply assert the secondary identifier. One example of the use of the secondary identity is the situation where an operator of a network has two applications that use an I2RS client. The first application is a weekly configuration application that uses the I2RS protocol to change configurations. The second application allows operators to makes emergency changes to routers in the network. Both of these applications use the same I2RS client to write to an I2RS agent. In order for traceability to determine which application (weekly configuration or emergency) wrote some configuration changes to a router, the I2RS client sends a different opaque value for each of the applications. The weekly configuration secondary opaque value could be "xzzy-splot" and the emergency secondary opaque value could be "splish-splash".
A second example is if the I2RS client is used for the monitoring of critical infrastructure. The operator of a network using the I2RS client may desire I2RS client redundancy where the monitoring application with the I2RS client is deployed on two different boxes with the same I2RS client identity (see Section 4.3 of [RFC7921]). These two monitoring applications pass to the I2RS client whether the application is the primary or back-up application, and the I2RS client passes this information in the I2RS secondary identifier, as the figure below shows. The primary application's secondary identifier is "primary-monitoring", and the back-up application secondary identifier is "backup-monitoring". The I2RS tracing information will include the secondary identifier information along with the transport information in the tracing file in the agent. Application A--I2RS client--Secure transport(#1) [I2RS identity 1, secondary identifier: "primary-monitoring"]--> Application B--I2RS client--Secure transport(#2) [I2RS identity 1, secondary identifier: "backup-monitoring"]--> Figure 2: Primary and Back-Up Application for Monitoring Identification Sent to Agent
SEC-REQ-12: A secure transport MUST be associated with a key management solution that can guarantee that only the entities having sufficient privileges can get the keys to encrypt/decrypt the sensitive data. SEC-REQ-13: A machine-readable mechanism to indicate that a data model contains nonconfidential data MUST be provided. A non- secure transport MAY be used to publish only read-scope or notification-scope data if the associated data model indicates that the data in question is nonconfidential. SEC-REQ-14: The I2RS protocol MUST be able to support multiple secure transport sessions providing protocol and data communication between an I2RS agent and client. However, a single connection between I2RS agent and client MAY elect to use a single secure transport session or a single non-secure transport session conforming to the requirements above. SEC-REQ-15: Deployment configuration knobs SHOULD be created to allow operators to send "nonconfidential" read scope (data or event streams) over a secure transport. SEC-REQ-16: The I2RS protocol makes use of both secure and non- secure transports, but this use MUST NOT be done in any way that weakens the secure transport protocol used in the I2RS protocol or other contexts that do not have this requirement for mixing secure and non-secure modes of operation. Explanation: The I2RS architecture defines three scopes: read, write, and notification. Non-secure data can only be used for read and notification scopes of "nonconfidential data". The configuration of ephemeral data in the I2RS agent uses write scope either for data or for configuration of event notification streams. The requirement to use secure transport for configuration prevents accidental or malevolent entities from altering the I2RS routing system through the I2RS agent. It is anticipated that the passing of most I2RS ephemeral state operational statuses SHOULD be done over a secure transport. In most circumstances, the secure transport protocol will be associated with a key management system. Most deployments of the I2RS protocol will allow for automatic key management systems. Since the data models for the I2RS protocol will control key routing functions, it is important that deployments of I2RS use automatic key management systems.
Per BCP 107 [RFC4107], while key management systems SHOULD be automatic, the systems MAY be manual in the following scenarios: a) The environment has limited bandwidth or high round-trip times. b) The information being protected has low value. c) The total volume of traffic over the entire lifetime of the long- term session key will be very low. d) The scale of the deployment is limited. Operators deploying the I2RS protocol selecting manual key management SHOULD consider both short- and medium-term plans. Deploying automatic systems initially may save effort in the long term.
SEC-REQ-19: The I2RS higher-layer protocol MUST provide a mechanism for message traceability (requirements in [RFC7922]) that supports the tracking higher-layer functions run across secure connection or a non-secure transport. Explanation: Most carriers do not want a router's configuration and data-flow statistics to be known by hackers or their competitors. While carriers may share peering information, most carriers do not share configuration and traffic statistics. To achieve this, the I2RS higher-layer protocol (e.g., NETCONF) requires access control (NETCONF Access Control Model [RFC6536]) for sensitive data needs to be provided; and the confidentiality protection on such data during transportation needs to be enforced. Integrity of data is important even if the I2RS protocol is sending nonconfidential data over a non-secure connection. The ability to trace I2RS protocol messages that enact I2RS transactions provides a minimal aid to helping operators check how messages enact transactions on a secure or non-secure transport. Contextual checks on specific nonconfidential data sent over a non-secure connection may indicate the data has been modified. RFC7921] specifies a "role" to categorize users into a group (rather than handling them individually) for access-control purposes (role-based access control). Therefore, an I2RS role specifies the access control for a group as being read, write, or notification. SEC-REQ-20: The rules around what I2RS security role is permitted to access and manipulate what information over a secure transport (which protects the data in transit) SHOULD ensure that data of any level of sensitivity is reasonably protected from being observed by those without permission to view it, so that privacy requirements are met. SEC-REQ-21: Role security MUST work when multiple transport connections are being used between the I2RS client and agent as the I2RS architecture [RFC7921] describes. Sec-REQ-22: If an I2RS agent or client is tightly correlated with a person, then the I2RS protocol and data models SHOULD provide additional security that protects the person's privacy.
Explanation: An I2RS higher-layer protocol uses a management protocol (e.g., NETCONF, RESTCONF) to pass messages in order to enact I2RS transactions. Role security must secure data (sensitive and normal data) in a router even when it is operating over multiple connections at the same time. NETCONF can run over TLS (over TCP or SCTP) or SSH. RESTCONF runs over HTTP over a secure transport (TLS). SCTP [RFC4960] provides security for multiple streams plus end-to-end transport of data. Some I2RS functions may wish to operate over DTLS [RFC6347], which runs over UDP ([RFC768]) and SCTP ([RFC5764]). Please note the security of the connection between application and I2RS client is outside of the I2RS protocol or I2RS interface. While I2RS clients are expected to be related to network devices and not individual people, if an I2RS client ran on a person's phone, then privacy protection to anonymize any data relating to a person's identity or location would be needed. A variety of forms of management may set policy on roles: "operator- applied knobs", roles that restrict personal access, data models with specific "privacy roles", and access filters. RFC7921].
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>. [RFC4107] Bellovin, S. and R. Housley, "Guidelines for Cryptographic Key Management", BCP 107, RFC 4107, DOI 10.17487/RFC4107, June 2005, <https://www.rfc-editor.org/info/rfc4107>. [RFC4949] Shirey, R., "Internet Security Glossary, Version 2", FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007, <https://www.rfc-editor.org/info/rfc4949>. [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May 2014, <https://www.rfc-editor.org/info/rfc7258>. [RFC7921] Atlas, A., Halpern, J., Hares, S., Ward, D., and T. Nadeau, "An Architecture for the Interface to the Routing System", RFC 7921, DOI 10.17487/RFC7921, June 2016, <https://www.rfc-editor.org/info/rfc7921>. [RFC7922] Clarke, J., Salgueiro, G., and C. Pignataro, "Interface to the Routing System (I2RS) Traceability: Framework and Information Model", RFC 7922, DOI 10.17487/RFC7922, June 2016, <https://www.rfc-editor.org/info/rfc7922>. [RFC7923] Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements for Subscription to YANG Datastores", RFC 7923, DOI 10.17487/RFC7923, June 2016, <https://www.rfc-editor.org/info/rfc7923>. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>. [RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI 10.17487/RFC0768, August 1980, <https://www.rfc-editor.org/info/rfc768>.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, DOI 10.17487/RFC2865, June 2000, <https://www.rfc-editor.org/info/rfc2865>. [RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol", RFC 4960, DOI 10.17487/RFC4960, September 2007, <https://www.rfc-editor.org/info/rfc4960>. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008, <https://www.rfc-editor.org/info/rfc5246>. [RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer Security (DTLS) Extension to Establish Keys for the Secure Real-time Transport Protocol (SRTP)", RFC 5764, DOI 10.17487/RFC5764, May 2010, <https://www.rfc-editor.org/info/rfc5764>. [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, <https://www.rfc-editor.org/info/rfc6241>. [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, January 2012, <https://www.rfc-editor.org/info/rfc6347>. [RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration Protocol (NETCONF) Access Control Model", RFC 6536, DOI 10.17487/RFC6536, March 2012, <https://www.rfc-editor.org/info/rfc6536>. [RFC6614] Winter, S., McCauley, M., Venaas, S., and K. Wierenga, "Transport Layer Security (TLS) Encryption for RADIUS", RFC 6614, DOI 10.17487/RFC6614, May 2012, <https://www.rfc-editor.org/info/rfc6614>. [RFC6733] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn, Ed., "Diameter Base Protocol", RFC 6733, DOI 10.17487/RFC6733, October 2012, <https://www.rfc-editor.org/info/rfc6733>. [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, <https://www.rfc-editor.org/info/rfc8040>.
[RFC8095] Fairhurst, G., Ed., Trammell, B., Ed., and M. Kuehlewind, Ed., "Services Provided by IETF Transport Protocols and Congestion Control Mechanisms", RFC 8095, DOI 10.17487/RFC8095, March 2017, <https://www.rfc-editor.org/info/rfc8095>. [RFC8242] Haas, J. and S. Hares, "Interface to the Routing System (I2RS) Ephemeral State Requirements", RFC 8242, DOI 10.17487/RFC8242, September 2017, <http://www.rfc-editor.org/info/rfc8242>.