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Internet LAMPS Working Group Internet-Draft The Enrollment over Secure Transport (EST, RFC7030) is ambiguous in its specification of the CSR Attributes Response. This has resulted in implementation challenges and implementor confusion. This document updates RFC7030 (EST) and clarifies how the CSR Attributes Response can be used by an EST server to specify both CSR attribute OIDs and also CSR attribute values that the server expects the client to include in subsequent CSR request.

Introduction Enrollment over Secure Transport (EST) has been used in a wide variety of applications. In particular, and describe a way to use it in order to build out an autonomic control plane (ACP) . The ACP requires that each node be given a very specific SubjectAltName. In the ACP specification, the solution was for the EST server to use section 2.6 of to convey to the EST client the actual SubjectAltName that will end up in its certificate. As a result of some implementation challenges, it came to light that this particular way of using the CSR attributes was not universally agreed upon, and it was suggested that it went contrary to section 2.6. Section 2.6 says that the CSR attributes "provide additional descriptive information that the EST server cannot access itself". After significant discussion, it has been determined that specification is sufficiently difficult to read that clarification is needed. This document motivates the different use cases, and provides additional worked out examples. This document also updates section 4.5 to include revised ASN.1 that covers all uses and is backward compatible with the existing use.

Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

CSR Attributes Handling

Current EST CSR Attributes Specification The ASN.1 for CSR Attributes as defined in EST section 4.5.2 is:

Revised/Simplified EST CSR Attributes Specification (XXX: This isn't really simpler, is it?) A key part that was unclear is that extAttr above could be an entire Extension, as per . This structure naturally includes both the extention ID, a critical bit, and the extension value. With this understand, the needs of and are satisfied, however with a change to the bits on the wire.

Co-existence with existing implementations

Examples

RFC8994/ACP subjectAltName with specific otherName included This is a dump in "dumpasn1" format of a CSR Attributes object which a specific otherName included.

EST server requires public keys of a specific size TBD

EST server requires a public key of a specific algorithm/curve TBD

EST server requires a specific extension to be present TBD

Security Considerations All security considertions from EST section 6 are applicable.

Identity and Privacy Considerations An EST server may use this mechanism to instruct the EST client about the identities it should include in the CSR it sends as part of enrollment. The client may only be aware of its IDevID Subject, which includes a manufacturer serial number. The EST server can use this mechanism to tell the client to include a specific fully qualified domain name in the CSR in order to complete domain ownership proofs required by the CA. Additionally, the EST server may deem the manufacturer serial number in an IDevID as personally identifiable information, and may want to specify a new random opaque identifier that the pledge should use in its CSR. This may be desirable if the CA and EST server have different operators.

IANA Considerations No requests are made to IANA.

Acknowledgements TODO

Changelog

References Normative References This memo profiles the X.509 v3 certificate and X.509 v2 certificate revocation list (CRL) for use in the Internet. An overview of this approach and model is provided as an introduction. The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms. Standard certificate extensions are described and two Internet-specific extensions are defined. A set of required certificate extensions is specified. The X.509 v2 CRL format is described in detail along with standard and Internet-specific extensions. An algorithm for X.509 certification path validation is described. An ASN.1 module and examples are provided in the appendices. [STANDARDS-TRACK] This document profiles certificate enrollment for clients using Certificate Management over CMS (CMC) messages over a secure transport. This profile, called Enrollment over Secure Transport (EST), describes a simple, yet functional, certificate management protocol targeting Public Key Infrastructure (PKI) clients that need to acquire client certificates and associated Certification Authority (CA) certificates. It also supports client-generated public/private key pairs as well as key pairs generated by the CA. Autonomic functions need a control plane to communicate, which depends on some addressing and routing. This Autonomic Control Plane should ideally be self-managing and be as independent as possible of configuration. This document defines such a plane and calls it the "Autonomic Control Plane", with the primary use as a control plane for autonomic functions. It also serves as a "virtual out-of-band channel" for Operations, Administration, and Management (OAM) communications over a network that provides automatically configured, hop-by-hop authenticated and encrypted communications via automatically configured IPv6 even when the network is not configured or is misconfigured. This document specifies automated bootstrapping of an Autonomic Control Plane. To do this, a Secure Key Infrastructure is bootstrapped. This is done using manufacturer-installed X.509 certificates, in combination with a manufacturer's authorizing service, both online and offline. We call this process the Bootstrapping Remote Secure Key Infrastructure (BRSKI) protocol. Bootstrapping a new device can occur when using a routable address and a cloud service, only link-local connectivity, or limited/disconnected networks. Support for deployment models with less stringent security requirements is included. Bootstrapping is complete when the cryptographic identity of the new key infrastructure is successfully deployed to the device. The established secure connection can be used to deploy a locally issued certificate to the device as well. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References Operations, Administration, and Maintenance (OAM), as per BCP 161, for data networks is often subject to the problem of circular dependencies when relying on connectivity provided by the network to be managed for the OAM purposes. Provisioning while bringing up devices and networks tends to be more difficult to automate than service provisioning later on. Changes in core network functions impacting reachability cannot be automated because of ongoing connectivity requirements for the OAM equipment itself, and widely used OAM protocols are not secure enough to be carried across the network without security concerns. This document describes how to integrate OAM processes with an autonomic control plane in order to provide stable and secure connectivity for those OAM processes. This connectivity is not subject to the aforementioned circular dependencies.