Secure Object Delivery Protocol (SODP) Server Interfaces: NSA's Profile for Delivery of Certificates, Certificate Revocation Lists (CRLs), and Symmetric Keys to Clients

Independent Submission                                        M. Jenkins
Request for Comments: 9152                                           NSA
Category: Informational                                        S. Turner
ISSN: 2070-1721                                                    sn3rd
                                                              April 2022


Secure Object Delivery Protocol (SODP) Server Interfaces: NSA's Profile
 for Delivery of Certificates, Certificate Revocation Lists (CRLs), and
                       Symmetric Keys to Clients

Abstract

   This document specifies protocol interfaces profiled by the United
   States National Security Agency (NSA) for National Security System
   (NSS) servers that provide public key certificates, Certificate
   Revocation Lists (CRLs), and symmetric keys to NSS clients.  Servers
   that support these interfaces are referred to as Secure Object
   Delivery Protocol (SODP) servers.  The intended audience for this
   profile comprises developers of client devices that will obtain key
   management services from NSA-operated SODP servers.  Interfaces
   supported by SODP servers include Enrollment over Secure Transport
   (EST) and its extensions as well as Certificate Management over CMS
   (CMC).

   This profile applies to the capabilities, configuration, and
   operation of all components of US National Security Systems (SP
   800-59).  It is also appropriate for other US Government systems that
   process high-value information.  It is made publicly available for
   use by developers and operators of these and any other system
   deployments.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not candidates 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/rfc9152.

Copyright Notice

   Copyright (c) 2022 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.

Table of Contents

   1.  Introduction
     1.1.  Documents to be Familiar With
     1.2.  Document Organization
     1.3.  Environment
   2.  Abstract Syntax Notation One
   3.  EST Interface
     3.1.  Hypertext Transfer Protocol Layer
     3.2.  Transport Layer Security
     3.3.  Eligibility
     3.4.  Authentication
     3.5.  Authorization
     3.6.  EST and EST Extensions
       3.6.1.  /pal
       3.6.2.  /cacerts
       3.6.3.  /simpleenroll
       3.6.4.  /simplereenroll
       3.6.5.  /fullcmc
       3.6.6.  /serverkeygen
       3.6.7.  /csrattrs
       3.6.8.  /crls
       3.6.9.  /symmetrickeys
       3.6.10. /eecerts, /firmware, /tamp
   4.  CMC Interface
     4.1.  RFC 5273 Transport Protocols
     4.2.  Eligibility
     4.3.  Authentication
     4.4.  Authorization
     4.5.  Full PKI Requests/Responses
   5.  Trust Anchor Profile
   6.  Non-Self-Signed Certification Authority Certificate Profile
   7.  End-Entity Certificate Profile
     7.1.  Source of Authority Certificate Profile
     7.2.  Client Certificate Profile
   8.  Relying Party Applications
   9.  CRL Profile
   10. IANA Considerations
   11. Security Considerations
   12. References
     12.1.  Normative References
     12.2.  Informative References
   Authors' Addresses

1.  Introduction

   This document specifies protocol interfaces profiled by the United
   States National Security Agency (NSA) for National Security System
   (NSS) servers that provide public key certificates, Certificate
   Revocation Lists (CRLs), and symmetric keys to NSS clients.  Servers
   that support these interfaces are referred to as Secure Object
   Delivery Protocol (SODP) servers.  The purpose of this document is to
   indicate options from, and requirements in addition to, the base
   specifications listed in Section 1.1 that are necessary for client
   interoperability with NSA-operated SODP servers.  Clients are always
   devices and need not implement all of the interfaces specified
   herein; clients are free to choose which interfaces to implement
   based on their operational requirements.  Interfaces supported by
   SODP servers include:

   *  Enrollment over Secure Transport (EST) [RFC7030] and its
      extensions [RFC8295], and

   *  Certificate Management over CMS (CMC) [RFC5274] [RFC6402] for both
      Simple Public Key Infrastructure (PKI) requests and responses
      (i.e., PKCS#10 requests and PKCS#7 responses) and Full PKI
      requests and responses.

   This profile applies to the capabilities, configuration, and
   operation of all components of US National Security Systems
   [SP-800-59].  It is also appropriate for other US Government systems
   that process high-value information.  It is made publicly available
   for use by developers and operators of these and any other system
   deployments.

   This profile conforms to the existing requirements of the NSA's
   Commercial National Security Algorithms (CNSAs).  As operational
   needs evolve over time, this profile will be updated to incorporate
   new commercial algorithms and protocols as they are developed and
   approved for use.

1.1.  Documents to be Familiar With

   Familiarity with the follow specifications is assumed:

   *  EST and EST extensions: [RFC7030] and [RFC8295]

   *  PKI-related specifications: [RFC2986], [RFC3739], [RFC5274],
      [RFC5280], [RFC5912], [RFC5913], [RFC5916], [RFC5917], [RFC6010],
      and [RFC6402]

   *  Key-format-related specifications: [RFC5915], [RFC5958],
      [RFC5959], [RFC6031], [RFC6032], [RFC6160], [RFC6161], [RFC6162],
      [RFC7191], [RFC7192], [RFC7292], and [RFC7906]

   *  CMS-related (Cryptographic Message Syntax) documents: [RFC5652]
      and [RFC6268]

   *  CNSA-related documents: [RFC8603], [RFC8755], [RFC8756], and
      [RFC9151]

   The requirements from RFCs apply throughout this profile and are
   generally not repeated here.  This document is purposely written
   without using the requirements language described in [RFC2119] and
   [RFC8174].

1.2.  Document Organization

   The document is organized as follows:

   *  The remainder of this section describes the operational
      environment used by clients to retrieve secure objects.

   *  Section 2 specifies the Abstract Syntax Notation One (ASN.1)
      version used.

   *  Section 3 specifies SODP's EST interface.

   *  Section 4 specifies SODP's CMC interfaces.

   *  Sections 5-7 specify Trust Anchor (TA), Certification Authority
      (CA), and End-Entity (EE) certificates, respectively.

   *  Sections 8 and 9 specify Relying Party Applications and CRL
      Profile, respectively.

1.3.  Environment

   Clients obtain secure "objects" or "packages" from the client-server-
   based environment.  Objects/packages vary based on the Source of
   Authority (SOA), but all objects are "secured" minimally through the
   use of one or more digital signatures and zero or more layers of
   encryption, as profiled in this document.  An SOA is the authority
   for the creation of objects that the client will recognize as valid.
   An SOA can delegate its authority to other actors; delegation occurs
   through the issuance of certificates.  An object or package is the
   generic term for certificates, certificate status information, and
   keys (both asymmetric and symmetric).  All of the objects except for
   the certificates and certificate status information are directly
   encapsulated in and protected by CMS content types.  CMS content
   types that provide security are referred to as "CMS-protecting
   content types".  All others are simply referred to as "CMS content
   types".  All secured objects are distributed either as CMS packages
   or as part of a CMS package.

   In the example depicted in Figure 1, there are two SOAs: one for
   symmetric keys, as depicted by the Key Trust Anchor (KTA), and one
   for public key certificates, as depicted by the PKI Trust Anchor
   (TA).  The KTA is responsible for the creation and distribution of
   symmetric keys.  The KTA delegates the creation and distribution
   responsibilities to separate entities through the issuance of
   certificates to a Key Source Authority (KSA) and a Key Distribution
   Authority (KDA).  The KSA generates the keys, digitally signs the
   keys, and encrypts the key for the end client using CMS content types
   for each step.  The KDA distributes the KSA-generated and KSA-
   protected key to the client; the key may also be signed by the KDA.
   The resulting CMS package is provided to the client through the EST
   extension's /symmetrickey service.  The PKI TA is responsible for the
   creation, distribution, and management of public key certificates.
   The PKI TA delegates these responsibilities to Certification
   Authorities (CAs), and CAs, in turn, are responsible for creating,
   distributing, and managing End-Entity (EE) certificates.  CAs
   distribute PKI-related information through the /cacerts, /crls,
   /eecerts, /fullcmc, /simpleenroll, /simplereenroll, and /csrattrs EST
   and EST extension services.

      +-----+                            +--------+
      | KTA |                            | PKI TA |
      +-----+                            +--------+
         |                                   |
         | Signs                             | Signs
         |                                   |
         +-------------+                     V
         |             |                   +----+
         V             V                   | CA |
      +-----+       +-----+                +----+
      | KSA |       | KDA |                   |
      +-----+       +-----+                   | Signs
         |           |                        |
         | Signs &   | Optionally             +---------------+
         | Encrypts  | Signs                  |               |
         |           |                        V               V
         |           |                +-------------+ +-------------+
         |           V                | Certificate | | Certificate |
     +---|-------------+              +-------------+ | Revocation  |
     |   V             | CMS Content                  | List        |
     | +-------------+ | Types                        +-------------+
     | | Key Package | |
     | +-------------+ |
     +-----------------+

     Figure 1: Operating Environment (Key and PKI Sources of Authority)

   For clients that support the CMC interface and not the EST interface,
   the environment includes only the PKI TAs.

2.  Abstract Syntax Notation One

   Implementations of this specification use the 2002/2008 ASN.1
   version; 2002/2008 ASN.1 modules can be found in [RFC5911],
   [RFC5912], and [RFC6268] (use [RFC6268] for the CMS syntax), while
   other specifications already include the 2002/2008 ASN.1 along with
   the 1988 ASN.1.  See Section 1.1 of [RFC6268] for a discussion about
   the differences between the 2002 and 2008 ASN.1 versions.

3.  EST Interface

   Client options for EST [RFC7030] and EST extensions [RFC8295] are
   specified in this section.

3.1.  Hypertext Transfer Protocol Layer

   Clients that receive redirection responses (3xx status codes) will
   terminate the connection ([RFC7030], Section 3.2.1).

   Per Section 2.2 of [RFC8295], clients indicate the format
   ("application/xml" or "application/json") of the PAL information
   ([RFC8295], Section 2.1.1) via the HTTP Accept header.

3.2.  Transport Layer Security

   TLS implementations are configured as specified in [RFC9151]; the
   notable exception is that only EC-based algorithms are used.

3.3.  Eligibility

   At the EST interface, servers only enroll clients that they have
   established a prior relationship with independently of the EST
   service.  To accomplish this, client owners/operators interact in
   person with the human acting as the Registration Authority (RA) to
   ensure the information included in the transmitted certificate
   request, which is sometimes called a Certificate Signing Request
   (CSR), is associated with a client.  The mechanism by which the
   owner/operator interacts with the RA as well as the information
   provided is beyond the scope of this document.  The information
   exchanged by the owner/operator might be something as simple as the
   subject name included in the CSR to be sent or a copy of the
   certificate that will be used to verify the certificate request,
   which is provided out of band.

3.4.  Authentication

   Mutual authentication occurs via "Certificate TLS Authentication"
   ([RFC7030], Section 2.2.1).  Clients provide their certificate to
   servers in the TLS Certificate message, which is sent in response to
   the server's TLS Certificate Request message.  Both servers and
   clients reject all attempts to authenticate based on certificates
   that cannot be validated back to an installed TA.

3.5.  Authorization

   Clients always use an explicit TA database ([RFC7030],
   Section 3.6.1).  At a minimum, clients support two TAs: one for the
   PKI and one for symmetric keys.

   Clients check that the server's certificate includes the id-kp-cmcRA
   Extended Key Usage (EKU) value ([RFC6402], Section 2.10).

   Clients that support processing of the CMS Content Constraints
   extension [RFC6010] ensure returned CMS content is from an SOA or an
   entity authorized by an SOA for that CMS content; see Section 7.1 for
   SOA certificates.

3.6.  EST and EST Extensions

   This section profiles SODP's interfaces for EST [RFC7030] and EST
   extensions [RFC8295].

3.6.1.  /pal

   The Package Availability List (PAL) is limited to 32 entries, where
   the 32nd PAL entry links to an additional PAL (i.e., PAL Package Type
   0001).

   The PAL is XML [XML].

3.6.2.  /cacerts

   The CA certificates located in the explicit TA database are
   distributed to the client when it is registered.  This TA
   distribution mechanism is out of scope.

   CA certificates provided through this service are as specified in
   Sections 5 and 6 of this document.

3.6.3.  /simpleenroll

   CSRs follow the specifications in Section 4.2 of [RFC8756], except
   that the CMC-specific ChangeSubjectName and the POP Link Witness V2
   attributes do not apply.  Only EC-based algorithms are used.

   Client certificates provided through this service are as specified in
   Section 7 of this document.

   The HTTP content type of "text/plain" ([RFC2046], Section 4.1) is
   used to return human-readable errors.

3.6.4.  /simplereenroll

   There are no additional requirements for requests beyond those
   specified in Sections 3.4 and 3.6.3 of this document.

   The HTTP content type of "text/plain" ([RFC2046], Section 4.1) is
   used to return human-readable errors.

3.6.5.  /fullcmc

   Requests are as specified in [RFC8756] with the notable exception
   that only EC-based algorithms are used.

   Additional attributes for returned CMS packages can be found in
   [RFC7906].

   Certificates provided through this service are as specified in
   Section 7 of this document.

3.6.6.  /serverkeygen

   PKCS#12 [RFC7292] -- sometimes referred to as "PFX" (Personal
   Information Exchange) or "P12" -- is used to provide server-generated
   asymmetric private keys and the associated certificate to clients.
   This interface is a one-way interface as the RA requests these from
   the server.

   PFXs [RFC7292] are exchanged using both password privacy mode and
   integrity password mode.  The PRF algorithm for PBKDF2 (the KDF for
   PBES2 and PBMAC1) is HMAC-SHA-384, and the PBES2 encryption scheme is
   AES-256.

   The HTTP content type of "text/plain" ([RFC2046], Section 4.1) is
   used to return human-readable errors.

   /serverkeygen/return is not supported at this time.

3.6.7.  /csrattrs

   Clients use this service to retrieve partially filled PKIRequests
   with no public key or proof-of-possession signature, i.e., their
   values are set to zero length, either a zero length BIT STRING or
   OCTET STRING.  The pKCS7PDU attribute, defined in [RFC2985], includes
   the partially filled PKIRequest as the only element in the CsrAttrs
   sequence.  Even though the CsrAttrs syntax is defined as a set, there
   is only ever exactly one instance of values present.

3.6.8.  /crls

   CRLs provided through this service are as specified in Section 9 of
   this document.

3.6.9.  /symmetrickeys

   Clients that claim to support SODP interoperation will be able to
   process the following messages from an SODP server:

   *  additional encryption and origin authentication ([RFC8295],
      Section 5); and

   *  server-provided Symmetric Key Content Type [RFC6032] encapsulated
      in an Encrypted Key Content Type using the EnvelopedData choice
      [RFC6033] with an SOA certificate that includes the CMS Content
      Constraints extension (see Section 7.1).

   Client-supported algorithms to decrypt the server-returned symmetric
   key are as follows:

   *  Message Digest: See Section 4 of [RFC8755].

   *  Digital Signature Algorithm: See Section 5 of [RFC8755].

   *  Key Agreement: See Section 6.1 of [RFC8755].

   *  Key Wrap: AES-256 Key Wrap with Padding [RFC6033] is used.
      AES-128 Key Wrap with Padding is not used.

   *  Content Encryption: AES-256 Key Wrap with Padding [RFC6033] is
      used.  AES-128 Key Wrap with Padding is not used.

   /symmetrickeys/return is not used at this time.

3.6.10.  /eecerts, /firmware, /tamp

   /eecerts, /firmware, and /tamp are not used at this time.

4.  CMC Interface

   Client options for CMC [RFC5274] [RFC6402] are specified in this
   section.

4.1.  RFC 5273 Transport Protocols

   Clients only use the HTTPS-based transport.  The TLS implementation
   and configuration are as specified in [RFC9151], with the notable
   exception that only EC-based algorithms are used.

   Clients that receive HTTP redirection responses (3xx status codes)
   will terminate the connection ([RFC7030], Section 3.2.1).

4.2.  Eligibility

   At the CMC interface, servers only enroll clients that they have
   established a prior relationship with independently of the EST
   service.  To accomplish this, client owners/operators interact in
   person with the human acting as the Registration Authority (RA) to
   ensure the information included in the transmitted certificate
   request, which is sometimes called a Certificate Signing Request
   (CSR), is associated with a client.  The mechanism by which the
   owner/operator interacts with the RA as well as the information
   provided is beyond the scope of this document.  The information
   exchanged by the owner/operator might be something as simple as the
   subject name included in the CSR to be sent or a copy of the
   certificate that will be used to verify the certificate request,
   which is provided out of band.

4.3.  Authentication

   Mutual authentication occurs via client and server signing of CMC
   protocol elements, as required by [RFC8756].  All such signatures are
   validated against an installed TA; any that fail validation are
   rejected.

4.4.  Authorization

   Clients support the simultaneous presence of as many TAs as are
   required for all of the functions of the client, and only these TAs.

   Clients check that the server's certificate includes the id-kp-cmcRA
   Extended Key Usage (EKU) value ([RFC6402], Section 2.10).

   Clients that support processing of the CMS Content Constraints
   extension [RFC6010] ensure returned CMS content is from an SOA or an
   entity authorized by an SOA for that CMS content; see Section 7.1 for
   SOA certificates.

4.5.  Full PKI Requests/Responses

   Requests are as specified in [RFC8756] with the notable exception
   that only EC-based algorithms are used.

   Additional attributes for returned CMS packages can be found in
   [RFC7906].

   Certificates provided through this service are as specified in
   Section 7 of this document.

5.  Trust Anchor Profile

   Clients are free to store the TA in the format of their choosing;
   however, servers provide TA information in the form of self-signed CA
   certificates.  This section documents requirements for self-signed
   certificates in addition to those specified in [RFC8603], which in
   turn specifies requirements in addition to those in [RFC5280].

   Only EC-based algorithms are used.

   Issuer and subject names are composed of only the following naming
   attributes: country name, domain component, organization name,
   organizational unit name, common name, state or province name,
   distinguished name qualifier, and serial number.

   In the Subject Key Identifier extension, the keyIdentifier is the 64
   low-order bits of the subject's subjectPublicKey field.

   In the Key Usage extension, the nonRepudiation bit is never set.

6.  Non-Self-Signed Certification Authority Certificate Profile

   This section documents requirements for non-self-signed CA
   certificates in addition to those specified in [RFC8603], which in
   turn specifies requirements in addition to those in [RFC5280].

   Only EC-based algorithms are used.

   Subject names are composed of only the following naming attributes:
   country name, domain component, organization name, organizational
   unit name, common name, state or province name, distinguished name
   qualifier, and serial number.

   In the Authority Key Identifier extension, the keyIdentifier choice
   is always used.  The keyIdentifier is the 64 low-order bits of the
   issuer's subjectPublicKey field.

   In the Subject Key Identifier extension, the keyIdentifier is the 64
   low-order bits of the subject's subjectPublicKey field.

   In the Key Usage extension, the nonRepudiation bit is never set.

   The Certificate Policies extension is always included, and
   policyQualifiers are never used.

   Non-self-signed CA certificates can also include the following:

   Name Constraints:  permittedSubtrees constraints are included, and
      excludedSubstree constraints are not.  Of the GeneralName choices,
      issuers support the following: rfc822Name, dNSName,
      uniformResourceIdentifier, and iPAddress (both IPv4 and IPv6) as
      well as hardwareModuleName, which is defined in [RFC4108].  Note
      that rfc822Name, dNSName, and uniformResourceIdentifier are
      defined as IA5 strings, and the character sets allowed are not
      uniform amongst these three name forms.

   CRL Distribution Points:  A distributionPoint is always the fullName
      choice.  The uniformResourceIdentifier GeneralName choice is
      always included, but others can also be used as long as the first
      element in the sequence of CRLDistributionPoints is the
      uniformResourceIdentifier choice.  The reasons and cRLIssuer
      fields are never populated.  This extension is never marked as
      critical.

   Authority Information Access:  Only one instance of AccessDescription
      is included.  accessMethod is id-caIssuers, and accessLocation's
      GeneralName is always the uniformResourceIdentifier choice.

   Extended Key Usage:  EST servers and RAs include the id-kp-cmcRA EKU,
      and the CAs include the id-kp-cmcCA, which are both specified in
      [RFC6402].

   Issuers include the Authority Clearance Constraints extension
   [RFC5913] in non-self-signed CA certificates that are issued to non-
   SOAs; values for the Certificate Policy (CP) Object Identifier (OID)
   and the supported classList values are found in the issuer's CP.
   Criticality is determined by the issuer, and a securityCategories is
   never included.  Only one instance of Clearance is generated in the
   AuthorityClearanceConstraints sequence.

   Issuers include a critical CMS Content Constraints extension
   [RFC6010] in CA certificates used to issue SOA certificates; this is
   necessary to enable enforcement of scope of the SOA authority.  The
   content types included depend on the packages the SOA sources but
   include key packages (i.e., Encrypted Key Packages, Symmetric Key
   Packages, and Asymmetric Key Packages).

7.  End-Entity Certificate Profile

   This section documents requirements for EE signature and key
   establishment certificates in addition to those listed in [RFC8603],
   which in turn specifies requirements in addition to those in
   [RFC5280].

   Only EC-based algorithms are used.

   Subject names are composed of the following naming attributes:
   country name, domain component, organization name, organizational
   unit name, common name, state or province name, distinguished name
   qualifier, and serial number.

   In the Authority Key Identifier extension, the keyIdentifier choice
   is always used.  The keyIdentifier is the 64 low-order bits of the
   issuer's subjectPublicKey field.

   In the Subject Key Identifier extension, the keyIdentifier is the 64
   low-order bits of the subject's subjectPublicKey field.

   In the Key Usage extension, signature certificates only assert
   digitalSignature, and key establishment certificates only assert
   keyAgreement.

   The Certificate Policies extension is always included, and
   policyQualifiers are never used.

   When included, the non-critical CRL Distribution Point extension's
   distributionPoint is always identified by the fullName choice.  The
   uniformResourceIdentifier GeneralName choice is always included, but
   others can also be used as long as the first element in the sequence
   of distribution points is the URI choice and it is an HTTP/HTTPS
   scheme.  The reasons and cRLIssuer fields are never populated.

   The following subsections provide additional requirements for the
   different types of EE certificates.

7.1.  Source of Authority Certificate Profile

   This section specifies the format for SOA certificates, i.e.,
   certificates issued to those entities that are authorized to create,
   digitally sign, encrypt, and distribute packages; these certificates
   are issued by non-PKI TAs.

   The Subject Alternative Name extension is always included.  The
   following choices are supported: rfc822Name, dNSName, ediPartyName,
   uniformResourceIdentifier, or iPAddress (both IPv4 and IPv6).  This
   extension is never critical.

   A critical CMS Content Constraints extension [RFC6010] is included in
   SOA signature certificates.  The content types included depend on the
   packages the SOA sources (e.g., Encrypted Key Packages, Symmetric Key
   Packages, and Asymmetric Key Packages).

7.2.  Client Certificate Profile

   This section specifies the format for certificates issued to clients.

   A non-critical Subject Directory Attributes extension is always
   included with the following attributes:

   *  Device Owner [RFC5916]

   *  Clearance Sponsor [RFC5917]

   *  Clearance [RFC5913]

   The following extensions are also included at the discretion of the
   CA:

   *  The Authority Information Access extension with only one instance
      of AccessDescription included. accessMethod is id-caIssuers, and
      accessLocation's GeneralName is always the
      uniformResourceIdentifier choice.

   *  A non-critical Subject Alternative Name extension that includes
      the hardwareModuleName form [RFC4108], rfc822Name, or
      uniformResourceIdentifier.

   *  A critical Subject Alternative Name extension that includes
      dNSName, rfc822Name, ediPartyName, uniformResourceIdentifier, or
      iPAddress (both IPv4 and IPv6).

8.  Relying Party Applications

   This section documents requirements for Relying Parties (RPs) in
   addition to those listed in [RFC8603], which in turn specifies
   requirements in addition to those in [RFC5280].

   Only EC-based algorithms are used.

   RPs support the Authority Key Identifier and the Subject Key
   Identifier extensions.

   RPs should support the following extensions: CRL Distribution Points,
   Authority Information Access, Subject Directory Attribute, Authority
   Clearance Constraints, and CMS Content Constraints.

   Within the Subject Directory Attribute extension, RPs should support
   the Clearance Sponsor, Clearance, and Device Owner attributes.

   RPs support the id-kp-cmcRA and id-kp-cmcCA EKUs.

   Failure to support extensions in this section might limit the
   suitability of a device for certain applications.

9.  CRL Profile

   This section documents requirements for CRLs in addition to those
   listed in [RFC8603], which in turn specifies requirements in addition
   to those in [RFC5280].

   Only EC-based algorithms are used.

   Two types of CRLs are produced: complete base CRLs and partitioned
   base CRLs.

   crlEntryExtensions are never included, and the reasons and cRLIssuer
   fields are never populated.

   All CRLs include the following CRL extensions:

   *  The Authority Key Identifier extension: The keyIdentifier is the
      64 low-order bits of the issuer's subjectPublicKey field.

   *  As per [RFC5280], the CRL Number extension.

   The only other extension included in partitioned base CRLs is the
   Issuing Distribution Point extension.  The distributionPoint is
   always identified by the fullName choice.  The
   uniformResourceIdentifier GeneralName choice is always included, but
   others can also be used as long as the first element in the sequence
   of distribution points is the uniformResourceIdentifier choice and
   the scheme is an HTTP/HTTPS scheme.  All other fields are omitted.

10.  IANA Considerations

   This document has no IANA actions.

11.  Security Considerations

   This entire document is about security.  This document profiles the
   use of many protocols and services: EST, CMC, and PKCS#10/#7/#12 as
   well as certificates, CRLs, and their extensions [RFC5280].  These
   have been cited throughout this document, and the specifications
   identified by those citations should be consulted for security
   considerations related to implemented protocols and services.

12.  References

12.1.  Normative References

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              DOI 10.17487/RFC2046, November 1996,
              <https://www.rfc-editor.org/info/rfc2046>.

   [RFC2985]  Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object
              Classes and Attribute Types Version 2.0", RFC 2985,
              DOI 10.17487/RFC2985, November 2000,
              <https://www.rfc-editor.org/info/rfc2985>.

   [RFC2986]  Nystrom, M. and B. Kaliski, "PKCS #10: Certification
              Request Syntax Specification Version 1.7", RFC 2986,
              DOI 10.17487/RFC2986, November 2000,
              <https://www.rfc-editor.org/info/rfc2986>.

   [RFC3739]  Santesson, S., Nystrom, M., and T. Polk, "Internet X.509
              Public Key Infrastructure: Qualified Certificates
              Profile", RFC 3739, DOI 10.17487/RFC3739, March 2004,
              <https://www.rfc-editor.org/info/rfc3739>.

   [RFC4108]  Housley, R., "Using Cryptographic Message Syntax (CMS) to
              Protect Firmware Packages", RFC 4108,
              DOI 10.17487/RFC4108, August 2005,
              <https://www.rfc-editor.org/info/rfc4108>.

   [RFC5274]  Schaad, J. and M. Myers, "Certificate Management Messages
              over CMS (CMC): Compliance Requirements", RFC 5274,
              DOI 10.17487/RFC5274, June 2008,
              <https://www.rfc-editor.org/info/rfc5274>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/info/rfc5280>.

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,
              <https://www.rfc-editor.org/info/rfc5652>.

   [RFC5911]  Hoffman, P. and J. Schaad, "New ASN.1 Modules for
              Cryptographic Message Syntax (CMS) and S/MIME", RFC 5911,
              DOI 10.17487/RFC5911, June 2010,
              <https://www.rfc-editor.org/info/rfc5911>.

   [RFC5912]  Hoffman, P. and J. Schaad, "New ASN.1 Modules for the
              Public Key Infrastructure Using X.509 (PKIX)", RFC 5912,
              DOI 10.17487/RFC5912, June 2010,
              <https://www.rfc-editor.org/info/rfc5912>.

   [RFC5913]  Turner, S. and S. Chokhani, "Clearance Attribute and
              Authority Clearance Constraints Certificate Extension",
              RFC 5913, DOI 10.17487/RFC5913, June 2010,
              <https://www.rfc-editor.org/info/rfc5913>.

   [RFC5915]  Turner, S. and D. Brown, "Elliptic Curve Private Key
              Structure", RFC 5915, DOI 10.17487/RFC5915, June 2010,
              <https://www.rfc-editor.org/info/rfc5915>.

   [RFC5916]  Turner, S., "Device Owner Attribute", RFC 5916,
              DOI 10.17487/RFC5916, June 2010,
              <https://www.rfc-editor.org/info/rfc5916>.

   [RFC5917]  Turner, S., "Clearance Sponsor Attribute", RFC 5917,
              DOI 10.17487/RFC5917, June 2010,
              <https://www.rfc-editor.org/info/rfc5917>.

   [RFC5958]  Turner, S., "Asymmetric Key Packages", RFC 5958,
              DOI 10.17487/RFC5958, August 2010,
              <https://www.rfc-editor.org/info/rfc5958>.

   [RFC5959]  Turner, S., "Algorithms for Asymmetric Key Package Content
              Type", RFC 5959, DOI 10.17487/RFC5959, August 2010,
              <https://www.rfc-editor.org/info/rfc5959>.

   [RFC6010]  Housley, R., Ashmore, S., and C. Wallace, "Cryptographic
              Message Syntax (CMS) Content Constraints Extension",
              RFC 6010, DOI 10.17487/RFC6010, September 2010,
              <https://www.rfc-editor.org/info/rfc6010>.

   [RFC6031]  Turner, S. and R. Housley, "Cryptographic Message Syntax
              (CMS) Symmetric Key Package Content Type", RFC 6031,
              DOI 10.17487/RFC6031, December 2010,
              <https://www.rfc-editor.org/info/rfc6031>.

   [RFC6032]  Turner, S. and R. Housley, "Cryptographic Message Syntax
              (CMS) Encrypted Key Package Content Type", RFC 6032,
              DOI 10.17487/RFC6032, December 2010,
              <https://www.rfc-editor.org/info/rfc6032>.

   [RFC6033]  Turner, S., "Algorithms for Cryptographic Message Syntax
              (CMS) Encrypted Key Package Content Type", RFC 6033,
              DOI 10.17487/RFC6033, December 2010,
              <https://www.rfc-editor.org/info/rfc6033>.

   [RFC6160]  Turner, S., "Algorithms for Cryptographic Message Syntax
              (CMS) Protection of Symmetric Key Package Content Types",
              RFC 6160, DOI 10.17487/RFC6160, April 2011,
              <https://www.rfc-editor.org/info/rfc6160>.

   [RFC6161]  Turner, S., "Elliptic Curve Algorithms for Cryptographic
              Message Syntax (CMS) Encrypted Key Package Content Type",
              RFC 6161, DOI 10.17487/RFC6161, April 2011,
              <https://www.rfc-editor.org/info/rfc6161>.

   [RFC6162]  Turner, S., "Elliptic Curve Algorithms for Cryptographic
              Message Syntax (CMS) Asymmetric Key Package Content Type",
              RFC 6162, DOI 10.17487/RFC6162, April 2011,
              <https://www.rfc-editor.org/info/rfc6162>.

   [RFC6268]  Schaad, J. and S. Turner, "Additional New ASN.1 Modules
              for the Cryptographic Message Syntax (CMS) and the Public
              Key Infrastructure Using X.509 (PKIX)", RFC 6268,
              DOI 10.17487/RFC6268, July 2011,
              <https://www.rfc-editor.org/info/rfc6268>.

   [RFC6402]  Schaad, J., "Certificate Management over CMS (CMC)
              Updates", RFC 6402, DOI 10.17487/RFC6402, November 2011,
              <https://www.rfc-editor.org/info/rfc6402>.

   [RFC7030]  Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
              "Enrollment over Secure Transport", RFC 7030,
              DOI 10.17487/RFC7030, October 2013,
              <https://www.rfc-editor.org/info/rfc7030>.

   [RFC7191]  Housley, R., "Cryptographic Message Syntax (CMS) Key
              Package Receipt and Error Content Types", RFC 7191,
              DOI 10.17487/RFC7191, April 2014,
              <https://www.rfc-editor.org/info/rfc7191>.

   [RFC7192]  Turner, S., "Algorithms for Cryptographic Message Syntax
              (CMS) Key Package Receipt and Error Content Types",
              RFC 7192, DOI 10.17487/RFC7192, April 2014,
              <https://www.rfc-editor.org/info/rfc7192>.

   [RFC7292]  Moriarty, K., Ed., Nystrom, M., Parkinson, S., Rusch, A.,
              and M. Scott, "PKCS #12: Personal Information Exchange
              Syntax v1.1", RFC 7292, DOI 10.17487/RFC7292, July 2014,
              <https://www.rfc-editor.org/info/rfc7292>.

   [RFC7906]  Timmel, P., Housley, R., and S. Turner, "NSA's
              Cryptographic Message Syntax (CMS) Key Management
              Attributes", RFC 7906, DOI 10.17487/RFC7906, June 2016,
              <https://www.rfc-editor.org/info/rfc7906>.

   [RFC8295]  Turner, S., "EST (Enrollment over Secure Transport)
              Extensions", RFC 8295, DOI 10.17487/RFC8295, January 2018,
              <https://www.rfc-editor.org/info/rfc8295>.

   [RFC8603]  Jenkins, M. and L. Zieglar, "Commercial National Security
              Algorithm (CNSA) Suite Certificate and Certificate
              Revocation List (CRL) Profile", RFC 8603,
              DOI 10.17487/RFC8603, May 2019,
              <https://www.rfc-editor.org/info/rfc8603>.

   [RFC8755]  Jenkins, M., "Using Commercial National Security Algorithm
              Suite Algorithms in Secure/Multipurpose Internet Mail
              Extensions", RFC 8755, DOI 10.17487/RFC8755, March 2020,
              <https://www.rfc-editor.org/info/rfc8755>.

   [RFC8756]  Jenkins, M. and L. Zieglar, "Commercial National Security
              Algorithm (CNSA) Suite Profile of Certificate Management
              over CMS", RFC 8756, DOI 10.17487/RFC8756, March 2020,
              <https://www.rfc-editor.org/info/rfc8756>.

   [RFC9151]  Cooley, D., "Commercial National Security Algorithm (CNSA)
              Suite Profile for TLS and DTLS 1.2 and 1.3", RFC 9151,
              DOI 10.17487/RFC9151, April 2022,
              <https://www.rfc-editor.org/info/rfc9151>.

   [SP-800-59]
              National Institute of Standards and Technology, "Guideline
              for Identifying an Information System as a National
              Security System", DOI 10.6028/NIST.SP.800-59, NIST Special
              Publication 800-59, August 2003,
              <https://csrc.nist.gov/publications/detail/sp/800-59/
              final>.

   [XML]      Bray, T., Paoli, J., Sperberg-McQueen, C.M., Maler, E.,
              and F. Yergeau, "Extensible Markup Language (XML) 1.0
              (Fifth Edition)", World Wide Web Consortium
              Recommendation REC-xml-20081126, November 2008,
              <https://www.w3.org/TR/2008/REC-xml-20081126/>.

12.2.  Informative References

   [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>.

   [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>.

Authors' Addresses

   Michael Jenkins
   National Security Agency
   Email: mjjenki@cyber.nsa.gov


   Sean Turner
   sn3rd
   Email: sean@sn3rd.com