Internet-Draft CoTS June 2023
Wallace, et al. Expires 7 December 2023 [Page]
Workgroup:
Remote ATtestation ProcedureS
Internet-Draft:
draft-ietf-rats-concise-ta-stores-01
Published:
Intended Status:
Standards Track
Expires:
Authors:
C. Wallace
Red Hound Software
R. Housley
Vigil Security, LLC
T. Fossati
arm
Y. Deshpande
arm

Concise TA Stores (CoTS)

Abstract

Trust anchor (TA) stores may be used for several purposes in the Remote Attestation Procedures (RATS) architecture including verifying endorsements, reference values, digital letters of approval, attestations, or public key certificates. This document describes a Concise Reference Integrity Manifest (CoRIM) extension that may be used to convey optionally constrained trust anchor stores containing optionally constrained trust anchors in support of these purposes.

About This Document

This note is to be removed before publishing as an RFC.

Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ietf-rats-concise-ta-stores/.

Discussion of this document takes place on the rats Working Group mailing list (mailto:rats@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/rats/. Subscribe at https://www.ietf.org/mailman/listinfo/rats/.

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 7 December 2023.

1. Introduction

The RATS architecture [RFC9334] uses the definition of a trust anchor from [RFC6024]: "A trust anchor represents an authoritative entity via a public key and associated data. The public key is used to verify digital signatures, and the associated data is used to constrain the types of information for which the trust anchor is authoritative." In the context of RATS, a trust anchor may be a public key or a symmetric key. This document focuses on trust anchors that are represented as public keys.

The Concise Reference Integrity Manifest (CoRIM) [I-D.draft-ietf-rats-corim] specification defines a binary encoding for reference values using the Concise Binary Object Representation (CBOR) [RFC8949]. Amongst other information, a CoRIM may include key material for use in verifying evidence from an attesting environment (see section 3.11 in [I-D.draft-ietf-rats-corim]). The extension in this document aims to enable public key material to be decoupled from reference data for several reasons, described below.

Trust anchor (TA) and certification authority (CA) public keys may be less dynamic than the reference data that comprises much of a reference integrity manifest (RIM). For example, TA and CA lifetimes are typically fairly long while software versions change frequently. Conveying keys less frequently and indepedent from reference data enables a reduction in size of RIMs used to convey dynamic information and may result in a reduction in the size of aggregated data transferred to a verifier. CoRIMs themselves are signed and some means of conveying CoRIM verification keys is required, though ultimately some out-of-band mechanism is required at least for bootstrapping purposes. Relying parties may verify attestations from both hardware and software sources and some trust anchors may be used to verify attestations from both hardware and software sources, as well. The verification information included in a CoRIM optionally includes a trust anchor, leaving trust anchor management to other mechanisms. Additionally, the CoRIM verification-map structure is tied to CoMIDs, leaving no simple means to convey verification information for CoSWIDs [I-D.draft-ietf-sacm-coswid].

This document defines means to decouple TAs and CAs from reference data and adds support for constraining the use of trust anchors, chiefly by limiting the environments to which a set of trust anchors is applicable. This constraints mechanism is similar to that in [fido-metadata] and [fido-service] and should align with existing attestation verification practices that tend to use per-vendor trust anchors. TA store instances may be further constrained using coarse-grained purpose values or a set of finer-grained permitted or excluded claims. The trust anchor formats supported by this draft allow for per-trust anchor constraints, if desired. Conveyance of trust anchors is the primary goal, CA certificates may optionally be included for convenience.

1.1. Constraints

This document aims to support different PKI architectures including scenarios with various combinations of the following characteristics:

  • TA stores that contain a TA or set of TAs from a single organization
  • TA stores that contain a set of TAs from multiple organizations
  • TAs that issue certificates to CAs within the same organiation as the TA
  • TAs that issue certificates to CAs from multiple organizations
  • CAs that issue certificates that may be used to verify attestations or certificates from the same organization as the TA and CA
  • CAs that issue certificates that may be used to verify attestations or certificates from multiple organizations

Subsequent specifications may define extensions to express constraints as well as processing rules for evaluating constraints expressed in TA stores, TAs, CA certificates and end entity (EE) certificates. Support for constraints is intended to enable misissued certificates to be rejected at verification time. Any public key that can be used to verify a certificate is assumed to also support verification of revocation information, subject to applicable constraints defined by the revocation mechanism.

2. Conventions and Definitions

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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

3. Trust anchor management for RATS

Within RATS, trust anchors may be used to verify digital signatures for a variety of objects, including entity attestation tokens (EATs), CoRIMs, X.509 CA certificates (possibly containing endorsement information), X.509 EE certificates (possibly containing endorsement or attestation information), other attestation data, digital letters of approval [dloa], revocation information, etc. Depending on context, a raw public key may suffice or additional information may be required, such as subject name or subject public key identifier information found in an X.509 certificate. Trust anchors are usually aggregated into sets that are referred to as "trust anchor stores". Different trust anchor stores may serve different functional purposes.

Historically, trust anchors and trust anchor stores are not constrained other than by the context(s) in which a trust anchor store is used. The path validation algorithm in [RFC5280] only lists name, public key, public key algorithm and public key parameters as the elements of "trust anchor information". However, there are environments that do constrain trust anchor usage. The RPKI uses extensions from trust anchor certificates as defined in [RFC3779]. FIDO provides a type of constraint by grouping attestation verification root certificates by authenticator model in [fido-metadata].

This document aims to support each of these types of models by allowing constrained or unconstrained trust anchors to be grouped by abstract purpose, i.e., similar to traditional trust anchor stores, or grouped by a set of constraints, such as vendor name.

3.1. TA and CA conveyance

An unsigned concise TA stores object is a list of one or more TA stores, each represented below as a concise-ta-store-map element.

concise-ta-stores
  concise-ta-store-map #1
  ...
  concise-ta-store-map #n

Each TA store instance identifies a target environment and features one or more public keys. Optional constraints on usage may be defined as well.

concise-ta-store-map
  language
  store-identity
  target environment
  abstract coarse-grained constraints on TA store usage
  concrete fine-grained constraints on TA store usage
  public keys (possibly included per-instance constraints)

The following sections define the structures to support the concepts shown above.

3.1.1. The concise-ta-stores Container

The concise-ta-stores type is the root element for distrbuting sets of trust anchor stores. It contains one or more concise-ta-store-map elements where each element in the list identifies the environments for which a given set of trust anchors is applicable, along with any constraints.

concise-ta-stores = [+ concise-ta-store]

The $concise-tag-type-choice [I-D.draft-ietf-rats-corim] is extended to include the concise-ta-stores structure. As shown in Section 4 of [I-D.draft-ietf-rats-corim], the $concise-tag-type-choice type is used within the unsigned-corim-map structure, which is used within COSE-Sign1-corim structure. The COSE-Sign1-corim provides for integrity of the CoTS data. CoTS structures are not intended for use as stand-alone, unsigned structures. The signature on a CoTS instance SHOULD be verified using a TA associated with the cots purpose (Section 3.3.1).

$concise-tag-type-choice /= #6.TBD(bytes .cbor concise-ta-stores)

3.1.2. The concise-ta-store-map Container

A concise-ta-store-map is a trust anchor store where the applicability of the store is established by the tastore.environment field with optional constraints on use of trust anchors found in the tastore.keys field defined by the tastore.purpose, tastore.perm_claims and tastore.excl_claims fields.

concise-ta-store-map = {
 ? tastore.language => language-type
 ? tastore.store-identity => tag-identity-map
 tastore.environments => environment-group-list
 ? tastore.purposes => [+ $$tas-list-purpose]
 ? tastore.perm_claims => [+ $$claims-set-claims]
 ? tastore.excl_claims => [+ $$claims-set-claims]
 tastore.keys => cas-and-tas-map
}

; concise-ta-store-map indices
tastore.language = 0
tastore.store-identity = 1
tastore.environment = 2
tastore.purpose = 3
tastore.perm_claims = 4
tastore.excl_claims = 5
tastore.keys = 6

The following describes each member of the concise-ta-store-map.

tastore.language:

A textual language tag that conforms with the IANA Language Subtag Registry [IANA.language-subtag-registry].

tastore.store-identity:

A composite identifier containing identifying attributes that enable global unique identification of a TA store instance across versions and facilitate linking from other artifacts. The tag-identity-map type is defined in [I-D.draft-ietf-rats-corim].

tastore.environment:

A list of environment definitions that limit the contexts for which the tastore.keys list is applicable. If the tastore.environment is empty, TAs in the tastore.keys list may be used for any environment.

tastore.purpose:

Contains a list of purposes (Section 3.3.1) for which the tastore.keys list may be used. When absent, TAs in the tastore.keys list may be used for any purpose. This field is simliar to the extendedKeyUsage extension defined in [RFC5280]. The initial list of purposes are: cots, corim, comid, coswid, eat, key-attestation, certificate

tastore.perm_claims:

Contains a list of claim values (Section 3.3.2) [I-D.draft-ietf-rats-eat] for which tastore.keys list MAY be used to verify. When this field is absent, TAs in the tastore.keys list MAY be used to verify any claim subject to other restrictions.

tastore.excl_claims:

Contains a list of claim values (Section 3.3.2) [I-D.draft-ietf-rats-eat] for which tastore.keys list MUST NOT be used to verify. When this field is absent, TAs in the tastore.keys list may be used to verify any claim subject to other restrictions.

tastore.keys:

Contains a list of one or more TAs and an optional list of one or more CA certificates.

The perm_claims and excl_claims constraints MAY alternatively be expressed as extensions in a TA or CA. Inclusion of support here is intended as an aid for environments that find CBOR encoding support more readily available than DER encoding support.

3.1.3. The cas-and-tas-map Container

The cas-and-tas-map container provides the means of representing trust anchors and, optionally, CA certificates.

trust-anchor = [
  format => $pkix-ta-type
  data => bstr
]

cas-and-tas-map = {
 tastore.tas => [ + trust-anchor ]
 ? tastore.cas => [ + pkix-cert-data ]
}

; cas-and-tas-map indices
tastore.tas = 0
tastore.cas = 1

; format values
$pkix-ta-type /= tastore.pkix-cert-type
$pkix-ta-type /= tastore.pkix-tainfo-type
$pkix-ta-type /= tastore.pkix-spki-type

tastore.pkix-cert-type = 0
tastore.pkix-tainfo-type = 1
tastore.pkix-spki-type = 2

; certificate type
pkix-cert-data = bstr

The tastore.tas element is used to convey one or more trust anchors and an optional set of one or more CA certificates. TAs are implicitly trusted, i.e., no verification is required prior to use. However, limitations on the use of the TA may be asserted in the corresponding concise-ta-store-map or within the TA itself. The tastore.cas field provides certificates that may be useful in the context where the corresponding concise-ta-store-map is used. These certificates are not implicitly trusted and MUST be validated to a trust anchor before use. End entity certificates SHOULD NOT appear in the tastore.cas list.

The structure of the data contained in the data field of a trust-anchor is indicated by the format field. The pkix-cert-type is used to represent a binary, DER-encoded X.509 Certificate as defined in Section 4.1 of [RFC5280]. The pkix-key-type is used to represent a binary, DER-encoded SubjectPublicKeyInfo as defined in Section 4.1 of [RFC5280]. The pkix-tainfo-type is used to represent a binary, DER-encoded TrustAnchorInfo as defined in Section 2 of [RFC5914].

The $pkix-ta-type provides an extensible means for representing trust anchor information. It is defined here as supporting the pkix-cert-type, pkix-spki-type or pkix-tainfo-type. The pkix-spki-type may be used where only a raw pubilc key is necessary. The pkix-cert-type may be used for most purposes, including scenarios where a raw public key is sufficient and those where additional information from a certificate is required. The pkix-tainfo-type is included to support scenarios where constraints information is directly associated with a public key or certificate (vs. constraints for a TA set as provided by tastore.purpose, tastore.perm_claims and tastore.excl_claims).

The pkix-cert-data type is used to represent a binary, DER-encoded X.509 Certificate.

3.2. Environment definition

3.2.1. The environment-group-list Array

In CoRIM, "composite devices or systems are represented by a collection of Concise Module Identifiers (CoMID) and Concise Software Identifiers (CoSWID)". For trust anchor management purposes, targeting specific devices or systems may be too granular. For example, a trust anchor or set of trust anchors may apply to multiple device models or versions. The environment-map definition as used in a CoRIM is tightly bound to a CoMID. To allow for distribution of key material applicable to a specific or range of devices or software, the envrionment-group-list and environment-group-map are defined as below. These aim to enable use of coarse-grained naturally occurring values, like vendor, make, model, etc. to determine if a set of trust anchors is applicable to an environment.

environment-group-list = [* environment-group-list-map]

environment-group-list-map = {
  ? tastore.environment_map => environment-map,
  ? tastore.concise_swid_tag => abbreviated-swid-tag,
  ? tastore.named_ta_store => named-ta-store,
}

; environment-group-list-map indices
tastore.environment_map = 0
tastore.abbreviated_swid_tag = 1
tastore.named_ta_store = 2

An environment-group-list is a list of one or more environment-group-list-map elements that are used to determine if a given context is applicable. An empty list signifies all contexts SHOULD be considered as applicable.

An environment-group-list-map is one of environment-map [I-D.draft-ietf-rats-corim], abbreviated-swid-tag-map (Section 3.2.2) or named-ta-store (Section 3.2.3).

As defined in [I-D.draft-ietf-rats-corim], an envirionment-map may contain class-map, $instance-id-type-choice, $group-id-type-choice.

QUESTION: Should the above dispense with environment-map and concise-swid-tag and use or define some identity-focused structure with information common to both (possibly class-map from [I-D.draft-ietf-rats-corim])? If not, should a more complete CoMID representation be used (instead of environment-map)?

3.2.2. The abbreviated-swid-tag-map Container

The abbreviated-swid-tag-map allows for expression of fields from a concise-swid-tag [I-D.draft-ietf-sacm-coswid] with all fields except entity designated as optional, compared to the concise-swid-tag definition that requires tag-id, tag-version and software-name to be present.

abbreviated-swid-tag-map = {
  ? tag-id => text / bstr .size 16,
  ? tag-version => integer,
  ? corpus => bool,
  ? patch => bool,
  ? supplemental => bool,
  ? software-name => text,
  ? software-version => text,
  ? version-scheme => $version-scheme,
  ? media => text,
  ? software-meta => one-or-more<software-meta-entry>,
  entity => one-or-more<entity-entry>,
  ? link => one-or-more<link-entry>,
  ? payload-or-evidence,
  * $$coswid-extension,
  global-attributes,
}

3.2.3. The named-ta-store Type

This specification allows for defining sets of trust anchors that are associated with an arbitrary name instead of relative to information typically expressed in a CoMID or CoSWID. Relying parties MUST be configured using the named-ta-store value to select a corresponding concise-ta-store-map for use.

named-ta-store = tstr

3.3. Constraints definition

3.3.1. The $$tas-list-purpose Type

The $$tas-list-purpose type provides an extensible means of expressions actions for which the corresponding keys are applicable. For example, trust anchors in a concise-ta-store-map with purpose field set to eat may not be used to verify certification paths. Extended key usage values corresponding to each purpose listed below (except for certificate) are defined in a companion specification.

$$tas-list-purpose /= "cots"
$$tas-list-purpose /= "corim"
$$tas-list-purpose /= "coswid"
$$tas-list-purpose /= "eat"
$$tas-list-purpose /= "key-attestation"
$$tas-list-purpose /= "certificate"
$$tas-list-purpose /= "dloa"

TODO: Define verification targets for each purpose.

QUESTION: Should this have a registry?

3.3.2. Claims

A concise-ta-store-map may include lists of permitted and/or excluded claims [I-D.draft-ietf-rats-eat] that limit the applicability of trust anchors present in a cas-and-tas-map. A subsequent specification will define processing rules for evaluating constraints expressed in TA stores, TAs, CA certificates and end entity certificates.

3.4. Processing a concise-ta-stores RIM

When verifying a signature using a public key that chains back to a concise-ta-stores instance, elements in the concise-ta-stores array are processed beginning with the first element and proceeding until either a matching set is found that serves the desired purpose or no more elements are available. Each element is evaluated relative to the context, i.e., environment, purpose, artifact contents, etc.

For example, when verifying a CoRIM, each element in a triples-group MUST have an environment value that matches an environment-group-list-map element associated with the concise-ta-store-map containing the trust anchor used to verify the CoMID. Similarly, when verifying a CoSWID, the values in a abbreviated-swid-tag element from the concise-ta-store-map MUST match the CoSWID tag being verified. When verifying a certificate with DICE attestation extension, the information in each DiceTcbInfo element MUST be consistent with an environment-group-list-map associated with the concise-ta-store-map.

3.5. Verifying a concise-ta-stores RIM

[I-D.draft-ietf-rats-corim] defers verification rules to [RFC8152] and this document follows suit with the additional recommendation that the public key used to verify the RIM SHOULD be present in or chain to a public key present in a concise-ta-store-map with purpose set to cots.

4. CDDL definitions

The CDDL definitions present in this document are provided below. Definitions from [I-D.draft-ietf-rats-corim] are not repeated here.

concise-ta-stores = [+ concise-ta-store-map]
$concise-tag-type-choice /= #6.TBD(bytes .cbor concise-ta-stores)

concise-ta-store-map = {
 ? tastore.language => language-type
 ? tastore.store-identity => tag-identity-map
 tastore.environments => environment-group-list
 ? tastore.purposes => [+ $$tas-list-purpose]
 ? tastore.perm_claims => [+ $$claims-set-claims]
 ? tastore.excl_claims => [+ $$claims-set-claims]
 tastore.keys => cas-and-tas-map
}

; concise-ta-store-map indices
tastore.language = 0
tastore.store-identity = 1
tastore.environment = 2
tastore.purpose = 3
tastore.perm_claims = 4
tastore.excl_claims = 5
tastore.keys = 6

trust-anchor = [
  format => $pkix-ta-type
  data => bstr
]

cas-and-tas-map = {
 tastore.tas => [ + trust-anchor ]
 ? tastore.cas => [ + pkix-cert-type ]
}

; cas-and-tas-map indices
tastore.tas = 0
tastore.cas = 1

; format values
$pkix-ta-type /= tastore.pkix-cert-type
$pkix-ta-type /= tastore.pkix-tainfo-type
$pkix-ta-type /= tastore.pkix-spki-type

tastore.pkix-cert-type = 0
tastore.pkix-tainfo-type = 1
tastore.pkix-spki-type = 2

; certificate type
pkix-cert-data = bstr

environment-group-list = [* environment-group-list-map]

environment-group-list-map = {
  ? environment-map => environment-map,
  ? concise-swid-tag => abbreviated-swid-tag,
  ? named-ta-store => named-ta-store,
}

abbreviated-swid-tag = {
  ? tag-version => integer,
  ? corpus => bool,
  ? patch => bool,
  ? supplemental => bool,
  ? software-name => text,
  ? software-version => text,
  ? version-scheme => $version-scheme,
  ? media => text,
  ? software-meta => one-or-more<software-meta-entry>,
  ? entity => one-or-more<entity-entry>,
  ? link => one-or-more<link-entry>,
  ? payload-or-evidence,
  * $$coswid-extension,
  global-attributes,
}

named-ta-store = tstr

$tas-list-purpose /= "cots"
$tas-list-purpose /= "corim"
$tas-list-purpose /= "comid"
$tas-list-purpose /= "coswid"
$tas-list-purpose /= "eat"
$tas-list-purpose /= "key-attestation"
$tas-list-purpose /= "certificate"
$tas-list-purpose /= "dloa"

5. Examples

The following examples are isolated concise-ta-store-map instances shown as JSON for ease of reading. The final example is an ASCII hex representation of a CBOR-encoded concise-ta-stores instance containing each example below (and using a placeholder value for the concise-ta-stores tag).

The TA store below contains a TA from a single organization ("Zesty Hands, Inc,") that is used to verify CoRIMs for that organization. Because this TA does not verify certificates, a bare public key is appropriate. It features a tag identity field containing a UUID for the tag identity and a version indication.

{
  "tag-identity": {
    "id": "ab0f44b1-bfdc-4604-ab4a-30f80407ebcc",
    "version": 5
  },
  "environments": [
    {
      "environment": {
        "class": {
          "vendor": "Worthless Sea, Inc."
        }
      }
    }
  ],
  "keys": {
    "tas": [
      {
        "format": 2,
        "data":
"MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAErYoMAdqe2gJT3CvCcifZxyE9+
N8T6Jy5zbeo5LYtnOipmi1wXA9/gNtlwAbRCRQitH/GEcvUaGlzPZxIOITV/g=="
      }
    ]
  }
}

The TA store below features three TAs from different organizations grouped as a TA store with the name "Miscellaneous TA Store". The first TA is an X.509 certificate. The second and third TAs are TrustAnchorInfo objects containing X.509 certificates. Though not shown in this example, constraints could be added to the TrustAnchorInfo elements, i.e., to restrict verification to attestations asserting a specific vendor name. It features a tag identity field containing a string as the tag identity with no version field present.

{
  "tag-identity": {
    "id": "some_tag_identity"
  },
  "environments": [
    {
      "namedtastore": "Miscellaneous TA Store"
    }
  ],
  "keys": {
    "tas": [
      {
        "format": 0,
        "data":
        "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="
      },
      {
        "format": 1,
        "data":
        "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="
      },
      {
        "format": 1,
        "data":
        "
ooIC1TCCAtEwWTATBgcqhkjOPQIBBggqhkjOPQMBBwNCAATN0f5kzywEzZOYbaV23O3
N8cku39JoLNjlHPwECbXDDWp0LpAO1z248/hoy6UW/TZMTPPR/93XwHsG16mSFy8XBB
SKhM/5gJWjvDbW7qUY1peNm9cfYDCCAlwwXDELMAkGA1UEBgwCVVMxHzAdBgNVBAoMF
lNub2JiaXNoIEFwcGFyZWwsIEluYy4xLDAqBgNVBAMMI1Nub2JiaXNoIEFwcGFyZWws
IEluYy4gVHJ1c3QgQW5jaG9yoIIB+jCCAZ+gAwIBAgIUEBuTRGXAEEVEHhu4xafAnqm
+qYgwCgYIKoZIzj0EAwIwXDELMAkGA1UEBgwCVVMxHzAdBgNVBAoMFlNub2JiaXNoIE
FwcGFyZWwsIEluYy4xLDAqBgNVBAMMI1Nub2JiaXNoIEFwcGFyZWwsIEluYy4gVHJ1c
3QgQW5jaG9yMB4XDTIyMDUxOTE1MTMwOFoXDTMyMDUxNjE1MTMwOFowXDELMAkGA1UE
BgwCVVMxHzAdBgNVBAoMFlNub2JiaXNoIEFwcGFyZWwsIEluYy4xLDAqBgNVBAMMI1N
ub2JiaXNoIEFwcGFyZWwsIEluYy4gVHJ1c3QgQW5jaG9yMFkwEwYHKoZIzj0CAQYIKo
ZIzj0DAQcDQgAEzdH+ZM8sBM2TmG2ldtztzfHJLt/SaCzY5Rz8BAm1ww1qdC6QDtc9u
PP4aMulFv02TEzz0f/d18B7BtepkhcvF6M/MD0wHQYDVR0OBBYEFIqEz/mAlaO8Ntbu
pRjWl42b1x9gMAsGA1UdDwQEAwIChDAPBgNVHRMBAf8EBTADAQH/MAoGCCqGSM49BAM
CA0kAMEYCIQC2cf43f3PPlCO6/dxv40ftIgxxToKHF72UzENv7+y4ygIhAIGtC/r6SG
aFMaP7zD2EloBuIXTtyWu8Hwl+YGdXRY93"
      }
    ]
  }
}

The TA Store below features one TA with an environment targeting CoSWIDs with entity named "Zesty Hands, Inc," and one permitted EAT claim for software named "Bitter Paper".

{
  "environments": [
    {
      "swidtag": {
        "entity": [
          {
            "entity-name": "Zesty Hands, Inc.",
            "role": "softwareCreator"
          }
        ]
      }
    }
  ],
  "permclaims": [
    {
      "swname": "Bitter Paper"
    }
  ],
  "keys": {
    "tas": [
      {
        "format": 0,
        "data":
        "
MIIB5TCCAYugAwIBAgIUC9xKoFF5UD5Y8nXVUkZzR7yvtTMwCgYIKoZIzj0EAwI
wUjELMAkGA1UEBgwCVVMxGjAYBgNVBAoMEVplc3R5IEhhbmRzLCBJbmMuMScwJQ
YDVQQDDB5aZXN0eSBIYW5kcywgSW5jLiBUcnVzdCBBbmNob3IwHhcNMjIwNTE5M
TUxMzA3WhcNMzIwNTE2MTUxMzA3WjBSMQswCQYDVQQGDAJVUzEaMBgGA1UECgwR
WmVzdHkgSGFuZHMsIEluYy4xJzAlBgNVBAMMHlplc3R5IEhhbmRzLCBJbmMuIFR
ydXN0IEFuY2hvcjBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABJfPbXDXajBADH
nx66tq1haIcSSHENT0wSB62u8C0ZhnE2eR8sKyn28tzDwhJcLy0v3uT1kJS2evQ
zMvDftcpECjPzA9MB0GA1UdDgQWBBT22tHlEou/DenpU0Ozccb3/+fibjALBgNV
HQ8EBAMCAoQwDwYDVR0TAQH/BAUwAwEB/zAKBggqhkjOPQQDAgNIADBFAiAdpYv
n+kQsbNhJ7zVnIkqSA8IlFYlmshr9QPMZLPNHmAIhAJgns+Chq6JRSjmU+m76n9
bGELiQX77ZP8tSUHVL6KpY"
      }
    ]
  }
}

The dump below shows the COSE-Sign1-corim contents from the ASCII hex above. A full base64-encoded version of this example is given in Appendix A

18([h'
A3012603746170706C69636174696F6E2F72696D2B63626F72085841A200A20
07441434D45204C7464207369676E696E67206B657901D8207468747470733A
2F2F61636D652E6578616D706C6501A200C11A61CE480001C11A69546780',
{},
h'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',
h'
19E82D7A5C7A73B44F06305AECF0EF8CF8764286323F6D2BA27D7291F92FF5B
0CF789F6FF88B7E2EE8EF262B4FA1DFD7D7AFB0AE2C0062C98DB332243B3E99
94'])

6. Security Considerations

As a profile of CoRIM, the security considerations from [I-D.draft-ietf-rats-corim] apply.

As a means of managing trust anchors, the security considerations from [RFC6024] and [RFC5934] apply. a CoTS signer is roughly analogous to a "management trust anchor" as described in [RFC5934].

7. IANA Considerations

7.1. CoRIM CBOR Tag Registration

IANA is requested to allocate tags in the "CBOR Tags" registry [IANA.cbor-tags], preferably with the specific value requested:

Table 1
Tag Data Item Semantics
507 tagged array Concise Trust Anchor Stores (CoTS)

8. References

8.1. Normative References

[I-D.draft-ietf-rats-corim]
Birkholz, H., Fossati, T., Deshpande, Y., Smith, N., and W. Pan, "Concise Reference Integrity Manifest", Work in Progress, Internet-Draft, draft-ietf-rats-corim-01, , <https://datatracker.ietf.org/doc/html/draft-ietf-rats-corim-01>.
[I-D.draft-ietf-rats-eat]
Lundblade, L., Mandyam, G., O'Donoghue, J., and C. Wallace, "The Entity Attestation Token (EAT)", Work in Progress, Internet-Draft, draft-ietf-rats-eat-19, , <https://datatracker.ietf.org/doc/html/draft-ietf-rats-eat-19>.
[I-D.draft-ietf-sacm-coswid]
Birkholz, H., Fitzgerald-McKay, J., Schmidt, C., and D. Waltermire, "Concise Software Identification Tags", Work in Progress, Internet-Draft, draft-ietf-sacm-coswid-24, , <https://datatracker.ietf.org/doc/html/draft-ietf-sacm-coswid-24>.
[IANA.cbor-tags]
IANA, "Concise Binary Object Representation (CBOR) Tags", <https://www.iana.org/assignments/cbor-tags>.
[IANA.language-subtag-registry]
IANA, "Language Subtag Registry", <https://www.iana.org/assignments/language-subtag-registry>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/rfc/rfc2119>.
[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, , <https://www.rfc-editor.org/rfc/rfc5280>.
[RFC5914]
Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor Format", RFC 5914, DOI 10.17487/RFC5914, , <https://www.rfc-editor.org/rfc/rfc5914>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8949]
Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", STD 94, RFC 8949, DOI 10.17487/RFC8949, , <https://www.rfc-editor.org/rfc/rfc8949>.

8.2. Informative References

[dloa]
GlobalPlatform, "GlobalPlatform Card - Digital Letter of Approval Version 1.0", , <https://globalplatform.org/wp-content/uploads/2015/12/GPC_DigitalLetterOfApproval_v1.0.pdf>.
[fido-metadata]
FIDO Alliance, "FIDO Metadata Statement", , <https://fidoalliance.org/specs/mds/fido-metadata-statement-v3.0-ps-20210518.html>.
[fido-service]
FIDO Alliance, "FIDO Metadata Service", , <https://fidoalliance.org/specs/mds/fido-metadata-service-v3.0-ps-20210518.html>.
[RFC3779]
Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP Addresses and AS Identifiers", RFC 3779, DOI 10.17487/RFC3779, , <https://www.rfc-editor.org/rfc/rfc3779>.
[RFC5934]
Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor Management Protocol (TAMP)", RFC 5934, DOI 10.17487/RFC5934, , <https://www.rfc-editor.org/rfc/rfc5934>.
[RFC6024]
Reddy, R. and C. Wallace, "Trust Anchor Management Requirements", RFC 6024, DOI 10.17487/RFC6024, , <https://www.rfc-editor.org/rfc/rfc6024>.
[RFC8152]
Schaad, J., "CBOR Object Signing and Encryption (COSE)", RFC 8152, DOI 10.17487/RFC8152, , <https://www.rfc-editor.org/rfc/rfc8152>.
[RFC9334]
Birkholz, H., Thaler, D., Richardson, M., Smith, N., and W. Pan, "Remote ATtestation procedureS (RATS) Architecture", RFC 9334, DOI 10.17487/RFC9334, , <https://www.rfc-editor.org/rfc/rfc9334>.

Appendix A. Examples Base64 Encodings

The base64 encoded data below represents a signed CoRIM that features a concise-ta-stores containing the three examples shown above.
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39fXr7CuLABiyY2zMiQ7PpmU

Acknowledgments

Thanks to Sabreen Kaur for spotting a bug in the examples.

Authors' Addresses

Carl Wallace
Red Hound Software
Russ Housley
Vigil Security, LLC
Thomas Fossati
arm
Yogesh Deshpande
arm