]> Entrust Limited

2500 Solandt Road – Suite 100 Ottawa, Ontario K2K 3G5 Canada mike.ounsworth@entrust.com

Entrust Limited

United Kingdom Richard.Kettlewell@entrust.com

Crypto4A Technologies Inc.

1550A Laperriere Ave Ottawa, Ontario K1Z 7T2 Canada jp@crypto4a.com

Siemens

Hannes.Tschofenig@gmx.net

Nokia

Bangalore Karnataka India kondtir@gmail.com

Beyond Identity

USA monty.wiseman@beyondidentity.com

Security RATS Internet-Draft This document specifies ASN.1 structures produced by an Attester as part of the remote attestation procedures and constitute Evidence. This document follows the Remote ATtestation procedureS (RATS) architecture where Evidence is sent by an Attester and processed by a Verifier.

Introduction Trusted execution environments, like secure elements and hardware security modules (HSMs), are now widely used, which provide a safe environment to place cryptographic key material and security sensitive code which uses it, such as signing and decryption services, secure boot, secure storage, and other essential security functions. These security functions are typically exposed through a narrow and well-defined interface, and can be used by operating system libraries and applications. Increasingly, parties that rely on these secure elements want evidence that the security sensitive operations are in fact being performed within a secure element. This evidence can pertain to the secure element platform itself, or to the storage and protection properties of the cryptographic keys, or both. This is generally referred to as remote attestation, and is covered by the Remote ATtestation procedureS (RATS) architecture . This document species an evidence data format specified in ASN.1 and re-using many data structures from the PKIX ASN.1 modules so to be a convenient format for secure elements and verifiers that are designed primarily for use within X.509 Public Key Infrastructures. When a Certificate Signing Request (CSR) library is requesting a certificate from a Certification Authority (CA), a PKI end entity may wish to provide Evidence of the security properties of the trusted execution environment in which the private key is stored. This Evidence is to be verified by a Relying Party, such as the Registration Authority or the Certification Authority as part of validating an incoming CSR against a given certificate policy. defines how to carry Evidence in either PKCS#10 or Certificate Request Message Format (CRMF) . is agnostic to the content and the encoding of Evidence. To offer interoperability it is necessary to define a format that is utilized in a specific deployment environment. Hardware security modules and other trusted execution environments, which have been using ASN.1-based encodings for a long time prefer the use of the same format throughout their software ecosystem. For those use cases this specification has been developed. This specification re-uses the claims defined in . While the encoding of the claims is different to what is defined in , the semantics of the claims is retained. This specification is not an EAP profile, as defined in Section 6 of This specification was designed to meet the requirements published by the CA Browser Forum to convey properties about hardware security models, such as non-exportability, which must be enabled for storing publicly-trusted code-signing keys. Hence, this specification is supposed to be used with the attestation extension for Certificate Signing Requests (CSRs), see . There are, however, other use cases where remote attestation may also be used, such as

• A Certification Authority receives a certificate signing request and wishes to verify that the subject public key was generated in an HSM (for example to satisfy CA/B Forum subscriber private key verification requirement). They may also wish to verify that the operations the HSM will allow for the corresponding private key are consistent with the purpose of the requested certificate.
• A user of a Cloud Service Provider's 'Bring Your Own Key' service wishes to transfer their locally-generated key securely to the CSP's service by encrypting it under the CSP's public key. As part of their due diligence on the CSP's key they wish to verify (1) that it was generated by an HSM and (2) may only be used to unwrap the key into an HSM (i.e. unwrap permission but not decrypt permission).
• An auditor of an identity provision service (or a competent end user) may wish to verify that keys representing end-user identities are held in an HSM and have permissions that are in line with the applicable regulations. For example, they may wish verify that the protection arrangements for assigned keys cannot be changed.
• A manufacturer needs to provision configuration info, software, and credentials to a device from remote. With the help of remote attestation the manufacturer is provided enough information to verify that information is only sent to devices it has built.

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 when, and only when, they appear in all capitals, as shown here. This document re-uses the terms defined in related to remote attestation. Readers of this document are assumed to be familiar with the following terms: Evidence, Claim, Attestation Result, Attester, Verifier, and Relying Party.

Attestation Evidence This specification defines the following Evidence format, which contains a set of claims. To protect Evidence against modification, it is protected with a digital signature. version MUST be set to 1.

Signing and Verification Procedure EDNOTE: Can we start our versions at some number to avoid versions that Crypto4A has already used?

Signing Procedure

1. The message to be signed is the TBSEvidenceStatement, including the SignatureInfo for each of the signatures to be performed.
2. Each signature is computed in parallel and placed into index of the signatureValues SEQUENCE that matches the position of the corresponding SignatureInfo in the signatureInfos sequence.

The signer MUST produce one signature per signatureInfo, it MUST NOT omit signatures and MUST NOT produce a subset of the signatures listed in signatureInfos.

Verification Procedure

1. The message to be verified is the TBSEvidenceStatement.
2. For each signatureInfo, the corresponding verification public key and signature algorithm is found according to the information contained in the SignatureInfo for that signature and any accompanying certificates or key material.
3. For each signature, the message is verified using the value from the corresponding element of the signatureValue sequence.
4. The PkixEvidenceStatement SHOULD be considered valid if and only if all signatures are valid; i.e. multiple signatures are to be treated as an AND mode. This item is a recommendation and not a hard requirement since verification policy is of course at the discretion of the Verifier.

EDNOTE: the major change here from the original Crypto4A QASM Attestation is that the original only includes the claims in the signature, whereas this includes everything, including the version, list of signature algorithms. This prevents possible attacks where those values are manipulated by attackers. We should debate whether the certificates should be protected by the signature. Pro: generally better for security to sign everything. Con: in some contexts, it may be difficult to have the certificates prior to signing, but that's ok because most evidence carrier formats also allow you to attach the signatures externally.

Claims Since no claims are marked as MANDATORY, the sequence 'claims' may be constituted of differing claims from one instance to the next. This is expected as each evidence statement may be providing information to support different use cases. Once an evidence statement is signed, the Attester is guaranteeing that all of the claims carried by the evidence statement are true. It is important to note that multiple claims in the sequence may have the same 'id'. Implementers should ensure that this case is handled by verifying logic. For ease of reading, claims have been separated into two lists: "platform claims" and "key claims".

Platform Claims

Key Claims Even though no specific claims are required, a Verifier or Relying Party MAY reject an Evidence claim if it is missing information required by the appraisal policy. For example, a Relying Party which requires a FIPS-certified device SHOULD reject Evidence if it does not contain sufficient information to determine the FIPS certification status of the device.

Device Identifier Devices assigned a Universal Entity ID compliant with RATS EAT SHOULD provide this in the Ueid or Sueid claim. Devices with a traditional human-readable serial number SHOULD provide this in the Hwserial claim. Both MAY be provided. The set {OemID, Hwmodel, Hwversion, Hwserial}, when provided, SHOULD represent a universally unique identification of the device. Where applicable, {OemID, Hwmodel, Hwversion} SHOULD match the way the device is identified in relevant endorsements, such as published FIPS or Common Criteria certificates.

ueid (Universal Entity ID) Claim The "ueid" claim conveys a UEID, which identifies an individual manufactured entity. This identifier is a globally unique and permanent identifier. See Section 4.2.1 of for a description of this claim. Three types of UEIDs are defined, which are distinguished via a type field. The ueid claim is defined as follows:

sueids (Semi-permanent UEIDs) Claim (SUEIDs) The "sueids" claim conveys one or more semi-permanent UEIDs (SUEIDs). An SUEID has the same format, characteristics and requirements as a UEID, but MAY change to a different value on entity life-cycle events while the ueid claim is permanent. An entity MAY have both a UEID and SUEIDs, neither, one or the other. There MAY be multiple SUEIDs and each has a text string label the purpose of which is to distinguish it from others. See Section 4.2.2 of for a description of this claim. The sueids claim is defined as follows:

oemid (Hardware OEM Identification) Claim The "oemid" claim identifies the Original Equipment Manufacturer (OEM) of the hardware. See Section 4.2.3 of for a description of this claim. The value of this claim depends on the type of OEMID and three types of IDs are defined:

• OEMIDs using a 128-bit random number. Section 4.2.3.1 of defines this type.
• an IEEE based OEMID using a global registry for MAC addresses and company IDs. Section 4.2.3.1 of defines this type.
• OEMIDs using Private Enterprise Numbers maintained by IANA. Section 4.2.3.3 of defines this type.

The oemid claim is defined as follows: Editor's Note: The value for the PEN is numeric. For the other two types it is a binary string.

hwmodel (Hardware Model) Claim The "hwmodel" claim differentiates hardware models, products and variants manufactured by a particular OEM, the one identified by OEM ID. It MUST be unique within a given OEM ID. The concatenation of the OEM ID and "hwmodel" give a global identifier of a particular product. The "hwmodel" claim MUST only be present if an "oemid" claim is present. See Section 4.2.4 of for a description of this claim. The hwmodel claim is defined as follows:

hwversion (Hardware Version) Claim The "hwversion" claim is a text string the format of which is set by each manufacturer. A "hwversion" claim MUST only be present if a "hwmodel" claim is present. See Section 4.2.5 of for a description of this claim. The hwversion claim is defined as follows:

Environment Identifier This claim MAY be used to identify a partition within a cryptographic device, or a logical environment that spans multiple cryptographic devices such as a Security World or a cloud tenant. The format of these identifiers will be vendor or environment specific.

Software Identifier SwName and Swversion together identify the device firmware and SHOULD match the way the firmware is identified in relevant endorsements, such as published FIPS or Common Criteria certificates.

OEM Boot

Dbgstat (Debug Status) The "dbgstat" claim applies to entity-wide or submodule-wide debug facilities and diagnostic hardware built into chips. It applies to any software debug facilities related to privileged software that allows system-wide memory inspection, tracing or modification of non-system software like user mode applications. See Section 4.2.9 of for a description of this claim and the semantic of the values in the enumerated list. The dbgstat claim is defined as follows:

Location Most HSMs will likely not know their own physical location, but cryptographic modules on mobile devices may.

Uptime The "uptime" claim contains the number of seconds that have elapsed since the entity or submodule was last booted.

Bootcount {sect-bootcount} The "bootcount" claim contains a count of the number times the entity or submodule has been booted. Support for this claim requires a persistent storage on the device.

Bootseed The "bootseed" claim contains a value created at system boot time that allows differentiation of attestation reports from different boot sessions of a particular entity (e.g., a certain UEID). This value is usually public. It is not a secret and MUST NOT be used for any purpose that a secret seed is needed, such as seeding a random number generator.

dloas (Digital Letters of Approval) The "dloas" claim conveys one or more Digital Letters of Approval (DLOAs). A DLOA is a document that describes a certification that an entity has received. Examples of certifications represented by a DLOA include those issued by Global Platform and those based on Common Criteria. The DLOA is unspecific to any particular certification type or those issued by any particular organization.

Endorsements This claim allows referencing third party endorsements; for example from the device vendor or a certification such as FIPS or Common Criteria. The content MAY be referenced by URI, or placed directly inline, but either way, the endorsement content or its URI MUST be known by the attester at the time that the evidence is generated. EDNOTE: this needs a bit of thought about what types of endorsements we will likely see, and whether OCTET STRING is the right format.

Manifests TODO -- rats-eat-4.2.15

Measurements TODO -- rats-eat-4.2.16

Measres (Software Measurement Results) TODO -- rats-eat-4.2.17

Submods (Submodules) TODO -- rats-eat-4.2.18

iat (Issuance Time) The time at which the evidence was created. Here we differ from the iat claim in rats-eat-4.3.1 in that we use the PKIX time format Time instead of the 64-bit CBOR time structure. It is recognized that many HSMs, especially if air-gapped, will not have an accurate system clock. If the system is not anticipated to have a reliable clock, then this claim SHOULD be omitted and the Nonce claim used instead.

intuse (Intended Use) Note: tags intentionally started at 1 to align with EAT. If the IANA registry of intended use claims is extended, then the this CHOICE MAY be extended using the same tag values as indicated in the EAT registry.

FipsMode The cryptographic module was booted in FIPS mode, including the required self-tests and any other requiremnts of its FIPS certificate. Note to verifiers and relying parties: "FIPS Mode" does not imply "FIPS Certified". For example, a device may have a FIPS Mode even if the device was never submitted for FIPS certification. This claim SHOULD only be taken in conjunction with a valid FIPS certification for this hardware and software version, and appraising any other claims as required by the FIPS certification.

VendorInfo This claim provides a place for vendor to place propriatary data; i.e. any proprietary data that does not fit in any other claim. Vendors must specify an OID and data type for their VendorInfo, and communicate this to verifiers who wish to parse this data.

NestedEvidences Composite devices may produce multiple signed evidence statements that need to be signed in a hiearchical manner. PkixEvidenceStatements MAY be nested.

Nonce The "nonce" claim is used to provide freshness. The Nonce claim is used to carry the challenge provided by the caller to demonstrate freshness of the generated token. The following constraints apply to the nonce-type:

• The length must be reasonable as it may be processed by end entities with limited resources. Therefore, it is RECOMMENDED that the length does not exceed 64 bytes.
• Only a single nonce value is conveyed.

The nonce claim is defined as follows: See Section 4.1 of for a description of this claim.

KeyId An identifier for the subject key. The format MAY be vendor-specific, but MUST be an ASCII value (IA5String).

PubKey The subject public key being attested by this evidence.

Purpose TODO: align with PKCS#11 Purposes

NonExportable TODO align with PKCS#11

Imported TODO align with PKCS#11

KeyExpiry If the key has a known expiry time or "not after" date.

Unrecognized claims This document does not define an exhaustive list of claims. New claims may be added in the future, including proprietary ones. As such, parsers SHOULD expect to encounter unrecognized claims, and to handle them gracefully. In general, the correct behaviour for a verifier will be to start with an appraisal policy of claims to look for, and where appropriate the expected values (for example, FipsMode: true), and any additional claims that may be in the evidence SHOULD be ignored.

Evidence Claims Certificate Extension This section specifies the syntax and semantics of the Evidence Claims certificate extension which provides a list of claims associated with the certificate subject appraised by the CA. The Evidence Claims certificate extension MAY be included in public key certificates . The Evidence Claims certificate extension MUST be identified by the following object identifier: This extension MUST NOT be marked critical. The Evidence Claims extension MUST have the following syntax: The EvidenceClaims represents an unsigned version of the evidence claims appraised by the CA. It MUST contain at least one claim. For privacy reasons, the CA MAY include only a subset of the EvidenceClaims that were presented to it, for example in an EvidenceBundle in a CSR. The CA may include in their certificate profile a list of verified evidence claims (identified by OID) that MAY be copied from the CSR to the certificate, while any other claims MUST NOT be copied. By removing the signature from the evidence, the CA is asserting that it has has verified the Evidence to chain to a root that the CA trusts, but it is not required to disclose in the final certificate what that root is. See for a discussion of privacy concerns related to re-publishing Evidence into a certificate.

ASN.1 Module This section provides an ASN.1 Module for the Evidence Claims certificate extension, and it follows the conventions established in and .

Implementation Considerations

API for requesting evidence from an attesting device While it is strictly outside the scope of this document to specify how a calling application can request evidence from a cryptographic device, two modes are suggested.

Request by ID and claim profile In this mode, the calling application request evidence about a given entity -- for example, a given EnvID or a given KeyID -- and the cryptographic device assembles a PkixEvidenceStatement containing as many claims as it is able to populate. Implementers may have named evidence profiles if it is desirable for the cryptographic device to respond with multiple different sets of claims.

Request by claim set In this mode, the calling application pre-constructs a sequence of EVIDENCE-CLAIM which is passed in to the attesting device. As a response, the attesting device returns a structure of type PkixEvidenceStatement which includes all the expected signatures. This mode is useful for attesting devices with more resources and used in situations where the supported evidence profiles may not be known during implementation. It is left to the implementer to choose the way that the desired claims are submitted to the attesting device, including which types of claims are recognized and how much information is provided by the caller. However, when using this mode: - an attesting device MUST reject the production of a PkixEvidenceStatement if any requested claim is not recognized; and, - an attesting device MUST reject the production of a PkixEvidenceStatement if any requested claim is not supported by the observed state (claim is deemed false). The use of this mode implies that the attesting device contains the logic necessary to interpret and verify the submitted claims.

Privacy Considerations

Publishing Evidence in a certificate The extension MUST NOT publish in the certificate any privacy-sensitive information that could compromise the end device. What counts as privacy-sensitive will vary by use case. For example, consider a few scenarios: First, consider a Hardware Security Module (HSM) backing a public code-signing service. The model and firmware patch level could be considered sensitive as it could give an attacker an advantage in exploiting known vulnerabilities against un-patched systems. Second, consider a certificate issued to a end-user mobile computing device, any sort of unique identifier could be used as a super-cookie for tracking purposes. Third, consider small IoT devices such as un-patchable wireless sensors. Here there may be no privacy concerns and in fact knowing exact hardware and firmware version information could help edge gateways to deny network access to devices with known vulnerabilities. Beyond that, a CA MUST have a configurable mechanism to control which information is to be copied from the provided Evidence into the certificate, for example this could be configured within a certificate profile or Certificate Practice Statement (CPS) and this must be considered on a case-by-base basis. To protect end-user privacy, CA operators should err on the side of caution and exclude information that is not clearly essential for security verification by relying parties. Avoiding unnecessary claims also mitigates the risk of targeted attacks, where an attacker could exploit knowledge of hardware versions, models, etc.

Security Considerations This specification re-uses the claims from the EAT specification and relies on the security protection offered by digital signatures. This digital signature is computed with the Attestation Key available on the device, see Section 12.1 of for considerations regarding the generation, the use and the protection of these Attestation Keys. Since the Attester located at the end entity creates the Evidence with claims defined in this document. This document inherits the remote attestation architecture described in . With the re-use of the claims from the security and privacy considerations apply also to this document even though the encoding in this specification is different from the encoding of claims discussed by . Evidence contains information that may be unique to a device and may therefore allow to single out an individual device for tracking purposes. Deployments that have privacy requirements must take appropriate measures to ensure that claim values can only identify a group of devices and that the Attestation Keys are used across a number of devices as well. To verify the Evidence, the primary need is to check the signature and the correct encoding of the claims. To produce the Attestation Result, the Verifier will use Endorsements, Reference Values, and Appraisal Policies. The policies may require that certain claims must be present and that their values match registered reference values. All claims may be worthy of additional appraisal.

IANA Considerations TBD: OIDs for all the claims listed in this document.

OIDs for Evidence Claims Certificate Extension For the EvidenceClaims certificate extension in , IANA is requested to assign an object identifier (OID) for the certificate extension. The OID for the certificate extension should be allocated in the "SMI Security for PKIX Certificate Extension" registry (1.3.6.1.5.5.7.1). For the ASN.1 Module in , IANA is requested to assign an object identifier (OID) for the module identifier. The OID for the module should be allocated in the "SMI Security for PKIX Module Identifier" registry (1.3.6.1.5.5.7.0).

References Normative References 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. In network protocol exchanges, it is often useful for one end of a communication to know whether the other end is in an intended operating state. This document provides an architectural overview of the entities involved that make such tests possible through the process of generating, conveying, and evaluating evidentiary Claims. It provides a model that is neutral toward processor architectures, the content of Claims, and protocols. 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] Security Theory LLC Mediatek USA Qualcomm Technologies Inc. Red Hound Software, Inc. An Entity Attestation Token (EAT) provides an attested claims set that describes state and characteristics of an entity, a device like a smartphone, IoT device, network equipment or such. This claims set is used by a relying party, server or service to determine the type and degree of trust placed in the entity. An EAT is either a CBOR Web Token (CWT) or JSON Web Token (JWT) with attestation-oriented claims. 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 This memo represents a republication of PKCS #10 v1.7 from RSA Laboratories' Public-Key Cryptography Standards (PKCS) series, and change control is retained within the PKCS process. The body of this document, except for the security considerations section, is taken directly from the PKCS #9 v2.0 or the PKCS #10 v1.7 document. This memo provides information for the Internet community. This document describes the Certificate Request Message Format (CRMF) syntax and semantics. This syntax is used to convey a request for a certificate to a Certification Authority (CA), possibly via a Registration Authority (RA), for the purposes of X.509 certificate production. The request will typically include a public key and the associated registration information. This document does not define a certificate request protocol. [STANDARDS-TRACK] The Public Key Infrastructure using X.509 (PKIX) certificate format, and many associated formats, are expressed using ASN.1. The current ASN.1 modules conform to the 1988 version of ASN.1. This document updates those ASN.1 modules to conform to the 2002 version of ASN.1. There are no bits-on-the-wire changes to any of the formats; this is simply a change to the syntax. This document is not an Internet Standards Track specification; it is published for informational purposes. This document describes a mechanism named "CCNinfo" that discovers information about the network topology and in-network cache in Content-Centric Networks (CCNs). CCNinfo investigates 1) the CCN routing path information per name prefix, 2) the Round-Trip Time (RTT) between the content forwarder and the consumer, and 3) the states of in-network cache per name prefix. CCNinfo is useful to understand and debug the behavior of testbed networks and other experimental deployments of CCN systems. This document is a product of the IRTF Information-Centric Networking Research Group (ICNRG). This document represents the consensus view of ICNRG and has been reviewed extensively by several members of the ICN community and the RG. The authors and RG chairs approve of the contents. The document is sponsored under the IRTF, is not issued by the IETF, and is not an IETF standard. This is an experimental protocol and the specification may change in the future. The Cryptographic Message Syntax (CMS) format, and many associated formats, are expressed using ASN.1. The current ASN.1 modules conform to the 1988 version of ASN.1. This document updates some auxiliary ASN.1 modules to conform to the 2008 version of ASN.1; the 1988 ASN.1 modules remain the normative version. There are no bits- on-the-wire changes to any of the formats; this is simply a change to the syntax. This document is not an Internet Standards Track specification; it is published for informational purposes. Entrust Limited Siemens Fraunhofer SIT Beyond Identity Intel Corporation A PKI end entity requesting a certificate from a Certification Authority (CA) may wish to offer trustworthy claims about the platform generating the certification request and the environment associated with the corresponding private key, such as whether the private key resides on a hardware security module. This specification defines an attribute and an extension that allow for conveyance of Evidence in Certificate Signing Requests (CSRs) such as PKCS#10 or Certificate Request Message Format (CRMF) payloads which provides an elegant and automatable mechanism for transporting Evidence to a Certification Authority. Including Evidence along with a CSR can help to improve the assessment of the security posture for the private key, and can help the Certification Authority to assess whether it satisfies the requested certificate profile. These Evidence Claims can include information about the hardware component's manufacturer, the version of installed or running firmware, the version of software installed or running in layers above the firmware, or the presence of hardware components providing specific protection capabilities or shielded locations (e.g., to protect keys). ITU-T n.d.

Acknowledgements This specification is the work of a design team created by the chairs of the LAMPS working group. This specification has been developed based on discussions in that design team. The following persons, in no specific order, contributed to the work: Richard Kettlewell, Chris Trufan, Bruno Couillard, Jean-Pierre Fiset, Sander Temme, Jethro Beekman, Zsolt Rózsahegyi, Ferenc Pető, Mike Agrenius Kushner, Tomas Gustavsson, Dieter Bong, Christopher Meyer, Michael StJohns, Carl Wallace, Michael Ricardson, Tomofumi Okubo, Olivier Couillard, John Gray, Eric Amador, Johnson Darren, Herman Slatman, Tiru Reddy, Thomas Fossati, Corey Bonnell, Argenius Kushner, James Hagborg.

ASN.1 Module TBD: Full ASN.1 goes in here.