]> Intel Corporation

james.d.beaney@intel.com

Altera Corporation

andrew.draper@altera.com

Intel Corporation

vincent.r.scarlata@intel.com

Intel Corporation

ned.smith@intel.com

Security Remote ATtestation ProcedureS attestation profile corim This document is a profile of various IETF and TCG standards that support remote attestation. The profile supports Intel-specific adaptations and extensions for Evidence, Endorsements and Reference Values. This profile describes apticulareplication of CoRIM, EAT, CMW, TCG concise evidence, and TCG DICE specifications. In particular, CoRIM is extended to define measurement types that are unique to Intel and defines Reference Values types that support matching Evidence based on range and subset comparison. Multiple Evidence formats are anticipated, based on IETF and TCG specifications. Evidence formats are mapped to Reference Values expressions based on CoRIM and CoRIM extensions found in this profile. The Evidence to Reference Values mappings are either documented by industry specifications or by this profile. Reference Value Providers and Endorsers may use this profile to author mainifests containing Reference Values and Endorsements that require Intel profile support from parser implementations. Parser implementations can recognize the Intel profile by profile identifier values contained within attestation conceptual mmessages and from profile parameters to media types or profile specific content format identifiers. About This Document The latest revision of this draft can be found at . Status information for this document may be found at . Discussion of this document takes place on the Remote ATtestation ProcedureS Working Group mailing list (), which is archived at . Subscribe at . Source for this draft and an issue tracker can be found at .

Introduction This profile describes extensions and restrictions placed on Reference Values, Endorsements, and Evidence that support attestation capabilities of Intel products containing Intel(R) SGX(TM) or Intel(R) TDX(TM) technology, or Intel(R) products that contain DICE root of trust, DICE layers , or modules that implement SPDM . The CoRIM specifications and define a baseline schema for Reference Values and Endorsements that form the foundation for the extensions defined in this profile. contains a foundational representation for Attester actual state that Evidence, as specified by , , and , Reference Values, and Endorsements can map to that helps ensure compatibility with a broad spectrum of Verifier implementations. The Reference Values extensions in this profile describe reference state that can be expressed as set membership or value ranges. This profile defines extensions to CoRIM that support appraisal matching that is based on set membership, masked values, and numeric ranges. The baseline CoRIM, as defined by is a subset of the Intel profile. Intel products that implement exclusively to the baseline CoRIM may not rely upon this profile. The Intel profile extensions may be generally useful. Implementations based on the Intel profile does not necessarily imply an implementation is an Intel product. This profile extends CoMID measurement-values-map, as defined by (see also ), with measurement types that are unique to Intel products. Some measurement types are specific to Reference Values where multiple reference states may be included in reference manifests. Intel profile extensions use a CBOR tagged value that defines a comparison operator and operands that instruct Verifiers regarding subset, range, and masked values matching semantics. For example, a numeric operator 'greater-than' instructs the Verifier to match a numeric Evidence value if it is greater than a numeric range operand. This profile follows the Verifier behavior defined by and extends Verifier behavior to include operator-operand matching. If no operator is specified by Reference Values statements, the Verifier defaults to baseline matching semantics. If Evidence matches Reference Values and Endorsements apply, Endorsed Values may be added to the accetped claims set. When all Evidence and Endorsements are processed, the Verifier's set of accepted claims is available for Attestation Results computations. This profile doesn't define Attestation Results. Rather, an Attestation Results profile, such as may be referenced instead. This profile is compatible with multiple Evidence formats, as defined by , , and . It describes considerations when mapping Evidence formats to CoRIM that a Verifier may use when performig appraisals.

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. The reader is assumed to be familiar with the terms defined in Section 4 of and .

Background Complex platforms may contain a variety of hardware components, several of which may contain a hardware root of trust. Each root of trust may anchor one or more layers resulting in multiple instances of attestation Evidence. Evidence may be integrity protected by digital signatures, such as certificates , tokens or by a secure transport . For example, a system bus may allow dynamically configured peripheral devices that have attestation capabilities. Confidential computing environments, such as SGX, may extend an initial boundary to include a peripheral, or a peer enclave, that together forms a network of trustworthy nodes that a remote attestation Verifier may need to appraise. Multiple Evidence blocks may be combined into a composite Evidence block that is more easily conveyed. Complex platforms may have one or more lead Attester endpoints that communicate with a remote Verifier to convey composite Evidence. The composition of the complex platform is partially represented in the composite Evidence. However, composite Evidence may not fully describe platform composition. A complex platform may consist of multiple subsystems, such as network adapters, storage controllers, memory controllers, special purpose processors, etc. The various sub-subsystem components vendors may create hardware bills of material (HBOM) that describe sub-system composition. A complex platform vendor may assemble various sub-system components whose composition is described by a platform HBOM. Although CoRIM may be used to create HBOMs, use of this profile for HBOM creation is unanticipated. Nevertheless, a complex system may contain multiple identical instances of sub-sytem components that produce identical Evidence blocks. Additionally, dynamic insertion or removal of a component may result in composite Evidence blocks that reflect this dynamism.

Profile Identifier This profile applies to Reference Values from a CoRIM manifest that a Verifier uses to process Evidence. Profile identifier structures are defined by CoRIM , EAT and Concise Evidence .

Intel Profile The profile identifier for the Intel Profile is the OID: {joint-iso-itu-t(2) country(16) us(840) organization(1) intel(113741) (1) intel-comid(16) profile(1)} 2.16.840.1.113741.1.16.1

Profile Specific Media and Content Types This profile uses the following media types:

• "application/eat+cwt"
• "application/eat+cwt; eat_profile=2.16.840.1.113741.1.16.1"
• "application/rim+cbor" (TBA)
• "application/rim+cbor" (TBA); profile=2.16.840.1.113741.1.16.1"

This profile uses the following content formats:

Content Type	C-F ID	TN Function
"application/eat+cwt"	263	1668547081
"application/eat+cwt; eat_profile=2.16.840.1.113741.1.16.1"	10005	1668556861
"application/toc+cbor"	10570	1668557428
"application/ce+cbor"	10571	1668557429

This profile uses the following top level CBOR tags (not already listed):

• 501, 570, 571

Attester Anatomy Attesters implement DICE layering using an initial Attesting Environment, also called a Root of Trust (RoT), that collection claims about one or more Target Environments. A Target Environment may become an Attesting Environment for a subsequent Target Environment, and so forth. There may be more than one RoT in the same Attester. Attesting Environments generate Evidence by signing collected claims using an Attestation Key. Environments may have other keys besides attestation keys. Keys can be regarded as claims that are collected and reported as Evidence. Keys can also be regarded as Target Environments that have measurements that are specific to the key. Confidential computing environments are Target Environments that can dynamically request Evidence from an Attesting Environment agent. Such Evidence may also be referred to as a 'Quote'. Each DICE layer may produce signed Evidence. Evidence formats include both signature and measurements formats. Signature formats may include a mix of X.509 certificates and EAT CWTs. Evidence measurements formats may include a mix of ASN.1 and CBOR, where ASN.1 uses DiceTcbInfo and related varients and CBOR uses concise evidence, and CMW. Multiple Evidence blocks may be bundled using CMW collections. Target Environments (other than cryptographic keys) are primarily identified using OIDs from Intel's OID arc (2.16.840.1.113741). Keys are identified using key identifiers, public key, or certificate digests as defined by $crypto-key-type-choice .

Evidence Profile Evidence may be integrity protected in various ways including: certificates , SPDM transcript , and CBOR web token (CWT) . Evidence contained in a certificate may be encoded using DiceTcbInfo and DiceTcbInfoSeq . Evidence contained in an SPDM payload may be encoded using the SPDM Measurement Block . Evidence may be formatted as concise-evidence and included in an alias certificate or an SPDM Measurement Manifest. The DiceTcbInfo and SPDM Evidence formats can be translated to CoMID. The concise evidence format is native to CoMID. This profile documents evidence mapping from DiceTcbInfo and SPDM Measurement Block to CoMID, as defined by . The CoMID extensions defined by this profile are applied to concise-evidence so that Verifiers that support this profile can consistently apply a common schema across Evidence, Reference Values, and Endorsements.

Evidence Hierarchy Evidence hierarchy refers to DICE layering where the platform bootstrap components double as Attesting Environments that collect measurements of the other bootstrap components (as Target Environments) until the quoting agent (e.g., SGX Quoting Enclave (QE), TDX Quoting TD (QTD)) is initialized. Tenant trusted execution environment (TEE) components can be dynamically loaded then request Evidence from its quoting agent. Quoting agents locally verify then sign measurments using the QTD / QE attestation key. A hierarchy of Evidence consisting of all the Evidence from a RoT to the tenant environment describes the Attester. A complex device may have multiple roots of trust, such as , each contributing an evidence hierarchy that results in several Evidence "chains", that together, constitute a complete Evidence hierarchy for the Attester device. The Evidence hierarchy should form a spanning tree that contains all Attester Evidence. All Attesting Environments within the device produce the spanning tree. CoRIM manifests contain Reference Values for the spanning tree so that Verifiers do not assume the spanning tree is defined by Evidence. Note that a failure or comporomise within the Attester device could result in a portion of the spanning tree being omitted. Example spanning tree:

• A DICE certificate chain with a DiceTcbInfo extension, a DiceTcbInfoSeq extension, and a ConceptualMessageWrapper (CMW) extension containing a CBOR-encoded tagged-concise-evidence.
• An SPDM alias intermediate certification chain containing a CMW extension, and an SPDM measurement manifest containing tagged-concise-evidence.

Concise Evidence Concise evidence is a CDDL representation of Evidence that uses expressions from CoMID, which is a subset of CoRIM. See and . Evidence describes the actual state of the Attester. tagged-concise-evidence uses a CBOR tag to identify concise-evidence . This profile is compatible with tagged-concise-evicence. CoRIM extensions, defined by this profile, are used by tagged-concise-evidence by extending measurement-values-map.

Reference Values and Endorsements Profile The CoRIM specifications and define a baseline schema for Reference Values and Endorsements in this profile. The profile defines extensions to CoRIM for measurement types that are not representable by CoRIM or are more conveniently represented.

CoRIM Extensions The Intel Profile extends measurement-values-map which is used by Evidence, Reference Values, and Endorsed Values by defining code points from the negative integer range. Reference Values extensions define types that can have multiple Reference Values that "match" a singleton Evidence value called "non-exact match" matching. Reference state expressions define non-exact-match matching semantics in terms of numeric ranges, date-time ranges, sets, and masks. Reference Values data types are identified by the CBOR tag #6.60010(...).

Expressions Expressions are used to specify richer Reference Values measurements that expect non-exact matching semantics. The Reference Value expression instructs the Verifier regarding matching parameters, such as greater-than or less-than, ranges, sets, etc. Typically, the Evidence value is one operand of an expression and the Reference Value contains the operator and additional operands. The operator and remaining operands are contained in an array. Expression arrays have an operator followed by zero or more operands. The operator definition identifies the additional operands and their data types. A Verifier forms an expression using Evidence as the first operand, obtains the operator from the first entry in the expression array, and any remaining array entries are operands. This document describes operations using infix notation where the first operand, operand_1, is obtained from Evidence, followed by the operator, followed by any remaining operands: operand_2, operand_3, etc... For example:

• From Evidence: operand_1, from Reference Values: [ operator, operand_2, operand_3, ... ].

Expression records are CBOR tagged to indicate the following CBOR is to be evaluated as an expression. Expression statements found in Reference Values informs the Verifier that Evidence is needed to complete the expression equation. Appraisal processing MUST evaluate the expression. This profile anticipates use of the CBOR tag #6.60010 to identify expression arrays. See . For example:

• #6.60010([ operator, operand_2, operand_3, ... ]).

Expression Operators There are several classes of operators as follows:

1. Numeric: The numeric operand can be an integer, unsigned integer, or floading point value.
2. Set: The set operand can be an set (array) of any primitive value or a set of arrays containing any primitive value. The position of the items in a set is unordered, while the position of items in an array within a set is ordered.
3. Date-Time: The date-time operators compare two date-time values, while the epoch operators determine if a date-time value is within a range defined by an epoch and a grece period relative to the epoch.
4. Mask: The mask operator compares two bit fields where a bit-field is compared to a second bit-field using a bit-field-mask that selects the bits to be compared. The bit-field may contain a sequence of bytes of any length. The bit-field-mask should be the same length as the bit-field.

Equivalence Operator By default, exact match rules are assumed. Consequently, no operator artifact is needed when Evidence values are identical to Reference Values.

Numeric Expressions Numeric operators apply to values that are integers, unsigned integers or floating point numbers. There are four numeric operators:

1. greater-than (gt),
2. greater-than-or-equal (ge),
3. less-than (lt),
4. less-than-or-equal (le).

The equals operator is not defined because an exact match rule is the default rule when an Evidence value is identical to a Reference Value. The numeric operator data type definitions are as follows: A numeric expression is an array containing a numeric operator and a numeric operand. The operand contains a numeric Reference Value that is matched with a numeric Evidence value. Evidence and Reference Values MUST be the same numeric type. For example, if a Reference Value numeric type is integer, then the Evidence numeric value must also be integer. This profile defines four macro numeric expressions, one for each numeric operator:

• tagged-numeric-gt,
• tagged-numeric-ge,
• tagged-numeric-lt,
• tagged-numeric-le.

In each case, the numeric operator is used to evaluate a Reference Value operand against an Evidence value operand that is obtained from Evidence. If the expression is read using infix notation, the first operand is Evidence, followed by the operator, followed by the Reference Value operand. Example:

• <evidence_numeric> <le> <reference_numeric>

The numeric expression definitions are as follows:

Set Expressions Set operators allow Reference Values, that are expressed as a set, to be compared with Evidence that is expressed as either a primitive value or a set. Set expression statements have two forms:

1. A binary relation between a primitive object 'O' and a set 'S', and
2. A binary relation between two sets, an Evidence set 'S1' and a Reference Values set 'S2'.

The first form, relation between an object and a set, has two operators:

• member and
• not-member.

The Evidence object 'O' is evaluated with the Reference Values set 'S'. The op.member and op.not-member operators expect a Reverence Value set as operand_2 and a primitive Evidence value as operand_1. Evaluation tests whether operand_1 is a member of the set operand_2. Example:

• <evidence-value> <set-operator> <reference-set>

The set data type definitions are defined as follows: A set expression array contins a set operator followed by a set of Reference Values. The set is defined by set-type. The set expression type definitions are as follows: Examples:

• <evidence_object> <member> <reference_set>
• <evidence_object> <not-member> <reference_set>

The Evidence object MUST NOT be nil. The Reference Values set may be the empty set. The second form, a relation between two sets, has three operators:

• subset,
• superset,
• disjoint.

The fist set, S1 is Evidence and set, S2 is the Reference Values set. The subset, superset, and disjoint operators test whether an Evidence set value satisfies a set operation, given a Reverence Value set. Examples:

• <evidence_set> <subset> <reference_set>
• <evidence_set> <superset> <reference_set>
• <evidence_set> <disjoint> <reference_set>

The Reference Values and Evidence sets may be the empty set. The set of sets data type definitions are as follows: For subset, every member in the Evidence set 'S1', MUST map to a member in the Reference Values set 'S2'. The Evidence set, 'S1', MAY be a proper subset of 'S2'. For example, if every member in set 'S1' maps to every member in set 'S2' then matching is successful. A successful result produces the set 'S1'. For superset, every member in the Reference Values set 'S2', MUST map to a member in the Evidence set 'S1'. A successful result produces the set 'S1'. For disjoint, every member in the Evidence set 'S1' MUST NOT map to any member in the Reference Values set 'S2'. A successful result produces the empty set. The set of sets expression definitions are as follows:

Time Expressions

Date-Time Expressions Date-time can be expressed in both string tdate or numeric time formats. There are four operators that are defined for date-time expressions:

1. lt determines if a date-time Evidence value is less than a Reference Values date-time.
2. le determines if a date-time Evidence value is less than or equal to a Reference Values date-time.
3. gt determines if a data-time Evidence value is greater than a Reference Values date-time.
4. ge determines if a data-time Evidence value is greater than or equal to a Reference Values date-time.

The date-time operators are in fact numeric. Expressions involving string date-time values must be converted to numeric format before the numeric comparison operator can be applied. The numeric date-time data type definitions are as follows: The string date-time data type definitions are as follows: The date-time expressions for evaluating time consist of a CBOR tagged record containing a time operator followed by a date-time value. The gt expression compares a date-time value contained in Evidence to a Reference Values date-time. If the Evidence date-time value is greater-than to the Reference Value, then the Evidence value is accepted. The ge expression compares a date-time value contained in Evidence to a Reference Values date-time. If the Evidence date-time value is greater-than-or-equal to the Reference Value, then the Evidence value is accepted. The lt expression compares a date-time value contained in Evidence to a Reference Values date-time. If the Evidence date-time value is less-than to the Reference Value, then the Evidence value is accepted. The le expression compares a date-time value contained in Evidence to a Reference Values date-time. If the Evidence date-time value is less-than-or-equal to the Reference Value, then the Evidence value is accepted. In infix notation, a date-time value reported as Evidence in operand_1. The Reference Value expression contains a time comparison operator and operand_2 contains a reference date-time. Example:

• <evidence_date_time> <gt> <reference_date_time>

The numeric date-time expression definitions are as follows: The string date-time expression definitions are as follows:

Epoch Expressions An epoch expression defines a timing window that can be used to determine recentness of a time stampped message. By default, the Verifier's current time implicitly defines an epoch. A grace period defines the epoch window differential, in seconds, that a timestamp must fall within to be valid. Epochs don't have to rely on current time. defines several. The epoch data type definitions are as follows: An epoch expression array contains an epoch-operator followed by a grace period in seconds that is optionally followed by a $tagged-epoch-id. Epoch operators can be: gt, ge, lt, or le. The operator defines the position of the grace window relative to the epoch and epoch-grace-seconds defines the size of the window in seconds. If the default epoch type is not used, $tagged-epoch-id defines the alternate epoch scheme. The $epoch-timestamp-type defines the timestamp type for the epoch scheme. By default, the timestamp is tdate. The tagged-epoch-expression is an epoch-expression preceded by a CBOR tag for an expression array that has the value #6.60010. The epoch expression definitions are as follows: A variety of epoch expressions can be defined that convenently constrain epoch definition. The tagged-exp-epoch-gt expression defines an epoch window that is greater than the current date and time by the supplied grace period. In infix notation, the timestamp value is within an epoch window that is defined by the current time, plus the grace period, and where the epoch-operator defines the shape of the epoch window. Example epoch expression:

• <evidence_timestamp> <epoch-operator> <grace_period> <current_time>

The Verifier adds grace_period to current_time to obtain the epoch window then applies the operator to determine if the evidence_timestamp is within the window.

Mask Expression Reference Values expressed as an array of bits or bytes that uses a mask can indicate to a Verifier which bits or bytes of Evidence to ignore. Reference Value and mask arrays MUST be the same length for the mask to be applied correctly. Normally, Evidence would not supply a mask, while Endorsed Values would. The mask-eq operator indicates that an Evidence value of type mask-type is compared with a Reference Value of type mask-type, and that a mask of type mask-type is applied to both values before comparing values. If the operator is mask-eq, then a binary equivalence comparison is applied. The Verifier MUST ensure the lengths of values and mask are equivalent. If the mask is shorter than the values, the mask is padded with zeros (0) until it is the same length as the largest value. If the Evidence or Reference Value length is shorter than the mask, the value is padded with zeros (0) to the length of the mask. The masked data type definitions are as follows: If the Evidence bit field is a different length from the Reference Value and mask, the shorter length bit field is padded with zeros to accommodate the larger bit field. The tagged-exp-mask-eq expression defines a tagged expression that applies the mask equivalence operator to an Evidence value and a Reference Value using the supplied mask. In infix notation, the Evidence value is operand_1, followed by the mask operator, followed by a Reference Value, operand_2, followed by the mask, operand_3. Example:

• <evidence_value> <mask-eq> <reference_value> <mask>

If each bit in Evidence has a corresponding matching bit in the Reference Value, then the Evidence value is accepted. The masked data expression definitions are as follows:

Measurement Extensions This profile extends the CoMID measurement-values-map with additional code point definitions, that accommodate Intel SGX and similar architectures. Measurement extensions don't change Verifier behavior. An extension enables the Verifier to validate the profile compliance of the input evidence and reference values, as it defines the acceptable data types in evidence and the expression operator that is explicitly supplied with the Reference Values, see . In cases where Evidence does not exactly match Reference Values, the operator definition determines the expected data types of the operands. Expected Verifier behavior is defined in

The tee-advisory-ids-type Measurement Extension The tee.advisory-ids extension allows the Attester to report known security advisories and a Reference Values Provider (RVP) to assert updated security advisories. The $tee-advisory-ids-type is used to specify a set of security advisories, where each is identified by a string identifier. Evidence may report a set of advisories the Attester believes are relevant. The set of advisories are constrained by the set-of-set-type structure. A Reference Values expression record is defined for this extension that applies the disjoint set operation to determine if there are advisories outstanding. If no advisories are outstanding, then the empty set signifies successful matching. The $tee-advisory-ids-type is a list of advisories when used as Endorsements or Evidence and a disjoint set of advisories when used as a Reference Value. $tee-advisory-ids-type ) $tee-advisory-ids-type /= set-type $tee-advisory-ids-type /= tagged-exp-not-member ]]>

The tee-attributes-type Measurement Extension The tee.attributes extension enables the Attester to report TEE attributes and an RVP to assert a reference TEE attributes and mask. The $tee-attributes-type is used to specify TEE attributes in 8 or 16 byte words. If Evidence uses an 8 byte mask, then the Reference Values expression also uses an 8 byte value and mask. The $tee-attributes-type is a singleton value omitting the mask value when used as Endorsement or Evidence and a tuple containing the reference and mask when used as a Reference Value. $tee-attributes-type ) $tee-attributes-type /= mask-type $tee-attributes-type /= tagged-exp-mask-eq ]]> Alternatively, the TEE attributes may be encoded using mkey where mkey contains the non-negative tee.attributes and mval.raw-value contains the $tee-attributes-type.mask-type value.

The tee-cryptokey-type Measurement Extension The tee.cryptokeys extension identifies cryptographic keys associated with a Target Environment. If multiple $crypto-key-type-choice measurements are supplied, array position disambiguates each entry. Appraisal compares values indexed by array position. [ + $tee-cryptokey-type ] ) $tee-cryptokey-type /= $crypto-key-type-choice ]]> Alternatively, the TEE cryptokeys may be encoded using mkey where mkey contains the non-negative tee.cryptokeys and mval.cryptokeys contains the $tee-cryptokey-type value.

The tee-date-type Measurement Extension The tee.tcbdate extension enables the Attester or Endorser to report the TEE date attribute and a RVP to assert a valid TEE matching operation. The $tee-date-type is a date-time string when used for Evidence or Endorsement. When used for a Reference Value, either a tagged-tdate-expression or a tagged-epoch-expression describes the TCB validity. $tee-date-type ) $tee-date-type /= tdate $tee-date-type /= tagged-exp-tdate-ge $tee-date-type /= tagged-exp-epoch-ge ]]> tdate strings must be converted to numeric time before the tdate-operator, which is a numeric operator, can be applied. Alternatively, the TEE tcbdate may be encoded using mkey where mkey contains the non-negative tee.tcbdate and mval.name contains the string representation $tee-date-type without the CBOR tag (i.e., ~tdate).

The tee-digest-type Measurement Extension The tee.mrtee and tee.mrsigner extensions enable the Attester to report digests for the SGX enclave or TDX TD (e.g., mrenclave, mrtd) and the signer (e.g., mrsigner) of the TEE digest. The $tee-digest-type is a record that contains the hash algorithm identifier and the digest value when used as Evidence. When used as Reference Values, a set of digests can be asserted. The Evidence digest record must be a member of the Reference Values set. $tee-digest-type ) $$measurement-values-map-extension //= ( &(tee.mrsigner: -84) => $tee-digest-type ) $tee-digest-type /= digest $tee-digest-type /= [ + digest ] $tee-digest-type /= tagged-exp-member ]]> Alternatively, the TEE digests may be encoded using mkey where mkey contains the non-negative tee.mrtee or tee.mrsigner and mval.digests contains the $tee-digest-type.[ + digest ] value.

The tee-epoch-type Measurement Extension The tee.epoch extension enables the Attester to report an epoch Evidence measurement, and a RVP to assert an epoch Reference Value. As Evidence, the $tee-epoch-type is a tdate timestamp. As a Reference Value, the $tee-epoch-type is a grace period, in seconds, that is relative to the Verifier's current date and time, and an epoch operator: gt, ge, lt, or le. The Verifier evaluates whether the timestamp is within the grace period relative to the current date and time. The current date and time is implicit, and is assumed to be in tdate format. The $tee-epoch-type is an $epoch-timestamp-type when used as Evidence or Endorsement and a $tagged-epoch-expression when used as a Reference Value. $tee-epoch-type ) $tee-epoch-type /= $epoch-timestamp-type $tee-epoch-type /= tagged-exp-epoch-gt ]]> Alternatively, for Evidence, the TEE epoch timestamp may be encoded using mkey where mkey contains the non-negative tee.epoch and mval.name contains the string representation $tagged-epoch-id without the CBOR tag (i.e., ~tdate).

The tee-instance-id-type Measurement Extension The tee.instance-id extension enables the Attester to report the (TBD:instance-id-description) Evidence value and the RVP to assert an exact-match Reference Value. The $tee-instance-id-type is an unsigned integer. The $tee-instance-type is an exact match measurement. $tee-instance-id-type ) $tee-instance-id-type /= uint $tee-instance-id-type /= bstr ]]> Alternatively, the TEE instance ID may be encoded using mkey where mkey contains the non-negative tee.instance-id and mval.raw-value contains the $tee-instance-id-type value.

The tee-isvprodid-type Measurement Extension The tee.isvprodid extension enables the Attester to report the ISV product identifier Evidence value and the RVP to assert an exact-match Reference Value. The $tee-isvprodid-type is an unsigned integer. The $tee-isvprodid-type is an exact match measurement. $tee-isvprodid-type ) $tee-isvprodid-type /= uint $tee-isvprodid-type /= bstr ]]> Alternatively, the TEE product ID may be encoded using mkey where mkey contains the non-negative tee.isvprodid and mval.raw-value contains the $tee-isvprodid-type value.

The tee-miscselect-type Measurement Extension The tee.miscselect extension enables the Attester to report the (TBD:miscselect-description) Evidence value and the RVP to assert a Reference Value and mask. The $tee-miscselect-type is a 4 byte value and mask. The $tee-miscselect-type is a singleton mask-type value when used as Endorsement or Evidence and a tagged-mask-expression when used a Reference Value. $tee-miscselect-type ) $tee-miscselect-type /= mask-type $tee-miscselect-type /= tagged-exp-mask-eq ]]> Alternatively, the TEE miscselect may be encoded using mkey where mkey contains the non-negative tee.miscselect and mval.raw-value contains the measurement value and mval.raw-value-mask` contains the mask value.

The tee-model-type Measurement Extension The tee.model extension enables the Attester to report the TEE model string as Evidence and the RVP to assert an exact-match Reference Value. The $tee-model-type is a string. The $tee-model-type is an exact match measurement. $tee-model-type ) $tee-model-type /= tstr ]]> Alternatively, the TEE model may be encoded using mkey where mkey contains the non-negative tee.model and mval.name contains the $tee-model-type value.

The tee-pceid-type Measurement Extension The tee.pceid extension enables the Attester to report the PCEID as Evidence and the RVP to assert an exact-match Reference Value. The $tee-pceid-type is a string. The $tee-pceid-type is an exact match measurement. $tee-pceid-type ) $tee-pceid-type /= tstr ]]> Alternatively, the PCEID may be encoded using mkey where mkey contains the non-negative tee.pceid and mval.name contains the $tee-pceid-type value.

The tee-svn-type Measurement Extension The tee.isvsvn extension enables the Attester to report the SVN for the independent software vendor supplied component as Evidence and the RVP to assert a Reference Value that is greater-than-or-equal to the reported SVN. The $tee-svn-type is either an unsigned integer when reported as Evidence, or a tagged numeric expression that contains an SVN and a numeric greater-than-or-equal operator. The Verifier ensures the Evidence value is greater-that-or-equal to the Reference Value. The $tee-svn-type is a numeric when used as Endorsement or Evidence and a tagged-numeric-expression when used as a Reference Value. $tee-svn-type ) $tee-svn-type /= numeric-type $tee-svn-type /= tagged-numeric-ge ]]> Alternatively, the TEE isvsvn may be encoded using mkey where mkey contains the non-negative tee.isvsvn and mval.svn contains the svn value as svn-type.

The tee-tcb-comp-svn-type Measurement Extension The tee.tcb-comp-svn extension enables the Attester to report an array of SVN values for the TCB when asserted as Evidence and an array of tagged-numeric-ge entries when asserted as a Reference Value. The $tee-tcb-comp-svn-type is an array containing 16 SVN values when reported as Evidence and an array of 16 expression records each containing the numeric ge operator and a reference SVN value. The Verifier evaluates each SVN in the Evidence array with the corresponding reference expression, by array position. If all Evidence values match their respective expressions, evaluation is successful. The array of SVN Evidence is accepted. $tee-tcb-comp-svn-type ) $tee-tcb-comp-svn-type /= [ 16*16 svn-type .within numeric-type ] $tee-tcb-comp-svn-type /= [ 16*16 tagged-numeric-ge ] ]]>

The tee-tcb-eval-num-type Measurement Extension The tee.tcb-eval-num extension enables the Attester to report a TCB evaluation number as Evidence and the RVP to assert a Reference Value expression that compares the tcb-eval-num Evidence with the Reference Value using the greater-than-or-equal operator. The $tee-tcb-eval-num-type is an unsigned integer when reported as Evidence and a tagged numeric expression when asserted as Reference Values. $tee-tcb-eval-num-type ) $tee-tcb-eval-num-type /= uint .within numeric-type $tee-tcb-eval-num-type /= tagged-numeric-ge ]]> Alternatively, the TEE tcb-eval-num Evidence may be encoded using mkey where mkey contains the non-negative tee.tcb-eval-num and mval.raw-value contains the tcb-eval-num encoded as 4-byte bstr value.

The tee-tcbstatus-type Measurement Extension The tee.tcb-status extension enables the Attester to report the status of the TEE trusted computing base (TCB) as an array of status strings, as Evidence, and the RVP to assert an array of status arrays as Reference Values where the Evidence array is a subset of the reference status arrays. The $tee-tcbstatus-type is a status array with a set expressions containing the subset operator when used as Evidence. When used as a Reference Value it is an array of status arrays. $tee-tcbstatus-type ) $tee-tcbstatus-type /= set-type $tee-tcbstatus-type /= tagged-exp-member ]]>

The tee-vendor-type Measurement Extension The tee.vendor extension enables the Attester to report the TEE vendor name as Evidence and for the RVP to assert the TEE vendor name. The $tee-vendor-type is a string containing the vendor name as a string. The vendor string in Evidence must exactly match the vendor string in Reference Values. The $tee-vendor-type is an exact match measurement. $tee-vendor-type ) $tee-vendor-type /= tstr ]]> Alternatively, the TEE vendor may be encoded using mkey where mkey contains the non-negative tee.vendor and mval.name contains the $tee-vendor-type value.

Appraisal Algorithm The Intel profile anticipates appraisal algorithms will be based on the appraisal algorithm defined in . This profile extends the appraisal algorithm to recognize profile extensions that form equations. An Evidence measurement forms one of the operands: (evidence operand). A Reference Value forms the operator and remaining operands: [(expression operator), (reference value operand), ...]. For example, if a numeric reference value is 14, and the expressions operator is gt the Reference Value might contain the Claim: #6.60010([ 1, 14]). Evidence might contain the measurement: '15'. In infix construction, the equation would be: (15) (gt) (14). The Verifier evaluates whether 15 is greater-than 14.

Complex Expressions Complex expressions can be used to assess whether the Target Environment is in a particular state before certain Endorsement claims can be asserted. For example, if an SGX enclave has an svn value that is less than the prescribed minimum svn, the enclave status may be considered "OutOfDate" or may have a known security advisory. The CoMID conditional-endorsement-triples or conditional-endorsement-series-triples describe complex Endorsement expressions. This profile uses these triples with the reference measurement values extensions described in .

Reporting Attestation Results Attestation verification can be performed by a pipeline consisting of multiple stages where each input manifest demarks a stage. The final stage prepares Attestation Results according to Relying Party specifications. This profile does not define an attestation results format. The Relying Party should specify suitable Attestation Results formats such as or . The precise Attestation Results format used, if negotiated by Verifier and Relying Party, should reference this profile to acknowledge that the Relying Party and Verifier both support the extensions defined in this document.

Security Considerations The security of this profile depends on the security considerations of the various normative references.

IANA Considerations

References Normative References Fraunhofer SIT Linaro arm Intel Huawei Technologies Remote Attestation Procedures (RATS) enable Relying Parties to assess the trustworthiness of a remote Attester and therefore to decide whether or not to engage in secure interactions with it. Evidence about trustworthiness can be rather complex and it is deemed unrealistic that every Relying Party is capable of the appraisal of Evidence. Therefore that burden is typically offloaded to a Verifier. In order to conduct Evidence appraisal, a Verifier requires not only fresh Evidence from an Attester, but also trusted Endorsements and Reference Values from Endorsers and Reference Value Providers, such as manufacturers, distributors, or device owners. This document specifies the information elements for representing Endorsements and Reference Values in CBOR format. Trusted Computing Group (TCG) Trusted Computing Group (TCG) Trusted Computing Group (TCG) Trusted Computing Group (TCG) Fraunhofer SIT Intel Linaro University of Applied Sciences Bonn-Rhein-Sieg Google LLC This document defines the RATS conceptual message wrapper (CMW) format, a type of encapsulation format that can be used for any RATS messages, such as Evidence, Attestation Results, Endorsements, and Reference Values. Additionally, the document describes a collection type that enables the aggregation of one or more CMWs into a single message. This document also defines corresponding CBOR tag, JSON Web Tokens (JWT) and CBOR Web Tokens (CWT) claims, as well as an X.509 extension. These allow embedding the wrapped conceptual messages into CBOR-based protocols, web APIs, and PKIX protocols. In addition, a Media Type and a CoAP Content-Format are defined for transporting CMWs in HTTP, MIME, CoAP and other Internet protocols. 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. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References 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] CBOR Web Token (CWT) is a compact means of representing claims to be transferred between two parties. The claims in a CWT are encoded in the Concise Binary Object Representation (CBOR), and CBOR Object Signing and Encryption (COSE) is used for added application-layer security protection. A claim is a piece of information asserted about a subject and is represented as a name/value pair consisting of a claim name and a claim value. CWT is derived from JSON Web Token (JWT) but uses CBOR rather than JSON. Fraunhofer SIT Arm Limited Huawei Technologies Universität Bremen TZI This document defines Epoch Markers as a way to establish a notion of freshness among actors in a distributed system. Epoch Markers are similar to "time ticks" and are produced and distributed by a dedicated system, the Epoch Bell. Systems that receive Epoch Markers do not have to track freshness using their own understanding of time (e.g., via a local real-time clock). Instead, the reception of a certain Epoch Marker establishes a new epoch that is shared between all recipients. Cisco Systems Fraunhofer SIT MIT Linaro Intel This document defines reusable Attestation Result information elements. When these elements are offered to Relying Parties as Evidence, different aspects of Attester trustworthiness can be evaluated. Additionally, where the Relying Party is interfacing with a heterogeneous mix of Attesting Environment and Verifier types, consistent policies can be applied to subsequent information exchange between each Attester and the Relying Party. Distributed Managability Task Force (DMTF) Trusted Computing Group (TCG) Microsoft Microsoft Intel Intel Intel Intel® Trust Domain Extensions (TDX) introduce architectural elements designed for the deployment of hardware-isolated virtual machines (VMs) known as trust domains (TDs). TDX is designed to provide a secure and isolated environment for running sensitive workloads or applications. This Entity Attestation Token (EAT) profile outlines claims for an Intel TDX attestation result which facilitate the establishment of trust between a relying party and the environment. Armidale Consulting Fraunhofer SIT Linaro In the IETF Remote Attestation Procedures (RATS) architecture, a Verifier accepts Evidence and, using Appraisal Policy typically with additional input from Endorsements and Reference Values, generates Attestation Results in formats that are useful for Relying Parties. This document illustrates the purpose and role of Endorsements and discusses some considerations in the choice of message format for Endorsements in the scope of the RATS architecture.

Acknowledgments The authors wish to thank Shanwei Cen, Piotr Zmijewski, Francisco J. Chinchilla, Yogesh Despande and Dionna Amalie Glaze for their valuable contributions.

Full Intel Profile CDDL $tee-advisory-ids-type ) $tee-advisory-ids-type /= set-type $tee-advisory-ids-type /= tagged-exp-not-member $$measurement-values-map-extension //= ( &(tee.attributes: -82) => $tee-attributes-type ) $tee-attributes-type /= mask-type $tee-attributes-type /= tagged-exp-mask-eq $$measurement-values-map-extension //= ( &(tee.cryptokeys: -91) => [ + $tee-cryptokey-type ] ) $tee-cryptokey-type /= $crypto-key-type-choice $$measurement-values-map-extension //= ( &(tee.tcbdate: -72) => $tee-date-type ) $tee-date-type /= tdate $tee-date-type /= tagged-exp-tdate-ge $tee-date-type /= tagged-exp-epoch-ge $$measurement-values-map-extension //= ( &(tee.mrtee: -83) => $tee-digest-type ) $$measurement-values-map-extension //= ( &(tee.mrsigner: -84) => $tee-digest-type ) $tee-digest-type /= digest $tee-digest-type /= [ + digest ] $tee-digest-type /= tagged-exp-member $$measurement-values-map-extension //= ( &(tee.epoch: -90) => $tee-epoch-type ) $tee-epoch-type /= $epoch-timestamp-type $tee-epoch-type /= tagged-exp-epoch-gt $$measurement-values-map-extension //= ( &(tee.instance-id: -77) => $tee-instance-id-type ) $tee-instance-id-type /= uint $tee-instance-id-type /= bstr $$measurement-values-map-extension //= ( &(tee.isvprodid: -85) => $tee-isvprodid-type ) $tee-isvprodid-type /= uint $tee-isvprodid-type /= bstr $$measurement-values-map-extension //= ( &(tee.miscselect: -81) => $tee-miscselect-type ) $tee-miscselect-type /= mask-type $tee-miscselect-type /= tagged-exp-mask-eq $$measurement-values-map-extension //= ( &(tee.model: -71) => $tee-model-type ) $tee-model-type /= tstr $$measurement-values-map-extension //= ( &(tee.pceid: -80) => $tee-pceid-type ) $tee-pceid-type /= tstr $$measurement-values-map-extension //= ( &(tee.isvsvn: -73) => $tee-svn-type ) $tee-svn-type /= numeric-type $tee-svn-type /= tagged-numeric-ge $$measurement-values-map-extension //= ( &(tee.tcb-comp-svn: -125) => $tee-tcb-comp-svn-type ) $tee-tcb-comp-svn-type /= [ 16*16 svn-type .within numeric-type ] $tee-tcb-comp-svn-type /= [ 16*16 tagged-numeric-ge ] $$measurement-values-map-extension //= ( &(tee-tcb-eval-num: -86) => $tee-tcb-eval-num-type ) $tee-tcb-eval-num-type /= uint .within numeric-type $tee-tcb-eval-num-type /= tagged-numeric-ge $$measurement-values-map-extension //= ( &(tee.tcbstatus: -88) => $tee-tcbstatus-type ) $tee-tcbstatus-type /= set-type $tee-tcbstatus-type /= tagged-exp-member $$measurement-values-map-extension //= ( &(tee.vendor: -70) => $tee-vendor-type ) $tee-vendor-type /= tstr ]]>