| Internet-Draft | Intel profile | September 2024 |
| Beaney, et al. | Expires 21 March 2025 | [Page] |
This document describes extensions to CoRIM that support Intel-specific Attester implementations and corresponding Endorsements and Reference Values. Multiple Evidence formats are anticipated, but all anticipated Evidence can be mapped to Reference Values expressions based on CoRIM and the 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 may use this profile to author mainifests containing Reference Values and Endorsements. Verifiers will recognize this profile by it's profile identifier and implement support for the extentions defined or may identify a suitable Verifier, or will refuse to process inputs.¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://nedmsmith.github.io/draft-cds-rats-intel-corim-profile/draft-cds-rats-intel-corim-profile.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-cds-rats-intel-corim-profile/.¶
Discussion of this document takes place on the Remote ATtestation ProcedureS 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/.¶
Source for this draft and an issue tracker can be found at https://github.com/nedmsmith/draft-cds-rats-intel-corim-profile.¶
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Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
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 [DICE.engine] root of trust, DICE layers [DICE.layer], or modules that implement SPDM [DMTF.SPDM].¶
CoRIM [DICE.CoRIM] and [I-D.ietf-rats-corim] define a baseline schema for Reference Values and Endorsements that form the foundation for the extensions defined in this profile. CoRIM is also the foundation for Evidence definitions as specified by [DICE.Attest], [TCG.concise-evidence], and [DMTF.SPDM] such that Evidence must be mapped to Reference Values defined by [DICE.CoRIM] and [I-D.ietf-rats-corim]. Additionally, this profile defines Reference Values extensions that express reference state that is super set or range of values. Evidence may be a value that is a subset or within the range specified by Reference Values extensions. This profile defines extensions to CoRIM that support matching based on set membership, masked values, and numeric ranges.¶
The baseline CoRIM, as defined by [DICE.CoRIM] is a subset of this profile. Intel products that implement exclusively to the baseline CoRIM may not rely upon this profile. However, the defined extensions may be generally useful such that implementation of the Intel profile need not imply the Attester, Verifier, Relying Party, Reference Value Provider, or Endorser role implementations must be Intel products.¶
This profile extends CoMID measurement-values-map, as defined by [DICE.CoRIM] (see also [I-D.ietf-rats-corim]), 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 [DICE.CoRIM] and extends Verifier behavior to include operator-operand matching. If no operator is specified by Reference Values statements, the Verifier defaults to baseline [DICE.CoRIM] 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 [I-D.kdyxy-rats-tdx-eat-profile] may be referenced instead.¶
This profile is compatible with multiple Evidence formats, as defined by [DICE.Attest], [TCG.concise-evidence], and [DMTF.SPDM]. It describes considerations when mapping Evidence formats to CoRIM [DICE.CoRIM] that a Verifier may use when performig appraisals.¶
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.¶
The reader is assumed to be familiar with the terms defined in Section 4 of [RFC9334] and [I-D.ietf-rats-endorsements].¶
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 [DICE.layer] resulting in multiple instances of attestation Evidence. Evidence may be integrity protected by digital signatures, such as certificates [DICE.Attest], tokens [RFC8392] or by a secure transport [DMTF.SPDM]. 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 [I-D.ietf-rats-msg-wrap] 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.¶
This profile applies to Reference Values from a CoRIM manifest that a Verifier uses to process Evidence.¶
The profile identifier structure is defined by CoRIM as:¶
$profile-type-choice /= uri $profile-type-choice /= tagged-oid-type¶
The profile identifier for this 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¶
This profile extends the baseline CoMID for Reference Values with an expression that informs Verifiers about non-exact-match matching semantics that include: ranges, sets, and masks.
It extends measurement-values-map which is used by Evidence, Reference Values, and Endorsed Values.¶
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 Section 10¶
For example:¶
#6.60010([ operator, operand_2, operand_3, ... ]).¶
There are several classes of operators as follows:¶
Numeric: The numeric operand can be an integer, unsigned integer, or floading point value.¶
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.¶
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.¶
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.¶
By default, exact match rules are assumed. Consequently, no operator artifact is needed when Evidence values are identical to Reference Values.¶
Numeric operators apply to values that are integers, unsigned integers or floating point numbers. There are four numeric operators:¶
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:¶
gt = 1 ge = 2 lt = 3 le = 4 numeric-type = integer / unsigned / float numeric-operator = gt / ge / lt / le numeric-expression = [ numeric-operator, numeric-type ] tagged-numeric-expression = #6.60010(numeric-expression)¶
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:¶
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:¶
tagged-numeric-gt = #6.60010( [
greater-than: gt .within numeric-operator,
reference-value: numeric-type ] )
tagged-numeric-ge = #6.60010( [
greater-than: ge .within numeric-operator,
reference-value: numeric-type ] )
tagged-numeric-lt = #6.60010( [
greater-than: lt .within numeric-operator,
reference-value: numeric-type ] )
tagged-numeric-le = #6.60010( [
greater-than: le .within numeric-operator,
reference-value: numeric-type ] )
¶
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:¶
A binary relation between a primitive object 'O' and a set 'S', and¶
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:¶
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:¶
member = 6 not-member = 7 set-type = [ * any ] set-operator = member / not-member set-expression = [ set-operator, set-type ] tagged-set-expression = #6.60010( set-expression )¶
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:¶
tagged-exp-member = #6.60010([
member .within set-operator, set-type ])
tagged-exp-not-member = #6.60010([
not-member .within set-operator, set-type ])
¶
Examples:¶
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:¶
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:¶
subset = 8 superset = 9 disjoint = 10 set-of-set-type = [ * [ + any ]] set-of-set-operator = subset / superset / disjoint set-of-set-expression = [ set-of-set-operator, set-of-set-type ] tagged-set-of-set-expression = #6.60010(set-of-set-expression)¶
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:¶
tagged-exp-subset = #6.60010([
subset .within set-of-set-operator, set-of-set-type ])
tagged-exp-superset = #6.60010([
superset .within set-of-set-operator, set-of-set-type ])
tagged-exp-disjoint = #6.60010([
disjoint .within set-of-set-operator, set-of-set-type ])
¶
Date-time can be expressed in both string tdate or numeric time formats.
There are four operators that are defined for date-time expressions:¶
lt determines if a date-time Evidence value is less than a Reference Values date-time.¶
le determines if a date-time Evidence value is less than or equal to a Reference Values date-time.¶
gt determines if a data-time Evidence value is greater than a Reference Values date-time.¶
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:¶
time-operator = numeric-operator time-expression = [ time-operator, time ] ;#6.1(number) tagged-time-expression = #6.60010( time-expression )¶
The string date-time data type definitions are as follows:¶
tdate-operator = numeric-operator ; converts tdate to numeric tdate-expression = [ tdate-operator, tdate ] ;#6.0(string) tagged-tdate-expression = #6.60010( tdate-expression )¶
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:¶
tagged-exp-time-gt = #6.60010([
gt .within time-operator,
time ])
tagged-exp-time-ge = #6.60010([
ge .within time-operator,
time ])
tagged-exp-time-lt = #6.60010([
lt .within time-operator,
time ])
tagged-exp-time-le = #6.60010([
le .within time-operator,
time ])
¶
The string date-time expression definitions are as follows:¶
tagged-exp-tdate-gt = #6.60010([
gt .within tdate-operator,
tdate ])
tagged-exp-tdate-ge = #6.60010([
ge .within tdate-operator,
tdate ])
tagged-exp-tdate-lt = #6.60010([
lt .within tdate-operator,
tdate ])
tagged-exp-tdate-le = #6.60010([
le .within tdate-operator,
tdate ])
¶
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. [I-D.birkholz-rats-epoch-markers] defines several.¶
The epoch data type definitions are as follows:¶
epoch-operator = numeric-operator
epoch-seconds-type = int
epoch-expression = [
epoch-operator,
grace-period: epoch-seconds-type,
? $tagged-epoch-id
]
tagged-epoch-expression = #6.60010( epoch-expression )
$tagged-epoch-id /= tdate
$epoch-timestamp-type /= $tagged-epoch-id
¶
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:¶
tagged-exp-epoch-gt = #6.60010([
gt .within epoch-operator
grace-period: epoch-seconds-type ])
tagged-exp-epoch-ge = #6.60010([
ge .within epoch-operator
grace-period: epoch-seconds-type ])
tagged-exp-epoch-lt = #6.60010([
lt .within epoch-operator
grace-period: epoch-seconds-type ])
tagged-exp-epoch-le = #6.60010([
le .within epoch-operator
grace-period: epoch-seconds-type ])
¶
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.¶
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:¶
mask-eq = 1 mask-operator = mask-eq mask-type = bstr mask-expression = [ mask-operator, value: mask-type, mask: mask-type ] tagged-mask-expression = #6.60010( mask-expression )¶
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:¶
tagged-exp-mask-eq = #6.60010([
mask-eq .within mask-operator,
value: mask-type, mask: mask-type ] )
¶
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 Section 5.1.1.¶
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 Section 7¶
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.¶
$$measurement-values-map-extension //= ( &(tee.advisory-ids: -89) => $tee-advisory-ids-type ) $tee-advisory-ids-type /= set-type $tee-advisory-ids-type /= tagged-exp-not-member¶
The tee.attributes extension enables the Attester to report TEE attributes and an RVP to assert a reference
TEE attributes and mask.¶
The $tee-attributes-type is used to specify TEE attributes in 8 or 16 byte words. If Evidence uses an 8 byte
mask, then the Reference Values expression also uses an 8 byte value and mask.¶
The $tee-attributes-type is a singleton value omitting the mask value when used as Endorsement or Evidence
and a tuple containing the reference and mask when used as a Reference Value.¶
$$measurement-values-map-extension //= ( &(tee.attributes: -82) => $tee-attributes-type ) $tee-attributes-type /= mask-type $tee-attributes-type /= tagged-exp-mask-eq¶
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.¶
$$measurement-values-map-extension //= ( &(tee.cryptokeys: -91) => [ + $tee-cryptokey-type ] ) $tee-cryptokey-type /= $crypto-key-type-choice¶
The tee.tcbdate extension enables the Attester or Endorser to report the TEE date attribute
and a RVP to assert a valid TEE matching operation.¶
The $tee-date-type is a date-time string when used for Evidence or Endorsement.
When used for a Reference Value, either a tagged-tdate-expression or a tagged-epoch-expression describes
the TCB validity.¶
$$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¶
tdate strings must be converted to numeric time before the tdate-operator, which is a numeric operator,
can be applied.¶
The tee.mrenclave and tee.mrsigner extensions enable the Attester to report digests for the SGX enclave,
a.k.a., Target Environment, and the signer, a.k.a., Attesting Environment, of the enclave 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.¶
$$measurement-values-map-extension //= ( &(tee.mrtee: -83) => $tee-digest-type ) $$measurement-values-map-extension //= ( &(tee.mrsigner: -84) => $tee-digest-type ) $tee-digest-type /= digest $tee-digest-type /= [ + digest ] $tee-digest-type /= tagged-exp-member¶
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.¶
$$measurement-values-map-extension //= ( &(tee.epoch: -90) => $tee-epoch-type ) $tee-epoch-type /= $epoch-timestamp-type $tee-epoch-type /= tagged-exp-epoch-gt¶
The tee.instance-id extension enables the Attester to report the (TBD:instance-id-description) Evidence value
and the RVP to assert an exact-match Reference Value.¶
The $tee-instance-id-type is an unsigned integer.¶
The $tee-instance-type is an exact match measurement.¶
$$measurement-values-map-extension //= ( &(tee.instance-id: -77) => $tee-instance-id-type ) $tee-instance-id-type /= uint $tee-instance-id-type /= bstr¶
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.¶
$$measurement-values-map-extension //= ( &(tee.isvprodid: -85) => $tee-isvprodid-type ) $tee-isvprodid-type /= uint $tee-isvprodid-type /= bstr¶
The tee.miscselect extension enables the Attester to report the (TBD:miscselect-description) Evidence value
and the RVP to assert a Reference Value and mask.¶
The $tee-miscselect-type is a 4 byte value and mask.¶
The $tee-miscselect-type is a singleton mask-type value when used as Endorsement or Evidence
and a tagged-mask-expression when used a Reference Value.¶
$$measurement-values-map-extension //= ( &(tee.miscselect: -81) => $tee-miscselect-type ) $tee-miscselect-type /= mask-type $tee-miscselect-type /= tagged-exp-mask-eq¶
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.¶
$$measurement-values-map-extension //= ( &(tee.model: -71) => $tee-model-type ) $tee-model-type /= tstr¶
The tee.pceid extension enables the Attester to report the (TBD:pceid-description) as Evidence
and the RVP to assert an exact-match Reference Value.¶
The $tee-pceid-type is a string.¶
The $tee-pceid-type is an exact match measurement.¶
$$measurement-values-map-extension //= ( &(tee.pceid: -80) => $tee-pceid-type ) $tee-pceid-type /= tstr¶
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.¶
$$measurement-values-map-extension //= ( &(tee.isvsvn: -73) => $tee-svn-type ) $tee-svn-type /= numeric-type $tee-svn-type /= tagged-numeric-ge¶
The tee.tcb-comp-svn extension enables the Attester to report an array of SVN values for the TCB when asserted
as Evidence and an array of tagged-numeric-ge entries when asserted as a Reference Value.¶
The $tee-tcb-comp-svn-type is an array containing 16 SVN values when reported as Evidence and an array of 16
expression records each containing the numeric ge operator and a reference SVN value.
The Verifier evaluates each SVN in the Evidence array with the corresponding reference expression,
by array position.
If all Evidence values match their respective expressions, evaluation is successful.
The array of SVN Evidence is accepted.¶
$$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 ]¶
The tee.tcb-eval-num extension enables the Attester to report a (TBD:tcb-eval-num-description)
as Evidence and the RVP to assert a Reference Value expression that compares the (TBD:tcb-eval-num-description) Evidence
to the Reference Value (TBD:tcb-eval-num-description) 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.¶
$$measurement-values-map-extension //= ( &(tee-tcb-eval-num: -86) => $tee-tcb-eval-num-type ) $tee-tcb-eval-num-type /= uint .within numeric-type $tee-tcb-eval-num-type /= tagged-numeric-ge¶
The tee.tcb-status extension enables the Attester to report the status of the TEE trusted computing base (TCB) as
an array of status strings, as Evidence, and the RVP to assert an array of status arrays as Reference Values where
the Evidence array is a subset of the reference status arrays.¶
The $tee-tcbstatus-type is a status array with a set expressions containing the subset operator when used as Evidence.
When used as a Reference Value it is an array of status arrays.¶
$$measurement-values-map-extension //= ( &(tee.tcbstatus: -88) => $tee-tcbstatus-type ) $tee-tcbstatus-type /= set-type $tee-tcbstatus-type /= tagged-exp-member¶
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.¶
$$measurement-values-map-extension //= ( &(tee.vendor: -70) => $tee-vendor-type ) $tee-vendor-type /= tstr¶
Evidence may be integrity protected in various ways including: certificates [RFC5280], SPDM transcript [DMTF.SPDM], and CBOR web token (CWT) [RFC8392].
Evidence contained in a certificate may be encoded using DiceTcbInfo and DiceTcbInfoSeq [DICE.Attest]. Evidence contained in an SPDM payload may
be encoded using the SPDM Measurement Block [DMTF.SPDM]. Evidence may be formatted as concise-evidence [TCG.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 [DICE.CoRIM].¶
The CoMID extensions defined by this profile, see Section 5.2, 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 refers to SGX layering where the SGX Platform Certification Enclave (PCE) collects measurements of the Quoting Enclave (QE) and the Quoting Enclaves collect measurments of their respective ISV enclaves (ISVE). A hierarchy of Evidence consisting of one PCE Evidence, one QE Evidence and one ISVE Evidence.¶
A complex device may have multiple roots of trust, such as [DICE.engine], 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)
[I-D.ietf-rats-msg-wrap] extension containing a CBOR-encoded tagged-concise-evidence.¶
An SPMD alias intermediate certification chain containing a CMW extension, and an SPDM measurement manifest containing
tagged-concise-evidence.¶
Concise evidence is a CDDL representation of Evidence that is derived from CoMID and CoSWID [RFC9393].
Evidence describes the actual state of the Attester.
tagged-concise-evidence uses a CBOR tag to identify concise-evidence [TCG.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.¶
The concise-evidence structure is defined as follows:¶
tagged-concise-evidence = #6.571(concise-evidence-map)
concise-evidence = concise-evidence-map
concise-evidence-map = {
&(ce.ev-triples: 0) => ev-triples-map
? &(ce.evidence-id: 1) => $evidence-id-type-choice
* $$concise-evidence-map-extension
}
$evidence-id-type-choice /= tagged-uuid-type
; additional evidence identifier types may be added here
ev-triples-map = non-empty< {
;? &(ce.evidence-triples: 0) => [ + reference-triple-record ]
; temporary workaround to non-speccompliant reference-triple-record
? &(ce.evidence-triples: 0) => [ + ce.evidence-triple-record ]
? &(ce.identity-triples: 1) => [ + identity-triple-record ]
? &(ce.dependency-triples: 2) => [ + domain-dependency-triple-record ]
? &(ce.domain-membership-triples: 3) => [ + domain-membership-triple-record ]
? &(ce.coswid-triples: 4) => [ + ev-coswid-triple-record ]
? &(ce.attest-key-triples: 5) => [ + attest-key-triple-record ]
* $$ev-triples-map-extension
} >
ev-coswid-triple-record = [
environment-map,
[ + ev-coswid-evidence-map ]
]
ev-coswid-evidence-map = {
? &(ce.coswid-tag-id: 0) => concise-swid-tag-id
&(ce.coswid-evidence: 1) => evidence-entry
? &(ce.authorized-by: 2) => [ + $crypto-key-type-choice ] ; see comid schema
}
; temporary workaround
ce.evidence-triple-record = [
environment-map
[ + measurement-map ]
]
¶
The Intel profile anticipates appraisal algorithms will be based on the appraisal algorithm defined in [I-D.ietf-rats-corim].
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 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 Section 5.2.¶
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 [I-D.ietf-rats-ar4si] or [I-D.kdyxy-rats-tdx-eat-profile].¶
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.¶
The security of this profile depends on the security considerations of the various normative references.¶
This document uses the IANA CBOR tag registry. See [IANA.CBOR]¶
The following CBOR tag has been assigned:¶
The authors wish to thank Shanwei Cen for valuable contributions.¶
tagged-numeric-gt = #6.60010( [
greater-than: gt .within numeric-operator,
reference-value: numeric-type ] )
tagged-numeric-ge = #6.60010( [
greater-than: ge .within numeric-operator,
reference-value: numeric-type ] )
tagged-numeric-lt = #6.60010( [
greater-than: lt .within numeric-operator,
reference-value: numeric-type ] )
tagged-numeric-le = #6.60010( [
greater-than: le .within numeric-operator,
reference-value: numeric-type ] )
gt = 1
ge = 2
lt = 3
le = 4
numeric-type = integer / unsigned / float
numeric-operator = gt / ge / lt / le
numeric-expression = [ numeric-operator, numeric-type ]
tagged-numeric-expression = #6.60010(numeric-expression)
member = 6
not-member = 7
set-type = [ * any ]
set-operator = member / not-member
set-expression = [ set-operator, set-type ]
tagged-set-expression = #6.60010( set-expression )
tagged-exp-member = #6.60010([
member .within set-operator, set-type ])
tagged-exp-not-member = #6.60010([
not-member .within set-operator, set-type ])
subset = 8
superset = 9
disjoint = 10
set-of-set-type = [ * [ + any ]]
set-of-set-operator = subset / superset / disjoint
set-of-set-expression = [ set-of-set-operator, set-of-set-type ]
tagged-set-of-set-expression = #6.60010(set-of-set-expression)
tagged-exp-subset = #6.60010([
subset .within set-of-set-operator, set-of-set-type ])
tagged-exp-superset = #6.60010([
superset .within set-of-set-operator, set-of-set-type ])
tagged-exp-disjoint = #6.60010([
disjoint .within set-of-set-operator, set-of-set-type ])
mask-eq = 1
mask-operator = mask-eq
mask-type = bstr
mask-expression = [ mask-operator, value: mask-type, mask: mask-type ]
tagged-mask-expression = #6.60010( mask-expression )
tagged-exp-mask-eq = #6.60010([
mask-eq .within mask-operator,
value: mask-type, mask: mask-type ] )
tagged-exp-tdate-gt = #6.60010([
gt .within tdate-operator,
tdate ])
tagged-exp-tdate-ge = #6.60010([
ge .within tdate-operator,
tdate ])
tagged-exp-tdate-lt = #6.60010([
lt .within tdate-operator,
tdate ])
tagged-exp-tdate-le = #6.60010([
le .within tdate-operator,
tdate ])
tdate-operator = numeric-operator ; converts tdate to numeric
tdate-expression = [ tdate-operator, tdate ] ;#6.0(string)
tagged-tdate-expression = #6.60010( tdate-expression )
tagged-exp-time-gt = #6.60010([
gt .within time-operator,
time ])
tagged-exp-time-ge = #6.60010([
ge .within time-operator,
time ])
tagged-exp-time-lt = #6.60010([
lt .within time-operator,
time ])
tagged-exp-time-le = #6.60010([
le .within time-operator,
time ])
time-operator = numeric-operator
time-expression = [ time-operator, time ] ;#6.1(number)
tagged-time-expression = #6.60010( time-expression )
tagged-exp-epoch-gt = #6.60010([
gt .within epoch-operator
grace-period: epoch-seconds-type ])
tagged-exp-epoch-ge = #6.60010([
ge .within epoch-operator
grace-period: epoch-seconds-type ])
tagged-exp-epoch-lt = #6.60010([
lt .within epoch-operator
grace-period: epoch-seconds-type ])
tagged-exp-epoch-le = #6.60010([
le .within epoch-operator
grace-period: epoch-seconds-type ])
epoch-operator = numeric-operator
epoch-seconds-type = int
epoch-expression = [
epoch-operator,
grace-period: epoch-seconds-type,
? $tagged-epoch-id
]
tagged-epoch-expression = #6.60010( epoch-expression )
$tagged-epoch-id /= tdate
$epoch-timestamp-type /= $tagged-epoch-id
$$measurement-values-map-extension //= (
&(tee.advisory-ids: -89) => $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
¶
tagged-concise-evidence = #6.571(concise-evidence-map)
concise-evidence = concise-evidence-map
concise-evidence-map = {
&(ce.ev-triples: 0) => ev-triples-map
? &(ce.evidence-id: 1) => $evidence-id-type-choice
* $$concise-evidence-map-extension
}
$evidence-id-type-choice /= tagged-uuid-type
; additional evidence identifier types may be added here
ev-triples-map = non-empty< {
;? &(ce.evidence-triples: 0) => [ + reference-triple-record ]
; temporary workaround to non-speccompliant reference-triple-record
? &(ce.evidence-triples: 0) => [ + ce.evidence-triple-record ]
? &(ce.identity-triples: 1) => [ + identity-triple-record ]
? &(ce.dependency-triples: 2) => [ + domain-dependency-triple-record ]
? &(ce.domain-membership-triples: 3) => [ + domain-membership-triple-record ]
? &(ce.coswid-triples: 4) => [ + ev-coswid-triple-record ]
? &(ce.attest-key-triples: 5) => [ + attest-key-triple-record ]
* $$ev-triples-map-extension
} >
ev-coswid-triple-record = [
environment-map,
[ + ev-coswid-evidence-map ]
]
ev-coswid-evidence-map = {
? &(ce.coswid-tag-id: 0) => concise-swid-tag-id
&(ce.coswid-evidence: 1) => evidence-entry
? &(ce.authorized-by: 2) => [ + $crypto-key-type-choice ] ; see comid schema
}
; temporary workaround
ce.evidence-triple-record = [
environment-map
[ + measurement-map ]
]
¶