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Group Membership & MEC Endorsment #168

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Group Membership & MEC Endorsment #168

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695cace
First draft Group and MEC Endorsement sections
yogeshbdeshpande Oct 12, 2023
69a494b
Address comments from last meeting
thomas-fossati Nov 24, 2023
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3 changes: 2 additions & 1 deletion cddl/corim-frags.mk
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,8 @@ COMID_FRAGS += cose-label-and-value.cddl
COMID_FRAGS += coswid-triple-record.cddl
COMID_FRAGS += crypto-key-type-choice.cddl
COMID_FRAGS += domain-dependency-triple-record.cddl
COMID_FRAGS += domain-membership-triple-record.cddl
COMID_FRAGS += group-membership-triple-record.cddl
COMID_FRAGS += mec-endorsement-triple-record.cddl
COMID_FRAGS += domain-type-choice.cddl
COMID_FRAGS += endorsed-triple-record.cddl
COMID_FRAGS += entity-map.cddl
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4 changes: 0 additions & 4 deletions cddl/domain-membership-triple-record.cddl
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This file was deleted.

105 changes: 15 additions & 90 deletions cddl/examples/comid-domain-mem.diag
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Expand Up @@ -8,107 +8,32 @@
}
],
/ triples / 4 : {
/ membership-triples / 5 : [
[ / domain - text / "XYZ_Root-of-trust",
[
/ environment-map / {
/ ** A Root of Trust module ** /
/ comid.class / 0 : {
/ comid.class-id / 0 :
/ tagged-oid-type / 111(h'0607517B010F6201'), / 2.1.123.1.15.98.1 /
/ comid.vendor / 1 : "XYZ.example"
}
}
]
],
[ / domain - int / 1,
[
/ environment-map / {
/ ** Layer 1 loader module 1 ** /
/ comid.class / 0 : {
/ comid.class-id / 0 :
/ tagged-oid-type / 111(h'0607517B010F0801'), / 2.1.123.1.15.8.1 /
/ comid.vendor / 1 : "LoadInc.example",
/ comid.layer / 3 : 1
}
},
/ environment-map / {
/ ** Layer 1 loader module 2 ** /
/ comid.class / 0 : {
/ comid.class-id / 0 :
/ tagged-oid-type / 111(h'0607517B010F0802'), / 2.1.123.1.15.8.2 /
/ comid.vendor / 1 : "LoadInc.example",
/ comid.layer / 3 : 1
}
/ group-triples / 5 : [
[
/ environment-map / {
/ comid.class / 0 : {
/ comid.class-id / 0 : / tagged-oid-type / 111(h'0607517B010F6201'), / 2.1.123.1.15.98.1 /
/ comid.vendor / 1 : "ACME Ltd.",
/ comid.model / 2 : "PSA RoT X"
}
]
],
[ / domain - text / "L1-extension",
[
/ environment-map / {
/ ** L1 Extension module 1 ** /
/ comid.class / 0 : {
/ comid.class-id / 0 :
/ tagged-oid-type / 111(h'0607517B010F0903'), / 2.1.123.1.15.9.3 /
/ comid.vendor / 1 : "LoadInc.example",
/ comid.layer / 3 : 1
}
}
]
],
[ / domain - tagged-uuid-type / 37(
h'67b28b6c34cc40a19117ab5b05911e37'
),
[
/ environment-map / {
/ ** Layer 2 design module 1 ** /
/ comid.class / 0 : {
/ comid.class-id / 0 :
/ tagged-oid-type / 111(h'0607517B010F0401'), / 2.1.123.1.15.4.1 /
/ comid.vendor / 1 : "FPGAsRuS.example",
/ comid.layer / 3 : 2
}
},
/ environment-map / {
/ ** Layer 2 design module 2 ** /
/ comid.class / 0 : {
/ comid.class-id / 0 :
/ tagged-oid-type / 111(h'0607517B010F0402'), / 2.1.123.1.15.4.2 /
/ comid.vendor / 1 : "FPGAsRuS.example",
/ comid.layer / 3 : 2
}
},
/ environment-map / {
/ ** Layer 2 design module 3 ** /
/ comid.class / 0 : {
/ comid.class-id / 0 :
/ tagged-oid-type / 111(h'0607517B010F0403'), / 2.1.123.1.15.4.3 /
/ comid.vendor / 1 : "FPGAsRuS.example",
/ comid.layer / 3 : 2
}
}
]
],
[ / domain - tagged-oid-type / 111(h'6086480186F84D010F0401'), / 2.16.840.1.113741.1.15.4.1 /
},
[
/ environment-map / {
/ ** ISV App module 1 ** /
/ comid.class / 0 : {
/ comid.class-id / 0 :
/ tagged-oid-type / 111(h'0607517B010F046301'), / 2.1.123.1.15.4.99.1 /
/ comid.vendor / 1 : "ISV-App.example"
/ comid.class-id / 0 : 37(h'57057d658db1403b9e387f9f0fa604cf'),
/ comid.vendor / 1 : "FW Manufacturer X",
/ comid.model / 2 : "BL"
}
},
/ environment-map / {
/ ** ISV App module 2 ** /
/ comid.class / 0 : {
/ comid.class-id / 0 :
/ tagged-oid-type / 111(h'0607517B010F046302'), / 2.1.123.1.15.4.99.2 /
/ comid.vendor / 1 : "ISV-App.example"
/ comid.class-id / 0 : 37(h'993a383a41134c999c333a13414a546d'),
/ comid.vendor / 1 : "FW Manufacturer X",
/ comid.model / 2 : "TF-M"
}
}
]
]
]
}
}
}
4 changes: 4 additions & 0 deletions cddl/group-membership-triple-record.cddl
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@@ -0,0 +1,4 @@
environment-bundle-triple-record = [
lead: environment-map
subs: [ + environment-map ]
]
5 changes: 5 additions & 0 deletions cddl/mec-endorsement-triple-record.cddl
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@@ -0,0 +1,5 @@
multi-env-conditional-endorsement-triple-record = [
env: environment-map
ends: [ + measurement-values-map ]
cond: [ + stateful-environment-record ]
]
Comment on lines +1 to +5
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@henkbirkholz henkbirkholz Nov 29, 2023 •
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Suggested change
multi-env-conditional-endorsement-triple-record = [
env: environment-map
ends: [ + measurement-values-map ]
cond: [ + stateful-environment-record ]
]
multi-env-conditional-endorsement-triple-record = [
cond: [ + stateful-environment-record ]
env: environment-map
ends: [ + measurement-values-map ]
]

4 changes: 3 additions & 1 deletion cddl/triples-map.cddl
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Original file line number Diff line number Diff line change
Expand Up @@ -10,12 +10,14 @@ triples-map = non-empty<{
? &(dependency-triples: 4) =>
[ + domain-dependency-triple-record ]
? &(membership-triples: 5) =>
[ + domain-membership-triple-record ]
[ + environment-bundle-triple-record ]
? &(coswid-triples: 6) =>
[ + coswid-triple-record ]
? &(conditional-endorsement-series-triples: 8) =>
[ + conditional-endorsement-series-triple-record ]
? &(conditional-endorsement-triples: 9) =>
[ + conditional-endorsement-triple-record ]
? &(mec-endorsement-triples: 10) =>
[ + multi-env-conditional-endorsement-triple-record ]
* $$triples-map-extension
}>
90 changes: 79 additions & 11 deletions draft-ietf-rats-corim.md
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Expand Up @@ -569,7 +569,7 @@ The following triples are currently defined:
* Device Identity triples: containing cryptographic credentials - for example, an IDevID - uniquely identifying a device ({{sec-comid-triple-identity}}).
* Attestation Key triples: containing cryptographic keys that are used to verify the integrity protection on the Evidence received from the Attester ({{sec-comid-triple-attest-key}}).
* Domain dependency triples: describing trust relationships between domains, i.e., collection of related environments and their measurements ({{sec-comid-triple-domain-dependency}}).
* Domain membership triples: describing topological relationships between (sub-)modules. For example, in a composite Attester comprising multiple sub-Attesters (sub-modules), this triple can be used to define the topological relationship between lead- and sub- Attester environments ({{sec-comid-triple-domain-membership}}).
* Environment bundle triples: describing topological relationships between (sub-)modules. For example, in a composite Attester comprising multiple sub-Attesters (sub-modules), this triple can be used to define the topological relationship between lead- and sub- Attester environments ({{sec-comid-triple-environment-bundle}}).
* CoMID-CoSWID linking triples: associating a Target Environment with existing CoSWID tags ({{sec-comid-triple-coswid}}).

## Structure
Expand Down Expand Up @@ -736,7 +736,7 @@ The following describes each member of the `triples-map`:
between domains. Described in {{sec-comid-triple-domain-dependency}}.

* `membership-triples` (index 5): Triples describing topological relationships
between (sub-)modules. Described in {{sec-comid-triple-domain-membership}}.
between (sub-)modules. Described in {{sec-comid-triple-environment-bundle}}.

* `coswid-triples` (index 6): Triples associating modules with existing CoSWID
tags. Described in {{sec-comid-triple-coswid}}.
Expand Down Expand Up @@ -822,7 +822,7 @@ UEID, UUID, or cryptographic key identifier.
{::include cddl/instance-id-type-choice.cddl}
~~~

##### Group
##### Group

A group carries a unique identifier that is reliably bound to a group of
Attesters, for example when a number of Attester are hidden in the same
Expand Down Expand Up @@ -1173,19 +1173,87 @@ trustworthiness properties of the subject domain exists.
{::include cddl/domain-dependency-triple-record.cddl}
~~~

#### Domain Membership Triple {#sec-comid-triple-domain-membership}
#### Environmnent Bundle Triple {#sec-comid-triple-environment-bundle}

A Domain Membership triple assigns domain membership to environments. The
subject identifies a domain ({{sec-comid-domain-type}}) that has a predicate
relationship to the object containing one or more environments. Endorsed
environments ({{sec-comid-triple-endval}}) membership is conditional upon
successful matching of Reference Values ({{sec-comid-triple-refval}}) to
Evidence.
In order to model hierarchical device composition, CoRIM authors need to identify all components in the composite device (see {{Section 3.3 of -rats-arch}}).
An environment bundle describes all target environments that a certain attesting environment is generating evidence about.
The parent-child relationship between the attesting environment and all target environments in question is expressed via the environment bundle triple:

~~~ cddl
{::include cddl/domain-membership-triple-record.cddl}
{::include cddl/group-membership-triple-record.cddl}
~~~

In the example composite device in {{composite}}, `env-1` is the Attesting Environment for `env-2` and `env-3`, while `env-2` is the Attesting Environment for `env-4`.
Appraisal starts from the top of the device hierarchy (`env-1`) and descends through all the sub-trees until all Target Environments have been visited.

~~~ aasvg
.-------.
| env-1 |
'---+---'
| .-------.
+--+ env-2 |
| '---+---'
| | .-------.
| +--+ env-4 |
| '-------'
| .-------.
+--+ env-3 |
'-------'
~~~
{: #composite artwork-align="center" title="Example Environments Composition"}

The two following group triples model the device hierarchy:

* The top-level with `env-1` as lead attester:

~~~
environment-bundle-triple-record = [
lead: env-1
subs: [ env-2, env-3 ]
]
~~~

* The sub-attester rooted at `env-2`:

~~~
environment-bundle-triple-record = [
lead: env-2
subs: [ env-4 ]
]
~~~

The `lead` environment is the environment bundle name.
Since it is expressed as an `environment-map`, it can itself appear as one of the `subs` elements of other `environment-bundle-triple-record`, thus allowing recursive composition.

The scope of a single `environment-bundle-triple-record` encompasses exactly two adjacent layers in a layered Attester.

#### Multi-Environment Conditional (MEC) Endorsements Triple {#sec-comid-triple-mec-endorsements}

The semantics of the Multi-Environment Conditional (MEC) Endorsements Triple is as follows:

> "IF accepted state matches the `cond` value, THEN `env` is associated with the endorsed value(s) `ends`."

~~~ cddl
{::include cddl/mec-endorsement-triple-record.cddl}
~~~

A `multi-env-conditional-endorsement-triple-record` has the following parameters:

* `env`: the environment to which the endorsed value (conditionally) applies
* `ends`: the endorsed value(s) associated with `env`
* `cond`: all target environments, along with a specific state, that need to match in order for the endorsement(s) to apply

All the entries in `cond` MUST match.

The order in which MEC Endorsement triples are evaluated is important: different sorting may produce different end-results in the computed ACS.

Therefore, the set of applicable MEC Endorsement triple MUST be topologically sorted based on the criterion that a MEC Endorsement triple is evaluated before another if its Target Environment and Endorsement pair is found in any of the stateful environments of the second triple.

Notes:

* In order to give the expected result, the condition must describe the expected context completely.
* The scope of a single MEC triple encompasses an arbitrary amount of environments across all layers in an Attester.

#### CoMID-CoSWID Linking Triple {#sec-comid-triple-coswid}

A CoSWID triple relates reference measurements contained in one or more CoSWIDs
Expand Down
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