Internet DRAFT - draft-ietf-teep-protocol
draft-ietf-teep-protocol
TEEP H. Tschofenig
Internet-Draft
Intended status: Standards Track M. Pei
Expires: 9 May 2024 Broadcom
D. Wheeler
Amazon
D. Thaler
Microsoft
A. Tsukamoto
ALAXALA Networks Corp.
6 November 2023
Trusted Execution Environment Provisioning (TEEP) Protocol
draft-ietf-teep-protocol-18
Abstract
This document specifies a protocol that installs, updates, and
deletes Trusted Components in a device with a Trusted Execution
Environment (TEE). This specification defines an interoperable
protocol for managing the lifecycle of Trusted Components.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on 9 May 2024.
Copyright Notice
Copyright (c) 2023 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.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Message Overview . . . . . . . . . . . . . . . . . . . . . . 5
4. Detailed Messages Specification . . . . . . . . . . . . . . . 6
4.1. Creating and Validating TEEP Messages . . . . . . . . . . 7
4.1.1. Creating a TEEP message . . . . . . . . . . . . . . . 7
4.1.2. Validating a TEEP Message . . . . . . . . . . . . . . 7
4.2. QueryRequest Message . . . . . . . . . . . . . . . . . . 8
4.3. QueryResponse Message . . . . . . . . . . . . . . . . . . 12
4.3.1. Evidence and Attestation Results . . . . . . . . . . 15
4.4. Update Message . . . . . . . . . . . . . . . . . . . . . 16
4.4.1. Scenario 1: Having one SUIT Manifest pointing to a URI
of a Trusted Component Binary . . . . . . . . . . . . 19
4.4.2. Scenario 2: Having a SUIT Manifest include the Trusted
Component Binary . . . . . . . . . . . . . . . . . . 22
4.4.3. Scenario 3: Supplying Personalization Data for the
Trusted Component Binary . . . . . . . . . . . . . . 23
4.5. Success Message . . . . . . . . . . . . . . . . . . . . . 25
4.6. Error Message . . . . . . . . . . . . . . . . . . . . . . 26
5. EAT Profile . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.1. Relationship to AR4SI . . . . . . . . . . . . . . . . . . 31
6. Mapping of TEEP Message Parameters to CBOR Labels . . . . . . 32
7. Behavior Specification . . . . . . . . . . . . . . . . . . . 34
7.1. TAM Behavior . . . . . . . . . . . . . . . . . . . . . . 34
7.1.1. Handling a QueryResponse Message . . . . . . . . . . 35
7.1.1.1. Handling an Attestation Result . . . . . . . . . 35
7.1.2. Handling a Success or Error Message . . . . . . . . . 37
7.2. TEEP Agent Behavior . . . . . . . . . . . . . . . . . . . 37
7.2.1. Handling a QueryRequest Message . . . . . . . . . . . 38
7.2.1.1. Handling an Attestation Result . . . . . . . . . 39
7.2.2. Handling an Update Message . . . . . . . . . . . . . 39
8. Cipher Suites . . . . . . . . . . . . . . . . . . . . . . . . 39
8.1. TEEP Messages . . . . . . . . . . . . . . . . . . . . . . 40
8.2. EATs and SUIT Reports . . . . . . . . . . . . . . . . . . 42
9. Attestation Freshness Mechanisms . . . . . . . . . . . . . . 44
10. Security Considerations . . . . . . . . . . . . . . . . . . . 44
11. Privacy Considerations . . . . . . . . . . . . . . . . . . . 47
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 47
12.1. Media Type Registration . . . . . . . . . . . . . . . . 47
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 48
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13.1. Normative References . . . . . . . . . . . . . . . . . . 48
13.2. Informative References . . . . . . . . . . . . . . . . . 50
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 52
B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 52
C. Complete CDDL . . . . . . . . . . . . . . . . . . . . . . . . 52
D. Examples of Diagnostic Notation and Binary Representation . . 56
D.1. QueryRequest Message . . . . . . . . . . . . . . . . . . 57
D.1.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 57
D.1.2. CBOR Binary Representation . . . . . . . . . . . . . 57
D.2. Entity Attestation Token . . . . . . . . . . . . . . . . 58
D.2.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 58
D.3. QueryResponse Message . . . . . . . . . . . . . . . . . . 59
D.3.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 59
D.3.2. CBOR Binary Representation . . . . . . . . . . . . . 60
D.4. Update Message . . . . . . . . . . . . . . . . . . . . . 61
D.4.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 61
D.4.2. CBOR Binary Representation . . . . . . . . . . . . . 62
D.5. Success Message . . . . . . . . . . . . . . . . . . . . . 62
D.5.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 62
D.5.2. CBOR Binary Representation . . . . . . . . . . . . . 63
D.6. Error Message . . . . . . . . . . . . . . . . . . . . . . 63
D.6.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 63
D.6.2. CBOR binary Representation . . . . . . . . . . . . . 63
E. Examples of SUIT Manifests . . . . . . . . . . . . . . . . . 64
Example 1: SUIT Manifest pointing to URI of the Trusted Component
Binary . . . . . . . . . . . . . . . . . . . . . . . . 64
CBOR Diagnostic Notation of SUIT Manifest . . . . . . . . . . 64
CBOR Binary in Hex . . . . . . . . . . . . . . . . . . . . . 65
Example 2: SUIT Manifest including the Trusted Component
Binary . . . . . . . . . . . . . . . . . . . . . . . . 66
CBOR Diagnostic Notation of SUIT Manifest . . . . . . . . . . 66
CBOR Binary in Hex . . . . . . . . . . . . . . . . . . . . . 67
Example 3: Supplying Personalization Data for Trusted Component
Binary . . . . . . . . . . . . . . . . . . . . . . . . 68
CBOR Diagnostic Notation of SUIT Manifest . . . . . . . . . . 68
CBOR Binary in Hex . . . . . . . . . . . . . . . . . . . . . 71
F. Examples of SUIT Reports . . . . . . . . . . . . . . . . . . 71
F.1. Example 1: Success . . . . . . . . . . . . . . . . . . . 72
F.2. Example 2: Faiure . . . . . . . . . . . . . . . . . . . . 72
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 73
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1. Introduction
The Trusted Execution Environment (TEE) concept has been designed to
separate a regular operating system, also referred as a Rich
Execution Environment (REE), from security-sensitive applications.
In a TEE ecosystem, device vendors may use different operating
systems in the REE and may use different types of TEEs. When Trusted
Component Developers or Device Administrators use Trusted Application
Managers (TAMs) to install, update, and delete Trusted Applications
and their dependencies on a wide range of devices with potentially
different TEEs then an interoperability need arises.
This document specifies the protocol for communicating between a TAM
and a TEEP Agent.
The Trusted Execution Environment Provisioning (TEEP) architecture
document [RFC9397] provides design guidance and introduces the
necessary terminology.
2. Terminology
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.
This specification re-uses the terminology defined in [RFC9397].
As explained in Section 4.4 of that document, the TEEP protocol
treats each Trusted Application (TA), any dependencies the TA has,
and personalization data as separate components that are expressed in
SUIT manifests, and a SUIT manifest might contain or reference
multiple binaries (see [I-D.ietf-suit-manifest] for more details).
As such, the term Trusted Component (TC) in this document refers to a
set of binaries expressed in a SUIT manifest, to be installed in a
TEE. Note that a Trusted Component may include one or more TAs and/
or configuration data and keys needed by a TA to operate correctly.
Each Trusted Component is uniquely identified by a SUIT Component
Identifier (see [I-D.ietf-suit-manifest] Section 8.7.2.2).
Attestation related terms, such as Evidence and Attestation Results,
are as defined in [RFC9334].
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3. Message Overview
The TEEP protocol consists of messages exchanged between a TAM and a
TEEP Agent. The messages are encoded in CBOR and designed to provide
end-to-end security. TEEP protocol messages are signed by the
endpoints, i.e., the TAM and the TEEP Agent, but Trusted Applications
may also be encrypted and signed by a Trusted Component Developer or
Device Administrator. The TEEP protocol not only uses CBOR but also
the respective security wrapper, namely COSE [RFC9052]. Furthermore,
for software updates the SUIT manifest format
[I-D.ietf-suit-manifest] is used, and for attestation the Entity
Attestation Token (EAT) [I-D.ietf-rats-eat] format is supported
although other attestation formats are also permitted.
This specification defines five messages: QueryRequest,
QueryResponse, Update, Success, and Error.
A TAM queries a device's current state with a QueryRequest message.
A TEEP Agent will, after authenticating and authorizing the request,
report attestation information, list all Trusted Components, and
provide information about supported algorithms and extensions in a
QueryResponse message. An error message is returned if the request
could not be processed. A TAM will process the QueryResponse message
and determine whether to initiate subsequent message exchanges to
install, update, or delete Trusted Applications.
+------------+ +-------------+
| TAM | |TEEP Agent |
+------------+ +-------------+
QueryRequest ------->
QueryResponse
<------- or
Error
With the Update message a TAM can instruct a TEEP Agent to install
and/or delete one or more Trusted Components. The TEEP Agent will
process the message, determine whether the TAM is authorized and
whether the Trusted Component has been signed by an authorized
Trusted Component Signer. A Success message is returned when the
operation has been completed successfully, or an Error message
otherwise.
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+------------+ +-------------+
| TAM | |TEEP Agent |
+------------+ +-------------+
Update ---->
Success
<---- or
Error
4. Detailed Messages Specification
TEEP messages are protected by the COSE_Sign1 or COSE_Sign structure
as described in Section 8.1. The TEEP protocol messages are
described in CDDL format [RFC8610] below.
teep-message = $teep-message-type .within teep-message-framework
teep-message-framework = [
type: $teep-type / $teep-type-extension,
options: { * teep-option },
* any; further elements, e.g., for data-item-requested
]
teep-option = (uint => any)
; messages defined below:
$teep-message-type /= query-request
$teep-message-type /= query-response
$teep-message-type /= update
$teep-message-type /= teep-success
$teep-message-type /= teep-error
; message type numbers, in one byte which could take a number from 0 to 23
$teep-type = (0..23)
TEEP-TYPE-query-request = 1
TEEP-TYPE-query-response = 2
TEEP-TYPE-update = 3
TEEP-TYPE-teep-success = 5
TEEP-TYPE-teep-error = 6
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4.1. Creating and Validating TEEP Messages
4.1.1. Creating a TEEP message
To create a TEEP message, the following steps are performed.
1. Create a TEEP message according to the description below and
populate it with the respective content. TEEP messages sent by
TAMs (QueryRequest and Update) can include a "token". The TAM
can decide, in any implementation-specific way, whether to
include a token in a message. The first usage of a token
generated by a TAM MUST be randomly created. Subsequent token
values MUST be different for each subsequent message created by a
TAM.
2. Create a COSE Header containing the desired set of Header
Parameters. The COSE Header MUST be valid per the [RFC9052]
specification.
3. Create a COSE_Sign1 or COSE_Sign object using the TEEP message as
the COSE_Sign1 or COSE_Sign Payload; all steps specified in
[RFC9052] for creating a COSE_Sign1 or COSE_Sign object MUST be
followed.
4.1.2. Validating a TEEP Message
When a TEEP message is received (see the ProcessTeepMessage
conceptual API defined in Section 6.2.1 of [RFC9397]), the following
validation steps are performed. If any of the listed steps fail,
then the TEEP message MUST be rejected.
1. Verify that the received message is a valid CBOR object.
2. Verify that the message contains a COSE_Sign1 or COSE_Sign
structure.
3. Verify that the resulting COSE Header includes only parameters
and values whose syntax and semantics are both understood and
supported or that are specified as being ignored when not
understood.
4. Follow the steps specified in Section 4 of [RFC9052] ("Signing
Objects") for validating a COSE_Sign1 or COSE_Sign object. The
COSE_Sign1 or COSE_Sign payload is the content of the TEEP
message.
5. Verify that the TEEP message is a valid CBOR map and verify the
fields of the TEEP message according to this specification.
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4.2. QueryRequest Message
A QueryRequest message is used by the TAM to learn information from
the TEEP Agent, such as the features supported by the TEEP Agent,
including cipher suites and protocol versions. Additionally, the TAM
can selectively request data items from the TEEP Agent by using the
data-item-requested parameter. Currently, the following features are
supported:
* Request for attestation information of the TEEP Agent,
* Listing supported extensions,
* Querying installed Trusted Components, and
* Request for logging information in SUIT Reports.
Like other TEEP messages, the QueryRequest message is signed, and the
relevant CDDL snippet is shown below. The complete CDDL structure is
shown in Appendix C.
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query-request = [
type: TEEP-TYPE-query-request,
options: {
? token => bstr .size (8..64),
? supported-freshness-mechanisms => [ + $freshness-mechanism ],
? challenge => bstr .size (8..512),
? versions => [ + version ],
? attestation-payload-format => text,
? attestation-payload => bstr,
? suit-reports => [ + bstr ],
* $$query-request-extensions,
* $$teep-option-extensions
},
supported-teep-cipher-suites: [ + $teep-cipher-suite ],
supported-suit-cose-profiles: [ + $suit-cose-profile ],
data-item-requested: uint .bits data-item-requested
]
version = uint .size 4
ext-info = uint .size 4
; data items as bitmaps
data-item-requested = &(
attestation: 0,
trusted-components: 1,
extensions: 2,
suit-reports: 3,
)
The message has the following fields:
type
The value of (1) corresponds to a QueryRequest message sent from
the TAM to the TEEP Agent.
token
The value in the token parameter is used to match responses to
requests, such as to look up any implementation-specific state it
might have saved about that request, or to ignore responses to
older QueryRequest messages before some configuration changes were
made that affected their content. This is particularly useful
when a TAM issues multiple concurrent requests to a TEEP Agent.
The token MUST be present if and only if the attestation bit is
clear in the data-item-requested value. When the attestation bit
is clear then a challenge will be included, which offers replay
protection capabilities. The size of the token is at least 8
bytes (64 bits) and maximum of 64 bytes. The first usage of a
token generated by a TAM MUST be randomly created. Subsequent
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token values MUST be different for each request message to
distinguish the correct response from multiple requests. The
token value MUST NOT be used for other purposes, such as a TAM to
identify the devices and/or a device to identify TAMs or Trusted
Components. The TAM SHOULD set an expiration time for each token
and MUST ignore any messages with expired tokens. The TAM MUST
expire the token value after receiving the first response
containing the token value and ignore any subsequent messages that
have the same token value.
supported-teep-cipher-suites
The supported-teep-cipher-suites parameter lists the TEEP cipher
suites supported by the TAM. Details about the cipher suite
encoding can be found in Section 8.1.
supported-suit-cose-profiles
The supported-suit-cose-profiles parameter lists the SUIT profiles
supported by the TAM for parsing SUIT Reports. Details about the
cipher suite encoding can be found in Section 8.2.
data-item-requested
The data-item-requested parameter indicates what information the
TAM requests from the TEEP Agent in the form of a bitmap.
attestation (1) With this value the TAM requests the TEEP Agent
to return an attestation payload, whether Evidence (e.g., an
EAT) or an Attestation Result, in the response.
trusted-components (2) With this value the TAM queries the TEEP
Agent for all installed Trusted Components.
extensions (4) With this value the TAM queries the TEEP Agent for
supported capabilities and extensions, which allows a TAM to
discover the capabilities of a TEEP Agent implementation.
suit-reports (8) With this value the TAM requests the TEEP Agent
to return SUIT Reports in the response.
Further values may be added in the future.
supported-freshness-mechanisms
The supported-freshness-mechanisms parameter lists the freshness
mechanism(s) supported by the TAM. Details about the encoding can
be found in Section 9. If this parameter is absent, it means only
the nonce mechanism is supported. It MUST be absent if the
attestation bit is clear.
challenge
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The challenge field is an optional parameter used for ensuring the
freshness of attestation Evidence returned with a QueryResponse
message. It MUST be absent if the attestation bit is clear or the
Passport model is used. When a challenge is provided in the
QueryRequest and Evidence in the form of an EAT is returned with a
QueryResponse message then the challenge contained in the
QueryRequest MUST be used to generate the EAT, by copying the
challenge into the eat_nonce claim (Section 4.1 of Section 5) if
the nonce-based freshness mechanism is used for attestation
Evidence. For more details about freshness of Evidence see
Section 9.
If any format other than EAT is used, it is up to that format to
define the use of the challenge field.
versions
The versions parameter enumerates the TEEP protocol version(s)
supported by the TAM. A value of 0 refers to the current version
of the TEEP protocol. If this field is not present, it is to be
treated the same as if it contained only version 0.
attestation-payload-format
The attestation-payload-format parameter indicates the IANA Media
Type of the attestation-payload parameter, where media type
parameters are permitted after the media type. For protocol
version 0, the absence of this parameter indicates that the format
is "application/eat+cwt; eat_profile=urn:ietf:rfc:rfcXXXX" (see
[I-D.ietf-rats-eat-media-type] for further discussion). (RFC-
editor: upon RFC publication, replace XXXX above with the RFC
number of this document.) It MUST be present if the attestation-
payload parameter is present and the format is not an EAT in CWT
format with the profile defined below in Section 5.
attestation-payload
The attestation-payload parameter contains Evidence or an
Attestation Result for the TEEP Agent to use to perform
attestation of the TAM. If the attestation-payload-format
parameter is absent, the attestation payload contained in this
parameter MUST be an Entity Attestation Token following the
encoding defined in [I-D.ietf-rats-eat]. See Section 4.3.1 for
further discussion.
suit-reports
If present, the suit-reports parameter contains a set of "boot"
(including starting an executable in an OS context) time SUIT
Reports of the TAM as defined by SUIT_Report in Section 4 of
[I-D.ietf-suit-report], encoded using COSE as discussed in
Section 8.2. SUIT Reports can be useful in QueryRequest messages
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to pass additional information about the TAM to the TEEP Agent
without depending on a Verifier including the relevant information
in the TAM's Attestation Results.
4.3. QueryResponse Message
The QueryResponse message is the successful response by the TEEP
Agent after receiving a QueryRequest message. As discussed in
Section 7.2, it can also be sent unsolicited if the contents of the
QueryRequest are already known and do not vary per message.
Like other TEEP messages, the QueryResponse message is signed, and
the relevant CDDL snippet is shown below. The complete CDDL
structure is shown in Appendix C.
query-response = [
type: TEEP-TYPE-query-response,
options: {
? token => bstr .size (8..64),
? selected-version => version,
? attestation-payload-format => text,
? attestation-payload => bstr,
? suit-reports => [ + bstr ],
? tc-list => [ + system-property-claims ],
? requested-tc-list => [ + requested-tc-info ],
? unneeded-manifest-list => [ + SUIT_Component_Identifier ],
? ext-list => [ + ext-info ],
* $$query-response-extensions,
* $$teep-option-extensions
}
]
requested-tc-info = {
component-id => SUIT_Component_Identifier,
? tc-manifest-sequence-number => uint .size 8,
? have-binary => bool
}
The QueryResponse message has the following fields:
type
The value of (2) corresponds to a QueryResponse message sent from
the TEEP Agent to the TAM.
token
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The value in the token parameter is used to match responses to
requests. The value MUST correspond to the value received with
the QueryRequest message if one was present, and MUST be absent if
no token was present in the QueryRequest.
selected-version
The selected-version parameter indicates the TEEP protocol version
selected by the TEEP Agent. The absence of this parameter
indicates the same as if it was present with a value of 0.
attestation-payload-format
The attestation-payload-format parameter indicates the IANA Media
Type of the attestation-payload parameter, where media type
parameters are permitted after the media type. For protocol
version 0, the absence of this parameter indicates that the format
is "application/eat+cwt; eat_profile=urn:ietf:rfc:rfcXXXX" (see
[I-D.ietf-rats-eat-media-type] for further discussion). (RFC-
editor: upon RFC publication, replace XXXX above with the RFC
number of this document.) It MUST be present if the attestation-
payload parameter is present and the format is not an EAT in CWT
format with the profile defined below in Section 5.
attestation-payload
The attestation-payload parameter contains Evidence or an
Attestation Result. This parameter MUST be present if the
QueryResponse is sent in response to a QueryRequest with the
attestation bit set. If the attestation-payload-format parameter
is absent, the attestation payload contained in this parameter
MUST be an Entity Attestation Token following the encoding defined
in [I-D.ietf-rats-eat]. See Section 4.3.1 for further discussion.
suit-reports
If present, the suit-reports parameter contains a set of "boot"
(including starting an executable in an OS context) time SUIT
Reports as defined by SUIT_Report in Section 4 of
[I-D.ietf-suit-report], encoded using COSE as discussed in
Section 8.2. If a token parameter was present in the QueryRequest
message the QueryResponse message is in response to, the suit-
report-nonce field MUST be present in the SUIT Report with a value
matching the token parameter in the QueryRequest message. SUIT
Reports can be useful in QueryResponse messages to pass
information to the TAM without depending on a Verifier including
the relevant information in Attestation Results.
tc-list
The tc-list parameter enumerates the Trusted Components installed
on the device in the form of system-property-claims objects, as
defined in Section 4 of [I-D.ietf-suit-report]. The system-
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property-claims can be used to learn device identifying
information and TEE identifying information for distinguishing
which Trusted Components to install in the TEE. This parameter
MUST be present if the QueryResponse is sent in response to a
QueryRequest with the trusted-components bit set.
requested-tc-list
The requested-tc-list parameter enumerates the Trusted Components
that are not currently installed in the TEE, but which are
requested to be installed, for example by an installer of an
Untrusted Application that has a TA as a dependency, or by a
Trusted Application that has another Trusted Component as a
dependency. Requested Trusted Components are expressed in the
form of requested-tc-info objects. A TEEP Agent can get this
information from the RequestTA conceptual API defined in [RFC9397]
section 6.2.1.
unneeded-manifest-list
The unneeded-manifest-list parameter enumerates the SUIT manifests
whose components are currently installed in the TEE, but which are
no longer needed by any other application. The TAM can use this
information in determining whether a SUIT manifest can be
unlinked. Each unneeded SUIT manifest is identified by its SUIT
Manifest Component ID (note that this is the Component ID for the
manifest itself, which is different from the Component ID of a
component installed by the manifest, see
[I-D.ietf-suit-trust-domains] for more discussion). A TEEP Agent
can get this information from the UnrequestTA conceptual API
defined in [RFC9397] section 6.2.1.
ext-list
The ext-list parameter lists the supported extensions. This
document does not define any extensions. This parameter MUST be
present if the QueryResponse is sent in response to a QueryRequest
with the extensions bit set.
The requested-tc-info message has the following fields:
component-id
A SUIT Component Identifier.
tc-manifest-sequence-number
The minimum suit-manifest-sequence-number value from a SUIT
manifest for the Trusted Component. If not present, indicates
that any sequence number will do.
have-binary
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If present with a value of true, indicates that the TEEP Agent
already has the Trusted Component binary and only needs an Update
message with a SUIT manifest that authorizes installing it. If
have-binary is true, the tc-manifest-sequence-number field MUST be
present.
4.3.1. Evidence and Attestation Results
Section 7 of [RFC9397] lists information that may appear in Evidence
depending on the circumstance. However, the Evidence is opaque to
the TEEP protocol and there are no formal requirements on the
contents of Evidence.
TAMs however consume Attestation Results and do need enough
information therein to make decisions on how to remediate a TEE that
is out of compliance, or update a TEE that is requesting an
authorized change. To do so, the information in Section 7 of
[RFC9397] is often required depending on the policy.
Attestation Results SHOULD use Entity Attestation Tokens (EATs). Use
of any other format, such as a widely implemented format for a
specific processor vendor, is permitted but increases the complexity
of the TAM by requiring it to understand the format for each such
format rather than only the common EAT format so is not recommended.
When an EAT is used, the following claims can be used to meet those
requirements, whether these claims appear in Attestation Results, or
in Evidence for the Verifier to use when generating Attestation
Results of some form:
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+=================+===========+====================================+
| Requirement | Claim | Reference |
+=================+===========+====================================+
| Freshness proof | nonce | Section 4.1 of [I-D.ietf-rats-eat] |
+-----------------+-----------+------------------------------------+
| Device unique | ueid | Section 4.2.1 of |
| identifier | | [I-D.ietf-rats-eat] |
+-----------------+-----------+------------------------------------+
| Vendor of the | oemid | Section 4.2.3 of |
| device | | [I-D.ietf-rats-eat] |
+-----------------+-----------+------------------------------------+
| Class of the | hwmodel | Section 4.2.4 of |
| device | | [I-D.ietf-rats-eat] |
+-----------------+-----------+------------------------------------+
| TEE hardware | hwversion | Section 4.2.5 of |
| type | | [I-D.ietf-rats-eat] |
+-----------------+-----------+------------------------------------+
| TEE hardware | hwversion | Section 4.2.5 of |
| version | | [I-D.ietf-rats-eat] |
+-----------------+-----------+------------------------------------+
| TEE firmware | manifests | Section 4.2.15 of |
| type | | [I-D.ietf-rats-eat] |
+-----------------+-----------+------------------------------------+
| TEE firmware | manifests | Section 4.2.15 of |
| version | | [I-D.ietf-rats-eat] |
+-----------------+-----------+------------------------------------+
Table 1
The "manifests" claim (see Section 4.2.15 of [I-D.ietf-rats-eat])
should include information about the TEEP Agent as well as any of its
dependencies such as firmware.
4.4. Update Message
The Update message is used by the TAM to install and/or delete one or
more Trusted Components via the TEEP Agent. It can also be used to
pass a successful Attestation Report back to the TEEP Agent when the
TAM is configured as an intermediary between the TEEP Agent and a
Verifier, as shown in the figure below, where the Attestation Result
passed back to the Attester can be used as a so-called "passport"
(see section 5.1 of [RFC9334]) that can be presented to other Relying
Parties.
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+---------------+
| Verifier |
+---------------+
^ | Attestation
Evidence | v Result
+---------------+
| TAM / |
| Relying Party |
+---------------+
QueryResponse ^ | Update
(Evidence) | | (Attestation
| v Result)
+---------------+ +---------------+
| TEEP Agent |------------>| Other |
| / Attester | Attestation | Relying Party |
+---------------+ Result +---------------+
Figure 1: Example use of TEEP and attestation
Like other TEEP messages, the Update message is signed, and the
relevant CDDL snippet is shown below. The complete CDDL structure is
shown in Appendix C.
update = [
type: TEEP-TYPE-update,
options: {
? token => bstr .size (8..64),
? unneeded-manifest-list => [ + SUIT_Component_Identifier ],
? manifest-list => [ + bstr .cbor SUIT_Envelope ],
? attestation-payload-format => text,
? attestation-payload => bstr,
? err-code => (0..23),
? err-msg => text .size (1..128),
* $$update-extensions,
* $$teep-option-extensions
}
]
The Update message has the following fields:
type
The value of (3) corresponds to an Update message sent from the
TAM to the TEEP Agent. In case of successful processing, a
Success message is returned by the TEEP Agent. In case of an
error, an Error message is returned. Note that the Update message
is used for initial Trusted Component installation as well as for
updates and deletes.
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token
The value in the token field is used to match responses to
requests.
unneeded-manifest-list
The unneeded-manifest-list parameter enumerates the SUIT manifests
to be unlinked. Each unneeded SUIT manifest is identified by its
SUIT Manifest Component ID. The SUIT manifest processor MAY
execute uninstall section in the manifest. See Section 7 of
[I-D.ietf-suit-trust-domains] for more information about the suit-
uninstall Command Sequence.
manifest-list
The manifest-list field is used to convey one or multiple SUIT
manifests to install. A manifest is a bundle of metadata about a
Trusted Component, such as where to find the code, the devices to
which it applies, and cryptographic information protecting the
manifest. The manifest may also convey personalization data.
Trusted Component binaries and personalization data can be signed
and encrypted by the same Trusted Component Signer. Other
combinations are, however, possible as well. For example, it is
also possible for the TAM to sign and encrypt the personalization
data and to let the Trusted Component Developer sign and/or
encrypt the Trusted Component binary.
attestation-payload-format
The attestation-payload-format parameter indicates the IANA Media
Type of the attestation-payload parameter, where media type
parameters are permitted after the media type. The absence of
this parameter indicates that the format is "application/eat+cwt;
eat_profile=urn:ietf:rfc:rfcXXXX" (see
[I-D.ietf-rats-eat-media-type] for further discussion). (RFC-
editor: upon RFC publication, replace XXXX above with the RFC
number of this document.) It MUST be present if the attestation-
payload parameter is present and the format is not an EAT in CWT
format with the profile defined below in Section 5.
attestation-payload
The attestation-payload parameter contains an Attestation Result.
This parameter If the attestation-payload-format parameter is
absent, the attestation payload contained in this parameter MUST
be an Entity Attestation Token following the encoding defined in
[I-D.ietf-rats-eat]. See Section 4.3.1 for further discussion.
err-code
The err-code parameter contains one of the error codes listed in
the Section 4.6, which describes the reasons for the error when
performing QueryResponse in the TAM.
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err-msg
The err-msg parameter is human-readable diagnostic text that MUST
be encoded using UTF-8 [RFC3629] in Net-Unicode format [RFC5198]
with a maximum of 128 bytes.
Note that an Update message carrying one or more SUIT manifests will
inherently involve multiple signatures, one by the TAM in the TEEP
message and one from a Trusted Component Signer inside each manifest.
This is intentional as they are for different purposes.
The TAM is what authorizes apps to be installed, updated, and deleted
on a given TEE and so the TEEP signature is checked by the TEEP Agent
at protocol message processing time. (This same TEEP security
wrapper is also used on messages like QueryRequest so that Agents
only send potentially sensitive data such as Evidence to trusted
TAMs.)
The Trusted Component signer on the other hand is what authorizes the
Trusted Component to actually run, so the manifest signature could be
checked at install time or load (or run) time or both, and this
checking is done by the TEE independent of whether TEEP is used or
some other update mechanism. See section 5 of [RFC9397] for further
discussion.
The Update Message has a SUIT_Envelope containing SUIT manifests.
Following are some example scenarios using SUIT manifests in the
Update Message.
4.4.1. Scenario 1: Having one SUIT Manifest pointing to a URI of a
Trusted Component Binary
In this scenario, a SUIT Manifest has a URI pointing to a Trusted
Component Binary.
A Trusted Component Developer creates a new Trusted Component Binary
and hosts it at a Trusted Component Developer's URI. Then the
Trusted Component Developer generates an associated SUIT manifest
with the filename "tc-uuid" that contains the URI. The filename "tc-
uuid" is used in Scenario 3 later.
The TAM receives the latest SUIT manifest from the Trusted Component
Developer, and the URI it contains will not be changeable by the TAM
since the SUIT manifest is signed by the Trusted Component Developer.
Pros:
* The Trusted Component Developer can ensure that the intact Trusted
Component Binary is downloaded by devices
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* The TAM does not have to send large Update messages containing the
Trusted Component Binary
Cons:
* The Trusted Component Developer must host the Trusted Component
Binary server
* The device must fetch the Trusted Component Binary in another
connection after receiving an Update message
* A device's IP address and therefore location may be revealed to
the Trusted Component Binary server
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+------------+ +-------------+
| TAM | | TEEP Agent |
+------------+ +-------------+
Update ---->
+=================== teep-protocol(TAM) ==================+
| TEEP_Message([ |
| TEEP-TYPE-update, |
| options: { |
| manifest-list: [ |
| += suit-manifest "tc-uuid" (TC Developer) ======+ |
| | SUIT_Envelope({ | |
| | manifest: { | |
| | install: { | |
| | override-parameters: { | |
| | uri: "https://example.org/tc-uuid.ta" | |
| | }, | |
| | fetch | |
| | } | |
| | } | |
| | }) | |
| +===============================================+ |
| ] |
| } |
| ]) |
+=========================================================+
and then,
+-------------+ +--------------+
| TEEP Agent | | TC Developer |
+-------------+ +--------------+
<----
fetch "https://example.org/tc-uuid.ta"
+======= tc-uuid.ta =======+
| 48 65 6C 6C 6F 2C 20 ... |
+==========================+
Figure 2: URI of the Trusted Component Binary
For the full SUIT Manifest example binary, see Appendix "Example 1:
SUIT Manifest pointing to URI of the Trusted Component Binary".
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4.4.2. Scenario 2: Having a SUIT Manifest include the Trusted Component
Binary
In this scenario, the SUIT manifest contains the entire Trusted
Component Binary as an integrated payload (see
[I-D.ietf-suit-manifest] Section 7.5).
A Trusted Component Developer delegates the task of delivering the
Trusted Component Binary to the TAM inside the SUIT manifest. The
Trusted Component Developer creates a SUIT manifest and embeds the
Trusted Component Binary, which is referenced in the suit-integrated-
payload element containing the fragment-only reference "#tc", in the
envelope. The Trusted Component Developer transmits the entire
bundle to the TAM.
The TAM serves the SUIT manifest containing the Trusted Component
Binary to the device in an Update message.
Pros:
* The device can obtain the Trusted Component Binary and the SUIT
manifest in one Update message.
* The Trusted Component Developer does not have to host a server to
deliver the Trusted Component Binary to devices.
Cons:
* The TAM must host the Trusted Component Binary rather than
delegating storage to the Trusted Component Developer.
* The TAM must deliver Trusted Component Binaries in Update
messages, which increases the size of the Update message.
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+------------+ +-------------+
| TAM | | TEEP Agent |
+------------+ +-------------+
Update ---->
+=========== teep-protocol(TAM) ============+
| TEEP_Message([ |
| TEEP-TYPE-update, |
| options: { |
| manifest-list: [ |
| +== suit-manifest(TC Developer) ==+ |
| | SUIT_Envelope({ | |
| | manifest: { | |
| | install: { | |
| | override-parameters: { | |
| | uri: "#tc" | |
| | }, | |
| | fetch | |
| | } | |
| | }, | |
| | "#tc": h'48 65 6C 6C ...' | |
| | }) | |
| +=================================+ |
| ] |
| } |
| ]) |
+===========================================+
Figure 3: Integrated Payload with Trusted Component Binary
For the full SUIT Manifest example binary, see Appendix "Example 2:
SUIT Manifest including the Trusted Component Binary".
4.4.3. Scenario 3: Supplying Personalization Data for the Trusted
Component Binary
In this scenario, Personalization Data is associated with the Trusted
Component Binary "tc-uuid" from Scenario 1.
The Trusted Component Developer places encrypted Personalization Data
in the SUIT manifest, and it will be delivered by the TAM. The SUIT
manifest processor decrypts it and then store it into file named
"config.json", and then install the dependency component.
The TAM delivers the SUIT manifest of the Personalization Data which
depends on the Trusted Component Binary from Scenario 1.
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+------------+ +-------------+
| TAM | | TEEP Agent |
+------------+ +-------------+
Update ---->
+================== teep-protocol(TAM) ======================+
| TEEP_Message([ |
| TEEP-TYPE-update, |
| options: { |
| manifest-list: [ |
| +========= suit-manifest(TC Developer) ============+ |
| | SUIT_Envelope({ | |
| | manifest: { | |
| | common: { | |
| | dependencies: { | |
| | dependency-prefix 1: { | |
| | [tc-uuid, 'suit'] | |
| | } | |
| | } | |
| | components: [ | |
| | ['config.json'] | |
| | ] | |
| | }, | |
| | dependency-resolution: { | |
| | override-parameters: { | |
| | uri: "https://example.org/tc-uuid" | |
| | }, | |
| | fetch | |
| | }, | |
| | install: { | |
| | set-component-index 0, | |
| | override-parameters: { | |
| | content: h'48FE0794...' | |
| | encryption-info: << ... >> | |
| | }, | |
| | write, | |
| | set-component-index 1, | |
| | process-dependency | |
| | } | |
| | } | |
| | }) | |
| +==================================================+ |
| ] |
| } |
| ]) |
+============================================================+
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Figure 4: Encrypted Personalization Data
For the full SUIT Manifest example binary, see Appendix "Example 3:
Supplying Personalization Data for Trusted Component Binary".
4.5. Success Message
The Success message is used by the TEEP Agent to return a success in
response to an Update message.
Like other TEEP messages, the Success message is signed, and the
relevant CDDL snippet is shown below. The complete CDDL structure is
shown in Appendix C.
teep-success = [
type: TEEP-TYPE-teep-success,
options: {
? token => bstr .size (8..64),
? msg => text .size (1..128),
? suit-reports => [ + SUIT_Report ],
* $$teep-success-extensions,
* $$teep-option-extensions
}
]
The Success message has the following fields:
type
The value of (5) corresponds to corresponds to a Success message
sent from the TEEP Agent to the TAM.
token
The value in the token parameter is used to match responses to
requests. It MUST match the value of the token parameter in the
Update message the Success is in response to, if one was present.
If none was present, the token MUST be absent in the Success
message.
msg
The msg parameter contains optional diagnostics information
encoded in UTF-8 [RFC3629] using Net-Unicode form [RFC5198] with
max 128 bytes returned by the TEEP Agent.
suit-reports
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If present, the suit-reports parameter contains a set of SUIT
Reports as defined in Section 4 of [I-D.ietf-suit-report]. If a
token parameter was present in the Update message the Success
message is in response to, the suit-report-nonce field MUST be
present in the SUIT Report with a value matching the token
parameter in the Update message.
4.6. Error Message
The Error message is used by the TEEP Agent to return an error in
response to a message from the TAM.
Like other TEEP messages, the Error message is signed, and the
relevant CDDL snippet is shown below. The complete CDDL structure is
shown in Appendix C.
teep-error = [
type: TEEP-TYPE-teep-error,
options: {
? token => bstr .size (8..64),
? err-msg => text .size (1..128),
? supported-teep-cipher-suites => [ + $teep-cipher-suite ],
? supported-freshness-mechanisms => [ + $freshness-mechanism ],
? supported-suit-cose-profiles => [ + $suit-cose-profile ],
? challenge => bstr .size (8..512),
? versions => [ + version ],
? suit-reports => [ + SUIT_Report ],
* $$teep-error-extensions,
* $$teep-option-extensions
},
err-code: (0..23)
]
; The err-code parameter, uint (0..23)
ERR_PERMANENT_ERROR = 1
ERR_UNSUPPORTED_EXTENSION = 2
ERR_UNSUPPORTED_FRESHNESS_MECHANISMS = 3
ERR_UNSUPPORTED_MSG_VERSION = 4
ERR_UNSUPPORTED_CIPHER_SUITES = 5
ERR_BAD_CERTIFICATE = 6
ERR_ATTESTATION_REQUIRED = 7
ERR_UNSUPPORTED_SUIT_REPORT = 8
ERR_CERTIFICATE_EXPIRED = 9
ERR_TEMPORARY_ERROR = 10
ERR_MANIFEST_PROCESSING_FAILED = 17
The Error message has the following fields:
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type
The value of (6) corresponds to an Error message sent from the
TEEP Agent to the TAM.
token
The value in the token parameter is used to match responses to
requests. It MUST match the value of the token parameter in the
message the Success is in response to, if one was present. If
none was present, the token MUST be absent in the Error message.
err-msg
The err-msg parameter is human-readable diagnostic text that MUST
be encoded using UTF-8 [RFC3629] using Net-Unicode form [RFC5198]
with max 128 bytes.
supported-teep-cipher-suites
The supported-teep-cipher-suites parameter lists the TEEP cipher
suite(s) supported by the TEEP Agent. Details about the cipher
suite encoding can be found in Section 8.1. This otherwise
optional parameter MUST be returned if err-code is
ERR_UNSUPPORTED_CIPHER_SUITES.
supported-freshness-mechanisms
The supported-freshness-mechanisms parameter lists the freshness
mechanism(s) supported by the TEEP Agent. Details about the
encoding can be found in Section 9. This otherwise optional
parameter MUST be returned if err-code is
ERR_UNSUPPORTED_FRESHNESS_MECHANISMS.
supported-suit-cose-profiles
The supported-suit-cose-profiles parameter lists the SUIT profiles
supported by the TEEP Agent. Details about the cipher suite
encoding can be found in Section 8.2. This otherwise optional
parameter MUST be returned if err-code is
ERR_UNSUPPORTED_SUIT_REPORT.
challenge
The challenge field is an optional parameter used for ensuring the
freshness of attestation Evidence included with a QueryRequest
message. When a challenge is provided in the Error message and
Evidence in the form of an EAT is returned with a QueryRequest
message then the challenge contained in the Error message MUST be
used to generate the EAT, by copying the challenge value into the
eat_nonce claim, as described in the EAT profile Section 5, if the
nonce-based freshness mechanism is used. For more details see
Section 9.
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If any format other than EAT is used, it is up to that format to
define the use of the challenge field.
versions
The versions parameter enumerates the TEEP protocol version(s)
supported by the TEEP Agent. This otherwise optional parameter
MUST be returned if err-code is ERR_UNSUPPORTED_MSG_VERSION.
suit-reports
If present, the suit-reports parameter contains a set of SUIT
Reports as defined in Section 4 of [I-D.ietf-suit-report]. If a
token parameter was present in the Update message the Error
message is in response to, the suit-report-nonce field MUST be
present in the SUIT Report with a value matching the token
parameter in the Update message.
err-code
The err-code parameter contains one of the error codes listed
below). Only selected values are applicable to each message.
This specification defines the following initial error messages:
ERR_PERMANENT_ERROR (1)
The received TEEP message contained incorrect fields or fields
that are inconsistent with other fields. For diagnosis purposes
it is RECOMMMENDED to identify the failure reason in the error
message field. A TEEP implementation receiving this error might
refuse to communicate further with the problematic TEEP message
sender, by silently dropping any TEEP messages received, for some
period of time until it has reason to believe it is worth trying
again, but it should take care not to give up on communication.
In contrast, ERR_TEMPORARY_ERROR is an indication that a more
aggressive retry is warranted.
ERR_UNSUPPORTED_EXTENSION (2)
The TEEP implementation does not support an extension included in
the TEEP message it received. For diagnosis purposes it is
RECOMMMENDED to identify the unsupported extension in the error
message field. A TAM implementation receiving this error might
retry sending the last message it sent to the sender of this
error, without using any TEEP extensions.
ERR_UNSUPPORTED_FRESHNESS_MECHANISMS (3)
The TEEP Agent does not support any freshness algorithm mechanisms
in the request message. A TAM receiving this error might retry
the request using a different set of supported freshness
mechanisms in the request message.
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ERR_UNSUPPORTED_MSG_VERSION (4)
The TEEP implementation does not support the TEEP protocol version
indicated in the received message. A TAM receiving this error
might retry the request using a different TEEP protocol version.
ERR_UNSUPPORTED_CIPHER_SUITES (5)
The TEEP Agent does not support any cipher suites indicated in the
request message. A TAM receiving this error might retry the
request using a different set of supported cipher suites in the
request message.
ERR_BAD_CERTIFICATE (6)
Processing of a certificate failed. For diagnosis purposes it is
RECOMMMENDED to include information about the failing certificate
in the error message field. For example, the certificate was of
an unsupported type, or the certificate was revoked by its signer.
A TEEP implementation receiving this error might attempt to use an
alternate certificate.
ERR_ATTESTATION_REQUIRED (7)
Indicates that the TEEP implementation sending this error requires
attestation of the TEEP imlementation receiving this error.
ERR_UNSUPPORTED_SUIT_REPORT (8)
Indicates that the TEEP Agent does not support the suit-cose-
profile of the SUIT Reports which was sent by the TAM. The TEEP
Agent must report the error code ERR_UNSUPPORTED_SUIT_REPORT
supplying the supported-suit-cose-profiles.
ERR_CERTIFICATE_EXPIRED (9)
A certificate has expired or is not currently valid. A TEEP
implementation receiving this error might attempt to renew its
certificate before using it again.
ERR_TEMPORARY_ERROR (10)
A miscellaneous temporary error, such as a memory allocation
failure, occurred while processing the TEEP message. A TEEP
implementation receiving this error might retry the last message
it sent to the sender of this error at some later point, which is
up to the implementation.
ERR_MANIFEST_PROCESSING_FAILED (17)
The TEEP Agent encountered one or more manifest processing
failures. If the suit-reports parameter is present, it contains
the failure details. A TAM receiving this error might still
attempt to install or update other components that do not depend
on the failed manifest.
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New error codes should be added sparingly, not for every
implementation error. That is the intent of the err-msg field, which
can be used to provide details meaningful to humans. New error codes
should only be added if the TAM is expected to do something
behaviorally different upon receipt of the error message, rather than
just logging the event. Hence, each error code is responsible for
saying what the behavioral difference is expected to be.
5. EAT Profile
The TEEP protocol operates between a TEEP Agent and a TAM. While the
TEEP protocol does not require use of EAT, use of EAT is encouraged
and Section 4.3 explicitly defines a way to carry an Entity
Attestation Token in a QueryResponse.
As discussed in Section 4.3.1, the content of Evidence is opaque to
the TEEP architecture, but the content of Attestation Results is not,
where Attestation Results flow between a Verifier and a TAM (as the
Relying Party). Although Attestation Results required by a TAM are
separable from the TEEP protocol per se, this section is included as
part of the requirements for building a compliant TAM that uses EATs
for Attestation Results.
Section 7 of [I-D.ietf-rats-eat] defines the requirement for Entity
Attestation Token profiles. This section defines an EAT profile for
use with TEEP.
* profile-label: The profile-label for this specification is the URI
<urn:ietf:rfc:rfcXXXX>. (RFC-editor: upon RFC publication, replace
XXXX with the RFC number of this document.)
* Use of JSON, CBOR, or both: CBOR only.
* CBOR Map and Array Encoding: Only definite length arrays and maps.
* CBOR String Encoding: Only definite-length strings are allowed.
* CBOR Preferred Serialization: Encoders must use preferred
serialization, and decoders need not accept non-preferred
serialization.
* CBOR Tags: CBOR Tags are not used.
* COSE/JOSE Protection: See Section 8.2.
* COSE/JOSE Algorithms: See Section 8.2.
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* Detached EAT Bundle Support: DEB use is permitted.
* Key Identification: COSE Key ID (kid) is used, where the key ID is
the hash of a public key (where the public key may be used as a
raw public key, or in a certificate) as specified in
[I-D.ietf-cose-key-thumbprint]. See Section 7.1.1.1 and
Section 7.2.1.1 for discussion on the choice of hash algorithm.
* Endorsement Identification: Optional, but semantics are the same
as in Verification Key Identification.
* Freshness: See Section 9 for details. When the eat_nonce claim is
used, the value is a single bstr.
* Claims Requirements:
- The following claims are required: ueid, oemid, hwmodel,
hwversion, manifests, and cnf. See Section 4.3.1 for
discussion. Other claims are optional.
- See Section 9 for discussion affecting whether the eat_nonce
claim is used.
- The sw-name claim for a Trusted Component holds the URI of the
SUIT manifest for that component.
- The manifests claim uses a SUIT manifest, where the manifest
body contains a SUIT_Reference as defined in Section 4 of
[I-D.ietf-suit-report], and the content type is as defined in
[I-D.ietf-suit-report].
A TAM implementation might simply accept a TEEP Agent as trustworthy
based on a successful Attestation Result, and if not then attempt to
update the TEEP Agent and all of its dependencies. This logic is
simple but it might result in updating some components that do not
need to be updated.
An alternate TAM implementation might use any Additional Claims to
determine whether the TEEP Agent or any of its dependencies are
trustworthy, and only update the specific components that are out of
date.
5.1. Relationship to AR4SI
[I-D.ietf-rats-ar4si] defines an EAT profile for arbitrary Relying
Parties to use with Attestation Results. However the TAM as a
Relying Party needs specific claims that are not required in the
AR4SI profile, and so needs its own more specific profile.
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In some deployments, a TAM can be used as an intermediary between
Verifier and a TEEP Agent acting as an Attester in the Passport model
or acting as a Relying Party in the Background Check Model of
[RFC9334]. This is depicted in the example in Figure 1. In such a
case, both profiles need to be obtained from the Verifier: one for
use by the TAM itself, and the other to pass on to the TEEP Agent.
When the TAM and Verifier are combined into the same implementation,
obtaining both profiles can be straightforward, but when they are on
different machines, the situation is more complex, especially if
Nonces are used to ensure freshness of Evidence. There are thus
several such cases:
1. The protocol between the TAM and the Verifier (which is outside
the scope of TEEP itself) allows requesting multiple Attestation
Results from the same Evidence. In this case, the TAM can
request both EAT profiles be returned.
2. The protocol between the TAM and the Verifier only allows
requesting one Attestation Result format, but the Evidence
freshness mechanism does not use Nonces. In this case, the TAM
can send the same Evidence in two separate requests, each
requesting a different EAT profile for the Attestation Results.
3. The protocol between the TAM and the Verifier only allows
requesting one Attestation Result format, and the Evidence
freshness mechanism uses Nonces. In this case, it is simpler to
not have the TAM be an intermediary, since the Verifier will
require a separate Nonce for each Attestation Result, but have
the Attester or Relying Party contact the Verifier directly to
get Attestation Results in the AR4SI profile.
6. Mapping of TEEP Message Parameters to CBOR Labels
In COSE, arrays and maps use strings, negative integers, and unsigned
integers as their keys. Integers are used for compactness of
encoding. Since the word "key" is mainly used in its other meaning,
as a cryptographic key, this specification uses the term "label" for
this usage as a map key.
This specification uses the following mapping:
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+================================+=======+
| Name | Label |
+================================+=======+
| supported-teep-cipher-suites | 1 |
+--------------------------------+-------+
| challenge | 2 |
+--------------------------------+-------+
| versions | 3 |
+--------------------------------+-------+
| supported-suit-cose-profiles | 4 |
+--------------------------------+-------+
| selected-version | 6 |
+--------------------------------+-------+
| attestation-payload | 7 |
+--------------------------------+-------+
| tc-list | 8 |
+--------------------------------+-------+
| ext-list | 9 |
+--------------------------------+-------+
| manifest-list | 10 |
+--------------------------------+-------+
| msg | 11 |
+--------------------------------+-------+
| err-msg | 12 |
+--------------------------------+-------+
| attestation-payload-format | 13 |
+--------------------------------+-------+
| requested-tc-list | 14 |
+--------------------------------+-------+
| unneeded-manifest-list | 15 |
+--------------------------------+-------+
| component-id | 16 |
+--------------------------------+-------+
| tc-manifest-sequence-number | 17 |
+--------------------------------+-------+
| have-binary | 18 |
+--------------------------------+-------+
| suit-reports | 19 |
+--------------------------------+-------+
| token | 20 |
+--------------------------------+-------+
| supported-freshness-mechanisms | 21 |
+--------------------------------+-------+
| err-code | 23 |
+--------------------------------+-------+
Table 2
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; labels of mapkey for teep message parameters, uint (0..23)
supported-teep-cipher-suites = 1
challenge = 2
versions = 3
supported-suit-cose-profiles = 4
selected-version = 6
attestation-payload = 7
tc-list = 8
ext-list = 9
manifest-list = 10
msg = 11
err-msg = 12
attestation-payload-format = 13
requested-tc-list = 14
unneeded-manifest-list = 15
component-id = 16
tc-manifest-sequence-number = 17
have-binary = 18
suit-reports = 19
token = 20
supported-freshness-mechanisms = 21
err-code = 23
7. Behavior Specification
Behavior is specified in terms of the conceptual APIs defined in
section 6.2.1 of [RFC9397].
7.1. TAM Behavior
When the ProcessConnect API is invoked, the TAM sends a QueryRequest
message.
When the ProcessTeepMessage API is invoked, the TAM first does
validation as specified in Section 4.1.2, and drops the message if it
is not valid. It may also do additional implementation specific
actions such as logging the results or attempting to update the TEEP
Agent to a version that does not send invalid messages. Otherwise,
it proceeds as follows.
If the message includes a token, it can be used to match the response
to a request previously sent by the TAM. The TAM MUST expire the
token value after receiving the first response from the device that
has a valid signature and ignore any subsequent messages that have
the same token value. The token value MUST NOT be used for other
purposes, such as a TAM to identify the devices and/or a device to
identify TAMs or Trusted Components.
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7.1.1. Handling a QueryResponse Message
If a QueryResponse message is received, the TAM verifies the presence
of any parameters required based on the data-items-requested in the
QueryRequest, and also validates that the nonce in any SUIT Report
matches the token sent in the QueryRequest message if a token was
present. If these requirements are not met, the TAM drops the
message and sends an Update message containing an appropriate err-
code and err-msg. It may also do additional implementation specific
actions such as logging the results. If the requirements are met,
processing continues as follows.
If a QueryResponse message is received that contains an attestation-
payload, the TAM checks whether it contains Evidence or an
Attestation Result by inspecting the attestation-payload-format
parameter. The media type defined in Section 5 indicates an
Attestation Result, though future extensions might also indicate
other Attestation Result formats in the future. Any other
unrecognized value indicates Evidence. If it contains an Attestation
Result, processing continues as in Section 7.1.1.1.
If the QueryResponse is instead determined to contain Evidence, the
TAM passes the Evidence (via some mechanism out of scope of this
document) to an attestation Verifier (see [RFC9334]) to determine
whether the Agent is in a trustworthy state. Once the TAM receives
an Attestation Result from the Verifier, processing continues as in
Section 7.1.1.1.
7.1.1.1. Handling an Attestation Result
The Attestation Result must first be validated as follows:
1. Verify that the Attestation Result was signed by a Verifier that
the TAM trusts.
2. Verify that the Attestation Result contains a "cnf" claim (as
defined in Section 3.1 of [RFC8747]) where the key ID is the hash
of the TEEP Agent public key used to verify the signature on the
TEEP message, and the hash is computed using the Digest Algorithm
specified by one of the SUIT profiles supported by the TAM
(SHA-256 for the ones mandated in this document).
See Sections 3.4 and 6 of [RFC8747] for more discussion.
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Based on the results of attestation (if any), any SUIT Reports, and
the lists of installed, requested, and unneeded Trusted Components
reported in the QueryResponse, the TAM determines, in any
implementation specific manner, which Trusted Components need to be
installed, updated, or deleted, if any. There are in typically three
cases:
1. Attestation failed. This indicates that the rest of the
information in the QueryResponse cannot necessarily be trusted,
as the TEEP Agent may not be healthy (or at least up to date).
In this case, the TAM might attempt to use TEEP to update any
Trusted Components (e.g., firmware, the TEEP Agent itself, etc.)
needed to get the TEEP Agent back into an up-to-date state that
would allow attestation to succeed. If the TAM does not have
permission to update such components (this can happen if
different TAMs manage different components in the device), the
TAM instead responds with an Update message containing an
appropriate err-msg, and err-code set to
ERR_ATTESTATION_REQUIRED.
2. Attestation succeeded (so the QueryResponse information can be
accepted as valid), but the set of Trusted Components needs to be
updated based on TAM policy changes or requests from the TEEP
Agent.
3. Attestation succeeded, and no changes are needed.
If any Trusted Components need to be installed, updated, or deleted,
the TAM sends an Update message containing SUIT Manifests with
command sequences to do the relevant installs, updates, or deletes.
It is important to note that the TEEP Agent's Update Procedure
requires resolving and installing any dependencies indicated in the
manifest, which may take some time, and the resulting Success or
Error message is generated only after completing the Update
Procedure. Hence, depending on the freshness mechanism in use, the
TAM may need to store data (e.g., a nonce) for some time. For
example, if a mobile device needs an unmetered connection to download
a dependency, it may take hours or longer before the device has
sufficient access. A different freshness mechanism, such as
timestamps, might be more appropriate in such cases.
If no Trusted Components need to be installed, updated, or deleted,
but the QueryResponse included Evidence, the TAM MAY (e.g., based on
attestation-payload-format parameters received from the TEEP Agent in
the QueryResponse) still send an Update message with no SUIT
Manifests, to pass the Attestation Result back to the TEEP Agent.
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7.1.2. Handling a Success or Error Message
If a Success or Error message is received containing one or more SUIT
Reports, the TAM also validates that the nonce in any SUIT Report
matches the token sent in the Update message, and drops the message
if it does not match. Otherwise, the TAM handles the update in any
implementation specific way, such as updating any locally cached
information about the state of the TEEP Agent, or logging the
results.
If an Error message is received with the error code
ERR_ATTESTATION_REQUIRED, it indicates that the TEEP Agent is
requesting attestation of the TAM. In this case, the TAM MUST send
another QueryRequest with an attestation-payload and optionally a
suit-report to the TEEP Agent.
If any other Error message is received, the TAM can handle it in any
implementation specific way, but Section 4.6 provides recommendations
for such handling.
7.2. TEEP Agent Behavior
When the RequestTA API is invoked, the TEEP Agent first checks
whether the requested TA is already installed. If it is already
installed, the TEEP Agent passes no data back to the caller.
Otherwise, if the TEEP Agent chooses to initiate the process of
requesting the indicated TA, it determines (in any implementation
specific way) the TAM URI based on any TAM URI provided by the
RequestTA caller and any local configuration, and passes back the TAM
URI to connect to. It MAY also pass back a QueryResponse message if
all of the following conditions are true:
* The last QueryRequest message received from that TAM contained no
token or challenge,
* The ProcessError API was not invoked for that TAM since the last
QueryResponse message was received from it, and
* The public key or certificate of the TAM is cached and not
expired.
When the RequestPolicyCheck API is invoked, the TEEP Agent decides
whether to initiate communication with any trusted TAMs (e.g., it
might choose to do so for a given TAM unless it detects that it has
already communicated with that TAM recently). If so, it passes back
a TAM URI to connect to. If the TEEP Agent has multiple TAMs it
needs to connect with, it just passes back one, with the expectation
that RequestPolicyCheck API will be invoked to retrieve each one
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successively until there are no more and it can pass back no data at
that time. Thus, once a TAM URI is returned, the TEEP Agent can
remember that it has already initiated communication with that TAM.
When the ProcessError API is invoked, the TEEP Agent can handle it in
any implementation specific way, such as logging the error or using
the information in future choices of TAM URI.
When the ProcessTeepMessage API is invoked, the Agent first does
validation as specified in Section 4.1.2, and if it is not valid then
the Agent responds with an Error message. Otherwise, processing
continues as follows based on the type of message.
7.2.1. Handling a QueryRequest Message
When a QueryRequest message is received, it is processed as follows.
If the TEEP Agent requires attesting the TAM and the QueryRequest
message did not contain an attestation-payload, the TEEP Agent MUST
send an Error Message with the error code ERR_ATTESTATION_REQUIRED
supplying the supported-freshness-mechanisms and challenge if needed.
Otherwise, processing continues as follows.
If the TEEP Agent requires attesting the TAM and the QueryRequest
message did contain an attestation-payload, the TEEP Agent checks
whether it contains Evidence or an Attestation Result by inspecting
the attestation-payload-format parameter. The media type defined in
Section 5 indicates an Attestation Result, though future extensions
might also indicate other Attestation Result formats in the future.
Any other unrecognized value indicates Evidence. If it contains an
Attestation Result, processing continues as in Section 7.2.1.1.
If the QueryRequest is instead determined to contain Evidence, the
TEEP Agent passes the Evidence (via some mechanism out of scope of
this document) to an attestation Verifier (see [RFC9334]) to
determine whether the TAM is in a trustworthy state. Once the TEEP
Agent receives an Attestation Result from the Verifier, processing
continues as in Section 7.2.1.1.
The TEEP Agent MAY also use (in any implementation specific way) any
SUIT Reports in the QueryRequest in determining whether it trusts the
TAM. If a SUIT Report uses a suit-cose-profile that the TEEP Agent
does not support, then the TEEP Agent MUST send an Error Message with
the error code ERR_UNSUPPORTED_SUIT_REPORT supplying the supported-
suit-cose-profiles. Otherwise, processing continues as follows.
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Once the Attestation Result is handled, or if the TEEP Agent does not
require attesting the TAM, the Agent responds with a QueryResponse
message if all fields were understood, or an Error message if any
error was encountered.
7.2.1.1. Handling an Attestation Result
The Attestation Result must first be validated as follows:
1. Verify that the Attestation Result was signed by a Verifier that
the TEEP Agent trusts.
2. Verify that the Attestation Result contains a "cnf" claim (as
defined in Section 3.1 of [RFC8747]) where the key ID is the hash
of the TAM public key used to verify the signature on the TEEP
message, and the hash is computed using the Digest Algorithm
specified by one of the SUIT profiles supported by the TEEP Agent
(SHA-256 for the ones mandated in this document).
See Sections 3.4 and 6 of [RFC8747] for more discussion.
7.2.2. Handling an Update Message
When an Update message is received, the Agent attempts to unlink any
SUIT manifests listed in the unneeded-manifest-list field of the
message, and responds with an Error message if any error was
encountered. If the unneeded-manifest-list was empty, or no error
was encountered processing it, the Agent attempts to update the
Trusted Components specified in the SUIT manifests by following the
Update Procedure specified in [I-D.ietf-suit-manifest], and responds
with a Success message if all SUIT manifests were successfully
installed, or an Error message if any error was encountered. It is
important to note that the Update Procedure requires resolving and
installing any dependencies indicated in the manifest, which may take
some time, and the Success or Error message is generated only after
completing the Update Procedure.
8. Cipher Suites
TEEP requires algorithms for various purposes:
* Algorithms for signing TEEP messages exchanged between the TEEP
Agent and the TAM.
* Algorithms for signing EAT-based Evidence sent by the Attester via
the TEEP Agent and the TAM to the Verifier.
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* Algorithms for encrypting EAT-based Evidence sent by the TEEP
Agent to the TAM. (The TAM will decrypt the encrypted Evidence
and will forward it to the Verifier.)
* Algorithms for signing and optionally encrypting SUIT reports sent
by the TEEP Agent to the TAM.
* Algorithms for signing and optionally encrypting SUIT manifests
sent by the Trusted Component Signer to the TEEP Agent.
Further details are provided for the protection of TEEP messages,
SUIT Reports, and EATs.
8.1. TEEP Messages
The TEEP protocol uses COSE for protection of TEEP messages in both
directions. To negotiate cryptographic mechanisms and algorithms,
the TEEP protocol defines the following cipher suite structure, which
is used to specify an ordered set of operations (e.g., sign) done as
part of composing a TEEP message. Although this specification only
specifies the use of signing and relies on payload encryption to
protect sensitive information, future extensions might specify
support for encryption and/or MAC operations if needed.
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; teep-cipher-suites
$teep-cipher-suite /= teep-cipher-suite-sign1-eddsa
$teep-cipher-suite /= teep-cipher-suite-sign1-es256
;The following two cipher suites have only a single operation each.
;Other cipher suites may be defined to have multiple operations.
;It is MANDATORY for TAM to support them, and OPTIONAL
;to support any additional ones that use COSE_Sign_Tagged, or other
;signing, encryption, or MAC algorithms.
teep-operation-sign1-eddsa = [ cose-sign1, cose-alg-eddsa ]
teep-operation-sign1-es256 = [ cose-sign1, cose-alg-es256 ]
teep-cipher-suite-sign1-eddsa = [ teep-operation-sign1-eddsa ]
teep-cipher-suite-sign1-es256 = [ teep-operation-sign1-es256 ]
;MANDATORY for TAM and TEEP Agent to support the following COSE
;operations, and OPTIONAL to support additional ones such as
;COSE_Sign_Tagged, COSE_Encrypt0_Tagged, etc.
cose-sign1 = 18 ; CoAP Content-Format value
;MANDATORY for TAM to support the following, and OPTIONAL to implement
;any additional algorithms from the IANA COSE Algorithms registry.
cose-alg-es256 = -7 ; ECDSA w/ SHA-256
cose-alg-eddsa = -8 ; EdDSA
Each operation in a given cipher suite has two elements:
* a COSE-type defined in Section 2 of [RFC9052] that identifies the
type of operation, and
* a specific cryptographic algorithm as defined in the COSE
Algorithms registry [COSE.Algorithm] to be used to perform that
operation.
A TAM MUST support both of the cipher suites defined above. A TEEP
Agent MUST support at least one of the two but can choose which one.
For example, a TEEP Agent might choose a given cipher suite if it has
hardware support for it. A TAM or TEEP Agent MAY also support any
other algorithms in the COSE Algorithms registry in addition to the
mandatory ones listed above. It MAY also support use with COSE_Sign
or other COSE types in additional cipher suites.
Any cipher suites without confidentiality protection can only be
added if the associated specification includes a discussion of
security considerations and applicability, since manifests may carry
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sensitive information. For example, Section 6 of [RFC9397] permits
implementations that terminate transport security inside the TEE and
if the transport security provides confidentiality then additional
encryption might not be needed in the manifest for some use cases.
For most use cases, however, manifest confidentiality will be needed
to protect sensitive fields from the TAM as discussed in Section 9.8
of [RFC9397].
The cipher suites defined above do not do encryption at the TEEP
layer, but permit encryption of the SUIT payload using a mechanism
such as [I-D.ietf-suit-firmware-encryption]. See Section 10 and
Section 8.2 for more discussion of specific payloads.
For the initial QueryRequest message, unless the TAM has more
specific knowledge about the TEEP Agent (e.g., if the QueryRequest is
sent in response to some underlying transport message that contains a
hint), the message does not use COSE_Sign1 with one of the above
cipher suites, but instead uses COSE_Sign with multiple signatures,
one for each algorithm used in any of the cipher suites listed in the
supported-teep-cipher-suites parameter of the QueryRequest, so that a
TEEP Agent supporting any one of them can verify a signature. If the
TAM does have specific knowledge about which cipher suite the TEEP
Agent supports, it MAY instead use that cipher suite with the
QueryRequest.
For an Error message with code ERR_UNSUPPORTED_CIPHER_SUITES, the
TEEP Agent MUST protect it with any of the cipher suites mandatory
for the TAM.
For all other TEEP messages between the TAM and TEEP Agent, the
selected TEEP cipher suite MUST be used in both directions.
8.2. EATs and SUIT Reports
TEEP uses COSE for confidentiality of EATs and SUIT Reports sent by a
TEEP Agent. The TEEP Agent obtains a signed EAT and then SHOULD
encrypt it using the TAM as the recipient. A SUIT Report is created
by a SUIT processor, which is part of the TEEP Agent itself. The
TEEP Agent is therefore in control of signing the SUIT Report and
SHOULD encrypt it. Again, the TAM is the recipient of the encrypted
content. For content-key distribution Ephemeral-Static Diffie-
Hellman (ES-DH) is used in this specification. See Section 8.5.5 and
Appendix B of [RFC9052] for more details. (If
[I-D.ietf-suit-firmware-encryption] is used, it is also the same as
discussed in Section 6.2 of that document.)
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ES-DH is a scheme that provides public key encryption given a
recipient's public key. Hence, the TEEP Agent needs to be in
possession of the public key of the TAM. See Section 5 of [RFC9397]
for more discussion of TAM keys used by the TEEP Agent. There are
multiple variants of this scheme; this document uses the variant
specified in Section 8.5.5 of [RFC9052].
The following two layer structure is used:
* Layer 0: Has a content encrypted with the Content Encryption Key
(CEK), a symmetric key. For encrypting SUIT Reports and EATs the
content MUST NOT be detached.
* Layer 1: Uses the AES Key Wrap algorithm to encrypt the randomly
generated CEK with the Key Encryption Key (KEK) derived with ES-
DH, whereby the resulting symmetric key is fed into the HKDF-based
key derivation function.
As a result, the two layers combine ES-DH with AES-KW and HKDF.
This document re-uses the CDDL defined in Section 6.2.3 of
[I-D.ietf-suit-firmware-encryption] and the context information
structure defined in Section 6.2.4 of
[I-D.ietf-suit-firmware-encryption] although with an important
modification. The COSE_KDF_Context.SuppPubInfo.other value MUST be
set to "SUIT Report Encryption" when a SUIT Report is encrypted and
MUST be set to "EAT Encryption" when an EAT is encrypted. The
COSE_KDF_Context.SuppPubInfo.other field captures the protocol in
which the ES-DH content key distribution algorithm is used.
This specification defines cipher suites for confidentiality
protection of EATs and SUIT Reports. The TAM MUST support each
cipher suite defined below, based on definitions in
[I-D.ietf-suit-mti]. A TEEP Agent MUST support at least one of the
cipher suites below but can choose which one. For example, a TEEP
Agent might choose a given cipher suite if it has hardware support
for it. A TAM or TEEP Agent MAY also support other algorithms in the
COSE Algorithms registry. It MAY also support use with COSE_Encrypt
or other COSE types in additional cipher suites.
; suit-cose-profile
$suit-cose-profile /= suit-sha256-es256-ecdh-a128ctr
$suit-cose-profile /= suit-sha256-eddsa-ecdh-a128ctr
$suit-cose-profile /= suit-sha256-es256-ecdh-a128gcm
$suit-cose-profile /= suit-sha256-eddsa-ecdh-chacha-poly
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9. Attestation Freshness Mechanisms
A freshness mechanism determines how a TAM can tell whether an
attestation payload provided in a QueryResponse is fresh. There are
multiple ways this can be done as discussed in Section 10 of
[RFC9334].
Each freshness mechanism is identified with an integer value, which
corresponds to an IANA registered freshness mechanism (see the IANA
Considerations section of
[I-D.ietf-rats-reference-interaction-models]). This document uses
the following freshness mechanisms which may be added to in the
future by TEEP extensions:
; freshness-mechanisms
FRESHNESS_NONCE = 0
FRESHNESS_TIMESTAMP = 1
$freshness-mechanism /= FRESHNESS_NONCE
$freshness-mechanism /= FRESHNESS_TIMESTAMP
An implementation MUST support the Nonce mechanism and MAY support
additional mechanisms.
In the Nonce mechanism, the attestation payload MUST include a nonce
provided in the QueryRequest challenge if the Background Check model
is used, or in the QueryRequest token if the Passport model is used.
The timestamp mechanism uses a timestamp determined via mechanisms
outside the TEEP protocol, and the challenge is only needed in the
QueryRequest message if a challenge is needed in generating the
attestation payload for reasons other than freshness.
If a TAM supports multiple freshness mechanisms that require
different challenge formats, the QueryRequest message can currently
only send one such challenge. This situation is expected to be rare,
but should it occur, the TAM can choose to prioritize one of them and
exclude the other from the supported-freshness-mechanisms in the
QueryRequest, and resend the QueryRequest with the other mechanism if
an ERR_UNSUPPORTED_FRESHNESS_MECHANISMS Error is received that
indicates the TEEP Agent supports the other mechanism.
10. Security Considerations
This section summarizes the security considerations discussed in this
specification:
Cryptographic Algorithms
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TEEP protocol messages exchanged between the TAM and the TEEP
Agent are protected using COSE. This specification relies on the
cryptographic algorithms provided by COSE. Public key based
authentication is used by the TEEP Agent to authenticate the TAM
and vice versa.
Attestation
A TAM relies on signed Attestation Results provided by a Verifier,
either obtained directly using a mechanism outside the TEEP
protocol (by using some mechanism to pass Evidence obtained in the
attestation payload of a QueryResponse, and getting back the
Attestation Results), or indirectly via the TEEP Agent forwarding
the Attestation Results in the attestation payload of a
QueryResponse. See the security considerations of the specific
mechanism in use (e.g., EAT) for more discussion.
An impersonation attack, where one TEEP Agent attempts to use the
attestation payload of another TEEP Agent, can be prevented using
a proof-of-possession approach. The "cnf" claim is mandatory in
the EAT profile for EAT for this purpose. See Section 6 of
[RFC8747] and Section 7.1.1.1 and Section 7.2.1.1 of this document
for more discussion.
Trusted Component Binaries
Each Trusted Component binary is signed by a Trusted Component
Signer. It is the responsibility of the TAM to relay only
verified Trusted Components from authorized Trusted Component
Signers. Delivery of a Trusted Component to the TEEP Agent is
then the responsibility of the TAM, using the security mechanisms
provided by the TEEP protocol. To protect the Trusted Component
binary, the SUIT manifest format is used and it offers a variety
of security features, including digital signatures and content
encryption, if a SUIT mechanism such as
[I-D.ietf-suit-firmware-encryption] is used.
Personalization Data
A Trusted Component Signer or TAM can supply personalization data
along with a Trusted Component. This data is also protected by a
SUIT manifest. Personalization data is signed and encrypted by a
Trusted Component Signer, if a SUIT mechanism such as
[I-D.ietf-suit-firmware-encryption] is used.
TEEP Broker
As discussed in section 6 of [RFC9397], the TEEP protocol
typically relies on a TEEP Broker to relay messages between the
TAM and the TEEP Agent. When the TEEP Broker is compromised it
can drop messages, delay the delivery of messages, and replay
messages but it cannot modify those messages. (A replay would be,
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however, detected by the TEEP Agent.) A compromised TEEP Broker
could reorder messages in an attempt to install an old version of
a Trusted Component. Information in the manifest ensures that
TEEP Agents are protected against such downgrade attacks based on
features offered by the manifest itself.
Replay Protection
The TEEP protocol supports replay protection as follows. The
transport protocol under the TEEP protocol might provide replay
protection, but may be terminated in the TEEP Broker which is not
trusted by the TEEP Agent and so the TEEP protocol does replay
protection itself. If attestation of the TAM is used, the
attestation freshness mechanism provides replay protection for
attested QueryRequest messages. If non-attested QueryRequest
messages are replayed, the TEEP Agent will generate QueryResponse
or Error messages, but the REE can already conduct Denial of
Service attacks against the TEE and/or the TAM even without the
TEEP protocol. QueryResponse messages have replay protection via
attestation freshness mechanism, or the token field in the message
if attestation is not used. Update messages have replay
protection via the suit-manifest-sequence-number (see
Section 8.4.2 of [I-D.ietf-suit-manifest]). Error and Success
messages have replay protection via SUIT Reports and/or the token
field in the message, where a TAM can detect which message it is
in response to.
Trusted Component Signer Compromise
A TAM is responsible for vetting a Trusted Component and before
distributing them to TEEP Agents.
It is RECOMMENDED to provide a way to update the trust anchor
store used by the TEE, for example using a firmware update
mechanism such as [I-D.ietf-rats-concise-ta-stores]. Thus, if a
Trusted Component Signer is later compromised, the TAM can update
the trust anchor store used by the TEE, for example using a
firmware update mechanism.
CA Compromise
The CA issuing certificates to a TEE or a Trusted Component Signer
might get compromised. It is RECOMMENDED to provide a way to
update the trust anchor store used by the TEE, for example by
using a firmware update mechanism, Concise TA Stores
[I-D.ietf-rats-concise-ta-stores], Trust Anchor Management
Protocol (TAMP) [RFC5934] or a similar mechanism. If the CA
issuing certificates to devices gets compromised then these
devices will be rejected by a TAM, if revocation is available to
the TAM.
TAM Certificate Expiry
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The integrity and the accuracy of the clock within the TEE
determines the ability to determine an expired TAM certificate, if
certificates are used.
Compromised Time Source
As discussed above, certificate validity checks rely on comparing
validity dates to the current time, which relies on having a
trusted source of time, such as [RFC8915]. A compromised time
source could thus be used to subvert such validity checks.
11. Privacy Considerations
Depending on the properties of the attestation mechanism, it is
possible to uniquely identify a device based on information in the
attestation payload or in the certificate used to sign the
attestation payload. This uniqueness may raise privacy concerns. To
lower the privacy implications the TEEP Agent MUST present its
attestation payload only to an authenticated and authorized TAM and
when using an EAT, it SHOULD use encryption as discussed in
[I-D.ietf-rats-eat], since confidentiality is not provided by the
TEEP protocol itself and the transport protocol under the TEEP
protocol might be implemented outside of any TEE. If any mechanism
other than EAT is used, it is up to that mechanism to specify how
privacy is provided.
Since SUIT Reports can also contain sensitive information, a TEEP
Agent SHOULD also encrypt SUIT Reports as discussed in Section 8.2.
In addition, in the usage scenario discussed in Section 4.4.1, a
device reveals its IP address to the Trusted Component Binary server.
This can reveal to that server at least a clue as to its location,
which might be sensitive information in some cases.
EATs and SUIT Reports from a TAM can also be present in a
QueryRequest. Typically, the ability to uniquely identify a TAM is
less of a concern than it is for TEEP Agents, but where
confidentiality is a concern for the TAM, such EATs and SUIT Reports
SHOULD be encrypted just like ones from TEEP Agents.
12. IANA Considerations
12.1. Media Type Registration
IANA is requested to assign a media type for application/teep+cbor.
Type name: application
Subtype name: teep+cbor
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Required parameters: none
Optional parameters: none
Encoding considerations: Same as encoding considerations of
application/cbor.
Security considerations: See Security Considerations Section of this
document.
Interoperability considerations: Same as interoperability
considerations of application/cbor as specified in [RFC8949].
Published specification: This document.
Applications that use this media type: TEEP protocol implementations
Fragment identifier considerations: N/A
Additional information: Deprecated alias names for this type: N/A
Magic number(s): N/A
File extension(s): N/A
Macintosh file type code(s): N/A
Person to contact for further information: teep@ietf.org
Intended usage: COMMON
Restrictions on usage: none
Author: See the "Authors' Addresses" section of this document
Change controller: IETF
13. References
13.1. Normative References
[COSE.Algorithm]
IANA, "COSE Algorithms", n.d.,
<https://www.iana.org/assignments/cose/
cose.xhtml#algorithms>.
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[I-D.ietf-cose-key-thumbprint]
Isobe, K., Tschofenig, H., and O. Steele, "CBOR Object
Signing and Encryption (COSE) Key Thumbprint", Work in
Progress, Internet-Draft, draft-ietf-cose-key-thumbprint-
04, 23 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-cose-
key-thumbprint-04>.
[I-D.ietf-rats-eat]
Lundblade, L., Mandyam, G., O'Donoghue, J., and C.
Wallace, "The Entity Attestation Token (EAT)", Work in
Progress, Internet-Draft, draft-ietf-rats-eat-22, 14
October 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-rats-eat-22>.
[I-D.ietf-suit-manifest]
Moran, B., Tschofenig, H., Birkholz, H., Zandberg, K., and
O. Rønningstad, "A Concise Binary Object Representation
(CBOR)-based Serialization Format for the Software Updates
for Internet of Things (SUIT) Manifest", Work in Progress,
Internet-Draft, draft-ietf-suit-manifest-24, 23 October
2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
suit-manifest-24>.
[I-D.ietf-suit-mti]
Moran, B., Rønningstad, O., and A. Tsukamoto, "Mandatory-
to-Implement Algorithms for Authors and Recipients of
Software Update for the Internet of Things manifests",
Work in Progress, Internet-Draft, draft-ietf-suit-mti-03,
23 October 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-suit-mti-03>.
[I-D.ietf-suit-report]
Moran, B. and H. Birkholz, "Secure Reporting of Update
Status", Work in Progress, Internet-Draft, draft-ietf-
suit-report-07, 11 September 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-suit-
report-07>.
[I-D.ietf-suit-trust-domains]
Moran, B. and K. Takayama, "SUIT Manifest Extensions for
Multiple Trust Domains", Work in Progress, Internet-Draft,
draft-ietf-suit-trust-domains-05, 11 September 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-suit-
trust-domains-05>.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/rfc/rfc3629>.
[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network
Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008,
<https://www.rfc-editor.org/rfc/rfc5198>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8747] Jones, M., Seitz, L., Selander, G., Erdtman, S., and H.
Tschofenig, "Proof-of-Possession Key Semantics for CBOR
Web Tokens (CWTs)", RFC 8747, DOI 10.17487/RFC8747, March
2020, <https://www.rfc-editor.org/rfc/rfc8747>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/rfc/rfc8949>.
[RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/rfc/rfc9052>.
13.2. Informative References
[I-D.ietf-rats-ar4si]
Voit, E., Birkholz, H., Hardjono, T., Fossati, T., and V.
Scarlata, "Attestation Results for Secure Interactions",
Work in Progress, Internet-Draft, draft-ietf-rats-ar4si-
05, 30 August 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-rats-
ar4si-05>.
[I-D.ietf-rats-concise-ta-stores]
Wallace, C., Housley, R., Fossati, T., and Y. Deshpande,
"Concise TA Stores (CoTS)", Work in Progress, Internet-
Draft, draft-ietf-rats-concise-ta-stores-01, 5 June 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-rats-
concise-ta-stores-01>.
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[I-D.ietf-rats-eat-media-type]
Lundblade, L., Birkholz, H., and T. Fossati, "EAT Media
Types", Work in Progress, Internet-Draft, draft-ietf-rats-
eat-media-type-04, 23 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-rats-
eat-media-type-04>.
[I-D.ietf-rats-reference-interaction-models]
Birkholz, H., Eckel, M., Pan, W., and E. Voit, "Reference
Interaction Models for Remote Attestation Procedures",
Work in Progress, Internet-Draft, draft-ietf-rats-
reference-interaction-models-08, 10 September 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-rats-
reference-interaction-models-08>.
[I-D.ietf-suit-firmware-encryption]
Tschofenig, H., Housley, R., Moran, B., Brown, D., and K.
Takayama, "Encrypted Payloads in SUIT Manifests", Work in
Progress, Internet-Draft, draft-ietf-suit-firmware-
encryption-18, 23 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-suit-
firmware-encryption-18>.
[RFC5934] Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor
Management Protocol (TAMP)", RFC 5934,
DOI 10.17487/RFC5934, August 2010,
<https://www.rfc-editor.org/rfc/rfc5934>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/rfc/rfc8610>.
[RFC8915] Franke, D., Sibold, D., Teichel, K., Dansarie, M., and R.
Sundblad, "Network Time Security for the Network Time
Protocol", RFC 8915, DOI 10.17487/RFC8915, September 2020,
<https://www.rfc-editor.org/rfc/rfc8915>.
[RFC9334] Birkholz, H., Thaler, D., Richardson, M., Smith, N., and
W. Pan, "Remote ATtestation procedureS (RATS)
Architecture", RFC 9334, DOI 10.17487/RFC9334, January
2023, <https://www.rfc-editor.org/rfc/rfc9334>.
[RFC9397] Pei, M., Tschofenig, H., Thaler, D., and D. Wheeler,
"Trusted Execution Environment Provisioning (TEEP)
Architecture", RFC 9397, DOI 10.17487/RFC9397, July 2023,
<https://www.rfc-editor.org/rfc/rfc9397>.
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A. Contributors
We would like to thank Brian Witten (Symantec), Tyler Kim (Solacia),
Nick Cook (Arm), and Minho Yoo (IoTrust) for their contributions to
the Open Trust Protocol (OTrP), which influenced the design of this
specification.
B. Acknowledgements
We would like to thank Eve Schooler for the suggestion of the
protocol name.
We would like to thank Kohei Isobe (TRASIO/SECOM), Ken Takayama
(SECOM), Kuniyasu Suzaki (TRASIO/AIST), Tsukasa Oi (TRASIO), and
Yuichi Takita (SECOM) for their valuable implementation feedback.
We would also like to thank Carsten Bormann and Henk Birkholz for
their help with the CDDL.
C. Complete CDDL
Valid TEEP messages adhere to the following CDDL data definitions,
except that SUIT_Envelope and SUIT_Component_Identifier are specified
in [I-D.ietf-suit-manifest].
This section is informative and merely summarizes the normative CDDL
snippets in the body of this document.
; DO NOT EDIT this cddl file manually.
; This cddl file is Auto-generated file from md file.
; Edit the md file and run make for generating this cddl file.
; Please do not forget to commit and push this cddl file to git repo
; every time you have revised the md file.
teep-message = $teep-message-type .within teep-message-framework
teep-message-framework = [
type: $teep-type / $teep-type-extension,
options: { * teep-option },
* any; further elements, e.g., for data-item-requested
]
teep-option = (uint => any)
; messages defined below:
$teep-message-type /= query-request
$teep-message-type /= query-response
$teep-message-type /= update
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$teep-message-type /= teep-success
$teep-message-type /= teep-error
; message type numbers, in one byte which could take a number from 0 to 23
$teep-type = (0..23)
TEEP-TYPE-query-request = 1
TEEP-TYPE-query-response = 2
TEEP-TYPE-update = 3
TEEP-TYPE-teep-success = 5
TEEP-TYPE-teep-error = 6
query-request = [
type: TEEP-TYPE-query-request,
options: {
? token => bstr .size (8..64),
? supported-freshness-mechanisms => [ + $freshness-mechanism ],
? challenge => bstr .size (8..512),
? versions => [ + version ],
? attestation-payload-format => text,
? attestation-payload => bstr,
? suit-reports => [ + bstr ],
* $$query-request-extensions,
* $$teep-option-extensions
},
supported-teep-cipher-suites: [ + $teep-cipher-suite ],
supported-suit-cose-profiles: [ + $suit-cose-profile ],
data-item-requested: uint .bits data-item-requested
]
version = uint .size 4
ext-info = uint .size 4
; data items as bitmaps
data-item-requested = &(
attestation: 0,
trusted-components: 1,
extensions: 2,
suit-reports: 3,
)
; teep-cipher-suites
$teep-cipher-suite /= teep-cipher-suite-sign1-eddsa
$teep-cipher-suite /= teep-cipher-suite-sign1-es256
;The following two cipher suites have only a single operation each.
;Other cipher suites may be defined to have multiple operations.
;It is MANDATORY for TAM to support them, and OPTIONAL
;to support any additional ones that use COSE_Sign_Tagged, or other
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;signing, encryption, or MAC algorithms.
teep-operation-sign1-eddsa = [ cose-sign1, cose-alg-eddsa ]
teep-operation-sign1-es256 = [ cose-sign1, cose-alg-es256 ]
teep-cipher-suite-sign1-eddsa = [ teep-operation-sign1-eddsa ]
teep-cipher-suite-sign1-es256 = [ teep-operation-sign1-es256 ]
;MANDATORY for TAM and TEEP Agent to support the following COSE
;operations, and OPTIONAL to support additional ones such as
;COSE_Sign_Tagged, COSE_Encrypt0_Tagged, etc.
cose-sign1 = 18 ; CoAP Content-Format value
;MANDATORY for TAM to support the following, and OPTIONAL to implement
;any additional algorithms from the IANA COSE Algorithms registry.
cose-alg-es256 = -7 ; ECDSA w/ SHA-256
cose-alg-eddsa = -8 ; EdDSA
; suit-cose-profile
$suit-cose-profile /= suit-sha256-es256-ecdh-a128ctr
$suit-cose-profile /= suit-sha256-eddsa-ecdh-a128ctr
$suit-cose-profile /= suit-sha256-es256-ecdh-a128gcm
$suit-cose-profile /= suit-sha256-eddsa-ecdh-chacha-poly
; freshness-mechanisms
FRESHNESS_NONCE = 0
FRESHNESS_TIMESTAMP = 1
$freshness-mechanism /= FRESHNESS_NONCE
$freshness-mechanism /= FRESHNESS_TIMESTAMP
query-response = [
type: TEEP-TYPE-query-response,
options: {
? token => bstr .size (8..64),
? selected-version => version,
? attestation-payload-format => text,
? attestation-payload => bstr,
? suit-reports => [ + bstr ],
? tc-list => [ + system-property-claims ],
? requested-tc-list => [ + requested-tc-info ],
? unneeded-manifest-list => [ + SUIT_Component_Identifier ],
? ext-list => [ + ext-info ],
* $$query-response-extensions,
* $$teep-option-extensions
}
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]
requested-tc-info = {
component-id => SUIT_Component_Identifier,
? tc-manifest-sequence-number => uint .size 8,
? have-binary => bool
}
update = [
type: TEEP-TYPE-update,
options: {
? token => bstr .size (8..64),
? unneeded-manifest-list => [ + SUIT_Component_Identifier ],
? manifest-list => [ + bstr .cbor SUIT_Envelope ],
? attestation-payload-format => text,
? attestation-payload => bstr,
? err-code => (0..23),
? err-msg => text .size (1..128),
* $$update-extensions,
* $$teep-option-extensions
}
]
teep-success = [
type: TEEP-TYPE-teep-success,
options: {
? token => bstr .size (8..64),
? msg => text .size (1..128),
? suit-reports => [ + SUIT_Report ],
* $$teep-success-extensions,
* $$teep-option-extensions
}
]
teep-error = [
type: TEEP-TYPE-teep-error,
options: {
? token => bstr .size (8..64),
? err-msg => text .size (1..128),
? supported-teep-cipher-suites => [ + $teep-cipher-suite ],
? supported-freshness-mechanisms => [ + $freshness-mechanism ],
? supported-suit-cose-profiles => [ + $suit-cose-profile ],
? challenge => bstr .size (8..512),
? versions => [ + version ],
? suit-reports => [ + SUIT_Report ],
* $$teep-error-extensions,
* $$teep-option-extensions
},
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err-code: (0..23)
]
; The err-code parameter, uint (0..23)
ERR_PERMANENT_ERROR = 1
ERR_UNSUPPORTED_EXTENSION = 2
ERR_UNSUPPORTED_FRESHNESS_MECHANISMS = 3
ERR_UNSUPPORTED_MSG_VERSION = 4
ERR_UNSUPPORTED_CIPHER_SUITES = 5
ERR_BAD_CERTIFICATE = 6
ERR_ATTESTATION_REQUIRED = 7
ERR_UNSUPPORTED_SUIT_REPORT = 8
ERR_CERTIFICATE_EXPIRED = 9
ERR_TEMPORARY_ERROR = 10
ERR_MANIFEST_PROCESSING_FAILED = 17
; labels of mapkey for teep message parameters, uint (0..23)
supported-teep-cipher-suites = 1
challenge = 2
versions = 3
supported-suit-cose-profiles = 4
selected-version = 6
attestation-payload = 7
tc-list = 8
ext-list = 9
manifest-list = 10
msg = 11
err-msg = 12
attestation-payload-format = 13
requested-tc-list = 14
unneeded-manifest-list = 15
component-id = 16
tc-manifest-sequence-number = 17
have-binary = 18
suit-reports = 19
token = 20
supported-freshness-mechanisms = 21
err-code = 23
D. Examples of Diagnostic Notation and Binary Representation
This section includes some examples with the following assumptions:
* The device will have two TCs with the following SUIT Component
Identifiers:
- [ 0x000102030405060708090a0b0c0d0e0f ]
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- [ 0x100102030405060708090a0b0c0d0e0f ]
* SUIT manifest-list is set empty only for example purposes (see
Appendix E for actual manifest examples)
D.1. QueryRequest Message
D.1.1. CBOR Diagnostic Notation
/ query-request = /
[
/ type: / 1 / TEEP-TYPE-query-request /,
/ options: /
{
/ token / 20 : h'A0A1A2A3A4A5A6A7A8A9AAABACADAEAF',
/ versions / 3 : [ 0 ] / 0 is current TEEP Protocol /
},
/ supported-teep-cipher-suites: / [
[ [ 18, -7 ] ] / Sign1 using ES256 /,
[ [ 18, -8 ] ] / Sign1 using EdDSA /
],
/ supported-suit-cose-profiles: / [
[-16, -7, -25, -65534] / suit-sha256-es256-ecdh-a128ctr /,
[-16, -8, -25, -65534] / suit-sha256-eddsa-ecdh-a128ctr /,
[-16, -7, -25, 1] / suit-sha256-es256-ecdh-a128gcm /,
[-16, -8, -25, 24] / suit-sha256-eddsa-ecdh-chacha-poly /
],
/ data-item-requested: / 3 / attestation | trusted-components /
]
D.1.2. CBOR Binary Representation
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85 # array(5)
01 # unsigned(1) / TEEP-TYPE-query-request /
A2 # map(2)
14 # unsigned(20) / token: /
50 # bytes(16)
A0A1A2A3A4A5A6A7A8A9AAABACADAEAF
03 # unsigned(3) / versions: /
81 # array(1) / [ 0 ] /
00 # unsigned(0)
82 # array(2) / supported-teep-cipher-suites /
81 # array(1)
82 # array(2)
12 # unsigned(18) / cose-sign1 /
26 # negative(6) / -7 = cose-alg-es256 /
81 # array(1)
82 # array(2)
12 # unsigned(18) / cose-sign1 /
27 # negative(7) / -8 = cose-alg-eddsa /
84 # array(4) / supported-suit-cose-profiles /
84 # array(4) / suit-sha256-es256-ecdh-a128ctr /,
2f # negative(15) / -16 = SHA-256 /
26 # negative(6) / -7 = ES256 /
38 18 # negative(24) / -25 = ECDH-ES + HKDF-256 /
39 fffd # negative(65533) / -65534 = A128CTR /
84 # array(4) / suit-sha256-eddsa-ecdh-a128ctr /
2f # negative(15) / -16 = SHA-256 /
27 # negative(7) / -8 = EdDSA /
38 18 # negative(24) / -25 = ECDH-ES + HKDF-256 /
39 fffd # negative(65533) / -65534 = A128CTR /
84 # array(4) / suit-sha256-es256-ecdh-a128gcm /
2f # negative(15) / -16 = SHA-256 /
26 # negative(6) / -7 = ES256 /
38 18 # negative(24) / -25 = ECDH-ES + HKDF-256 /
01 # unsigned(1) / A128GCM /
84 # array(4) / suit-sha256-eddsa-ecdh-chacha-poly /
2f # negative(15) / -16 = SHA-256 /
27 # negative(7) / EdDSA /
38 18 # negative(24) / -25 = ECDH-ES + HKDF-256 /
18 18 # unsigned(24) / 24 = ChaCha20/Poly1305 /
03 # unsigned(3) / attestation | trusted-components /
D.2. Entity Attestation Token
This is shown below in CBOR diagnostic form. Only the payload signed
by COSE is shown.
D.2.1. CBOR Diagnostic Notation
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/ eat-claim-set = /
{
/ cnf / 8: {
/ kid / 3 : h'ba7816bf8f01cfea414140de5dae2223'
h'b00361a396177a9cb410ff61f20015ad'
},
/ eat_nonce / 10: h'948f8860d13a463e8e',
/ ueid / 256: h'0198f50a4ff6c05861c8860d13a638ea',
/ oemid / 258: h'894823', / IEEE OUI format OEM ID /
/ hwmodel / 259: h'549dcecc8b987c737b44e40f7c635ce8'
/ Hash of chip model name /,
/ hwversion / 260: ["1.3.4", 1], / Multipartnumeric /
/ manifests / 273: [
[ 60, / application/cbor, TO BE REPLACED /
/ with the format value for a /
/ SUIT_Reference once one is allocated /
{ / SUIT_Reference /
/ suit-report-manifest-uri / 1: "https://example.com/manifest.cbor",
/ suit-report-manifest-digest / 0:[
/ algorithm-id / -16 / "sha256" /,
/ digest-bytes / h'a7fd6593eac32eb4be578278e6540c5c'
h'09cfd7d4d234973054833b2b93030609'
]
}
]
]
}
D.3. QueryResponse Message
D.3.1. CBOR Diagnostic Notation
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/ query-response = /
[
/ type: / 2 / TEEP-TYPE-query-response /,
/ options: /
{
/ token / 20 : h'A0A1A2A3A4A5A6A7A8A9AAABACADAEAF',
/ selected-version / 6 : 0,
/ attestation-payload / 7 : h'' / empty only for example purpose /,
/ tc-list / 8 : [
{
/ system-component-id / 0 : [ h'0102030405060708090A0B0C0D0E0F' ],
/ suit-parameter-image-digest / 3: << [
/ suit-digest-algorithm-id / -16 / SHA256 /,
/ suit-digest-bytes / h'A7FD6593EAC32EB4BE578278E6540C5C09CFD7D4D234973054833B2B93030609'
/ SHA256 digest of tc binary /
] >>
}
]
}
]
D.3.2. CBOR Binary Representation
82 # array(2)
02 # unsigned(2) / TEEP-TYPE-query-response /
A4 # map(4)
14 # unsigned(20) / token: /
50 # bytes(16)
A0A1A2A3A4A5A6A7A8A9AAABACADAEAF
06 # unsigned(6) / selected-version: /
00 # unsigned(0)
07 # unsigned(7) / attestation-payload: /
40 # bytes(0)
# ""
08 # unsigned(8) / tc-list: /
81 # array(1)
A2 # map(2)
00 # unsigned(0) / system-component-id: /
81 # array(1)
4F # bytes(15)
0102030405060708090A0B0C0D0E0F
03 # unsigned(3) / suit-parameter-image-digest: /
58 24 # bytes(36)
822F5820A7FD6593EAC32EB4BE578278E6540C5C09CFD7D4D234973054833B2B93030609
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D.4. Update Message
D.4.1. CBOR Diagnostic Notation
/ update = /
[
/ type: / 3 / TEEP-TYPE-update /,
/ options: /
{
/ token / 20 : h'A0A1A2A3A4A5A6A7A8A9AAABACADAEAF',
/ manifest-list / 10 : [
<<
/ SUIT_Envelope / {
/ suit-authentication-wrapper / 2: << [
<< [
/ suit-digest-algorithm-id: / -16 / suit-cose-alg-sha256 /,
/ suit-digest-bytes: / h'DB601ADE73092B58532CA03FBB663DE49532435336F1558B49BB622726A2FEDD'
] >>,
<< / COSE_Sign1_Tagged / 18( [
/ protected: / << {
/ algorithm-id / 1: -7 / ES256 /
} >>,
/ unprotected: / {},
/ payload: / null,
/ signature: / h'5B2D535A2B6D5E3C585C1074F414DA9E10BD285C99A33916DADE3ED38812504817AC48B62B8E984EC622785BD1C411888BE531B1B594507816B201F6F28579A4'
] ) >>
] >>,
/ suit-manifest / 3: << {
/ suit-manifest-version / 1: 1,
/ suit-manifest-sequence-number / 2: 3,
/ suit-common / 3: << {
/ suit-components / 2: [
[
h'544545502D446576696365', / "TEEP-Device" /
h'5365637572654653', / "SecureFS" /
h'8D82573A926D4754935332DC29997F74', / tc-uuid /
h'7461' / "ta" /
]
],
/ suit-common-sequence / 4: << [
/ suit-directive-override-parameters / 20, {
/ suit-parameter-vendor-identifier / 1: h'C0DDD5F15243566087DB4F5B0AA26C2F',
/ suit-parameter-class-identifier / 2: h'DB42F7093D8C55BAA8C5265FC5820F4E',
/ suit-parameter-image-digest / 3: << [
/ suit-digest-algorithm-id: / -16 / suit-cose-alg-sha256 /,
/ suit-digest-bytes: / h'8CF71AC86AF31BE184EC7A05A411A8C3A14FD9B77A30D046397481469468ECE8'
] >>,
/ suit-parameter-image-size / 14: 20
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},
/ suit-condition-vendor-identifier / 1, 15,
/ suit-condition-class-identifier / 2, 15
] >>
} >>,
/ suit-install / 9: << [
/ suit-directive-override-parameters / 20, {
/ suit-parameter-uri / 21: "https://example.org/8d82573a-926d-4754-9353-32dc29997f74.ta"
},
/ suit-directive-fetch / 21, 15,
/ suit-condition-image-match / 3, 15
] >>
} >>
}
>>
] / array of bstr wrapped SUIT_Envelope /
}
]
D.4.2. CBOR Binary Representation
82 # array(2)
03 # unsigned(3) / TEEP-TYPE-update /
A2 # map(2)
14 # unsigned(20) / token: /
50 # bytes(16)
A0A1A2A3A4A5A6A7A8A9AAABACADAEAF
0A # unsigned(10) / manifest-list: /
81 # array(1)
59 014E # bytes(336)
A2025873825824822F5820DB601ADE73092B58532CA03FBB663DE495
32435336F1558B49BB622726A2FEDD584AD28443A10126A0F658405B2D53
5A2B6D5E3C585C1074F414DA9E10BD285C99A33916DADE3ED38812504817
AC48B62B8E984EC622785BD1C411888BE531B1B594507816B201F6F28579
A40358D4A401010203035884A20281844B544545502D4465766963654853
65637572654653508D82573A926D4754935332DC29997F74427461045854
8614A40150C0DDD5F15243566087DB4F5B0AA26C2F0250DB42F7093D8C55
BAA8C5265FC5820F4E035824822F58208CF71AC86AF31BE184EC7A05A411
A8C3A14FD9B77A30D046397481469468ECE80E14010F020F0958458614A1
15783B68747470733A2F2F6578616D706C652E6F72672F38643832353733
612D393236642D343735342D393335332D3332646332393939376637342E
7461150F030F
D.5. Success Message
D.5.1. CBOR Diagnostic Notation
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/ teep-success = /
[
/ type: / 5 / TEEP-TYPE-teep-success /,
/ options: /
{
/ token / 20 : h'A0A1A2A3A4A5A6A7A8A9AAABACADAEAF'
}
]
D.5.2. CBOR Binary Representation
82 # array(2)
05 # unsigned(5) / TEEP-TYPE-teep-success /
A1 # map(1)
14 # unsigned(20) / token: /
50 # bytes(16)
A0A1A2A3A4A5A6A7A8A9AAABACADAEAF
D.6. Error Message
D.6.1. CBOR Diagnostic Notation
/ teep-error = /
[
/ type: / 6 / TEEP-TYPE-teep-error /,
/ options: /
{
/ token / 20 : h'A0A1A2A3A4A5A6A7A8A9AAABACADAEAF',
/ err-msg / 12 : "disk-full"
},
/ err-code: / 17 / ERR_MANIFEST_PROCESSING_FAILED /
]
D.6.2. CBOR binary Representation
83 # array(3)
06 # unsigned(6) / TEEP-TYPE-teep-error /
A2 # map(2)
14 # unsigned(20) / token: /
50 # bytes(16)
A0A1A2A3A4A5A6A7A8A9AAABACADAEAF
0C # unsigned(12) / err-msg: /
69 # text(9)
6469736B2D66756C6C # "disk-full"
11 # unsigned(17) / ERR_MANIFEST_PROCESSING_FAILED /
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E. Examples of SUIT Manifests
This section shows some examples of SUIT manifests described in
Section 4.4.
The examples are signed using the following ECDSA secp256r1 key with
SHA256 as the digest function.
COSE_Sign1 Cryptographic Key:
-----BEGIN PRIVATE KEY-----
MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgApZYjZCUGLM50VBC
CjYStX+09jGmnyJPrpDLTz/hiXOhRANCAASEloEarguqq9JhVxie7NomvqqL8Rtv
P+bitWWchdvArTsfKktsCYExwKNtrNHXi9OB3N+wnAUtszmR23M4tKiW
-----END PRIVATE KEY-----
The corresponding public key can be used to verify these examples:
-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEhJaBGq4LqqvSYVcYnuzaJr6qi/Eb
bz/m4rVlnIXbwK07HypLbAmBMcCjbazR14vTgdzfsJwFLbM5kdtzOLSolg==
-----END PUBLIC KEY-----
Example 1: SUIT Manifest pointing to URI of the Trusted Component Binary
CBOR Diagnostic Notation of SUIT Manifest
/ SUIT_Envelope / {
/ authentication-wrapper / 2: << [
<< [
/ digest-algorithm-id: / -16 / SHA256 /,
/ digest-bytes: / h'EF53C7F719CB10041233850AE3211D62CEC9528924E656607688E77BC14886A0'
] >>,
<< / COSE_Sign1_Tagged / 18([
/ protected: / << {
/ algorithm-id / 1: -7 / ES256 /
} >>,
/ unprotected: / {},
/ payload: / null,
/ signature: / h'7E367F9E124859473FBDF3D6312AA8943617B41AE4782FCA0E77A492C51F8A7252EA42C23D722E787AA235B5175DBE61DDF8F16F956E0317B9550A04BF9165DD'
]) >>
] >>,
/ manifest / 3: << {
/ manifest-version / 1: 1,
/ manifest-sequence-number / 2: 3,
/ common / 3: << {
/ components / 2: [
[
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'TEEP-Device',
'SecureFS',
h'8D82573A926D4754935332DC29997F74', / tc-uuid /
'ta'
]
],
/ shared-sequence / 4: << [
/ directive-override-parameters / 20, {
/ parameter-vendor-identifier / 1: h'C0DDD5F15243566087DB4F5B0AA26C2F',
/ parameter-class-identifier / 2: h'DB42F7093D8C55BAA8C5265FC5820F4E',
/ parameter-image-digest / 3: << [
/ digest-algorithm-id: / -16 / SHA256 /,
/ digest-bytes: / h'8CF71AC86AF31BE184EC7A05A411A8C3A14FD9B77A30D046397481469468ECE8'
] >>,
/ parameter-image-size / 14: 20
},
/ condition-vendor-identifier / 1, 15,
/ condition-class-identifier / 2, 15
] >>
} >>,
/ manifest-component-id / 5: [
'TEEP-Device',
'SecureFS',
h'8D82573A926D4754935332DC29997F74', / tc-uuid /
'suit'
],
/ install / 17: << [
/ directive-override-parameters / 20, {
/ parameter-uri / 21: "https://example.org/8d82573a-926d-4754-9353-32dc29997f74.ta"
},
/ directive-fetch / 21, 15,
/ condition-image-match / 3, 15
] >>,
/ uninstall / 24: << [
/ directive-unlink / 33, 15
] >>
} >>
}
CBOR Binary in Hex
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A2025873825824822F5820EF53C7F719CB10041233850AE3211D62CEC952
8924E656607688E77BC14886A0584AD28443A10126A0F658407E367F9E12
4859473FBDF3D6312AA8943617B41AE4782FCA0E77A492C51F8A7252EA42
C23D722E787AA235B5175DBE61DDF8F16F956E0317B9550A04BF9165DD03
590108A601010203035884A20281844B544545502D446576696365485365
637572654653508D82573A926D4754935332DC29997F7442746104585486
14A40150C0DDD5F15243566087DB4F5B0AA26C2F0250DB42F7093D8C55BA
A8C5265FC5820F4E035824822F58208CF71AC86AF31BE184EC7A05A411A8
C3A14FD9B77A30D046397481469468ECE80E14010F020F05844B54454550
2D446576696365485365637572654653508D82573A926D4754935332DC29
997F7444737569741158458614A115783B68747470733A2F2F6578616D70
6C652E6F72672F38643832353733612D393236642D343735342D39333533
2D3332646332393939376637342E7461150F030F1818448218210F
Example 2: SUIT Manifest including the Trusted Component Binary
CBOR Diagnostic Notation of SUIT Manifest
/ SUIT_Envelope / {
/ authentication-wrapper / 2: << [
<< [
/ digest-algorithm-id: / -16 / SHA256 /,
/ digest-bytes: / h'526A85341DE35AFA4FAF9EDDDA40164525077DC45DFBE25785B9FF40683EE881'
] >>,
<< / COSE_Sign1_Tagged / 18([
/ protected: / << {
/ algorithm-id / 1: -7 / ES256 /
} >>,
/ unprotected: / {},
/ payload: / null,
/ signature: / h'4B57A8102D0D86B83BA0368E118917D87DBF7815DC31B19DEB7E154F3D191A1434ADFAE27D5AED39C07A2A4B2A0D78031E73B23D679507C4953DD9E00CA7E541'
]) >>
] >>,
/ manifest / 3: << {
/ manifest-version / 1: 1,
/ manifest-sequence-number / 2: 3,
/ common / 3: << {
/ components / 2: [
[
'TEEP-Device',
'SecureFS',
h'8D82573A926D4754935332DC29997F74', / tc-uuid /
'ta'
]
],
/ shared-sequence / 4: << [
/ directive-override-parameters / 20, {
/ parameter-vendor-identifier / 1: h'C0DDD5F15243566087DB4F5B0AA26C2F',
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/ parameter-class-identifier / 2: h'DB42F7093D8C55BAA8C5265FC5820F4E',
/ parameter-image-digest / 3: << [
/ digest-algorithm-id: / -16 / SHA256 /,
/ digest-bytes: / h'8CF71AC86AF31BE184EC7A05A411A8C3A14FD9B77A30D046397481469468ECE8'
] >>,
/ parameter-image-size / 14: 20
},
/ condition-vendor-identifier / 1, 15,
/ condition-class-identifier / 2, 15
] >>
} >>,
/ manifest-component-id / 5: [
'TEEP-Device',
'SecureFS',
h'8D82573A926D4754935332DC29997F74', / tc-uuid /
'suit'
],
/ install / 17: << [
/ directive-override-parameters / 20, {
/ uri / 21: "#tc"
},
/ directive-fetch / 21, 15,
/ condition-image-match / 3, 15
] >>,
/ uninstall / 24: << [
/ directive-unlink / 33, 15
] >>
} >>,
"#tc" : 'Hello, Secure World!'
}
CBOR Binary in Hex
A3025873825824822F5820526A85341DE35AFA4FAF9EDDDA40164525077D
C45DFBE25785B9FF40683EE881584AD28443A10126A0F658404B57A8102D
0D86B83BA0368E118917D87DBF7815DC31B19DEB7E154F3D191A1434ADFA
E27D5AED39C07A2A4B2A0D78031E73B23D679507C4953DD9E00CA7E54103
58CEA601010203035884A20281844B544545502D44657669636548536563
7572654653508D82573A926D4754935332DC29997F744274610458548614
A40150C0DDD5F15243566087DB4F5B0AA26C2F0250DB42F7093D8C55BAA8
C5265FC5820F4E035824822F58208CF71AC86AF31BE184EC7A05A411A8C3
A14FD9B77A30D046397481469468ECE80E14010F020F05844B544545502D
446576696365485365637572654653508D82573A926D4754935332DC2999
7F744473756974114C8614A11563237463150F030F1818448218210F6323
74635448656C6C6F2C2053656375726520576F726C6421
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Example 3: Supplying Personalization Data for Trusted Component Binary
This example uses the following parameters:
* Algorithm for payload encryption: AES-CTR-128
* Algorithm id for key wrap: ECDH-ES + HKDF-256
* KEK (Receiver's Private Key):
- kty: EC2
- crv: P-256
- x: h'5886CD61DD875862E5AAA820E7A15274C968A9BC96048DDCACE32F50C3
651BA3'
- y: h'9EED8125E932CD60C0EAD3650D0A485CF726D378D1B016ED4298B2961E
258F1B'
- d: h'60FE6DD6D85D5740A5349B6F91267EEAC5BA81B8CB53EE249E4B4EB102
C476B3'
* COSE_KDF_Context
- AlgorithmID: -65534 (A128CTR)
- SuppPubInfo
o keyDataLength: 128
o protected: << {/ alg / 1: -25 / ECDH-ES+HKDF-256 / } >>
o other: 'SUIT Payload Encryption'
CBOR Diagnostic Notation of SUIT Manifest
/ SUIT_Envelope / {
/ authentication-wrapper / 2: << [
<< [
/ digest-algorithm-id: / -16 / SHA256 /,
/ digest-bytes: / h'0936A4CF3A75D96B43BF88FA6AFA4220800EDC20C32B489BAAAF02EF72438A26'
] >>,
<< / COSE_Sign1_Tagged / 18([
/ protected: / << {
/ algorithm-id / 1: -7 / ES256 /
} >>,
/ unprotected: / {},
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/ payload: / null,
/ signature: / h'104D09EE04B4B10D67A6CA9D9C638044FE4F09B870CADFBA191997749D43C30BD15E01240FA6B681280769BAA090C0234B7BECD4008C2AD9D35E4349C56C07DC'
]) >>
] >>,
/ manifest / 3: << {
/ manifest-version / 1: 1,
/ manifest-sequence-number / 2: 3,
/ common / 3: << {
/ dependencies / 1: {
/ component-index / 1: {
/ dependency-prefix / 1: [
'TEEP-Device',
'SecureFS',
h'8D82573A926D4754935332DC29997F74', / tc-uuid /
'suit'
]
}
},
/ components / 2: [
[
'TEEP-Device',
'SecureFS',
'config.json'
]
],
/ shared-sequence / 4: << [
/ directive-set-component-index / 12, 0,
/ directive-override-parameters / 20, {
/ parameter-vendor-identifier / 1: h'C0DDD5F15243566087DB4F5B0AA26C2F',
/ parameter-class-identifier / 2: h'DB42F7093D8C55BAA8C5265FC5820F4E'
},
/ condition-vendor-identifier / 1, 15,
/ condition-class-identifier / 2, 15
] >>
} >>,
/ manifest-component-id / 5: [
'TEEP-Device',
'SecureFS',
'config.suit'
],
/ validate / 7: << [
/ directive-set-component-index / 12, 0,
/ directive-override-parameters / 20, {
/ NOTE: image-digest and image-size of plaintext config.json /
/ parameter-image-digest / 3: << [
/ digest-algorithm-id: / -16 / SHA256 /,
/ digest-bytes: / h'8273468FB64BD84BB04825F8371744D952B751C73A60F455AF681E167726F116'
] >>,
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/ image-size / 14: 61
},
/ condition-image-match / 3, 15
] >>,
/ dependency-resolution / 15: << [
/ directive-set-component-index / 12, 1,
/ directive-override-parameters / 20, {
/ parameter-image-digest / 3: << [
/ algorithm-id / -16 / SHA256 /,
/ digest-bytes / h'EF53C7F719CB10041233850AE3211D62CEC9528924E656607688E77BC14886A0'
] >>,
/ parameter-image-size / 14: 389,
/ uri / 21: "https://example.org/8d82573a-926d-4754-9353-32dc29997f74.suit"
},
/ directive-fetch / 21, 2,
/ directive-process-dependency / 11, 15
] >>,
/ install / 17: << [
/ directive-set-component-index / 12, 1,
/ directive-process-dependency / 11, 0,
/ NOTE: fetch encrypted firmware /
/ directive-set-component-index / 12, 0,
/ directive-override-parameters / 20, {
/ NOTE: encrypted payload and encryption-info /
/ parameter-content / 18: h'8E8E6E4C63DEC2B1EC68720EBDF9636B9409485C296EF68EB79F93CCB1A1B136DD227BAC33CFD93F7A98F1CD020E559B8EBC33CE7C5009A47EB3D11574',
/ parameter-encryption-info / 19: << 96([
/ protected: / << {
/ alg / 1: -65534 / A128CTR /
} >>,
/ unprotected: / {
/ IV / 5: h'6CE59E41746D36492CAFCB9E3C2E85A2'
},
/ payload: / null / detached ciphertext /,
/ recipients: / [
[
/ protected: / << {
/ alg / 1: -25 / ECDH-ES + HKDF-256 /
} >>,
/ unprotected: / {
/ ephemeral key / -1: {
/ kty / 1: 2 / EC2 /,
/ crv / -1: 1 / P-256 /,
/ x / -2: h'C32A41E1853B16DA0319654C438EA6882BB119670C8F1C84980CDFD1BBDB60E3',
/ y / -3: h'764A34B5D63F800A46384BA6474BA8C7FEEE7CCF9C74B84C9E2E4CF62C00A235'
}
},
/ payload: / h''
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]
]
]) >>
},
/ decrypt encrypted firmware /
/ directive-write / 18, 15 / consumes the SUIT_Encryption_Info above /
/ NOTE: decrypted payload would be ``{"name":"FOO Bar","secret":"0123456789abfcdef0123456789abcd"}'' /
] >>,
/ uninstall / 24: << [
/ directive-set-component-index / 12, 1,
/ directive-process-dependency / 11, 0,
/ directive-set-component-index / 12, 0,
/ directive-unlink / 33, 15
] >>
} >>
}
CBOR Binary in Hex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F. Examples of SUIT Reports
This section shows some examples of SUIT reports.
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F.1. Example 1: Success
SUIT Reports have no records if no conditions have failed. The URI
in this example is the reference URI provided in the SUIT manifest.
{
/ suit-report-manifest-digest / 1:<<[
/ algorithm-id / -16 / "sha256" /,
/ digest-bytes / h'a7fd6593eac32eb4be578278e6540c5c'
h'09cfd7d4d234973054833b2b93030609'
]>>,
/ suit-report-manifest-uri / 2: "tam.teep.example/personalisation",
/ suit-report-records / 4: []
}
F.2. Example 2: Faiure
{
/ suit-report-manifest-digest / 1:<<[
/ algorithm-id / -16 / "sha256" /,
/ digest-bytes / h'a7fd6593eac32eb4be578278e6540c5c09cfd7d4d234973054833b2b93030609'
]>>,
/ suit-report-manifest-uri / 2: "tam.teep.example/personalisation",
/ suit-report-records / 4: [
{
/ suit-record-manifest-id / 1:[],
/ suit-record-manifest-section / 2: 7 / dependency-resolution /,
/ suit-record-section-offset / 3: 66,
/ suit-record-dependency-index / 5: 0,
/ suit-record-failure-reason / 6: 404
}
]
}
where the dependency-resolution refers to:
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{
authentication-wrapper,
/ manifest / 3:<<{
/ manifest-version / 1:1,
/ manifest-sequence-number / 2:3,
common,
dependency-resolution,
install,
validate,
run,
text
}>>,
}
and the suit-record-section-offset refers to:
<<[
/ directive-set-dependency-index / 13,0,
/ directive-set-parameters / 19,{
/ uri / 21:'tam.teep.example/'
'edd94cd8-9d9c-4cc8-9216-b3ad5a2d5b8a',
} ,
/ directive-fetch / 21,2,
/ condition-image-match / 3,15
]>>,
Authors' Addresses
Hannes Tschofenig
Austria
Email: hannes.tschofenig@gmx.net
Mingliang Pei
Broadcom
United States of America
Email: mingliang.pei@broadcom.com
David Wheeler
Amazon
United States of America
Email: davewhee@amazon.com
Dave Thaler
Microsoft
United States of America
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Email: dave.thaler.ietf@gmail.com
Akira Tsukamoto
ALAXALA Networks Corp.
Japan
Email: akira.tsukamoto@alaxala.com
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