Trusted Execution Environment Provisioning (TEEP) Protocol
draft-ietf-teep-protocol-06
TEEP H. Tschofenig
Internet-Draft Arm Ltd.
Intended status: Standards Track M. Pei
Expires: January 13, 2022 Broadcom
D. Wheeler
Amazon
D. Thaler
Microsoft
A. Tsukamoto
AIST
July 12, 2021
Trusted Execution Environment Provisioning (TEEP) Protocol
draft-ietf-teep-protocol-06
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
Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on January 13, 2022.
Copyright Notice
Copyright (c) 2021 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Message Overview . . . . . . . . . . . . . . . . . . . . . . 4
4. Detailed Messages Specification . . . . . . . . . . . . . . . 5
4.1. Creating and Validating TEEP Messages . . . . . . . . . . 5
4.1.1. Creating a TEEP message . . . . . . . . . . . . . . . 5
4.1.2. Validating a TEEP Message . . . . . . . . . . . . . . 6
4.2. QueryRequest Message . . . . . . . . . . . . . . . . . . 6
4.3. QueryResponse Message . . . . . . . . . . . . . . . . . . 9
4.3.1. Evidence . . . . . . . . . . . . . . . . . . . . . . 11
4.4. Update Message . . . . . . . . . . . . . . . . . . . . . 12
4.5. Success Message . . . . . . . . . . . . . . . . . . . . . 14
4.6. Error Message . . . . . . . . . . . . . . . . . . . . . . 15
5. Mapping of TEEP Message Parameters to CBOR Labels . . . . . . 17
6. Behavior Specification . . . . . . . . . . . . . . . . . . . 18
6.1. TAM Behavior . . . . . . . . . . . . . . . . . . . . . . 18
6.2. TEEP Agent Behavior . . . . . . . . . . . . . . . . . . . 19
7. Ciphersuites . . . . . . . . . . . . . . . . . . . . . . . . 20
8. Freshness Mechanisms . . . . . . . . . . . . . . . . . . . . 21
9. Security Considerations . . . . . . . . . . . . . . . . . . . 21
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
10.1. Media Type Registration . . . . . . . . . . . . . . . . 23
10.2. Ciphersuite Registry . . . . . . . . . . . . . . . . . . 24
10.3. Freshness Mechanism Registry . . . . . . . . . . . . . . 24
10.4. CBOR Tag Registry . . . . . . . . . . . . . . . . . . . 25
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
11.1. Normative References . . . . . . . . . . . . . . . . . . 25
11.2. Informative References . . . . . . . . . . . . . . . . . 26
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 27
B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27
C. Complete CDDL . . . . . . . . . . . . . . . . . . . . . . . . 27
D. Examples of Diagnostic Notation and Binary Representation . . 31
D.1. Some assumptions in examples . . . . . . . . . . . . . . 31
D.2. QueryRequest Message . . . . . . . . . . . . . . . . . . 31
D.2.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 32
D.2.2. CBOR Binary Representation . . . . . . . . . . . . . 32
D.3. Entity Attestation Token . . . . . . . . . . . . . . . . 32
D.3.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 33
D.4. QueryResponse Message . . . . . . . . . . . . . . . . . . 33
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D.4.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 33
D.4.2. CBOR Binary Representation . . . . . . . . . . . . . 34
D.5. Update Message . . . . . . . . . . . . . . . . . . . . . 35
D.5.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 35
D.5.2. CBOR Binary Representation . . . . . . . . . . . . . 35
D.6. Success Message . . . . . . . . . . . . . . . . . . . . . 36
D.6.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 36
D.6.2. CBOR Binary Representation . . . . . . . . . . . . . 36
D.7. Error Message . . . . . . . . . . . . . . . . . . . . . . 36
D.7.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 36
D.7.2. CBOR binary Representation . . . . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37
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 [I-D.ietf-teep-architecture] 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
[I-D.ietf-teep-architecture].
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).
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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).
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 [RFC8152]. 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
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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.
+------------+ +-------------+
| TAM | |TEEP Agent |
+------------+ +-------------+
Update ---->
Success
<---- or
Error
4. Detailed Messages Specification
TEEP messages are protected by the COSE_Sign1 structure. The TEEP
protocol messages are described in CDDL format [RFC8610] below.
{
teep-message => (query-request /
query-response /
update /
teep-success /
teep-error ),
}
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 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 [RFC8152]
specification.
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3. Create a COSE_Sign1 object using the TEEP message as the
COSE_Sign1 Payload; all steps specified in [RFC8152] for creating
a COSE_Sign1 object MUST be followed.
4. Prepend the COSE object with the TEEP CBOR tag to indicate that
the CBOR-encoded message is indeed a TEEP message.
4.1.2. Validating a TEEP Message
When TEEP message is received (see the ProcessTeepMessage conceptual
API defined in [I-D.ietf-teep-architecture] section 6.2.1), 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. Remove the TEEP message CBOR tag and verify that one of the COSE
CBOR tags follows it.
3. Verify that the message contains a COSE_Sign1 structure.
4. 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.
5. Follow the steps specified in Section 4 of [RFC8152] ("Signing
Objects") for validating a COSE_Sign1 object. The COSE_Sign1
payload is the content of the TEEP message.
6. Verify that the TEEP message is a valid CBOR map and verify the
fields of the TEEP message according to this specification.
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 ciphersuites, and protocol versions. Additionally, the TAM
can selectively request data items from the TEEP Agent via the
request parameter. Currently, the following features are supported:
o Request for attestation information,
o Listing supported extensions,
o Querying installed Trusted Components, and
o Listing supported SUIT commands.
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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.
query-request = [
type: TEEP-TYPE-query-request,
options: {
? token => bstr .size (8..64),
? supported-cipher-suites => [ + suite ],
? supported-freshness-mechanisms => [ + freshness-mechanism ],
? challenge => bstr .size (8..512),
? versions => [ + version ],
? ocsp-data => bstr,
* $$query-request-extensions
* $$teep-option-extensions
},
data-item-requested: data-item-requested
]
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. 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. The size of the token is at least 8 bytes (64
bits) and maximum of 64 bytes, which is the same as in an EAT
Nonce Claim (see [I-D.ietf-rats-eat] Section 3.3).
data-item-requested
The data-item-requested parameter indicates what information the
TAM requests from the TEEP Agent in the form of a bitmap. Each
value in the bitmap corresponds to an IANA registered information
element. This specification defines the following initial set of
information elements:
attestation (1) With this value the TAM requests the TEEP Agent
to return attestation evidence (e.g., an EAT) in the response.
trusted-components (2) With this value the TAM queries the TEEP
Agent for all installed Trusted Components.
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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-commands (8) With this value the TAM queries the TEEP Agent
for supported commands offered by the SUIT manifest
implementation.
Further values may be added in the future via IANA registration.
supported-cipher-suites
The supported-cipher-suites parameter lists the ciphersuite(s)
supported by the TAM. If this parameter is not present, it is to
be treated the same as if it contained both ciphersuites defined
in this document. Details about the ciphersuite encoding can be
found in Section 7.
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 8. If this parameter is absent, it means only
the nonce mechanism is supported.
challenge
The challenge field is an optional parameter used for ensuring the
freshness of the attestation evidence returned with a
QueryResponse message. It MUST be absent if the attestation bit
is clear (since the token is used instead in that case). When a
challenge is provided in the QueryRequest and an EAT is returned
with the QueryResponse message then the challenge contained in
this request MUST be copied into the nonce claim found in the EAT.
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.
ocsp-data
The ocsp-data parameter contains a list of OCSP stapling data
respectively for the TAM certificate and each of the CA
certificates up to, but not including, the trust anchor. The TAM
provides OCSP data so that the TEEP Agent can validate the status
of the TAM certificate chain without making its own external OCSP
service call. OCSP data MUST be conveyed as a DER-encoded OCSP
response (using the ASN.1 type OCSPResponse defined in [RFC6960]).
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The use of OCSP is OPTIONAL to implement for both the TAM and the
TEEP Agent. A TAM can query the TEEP Agent for the support of
this functionality via the capability discovery exchange, as
described above.
4.3. QueryResponse Message
The QueryResponse message is the successful response by the TEEP
Agent after receiving a QueryRequest 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-cipher-suite => suite,
? selected-version => version,
? evidence-format => text,
? evidence => bstr,
? tc-list => [ + tc-info ],
? requested-tc-list => [ + requested-tc-info ],
? unneeded-tc-list => [ + SUIT_Component_Identifier ],
? ext-list => [ + ext-info ],
* $$query-response-extensions,
* $$teep-option-extensions
}
]
tc-info = {
component-id => SUIT_Component_Identifier,
? tc-manifest-sequence-number => .within uint .size 8
}
requested-tc-info = {
component-id => SUIT_Component_Identifier,
? tc-manifest-sequence-number => .within 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.
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token
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-cipher-suite
The selected-cipher-suite parameter indicates the selected
ciphersuite. Details about the ciphersuite encoding can be found
in Section 7.
selected-version
The selected-version parameter indicates the TEEP protocol version
selected by the TEEP Agent. The absense of this parameter
indicates the same as if it was present with a value of 0.
evidence-format
The evidence-format parameter indicates the IANA Media Type of the
attestation evidence contained in the evidence parameter. It MUST
be present if the evidence parameter is present and the format is
not an EAT.
evidence
The evidence parameter contains the attestation evidence. This
parameter MUST be present if the QueryResponse is sent in response
to a QueryRequest with the attestation bit set. If the evidence-
format parameter is absent, the attestation evidence 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.
tc-list
The tc-list parameter enumerates the Trusted Components installed
on the device in the form of tc-info objects. 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 UnrequestTA conceptual API defined in
[I-D.ietf-teep-architecture] section 6.2.1.
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unneeded-tc-list
The unneeded-tc-list parameter enumerates the Trusted Components
that 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 Trusted Component can be deleted. Each
unneeded Trusted Component is identified by its SUIT Component
Identifier. A TEEP Agent can get this information from the
UnrequestTA conceptual API defined in [I-D.ietf-teep-architecture]
section 6.2.1.
ext-list
The ext-list parameter lists the supported extensions. This
document does not define any extensions.
The tc-info object has the following fields:
component-id
A SUIT Component Identifier.
tc-manifest-sequence-number
The suit-manifest-sequence-number value from the SUIT manifest for
the Trusted Component, if a SUIT manifest was used.
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
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
Section 7.1 of [I-D.ietf-teep-architecture] lists information that
may be required in the evidence depend on the circumstance. When an
Entity Attestation Token is used, the following claims can be used to
meet those requirements:
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+------------+---------------------+--------------------------------+
| Requiremen | Claim | Reference |
| t | | |
+------------+---------------------+--------------------------------+
| Device | device-identifier | [I-D.birkholz-rats-suit-claims |
| unique | | ] section 3.1.3 |
| identifier | | |
| Vendor of | vendor-identifier | [I-D.birkholz-rats-suit-claims |
| the device | | ] section 3.1.1 |
| Class of | class-identifier | [I-D.birkholz-rats-suit-claims |
| the device | | ] section 3.1.2 |
| TEE | chip-version-scheme | [I-D.ietf-rats-eat] section |
| hardware | | 3.7 |
| type | | |
| TEE | chip-version-scheme | [I-D.ietf-rats-eat] section |
| hardware | | 3.7 |
| version | | |
| TEE | component- | [I-D.birkholz-rats-suit-claims |
| firmware | identifier | ] section 3.1.4 |
| type | | |
| TEE | version | [I-D.birkholz-rats-suit-claims |
| firmware | | ] section 3.1.8 |
| version | | |
| Freshness | nonce | [I-D.ietf-rats-eat] section |
| proof | | 3.3 |
+------------+---------------------+--------------------------------+
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.
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),
? manifest-list => [ + bstr .cbor SUIT_Envelope ],
* $$update-extensions,
* $$teep-option-extensions
}
]
The Update message has the following fields:
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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.
token
The value in the token field is used to match responses to
requests.
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.
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
[I-D.ietf-teep-architecture] for further discussion.
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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
If present, the suit-reports parameter contains a set of SUIT
Reports as defined in Section 4 of [I-D.moran-suit-report]. If
the suit-report-nonce field is present in the SUIT Report, is
value MUST match the value of the token parameter in the Update
message the Success message is in response to.
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4.6. Error Message
The Error message is used by the TEEP Agent to return an error in
response to an Update message.
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-cipher-suites => [ + suite ],
? supported-freshness-mechanisms => [ + freshness-mechanism ],
? versions => [ + version ],
? suit-reports => [ + suit-report ],
* $$teep-error-extensions,
* $$teep-option-extensions
},
err-code: uint (0..23)
]
The Error message has the following fields:
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
Update 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-cipher-suites
The supported-cipher-suites parameter lists the ciphersuite(s)
supported by the TEEP Agent. Details about the ciphersuite
encoding can be found in Section 7. This field is optional but
MUST be returned with the ERR_UNSUPPORTED_CRYPTO_ALG error
message.
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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 8. If this parameter is absent,
it means only the nonce mechanism is supported.
versions
The versions parameter enumerates the TEEP protocol version(s)
supported by the TEEP Agent. This otherwise optional parameter
MUST be returned with the ERR_UNSUPPORTED_MSG_VERSION error
message.
suit-reports
If present, the suit-reports parameter contains a set of SUIT
Reports as defined in Section 4 of [I-D.moran-suit-report]. If
the suit-report-nonce field is present in the SUIT Report, is
value MUST match the value of the token parameter in the Update
message the Error message is in response to.
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 TEEP request 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.
A TAM receiving this error might refuse to communicate further
with the TEEP Agent 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 when there is no attestation evidence
indicating that the error is genuine. In contrast,
ERR_TEMPORARY_ERROR is an indication that a more agressive retry
is warranted.
ERR_UNSUPPORTED_EXTENSION (2)
The TEEP Agent does not support an extension included in the
request message. For diagnosis purposes it is RECOMMMENDED to
identify the unsupported extension in the error message. A TAM
receiving this error might retry the request without using
extensions.
ERR_UNSUPPORTED_MSG_VERSION (4)
The TEEP Agent does not support the TEEP protocol version
indicated in the request message. A TAM receiving this error
might retry the request using a different TEEP protocol version.
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ERR_UNSUPPORTED_CRYPTO_ALG (5)
The TEEP Agent does not support the cryptographic algorithm
indicated in the request message. A TAM receiving this error
might retry the request using a different cryptographic algorithm.
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. For example, the certificate was of an
unsupported type, or the certificate was revoked by its signer. A
TAM receiving this error might attempt to use an alternate
certificate.
ERR_CERTIFICATE_EXPIRED (9)
A certificate has expired or is not currently valid. A TAM
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 request message. A TAM
receiving this error might retry the same request at a later point
in time.
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.
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. 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-cipher-suites | 1 |
| challenge | 2 |
| version | 3 |
| ocsp-data | 4 |
| selected-cipher-suite | 5 |
| selected-version | 6 |
| evidence | 7 |
| tc-list | 8 |
| ext-list | 9 |
| manifest-list | 10 |
| msg | 11 |
| err-msg | 12 |
| evidence-format | 13 |
| requested-tc-list | 14 |
| unneeded-tc-list | 15 |
| component-id | 16 |
| tc-manifest-sequence-number | 17 |
| have-binary | 18 |
| suit-reports | 19 |
| token | 20 |
| supported-freshness-mechanisms | 21 |
+--------------------------------+-------+
6. Behavior Specification
Behavior is specified in terms of the conceptual APIs defined in
section 6.2.1 of [I-D.ietf-teep-architecture].
6.1. 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. 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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If a QueryResponse message is received that contains evidence, the
evidence is passed to an attestation Verifier (see
[I-D.ietf-rats-architecture]) to determine whether the Agent is in a
trustworthy state. Based on the results of attestation, 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. 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.
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 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.
6.2. 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.
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 drops the message if it
is not valid. Otherwise, processing continues as follows based on
the type of message.
When a QueryRequest message is received, the Agent responds with a
QueryResponse message if all fields were understood, or an Error
message if any error was encountered.
When an Update message is received, 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.
7. Ciphersuites
A ciphersuite consists of an AEAD algorithm, a MAC algorithm, and a
signature algorithm. Each ciphersuite is identified with an integer
value, which corresponds to an IANA registered ciphersuite (see
Section 10.2. This document specifies two ciphersuites.
+-------+------------------------------------------------+
| Value | Ciphersuite |
+-------+------------------------------------------------+
| 1 | AES-CCM-16-64-128, HMAC 256/256, X25519, EdDSA |
| 2 | AES-CCM-16-64-128, HMAC 256/256, P-256, ES256 |
+-------+------------------------------------------------+
A TAM MUST support both ciphersuites. A TEEP Agent MUST support at
least one of the two but can choose which one. For example, a TEEP
Agent might choose ciphersuite 2 if it has hardware support for it.
Any ciphersuites without confidentiality protection can only be added
if the associated specification includes a discussion of security
considerations and applicability, since manifests may carry sensitive
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information. For example, Section 6 of [I-D.ietf-teep-architecture]
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 [I-D.ietf-teep-architecture].
8. Freshness Mechanisms
A freshness mechanism determines how a TAM can tell whether evidence
provided in a Query Response is fresh. There are multiple ways this
can be done as discussed in Section 10 of
[I-D.ietf-rats-architecture].
Each freshness mechanism is identified with an integer value, which
corresponds to an IANA registered freshness mechanism (see
Section 10.3. This document defines the following freshness
mechanisms:
+-------+---------------------+
| Value | Freshness mechanism |
+-------+---------------------+
| 1 | Nonce |
| 2 | Timestamp |
| 3 | Epoch ID |
+-------+---------------------+
In the Nonce mechanism, the evidence MUST include a nonce provided in
the QueryRequest challenge. In other mechanisms, a timestamp or
epoch ID determined via mechanisms outside the TEEP protocol is used,
and the challenge is only needed in the QueryRequest message if a
challenge is needed in generating evidence for reasons other than
freshness.
9. Security Considerations
This section summarizes the security considerations discussed in this
specification:
Cryptographic Algorithms
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
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A TAM can rely on the attestation evidence provided by the TEEP
Agent. To sign the attestation evidence, it is necessary for the
device to possess a public key (usually in the form of a
certificate [RFC5280]) along with the corresponding private key.
Depending on the properties of the attestation mechanism, it is
possible to uniquely identify a device based on information in the
attestation evidence or in the certificate used to sign the
attestation evidence. This uniqueness may raise privacy concerns.
To lower the privacy implications the TEEP Agent MUST present its
attestation evidence only to an authenticated and authorized TAM
and when using EATS, 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 EATs is used, it is up to that mechanism to
specify how privacy is provided.
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 digitial signatures and symmetric
encryption.
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 signed and encrypted by a
Trusted Component Signer other than the TAM is opaque to the TAM.
TEEP Broker
As discussed in section 6 of [I-D.ietf-teep-architecture], 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, 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.
Trusted Component Signer Compromise
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The QueryRequest message from a TAM to the TEEP Agent can include
OCSP stapling data for the TAM's certificate and for intermediate
CA certificates up to, but not including, the trust anchor so that
the TEEP Agent can verify the certificate's revocation status. A
certificate revocation status check on a Trusted Component Signer
certificate is OPTIONAL by a TEEP Agent. A TAM is responsible for
vetting a Trusted Component and before distributing them to TEEP
Agents, so TEEP Agents can instead simply trust that a Trusted
Component Signer certificate's status was done by the TAM.
CA Compromise
The CA issuing certificates to a TAM or a Trusted Component Signer
might get compromised. A compromised intermediate CA certificate
can be detected by a TEEP Agent by using OCSP information,
assuming the revocation information is available. Additionally,
it is RECOMMENDED to provide a way to update the trust anchor
store used by the TEE, for example using a firmware update
mechanism. If the CA issuing certificates to devices gets
compromised then these devices might be rejected by a TAM, if
revocation is available to the TAM.
Compromised TAM
The TEEP Agent SHOULD use OCSP information to verify the validity
of the TAM's certificate (as well as the validity of intermediate
CA certificates). The integrity and the accuracy of the clock
within the TEE determines the ability to determine an expired or
revoked certificate. OCSP stapling data includes signature
generation time, allowing certificate validity dates to be
compared to the current time.
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.
10. IANA Considerations
10.1. Media Type Registration
IANA is requested to assign a media type for application/teep+cbor.
Type name: application
Subtype name: teep+cbor
Required parameters: none
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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 [RFC7049].
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
10.2. Ciphersuite Registry
IANA is also requested to create a new registry for ciphersuites, as
defined in Section 7.
10.3. Freshness Mechanism Registry
IANA is also requested to create a new registry for freshness
mechanisms, as defined in Section 8.
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10.4. CBOR Tag Registry
IANA is requested to register a CBOR tag in the "CBOR Tags" registry
for use with TEEP messages.
The registry contents is:
o CBOR Tag: TBD1
o Data Item: TEEP Message
o Semantics: TEEP Message, as defined in draft-ietf-teep-protocol
(TODO: replace with RFC once published)
o Reference: draft-ietf-teep-protocol (TODO: replace with RFC once
published)
o Point of Contact: TEEP working group (teep@ietf.org)
11. References
11.1. Normative References
[I-D.ietf-rats-architecture]
Birkholz, H., Thaler, D., Richardson, M., Smith, N., and
W. Pan, "Remote Attestation Procedures Architecture",
draft-ietf-rats-architecture-12 (work in progress), April
2021.
[I-D.ietf-rats-eat]
Mandyam, G., Lundblade, L., Ballesteros, M., and J.
O'Donoghue, "The Entity Attestation Token (EAT)", draft-
ietf-rats-eat-10 (work in progress), June 2021.
[I-D.ietf-suit-manifest]
Moran, B., Tschofenig, H., Birkholz, H., and K. Zandberg,
"A Concise Binary Object Representation (CBOR)-based
Serialization Format for the Software Updates for Internet
of Things (SUIT) Manifest", draft-ietf-suit-manifest-14
(work in progress), July 2021.
[I-D.moran-suit-report]
Moran, B., "Secure Reporting of Update Status", draft-
moran-suit-report-01 (work in progress), February 2021.
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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/info/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/info/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/info/rfc5198>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A.,
Galperin, S., and C. Adams, "X.509 Internet Public Key
Infrastructure Online Certificate Status Protocol - OCSP",
RFC 6960, DOI 10.17487/RFC6960, June 2013,
<https://www.rfc-editor.org/info/rfc6960>.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/info/rfc7049>.
[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/info/rfc8152>.
[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/info/rfc8174>.
11.2. Informative References
[I-D.birkholz-rats-suit-claims]
Birkholz, H. and B. Moran, "Trustworthiness Vectors for
the Software Updates of Internet of Things (SUIT) Workflow
Model", draft-birkholz-rats-suit-claims-02 (work in
progress), July 2021.
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[I-D.ietf-teep-architecture]
Pei, M., Tschofenig, H., Thaler, D., and D. Wheeler,
"Trusted Execution Environment Provisioning (TEEP)
Architecture", draft-ietf-teep-architecture-15 (work in
progress), July 2021.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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/info/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/info/rfc8915>.
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), 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 MUST adhere to the following CDDL data
definitions, except that "SUIT_Envelope" and
"SUIT_Component_Identifier" are specified in
[I-D.ietf-suit-manifest].
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teep-message = $teep-message-type .within teep-message-framework
SUIT_Envelope = any
teep-message-framework = [
type: uint (0..23) / $teep-type-extension,
options: { * teep-option },
* uint; further integers, 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, uint (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
version = .within uint .size 4
ext-info = .within uint .size 4
; data items as bitmaps
data-item-requested = $data-item-requested .within uint .size 8
attestation = 1
$data-item-requested /= attestation
trusted-components = 2
$data-item-requested /= trusted-components
extensions = 4
$data-item-requested /= extensions
suit-commands = 8
$data-item-requested /= suit-commands
query-request = [
type: TEEP-TYPE-query-request,
options: {
? token => bstr .size (8..64),
? supported-cipher-suites => [ + suite ],
? supported-freshness-mechanisms => [ + freshness-mechanism ],
? challenge => bstr .size (8..512),
? versions => [ + version ],
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? ocsp-data => bstr,
* $$query-request-extensions
* $$teep-option-extensions
},
data-item-requested: data-item-requested
]
; ciphersuites
suite = $TEEP-suite .within uint .size 4
TEEP-AES-CCM-16-64-128-HMAC256--256-X25519-EdDSA = 1
TEEP-AES-CCM-16-64-128-HMAC256--256-P-256-ES256 = 2
$TEEP-suite /= TEEP-AES-CCM-16-64-128-HMAC256--256-X25519-EdDSA
$TEEP-suite /= TEEP-AES-CCM-16-64-128-HMAC256--256-P-256-ES256
; freshness-mechanisms
freshness-mechanism = $TEEP-freshness-mechanism .within uint .size 4
FRESHNESS_NONCE = 0
FRESHNESS_TIMESTAMP = 1
FRESHNESS_EPOCH_ID = 2
$TEEP-freshness-mechanism /= FRESHNESS_NONCE
$TEEP-freshness-mechanism /= FRESHNESS_TIMESTAMP
$TEEP-freshness-mechanism /= FRESHNESS_EPOCH_ID
query-response = [
type: TEEP-TYPE-query-response,
options: {
? token => bstr .size (8..64),
? selected-cipher-suite => suite,
? selected-version => version,
? evidence-format => text,
? evidence => bstr,
? tc-list => [ + tc-info ],
? requested-tc-list => [ + requested-tc-info ],
? unneeded-tc-list => [ + SUIT_Component_Identifier ],
? ext-list => [ + ext-info ],
* $$query-response-extensions,
* $$teep-option-extensions
}
]
tc-info = {
component-id => SUIT_Component_Identifier,
? tc-manifest-sequence-number => .within uint .size 8
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}
requested-tc-info = {
component-id => SUIT_Component_Identifier,
? tc-manifest-sequence-number => .within uint .size 8
? have-binary => bool
}
update = [
type: TEEP-TYPE-update,
options: {
? token => bstr .size (8..64),
? manifest-list => [ + bstr .cbor SUIT_Envelope ],
* $$update-extensions,
* $$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-cipher-suites => [ + suite ],
? supported-freshness-mechanisms => [ + freshness-mechanism ],
? versions => [ + version ],
? suit-reports => [ + suit-report ],
* $$teep-error-extensions,
* $$teep-option-extensions
},
err-code: uint (0..23)
]
; The err-code parameter, uint (0..23)
ERR_PERMANENT_ERROR = 1
ERR_UNSUPPORTED_EXTENSION = 2
ERR_UNSUPPORTED_MSG_VERSION = 4
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ERR_UNSUPPORTED_CRYPTO_ALG = 5
ERR_BAD_CERTIFICATE = 6
ERR_CERTIFICATE_EXPIRED = 9
ERR_TEMPORARY_ERROR = 10
ERR_MANIFEST_PROCESSING_FAILED = 17
; labels of mapkey for teep message parameters, uint (0..23)
supported-cipher-suites = 1
challenge = 2
versions = 3
ocsp-data = 4
selected-cipher-suite = 5
selected-version = 6
evidence = 7
tc-list = 8
ext-list = 9
manifest-list = 10
msg = 11
err-msg = 12
evidence-format = 13
requested-tc-list = 14
unneeded-tc-list = 15
component-id = 16
tc-manifest-sequence-number = 17
have-binary = 18
suit-reports = 19
token = 20
D. Examples of Diagnostic Notation and Binary Representation
D.1. Some assumptions in examples
o OCSP stapling data = h'010203'
o TEEP Device will have two TCs with the following SUIT Component
Identifiers:
* [ 0x000102030405060708090a0b0c0d0e0f ]
* [ 0x100102030405060708090a0b0c0d0e0f ]
o SUIT manifest-list is set empty only for example purposes
D.2. QueryRequest Message
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D.2.1. CBOR Diagnostic Notation
/ query-request = /
[
1, / type : TEEP-TYPE-query-request = 1 (uint (0..23)) /
/ options : /
{
20 : 0xa0a1a2a3a4a5a6a7a8a9aaabacadaeaf,
/ token = 20 (mapkey) :
h'a0a1a2a3a4a5a6a7a8a9aaabacadaeaf' (bstr .size (8..64)),
generated by TAM /
1 : [ 1 ], / supported-cipher-suites = 1 (mapkey) :
TEEP-AES-CCM-16-64-128-HMAC256--256-X25519-EdDSA =
[ 1 ] (array of .within uint .size 4) /
3 : [ 0 ], / version = 3 (mapkey) :
[ 0 ] (array of .within uint .size 4) /
4 : h'010203' / ocsp-data = 4 (mapkey) : 0x010203 (bstr) /
},
3 / data-item-requested :
attestation | trusted-components = 3 (.within uint .size 8) /
]
D.2.2. CBOR Binary Representation
83 # array(3)
01 # unsigned(1) uint (0..23)
A4 # map(4)
14 # unsigned(20) uint (0..23)
4F # bytes(16) (8..64)
A0A1A2A3A4A5A6A7A8A9AAABACADAEAF
01 # unsigned(1) uint (0..23)
81 # array(1)
01 # unsigned(1) within uint .size 4
03 # unsigned(3) uint (0..23)
81 # array(1)
00 # unsigned(0) within uint .size 4
04 # unsigned(4) uint (0..23)
43 # bytes(3)
010203 # "\x01\x02\x03"
03 # unsigned(3) .within uint .size 8
D.3. Entity Attestation Token
This is shown below in CBOR diagnostic form. Only the payload signed
by COSE is shown.
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D.3.1. CBOR Diagnostic Notation
/ eat-claim-set = /
{
/ issuer / 1: "joe",
/ timestamp (iat) / 6: 1(1526542894)
/ nonce / 10: h'948f8860d13a463e8e',
/ secure-boot / 15: true,
/ debug-status / 16: 3, / disabled-permanently /
/ security-level / <TBD>: 3, / secure-restricted /
/ device-identifier / <TBD>: h'e99600dd921649798b013e9752dcf0c5',
/ vendor-identifier / <TBD>: h'2b03879b33434a7ca682b8af84c19fd4',
/ class-identifier / <TBD>: h'9714a5796bd245a3a4ab4f977cb8487f',
/ chip-version-scheme / <TBD>: "MyTEE v1.0",
/ component-identifier / <TBD>: h'60822887d35e43d5b603d18bcaa3f08d',
/ version / <TBD>: "v0.1"
}
D.4. QueryResponse Message
D.4.1. CBOR Diagnostic Notation
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/ query-response = /
[
2, / type : TEEP-TYPE-query-response = 2 (uint (0..23)) /
/ options : /
{
20 : 0xa0a1a2a3a4a5a6a7a8a9aaabacadaeaf,
/ token = 20 (mapkey) :
h'a0a1a2a3a4a5a6a7a8a9aaabacadaeaf' (bstr .size (8..64)),
given from TAM's QueryRequest message /
5 : 1, / selected-cipher-suite = 5 (mapkey) :
TEEP-AES-CCM-16-64-128-HMAC256--256-X25519-EdDSA =
1 (.within uint .size 4) /
6 : 0, / selected-version = 6 (mapkey) :
0 (.within uint .size 4) /
7 : ... / evidence = 7 (mapkey) :
Entity Attestation Token /
8 : [ / tc-list = 8 (mapkey) : (array of tc-info) /
{
16 : [ 0x000102030405060708090a0b0c0d0e0f ] / component-id =
16 (mapkey) : [ h'000102030405060708090a0b0c0d0e0f' ]
(SUIT_Component_Identifier = [* bstr]) /
},
{
16 : [ 0x100102030405060708090a0b0c0d0e0f ] / component-id =
16 (mapkey) : [ h'100102030405060708090a0b0c0d0e0f' ]
(SUIT_Component_Identifier = [* bstr]) /
}
]
}
]
D.4.2. CBOR Binary Representation
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82 # array(2)
02 # unsigned(2) uint (0..23)
A5 # map(5)
14 # unsigned(20) uint (0..23)
4F # bytes(16) (8..64)
A0A1A2A3A4A5A6A7A8A9AAABACADAEAF
05 # unsigned(5) uint (0..23)
01 # unsigned(1) .within uint .size 4
06 # unsigned(6) uint (0..23)
00 # unsigned(0) .within uint .size 4
07 # unsigned(7) uint (0..23)
... # Entity Attestation Token
08 # unsigned(8) uint (0..23)
82 # array(2)
81 # array(1)
4F # bytes(16)
000102030405060708090A0B0C0D0E0F
81 # array(1)
4F # bytes(16)
100102030405060708090A0B0C0D0E0F
D.5. Update Message
D.5.1. CBOR Diagnostic Notation
/ update = /
[
3, / type : TEEP-TYPE-update = 3 (uint (0..23)) /
/ options : /
{
20 : 0xa0a1a2a3a4a5a6a7a8a9aaabacadaeaf,
/ token = 20 (mapkey) :
h'a0a1a2a3a4a5a6a7a8a9aaabacadaeaf' (bstr .size (8..64)),
generated by TAM /
10 : [ ] / manifest-list = 10 (mapkey) :
[ ] (array of bstr wrapped SUIT_Envelope(any)) /
/ empty, example purpose only /
}
]
D.5.2. CBOR Binary Representation
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82 # array(2)
03 # unsigned(3) uint (0..23)
A3 # map(3)
14 # unsigned(20) uint (0..23)
4F # bytes(16) (8..64)
A0A1A2A3A4A5A6A7A8A9AAABACADAEAF
0A # unsigned(10) uint (0..23)
80 # array(0)
D.6. Success Message
D.6.1. CBOR Diagnostic Notation
/ teep-success = /
[
5, / type : TEEP-TYPE-teep-success = 5 (uint (0..23)) /
/ options : /
{
20 : 0xa0a1a2a3a4a5a6a7a8a9aaabacadaeaf,
/ token = 20 (mapkey) :
h'a0a1a2a3a4a5a6a7a8a9aaabacadaeaf' (bstr .size (8..64)),
given from TAM's Update message /
}
]
D.6.2. CBOR Binary Representation
82 # array(2)
05 # unsigned(5) uint (0..23)
A1 # map(1)
14 # unsigned(20) uint (0..23)
4F # bytes(16) (8..64)
A0A1A2A3A4A5A6A7A8A9AAABACADAEAF
D.7. Error Message
D.7.1. CBOR Diagnostic Notation
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/ teep-error = /
[
6, / type : TEEP-TYPE-teep-error = 6 (uint (0..23)) /
/ options : /
{
20 : 0xa0a1a2a3a4a5a6a7a8a9aaabacadaeaf,
/ token = 20 (mapkey) :
h'a0a1a2a3a4a5a6a7a8a9aaabacadaeaf' (bstr .size (8..64)),
given from TAM's Update message /
12 : "disk-full" / err-msg = 12 (mapkey) :
"disk-full" (text .size (1..128)) /
},
17, / err-code : ERR_MANIFEST_PROCESSING_FAILED = 17 (uint (0..23)) /
]
D.7.2. CBOR binary Representation
83 # array(3)
06 # unsigned(6) uint (0..23)
A2 # map(2)
14 # unsigned(20) uint (0..23)
4F # bytes(16) (8..64)
A0A1A2A3A4A5A6A7A8A9AAABACADAEAF
0C # unsigned(12) uint (0..23)
69 # text(9) (1..128)
6469736B2D66756C6C # "disk-full"
11 # unsigned(17) uint (0..23)
Authors' Addresses
Hannes Tschofenig
Arm Ltd.
Absam, Tirol 6067
Austria
Email: hannes.tschofenig@arm.com
Mingliang Pei
Broadcom
350 Ellis St
Mountain View, CA 94043
USA
Email: mingliang.pei@broadcom.com
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David Wheeler
Amazon
US
Email: davewhee@amazon.com
Dave Thaler
Microsoft
US
Email: dthaler@microsoft.com
Akira Tsukamoto
AIST
JP
Email: akira.tsukamoto@aist.go.jp
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