TEEP H. Tschofenig Internet-Draft Arm Ltd. Intended status: Standards Track M. Pei Expires: 28 April 2022 Broadcom D. Wheeler Amazon D. Thaler Microsoft A. Tsukamoto AIST 25 October 2021 Trusted Execution Environment Provisioning (TEEP) Protocol draft-ietf-teep-protocol-07 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 working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 28 April 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 publication of this document. Tschofenig, et al. Expires 28 April 2022 [Page 1] Internet-Draft TEEP Protocol October 2021 Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. 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 . . . . . . 18 6. Behavior Specification . . . . . . . . . . . . . . . . . . . 20 6.1. TAM Behavior . . . . . . . . . . . . . . . . . . . . . . 20 6.2. TEEP Agent Behavior . . . . . . . . . . . . . . . . . . . 21 7. Ciphersuites . . . . . . . . . . . . . . . . . . . . . . . . 22 8. Freshness Mechanisms . . . . . . . . . . . . . . . . . . . . 22 9. Security Considerations . . . . . . . . . . . . . . . . . . . 23 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 10.1. Media Type Registration . . . . . . . . . . . . . . . . 25 10.2. Ciphersuite Registry . . . . . . . . . . . . . . . . . . 26 10.3. Freshness Mechanism Registry . . . . . . . . . . . . . . 27 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 27 11.1. Normative References . . . . . . . . . . . . . . . . . . 27 11.2. Informative References . . . . . . . . . . . . . . . . . 29 A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 29 B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 30 C. Complete CDDL . . . . . . . . . . . . . . . . . . . . . . . . 30 D. Examples of Diagnostic Notation and Binary Representation . . 34 D.1. QueryRequest Message . . . . . . . . . . . . . . . . . . 34 D.1.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 34 D.1.2. CBOR Binary Representation . . . . . . . . . . . . . 34 D.2. Entity Attestation Token . . . . . . . . . . . . . . . . 35 D.2.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 35 D.3. QueryResponse Message . . . . . . . . . . . . . . . . . . 35 D.3.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 35 D.3.2. CBOR Binary Representation . . . . . . . . . . . . . 36 D.4. Update Message . . . . . . . . . . . . . . . . . . . . . 37 Tschofenig, et al. Expires 28 April 2022 [Page 2] Internet-Draft TEEP Protocol October 2021 D.4.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 37 D.4.2. CBOR Binary Representation . . . . . . . . . . . . . 37 D.5. Success Message . . . . . . . . . . . . . . . . . . . . . 38 D.5.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 38 D.5.2. CBOR Binary Representation . . . . . . . . . . . . . 38 D.6. Error Message . . . . . . . . . . . . . . . . . . . . . . 38 D.6.1. CBOR Diagnostic Notation . . . . . . . . . . . . . . 38 D.6.2. CBOR binary Representation . . . . . . . . . . . . . 39 E. Examples of SUIT Manifests . . . . . . . . . . . . . . . . . 39 E.1. Install a Trusted Component . . . . . . . . . . . . . . . 39 E.2. Delete a Trusted Component . . . . . . . . . . . . . . . 43 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 45 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). Tschofenig, et al. Expires 28 April 2022 [Page 3] Internet-Draft TEEP Protocol October 2021 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 Tschofenig, et al. Expires 28 April 2022 [Page 4] Internet-Draft TEEP Protocol October 2021 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. +------------+ +-------------+ | 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. Tschofenig, et al. Expires 28 April 2022 [Page 5] Internet-Draft TEEP Protocol October 2021 2. Create a COSE Header containing the desired set of Header Parameters. The COSE Header MUST be valid per the [RFC8152] specification. 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. 4.1.2. 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. Verify that the message contains a COSE_Sign1 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 [RFC8152] ("Signing Objects") for validating a COSE_Sign1 object. The COSE_Sign1 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. 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: * Request for attestation information, * Listing supported extensions, * Querying installed Trusted Components, and * Listing supported SUIT commands. Tschofenig, et al. Expires 28 April 2022 [Page 6] Internet-Draft TEEP Protocol October 2021 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 ], * $$query-request-extensions * $$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). The first usage of a token generated by a TAM MUST be randomly created. Subsequent 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. data-item-requested Tschofenig, et al. Expires 28 April 2022 [Page 7] Internet-Draft TEEP Protocol October 2021 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. 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. 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 a QueryResponse message then the challenge contained in this request MUST be used to generate the EAT, such as by copying the challengt into the nonce claim found in the EAT if using the Nonce freshness mechanism. For more details see Section 8. If any format other than EAT is used, it is up to that format to define the use of the challenge field. Tschofenig, et al. Expires 28 April 2022 [Page 8] Internet-Draft TEEP Protocol October 2021 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. 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. Tschofenig, et al. Expires 28 April 2022 [Page 9] Internet-Draft TEEP Protocol October 2021 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. Tschofenig, et al. Expires 28 April 2022 [Page 10] Internet-Draft TEEP Protocol October 2021 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. This parameter MUST be present if the QueryResponse is sent in response to a QueryRequest with the extensions bit set. 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: Tschofenig, et al. Expires 28 April 2022 [Page 11] Internet-Draft TEEP Protocol October 2021 +===========+=====================+=================================+ |Requirement|Claim | Reference | +===========+=====================+=================================+ |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 | [I-D.ietf-rats-eat] section 3.7 | |hardware | | | |type | | | +-----------+---------------------+---------------------------------+ |TEE |chip-version | [I-D.ietf-rats-eat] section 3.7 | |hardware | | | |version | | | +-----------+---------------------+---------------------------------+ |TEE |component-identifier | [I-D.birkholz-rats-suit-claims] | |firmware | | 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 3.3 | |proof | | | +-----------+---------------------+---------------------------------+ Table 1 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. Tschofenig, et al. Expires 28 April 2022 [Page 12] Internet-Draft TEEP Protocol October 2021 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: 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.) Tschofenig, et al. Expires 28 April 2022 [Page 13] Internet-Draft TEEP Protocol October 2021 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. 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 Tschofenig, et al. Expires 28 April 2022 [Page 14] Internet-Draft TEEP Protocol October 2021 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. 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. Tschofenig, et al. Expires 28 April 2022 [Page 15] Internet-Draft TEEP Protocol October 2021 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 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 8. This otherwise optional parameter MUST be returned if err-code is ERR_UNSUPPORTED_FRESHNESS_MECHANISMS. 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.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. Tschofenig, et al. Expires 28 April 2022 [Page 16] Internet-Draft TEEP Protocol October 2021 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_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. 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. ERR_UNSUPPORTED_CIPHER_SUITES (5) The TEEP Agent does not support any ciphersuites indicated in the request message. A TAM receiving this error might retry the request using a different set of supported ciphersuites 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. 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. Tschofenig, et al. Expires 28 April 2022 [Page 17] Internet-Draft TEEP Protocol October 2021 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: Tschofenig, et al. Expires 28 April 2022 [Page 18] Internet-Draft TEEP Protocol October 2021 +================================+=======+ | Name | Label | +================================+=======+ | supported-cipher-suites | 1 | +--------------------------------+-------+ | challenge | 2 | +--------------------------------+-------+ | version | 3 | +--------------------------------+-------+ | 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 | +--------------------------------+-------+ Table 2 Tschofenig, et al. Expires 28 April 2022 [Page 19] Internet-Draft TEEP Protocol October 2021 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. 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. Tschofenig, et al. Expires 28 April 2022 [Page 20] Internet-Draft TEEP Protocol October 2021 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 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. Tschofenig, et al. Expires 28 April 2022 [Page 21] Internet-Draft TEEP Protocol October 2021 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 | +-------+------------------------------------------------+ Table 3 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 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: Tschofenig, et al. Expires 28 April 2022 [Page 22] Internet-Draft TEEP Protocol October 2021 +=======+=====================+ | Value | Freshness mechanism | +=======+=====================+ | 1 | Nonce | +-------+---------------------+ | 2 | Timestamp | +-------+---------------------+ | 3 | Epoch ID | +-------+---------------------+ Table 4 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. 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. 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 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 Tschofenig, et al. Expires 28 April 2022 [Page 23] Internet-Draft TEEP Protocol October 2021 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 A TAM is responsible for vetting a Trusted Component and before distributing them to TEEP Agents. Tschofenig, et al. Expires 28 April 2022 [Page 24] Internet-Draft TEEP Protocol October 2021 It is RECOMMENDED to provide a way to update the trust anchor store used by the TEE, for example using a firmware update mechanism. 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 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. TAM Certificate Expiry 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. 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 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]. Tschofenig, et al. Expires 28 April 2022 [Page 25] Internet-Draft TEEP Protocol October 2021 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. Name of registry: TEEP Ciphersuites Policy: Specification Required Additional requirements: The specification must document relevant security considerations. Initial values: +=======+=========================+===============+ | Value | Ciphersuite | Specification | +=======+=========================+===============+ | 1 | AES-CCM-16-64-128, HMAC | RFC TBD | | | 256/256, X25519, EdDSA | Section 7 | +-------+-------------------------+---------------+ | 2 | AES-CCM-16-64-128, HMAC | RFC TBD | | | 256/256, P-256, ES256 | Section 7 | +-------+-------------------------+---------------+ Table 5 Tschofenig, et al. Expires 28 April 2022 [Page 26] Internet-Draft TEEP Protocol October 2021 [RFC Editor: please replace TBD above with the number assigned to this document] 10.3. Freshness Mechanism Registry IANA is also requested to create a new registry for freshness mechanisms. Name of registry: TEEP Freshness Mechanisms Policy: Specification Required Additional requirements: The specification must document relevant security considerations. Initial values: +=======+=====================+===================+ | Value | Freshness mechanism | Specification | +=======+=====================+===================+ | 1 | Nonce | RFC TBD Section 8 | +-------+---------------------+-------------------+ | 2 | Timestamp | RFC TBD Section 8 | +-------+---------------------+-------------------+ | 3 | Epoch ID | RFC TBD Section 8 | +-------+---------------------+-------------------+ Table 6 [RFC Editor: please replace TBD above with the number assigned to this document] 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", Work in Progress, Internet-Draft, draft-ietf-rats-architecture- 12, 23 April 2021, . Tschofenig, et al. Expires 28 April 2022 [Page 27] Internet-Draft TEEP Protocol October 2021 [I-D.ietf-rats-eat] Lundblade, L., Mandyam, G., and J. O'Donoghue, "The Entity Attestation Token (EAT)", Work in Progress, Internet- Draft, draft-ietf-rats-eat-11, 24 October 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", Work in Progress, Internet- Draft, draft-ietf-suit-manifest-14, 12 July 2021, . [I-D.moran-suit-report] Moran, B., "Secure Reporting of Update Status", Work in Progress, Internet-Draft, draft-moran-suit-report-01, 22 February 2021, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 2003, . [RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008, . [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, . [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, October 2013, . [RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)", RFC 8152, DOI 10.17487/RFC8152, July 2017, . Tschofenig, et al. Expires 28 April 2022 [Page 28] Internet-Draft TEEP Protocol October 2021 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 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", Work in Progress, Internet-Draft, draft-birkholz- rats-suit-claims-02, 12 July 2021, . [I-D.ietf-teep-architecture] Pei, M., Tschofenig, H., Thaler, D., and D. Wheeler, "Trusted Execution Environment Provisioning (TEEP) Architecture", Work in Progress, Internet-Draft, draft- ietf-teep-architecture-15, 12 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, . [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, . [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, . 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. Tschofenig, et al. Expires 28 April 2022 [Page 29] Internet-Draft TEEP Protocol October 2021 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]. 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 Tschofenig, et al. Expires 28 April 2022 [Page 30] Internet-Draft TEEP Protocol October 2021 ; 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 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 ], * $$query-request-extensions * $$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), Tschofenig, et al. Expires 28 April 2022 [Page 31] Internet-Draft TEEP Protocol October 2021 ? 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 } 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: { Tschofenig, et al. Expires 28 April 2022 [Page 32] Internet-Draft TEEP Protocol October 2021 ? 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_FRESHNESS_MECHANISMS = 3 ERR_UNSUPPORTED_MSG_VERSION = 4 ERR_UNSUPPORTED_CIPHER_SUITES = 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 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 Tschofenig, et al. Expires 28 April 2022 [Page 33] Internet-Draft TEEP Protocol October 2021 D. Examples of Diagnostic Notation and Binary Representation This section includes some examples with the following assumptions: * TEEP Device will have two TCs with the following SUIT Component Identifiers: - [ 0x000102030405060708090a0b0c0d0e0f ] - [ 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 = / [ 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) / }, 3 / data-item-requested : attestation | trusted-components = 3 (.within uint .size 8) / ] D.1.2. CBOR Binary Representation Tschofenig, et al. Expires 28 April 2022 [Page 34] Internet-Draft TEEP Protocol October 2021 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.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 / 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 / 14: 3, / secure-restricted / / device-identifier / : h'e99600dd921649798b013e9752dcf0c5', / vendor-identifier / : h'2b03879b33434a7ca682b8af84c19fd4', / class-identifier / : h'9714a5796bd245a3a4ab4f977cb8487f', / chip-version / 26: [ "MyTEE", 1 ], / component-identifier / : h'60822887d35e43d5b603d18bcaa3f08d', / version / : "v0.1" } D.3. QueryResponse Message D.3.1. CBOR Diagnostic Notation Tschofenig, et al. Expires 28 April 2022 [Page 35] Internet-Draft TEEP Protocol October 2021 / 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.3.2. CBOR Binary Representation Tschofenig, et al. Expires 28 April 2022 [Page 36] Internet-Draft TEEP Protocol October 2021 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.4. Update Message D.4.1. 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.4.2. CBOR Binary Representation Tschofenig, et al. Expires 28 April 2022 [Page 37] Internet-Draft TEEP Protocol October 2021 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.5. Success Message D.5.1. 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.5.2. 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.6. Error Message D.6.1. CBOR Diagnostic Notation Tschofenig, et al. Expires 28 April 2022 [Page 38] Internet-Draft TEEP Protocol October 2021 / 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.6.2. 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) E. Examples of SUIT Manifests This section shows some examples of SUIT manifests for a case where the TEE will use a Trusted Application (TA) for OP-TEE on Arm TrustZone, storing the TA in Replay Protected Memory Block (RPMB) secure storage in a file named "edd94cd8-9d9c-4cc8-9216- b3ad5a2d5b8a.ta". The TA developer places personalization data for the device on an HTTPS server and puts the URI in the TA manifest. The personalization data will also be stored in RPMB secure storage in a file named "config.json". E.1. Install a Trusted Component This sample manifest installs a Trusted Component that depends on personalization data resolved separately. TA Manifest: Tschofenig, et al. Expires 28 April 2022 [Page 39] Internet-Draft TEEP Protocol October 2021 107({ / authentication-wrapper / 2:<<[ digest: <<[ / algorithm-id / -16 / "sha256" /, / digest-bytes / h'd6c1fc7200483092e2db59d4907f9b15' h'05cb3af2795cf78f7ae3d88166fdf743' ]>>, signature: <<18([ / protected / <<{ / alg / 1:-7 / "ES256" /, }>>, / unprotected / {}, / payload / F6 / nil /, / signature / h'd11a2dd9610fb62a707335f584079225' h'709f96e8117e7eeed98a2f207d05c8ec' h'fba1755208f6abea977b8a6efe3bc2ca' h'3215e1193be201467d052b42db6b7287' ])>> ]>>, / manifest / 3:<<{ / manifest-version / 1:1, / manifest-sequence-number / 2:3, / common / 3:<<{ / components / 2:[ ["OP-TEE","RPMB","edd94cd8-9d9c-4cc8-9216- b3ad5a2d5b8a","ta"] ], / common-sequence / 4:<<[ / directive-override-parameters / 20,{ / vendor-id / 1:h'c0ddd5f15243566087db4f5b0aa26c2f', / class-id / 2:h'db42f7093d8c55baa8c5265fc5820f4e', / image-digest / 3:<<[ / algorithm-id / -16 / "sha256" /, / digest-bytes / h'00112233445566778899aabbccddeeff' h'0123456789abcdeffedcba9876543210' ]>>, / image-size / 14:76778, }, / condition-vendor-identifier / 1,15, / condition-class-identifier / 2,15 ]>>, }>>, / install / 9:<<[ / directive-set-parameters / 19,{ / uri / 21: 'https://teep.example/edd94cd8-9d9c-4cc8-9216-b3ad5a2d5b8a.ta', } , / directive-fetch / 21,2, / condition-image-match / 3,15 Tschofenig, et al. Expires 28 April 2022 [Page 40] Internet-Draft TEEP Protocol October 2021 ]>>, / validate / 10:<<[ / condition-image-match / 3,15 ]>>, / run / 12:<<[ / directive-run / 23,2 ]>>, / text / 13:<<{ [ h'4f502d544545', h'44f301', h'edd94cd89d9c4cc89216b3ad5a2d5b8a', h'7461' ]:{ / model-name / 2: 'OP-TEE on TF-A on TrustZone', / vendor-domain / 3:'teep.example' } }>> }>> }) Personalization Data Manifest: 107({ 2:<<[ digest: <<[ / algorithm-id / -16 / "sha256" /, / digest-bytes / h'a7fd6593eac32eb4be578278e6540c5c' h'09cfd7d4d234973054833b2b93030609' ]>> ]>>, / manifest / 3:<<{ / manifest-version / 1:1, / manifest-sequence-number / 2:3, / dependencies / 1:[ { / dependency-digest / 1:[ / algorithm-id / -16 / "sha256" /, / digest-bytes / h'd6c1fc7200483092e2db59d4907f9b15' h'05cb3af2795cf78f7ae3d88166fdf743' ] } ], / components / 2:[ ["OP-TEE","RPMB","config.json"] ], / common-sequence / 4:<<[ / directive-set-component-index / 12,0, Tschofenig, et al. Expires 28 April 2022 [Page 41] Internet-Draft TEEP Protocol October 2021 / directive-override-parameters / 20,{ / vendor-id / 1:h'ec41787224345ae580003de697ff8d43' / ec417872-2434-5ae5-8000-3de697ff8d43 /, / class-id / 2:h'eb1701b48be85709aca0adf89f056a64' / eb1701b4-8be8-5709-aca0-adf89f056a64 /, / image-digest / 3:<<[ / algorithm-id / -16 / "sha256" /, / digest-bytes / h'aaabcccdeeef00012223444566678889' h'abbbcdddefff01112333455567778999' ]>> }, / condition-vendor-identifier / 1,15, / condition-class-identifier / 2,15 ]>>, / dependency-resolution / 7:<<[ / directive-set-dependency-index / 13,0, / directive-set-parameters / 19,{ / uri / 21:'tam.teep.example/' 'edd94cd8-9d9c-4cc8-' '9216-b3ad5a2d5b8a.suit', }, / directive-fetch / 21,2, / condition-image-match / 3,15 ]>>, / install / 9:<<[ / directive-set-component-index / 12,0, / directive-set-parameters / 19,{ / uri / 21: 'http://tam.teep.example/config.json', }, / directive-set-dependency-index / 13,0, / directive-process-dependency / 18,0, / directive-set-component-index / 12,0, / directive-fetch / 21,2, / condition-image-match / 3,15 ]>>, / validate / 10:<<[ / directive-set-component-index / 12,0, / condition-image-match / 3,15, / directive-set-dependency-index / 13,0, / directive-process-dependency / 18,0 ]>>, / run / 12:<<[ / directive-set-dependency-index / 13,0, / directive-process-dependency / 18,0 ]>>, / text / 13:<<{ [h'4f502d544545', h'44f301', Tschofenig, et al. Expires 28 April 2022 [Page 42] Internet-Draft TEEP Protocol October 2021 h'636f6e6669672e6a736f6e']:{ / model-name / 2: 'Personalised OP-TEE on TF-A on TrustZone', / vendor-domain / 3:'tam.teep.example', }, [ h'4f502d544545', h'44f301', h'edd94cd89d9c4cc89216b3ad5a2d5b8a', h'7461' ]:{ / model-name / 2:'OP-TEE on TF-A on TrustZone', / vendor-domain / 3:'teep.example' } }>> }>> }) E.2. Delete a Trusted Component This sample manifest removes a Trusted Component and its dependency. 107({ / authentication-wrapper / 2:<<[ digest: <<[ / algorithm-id / -16 / "sha256" /, / digest-bytes / h'a6c4590ac53043a98e8c4106e1e31b305516d7cf0a655eddfac6d45c810e036a' ]>>, signature: <<18([ / protected / <<{ / alg / 1:-7 / "ES256" /, }>>, / unprotected / { }, / payload / F6 / nil /, / signature / h'd11a2dd9610fb62a707335f58407922570 9f96e8117e7eeed98a2f207d05c8ecfba1755208f6abea977b8a6efe3bc2ca3215e119 3be201467d052b42db6b7287' ])>> ] ]>>, / manifest / 3:<<{ / manifest-version / 1:1, / manifest-sequence-number / 2:0, / common / 3:<<{ / components / 2:[ [h'00'] ], Tschofenig, et al. Expires 28 April 2022 [Page 43] Internet-Draft TEEP Protocol October 2021 / common-sequence / 4:<<[ / directive-override-parameters / 20,{ / vendor-id / 1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf- be9d-e663e4d41ffe /, / class-id / 2:h'1492af1425695e48bf429b2d51f2ab45' / 1492af14-2569-5e48-bf42-9b2d51f2ab45 /, / image-digest / 3:<<[ / algorithm-id / -16 / "sha256" /, / digest-bytes / h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210' ]>>, / image-size / 14:34768, } , / condition-vendor-identifier / 1,15 , / condition-class-identifier / 2,15 ]>>, }>>, / validate / 10:<<[ / condition-image-match / 3,15 ]>>, / run / 12:<<[ / directive-run / 23,2 ]>>, }>>, }) Total size of Envelope without COSE authentication object: 161 Envelope: d86ba2025827815824822f5820a6c4590ac53043a98e8c4106e1e31b3055 16d7cf0a655eddfac6d45c810e036a035871a50101020003585fa2028181 41000458568614a40150fa6b4a53d5ad5fdfbe9de663e4d41ffe02501492 af1425695e48bf429b2d51f2ab45035824822f5820001122334455667788 99aabbccddeeff0123456789abcdeffedcba98765432100e1987d0010f02 0f0a4382030f0c43821702 Total size of Envelope with COSE authentication object: 237 Envelope with COSE authentication object: Tschofenig, et al. Expires 28 April 2022 [Page 44] Internet-Draft TEEP Protocol October 2021 d86ba2025873825824822f5820a6c4590ac53043a98e8c4106e1e31b3055 16d7cf0a655eddfac6d45c810e036a584ad28443a10126a0f65840d11a2d d9610fb62a707335f584079225709f96e8117e7eeed98a2f207d05c8ecfb a1755208f6abea977b8a6efe3bc2ca3215e1193be201467d052b42db6b72 87035871a50101020003585fa202818141000458568614a40150fa6b4a53 d5ad5fdfbe9de663e4d41ffe02501492af1425695e48bf429b2d51f2ab45 035824822f582000112233445566778899aabbccddeeff0123456789abcd effedcba98765432100e1987d0010f020f0a4382030f0c43821702 Authors' Addresses Hannes Tschofenig Arm Ltd. 6067 Absam Austria Email: hannes.tschofenig@arm.com Mingliang Pei Broadcom 350 Ellis St Mountain View, CA 94043 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 Email: dthaler@microsoft.com Akira Tsukamoto AIST Japan Email: akira.tsukamoto@aist.go.jp Tschofenig, et al. Expires 28 April 2022 [Page 45]