diff --git a/draft-ietf-teep-opentrustprotocol.xml b/draft-ietf-teep-opentrustprotocol.xml new file mode 100644 index 0000000..065905d --- /dev/null +++ b/draft-ietf-teep-opentrustprotocol.xml @@ -0,0 +1,810 @@ + + + + + + + + + + + + + + + + + + + + +]> + + + + + + + + + + + The Open Trust Protocol (OTrP) + + + Symantec +
+ + 350 Ellis St + Mountain View + CA + 94043 + USA + + mingliang_pei@symantec.com +
+ + + + Intercede +
+ + St. Mary's Road, Lutterworth + Leicestershire + LE17 + 4PS + Great Britain + + andrew.atyeo@intercede.com +
+ + + + Arm Ltd. +
+ + 110 Fulbourn Rd + Cambridge + CB1 + 9NJ + Great Britain + + hannes.tschofenig@arm.com +
+ + + + Intel +
+ + + + + + US + + david.m.wheeler@intel.com +
+ + + + Microsoft +
+ + + + + US + + dthaler@microsoft.com +
+ + + + + Security + TEEP + Trusted Execution Environment + + This document specifies the Open Trust Protocol (OTrP) version 2, a + protocol that provisions and installs, updates, and deletes Trusted Applications + in a device with a Trusted Execution Environment (TEE). + + + + + +
+ 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 an TEE + ecosystem, different device vendors may use different operating systems in the + REE and may use different types of TEEs. When application providers or + device administrators use Trusted Application Managers (TAMs) to install, update, + and delete Trusted Applications (TAs) on a wide range of devices with potentially + different TEEs then an interoperability need arises. + + This document specifies version 2 of the Open Trust Protocol (OTrP), a protocol + for communicating between an OTrP server (as part of a TAM) and an OTrP client + (which is a client-side component running in the REE). + + + The Trusted Execution Environment Provisioning (TEEP) architecture + document has set to provide a design guidance + for such an interoperable protocol. + + +
+ +
+ + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in + . + + This specification re-uses the terminology defined in + . + +
+ + +
+ OTrP consists of a couple of messages exchanged between a TAM and an OTrP Agent via an OTrP Broker. + The messages are encoded either in JSON or CBOR and designed to provide end-to-end security. + OTrP messages are signed and/or encrypted by the endpoints, i.e., TAM and OTrP Agent, but trusted + applications may as well be encrypted and signed by the service provider. OTrP not only re-uses + JSON and CBOR but also the respective security wrappers, namely JOSE (JWS + and JWE , to be more specific) and COSE . Furthermore, + for attestation the Entity Attestation Token (EAT) and for software updates the SUIT + manifest format is re-used. + + + + This specification defines six messages. + + + + A TAM queries a device's current state with a QueryRequest message. + An OTrP Agent will, after authenticating and authorizing the request, report + attestation information, list all TAs, 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 subsequent message exchanges to install, update, or delete trusted applications + shall be initiated. + +
+ + + QueryResponse + + <------- or + + Error + ]]> +
+ + + +With the TrustedAppInstall message a TAM can instruct an OTrP Agent to install a TA. +The OTrP Agent will process the message, determine whether the TAM is authorized and whether the +TA has been signed by an authorized SP. In addition to the binary, the TAM may also provide +personalization data. If the TrustedAppInstall message was processed successfully then a +Success message is returned to the TAM, an Error message otherwise. + +
+ + + Success + + <---- or + + Error + ]]> +
+ + +With the TrustedAppDelete message a TAM can instruct an OTrP Agent to delete one or multiple TA(s). +A Success message is returned when the operation has been completed successfully, and an Error message +otherwise. + +
+ + + Success + + <---- or + + Error + ]]> +
+ + +
+ + +
+ + For a CBOR-based encoding the following security wrapper is used (described in CDDL format ). + +
+ bstr .cbor + Msg_AuthEnc_Wrapper / nil, + otrp-message => (QueryRequest / + QueryResponse / + TrustedAppInstall / + TrustedAppDelete / + Error / + Success ), +} + +msg-authenc-wrapper = 1 +otrp-message = 2 + +Msg_AuthEnc_Wrapper = [ * (COSE_Mac_Tagged / + COSE_Sign_Tagged / + COSE_Mac0_Tagged / + COSE_Sign1_Tagged)] + ]]> +
+ + +A future version of this specification will also describe the security wrapper for JSON (in CDDL format). + + + +
+ +
+ + + A QueryRequest message is signed by the TAM and has the following fields: + + + +TYPE = 1 corresponds to a QueryRequest message sent from the TAM to the OTrP Agent. + +The value in the TOKEN field is used to match requests to responses. + +The REQUEST field indicates what information the TAM requests from the OTrP Agent in form of a list of integer values. Each integer value corresponds to an IANA registered information element. This specification defines the initial set of information elements. With 'attestation' (1) the TAM requests the OTrP Agent to return an EAT entity attestation token in the response, with 'ta' (2) the TAM wants to query the OTrP Agent for all installed TAs, and with 'ext' (3) the TAM wants to query the OTrP Agent for supported extensions. Further values may be added in the future via IANA registration. + +The CIPHER_SUITE field lists the ciphersuite(s) supported by the TAM. + + NONCE is an optional field used for ensuring the refreshness of the Entity Attestation Token (EAT) contained in the response. + +The VERSION field lists the version(s) supported by the TAM. For this version of the specification this field can be omitted. + +The OCSP_DATA field contains a list of OCSP stapling data respectively for the TAM certificate and each of the CA certificates up to the root certificate. The TAM provides OCSP data so that the OTrP Agent can validate the status of the TAM certificate chain without making its own external OCSP service call. + + + + +
+ +
+ + The QueryResponse message is signed and encrypted by the OTrP Agent and returned to the TAM. It has the following fields: + + + +TYPE = 2 corresponds to a QueryResponse message sent from the OTrP Agent to the TAM. + +The value in the TOKEN field is used to match requests to responses. The value MUST correspond to the value received with the QueryRequest. + +The SELECTED_CIPHER_SUITE field indicates the selected ciphersuite. + +The SELECTED_VERSION field indicates the OTrP protocol version selected by the OTrP Agent. + +The EAT field contains an Entity Attestation Token following the encoding defined in . + +The TA_LIST field enumerates the trusted applications installed on the device in form of ta_ids, i.e., a vendor id/class id/device id triple. + +The EXT_LIST field lists the supported extensions. This document does not define any extensions. + + + + +
+ +
+ + +The TrustedAppInstall message is MACed and encrypted by the TAM and has the following fields: + + + +TYPE = 3 corresponds to a TrustedAppInstall message sent from the TAM to the OTrP Agent. In case of successful processing, an Success +message is returned by the OTrP Agent. In case of an error, an Error message is returned. Note that the TrustedAppInstall message +is used for initial TA installation but also for TA updates. + +The value in the TOKEN field is used to match requests to responses. + +The TA field is used to convey one or multiple SUIT manifests. The SUIT manifest contains the code for the trusted app but +may also convey personalization data. TA binaries and personalization data is often signed and encrypted by the SP. 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 SP sign and/or encrypt the TA binary. + + + + + +
+ +
+ + +The TrustedAppDelete message is MACed and encrypted by the TAM and has the following fields: + + + +TYPE = 4 corresponds to a TrustedAppDelete message sent from the TAM to the OTrP Agent. In case of successful processing, an Success +message is returned by the OTrP Agent. In case of an error, an Error message is returned. + + +The value in the TOKEN field is used to match requests to responses. + +The TA_LIST field enumerates the TAs to be deleted. + + + + + +
+ +
+ + +The Success message is MACed and encrypted by the OTrP Agent and has the following fields: + + + +TYPE = 5 corresponds to a Error message sent from the OTrP Agent to the TAM. + +The value in the TOKEN field is used to match requests to responses. + +The MSG field contains optional diagnostics information encoded in UTF-8 returned by the OTrP Agent. + + + + + +
+ +
+ + + +If possible, the Error message is MACed and encrypted by the OTrP Agent. Unprotected Error messages MUST be handled with care by the TAM due to possible downgrading attacks. It has the following fields: + + + +TYPE = 6 corresponds to a Error message sent from the OTrP Agent to the TAM. + +The value in the TOKEN field is used to match requests to responses. + +The ERR_CODE field is populated with values listed in a registry (with the initial set of error codes listed below). Only selected messages are applicable to each message. + +The ERR_MSG message is a human-readable diagnostic message that MUST be encoded using UTF-8 using Net-Unicode form . + +The VERSION field enumerates the protocol version(s) supported by the OTrP Agent. This field is optional but MUST be returned with the ERR_UNSUPPORTED_MSG_VERSION error message. + +The CIPHER_SUITE field lists the ciphersuite(s) supported by the OTrP Agent. This field is optional but MUST be returned with the ERR_UNSUPPORTED_CRYPTO_ALG error message. + + + +This specification defines the following initial error messages. Additional error code can be registered with IANA. + + + + The OTrP Agent sends this error message when + a request contains incorrect fields or fields that are inconsistent with other fields. + + The OTrP Agent sends this error message when + it recognizes an unsupported extension or unsupported message. + + The OTrP Agent sends this error message when + it fails to verify the signature of the message. + + The OTrP Agent receives a message but does not + support the indicated version. + + The OTrP Agent receives a request message + encoded with an unsupported cryptographic algorithm. + + The OTrP Agent returns this error + when processing of a certificate failed. For diagnosis purposes it is + RECOMMMENDED to include information about the failing certificate + in the error message. + + The OTrP Agent returns this error + when a certificate was of an unsupported type. + + The OTrP Agent returns this error + when a certificate was revoked by its signer. + + The OTrP Agent returns this error + when a certificate has expired or is not currently + valid. + + The OTrP Agent returns this error when a miscellaneous + internal error occurred while processing the request. + + This error is reported when a device + resource isn't available anymore, such as storage space is full. + + This error will occur when the target TA does not + exist. This error may happen when the TAM has stale information and + tries to delete a TA that has already been deleted. + + While installing a TA, a TEE will return + this error if the TA has already been installed. + + The OTrP Agent returns this error when + it does not recognize the format of the TA binary. + + The OTrP Agent returns this error when + it fails to decrypt the TA binary. + + The OTrP Agent returns this error when + it fails to decompress the TA binary. + + The OTrP Agent returns this error when + manifest processing failures occur that are less specific than + ERR_TA_UNKNOWN_FORMAT, ERR_TA_UNKNOWN_FORMAT, and ERR_TA_DECOMPRESSION_FAILED. + + The OTrP Agent returns this error when + it fails to process the provided personalization data. + + + + +
+ + + +
+ + This section summarizes the security considerations discussed in this + specification: + + + + + This specification relies on the cryptographic algorithms provided + by the security wrappers JOSE and COSE, respectively. A companion document + makes algorithm recommendations but this document is written in an algorithm-agnostic way. + OTrP messages between the TAM and the OTrP Agent are protected using JWS and JWE (for + JSON-encoded messages) and COSE (for CBOR-encoded messages). Public key based authentication + is used to by the OTrP Agent to authenticate the TAM and vice versa. + + + + + A TAM may rely on the attestation information provided by the OTrP Agent and the + Entity Attestation Token is re-used to convey this information. To sign the Entity Attestation + Token it is necessary for the device to possess a public key (usually in the form of a certificate) + 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 + information or in the certificate used to sign the attestation token. + This uniqueness may raise privacy concerns. To lower the privacy implications the + OTrP Agent MUST present its attestation information only to an + authenticated and authorized TAM. + + + + TA binaries are provided by the SP.It is the responsibility + of the TAM to relay only verified TAs from authorized SPs. + Delivery of that TA to the OTrP Agent is then the responsibility + of the TAM and the OTrP Broker, using the security mechanisms provided by the OTrP. + To protect the TA binary the SUIT manifest is re-used and it offers a varity of + security features, including digitial signatures and symmetric encryption. + + + + An SP or a TAM can supply personalization data along with a TA. + This data is also protected by a SUIT manifest. + The personalization data may be itself is (or can be) opaque to the TAM. + + + + OTrP relies on the OTrP Broker to relay messages between the TAM and the OTrP Agent. + When the OTrP Broker is compromised it can drop, relay, and replay messages but it cannot + modify those messages. A compromised OTrP Broker could reorder TAM messages to install an old + version of a TA. Information in the manifest ensures that the OTrP Agents are + protected against such downgrading attacks. + + + The QueryRequest message from a TAM to the OTrP Agent may include + OCSP stapling data for the TAM's signer certificate and for + intermediate CA certificates up to the root certificate so that the OTrP Agent + can verify the certificate's revocation status. + + A certificate revocation status check on a TA signer certificate is + OPTIONAL by an OTrP Agent. A TAM is responsible for vetting a TA and + before distributing them to OTrP Agents. The OTrP Agents will + trust a TA signer certificate's validation status done by a TAM. + + + + The CA issuing certificates to a TAM or an SP may get compromised. + A compromised + intermediate CA certificates can be detected by an OTrP 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 device, 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. + + + + The OTrP Agent SHOULD use OCSP information to verify the validity of the TAM-provided + 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 since OCSP + stapling includes signature + generation time, certificate validity dates are compared to the current + time. + + + + +
+ + +
+ There are two IANA requests: a media type and list of error codes. + + IANA is requested to assign a media type for + application/otrpv2+json. + + + application + otrp+json + none + none + Same as encoding considerations of + application/json as specified in Section 11 of + See Security Considerations Section of this document. + Same as interoperability + considerations of application/json as specified in + + This document. + OTrPv2 implementations + N/A + + + N/A + N/A + N/A + N/A + + + + teep@ietf.org + COMMON + none + See the "Authors' Addresses" section of this document + IETF + + + + IANA is requested to assign a media type for + application/otrpv2+cbor. + + + application + otrpv2+cbor + none + none + Same as encoding considerations of + application/cbor + See Security Considerations Section of this document. + Same as interoperability + considerations of application/cbor as specified in + + This document. + OTrPv2 implementations + N/A + + + N/A + N/A + N/A + N/A + + + + teep@ietf.org + COMMON + none + See the "Authors' Addresses" section of this document + IETF + + + + IANA is also requested to create a new registry for the error codes defined in + . + + + + Registration requests are evaluated using the criteria described in + the Claim Key instructions in the registration template below after a + three-week review period on the otrp-reg-review@ietf.org mailing list, + on the advice of one or more Designated Experts . However, + to allow for the allocation of values prior to publication, the + Designated Experts may approve registration once they are satisfied + that such a specification will be published. + + Registration requests sent to the mailing list for review should use + an appropriate subject (e.g., "Request to register an error code: example"). + Registration requests that are undetermined for a period longer than + 21 days can be brought to the IESG's attention (using the + iesg@ietf.org mailing list) for resolution. + + Criteria that should be applied by the Designated Experts includes + determining whether the proposed registration duplicates existing + functionality, whether it is likely to be of general applicability or + whether it is useful only for a single extension, and whether the + registration description is clear. + + IANA must only accept registry updates from the Designated Experts + and should direct all requests for registration to the review mailing + list. + +
+ + + + + + &RFC2119; + &RFC4648; + &RFC7159; + &RFC7515; + &RFC7516; + &RFC7517; + &RFC7518; + &RFC8152; + &RFC3629; + &RFC5198; + &RFC7049; + &I-D.ietf-rats-eat; + + + + + &I-D.ietf-teep-architecture; + &I-D.ietf-cbor-cddl; + &RFC8126; + + + +
+ We thank Alin Mutu for his contribution to many discussion that helped + to design the trust flow mechanisms, and the creation of the flow diagrams. + We also thank the following people (in alphabetical order) for their input + and review: Sangsu Baek, Rob Coombs, Dapeng Liu, and + Pengfei Zhao. + +
+ +
+ + We would like to thank the following individuals for their contributions to an earlier version + of this specification. + +
+ +
+
+ + +