ETSI TS 103 544-4 V1.3.1 (2019-10)

Publicly Available Specification (PAS); Intelligent Transport Systems (ITS); MirrorLink®; Part 4: Device Attestation Protocol (DAP)

RTS/ITS-98-4

General Information

• Status: Published
• Publication Date: 08-Oct-2019
• Technical Committee: ITS - Intelligent Transport Systems
• Current Stage: 12 - Completion
• Due Date: 30-Sep-2019
• Completion Date: 09-Oct-2019

Standards Content (Sample)

ETSI TS 103 544-4 V1.3.1 (2019-10)






TECHNICAL SPECIFICATION
Publicly Available Specification (PAS);
Intelligent Transport Systems (ITS);
®
MirrorLink ;
Part 4: Device Attestation Protocol (DAP)
CAUTION
The present document has been submitted to ETSI as a PAS produced by CCC and
approved by the ETSI Technical Committee Intelligent Transport Systems (ITS).
CCC is owner of the copyright of the document CCC-TS-014 and/or had all relevant rights and had assigned said rights to ETSI
on an "as is basis". Consequently, to the fullest extent permitted by law, ETSI disclaims all warranties whether express, implied,
statutory or otherwise including but not limited to merchantability, non-infringement of any intellectual property rights of third
parties. No warranty is given about the accuracy and the completeness of the content of the present document.

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2 ETSI TS 103 544-4 V1.3.1 (2019-10)



Reference
RTS/ITS-98-4
Keywords
interface, ITS, PAS, smartphone

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©ETSI 2019.
© Car Connectivity Consortium 2011-2019.
All rights reserved.
ETSI logo is a Trade Mark of ETSI registered for the benefit of its Members.
MirrorLink® is a registered trademark of Car Connectivity Consortium LLC.
RFB® and VNC® are registered trademarks of RealVNC Ltd.
UPnP® is a registered trademark of Open Connectivity Foundation, Inc.
Other names or abbreviations used in the present document may be trademarks of their respective owners.
DECT™, PLUGTESTS™, UMTS™ and the ETSI logo are trademarks of ETSI registered for the benefit of its Members.

3GPP™ and LTE™ are trademarks of ETSI registered for the benefit of its Members and
of the 3GPP Organizational Partners.
oneM2M™ logo is a trademark of ETSI registered for the benefit of its Members and
of the oneM2M Partners.
®
GSM and the GSM logo are trademarks registered and owned by the GSM Association.
ETSI

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3 ETSI TS 103 544-4 V1.3.1 (2019-10)
Contents
Intellectual Property Rights . 4
Foreword . 4
Modal verbs terminology . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 5
2.2 Informative references . 6
3 Definition of terms, symbols and abbreviations . 6
3.1 Terms . 6
3.2 Symbols . 6
3.3 Abbreviations . 7
4 Managing a DAP Session . 7
4.1 Bindings . 7
4.1.1 TCP Binding . 7
4.1.1.1 Identifying DAP Server . 7
4.1.1.2 Device Attestation Launch . 8
4.1.2 Intentionally Terminating the DAP Session . 8
4.1.3 Unintentionally Terminating the DAP Session . 8
4.2 Other Bindings . 8
4.3 Testing Considerations . 8
5 Device Attestation Protocol . 9
Annex A (normative): XSD Schema . 18
Annex B (informative): Authors and Contributors . 20
History . 21


ETSI

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4 ETSI TS 103 544-4 V1.3.1 (2019-10)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Intelligent Transport Systems
(ITS).
The present document is part 4 of a multi-part deliverable. Full details of the entire series can be found in part 1 [i.1].
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.

ETSI

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5 ETSI TS 103 544-4 V1.3.1 (2019-10)
1 Scope
®
The present document is part of the MirrorLink specification which specifies an interface for enabling remote user
interaction of a mobile device via another device. The present document is written having a vehicle head-unit to interact
with the mobile device in mind, but it will similarly apply for other devices, which provide a color display, audio
input/output and user input mechanisms.
The term "device attestation" in this context refers to the MirrorLink client verifying that the MirrorLink server is from
a compliant manufacturer and running approved software. The attestation will be based on standard X.509 certificates
®
[2] and attestation mechanisms defined by Trusted Computing Group .
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] W3C Recommendation 11 April 2013: "XML Signature Syntax and Processing Version 1.1".
NOTE: Available at http://www.w3.org/TR/xmldsig-core/.
[2] IETF RFC 5280: "Internet X.509 Public Key Infrastructure Certificate", May 2008.
NOTE: Available at http://tools.ietf.org/html/rfc5280.
[3] IETF RFC 3279: "Algorithms and Identifiers for the Internet X.509 Public Key Infrastructure
Certificate and Certificate Revocation List (CRL) Profile", April 2002.
NOTE: Available at http://tools.ietf.org/html/rfc3279.
[4] Trusted Platform Module (TPM) specifications, Version 1.2.
NOTE: Available at http://www.trustedcomputinggroup.org/resources/tpm-main-specification.
[5] TCG Mobile Trusted Module Specification, Version 1.0, April 2010.
NOTE: Available at https://trustedcomputinggroup.org/resource/mobile-phone-work-group-mobile-trusted-
module-specification/.
[6] Recommendation ITU-T X.690 (08/2015): "Information technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER)".
[7] ETSI TS 103 544-12 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 12: UPnP Server Device".
[8] ETSI TS 103 544-9 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 9: UPnP Application Server Service".
[9] ETSI TS 103 544-10 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 10: UPnP Client Profile Service".
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6 ETSI TS 103 544-4 V1.3.1 (2019-10)
[10] ETSI TS 103 544-2 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 2: Virtual Network Computing (VNC) based Display and
Control".
[11] ETSI TS 103 544-3 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 3: Audio".
[12] Trusted Computing Group, "Credentials Profiles Specification 1.1", May 2007.
NOTE: Available at http://www.trustedcomputinggroup.org/resources/infrastructure-work-group-tcg-credential-
profiles-specification.
[13] ETSI TS 103 544-5 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 5: Common Data Bus (CDB)".
[14] ETSI TS 103 544-17 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 17: MirrorLink over Wi-Fi Display (WFD)".
[15] ETSI TS 103 544-21 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 21: High Speed Media Link (HSML)".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI TS 103 544-1 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 1: Connectivity".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
pointer event: touch screen action in which the user touches the screen with one (virtual) finger only at a single
location
touch event: touch screen action in which the user touches the screen with two or more separate fingers at different
locations
NOTE: Touch events are used to describe more complex touch action, like pinch-open or pinch-close.
3.2 Symbols
For the purposes of the present document, the following symbols apply:
PK Public key of device A.
A
PK Public key of the CCC root CA.
CCC
PK Public key of the CTS root CA (for testing purpose).
CTS
PKCTSD Public key of the CTS Device (for testing purpose).
PK Public key of the CTS Manufacturer CA (for testing purpose).
CTSM
PK Public key of a Server Device.
SD
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7 ETSI TS 103 544-4 V1.3.1 (2019-10)
PK Public key of a Server Manufacturer CA.
SM
SK Private key of device A.
A
SK Private key of device B.
B
SK Private key of the CCC root CA.
CCC
SK Private key of the CTS root CA (for testing purpose).
CTS
SK Private key of the CTS Device (for testing purpose).
CTSD
SK Private key of the CTS Manufacturer CA (for testing purpose).
CTSM
SK Private key of a Server Device.
SD
SK Private key of a Server Manufacturer CA.
SM
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
ASN.1 Abstract Syntax Notation One
CA Certification Authority
CCC Car Connectivity Consortium
CDB Common Data Bus
CTS Conformance Test System
DAP Device Attestation Protocol
DER Distinguished Encoding Rules
HSML High-Spead Media Link
HTTP HyperText Transfer Protocol
IP Internet Protocol
ML MirrorLink
MTM Mobile Trusted Module
OID Object IDentifier
OS Operating System
PCR Platform Configuration Register
PKCS Public Key Cryptography Standards
RFB Remote Framebuffer
RSA Rivest-Shamir-Adleman
RTP Real-time Transport Protocol
SHA Secure Hash Algorithm
SOAP Simple Object Access Protocol
TCP Transmission Control Protocol
TPM Trusted Platform Module
UDP User Datagram Protocol
UINT Unsigned INTeger
UPnP Universal Plug and Play
URL Universal Resource Locator
VNC Virtual Network Computing
WFD Wi-Fi Display
XML eXtensible Markup Language
XSD XML Schema Definition
4 Managing a DAP Session
4.1 Bindings
4.1.1 TCP Binding
4.1.1.1 Identifying DAP Server
The identification of the DAP server is described in [8].
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8 ETSI TS 103 544-4 V1.3.1 (2019-10)
4.1.1.2 Device Attestation Launch
The DAP server start-up is facilitated via the UPnP TmApplicationServer:1 service LaunchApplication action, as
defined in [8]. The LaunchApplication action shall return with a URL to the DAP server.
If the returned URL is already used from any established DAP session, this session will continue without any change.
Otherwise a new DAP session shall be established, given the following steps:
a) DAP server shall listen for the DAP client to make TCP connection at the provided URL for at least 10 s.
b) DAP client shall make a TCP connection to the provided URL.
c) DAP server and client shall start DAP according to the steps defined in Clause 5.
4.1.2 Intentionally Terminating the DAP Session
The DAP server shall not intentionally terminate a DAP session.
The DAP client shall intentionally terminate a DAP session, using the following steps:
1) UPnP Control Point uses TmApplicationServer:1 service's TerminateApplication SOAP action to send
termination request.
2) DAP client shall disconnect the TCP connection.
3) DAP server should disconnect the TCP connection on detection of the client TCP disconnect or 5 s after
responding to the TerminateApplication SOAP action, whichever comes first.
The DAP client shall wait for any outstanding Device Attestation Response messages, for at least 10 s, prior to
terminating the DAP session. The DAP Server shall provide a DAP response to any DAP request within 10 s.
4.1.3 Unintentionally Terminating the DAP Session
Unintentional termination of the DAP session may happen at any time due to error conditions. In the case of
unintentional termination of the DAP session, the respective DAP server or client shall disconnect the TCP connection.
The respective counterpart should disconnect as well.
If the MirrorLink Client decides to re-establish the DAP session, it shall follow the steps given in clause 4.1.1.2.
To avoid the DAP server or client being in a TCP TIME-WAIT time-out loop as a result of an unintentional active
disconnect, the TCP socket should be established using the SO_REUSEADDR option (or similar platform specific
variant), allowing the operating system to reuse a port address, even it is currently in the TIME-WAIT state or the DAP
server should use a different, unaffected port number.
4.2 Other Bindings
Besides TCP/IP, it will be possible to run MirrorLink Device Attestation Protocol on top of other protocols like
Bluetooth RFCOMM, but how to discover and establish connection for such configuration is outside the scope of the
present document.
4.3 Testing Considerations
If the MirrorLink Client is in a dedicated testing state (as part of the MirrorLink Certification), it shall launch a new
DAP session (either initiated automatically or manually from the user), whenever the DAP server has unintentionally
terminated the DAP session.
The MirrorLink Client shall have a mechanism to allow a test engineer to launch a DAP session (either automatically or
manually).
For DAP testing purposes, the MirrorLink Client shall use a CTS root certificate to validate responses from the CTS
Server. This CTS root certificate shall be decoupled from the regular CCC root certificate used during production.
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9 ETSI TS 103 544-4 V1.3.1 (2019-10)
The CTS root certificate shall be accepted from the MirrorLink Client in test setup only. The CTS public key (DER
encoded) and the 32-byte SHA-256 hash of the CTS public key (Base64 encoded) are provided separately.
The DAP trust chain, for testing purposes is shown in Figure 1.

Figure 1: Device Attestation Certification Infrastructure - Testing Only
The MirrorLink Client shall not accept and request the CTS root certificate outside DAP testing and certification.
For testing MirrorLink Servers, the CTS shall only accept legitimate certificates signed by the CCC's Root Certificate.
5 Device Attestation Protocol
The prerequisite of successful Device Attestation Protocol run is that the MirrorLink server has a X.509 device
certificate (with Extended Key Usage tcg-kp-AIKCertificate OID 2.23.133.8.3 as specified in clause 3.5 of [12]) for its
device key pair from the server device manufacturer. The MirrorLink Client shall not expect other X.509 certificate
extensions, mandated e.g. in clause 3.4 or 3.5 of [12]. Additionally, the server shall have one X.509 manufacturer
certificate signed from the CCC DAP management system. The server device's private key(s) shall be stored securely.
The secure storage is manufacturer specific and may use:
1) hardware-based Mobile Trusted Module (MTM) [5] implementation or equivalent;
2) storage on OS, which integrity has been verified with hardware-assisted secure boot process; or
3) storage on OS alone.
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10 ETSI TS 103 544-4 V1.3.1 (2019-10)

Figure 2: Device Attestation Certification Infrastructure
MirrorLink assumes pre-established trust relationships and security associations between the MirrorLink server device
manufacturers and MirrorLink client device manufacturers via a central CCC controlled DAP Management System
which extends to both client and server devices. This is achieved using a standard X.509 certificate chain.
The key pair SK /PK , as shown in Figure 2 consists of the private key SK and the public key PK . The certificate
A A A A
Cert = Sig(SK , PK ) is an X.509 public key certificate with subject public key PK and signed with private
A B A A
key SK (i.e. the certificate issuer is B).
B
After the MirrorLink Server device manufacturers have been certified from the central CCC DAP management system
(Cert = Sig(SK , PK )), they can certify individual devices they produce (Cert = Sig(SK ,
SM CCC SM SD SM
PK )). Again, MirrorLink specifies using standard X.509 certificates. This certification will typically take place
SD
during device manufacturing time, but some device manufacturers may have proprietary mechanisms and the device
cert may be bootstrapped during first boot. This operation is done only once per each device.
Using the device certificate, the MirrorLink Server device can authenticate/attest itself to the MirrorLink Client device.
For this MirrorLink specifies using Device Attestation Protocol (DAP). This process (DAP) will be run for each
connection from a MirrorLink Server device to the MirrorLink Client device. Both the device and the manufacturer
certificates are included in the DAP message exchange. Using this chain of certificates, the MirrorLink Client device
can verify at runtime that the MirrorLink Server device is a genuine/compliant device from an authorized MirrorLink
Server device manufacturer. The MirrorLink Client shall have the public key PK available, to be able to validate the
CCC
MirrorLink Server device manufacturer certificate.
An overview of device and software attestation protocol is shown in Figure 3 below. The protocol is two-flow protocol:
MirrorLink client sends attestationRequest message and MirrorLink server replies with attestationResponse message.
Both of these messages are XML formatted.
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11 ETSI TS 103 544-4 V1.3.1 (2019-10)

Figure 3: Device and software attestation protocol overview
In more detail, the Device Attestation Protocol consists of following steps:
1) Device Attestation Client first picks random nonce and sends that together with identifier of the requested
attested component(s) to Device Attestation Server as part of AttestationRequest message.
2) Device Attestation Server is a trusted software component on the MirrorLink server device. It first measures
the requested component(s).
NOTE: Measurement of a software component is a platform specific mechanism of identifying a software
component on the device. In practice, this could involve verification of a unique software component
identifier provided by the underlying operating system security framework, or calculation of a hash over
the software component binary executable, or other equivalent mechanisms.
If the measurement does not match expected value, the Device Attestation Server sends a DAP
AttestationResponse with error code 5. If the measurement matches expected value, the Device Attestation
Server proceeds with the next step of the attestation protocol as shown in Figure 3. The Device Attestation
Server first reads current value of Platform Configuration Register (PCR) 10 from Mobile Trusted Module
using TPM_PCRRead command [4]. Device Attestation Server saves the current PCR value for later use.
(Device Attestation Server protection and software component measurement mechanisms are platform and
implementation specific and intentionally left out of the present document).
3) Device Attestation Server extends attestationEvidence to PCR 10 using TPM_Extend command [4].
attestationEvidence = componentID || URL || SHA1(applicationPublicKey), where || denotes to concatenation
(for more details on these data elements, see descriptions of attestationRequest and attestationResponse
below).
4) Device Attestation Server performs TPM_Quote command [4] on PCR 10 using the nonce as an input. This
operation signs the PCR structure using a certified device key. The TPM_Quote operation returns
TPM_PCR_COMPOSITE structure using which the server constructs matching TPM_QUOTE_INFO
structure.
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12 ETSI TS 103 544-4 V1.3.1 (2019-10)
5) The saved PCR value, the resulting TPM_Quote signature, URL, the device certificate, and the device
manufacturer certificate are sent to Device Attestation Client as part of AttestationResponse. Device
Attestation Client verifies the device manufacturer certificate (using pre-installed trust root), verifies device
certificate using verified device manufacturer certificate, and finally verifies the attestation signature with
respect to the TPM_QUOTE_INFO using the verified device certificate.
Implementation considerations:
It is the responsibility of the MirrorLink Server that the usage of certified device key is restricted to authorized
components only, such as hardware-based MTM implementation or trusted software component. The exact
protection mechanisms are platform and implementation specific.
The elements of attestationRequest XML message shall be as defined in Table 1. The XSD schema of the XML shall be
as given in Annex A.
Table 1: Device Attestation - attestationRequest elements
Element Description Parent Availability
attestationRequest Main container of attestation request None Optional
attestation
version MirrorLink Version information Mandatory
Request
majorVersion Major version number version Mandatory
minorVersion Minor version number version Mandatory
Identifier of the trust root used by MirrorLink client for
attestation verification. 32-byte SHA-256 hash of attestation
trustRoot Mandatory
Certificate Authority's root public key Base64 Request
encoded from SubjectPublicKeyInfo DER format [1]
attestation
nonce 20-byte random number Base64-encoded [1] Mandatory
Request
Identifier of the software component to be attested. attestation
componentID Mandatory
Possible values are described in Table 2 Request

Device Attestation Protocol can be used to enable the following attestations:
• Attest that the connected MirrorLink Server device is manufactured from a trusted manufacturer.
• Attest that software components on the connected MirrorLink Server device are original (i.e. certified).
The components, which can be attested, shall be as defined in Table 2 with their component IDs. The Protocol ID is
used as part of the attestation's response URL binding.
Table 2: Device Attestation - Component List
componentID Description of what functionality is attested Protocol ID
TerminalMode:V
VNC server functionality as specified in [10]. VNC
NC-Server
UPnP TmServerDevice server services as specified in [7], [8] and
[9].
TerminalMode:U
The attestation includes the service advertisements, using UDP HTTP
PnP-Server
broadcasts and the SOAP and eventing mechanisms based on
HTTP.
TerminalMode:R
RTP-Server as specified in [11]. RTP
TP-Server
TerminalMode:R
RTP-Client as specified in [11]. RTP
TP-Client
MirrorLink:CDB-
CDB Endpoint, as specified in [13] ( ≥ MirrorLink 1.1). CDB
Endpoint
MirrorLink:WFD:
WFD Source, as specified in [14] ( ≥ MirrorLink 1.2). WFD
RTSP
MirrorLink:HSML HSML Source as specified in [15] ( ≥ MirrorLink 1.2). VNC
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