Network Working Group M. Msahli, Ed.
Internet-Draft Telecom ParisTech
Intended status: Experimental N. Cam-Winget, Ed.
Expires: January 23, 2020 Cisco
July 22, 2019
TLS Authentication using IEEE 1609.2 certificates
draft-msahli-ise-ieee1609-00
Abstract
This document specifies the use of a new certificate type to
authenticate TLS entities. The goal is to enable the use of a
certificate specified by the IEEE and the European Telecommunications
Standards Institute (ETSI). This specification defines an
experimental change of TLS to support a new certificate type.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 23, 2020.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Experiment Overview . . . . . . . . . . . . . . . . . . . 2
2. Requirements Terminology . . . . . . . . . . . . . . . . . . 3
3. Extension Overview . . . . . . . . . . . . . . . . . . . . . 3
4. TLS Client and Server Handshake . . . . . . . . . . . . . . . 4
4.1. Client Hello . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Server Hello . . . . . . . . . . . . . . . . . . . . . . 6
5. Certificate Verification . . . . . . . . . . . . . . . . . . 7
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. TLS Server and TLS Client use the 1609Dot2 Certificate . 8
6.2. TLS Client uses the IEEE 1609.2 certificate and TLS
Server uses the X.509 certificate . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 9
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
11.1. Normative References . . . . . . . . . . . . . . . . . . 10
11.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
The TLS protocol [RFC8446] uses X.509 and Raw Public Key in order to
authenticate servers and clients. This document describes an
experimental use of the certificate specified by the IEEE in
[IEEE1609.2] and profiled by the European Telecommunications
Standards Institute (ETSI) in [TS103097]. These standards specify
secure communications in vehicular environments. The certificate
types are optimized for bandwidth and processing time to support
delay-sensitive applications, and also to provide both authentication
and authorization information to enable fast access control decisions
in ad hoc networks such as are found in Intelligent Transportation
System (ITS). We define an experimental extension following the
[RFC7250].
1.1. Experiment Overview
This document describes an experimental extension of TLS security
model. We are using a form of certificate that has not traditionally
been used in IETF works. Systems using this Experimental approach
are segregated from system using standard TLS by the use of a new
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Certificate Type value, reserved through IANA. The implementation of
TLS is not involved in the Experiment and it will not be able to
interact with an Experimental implementation. In fact, an
implementation of TLS can recognize that the Certificate Type value
used in this document is unknown. This design has been requested by
stakeholders in the Cooperative ITS community including ISO
internationally, and SAE in the US and ETSI in EU , in order to
support the deployment of a number of use cases in cooperative ITS
and it is anticipated that its use will be widespread.
There is no IPR that needs to be disclosed by the authors or
contributors under the IETF's rules set out in BCP 78 and BCP 79.
2. Requirements 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.
3. Extension Overview
For TLS 1.2[RFC5246], the "extension_data" field SHALL follow the
[RFC7250]. In case of TLS 1.3, the "extension_data" field SHALL
contain a list of supported certificate types proposed by the client
as provided in the figure below:
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/* Managed by IANA */
enum {
X509(0),
RawPublicKey(2),
1609Dot2(3),
(255)
} CertificateType;
struct {
select (certificate_type) {
/* certificate type defined in this document.*/
case 1609Dot2:
opaque cert_data<1..2^24-1>;
/* RawPublicKey defined in RFC 7250*/
case RawPublicKey:
opaque ASN.1_subjectPublicKeyInfo<1..2^24-1>;
/* X.509 certificate defined in RFC 5246*/
case X.509:
opaque cert_data<1..2^24-1>;
};
Extension extensions<0..2^16-1>;
} CertificateEntry;
In case where the TLS server accepts the described extension, it
selects one of the certificate types. Note that a server MAY
authenticate the client using other authentication methods. The end-
entity certificate's public key MUST be compatible with one of the
certificate types listed in the extension described above.
4. TLS Client and Server Handshake
The "client_certificate_type" and "server_certificate_type"
extensions MUST be sent in handshake phase as illustrated in figure 1
below.
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Client Server
Key ^ ClientHello
Exch | + server_certificate_type*
| + client_certificate_type*
| + key_share*
v + signature_algorithms* -------->
ServerHello ^ Key
+ key_share* v Exch
{EncryptedExtensions} ^ Server
{+ server_certificate_type*}| Params
{+ client_certificate_type*}|
{CertificateRequest*} v
{Certificate*} ^
{CertificateVerify*} | Auth
{Finished} v
<------- [Application Data*]
^ {Certificate*}
Auth | {CertificateVerify*}
v {Finished} -------->
[Application Data] <-------> [Application Data]
+ Indicates noteworthy extensions sent in the
previously noted message.
* Indicates optional or situation-dependent
messages/extensions that are not always sent.
{} Indicates messages protected using keys
derived from a [sender]_handshake_traffic_secret.
[] Indicates messages protected using keys
derived from [sender]_application_traffic_secret_N.
Figure 1: Message Flow with certificate type extension for Full TLS
1.3 Handshake
In case of TLS 1.3 and in order to negotiate the support of IEEE
1609.2 or ETSI TS 103097 certificate-based authentication, the
clients and the servers MAY include the extension of type
"client_certificate_type" and "server_certificate_type" in the
extended Client Hello and "EncryptedExtensions". In case of TLS 1.2,
used extensions are in Client Hello and Server Hello.
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4.1. Client Hello
In order to indicate the support of IEEE 1609.2 or ETSI TS 103097
certificates, client MUST include an extension of type
"client_certificate_type" and "server_certificate_type" in the
extended Client Hello message. The Hello extension is described in
Section 4.1.2 of TLS 1.3 [RFC8446].
The extension 'client_certificate_type' sent in the client hello MAY
carry a list of supported certificate types, sorted by client
preference. It is a list in the case where the client supports
multiple certificate types.
In both TLS 1.2 and 1.3, the rules if client Certificate and
CertificateVerify messages appear is as follows:
- Client Certificate message is present if and only if server sent
a CertificateRequest message.
- Client CertificateVerify message is present if and only if the
Client Certificate message is present and contains non-empty
certificate list.
All implementations SHOULD be prepared to handle extraneous
certificates and arbitrary orderings from any TLS version, with the
exception of the end-entity certificate which MUST be first.
4.2. Server Hello
When the server receives the Client Hello containing the
client_certificate_type extension and/or the server_certificate_type
extension, the following options are possible:
- The server supports the extension described in this document.
It selects a certificate type from the client_certificate_type
field in the extended Client Hello and SHALL take into account the
client authentication list priority.
- The server does not support any of the proposed certificate type
and terminates the session with a fatal alert of type
"unsupported_certificate".
- The server does not support the extension defined in this
document. In this case, the server returns the server hello
without the extensions defined in this document.
- The server supports the extension defined in this document, but
it does not have any certificate type in common with the client.
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Then, the server terminates the session with a fatal alert of type
"unsupported_certificate".
- The server supports the extensions defined in this document and
has at least one certificate type in common with the client. In
this case, the server MAY include the client_certificate_type
extension in the Server Hello for TLS 1.2 or in Encrypted
Extension for TLS 1.3. Then, the server requests a certificate
from the client (via the certificate_request message)
It is worth to mention that the TLS client or server public keys are
obtained from an online repository.
5. Certificate Verification
Verification of an IEEE 1609.2/ ETSI TS 103097 certificates or
certificate chain is described in section 5.1 of [IEEE1609.2]. In
the case of TLS 1.3 and when the certificate_type is 1609Dot2, the
CertificateVerify contents and processing are different than for the
CertificateVerify message specified for other values of
certificate_type in [RFC8446]. In this case, the CertificateVerify
message contains a Canonical Octet Encoding Rules (COER)-encoded
Ieee1609Dot2Data of type signed as specified in [IEEE1609.2],
[IEEE1609.2b], where:
payload contains an extDataHash containing the SHA-256 hash of the
data the signature is calculated over. This is identical to the
data the signature is calculated over in standard TLS, which is
reproduced below for clarity.
psid indicates the application activity that the certificate is
authorizing.
generationTime is the current time.
pduFunctionalType (as specified in [IEEE1609.2b]) is present and
is set equal to tlsHandshake (1).
All other fields in the headerInfo are omitted.
The message input to the signature calculation is the usual message
input for TLS 1.3, as specified in [RFC8446] section 4.4.3,
consisting of pad, context string, separator and content, where
content is Transcript- Hash(Handshake Context, Certificate).
The signature and verification are carried out as specified in
[IEEE1609.2].
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6. Examples
Some of exchanged messages examples are illustrated in Figures 2 and
3.
6.1. TLS Server and TLS Client use the 1609Dot2 Certificate
This section shows an example where the TLS client as well as the TLS
server use the IEEE 1609.2 certificate. In consequence, both the
server and the client populate the client_certificate_type and
server_certificate_type with extension IEEE 1609.2 certificates as
mentioned in figure 2.
Client Server
ClientHello,
client_certificate_type*=1609Dot2,
server_certificate_type*=1609Dot2, --------> ServerHello,
{EncryptedExtensions}
{client_certificate_type*=1609Dot2}
{server_certificate_type*=1609Dot2}
{CertificateRequest*}
{Certificate*}
{CertificateVerify*}
{Finished}
{Certificate*} <------- [Application Data*]
{CertificateVerify*}
{Finished} -------->
[Application Data] <-------> [Application Data]
Figure 2: TLS Client and TLS Server use the IEEE 1609.2 certificate
6.2. TLS Client uses the IEEE 1609.2 certificate and TLS Server uses
the X.509 certificate
This example shows the TLS authentication, where the TLS Client
populates the server_certificate_type extension with the X.509
certificate and Raw Public Key type as presented in figure 3. the
client indicates its ability to receive and to validate an X.509
certificate from the server. The server chooses the X.509
certificate to make its authentication with the Client.
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Client Server
ClientHello,
client_certificate_type*=(1609Dot2),
server_certificate_type*=(1609.9Dot,
X509,RawPublicKey), -----------> ServerHello,
{EncryptedExtensions}
{client_certificate_type*=1609Dot2}
{server_certificate_type*=X509}
{Certificate*}
{CertificateVerify*}
{Finished}
<--------- [Application Data*]
{Finished} --------->
[Application Data] <--------> [Application Data]
Figure 3: TLS Client uses the IEEE 1609.2 certificate and TLS Server
uses the X.509 certificate
7. Security Considerations
This section provides an overview of the basic security
considerations which need to be taken into account before
implementing the necessary security mechanisms. The security
considerations described throughout [RFC8446] regarding the supported
groups and signature algorithms apply here as well.
TLS extensions to be considered are:
The "client_certificate_type" [IANA value 19] extension who's
purpose was previously described in [RFC7250].
The "server_certificate_type" [IANA value 20] extension who's
purpose was previously described in [RFC7250].
8. Privacy Considerations
For privacy considerations in a vehicular environment the use of IEEE
1609.2/ETSI TS 103097 certificate is recommended for many reasons:
In order to address the risk of a personal data leakage, messages
exchanged for V2V communications are signed using IEEE 1609.2/ETSI
TS 103097 pseudonym certificates
The purpose of these certificates is to provide privacy relying on
geographical and/or temporal validity criteria, and minimizing the
exchange of private data
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9. IANA Considerations
IANA is requested to update the registry to reference the RFC.
Existing IANA references have not been updated yet to point to this
document.
10. Acknowledgements
The authors wish to thank Eric Rescola and Ilari Liusvaara for their
feedback and suggestions on improving this document. Thanks are due
to Sean Turner for his valuable and detailed comments. Special
thanks to Panos Kampanakis, Jasja Tijink and Maik Seewald for their
guidance and support of the draft.
11. References
11.1. Normative References
[IEEE1609.2]
"IEEE Standard for Wireless Access in Vehicular
Environments - Security Services for Applications and
Management Messages", 2016.
[IEEE1609.2b]
"IEEE Standard for Wireless Access in Vehicular
Environments--Security Services for Applications and
Management Messages - Amendment 2--PDU Functional Types
and Encryption Key Management", 2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", August 2008.
[RFC7250] Wouters, P., Tschofenig, H., Weiler, S., and T. Kivinen,
"Using Raw Public Keys in Transport Layer Security (TLS)
and Datagram Transport Layer Security (DTLS)", June 2014.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", May 2017.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", August 2018.
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[TS103097]
"ETSI TS 103 097 : Intelligent Transport Systems (ITS);
Security; Security header and certificate formats".
11.2. Informative References
[draft-serhrouchni-tls-certieee1609-00]
KAISER, A., LABIOD, H., LONC, B., MSAHLI, M., and A.
SERHROUCHNI, "Transport Layer Security (TLS)
Authentication using ITS ETSI and IEEE certificates",
august 2017.
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Appendix A. Contributors
o Houda Labiod
Telecom ParisTech
houda.labiod@telecom-paristech.fr
o Ahmed Serhrouchni
Telecom ParisTech
ahmed.serhrouchni@telecom-paristech.fr
o William Whyte
Onboard Security
wwhyte@onboardsecurity.com
Authors' Addresses
Mounira Msahli (editor)
Telecom ParisTech
France
EMail: mounira.msahli@telecom-paristech.fr
Nancy Cam-Winget (editor)
Cisco
USA
EMail: ncamwing@cisco.com
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