| TLS Working Group | P. Kampanakis, Ed. |
| Internet-Draft | Cisco |
| Intended status: Informational | M. Msahli, Ed. |
| Expires: February 21, 2019 | Telecom ParisTech |
| August 20, 2018 |
TLS 1.3 Authentication using ETSI TS 103 097 and IEEE 1609.2 certificates
draft-tls-certieee1609-01.txt
This document specifies the use of two new certificate types to authenticate TLS entities. The first type enables the use of a certificate specified by the Institute of Electrical and Electronics Engineers (IEEE) [IEEE1609.2] and the second by the European Telecommunications Standards Institute (ETSI) [TS103097].
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At present, TLS 1.3 protocol [RFC8446] uses X509 and Raw Public Key in order to authenticate servers and clients. This document describes the use of certificates specified either by the Institute of Electrical and Electronics Engineers (IEEE) [IEEE1609.2] or the European Telecommunications Standards Institute (ETSI) [TS103097]. These standards are defined in order to secure communications in vehicular environments. Existing authentication methods, such as X509 and Raw Public Key, are designed for Internet use, particularly for flexibility and extensibility, and are not optimized for bandwidth and processing time to support delay-sensitive applications. This is why size-optimized certificates that meet the ITS requirements were designed and standardized.
Two new values referring the previously mentioned certificates will be added to the "client_certificate_type" and the "server_certificate_type" extensions defined in [RFC7250].
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 [RFC2119].
/* Managed by IANA */
enum {
X509(0),
RawPublicKey(2),
1609Dot2(?), /* Number 3 will be requested for 1609.2 */
(255)
103097(?), /* Number 4 will be requested for 103097 */
(255)
} CertificateType;
struct {
select (certificate_type) {
/* certificate type defined in this document.*/
case 103097:
opaque cert_data<1..2^24-1>;
/* 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;
The extension format for extended Client Hello and Server Hello uses the "extension_data" field of the "Certificate_Type_Extension" structue defined in RFC7250. The CertificateType structure is an enum with values taken from the TLS 1.3 Certificate Types. 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. The extension_data" field of this extension SHALL contain a list of supported certificate types proposed by the client as provided in figure below:
In case where TLS server accepts the described extension, it selects one of the certificate types in the extension described here. Note that a server MAY authenticate the client using other authentication methods. The client MAY at its discretion either continue the handshake, or respond with a fatal message alert.
The end-entity certificate's public key has to be compatible with one of the certificate types listed in extension described here.
Servers aware of the extension described here but not wishing to use it, SHOULD gracefully not proceed with the negotiation.
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
The "client_certificate_type" and "server_certificate_type" messages MUST be sent in handshake phase as illustrated in Figure 1 below. The reply of the server MUST be sent in EncryptedExtensions.
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"to the extended client hello message. The hello extension mechanism 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.
Client MAY respond along with supported certificate by sending a "Certificate" message immediately followed by the "CetificateVerify" message.
When the server receives the client hello containing the client_certificate_type extension and/or the server_certificate_type extension. The following outcomes are possible:
Verification of an IEEE 1609.2 certificate or certificate chain is described in section 5.5.2 of [IEEE1609.2].
Verification of ETSI TS 103 097 certificate or certificate chain is described in [TS103097].
Some of exchanged messages examples are illustrated in Figures 2 and 3.
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
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*=(X.509),
server_certificate_type*=(1609Dot2), -------> ServerHello,
{EncryptedExtensions}
{client_certificate_type*=X.509}
{server_certificate_type*=1609Dot2}
{Certificate*}
{CertificateVerify*}
{Finished}
<--------- [Application Data*]
{Finished} --------->
[Application Data] <--------> [Application Data]
Figure 3: TLS Server uses the IEEE 1609.2 certificate and TLS Client uses the X 509 certificate
This example shows the TLS authentication, where the TLS client indicates its ability to receive and to validate an IEEE 1609.2 certificate from the server. Therefore, the client populates the server_certificate_type extension with the IEEE 1609.2 certificate type as presented in figure 3.
Client Server
ClientHello,
client_certificate_type*=(103097),
server_certificate_type*=(1609Dot2), -------> ServerHello,
{EncryptedExtensions}
{client_certificate_type*=103097}
{server_certificate_type*=1609Dot2}
{Certificate*}
{CertificateVerify*}
{Finished}
<--------- [Application Data*]
{Finished} --------->
[Application Data] <--------> [Application Data]
Figure 4: TLS Server uses the IEEE 1609.2 certificate and TLS Client uses the ETSI TS 103097 certificate
This section shows an example combining an IEEE 1609.2 certificate and an ETSI TS 103097 certificate. The client uses the ETSI TS 103097 certificate for client authentication, and the server provides an IEEE 1609.2 certificate. This exchange starts with the client indicating its ability to process an IEEE 1609.2 certificate if provided by the server. For client authentication, the server indicates that it has selected the ETSI TS 103097 format and requests the certificate from the client as presented in figure 4.
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] apply here as well.
For security considerations in a vehicular environment, the minimal use of any TLS extensions is recommended such as :
For privacy considerations in a vehicular environment the use of ETSI TS 103097 and IEEE 1609.2 certificates is recommended for many reasons:
Existing IANA references have not been updated yet to point to this document.
IANA is asked to register two new values in the "TLS Certificate Types" registry of Transport Layer Security (TLS) Extensions [TLS-Certificate-Types-Registry], as follows:
This document borrows a lot from [draft-serhrouchni-tls-certieee1609-00]. The authors wish to thank Eric Rescola and Ilari Liusvaara and William Whyte for their feedback and suggestions on improving this document. Thanks are due to Sean Turner for his valuable and detailed comments.
| [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. |