Updates for PCEPS: TLS Connection Establishment Restrictions

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 12 July 2024.¶

Copyright Notice

Copyright (c) 2024 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. 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶

Table of Contents

1. Introduction

Section 3.4 of [RFC8253] specifies TLS connection establishment restrictions for PCEPS; PCEPS refers to usage of TLS to provide a secure transport for PCEP (Path Computation Element Communication Protocol) [RFC5440]. This document adds restrictions to specify what PCEPS implementations do if they support more than one version of the TLS protocol, e.g., TLS 1.2 [RFC5246] and TLS 1.3 [I-D.ietf-tls-rfc8446bis], and to restrict the use of TLS 1.3's early data, which is also known as 0-RTT data. All other provisions set forth in [RFC8253] are unchanged, including connection initiation, message framing, connection closure, certificate validation, peer identity, and failure handling.¶

2. Conventions and Definitions

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. TLS Connection Establishment Restrictions

Section 3.4 of [RFC8253] Step 1 includes restrictions on PCEPS TLS connection establishment. This document adds the following restrictions:¶

• Implementations that support multiple versions of the TLS protocol MUST prefer to negotiate the latest version of the TLS protocol; see Section 4.2.1 of [I-D.ietf-tls-rfc8446bis].¶

• PCEPS implementations that support TLS 1.3 or later MUST NOT use early data.¶

NOTE:

Early data (aka 0-RTT data) is a mechanism defined in TLS 1.3 [I-D.ietf-tls-rfc8446bis] that allows a client to send data ("early data") as part of the first flight of messages to a server. Note that TLS 1.3 can be used without early data as per Appendix F.5 of [I-D.ietf-tls-rfc8446bis]. In fact, early data is permitted by TLS 1.3 only when the client and server share a Pre-Shared Key (PSK), either obtained externally or via a previous handshake. The client uses the PSK to authenticate the server and to encrypt the early data.¶

NOTE:

As noted in Section 2.3 of [I-D.ietf-tls-rfc8446bis], the security properties for early data are weaker than those for subsequent TLS- protected data. In particular, early data is not forward secret, and there is no protection against the replay of early data between connections. Appendix E.5 of [I-D.ietf-tls-rfc8446bis] requires applications not use early data without a profile that defines its use.¶

4. Security Considerations

The Security Considerations of PCEP [RFC5440], [RFC8231], [RFC8253], [RFC8281], and [RFC8283]; TLS 1.2 [RFC5246]; TLS 1.3 [I-D.ietf-tls-rfc8446bis], and; [RFC9325] apply here as well.¶

5. IANA Considerations

There are no IANA considerations.¶

6. Implementation Status

This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in [RFC7942]. The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalogue of available implementations or their features. Readers are advised to note that other implementations may exist.¶

According to [RFC7942], "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit".¶

At the time of posting the -04 version of this document, there are no known implementations of this mechanism. It is believed that one vendor has implementation, but these plans are too vague to make any further assertions.¶

Acknowledgments

We would like to thank Adrian Farrel, Stephane Litkowski, Cheng Li, and Andrew Stone for their review.¶

Authors' Addresses