PCEPS with TLS 1.3

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Table of Contents

1. Introduction

[RFC8253] defines how to protect PCEP messages [RFC5440] with TLS 1.2 [RFC5246]. This document describes defines how to protect PCEP messages with TLS 1.3 [I-D.ietf-tls-rfc8446bis].¶

[Editor's Note: The reference to [I-D.ietf-tls-rfc8446bis] could be changed to RFC 8446 incase the progress of the bis draft is slower than the progression of this document.]¶

This document addresses cipher suites and the use of 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. Early Data

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.¶

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. This document specifies that PCEPS implementations that support TLS 1.3 MUST NOT use early data.¶

4. Cipher Suites

Implementations that support TLS 1.3 [I-D.ietf-tls-rfc8446bis] are REQUIRED to support the mandatory-to-implement cipher suites listed in Section 9.1 of [I-D.ietf-tls-rfc8446bis].¶

Implementations that support TLS 1.3 MAY implement additional TLS cipher suites that provide mutual authentication and confidentiality, which are required for PCEP.¶

PCEPS Implementations SHOULD follow the recommendations given in [I-D.ietf-uta-rfc7525bis].¶

So, this is what {{Section 9.1 of I-D.ietf-tls-rfc8446bis}} says:

  A TLS-compliant application MUST implement the TLS_AES_128_GCM_SHA256
  [GCM] cipher suite and SHOULD implement the TLS_AES_256_GCM_SHA384
  [GCM] and TLS_CHACHA20_POLY1305_SHA256 [RFC8439] cipher suites (see
  Appendix B.4).

  A TLS-compliant application MUST support digital signatures with
  rsa_pkcs1_sha256 (for certificates), rsa_pss_rsae_sha256 (for
  CertificateVerify and certificates), and ecdsa_secp256r1_sha256.  A
  TLS-compliant application MUST support key exchange with secp256r1
  (NIST P-256) and SHOULD support key exchange with X25519 [RFC7748].

Is there any reason to narrow the algorithm choices?

My guess is not.  These ought to be available in all TLS libraries.

5. Security Considerations

The Security Considerations in TLS 1.3 are specified in [I-D.ietf-tls-rfc8446bis].¶

The recommendations regarding Diffie-Hellman exponent reuse are specified in Section 7.4 of [I-D.ietf-uta-rfc7525bis].¶

The key Security Considerations for PCEP are described in [RFC5440], [RFC8231], [RFC8281], and [RFC8283].¶

The Path Computation Element (PCE) defined in [RFC4655] is an entity that is capable of computing a network path or route based on a network graph, and applying computational constraints. A Path Computation Client (PCC) may make requests to a PCE for paths to be computed. PCEP is the communication protocol between a PCC and PCE and is defined in [RFC5440]. Stateful PCE [RFC8231] specifies a set of extensions to PCEP to enable control of TE-LSPs by a PCE that retains the state of the LSPs provisioned in the network (a stateful PCE). [RFC8281] describes the setup, maintenance, and teardown of LSPs initiated by a stateful PCE without the need for local configuration on the PCC, thus allowing for a dynamic network that is centrally controlled. [RFC8283] introduces the architecture for PCE as a central controller¶

TLS 1.3 mutual authentication is used to ensure that only authorized users and systems are able to send and receive PCEP messages. To this end, neither the PCC nor the PCE should establish a PCEPS with TLS 1.3 connection with an unknown, unexpected, or incorrectly identified peer; see Section 3.5 of [RFC5440]. If deployments make use of a trusted list of Certification Authority (CA) certificates [RFC5280], then the listed CAs should only issue certificates to parties that are authorized to access the PCE. Doing otherwise will allow certificates that were issued for other purposes to be inappropriately accepted by a PCE.¶

The recommendations regarding certificate revocation checking are specified in Section 7.5 of [I-D.ietf-uta-rfc7525bis].¶

6. IANA Considerations

There are no IANA considerations.¶

Acknowledgments

We would like to thank Adrian Farrel for their review.¶

Authors' Addresses