NETCONF over TLS 1.3

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Table of Contents

1. Introduction

[RFC7589] defines how to protect NETCONF messages [RFC6241] with TLS 1.2 [RFC5246]. This document describes defines how to protect NETCONF messages with TLS 1.3 [I-D.ietf-tls-rfc8446bis].¶

This document addresses cipher suites and the use of early data, which is also known as 0-RTT data. It also updates the "netconf-tls" IANA Registered Port Number entry to refer to this document. All other provisions set forth in [RFC7589] are unchanged, including connection initiation, message framing, connection closure, certificate validation, server identity, and client identity.¶

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. Early data is permitted by TLS 1.3 when the client and server share a 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 are no protection against the replay of early data between connections. Appendix E.5 of [I-D.ietf-tls-rfc8446bis] requires applicaitons not use early data without a profile that defines its use. This document specifies that implementations MUST NOT use early data.¶

4. Cipher Suites

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

Implementations MAY implement additional TLS cipher suites that provide mutual authentication and confidentiality, which are required for NETCONF [RFC6241].¶

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

Please review the Security Considerations in TLS 1.3 [I-D.ietf-tls-rfc8446bis].¶

Please review the recommendations regarding Diffie-Hellman exponent reuse in Section 7.4 of [I-D.ietf-uta-rfc7525bis].¶

Please review the Security Considerations in NETCONF [RFC6241].¶

NETCONF is used to access configuration and state information and to modify configuration information. TLS 1.3 mutual authentication is used to ensure that only authorized users and systems are able to view the NETCONF server's configuration and state or to modify the NETCONF server's configuration. To this end, neither the client nor the server should establish a NETCONF over TLS 1.3 connection with an unknown, unexpected, or incorrect peer identity; see Section 7 of [RFC7589]. If deployments make use of this list of Certification Authority (CA) certificates [RFC5280], then the listed CAs should only issue certificates to parties that are authorized to access the NETCONF servers. Doing otherwise will allow certificates that were issued for other purposes to be inappropriately accepted by a NETCONF server.¶

Please review [RFC6125] for further details on generic host name validation in the TLS context.¶

Please review the recommendations regarding certificate revocation checking in Section 7.5 of [I-D.ietf-uta-rfc7525bis].¶

[RFC5539] assumes that the end-of-message (EOM) sequence, ]]>]]>, cannot appear in any well-formed XML document, which turned out to be mistaken. The EOM sequence can cause operational problems and open space for attacks if sent deliberately in NETCONF messages. While it is possible, the likelihood is believed to be very low. The EOM sequence is used for the initial <hello> message to avoid incompatibility with existing implementations. When the client and server both implement the :base:1.1 capability, a proper framing protocol (see Section 3 of [RFC7589]) is used for the rest of the NETCONF session, to avoid injection attacks.¶

6. IANA Considerations

IANA is requested to add a reference to this document in the "netconf-tls" entry in the "Registered Port Numbers". The updated registry entry would appear as follows:¶

 Service Name:           netconf-tls
 Transport Protocol(s):  TCP
 Assignee:               IESG <iesg@ietf.org>
 Contact:                IETF Chair <chair@ietf.org>
 Description:            NETCONF over TLS
 Reference:              RFC 7589, [THIS RFC]
 Port Number:            6513

Acknowledgments

We would like to thank the following people TBD.¶

Authors' Addresses