NETCONF Working Group M. Badra Internet-Draft LIMOS Laboratory Obsoletes: 5539 (if approved) A. Luchuk Intended status: Standards Track SNMP Research, Inc. Expires: August 2, 2014 J. Schoenwaelder Jacobs University Bremen January 29, 2014 Using the NETCONF Protocol over Transport Layer Security (TLS) draft-ietf-netconf-rfc5539bis-05 Abstract The Network Configuration Protocol (NETCONF) provides mechanisms to install, manipulate, and delete the configuration of network devices. This document describes how to use the Transport Layer Security (TLS) protocol to secure the exchange of NETCONF messages. This document obsoletes RFC 5539 and it adds an optional mechanism to establish the underlying TCP connection from the NETCONF server to the NETCONF client (call home). 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 http://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 August 2, 2014. Copyright Notice Copyright (c) 2014 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents Badra, et al. Expires August 2, 2014 [Page 1] Internet-Draft NETCONF over TLS January 2014 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Applicability Statement . . . . . . . . . . . . . . . . . 3 2. NETCONF over TLS . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Connection Initiation . . . . . . . . . . . . . . . . . . 3 2.1.1. Client to Server . . . . . . . . . . . . . . . . . . . 4 2.1.2. Server to Client (Call Home) . . . . . . . . . . . . . 4 2.1.3. Port Number Usage . . . . . . . . . . . . . . . . . . 4 2.2. Message Framing . . . . . . . . . . . . . . . . . . . . . 5 2.3. Connection Closure . . . . . . . . . . . . . . . . . . . . 5 2.4. X.509-based Authentication, Identification and Authorization . . . . . . . . . . . . . . . . . . . . . . 5 2.4.1. Server Identity . . . . . . . . . . . . . . . . . . . 5 2.4.2. Client Identity . . . . . . . . . . . . . . . . . . . 6 2.5. Pre-Shared-Key-based Authentication, Identification and Authorization . . . . . . . . . . . . . . . . . . . . 7 2.6. Cipher Suites . . . . . . . . . . . . . . . . . . . . . . 7 3. Security Considerations . . . . . . . . . . . . . . . . . . . 7 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 6. Contributor's Address . . . . . . . . . . . . . . . . . . . . 9 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 7.1. Normative References . . . . . . . . . . . . . . . . . . . 9 7.2. Informative References . . . . . . . . . . . . . . . . . . 10 Appendix A. Change Log (to be removed by RFC Editor before publication) . . . . . . . . . . . . . . . . . . . . 10 A.1. draft-ietf-netconf-rfc5539bis-05 . . . . . . . . . . . . . 10 A.2. draft-ietf-netconf-rfc5539bis-04 . . . . . . . . . . . . . 11 A.3. draft-ietf-netconf-rfc5539bis-03 . . . . . . . . . . . . . 11 A.4. draft-ietf-netconf-rfc5539bis-02 . . . . . . . . . . . . . 11 A.5. draft-ietf-netconf-rfc5539bis-00 . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Badra, et al. Expires August 2, 2014 [Page 2] Internet-Draft NETCONF over TLS January 2014 1. Introduction The NETCONF protocol [RFC6241] defines a mechanism through which a network device can be managed. NETCONF is connection-oriented, requiring a persistent connection between peers. This connection must provide integrity, confidentiality, peer authentication, and reliable, sequenced data delivery. This document defines "NETCONF over TLS", which includes support for certificate and pre-shared key (PSK)-based authentication and key derivation, utilizing the protected ciphersuite negotiation, mutual authentication, and key management capabilities of the TLS (Transport Layer Security) protocol, described in [RFC5246]. It also provides an optional mechanism to establish the underlying TCP connection from the NETCONF server to the NETCONF client (call home). 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]. 1.1. Applicability Statement The "call home" technique described in Section 2.1.2 of this document MUST only be used for a NETCONF server to initiate a connection to a NETCONF client, as described in this document. The reason for this restriction is that different protocols have different security assumptions. This specification requires NETCONF clients and servers to verify the identity of the other party before the NETCONF session is started. Further, strong cryptographic authentication is used for both the NETCONF client and server. This reduces the risk that a malicious party could impersonate a NETCONF server and contact the NETCONF client using the "call home" technique. Protocols other than NETCONF might not be so well protected. 2. NETCONF over TLS Since TLS is application-protocol-independent, NETCONF can operate on top of the TLS protocol transparently. This document defines how NETCONF can be used within a TLS session. 2.1. Connection Initiation In many deployments, the NETCONF client will initiate the connection to a NETCONF server as described in Section 2.1.1. However, in order to use NETCONF in environments where middleboxes [RFC3234] prevent Badra, et al. Expires August 2, 2014 [Page 3] Internet-Draft NETCONF over TLS January 2014 the client from establishing the connection, the server may initiate the connection as described in Section 2.1.2 (call home). 2.1.1. Client to Server The peer acting as the NETCONF client MUST act as the TLS client. The TLS client actively opens the TLS connection and the TLS server passively listens for the incoming TLS connection on the TCP port 6513. The TLS client MUST therefore send the TLS ClientHello message to begin the TLS handshake. Once the TLS handshake has finished, the client and the server MAY begin to exchange NETCONF messages. Client and server identity verification (as described in Section 2.4 and Section 2.5) is done before the message is sent. This means that the identity verification is completed before the NETCONF session has started. 2.1.2. Server to Client (Call Home) The peer acting as the NETCONF server first actively opens a TCP connection to the NETCONF client using the default port number YYYY. Once the connection has been established, the NETCONF client, which has accepted the incoming TCP connection, takes initiative. It from now on MUST act as the TLS client and it therefore sends the TLS ClientHello message to begin the TLS handshake. Once the TLS handshake has finished, the client and the server MAY begin to exchange NETCONF messages. Client and server identity verification (as described in Section 2.4 and Section 2.5) is done before the message is sent. This means that the identity verification is completed before the NETCONF session has started. 2.1.3. Port Number Usage A NETCONF client and a NETCONF server provide two different services. The NETCONF server executes RPC requests and manipulates local datastores while the NETCONF client invokes RPC requests. It is possible to have both a NETCONF server and a NETCONF client running on the same node. The well-known port number 6513 is used by NETCONF servers to listen for connections established by NETCONF clients. NETCONF clients connect to the server on the server port 6513 in order to execute RPC calls on the server. The port number YYYY is used by NETCONF clients that support call- home to listen for incoming connections. A NETCONF server using call-home will connect to a NETCONF client in order to let the client subsequently initiate RPC calls. Badra, et al. Expires August 2, 2014 [Page 4] Internet-Draft NETCONF over TLS January 2014 2.2. Message Framing All NETCONF messages MUST be sent as TLS "application data". It is possible that multiple NETCONF messages be contained in one TLS record, or that a NETCONF message be transferred in multiple TLS records. The previous version [RFC5539] of this document used the framing sequence defined in [RFC4742], under the assumption that it could not be found in well-formed XML documents. However, this assumption is not correct [RFC6242]. In order to solve this problem, this document adopts the framing protocol defined in [RFC6242] as follows: The message MUST be followed by the character sequence ]]>]]>. Upon reception of the message, the receiving peer's TLS Transport layer conceptually passes the message to the Messages layer. If the :base:1.1 capability is advertised by both peers, the chunked framing mechanism defined in Section 4.2 of [RFC6242] is used for the remainder of the NETCONF session. Otherwise, the old end-of-message-based mechanism (see Section 4.3 of [RFC6242]) is used. 2.3. Connection Closure A NETCONF server will process NETCONF messages from the NETCONF client in the order in which they are received. A NETCONF session is closed using the operation. When the NETCONF server processes a operation, the NETCONF server SHALL respond and close the TLS session as described in [RFC5246] Section 7.2.1. The NETCONF server MUST NOT process any NETCONF messages received after the operation. 2.4. X.509-based Authentication, Identification and Authorization Implementations MAY optionally support TLS certificate-based authentication [RFC5246]. If the implementation supports TLS certificate-based authentication, then the following sections apply. 2.4.1. Server Identity If the certificate presented by a NETCONF server has passed certification path validation [RFC5280] to a configured trust anchor, the NETCONF client MUST carefully examine the certificate presented by the server to determine if it meets the client's expectations. Particularly, the NETCONF client MUST check its understanding of the NETCONF server hostname against the server's identity as presented in the server Certificate message, in order to prevent man-in-the-middle attacks. Badra, et al. Expires August 2, 2014 [Page 5] Internet-Draft NETCONF over TLS January 2014 Matching is performed according to the rules and guidelines defined in [RFC6125]. If the match fails, the NETCONF client MUST either ask for explicit user confirmation or terminate the connection and indicate the NETCONF server's identity is suspect. Additionally, NETCONF clients MUST verify the binding between the identity of the NETCONF servers to which they connect and the public keys presented by those servers. NETCONF clients SHOULD implement the algorithm in Section 6 of [RFC5280] for general certificate validation, but MAY supplement that algorithm with other validation methods that achieve equivalent levels of verification (such as comparing the NETCONF server certificate against a local store of already-verified certificates and identity bindings). If the NETCONF client has external information as to the expected identity of the NETCONF server, the hostname check MAY be omitted. 2.4.2. Client Identity The NETCONF server MUST verify the identity of the NETCONF client to ensure that the incoming request to establish a NETCONF session is legitimate before the NETCONF session is started. The NETCONF protocol [RFC6241] requires that the transport protocol's authentication process MUST result in an authenticated NETCONF client identity whose permissions are known to the server. The authenticated identity of a client is commonly referred to as the NETCONF username. The username provided by the NETCONF over TLS implementation will be made available to the NETCONF message layer as the NETCONF username without modification. If the username does not comply to the NETCONF requirements on usernames [RFC6241], i.e., the username is not representable in XML, the TLS session MUST be dropped. 2.4.2.1. Deriving NETCONF Usernames from X.509 Certificates After completing the TLS handshake, the NETCONF server attempts to derive a NETCONF username from the X.509 certificate presented by the NETCONF client. If the NETCONF server cannot derive a valid NETCONF username from the presented certificate, then the NETCONF server MUST close the TLS connection, and MUST NOT accept NETCONF messages over it. The NETCONF server uses the algorithm defined in [I-D.ietf-netmod-snmp-cfg] to extract a NETCONF username from the X.509 certificate presented by the NETCONF client. The cert-to-name list in the ietf-netconf-server YANG module, defined in [I-D.kwatsen-netconf-server], specifies how a NETCONF server transforms a certificate into a NETCONF username. Badra, et al. Expires August 2, 2014 [Page 6] Internet-Draft NETCONF over TLS January 2014 2.5. Pre-Shared-Key-based Authentication, Identification and Authorization Implementations MAY optionally support TLS Pre-Shared Key (PSK) authentication [RFC4279]. RFC4279 describes pre-shared key ciphersuites for TLS. The description of the psk-maps container in the ietf-netconf-server YANG module, defined in [I-D.kwatsen-netconf-server], specifies how a NETCONF server associates a TLS pre-shared key with a NETCONF username. 2.6. Cipher Suites Implementations of the protocol specified in this document MAY implement any TLS cipher suite that provides mutual authentication [RFC5246]. However, implementations MUST support TLS 1.2 [RFC5246] and are REQUIRED to support the mandatory-to-implement cipher suite, which is TLS_RSA_WITH_AES_128_CBC_SHA. This document is assumed to apply to future versions of TLS; in which case, the mandatory-to- implement cipher suite for the implemented version MUST be supported. 3. Security Considerations The security considerations described throughout [RFC5246] and [RFC6241] apply here as well. This document in its current version does not support third-party authentication (e.g., backend Authentication, Authorization, and Accounting (AAA) servers) due to the fact that TLS does not specify this way of authentication and that NETCONF depends on the transport protocol for the authentication service. If third-party authentication is needed, SSH transport can be used. An attacker might be able to inject arbitrary NETCONF messages via some application that does not carefully check exchanged messages. When the :base:1.1 capability is not advertised by both peers, an attacker might be able to deliberately insert the delimiter sequence ]]>]]> in a NETCONF message to create a DoS attack. If the :base:1.1 capability is not advertised by both peers, applications and NETCONF APIs MUST ensure that the delimiter sequence ]]>]]> never appears in NETCONF messages; otherwise, those messages can be dropped, garbled, or misinterpreted. More specifically, if the delimiter sequence is found in a NETCONF message by the sender side, a robust implementation of this document SHOULD warn the user that illegal characters have been discovered. If the delimiter sequence is found in a NETCONF message by the receiver side (including any XML attribute values, XML comments, or processing instructions), a robust implementation of this document MUST silently discard the message Badra, et al. Expires August 2, 2014 [Page 7] Internet-Draft NETCONF over TLS January 2014 without further processing and then stop the NETCONF session. Finally, this document does not introduce any new security considerations compared to [RFC6242]. 4. IANA Considerations Based on the previous version of this document, RFC 5539, IANA has assigned a TCP port number (6513) in the "Registered Port Numbers" range with the service name "netconf-tls". This port will be the default port for NETCONF over TLS, as defined in Section 2.1.1. Below is the registration template following the rules in [RFC6335]. Service Name: netconf-tls Transport Protocol(s): TCP Assignee: IESG Contact: IETF Chair Description: NETCONF over TLS Reference: RFC XXXX Port Number: 6513 This document requests that IANA assigns a TCP port number in the "Registered Port Numbers" range with the service name "netconf-tls-ch". This port will be the default port for NETCONF over TLS when the NETCONF server calls home, as defined in Section 2.1.2. Below is the registration template following the rules in [RFC6335]. Service Name: netconf-tls-ch Transport Protocol(s): TCP Assignee: IESG Contact: IETF Chair Description: NETCONF over TLS (call home) Reference: RFC XXXX Port Number: YYYY 5. Acknowledgements A significant amount of the text in Section 2.4 was lifted from [RFC4642]. The authors like to acknowledge Martin Bjorklund, Olivier Coupelon, Badra, et al. Expires August 2, 2014 [Page 8] Internet-Draft NETCONF over TLS January 2014 Mehmet Ersue, Miao Fuyou, David Harrington, Alfred Hoenes, Simon Josefsson, Eric Rescorla, Dan Romascanu, Kent Watsen, Bert Wijnen and the NETCONF mailing list members for their comments on this document. Charlie Kaufman, Pasi Eronen, and Tim Polk provided a the thorough review of previous versions of this document. Stephen Hanna wrote the initial text for the applicability statement. Juergen Schoenwaelder and was partly funded by Flamingo, a Network of Excellence project (ICT-318488) supported by the European Commission under its Seventh Framework Programme. 6. Contributor's Address Ibrahim Hajjeh Ineovation France EMail: ibrahim.hajjeh@ineovation.fr 7. References 7.1. Normative References [I-D.ietf-netmod-snmp-cfg] Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for SNMP Configuration", draft-ietf-netmod-snmp-cfg-03 (work in progress), November 2013. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4279] Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)", RFC 4279, December 2005. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, May 2008. [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 Badra, et al. Expires August 2, 2014 [Page 9] Internet-Draft NETCONF over TLS January 2014 (PKIX) Certificates in the Context of Transport Layer Security (TLS)", RFC 6125, March 2011. [RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, June 2011. [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, June 2011. [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. Cheshire, "Internet Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number Registry", BCP 165, RFC 6335, August 2011. 7.2. Informative References [I-D.kwatsen-netconf-server] Watsen, K. and J. SchoeCnwaelder, "A YANG Data Model for NETCONF Server Configuration", draft-kwatsen-netconf-server-00 (work in progress), January 2014. [RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and Issues", RFC 3234, February 2002. [RFC4642] Murchison, K., Vinocur, J., and C. Newman, "Using Transport Layer Security (TLS) with Network News Transfer Protocol (NNTP)", RFC 4642, October 2006. [RFC4742] Wasserman, M. and T. Goddard, "Using the NETCONF Configuration Protocol over Secure SHell (SSH)", RFC 4742, December 2006. [RFC5539] Badra, M., "NETCONF over Transport Layer Security (TLS)", RFC 5539, May 2009. Appendix A. Change Log (to be removed by RFC Editor before publication) A.1. draft-ietf-netconf-rfc5539bis-05 o Removed the YANG configuration data model since it became a separate document. o Added reference to RFC 3234 plus editorial updates. Badra, et al. Expires August 2, 2014 [Page 10] Internet-Draft NETCONF over TLS January 2014 A.2. draft-ietf-netconf-rfc5539bis-04 o Added the applicability statement proposed by Stephen Hanna. o Added call-home configuration objects and a tls-call-home feature. o Rewrote the text such that the role swap happens right after the TCP connection has been established. A.3. draft-ietf-netconf-rfc5539bis-03 o Added support for call home (allocation of a new port number, rewrote text to allow a NETCONF client to be a TLS server and a NETCONF server to be a TLS client). o Merged sections 2 and 3 into a new section 2 and restructured the text. o Extended the IANA considerations section. o Using the cert-to-name mapping grouping from the SNMP configuration data model and updated the examples. o Creating an extensible set of YANG (sub)modules for NETCONF following the (sub)module structure of the SNMP configuration model. A.4. draft-ietf-netconf-rfc5539bis-02 o Addressed remaining issues identified at IETF 85 * Harmonized the cert-maps container of the YANG module in this draft with the tlstm container in the ietf-snmp-tls sub-module specified in draft-ietf-netmod-snmp-cfg. Replaced the children of the cert-maps container with the children copied from the tlstm container of the ietf-snmp-tls sub-module. * Added an overview of data model in the ietf-netconf-tls YANG module. * Added example configurations. o Addessed issues posted on NETCONF WG E-mail list. o Deleted the superfluous tls container that was directly below the netconf-config container. Badra, et al. Expires August 2, 2014 [Page 11] Internet-Draft NETCONF over TLS January 2014 o Added a statement to the text indicating that support for mapping X.509 certificates to NETCONF usernames is optional. This is analogous to existing text indicating that support for mapping pre-shared keys to NETCONF usernames is optional. Resource- constrained systems now can omit support for mapping X.509 certificates to NETCONF usernames and still comply with this specification. o Clarified the document structure by promoting the sections of the document related to the data model. o Updated author's addresses. A.5. draft-ietf-netconf-rfc5539bis-00 o Remove the reference to BEEP. o Rename host-part to domain-part in the description of RFC822. Authors' Addresses Mohamad Badra LIMOS Laboratory Email: mbadra@gmail.com Alan Luchuk SNMP Research, Inc. 3001 Kimberlin Heights Road Knoxville, TN 37920 US Phone: +1 865 573 1434 Email: luchuk@snmp.com URI: http://www.snmp.com/ Badra, et al. Expires August 2, 2014 [Page 12] Internet-Draft NETCONF over TLS January 2014 Juergen Schoenwaelder Jacobs University Bremen Campus Ring 1 28759 Bremen Germany Phone: +49 421 200 3587 Email: j.schoenwaelder@jacobs-university.de URI: http://www.jacobs-university.de/ Badra, et al. Expires August 2, 2014 [Page 13]