NETCONF Working Group Mohamad Badra Internet Draft LIMOS Laboratory Intended status: Standards Track
September 2,October 17, 2008 NETCONF over Transport Layer Security (TLS) draft-ietf-netconf-tls-04.txtdraft-ietf-netconf-tls-05.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on March 2,April 17, 2009. Copyright Notice Copyright (C) The IETF Trust (2008). 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 ProtocolSecurity (TLS) protocol to secure NETCONF exchanges. Table of Contents 1. Introduction...................................................3 1.1. Conventions used in this document.........................3 2. NETCONF over TLS...............................................3 2.1. Connection Initiation.....................................3 2.2. Connection Closure........................................4 3. Endpoint Authentication and Identification.....................4Identification.....................5 3.1. Server Identity...........................................5 3.2. Client Identity...........................................6 3.3. Pre-shared key Authentication.............................64. Cipher Suite Requirements......................................7 5.Security Considerations........................................7 6.Considerations........................................6 5. IANA Considerations............................................7 7.Considerations............................................6 6. Acknowledgments................................................7 8. References.....................................................8 8.1.7. References.....................................................7 7.1. Normative References......................................8References......................................7 Author's Addresses................................................8 Intellectual Property and Copyright Statement.....................8 1. Introduction The NETCONF protocol [RFC4741] defines a simplemechanism through which a network device can be managed. NETCONF is connection- oriented,connection-oriented, requiring a persistent connection between peers. This connection must provide reliable, sequenced data delivery, integrity and confidentiality and peers authentication. This document describes how to usedefines "NETCONF over TLS", which includes support for certificate-based mutual authentication and key derivation, utilizing the protected ciphersuite negotiation, mutual authentication and key management capabilities of the TLS [RFC5246] to secure NETCONF connections.(Transport Layer Security) protocol, described in [RFC5246]. Throughout this document, the terms "client" and "server" are used to refer to the two ends of the TLS connection. The client actively opens the TLS connection, and the server passively listens for the incoming TLS connection. The terms "manager" and "agent" are used to refer to the two ends of the NETCONF protocol session. The manager issues NETCONF remote procedure call (RPC) commands, and the agent replies to those commands. When NETCONF is run over TLS using the mapping defined in this document, the client is always the manager, and the server is always the agent. 1.1. Conventions used in this document 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 RFC-2119 [RFC2119]. 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 Transport Layer Security (TLS)TLS session. 2.1. Connection Initiation The peer acting as the NETCONF manager MUST also act as the TLS client. It MUST connect to the server that passively listens for the incoming TLS connection on the IANA-to-be-assignedTCP port <TBA>.<IANA-to-be-assigned>. (Note to RFC Editor: please replace <IANA-to-be-assigned> with the IANA- assigned value, and remove this note). It MUST therefore send the TLS ClientHello to begin the TLS handshake. Once the TLS handshake has beenfinished, the client and the server MAY then send theirbegin to exchange NETCONF exchanges.data. In particular, the client will send complete XML documents to the server containing <rpc> elements, and the server will respond with complete XML documents containing <rpc-reply> elements. The client MAY indicate interest in receiving event notifications from a NETCONFserver by creating a subscription to receive event notifications [RFC5277], in which the NETCONFserver replies to indicate whether the subscription request was successful and, if it was successful, begins sending the event notifications to the NETCONFclient as the events occur within the system. All these elements are encapsulated intoNETCONF messages MUST be sent as TLS records of type"application data". These records are protected using theIt is possible that multiple NETCONF messages be contained in one TLS material keys.record, or that a NETCONF message be transferred in multiple TLS records. Current NETCONF messages don't include a message's length. This document uses consequently the same delimiter sequence defined in [RFC4742] and therefore the special character sequence, ]]>]]>, to delimit XML documents. 2.2. Connection Closure Either NETCONF peer MAY stopImplementation of the NETCONF connection atprotocol specified in this document MAY implement any time and therefore notify the other NETCONF peerTLS cipher suite that no more data on this channel will be sentprovides certificate-based mutual authentication [RFC5246]. Implementations MUST support TLS 1.2 [RFC5246] and that any data received after a closure request will be ignored.are REQUIRED to support the mandatory to implement cipher suite, which is TLS_RSA_WITH_AES_128_CBC_SHA. This MAY happen when no datadocument is received from a connectionassumed to apply to future versions of TLS, in which case the mandatory to implement cipher suite for a long time, wherethe application decides what "long" means.implemented version MUST be supported. 2.2. Connection Closure A TLS hasclient (NETCONF manager) MUST close the ability for secureassociated TLS connection closure using the Alert protocol. When the NETCONF peer closesif the connection is not expected to issues any NETCONF connection, itRPC commands later. It MUST send a TLS close_notify alert before closing the TCPconnection. Any data received after a closure alert is ignored. Unless a fatal error has occurred, each party is requiredThe TLS client MAY choose to send anot wait for the TLS server (NETCONF agent) close_notify alert before closingand simply close the write side ofconnection, thus generating an incomplete close on the connection [RFC5246]. The other partyTLS server side. Once the TLS server gets a close_notify from the TLS client, it MUST respondreply with a close_notify alert of its own and close downunless it becomes aware that the connection immediately, discarding any pending writes. It is not required forhas already been closed by the initiator ofTLS client (e.g., the close to waitclosure was indicated by TCP). When no data is received from a connection for a long time (where the responding close_notify alert before closing the read side ofapplication decides what "long" means), a NETCONF peer MAY close the connection. 3. Endpoint Authentication and IdentificationThe NETCONF requires that its transport provide mutual authentication of client and server, so cipher suites that are anonymous or which only authenticate the server to the clientpeer MUST NOT be used with NETCONF. This document specifies howattempt to use TLSinitiate an exchange of close_notify alerts with endpoint authentication, which can be based on either preshared keys [RFC4279] or public key certificates [RFC5246]. Some cipher suites (e.g. TLS_RSA_PSK_WITH_AES_128_CBC_SHA) use both. Section 3.1 describes how the client authenticatesthe server if public key certificates are provided by the server, section 3.2 describes howother NETCONF peer before closing the server authenticatesconnection. The close_notify's sender that is unprepared to receive any more data MAY close the client if public key certificates are provided byconnection after sending the client, and section 3.3 describes howclose_notify alert, thus generating an incomplete close on the client and server mutually authenticate one another using a pre-shared key (PSK).close_notify's receiver side. 3. Endpoint Authentication and Identification 3.1. Server Identity During the TLS negotiation, the client MUST carefully examine the certificate presented by the server to determine if it meets their expectations. Particularly, the client MUST check its understanding of the server hostname against the server's identity as presented in the server Certificate message, in order to prevent man-in-the-middle attacks. Matching is performed according to thesethe rules [RFC4642]:below (following the example of [RFC4642]): - The client MUST use the server hostname it used to open the connection (or the hostname specified in TLS "server_name" extension [RFC4366]) as the value to compare against the server name as expressed in the server certificate. The client MUST NOT use any form of the server hostname derived from an insecure remote source (e.g., insecure DNS lookup). CNAME canonicalization is not done. - If a subjectAltName extension of type dNSName is present in the certificate, it MUST be used as the source of the server's identity. - Matching is case-insensitive. - A "*" wildcard character MAY be used as the left-most name component in the certificate. For example, *.example.com would match a.example.com, foo.example.com, etc., but would not match example.com. - If the certificate contains multiple names (e.g., more than one dNSName field), then a match with any one of the fields is considered acceptable. If the match fails, the client MUST either ask for explicit user confirmation or terminate the connection and indicate the server's identity is suspect. Additionally, clients MUST verify the binding between the identity of the servers to which they connect and the public keys presented by those servers. 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 server certificate against a local store of already-verified certificates and identity bindings). If the client has external information as to the expected identity of the server, the hostname check MAY be omitted. 3.2. Client Identity Typically, the server has no external knowledge of what the client's identity ought to be and so checks (other than that the client has a certificate chain rooted in an appropriate CA) are not possible. If a server has such knowledge (typically from some source external to NETCONF or TLS) it MUST check the identity as described above. 3.3. Pre-shared key Authentication [RFC4279] supports authentication based on pre-shared keys (PSKs). These pre-shared keys are symmetric keys, shared in advance among the communicating parties. The PSK can be generated in many ways and its length is variable. It is RECOMMENDED that implementations that allow the administrator to manually configure the PSK also provide functionality for generating a new random PSK, taking [RFC4086] into account. If both the client and the server agree on using the pre-shared key authentication, the server can provide a "PSK identity hint" in the ServerKeyExchange message. If a hint is provided, the psk_identity_hint is encoded in the same way as in [RFC4279] and should be a string representation of the name of the server recognizable to the administrator or his software. In the case where the user types a server name to connect to, it should be that string. If the string the user enters differs from the one returned as psk_identity_hint, the software could display the server's name and ask the user to confirm. For automated scripts, the names could be expected to match. It is highly recommended that implementations set the psk_identity_hint to the DNS name of the NETCONF server (i.e., the TLS server). It is RECOMMENDED that users choose different PSKs for the different servers they manage. [RFC4279] defines some conformance requirements for the PSK, for the PSK identity encoding and for the identity hint. Moreover, it describes the management interface requirements for entering the PSK and/or PSK identity (See Section 5 of [RFC4279] for a more detailed description of these requirements). Those same requirements apply here as well.4. Cipher Suite Requirements A compliant implementation of the protocol specified in this document MUST implement the cipher suite TLS_DHE_PSK_WITH_AES_128_CBC_SHA and MAY implement any TLS cipher suite that provides mutual authentication. 5.Security Considerations The security considerations described throughout [RFC5246] and [RFC4279]apply here as well. This document in its current version doesn't support third party authentication due to the fact that TLS doesn't specify this way of authentication and that NETCONF depends on the transport protocol for the authentication service. If third party authentication is needed, BEEP or SSH transport can be used. As with all schemes involving shared keys, special care should be taken to protect the shared secret as well as to limit its exposure over time. Alternatively, using certificates would provide better protection. 6.5. IANA Considerations IANA is requested to assign a TCP port number thatin the "Registered Port Numbers" range with the name "netconf-tls". This port will be the default port for NETCONF over TLS sessionsTLS, as defined in this document. IANA has assigned port <TBA> for this purpose. 7.Registration Contact: Mohamad Badra, firstname.lastname@example.org. Transport Protocol: TCP. Port Number: TBA-by-IANA (if possible, please assign 6513). Broadcast, Multicast or Anycast: Anycast. Port Name: netconf-tls. Service Name: netconf. Reference: draft-ietf-netconf-tls-05. 6. Acknowledgments A significant amount of the text in Section 3.13 was lifted from [RFC4642]. The author would like to acknowledge David Harrington, Miao Fuyou, Eric Rescorla, Juergen Schoenwaelder, Simon Josefsson, Olivier Coupelon and the NETCONF mailing list members for their comments on the document. The author appreciates also Bert Wijnen, Mehmet Ersue and Dan Romascanu for their efforts on issues resolving discussion, and Charlie Kaufman, Pasi Eronen and Tim Polk for the thorough review of this document. 8.7. References 22.214.171.124. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4086] Eastlake, D., 3rd, Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005. [RFC4279] Eronen, P. and H. Tschofenig., "Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)", RFC 4279, December 2005.[RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., and T. Wright, "Transport Layer Security (TLS) Extensions", RFC 4366, April 2006. [RFC4642] Murchison, K., Vinocur, J., Newman, C., "Using Transport Layer Security (TLS) with Network News Transfer Protocol (NNTP)", RFC 4642, October 2006 [RFC4741] Enns, R., "NETCONF Configuration Protocol", RFC 4741, December 2006. [RFC4742] Wasserman, M. and T. Goddard, "Using the NETCONF Configuration Protocol over Secure Shell (SSH)", RFC 4742, December 2006. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol 1.2", RFC5246, August 2008. [RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event Notifications", RFC 5277, July 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. Author's Addresses Mohamad Badra LIMOS Laboratory - UMR6158, CNRS France Email: email@example.com Contributors Ibrahim Hajjeh INEOVATION France Email: firstname.lastname@example.orgIbrahim.email@example.com Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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