Network Working Group M. Wasserman Internet-Draft ThingMagic Expires: April 8, 2005 T. Goddard ICEsoft Technologies, Inc. October 8, 2004 Using the NETCONF Configuration Protocol over Secure Shell (SSH) draft-ietf-netconf-ssh-02.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. 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 become aware will be disclosed, in accordance with RFC 3668. 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 April 8, 2005. Copyright Notice Copyright (C) The Internet Society (2004). Abstract This document describes a simple method for invoking and running the NETCONF configuration protocol within a Secure Shell (SSH) session as an SSH subsystem. Wasserman & Goddard Expires April 8, 2005 [Page 1] Internet-Draft NETCONF over SSH October 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Starting NETCONF over SSH . . . . . . . . . . . . . . . . . . 3 2.1 Capabilities Exchange . . . . . . . . . . . . . . . . . . 4 3. Using NETCONF over SSH . . . . . . . . . . . . . . . . . . . . 5 4. Exiting the NETCONF Subsystem . . . . . . . . . . . . . . . . 6 5. Running NETCONF from an SSH Shell . . . . . . . . . . . . . . 7 5.1 Starting a NETCONF Shell Session . . . . . . . . . . . . . 7 5.2 Exiting a NETCONF Shell Session . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 9.1 Normative References . . . . . . . . . . . . . . . . . . . . 10 9.2 Informative References . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 11 Intellectual Property and Copyright Statements . . . . . . . . 13 Wasserman & Goddard Expires April 8, 2005 [Page 2] Internet-Draft NETCONF over SSH October 2004 1. Introduction The NETCONF protocol [I-D.ietf-netconf-prot] is an XML-based protocol used to manage the configuration of networking equipment. NETCONF is defined to be session-layer and transport independent, allowing mappings to be defined for multiple session-layer or transport protocols. This document defines how XMLCONF can be used within a Secure Shell (SSH) session, using the SSH connection protocol [I-D.ietf-secsh-connect] over the SSH transport protocol [I-D.ietf-secsh-transport]. This mapping will allow NETCONF to be executed from a secure shell session by a user or a simple script. Throughout this document, the terms "client" and "server" are used to refer to the two ends of the SSH transport connection. The client actively opens the SSH connection, and the server passively listens for the incoming SSH connection. The terms "manager" and "agent" are used to refer to the two ends of the NETCONF protocol session. The manager issues NETCONF RPC commands, and the agent replies to those commands. When NETCONF is run over SSH using the mapping defined in this document, the client is always the manager, and the server is always the agent. 2. Starting NETCONF over SSH To run NETCONF over SSH, the client will first establish an SSH transport connection using the SSH transport protocol, and the client and server will exchange keys for message integrity and encryption. The client will then invoke the "ssh-userauth" service to authenticate the user, as described in the SSH authentication protocol [I-D.ietf-secsh-userauth]. Once the user has been successfully authenticated, the client will invoke the "ssh-connection" service, also known as the SSH connection protocol. After the ssh-connection service is established, the client will open a channel of type "session", which will result in an SSH session. Once the SSH session has been established, the user (or script) will invoke NETCONF as an SSH subsystem called "netconf". Running NETCONF as an SSH subsystem avoids the need for the script to recognize shell prompts or skip over extraneous information, such as a system message that is printed at shell start-up. In order to allow NETCONF traffic to be easily identified and filtered by firewalls and other network devices, NETCONF servers MUST default to providing access to the "netconf" SSH subsystem only when the SSH session is established using the IANA-assigned TCP port . Servers SHOULD be configurable to allow access to the netconf SSH subsystem over other ports. Wasserman & Goddard Expires April 8, 2005 [Page 3] Internet-Draft NETCONF over SSH October 2004 To the user (or script), running NETCONF as an SSH subsystem may look similar to the following example. Although this example shows the text transmitted by both sides, the server MUST NOT echo the commands that it receives back to the client. [user@client]$ ssh -s server.example.org netconf Enter passphrase for key '/foo/.ssh/id_dsa': urn:ietf:params:xml:ns:netconf:base:1.0 urn:ietf:params:xml:ns:netconf:base:1.0#lock ]]>]]> urn:ietf:params:xml:ns:netconf:base:1.0 ]]>]]> While the NETCONF subsystem is active, the NETCONF manager can interact with the NETCONF agent by sending complete XML documents containing NETCONF RPC elements, and the NETCONF agent will respond by sending complete XML documents containing appropriate RPC replies. 2.1 Capabilities Exchange As indicated in the example above, the server MUST indicate its capabilities by sending an XML document containing a element as soon as the NETCONF session is established. The user (or the user's expect script) can parse this message to determine which NETCONF capabilities are supported by the server. Wasserman & Goddard Expires April 8, 2005 [Page 4] Internet-Draft NETCONF over SSH October 2004 The client must also send an XML document containing a element to indicate the client's capabilities to the server. The document containing the element must be the first XML document that the client sends after the NETCONF session is established. Although the example shows the server sending a $lt;hello> message followed by the client's message, both sides will send the message as soon as the NETCONF subsystem is initialized, perhaps simultaneously. 3. Using NETCONF over SSH A NETCONF over SSH session consists of the manager and agent exchanging complete XML documents. Once the session has been established and capabilities have been exchanged, the manager will send complete XML documents to the server containing elements, and the agent will respond with complete XML documents containing elements. As the previous example illustrates, a special character sequence, ]]>]]>, is sent after each XML document in the NETCONF exchange. This character sequence cannot legally appear in an XML document, so it can be unambigiously used to indentify the end of the current document in the event of an XML syntax or parsing error, allowing resynchronization of the NETCONF exchange. To continue the example given above, an XMLCONF over SSH session to retrieve a set of configuration information might look like this: Wasserman & Goddard Expires April 8, 2005 [Page 5] Internet-Draft NETCONF over SSH October 2004 ]]>]]> rootsuperuser fredadmin barneyadmin ]]>]]> 4. Exiting the NETCONF Subsystem Exiting NETCONF is accomplished using the operation. An agend will processed RPC messages from the manager in the order in which the are received. When the agent processes a command is, the agent shall respond, terminate the SSH session, and close the TCP connection. The agent MUST NOT process any RPC commands received on the current session after the command. To continue the example used in previous sections, an existing NETCONF subsystem session could be closed as follows: Wasserman & Goddard Expires April 8, 2005 [Page 6] Internet-Draft NETCONF over SSH October 2004 ]]>]]> [user@client]$ ]]>]]> 5. Running NETCONF from an SSH Shell The techniques described in this document could be used to access the NETCONF protocol over the SSH shell session, or from other shell types such as a console session or a Telnet [RFC0854] connection. However, there are serious security implications associated with allowing NETCONF access via any method that does not provide strong support for user authentication, server authentication and data privacy. See the Security Considerations section for more details. If the server supports NETCONF invocation from an SSH shell session, the user may choose to invoke a NETCONF program from the shell command line. This would involve using SSH to establish a shell session, and entering the name of a NETCONF program (with the full path, if necessary) at the remote shell prompt. 5.1 Starting a NETCONF Shell Session To the user, the establishment of an SSH shell and the invocation of the NETCONF program may look similar to the following example: Wasserman & Goddard Expires April 8, 2005 [Page 7] Internet-Draft NETCONF over SSH October 2004 [user@client]$ ssh server.example.org user@server.example.org's password: ******** [user@server]$ netconf http://ietf.org/xmlconf/1.0/base http://ietf.org/xmlconf/1.0/base#lock ]]>]]> 5.2 Exiting a NETCONF Shell Session When the user has run NETCONF from a shell, he will need to exit the NETCONF program using the operation, and then exit the remote shell to return to the local shell. To continue the example used in previous sections, an existing NETCONF shell session could be closed as follows: Wasserman & Goddard Expires April 8, 2005 [Page 8] Internet-Draft NETCONF over SSH October 2004 ]]>]]> ]]>]]> [user@server]$ exit [user@client]$ 6. Security Considerations NETCONF is used to access and modify configuration and state information, so the ability to access this protocol should be limited to users and systems that are authorized to view or modify the agent's configuration and state data. The identity of the server MUST be verified and authenticated by the client before password-based authentication data or any configuration data is sent to the server. The identity of the client MUST also be verified and authenticated by the server to ensure that the incoming client request is legitimate before any configuration or state data is sent to the client. Neither side should establish a NETCONF over SSH connection with an unknown, unexpected or incorrect identity on the opposite side. Configuration data may include sensitive information, such as usernames or security keys. So, NETCONF should only be used over communications channels that provide strong encryption for data privacy. This document defines a NETCONF over SSH mapping which provides for support of strong encryption and authentication. Wasserman & Goddard Expires April 8, 2005 [Page 9] Internet-Draft NETCONF over SSH October 2004 If the NETCONF server provides remote shell access through insecure protocols, such as Telnet, care should be taken to prevent execution of the NETCONF program when strong user authentication or data privacy is not available. Because it may be difficult or impossible in some operating environments to determine whether a shell command was accessed over a secure protocol such as SSH or an insecure protocol such as Telnet, it may be necessary to disable insecure shell access to the system to prevent insecure access to the NETCONF program. Alternatively, it would be possible to disable NETCONF access from the command line, only allowing NETCONF to be accessed through invocation of the SSH "netconf" subsystem. This document requires that servers default to allowing access to the "netconf" SSH subsystem only when using a specific TCP port assigned by IANA for this purpose. This will allow NETCONF over SSH traffic to be easily identified and filtered by firewalls and other network nodes. However, it will also allow NETCONF over SSH traffic to be more easily identified by attackers. This document also recommends that servers be configurable to allow access to the "netconf" SSH subsystem over other ports. Use of that configuration option without corresponding changes to firewall or network device configuration may unintentionally result in the ability for nodes outside of the firewall or other administrative boundary to gain access to "netconf" SSH subsystem. 7. IANA Considerations IANA is requested to assign a TCP port number which will be the default port for NETCONF over SSH sessions as defined in this document. 8. Acknowledgements This document was written using the xml2rfc tool described in RFC 2629 [RFC2629]. Extensive input was received from the members of the NETCONF design team, including: Andy Bierman, Weijing Chen, Rob Enns, Wes Hardaker, David Harrington, Eliot Lear, Simon Leinen, Phil Shafer, Juergen Schoenwaelder and Steve Waldbusser. The following people have also reviewed this document and provided valuable input: Bill Sommerfeld. 9. References 9.1 Normative References [I-D.ietf-netconf-prot] Wasserman & Goddard Expires April 8, 2005 [Page 10] Internet-Draft NETCONF over SSH October 2004 Enns, R., "NETCONF Configuration Protocol", draft-ietf-netconf-prot-03 (work in progress), June 2004. [I-D.ietf-secsh-connect] Ylonen, T., Kivinen, T., Rinne, T. and S. Lehtinen, "SSH Connection Protocol", draft-ietf-secsh-connect-19 (work in progress), June 2004. [I-D.ietf-secsh-transport] Ylonen, T. and C. Lonvick, "SSH Transport Layer Protocol", draft-ietf-secsh-transport-18 (work in progress), June 2004. [I-D.ietf-secsh-userauth] Ylonen, T. and C. Lonvick, "SSH Authentication Protocol", draft-ietf-secsh-userauth-21 (work in progress), June 2004. 9.2 Informative References [RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol Specification", STD 8, RFC 854, May 1983. [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, June 1999. [RFC3667] Bradner, S., "IETF Rights in Contributions", BCP 78, RFC 3667, February 2004. [RFC3668] Bradner, S., "Intellectual Property Rights in IETF Technology", BCP 79, RFC 3668, February 2004. Authors' Addresses Margaret Wasserman ThingMagic One Broadway, 14th Floor Cambridge, MA 02142 USA Phone: +1 617 758-4177 EMail: margaret@thingmagic.com URI: http://www.thingmagic.com Wasserman & Goddard Expires April 8, 2005 [Page 11] Internet-Draft NETCONF over SSH October 2004 Ted Goddard ICEsoft Technologies, Inc. Suite 300, 1717 10th St. NW Calgary, AB T2M 4S2 Canada Phone: +1 403 663-3322 EMail: ted.goddard@icesoft.com URI: http://www.icesoft.com Wasserman & Goddard Expires April 8, 2005 [Page 12] Internet-Draft NETCONF over SSH October 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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Disclaimer of Validity 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 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. Copyright Statement Copyright (C) The Internet Society (2004). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Wasserman & Goddard Expires April 8, 2005 [Page 13]