NETCONF Working Group M. Badra Internet-Draft DU Obsoletes: 5539 (if approved) February 13, 2012 Intended status: Standards Track Expires: August 16, 2012 NETCONF Over Transport Layer Security (TLS) draft-badra-netconf-rfc5539bis-01 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 NETCONF exchanges. This document obsoletes RFC 5539. 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 16, 2012. Copyright Notice Copyright (c) 2012 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 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 Badra Expires August 16, 2012 [Page 1] Internet-Draft NETCONF over TLS February 2012 described in the Simplified BSD License. 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, Identification and Authorization . . 5 3.1. Server Identity . . . . . . . . . . . . . . . . . . . . . 5 3.2. Client Identity . . . . . . . . . . . . . . . . . . . . . 6 3.2.1. Deriving NETCONF Usernames From NETCONF Client Certificates . . . . . . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . 16 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 7. Contributor's Address . . . . . . . . . . . . . . . . . . . . 18 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8.1. Normative References . . . . . . . . . . . . . . . . . . . 18 8.2. Informative References . . . . . . . . . . . . . . . . . . 19 Appendix A. Change Log (to be removed by RFC Editor before publication) . . . . . . . . . . . . . . . . . . . . 19 A.1. From -00 to -01 . . . . . . . . . . . . . . . . . . . . . 19 A.2. From RFC5539 to draft-badra-netconf-rfc5539bis-00 . . . . 19 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 20 Badra Expires August 16, 2012 [Page 2] Internet-Draft NETCONF over TLS February 2012 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]. 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 [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 TLS session. 2.1. Connection Initiation The peer acting as the NETCONF client MUST also act as the TLS client. It MUST connect to the server that passively listens for the incoming TLS connection on the TCP port 6513. It 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 data. In particular, the client will send complete XML documents to the server containing elements, and the server will respond with complete XML documents containing elements. The client MAY indicate interest in receiving event notifications from a server by creating a subscription to receive event notifications [RFC5277]. In this case, the server replies to indicate whether the subscription request was successful and, if it was successful, the server begins sending the event notifications to the client as the events occur within the system. 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. Badra Expires August 16, 2012 [Page 3] Internet-Draft NETCONF over TLS February 2012 The previous version [RFC5539] of this document used the same framing sequence defined in [RFC6242], 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, and at the same time be compatible with existing implementations, this document uses the framing protocol defined in [RFC6242] as following : 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. Implementation of the protocol specified in this document MAY implement any TLS cipher suite that provides mutual authentication [RFC5246]. 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. 2.2. Connection Closure A TLS client MUST close the associated TLS connection if the connection is not expected to issue any NETCONF RPC commands later. It MUST send a TLS close_notify alert before closing the connection. The TLS client MAY choose to not wait for the TLS server close_notify alert and simply close the connection, thus generating an incomplete close on the TLS server side. Once the TLS server gets a close_notify from the TLS client, it MUST reply with a close_notify unless it becomes aware that the connection has already been closed by the TLS client (e.g., the closure was indicated by TCP). When no data is received from a connection for a long time (where the application decides what "long" means), a NETCONF peer MAY close the connection. The NETCONF peer MUST attempt to initiate an exchange of close_notify alerts with the other NETCONF peer before closing the connection. The close_notify's sender that is unprepared to receive any more data MAY close the connection after sending the close_notify alert, thus generating an incomplete close on the close_notify's receiver side. Badra Expires August 16, 2012 [Page 4] Internet-Draft NETCONF over TLS February 2012 3. Endpoint Authentication, Identification and Authorization 3.1. Server Identity During the TLS negotiation, the client MUST carefully examine the certificate presented by the server to determine if it meets the client's 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 the rules below (following the example of [RFC4642]): o The client MUST use the server hostname it used to open the connection (or the hostname specified in the TLS "server_name" extension [RFC5246]) 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. o If a subjectAltName extension of type dNSName is present in the certificate, it MUST be used as the source of the server's identity. o Matching is case-insensitive. o A "*" wildcard character MAY be used as the leftmost name component in the certificate. For example, *.example.com would match a.example.com, foo.example.com, etc., but would not match example.com. o 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 Badra Expires August 16, 2012 [Page 5] Internet-Draft NETCONF over TLS February 2012 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 The server MUST verify the identity of the client to ensure that the incoming client request is legitimate before any configuration or state data is sent to or received from the client. The NETCONF protocol [RFC6241] requires that the transport protocol's authentication process MUST result in an authenticated 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 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. Algorithms for mapping certificates or PSK identities (sent by the client) to NETCONF usernames are described below. 3.2.1. Deriving NETCONF Usernames From NETCONF Client Certificates The algorithm for deriving NETCONF usernames from TLS certificates is patterned after the algorithm for deriving tmSecurityNames from TLS certificates specified in Transport Layer Security (TLS) Transport Model for the Simple Network Management Protocol (SNMP) [RFC6353]. The NETCONF server MUST implement the algorithms for deriving NETCONF usernames from presented certificates that are documented in the ietf-netconf-tls YANG module. This YANG module lets the NETCONF security administrator configure how the NETCONF server derives NETCONF usernames from presented certificates. It also lets different certificate-to-username derivation algorithms be used for different certificates. When a NETCONF server accepts a TLS connection from a NETCONF client, the NETCONF server attempts to derive a NETCONF username from the certificate presented by the NETCONF client. If the NETCONF server cannot derive a valid NETCONF username from the client's presented certificate, then the NETCONF server MUST close the TLS connection, and MUST NOT accept NETCONF messages over it. The NETCONF server MAY use any of the following algorithms to produce the NETCONF username from the certificate presented by the NETCONF client: Badra Expires August 16, 2012 [Page 6] Internet-Draft NETCONF over TLS February 2012 o Map a certificate directly to a specified, pre-configured, NETCONF username; o Extract the subjectAltName's rfc822Name from the certificate, then use the extracted rfc822Name as the NETCONF username; o Extract the subjectAltName's dnsName from the certificate, then use the extracted dnsName as the NETCONF username; o Extract the subjectAltName's iPAddress from the certificate, then use the extracted iPAddress as the NETCONF username; o Examine the subjectAltName's rfc822Name, dnsName, and iPAddress fields in a pre-defined order. Return the value from the first subjectAltName field that is examined, defined, and populated with a non-empty value. If no subjectAltName field of a specific type is defined, then the examination skips that field and proceeds to examine the next field type. If a subjectAltName field is defined, but the value is not populated, or is populated by an empty value, then the examination skips that field and proceeds to examine the next field type. The NETCONF server MUST implement all of these algorithms, and allow the deployer to choose the algorithm used. The certificate-to- username-transforms container in the ietf-netconf-tls YANG module specifies how a NETCONF server transforms a certificate into a NETCONF username. 3.2.1.1. Identifying a Certificate A client certificate has an identity: the certificate. The TLS and corresponding protocols provide an identity. The identity shows that "this client certificate has shown that it, indeed, is on the other side of the connection". With a complete certificate, the certificate receiver can be certain that for someone or something on the other side to use that certificate successfully, it has the associated private key. The problem with using the entire certificates as the identity is that they are difficult for people to use. It is generally accepted that a fingerprint of a certificate is not likely to come up with a collision against a fingerprint of another (different) certificate. Thus, assuming a good hash algorithm, a fingerprint can be a safe short-hand for identifying a certificate. If a locally held copy of a trusted CA certificate is configured in the transformation container, and that CA certificate was used to validate the path to the presented certificate, then the NETCONF Badra Expires August 16, 2012 [Page 7] Internet-Draft NETCONF over TLS February 2012 server SHOULD use that list entry in the transformation container. All presented certificates validated by the configured CA certificate will be transformed to NETCONF usernames using the same transformation algorithm. 3.2.1.2. Deriving NETCONF Usernames From PSK identities Implementations MAY optionally support TLS Pre-Shared Key (PSK) authentication [RFC4279]. RFC4279 describes pre-shared key ciphersuites for TLS. During the TLS Handshake, the client indicates which key to use by including a "PSK identity" in the TLS ClientKeyExchange message [RFC4279]. On the server side, this PSK identity is used to look up the key corresponding to the presented PSK identity. If the selected pre-shared keys match and the key is valid, then the client is authenticated and the NETCONF username associated with the PSK identity. For details on how the PSK identity MAY be encoded in UTF-8, see section 5.1. of RFC [RFC6241]. 3.2.1.3. Remote Configuration The ietf-netconf-tls YANG module defines objects for remotely configuring the mapping of TLS certficates and of PSK Identities to NETCONF usernames. module ietf-netconf-tls { namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-tls"; prefix "nctls"; import ietf-yang-types { prefix yang; } organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: WG List: WG Chair: Mehmet Ersue WG Chair: Bert Wijnen Badra Expires August 16, 2012 [Page 8] Internet-Draft NETCONF over TLS February 2012 Editor: Mohamad Badra "; description "This module applies to NETCONF over TLS. It specifies how NETCONF servers transform X.509 certificates presented by clients into NETCONF usernames. It also specifies how NETCONF clients transform NETCONF usernames into X.509 certificates for presentation to NETCONF servers. This YANG module is patterned after, and closely models, parts of the SNMP-TLS-TM-MIB defined in RFC 6353. Much of the description text has been copied directly from the SNMP-TLS-TM-MIB, and modified as necessary. Copyright (c) 2012 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices."; // RFC Ed.: replace XXXX with actual RFC number and // remove this note // RFC Ed.: please update the date to the date of publication revision "2012-02-13" { description "Initial version"; reference "RFC XXXX: NETCONF over Transport Layer Security (TLS)"; } typedef tls-fingerprint-type { type binary { length "0..255"; } description "A fingerprint value that can be used to uniquely reference other data of potentially arbitrary length. An tls-fingerprint-type value is composed of a 1-octet hashing Badra Expires August 16, 2012 [Page 9] Internet-Draft NETCONF over TLS February 2012 algorithm identifier followed by the fingerprint value. The octet value encoded is taken from the IANA TLS HashAlgorithm Registry (RFC 5246). The remaining octets are filled using the results of the hashing algorithm. This typedef allows for a zero-length (blank) tls-fingerprint-type value for use in containers where the fingerprint value MAY be optional. YANG definitions or implementations MAY refuse to accept a zero-length value as appropriate."; } // // Objects related to deriving NETCONF usernames from X.509 certificates. // leaf certificate-to-username-transform-count { type yang:gauge32; description "A count of the number of certificate-to-username-transforms."; config false; } leaf certificate-to-username-transform-last-changed { type yang:date-and-time; description "The date and time when the certificate-to-username-transforms was last modified through any means. The value 0 means the certificate-to-username-transforms has not been modified since the NETCONF server was started."; config false; } container certificate-to-username-transforms { config true; description "This container is used by a NETCONF server to map the NETCONF client's presented X.509 certificate to a NETCONF username. On an incoming TLS connection, the client's presented certificate MUST either be validated based on an established trust anchor, or it MUST directly match a fingerprint in this container. This container does not provide any mechanisms for configuring the trust anchors; the transfer of any needed trusted certificates for path validation is expected to occur through an out-of-band transfer. Once the certificate has been found acceptable (either by path validation or directly matching a fingerprint in this container), this container is consulted to determine the appropriate Badra Expires August 16, 2012 [Page 10] Internet-Draft NETCONF over TLS February 2012 NETCONF username to associate with the remote connection. This is done by considering each active list entry from this container in prioritized order according to its index value. Each list entry's certificate-fingerprint value determines whether the list entry is a match for the incoming connection: 1) If the list entry's certificate-fingerprint value matches that of the presented certificate, then consider the list entry as a successful match. 2) If the list entry's certificate-fingerprint value matches that of a locally held copy of a trusted CA certificate, and that CA certificate was used to validate the path to the presented certificate, then consider the list entry as a successful match. This feature lets the NETCONF server derive NETCONF usernames from all certificates signed by the trusted CA certificate. The NETCONF server will derive all NETCONF usernames using the same derivation algorithm. The NETCONF server requires only a single container entry to configure this behavior. Once a matching list entry has been found, the NETCONF server uses the map-type value to determine how the NETCONF username associated with the session should be determined. See the map- type leaf's description for details on determining the NETCONF username value. If it is impossible to determine a NETCONF username from the list entry's data combined with the data presented in the certificate, then additional list entries MUST be searched looking for another potential match. If a resulting NETCONF username mapped from a given list entry is not compatible with the needed requirements of a NETCONF username, then it MUST be considered an invalid match and additional list entries MUST be searched looking for another potential match. If no matching and valid list entry can be found, then the NETCONF server MUST close the connection, and MUST NOT accept NETCONF messages over it. Non-consecutive values of index are acceptable and implementations should continue to the next highest numbered list entry. It is recommended that administrators skip index values to leave room for the insertion of future list entries (for example, use values of 10 and 20 when creating initial list entries). Security administrators are encouraged to make use of certificates Badra Expires August 16, 2012 [Page 11] Internet-Draft NETCONF over TLS February 2012 with subjectAltName fields that can be used as NETCONF usernames so that a single root CA certificate can allow all child certificate's subjectAltName to map directly to a NETCONF usernames via a 1:1 transformation. However, this container is flexible to allow for situations where existing deployed certificate infrastructures do not provide adequate subjectAltName values for use as NETCONF usernames."; // Certificates MAY also be mapped to NETCONF usernames using the // CommonName portion of the Subject field. However, the usage // of the CommonName field is deprecated and thus this usage is // NOT RECOMMENDED. Direct mapping from each individual // certificate fingerprint to a NETCONF username is also possible // but requires one entry in the container per NETCONF username and // requires more management operations to completely configure a // device."; list certificate-to-username-transform { key "index"; description "A single list entry that specifies a mapping for an incoming TLS certificate to a NETCONF username."; leaf index { type uint32 { range "1..4294967295"; } description "A unique, prioritized index for the given entry. Lower numbers indicate a higher priority."; } leaf certificate-fingerprint { type tls-fingerprint-type { length "1..255"; } description "A cryptographic hash of a X.509 certificate. The results of a successful matching fingerprint to either the trusted CA in the certificate validation path or to the certificate itself is dictated by the map-type leaf."; } leaf map-type { type enumeration { enum specified { value 1; } enum rfc822Name { value 2; } enum dnsName { value 3; } Badra Expires August 16, 2012 [Page 12] Internet-Draft NETCONF over TLS February 2012 enum ipAddress { value 4; } enum rfc822Name-dnsName-ipAddress { value 5; } enum rfc822Name-ipAddress-dnsName { value 6; } enum dnsName-ipAddress-rfc822Name { value 7; } enum dnsName-rfc822Name-ipAddress { value 8; } enum ipAddress-dnsName-rfc822Name { value 9; } enum ipAddress-rfc822Name-dnsName { value 10; } } description "Specifies the algorithm for deriving a NETCONF username from a certificate. If a mapping succeeds, then it will return a NETCONF username. If the resulting mapped value is not compatible with the needed requirements of a NETCONF username, then future list entries MUST be searched for additional NETCONF username matches to look for a mapping that succeeds. For each enumerated value listed above, the NETCONF server derives the NETCONF from the presented client certificate as described: specified Directly specifies the NETCONF username to be used for this certificate. The value of the NETCONF username to use is specified in the data leaf of the list. The data leaf MUST contain a non-zero length value or the mapping described in this list entry MUST be considered a failure. rfc822Name Maps a subjectAltName's rfc822Name to a NETCONF username. The local part of the rfc822Name is passed unaltered but the host-part of the name MUST be passed in lowercase. This mapping results in a 1:1 correspondence between equivalent subjectAltName rfc822Name values and NETCONF username values except that the host-part of the name MUST be passed in lowercase. Example rfc822Name Field: FooBar@Example.COM is mapped to NETCONF username: FooBar@example.com. dnsName Maps a subjectAltName's dNSName to a NETCONF username after Badra Expires August 16, 2012 [Page 13] Internet-Draft NETCONF over TLS February 2012 first converting it to all lowercase (RFC 5280 does not specify converting to lowercase so this involves an extra step). This mapping results in a 1:1 correspondence between subjectAltName dNSName values and the NETCONF username values. reference: RFC 5280 - Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile. ipAddress Maps a subjectAltName's iPAddress to a NETCONF username by transforming the binary encoded address as follows: 1) for IPv4, the value is converted into a decimal-dotted quad address (e.g., '192.0.2.1'). 2) for IPv6 addresses, the value is converted into a 32-character all lowercase hexadecimal string without any colon separators. This mapping results in a 1:1 correspondence between subjectAltName iPAddress values and the NETCONF username values. rfc822Name-dnsName-ipAddress rfc822Name-ipAddress-dnsName dnsName-ipAddress-rfc822Name dnsName-rfc822Name-ipAddress ipAddress-dnsName-rfc822Name ipAddress-rfc822Name-dnsName For each of these enumerations, the NETCONF server derives the NETCONF username in a similar manner. The NETCONF server derives the NETCONF username from the subjectAltName fields rfc822Name, dnsName, and ipAddress, as described in sections above. However, each of these subjectAltName fields is examined in the order specified by the enumeration name. The first matching subjectAltName value found in the certificate MUST be used when deriving the NETCONF username. For example, the rfc822Name-dnsName-ipAddress enumeration specifies the NETCONF server first examines the rfc822Name, then examines the dnsName, then finally examines the ipAddress. In contrast, the ipAddress-rfc822Name-dnsName enumeration specifies the NETCONF server first examines the ipAddress name, then examines the rfc822Name, then finally examines the dnsName. Badra Expires August 16, 2012 [Page 14] Internet-Draft NETCONF over TLS February 2012 These mappings result in a 1:1 correspondence between subjectAltName values and NETCONF username values. The sub-mapping algorithms produced by these combined algorithms cannot produce conflicting results between themselves."; } // leaf map-type leaf data { type string { length "1..max"; } description "Auxiliary data used as optional configuration information for a given mapping specified by the map-type leaf. Only some mapping systems will make use of this leaf. When the NETCONF server derives the NETCONF username from the client's presented certificate, the value in this leaf MUST be ignored for any mapping type that does not require data present in this leaf."; } } // list certificate-to-username-transform } // container certificate-to-username-transform container psk-map { list psk { key psk-identity; leaf psk-identity { type string; description "The PSK identity encoded as a UTF-8 string."; reference "RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)"; } leaf user-name { type nacm:user-name-type; mandatory true; description "The NETCONF username associated with this PSK identity."; } leaf valid-not-before { type yang:date-and-time; description "This PSK identity is not valid before the given data and time."; } Badra Expires August 16, 2012 [Page 15] Internet-Draft NETCONF over TLS February 2012 leaf valid-not-after { type yang:date-and-time; description "This PSK identity is not valid before the given data and time."; } leaf key { type binary; nacm:default-deny-all; description "The key associated with the PSK identity"; } } } // container psk-identity-to-username-transform } 4. 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, BEEP or 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 without further processing and then stop the NETCONF session. Badra Expires August 16, 2012 [Page 16] Internet-Draft NETCONF over TLS February 2012 Finally, this document does not introduce any new security considerations compared to [RFC6242]. 5. 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 name "netconf-tls". This port will be the default port for NETCONF over TLS, as defined in this document. Registration Contact: Mohamad Badra, mbadra@gmail.com. Transport Protocol: TCP. Port Number: 6513 Broadcast, Multicast or Anycast: No. Port Name: netconf-tls. Service Name: netconf. Reference: RFC 5539 6. Acknowledgements A significant amount of the text in Section 3 was lifted from [RFC4642]. The author would like to acknowledge David Harrington, Miao Fuyou, Eric Rescorla, Juergen Schoenwaelder, Simon Josefsson, Olivier Coupelon, Alfred Hoenes, and the NETCONF mailing list members for their comments on the document. The author also appreciates 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 previous versions of this document. Badra Expires August 16, 2012 [Page 17] Internet-Draft NETCONF over TLS February 2012 7. Contributor's Address Ibrahim Hajjeh Ineovation France EMail: ibrahim.hajjeh@ineovation.fr Alan Luchuk SNMP Research, Inc. 3001 Kimberlin Heights Road Knoxville, TN 37920-9716 EMail: luchuk@snmp.com Juergen Schoenwaelder Jacobs University Bremen Campus Ring 1 28725 Bremen Germany EMail: j.schoenwaelder@jacobs-university.de 8. References 8.1. Normative References [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. [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, June 2011. [RFC6353] Hardaker, W., "Transport Layer Security (TLS) Transport Model for the Simple Network Management Protocol (SNMP)", Badra Expires August 16, 2012 [Page 18] Internet-Draft NETCONF over TLS February 2012 RFC 6353, July 2011. 8.2. Informative References [RFC4642] Murchison, K., Vinocur, J., and C. Newman, "Using Transport Layer Security (TLS) with Network News Transfer Protocol (NNTP)", RFC 4642, October 2006. [RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event Notifications", RFC 5277, July 2008. [RFC5539] Badra, M., "NETCONF over Transport Layer Security (TLS)", RFC 5539, May 2009. [RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, June 2011. Appendix A. Change Log (to be removed by RFC Editor before publication) A.1. From -00 to -01 o Move RFC5539 to informative references and remove RFC4742. o Shorten the YANG object names; o Extend the YANG module to support configuration of PSK; A.2. From RFC5539 to draft-badra-netconf-rfc5539bis-00 o Added text on how the generation of a NETCONF username is done. o Added text on how does this document fulfill the requirements in 6241 for the format of the username. o Removed unneeded wording about client/server, and changed use of client/server, manager/agent to SSH client/server and NETCONF client/server. o Added text to Security Considerations about EOM issues. o Added option for the chunked encoding described in RFC6242. o Added 1.1 capability to enable the chunked encoding described in RFC6242. Badra Expires August 16, 2012 [Page 19] Internet-Draft NETCONF over TLS February 2012 Author's Address Mohamad Badra Dhofar University Email: mbadra@gmail.com Badra Expires August 16, 2012 [Page 20]