Extensible Provisioning Protocol (EPP) Transport Over TCP
The information below is for an old version of the document that is already published as an RFC.
This is an older version of an Internet-Draft that was ultimately published as RFC 3734.
|Last updated||2015-10-14 (Latest revision 2003-01-29)|
|RFC stream||Internet Engineering Task Force (IETF)|
|Additional resources||Mailing list discussion|
|IESG||IESG state||RFC 3734 (Proposed Standard)|
|Responsible AD||Ted Hardie|
|Send notices to||(None)|
Internet Engineering Task Force S. Hollenbeck Internet-Draft VeriSign, Inc. January 29, 2003 Expires: July 29, 2003 Extensible Provisioning Protocol Transport Over TCP <draft-ietf-provreg-epp-tcp-06.txt> Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. Abstract This document describes how an Extensible Provisioning Protocol (EPP) session is mapped onto a single Transmission Control Protocol (TCP) connection. This mapping requires use of the Transport Layer Security (TLS) protocol to protect information exchanged between an EPP client and an EPP server. 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]. Hollenbeck Expires July 29, 2003 [Page 1] Internet-Draft EPP TCP Transport January 29, 2003 Table of Contents 1. Introduction ................................................. 3 2. Session Management ........................................... 4 3. Message Exchange ............................................. 5 4. Data Unit Format ............................................. 7 5. Transport Considerations ..................................... 8 6. Internationalization Considerations .......................... 9 7. IANA Considerations .......................................... 9 8. Security Considerations ...................................... 10 9. Acknowledgements ............................................. 11 10. References .................................................. 11 11. Author's Address ............................................ 11 A. Revisions From Previous Version .............................. 12 B. Full Copyright Statement ..................................... 13 Hollenbeck Expires July 29, 2003 [Page 2] Internet-Draft EPP TCP Transport January 29, 2003 1. Introduction This document describes how the Extensible Provisioning Protocol (EPP) is mapped onto a single client-server TCP connection. Security services beyond those defined in EPP are provided by the Transport Layer Security (TLS) Protocol [RFC2246]. EPP is described in [EPP]. TCP is described in [RFC793]. Hollenbeck Expires July 29, 2003 [Page 3] Internet-Draft EPP TCP Transport January 29, 2003 2. Session Management Mapping EPP session management facilities onto the TCP service is straight forward. An EPP session first requires creation of a TCP connection between two peers, one that initiates the connection request and one that responds to the connection request. The initiating peer is called the "client", and the responding peer is called the "server". An EPP server MUST listen for TCP connection requests on a standard TCP port assigned by IANA. The client MUST issue an active OPEN call, specifying the TCP port number on which the server is listening for EPP connection attempts. The server MUST respond with a passive OPEN call, which the client MUST acknowledge to establish the connection. The EPP server MUST return an EPP <greeting> to the client after the TCP session has been established. An EPP session is normally ended by the client issuing an EPP <logout> command. A server receiving an EPP <logout> command MUST end the EPP session and close the TCP connection through an active CLOSE call. The client MUST respond with a passive CLOSE call. A client MAY end an EPP session by issuing an active CLOSE call. A server SHOULD respond with a passive CLOSE call. A server MAY limit the life span of an established TCP connection. EPP sessions that are inactive for more than a server-defined period MAY be ended by a server issuing an active CLOSE call. A server MAY also close TCP connections that have been open and active for longer than a server-defined period. Peers SHOULD respond to an active CLOSE call with a passive CLOSE call. The closing peer MAY issue an ABORT call if the responding peer does not respond to the active CLOSE call. Hollenbeck Expires July 29, 2003 [Page 4] Internet-Draft EPP TCP Transport January 29, 2003 3. Message Exchange With the exception of the EPP server greeting, EPP messages are initiated by the EPP client in the form of EPP commands. An EPP server MUST return an EPP response to an EPP command on the same TCP connection that carried the command. If the TCP connection is closed after a server receives and successfully processes a command but before the response can be returned to the client, the server MAY attempt to undo the effects of the command to ensure a consistent state between the client and the server. EPP commands are idempotent, so processing a command more than once produces the same net effect on the repository as successfully processing the command once. An EPP client streams EPP commands to an EPP server on an established TCP connection. A client MAY but SHOULD NOT establish multiple TCP connections to create multiple command exchange channels. A server SHOULD limit a client to a maximum number of TCP connections based on server capabilities and operational load. EPP describes client-server interaction as a command-response exchange where the client sends one command to the server and the server returns one response to the client. A client might be able to realize a slight performance gain by pipelining (sending more than one command before a response for the first command is received) commands with TCP transport, but this feature does not change the basic single command, single response operating mode of the core protocol. The amount of data that can be outstanding is limited to the current TCP window size. Each EPP data unit MUST contain a single EPP message. Commands MUST be processed independently and in the same order as sent from the client. A server SHOULD impose a limit on the amount of time required for a client to issue a well-formed EPP command. A server SHOULD end an EPP session and close an open TCP connection if a well-formed command is not received within the time limit. A general state machine for an EPP server is described in section 2 of [EPP]. General client-server message exchange using TCP transport is illustrated in Figure 1. Hollenbeck Expires July 29, 2003 [Page 5] Internet-Draft EPP TCP Transport January 29, 2003 Client Server | | | Connect | | >>------------------------------->> | | | | Send Greeting | | <<-------------------------------<< | | | | Send <login> | | >>------------------------------->> | | | | Send Response | | <<-------------------------------<< | | | | Send Command | | >>------------------------------->> | | | | Send Response | | <<-------------------------------<< | | | | Send Command X | | >>------------------------------->> | | | | Send Command Y | | >>---------------+ | | | | | | | | Send Response X | | <<---------------(---------------<< | | | | | | | | +--------------->> | | | | Send Response Y | | <<-------------------------------<< | | | | Send <logout> | | >>------------------------------->> | | | | Send Response & Disconnect | | <<-------------------------------<< | | | Figure 1: TCP Client-Server Message Exchange Hollenbeck Expires July 29, 2003 [Page 6] Internet-Draft EPP TCP Transport January 29, 2003 4. Data Unit Format The data field of the TCP header MUST contain an EPP data unit. The EPP data unit contains two fields: a 32-bit header that describes the total length of the data unit, and the EPP XML instance. EPP Data Unit Format (one tick mark represents one bit position): 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Total Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | EPP XML Instance | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+//-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Total Length (32 bits): The total length of the EPP data unit measured in octets in network (big endian) byte order. The octets contained in this field MUST be included in the total length calculation. EPP XML Instance (variable length): The EPP XML instance carried in the data unit. Hollenbeck Expires July 29, 2003 [Page 7] Internet-Draft EPP TCP Transport January 29, 2003 5. Transport Considerations Section 2.1 of the EPP core protocol specification [EPP] describes considerations to be addressed by protocol transport mappings. This mapping addresses each of the considerations using a combination of features described in this document and features provided by TCP as follows: - TCP includes features to provide reliability, flow control, ordered delivery, and congestion control. Section 1.5 of RFC 793 [RFC793] describes these features in detail; congestion control principles are described further in RFC 2581 [RFC2581] and RFC 2914 [RFC2914]. TCP is a connection-oriented protocol, and Section 2 of this mapping describes how EPP sessions are mapped to TCP connections. - Sections 2 and 3 of this mapping describe how the stateful nature of EPP is preserved through managed sessions and controlled message exchanges. - Section 3 of this mapping notes that command pipelining is possible with TCP, though batch-oriented processing (combining multiple EPP commands in a single data unit) is not permitted. - Section 4 of this mapping describes features to frame data units by explicitly specifying the number of octets used to represent a data unit. Hollenbeck Expires July 29, 2003 [Page 8] Internet-Draft EPP TCP Transport January 29, 2003 6. Internationalization Considerations This mapping does not introduce or present any internationalization or localization issues. 7. IANA Considerations Mapping EPP onto TCP requires a TCP port assignment from IANA for public operation. TCP port 3121 (a port number in the user port range) has been assigned by IANA for development and test purposes. A system port will need to be assigned, and this user port assignment will need to be reclaimed, if this document advances to RFC status. System Port number XXX - TBA by IANA. Hollenbeck Expires July 29, 2003 [Page 9] Internet-Draft EPP TCP Transport January 29, 2003 8. Security Considerations EPP as-is provides only simple client authentication services using identifiers and plain text passwords. A passive attack is sufficient to recover client identifiers and passwords, allowing trivial command forgery. Protection against most other common attacks MUST be provided by other layered protocols. EPP provides protection against replay attacks through command idempotency. A replayed or repeated command will not change the state of any object in any way, though denial of service through consumption of connection resources is a possibility. When layered over TCP, the Transport Layer Security (TLS) Protocol described in [RFC2246] MUST be used to prevent eavesdropping, tampering, and command forgery attacks. Implementations of TLS often contain a US-exportable cryptographic mode that SHOULD NOT be used to protect EPP. Clients and servers desiring high security SHOULD instead use TLS with cryptographic algorithms that are less susceptible to compromise. Mutual client and server authentication using the TLS Handshake Protocol is REQUIRED. Signatures on the complete certificate chain for both client machine and server machine MUST be validated as part of the TLS handshake. Information included in the client and server certificates, such as validity periods and machine names, MUST also be validated. EPP service MUST NOT be granted until successful completion of a TLS handshake and certificate validation, ensuring that both the client machine and the server machine have been authenticated and cryptographic protections are in place. Authentication using the TLS Handshake Protocol confirms the identity of the client and server machines. EPP uses an additional client identifier and password to identify and authenticate the client's user identity to the server, supplementing the machine authentication provided by TLS. The identity described in the client certificate and the identity described in the EPP client identifier can differ, as a server can assign multiple user identities for use from any particular client machine. EPP TCP servers are vulnerable to common TCP denial of service attacks including TCP SYN flooding. Servers SHOULD take steps to minimize the impact of a denial of service attack using combinations of easily implemented solutions, such as deployment of firewall technology and border router filters to restrict inbound server access to known, trusted clients. Hollenbeck Expires July 29, 2003 [Page 10] Internet-Draft EPP TCP Transport January 29, 2003 9. Acknowledgements This document was originally written as an individual submission Internet-Draft. The provreg working group later adopted it as a working group document and provided many invaluable comments and suggested improvements. The author wishes to acknowledge the efforts of WG chairs Edward Lewis and Jaap Akkerhuis for their process and editorial contributions. Specific suggestions that have been incorporated into this document were provided by Chris Bason, Randy Bush, Patrik Faltstrom, Ned Freed, James Gould, Dan Manley, and John Immordino. 10. References Normative References: [EPP] S. Hollenbeck: "Extensible Provisioning Protocol", work in progress. [RFC793] J. Postel: "Transmission Control Protocol", STD 7, RFC 793, September 1981. [RFC2119] S. Bradner: "Key Words for Use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2246] T. Dierks and C. Allen: "The TLS Protocol Version 1.0", RFC 2246, January 1999. [RFC2581] M. Allman et al.: "TCP Congestion Control", RFC 2581, April 1999. [RFC2914] S. Floyd: "Congestion Control Principles", BCP 41, RFC 2914, September 2000. Informative References: None 11. Author's Address Scott Hollenbeck VeriSign Global Registry Services 21345 Ridgetop Circle Dulles, VA 20166-6503 USA firstname.lastname@example.org Hollenbeck Expires July 29, 2003 [Page 11] Internet-Draft EPP TCP Transport January 29, 2003 A. Revisions From Previous Version (Note to RFC editor: please remove this section completely before publication as an RFC.) -05 to -06 (IESG review): Removed "This document is being discussed" paragraph from section 1. Modified MAY/SHOULD text in section 3, paragraph 2. More text in section 8 to describe the relationship between TLS authentication and EPP ID/password authentication. Added references to RFCs 2581 and 2914. Hollenbeck Expires July 29, 2003 [Page 12] Internet-Draft EPP TCP Transport January 29, 2003 B. Full Copyright Statement Copyright (C) The Internet Society 2002. All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Hollenbeck Expires July 29, 2003 [Page 13]