RFC 4934
Extensible Provisioning Protocol (EPP) Transport Over TCP
RFC 4934: Extensible Provisioning Protocol (EPP) Transport over TCP 🎀
okay bestie, so this is RFC 4934 💖 It's a Standards Track doc, which means it's an actual Internet standard and not just vibes ✨. S. Hollenbeck from VeriSign, Inc. wrote it for the Network Working Group, and it dropped in May 2007 🧚. It obsoletes RFC 3734, so this is the glow-up version 💅. The header doesn't list any RFCs it updates.
Status of This Memo 📜
okay so this section says this is an Internet standards track protocol 🦋 for the whole Internet community, and it's literally asking for discussion and suggestions for improvements 💜. If you want the standardization state and status of this protocol, check the current edition of the "Internet Official Protocol Standards" (STD 1) 🔍. And distribution of this memo is unlimited 🌈.
Copyright Notice ⭐
Copyright (C) The IETF Trust (2007). ngl that's the whole legal flex 💅
Abstract 🌸
tea time ☕ This doc explains how an EPP session gets mapped onto one single TCP connection 🔥. That mapping requires using TLS to protect the info swapped between an EPP client and an EPP server 🔒. And it obsoletes RFC 3734 🙈.
Table of Contents 📚
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions Used in This Document . . . . . . . . . . . . . 2
2. Session Management . . . . . . . . . . . . . . . . . . . . . . 2
3. Message Exchange . . . . . . . . . . . . . . . . . . . . . . . 2
4. Data Unit Format . . . . . . . . . . . . . . . . . . . . . . . 5
5. Transport Considerations . . . . . . . . . . . . . . . . . . . 5
6. Internationalization Considerations . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . . 8
Appendix A. Changes from RFC 3734 . . . . . . . . . . . . . . . . 91. Introduction ✨
so this doc is about how EPP gets mapped onto a single client-server TCP connection 🧚. Extra security beyond what EPP already defines comes from the Transport Layer Security (TLS) Protocol [RFC2246] 🔐. EPP itself is described in [RFC4930], and TCP is described in [RFC0793] 📚. And yep, this one obsoletes RFC 3734 [RFC3734] 💜.
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. Session Management 🦋
mapping session management onto TCP is lowkey straightforward 💅 An EPP session starts with creating a TCP connection between two peers. One peer initiates the connection request, and the other one responds to it. The initiator is called the "client" and the responder 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 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 with a CLOSE call. A client MAY end an EPP session by issuing a 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 a CLOSE call. A server MAY also close TCP connections that have been open and active for longer than a server-defined period 🙈
3. Message Exchange 💌
except for the EPP server greeting, EPP messages are kicked off 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 gets closed after a server receives and successfully processes a command but before the response can make it back to the client, the server MAY attempt to undo the effects of the command so the client and server stay in a consistent state 🔄 EPP commands are idempotent, so processing a command more than once produces the same net effect on the repository as processing it once 🍓
An EPP client streams EPP commands to an EPP server on an established TCP connection 🌊 A client MUST NOT distribute commands from a single EPP session over multiple TCP connections 🚫 A client MAY establish multiple TCP connections to support multiple EPP sessions, with each session mapped to a single connection ✨ 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 get a slight performance gain by pipelining commands with TCP transport (sending more than one command before a response for the first command is received). But this feature does not change the basic single command, single response operating mode of the core protocol 🦋
Each EPP data unit MUST contain a single EPP message. Commands MUST be processed independently and in the same order as they were 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 [RFC4930] 🧠 General client-server message exchange using TCP transport is illustrated in Figure 1 🖼️
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 Exchange4. Data Unit Format 📦
okay so the EPP data unit has two fields: a 32-bit header that describes the total length of the data unit, and the EPP XML instance 🎀 To get the length of the EPP XML instance, you subtract four octets from the total length of the data unit. A receiver must successfully read that many octets to retrieve the complete EPP XML instance before processing the EPP message 🫶
here's the layout (one tick mark is 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 💜
5. Transport Considerations 🚚
Section 2.1 of the EPP core protocol specification [RFC4930] describes considerations that protocol transport mappings need to address 🧐 This mapping handles each of those considerations with a mix of features from this document and features TCP already provides, like so:
- TCP includes features to provide reliability, flow control, ordered delivery, and congestion control. Section 1.5 of RFC 793 [RFC0793] describes these features in detail, and 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. 🖍️
6. Internationalization Considerations 🌍
this mapping does not introduce or present any internationalization or localization issues 🫶
7. IANA Considerations 🏷️
System port number 700 has been assigned by the IANA for mapping EPP onto TCP. 🎀
User port number 3121 (which was used for development and test purposes) has been reclaimed by the IANA 🦋
8. Security Considerations 🔒✨
Okay bestie, this is the serious part, so buckle up 😭 EPP as-is only has super basic client auth: identifiers and plain text passwords. A passive attack is enough to recover client identifiers and passwords, which makes command forgery trivial 💀. Protection against most other common attacks MUST be provided by other layered protocols, so EPP needs its besties to cover it 🫶.
When EPP runs over TCP, the Transport Layer Security (TLS) Protocol version 1.0 [RFC2246] or its successors (such as TLS 1.1 [RFC4346]) MUST be used to provide integrity, confidentiality, and mutual strong client-server authentication, and you should use the latest version that both parties support 🔐. Lowkey, TLS implementations often ship with a weak cryptographic mode that SHOULD NOT be used to protect EPP. Clients and servers who want high security SHOULD instead use TLS with cryptographic algorithms that are less susceptible to compromise. Main character energy only 💅.
Mutual client and server authentication using the TLS Handshake Protocol is REQUIRED 🙌. Signatures on the complete certification path for both the client machine and the server machine MUST be validated as part of the TLS handshake. Information in the client and server certificates, like validity periods and machine names, MUST also be validated. If you want the full tea on certification path validation, check out RFC 3280 [RFC3280]. EPP service MUST NOT be granted until the TLS handshake and certificate validation both finish successfully. That way both machines are authenticated and the crypto protections are actually in place ✨.
The TLS handshake confirms the identity of the client and server machines. EPP then uses an extra client identifier and password to authenticate the client's user identity, which supplements the machine auth from TLS 🧚. The identity in the client certificate and the identity in the EPP client identifier can be different, since a server can assign multiple user identities for use from any one client machine. Acceptable certificate identities MUST be negotiated between client operators and server operators using an out-of-band mechanism. Presented certificate identities MUST match negotiated identities before EPP service is granted. No vibes-based trust here 👑.
There is a real risk of login credential compromise if a client doesn't properly identify the server before starting an EPP session 😬. Before sending login credentials, the client needs to confirm that the server certificate received in the TLS handshake is an expected certificate for that server. The client also needs to confirm that the greeting from the server contains expected identification information. After the TLS session is set up and an EPP greeting arrives on a protected TCP connection, clients MUST compare the certificate subject and/or subjectAltName to the expected server identification information, and abort processing if a mismatch is detected. If certificate validation succeeds, the client still needs to make sure the information in the certificate and greeting is consistent and appropriate. As described above, both checks typically require an out-of-band exchange to identify expected values before any in-band connections are attempted 🔍.
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 by combining easily implemented solutions, such as firewall technology and border router filters that restrict inbound server access to known, trusted clients 🛡️.
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 gave many invaluable comments and suggested improvements 🌸. The author wants to give a shoutout to WG chairs Edward Lewis and Jaap Akkerhuis for their process and editorial contributions 👑.
Specific suggestions that made it into this document came from Chris Bason, Randy Bush, Patrik Faltstrom, Ned Freed, James Gould, Dan Manley, and John Immordino 💖.
10. References 📚
10.1. Normative References
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
[RFC4930] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)",
RFC 4930, May 2007.10.2. Informative References
[RFC2581] Allman, M., Paxson, V., and W. Stevens, "TCP Congestion
Control", RFC 2581, April 1999.
[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41,
RFC 2914, September 2000.
[RFC3280] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
X.509 Public Key Infrastructure Certificate and
Certificate Revocation List (CRL) Profile", RFC 3280,
April 2002.
[RFC3734] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
Transport Over TCP", RFC 3734, March 2004.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.Appendix A. Changes from RFC 3734 🦋
- Minor reformatting from converting the I-D source format from nroff to XML 🖊️.
- Updated Security Considerations to put strong authentication on the list of needed security services. The paragraph describing replay attacks was removed because it isn't specific to TCP. New text describing this issue has been added to RFC 4930 💅.
- Modified the description of TCP operation as a result of IESG evaluation 🔥.
- Moved RFCs 2581 and 2914 from the normative reference section to the informative reference section 📖.
- Added informative references to RFCs 3280 and 4346, plus descriptive text for each, as a result of IESG evaluation 🌈.
- Revised Security Considerations as a result of IESG evaluation 🔐.
- Updated EPP references ✨.
Author's Address 💌
Scott Hollenbeck
VeriSign, Inc.
21345 Ridgetop Circle
Dulles, VA 20166-6503
US
EMail: shollenbeck@verisign.comFull Copyright Statement ©
Copyright (C) The IETF Trust (2007).
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.
Intellectual Property 🧾
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. It also doesn't claim to have made any independent effort to identify any such rights. Info on the procedures for rights in RFC documents can be found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat, any assurances of licenses to be made available, or the result of an attempt to obtain a general license or permission for implementers or users of this specification to use such proprietary rights can be obtained from the IETF online IPR repository at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology required to implement this standard. Please send that info to the IETF at ietf-ipr@ietf.org 📬.
Acknowledgement 💜
Funding for the RFC Editor function is currently provided by the Internet Society 🌷.
📦 where this page comes from
- ietf: rfc4934 2007-05
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms