Extensible Provisioning Protocol (EPP) Transport over HTTPS
IIT-CNR/Registro.itVia Moruzzi,1PisaIT56124mario.loffredo@iit.cnr.ithttps://www.iit.cnr.itIIT-CNR/Registro.itVia Moruzzi,1PisaIT56124lorenzo.luconi@iit.cnr.ithttps://www.iit.cnr.itIIT-CNR/Registro.itVia Moruzzi,1PisaIT56124maurizio.martinelli@iit.cnr.ithttps://www.iit.cnr.itVeriSign, Inc.12061 Bluemont WayRestonVA20190USdkeathley@verisign.comhttp://www.verisigninc.comVeriSign, Inc.12061 Bluemont WayRestonVA20190USjgould@verisign.comhttp://www.verisigninc.com
ART
Internet Engineering Task Forceepp httpsThis document describes how an Extensible Provisioning Protocol (EPP)
connection is mapped onto a Hypertext Transfer Protocol (HTTP) session. EPP
over HTTP (EoH) requires the use of Transport Layer Security (TLS) to secure
EPP information (i.e. HTTPS).This document describes how EPP is mapped onto
HTTP . Note that there are several versions of HTTP
currently in use, including: HTTP/1.1 , HTTP/2
, and HTTP/3 . As the
differences among such versions do not affect the EPP mapping described in
this document, hereinafter the version number is omitted except for presenting
the special features in the underlying layers of the HTTP stack.HTTP represents a higher-level abstraction of a network connection,
removing the need to directly deal with all of the lower-level details of
transport protocols. This makes HTTP much more compatible with cloud-native
infrastructures, and facilitates faster development times and reduced
maintenance costs in such environments.Security services beyond those defined in EPP are provided by TLS via HTTPS
.Conventions Used in This DocumentThe key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
when, and only when, they appear in all capitals, as
shown here.Mapping EPP session management facilities onto HTTP is
accomplished using existing HTTP methods, namely GET and POST. An EPP
session exists on top of an EPP 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 implementing this specification MUST
listen for HTTP session requests on a standard HTTP port assigned by IANA.Even though HTTP itself is stateless, a stateful EPP session can be
achieved using the mechanism described in . This
mechanism uses "Set-Cookie" and "Cookie" HTTP headers to facilitate a stateful
HTTP session. Such a session is initiated by the client via sending a GET
request to the sever. The GET request MUST include "application/epp+xml"
() in the "Accept" HTTP header. The server
MUST include the EPP Greeting in the response. The EPP Greeting must include
"application/epp+xml" in the "Content-Type" header with the character encoding
of the EPP XML (e.g., "application/epp+xml;charset=UTF-8")
and MUST include ""no-cache" in the "Cache-Control" header and
include "0" in the "Expires" header to disable caching. The server MUST use the
"Set-Cookie" header to include a token that represents the identifier of the
HTTP session. All subsequent HTTP requests that include the HTTP session
identifier in the "Cookie" header will be treated as part of the session. The
HTTP session represents an EPP connection, referred to as an EPP over HTTP
(EoH) connection, which is initiated by the initial GET request.The EPP session begins with a successful EPP <login> command on the
EoH connection and can be referred to as an EPP over HTTP (EoH) session.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. A server MAY also end an EPP session that has been
either active or inactve for longer than a server-defined period. A server MAY
end the HTTP session after ending the EPP session.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. With the exception of the EPP Greeting, EPP messages
are initiated by the EPP client in the form of EPP commands. An EPP client
MUST send all commands as HTTP POST requests
(). Each POST request MUST include the
HTTP session identifier in the "Cookie" header and "application/epp+xml"
in the "Accept" header. An EPP server MUST return an EPP response to an
EPP command in the HTTP response to the respective HTTP request.
The EPP command and the EPP response MUST include "application/epp+xml" in
the "Content-Type" header with the character encoding of the EPP XML
(e.g., "application/epp+xml;charset=UTF-8").
The EPP response MUST include "no-cache" in the "Cache-Control" header and
include "0" in the "Expires" header to disable caching.HTTP does not guarantee that POST requests are idempotent. However, the
semantics of EPP do require EPP commands to be idempotent, so processing a
command more than once will produce the same net effect on the repository as
successfully processing the command once.The EPP command XML is framed by the content of the HTTP POST request, and
the EPP response XML is framed by the content of the HTTP response. Each HTTP
request MUST contain a single EPP message, and each HTTP response MUST contain
a single EPP response. Commands MUST be processed independently and in the
same order as received from the client.Servers MUST NOT use HTTP return codes to signal clients about the failure
of the EPP commands. The HTTP code 200 MUST be used for both
successful and unsuccessful EPP requests. Servers MUST use HTTP codes to
signal clients about the failure of the HTTP requests.Servers MUST return an EPP 2002 response (i.e. Command use error) if the
client issues an EPP command with either an empty or an invalid HTTP session
identifier.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 if a
well-formed command is not received within the time limit.HTTP/2 and HTTP/3 support a multiplexing feature that was introduced to
address head-of-line blocking issues in previous HTTP versions. In the context
of multiple requests being sent on a single HTTP connection, multiplexing
allows the delivery of responses in a different order from how the requests
were made. Due to this behavior, pipelining MUST NOT be used by EoH clients.
EoH clients MUST wait for a server response to a command before sending a
subsequent command.A general state machine for an EPP server is described in
. A general client-server message
exchange using HTTP is illustrated in Figure 1.
>------------------------------->> |
| |
| Send Greeting |
| <<-------------------------------<< |
| |
| POST |
| >>------------------------------->> |
| |
| Send Response |
| <<-------------------------------<< |
| |
| POST Command X |
| >>------------------------------->> |
| |
| Send Response X |
| <<-------------------------------<< |
| |
| POST Command Y |
| >>------------------------------->> |
| |
| Send Response Y |
| <<-------------------------------<< |
| . |
.
.
| POST |
| >>------------------------------->> |
| |
| Send Response |
| <<-------------------------------<< |
Figure 1: HTTP Client-Server Message Exchange
]]>The EPP server MUST follow the "EPP Server State Machine" procedure
described in . describes considerations to be
addressed by protocol transport mappings. This document addresses each
of those considerations using a combination of features of the HTTP
protocol itself and features of this document.
Command Order: includes a requirement
for ordered message delivery.
Session Mapping: EPP session management is described in
of this document.
Stateful Nature: Achieving the stateful nature of EPP is described in
.
Frame Data Units: of this document describes how each
EPP command is framed within the content of HTTP requests and responses.
Congestion Avoidance: confirms
congestion avoidance as a feature of HTTP.
Reliability: confirms reliable
message delivery as a feature of HTTP.
Pipelining: of this document
stipulates that command pipelining must not be used in EoH.
This specification does not request any actions by IANA.Implementation StatusNote to RFC Editor: Please remove this section and the reference to
before publication.This section records the status of known implementations of the
protocol defined by this specification at the time of posting of
this Internet-Draft, and is based on a proposal described in .
The description of implementations in this section is
intended to assist the IETF in its decision processes in
progressing drafts to RFCs. Please note that the listing of any
individual implementation here does not imply endorsement by the
IETF. Furthermore, no effort has been spent to verify the
information presented here that was supplied by IETF contributors.
This is not intended as, and must not be construed to be, a
catalog of available implementations or their features. Readers
are advised to note that other implementations may exist.According to , "this will allow reviewers and working
groups to assign due consideration to documents that have the
benefit of running code, which may serve as evidence of valuable
experimentation and feedback that have made the implemented
protocols more mature. It is up to the individual working groups
to use this information as they see fit".Verisign EPP SDKOrganization: Verisign Inc.Name: Verisign EPP SDKDescription: The Verisign EPP SDK includes both a full client implementation
and a full server stub implementation of draft-loffredo-regext-epp-over-http. Both
HTTP/1.1 and HTTP/2 were implemented, but HTTP/3 was not due to the lack of support
of the underlying library.Level of maturity: DevelopmentCoverage: All aspects of the protocol are implemented with HTTP/1.1 and HTTP/2.Licensing: GNU Lesser General Public LicenseContact: jgould@verisign.comURL: https://www.verisign.com/en_US/channel-resources/domain-registry-products/epp-sdksSince client credentials are included in the EPP <login> command, HTTPS
() MUST be used to protect them from
disclosure while in transit. HTTPS indicates that TLS is being used to secure
the HTTP connection between the client and server. Transferring over TLS also
prevents sniffing the HTTP session identifier and, consequently, impersonating
a client to perform actions on registrars' objects. Servers are REQUIRED to
support TLS 1.2 or higher.Servers are RECOMMENDED to implement additional measures to verify the
client. These measures include IP allow-listing and locking the HTTP session
identifier to the client's IP address.HTTP session identifiers SHOULD be randomly generated to mitigate the risk
of obtaining a valid one through a brute-force search. A HTTP session
identifier SHOULD be at least 128 bits or 16 bytes long. An example of a
reliable HTTP session identifier is the Universally Unique Identifier (UUID).
Servers MAY limit the lifetime of active sessions to avoid them being
exchanged for a long time.The following measures MAY also be taken to control cookies usage:
Restricting their scope through the "Domain" and "Path" attributes
Limiting their lifetime through the "Max-Age" and "Expire" attributes
Other attributes that are normally used to secure the cookies and prevent
them to be accessed by unintended parties or scripts, such as "HttpOnly" and
"Secure", are meaningless in this context. Finally, servers are RECOMMENDED to
perform additional checks to limit the rate of open EPP sessions and HTTP
connections to mitigate the risk of congestion of requests. Here again, IP
allow-listing could also be implemented to prevent DDoS attacks.As a further measure to enforce the security, servers MUST require
clients to present a digital certificate. Clients who possess and present a
valid X.509 digital certificate, issued by a recognized Certification
Authority (CA), could be identified and authenticated by a server who trusts
the corresponding CA. This certificate-based mechanism is supported by HTTPS
and can be used with EPP over HTTP.If the EPP server is configured as a load balancer routing the requests to
a pool of backend servers, some of the aforementioned checks SHOULD be
implemented on the load balancer side.The authors wish to acknowledge the input from the .IT technical team.Change HistoryChange from 02 to 03
Added Dan Keathley and James Gould as co-authors.
Change from 03 to 04
Clarified the difference between an EoH connection and an EPP session.
Added inclusion of the "Content-Type" header in every request and response except for the initial GET establishing the EoH connection.
Revised the Security Considerations section.
Change from 04 to 05
Added the Implementation Status section with the Verisign EPP SDK implementation.
Removed the "Internationalization Considerations" section and added the EoH character encoding matching the EPP XML character encoding
for the EPP Greeting, the EPP commands, and the EPP responses.
Added inclusion of the "Cache-Control" and "Expires" headers for the the EPP Greeting, the EPP commands, and the EPP responses.