epp_proxy

An application that translates EPP over TCP connection into set of predefined HTTP calls.

Serves as direct replacement for mod_epp (https://github.com/mod-epp/mod-epp), and tries to emulate it's behaviour to the biggest possible extent.

Aside from the standard library of Erlang/OTP, it uses hackney for making HTTP requests and lager for logging.

Code style

We enforce the style from Erlang's own configuration. You can use the rebar3_fmt plugin to do it for you:

$ rebar3 fmt

Design

Translation of EPP calls

The application listens on predefined TCP port for formatted EPP frames and translates them into HTTP requests according to the following matrix. Application performs regex search for clTRID and an XPATH search for command name. It does not check against any XSD schema.

EPP Command	HTTP request	Parameters	Headers	Payload Type	Cookies
hello	GET /epp_session_url/hello		SSL-CLIENT-CERT, SSL-CLIENT-S-DN-CN, User-Agent, X-Forwarded-for		session
login	POST /epp_session_url/login	raw_frame, clTRID	SSL-CLIENT-CERT, SSL-CLIENT-S-DN-CN, User-Agent, X-Forwarded-for	form/multipart	session
logout	POST /epp_session_url/logout	raw_frame, clTRID	SSL-CLIENT-CERT, SSL-CLIENT-S-DN-CN, User-Agent, X-Forwarded-for	form/multipart	session
poll	POST /epp_command_url/poll	raw_frame, clTRID	SSL-CLIENT-CERT, SSL-CLIENT-S-DN-CN, User-Agent, X-Forwarded-for	form/multipart	session
check	POST /epp_command_url/check	raw_frame, clTRID	SSL-CLIENT-CERT, SSL-CLIENT-S-DN-CN, User-Agent, X-Forwarded-for	form/multipart	session
info	POST /epp_command_url/info	raw_frame, clTRID	SSL-CLIENT-CERT, SSL-CLIENT-S-DN-CN, User-Agent, X-Forwarded-for	form/multipart	session
create	POST /epp_command_url/create	raw_frame, clTRID	SSL-CLIENT-CERT, SSL-CLIENT-S-DN-CN, User-Agent, X-Forwarded-for	form/multipart	session
delete	POST /epp_command_url/delete	raw_frame, clTRID	SSL-CLIENT-CERT, SSL-CLIENT-S-DN-CN, User-Agent, X-Forwarded-for	form/multipart	session
renew	POST /epp_command_url/renew	raw_frame, clTRID	SSL-CLIENT-CERT, SSL-CLIENT-S-DN-CN, User-Agent, X-Forwarded-for	form/multipart	session
update	POST /epp_command_url/update	raw_frame, clTRID	SSL-CLIENT-CERT, SSL-CLIENT-S-DN-CN, User-Agent, X-Forwarded-for	form/multipart	session
ANY (error)	GET /epp_error_url	msg, code, clTRID	SSL-CLIENT-CERT, SSL-CLIENT-S-DN-CN, User-Agent, X-Forwarded-for	query params	session

Error route is used in case EPP frame is malformed.

The application performs TLS handshake, checks certficate against provided revocation list and acts as TLS termination proxy, passing on the certificate information downstream as HTTP headers. It also passes on the client IP address.

Supervision Tree

The application leverages OTP to isolate EPP clients from one another, each connection is owned by its own process. There are two processes that accept the connections and spin off workers, those are supervised in "one for one" strategy.

Build

You need Erlang/OTP release 21 and Rebar3 to build it. No other versions than 21 were tested.

$ rebar3 compile

epp_proxy should be deployed as a self-contained Erlang application (release). You can create one with one of the following commands:

$ rebar3 release # Creates a release locally.
$ rebar3 tar # Creates an archive that can be shipped to another machine
$ rebar3 as prod release tar # Combines the steps above into single one, uses production profile.

Configuration

Configuration for the application tries to emulate the mod_epp configuration as close as possible to make migration easier. The configuration is placed in config/sys.config file, it takes a format of Erlang property list.

Configuration variables

Variable name	Expected values	Apache equivalent	Definition
dev_mode	true, false	None	Enables TCP access without TLS.
tls_port	700	Listen	At which port should we open a TLS socket. Default is 700.
tcp_port	70000	Listen	At which port should we open a TCP socket. Only in dev_mode.
epp_session_url	https://example.com/epp/session	EppSessionRoot	HTTP address of the session endpoints including schema and port.
epp_command_url	https://example.com/epp/command	EppCommandRoot	HTTP address of the command endpoints including schema and port.
epp_error_url	https://example.com/epp/error	EppErrorRoot	HTTP address of the error endpoints including schema and port.
cacertfile_path	/opt/ca/ca.crt.pem	SSLCACertificateFile	Where is the client root CA located.
certfile_path	/opt/ca/server.crt.pem	SSLCertificateFile	Where is the server certificate located.
keyfile_path	/opt/ca/server.key.pem	SSLCertificateKeyFile	Where is the server key located.
crlfile_path	/opt/ca/crl.pem	SSLCARevocationFile	Where is the CRL file located.

Migrating from mod_epp

Checklist of steps to perform if you want to migrate from mod_epp, but still use Apache to be a reverse proxy.

1. Remove SSL-CLIENT-S-DN-CN and SSL-CLIENT-CERT headers from Apache. Epp_proxy takes care of those.
2. Install this project to desired location.
3. Ensure that the user who will run epp_proxy has access to all certificate files.
4. Set up syslog in config/sys.config.
5. If you do not feel comfortable using Erlang configuration file, you can use command line arguments and flags in format of /epp_proxy/rel/bin/epp_proxy -epp_proxy tls_port 444, where -epp_proxy is name of application, followed by configuration parameter name and value.

TODO

1. Ensure CRL gets updated periodically without a need for restart of the service