= Proxying RadSec and enabling PROXY Protocol

This guide shows how to set up FreeRADIUS to serve RadSec connections, fronted
by either HAproxy or Traefik as Layer 4 proxies that pass on the original
client connection information using PROXY Protocol.

It is not a comprehensive guide to using RadSec with FreeRADIUS. It presents a
basic configuration that uses an example CA and does not validate certificate
attributes or perform revokation status.


== Introduction

FreeRADIUS supports receiving RADIUS requests over TLS-enabled TCP connections
and supports proxying of requests over TCP connections to another TLS-enabled
homeserver. The protocol for RADIUS over TLS is called "RadSec" and is defined
in RFC 6614.

FreeRADIUS is a capable and performant application-aware ("Layer 7") proxy /
load-balancer for RadSec and other forms of RADIUS traffic.


=== Layer 4 proxying

Rather than use an application-aware proxy it is sometimes better to reduce the
performance impact incurred by re-encoding an application protocol by using a
"Layer 4" proxy that operates at the level of individual connections without
regard for the application protocol. Such a proxy is more of a "bump in the
wire" than a request buffer and minimises the latency incurred due to proxying.

It is common to see software such as HAproxy and Traefik used in Layer 4 mode
in place of FreeRADIUS for purposes such as connection load balancing. In
addition to improved performance, these tools have the benefit that they
typically support dynamic service discovery and "hitless" reloads to
automatically adapt their connection routing based on changes to backend
services such as the introduction of new nodes with even a momentary loss of
service.


=== Loss of connection information

When TCP connections are relayed through Layer 4 proxies the information
about the originating source of the connection is no longer known to the
backend service, unless it is otherwise made available. Identifying the
originator of connections is often necessary for security purposes and for
request processing.

Whilst many application protcols support headers that allow proxies to preserve
connection information these are not helpful in the context of Layer 4
proxying: The process of populating headers requires knowledge of the
application protocol to re-encode requests as they are transmitted between the
frontend and backend connections.


=== PROXY Protocol

PROXY Protocol overcomes this limitation by allowing the original connection
information to be provided to the backend at the start of the TCP connection.
After this initial data is encoded the remainder of the conversation then
proceeds as normal. However now that the connection information is known to the
backend server it is able to process requests made on the connection as though
the connection were being made directly by the client and not via the proxy.

PROXY Protocol is specified in this document:
http://www.haproxy.org/download/1.8/doc/proxy-protocol.txt


== Requirements

PROXY Protocol Version 1 is supported by FreeRADIUS v3.0.24 and later versions.

You will require the following set of VMs or containers, each with their own
IP address:

[cols="1,1,1"]
|===
|Hostname|IP address|Purpose

|radseccli
|172.23.0.2
|FreeRADIUS configured to provide a RadSec test client

|radsecsvr
|172.23.0.3
|FreeRADIUS configured as a RadSec server

|haproxy
|172.23.0.4
|HAproxy in Layer 4 mode to the FreeRADIUS RadSec backend
|===

Optionally you may want to configure a host to run Traefik within a Docker
container using host mode networking, perhaps configured by Docker Compose,
however the installation is beyond the scope of this guide:

[cols="1,1,1"]
|===
|traefik
|172.23.0.5
|Traefik configured as a TCP router with TLS passthrough to the FreeRADIUS RadSec backend
|===

The hostnames and IP addresses provided above are for examples purposes and are
used throughout the remainder of this guide. This guide provides commands and
output for CentOS. Other distributions will have minor differences, including
the location of the FreeRADIUS configuration (the "raddb").

[NOTE]
====
You can choose to use your own hostname, IP addresses and OS distribution. You
could also use official Docker images provided by the respecitive projects,
however these prescribe methods for configuring and managing the services
that are not typical for a normal package installation which would provide a
distraction if used for by guide.
====


== Sections in this guide

This guide is organised into four parts that should be read in order:

1. xref:protocols/proxy/enable_radsec.adoc[Enabling RadSec]
2. xref:protocols/proxy/radsec_client.adoc[Configuring a test RadSec client]
3. xref:protocols/proxy/radsec_with_haproxy.adoc[Proxying RadSec with HAproxy]
4. xref:protocols/proxy/radsec_with_traefik.adoc[Proxying RadSec with Traefik]
5. xref:protocols/proxy/enable_proxy_protocol.adoc[Enabling PROXY Protocol for RadSec]