Setting up encrypted tunnel using stunnel

To implement encrypted communication between Redis masters and slaves, we recommend using stunnel. Stunnel works as TLS encryption wrapper between client and server.

This step-by-step tutorial will explain how to install and configure stunnel proxies on FreeBSD client and server.

Alternatively, for DigitalOcean’s managed Redis, there is a community tutorial available.

Configuration procedures for other operating systems are very similar. For simplicity, this tutorial only covers replication to one client host as this configuration does not require individual preshared keys for each of the clients.

Introduction

Assuming we have 3 Redis instances on both server and client, listening sockets on the server (master side):

instance Redis socket stunnel socket
redis localhost:6379 -
bayes localhost:6378 master.example.com:6478
fuzzy localhost:6377 master.example.com:6477

As the instance named redis should not be mirrored, we will replicate fuzzy and bayes instances. So we need to setup 2 TLS tunnels.

Installation

First install the security/stunnel package:

# pkg install stunnel

Create pid-file directory:

# mkdir /var/run/stunnel && chown stunnel:stunnel /var/run/stunnel

To enable stunnel add the following lines to the /etc/rc.conf:

stunnel_enable="YES"
stunnel_pidfile="/var/run/stunnel/stunnel.pid"

Server configuration (master side)

/usr/local/etc/stunnel/stunnel.conf:

setuid = stunnel
setgid = nogroup

pid = /var/run/stunnel/stunnel.pid

[bayes]
accept  = 6478
connect = 6378
ciphers = PSK
PSKsecrets = /usr/local/etc/stunnel/psk.txt

[fuzzy]
accept  = 6477
connect = 6377
ciphers = PSK
PSKsecrets = /usr/local/etc/stunnel/psk.txt

Client configuration (slave side)

/usr/local/etc/stunnel/stunnel.conf:

setuid = stunnel
setgid = nogroup

pid = /var/run/stunnel/stunnel.pid

[bayes]
client = yes
accept  = localhost:6478
connect = master.example.com:6478
ciphers = PSK
PSKsecrets = /usr/local/etc/stunnel/psk.txt

[fuzzy]
client = yes
accept  = localhost:6477
connect = master.example.com:6477
ciphers = PSK
PSKsecrets = /usr/local/etc/stunnel/psk.txt

Preshared keys

Create /usr/local/etc/stunnel/psk.txt . The psk.txt file contains one line for each client:

test1:oaP4EishaeSaishei6rio6xeeph3az

Do not use example passwords.

As both bayes and fuzzy Redis instances located at the same host we can share the same key between them.

Since this file should be kept secret set secure permissions on it:

# chmod 600 /usr/local/etc/stunnel/psk.txt

Starting stunnel

# service stunnel start

Testing

From the client host use the redis-cli utility to connect to the remote instances:

# redis-cli -p 6477
# redis-cli -p 6478

Given that it connected, you are clear to proceed with configuring replication between Redis instances.