Setting up the CA
Follow the steps on setting up a Certificate Authority (CA) using OpenSSL.
Issuing the client certificate and private key
Once the CA has been configured, we will generate a private key and an unsigned public key digital certificate.
# openssl req -new -days 365 -newkey rsa:1024 \
-keyout sslkey.pem -out unsigned.pem
The unsigned public key digital certificate, [...]

FreeBSD supports OpenBSD’s powerful firewall PF since version 5.3. The scenario I was pursuing was firewalling one of my FreeBSD machines:
Incoming firewalling

Only incoming SSH connections from known SSH clients should be accepted.
Only incoming Syslog traffic from known Syslog clients should be accepted.
Only incoming ICMP Echo-Reply, ICMP Echo-Request and ICMP Destination-Unreachable datagrams should be accepted. Any [...]

FreeBSD uses syslog by default. However, syslog is very old and inflexible, so I decided to replace it with syslog-ng. syslog-ng syntax is far more easier to read and understand than syslog’s one.
syslog-ng uses the following elements to determine what to log and where to log it:

Source: Defines where log entries do come from. For [...]