OpenVPN

pacman -S easy-rsa
cd /etc/easy-rsa
export EASYRSA=$(pwd)
easyrsa init-pki
easyrsa build-ca
 
# The CA cert and key will be generated
# see /etc/easy-rsa/pki/ca.crt
# and /etc/easy-rsa/pki/private/ca.key
 
# copy the CA cert to the openvpn directory
cp /etc/easy-rsa/pki/ca.crt /etc/openvpn/server/ca.crt

# cert request
easyrsa gen-req servername nopass
easyrsa gen-req clientname nopass
 
# self-sign
easyrsa sign-req server servername
easyrsa sign-req client clientname
 
# the generated cert will be saved to：
/etc/easy-rsa/pki/reqs/servername.req
/etc/easy-rsa/pki/private/servername.key
/etc/easy-rsa/pki/issued/servername.crt
 
/etc/easy-rsa/pki/reqs/clientname.req
/etc/easy-rsa/pki/private/clientname.key
/etc/easy-rsa/pki/issued/clientname.crt
 
# copy the server cert to the openvpn server directory
cp /etc/easy-rsa/pki/issued/servername.crt /etc/openvpn/server/servername.crt
cp /etc/easy-rsa/pki/private/servername.key /etc/openvpn/server/servername.key

openssl dhparam -out /etc/openvpn/server/dh.pem 2048

openvpn --genkey --secret /etc/openvpn/server/ta.key

cp /usr/share/openvpn/examples/server.conf /etc/openvpn/server/server.conf
 
# add following for better cipher
cipher AES-256-CBC
auth SHA512
tls-version-min 1.2
tls-cipher TLS-DHE-RSA-WITH-AES-256-GCM-SHA384:TLS-DHE-RSA-WITH-AES-128-GCM-SHA256:TLS-DHE-RSA-WITH-AES-256-CBC-SHA:TLS-DHE-RSA-WITH-CAMELLIA-256-CBC-SHA:TLS-DHE-RSA-WITH-AES-128-CBC-SHA:TLS-DHE-RSA-WITH-CAMELLIA-128-CBC-SHA
 
# shared port 443
proto tcp
port 443
port-share 127.0.0.1 4443 # e.g. nginx open port at 4443

iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE

# combine cert into p12 format
openssl pkcs12 -export -out cert_key.p12 -inkey client.key -in client.crt -certfile ca.crt -nodes
# import cert into yubikey
yubico-piv-tool -s 9a -i cert_key.p12 -K PKCS12 -a import-key -a import-cert -k
# show id
openvpn --show-pkcs11-ids opensc-pkcs11.so
# client config: replace cert and key section with following
pkcs11-id piv_II/PKCS.................... # replace this with the id in the previous command output
pkcs11-providers opensc-pkcs11.so