OpenVPN: SSL and hostname configuration

We already have our OpenVPN AS running in Production, so a few more posts about last steps in its configuration.

For now – need to configure SSL to avoid alerts in clients browsers.

OpenVPN AS documentation for SSL setup – here>>>.

Contents

Let’s Encrypt

Install Let’s Encrypt client:

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root@openvpnas2:~# git clone https://github.com/letsencrypt/letsencrypt /opt/letsencrypt

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Open port 80 in your AWS Security Group – it’s safe as OpenVPN AS listen on the 443 for clients and 943 for the admin page access.

Obtain a new certificate:

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root@openvpnas2:~# /opt/letsencrypt/letsencrypt-auto certonly -d vpn.example.com
...
1: Spin up a temporary webserver (standalone)
...
IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/vpn.example.com/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/vpn.example.com/privkey.pem

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SSL in OpenVPN AS

You can change certificates using Admin UI in the Web Server Configuration, or using CLI.

On the first run OpenVPN AS generates self-signed certificates stored in the /usr/local/openvpn_as/etc/web-ssl/ directory:

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root@openvpnas2:~# ls -l /usr/local/openvpn_as/etc/web-ssl/
total 16
-rw-r--r-- 1 root root 1111 Feb 21 14:50 ca.crt
-rw------- 1 root root 1708 Feb 21 14:50 ca.key
-rw-r--r-- 1 root root 1082 Feb 21 14:50 server.crt
-rw------- 1 root root 1704 Feb 21 14:50 server.key

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They are kind of failover-certificates in case if others will be broken.

To configure SSL we need to have three files, in case of using Let’s Encrypt we will use next files to create them:

*.crt – it’s our fullchain.pem file
*.key – privkey.pem file
*.bundle – will be created from fullchain.pem and privkey.pem

Check Let’s Encrypt existing files:

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root@openvpnas2:/etc/letsencrypt/live/vpn.example.com# ls -l
total 4
lrwxrwxrwx 1 root root  42 Feb 22 10:56 cert.pem -> ../../archive/vpn.example.com/cert1.pem
lrwxrwxrwx 1 root root  43 Feb 22 10:56 chain.pem -> ../../archive/vpn.example.com/chain1.pem
lrwxrwxrwx 1 root root  47 Feb 22 10:56 fullchain.pem -> ../../archive/vpn.example.com/fullchain1.pem
lrwxrwxrwx 1 root root  45 Feb 22 10:56 privkey.pem -> ../../archive/vpn.example.com/privkey1.pem

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Install private key to OpenVPN server:

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root@openvpnas2:/etc/letsencrypt/live/vpn.example.com# /usr/local/openvpn_as/scripts/sacli --key "cs.priv_key" --value_file "privkey.pem" ConfigPut
[True, {}]

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Install its public cert:

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root@openvpnas2:/etc/letsencrypt/live/vpn.example.com# /usr/local/openvpn_as/scripts/sacli --key "cs.cert" --value_file "fullchain.pem" ConfigPut
[True, {}]

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“Generate” bundle – just by using cat for the fullchain.pem and privkey.pem:

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root@openvpnas2:/etc/letsencrypt/live/vpn.example.com# cat fullchain.pem privkey.pem > bundle.pem

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Add it to the OpenVPN AS:

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root@openvpnas2:/etc/letsencrypt/live/vpn.example.com# /usr/local/openvpn_as/scripts/sacli --key "cs.ca_bundle" --value_file "bundle.pem" ConfigPut
[True, {}]

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Restart service:

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root@openvpnas2:/etc/letsencrypt/live/vpn.example.com# /usr/local/openvpn_as/scripts/sacli start
RunStart warm None
{
  "errors": {}, 
  "service_status": {
    "api": "on", 
    "auth": "on", 
    "bridge": "on", 
    "client_query": "restarted", 
    "crl": "on", 
    "daemon_pre": "on", 
    "db_push": "on", 
    "ip6tables_live": "on", 
    "ip6tables_openvpn": "on", 
    "iptables_live": "on", 
    "iptables_openvpn": "on", 
    "iptables_web": "restarted", 
    "license": "on", 
    "log": "on", 
    "openvpn_0": "on", 
    "openvpn_1": "on", 
    "user": "on", 
    "web": "restarted"
  }
}
WILL_RESTART ['web', 'client']

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Check UI now: