Difference between revisions of "VPN"

Revision as of 10:23, 9 July 2021

The Software Heritage server and the VMs running on it are severely firewalled. To get onto their network unrestricted, a VPN based on OpenVPN is available.

The setup is client-server, with per-client certificates.

OpenVPN client configuration

Raw OpenVPN

Sample configuration file, e.g., /etc/openvpn/swh.conf:

remote vpn.softwareheritage.org
ns-cert-type server 
comp-lzo 
nobind
dev tun
proto udp 
port 1194 
log /var/log/openvpn.log
up-restart 
persist-key 
persist-tun 
client 
ca /etc/openvpn/keys/softwareheritage-ca.crt
cert /etc/openvpn/keys/softwareheritage.crt
key /etc/openvpn/keys/softwareheritage.key
user nobody
group nogroup

# If you are using resolvconf, add this:
# Make sure you add louvre to /etc/hosts to avoid issues in using the vpn-provided DNS server.
script-security 2
up /etc/openvpn/update-resolv-conf
down /etc/openvpn/update-resolv-conf

# If you want the connection to persist when your network fails, add this:
ping-restart 10

In addition to the above configuration file, you will need to install the following 3 files under /etc/openvpn/keys (matching the paths within the sample above):

softwareheritage-ca.crt: public certificate for the Software Heritage certification authority (CA)
softwareheritage.crt: public, client-specific (certificate signed by the admin, see below)
softwareheritage.key: private, client-specific key (generated by the user, see below)

Activate the openvpn server

as root, run

  systemctl enable openvpn@swh.service
  systemctl start openvpn@swh.service
  systemctl status openvpn@swh.service

Note: Internally, the `swh` must match the /etc/openvpn/swh.conf filename.

Excerpt of a successful start:

 root@machine:~# systemctl status openvpn@swh.service
 openvpn@swh.service - OpenVPN connection to swh
  Loaded: loaded (/lib/systemd/system/openvpn@.service; indirect; vendor preset: enabled)
  Active: active (running) since Thu 2020-12-17 19:03:29 IST; 22min ago
    Docs: man:openvpn(8)
          https://community.openvpn.net/openvpn/wiki/Openvpn24ManPage
          https://community.openvpn.net/openvpn/wiki/HOWTO
Main PID: 12302 (openvpn)
  Status: "Initialization Sequence Completed"
   Tasks: 1 (limit: 4915)
  CGroup: /system.slice/system-openvpn.slice/openvpn@swh.service
          └─12302 /usr/sbin/openvpn --daemon ovpn-swh --status /run/openvpn/swh.status 10 --cd /etc/openvpn --script-security 2 --config /etc/openvpn/swh.conf --writepid /run/openvpn/swh.pid

Dec 17 19:03:29 machine systemd[1]: Starting OpenVPN connection to swh... Dec 17 19:03:29 machine systemd[1]: Started OpenVPN connection to swh.

Network Manager GUI

You need network-manager-openvpn and network-manager-openvpn-gnome for the configuration gui.

Obtaining a client certificate

For users

Generate a keypair (key + certificate signing request) using the following command:

openssl req -new -newkey rsa:2048 -nodes -keyout openvpn.key -out openvpn.csr -subj "/CN=<your username>"

Please replace <your username> with something that uniquely identifies the certificate.

Make sure openvpn.key is stored in a safe place (it's your private key, which will allow anyone to connect to the VPN).

Provide the CSR file to a sysadmin through a reasonably authenticated medium.

For admins

On the firewall (192.168.50.1), go to the System / Trust / Certificates page
click on the add button on the upper right

On the Method list, choose "Sign a certificate Signing Request"

Fetch the CSR file provided by the user, for instance with scp USERNAME.csr louvre:

Enter the user name on the descriptive name
Select "OpenVPN Software Heritage (louvre)" as Certificate Authority
Enter the duration, usually 10 years
Paste the csr
Validate

check the details of the csr and validate

Revoking a client certificate

On the firewall (master) [1]:

go to the [System / Trust / Revocation] page
edit the "OpenVPN certificate revocation list" CRL

go to the bottom of the page

select the certificate to revoke
Add

The counter of revoked certificate should be increased by one on for the OpenVPN CSR on the CSR list

/etc/hosts entries

Once the Vpn is setup on your machine, you can access Software Heritage hosts via their private IP addresses; see Network configuration.

OpenVPN now pushes the address of our DNS server (192.168.100.29, pergamon).

You might want to add louvre.softwareheritage.org in your /etc/hosts to avoid a bootstrap problem if the "on-vpn" DNS server is in your resolv.conf.

@@ Line 119: / Line 119: @@
 == Revoking a client certificate ==
-On louvre:
+On the firewall (master) [https://192.168.50.1]:
+* go to the [[https://192.168.50.1/system_crlmanager.php System / Trust / Revocation]] page
+* edit the "OpenVPN certificate revocation list" CRL
-<pre>
+[[File:Vpn-crl-list.png]]
-root@louvre:~# cd /etc/openvpn/keys
-root@louvre:/etc/openvpn/keys# ./easyrsa revoke USERNAME
-[ say yes ]
-root@louvre:/etc/openvpn/keys# ./easyrsa gen-crl; chmod a+r pki/crl.pem
-</pre>
-OpenVPN re-reads the CRL at each connection (which is why we need the CRL to be world-readable), so once the cert is revoked, there's nothing more to do. If you want to make sure the client is disconnected, you need to restart OpenVPN (which will make all clients reconnect).
+* go to the bottom of the page
+[[File:Vpn-csr-certificate.png]]
+* select the certificate to revoke
+* Add
+The counter of revoked certificate should be increased by one on for the OpenVPN CSR on the CSR list
 == /etc/hosts entries ==