Certificates for communication within the cluster

Each Proxmox VE cluster creates its own internal Certificate Authority (CA) and generates a self-signed certificate for each node. These certificates are used for encrypted communication with the cluster’s pveproxy service and the Shell/Console feature if SPICE is used.

The CA certificate and key are stored in the Proxmox Cluster File System (pmxcfs).

Certificates for API and web GUI

The REST API and web GUI are provided by the pveproxy service, which runs on each node.

You have the following options for the certificate used by pveproxy:

  1. By default the node-specific certificate in /etc/pve/nodes/NODENAME/pve-ssl.pem is used. This certificate is signed by the cluster CA and therefore not trusted by browsers and operating systems by default.

  2. use an externally provided certificate (e.g. signed by a commercial CA).

  3. use ACME (e.g., Let’s Encrypt) to get a trusted certificate with automatic renewal.

For options 2 and 3 the file /etc/pve/local/pveproxy-ssl.pem (and /etc/pve/local/pveproxy-ssl.key, which needs to be without password) is used.

Certificates are managed with the Proxmox VE Node management command (see the pvenode(1) manpage).

Warning Do not replace or manually modify the automatically generated node certificate files in /etc/pve/local/pve-ssl.pem and /etc/pve/local/pve-ssl.key or the cluster CA files in /etc/pve/pve-root-ca.pem and /etc/pve/priv/pve-root-ca.key.

Getting trusted certificates via ACME

Proxmox VE includes an implementation of the Automatic Certificate Management Environment ACME protocol, allowing Proxmox VE admins to interface with Let’s Encrypt for easy setup of trusted TLS certificates which are accepted out of the box on most modern operating systems and browsers.

Currently the two ACME endpoints implemented are Let’s Encrypt (LE) and its staging environment (see https://letsencrypt.org), both using the standalone HTTP challenge.

Because of rate-limits you should use LE staging for experiments.

There are a few prerequisites to use Let’s Encrypt:

  1. Port 80 of the node needs to be reachable from the internet.

  2. There must be no other listener on port 80.

  3. The requested (sub)domain needs to resolve to a public IP of the Node.

  4. You have to accept the ToS of Let’s Encrypt.

At the moment the GUI uses only the default ACME account.

Example: Sample pvenode invocation for using Let’s Encrypt certificates
root@proxmox:~# pvenode acme account register default mail@example.invalid
Directory endpoints:
0) Let's Encrypt V2 (https://acme-v02.api.letsencrypt.org/directory)
1) Let's Encrypt V2 Staging (https://acme-staging-v02.api.letsencrypt.org/directory)
2) Custom
Enter selection:
1

Attempting to fetch Terms of Service from 'https://acme-staging-v02.api.letsencrypt.org/directory'..
Terms of Service: https://letsencrypt.org/documents/LE-SA-v1.2-November-15-2017.pdf
Do you agree to the above terms? [y|N]y

Attempting to register account with 'https://acme-staging-v02.api.letsencrypt.org/directory'..
Generating ACME account key..
Registering ACME account..
Registration successful, account URL: 'https://acme-staging-v02.api.letsencrypt.org/acme/acct/xxxxxxx'
Task OK
root@proxmox:~# pvenode acme account list
default
root@proxmox:~# pvenode config set --acme domains=example.invalid
root@proxmox:~# pvenode acme cert order
Loading ACME account details
Placing ACME order
Order URL: https://acme-staging-v02.api.letsencrypt.org/acme/order/xxxxxxxxxxxxxx

Getting authorization details from
'https://acme-staging-v02.api.letsencrypt.org/acme/authz/xxxxxxxxxxxxxxxxxxxxx-xxxxxxxxxxxxx-xxxxxxx'
... pending!
Setting up webserver
Triggering validation
Sleeping for 5 seconds
Status is 'valid'!

All domains validated!

Creating CSR
Finalizing order
Checking order status
valid!

Downloading certificate
Setting pveproxy certificate and key
Restarting pveproxy
Task OK

Automatic renewal of ACME certificates

If a node has been successfully configured with an ACME-provided certificate (either via pvenode or via the GUI), the certificate will be automatically renewed by the pve-daily-update.service. Currently, renewal will be attempted if the certificate has expired or will expire in the next 30 days.