[[sysadmin_certificate_management]]
Certificate Management
----------------------

Access to the web-based administration interface is always encrypted through
`https`.  Each {pmg} host creates by default its own (self-signed) certificate.
This certificate is used for encrypted communication with the host's `pmgproxy`
service, for any API call between a user and the web-interface or between nodes
in a cluster.

Certificate verification in a {pmg} cluster is done based on pinning the
certificate fingerprints in the cluster configuration and verifying that they
match on connection.

[[sysadmin_certs_api_gui]]
Certificates for the API and SMTP
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

{pmg} uses two different certificates:

* `/etc/pmg/pmg-api.pem`: the required certificate used for {pmg} API requests.
* `/etc/pmg/pmg-tls.pem`: the optional certificate used for SMTP TLS
  connections, see xref:pmgconfig_mailproxy_tls[mailproxy TLS configuration]
  for details.

You have the following options for these certificates:

1. Keep using the default self-signed certificate in `/etc/pmg/pmg-api.pem`.
2. Use an externally provided certificate (for example, signed by a commercial
Certificate Authority (CA)).
3. Use an ACME provider like Let's Encrypt to get a trusted certificate with
automatic renewal; this is also integrated in the {pmg} API and web interface.

Certificates are managed through the {pmg} web-interface/API or using the
`pmgconfig` CLI tool.

[[sysadmin_certs_upload_custom]]
Upload Custom Certificate
~~~~~~~~~~~~~~~~~~~~~~~~~

If you already have a certificate which you want to use for a {pmg} host, you
can simply upload that certificate over the web interface.

[thumbnail="screenshot/pmg-gui-certs-upload-custom.png"]

Note that any certificate key files must not be password protected.

[[sysadmin_certs_get_trusted_acme_cert]]
Trusted certificates via Let's Encrypt (ACME)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

{PMG} includes an implementation of the **A**utomatic **C**ertificate
**M**anagement **E**nvironment (**ACME**) protocol, allowing {pmg} admins to
use an ACME provider like Let's Encrypt for easy setup of TLS certificates,
which are accepted and trusted by modern operating systems and web browsers
out of the box.

Currently, the two ACME endpoints implemented are the
https://letsencrypt.org[Let's Encrypt (LE)] production and staging
environments. Our ACME client supports validation of `http-01` challenges using
a built-in web server and validation of `dns-01` challenges using a DNS plugin
supporting all the DNS API endpoints https://acme.sh[acme.sh] does.

[[sysadmin_certs_acme_account]]
ACME Account
^^^^^^^^^^^^

[thumbnail="screenshot/pmg-gui-acme-create-account.png"]

You need to register an ACME account per cluster, with the endpoint you want to
use. The email address used for that account will serve as the contact point for
renewal-due or similar notifications from the ACME endpoint.

You can register or deactivate ACME accounts over the web interface
`Certificates -> ACME Accounts` or using the `pmgconfig` command-line tool.
----
 pmgconfig acme account register <account-name> <mail@example.com>
----

TIP: Because of https://letsencrypt.org/docs/rate-limits/[rate-limits] you
should use LE `staging` for experiments or if you use ACME for the very first
time until all is working there, and only then switch over to the production
directory.

[[sysadmin_certs_acme_plugins]]
ACME Plugins
^^^^^^^^^^^^

The ACME plugin's role is to provide automatic verification that you, and thus
the {pmg} cluster under your operation, are the real owner of a domain. This is
the basic building block of automatic certificate management.

The ACME protocol specifies different types of challenges, for example the
`http-01`, where a web server provides a file with a specific token to prove
that it controls a domain. Sometimes this isn't possible, either because of
technical limitations or if the address of a record is not reachable from the
public internet. The `dns-01` challenge can be used in such cases. This
challenge is fulfilled by creating a certain DNS record in the domain's zone.

[thumbnail="screenshot/pmg-gui-acme-create-challenge-plugin.png"]

{pmg} supports both of those challenge types out of the box, you can configure
plugins either over the web interface under `Certificates -> ACME Challenges`,
or using the `pmgconfig acme plugin add` command.

ACME Plugin configurations are stored in `/etc/pmg/acme/plugins.cfg`.
A plugin is available for all nodes in the cluster.

Domains
^^^^^^^

You can add new or manage existing domain entries under `Certificates`, or
using the `pmgconfig` command.

[thumbnail="screenshot/pmg-gui-acme-add-domain.png"]

After configuring the desired domain(s) for a node and ensuring that the
desired ACME account is selected, you can order your new certificate over the
web-interface. On success, the interface will reload after roughly 10 seconds.

Renewal will happen xref:sysadmin_certs_acme_automatic_renewal[automatically].

[[sysadmin_certs_acme_http_challenge]]
ACME HTTP Challenge Plugin
~~~~~~~~~~~~~~~~~~~~~~~~~~

There is always an implicitly configured `standalone` plugin for validating
`http-01` challenges via the built-in web server spawned on port 80.

NOTE: The name `standalone` means that it can provide the validation on its
own, without any third party service. So this plugin also works for cluster
nodes.

There are a few prerequisites to use this for certificate management with Let's
Encrypts ACME.

* You have to accept the ToS of Let's Encrypt to register an account.
* **Port 80** of the node needs to be reachable from the internet.
* There **must** be no other listener on port 80.
* The requested (sub)domain needs to resolve to a public IP of the {pmg} host.


[[sysadmin_certs_acme_dns_challenge]]
ACME DNS API Challenge Plugin
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

On systems where external access for validation via the `http-01` method is
not possible or desired, it is possible to use the `dns-01` validation method.
This validation method requires a DNS server that allows provisioning of `TXT`
records via an API.

[[sysadmin_certs_acme_dns_api_config]]
Configuring ACME DNS APIs for validation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

{pmg} re-uses the DNS plugins developed for the `acme.sh`
footnote:[acme.sh https://github.com/acmesh-official/acme.sh] project. Please
refer to its documentation for details on configuration of specific APIs.

The easiest way to configure a new plugin with the DNS API is using the web
interface (`Certificates -> ACME Accounts/Challenges`).

[thumbnail="screenshot/pmg-gui-acme-create-challenge-plugin.png"]

Here you can add a new challenge plugin by selecting your API provider and
entering the credential data to access your account over their API.

TIP: See the acme.sh
https://github.com/acmesh-official/acme.sh/wiki/dnsapi#how-to-use-dns-api[How to use DNS API]
wiki for more detailed information about getting API credentials for your
provider. Configuration values do not need to be quoted with single or double
quotes; for some plugins that is even an error.

As there are many DNS providers and API endpoints, {pmg} automatically generates
the form for the credentials, but not all providers are annotated yet. For those
you will see a bigger text area, into which you simply need to copy all the
credential's `KEY`=`VALUE` pairs.

DNS Validation through CNAME Alias
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

A special `alias` mode can be used to handle validation on a different
domain/DNS server, in case your primary/real DNS does not support provisioning
via an API. Manually set up a permanent `CNAME` record for
`_acme-challenge.domain1.example` pointing to `_acme-challenge.domain2.example`,
and set the `alias` property in the {pmg} node configuration file
`/etc/pmg/node.conf` to `domain2.example` to allow the DNS server of
`domain2.example` to validate all challenges for `domain1.example`.

[[sysadmin_certs_acme_dns_wildcard]]
Wildcard Certificates
^^^^^^^^^^^^^^^^^^^^^

Wildcard DNS names start with a `*.` prefix and are considered valid for all
(one-level) subdomain names of the verified domain. So a certificate for
`*.domain.example` is valid for `foo.domain.example` and
`bar.domain.example`, but not for `baz.foo.domain.example`.

Currently, you can only create wildcard certificates with the
https://letsencrypt.org/docs/challenge-types/#dns-01-challenge[DNS challenge type].


Combination of Plugins
^^^^^^^^^^^^^^^^^^^^^^

Combining `http-01` and `dns-01` validation is possible in case your node is
reachable via multiple domains with different requirements / DNS provisioning
capabilities. Mixing DNS APIs from multiple providers or instances is also
possible by specifying different plugin instances per domain.

TIP: Accessing the same service over multiple domains increases complexity and
should be avoided if possible.

[[sysadmin_certs_acme_automatic_renewal]]
Automatic renewal of ACME certificates
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If a node has been successfully configured with an ACME-provided certificate
(either via pmgconfig or via the web-interface/API), the certificate will be
renewed automatically by the `pmg-daily.service`. Currently, renewal is
triggered if the certificate either has already expired or if it will expire in
the next 30 days.

Manually Change Certificate over the Command Line
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If you want to get rid of certificate verification warnings, you have to
generate a valid certificate for your server.

Log in to your {pmg} via ssh or use the console:

----
openssl req -newkey rsa:2048 -nodes -keyout key.pem -out req.pem
----

Follow the instructions on the screen, for example:

----
Country Name (2 letter code) [AU]: AT
State or Province Name (full name) [Some-State]:Vienna
Locality Name (eg, city) []:Vienna
Organization Name (eg, company) [Internet Widgits Pty Ltd]: Proxmox GmbH
Organizational Unit Name (eg, section) []:Proxmox Mail Gateway
Common Name (eg, YOUR name) []: yourproxmox.yourdomain.com
Email Address []:support@yourdomain.com

Please enter the following 'extra' attributes to be sent with your certificate request
A challenge password []: not necessary
An optional company name []: not necessary
----

After you have finished the certificate request, you have to send the file
`req.pem` to your Certification Authority (CA). The CA will issue the
certificate (BASE64 encoded), based on your request – save this file as
`cert.pem` to your {pmg}.

To activate the new certificate, do the following on your {pmg}:

----
cat key.pem cert.pem >/etc/pmg/pmg-api.pem
----

Then restart the API servers:

----
systemctl restart pmgproxy
----

Test your new certificate, using your browser.

NOTE: To transfer files to and from your {pmg}, you can use secure copy: If your
desktop runs Linux, you can use the `scp` command-line tool. If your desktop PC
runs windows, please use an scp client like WinSCP (see https://winscp.net/).

Change Certificate for Cluster Setups
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If you change the API certificate of an active cluster node manually, you also
need to update the pinned fingerprint inside the cluster configuration.

You can do that by executing the following command on the host where the
certificate changed:

----
pmgcm update-fingerprints
----

Note, this will be done automatically if using the integrated ACME (for
example, through Let's Encrypt) feature.
