certs: document new ACME implementation, move to configuration section

Based on the documentation of PVE.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

pmg-admin-guide.adoc

@@ -96,10 +96,6 @@ include::pmg-bibliography.adoc[]
 
 :leveloffset: 0
 
-[appendix]
-include::pmg-ssl-certificate.adoc[]
-
-
 [appendix]
 Command Line Interface
 ----------------------

pmg-ssl-certificate.adoc

@@ -1,9 +1,215 @@
-SSL certificate
----------------
+[[sysadmin_certificate_management]]
+Certificate Management
+----------------------
 
-Access to the administration web interface is always done via
-`https`. The default certificate is never valid for your browser and
-you always get warnings.
+Access to the administration web-interface is always encrypted through `https`.
+Each {pmg} host creates by default its own (self-signed) Certificate Authority
+(CA) and generates a certificate for the node which gets signed by the
+aforementioned CA.
+These certificates are used for encrypted communication with
+the cluster's `pmgproxy` service for any API call, between an user and the
+web-interface or between nodes in a cluster.
+
+[[sysadmin_certs_api_gui]]
+Certificates for the API and SMTP
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+{pmg} knows 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 those 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 Webinterface.
+
+Certificates are managed through the {pmg} web-interface/API or using the
+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 upload that certificate simply over the web interface.
+
+[thumbnail="pmg-gui-certs-upload-custom.png"]
+
+Note that any certificates key file 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
+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 the
+https://letsencrypt.org[Let's Encrypt (LE)] production and its staging
+environment. Our ACME client supports validation of `http-01` challenges using
+a built-in webserver 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="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 server as 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 plugins task 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 basis building block for automatic certificate management.
+
+The ACME protocol specifies different types of challenges, for example the
+`http-01` where a webserver provides a file with a certain value to prove that
+it controls a domain. Sometimes this isn't possible, either because of
+technical limitations or if the address a domain points to is not reachable
+from the public internet. For such cases, one could use the `dns-01` challenge.
+This challenge also provides a certain value, but through a DNS record on the
+authority name server of the domain, rather than over a text file.
+
+[thumbnail="pmg-gui-acme-create-challenge-plugin.png"]
+
+{pve} supports both of those challenge types out of the box, you can configure
+plugins either over the web interface under `Datacenter -> ACME`, or using the
+`pvenode acme plugin add` command.
+
+ACME Plugin configurations are stored in `/etc/pve/priv/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="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 circa 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 webserver spawned on port 80.
+
+NOTE: The name `standalone` means that it can provide the validation on it's
+own, without any third party service. So, this plugin works also for cluster
+nodes.
+
+There are a few prerequisites to use it 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
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+{PVE} 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="pmg-gui-acme-create-challenge-plugin.png"]
+
+Add a new challenge plugin, here you can select your API provider, enter 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} autogenerates the form
+for the credentials, but not all providers are annotated yet. For those you
+will see a bigger text area, simply copy all the credentials `KEY`=`VALUE`
+pairs in there.
+
+DNS Validation through CNAME Alias
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+A special `alias` mode can be used to handle the 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`.
+
+
+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
+automatically renewed by the `pmg-daily.service`. Currently, renewal is
+triggered if the certificate either already expired or if it will expire in the
+next 30 days.
+
+Manually Change Certificate over Command-Line
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 If you want to get rid of these warnings, you have to generate a valid
 certificate for your server.
@@ -49,21 +255,22 @@ systemctl restart pmgproxy
 
 Test your new certificate by using your browser.
 
-NOTE: To transfer files from and to your {pmg}, you can use secure
-copy: If you desktop is Linux, you can use the `scp` command line
-tool. If your desktop PC is windows, please use a scp client like
-WinSCP (see https://winscp.net/).
-
+NOTE: To transfer files from and to your {pmg}, you can use secure copy: If you
+desktop is Linux, you can use the `scp` command line tool. If your desktop PC
+is windows, please use a scp client like WinSCP (see https://winscp.net/).
 
 Change Certificate for Cluster Setups
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-If you change the API certificate of an active cluster node, you also
-need to update the fingerprint inside the cluster configuration file
-`cluster.conf`. It is best to edit that file on the master node.
+If you change the API certificate of an active cluster node manually, you also
+need to update the pinned fingerprint inside the cluster configuration.
 
-To show the actual fingerprint use:
+You can do that by executing the following command on the host where the
+certificate changed:
 
 ----
-openssl x509 -in /etc/pmg/pmg-api.pem -noout -fingerprint -sha256
+pmgcm update-fingerprints
 ----
+
+Note, this will be done automatically if using the integrated ACME (for
+example, through Let's Encrypt) feature.

pmgconfig.adoc

@@ -288,6 +288,8 @@ using the following configuration keys:
 include::pmg.admin-conf-opts.adoc[]
 
 
+include::pmg-ssl-certificate.adoc[]
+
 Mail Proxy Configuration
 ------------------------