chore(lego): add README, extract systemd user pattern into defaults

roles/lego/README.md

@@ -0,0 +1,42 @@
+# `finallycoffee.base.lego` ansible role
+
+This role can be used to retrieve ACME certificates on the target host. It uses `lego` for that, and with systemd template units provides an easy way to configure and monitor the status for each certificate.
+
+## Requirements
+
+- `systemd`
+- write access to /tmp to unpack the lego release tarball during installation
+- write access to /opt/lego (or whatever `lego_base_path` is set to) for configuration and certificate data
+- `become` privileges of the `ansible_user` on the target
+
+## Usage
+
+### Required configuration
+
+- `lego_instance` - used for allowing multiple lego jobs to run with systemd template units. recommended to be set to the CN / first SAN of the certificate.
+- `lego_cert_domains` - list of FQDNs to request a certificate for
+- `lego_acme_account_email` - when using letsencrypt, a contact email is mandatory
+
+### Proxies / Registries
+
+The role ensure `lego` is downloaded from the github release page. If you are behind a proxy or use a registry like Nexus3, set `lego_release_archive_server`.
+
+### ACME server
+
+Per default, the Letsencrypt Staging ACME server is configured. Set `lego_acme_server_url` from `lego_letsencrypt_server_urls.{qa,prod}` or configure your own ACME v2 server directly.
+
+### Certificate
+
+To set for which domains to request a certificate for, set them as a list of SANs in `lego_cert_domains`. The default key type is EC256 and can be overridden using `lego_cert_key_type`.
+
+Set the type of challenge in `lego_acme_challenge_type` (to either `http` or `dns`), and `lego_acme_challenge_provider` to, for example, `rfc2136` for DNS challenges using the DNSUPDATE mechanism. If your challenge needs additional data, set that in `lego_command_config` as a dictionary analog to `lego_base_command_config` (see [defaults](defaults/main.yml)).
+
+## Trivia
+
+### Architecture
+
+By default, the lego distribution for `linux` on `amd64` is downloaded. If your target needs a different architecture or target OS, adjust this in `lego_os` and `lego_architecture`, cross-checking with the [lego GitHub release page](https://github.com/go-acme/lego/releases/tag/v4.17.4) for upstream availability.
+
+### User management
+
+The role will attempt to create user+group for each seperate lego instance for data isolation (i.e. to avoid leaking a TSIG key from one lego instance to other services). The user and group are of the form `acme-{{ lego_instance }}`. Beware that changing this in `lego_cert_{user,group}` also requires `lego_systemd_{user,group}` to be adjusted!

roles/lego/defaults/main.yml

@@ -5,6 +5,8 @@ lego_instance: default
 lego_base_path: "/opt/lego"
 lego_cert_user: "acme-{{ lego_instance }}"
 lego_cert_group: "{{ lego_cert_user }}"
+lego_systemd_user: "acme-%i"
+lego_systemd_group: "{{ lego_systemd_user }}"
 lego_instance_base_path: "{{ lego_base_path }}/instances"
 lego_instance_path: "{{ lego_instance_base_path }}/{{ lego_instance }}"
 

roles/lego/templates/lego@.service.j2

@@ -4,8 +4,8 @@ Description=Run lego (letsencrypt client in go)
 [Service]
 Type=oneshot
 EnvironmentFile={{ lego_base_path }}/%i.conf
-User=acme-%i
+User={{ lego_systemd_user }}
-Group=acme-%i
+Group={{ lego_systemd_group }}
 ExecStart={{ lego_base_path }}/run.sh
 
 [Install]