Docs - Let's Encrypt - Add ACME DNS Example (#851)

* Add acme-dns-client instructions

* Added acmedns example

* Updated to bring indentation back for note

* Fixed spelling and formatting error

docs/letsencrypt.md

@@ -9,10 +9,10 @@ file system, special tools around Certbot are required to work with certificates
     This feature is available on images as old as 2022.06.19 since it requires [PST storage partition on SD card](pst.md).
     Ports 80+443 need to be opened if you are port forwarding for this to work properly.
 
-
 ## Basic setup
 
 1. Update the OS and make sure that you are using a new image with [PST storage](pst.md).
+
    ```
    # rw
    # pacman -Syu
@@ -20,15 +20,18 @@ file system, special tools around Certbot are required to work with certificates
    ...
    # kvmd-pstrun -- true
    ```
+
    If the storage is not available, you need to [reflash the OS image](flashing_os.md) to the latest one from our official website.
 
 2. Switch filesystem to RW and obtain the certificate (for example, `pikvm.example.com`. The method depends on the network configuration. In the simplest case, if PiKVM is open for access from the Internet, it is recommended to use the webroot. Another examples will be described below.
+
    ```
    # rw
    # kvmd-certbot certonly_webroot --agree-tos -n --email user@example.com -d pikvm.example.com
    ```
 
 3. Install the certificate for KVMD-Nginx and (optionally) [KVMD-VNC](vnc.md). Running services will be restarted/reloaded automatically. Switch filesystem to RO.
+
    ```
    # kvmd-certbot install_nginx pikvm.example.com
    # kvmd-certbot install_vnc pikvm.example.com
@@ -36,6 +39,7 @@ file system, special tools around Certbot are required to work with certificates
    ```
 
 4. Check the renewal immediately, just for testing:
+
    ```
    # kvmd-certbot renew --force-renewal
    ```
@@ -50,12 +54,14 @@ file system, special tools around Certbot are required to work with certificates
 This example shows that PiKVM may not be accessible from the internet, but you can still get a certificate if you use Cloudflare DNS.
 
 1. Switch filesystem to RW and install the Cloudflare DNS plugin:
+
    ```
    # rw
    # pacman -Syu certbot-dns-cloudflare
    ```
 
 2. Prepare the environment for the DNS plugin (place the auth data):
+
    ```
    # kvmd-pstrun -- mkdir -p /var/lib/kvmd/pst/data/certbot/runroot
    # kvmd-pstrun -- nano /var/lib/kvmd/pst/data/certbot/runroot/.cloudflare.auth
@@ -63,6 +69,7 @@ This example shows that PiKVM may not be accessible from the internet, but you c
    ```
 
 3. Obtain the certificate:
+
    ```
    # kvmd-certbot certonly \
        --dns-cloudflare \
@@ -76,12 +83,12 @@ This example shows that PiKVM may not be accessible from the internet, but you c
 
 4. Next follow the basic guide.
 
-
 ## Route53 DNS
 
 This example shows that PiKVM may not be accessible from the internet, but you can still get a certificate if you use AWS Route53 DNS. Make sure you are running an image newer than 2022.06.20 and kvmd version 3.119-1 or greater.
 
 1. Switch filesystem to RW and install the Route53 DNS plugin:
+
    ```
    # rw
    # pacman -Syu certbot-dns-route53
@@ -102,26 +109,18 @@ This example shows that PiKVM may not be accessible from the internet, but you c
      "Statement": [
        {
          "Effect": "Allow",
-                "Action": [
+         "Action": ["route53:ListHostedZones", "route53:GetChange"],
-                    "route53:ListHostedZones",
+         "Resource": ["*"]
-                    "route53:GetChange"
-                ],
-                "Resource": [
-                    "*"
-                ]
        },
        {
-                "Effect" : "Allow",
+         "Effect": "Allow",
-                "Action" : [
+         "Action": ["route53:ChangeResourceRecordSets"],
-                    "route53:ChangeResourceRecordSets"
+         "Resource": ["arn:aws:route53:::hostedzone/YOURHOSTEDZONEID"]
-                ],
-                "Resource" : [
-                    "arn:aws:route53:::hostedzone/YOURHOSTEDZONEID"
-                ]
        }
      ]
    }
    ```
+
    Make sure you replace YOURHOSTEDZONEID with the instance ID of your hosted zone.
 
    Once the user is created don’t forget to download and save your access key and secret access key (somewhere secure, these are as sensitive as your passwords).
@@ -129,14 +128,17 @@ This example shows that PiKVM may not be accessible from the internet, but you c
 3. Setup credentials:
 
    We now need to put the AWS credentials on the PiKVM so the certbot can use them.
+
    ```
    kvmd-pstrun -- mkdir -p /var/lib/kvmd/pst/data/certbot/runroot
    ```
 
    Copy and paste your AWS credentials into the nano editor and save the file.
+
    ```
    # kvmd-pstrun -- nano /var/lib/kvmd/pst/data/certbot/runroot/.route53.auth
    ```
+
    Here is an example .route53.auth file. Replace the placeholders with the access key and secret access key that you just saved from AWS and fill them in.
 
    ```ini
@@ -146,11 +148,13 @@ This example shows that PiKVM may not be accessible from the internet, but you c
    ```
 
    Update permissions:
+
    ```
    # kvmd-pstrun -- chmod 600 /var/lib/kvmd/pst/data/certbot/runroot/.route53.auth
    ```
 
 4. Obtain the certificate:
+
    ```
    # export AWS_SHARED_CREDENTIALS_FILE="/var/lib/kvmd/pst/data/certbot/runroot/.route53.auth"
    # kvmd-certbot certonly \
@@ -161,18 +165,103 @@ This example shows that PiKVM may not be accessible from the internet, but you c
        -d pikvm.example.com
    ```
 
-4. Enable automatic certificate renewal:
+5. Enable automatic certificate renewal:
 
    Create the file: `/etc/conf.d/kvmd-certbot` with the following contents so the renewall service can find the authentication file containing the AWS credentials:
+
    ```
    AWS_SHARED_CREDENTIALS_FILE="/var/lib/kvmd/pst/data/certbot/runroot/.route53.auth"
    ```
 
    Now enable the renewal service:
+
    ```
    # systemctl enable --now kvmd-certbot.timer
    ```
 
+## ACME DNS
+
+[ACME DNS](https://github.com/joohoi/acme-dns) is a _"Limited DNS server with RESTful HTTP API to handle ACME DNS challenges easily and securely."_ The [acme-dns-client](https://github.com/acme-dns/acme-dns-client) works, in conjunction, with Certbot (**`kvmd-certbot`**) to enable **`DNS-01`** challenge support via ACME DNS.
+
+These instructions are for how to install and use the **`acme-dns-client`** with ACME DNS for PiKVM.
+
+Assumptions:
+
+- ACME DNS is already set up and functioning in the environment
+- ACME DNS Server is **`auth.example.org`**
+- PiKVM Fully Qualified Domain Name (FQDN) is **`pikvm.example.org`**
+- PiKVM is running on a supported Raspberry Pi using the [PiKVM OS](https://github.com/pikvm/os) (which is 32-bit as of the writing of this documentation)
+- All configuration examples below are as user **`root`** via a terminal session to PiKVM
+
+Not in Scope:
+
+- Installation and Setup of ACME DNS Server
+
+1. Ensure that Step 1 from [Basic Setup](https://docs.pikvm.org/letsencrypt/#basic-setup) has been completed
+2. Visit the [Releases](https://github.com/acme-dns/acme-dns-client/releases) page to get the URL for the latest **`acme-dns-client`** release.  
+    !!! note
+        PiKVM OS is 32-bit, which is **`linux_armv6`**.
+
+3. Install **`acme-dns-client`**
+
+   The **`acme-dns-client`** is not distributed by **`pacman`** and is a manual installation. The steps below are for:
+
+   - Creating a folder for **`acme-dns-client`**
+   - Downloading and extracting the **`acme-dns-client`** TAR from Github
+   - Moving the **`acme-dns-client`** binary to the created folder
+   - Cleaning up files from the download
+   - Creating the necessary persistent symbolic link to allow **`acme-dns-client`** to be ran
+   - Initialize **`acme-dns-client`**
+
+    !!! note
+        Make sure to replace the URL below with the one gathered from Step 1. As of the writing of this documentation, the latest (and demonstrated) version is **v0.3**.
+
+   ```sh
+   mkdir /etc/acmedns
+   curl -LO https://github.com/acme-dns/acme-dns-client/releases/download/v0.3/acme-dns-client_0.3_linux_armv6.tar.gz
+   tar -zxvf acme-dns-client_0.3_linux_armv6.tar.gz
+   mv acme-dns-client /etc/acmedns/acme-dns-client
+   ln -sf /etc/acmedns/acme-dns-client /usr/local/bin/acme-dns-client
+   rm LICENSE
+   rm README.md
+   rm acme-dns-client_0.3_linux_armv6.tar.gz
+   acme-dns-client
+   ```
+
+4. Register **`acme-dns-client`** with ACME DNS  
+    !!! note
+        This is interactive, follow instructions for creating and verifying the appropriate `CNAME` record.  
+   
+   ```sh
+   acme-dns-client register -d pikvm.example.org -s http://auth.example.org
+   ```
+
+   Once registration is complete ownership of `clientstorage.json` must be changed to `kvmd-certbot`.
+   
+   ```sh
+   chown kvmd-certbot:kvmd-certbot /etc/acmedns/clientstorage.json
+   ```
+
+    !!! note
+        If using `acme-dns-client` on an internal/private domain with an ACME compatible Certificate Authority do not forget to add `-ns <dns-server-ip>:<dns-server-port>` to `acme-dns-client register`
+
+5. Register Certbot
+
+   ```sh
+   kvmd-certbot register
+   ```
+
+6. Request Certificate via Certbot
+
+   ```sh
+   kvmd-certbot certonly --manual --preferred-challenges dns --manual-auth-hook 'acme-dns-client' -d pikvm.example.org
+   ```
+
+    !!! note
+        If using an ACME compatible Certificate Authority (other than Let's Encrypt) do not forget to add `--server https://ca.example.org/acme/acme/directory` to `kvmd-certbot`
+
+7. Follow steps 3 through 5 under [Basic Setup](https://docs.pikvm.org/letsencrypt/#basic-setup) to complete setup and renewal of certificates
+
 ## Wireguard proxy
 
 If you don't have public IP, and you don't want to put your API keys in PiKVM,
@@ -181,6 +270,7 @@ serve ACME challenges from a host they can reach from the Internet (e.g. VPS),
 to which you'll connect over wireguard.
 
 The example assumes:
+
 - FQDN of your pikvm is `pikvm1.int.example`;
 - FQDN of the proxy VPS is `acme-proxy.example`;
 - public IP addresses of VPS are `198.51.100.1` and `2001:db8::1`;
@@ -189,6 +279,7 @@ The example assumes:
 1. Setup wireguard and ensure it's working.
 
 2. Setup public DNS zone to point the domain address at the public VPS:
+
    ```zone
    acme-proxy.example. IN A      198.51.100.1
    acme-proxy.example. IN AAAA   2001:db8::1
@@ -197,6 +288,7 @@ The example assumes:
 
 3. On the public VPS, configure HTTP proxy to forward
    `/.well-known/acme-challenge` to PiKVM. For example in nginx:
+
    ```nginx
    server {
        listen 80;