How to do that: Step by Step

A site by: Robert Baldwin

Protect HomeAssistant using CloudFlare mTLS

How to protect HomeAssistant using Cloudflare mTLS

Before you begin pick a new subdomain for the service you wish to protect by mTLS. For example ha-mobile. We will use this later when configuring mTLS and the service public hostname. These instructions assume you already have a domain and subdomain configured with cloudflare and have already configured the tunnel.

1) If you do not have OpenSSL, download OpenSSL.

Redhat/CentOS:

# yum install openssl

Ubuntu:

# sudo apt install openssl

Windows:

I used firedaemon's binaries found on the openssl.org list here: https://wiki.openssl.org/index.php/Binaries

Firedaemon's URL:

https://www.firedaemon.com/get-openssl

Click the Windows Start button and type "edit the system environment variables"

click "Environment Variables" button at bottom of window.

create new varible "OPENSSL_HOME" with value: C:\Program Files\FireDaemon OpenSSL 3

Edit path variable add new entry

"%OPENSSL_HOME%\bin"

REBOOT

Test openssl is installed and executable at the command prompt.

openssl --version

Example Output:

C:\Windows\System32>openssl --version

OpenSSL 3.3.0 9 Apr 2024 (Library: OpenSSL 3.3.0 9 Apr 2024)

2) Go to the cloudflare dashboard (https://dash.cloudflare.com)

3) Click on your domain

4) Generate a client certificate in Cloudflare

4a) Click SSL/TLS on lefthand panel

4b) Click Client Certficates

4c) Click Create Certificate

4d) Leave All values default and click Create.

4e) copy and paste the certificate into notepad and save it as cf.pem

4f) copy and paste the private key into notepad and save it as cf.key

5) Choose which host(s) you wish to enable mTLS

ie: ha-mobile.example.com

6) Create an mTLS Rule by clicking "Create mTLS Rule"

6a) Make it match the below rule.

6b) Click Deploy

Return to the cloudflare dashboard https://dash.cloudflare.com

7) Goto your CloudFlare Tunnel Configuration by clicking Zero Trust, then Network, then Tunnels

8) Click the hamburger button on the far right of your tunnel name and click Configure.

9) Click Public Hostname

10) Add a new Public Hostname ie: ha-mobile.example.com

The service is now secured by your client certificate and will be inaccessible from device which do not have your client certificate. Next you will need to install that certificate on your mobile device.

11) We need to convert the certificate and key into a format that Android can import.

Use the following command to convert these two files into a pfx file, which is can be imported into Android.

openssl pkcs12 -export -out ha-mobile.pfx -inkey cf.key -in cf.pem

Note: You'll be prompted for a password. Enter a password which you'll remember. You'll be prompted for this password when importing the certificate in the next step 13.

12) Copy this file(ha-mobile.pfx) to your Mobile device's local storage or to Google Drive.

13) Import the pfx file to your Android Device.

Android 14+

Go to Settings -> Security & Privacy -> More Security & Privacy -> Encryption & Credentials -> Install Certficate -> VPN & app user certificate
then locate the file you transferred in the previous step.

Be sure give the certificate a sensible name so that in the future you'll remembers what it is.

Note: You'll be prompted for a password when importing the pfx, enter the password you specified in step 11.

14) Configure HomeAssistant mobile app with your new URL https://ha-mobile.example.com you'll be prompted to select the certificate to use. Select the certificate you imported in the prior steps.

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