Important note about SSL VPN compatibility for 20.0 MR1 with EoL SFOS versions and UTM9 OS. Learn more in the release notes.

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Sophos Firewall: [LetsEncrypt] How To in Sophos Firewall

LuCar Toni

Disclaimer: This information is provided as-is for the benefit of the Community. Please contact Sophos Professional Services if you require assistance with your specific environment.

Overview

    This recommended Read reviews different options for obtaining a Let's Encrypt certificate.

    Update

    Update: V21.0 supports Lets Encrypt onboard:  Sophos Firewall v21 Early Access Announcement  
    Note: Make sure your Sophos Firewall time is correct to avoid potential Certificate Trust issues

    UTM has LE Support for WAF (since UTM9.6). However, you can also use LE certificates on Sophos. Many people do not know that you need a small Linux server and 5-10 minutes of your time every three months. You can automate this. 

    First, I want to share LE's "how it works" page. https://letsencrypt.org/how-it-works/

    My Setup

    Internet - Sophos - Ubuntu 20.04 LTS
    Ubuntu has "certbot" installed. Feel free to use other LE modules.
    https://certbot.eff.org/ https://certbot.eff.org/lets-encrypt/ubuntubionic-apache
    Follow straight the Guide for your OS. I am relying fully on those apps for the renewal process.  

    Next, I am choosing the HTTP-01 method for LE, so I need a DNAT for LE to my Ubuntu.

    (V18). 

    PS: I am using HTTP DNAT for the renewal process and will deactivate those rules afterward. But you can also use only the LE IPs: 
    https://community.letsencrypt.org/t/can-i-get-list-ip-from-letsencrypt/57117
    PS2: As explained in this Community thread, you could switch to the DNS validation.  

    The next step would be to check your Domain. Your DNS A-Record should point to your WAN IP. Otherwise, this process won’t work. 
    So perform a dig / nslookup of your domain. It’ll point to your WAN IP, so your DNAT will work, and HTTP packets will be forwarded to Certbot. 
    You can also use the Sophos free DDNS service. https://community.sophos.com/kb/en-us/123126 

    Certbot

    Let us start Certbot and try it. 
    My renewal process is straightforward:


    (Be careful: LE blocks you after a couple of "failed" requests for some time, so check everything.)
    Ultimately, you’ll get four files on your Linux: Public, Chain, Fullchain, and Privatekey Certificates. 

    Upload to Sophos Firewall

    You’ll use this Public and Privatkey certificate. 
    There are a couple of approaches to upload this to Sophos. 

    The first LE Cert can be uploaded. 
    It would be best to use the Public.pem in "Certificate" and the Privatkey in "Private key." 
    PS: you have to rename the Privatkey.pem to Privatkey.key. Otherwise, Sophos won’t take this certificate. 

    Optionally, you can upload the other Chain and fullchain Certificates under Certificate Authorities (Without Private key). 
    Now, you can use this Certificate for WAF/Webadmin. 

    In renewal (each 90 Days), choose a process.

    Automation 

    You can upload the new LE certificate with another Name and replace it in WAF/Webadmin. 
    Or you can "update" the current LE certificate with the new public.pem / private.key. However, for this method, you have to switch to a fallback certificate in WAF/Webadmin because Sophos can't update a currently used certificate.  

    After all, those steps are manually processed every 90 days. 
    You can "script" this if you want to. Basically, upload the certificate to Sophos every 90 Days. 


    Other members of the community have already performed scripts for this.

    If you want to script this, this community can help you if you struggle with a point.
    So kindly open a new thread with your issue with the API, and we’ll try to find a solution. 

    Sophos Factory

    Sophos Factory brings a new Tool to automate Script-based approaches. This means you can easily run a Script like Certbot or Lego in a Sophos Factory environment to generate and upload the certificate to the Sophos Firewall. 

    Sophos Factory offers a free Community Edition. https://community.sophos.com/sophos-factory/ https://community.sophos.com/sophos-factory/b/release-notes-news/posts/get-started-here-sophos-factory-offer-automation-for-all-with-its-free-community-edition

    Within Sophos Factory, it could look like this:

    Each step is a scripting component. Using tools like Lego and Github, the "Pipeline" will run once, generate the certificate, and upload it to the Firewall. 

    Contribution:
          https://zerossl.com/free-ssl/#crt Free alternative to this approach
    For the Github script. 
     Thanks for the PHP Script! 
     for a Powershell Script with WAF integration. 
     is for another version of a Powershell script. 



    Revamped RR
    [edited by: Erick Jan at 3:35 AM (GMT -7) on 10 Oct 2024]
    Parents Reply
    • in reply to LuCar Toni

      There are certain devices I don't want to get out to the internet for any reason (think chinese cameras).  But they need to be sync'd to the same time source for chain of custody reasons. 
      I'm currently running a separate time server but I'd rather have it on the FW like the old UTM.
      Unless someone can sight a best practice to the contrary?

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