SOPHOS XG: Use Azure MFA for SSLVPN and Userportal

Inspiration for this post, was taken from: https://rieskaniemi.com/azure-mfa-with-sophos-xg-firewall/

Some of the things that I’ve seen at work, is that Sophos XG VPN users are using one token for Sophos SSLVPN and another for ex. Office 365 services. Both tokens can be in Microsoft Authenticator, but only the one that Office 365 is using, can do the “pop-up”, letting the user easy sign-in, like this:

Microsoft Authenticator beta app for iOS and Android updated with ...

Nonetheless it’s easier for the IT dept. (and the user!) to maintain only one token solution 🙂

Here is the auth flow for Azure MFA with NPS Extension:

Nice isn’t it 😉

So how to fix?

We setup Sophos XG for RADIUS validation for SSLVPN and UserPortal access, and if you use the built-in OTP solution, disable that 🙂

To get started:

  • If you do not have MFA enabled for your Office 365/Azure AD account’s you can enable it through following link: https://aka.ms/mfasetup
  • And of course you need to have set Azure AD Connect to get your on-premise talking with Azure, I will not go into the details with this here, as I assume this is already setup and working 🙂

Let’s go:

  1. Install the Network Policy Server (NPS) role on your member server or domain controller. Refering to the Network Policy Server Best Practices, then you will find this “To optimize NPS authentication and authorization response times and minimize network traffic, install NPS on a domain controller.” So we will go ahead and place this on the domain controller, but remember it’s also possible to do it on a domain joined member server!
  2. Press “Next” and the installation begins:

  3. After installation has ended, go and join the NPS to the Active Directory, right-click NPS (Local):
    Register server in Active Directory menu option

  4. Download and install the NPS Extension for Azure MFA here:
    https://www.microsoft.com/en-us/download/details.aspx?id=54688
    Note: As i did try this on a server with already setup NPS, it failed with the other mechanisms, because of this:
    https://docs.microsoft.com/en-us/azure/active-directory/authentication/howto-mfa-nps-extension#control-radius-clients-that-require-mfa

    Control RADIUS clients that require MFA

    Once you enable MFA for a RADIUS client using the NPS extension, all authentications for this client are required to perform MFA. If you want to enable MFA for some RADIUS clients but not others, you can configure two NPS servers and install the extension on only one of them.

    Configure RADIUS clients that you want to require MFA to send requests to the NPS server configured with the extension, and other RADIUS clients to the NPS server not configured with the extension.”

    So the “workround” is to run the MFA for the Sophos on a seprate NPS instance 🙂

  5. After it’s installed, go and follow the configure is like it’s stated here (Find TenantID and run Powershell script):
    https://docs.microsoft.com/en-us/azure/active-directory/authentication/howto-mfa-nps-extension#azure-active-directory
  6. Go and configure your radius Client, here it’s the XG:

    Remember the secret, we need it later on 🙂

  7. Create a “Connection request policy”:


    Type here the IP of the XG

    Just set like above, and the rest of the settings, just leave them to their defaults 🙂

  8. Now create a “Network Policy”

    Add a domain group, that shall have this access, to simplify, here I have choose domain\Domain Users
    Now the EAP types, XG does only support PAP, as far as I have tested:


    You will get a warning telling you that you have choosen unencrypted auth (locally – not on the Internet!), just press OK.
    Just left the rest to their default’s and save the policy.

  9. Now to create a firewall rule:

  10. Now to setup the XG for this:

    Press ADD:

    Remember to choose RADIUS:

    Fill in as your environment matches:

    Type in the secret you wrote down earlier and create a host object for your NPS, also remember to change the timeout from 3 to 15 secs!

    You can now test is the authentication through NPS and Azure MFA is working, change Group name attribute to “SF_AUTH”

    Press the TEST CONNECTION butoon:

    type in a users username (e.mail adress) and password, and your phone should pop-up with Microsoft Authenticator 🙂

    You should see this soon after you accept the token:

  11. Now head over to the Authentication –> Services section:

    Add the new RADIUS server to:
    – User portal authentication methods
    – SSL VPN authentication methods

    Also make sure that the group your AD / RADIUS users are in, is added to the SSLVPN profile:

  12. Now login to the User Portal and download a VPN client (You cannot use the old ones, if you already had thoose installed)
  13. Now connect through VPN, type in your full email in username and your password, then wait for MS Authenticator to pop-up, accept the token and you are logged into VPN 🙂

Sources:

https://docs.microsoft.com/en-us/azure/active-directory/authentication/howto-mfa-nps-extension-vpn

https://docs.microsoft.com/en-us/windows-server/networking/technologies/nps/nps-best-practices

https://community.sophos.com/kb/en-us/127328

10 Comments

  1. Admin IT

    Thanks so much for the guide. It’s very useful and everything is working.
    However, login to the user portal doesn’t work.
    Also as users don’t usually have admin rights to install software, is it possible to deploy remotely the client and its settings?

    many thanks

    Reply
    1. Martin (Post author)

      Hi,

      You may look into which users have rights for the userportal, tryk with ANY to get started, I think you have other groups than ad / radius maybe? 🙂

      You can deploy via GPO, you can use the Sophos Connect VPN vcleint if you are on the way to SFOS? 🙂

      https://martinsblog.dk/sophos-connect-migration-script-from-utm-sslvpn/

      Regards Martin

      Reply
  2. seb33

    Hi. nice howto and very appreciated ! however, im stuck at testing connection when adding server in XG. I get error on the NPS, stating : an extension DLL rejected the connection request. I would have 1st testing the connection before installing the MFA ext, unsucessful, nps was saying there was mismatch or non existing user.

    What exactly is the SF_Auth attribute ? how could have test the same setup without MFA enable ?

    Reply
    1. Martin (Post author)

      Got it from here:

      https://support.sophos.com/support/s/article/KB-000036916?language=en_US

      Add the Filter-Id attribute value needed to meet your network security requirements. In this example, the Filter-Id value is set to SF_AUTH which is used in Group Name Attribute when adding an external RADIUS server in Sophos Firewall.

      Any help? 🙂

      Reply
  3. Alex

    Hi Martin,

    thank you for the tutorial. In my test environment I implemented it and it looks good up to the step that it sends me the request to the smartphone. Unfortunately I can’t use the latest Sophos Connect VPN client with it. With the old Sophos VPN client the request comes and often you have to do the login twice until the connection is established. Remedy is then in the Config file to set the value “route-delay” from 4 to 2 down. Nothing helps with Sophos Connect.

    Do you have an idea for this?

    Thank you in advance.

    Many greetings
    Alex

    Reply
    1. Martin (Post author)

      Hi Alex,
      Funny it is, I have it working fine with the old client and Sophos Connect, no double confirmations needed.

      Have you set the readius timeout to a higher value than standard? 15 sec+

      Reply
      1. Alex

        Hi Martin,

        thank you for the super fast feedback.

        Are you on the Sophos community as “twister5800”?

        Would then continue the question in the community. 😉

        It’s really crazy. Everything works for me. On the Sophos XG the test runs through and I can use the MS Auth. to confirm the login and get a response. Same with the Sophos Connect client, however it then also runs auth-failure and you can see in the log that it tries twice. I have the impression, whether Sophos Connect or the old Sophos SSL VPN client. Both try to reconnect way too fast and then run into an error. With the old client helps as already written, the entry route-delay 2. But the solution is also not nice.

        I have now tested the timing of 5-30 sec through all the same problem.

        Without MFA against Active Directory it works immediately.

        Let’s see if the Sophos community has a tip for this.

        Many greetings
        Alex

        Reply
        1. Martin (Post author)

          Hi Alex,

          yes it’s me 🙂

          Try to run ALL the points in the guide through, just a minor click the wrong place, can make it all fall apart 🙂

          Also remember under authentication SSLVPN put the RADIUS server on the top of the list.

          OK with community 🙂

          Regards Martin

          Reply
          1. Alex

            Hi Martin,

            thank you. I have dopple checked now every step. No idea more.

            Let`s try the Community.

            Thank you very much.

            Regards
            Alex

          2. Alex

            Hi Martin,
            I have just solved my problem. See Sophos Community for details. Thank you anyway for your support.
            Many greetings
            Alex

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