Thoughts and Observations on Azure Active Directory Domain Services

I would not recommend setting up a Windows Server Domain Services role for the first time flying blind. Whilst not necessarily classing myself as a “newbie” in this respect, I have only run through this a few times in the past within lab environments. The process is always tricky - not just in deploying out the role in the first instance, but more via the many quirks that get thrown up as you try to accomplish what should be simple tasks, such as domain joining devices or getting DNS settings correctly mapped out. These and other tiresome rat races can leave you with a severely scratched head and distract you from your ultimate goal.

For this reason, you could argue that Azure Active Directory Domain Services (or AADDS) is the perfect solution for “newbies”. The thing I like the most about it is that a lot of the hassle I make reference to above is something you will never see a sight of, thanks to the fact that Microsoft manages most aspects of the deployment behind the scenes. In addition, the step-by-step guides available on the Microsoft Docs website provide a very clear and no-nonsense holding hand through every step of an Azure Domain Services rollout. What this ultimately means is that you can spend more time on achieving your end goal and reduce the need for extensive administration of the solution following its rollout. Having said that, it is always useful to ensure that you have thoroughly tested any solution as extensively as possible for your particular scenario, as this will always throw up some potential issues or useful tips to remember in future; AADDS is no exception to this rule.

Having recently worked closely with AADDS, in this weeks blog post, I wanted to share some of my detailed thoughts regarding the solution in practice and a few things to remember if you are checking it out for the first time.

Resetting AADDS User passwords could become the bane of your existence

If you are creating an AADDS resource in isolation to any existing identity providers you have in place (i.e. there is no requirement to use Azure AD Connect with an On-Premise Domain Server), then be aware that you will have to set up a users password twice before they will be able to login to the domain. Microsoft explains better than I can why this is:

To authenticate users on the managed domain, Azure Active Directory Domain Services needs credential hashes in a format that’s suitable for NTLM and Kerberos authentication. Azure AD does not generate or store credential hashes in the format that’s required for NTLM or Kerberos authentication, until you enable Azure Active Directory Domain Services for your tenant. For obvious security reasons, Azure AD also does not store any password credentials in clear-text form. Therefore, Azure AD does not have a way to automatically generate these NTLM or Kerberos credential hashes based on users’ existing credentials…If your organization has cloud-only user accounts, all users who need to use Azure Active Directory Domain Services must change their passwords

Source: https://docs.microsoft.com/en-us/azure/active-directory-domain-services/active-directory-ds-getting-started-password-sync

The above article goes into the required steps that need to be followed for each user account that is created and, at the time of writing, I do not believe there is any way of automating this process. Whether you choose to complete these steps yourself or get your end users to do so instead is up to you, but there is a good chance that if a user is experiencing login issues with an AADDS account, then the steps in the above article have not been followed correctly.

Make sure you’re happy with your chosen DNS Name

When first creating your Domain Services resource, you need to be pretty certain your desired DNS domain name will not be subject to change in the future. After some fruitless digging around on the portal and an escalated support request to Microsoft, I was able to confirm that there is no way this can be changed after the Domain Services resource is deployed; your only recourse is to recreate the resource from scratch with your newly desired DNS domain name. This could prove to be problematic if, say, you wish to change the domain name of your in-development domain services account from the default onmicrosoft.com domain to a bespoke one…after you have already joined Virtual Machines to your new domain : / Some efficient use of the Azure templates feature can save you some aggro here, but not if you have already expended considerable effort on bespoke customisation on each of your VM’s operating systems.

Be aware of what’s supported….and what isn’t

There are a few articles that Microsoft have published that can help you to determine whether AADDS is right for your particular scenario:

Whilst these are invaluable and, admittedly, demonstrate the wide-feature array contained with AADDS, there are still a few hidden “gotchas” to be aware of. The articles above hint towards some of these:

Only one AADDS resource is allowed per Azure tenant. You will need to configure a clean Active Directory tenant (and therefore a separate Azure portal) for any additional AADDS resource you wish to setup, which also requires an appropriate subscription for billing. This could result in ever-growing complexity to your Azure footprint.
AADDS is a continually billable service. Unlike VM’s, which can be set to Stopped (unallocated**)** status at any time and, therefore, not incur any usage charges, your Domain Services resource will incur fees as soon as you create it and only cease when the resource is deleted.

One unsupported feature that the above articles do not provide any hint towards is Managed Service Accounts. Introduced as part of Windows Server 2008 R2, they provide a more streamlined means of managing service accounts for applications running on Windows Server, reducing the requirement to maintain passwords for these accounts and allowing administrators to provide domain-level privileges to essential service account objects. I try to use them whenever I can in conjunction with SQL Server installations, particularly if the service accounts for SQL need to access network-level resources that are secured via a security group or similar and I would encourage you to read up on them further to see if they could be a help within your SQL Server deployments.

Back to the topic at hand - if you attempt to create a Managed Service Account via PowerShell, you will receive an error message saying that they are not supported within the domain. So, assuming that you are wanting to go ahead and deploy SQL Server on an AADDS joined VM, you would have to revert back to using standard Active Directory user accounts for your Service Accounts to achieve the same functionality. Not great if you also have to enforce password refresh policies, but it would be the only supported workaround in this situation.

Conclusion or Wot I Think

When reviewing potential new IT vendors or products, I always try and judge “how dirty handed” I would need to get with it. What I mean by this is the level of involvement myself, or a business, would need to invest in managing physical server hardware, backend elements of the infrastructure or any aspect of the solution that requires an inordinate amount of time poking around the innards of to troubleshoot basic problems. The great benefit of services such as Azure is that a lot of this pain is taken away by default - for example, there is no need to manage server, firewall and networking hardware at all, as Microsoft does this for you. AADDS goes a step further by removing the need to manage the server aspect of a Domain Services deployment, allowing you to focus more on building out your identities and integrating them within your chosen application. Whilst it does need some work to get it up to an acceptable level of parity with a “do-it-yourself” Domain Server (for example, extensive PowerShell support for the completion of common tasks), the service is still very much in a developed and user-friendly state to warrant further investigation - particularly if you have a simplified Active Directory Domain in place or are looking to migrate across to Active Directory from another vendor. £80 per month for a directory smaller than 25,000 objects is also not an exorbitant price to pay as well, so I would definitely recommend you check AADDS out to see if it could be a good fit for your organisation/application in the near future.