Azure Windows Security Baseline

I was designing a deployment around Azure Virtual Desktop utilizing Azure Active Directory, not AADDS or ADDS and when checking a test deploy for compliance against the NIST 800-171 Azure Policy, it showed the Azure Baseline is not being met. In a domain, I wouldn’t worry since group policy will fix this right up, but what about non domain join? What about custom images? Yeah, I guess we could manually set everything then image it, but I prefer a clean base then apply configuration during my image build. Let’s take a look how to hit this compliance checkbox.

I recalled that Microsoft released STIG templates and found the blog post Announcing Azure STIG solution templates to accelerate compliance for DoD – Azure Government (microsoft.com). I was hoping their efforts would make my life a little bit easier, but after a test deploy, I saw 33 items still not in compliance.

Looking at the workflow, it is ideally how i’d like my image process to look in my pipeline.

Deploy a baseline image, apply some scripts and then I can generate a custom image to a shared gallery for use. I didn’t want to reinvent the wheel, so I started researching if anyone has done this already. I found a repo https://github.com/Cloudneeti/os-harderning-scripts/ that looked promising, but it was a year old and I noticed some things incorrect with the script such as incorrect registry paths, commented out DSC snippets, etc. This did do a good bulk, but just needed cleaned up and things added. Looking at the commented code, it was around user rights assignments. Now, the DSC module for user right assessments is old and I haven’t seen a commit in there for years. Playing around, it seems that some settings can not be set. I didn’t want to hack together stuff using secedit, so I found a neat script https://blakedrumm.com/blog/set-and-check-user-rights-assignment/ that I could just pass in the required rights and move on. Everything worked except for SeDenyRemoteInteractiveLogonRight. When the right doesn’t exist in the exported config, it couldn’t add it. So, I just wrote the snippet to add the last right.


$tempFolderPath = Join-Path $Env:Temp $(New-Guid)
New-Item -Type Directory -Path $tempFolderPath | Out-Null
secedit.exe /export /cfg $tempFolderPath\security-policy.inf


#get line number
$file = gci -literalpath "$tempFolderPath\security-policy.inf" -rec | % {
$line = Select-String -literalpath $_.fullname -pattern "Privilege Rights" | select -ExpandProperty LineNumber
}

#add string
$fileContent = Get-Content "$tempFolderPath\security-policy.inf"
$fileContent[$line-1] += "`nSeDenyRemoteInteractiveLogonRight = *S-1-5-32-546"
$fileContent | out-file "$tempFolderPath\security-policy.inf" -Encoding unicode

secedit.exe /configure /db c:\windows\security\local.sdb /cfg "$tempFolderPath\security-policy.inf"
rm -force "$tempFolderPath\security-policy.inf" -confirm:$false

After running PowerShell DSC and script, the Azure baseline comes back fully compliant. I have tested this on Windows Server 2019 and Windows 10.

You can grab the files in my repo https://github.com/jrudley/azurewindowsbaseline

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