Host CRL and AIA for your internal PKI in Microsoft Azure Web App

When you have an internal PKI solution you have to consider where to host your CRL and AIA. They are both important  and must be available for the client when your internal certificates are in use. By default (but you should never use default settings in PKI) the files are stored in the CA server and available through SMB and HTTP (and LDAP if domain joined). Not only do you have to make your CA server available through these ports but if your clients are outside the company network then your CA must be available there as well. Needless to day, this is not a good practice.

Normally you would publish CRL and AIA on a webserver in your DMZ, make it redundant and such, but if you’re going through all that work you might as well use the opportunity to take it all the way to the cloud. Microsoft Azure can provide cheap (or even free) website where the CRL and AIA can be published and it will be globally available and redundant.

If you are new to Microsoft Azure then this is a very good opportunity to take the first step and learn the basics about it. Although the CRL and AIA are important, this solution is easy to implement and you get to learn the basics of Azure as you go.

Set up Azure web app

You need to register an account in Microsoft Azure first and there create a new Resource Group with a logical name. Inside the resource group I suggest you first make an App service Plan before you create the web app itself.

Under “App service plan/Location” you can choose to set up the pricing and location (which azure data center) you want to store the website. In this example I chose an existing app service plan. After the website is created you can create additional App service plans and later just assign your websites to these.


Pricing and features

In “App services” you can add “App service plan” and select another pricing tier. Notice you get a brief summary of features available along with a rough price estimation pr month. For the CRL and AIA you won’t need a lot of processing power, storage space or deployment slots. If you want to use your custom domain name then “D1 Shared” is the minimum pricing tier. It is not available in the free tier. Without custom domain name your URL for CRL and AIA will be “(yourwebsitename)” which will work perfectly but you can’t bring that domain name with you if you want to host your CRL and AIA somewhere else at a later time. In that case you have to renew all CA certs, and their issued certs with updated URL to the CRL and AIA or stick with Azure web app. So I recommend using your own domain name for the flexibility it provides.


When you have the proper pricing tier selected you can register your custom domain with the app service. Select “Custom domain” on the left side when you are in the web app and follow the instructions there.

Double escaping

The delta CRL has a ‘+’ in the end of the filename s in order for this to work you have to enable double escaping on the website or the delta CRL will be unavailable. There are no settings for this in the GUI as I am aware of, but you can create a new text file named “web.config” (no .txt extension)  with the following content and upload it to the root of the web app (site/wwwroot).

<?xml version=”1.0″ encoding=”utf-8″ ?>
<requestFiltering allowDoubleEscaping=’true’ />


Upload the files

There are many ways to upload both the cert-files and the web.config file up to the azure Web app and I won’t cover all the options here. If you go to “Properties” on the web app you will find all the information you need to upload files to the website in different ways. In “deployment options” you find options for source control and deployment. For my private PKI I picked a simple scheduled task which opens and FTP session and uploads the cert-files and web.config into /site/wwwroot in Azure using WinSCP which is my favorite FTP client.


Thanks for reading everyone. Wish you all a happy new year



Setting up Office 365 using Azure DNS

Do you use Azure DNS? Azure DNS provide hosting of your DNS zones in the Azure infrastructure meaning that not only do you get the fault-tolerance, audit logging and SLA (99.99%) but you can also manage your DNS zones using Powershell. I recommend you read about it on including the FAQ and pricing information.

Implementing Office 365 requires a bit of DNS changes, and using Powershell this is very, very easy in Azure DNS. You need an account in Azure with admin-rights for Azure DNS, the name of the zone and the resource group it belongs to.

Change the input values to match the your environment and run this script from an editor (Powershell ISE or Visual Studio Code)

# This script automatically configures Azure DNS for O365
# Written by Per-Torben Sørensen (
# Version: 1.0
# Input values below
$azureadmin = “” # admin user in azure portal with DNS rights
$ttl = “600” # TTL for all records (in seconds)
$rgname = “testazuredns” # Use Get-AzureRmDnsZone after login to find this
$proofvalue = “MS=ms12345678” # Proof of ownership from the Office 365 portal
# Variables below
$cred = Get-Credential -Message “Log on” -UserName $azureadmin
$runscript = $false # Failsafe for accidental running
if ($runscript -eq $false)
Write-Host -ForegroundColor Red “Do NOT run this script non-interactively! Run from editor”
# Log on Azure RM and set DNS variable
Login-AzureRmAccount -Credential $cred
$dnszone = Get-AzureRmDnsZone -Name $zonename -ResourceGroupName $rgname
# Creating first TXT record (Proof of domain ownership)
New-AzureRmDnsRecordSet -Zone $dnszone -Name “@” -RecordType TXT -Ttl $ttl -DnsRecords (New-AzureRmDnsRecordConfig -Value “$($proofvalue)”)
# Create CNAME records
New-AzureRmDnsRecordSet -Zone $dnszone -Name “autodiscover” -RecordType CNAME -Ttl $ttl -DnsRecords (New-AzureRmDnsRecordConfig -cname “”)
New-AzureRmDnsRecordSet -Zone $dnszone -Name “sip” -RecordType CNAME -Ttl $ttl -DnsRecords (New-AzureRmDnsRecordConfig -cname “”)
New-AzureRmDnsRecordSet -Zone $dnszone -Name “lyncdiscover” -RecordType CNAME -Ttl $ttl -DnsRecords (New-AzureRmDnsRecordConfig -cname “”)
New-AzureRmDnsRecordSet -Zone $dnszone -Name “msoid” -RecordType CNAME -Ttl $ttl -DnsRecords (New-AzureRmDnsRecordConfig -cname “”)
New-AzureRmDnsRecordSet -Zone $dnszone -Name “enterpriseregistration” -RecordType CNAME -Ttl $ttl -DnsRecords (New-AzureRmDnsRecordConfig -cname “”)
New-AzureRmDnsRecordSet -Zone $dnszone -Name “enterpriseenrollment” -RecordType CNAME -Ttl $ttl -DnsRecords (New-AzureRmDnsRecordConfig -cname “”)
# Modifies the existing TXT record
$txtrecord = Get-AzureRmDnsRecordSet -Zone $dnszone -Name “@” -RecordType TXT
Add-AzureRmDnsRecordConfig -RecordSet $txtrecord -Value “v=spf1 -all”
Set-AzureRmDnsRecordSet -RecordSet $txtrecord
# Create SRV records
New-AzureRmDnsRecordSet -Zone $dnszone -Name “_sip._tls” -RecordType SRV -Ttl $ttl -DnsRecords (New-AzureRmDnsRecordConfig -Priority 100 -Weight 1 -Port 443 -Target
New-AzureRmDnsRecordSet -Zone $dnszone -Name “_sipfederationtls._tcp” -RecordType SRV -Ttl $ttl -DnsRecords (New-AzureRmDnsRecordConfig -Priority 100 -Weight 1 -Port 5061 -Target
$exchadr = ($zonename -replace “\.”,”-“)
$exchadr +=””
$mxrecords = @()
$mxrecords = New-AzureRmDnsRecordConfig -Exchange $exchadr -Preference 0
New-AzureRmDnsRecordSet -Zone $dnszone -Name “@” -RecordType MX -Ttl $ttl -DnsRecords $mxrecords
# This line allows you to select one or several DNS records and delete them from zone
Get-AzureRmDnsRecordSet -Zone $dnszone | Out-GridView -Title “Select record to delete” -OutputMode Multiple | Remove-AzureRmDnsRecordSet

What is Azure Domain Services?

Azure Active Directory (AAD) is, as I’m sure you know, the identity services in Microsoft Azure. Unlike Windows Active Directory (WAD) which has been with us since Windows 2000, AAD doesn’t use Kerberos for authentication since Kerberos isn’t suited for internet traffic and slow/unreliable WAN connection. Obviously the major drawback is that AAD can’t communicate directly with most of our current applications and systems.

To combat this drawback, Microsoft has released Azure Domain Services (currently in preview) which is a feature that allows one AAD to communicate with Kerberos over one virtual network. This is NOT a full version of WAD, it is only AAD made Kerberos-enabled which gives you access to a some of the features from WAD, most of them are read-only however.

This is essentially “domain controller-as-a-service”, so there is no FSMO roles, AD sites, Global Catalog, schema extentions and such to configure or troubleshoot. After deployment you get 2 IP addresses to use as primary and secondary DNS server, which in turn lets you communicate with AAD using Kerberos. This includes joining the domain with you servers and clients. This feature is not to be confused with Windows 10 Azure device join which it something entirely different.

Also I want to remind you that this feature is in preview so things are likely to change from what you can read here.

Implementing Azure Domain Services

Implementing Azure Domain Services is very easy.

  1. Create a group named “AAD DC Administrators” and join the user accounts you want as your admin account to this group. The members won’t be Domain Admins as we are used to from WAD, but this is as close as you get.ads0b
  2. In the Azure portal, find you AAD and under configure you’ll find this setting to enable Azure Domain Servicesads01
  3. When enabled you have to select your domain DNS name and which virtual network this AAD will provide Kerberos over. If this network has a site 2 site VPN, your AAD will be available to resources on-premises.ads2
  4. Notice this message, which says you need password synchronization in order to log on AAD using Kerberos. This also means that Federation is not supported. The procedure is different for cloud accounts and on-prem accounts, but the link in the message describes very well what you need to do, so I’ll just link it here.ads3
  5. Now you have to wait..a lot. Enabling this takes a long time, about 20-30 minutes. Eventually you’ll get the 2 IP addresses you need to use to reach your domain. You should add both as DNS servers in your virtual network in Azure. It will take some time before the vm’s in Azure are updated so you can either refresh the IP’s or give the servers a reboot.ads5
  6. I have a cloud-only user to function as my admin account, so before I can join my servers to the AAD, I have to reset its password to generate the hash (step 4) so I do so at where you find the change password option. (“Endre passord”, sorry this screenshot is in norwegian)ads9
  7. And finally my server has the correct DNS servers and it can join AAD as if it was an ordinary WAD. ads6










Taking a closer look at an AAD-joined server

After my server joined my AAD and rebooted it’s available for my AzureAdmin account. So let’s take a closer look on how this works. Starting at the local administrator group on my member server where you see the group we added in step 1 thereby giving me access to the server.












So naturally I install the RSAT for AD and Group Policy and start to play around.

First of all having a look at FSMO roles:



AD sites and services won’t show anything but an error, so nothing to see there.

AD domain and trust just shows us the usual information with no ability to change anything at all.

AD users and computers on the other hand is a little more interesting. Here we see the AAD OU structure and we have our users and groups from the Azure portal in “AADDC Users” and our newly joined member server in “AADDC Computers”. This view seem to be completely read-only and nothing can be changed or edited. Note there is no “Domain Controller” container.ads_aduc1








Turns out I can create a new OU on the domain level and in here I can create new groups and users which I can edit. As of now this seem to have no function at all as I can’t authenticate with this new user account and it doesn’t show up in the Azure portal.


Group Policy is even more interesting.









There are 4 GPO’s present Default domain and domain controller policy, plus AADDC Computers and AADDS Users (both linked to the OU with the corresponding name).  Those last 2 GPO’s can be edited so you are able to deploy some GPO settings to your domain joined computers and users. You can also change GPO links, enforce, block inheritance and change GPO Staus (disable all users or/and computer settings) However you can’t do any of the following:

  • Create new GPO or delete existing ones
  • Change GPO security filtering
  • Create WMI filters
  • GPO links












DNS: Your account will not have any DNS server rights so trying to connect a DNS console againt the DC will only throw an access denied error.

Add domain controllers: No, you can’t promote an azure vm as an additional Domain Controller 😉


I think Azure Domain Services is a curious thing, while being far from a replacement for you WAD, it does provide the ability to join servers and clients to an AAD and communicate with each other using Kerberos. You can of course use it as if it was a normal WAD, but the management of both users and computer are very limited. Communication using Kerberos is the whole point of this feature and it should open up some new possibilities in both hybrid environments and perhaps also during migration from on-premises to cloud. Another possible application for this feature could be in combination with Azure Remote App.

Again this feature is in preview so I’m sure the re will be changes coming, probably based quite a bit on user feedback.