Thursday, November 26, 2020

Can Azure WVD inbound traffic pass through my firewall?

11 min to read.


Corona Virus is giving birth to new technologies and new way of working!

Remote work has been in the center of technology discussion in all organizations. Azure Windows Virtual Desktop has been on leading front to enable organization to enable remote working.

When we talk to security teams about remote working using Azure WVD; every organization wants remote working incoming traffic to flow through their perimeter firewall deployed on Azure. This is obvious because all incoming traffic will be coming from internet and getting into Azure WVD environment of customer.

This is fair ask and every organizations security team wants to monitor all incoming traffic from internet.

So obvious question that comes to Azure Architects is -

Can you please make sure that all incoming/ inbound/ ingress traffic from client devices to Azure WVD flows through our Firewall devices hosted on Azure?

The answer is Yes.

However in my opinion the question is incorrect!

How? Let’s talk about it.

Azure WVD and Reverse Connect

See, I am not blaming security team for asking incorrect question; it is more of unawareness of how Azure WVD connection work. It is more of responsibility of Azure Architects working within an organization to make Security teams aware of how Azure WVD traffic flow and connections work.

Reverse connect is a unique technology offered only on Azure WVD. Reverse connect technology means your WVD host VM doesn’t need any inbound ports to be opened. Even the default RDP port, TCP/3389, doesn’t have to be open. Instead, an agent creates an outbound connection using TCP/443 into the Windows Virtual Desktop management service.

Most of the time we misunderstand the Azure WVD Reverse Connect as shown in the Red color line in below diagram [click to get better view] - 


As per general understanding I have observed below understanding of the traffic flow –

1.      Client device connects to WVD common URL either from browser or from app installed on client machine. This traffic flows over internet.

2.      The request from client machine is forwarded to WVD management control plane.

3.      The broker in WVD management service initiates connection to actual WVD host. This traffic also flows over internet.

In above traffic flow the traffic is reaching to WVD host VM directly without passing through the firewall device.

This is not correct understanding.

Reverse connect means Broker will not initiate the traffic to WVD host VM rather WVD host VM will initiate the connection to Broker of WVD management service.

This means the traffic to connect to WVD host is OUTBOUND/ EGRESS/ OUTGOING traffic from WVD host and not INCOMING/ INBOUND/ INGRESS traffic to WVD host VM.

Passing WVD host connection traffic through Firewall

Now that we understand about WVD host making outbound call for honoring connection requests; we just need to have this traffic going through Firewall device. The firewall device can be either NVA or Azure Firewall.

To pass this outbound traffic initiated from WVD host VM through firewall we will need to add UDR – User Defined Route on WVD Subnet. The routes will be as follows –

-        If destination is on-premises then next hop is Gateway

-        If destination is then next hop is firewall device private IP

The connection traffic will be falling under the category of This way connection traffic initiated from WVD host VM will also pass through Firewall device.

This way security teams requirements will also be satisfied as now they actually can inspect outgoing traffic in firewall from WVD Subnet.

Refer to below diagram – [click to get better view]


The correct network traffic flow will be as follows shown in green in diagram –

1.      Client device connects to WVD common URL either from browser or from app installed on client machine. This traffic flows over internet.

2.      The request from client machine is forwarded to WVD management control plane.

3.      The WVD host VM has an agent running on top of it. This agent then initiates the traffic to WVD management service as an OUTBOUND connection.

4.      WVD management service traffic falls under category of and hence the traffic is forwarded to firewall device.

5.      From firewall device the traffic goes to WVD management service.

6.      After successful authentication from user the actual connectivity is established between client device and WVD host VM.

All of this communication happens over 443 and there is no requirement of opening 3389 default RDP port anywhere. This is the beauty of  WVD reverse connect.

Wrapping up

Remember, there is no Inbound traffic in case of connecting to WVD host VM.

Therefore correct question to security teams –

Can you allow WVD connection traffic to pass through my firewall device?

Answer - Yes using UDR on WVD subnet; we can pass WVD connection traffic to flow from firewall device.


Hope this article helped to design your WVD deployment architecture in right way and gave better understanding of WVD traffic flow.

Happy Remote working!!

A humble request!

Internet is creating a lot of digital garbage. If you feel this a quality blog and someone will definitely get benefited, don't hesitate to hit share button present below. Your one share will save many precious hours of a developer. Thank you.

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Tuesday, April 28, 2020

Run Android emulator and Android Studio on Azure VM using Hyper V

14 min to read.


Due to Corona outbreak, times are hard! Please take care everyone! I wish good health for all! Stay safe!

There is another outbreak I am seeing – Making Development environment available on Azure to enable Work from home. Almost in every customer call I hear about requirement to enable Development Environment on Azure and accessing it from Home laptop/ PC and continue the business.

In the era of “Mobile first” almost every big enterprise, every Small and Medium Business (SMB), every Start up company have mobile development teams. They use variety of tools and one of the important IDE used for Mobile development is “Android Studio”.

Installing and running Android studio is smooth; however Android emulator installation fails on Azure VM. It is not straight forward. In this blog we will see “how to enable Android emulator with Android Studio on Azure VM”.

Let’s go!

Concept - Android Emulator and VM Acceleration

Without a virtualization technology and VM acceleration, the Android emulator must translate the machine code from the VM block by block to conform to the architecture of the host computer. This process can be quite slow. 

With a hypervisor, the VM and the architecture of the computer running emulator match, so the emulator can run code directly on the processor using the hypervisor. This improvement drastically increases both the speed and performance of the android emulator.

This concept is well suited for hardware. For example, if you have laptop then Android emulator can work like a charm. Because the required hardware for VM acceleration is provided by underlying laptop on which you are running Android Studio and hypervisor for emulator runs on laptop hardware.

Android Emulator and Intel HAXM

Android emulator is default based on Intel Hardware Accelerated Execution manager [HAXM]. This is Virtualization technology used behind the scene by Android studio to run the android emulator. HAXM is installed as a part of installation process of Android Studio as well.

So on Azure VM where we plan to run the Android simulator, Intel HAXM should be installed and present.
At the same time Intel HAXM and Hyper V are mutually exclusive. Means, if you have Hyper V enabled then HAXM can’t be installed and vice versa.

Installation of HAXM on Azure VM is not a problem. The VM series is a problem. When you say I want to install the HAXM; Hyper V should be disabled. Most of the VM series today have Hyper V “some way” enabled or not supported.

Remember Azure VM itself is a VM. Means it is based on Hyper V behind the scene already. Now on top of this VM you want to install another Hypervisor – either HAXM or Hyper V. The only series that supports the Hyper V on Azure VM itself is Hyperthreaded VMs – Dsv3 and Esv3 series or Dv3 and Ev3 series.

This Azure VM series support nested virtualization; because it supports running Hyper V on top of it or running any other hypervisor on top of it. Therefore installation of HAXM on Azure VM will succeed only on these Azure VMs and other will fail.

Now even if we install HAXM successfully on Azure VM and then install Android Studio with emulator successfully; the emulator will not work. I have experienced many errors as described below -

“error while loading state for instance 0x0 of device 'goldfish_pipe'”.

“Unfortunately, the Android emulator can’t support virtual machine acceleration from within a virtual machine.”

Android Emulator and WHPX

Microsoft Visual Studio has Android Emulator. It uses WHPX technology behind the scene. However it works on hardware. Means it can run well on your laptop but not on Azure VM. I could not start Android Emulator on Azure VM. When I attach the Visual Studio Android Emulator to Android Studio; it fails with many errors.
So what is the solution?

Solution and Architecture

Well, the solution provided will not help to run the latest version of Android emulator. However you will be able to make the Android Emulator work on Azure VM with “Older version”.

For this we will leverage “VS Emulator for Android” which is earlier version of Android Emulator Microsoft had released prior to current version of “hardware acceleration” based Android emulator.

So overall solution looks as follow – [click to get better view].

As a part of the solution make sure you provision VM with v3 series. I have selected Ds4v3 VM on Azure portal and provisioned it. By default allow the internet access to this VM so that we can download required software. As per the diagram I have attached public IP to my VM. So take RDP over public IP.

After RDP, install the software in the order mentioned below.

Visual Studio Emulator for Android – Life saver!

I have selected below version [click to get better view] of Windows 10 for provisioning VM on Azure. Also I have selected Ds4v3 series and Gen1 for provisioning. Go ahead and provision Azure VM.

Install Hyper V

Login to your VM and configure Hyper V on top of it. Open Run window -> type “appwiz.cpl” -> Click on “Turn windows feature on or off” -> Select all options against Hyper V option -> Select option “Windows Hypervisor platform”. After successful installation restart VM. Refer below [click to get better view].

Install Java

VS Emulator for Android requires Java. Therefore install using the link -
Restart the machine.

Install Visual Studio Emulator for Android

Go to this page - Install VS emulator for Android. Remember we don’t have to install the complete Visual Studio here. The Visual Studio based Android emulator is based on Hardware acceleration and it will not work on Azure VM. At least I could not make it work after lot of attempts.

Successful installation screen shown below. It should also appear in start menu. [click to get better view].

After installation restart the Azure VM.

Install Android Studio

Install Android Studio from the link - Current version as of today is Android Studio 3.6.3. Install with default selected options. After successful installation you will see an option “start android studio”. Select this option and click finish as shown [click to get better view].

This launches the Android Studio and further starts configuration of Android Emulator. Continue with standard configuration with default options selected. You will see that HAXM installation failed. This is expected behavior as Hyper V is already enabled; HAXM is bound to fail. You will get screenshot as follows [click to get better view] –

This completes the installation of all required software. Restart the machine.

Integrating Android Studio to use Visual Studio Emulator for Android

The default path of Android SDK for me is - C:\Users\kunal\AppData\Local\Android\Sdk. This is default path.

We need to set a specific registry key to tell Visual Studio Emulator for Android where the Android Sdk is located. To set the needed registry key, run the script below in PowerShell on the Azure VM. If you have installed it on different path then change the below path in script accordingly.

$androidSdkPath = Resolve-Path $(Join-Path "$($env:APPDATA)" "../Local/Android/Sdk")

$registryKeyPath = "HKLM:Software\WOW6432NODE\Android Sdk Tools"
New-Item -Path $registryKeyPath
New-ItemProperty -Path $registryKeyPath -Name Path -PropertyType String -Value $androidSdkPath

Successful execution of the script will have below view [click to get better view].

Running Android Studio with VS Emulator for Android

First open Visual Studio Emulator for Android. On the launch screen you will see all version available in this emulator. You will see the last version that were available on this was API 23 Marshmallow. Refer below screenshot [click to get better view].

From above screen I downloaded the red marked device for emulator. When you click on Green checkmark then Device emulator starts as shown below [click to get better view].

Now open Android Studio. Click on “Start a new Android Project” on start screen. Then Select the Project Template as Basic Activity. Click Next. On “Configure your project” screen I selected Java as Language and kept rest of the setting as is. Click Finish. The creation of new project will take few mins. Final screen will be visible as shown. As you can see, VS Emulator is also visible on the below diagram. This means Android Studio has picked up VS Emulator for Android [click to get better view].

Go ahead and click on Run to deploy your test application on this emulator.

Post deployment you will see your application running on Visual Studio Emulator for Android as shown below [click to get better view].

Follow general security best practices when you take RDP over internet to this VM. Like whitelisting incoming IP in NSG etc.


Visual Studio emulator for android is obsolete version and has last version of android available as API 23 – Android 6.0 - Marshmallow. However currently Android is running with version API 29 – Android 10.0 - Q.
I know we are not running on latest version however this workaround unblocks us in current Covid-19 situation.

Also, on top of this page -, it explains you that current version of Android Emulator uses hardware acceleration. VS Emulator for Android is older version of it and not recommended. 

However I chose this solution to my customers as of now; as this unblocks the customer immediately with the power of Azure cloud.

Also, right now my customer was not able to perform any android specific development task due to Corona virus situation. So even if older version, at least customer was able to continue the business and that was more important.

I repeat, the above approach of using older version of VS emulator is obsolete. For best experience you should switch to Hardware based emulator either using HAXM or WHPX. The above stated approach is a workaround for now. May be in future Microsoft Azure may release “absolutely non restricted Hyper V” supporting VMs and it may work.

Please note, this recommendation is my personal recommendation and in no way it represents the company I work for.

Bonus Tip

You can very well use this approach with Azure Windows Virtual Desktop [WVD]. Plus on top of it if you want to test your APK by device connection to USB; then you can enable local laptop USB while you take RDP to WVD and make it work.


Hope this article helped you to get started on Android Studio and Android emulator with Azure VM quickly. Let me know your views in comments section below to improve and what are your thoughts on this approach.
Happy emulating!!

A humble request!

Internet is creating a lot of digital garbage. If you feel this a quality blog and someone will definitely get benefited, don't hesitate to hit share button present below. Your one share will save many precious hours of a developer. Thank you.

Next Related Posts

Friday, April 17, 2020

Azure Function for generating Azure AD Token using .NET core

10 min to read.


Development is a struggle, a continuous struggle. With serverless this struggle is becoming more and more imminent. Developers are still trying to get comfortable to serverless technologies.

Azure Function is one of the key serverless offering today on Azure. Azure Function is becoming backbone for many serverless and micro service based applications.

Recently after writing Azure AD token generator using .NET Core; immediately got a lot of requests to make this code run in Azure Function and here we are!

So in this blog we will create Azure Function to generate Azure AD token using .NET core.

Let’s go!


Refer to below diagram [Click to get better view] for overall components used for running this code in Azure Function.

To publish the code of Azure AD token generator using .NET core to Azure Function, I plan to use Visual Studio. Publish operation from Visual studio to Azure Function is deployed as .zip file.

When we create Azure Function, creating an Azure storage account is also important and mandatory step. When we publish code from Visual studio, behind the scene Azure Files share is created in associated storage account and .Zip is actually copied to File Share.

This File Share will then mapped to Azure Function compute behind the scene and then used for running the actual application from Bin folder as shown above.

To get administrative access to runtime of Function keys are used. These keys are stored securely in Blob Storage which also get automatically created in the associated Storage account.

Making Azure Function async

First create Azure function project as shown below in Visual Studio – [click to get better view]

If you have seen the GitHub code of Azure AD Token generator using .NET core, you will observe that entire code is built using Async mechanism and token is also received in async way. When we create Azure Function project by default Azure Function startup method is not async. So let us make it async as shown below – [Click to get better view]

Then copy the code from GitHub and remove all Console specific methods. Instead make all methods to log information as shown in below screenshot – [click to get better view]

Publishing from Visual Studio

After completing code changes, it is time to publish to Azure Function. Either you can create new Azure Function from the Azure portal and specify the same during Publish method or simply create new Resource Group, Function from Visual Studio publish screen itself. In this tutorial, I am creating new Azure Function from Azure Portal as shown below – [click to get better view]

I have created TimerTrigger function. Then click on Publish button of your Azure Function project from Solution Explorer and make sure you select existing Function to create Publish Profile as shown below – [click to get better view]

Then continue further to publish to Azure Function.

Benefits of running Azure function from package file

Now in above screenshot of Creating profile you might have observed as checkbox – “Run from a package file”.
This is really important. This directly sets the Azure Function to run from package file only. Means your Azure Functions runs directly from a deployment package file in your Function App. By running function from package file you –

       1.      Reduces the risk of file copy locking issues
2.      Improves performance of Function App drastically
3.      Code start time is reduced
4.      Unwanted files are automatically removed from final deployment package.

My current Function app is based on Windows and .NET core therefore in Architecture diagram you might have observed below setting –


This setting tells Function app to run from package file. You can also view this setting from “Application Settings” tab in Azure Function as shown below – [click to get better view]

Other ways of deployment

I can also write the code Azure function directly in Azure portal editor. However I have seen lot of issues in adding Nuget package reference in Azure function. Deploying from Visual Studio[for .NET code], VS code [all other languages including .NET] makes it easy in all respect; as all dependent assemblies, files get packaged in .zip.

When you deploy the Azure Function from Visual Studio with .zip package deployment; automatically your Azure Function will become read only and will show message as shown below –

Your app is currently in read only mode because you are running from a package file. To make any changes update the content in your zip file and WEBSITE_RUN_FROM_PACKAGE app setting.

Well, this is fine because anyways deployment is governed by Visual Studio. So we don’t need to make any changes in the code from portal. So Function becoming read only is fine. Rest of the platform specific features never become read only.  So I will definitely recommend to deploy the Azure function using VS or VS Code or using DevOps.

Verifying the .zip package and Azure File Share

After deployment, you can verify that .zip package is actually present in Azure File Share of the storage account and it is mapped to D drive on Kudu Console of Azure Function. See below - [Click to get better view]

Running the Azure Function and view the Azure AD Token

Run the Function and you should be able to view the generated Azure AD Token as shown below – [Click to get better view] –

I created TimerTrigger Azure Function to get Azure AD token on timely basis. This is because my next blog is based on Azure API Management monitoring which requires Azure AD token generation on timely basis from Function. You can also use HttpTrigger for Azure Function to generate Azure AD Token. So stay tuned for next blog soon!


Hope this article helped you to get Serverless Azure Function for generating Azure AD token using .NET core. Let me know your views in comments section below to improve and what are your thoughts on this approach.

Happy token generating!!

A humble request!

Internet is creating a lot of digital garbage. If you feel this a quality blog and someone will definitely get benefited, don't hesitate to hit share button present below. Your one share will save many precious hours of a developer. Thank you.

Next Related Posts

Saturday, April 4, 2020

Azure AD Token Generator using .NET Core

10 min to read.


Change is inevitable. With .NET Framework becoming legacy and .NET core stated as future; many migration projects are getting triggered. Also for new projects, development choice is .NET core by default.

Last year in April 2019 I wrote a blog post on How to create service principal or App registration in Azure AD.

This is one of the most visited blog post. Reason is simple. Any functionality having requirement of invoking Azure REST API requires Azure AD token generation. This helps in performing management tasks against Azure environment; and hence it is crucial.

The last year blog is based on .NET framework.

With .NET core becoming more and more obvious choice, I thought it is time to have new blog post and new code base for “.NET core based Azure AD Token generator using Service principal.”

Let’s go!

Why I need to generate the Azure AD Token?

This is common question I get. What are the scenarios where I need to generate Azure Ad token from code and use it? Therefore below diagram lists few tasks where I will use Azure AD token generator code. Click on below diagram to get better view.

App registration and assign permissions to Azure AD application

The concepts of Azure AD Service principal, application registration, process of creating service principal remains same for .Net core too.

The only change we will see is in codebase.

So follow my earlier blog and perform below tasks –
       1.       Create Azure Service Principal by app registration
2.      Record Tenant ID, Application ID and Secret key
3.      Assign correct permissions to Azure AD app

By following earlier blog if you are still not clear then refer to document to understand – How and Why applications are added to Azure AD.

.NET Core code base for Azure AD token generation

Let us understand the code base for .NET core. The code now fundamentally is different than .NET framework. However Tenant ID, Application ID and Secret Key of Azure AD will be leveraged same as .NET framework code.
Build confidential client application as below – [click to enlarge]

This class is present in Nuget package Microsoft.Identity.Client and I am using 4.10.0 version for this project.

Azure AD authentication has many flows applicable. The current flow we are using in our code is “Azure AD Client Credentials” flow. For client credential flow we have to provide scope.

Scope is a boundary for which granted access token will be valid. If you request token for one scope and use for another; request will be denied. Example, you provide scope while requesting token from Azure AD as [Log analytics resource scopes].

Means with generated token we can perform operation ONLY on Log Analytics. Post getting token if you try to access Azure Storage resource with scope as then it will be denied. So providing correct scope is crucial.

The format of scope for “Client Credentials” is always of the shape “resource/.default”. So configure the scope as below. In my example I am leveraging scope for Azure Log Analytics. [click to enlarge below].

Now for this scope we retrieve the Access Token as below – [click to enlarge].

Further we can use this token with Postman to perform Azure management operation. Alternatively, we can also integrate this code in Azure functions, or applications to get token at runtime without user credentials and perform required administrative operation against azure environment.

Download  code

Entire code is available for download from github at the link  -


Hope this article helped you to get quick code for generating Azure AD token using .NET core. Let me know your views in comments section below to improve and what are your thoughts on this approach.
Happy token generating!!

A humble request!

Internet is creating a lot of digital garbage. If you feel this a quality blog and someone will definitely get benefited, don't hesitate to hit share button present below. Your one share will save many precious hours of a developer. Thank you.

Next Related Posts

Start stop multiple Azure VMs and save cost. This uses Azure AD application behind the scenes.