Authenticate .NET apps to Azure services during local development using developer accounts

When creating cloud applications, developers need to debug and test applications on their local workstation. When an application is run on a developer's workstation during local development, it still must authenticate to any Azure services used by the app. This article covers how to use a developer's Azure credentials to authenticate the app to Azure during local development.

For an app to authenticate to Azure during local development using the developer's Azure credentials, the developer must be signed-in to Azure from the VS Code Azure Tools extension, the Azure CLI, or Azure PowerShell. The Azure SDK for .NET is able to detect that the developer is signed-in from one of these tools and then obtain the necessary credentials from the credentials cache to authenticate the app to Azure as the signed-in user.

This approach is easiest to set up for a development team since it takes advantage of the developers' existing Azure accounts. However, a developer's account will likely have more permissions than required by the application, therefore exceeding the permissions the app will run with in production. As an alternative, you can create application service principals to use during local development which can be scoped to have only the access needed by the app.

1 - Create Azure AD group for local development

Since there are almost always multiple developers who work on an application, it's recommended to first create an Azure AD group to encapsulate the roles (permissions) the app needs in local development. This offers the following advantages.

• Every developer is assured to have the same roles assigned since roles are assigned at the group level.
• If a new role is needed for the app, it only needs to be added to the Azure AD group for the app.
• If a new developer joins the team, they simply must be added to the correct Azure AD group to get the correct permissions to work on the app.

If you have an existing Azure AD group for your development team, you can use that group. Otherwise, complete the following steps to create an Azure AD group.

Azure portal

Instructions	Screenshot
Navigate to the Azure Active Directory page in the Azure portal by typing Azure Active Directory into the search box at the top of the page and then selecting Azure Active Directory from under services.
On the Azure Active Directory page, select Groups from the left-hand menu.
On the All groups page, select New group.
On the New Group page: Group type → Security Group name → A name for the security group, typically created from the application name. It is also helpful to include a string like local-dev in the name of the group to indicate the purpose of the group. Group description → A description of the purpose of the group. Select the No members selected link under Members to add members to the group.
On the Add members dialog box: Use the search box to filter the list of user names in the list. Select the user(s) for local development for this app. As objects are selected, they will move to the Selected items list at the bottom of the dialog. When finished, select the Select button.
Back on the New group page, select Create to create the group. The group will be created and you will be taken back to the All groups page. It may take up to 30 seconds for the group to appear and you may need to refresh the page due to caching in the Azure portal.

Azure CLI

The az ad group create command is used to create groups in Azure Active Directory. The --display-name and --main-nickname parameters are required. The name given to the group should be based on the name of the application. It's also useful to include a phrase like 'local-dev' in the name of the group to indicate the purpose of the group.

az ad group create \
    --display-name MyDisplay \
    --mail-nickname MyDisplay  \
    --description <group-description>

To add members to the group, you'll need the object ID of Azure user. Use the az ad user list to list the available service principals. The --filter parameter command accepts OData style filters and can be used to filter the list on the display name of the user as shown. The --query parameter limits to columns to only those of interest.

az ad user list \
    --filter "startswith(displayName, 'Bob')" \
    --query "[].{objectId:objectId, displayName:displayName}" \
    --output table

The az ad group member add command can then be used to add members to groups.

az ad group member add \
    --group <group-name> \
    --member-id <object-id>

2 - Assign roles to the Azure AD group

Next, you need to determine what roles (permissions) your app needs on what resources and assign those roles to your app. In this example, the roles will be assigned to the Azure Active Directory group created in step 1. Roles can be assigned a role at a resource, resource group, or subscription scope. This example will show how to assign roles at the resource group scope since most applications group all their Azure resources into a single resource group.

Azure portal

Instructions	Screenshot
Locate the resource group for your application by searching for the resource group name using the search box at the top of the Azure portal. Navigate to your resource group by selecting the resource group name under the Resource Groups heading in the dialog box.
On the page for the resource group, select Access control (IAM) from the left-hand menu.
On the Access control (IAM) page: Select the Role assignments tab. Select + Add from the top menu and then Add role assignment from the resulting drop-down menu.
The Add role assignment page lists all of the roles that can be assigned for the resource group. Use the search box to filter the list to a more manageable size. This example shows how to filter for Storage Blob roles. Select the role that you want to assign. Select Next to go to the next screen.
The next Add role assignment page allows you to specify what user to assign the role to. Select User, group, or service principal under Assign access to. Select + Select members under Members A dialog box will open on the right-hand side of the Azure portal.
In the Select members dialog: The Select text box can be used to filter the list of users and groups in your subscription. If needed, type the first few characters of the local development Azure AD group you created for the app. Select the local development Azure AD group associated with your application. Select Select at the bottom of the dialog to continue.
The Azure AD group will now show as selected on the Add role assignment screen. Select Review + assign to go to the final page and then Review + assign again to complete the process.

Azure CLI

An application service principal is assigned a role in Azure using the az role assignment create command.

az role assignment create --assignee "{appId}" \
    --role "{roleName}" \
    --resource-group "{resourceGroupName}"

To get the role names that a service principal can be assigned to, use the az role definition list command.

az role definition list --query "sort_by([].{roleName:roleName, description:description}, &roleName)" --output table

For example, to allow the application service principal with the appId of 00000000-0000-0000-0000-000000000000 read, write, and delete access to Azure Storage blob containers and data to all storage accounts in the msdocs-dotnet-sdk-auth-example resource group, you would assign the application service principal to the Storage Blob Data Contributor role using the following command.

az role assignment create --assignee "00000000-0000-0000-0000-000000000000" \
    --role "Storage Blob Data Contributor" \
    --resource-group "msdocs-dotnet-sdk-auth-example"

For information on assigning permissions at the resource or subscription level using the Azure CLI, see the article Assign Azure roles using the Azure CLI.

3 - Sign-in to Azure using .NET Tooling

Next you need to sign in to Azure using one of several .NET tooling options. The account you sign into should also exist in the Azure Active Directory group you created and configured earlier.

Visual Studio

On the top menu of Visual Studio, navigate to Tools > Options to open the options dialog. In the search bar in the upper left, type Azure to filter the options. Under the Azure Service Authentication, choose Account Selection.

Select the drop-down menu under Choose an account and choose to add a Microsoft Account. A window will open prompting you to pick an account. Enter the credentials for your desired Azure account, and then select the confirmation.

VS Code Azure Tools extension

For an app to use the developer credentials from VS Code, the VS Code Azure Tools extension must be installed in VS Code.

Install the Azure Tools extensions for VS Code

On the left-hand panel, you'll see an Azure icon. Select this icon, and a control panel for Azure services will appear. Choose Sign in to Azure... under any service to complete the authentication process for the Azure tools in Visual Studio Code.

Azure CLI

Open a terminal on your developer workstation and sign-in to Azure from the Azure CLI.

az login

Azure PowerShell

Open a terminal on your developer workstation and sign-in to Azure from Azure PowerShell.

Connect-AzAccount

4 - Implement DefaultAzureCredential in your application

DefaultAzureCredential supports multiple authentication methods and determines the authentication method being used at runtime. In this way, your app can use different authentication methods in different environments without implementing environment specific code.

The order and locations in which DefaultAzureCredential looks for credentials is found at DefaultAzureCredential.

To implement DefaultAzureCredential, first add the Azure.Identity and optionally the Microsoft.Extensions.Azure packages to your application. You can do this using either the command line or the NuGet Package Manager.

Command Line

Open a terminal environment of your choice in the application project directory and enter the command below.

dotnet add package Azure.Identity
dotnet add package Microsoft.Extensions.Azure

NuGet Package Manager

Right click on your project node in Visual Studio and select Manage NuGet Packages. Search for Azure.Identity in the search field, and install the matching package. Repeat this process for the Microsoft.Extensions.Azure package as well.

Azure services are generally accessed using corresponding client classes from the SDK. These classes and your own custom services should be registered in the Program.cs file so they can be accessed via dependency injection throughout your app. Inside of Program.cs, follow the steps below to correctly setup your service and DefaultAzureCredential.

1. Include the Azure.Identity and Microsoft.Extensions.Azure namespaces with a using statement.
2. Register the Azure service using relevant helper methods.
3. Pass an instance of the DefaultAzureCredential object to the UseCredential method.

An example of this is shown in the following code segment.

using Microsoft.Extensions.Azure;
using Azure.Identity;

// Inside of Program.cs
builder.Services.AddAzureClients(x =>
{
    x.AddBlobServiceClient(new Uri("https://<account-name>.blob.core.windows.net"));
    x.UseCredential(new DefaultAzureCredential());
});

Alternatively, you can also utilize DefaultAzureCredential in your services more directly without the help of additional Azure registration methods, as seen below.

using Azure.Identity;

// Inside of Program.cs
builder.Services.AddSingleton<BlobServiceClient>(x => 
    new BlobServiceClient(
        new Uri("https://<account-name>.blob.core.windows.net"),
        new DefaultAzureCredential()));

When the above code is run on your local workstation during local development, it will look in the environment variables for an application service principal or at Visual Studio, VS Code, the Azure CLI, or Azure PowerShell for a set of developer credentials, either of which can be used to authenticate the app to Azure resources during local development.

When deployed to Azure this same code can also authenticate your app to other Azure resources. DefaultAzureCredential can retrieve environment settings and managed identity configurations to authenticate to other services automatically.