Azure Function Authorization Level Best Practices

To ensure secure and efficient Azure Function operations, it's essential to configure the right authorization level. This means setting the correct permissions for your functions to run.

Choosing the correct authorization level can be a bit tricky, but understanding the different options is key. There are three main levels: Anonymous, Function, and Admin.

The Anonymous level allows anyone to invoke your function without authentication, which can be a security risk if not handled properly. This level is often used for public APIs or demos.

Function level authorization, on the other hand, restricts access to only the Azure Function runtime, which is a more secure option. This level is ideal for internal APIs or when you need to control access to specific functions.

Admin level authorization grants full access to the function, which is typically used for development and testing purposes only. This level should be avoided in production environments due to the high security risk.

Authorization level is a string value that indicates the kind of authorization key required to access a function endpoint. It can be one of the following values: anonymous, function, or admin.

The anonymous level requires no access key, while the function level requires a function-specific key. The admin level requires the master key to access the endpoint.

By default, authorization defaults to the function level when a level isn't explicitly set. However, the default authorization level depends on the version of the Node.js model being used.

Here are the default authorization levels for different Node.js model versions:

Unless the authorization level is set to anonymous, requests must include an access key in the request. Access keys can be included in a query string variable named code or in an x-functions-key HTTP header.

Function security is crucial to protect your Azure Functions from unauthorized access. You can use access keys to make it harder to access your function endpoints, unless the authorization level is set to anonymous.

Unless the authorization level on an HTTP triggered function is set to anonymous, requests must include an access key in the request. The key can be included in a query string variable named code, or in an x-functions-key HTTP header. You can also allow anonymous requests, which don't require keys.

Here are the supported authorization levels for an HTTP trigger template:

To configure the authorization level, you can use the authLevel property in the binding JSON. When running functions locally, authorization is disabled regardless of the specified authorization level setting.

In Azure Functions, the HttpTriggerAttribute is used to define the HTTP endpoint for your function. This attribute supports various parameters to customize the endpoint's behavior.

The AuthLevel parameter determines what keys, if any, need to be present on the request to invoke the function. You can choose from the supported values listed in the Authorization level documentation.

When specifying the Methods parameter, you can define an array of HTTP methods to which the function responds. If left unspecified, the function will respond to all HTTP methods.

The Route parameter defines the route template, controlling which request URLs your function responds to. If not provided, the default value is the function name.

Here's a summary of the HttpTriggerAttribute's parameters:

In in-process functions, an additional parameter called WebHookType is supported. This parameter is used to configure the HTTP trigger as a webhook receiver for a specific provider, and is only available in version 1.x runtime.

Azure Function authorization level is a crucial aspect to consider when building cloud-based applications. There are several authentication methods available to secure your function endpoints.

You can use Azure API Management (APIM) to authenticate requests, which provides various API security options for incoming requests.

To authenticate requests, you can also use access key authorization, which requires an access key in the request. The access key can be included in a query string variable named code or in an x-functions-key HTTP header.

API key in the request header is another authentication method available, which is a built-in feature of Azure Functions. This can be achieved by setting the value of the OpenApiSecurityAttribute decorator.

Alternatively, you can enable App Service Authentication/Authorization, which allows you to use Microsoft Entra ID and several third-party identity providers to authenticate clients.

OpenID Connect auth flow is also an option, which uses the authentication code flow or the implicit flow. The implicit flow is shown in the example, where the client ID value is entered to redirect to Azure Active Directory to sign in and give access to the access token.

Here are the different authentication methods available:

These authentication methods can be used to secure your function endpoints and ensure that only authorized clients can access your application.

Access to authenticated client information is currently only available for .NET languages, and it also isn't supported in version 1.x of the Functions runtime.

The authenticated user is available via HTTP Headers, and the ClaimsPrincipal can simply be included as an extra parameter in the function signature.

The goal is to run your function app with the lowest possible permissions. Permissions are effective at the function app level, and the Contributor role is required to perform most function app-level tasks.

Azure roles supported by Functions are Contributor, Owner, and Reader. Only the Owner role can delete a function app.

You can grant your application two types of identities: a system-assigned identity and a user-assigned identity. A system-assigned identity is tied to the app and is deleted if the app is deleted, while a user-assigned identity is a standalone Azure resource that can be assigned to your app.

Here is a summary of Azure roles supported by Functions:

Client identities are a powerful way to manage access to Azure services, and they're particularly useful when working with Azure Functions.

You can view information about authenticated clients from your code, which is available as request headers injected by the platform, or by reading this information from binding data.

This feature is currently only available for .NET languages and isn't supported in version 1.x of the Functions runtime.

The authenticated user is available via HTTP Headers, or the ClaimsPrincipal can simply be included as an extra parameter in the function signature.

Identities can be used in place of secrets for connecting to some resources, which has the advantage of not requiring the management of a secret, and it provides more fine-grained access control and auditing.

Some Azure Functions binding extensions can be configured to access services using identity-based connections.

User management permissions are an essential aspect of Azure Functions. You can manage permissions using Azure role-based access control (Azure RBAC).

Azure Functions supports three built-in Azure roles: Contributor, Owner, and Reader. These roles determine what actions you can perform on your function app.

The Contributor role is required to perform most function app-level tasks. You'll need this role to create, update, or delete function apps, as well as to configure settings and manage resources.

To view log data in Application Insights, you'll need the Monitoring Reader permission in addition to the Contributor role.

Only the Owner role can delete a function app. This means that if you need to delete an app, you'll need to have the Owner role assigned to you.

Here's a summary of the supported Azure roles for Functions:

Azure Functions requires careful consideration of security and deployment when setting the authorization level. Secure deployment is crucial, and Azure Functions tooling integration makes it easy to publish local function project code to Azure.

To secure your function app deployments, you'll need to understand how deployment works and use deployment credentials. These credentials are used to secure your function app deployments and are managed by the App Service platform.

There are two kinds of deployment credentials: user-level credentials and app-level credentials. User-level credentials are one set of credentials for the entire Azure account, while app-level credentials are one set of credentials for each app.

Here are the key differences between user-level and app-level credentials:

Don't share user-level credentials with other Azure users.

Azure Functions tooling integration makes it easy to publish local function project code to Azure. This integration simplifies the deployment process, but it's essential to understand how deployment works to ensure security for your Azure Functions topology.

Deployment credentials are managed by the App Service platform and are encrypted at rest. This means that your credentials are protected from unauthorized access.

To secure your function app deployments, you'll need to use a set of deployment credentials. There are two types of deployment credentials: user-level credentials and app-level credentials.

Here are the key differences between user-level and app-level credentials:

User-level credentials are the default set that's surfaced in the portal GUI. They can be used by any user who has been granted app access via Role-Based Access Control (RBAC) or coadmin permissions. However, it's essential to note that you should not share these credentials with other Azure users.

App-level credentials, on the other hand, are generated automatically at app creation and can only be used to deploy to that specific app. They can be reset anytime, but only by a user who has contributor or higher permissions on the app.

To get started with Azure Functions, you'll want to dive into the essentials before creating your first function app.

You can use access keys to make it harder to access your function endpoints, which is a good practice to follow. Unless the authorization level on an HTTP triggered function is set to anonymous, requests must include an access key in the request.

To enable App Service Authentication and Authorization, you can use Microsoft Entra ID and several third-party identity providers to authenticate clients.

You can use this strategy to implement custom authorization rules for your functions and work with user information from your function code.

To learn more, see Authentication and authorization in Azure App Service and Working with client identities.

Implementing App Service Authentication and Authorization is a crucial step in securing your function endpoints, as it provides a higher level of security than just using access keys.

Access keys can provide some mitigation for unwanted access, but they are not enough to truly secure your function endpoints.

You can secure the entire application architecture inside a virtual network using private endpoints or by running in isolation for the highest level of security.

Unless the authorization level on an HTTP triggered function is set to anonymous, requests must include an access key in the request to access your function endpoints.

To get started with Azure Functions, you'll need to have a Function App set up. This is where your function will live, so make sure it's created first.

You can set up a Function App by following the process outlined in the Azure portal. Once you have your Function App set up, it's time to create your first function.

To create your first function, navigate to your newly created Function App in the Azure portal and click on the "+ New function" button. This will add a new function to your Function App.

The next step is to choose a trigger for your function. For a simple HTTP-triggered function, select "HTTP trigger" as the trigger type. Give your function a name and choose the appropriate authorization level, then click on "Create".

Here are the steps to create a new function summarized:

Minimizing the number of functions with access to specific credentials is key to securing your application. Consider moving functions that don't use those credentials to a separate function app.

You can always use techniques such as function chaining to pass data between functions in different function apps. This approach helps to limit the permissions of each function, making it more difficult for an attacker to access sensitive data.