Credential chains in the Azure Identity client library for Java

The Azure Identity client library provides credentials—public classes that implement the Azure Core library's TokenCredential interface. A credential represents a distinct authentication flow for acquiring an access token from Microsoft Entra ID. These credentials can be chained together to form an ordered sequence of authentication mechanisms to be attempted.

How a chained credential works

At runtime, a credential chain attempts to authenticate using the sequence's first credential. If that credential fails to acquire an access token, the next credential in the sequence is attempted, and so on, until an access token is successfully obtained. The following sequence diagram illustrates this behavior:

Why use credential chains

A chained credential can offer the following benefits:

• Environment awareness: Automatically selects the most appropriate credential based on the environment in which the app is running. Without it, you'd have to write code like this:

  import com.azure.core.credential.TokenCredential;
  import com.azure.identity.AzureCliCredentialBuilder;
  import com.azure.identity.ManagedIdentityCredentialBuilder;
  
  // Code omitted for brevity
  
  TokenCredential credential = null;
  
  // Set up credential based on environment (Azure or local development)
  String environment = System.getenv("ENV");
  
  if (environment != null && environment.equals("production")) {
      credential = new ManagedIdentityCredentialBuilder()
          .clientId(userAssignedClientId)
          .build();
  } else {
      credential = new AzureCliCredentialBuilder()
          .build();
  }
  

• Seamless transitions: Your app can move from local development to your staging or production environment without changing authentication code.

• Improved resiliency: Includes a fallback mechanism that moves to the next credential when the prior fails to acquire an access token.

How to choose a chained credential

There are two disparate philosophies to credential chaining:

• Use a preconfigured chain: Start with an opinionated, preconstructed chain that accommodates the most common authentication scenarios. For this approach, see the DefaultAzureCredential overview section.
• "Build up" a chain: Start with an empty chain and include only what you need. For this approach, see the ChainedTokenCredential overview section.

DefaultAzureCredential overview

DefaultAzureCredential is an opinionated, preconfigured chain of credentials. It's designed to support many environments, along with the most common authentication flows and developer tools. In graphical form, the underlying chain looks like this:

The order in which DefaultAzureCredential attempts credentials follows.

In its simplest form, you can use the parameterless version of DefaultAzureCredential as follows:

import com.azure.identity.DefaultAzureCredential;
import com.azure.identity.DefaultAzureCredentialBuilder;

// Code omitted for brevity

DefaultAzureCredential credential = new DefaultAzureCredentialBuilder()
    .build();

ChainedTokenCredential overview

ChainedTokenCredential is an empty chain to which you add credentials to suit your app's needs. For example:

import com.azure.identity.AzureCliCredential;
import com.azure.identity.AzureCliCredentialBuilder;
import com.azure.identity.ChainedTokenCredential;
import com.azure.identity.ChainedTokenCredentialBuilder;
import com.azure.identity.ManagedIdentityCredential;
import com.azure.identity.ManagedIdentityCredentialBuilder;

// Code omitted for brevity

ManagedIdentityCredential miCredential = new ManagedIdentityCredentialBuilder()
    .clientId(userAssignedClientId)
    .build();
AzureCliCredential cliCredential = new AzureCliCredentialBuilder()
    .build();

ChainedTokenCredential credential = new ChainedTokenCredentialBuilder()
    .addLast(miCredential)
    .addLast(cliCredential)
    .build();

The preceding code sample creates a tailored credential chain comprised of two credentials. The user-assigned managed identity variant of ManagedIdentityCredential is attempted first, followed by AzureCliCredential, if necessary. In graphical form, the chain looks like this:

Usage guidance for DefaultAzureCredential

DefaultAzureCredential is undoubtedly the easiest way to get started with the Azure Identity client library, but with that convenience comes tradeoffs. Once you deploy your app to Azure, you should understand the app's authentication requirements. For that reason, strongly consider moving from DefaultAzureCredential to one of the following solutions:

• A specific credential implementation, such as ManagedIdentityCredential.
• A pared-down ChainedTokenCredential implementation optimized for the Azure environment in which your app runs.

Here's why:

• Debugging challenges: When authentication fails, it can be challenging to debug and identify the offending credential. You must enable logging to see the progression from one credential to the next and the success/failure status of each. For more information, see Debug a chained credential.
• Performance overhead: The process of sequentially trying multiple credentials can introduce performance overhead. For example, when running on a local development machine, managed identity is unavailable. Consequently, ManagedIdentityCredential always fails in the local development environment.
• Unpredictable behavior: DefaultAzureCredential checks for the presence of certain environment variables. It's possible that someone could add or modify these environment variables at the system level on the host machine. Those changes apply globally and therefore alter the behavior of DefaultAzureCredential at runtime in any app running on that machine.

Debug a chained credential

To diagnose an unexpected issue or to understand what a chained credential is doing, enable logging in your app.

For illustration purposes, assume the parameterless form of DefaultAzureCredential is used to authenticate a request to a Blob Storage account. The app runs in the local development environment, and the developer authenticated to Azure using the Azure CLI. When the app is run, the following pertinent entries appear in the output:

[main] INFO com.azure.identity.ChainedTokenCredential - Azure Identity => Attempted credential EnvironmentCredential is unavailable.
[main] INFO com.azure.identity.ChainedTokenCredential - Azure Identity => Attempted credential WorkloadIdentityCredential is unavailable.
[ForkJoinPool.commonPool-worker-1] WARN com.microsoft.aad.msal4j.ConfidentialClientApplication - [Correlation ID: aaaa0000-bb11-2222-33cc-444444dddddd] Execution of class com.microsoft.aad.msal4j.AcquireTokenByClientCredentialSupplier failed: java.util.concurrent.ExecutionException: com.azure.identity.CredentialUnavailableException: ManagedIdentityCredential authentication unavailable. Connection to IMDS endpoint cannot be established.
[main] INFO com.azure.identity.ChainedTokenCredential - Azure Identity => Attempted credential ManagedIdentityCredential is unavailable.
[main] INFO com.azure.identity.ChainedTokenCredential - Azure Identity => Attempted credential SharedTokenCacheCredential is unavailable.
[main] INFO com.azure.identity.ChainedTokenCredential - Azure Identity => Attempted credential IntelliJCredential is unavailable.
[main] INFO com.azure.identity.ChainedTokenCredential - Azure Identity => Attempted credential AzureCliCredential returns a token

In the preceding output, notice that:

• EnvironmentCredential, WorkloadIdentityCredential, ManagedIdentityCredential, SharedTokenCacheCredential, and IntelliJCredential each failed to acquire a Microsoft Entra access token, in that order.
• The AzureCliCredential.getToken call succeeds, as indicated by the returns a token-suffixed entry. Since AzureCliCredential succeeded, no credentials beyond it were tried.