Authenticate with an Azure container registry

• 01/30/2020
• 5 minutes to read
• • d
  • r
  • k
  • v
  • n
  • +12

There are several ways to authenticate with an Azure container registry, each of which is applicable to one or more registry usage scenarios.

Recommended ways include authenticating to a registry directly via individual login, or your applications and container orchestrators can perform unattended, or "headless," authentication by using an Azure Active Directory (Azure AD) service principal.

Authentication options

The following table lists available authentication methods and typical scenarios. See linked content for details.

Individual login with Azure AD

When working with your registry directly, such as pulling images to and pushing images from a development workstation to a registry you created, authenticate by using your individual Azure identity. Sign in to the Azure CLI with az login, and then run the az acr login command:

az login
az acr login --name <acrName>

When you log in with az acr login, the CLI uses the token created when you executed az login to seamlessly authenticate your session with your registry. To complete the authentication flow, the Docker CLI and Docker daemon must be installed and running in your environment. az acr login uses the Docker client to set an Azure Active Directory token in the docker.config file. Once you've logged in this way, your credentials are cached, and subsequent docker commands in your session do not require a username or password.

For registry access, the token used by az acr login is valid for 3 hours, so we recommend that you always log in to the registry before running a docker command. If your token expires, you can refresh it by using the az acr login command again to reauthenticate.

Using az acr login with Azure identities provides Azure role-based access control (Azure RBAC). For some scenarios, you may want to log in to a registry with your own individual identity in Azure AD, or configure other Azure users with specific Azure roles and permissions. For cross-service scenarios or to handle the needs of a workgroup or a development workflow where you don't want to manage individual access, you can also log in with a managed identity for Azure resources.

az acr login with --expose-token

In some cases, you might need to authenticate with az acr login when the Docker daemon isn't running in your environment. For example, you might need to run az acr login in a script in Azure Cloud Shell, which provides the Docker CLI but doesn't run the Docker daemon.

For this scenario, run az acr login first with the --expose-token parameter. This option exposes an access token instead of logging in through the Docker CLI.

az acr login --name <acrName> --expose-token

Output displays the access token, abbreviated here:

{
  "accessToken": "eyJhbGciOiJSUzI1NiIs[...]24V7wA",
  "loginServer": "myregistry.azurecr.io"
}

Then, run docker login, passing 00000000-0000-0000-0000-000000000000 as the username and using the access token as password:

docker login myregistry.azurecr.io --username 00000000-0000-0000-0000-000000000000 --password eyJhbGciOiJSUzI1NiIs[...]24V7wA

Service principal

If you assign a service principal to your registry, your application or service can use it for headless authentication. Service principals allow Azure role-based access control (Azure RBAC) to a registry, and you can assign multiple service principals to a registry. Multiple service principals allow you to define different access for different applications.

The available roles for a container registry include:

• AcrPull: pull

• AcrPush: pull and push

• Owner: pull, push, and assign roles to other users

For a complete list of roles, see Azure Container Registry roles and permissions.

For CLI scripts to create a service principal for authenticating with an Azure container registry, and more guidance, see Azure Container Registry authentication with service principals.

Admin account

Each container registry includes an admin user account, which is disabled by default. You can enable the admin user and manage its credentials in the Azure portal, or by using the Azure CLI or other Azure tools. The admin account has full permissions to the registry.

The admin account is currently required for some scenarios to deploy an image from a container registry to certain Azure services. For example, the admin account is needed when you deploy a container image in the portal from a registry directly to Azure Container Instances or Azure Web Apps for Containers.

The admin account is provided with two passwords, both of which can be regenerated. Two passwords allow you to maintain connection to the registry by using one password while you regenerate the other. If the admin account is enabled, you can pass the username and either password to the docker login command when prompted for basic authentication to the registry. For example:

docker login myregistry.azurecr.io 

For best practices to manage login credentials, see the docker login command reference.

To enable the admin user for an existing registry, you can use the --admin-enabled parameter of the az acr update command in the Azure CLI:

az acr update -n <acrName> --admin-enabled true

You can enable the admin user in the Azure portal by navigating your registry, selecting Access keys under SETTINGS, then Enable under Admin user.

Next steps

• Push your first image using the Azure CLI