Choose how to authorize access to blob data with Azure CLI

Azure Storage provides extensions for Azure CLI that enable you to specify how you want to authorize operations on blob data. You can authorize data operations in the following ways:

  • With an Azure Active Directory (Azure AD) security principal. Microsoft recommends using Azure AD credentials for superior security and ease of use.
  • With the account access key or a shared access signature (SAS) token.

Specify how data operations are authorized

Azure CLI commands for reading and writing blob data include the optional --auth-mode parameter. Specify this parameter to indicate how a data operation is to be authorized:

  • Set the --auth-mode parameter to login to sign in using an Azure AD security principal (recommended).
  • Set the --auth-mode parameter to the legacy key value to attempt to retrieve the account access key to use for authorization. If you omit the --auth-mode parameter, then the Azure CLI also attempts to retrieve the access key.

To use the --auth-mode parameter, make sure that you have installed Azure CLI version 2.0.46 or later. Run az --version to check your installed version.

Note

When a storage account is locked with an Azure Resource Manager ReadOnly lock, the List Keys operation is not permitted for that storage account. List Keys is a POST operation, and all POST operations are prevented when a ReadOnly lock is configured for the account. For this reason, when the account is locked with a ReadOnly lock, users who do not already possess the account keys must use Azure AD credentials to access blob data.

Important

If you omit the --auth-mode parameter or set it to key, then the Azure CLI attempts to use the account access key for authorization. In this case, Microsoft recommends that you provide the access key either on the command or in the AZURE_STORAGE_KEY environment variable. For more information about environment variables, see the section titled Set environment variables for authorization parameters.

If you do not provide the access key, then the Azure CLI attempts to call the Azure Storage resource provider to retrieve it for each operation. Performing many data operations that require a call to the resource provider may result in throttling. For more information about resource provider limits, see Scalability and performance targets for the Azure Storage resource provider.

Authorize with Azure AD credentials

When you sign in to Azure CLI with Azure AD credentials, an OAuth 2.0 access token is returned. That token is automatically used by Azure CLI to authorize subsequent data operations against Blob or Queue storage. For supported operations, you no longer need to pass an account key or SAS token with the command.

You can assign permissions to blob data to an Azure AD security principal via Azure role-based access control (Azure RBAC). For more information about Azure roles in Azure Storage, see Assign an Azure role for access to blob data.

Permissions for calling data operations

The Azure Storage extensions are supported for operations on blob data. Which operations you may call depends on the permissions granted to the Azure AD security principal with which you sign in to Azure CLI. Permissions to Azure Storage containers are assigned via Azure RBAC. For example, if you are assigned the Storage Blob Data Reader role, then you can run scripting commands that read data from a container. If you are assigned the Storage Blob Data Contributor role, then you can run scripting commands that read, write, or delete a container or the data it contains.

For details about the permissions required for each Azure Storage operation on a container, see Call storage operations with OAuth tokens.

Example: Authorize an operation to create a container with Azure AD credentials

The following example shows how to create a container from Azure CLI using your Azure AD credentials. To create the container, you'll need to sign in to the Azure CLI, and you'll need a resource group and a storage account. To learn how to create these resources, see Quickstart: Create, download, and list blobs with Azure CLI.

  1. Before you create the container, assign the Storage Blob Data Contributor role to yourself. Even though you are the account owner, you need explicit permissions to perform data operations against the storage account. For more information about assigning Azure roles, see Assign an Azure role for access to blob data.

    Important

    Azure role assignments may take a few minutes to propagate.

  2. Call the az storage container create command with the --auth-mode parameter set to login to create the container using your Azure AD credentials. Remember to replace placeholder values in angle brackets with your own values:

    az storage container create \
        --account-name <storage-account> \
        --name sample-container \
        --auth-mode login
    

Authorize with the account access key

If you possess the account key, you can call any Azure Storage data operation. In general, using the account key is less secure. If the account key is compromised, all data in your account may be compromised.

The following example shows how to create a container using the account access key. Specify the account key, and provide the --auth-mode parameter with the key value:

az storage container create \
    --account-name <storage-account> \
    --name sample-container \
    --account-key <key>
    --auth-mode key

Important

When a storage account is locked with an Azure Resource Manager ReadOnly lock, the List Keys operation is not permitted for that storage account. List Keys is a POST operation, and all POST operations are prevented when a ReadOnly lock is configured for the account. For this reason, when the account is locked with a ReadOnly lock, users must access data with Azure AD credentials.

Authorize with a SAS token

If you possess a SAS token, you can call data operations that are permitted by the SAS. The following example shows how to create a container using a SAS token:

az storage container create \
    --account-name <storage-account> \
    --name sample-container \
    --sas-token <token>

Set environment variables for authorization parameters

You can specify authorization parameters in environment variables to avoid including them on every call to an Azure Storage data operation. The following table describes the available environment variables.

Environment variable Description
AZURE_STORAGE_ACCOUNT The storage account name. This variable should be used in conjunction with either the storage account key or a SAS token. If neither are present, the Azure CLI attempts to retrieve the storage account access key by using the authenticated Azure AD account. If a large number of commands are executed at one time, the Azure Storage resource provider throttling limit may be reached. For more information about resource provider limits, see Scalability and performance targets for the Azure Storage resource provider.
AZURE_STORAGE_KEY The storage account key. This variable must be used in conjunction with the storage account name.
AZURE_STORAGE_CONNECTION_STRING A connection string that includes the storage account key or a SAS token. This variable must be used in conjunction with the storage account name.
AZURE_STORAGE_SAS_TOKEN A shared access signature (SAS) token. This variable must be used in conjunction with the storage account name.
AZURE_STORAGE_AUTH_MODE The authorization mode with which to run the command. Permitted values are login (recommended) or key. If you specify login, the Azure CLI uses your Azure AD credentials to authorize the data operation. If you specify the legacy key mode, the Azure CLI attempts to query for the account access key and to authorize the command with the key.

Next steps