Secure access to data in Azure Cosmos DB

APPLIES TO: SQL API

This article provides an overview of data access control in Azure Cosmos DB.

Azure Cosmos DB provides three ways to control access to your data.

Access control type Characteristics
Primary/secondary keys Shared secret allowing any management or data operation. It comes in both read-write and read-only variants.
Role-based access control Fine-grained, role-based permission model using Azure Active Directory (AAD) identities for authentication.
Resource tokens Fine-grained permission model based on native Azure Cosmos DB users and permissions.

Primary/secondary keys

Primary/secondary keys provide access to all the administrative resources for the database account. Each account consists of two keys: a primary key and secondary key. The purpose of dual keys is to let you regenerate, or roll keys, providing continuous access to your account and data. To learn more about primary/secondary keys, see the Database security article.

Key rotation and regeneration

Note

The following section describes the steps to rotate and regenerate keys for the SQL API. If you're using a different API, see the Azure Cosmos DB API for Mongo DB, Cassandra API, Gremlin API, or Table API sections.

To monitor your account for key updates and key regeneration, see monitor key updates with metrics and alerts article.

The process of key rotation and regeneration is simple. First, make sure that your application is consistently using either the primary key or the secondary key to access your Azure Cosmos DB account. Then, follow the steps outlined below.

  1. Navigate to your Azure Cosmos DB account on the Azure portal.

  2. Select Keys from the left menu, then select Regenerate Secondary Key from the ellipsis on the right of your secondary key.

    Screenshot of the Azure portal showing how to regenerate the secondary key

  3. Validate that the new secondary key works consistently against your Azure Cosmos DB account. Key regeneration can take anywhere from one minute to multiple hours depending on the size of the Cosmos DB account.

  4. Replace your primary key with the secondary key in your application.

  5. Go back to the Azure portal and trigger the regeneration of the primary key.

    Screenshot of the Azure portal showing how to regenerate the primary key

Code sample to use a primary key

The following code sample illustrates how to use a Cosmos DB account endpoint and primary key to instantiate a CosmosClient:

// Read the Azure Cosmos DB endpointUrl and authorization keys from config.
// These values are available from the Azure portal on the Azure Cosmos DB account blade under "Keys".
// Keep these values in a safe and secure location. Together they provide Administrative access to your Azure Cosmos DB account.

private static readonly string endpointUrl = ConfigurationManager.AppSettings["EndPointUrl"];
private static readonly string authorizationKey = ConfigurationManager.AppSettings["AuthorizationKey"];

CosmosClient client = new CosmosClient(endpointUrl, authorizationKey);

Role-based access control

Azure Cosmos DB exposes a built-in role-based access control (RBAC) system that lets you:

  • Authenticate your data requests with an Azure Active Directory (AAD) identity.
  • Authorize your data requests with a fine-grained, role-based permission model.

Azure Cosmos DB RBAC is the ideal access control method in situations where:

  • You don't want to use a shared secret like the primary key, and prefer to rely on a token-based authentication mechanism,
  • You want to use Azure AD identities to authenticate your requests,
  • You need a fine-grained permission model to tightly restrict which database operations your identities are allowed to perform,
  • You wish to materialize your access control policies as "roles" that you can assign to multiple identities.

See Configure role-based access control for your Azure Cosmos DB account to learn more about Azure Cosmos DB RBAC.

Resource tokens

Resource tokens provide access to the application resources within a database. Resource tokens:

  • Provide access to specific containers, partition keys, documents, attachments, stored procedures, triggers, and UDFs.
  • Are created when a user is granted permissions to a specific resource.
  • Are recreated when a permission resource is acted upon on by POST, GET, or PUT call.
  • Use a hash resource token specifically constructed for the user, resource, and permission.
  • Are time bound with a customizable validity period. The default valid time span is one hour. Token lifetime, however, may be explicitly specified, up to a maximum of five hours.
  • Provide a safe alternative to giving out the primary key.
  • Enable clients to read, write, and delete resources in the Cosmos DB account according to the permissions they've been granted.

You can use a resource token (by creating Cosmos DB users and permissions) when you want to provide access to resources in your Cosmos DB account to a client that cannot be trusted with the primary key.

Cosmos DB resource tokens provide a safe alternative that enables clients to read, write, and delete resources in your Cosmos DB account according to the permissions you've granted, and without need for either a primary or read only key.

Here is a typical design pattern whereby resource tokens may be requested, generated, and delivered to clients:

  1. A mid-tier service is set up to serve a mobile application to share user photos.

  2. The mid-tier service possesses the primary key of the Cosmos DB account.

  3. The photo app is installed on end-user mobile devices.

  4. On login, the photo app establishes the identity of the user with the mid-tier service. This mechanism of identity establishment is purely up to the application.

  5. Once the identity is established, the mid-tier service requests permissions based on the identity.

  6. The mid-tier service sends a resource token back to the phone app.

  7. The phone app can continue to use the resource token to directly access Cosmos DB resources with the permissions defined by the resource token and for the interval allowed by the resource token.

  8. When the resource token expires, subsequent requests receive a 401 unauthorized exception. At this point, the phone app re-establishes the identity and requests a new resource token.

    Azure Cosmos DB resource tokens workflow

Resource token generation and management are handled by the native Cosmos DB client libraries; however, if you use REST you must construct the request/authentication headers. For more information on creating authentication headers for REST, see Access Control on Cosmos DB Resources or the source code for our .NET SDK or Node.js SDK.

For an example of a middle tier service used to generate or broker resource tokens, see the ResourceTokenBroker app.

Users

Azure Cosmos DB users are associated with a Cosmos database. Each database can contain zero or more Cosmos DB users. The following code sample shows how to create a Cosmos DB user using the Azure Cosmos DB .NET SDK v3.

//Create a user.
Database database = benchmark.client.GetDatabase("SalesDatabase");

User user = await database.CreateUserAsync("User 1");

Note

Each Cosmos DB user has a ReadAsync() method that can be used to retrieve the list of permissions associated with the user.

Permissions

A permission resource is associated with a user and assigned to a specific resource. Each user may contain zero or more permissions. A permission resource provides access to a security token that the user needs when trying to access a specific container or data in a specific partition key. There are two available access levels that may be provided by a permission resource:

  • All: The user has full permission on the resource.
  • Read: The user can only read the contents of the resource but cannot perform write, update, or delete operations on the resource.

Note

In order to run stored procedures the user must have the All permission on the container in which the stored procedure will be run.

If you enable the diagnostic logs on data-plane requests, the following two properties corresponding to the permission are logged:

  • resourceTokenPermissionId - This property indicates the resource token permission Id that you have specified.

  • resourceTokenPermissionMode - This property indicates the permission mode that you have set when creating the resource token. The permission mode can have values such as "all" or "read".

Code sample to create permission

The following code sample shows how to create a permission resource, read the resource token of the permission resource, and associate the permissions with the user created above.

// Create a permission on a container and specific partition key value
Container container = client.GetContainer("SalesDatabase", "OrdersContainer");
user.CreatePermissionAsync(
    new PermissionProperties(
        id: "permissionUser1Orders",
        permissionMode: PermissionMode.All,
        container: container,
        resourcePartitionKey: new PartitionKey("012345")));

Code sample to read permission for user

The following code snippet shows how to retrieve the permission associated with the user created above and instantiate a new CosmosClient on behalf of the user, scoped to a single partition key.

//Read a permission, create user client session.
PermissionProperties permissionProperties = await user.GetPermission("permissionUser1Orders")

CosmosClient client = new CosmosClient(accountEndpoint: "MyEndpoint", authKeyOrResourceToken: permissionProperties.Token);

Differences between RBAC and resource tokens

Subject RBAC Resource tokens
Authentication With Azure Active Directory (Azure AD). Based on the native Azure Cosmos DB users
Integrating resource tokens with Azure AD requires extra work to bridge Azure AD identities and Azure Cosmos DB users.
Authorization Role-based: role definitions map allowed actions and can be assigned to multiple identities. Permission-based: for each Azure Cosmos DB user, you need to assign data access permissions.
Token scope An AAD token carries the identity of the requester. This identity is matched against all assigned role definitions to perform authorization. A resource token carries the permission granted to a specific Azure Cosmos DB user on a specific Azure Cosmos DB resource. Authorization requests on different resources may requires different tokens.
Token refresh The AAD token is automatically refreshed by the Azure Cosmos DB SDKs when it expires. Resource token refresh is not supported. When a resource token expires, a new one needs to be issued.

Add users and assign roles

To add Azure Cosmos DB account reader access to your user account, have a subscription owner perform the following steps in the Azure portal.

  1. Open the Azure portal, and select your Azure Cosmos DB account.
  2. Click the Access control (IAM) tab, and then click + Add role assignment.
  3. In the Add role assignment pane, in the Role box, select Cosmos DB Account Reader Role.
  4. In the Assign access to box, select Azure AD user, group, or application.
  5. Select the user, group, or application in your directory to which you wish to grant access. You can search the directory by display name, email address, or object identifiers. The selected user, group, or application appears in the selected members list.
  6. Click Save.

The entity can now read Azure Cosmos DB resources.

Delete or export user data

As a database service, Azure Cosmos DB enables you to search, select, modify and delete any data located in your database or containers. It is however your responsibility to use the provided APIs and define logic required to find and erase any personal data if needed. Each multi-model API (SQL, MongoDB, Gremlin, Cassandra, Table) provides different language SDKs that contain methods to search and delete data based on custom predicates. You can also enable the time to live (TTL) feature to delete data automatically after a specified period, without incurring any additional cost.

Note

For information about viewing or deleting personal data, see Azure Data Subject Requests for the GDPR. For more information about GDPR, see the GDPR section of the Microsoft Trust Center and the GDPR section of the Service Trust portal.

Next steps