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Microsoft Entra ID and PostgreSQL authentication with Azure Cosmos DB for PostgreSQL

  • Článok

APPLIES TO: Azure Cosmos DB for PostgreSQL (powered by the Citus database extension to PostgreSQL)

Azure Cosmos DB for PostgreSQL supports PostgreSQL authentication and integration with Microsoft Entra ID. Each Azure Cosmos DB for PostgreSQL cluster is created with native PostgreSQL authentication enabled and one built-in PostgreSQL role named citus. You can add more native PostgreSQL roles after cluster provisioning is completed.

You can also enable Microsoft Entra ID (formerly Azure Active Directory) authentication on a cluster in addition to the PostgreSQL authentication method or instead of it. You can configure authentication methods on each Azure Cosmos DB for PostgreSQL cluster independently. If you need to change authentication method, you can do it at any time after cluster provisioning is completed. Changing authentication methods doesn't require cluster restart.

PostgreSQL authentication

The PostgreSQL engine uses roles to control access to database objects. A newly created Azure Cosmos DB for PostgreSQL cluster comes with several roles predefined:

Since Azure Cosmos DB for PostgreSQL is a managed PaaS service, only Microsoft can sign in with the postgres superuser role. For limited administrative access, Azure Cosmos DB for PostgreSQL provides the citus role.

The managed service needs to replicate all PostgreSQL roles to all nodes in a cluster. To facilitate this requirement, all other PostgreSQL roles need to be created using Azure Cosmos DB for PostgreSQL management capabilities.

The Citus role

Permissions for the citus role:

  • Read all configuration variables, even variables normally visible only to superusers.
  • Read all pg_stat_* views and use various statistics-related extensions--even views or extensions normally visible only to superusers.
  • Execute monitoring functions that might take ACCESS SHARE locks on tables, potentially for a long time.
  • Create PostgreSQL extensions.

Notably, the citus role has some restrictions:

  • Can't create roles
  • Can't create databases

citus role can't be deleted but would be disabled if 'Microsoft Entra ID authentication only' authentication method is selected on cluster.

Microsoft Entra ID authentication

Microsoft Entra ID (formerly Azure Active Directory) authentication is a mechanism of connecting to Azure Cosmos DB for PostgreSQL using identities defined in Microsoft Entra ID. With Microsoft Entra ID authentication, you can manage database user identities and other Microsoft services in a central location, which simplifies permission management.

Benefits of using Microsoft Entra ID include:

  • Authentication of users across Azure Services in a uniform way
  • Management of password policies and password rotation in a single place
  • Multiple forms of authentication supported by Microsoft Entra ID, which can eliminate the need to store passwords
  • Microsoft Entra ID authentication uses PostgreSQL database roles to authenticate identities at the database level
  • Support of token-based authentication for applications connecting to Azure Cosmos DB for PostgreSQL

Manage PostgreSQL access for Microsoft Entra ID principals

When Microsoft Entra ID authentication is enabled and Microsoft Entra ID principal is added as a Microsoft Entra ID administrator, the account gets the same privileges as the citus role. The Microsoft Entra ID administrator sign-in can be a Microsoft Entra ID user, Service Principal, or Managed Identity. Multiple Microsoft Entra ID administrators can be configured at any time and you can optionally disable PostgreSQL (password) authentication to the Azure Cosmos DB for PostgreSQL cluster for better auditing and compliance needs.

Additionally, any number of nonadmin Microsoft Entra ID roles can be added to a cluster at any time once Microsoft Entra ID authentication is enabled. Database permissions for nonadmin Microsoft Entra ID roles are managed similar to regular roles.

Connect using Microsoft Entra ID identities

Microsoft Entra ID authentication supports the following methods of connecting to a database using Microsoft Entra ID identities:

  • Microsoft Entra ID Password
  • Microsoft Entra ID integrated
  • Microsoft Entra ID Universal with MFA
  • Using Microsoft Entra ID Application certificates or client secrets
  • Managed Identity

Once you've authenticated against the Microsoft Entra ID, you then retrieve a token. This token is your password for logging in.

Other considerations

  • Multiple Microsoft Entra ID principals (a user, service principal, or managed identity) can be configured as Microsoft Entra ID administrator for an Azure Cosmos DB for PostgreSQL cluster at any time.
  • If a Microsoft Entra ID principal is deleted from Microsoft Entra ID service, it still remains as a PostgreSQL role on the cluster, but it's no longer able to acquire new access token. In this case, although the matching role still exists in the Postgres database it's unable to authenticate to the cluster nodes. Database administrators need to transfer ownership and drop such roles manually.

Note

Login with the deleted Microsoft Entra ID user can still be done till the token expires (up to 90 minutes from token issuing). If you also remove the user from Azure Cosmos DB for PostgreSQL cluster this access will be revoked immediately.

  • Azure Cosmos DB for PostgreSQL matches access tokens to the database role using the user’s unique Microsoft Entra ID user ID, as opposed to using the username. If a Microsoft Entra ID user is deleted and a new user is created with the same name, Azure Cosmos DB for PostgreSQL considers that a different user. Therefore, if a user is deleted from Microsoft Entra ID and a new user is added with the same name the new user would be unable to connect with the existing role.

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