Authorization in Analysis Services
Authorization is a critical aspect of SQL Server Analysis Services (SSAS) security. It defines who can access which securable objects and what actions they are allowed to perform on those objects. While authentication verifies the identity of a user, authorization determines their permissions.
Key Concepts
- Principals: Users, groups, or roles that are granted permissions. In SSAS, principals are typically Windows users or groups.
- Securables: The objects within Analysis Services that can be secured. This includes databases, cubes, dimensions, measures, rows, columns, and more.
- Permissions: The specific rights granted to a principal on a securable object. Common permissions include Read, Read Definition, Read Security, Write, and Control.
- Roles: A collection of permissions granted to a set of principals. Roles provide an efficient way to manage permissions for groups of users with similar access needs.
How Authorization Works in SSAS
Analysis Services employs a hierarchical security model. Permissions are typically inherited from parent objects to child objects, although explicit permissions can override inherited ones. The general flow of authorization is:
- A user connects to Analysis Services and is authenticated.
- When the user attempts to access a securable object, Analysis Services checks the permissions associated with that object.
- Permissions are evaluated based on the user's membership in Windows groups and Analysis Services roles.
- If the user has the necessary permissions (either directly or through role membership) for the requested action on the object, access is granted. Otherwise, access is denied.
Managing Authorization
Authorization is managed through SQL Server Management Studio (SSMS) or programmatically using AMO (Analysis Management Objects).
Using SQL Server Management Studio (SSMS)
SSMS provides a graphical interface for managing SSAS security:
- Connect to your SSAS instance in SSMS.
- Right-click on the Analysis Services instance, server, database, or specific object (e.g., a cube).
- Select "Properties" or "Security" (depending on the object) to access the security settings.
- For server-level security, navigate to the "Security" page.
- For database-level security, right-click the database, select "Properties," and then navigate to "Security." Here you can manage roles.
- To define roles, right-click on the "Roles" folder within a database in SSMS and select "New Role."
- In the role properties, you can:
- Specify the role name and members (users or groups).
- Grant permissions to various securable objects within the database.
Understanding Permissions
The following table lists common permissions available in SSAS:
| Permission | Description |
|---|---|
| Read | Allows users to browse data and metadata for the securable object. |
| ReadDefinition | Allows users to read the definition of the securable object (e.g., cube structure, dimension attributes). |
| ReadSecurity | Allows users to view the security settings (permissions and roles) of the securable object. |
| Write | Allows users to modify the securable object. This permission is rarely granted to end-users and is typically reserved for administrators. |
| Control | Grants full control over the securable object, including the ability to grant permissions to others. This is a powerful permission, usually reserved for administrators. |
Best Practices for Authorization
- Principle of Least Privilege: Grant only the permissions necessary for users to perform their tasks.
- Use Roles Extensively: Roles simplify management and ensure consistency.
- Leverage Windows Groups: Assign users to Windows groups and then grant permissions to those groups through SSAS roles. This makes user management easier.
- Regularly Review Permissions: Periodically audit your security settings to ensure they are still appropriate and no unauthorized access is possible.
- Document Your Security Model: Maintain clear documentation of your roles, permissions, and the rationale behind them.
Advanced Authorization Scenarios
Beyond basic object-level permissions, SSAS supports more granular authorization:
- Cell Security: Restrict access to specific data cells within a cube based on user or role. This is often achieved using RLS (Row-Level Security) and can be complex to implement.
- Dimension Security: Limit access to specific members of a dimension (e.g., restricting a sales manager from seeing data for regions they don't manage).
Implementing robust authorization is crucial for protecting your sensitive business intelligence data and ensuring that users only see what they are authorized to see.