Understanding Authorization in Azure Active Directory

Authorization is a critical component of any secure application or service. In the context of Azure Active Directory (Azure AD), authorization determines what actions authenticated users or applications are permitted to perform on specific resources. Unlike authentication, which verifies who you are, authorization verifies what you can do.

The Role of Azure AD in Authorization

Azure AD acts as the central identity provider and authorization manager for a vast array of Microsoft services and custom applications. It leverages a robust framework to define and enforce access policies. Key concepts in Azure AD authorization include:

• Roles: Predefined sets of permissions that grant specific administrative or operational capabilities. Examples include Global Administrator, User Administrator, and Application Administrator.
• Role-Based Access Control (RBAC): A mechanism that assigns roles to users, groups, or service principals, granting them specific permissions on Azure resources.
• Access Policies: Granular definitions of what actions can be performed on a particular resource, often specified in JSON format.
• Conditional Access: Policies that enforce access controls based on conditions such as user location, device state, application, and real-time risk detection.

Authorization Models in Azure AD

Azure AD supports several authorization models, each suited for different scenarios:

1. Azure RBAC (Resource Management)

This is the primary model for controlling access to Azure resources like virtual machines, storage accounts, and databases. You assign roles (e.g., Reader, Contributor, Owner) to principals (users, groups, service principals) at different scopes (management group, subscription, resource group, or resource). Azure RBAC uses a JSON-based access control list (ACL) structure internally.

{
  "properties": {
    "roleDefinitionId": "/subscriptions/.../providers/Microsoft.Authorization/roleDefinitions/b24988ac-6180-42a0-ab88-20f73814fb7d",
    "principalId": "c20244f4-a522-4f70-929c-0488654b982e",
    "principalType": "User",
    "scope": "/subscriptions/...",
    "assignableScopes": [
      "/subscriptions/..."
    ]
  }
}
                

2. Application Roles (App Roles)

Used to authorize users or applications to access specific functionalities within a web API or application registered in Azure AD. An application can expose its own custom roles that can be assigned to users or groups.

3. OAuth 2.0 Scopes and Permissions

When an application requests access to a user's data or an API, it specifies requested permissions (scopes). Azure AD validates these requests and issues an access token containing the granted scopes, which the resource server then uses to authorize the request.

Implementing Effective Authorization

To ensure robust security, consider the following best practices:

• Principle of Least Privilege: Grant only the necessary permissions to users and applications.
• Regular Audits: Periodically review role assignments and access policies.
• Leverage Groups: Assign roles and permissions to Azure AD groups rather than individual users for easier management.
• Use Conditional Access: Implement policies to add layers of security based on context.
• Secure Service Principals: Manage credentials for service principals carefully and rotate them regularly.

Understanding and correctly implementing authorization within Azure AD is fundamental to protecting your cloud resources and data from unauthorized access.