Dynamic Authorization Policies

In this lesson, you will learn how to evolve your static Policy-Based Authorization architecture to load access requirements from a database or remote service at runtime.

Why Go Dynamic?

In standard policy-based authorization, rules are typically hardcoded using options.AddPolicy(...) in your Program.cs file. While this works for static roles, it becomes a maintenance nightmare if your business rules change frequently—such as giving a manager temporary "Edit" access to a specific project without deploying new code. Dynamic authorization allows your application to "look up" the rules on the fly.

The Core Concept: IAuthorizationPolicyProvider

To make authorization dynamic, you must implement a custom IAuthorizationPolicyProvider. This interface acts as a gatekeeper; whenever the middleware checks a policy, it asks your provider for the policy definition.

Instead of relying on the static options, your provider can query a database or cache to build the AuthorizationPolicy object in real-time.

public class DynamicPolicyProvider : IAuthorizationPolicyProvider
{
    public async Task<AuthorizationPolicy?> GetPolicyAsync(string policyName)
    {
        // 1. Check if the policy exists in your DB or Cache
        var rule = await _dbContext.AuthorizationRules.FirstOrDefaultAsync(r => r.Name == policyName);
        
        if (rule != null)
        {
            // 2. Build the policy dynamically
            return new AuthorizationPolicyBuilder()
                .RequireClaim(rule.ClaimType, rule.ClaimValue)
                .Build();
        }

        // 3. Fall back to default behavior
        return await _fallbackProvider.GetPolicyAsync(policyName);
    }
}

How it Works

1. Request Interception: When a user hits an endpoint decorated with [Authorize(Policy = "AccessProjectX")], the framework calls GetPolicyAsync("AccessProjectX").
2. Runtime Retrieval: Your custom provider reaches out to your database, fetches the current requirement, and constructs the policy.
3. Evaluation: The framework takes that returned policy and evaluates it against the user’s current claims as usual.

By decoupling authorization rules from the application source code, you gain the ability to manage complex, shifting access permissions through an admin UI rather than through constant code deployments.

Key Takeaway: By implementing a custom IAuthorizationPolicyProvider, you shift authorization logic from static configuration files into a dynamic, data-driven lookup that updates instantly without requiring a service restart.