Unraveling the Mystery: Can You Get the Exact Requested Resource in Keycloak Policy Evaluation?

In the realm of Identity and Access Management (IAM), Keycloak stands tall as a robust and feature-rich solution. One of the most powerful features of Keycloak is its policy-based access control, which allows administrators to define fine-grained access control rules for their resources. But, have you ever wondered, “Is it possible to get the exact requested resource for which a policy gets evaluated in Keycloak?” In this article, we’ll embark on a journey to uncover the answer to this intriguing question.

What is Policy Evaluation in Keycloak?

Before we dive into the main topic, let’s quickly revisit the concept of policy evaluation in Keycloak. In Keycloak, policies are used to define access control rules for resources. When a user requests access to a resource, Keycloak evaluates the relevant policies to determine whether the user should be granted access. This evaluation process involves checking the user’s attributes, group memberships, and other factors against the conditions defined in the policy.

Keycloak provides various types of policies, including:

• Logic-based policies: These policies use logical operators (AND, OR, NOT) to evaluate conditions.
• Role-based policies: These policies grant access based on the user’s role assignments.
• JavaScript-based policies: These policies use custom JavaScript code to evaluate conditions.

The Quest for the Exact Requested Resource

Now, let’s get back to our main question: “Is it possible to get the exact requested resource for which a policy gets evaluated in Keycloak?” The short answer is: yes, it is possible. But, before we explore the how, let’s understand why this is important.

In many scenarios, having access to the exact requested resource can be crucial for policy evaluation. For instance, imagine a scenario where you want to grant access to a specific file only if the user has a certain attribute or role. Without knowing the exact resource being requested, it’s challenging to make an informed decision about access.

Approach 1: Using the `resource` Attribute in Policy Definitions

One way to get the exact requested resource is by using the `resource` attribute in policy definitions. This attribute allows you to specify the resource being protected by the policy.

<policy>
  <name>My Policy</name>
  <description>Policy to protect a specific file</description>
  <resource>http://example.com/files/confidential.txt</resource>
  <rules>
    <rule>
      <name>Confidential File Access</name>
      <condition>user.hasAttribute('confidential_file_access')</condition>
    </rule>
  </rules>
</policy>

In the example above, the `resource` attribute specifies the exact URL of the file being protected. When a user requests access to this file, Keycloak will evaluate the policy and check if the user has the required attribute (`confidential_file_access`).

Approach 2: Using the `evaluate()` Function in JavaScript Policies

Another way to get the exact requested resource is by using the `evaluate()` function in JavaScript policies. This function allows you to execute custom JavaScript code during policy evaluation.

<policy>
  <name>My JavaScript Policy</name>
  <description>Policy to protect a specific file using JavaScript</description>
  <script>
    function evaluate(context) {
      var resource = context.resource;
      if (resource.uri == 'http://example.com/files/confidential.txt') {
        // Grant access if the user has the required attribute
        return user.hasAttribute('confidential_file_access');
      } else {
        // Deny access for all other resources
        return false;
      }
    }
  </script>
</policy>

In this example, the `evaluate()` function is used to get the exact requested resource using the `context.resource` object. The policy then checks if the user has the required attribute (`confidential_file_access`) and grants or denies access accordingly.

Approach 3: Using the `getResource()` Method in Custom Authenticators

Another approach to get the exact requested resource is by using the `getResource()` method in custom authenticators. Custom authenticators are a powerful feature in Keycloak that allows you to implement custom authentication logic.

public class MyCustomAuthenticator extends Authenticator {
  
  @Override
  publicRetVal authenticate(AuthenticationFlowError error) {
    // Get the requested resource
    Resource resource = getContext().getResourceManager().getResource(getContext().getHttpRequest().getURI());
    // Evaluate the policy based on the resource
    Policy policy = getPolicyManager().getPolicy(resource);
    if (policy != null) {
      // Evaluate the policy
      Boolean outcome = policy.evaluate(getContext());
      if (outcome) {
        // Grant access
        return newRetVal();
      } else {
        // Deny access
        return error;
      }
    }
    // Deny access if no policy is found
    return error;
  }
}

In this example, the `getResource()` method is used to get the exact requested resource from the `ResourceManager`. The custom authenticator then evaluates the policy based on the resource and grants or denies access accordingly.

Conclusion

In conclusion, getting the exact requested resource for which a policy gets evaluated in Keycloak is indeed possible. By using the `resource` attribute in policy definitions, the `evaluate()` function in JavaScript policies, or the `getResource()` method in custom authenticators, you can create fine-grained access control rules that take into account the exact resource being requested.

Remember, having access to the exact requested resource is crucial for making informed decisions about access control. By leveraging these approaches, you can create robust and scalable access control solutions using Keycloak.

Bonus: Best Practices for Policy Evaluation in Keycloak

Here are some bonus best practices for policy evaluation in Keycloak:

1. Use specific resource definitions: When defining policies, use specific resource definitions to avoid ambiguity.
2. Keep policies simple and concise: Avoid complex policies with multiple conditions. Instead, break them down into smaller, more manageable policies.
3. Use JavaScript policies judiciously: JavaScript policies can be powerful, but they can also be resource-intensive. Use them sparingly and only when necessary.
4. Test policies thoroughly: Always test policies thoroughly to ensure they are working as intended.
5. Monitor policy evaluation logs: Regularly monitor policy evaluation logs to identify potential issues and optimize policy performance.

Approach	Description	Pros	Cons
Using the `resource` attribute	Specify the exact resource in the policy definition	Easy to implement, simple to maintain	Limited flexibility, may not work for dynamic resources
Using the `evaluate()` function in JavaScript policies	Execute custom JavaScript code during policy evaluation	Highly flexible, can handle complex scenarios	Can be resource-intensive, may require advanced JavaScript skills
Using the `getResource()` method in custom authenticators	Get the exact requested resource using the `ResourceManager`	Provides fine-grained control, can handle dynamic resources	Requires advanced Java skills, may require additional development effort

By following these best practices and using the approaches outlined in this article, you can create robust and scalable access control solutions using Keycloak.

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