已实现并注册调用其他服务API的AttributeProvider，如何从中访问策略数据？

Great to hear your AttributeProvider is registered and running without hitches! Let's break down the common ways to access policy data within your implementation, based on typical authorization system patterns:

1. Extract Policy Data from the Provider Context #

Most authorization frameworks pass a context object to your AttributeProvider when it's invoked. This context usually includes metadata about the policy being evaluated—like its ID, raw content, or associated attributes. You can directly pull this data from the context to generate your custom attributes.

Here's a concrete example (Java-style, common in frameworks like Keycloak or Ory Keto):

public class CustomAttributeProvider implements AttributeProvider {
    @Override
    public Map<String, Object> getAttributes(AttributeEvaluationContext context) {
        // Fetch the full policy object from the context
        Policy activePolicy = context.getEvaluatedPolicy();
        
        // Extract specific fields from the policy
        String policyName = activePolicy.getName();
        int policyPriority = activePolicy.getPriority();
        
        // Return attributes derived from the policy data
        return Map.of(
            "policy_name", policyName,
            "policy_priority", policyPriority,
            "is_high_priority", policyPriority > 5
        );
    }
}

2. Query Policy Data via the Authorization System's Internal API #

If the context doesn't expose the full policy data directly, you can integrate a client for your authorization system's policy management API into your AttributeProvider. This lets you fetch policy details using identifiers (like policy ID) from the context.

Example in Python (for a hypothetical authorization service):

class CustomAttributeProvider:
    def __init__(self, policy_service_client):
        # Inject a pre-configured client for your policy service
        self.policy_client = policy_service_client

    def get_attributes(self, evaluation_context):
        # Get the policy ID from the evaluation context
        target_policy_id = evaluation_context.get("policy_id")
        
        # Fetch full policy data from the service API
        policy_details = self.policy_client.get_policy(target_policy_id)
        
        # Generate attributes based on the policy's rules or metadata
        return {
            "policy_scope": policy_details.get("scope"),
            "allowed_actions": policy_details.get("allowed_actions"),
            "policy_owner": policy_details.get("owner")
        }

Key Considerations #

• Permissions: Ensure your AttributeProvider has the necessary permissions to read policy data from the authorization system. This might involve setting up a service account with read access to policy resources.
• Caching: To avoid repeated API calls and improve performance, cache frequently accessed policy data (just make sure to invalidate the cache when policies are updated).
• Consistency: In distributed systems, verify that the policy data you fetch is the latest version—some systems include version identifiers in policy objects to help with this.

内容的提问来源于stack exchange，提问作者Vadim