Using IAM Policy Conditions for Fine-Grained Access Control

Introduction

In this lesson, we will explore how to use IAM policy conditions to implement fine-grained access control in AWS. IAM policy conditions allow you to specify additional restrictions on when a policy should be applied, providing granular control over access to AWS resources. We will cover the basics of IAM policies, how to use conditions to enforce access control, and provide practical examples using AWS CDK with Typescript.

IAM Policy Basics

IAM policies are JSON documents that define permissions for AWS resources. They consist of statements that specify the actions allowed or denied, the resources to which the policy applies, and the conditions under which the policy is enforced. Conditions are optional elements that allow you to further restrict access based on factors such as time, IP address, or user identity.

Using Conditions for Fine-Grained Access Control

To implement fine-grained access control using IAM policy conditions, you can specify conditions in the policy statement. Conditions are evaluated at runtime, allowing you to dynamically control access based on various factors. Some common condition keys include aws:RequestedRegion, aws:UserAgent, and aws:MultiFactorAuthPresent.

Let’s walk through a practical example of using IAM policy conditions to restrict access to an S3 bucket based on the requester’s IP address.

Example: Restricting Access to an S3 Bucket by IP Address

import * as iam from '@aws-cdk/aws-iam';
import * as s3 from '@aws-cdk/aws-s3';

const bucket = new s3.Bucket(this, 'MyBucket');

const policyStatement = new iam.PolicyStatement({
  actions: ['s3:GetObject'],
  resources: [bucket.arnForObjects('*')],
  conditions: {
    'IpAddress': {
      'aws:SourceIp': ['192.168.1.0/24']
    }
  }
});

bucket.addToResourcePolicy(policyStatement);

In this example, we create an IAM policy statement that allows the s3:GetObject action on objects in the S3 bucket only if the request originates from the IP address range 192.168.1.0/24.

Conclusion

In this lesson, we learned how to use IAM policy conditions for fine-grained access control in AWS. By specifying conditions in IAM policy statements, you can enforce additional restrictions on access to resources based on various factors. This allows you to implement granular access control policies that meet the specific security requirements of your organization.