3.1.1. IAM Roles & Policies for Application Access

First Principle: IAM roles and policies provide the fundamental mechanism for granting AWS services and applications the precise, least privilege access they need to interact with other AWS resources, enhancing security and avoiding static credentials.

For developers, understanding how to apply AWS Identity and Access Management (IAM) is crucial for building secure applications. Instead of embedding static access keys directly in your application code, applications should assume IAM roles.

Key Concepts of IAM Roles & Policies for Application Access:

• IAM Roles: (Secure IAM identities that grant temporary permissions to AWS services or applications.)
  • How they work: An application (e.g., running on an EC2 instance, as a Lambda function) assumes an IAM role to obtain temporary security credentials. AWS manages the rotation of these credentials.
  • Benefits: Avoids hardcoding credentials, improves security by using temporary credentials, and simplifies credential management.
• IAM Policies: (JSON documents that define specific permissions.)
  • Attachment: Policies are attached to IAM roles to define what actions the application is allowed to perform on which resources (e.g., s3:GetObject on a specific Amazon S3 bucket).
  • Principle of Least Privilege: Always grant only the minimum permissions necessary for the application to function.
• Instance Profiles: (A container for an IAM role that you can use to pass role information to an EC2 instance when it launches.) Used to associate an IAM role with an EC2 instance.

Scenario: You're developing a Lambda function that needs to upload files to an Amazon S3 bucket and read items from an Amazon DynamoDB table. You want to ensure it has only the necessary permissions and avoid storing any credentials in the function's code.

Reflection Question: How does creating an IAM role with a specifically scoped IAM policy for your Lambda function enable secure, least-privilege access to S3 and DynamoDB without hardcoding credentials?