IAM Roles and Policies

IAM Roles and Policies are essential for managing permissions and securing access in AWS. Roles allow you to delegate permissions without sharing long-term credentials, while policies specify the permissions that are granted or denied. This chapter explores these components, providing insights into their use and best practices for secure management.

IAM Roles act as temporary security credentials that AWS services, users, or external identities can assume. They enhance security by eliminating the need for static credentials, thus reducing the exposure of access keys. Roles can be:

• Service Roles: Used by AWS services like EC2 or Lambda to securely interact with other AWS services;
• Web Identity Federation Roles: Allow users authenticated through external identity providers like Amazon Cognito or Google to access AWS resources;
• SAML 2.0 Federation Roles: Integrate with corporate directories for single sign-on capabilities;
• Cross-Account Access Roles: Enable users from one AWS account to access resources in another account.

Each role has a Trust Policy that specifies which entities can assume the role, forming the basis of the trust relationship in AWS.

IAM Policies define what actions are allowed or denied on AWS resources. These policies are written in JSON and include key elements such as:

• Effect: Indicates if the action is allowed or denied;
• Action: Specifies the operations that can be performed;
• Resource: Identifies the AWS resources where actions can be executed;
• Condition: Optional constraints, like time or IP address restrictions, that determine when the policy applies.

There are two main types of policies:

• Identity-Based Policies: These can be either managed (predefined by AWS or custom-created) or inline (specific to one user, group, or role);
• Resource-Based Policies: Directly attached to resources like S3 buckets or Lambda functions, defining what actions users or roles can perform.

Permissions Boundaries further restrict the maximum permissions an identity can have, ensuring that no role or user exceeds the defined limits.

Creating IAM Policies can be done using AWS's Visual Policy Editor for ease or the JSON Editor for more detailed control. Here are some best practices:

• Least Privilege: Only give permissions necessary for the task;
• Explicit Deny: Use this to override any allow permissions for critical security;
• Conditions: Restrict access based on specific conditions like time or IP address.

Before deploying, use the Policy Simulator to test how policies will work in your AWS environment, ensuring they function as expected.

To use roles, attach them to entities like EC2 instances, which can then access resources like S3 using temporary credentials from the instance metadata service. Roles are crucial in scenarios like cross-account access or federated identity, where users from external systems securely interact with AWS resources.

Security with roles and policies involves:

• Avoiding Overly Permissive Policies: Keep permissions strict to prevent security vulnerabilities;
• Regular Audits: Periodically review roles and policies to maintain compliance and security;
• Conditions: Use conditions to refine access control;
• Role Chaining: Manage carefully to prevent unintended permission escalations.

In summary, mastering IAM Roles and Policies is crucial for securing access in AWS. By applying these concepts carefully, you enhance the security of your AWS infrastructure. Proceed to the next module to learn more about AWS security best practices.