Identity-based policies are JSON documents that define permissions for AWS IAM identities such as users, groups, and roles. These policies control what actions an identity can perform on which AWS resources and under what conditions.
There are three types of identity-based policies:
1. **AWS Mana…Identity-based policies are JSON documents that define permissions for AWS IAM identities such as users, groups, and roles. These policies control what actions an identity can perform on which AWS resources and under what conditions.
There are three types of identity-based policies:
1. **AWS Managed Policies**: Pre-built policies created and maintained by AWS. These are standalone policies that can be attached to multiple users, groups, or roles across your account. Examples include AmazonS3ReadOnlyAccess and PowerUserAccess.
2. **Customer Managed Policies**: Custom policies that you create and manage in your AWS account. These provide more precise control over permissions and can be tailored to your specific organizational requirements. You can attach them to multiple identities and version them for easier management.
3. **Inline Policies**: Policies embedded within a single user, group, or role. They maintain a strict one-to-one relationship with the identity and are deleted when you delete the identity.
Identity-based policies follow the standard IAM policy structure containing:
- **Version**: Policy language version (typically "2012-10-17")
- **Statement**: One or more permission statements including Effect (Allow/Deny), Action (specific API operations), Resource (ARN of affected resources), and optional Condition elements
Key characteristics include:
- They are attached to IAM principals (users, groups, roles)
- Multiple policies can be attached to a single identity
- Permissions are cumulative across all attached policies
- An explicit Deny always overrides any Allow
Best practices for developers include:
- Following the principle of least privilege
- Using AWS managed policies when possible
- Regularly reviewing and auditing policies
- Testing policies using the IAM Policy Simulator
Understanding identity-based policies is essential for implementing secure applications on AWS and ensuring proper access control throughout your development lifecycle.
Identity-based Policies in AWS - Complete Guide for AWS Developer Associate Exam
What are Identity-based Policies?
Identity-based policies are JSON permission documents that you attach to IAM identities such as users, groups of users, or roles. These policies define what actions an identity can perform on which AWS resources and under what conditions.
Why are Identity-based Policies Important?
Identity-based policies are fundamental to AWS security because they:
• Control Access: They determine who can do what in your AWS environment • Follow Least Privilege: Enable you to grant only the permissions necessary for a task • Provide Flexibility: Can be customized for specific use cases and requirements • Enable Auditing: Make it easier to track and review permissions granted to identities • Support Compliance: Help meet regulatory and organizational security requirements
Types of Identity-based Policies
1. AWS Managed Policies Pre-built policies created and maintained by AWS. Examples include AmazonS3ReadOnlyAccess and PowerUserAccess. These are useful for common use cases and are automatically updated by AWS.
2. Customer Managed Policies Custom policies that you create and manage in your AWS account. These provide more precise control and can be tailored to your specific requirements.
3. Inline Policies Policies embedded within a single user, group, or role. They maintain a strict one-to-one relationship between the policy and the identity. These are useful when you want to ensure the policy is deleted when the identity is deleted.
How Identity-based Policies Work
Identity-based policies follow this structure:
• Effect: Either Allow or Deny • Action: The specific API operations permitted or denied (e.g., s3:GetObject) • Resource: The AWS resources the policy applies to (specified by ARN) • Condition: Optional circumstances under which the policy is in effect
Policy Evaluation Logic: 1. By default, all requests are denied (implicit deny) 2. An explicit allow overrides the implicit deny 3. An explicit deny always overrides any allows 4. Policies are evaluated together - if any policy denies access, the request is denied
• Identity-based: Attached to IAM users, groups, or roles - specify what the identity can do • Resource-based: Attached to resources like S3 buckets - specify who can access the resource
Identity-based policies require a Principal to be established through the attachment, while resource-based policies must include a Principal element in the policy document.
Exam Tips: Answering Questions on Identity-based Policies
Tip 1: Remember that AWS managed policies are ideal when you need standard permissions and want AWS to maintain updates. Choose customer managed policies when you need custom, reusable permissions.
Tip 2: Inline policies should be selected when the policy must be deleted along with the identity, or when you need a strict one-to-one relationship.
Tip 3: Always remember the deny-by-default principle. If a question asks about why access is denied, check if there is an explicit Allow statement.
Tip 4: Explicit Deny always wins. If both Allow and Deny exist for the same action, Deny takes precedence.
Tip 5: For cross-account access scenarios, identity-based policies on the requesting account and resource-based policies on the resource account typically need to work together.
Tip 6: Pay attention to the Resource element - wildcards (*) grant broad access, while specific ARNs limit access to particular resources.
Tip 7: When a question mentions least privilege, look for answers that grant the minimum necessary permissions using specific actions and resources.
Tip 8: Conditions in policies add another layer of control - look for answers that use conditions when the scenario requires access based on IP address, time, MFA status, or other factors.
Common Exam Scenarios
• Granting an EC2 instance access to S3: Use an IAM role with an identity-based policy attached • Allowing a user to manage their own credentials: Use identity-based policies with condition keys like aws:username • Restricting access to specific regions: Use the aws:RequestedRegion condition key in the policy