In AWS Identity and Access Management (IAM), Identity-Based Policies are used to assign permissions to IAM users, groups, or roles. These policies define what actions are allowed or denied on specified resources, based on the identity of the user or role performing the action. Identity-based policies are essential for controlling access to AWS resources and ensuring that users only have the necessary privileges to perform specific tasks.
This guide will walk you through the process of creating and applying identity-based policies in AWS IAM.
1. Prerequisites
Before you begin, ensure that you have:
AWS account with IAM permissions to create and manage users, groups, and policies.
Access to the AWS Management Console or AWS CLI.
A basic understanding of IAM concepts such as users, roles, policies, and permissions.
2. Understanding Identity-Based Policies
Identity-based policies are JSON documents that are directly attached to IAM identities (users, groups, or roles). These policies contain statements that specify the allowed or denied actions on resources in AWS. The policy consists of the following components:
Version: Specifies the policy language version.
Statement: Contains one or more individual permission statements.
Effect: Indicates whether the action is allowed or denied.
Action: Lists the AWS service actions allowed or denied.
Resource: Specifies the resource(s) to which the actions apply.
Condition (Optional): Further restricts the permission based on specific conditions.
—
3. Creating an Identity-Based Policy
Let’s create an identity-based policy that grants an IAM user permission to list and read objects from an S3 bucket.
Step 1: Access IAM in the AWS Console
1. Navigate to the IAM service in the AWS Management Console.
2. On the left-hand sidebar, select Policies under the Access Management section.
Step 2: Create a New Policy
1. Click on the Create Policy button.
2. Choose the JSON tab to input the policy directly.
Step 3: Define the Policy
Use the following example to create a policy that allows a user to list and get objects from an S3 bucket.
{
“Version”: “2012-10-17”,
“Statement”: [
{
“Effect”: “Allow”,
“Action”: [
“s3:ListBucket”,
“s3:GetObject”
],
“Resource”: [
“arn:aws:s3:::my-example-bucket”,
“arn:aws:s3:::my-example-bucket/*”
]
}
]
}
This policy allows the user to:
List the contents of the bucket (s3:ListBucket).
Get objects from the bucket (s3:GetObject).
Step 4: Review and Create the Policy
1. Review the policy for accuracy.
2. Provide a name (e.g., S3ReadOnlyPolicy) and description for the policy.
3. Click Create policy to save the policy.
4. Attaching the Policy to an IAM User
Once the identity-based policy is created, you need to attach it to an IAM user or group.
Step 1: Access IAM User Management
1. Go to IAM > Users in the AWS Management Console.
2. Select the IAM user to which you want to apply the policy.
Step 2: Attach the Policy
1. In the Permissions tab, click Add permissions.
2. Choose Attach policies directly.
3. Search for the S3ReadOnlyPolicy that was created earlier and select it.
4. Click Next: Review, then Add permissions.
The IAM user now has the permissions defined in the policy.
5. Verifying Policy Execution
To ensure the policy is functioning as intended, you can perform the following actions:
1. Use AWS CLI: From the IAM user’s account, try running the aws s3 ls command to list the contents of the S3 bucket:
aws s3 ls s3://my-example-bucket
If the user has the right permissions, they should be able to list the bucket contents.
2. Try Accessing Objects: Attempt to download an object from the bucket:
aws s3 cp s3://my-example-bucket/my-file.txt .
If the user encounters issues, verify the permissions and ensure the correct resource ARN is specified.
6. Best Practices for Identity-Based Policies
Principle of Least Privilege: Always grant only the permissions necessary for a user to perform their job.
Use Groups for Multiple Users: Assign policies to groups, not individual users, to simplify management.
Use Conditions: Define conditions to restrict access based on factors like source IP or time of day.
Regularly Review Policies: Periodically audit and review policies to ensure compliance with security standards.
Conclusion
Identity-based policies in IAM are critical for defining and controlling access to AWS resources. By following the steps outlined in this guide, you can create granular, secure permissions that ensure users have the right level of access to perform their tasks. Always aim to apply the principle of least privilege and regularly review your policies to maintain a secure AWS environment.
The article above is rendered by integrating outputs of 1 HUMAN AGENT & 3 AI AGENTS, an amalgamation of HGI and AI to serve technology education globally.