Creating Custom IAM Policies in AWS

Amazon Web Services (AWS) offers a comprehensive identity and access management (IAM) system that enables users to securely control access to AWS services. A key feature of IAM is the ability to create custom policies, allowing for fine-grained permissions over resources. In this blog post, we will guide you through the process of creating custom IAM policies in AWS and demonstrate how AWS Management Services can help you securely manage access to your AWS environment.

What are IAM Policies?

IAM policies are JSON documents that define permissions for AWS resources. These permissions allow you to control who can access what in your AWS environment and what actions they can perform. Policies are attached to IAM users, groups, or roles to grant access to specific services, actions, or resources.

AWS provides many predefined managed policies that cover common use cases. However, sometimes your requirements might be more specific, and you need to create a custom policy to suit your needs. For example, you might want to:

• Grant users access only to certain EC2 instances or S3 buckets.
• Limit permissions to specific actions like s3:GetObject instead of giving full access to S3.
• Define more complex conditions, such as restricting access based on IP address or time of day.

Create a Custom IAM Policy in AWS

1. Sign in to the AWS Management Console.
2. In the search bar, type IAM and select IAM to open the IAM Dashboard.
3. In the IAM dashboard, on the left-hand side, choose Policies under the Access     Management section.
4. Click Create Policy.
5. You’ll be presented with two options: Visual Editor and JSON. You can either use the visual editor to build your policy step by step, or write the policy directly in JSON.

For  example, let’s say we want to create a custom policy for stopping and starting instances based on instance id.

Here’s an example of a custom policy in JSON format:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "ec2:StartInstances",
        "ec2:StopInstances"
      ],
      "Resource": [
        "arn:aws:ec2:region:account-id:instance/i-instance1_id",
        "arn:aws:ec2:region:account-id:instance/i-instance2_id"
      ]
    }
  ]
}

Creating custom IAM policies in AWS allows you to tailor access to resources based on specific needs and requirements. By using the visual editor or JSON format, you can build policies that control access to services, actions, and resources in a granular way. Always follow best practices, including the principle of least privilege, to secure your AWS environment.

Use Cases for Custom Policies

Restricting Access to Specific Resources:

You can create a custom policy that restricts access to only certain resources, like specific EC2 instances, S3 buckets, or DynamoDB tables.

Time-Based Access:

Use conditions to create policies that grant access only during specific hours of the day or on certain days.

IP Address Restrictions:

Apply policies that only allow access from specific IP addresses or address ranges.

Restricting the Use of Certain Actions:

You can create policies that prevent specific actions, like stopping or terminating EC2 instances, while allowing other actions such as starting or describing instances.

If you need assistance to Create Custom IAM Policies in AWS, feel free to contact us.