Today I am going to write about Access Management Policies on Amazon Web Services. We will be discussing Identity-Based Policies today, looking at how they are applied, and some best practices with regards to how they are constructed.

In the ever-expanding landscape of cloud computing, security and access control are paramount. Amazon Web Services (AWS) provides an array of robust tools to manage access and permissions, and one of the fundamental components is Identity and Access Management (IAM). Within IAM, AWS Access Policies play a pivotal role in defining who can access what resources and what actions they can perform.

What Are AWS Access Policies?

In a nutshell, an AWS Access Policy is a set of permissions that you can attach to an identity, such as an IAM user, group, or role. These policies explicitly define the actions (e.g., read, write, delete) and the resources (e.g., S3 buckets, EC2 instances) that are accessible. In essence, they determine the level of control and authority an entity has within your AWS environment.

Key Components of AWS Access Policies

  1. Statements: Access policies consist of one or more statements. Each statement includes the following:
    • Effect: This specifies whether the statement allows or denies access. You can set it to “Allow” or “Deny” based on your requirements.
    • Action: Describes the action that is allowed or denied, e.g., “s3:ListBucket” or “ec2:StartInstances.”
    • Resource: Identifies the AWS resources to which the policy applies, e.g., an S3 bucket or an EC2 instance.
  2. Version: The policy version, which defines the structure and elements of the policy language.
  3. Policy Type: There are two main policy types:
    • Managed Policies: These are policies created and managed independently from an IAM identity. They can be attached to multiple users, groups, or roles.
    • Inline Policies: These are policies attached directly to a single IAM identity, providing a fine-grained control mechanism.

An example of an IAM Access Policy is included below, taken from AWS’ documentation on the topic. 

{
  "Version": "2012-10-17",
  "Statement": {
    "Effect": "Allow",
    "Action": "s3:ListBucket",
    "Resource": "arn:aws:s3:::example_bucket"
  }
}

As a concise example, the above policy is giving the “Allow” permission to the Action of Listing the Contents of an S3 bucket identified by the Resource tag. So whoever this Policy is applied to, can see what contents are within the named S3 bucket.

Writing AWS Access Policies

Writing effective access policies requires careful consideration of your organization’s security and operational requirements. Here are some key pointers:

  • Start with the principle of least privilege: Only grant permissions that are absolutely necessary for an entity to perform its tasks.
  • Use AWS policy templates: AWS provides predefined policy templates that align with common use cases, making it easier to create policies for various services. Some of these examples include, but are not limited to:
    • AdminstratorAccess
    • ReadOnlyAccess
    • DataScientist
    • NetworkAdministrator
    • And many others, by Role and by Level
  • Regularly review and update policies: As your infrastructure evolves, access requirements may change. Regularly review and update policies to ensure they remain relevant and secure.
  • Prefer Managed Policies to Inline Policies: When applying Policies to Users, you should organize by Group (for example, a “Developers” group, or an “Administrators” group, and apply policies to those groups. You can then have Users join those groups, and they will receive the proper policies. This simplifies User roles and makes it easier to track what User has what Permissions

Attaching and Testing Policies

After creating or selecting a policy, you’ll need to attach it to the relevant IAM users, groups, or roles. It’s crucial to test the policies thoroughly to ensure that access permissions align with your expectations. AWS provides simulation tools and policy evaluation to help verify the policies’ effectiveness.

AWS Access Policies are a vital component of your cloud security strategy, enabling you to define and enforce access control across your AWS resources. Understanding how to create, manage, and maintain these policies is key to maintaining a secure and well-organized AWS environment.

In upcoming blog posts, we’ll delve deeper into IAM, exploring various IAM best practices, advanced policy management, and real-world scenarios. Stay tuned for more insights into managing your AWS infrastructure securely and efficiently.

Citations

  1. https://docs.aws.amazon.com/IAM/latest/UserGuide/access_policies.html
  2. https://docs.aws.amazon.com/singlesignon/latest/userguide/permissionsetpredefined.html
  3. https://www.udemy.com/share/101WgC3@4W_y9aP7UFSL4I2w98KSk5YfOdOUVOZaBCArICBZJ5qERUFlIOm7LJOADD8sBNVI/
By : Gideon