AWS S3 Cross Account Access Configuration for Multi-Account Environments

Configuring AWS S3 cross account access is a crucial step in multi-account environments. This allows for secure sharing of resources between accounts.

To achieve this, AWS Identity and Access Management (IAM) roles come into play. IAM roles enable trusted accounts to assume roles in other accounts.

In a multi-account environment, each account is a separate entity with its own IAM role. This allows for fine-grained access control and secure access to resources across accounts.

Before you start setting up AWS S3 cross-account access, you'll need to meet a few prerequisites.

You'll need two separate AWS accounts, one for Production (Account A) and one for Development (Account B).

It's essential to have an Amazon S3 bucket created in Account A.

You won't need to create any users or groups in Account A.

To grant access to Account A's resources from Account B, you'll need an IAM user in Account B.

To set up cross-account access, you'll need the Account ID of Account B, which can be obtained from the AWS Management Console.

You can find more information on creating IAM users and obtaining Account IDs in the AWS documentation.

To set up cross-account access, you need to create an IAM role on AWS. This role will allow users from another account to access resources in your account.

You can create the IAM role by logging into the AWS Management Console, navigating to the IAM console, and clicking on "Roles" and then "Create role." Select "Another AWS account" as the trusted entity type and enter the account ID of the account you want to grant access to.

Here's a step-by-step guide to creating the IAM role:

Note that you'll also need to create an inline policy for the user in the other account that you want to grant access to. This policy will allow the user to assume the role you just created.

Setting up an S3 bucket is a crucial step in cross-account access setup. It's essential to have the right permissions in place to ensure seamless access between accounts.

To allow cross-account lambda role access, you'll need to set up a bucket policy that grants the necessary permissions. This policy should allow the lambda role to perform S3 operations.

A well-structured bucket policy will ensure that your S3 bucket is secure and accessible to the right accounts. By setting up a bucket policy, you can control who has access to your S3 bucket and what actions they can perform.

You'll want to make sure your bucket policy includes the necessary permissions for the lambda role to access the S3 bucket and perform operations. This will ensure that your cross-account access setup is secure and functional.

To set up a KMS key, you need to associate it with your S3 bucket. This step is crucial for enabling encryption and decryption of S3 bucket data using the KMS key. If the bucket is associated with the KMS key, a cross-account lambda role must be authorized to avoid a 401 unauthorized error.

To achieve this, you'll need to modify the existing KMS key policy to permit cross-region lambda roles to perform encryption or decryption operations. Go to the KMS dashboard and choose the key that's linked to the S3 bucket. Then, select the "Key Policy" tab and add the key policy.

You'll need to specify the necessary permissions in the key policy to enable the cross-account lambda role. This involves allowing the role to perform encryption or decryption operations on the S3 bucket.

To create an IAM policy and role, you'll need to choose "AWS service" as the trusted identity type and "Lambda" as the use case. This allows Lambda to access a cross-account S3 bucket.

You'll then click on the "Create policy" button to add the role policy. This role policy enables Lambda to access a cross-account S3 bucket, which requires specifying the S3 bucket name and KMS key.

Once the role policy is created successfully, you'll map it to the role. Select the policy and click the "Next" button. You'll then provide the role name and click the "Create role" button.

The role is created successfully; then, we will use this role for lambda in the coming step.

S3 access issues can be frustrating and time-consuming to resolve.

In S3, access issues are often caused by incorrect IAM policies or permissions, which can be tricky to troubleshoot.

The IAM policy for cross-account access must include the "s3:GetObject" action, as seen in the example policy in the "Configuring IAM Policies" section.

Incorrectly configured IAM policies can lead to access denied errors, such as the "Access Denied" error message shown in the "Troubleshooting Access Denied Errors" section.

To resolve access issues, it's essential to understand the IAM policy hierarchy and how it affects access to S3 buckets, as explained in the "IAM Policy Hierarchy" section.

To test cross-account access to S3, you can switch roles using the AWS Console. This allows you to assume the role of another account and verify access to their S3 buckets.

Log on as the devTest user and switch roles to access Account A's S3 buckets. Enter the Account A account ID and the CrossAccountSignin role in the Console to switch roles successfully.

Upon a successful login, you should see the new Assume Role at the top right of the main menu. This indicates that you have successfully switched roles and can now access Account A's S3 buckets.

To verify access, navigate to the S3 service and check if the buckets of Account A are accessible. You can do this by clicking on Services and then s3 in the menu bar at the top.

To revert back to the devTest user, click on AssumeRole in the menu bar at the top and then click Back to devTest.