Cross-account access

In the AWS multi-account ecosystem, IAM identities in one account often require access to resources in another. AWS addresses this through role-based cross-account access. Here, the trusting account stipulates which external accounts can tap into its resources. Conversely, the trusted account designates which entities are permitted to assume specific roles. This mechanism eliminates the need to share access keys between accounts, enhancing security. For example, a developer in a development AWS account might need to access a database in a production AWS account. Instead of granting direct access, a role with the necessary permissions can be assumed.

Sharing resources at scale

Managing IAM in large-scale deployments can be challenging, but efficient resource sharing across multiple accounts is equally important. AWS Resource Access Manager (RAM) addresses this need by simplifying the sharing of resources such as subnets, transit gateways, or RDS Aurora clusters across multiple accounts. This service is particularly valuable in scenarios where, for instance, a shared Aurora cluster is accessed by various development teams using different accounts. Traditionally, managing access for each team would require individual configurations, risking inconsistencies and security gaps. RAM, however, streamlines this process by enabling the creation of resource shares that define which accounts can access the shared resources, along with precise control over their permissions. Under the hood, RAM creates specific resource-based policies, even for resource types that typically do not support such policies directly through IAM. RAM plays a crucial role in helping large organizations avoid resource duplication and manage who has access to those resources centrally.

Automating IAM implementation in a DevOps world

In the age of DevOps, automation is king. The same holds true for IAM. Infrastructure as code (IaC) tools, such as CloudFormation and Terraform, allow for the automated provisioning of AWS resources, including IAM configurations. This automation ensures that IAM configurations are consistent, version-controlled, and replicable across environments. Such automation is especially crucial in large-scale and multi-account settings, where manual configurations can become untenable. AWS Config complements this by continuously monitoring AWS resource configurations, ensuring they comply with desired setups. For instance, if an IAM policy that is too permissive is detected, AWS Config can automatically rectify it.