Achieving AWS S3 Least Privilege with Read-Only Roles

You need access, but you don’t trust anyone with more than they need. In AWS S3, the principle of least privilege is your weapon.

Least privilege means assigning only the permissions required for the job. Nothing more. Nothing hidden. For S3 read-only roles, that means allowing GetObject and ListBucket, and blocking write, delete, and policy changes. This is the safest path to control data without exposing it to loss or tampering.

Start with IAM. Create a policy that uses "Effect": "Allow" for s3:GetObject and s3:ListBucket. Scope it to specific resource ARNs. Avoid wildcards where possible. Attach this policy to a role instead of a user to make rotation and auditing easier. Keep your trust policy tight—limit principals to the exact services or accounts that require access.

Audit it. Turn on S3 server access logging to track every read request. Use CloudTrail to record IAM events. Confirm that no other permission creep has slipped in. If you see s3:Put* or s3:Delete* anywhere, strip them. Every minute with broader privileges is a risk window.

Keep boundaries clear. Combine least privilege with encryption at rest and in transit, so even read-only data is protected from interception. Use condition keys in your IAM policy to enforce IP ranges or VPC access points, making sure reads happen only from trusted networks.

This is how you achieve real S3 least privilege read-only roles—tight permissions, clear resource scopes, constant auditing, and layered network controls. AWS gives you the primitives. Security comes from how precisely you use them.

See how hoop.dev can enforce least privilege on AWS S3 read-only roles and spin it up live in minutes.