Kerberos Authentication with AWS S3 Read-Only IAM Roles

The lock snaps shut. Only the right key can open it. In AWS, that key can be Kerberos authentication paired with a read-only IAM role for Amazon S3.

Kerberos AWS S3 read-only roles give precise, enforceable control over who can view objects without allowing changes or deletions. Kerberos handles authentication with tickets and encrypted exchanges. AWS Identity and Access Management (IAM) defines the role’s capabilities. Together, they form a hardened access pattern suitable for compliance-heavy storage systems, data analytics pipelines, and secure archival.

To set up Kerberos with AWS S3 read-only roles, start by configuring your service or application to authenticate using Kerberos tickets. This usually means integrating with a Key Distribution Center (KDC) that issues credentials for your users or service principals. In parallel, create an IAM role in AWS with the minimal policy needed to list and get objects:

{
 "Version": "2012-10-17",
 "Statement": [
 {
 "Effect": "Allow",
 "Action": [
 "s3:GetObject",
 "s3:ListBucket"
 ],
 "Resource": [
 "arn:aws:s3:::your-bucket-name",
 "arn:aws:s3:::your-bucket-name/*"
 ]
 }
 ]
}

Attach this role to the AWS resource your Kerberos-authenticated application uses—whether it’s an EC2 instance or a container within ECS or EKS. The role will enforce read-only access even after Kerberos grants authentication. This separation of duties reduces risk: Kerberos decides if the user is valid, IAM decides what they are allowed to do.

When scaling, consider session duration settings, ticket lifetimes, and AWS temporary security credentials. Keep Kerberos and IAM logs enabled to monitor access events. Regularly audit the IAM policy to ensure no write permissions creep in.

This Kerberos AWS S3 read-only role setup prevents unauthorized writes while keeping data accessible to trusted identities. It’s controlled, secure, and efficient. You can apply it to production workloads without impacting performance.

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