What would you like to be added?

EC2 instance identities (https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-identity-roles.html) are unique ad-hoc IAM roles assigned to EC2 Instances. They are not currently supported by aws-iam-authenticator

Why is this needed?

opened to match pull request [https://github.com//pull/693]

First and foremost because they're there and support can be enabled. As implemented, aws-iam-authenticator throws an incorrect error.

I envision two possible use cases: cluster admission control and limited pre-access.

1. cluster admission control - in this scenario, a node candidate will be unable to connect as a node to the cluster until authorized by some other means (let's say an integrity check or security audit). A single IAM role shared by many nodes is unsuitable for this purpose, but ad-hoc identities are. The authorizing mechanism will add the relevant credentials to the auth-map once the node has been vetted.

2. limited pre-access. while candidate nodes are assumed to have system:nodes / system:bootstrapper privileges which are elevated, using them directly may be undesirable security-wise, for two reasons:

a. it may rightfully trigger a violation from monitoring tools
b. it entails using a superuser for what may be better served by a user with limited access

thus, using a scoped user for AWS identities may allow e.g. read-only access for data that might be useful by the node to configure/tune itself or other such customizations.

Anything else we need to know?

No response