Support managed session policies in assume_role configuration block

[timoguin]

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Description

Allow scoping down IAM role permissions using managed IAM policies. In addition to the STS Policy parameter, there is now a PolicyArns parameter that allows passing up to 10 managed policies for the session.

There are a lot of benefits to this approach over passing the policy as a JSON string. I've highlighted a few reasons in the linked issue for the Terraform S3 backend. I've also opened an issue for the aws-sdk-go-base, since that is what actually drives the auth for the S3 backend and the provider. I've linked them both in the references below.

New or Affected Resource(s)

This would just add an optional argument to the AWS provider configuration.

Potential Terraform Configuration

provider "aws" {
  assume_role {
    role_arn = "arn:aws:iam::0000000000000:role/MooCow"

    policy_arns = [
      "arn:aws:iam::0000000000000:policy/Foo",
      "arn:aws:iam::0000000000000:policy/AnotherFoo",
      "arn:aws:iam::0000000000000:policy/OkayThatIsEnoughPoliciesNow",
    ]
  }
}

References

• Related aws-sdk-go-base issue: Support managed session policies for assume_role configuration aws-sdk-go-base#11
• Related Terraform issue: S3 backend: Support policy ARNs argument for assume role configuration terraform#22601
• https://docs.aws.amazon.com/STS/latest/APIReference/API_AssumeRole.html
• https://aws.amazon.com/blogs/security/create-fine-grained-session-permissions-using-iam-managed-policies/

[timoguin]

Unfortunately, this isn't supported yet by the AWS Go SDK. I created an issue: aws/aws-sdk-go#2794.

Edit to the above message: Support in the Go SDK is present. See my comment on the related issue for the aws-go-sdk-base for more detail: hashicorp/aws-sdk-go-base#11 (comment)

[bflad]

Support for this (new policy_arns argument in the provider assume_role configuration block) has been merged and will release with version 3.0.0 of the Terraform AWS Provider, likely in about two weeks. Please note this enhancement was also applied for the Terraform S3 Backend (part of Terraform CLI codebase) as part of 0.13.0-beta2.

[ghost]

This has been released in version 3.0.0 of the Terraform AWS provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template for triage. Thanks!

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!