AWS IAM role allows all services or principals to be assumed

Description

The IAM role is an identity with specific permissions. An IAM role is similar to an IAM user: it has an AWS identity with permission policies that determine what the identity can and cannot do in AWS. When a user assumes a role, it is provided with temporary security credentials for a bounded session. The list of principals able to assume a role should be limited as much as possible, and should not include "*", meaning that any authenticated identity across all of AWS can assume the role. We recommend that you define fine-grained roles for specific services or principles. For example, when setting up an AWS service role it is recommended to include only the permissions required for the service to access the AWS resources required. Alternatively, you can use a principal as an entity that can perform actions and access resources. The main benefit of the principal entity is to limit the use of wildcards in the policy document.

Code Example

resource "aws_iam_role" "test_role" {
  name = "test_role"
    ...
  assume_role_policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": "sts:AssumeRole",
      "Principal": {
        "AWS": [
-         "*"
        ]
      },
      "Effect": "Allow",
      "Sid": ""
    }
}
}

Remediation

• AWS IAM Console*

. Log in to the AWS Management Console at https://console.aws.amazon.com/.

. Open the https://console.aws.amazon.com/iam/ [Amazon IAM console].

. Click * Roles*, and find the role to update.

. Click the * Trust relationships* tab.

. Click * Show policy document* or * Edit trust relationship* to view the policy document.

. After clicking * Edit trust relationship*, remove any "Allow" statements that have an AWS Principal including "*".

. Click * Update Trust Policy*. === Fix - Buildtime

Terraform

Rule Details

Field	Value
ID	IAC-0113
Severity	HIGH
IaC Type	Cloudformation
Frameworks	CloudFormation, Terraform, TerraformPlan, Serverless
Checkov ID	CKV_AWS_60

References

• Checkov Rule

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