Role with privilege escalation by actions 'cloudformation:CreateStack' and 'iam:PassRole'

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Metadata

Id: be2aa235-bd93-4b68-978a-1cc65d49082f

Cloud Provider: AWS

Platform: Terraform

Severity: Medium

Category: Access Control

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Description

Granting an IAM role permissions for both cloudformation:CreateStack and iam:PassRole actions with the resource set to "*" allows users with this role to launch CloudFormation stacks that assume any IAM role in the account, leading to privilege escalation. This vulnerability means an attacker could potentially create resources with elevated privileges or gain full administrative access to the AWS environment. To mitigate this, avoid assigning overly permissive policies, and instead restrict iam:PassRole and cloudformation:CreateStack to only trusted roles and explicitly specify the allowed resource ARNs in the policy’s Resource attribute.

Compliant Code Examples

resource "aws_iam_user" "cosmic2" {
  name = "cosmic2"
}

resource "aws_iam_user_policy" "inline_policy_run_instances2" {
  name = "inline_policy_run_instances"
  user = aws_iam_user.cosmic2.name

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Action = [
          "ec2:Describe*",
        ]
        Effect   = "Allow"
        Resource = "*"
      },
    ]
  })
}

Non-Compliant Code Examples

resource "aws_iam_role" "cosmic" {
  name = "cosmic"
}

resource "aws_iam_role_policy" "test_inline_policy" {
  name = "test_inline_policy"
  role = aws_iam_role.cosmic.name

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Action = [
          "cloudformation:CreateStack",
        ]
        Effect   = "Allow"
        Resource = "*"
      },
    ]
  })
}


resource "aws_iam_policy_attachment" "test-attach" {
  name       = "test-attachment"
  roles      = [aws_iam_role.cosmic.name]
  policy_arn = aws_iam_policy.policy.arn
}


resource "aws_iam_policy" "policy" {
  name        = "test-policy"
  description = "A test policy"

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Action = [
          "iam:PassRole",
        ]
        Effect   = "Allow"
        Resource = "*"
      },
    ]
  })
}