Role with privilege escalation by actions 'ec2:RunInstances' and 'iam:PassRole'

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Metadata

Id: terraform-aws-role-with-privilege-escalation-by-actions-iam-passrole-and-ec2-runinstances

Cloud Provider: AWS

Platform: Terraform

Severity: Medium

Category: Access Control

Learn More

Description

Granting an IAM role permissions for both ec2:RunInstances and iam:PassRole with their Resource attribute set to "*" enables a privilege escalation pathway in AWS. This configuration allows any user or entity assuming the role to launch new EC2 instances and assign any IAM role in the account to those instances, including roles with more expansive permissions. As a result, attackers can potentially gain administrative access by launching an instance with a privileged role, bypassing the originally intended limitations. If left unaddressed, this misconfiguration can result in full compromise of the AWS account’s resources, leading to data loss, service disruption, or unauthorized access to sensitive workloads.

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 = [
          "ec2:RunInstances",
        ]
        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 = "*"
      },
    ]
  })
}