EC2 Instance Using Default Security Group

• Query id: 08b81bb3-0985-4023-8602-b606ad81d279
• Query name: EC2 Instance Using Default Security Group
• Platform: CloudFormation
• Severity: Low
• Category: Access Control
• URL: Github

Description

EC2 instances should not use default security group(s)
Documentation

Code samples

Code samples with security vulnerabilities

Positive test num. 1 - yaml file

 Resources:
  MyEC2Instance: 
      Type: AWS::EC2::Instance
      Properties: 
        ImageId: "ami-79fd7eee"
        KeyName: "testkey"
        SecurityGroups: 
          - !Ref default
        BlockDeviceMappings: 
        - DeviceName: "/dev/sdm"
          Ebs: 
            VolumeType: "io1"
            Iops: "200"
            DeleteOnTermination: "false"
            VolumeSize: "20"
        - DeviceName: "/dev/sdk"
          NoDevice: {}

Positive test num. 2 - json file

{
  "Resources": {
    "MyEC2Instance": {
      "Properties": {
        "BlockDeviceMappings": [
          {
            "DeviceName": "/dev/sdm",
            "Ebs": {
              "DeleteOnTermination": "false",
              "Iops": "200",
              "VolumeSize": "20",
              "VolumeType": "io1"
            }
          },
          {
            "DeviceName": "/dev/sdk",
            "NoDevice": {}
          }
        ],
        "ImageId": "ami-79fd7eee",
        "KeyName": "testkey",
        "SecurityGroups": [
          "default"
        ]
      },
      "Type": "AWS::EC2::Instance"
    }
  }
}

Code samples without security vulnerabilities

Negative test num. 1 - yaml file

 Resources:
  MyEC2Instancee: 
      Type: AWS::EC2::Instance
      Properties: 
        ImageId: "ami-79fd7eee"
        KeyName: "testkey"
        SecurityGroups: 
          - !Ref my_sg
        BlockDeviceMappings: 
        - DeviceName: "/dev/sdm"
          Ebs: 
            VolumeType: "io1"
            Iops: "200"
            DeleteOnTermination: "false"
            VolumeSize: "20"
        - DeviceName: "/dev/sdk"
          NoDevice: {}

Negative test num. 2 - json file

{
  "Resources": {
    "MyEC2Instancee": {
      "Properties": {
        "BlockDeviceMappings": [
          {
            "DeviceName": "/dev/sdm",
            "Ebs": {
              "DeleteOnTermination": "false",
              "Iops": "200",
              "VolumeSize": "20",
              "VolumeType": "io1"
            }
          },
          {
            "DeviceName": "/dev/sdk",
            "NoDevice": {}
          }
        ],
        "ImageId": "ami-79fd7eee",
        "KeyName": "testkey",
        "SecurityGroups": [
          "my_sg"
        ]
      },
      "Type": "AWS::EC2::Instance"
    }
  }
}