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Insecure service configuration - EC2

Description​

Some EC2 instances have insecure configurations that an attacker can use to access or interrupt critical aplication processes

Impact​

Compromise the security of one or several EC2 Instances

Recommendation​

Perform a hardening process over all the EC2 instances, by following the recomended best practices

Threat​

Internet attacker with access to the AWS console.

Expected Remediation Time​

⌚ 45 minutes.

Score​

Default score using CVSS 3.1. It may change depending on the context of the vulnerability.

Base​

  • Attack vector: N
  • Attack complexity: L
  • Privileges required: H
  • User interaction: N
  • Scope: U
  • Confidentiality: N
  • Integrity: N
  • Availability: H

Temporal​

  • Exploit code madurity: P
  • Remediation level: O
  • Report confidence: X

Result​

  • Vector string: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:X
  • Score:
    • Base: 4.9
    • Temporal: 4.4
  • Severity:
    • Base: Medium
    • Temporal: Medium

Code Examples​

Compliant code​

All EC2 instances are securely configured

Resources:
  MyLaunchTemplate:
    Type: AWS::EC2::LaunchTemplate
    Properties:
      LaunchTemplateName: MyLaunchTemplate
      LaunchTemplateData:
        IamInstanceProfile:
          Arn:
            - MyIamInstanceProfile
            - Arn
        DisableApiTermination: true
        ImageId: ami-04d5cc9b88example
        InstanceInitiatedShutdownBehavior: terminate
        InstanceType: t2.micro
        KeyName: MyKeyPair
        SecurityGroupIds:
          - sg-083cd3bfb8example
MyLaunchTemplate:
  Type: AWS::EC2::LaunchTemplate
  Properties:
    LaunchTemplateName: MyLaunchTemplate
    LaunchTemplateData:
      IamInstanceProfile:
        Arn:
          - MyIamInstanceProfile
          - Arn
      DisableApiTermination: true
      ImageId: ami-04d5cc9b88example
      InstanceInitiatedShutdownBehavior: terminate
      InstanceType: t2.micro
      KeyName: MyKeyPair
      SecurityGroupIds:
        - sg-083cd3bfb8example

Non compliant code​

The EC2 instance has an insecure configuration, it has the disable api termination set to true

Resources:
  MyLaunchTemplate:
    Type: AWS::EC2::LaunchTemplate
    Properties:
      LaunchTemplateName: MyLaunchTemplate
      LaunchTemplateData:
        IamInstanceProfile:
          Arn:
            - MyIamInstanceProfile
            - Arn
        DisableApiTermination: true
        ImageId: ami-04d5cc9b88example
        InstanceInitiatedShutdownBehavior: stop
        InstanceType: t2.micro
        KeyName: MyKeyPair
        SecurityGroupIds:
          - sg-083cd3bfb8example

An EC2 instance has the associate_public_ip_address missconfigured

resource "aws_launch_template" "foo" {
  name = "foo"
  iam_instance_profile {
    name = "test"
  }
  network_interfaces {
    associate_public_ip_address = true
  }
}

An EC2 instance has the InstanceInitiatedShutdownBehavior missconfigured

MyLaunchTemplate:
  Type: AWS::EC2::LaunchTemplate
  Properties:
    LaunchTemplateName: MyLaunchTemplate
    LaunchTemplateData:
      IamInstanceProfile:
        Arn:
          - MyIamInstanceProfile
          - Arn
      DisableApiTermination: true
      ImageId: ami-04d5cc9b88example
      InstanceInitiatedShutdownBehavior: stop
      InstanceType: t2.micro
      KeyName: MyKeyPair
      SecurityGroupIds:
        - sg-083cd3bfb8example

Using the AWS CLI, check if the EC2 instance uses IAM Roles instead of IAM access keys

$ aws ec2 describe-instances
      --region us-east-1
      --instance-ids {EC2_id}
      --query 'Reservations[*].Instances[*].IamInstanceProfile'

If the command output is an empty array, the selected EC2 instance does not have associated IAM Roles, which is considered an insecure service configuration

Requirements​

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