ec2-unrestricted-telnet: Restrict EC2 Telnet Access

id: ec2-unrestricted-telnet
info:
  name: Restrict EC2 Telnet Access
  author: princechaddha
  severity: critical
  description: |
    Checks for unrestricted inbound Telnet access (TCP port 23) in Amazon EC2 security groups, highlighting potential security risks.
  impact: |
    Unrestricted Telnet access can expose EC2 instances to unauthorized access and potential security breaches.
  remediation: |
    Restrict inbound Telnet access by updating EC2 security group rules to allow only trusted IP ranges or disabling Telnet if not required.
  reference:
    - https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/authorizing-access-to-an-instance.html
  tags: cloud,devops,aws,amazon,ec2,aws-cloud-config

variables:
  region: "us-east-1"

self-contained: true
code:
  - engine:
      - sh
      - bash
    source: |
      aws ec2 describe-security-groups --region $region --filters Name=ip-permission.from-port,Values=23 Name=ip-permission.to-port,Values=23 Name=ip-permission.cidr,Values='0.0.0.0/0' --output json --query 'SecurityGroups[*].GroupId'

    extractors:
      - type: json
        name: securitygroup
        internal: true
        json:
          - '.[]'

      - type: dsl
        dsl:
          - 'securitygroup + " security group(s) alows unrestricted access (0.0.0.0/0 or ::/0) on TCP port 23"'
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