Skip to content

Latest commit

 

History

History
271 lines (215 loc) · 14.4 KB

sec-design.md

File metadata and controls

271 lines (215 loc) · 14.4 KB

Okay, let's create a detailed design document for the Chameleon project, focusing on aspects relevant for threat modeling.

BUSINESS POSTURE

Chameleon appears to be a personal or small-team project focused on providing a simple, self-hosted, and customizable URL shortening service. The primary business goals likely revolve around:

  • Providing a functional and reliable URL shortening service.
  • Allowing users to customize short URLs (brands, keywords).
  • Offering a degree of control over data and privacy (self-hosted).
  • Potentially, gathering basic analytics on link usage (though this isn't explicitly stated, it's a common feature of such services).
  • Ease of deployment and maintenance.

Given the likely small scale and personal/small-team nature, the risk appetite might be higher than a large enterprise. However, certain risks are still critical:

  • Data Loss/Corruption: Loss of the URL mapping data would render the service unusable.
  • Service Unavailability: Downtime would directly impact users relying on the shortened links.
  • Malicious Use: The service could be abused to mask malicious URLs, potentially harming users and damaging the reputation of the service/host.
  • Unauthorized Access: An attacker gaining administrative access could modify or delete links, or redirect them to malicious destinations.
  • Data Breach: While the data stored might not be highly sensitive (primarily URLs), a breach could still expose user-created links and potentially some usage patterns.

SECURITY POSTURE

Based on the repository, the following security controls and accepted risks can be identified:

  • security control: Basic Authentication: The application uses basic authentication (username/password) for the admin interface, as seen in the app.py and templates/admin.html.
  • security control: Limited Input Validation: There's some basic input validation for URLs in app.py, checking for a valid URL format.
  • security control: SQLite Database: The use of SQLite simplifies deployment and reduces external dependencies, but requires careful consideration of file permissions and backup strategies.
  • security control: Docker Deployment: The provided Dockerfile and docker-compose.yml simplify deployment and ensure consistent environments.
  • security control: No HTTPS by default: The application, as provided, does not enforce HTTPS. This is a significant security concern.
  • accepted risk: Limited Rate Limiting: There's no apparent rate limiting, making the service potentially vulnerable to abuse and denial-of-service attacks.
  • accepted risk: No CSRF Protection: There's no apparent protection against Cross-Site Request Forgery (CSRF) attacks.
  • accepted risk: No Input Sanitization: There is no sanitization of user input, making the service potentially vulnerable to Cross-Site Scripting (XSS) attacks.
  • accepted risk: Basic Authentication: Basic authentication sends credentials in plain text if HTTPS is not used.
  • accepted risk: Hardcoded Secret Key: The Flask secret key is hardcoded in app.py. This is a major security vulnerability.
  • accepted risk: No Audit Logging: There is no audit logging.

Recommended Security Controls (High Priority):

  • Implement HTTPS: Enforce HTTPS using a reverse proxy (like Nginx or Caddy) with a valid SSL/TLS certificate. This is crucial for protecting credentials and data in transit.
  • Implement CSRF Protection: Use a library like Flask-WTF to protect against CSRF attacks.
  • Implement Input Sanitization: Sanitize all user input to prevent XSS attacks.
  • Implement Rate Limiting: Implement rate limiting to prevent abuse and denial-of-service attacks.
  • Secure Secret Key Management: Do not hardcode the secret key. Use environment variables or a dedicated secret management solution.
  • Implement Stronger Password Hashing: Use a strong password hashing algorithm (e.g., bcrypt, scrypt) instead of storing passwords in plain text or using weak hashing.
  • Implement Regular Backups: Implement a robust backup strategy for the SQLite database.
  • Implement Audit Logging: Implement audit logging to track user actions and potential security events.

Security Requirements:

  • Authentication:

    • The system MUST use strong password hashing for storing user credentials.
    • The system MUST enforce HTTPS to protect credentials in transit.
    • The system SHOULD implement multi-factor authentication (MFA) for administrative access.

  • Authorization:

    • The system MUST restrict access to administrative functions to authorized users only.
    • The system SHOULD implement role-based access control (RBAC) if different user roles are required.

  • Input Validation:

    • The system MUST validate all user input to ensure it conforms to expected formats and lengths.
    • The system MUST reject any input that contains potentially malicious characters or patterns.

  • Cryptography:

    • The system MUST use HTTPS for all communication.
    • The system MUST use a strong, randomly generated secret key for Flask.
    • The system SHOULD use a cryptographically secure random number generator for generating short URLs.

  • Output Encoding:

    • The system MUST encode all output to prevent XSS attacks.

DESIGN

C4 CONTEXT

graph LR
    subgraph chameleon_context
        User["User"] --> Chameleon["Chameleon URL Shortener"]
        Chameleon --> RedirectedWebsite["Redirected Website"]
        Admin["Administrator"] --> Chameleon
    end
Loading

Element Descriptions:

  • Element:

    • Name: User
    • Type: Person
    • Description: A person who clicks on a shortened URL created by Chameleon.
    • Responsibilities: Clicks on shortened URLs.
    • Security controls: None (relies on the security of Chameleon and the Redirected Website).

  • Element:

    • Name: Chameleon URL Shortener
    • Type: Software System
    • Description: The URL shortening application.
    • Responsibilities: Stores URL mappings, redirects users to the original URLs, provides an administrative interface.
    • Security controls: Basic Authentication, Input Validation, Docker Deployment.

  • Element:

    • Name: Redirected Website
    • Type: Software System
    • Description: The website that the user is ultimately redirected to.
    • Responsibilities: Serving the content requested by the user.
    • Security controls: Not controlled by Chameleon (relies on the security of the external website).

  • Element:

    • Name: Administrator
    • Type: Person
    • Description: A person who manages the Chameleon service.
    • Responsibilities: Creates and manages short URLs, configures the application.
    • Security controls: Basic Authentication (access to the admin interface).

C4 CONTAINER

graph LR
    subgraph chameleon_container
        User["User"] --> WebApp["Web Application (Flask)"]
        Admin["Administrator"] --> WebApp
        WebApp --> Database["Database (SQLite)"]
        WebApp --> RedirectedWebsite["Redirected Website"]
    end
Loading

Element Descriptions:

  • Element:

    • Name: User
    • Type: Person
    • Description: A person who clicks on a shortened URL.
    • Responsibilities: Clicks on shortened URLs.
    • Security controls: None (relies on the security of the Web Application and the Redirected Website).

  • Element:

    • Name: Administrator
    • Type: Person
    • Description: A person who manages the Chameleon service.
    • Responsibilities: Creates and manages short URLs, configures the application.
    • Security controls: Basic Authentication (access to the admin interface).

  • Element:

    • Name: Web Application (Flask)
    • Type: Web Application
    • Description: The core application logic, built using the Flask framework.
    • Responsibilities: Handles HTTP requests, interacts with the database, renders templates, performs redirects.
    • Security controls: Basic Authentication, Input Validation.

  • Element:

    • Name: Database (SQLite)
    • Type: Database
    • Description: Stores the URL mappings (short URL and original URL).
    • Responsibilities: Persistently stores data.
    • Security controls: File system permissions (managed by the operating system and Docker).

  • Element:

    • Name: Redirected Website
    • Type: Software System
    • Description: The website that the user is ultimately redirected to.
    • Responsibilities: Serving the content requested by the user.
    • Security controls: Not controlled by Chameleon (relies on the security of the external website).

DEPLOYMENT

Possible deployment solutions:

  1. Docker Compose (as provided in the repository): Simplest for local development and small-scale deployments.
  2. Docker Swarm: For higher availability and scalability.
  3. Kubernetes: For more complex deployments with advanced features like auto-scaling and rolling updates.
  4. Cloud-based container services (e.g., AWS ECS, Google Cloud Run, Azure Container Instances): Managed container services that simplify deployment and scaling.
  5. Traditional VM deployment: Deploying the application directly on a virtual machine (less recommended due to increased management overhead).

Chosen solution (for detailed description): Docker Compose

graph LR
    subgraph docker_compose_deployment
        Internet["Internet"] --> ReverseProxy["Reverse Proxy (e.g., Nginx, Caddy)"]
        ReverseProxy -- HTTPS --> ChameleonContainer["Chameleon Container (Docker)"]
        ChameleonContainer --> DatabaseVolume["Database Volume (SQLite)"]
    end
Loading

Element Descriptions:

  • Element:

    • Name: Internet
    • Type: External
    • Description: The public internet.
    • Responsibilities: Routing traffic to the server.
    • Security controls: Relies on network-level security (firewalls, etc.).

  • Element:

    • Name: Reverse Proxy (e.g., Nginx, Caddy)
    • Type: Web Server
    • Description: A reverse proxy server that handles HTTPS termination and forwards requests to the Chameleon container.
    • Responsibilities: Handling HTTPS, caching, load balancing (potentially), providing SSL/TLS certificates.
    • Security controls: HTTPS configuration, certificate management, potentially Web Application Firewall (WAF) rules.

  • Element:

    • Name: Chameleon Container (Docker)
    • Type: Container
    • Description: The Docker container running the Chameleon application.
    • Responsibilities: Running the Flask application.
    • Security controls: Container isolation, limited privileges (if configured correctly).

  • Element:

    • Name: Database Volume (SQLite)
    • Type: Data Volume
    • Description: A Docker volume that stores the SQLite database file.
    • Responsibilities: Persisting the database data.
    • Security controls: File system permissions (managed by Docker and the host operating system).

BUILD

The project uses a simple build process based on Docker.

graph LR
    Developer["Developer"] --> Git["Git Repository (GitHub)"]
    Git --> DockerBuild["Docker Build (docker build)"]
    DockerBuild --> DockerImage["Docker Image"]
    DockerImage --> DockerHub["Docker Hub (or other registry, optional)"]
Loading
  • Developer writes code and commits it to the Git repository.
  • The docker build command is used to create a Docker image. This command uses the Dockerfile in the repository.
  • The Dockerfile specifies the base image (Python 3.9-slim-buster), copies the application code, installs dependencies (using pip), and sets the command to run the application.
  • The resulting Docker image can be pushed to a container registry (like Docker Hub) for distribution.
  • No CI is used.
  • No SAST scanners are used.
  • No linters are used.

Security Controls in Build Process:

  • security control: Dependency Management: The requirements.txt file lists the project's dependencies. It's important to regularly check for vulnerabilities in these dependencies.
  • security control: Docker Image Security: Using a slim base image (python:3.9-slim-buster) reduces the attack surface compared to larger images.

Recommended Improvements:

  • Implement CI/CD: Use a CI/CD platform (like GitHub Actions, GitLab CI, Jenkins) to automate the build, test, and deployment process.
  • Integrate SAST: Integrate Static Application Security Testing (SAST) tools into the build process to identify potential vulnerabilities in the code.
  • Integrate SCA: Integrate Software Composition Analysis (SCA) tools to scan dependencies for known vulnerabilities.
  • Use Linters: Use linters (like flake8 for Python) to enforce code style and identify potential errors.
  • Sign Docker Images: Digitally sign Docker images to ensure their integrity and authenticity.

RISK ASSESSMENT

  • Critical Business Processes:

    • URL Redirection: The core functionality of the service.
    • URL Management: The ability to create, modify, and delete short URLs.

  • Data to Protect:

    • URL Mappings: (short URL, original URL, creation date, potentially user ID/metadata). Sensitivity: Medium (loss of this data would break the service; exposure could reveal user link patterns).
    • User Credentials (if stored): Sensitivity: High (compromise would allow unauthorized access). Currently, basic authentication is used, which is highly insecure without HTTPS.
    • Application Configuration: Sensitivity: Medium (exposure could reveal vulnerabilities or misconfigurations).

QUESTIONS & ASSUMPTIONS

  • Questions:

    • Are there any plans for user registration or more granular access control?
    • Is there a need for detailed analytics on link usage?
    • What is the expected traffic volume and scaling requirements?
    • What is the backup and recovery strategy for the database?
    • Is there any existing infrastructure (e.g., reverse proxy, monitoring) that can be leveraged?
    • Are there any regulatory or compliance requirements that need to be considered?

  • Assumptions:

    • BUSINESS POSTURE: The project is intended for personal or small-team use, with a relatively high risk tolerance.
    • SECURITY POSTURE: The current security posture is minimal, with several significant vulnerabilities. HTTPS is not enforced, and basic authentication is used.
    • DESIGN: The application is relatively simple, with a single Flask application and an SQLite database. The deployment is assumed to be using Docker Compose, with a reverse proxy for HTTPS termination. The build process is manual, using docker build.