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sec-design.md

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Okay, let's create a design document for the mail project (a simple Go web server) from the provided GitHub repository, keeping in mind the threat modeling context.

BUSINESS POSTURE

Business Priorities and Goals:

  • Provide a simple, functional web application demonstrating basic Go web server capabilities. This appears to be a learning/demonstration project rather than a production-ready application.
  • Offer a minimal, easily deployable example.
  • Potentially serve as a foundation for more complex web applications.

Most Important Business Risks:

  • Since this is likely a demonstration project, the primary risk is misrepresenting the security posture of the application. If someone were to use this as a starting point for a production system without significant security enhancements, it would expose them to substantial risk. It's crucial to clearly communicate the non-production-ready nature of the code.
  • Vulnerabilities in the application, even if a demo, could be exploited to compromise the host system or network it's running on, especially if deployed carelessly.
  • Lack of proper error handling and input validation could lead to unexpected behavior or crashes, hindering its usefulness as a learning tool.

SECURITY POSTURE

Existing Security Controls:

  • security control: The code uses Go's built-in net/http package, which provides some inherent protection against certain web vulnerabilities (e.g., compared to writing a raw socket server). Implemented in Go standard library.
  • security control: The server listens on a specific port (8080), limiting exposure compared to listening on all interfaces. Described in main.go.

Accepted Risks:

  • accepted risk: The application lacks any form of authentication or authorization. It's assumed that access control will be managed externally (e.g., by network firewalls) if necessary.
  • accepted risk: There is no input validation. The / endpoint simply returns a hardcoded string. If the application were to handle user input, this would be a major vulnerability.
  • accepted risk: There is no error handling beyond the basic log.Fatal(http.ListenAndServe(...)). More robust error handling would be needed for a production system.
  • accepted risk: The application does not use HTTPS. All communication is unencrypted.
  • accepted risk: No protection against common web vulnerabilities (XSS, CSRF, SQLi, etc.) is implemented, as the application doesn't handle user input or interact with a database.
  • accepted risk: No security headers (e.g., HSTS, Content Security Policy) are set.
  • accepted risk: Dependencies are not explicitly managed or scanned for vulnerabilities.
  • accepted risk: No logging or auditing is implemented.

Recommended Security Controls (High Priority):

  • security control: Implement HTTPS using TLS certificates. This is crucial for any web application, even for demonstration purposes, to protect against eavesdropping.
  • security control: Add basic security headers (e.g., HSTS, Content Security Policy, X-Frame-Options) to mitigate common web vulnerabilities.
  • security control: If the application is expanded to handle user input, implement robust input validation and sanitization.
  • security control: Implement proper error handling and logging.
  • security control: Use a dependency management tool (like Go Modules) and scan dependencies for known vulnerabilities.
  • security control: Consider adding a simple linter to the build process to catch potential security issues early.

Security Requirements:

  • Authentication: Currently not required. If user-specific functionality is added, a secure authentication mechanism (e.g., OAuth 2.0, OpenID Connect) should be implemented.
  • Authorization: Currently not required. If roles or permissions are introduced, a robust authorization system should be implemented.
  • Input Validation: Crucially important if the application is modified to accept user input. All input should be validated against a strict whitelist of allowed characters and formats.
  • Cryptography: HTTPS (TLS) should be used for all communication. If sensitive data is stored or processed, appropriate encryption mechanisms should be used.

DESIGN

C4 CONTEXT

graph LR
    User["User"] --> MailApp["Mail Application (Go Web Server)"]
    classDef default fill:#fff,stroke:#000,stroke-width:2px,color:#000
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C4 Context Element List:

  • Element:

    • Name: User
    • Type: Person
    • Description: A user interacting with the Mail Application via a web browser.
    • Responsibilities: Accessing the web application's endpoints.
    • Security controls: None (relies on the application's security controls).

  • Element:

    • Name: Mail Application (Go Web Server)
    • Type: Software System
    • Description: A simple Go web server that responds to HTTP requests.
    • Responsibilities: Serving a single endpoint ("/") that returns a "Hello, World!" message.
    • Security controls: Basic security provided by the Go net/http package; listens on a specific port.

C4 CONTAINER

graph LR
    User["User"] --> WebServer["Web Server (Go)"]
    classDef default fill:#fff,stroke:#000,stroke-width:2px,color:#000
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C4 Container Element List:

  • Element:

    • Name: User
    • Type: Person
    • Description: A user interacting with the Mail Application via a web browser.
    • Responsibilities: Accessing the web application's endpoints.
    • Security controls: None (relies on the application's security controls).

  • Element:

    • Name: Web Server (Go)
    • Type: Container (Go executable)
    • Description: The Go web server built from main.go.
    • Responsibilities: Handling HTTP requests and returning responses.
    • Security controls: Basic security provided by the Go net/http package; listens on a specific port.

DEPLOYMENT

Possible Deployment Solutions:

  1. Bare-metal server or Virtual Machine (VM): The Go executable can be directly deployed to a server and run as a process.
  2. Containerized deployment (Docker): The Go application can be packaged into a Docker container and deployed to any Docker-compatible environment (e.g., Kubernetes, Docker Swarm, cloud provider container services).
  3. Serverless deployment (e.g., AWS Lambda, Google Cloud Functions): While this example is a simple HTTP server, it could be adapted to fit a serverless model, although it's not the most natural fit.

Chosen Deployment Solution (Docker):

graph LR
    DockerHost["Docker Host"] --> DockerContainer["Docker Container (Mail App)"]
    DockerContainer --> GoExecutable["Go Executable"]
    User["User"] --> DockerHost
    classDef default fill:#fff,stroke:#000,stroke-width:2px,color:#000
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Deployment Element List:

  • Element:

    • Name: User
    • Type: Person
    • Description: A user interacting with the deployed Mail Application.
    • Responsibilities: Accessing the web application.
    • Security controls: None (relies on the application and network security).

  • Element:

    • Name: Docker Host
    • Type: Infrastructure Node (Server/VM)
    • Description: A server or VM running the Docker engine.
    • Responsibilities: Hosting and running Docker containers.
    • Security controls: Operating system security, firewall, potentially intrusion detection/prevention systems.

  • Element:

    • Name: Docker Container (Mail App)
    • Type: Container
    • Description: A Docker container running the Go web server.
    • Responsibilities: Isolating the Go application and its dependencies.
    • Security controls: Container isolation, potentially restricted resource access (CPU, memory).

  • Element:

    • Name: Go Executable
    • Type: Application
    • Description: The compiled Go web server binary.
    • Responsibilities: Handling HTTP requests.
    • Security controls: Basic security provided by the Go net/http package.

BUILD

The build process is very simple for this project. There's no explicit build system (like Makefiles or CI pipelines) defined in the repository.

Build Process (Manual):

  1. Developer writes Go code (main.go).
  2. Developer uses the Go compiler (go build) to create an executable.
  3. (Optional) Developer creates a Dockerfile to package the executable into a container.
  4. (Optional) Developer builds a Docker image using docker build.

Build Process (with GitHub Actions - Recommended):

graph LR
    Developer["Developer"] -- Push Code --> GitHubRepo["GitHub Repository"]
    GitHubRepo -- Trigger --> GitHubActions["GitHub Actions"]
    GitHubActions -- Build --> GoExecutable["Go Executable"]
    GitHubActions -- Test --> TestResults["Test Results"]
    GitHubActions -- Docker Build --> DockerImage["Docker Image"]
    DockerImage -- Push --> ContainerRegistry["Container Registry"]
    classDef default fill:#fff,stroke:#000,stroke-width:2px,color:#000
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Security Controls in Build Process:

  • security control: (Recommended) Use GitHub Actions (or similar CI/CD) to automate the build and testing process.
  • security control: (Recommended) Integrate a linter (e.g., golangci-lint) into the build process to catch potential code quality and security issues.
  • security control: (Recommended) Integrate a static analysis security testing (SAST) tool (e.g., gosec) to scan for potential vulnerabilities.
  • security control: (Recommended) If using Docker, use a minimal base image (e.g., scratch or alpine) to reduce the attack surface.
  • security control: (Recommended) Scan the Docker image for vulnerabilities using a container scanning tool (e.g., Trivy, Clair).
  • security control: (Recommended) Sign the Docker image to ensure its integrity.
  • security control: (Recommended) Use a secure container registry (e.g., Docker Hub with private repositories, AWS ECR, Google Container Registry) to store the built image.

RISK ASSESSMENT

Critical Business Processes:

  • For this demo project, there are no critical business processes in the traditional sense. The "process" is simply serving a static "Hello, World!" response. If this were a real application, the critical processes would depend on its functionality (e.g., handling user data, processing payments, etc.).

Data to Protect and Sensitivity:

  • Currently, the application does not handle any user data or sensitive information. If it were expanded, the data to protect would depend on the application's purpose. Examples:
    • Usernames, passwords, email addresses (highly sensitive)
    • Personal information (PII) (highly sensitive)
    • Financial data (highly sensitive)
    • Application configuration data (potentially sensitive)
    • Logs (potentially sensitive, depending on what's logged)

QUESTIONS & ASSUMPTIONS

Questions:

  • What is the intended long-term purpose of this project? Is it purely for demonstration, or will it be evolved into a more complex application?
  • What is the target deployment environment? (This influences the choice of deployment solution and security considerations.)
  • What level of traffic is expected? (This impacts scalability and performance requirements.)
  • Are there any specific compliance requirements (e.g., GDPR, HIPAA)?

Assumptions:

  • BUSINESS POSTURE: The project is primarily for learning and demonstration purposes. It is not intended for production use without significant security enhancements.
  • SECURITY POSTURE: The current security posture is very weak. It's assumed that anyone using this code understands the risks and will implement appropriate security controls if they adapt it for a real-world application.
  • DESIGN: The design is extremely simple, reflecting the minimal functionality of the application. It's assumed that the design will evolve significantly if the application's functionality is expanded.