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sec-design.md

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

BUSINESS POSTURE

NUKE Build is a cross-platform, open-source build automation system. It aims to simplify the creation of complex build processes using C#. The primary business goals and priorities are:

  • Provide a reliable and consistent build experience across different operating systems (Windows, macOS, Linux).
  • Enable developers to define builds in a strongly-typed language (C#), leveraging existing .NET skills and tooling.
  • Offer a user-friendly and maintainable alternative to complex shell scripts or XML-based build configurations.
  • Foster a strong community and ecosystem around the project.
  • Reduce the learning curve for build automation, making it accessible to a wider range of developers.
  • Ensure build processes are testable and debuggable.
  • Facilitate integration with various CI/CD systems.

Based on these priorities, the most important business risks are:

  • Malicious code injection into the build process, potentially compromising build artifacts or the build environment itself.
  • Vulnerabilities in NUKE or its dependencies that could be exploited to disrupt builds or gain unauthorized access.
  • Inconsistent or unreliable build results, leading to deployment issues or software defects.
  • Lack of adoption due to complexity or perceived lack of features compared to other build systems.
  • Supply chain attacks targeting NUKE's dependencies or distribution channels.
  • Compromised build server leading to leakage of sensitive information (e.g., API keys, signing certificates).

SECURITY POSTURE

Existing security controls and accepted risks (as inferred from the repository and general best practices):

  • security control: Code signing of releases (likely, but needs verification). Where: Release process.
  • security control: Use of static analysis tools (likely, but needs verification). Where: Build process.
  • security control: Dependency management using NuGet. Where: Project files (.csproj).
  • security control: Community contributions and code reviews. Where: GitHub pull requests.
  • security control: Use of HTTPS for communication with external services (assumed). Where: Network communication within build scripts.
  • accepted risk: Reliance on third-party NuGet packages, introducing potential supply chain risks.
  • accepted risk: Potential for user-introduced vulnerabilities in build scripts (C# code).
  • accepted risk: Limited control over the security of individual developer workstations.

Recommended security controls (high priority):

  • security control: Implement a Software Bill of Materials (SBOM) generation process for each release.
  • security control: Integrate Software Composition Analysis (SCA) tools to identify known vulnerabilities in dependencies.
  • security control: Enforce strong authentication and authorization for access to the build server and related resources.
  • security control: Implement regular security audits and penetration testing of the build infrastructure.
  • security control: Provide clear security guidelines and best practices for writing secure build scripts.
  • security control: Use of sandboxing or containerization to isolate build processes.

Security Requirements:

  • Authentication:
    • Build scripts should not store credentials directly. Use environment variables or secure configuration mechanisms.
    • Access to the build server should require strong authentication (e.g., multi-factor authentication).
  • Authorization:
    • Restrict access to sensitive build operations and resources based on the principle of least privilege.
    • Implement role-based access control (RBAC) for managing build server permissions.
  • Input Validation:
    • Validate all inputs to build scripts, including parameters, environment variables, and file paths.
    • Sanitize user-provided data to prevent code injection vulnerabilities.
  • Cryptography:
    • Use strong cryptographic algorithms and protocols for secure communication and data protection.
    • Securely manage cryptographic keys and certificates.
    • Sign build artifacts to ensure integrity and authenticity.
  • Output validation:
    • Validate output of all external tools.

DESIGN

C4 CONTEXT

graph LR
    Developer["Developer"]
    NUKE["NUKE Build System"]
    NuGet["NuGet Package Manager"]
    CI_CD["CI/CD System"]
    VersionControl["Version Control System"]
    Test_Environments["Test Environments"]
    Production_Environment["Production Environment"]

    Developer -- "Writes build scripts\n(C#)" --> NUKE
    NUKE -- "Fetches dependencies" --> NuGet
    NUKE -- "Executes build tasks" --> CI_CD
    NUKE -- "Pulls source code" --> VersionControl
    CI_CD -- "Deploys to" --> Test_Environments
    CI_CD -- "Deploys to" --> Production_Environment
    VersionControl -- "Code" --> Developer
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Element Descriptions:

  • Element:

    • Name: Developer
    • Type: Person
    • Description: A software developer who writes and maintains the build scripts using C#.
    • Responsibilities: Writing build logic, configuring build parameters, integrating with external tools.
    • Security controls: Secure coding practices, strong authentication to development tools.

  • Element:

    • Name: NUKE Build System
    • Type: Software System
    • Description: The core build automation system that executes the build scripts.
    • Responsibilities: Parsing build scripts, managing dependencies, executing build tasks, reporting results.
    • Security controls: Input validation, dependency management, secure execution environment (sandboxing/containerization - recommended).

  • Element:

    • Name: NuGet Package Manager
    • Type: External System
    • Description: The package manager for .NET libraries, used to manage NUKE's dependencies.
    • Responsibilities: Providing access to a repository of .NET packages.
    • Security controls: Package signing, vulnerability scanning (SCA - recommended).

  • Element:

    • Name: CI/CD System
    • Type: External System
    • Description: A continuous integration and continuous delivery system (e.g., GitHub Actions, Jenkins, Azure DevOps).
    • Responsibilities: Triggering builds, running tests, deploying artifacts.
    • Security controls: Strong authentication, access control, secure configuration.

  • Element:

    • Name: Version Control System
    • Type: External System
    • Description: A system for managing source code (e.g., Git).
    • Responsibilities: Storing source code, tracking changes, managing branches.
    • Security controls: Access control, branch protection rules.

  • Element:

    • Name: Test Environments
    • Type: External System
    • Description: Environments used for testing the software being built.
    • Responsibilities: Running automated tests, providing feedback on build quality.
    • Security controls: Isolation from production, secure configuration.

  • Element:

    • Name: Production Environment
    • Type: External System
    • Description: The environment where the final software is deployed and used.
    • Responsibilities: Running the production software.
    • Security controls: Strong security hardening, monitoring, intrusion detection.

C4 CONTAINER

graph LR
    Developer["Developer"]
    NUKE_CLI["NUKE CLI"]
    Build_Project["Build Project\n(C#)"]
    External_Tools["External Tools\n(e.g., MSBuild, dotnet)"]
    NuGet["NuGet"]

    Developer -- ".nuke" --> NUKE_CLI
    NUKE_CLI -- "Executes" --> Build_Project
    Build_Project -- "Calls" --> External_Tools
    Build_Project -- "Uses" --> NuGet
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Element Descriptions:

  • Element:

    • Name: Developer
    • Type: Person
    • Description: A software developer.
    • Responsibilities: Writing and maintaining build scripts.
    • Security controls: Secure coding practices.

  • Element:

    • Name: NUKE CLI
    • Type: Application
    • Description: The command-line interface for interacting with NUKE.
    • Responsibilities: Parsing commands, loading build projects, initiating build execution.
    • Security controls: Input validation.

  • Element:

    • Name: Build Project (C#)
    • Type: Application
    • Description: The C# project containing the build logic.
    • Responsibilities: Defining build targets, tasks, and dependencies.
    • Security controls: Secure coding practices, input validation, dependency management.

  • Element:

    • Name: External Tools (e.g., MSBuild, dotnet)
    • Type: Application
    • Description: External tools used by the build process.
    • Responsibilities: Compiling code, running tests, packaging applications.
    • Security controls: Secure configuration, regular updates.

  • Element:

    • Name: NuGet
    • Type: External System
    • Description: The NuGet package manager.
    • Responsibilities: Providing access to .NET packages.
    • Security controls: Package signing, vulnerability scanning (SCA - recommended).

DEPLOYMENT

NUKE itself is a .NET tool and can be deployed in several ways:

  1. Global Tool: Installed globally on a machine using dotnet tool install -g Nuke.GlobalTool.
  2. Local Tool: Installed locally within a project using dotnet new tool-manifest and dotnet tool install Nuke.GlobalTool.
  3. Project Dependency: Referenced as a regular NuGet package within a project.

The most common and recommended approach is to use a local tool. This ensures that the correct version of NUKE is used for each project and avoids conflicts between different projects. We will describe this approach.

graph LR
    BuildServer["Build Server"]
    DotnetSDK["dotnet SDK"]
    NUKE_Local["NUKE (Local Tool)"]
    FileSystem["File System"]

    BuildServer -- "Contains" --> DotnetSDK
    BuildServer -- "Contains" --> FileSystem
    DotnetSDK -- "Installs" --> NUKE_Local
    NUKE_Local -- "Writes to" --> FileSystem
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Element Descriptions:

  • Element:

    • Name: Build Server
    • Type: Infrastructure
    • Description: The machine where the build process runs.
    • Responsibilities: Providing the environment for executing builds.
    • Security controls: Strong authentication, access control, regular security updates, firewall.

  • Element:

    • Name: dotnet SDK
    • Type: Software
    • Description: The .NET SDK, used to build and run .NET applications.
    • Responsibilities: Providing the tools for building and running .NET code.
    • Security controls: Regular updates, secure configuration.

  • Element:

    • Name: NUKE (Local Tool)
    • Type: Software
    • Description: The NUKE build tool, installed as a local tool.
    • Responsibilities: Executing the build scripts.
    • Security controls: Input validation, secure execution environment (sandboxing/containerization - recommended).

  • Element:

    • Name: File System
    • Type: Infrastructure
    • Description: The file system of the build server.
    • Responsibilities: Storing source code, build artifacts, and temporary files.
    • Security controls: Access control, encryption (if sensitive data is stored).

BUILD

The build process for NUKE itself (and projects using NUKE) typically involves the following steps:

  1. Developer: A developer writes or modifies the build script (C# code) on their local machine.
  2. Version Control: The developer commits and pushes the changes to a version control system (e.g., Git).
  3. CI/CD Trigger: A CI/CD system (e.g., GitHub Actions) detects the changes and triggers a build.
  4. Build Server: The CI/CD system provisions a build server (or uses a pre-configured one).
  5. Source Code Retrieval: The build server retrieves the source code from the version control system.
  6. Dependency Restoration: The build server restores NuGet packages (including NUKE, if it's a project dependency, or installs it as a global/local tool).
  7. Build Execution: The build server executes the NUKE build script (using dotnet nuke or similar).
  8. Testing: The build script executes tests.
  9. Artifact Creation: The build script creates build artifacts (e.g., NuGet packages, executables, deployment packages).
  10. Artifact Publishing: The build script publishes the artifacts to a repository (e.g., NuGet.org, a private artifact repository).
  11. Deployment (Optional): The CI/CD system deploys the artifacts to a target environment.
graph LR
    Developer["Developer"]
    VersionControl["Version Control\n(e.g., Git)"]
    CI_CD["CI/CD System\n(e.g., GitHub Actions)"]
    BuildServer["Build Server"]
    DotnetSDK["dotnet SDK"]
    NUKE_Tool["NUKE (Global/Local Tool)"]
    Build_Project["Build Project\n(C#)"]
    External_Tools["External Tools\n(e.g., MSBuild)"]
    NuGet["NuGet"]
    Artifact_Repository["Artifact Repository"]

    Developer -- "Commits code" --> VersionControl
    VersionControl -- "Triggers build" --> CI_CD
    CI_CD -- "Provisions" --> BuildServer
    BuildServer -- "Contains" --> DotnetSDK
    BuildServer -- "Contains" --> NUKE_Tool
    BuildServer -- "Contains" --> Build_Project
    DotnetSDK -- "Restores/Installs" --> NUKE_Tool
    DotnetSDK -- "Restores" --> Build_Project
    Build_Project -- "Uses" --> NuGet
    Build_Project -- "Calls" --> External_Tools
    NUKE_Tool -- "Executes" --> Build_Project
    Build_Project -- "Creates" --> Artifact_Repository
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Security Controls in the Build Process:

  • security control: Version control: Use of a secure version control system with access control and branch protection.
  • security control: CI/CD system: Secure configuration of the CI/CD system, including strong authentication and authorization.
  • security control: Dependency management: Use of NuGet with package signing and vulnerability scanning (SCA - recommended).
  • security control: Static analysis: Use of static analysis tools to identify potential code vulnerabilities (SAST - recommended).
  • security control: Dynamic analysis: Use of dynamic analysis tools during testing (DAST - recommended).
  • security control: Artifact signing: Signing build artifacts to ensure integrity and authenticity.
  • security control: Secure build server: Hardening and regular security updates for the build server.
  • security control: Supply chain security: SBOM generation and SCA (recommended).

RISK ASSESSMENT

  • Critical Business Processes:

    • Software development and release: NUKE is crucial for automating the build and release process, ensuring consistency and reliability.
    • Continuous integration and delivery: NUKE integrates with CI/CD systems to enable automated builds, testing, and deployment.

  • Data to Protect:

    • Source code: The source code of the software being built, which may contain intellectual property or sensitive information. Sensitivity: High.
    • Build scripts: The C# code defining the build process, which could be a target for malicious code injection. Sensitivity: High.
    • Build artifacts: The output of the build process (e.g., executables, libraries, packages), which could be tampered with. Sensitivity: High.
    • Credentials and secrets: API keys, passwords, and other secrets used during the build process (should not be stored in the code or build scripts). Sensitivity: Critical.
    • Dependency information: Information about the dependencies used by the project, which could be used to identify vulnerabilities. Sensitivity: Medium.

QUESTIONS & ASSUMPTIONS

  • Questions:

    • What specific CI/CD systems are used with NUKE in practice?
    • What are the current practices for code signing releases?
    • Are static analysis tools currently used in the build process?
    • What is the level of security awareness and training among developers using NUKE?
    • What are the specific security requirements for different projects using NUKE?
    • Are there any existing security audits or penetration testing reports for NUKE or related infrastructure?
    • What is process of reporting security vulnerabilities?

  • Assumptions:

    • Developers are using secure development practices when writing build scripts.
    • HTTPS is used for all network communication with external services.
    • The build server is reasonably secure, with basic security measures in place.
    • Developers are aware of the risks of using third-party NuGet packages.
    • The project follows semantic versioning.
    • Basic logging is implemented.