sec-design.md

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

BUSINESS POSTURE

OkHttp is a widely used, open-source HTTP client for Java, Kotlin, and Android. It's a foundational component for many applications, including those built by Square and numerous other companies and individual developers.

Priorities and Goals:

• Provide a fast, reliable, and efficient HTTP client.
• Support modern HTTP features (HTTP/2, HTTP/3, connection pooling, etc.).
• Maintain backward compatibility where feasible.
• Offer a clean and easy-to-use API.
• Ensure high performance and low resource consumption.
• Be a trustworthy and secure component for network communication.

Business Risks:

• Vulnerabilities in OkHttp could be exploited to compromise a vast number of applications that rely on it. This is the most significant risk.
• Performance issues or bugs could disrupt applications and services.
• Lack of support for new HTTP standards could limit its usefulness in the future.
• Compatibility issues could break existing applications.
• Reputational damage due to security incidents or major bugs.

SECURITY POSTURE

Existing Security Controls:

• security control: Secure Coding Practices: The project appears to follow secure coding practices, based on a review of the codebase and issue tracker. This includes addressing common vulnerabilities like injection flaws, buffer overflows, and improper error handling. Implemented in source code.
• security control: Regular Updates: The project is actively maintained, with frequent releases that include bug fixes and security patches. Described in release notes.
• security control: Dependency Management: OkHttp manages its dependencies carefully, aiming to use up-to-date and secure versions of libraries. Described in build configuration files.
• security control: TLS/SSL Support: OkHttp provides robust support for TLS/SSL, allowing secure communication with HTTPS servers. Implemented in source code.
• security control: Certificate Pinning: OkHttp supports certificate pinning, which helps prevent man-in-the-middle attacks. Implemented in source code.
• security control: Fuzz Testing: OkHttp uses fuzz testing (OSS-Fuzz) to proactively identify potential vulnerabilities. Described in project documentation and configuration.
• security control: Code Reviews: Code changes are subject to review before being merged. Implemented in GitHub pull request process.
• security control: Static Analysis: Static analysis tools are used to identify potential security issues. Implemented in CI workflows.

Accepted Risks:

• accepted risk: Reliance on Underlying Platform Security: OkHttp relies on the security of the underlying operating system and Java/Kotlin runtime environment for some aspects of its security.
• accepted risk: Potential for Unknown Vulnerabilities: Like any complex software, there's always a risk of undiscovered vulnerabilities.

Recommended Security Controls:

• security control: Regular Security Audits: Conduct periodic independent security audits to identify potential vulnerabilities that might be missed by internal reviews.
• security control: Enhanced Input Validation: While OkHttp likely performs input validation, a dedicated review focusing specifically on input validation for all user-supplied data (URLs, headers, etc.) is recommended.
• security control: Content Security Policy (CSP) Support (for WebView interactions): If OkHttp is used in contexts where it interacts with WebViews, consider adding support for CSP to mitigate XSS risks.

Security Requirements:

• Authentication:

  • Support for standard HTTP authentication schemes (Basic, Bearer, Digest).
  • Secure handling of credentials (avoiding storage in logs or insecure locations).
  • Support for custom authentication mechanisms.

• Authorization:

  • OkHttp itself doesn't handle application-level authorization, but it should provide mechanisms for applications to manage authorization headers and tokens.

• Input Validation:

  • Strict validation of all user-supplied data, including URLs, headers, and request bodies.
  • Protection against common injection attacks (e.g., header injection).

• Cryptography:

  • Support for strong TLS/SSL configurations.
  • Secure random number generation for cryptographic operations.
  • Proper handling of certificates and keys.
  • Support for modern cryptographic algorithms.

DESIGN

C4 CONTEXT

graph LR
    subgraph OkHttp Context
        User["User/Application"] -- Uses --> OkHttp["OkHttp Library"]
    end
    OkHttp -- Makes Requests to --> RemoteServer["Remote Server (HTTP/HTTPS)"]
    OkHttp -- Uses --> SystemDNS["System DNS Resolver"]
    OkHttp -- Uses --> SystemTLS["System TLS Implementation"]

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Element Descriptions:

• 1. Name: User/Application
  • 2. Type: User/External System
  • 3. Description: An application or user that utilizes the OkHttp library to make HTTP requests.
  • 4. Responsibilities: Initiates HTTP requests, provides request parameters (URL, headers, body), handles responses.
  • 5. Security controls: Responsible for application-level security, including authentication and authorization.
• 1. Name: OkHttp Library
  • 2. Type: System
  • 3. Description: The OkHttp library itself.
  • 4. Responsibilities: Provides an API for making HTTP requests, handles connection pooling, manages caching, performs request/response processing, enforces security policies (e.g., certificate pinning).
  • 5. Security controls: TLS/SSL support, certificate pinning, input validation, secure coding practices, fuzz testing.
• 1. Name: Remote Server (HTTP/HTTPS)
  • 2. Type: External System
  • 3. Description: A remote server that OkHttp communicates with via HTTP or HTTPS.
  • 4. Responsibilities: Responds to HTTP requests, provides data.
  • 5. Security controls: Server-side security controls (e.g., web server security, application security).
• 1. Name: System DNS Resolver
  • 2. Type: External System
  • 3. Description: The system's DNS resolver, used to resolve hostnames to IP addresses.
  • 4. Responsibilities: Resolves domain names.
  • 5. Security controls: Relies on system DNS security.
• 1. Name: System TLS Implementation
  • 2. Type: External System
  • 3. Description: The system's TLS implementation, used for secure HTTPS connections.
  • 4. Responsibilities: Handles TLS handshake, encryption/decryption.
  • 5. Security controls: Relies on system TLS security.

C4 CONTAINER

In the case of OkHttp, the container diagram is essentially an extension of the context diagram, as OkHttp is a library, not a multi-container application.

graph LR
    subgraph OkHttp Container
        User["User/Application"] -- Uses --> OkHttpClient["OkHttpClient (API)"]
    end
    OkHttpClient -- Manages --> ConnectionPool["Connection Pool"]
    OkHttpClient -- Creates --> Request["Request Object"]
    OkHttpClient -- Processes --> Response["Response Object"]
    Request -- Contains --> URL["URL"]
    Request -- Contains --> Headers["Headers"]
    Request -- Contains --> Body["Request Body"]
    Response -- Contains --> Headers["Headers"]
    Response -- Contains --> Body["Response Body"]
    ConnectionPool -- Manages --> Connection["Connection"]
    Connection -- Uses --> SystemDNS["System DNS Resolver"]
    Connection -- Uses --> SystemTLS["System TLS Implementation"]
    Connection -- Connects to --> RemoteServer["Remote Server (HTTP/HTTPS)"]

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Element Descriptions:

• 1. Name: User/Application
  • 2. Type: User/External System
  • 3. Description: An application or user that utilizes the OkHttp library.
  • 4. Responsibilities: Initiates HTTP requests, provides request parameters, handles responses.
  • 5. Security controls: Responsible for application-level security.
• 1. Name: OkHttpClient (API)
  • 2. Type: Container
  • 3. Description: The main entry point for using OkHttp. Provides methods for creating and configuring HTTP clients.
  • 4. Responsibilities: Manages configuration, connection pooling, interceptors, and dispatching requests.
  • 5. Security controls: Configurable security settings (e.g., TLS versions, certificate pinning).
• 1. Name: Connection Pool
  • 2. Type: Container
  • 3. Description: Manages a pool of reusable connections to reduce latency.
  • 4. Responsibilities: Creates, manages, and reuses connections to remote servers.
  • 5. Security controls: Connection reuse can improve performance, reducing the overhead of repeated TLS handshakes.
• 1. Name: Request Object
  • 2. Type: Container
  • 3. Description: Represents an HTTP request.
  • 4. Responsibilities: Contains the URL, headers, and body of the request.
  • 5. Security controls: Input validation should be performed on the components of the request.
• 1. Name: Response Object
  • 2. Type: Container
  • 3. Description: Represents an HTTP response.
  • 4. Responsibilities: Contains the status code, headers, and body of the response.
  • 5. Security controls: Response parsing should be done securely to prevent vulnerabilities.
• 1. Name: URL
  • 2. Type: Component
  • 3. Description: The URL of the request.
  • 4. Responsibilities: Specifies the target resource.
  • 5. Security controls: URL validation is crucial to prevent attacks.
• 1. Name: Headers
  • 2. Type: Component
  • 3. Description: HTTP headers.
  • 4. Responsibilities: Provide metadata about the request or response.
  • 5. Security controls: Header validation is important to prevent injection attacks.
• 1. Name: Body
  • 2. Type: Component
  • 3. Description: The request or response body.
  • 4. Responsibilities: Contains the data being sent or received.
  • 5. Security controls: Body handling should be secure, especially when dealing with user-supplied data.
• 1. Name: Connection
  • 2. Type: Container
  • 3. Description: A single connection to a remote server.
  • 4. Responsibilities: Handles the actual sending and receiving of data.
  • 5. Security controls: Uses TLS for secure connections.
• 1. Name: System DNS Resolver
  • 2. Type: External System
  • 3. Description: The system's DNS resolver.
  • 4. Responsibilities: Resolves domain names.
  • 5. Security controls: Relies on system DNS security.
• 1. Name: System TLS Implementation
  • 2. Type: External System
  • 3. Description: The system's TLS implementation.
  • 4. Responsibilities: Handles TLS handshake, encryption/decryption.
  • 5. Security controls: Relies on system TLS security.
• 1. Name: Remote Server (HTTP/HTTPS)
  • 2. Type: External System
  • 3. Description: A remote server.
  • 4. Responsibilities: Responds to HTTP requests.
  • 5. Security controls: Server-side security controls.

DEPLOYMENT

OkHttp is a library, so "deployment" in the traditional sense doesn't apply. Instead, it's integrated into other applications. However, we can describe how it's typically used and the environments it might run in.

Possible Deployment Solutions:

1. Android Applications: OkHttp is commonly used within Android apps.
2. Java/Kotlin Server-Side Applications: OkHttp can be used in server-side applications running on various platforms (Linux, Windows, macOS) and cloud environments (AWS, GCP, Azure, etc.).
3. Java/Kotlin Desktop Applications: OkHttp can be used in desktop applications.

Chosen Solution (Android Application):

graph TD
    subgraph Android Device
        subgraph Application["Android Application"]
            OkHttp["OkHttp Library"]
        end
        OS["Android OS"]
    end
    Application -- Network --> Internet["Internet"]
    Internet -- Connects to --> RemoteServer["Remote Server"]
    OS -- Provides --> SystemDNS["System DNS Resolver"]
    OS -- Provides --> SystemTLS["System TLS Implementation"]

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Element Descriptions:

• 1. Name: Android Device
  • 2. Type: Deployment Node
  • 3. Description: A physical or emulated Android device.
  • 4. Responsibilities: Runs the Android operating system and applications.
  • 5. Security controls: Android OS security features, app sandboxing.
• 1. Name: Android Application
  • 2. Type: Software System Instance
  • 3. Description: An Android application that uses OkHttp.
  • 4. Responsibilities: Performs application-specific tasks, uses OkHttp for network communication.
  • 5. Security controls: Application-level security, secure use of OkHttp.
• 1. Name: OkHttp Library
  • 2. Type: Library
  • 3. Description: The OkHttp library integrated into the Android application.
  • 4. Responsibilities: Handles HTTP requests and responses.
  • 5. Security controls: OkHttp's internal security controls.
• 1. Name: Android OS
  • 2. Type: Operating System
  • 3. Description: The Android operating system.
  • 4. Responsibilities: Provides system services, including network access.
  • 5. Security controls: Android OS security features.
• 1. Name: Internet
  • 2. Type: Network
  • 3. Description: The internet.
  • 4. Responsibilities: Connects the device to remote servers.
  • 5. Security controls: Network-level security (e.g., firewalls).
• 1. Name: Remote Server
  • 2. Type: External System
  • 3. Description: A remote server.
  • 4. Responsibilities: Responds to HTTP requests.
  • 5. Security controls: Server-side security controls.
• 1. Name: System DNS Resolver
  • 2. Type: External System
  • 3. Description: The system's DNS resolver.
  • 4. Responsibilities: Resolves domain names.
  • 5. Security controls: Relies on system DNS security.
• 1. Name: System TLS Implementation
  • 2. Type: External System
  • 3. Description: The system's TLS implementation.
  • 4. Responsibilities: Handles TLS handshake, encryption/decryption.
  • 5. Security controls: Relies on system TLS security.

BUILD

OkHttp uses Gradle as its build system and GitHub Actions for CI/CD.

graph LR
    Developer["Developer"] -- Commits Code to --> GitHub["GitHub Repository"]
    GitHub -- Triggers --> GitHubActions["GitHub Actions (CI)"]
    GitHubActions -- Runs --> GradleBuild["Gradle Build"]
    GradleBuild -- Performs --> StaticAnalysis["Static Analysis (Ktlint, Detekt)"]
    GradleBuild -- Performs --> UnitTests["Unit Tests"]
    GradleBuild -- Performs --> FuzzTesting["Fuzz Testing (OSS-Fuzz)"]
    GradleBuild -- Produces --> Artifacts["Artifacts (JAR Files)"]
    Artifacts -- Published to --> MavenCentral["Maven Central"]

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Build Process Security Controls:

• security control: Source Code Management (GitHub): Uses Git for version control, providing a history of changes and enabling collaboration.
• security control: CI/CD (GitHub Actions): Automates the build, test, and release process, ensuring consistency and reducing manual errors.
• security control: Static Analysis (Ktlint, Detekt): Uses static analysis tools to identify potential code quality and security issues.
• security control: Unit Tests: Includes a comprehensive suite of unit tests to verify the correctness of the code.
• security control: Fuzz Testing (OSS-Fuzz): Uses fuzz testing to proactively identify potential vulnerabilities.
• security control: Dependency Management (Gradle): Uses Gradle to manage dependencies, allowing for controlled updates and vulnerability scanning.
• security control: Artifact Repository (Maven Central): Publishes artifacts to Maven Central, a widely used and trusted repository.

RISK ASSESSMENT

Critical Business Processes:

• Secure and reliable network communication for applications using OkHttp.
• Maintaining the trust and reputation of OkHttp as a secure and dependable library.

Data to Protect:

• Data in Transit: Data transmitted between applications and servers using OkHttp. Sensitivity varies greatly depending on the application (e.g., user credentials, personal data, financial information). High Sensitivity
• Source Code: The OkHttp source code itself. While publicly available, unauthorized modifications could introduce vulnerabilities. Medium Sensitivity
• Configuration Data: Configuration settings used by OkHttp (e.g., timeouts, proxy settings). Incorrect configuration could lead to security issues. Medium Sensitivity

QUESTIONS & ASSUMPTIONS

Questions:

• Are there any specific compliance requirements (e.g., PCI DSS, HIPAA) that applications using OkHttp commonly need to meet? This would influence recommendations for TLS configurations and data handling.
• What is the process for handling reported security vulnerabilities? Is there a bug bounty program?
• Are there any plans to support post-quantum cryptography in the future?

Assumptions:

• BUSINESS POSTURE: It's assumed that maintaining a strong security posture is a high priority for the OkHttp project due to its widespread use and potential impact on numerous applications.
• SECURITY POSTURE: It's assumed that the existing security controls are implemented effectively and regularly reviewed.
• DESIGN: It's assumed that developers using OkHttp are responsible for implementing application-level security controls and securely handling sensitive data.