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BUSINESS POSTURE

  • Business Priorities and Goals:
  • Simplify HTTP client implementation for Android and Java developers.
  • Provide a type-safe and efficient way to interact with RESTful APIs.
  • Enhance developer productivity by abstracting away low-level HTTP concerns.
  • Promote code readability and maintainability in applications that consume web services.
  • Business Risks:
  • Security vulnerabilities in Retrofit library could compromise applications using it.
  • Performance bottlenecks in Retrofit could impact application responsiveness.
  • Incompatibility issues with evolving backend APIs could break applications.
  • Lack of proper security guidance for developers could lead to insecure usage of Retrofit.

SECURITY POSTURE

  • Existing Security Controls:
  • security control: HTTPS support is implicitly provided by underlying HTTP client (OkHttp). Implemented in OkHttp library.
  • security control: Input validation is expected to be implemented by the application using Retrofit, before sending data to backend services. Implemented in user application code.
  • accepted risk: Reliance on user applications to correctly implement authentication and authorization.
  • accepted risk: Vulnerabilities in underlying OkHttp library.
  • accepted risk: Misconfiguration of Retrofit by developers leading to insecure communication.
  • Recommended Security Controls:
  • security control: Dependency scanning of Retrofit's dependencies to identify and address known vulnerabilities.
  • security control: Static Application Security Testing (SAST) on Retrofit codebase to identify potential security flaws.
  • security control: Provide security guidelines and best practices for developers using Retrofit, emphasizing secure configuration and usage.
  • Security Requirements:
  • Authentication:
  • Requirement: Retrofit itself does not handle authentication, it relies on the application to provide authentication tokens or credentials.
  • Requirement: Applications using Retrofit MUST implement appropriate authentication mechanisms based on the backend API requirements.
  • Authorization:
  • Requirement: Retrofit itself does not handle authorization, it relies on the application to ensure proper authorization logic.
  • Requirement: Applications using Retrofit MUST implement authorization checks to control access to backend resources.
  • Input Validation:
  • Requirement: Retrofit should perform basic input validation to prevent common injection attacks, especially in areas where user-provided data might influence HTTP requests.
  • Requirement: Applications using Retrofit MUST perform thorough input validation on data received from backend services and data sent to backend services.
  • Cryptography:
  • Requirement: Retrofit MUST support and encourage the use of HTTPS for all communication to ensure data confidentiality and integrity in transit.
  • Requirement: Retrofit should not implement custom cryptography but rely on well-established and vetted cryptographic libraries provided by the underlying platform (Java/Android).

DESIGN

C4 CONTEXT

flowchart LR
    subgraph "External Systems"
        BackendService["Backend Service\n(REST API)"]
    end
    subgraph "Users"
        Developer["Developer\n(Application Developer)"]
    end
    SystemBoundary["Retrofit Library"]
    SystemBoundary --> Developer
    SystemBoundary --> BackendService
    SystemBoundary --> UnderlyingHTTPClient["Underlying HTTP Client\n(OkHttp)"]
    Developer --> SystemBoundary
    BackendService --> SystemBoundary
    UnderlyingHTTPClient --> SystemBoundary
    style SystemBoundary fill:#f9f,stroke:#333,stroke-width:2px
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  • Context Diagram Elements:
    • Name: Developer
    • Type: Person
    • Description: Software developer who uses Retrofit library to build Android and Java applications that consume RESTful APIs.
    • Responsibilities: Integrate Retrofit into applications, define API interfaces, handle API responses, manage authentication and authorization.
    • Security controls: Responsible for secure usage of Retrofit, including proper input validation, authentication, and authorization implementation in their applications.
    • Name: Retrofit Library
    • Type: System
    • Description: Type-safe HTTP client library for Android and Java. Simplifies the process of making HTTP requests to RESTful APIs.
    • Responsibilities: Generate HTTP client code from API interface definitions, handle request serialization and response deserialization, manage HTTP connections, provide a high-level API for making HTTP requests.
    • Security controls: Relies on underlying HTTP client for transport security (HTTPS), provides mechanisms for request and response interception, expects secure configuration by developers.
    • Name: Backend Service
    • Type: System
    • Description: RESTful API that provides data and functionality to applications using Retrofit.
    • Responsibilities: Process API requests, provide data responses, implement API authentication and authorization.
    • Security controls: Implements API security measures, including authentication, authorization, input validation, and protection against common web vulnerabilities.
    • Name: Underlying HTTP Client
    • Type: System
    • Description: HTTP client library (OkHttp) used by Retrofit to handle low-level HTTP communication.
    • Responsibilities: Manage HTTP connections, handle HTTP requests and responses, implement HTTP protocols, provide TLS/SSL for HTTPS.
    • Security controls: Implements transport layer security (TLS/SSL) for HTTPS, handles HTTP protocol security aspects.

C4 CONTAINER

flowchart LR
    subgraph "Retrofit Library"
        ContainerLibrary["Retrofit Core\n(Java/Kotlin Library)"]
        ContainerAnnotations["Annotations Processor\n(Java)"]
    end
    ContainerLibrary --> UnderlyingHTTPClient["OkHttp Client\n(Java Library)"]
    Developer["Developer Application Code"] --> ContainerLibrary
    ContainerAnnotations --> ContainerLibrary: Generates Code
    style ContainerLibrary fill:#f9f,stroke:#333,stroke-width:2px
    style ContainerAnnotations fill:#f9f,stroke:#333,stroke-width:2px
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  • Container Diagram Elements:
    • Name: Retrofit Core
    • Type: Container - Library
    • Description: Core logic of the Retrofit library, written in Java and Kotlin. Provides the main API for developers to define and use REST API interfaces.
    • Responsibilities: API interface processing, request building, response handling, integration with annotation processor and underlying HTTP client.
    • Security controls: Input validation on API interface definitions, secure handling of request and response data, relies on underlying HTTP client for transport security.
    • Name: Annotations Processor
    • Type: Container - Build-time Component
    • Description: Java annotation processor that generates implementation code based on API interface definitions with Retrofit annotations.
    • Responsibilities: Code generation during compilation, processing annotations to create HTTP client implementations.
    • Security controls: Secure code generation practices, prevention of code injection vulnerabilities during code generation.
    • Name: OkHttp Client
    • Type: Container - Library
    • Description: Underlying HTTP client library (OkHttp) used by Retrofit for actual HTTP communication.
    • Responsibilities: HTTP connection management, request execution, response handling, TLS/SSL for HTTPS, HTTP protocol implementation.
    • Security controls: Transport layer security (TLS/SSL), HTTP protocol security, vulnerability management of OkHttp library itself.

DEPLOYMENT

flowchart LR
    subgraph "Developer Machine"
        DeveloperAppCode["Developer Application Code"]
        RetrofitLib["Retrofit Library"]
        OkHttpLib["OkHttp Library"]
    end
    subgraph "Target Environment (e.g., Android Device, Java Server)"
        ApplicationInstance["Application Instance\n(Running Application)"]
        DeployedRetrofit["Retrofit Library\n(Deployed)"]
        DeployedOkHttp["OkHttp Library\n(Deployed)"]
    end
    DeveloperAppCode --> RetrofitLib: Compile-time Dependency
    RetrofitLib --> OkHttpLib: Runtime Dependency
    ApplicationInstance --> DeployedRetrofit: Runtime Usage
    DeployedRetrofit --> DeployedOkHttp: Runtime Usage
    DeployedOkHttp --> Network["Network"]
    Network --> BackendService["Backend Service"]
    style ApplicationInstance fill:#f9f,stroke:#333,stroke-width:2px
    style DeployedRetrofit fill:#f9f,stroke:#333,stroke-width:2px
    style DeployedOkHttp fill:#f9f,stroke:#333,stroke-width:2px
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  • Deployment Diagram Elements:
    • Name: Developer Application Code
    • Type: Component - Code
    • Description: Application code written by developers that utilizes Retrofit library.
    • Responsibilities: Defining API interfaces, using Retrofit to make API calls, handling responses, implementing application logic.
    • Security controls: Application-level security controls, input validation, authentication, authorization, secure data handling.
    • Name: Retrofit Library (Deployed)
    • Type: Component - Library
    • Description: Deployed instance of the Retrofit library within the target application environment.
    • Responsibilities: Providing HTTP client functionality to the application at runtime.
    • Security controls: Inherits security controls from the library itself and the underlying platform.
    • Name: OkHttp Library (Deployed)
    • Type: Component - Library
    • Description: Deployed instance of the OkHttp library within the target application environment.
    • Responsibilities: Handling low-level HTTP communication at runtime.
    • Security controls: Transport layer security (TLS/SSL), HTTP protocol security, vulnerability management of OkHttp library.
    • Name: Application Instance
    • Type: Environment - Runtime Environment
    • Description: Running instance of the application that uses Retrofit, deployed in the target environment (e.g., Android device, Java server).
    • Responsibilities: Executing application code, running Retrofit and OkHttp libraries, interacting with the network and backend services.
    • Security controls: Operating system security, runtime environment security, application-level security controls.
    • Name: Network
    • Type: Infrastructure - Network
    • Description: Network infrastructure connecting the application instance to the backend service.
    • Responsibilities: Network communication, data transmission.
    • Security controls: Network security controls, firewalls, intrusion detection systems, network segmentation.
    • Name: Backend Service
    • Type: System - External System
    • Description: Backend REST API service that the application communicates with over the network.
    • Responsibilities: Processing API requests, providing data responses, implementing backend logic.
    • Security controls: Backend security controls, API security, server security, data security.

BUILD

flowchart LR
    subgraph "Developer Environment"
        Developer["Developer"]
        SourceCode["Source Code\n(GitHub)"]
    end
    subgraph "CI Environment (GitHub Actions)"
        CI["CI System\n(GitHub Actions)"]
        BuildArtifacts["Build Artifacts\n(JAR/AAR)"]
    end
    Developer --> SourceCode: Push Code
    SourceCode --> CI: Trigger Build
    CI --> BuildArtifacts: Produce Artifacts
    CI --> SecurityChecks["Security Checks\n(SAST, Dependency Scan)"]
    SecurityChecks --> CI: Report
    CI --> ArtifactRepository["Artifact Repository\n(Maven Central)"] : Publish Artifacts
    BuildArtifacts --> ArtifactRepository
    style CI fill:#f9f,stroke:#333,stroke-width:2px
    style SecurityChecks fill:#f9f,stroke:#333,stroke-width:2px
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  • Build Process Elements:
    • Name: Developer
    • Type: Person
    • Description: Software developer contributing to the Retrofit project.
    • Responsibilities: Writing code, committing changes, creating pull requests.
    • Security controls: Secure coding practices, code review, authentication to GitHub.
    • Name: Source Code
    • Type: Component - Code Repository
    • Description: GitHub repository hosting the Retrofit source code.
    • Responsibilities: Version control, code storage, collaboration platform.
    • Security controls: Access control to repository, branch protection, audit logs.
    • Name: CI System
    • Type: System - Automation System
    • Description: GitHub Actions CI environment used for building, testing, and publishing Retrofit.
    • Responsibilities: Automated build process, running tests, performing security checks, publishing artifacts.
    • Security controls: Secure CI configuration, access control to CI system, secrets management, build isolation.
    • Name: Security Checks
    • Type: Component - Security Tooling
    • Description: Automated security checks integrated into the CI pipeline, including SAST and dependency scanning.
    • Responsibilities: Identifying potential security vulnerabilities in code and dependencies.
    • Security controls: Regularly updated security rules, vulnerability databases, reporting mechanisms.
    • Name: Build Artifacts
    • Type: Data - Software Artifacts
    • Description: Compiled JAR and AAR files produced by the build process.
    • Responsibilities: Packaging and distributing the Retrofit library.
    • Security controls: Artifact signing, integrity checks, secure storage.
    • Name: Artifact Repository
    • Type: System - Repository
    • Description: Maven Central repository where Retrofit artifacts are published for public consumption.
    • Responsibilities: Hosting and distributing Retrofit library artifacts.
    • Security controls: Repository security controls, artifact verification, access control.

RISK ASSESSMENT

  • Critical Business Processes:
  • Ensuring secure and reliable communication between applications and backend services for applications using Retrofit.
  • Maintaining the integrity and availability of the Retrofit library for developers.
  • Data to Protect and Sensitivity:
  • Retrofit library code itself (low sensitivity, publicly available on GitHub, but integrity is important).
  • Build process and signing keys (high sensitivity, compromise could lead to malicious library versions).
  • User data transmitted through applications using Retrofit (sensitivity depends on the application, could be highly sensitive PII, financial data, etc.).

QUESTIONS & ASSUMPTIONS

  • Business Posture Questions:
  • What is the expected risk appetite for applications using Retrofit? (Assumption: Varies depending on the application, Retrofit should aim for high security).
  • Are there specific compliance requirements for applications using Retrofit? (Assumption: Retrofit should be designed to facilitate compliance, e.g., with HTTPS enforcement).
  • Security Posture Questions:
  • What security testing is currently performed on Retrofit codebase? (Assumption: Basic testing, recommended to enhance with SAST and dependency scanning).
  • Are there documented security guidelines for developers using Retrofit? (Assumption: Basic usage guidelines, recommended to add specific security best practices).
  • What is the process for handling security vulnerabilities reported in Retrofit or its dependencies? (Assumption: Standard open-source vulnerability disclosure and patching process).
  • Design Questions:
  • Are there plans to incorporate more security features directly into Retrofit library? (Assumption: Focus is on providing secure defaults and guidance, not implementing application-level security features).
  • How is input validation handled within Retrofit itself? (Assumption: Limited input validation, primarily responsibility of user applications).
  • What are the considerations for secure configuration of Retrofit by developers? (Assumption: Developers need clear guidance on secure configuration options, e.g., HTTPS enforcement).