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BUSINESS POSTURE

This project, the mail Ruby library, aims to simplify email handling for Ruby developers. It provides a comprehensive set of tools for parsing, generating, and sending emails within Ruby applications.

  • Business Priorities and Goals:

    • Primary goal: Provide a robust and easy-to-use Ruby library for email processing.
    • Enable Ruby developers to efficiently integrate email functionality into their applications.
    • Maintain compatibility with email standards and protocols.
    • Ensure the library is reliable and performant for handling email operations.
    • Foster a community around the library for contributions and improvements.

  • Business Risks:

    • Security vulnerabilities in the library could lead to email injection attacks, data breaches, or denial of service.
    • Compatibility issues with evolving email standards or Ruby versions could reduce adoption and utility.
    • Performance bottlenecks in email processing could negatively impact application performance.
    • Lack of community support or maintenance could lead to stagnation and security risks over time.
    • Incorrect handling of email content could lead to data loss or corruption.

SECURITY POSTURE

  • Security Controls:

    • security control: Code review process for contributions (Implicit in open-source development).
    • security control: Unit and integration tests to ensure code correctness and prevent regressions (Present in the repository).
    • security control: Dependency management using Bundler to manage and track external libraries (Standard Ruby practice).

  • Accepted Risks:

    • accepted risk: Reliance on community contributions for security vulnerability identification and patching.
    • accepted risk: Potential for undiscovered vulnerabilities in dependencies.
    • accepted risk: Risk of vulnerabilities introduced through contributed code.

  • Recommended Security Controls:

    • security control: Implement automated static application security testing (SAST) in the CI/CD pipeline to identify potential vulnerabilities in the code.
    • security control: Implement dependency scanning to identify known vulnerabilities in used dependencies.
    • security control: Establish a clear process for reporting and handling security vulnerabilities.
    • security control: Regularly update dependencies to patch known vulnerabilities.
    • security control: Consider adding fuzz testing to discover unexpected input handling issues.

  • Security Requirements:

    • Authentication:
      • Requirement: The library itself does not handle authentication as it's a client-side library. Authentication is the responsibility of the application using the library when connecting to SMTP servers or email services.
      • Requirement: If the library provides any helper functions for authentication (e.g., for SMTP), these must securely handle credentials and connection establishment.
    • Authorization:
      • Requirement: The library does not handle authorization. Authorization is managed by the application using the library and the email services it interacts with.
    • Input Validation:
      • Requirement: The library must perform robust input validation on all email components (headers, body, attachments) to prevent injection attacks (e.g., email header injection, command injection via email content).
      • Requirement: Input validation should handle various email encoding formats and character sets correctly to avoid bypasses.
    • Cryptography:
      • Requirement: The library should support secure email protocols like TLS/SSL for SMTP connections to protect email transmission in transit.
      • Requirement: If the library handles email encryption or signing (e.g., S/MIME, PGP), it must use established and secure cryptographic libraries and algorithms.
      • Requirement: Ensure proper handling of cryptographic keys and certificates if encryption or signing features are implemented.

DESIGN

C4 CONTEXT

flowchart LR
    subgraph "Email System Context"
    center["Mail Ruby Library"]
    end

    RubyApp["Ruby Application"]
    SMTP["SMTP Server"]
    EmailClient["Email Client"]

    RubyApp --> center: Uses
    center --> SMTP: Sends Emails via
    center <-- EmailClient: Receives Emails via (Parsing)

    style center fill:#f9f,stroke:#333,stroke-width:2px
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  • Context Diagram Elements:
      • Name: Mail Ruby Library
      • Type: Software Library
      • Description: A Ruby library for parsing, generating, and sending emails. It simplifies email handling within Ruby applications.
      • Responsibilities:
        • Parsing email messages from various sources.
        • Generating email messages according to email standards.
        • Handling email encoding and decoding.
        • Providing an API for Ruby applications to interact with email functionality.
      • Security controls:
        • Input validation on email data.
        • Secure handling of email content to prevent injection attacks.
        • Support for secure communication protocols (e.g., TLS/SSL for SMTP).
      • Name: Ruby Application
      • Type: Software System
      • Description: A Ruby application that utilizes the mail library to implement email-related features, such as sending notifications, processing incoming emails, or managing email campaigns.
      • Responsibilities:
        • Integrating the mail library into its codebase.
        • Using the library's API to perform email operations.
        • Authenticating with SMTP servers or email services.
        • Managing email content and user interactions related to email.
      • Security controls:
        • Authentication and authorization for email sending and receiving.
        • Secure storage of email credentials if needed.
        • Proper handling of user data within emails.
        • Input validation on data before using it with the mail library.
      • Name: SMTP Server
      • Type: Infrastructure System
      • Description: A Simple Mail Transfer Protocol (SMTP) server responsible for relaying outgoing emails from the Ruby application (via the mail library) to recipient mail servers.
      • Responsibilities:
        • Receiving emails from the mail library (via Ruby Application).
        • Routing emails to destination mail servers.
        • Ensuring reliable email delivery.
        • Potentially providing authentication mechanisms for sending emails.
      • Security controls:
        • SMTP server security configurations (e.g., TLS/SSL, authentication mechanisms).
        • Access control to prevent unauthorized email relaying.
        • Anti-spam and anti-malware measures.
      • Name: Email Client
      • Type: Software Application
      • Description: An email client application (e.g., Thunderbird, Outlook, webmail) used by recipients to read emails sent by the Ruby application (processed by the mail library). It can also represent a system sending emails that the Ruby application might parse using the library.
      • Responsibilities:
        • Displaying emails to users.
        • Allowing users to compose and send emails.
        • Potentially sending emails that might be parsed by a Ruby application using the mail library.
      • Security controls:
        • Email client security features (e.g., anti-phishing, anti-malware).
        • Secure handling of user credentials and email data.
        • Rendering emails safely to prevent malicious content execution.

C4 CONTAINER

flowchart LR
    subgraph "Ruby Application Container"
    RubyApp["Ruby Application Code"]
    MailLibrary["Mail Ruby Library"]
    end

    RubyApp --> MailLibrary: Uses Library

    style RubyApp fill:#f9f,stroke:#333,stroke-width:2px
    style MailLibrary fill:#f9f,stroke:#333,stroke-width:2px
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  • Container Diagram Elements:
      • Name: Ruby Application Code
      • Type: Application Container
      • Description: Represents the Ruby application code that utilizes the mail library. This is where the application-specific logic resides, including how it uses the email functionality provided by the library.
      • Responsibilities:
        • Application-specific logic for email handling.
        • Calling the mail library's API to perform email operations.
        • Managing application configuration and data.
      • Security controls:
        • Application-level authentication and authorization.
        • Input validation of application data before using the mail library.
        • Secure coding practices within the application.
      • Name: Mail Ruby Library
      • Type: Library Container
      • Description: The mail Ruby library itself, providing the core email processing functionalities. It's a dependency included within the Ruby application.
      • Responsibilities:
        • Parsing email messages.
        • Generating email messages.
        • Handling email encoding and decoding.
        • Providing a well-defined API for Ruby applications.
      • Security controls:
        • Input validation within the library.
        • Secure coding practices in the library's codebase.
        • Protection against common email-related vulnerabilities (e.g., injection attacks).

DEPLOYMENT

Deployment of the mail library is inherently tied to the deployment of the Ruby application that uses it. The library itself is not deployed as a standalone service. It's included as a dependency within a Ruby application's deployment.

Deployment Architecture: Ruby Application Deployment

flowchart LR
    subgraph "Deployment Environment"
        subgraph "Application Server"
            RubyAppInstance["Ruby Application Instance"]
            MailLibraryInstance["Mail Ruby Library Instance"]
        end
    end

    RubyAppInstance --> MailLibraryInstance: Uses
    RubyAppInstance --> SMTP: Sends Emails

    SMTP["SMTP Server"]

    style RubyAppInstance fill:#f9f,stroke:#333,stroke-width:2px
    style MailLibraryInstance fill:#f9f,stroke:#333,stroke-width:2px
    style SMTP fill:#ccf,stroke:#333,stroke-width:2px
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  • Deployment Diagram Elements:
      • Name: Ruby Application Instance
      • Type: Software Instance
      • Description: A running instance of the Ruby application that incorporates the mail library. This instance executes the application's code and utilizes the library for email operations.
      • Responsibilities:
        • Running the Ruby application logic.
        • Executing code that calls the mail library.
        • Managing application resources and processes.
      • Security controls:
        • Application server security configurations.
        • Operating system security hardening.
        • Network security controls around the application server.
      • Name: Mail Ruby Library Instance
      • Type: Library Instance
      • Description: The instance of the mail Ruby library loaded and used by the Ruby application instance. It's not a separate deployable unit but part of the application runtime.
      • Responsibilities:
        • Providing email processing functionalities to the Ruby application instance.
        • Executing library code in response to application calls.
      • Security controls:
        • Security of the library code itself (as built and distributed).
        • Isolation within the application process.
      • Name: SMTP Server
      • Type: Infrastructure Instance
      • Description: An SMTP server instance that the Ruby application instance connects to for sending emails. This could be a cloud-based SMTP service or a self-hosted server.
      • Responsibilities:
        • Receiving and relaying emails from the Ruby application instance.
        • Handling email delivery to recipients.
      • Security controls:
        • SMTP server security configurations (TLS, authentication).
        • Network security controls around the SMTP server.
        • Monitoring and logging of SMTP traffic.

BUILD

flowchart LR
    subgraph "Developer Environment"
        Developer["Developer"]
        CodeRepo["Code Repository (GitHub)"]
    end

    subgraph "CI/CD Pipeline"
        CI["CI Server (GitHub Actions)"]
        BuildProcess["Build Process"]
        ArtifactRepo["Artifact Repository (rubygems.org)"]
    end

    Developer --> CodeRepo: Code Commit
    CodeRepo --> CI: Trigger Build
    CI --> BuildProcess: Run Build
    BuildProcess --> ArtifactRepo: Publish Artifact (Gem)

    style Developer fill:#ccf,stroke:#333,stroke-width:2px
    style CodeRepo fill:#ccf,stroke:#333,stroke-width:2px
    style CI fill:#f9f,stroke:#333,stroke-width:2px
    style BuildProcess fill:#f9f,stroke:#333,stroke-width:2px
    style ArtifactRepo fill:#ccf,stroke:#333,stroke-width:2px
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  • Build Process Elements:
      • Name: Developer
      • Type: Human Role
      • Description: Software developers who write, test, and contribute code to the mail library project.
      • Responsibilities:
        • Writing code for new features and bug fixes.
        • Running local tests and ensuring code quality.
        • Committing code changes to the code repository.
      • Security controls:
        • Secure development practices.
        • Code review process.
        • Access control to the code repository.
      • Name: Code Repository (GitHub)
      • Type: Software Service
      • Description: A version control system (GitHub) that stores the source code of the mail library and manages code changes.
      • Responsibilities:
        • Storing the project's source code.
        • Managing code versions and branches.
        • Tracking code changes and history.
        • Providing access control to the codebase.
      • Security controls:
        • Access control and authentication for developers.
        • Branch protection and code review workflows.
        • Audit logging of code changes.
      • Name: CI Server (GitHub Actions)
      • Type: Software Service
      • Description: A Continuous Integration (CI) server (GitHub Actions, in this case, likely) that automates the build, test, and potentially deployment processes when code changes are pushed to the repository.
      • Responsibilities:
        • Automating the build process.
        • Running automated tests (unit, integration, etc.).
        • Performing static analysis and security checks.
        • Publishing build artifacts.
      • Security controls:
        • Secure configuration of CI pipelines.
        • Secrets management for build credentials.
        • Isolation of build environments.
        • Security scanning tools integrated into the pipeline (SAST, dependency scanning - recommended).
      • Name: Build Process
      • Type: Automated Process
      • Description: The sequence of automated steps performed by the CI server to compile, test, and package the mail library.
      • Responsibilities:
        • Compiling the Ruby code (though Ruby is interpreted, build process includes other steps).
        • Running unit and integration tests.
        • Performing code linting and style checks.
        • Packaging the library as a Ruby gem.
        • Potentially running security scans (SAST, dependency checks - recommended).
      • Security controls:
        • Secure build scripts and configurations.
        • Use of trusted build tools and environments.
        • Implementation of security checks within the build process (SAST, dependency scanning).
      • Name: Artifact Repository (rubygems.org)
      • Type: Software Service
      • Description: A repository (rubygems.org) where the compiled and packaged mail library (as a Ruby gem) is published and made available for download by Ruby developers.
      • Responsibilities:
        • Storing and distributing the mail library gem.
        • Providing versioning and dependency management for the gem.
        • Ensuring availability and integrity of the gem.
      • Security controls:
        • Access control for publishing gems.
        • Integrity checks for published gems (e.g., checksums).
        • Vulnerability scanning of published gems (rubygems.org might perform some checks).

RISK ASSESSMENT

  • Critical Business Processes:

    • For the mail library itself, the critical process is providing a secure and reliable library for email handling. Failure in this process can impact all applications that depend on it.
    • For applications using the mail library, critical business processes could include:
      • Sending transactional emails (e.g., password resets, order confirmations).
      • Receiving and processing customer inquiries via email.
      • Email marketing campaigns.
      • System monitoring and alerting via email.

  • Data to Protect and Sensitivity:

    • Data handled by the mail library includes:
      • Email content (headers, body, attachments): Sensitivity depends on the application using the library. Could range from low (system notifications) to high (personal or confidential information in emails).
      • Email metadata (sender, recipient, timestamps): Can be sensitive depending on context and regulations (e.g., GDPR).
      • Credentials for SMTP servers or email services: Highly sensitive, must be protected to prevent unauthorized email sending.
    • Sensitivity levels:
      • Low: Publicly available information in emails.
      • Medium: Non-public, non-critical business information in emails.
      • High: Personally identifiable information (PII), confidential business data, financial information, or protected health information (PHI) in emails.

QUESTIONS & ASSUMPTIONS

  • Questions:

    • What is the intended scope of security features for the mail library itself? Should it actively prevent common email vulnerabilities, or primarily provide tools for applications to do so?
    • Are there specific compliance requirements (e.g., GDPR, HIPAA) that applications using this library might need to adhere to when handling email data?
    • What is the process for reporting and addressing security vulnerabilities in the mail library?
    • Are there any existing security scanning or testing practices in place for the mail library project beyond standard testing?

  • Assumptions:

    • BUSINESS POSTURE: The primary business goal is to provide a useful and reliable open-source library for the Ruby community. Security is a significant concern for the library's users.
    • SECURITY POSTURE: Current security controls are primarily based on standard open-source development practices (code review, testing). There's room for improvement in automated security testing and vulnerability management.
    • DESIGN: The library is designed to be a client-side library used within Ruby applications. It focuses on email parsing, generation, and basic sending functionalities, leaving higher-level security concerns (like authentication and authorization) to the application using it. The build process is assumed to be using standard Ruby gem packaging and publishing practices, potentially leveraging GitHub Actions for CI.