Skip to content

Latest commit

 

History

History
278 lines (231 loc) · 22.3 KB

sec-design.md

File metadata and controls

278 lines (231 loc) · 22.3 KB

Project Design Document: terminal.gui - Cross-Platform Terminal UI Toolkit

Version: 1.1 Date: October 26, 2023 Author: AI Expert (You) Project Link: https://github.com/gui-cs/terminal.gui

1. Introduction

This document provides a detailed design overview of the terminal.gui project, a cross-platform terminal UI toolkit for .NET. This document is intended to serve as a foundation for subsequent threat modeling activities. It outlines the system's architecture, components, data flow, and key technologies involved. Understanding the design is crucial for identifying potential security vulnerabilities and developing appropriate mitigation strategies. This document builds upon the previous version by providing more detailed component descriptions, clarifying data flow, and adding sections on technology stack, deployment, and preliminary security considerations.

2. Project Overview

terminal.gui is a .NET library that enables developers to create rich, interactive, and visually appealing terminal-based user interfaces (TUIs). It provides a widget-based framework, similar to GUI toolkits, but specifically designed for text-based terminals. This allows developers to build applications that run in terminal emulators across various operating systems (Linux, macOS, Windows) without requiring a graphical environment.

Key Features:

  • Cross-Platform Compatibility: Designed to work on multiple operating systems with terminal support (Linux, macOS, Windows, and potentially others).
  • Widget-Based Architecture: Offers a rich set of pre-built UI components (widgets) like buttons, text boxes, labels, lists, menus, dialogs, and more complex views like trees and tab views.
  • Layout Management: Provides flexible layout mechanisms (e.g., absolute positioning, relative layouts, and potentially constraint-based layouts) for arranging widgets within the terminal.
  • Event Handling: Robust event system supporting keyboard, mouse, and other input events, enabling interactive applications.
  • Theming and Styling: Customizable appearance through color schemes and potentially more advanced styling options.
  • Accessibility: Designed with accessibility in mind, aiming to create TUIs usable by people with disabilities (e.g., screen reader compatibility).
  • .NET Standard Library: Implemented as a .NET Standard library for broad compatibility across different .NET runtimes (.NET Framework, .NET Core, .NET).
  • Extensibility: Designed to be extensible, allowing developers to create custom widgets and drivers.

3. Goals and Objectives

The primary goals of terminal.gui are:

  • Provide a comprehensive and feature-rich toolkit for building sophisticated TUIs in .NET.
  • Enable true cross-platform development of terminal applications with minimal platform-specific code.
  • Significantly simplify the development process for creating interactive and user-friendly terminal interfaces, reducing boilerplate and complexity.
  • Offer a programming model that is intuitive and familiar to developers with experience in GUI frameworks, leveraging object-oriented principles and event-driven programming.
  • Achieve high performance and responsiveness, even in resource-constrained terminal environments, ensuring a smooth user experience.
  • Prioritize accessibility, making terminal applications usable by a wider audience, including users who rely on assistive technologies.
  • Foster a vibrant and active open-source community around the project, encouraging contributions and ensuring long-term sustainability.

4. System Architecture

4.1. High-Level Architecture

The following diagram illustrates the high-level architecture of an application using terminal.gui:

graph LR
    subgraph "Terminal Emulator"
        "A"("Terminal Emulator")
    end
    subgraph "Application using terminal.gui"
        "B"(".NET Application Code") --> "C"("terminal.gui Library");
        "C" --> "D"("Input Handling");
        "C" --> "E"("Layout Engine");
        "C" --> "F"("Rendering Engine");
        "C" --> "G"("Widget Library");
        "D" --> "A";
        "F" --> "A";
    end
Loading

Description:

  1. Terminal Emulator ("A"): This is the external application responsible for displaying text-based output and capturing user input. It acts as the interface between the user and the terminal.gui application. Different terminal emulators may have varying capabilities and security features. Examples include:

    • Linux/macOS: xterm, gnome-terminal, konsole, iTerm2, Terminal.app, etc.
    • Windows: Windows Console Host (conhost.exe), Windows Terminal.
    • Remote Terminals: SSH clients, telnet clients.

  2. .NET Application Code ("B"): This represents the application logic developed by the user. It's written in C# or another .NET language and utilizes the terminal.gui library to construct the TUI. This code defines the application's behavior, data handling, and responses to user interactions.

  3. terminal.gui Library ("C"): This is the core .NET library that provides the TUI framework. It encapsulates the logic for managing the terminal UI and is composed of several key modules:

    • Input Handling ("D"): This module is responsible for capturing raw input events from the Terminal Emulator (keyboard input, mouse events, window resize events, etc.). It translates these raw events into higher-level input events that terminal.gui can process.
    • Layout Engine ("E"): The Layout Engine determines the size and position of each widget on the screen. It takes into account layout constraints, widget properties, and available terminal space to arrange the UI elements effectively.
    • Rendering Engine ("F"): The Rendering Engine is responsible for drawing the UI. It takes the layout information and widget states and translates them into character sequences and ANSI escape codes (or platform-specific terminal control sequences) that the Terminal Emulator understands to display the UI. It manages the screen buffer and efficiently updates only the changed portions of the terminal.
    • Widget Library ("G"): This is a collection of reusable UI components (widgets) that developers can use to build their TUIs. Widgets encapsulate both visual representation and interactive behavior. Examples include Button, Label, TextField, ListView, Menu, Dialog, FrameView, TabView, TreeView, ProgressBar, CheckBox, RadioButton, and more.

Data Flow (High-Level):

  1. Input: User interacts with the Terminal Emulator ("A") (e.g., presses a key, moves the mouse, clicks a button).
  2. Input Transmission: The Terminal Emulator sends raw input data to the application.
  3. Input Handling ("D"): The Input Handling module within terminal.gui receives and processes this raw input. It interprets the input stream, identifies specific events (key presses, mouse clicks, etc.), and converts them into terminal.gui event objects.
  4. Event Routing: These event objects are then routed to the appropriate widgets or application logic based on focus, event type, and widget hierarchy.
  5. Application Logic ("B"): The application code responds to these events. This might involve updating data, changing the UI state, or performing actions based on user input.
  6. Layout Update (Conditional): If the application logic changes the UI structure or widget properties that affect layout, the Layout Engine ("E") is triggered to recalculate widget positions and sizes.
  7. Rendering ("F"): The Rendering Engine ("F") takes the updated UI state and layout information. It determines what needs to be redrawn on the terminal screen. It then generates the necessary character sequences and terminal control codes to represent the UI in the terminal.
  8. Output Transmission: The Rendering Engine sends these character sequences and control codes to the Terminal Emulator ("A").
  9. Display Update: The Terminal Emulator interprets the received data and updates the terminal display, reflecting the changes in the TUI.

4.2. Component-Level Architecture

The following diagram provides a more detailed view of the key components within the terminal.gui library:

graph LR
    subgraph "terminal.gui Library"
        subgraph "Core"
            "A"("Application");
            "B"("View");
            "C"("Window");
            "D"("Toplevel");
            "E"("Widget");
            "F"("LayoutManager");
            "G"("InputManager");
            "H"("ColorScheme");
            "I"("Driver (ConsoleDriver)");
            "J"("Screen");
            "K"("Clipboard");
            "L"("Themes");
        end
        subgraph "Widgets"
            "M"("Button");
            "N"("Label");
            "O"("TextField");
            "P"("ListView");
            "Q"("Menu");
            "R"("Dialog");
            "S"("FrameView");
            "T"("TabView");
            "U"("TreeView");
            "V"("ProgressBar");
            "W"("CheckBox");
            "X"("RadioButton");
            "Y"("ComboBox");
            "Z"("TextView");
            "AA"("DateField");
            "BB"("TimeField");
        end
        subgraph "Input Handling"
            "CC"("Keyboard Input");
            "DD"("Mouse Input");
            "EE"("HotKey Handling");
            "FF"("Command Handling");
        end
        subgraph "Rendering"
            "GG"("Screen Buffer");
            "HH"("Attribute Management");
            "II"("Character Encoding");
            "JJ"("Cursor Management");
            "KK"("ANSI/VT100 Support");
        end
    end

    "A" --> "D";
    "D" --> "C";
    "C" --> "B";
    "B" --> "E";
    "E" --> "F";
    "E" --> "H";
    "A" --> "G";
    "G" --> "CC";
    "G" --> "DD";
    "G" --> "EE";
    "G" --> "FF";
    "A" --> "I";
    "I" --> "J";
    "A" --> "K";
    "A" --> "L";
    "F" --> "E";
    "E" --> "GG";
    "GG" --> "HH";
    "GG" --> "II";
    "GG" --> "JJ";
    "GG" --> "KK";

    "E" --> "M";
    "E" --> "N";
    "E" --> "O";
    "E" --> "P";
    "E" --> "Q";
    "E" --> "R";
    "E" --> "S";
    "E" --> "T";
    "E" --> "U";
    "E" --> "V";
    "E" --> "W";
    "E" --> "X";
    "E" --> "Y";
    "E" --> "Z";
    "E" --> "AA";
    "E" --> "BB";
Loading

Component Descriptions (Component Level):

  • Application ("A"): The central orchestrator of a terminal.gui application. It manages the main loop, input processing, screen updates, and overall application lifecycle. It initializes the ConsoleDriver, InputManager, and Clipboard. It also manages Toplevel views.
  • View ("B"): The base class for all visual elements in terminal.gui, including Window, Widget, and Toplevel. It defines properties and methods for positioning, sizing, drawing, event handling, focus management, and more.
  • Window ("C"): A specialized View that represents a top-level window within the terminal. It typically has a border and can contain other Views and Widgets.
  • Toplevel ("D"): Represents the outermost container for a user interface. An Application can have multiple Toplevels (though typically one main one). Toplevels are root-level views that are managed by the Application.
  • Widget ("E"): A concrete UI control derived from View, providing specific interactive elements like buttons, text fields, lists, etc. Each widget has its own visual representation and event handling logic.
  • LayoutManager ("F"): Responsible for calculating and managing the layout of Views and Widgets. It may implement different layout algorithms or strategies.
  • InputManager ("G"): Handles all input events from the console. It processes keyboard and mouse input, dispatches events to focused views, and manages hotkeys and commands.
  • ColorScheme ("H"): Defines the color palette used to render UI elements. It allows for theming and customization of the application's appearance.
  • Driver (ConsoleDriver) ("I"): An abstraction layer that interacts directly with the underlying console or terminal. ConsoleDriver is the primary driver and uses platform-specific APIs (e.g., P/Invoke on Windows, termios on Linux/macOS) to control the terminal. Other drivers could potentially be implemented for different output targets.
  • Screen ("J"): Represents the terminal screen buffer. It's used by the Rendering Engine to store the characters and attributes to be displayed.
  • Clipboard ("K"): Provides access to the system clipboard for copy and paste operations within the terminal application.
  • Themes ("L"): Manages and applies visual themes to the application, potentially allowing users to switch between different color schemes and styles.

Input Handling Components:

  • Keyboard Input ("CC"): Handles keyboard events, including key presses, key releases, and special key combinations.
  • Mouse Input ("DD"): Handles mouse events, such as mouse movement, button clicks, scrolling, and potentially mouse drag events.
  • HotKey Handling ("EE"): Manages application-level and view-specific hotkeys (keyboard shortcuts) for triggering actions.
  • Command Handling ("FF"): Provides a mechanism for defining and executing commands, often triggered by hotkeys or menu selections.

Rendering Components:

  • Screen Buffer ("GG"): A memory buffer that stores the characters and attributes (colors, styles) to be displayed on the terminal.
  • Attribute Management ("HH"): Handles the application of visual attributes (colors, bold, italics, etc.) to characters in the screen buffer, based on the ColorScheme and widget styles.
  • Character Encoding ("II"): Manages character encoding to ensure proper display of text in different languages and character sets supported by the terminal.
  • Cursor Management ("JJ"): Controls the visibility, position, and shape of the terminal cursor.
  • ANSI/VT100 Support ("KK"): Implements support for ANSI escape codes and VT100 terminal control sequences, which are used to control terminal formatting and behavior across different platforms.

4.3. Technology Stack

  • Programming Language: C#
  • .NET Platform: .NET Standard Library (targeting .NET Framework, .NET Core, .NET)
  • Console Interaction:
    • Windows: P/Invoke to access Windows Console API.
    • Linux/macOS: termios and other POSIX terminal APIs, likely accessed via P/Invoke or similar mechanisms.
  • Character Encoding: Supports various character encodings, likely including UTF-8 as a primary encoding.
  • Terminal Control Sequences: Primarily uses ANSI escape codes (VT100 compatible) for terminal manipulation.

4.4. Deployment Model

Applications built with terminal.gui are typically deployed as:

  • Self-Contained Executables: Deploying the application as a self-contained executable ensures that all necessary .NET runtime components are included, simplifying deployment and ensuring consistent behavior across different environments.
  • Framework-Dependent Executables: Alternatively, applications can be deployed as framework-dependent executables, relying on the presence of a compatible .NET runtime on the target system. This reduces the deployment size but requires the user to have the correct .NET runtime installed.
  • Cross-Platform Distribution: Due to .NET's cross-platform nature and terminal.gui's design, applications can be distributed to Linux, macOS, and Windows systems with minimal or no platform-specific modifications. Distribution methods can include:
    • Package Managers: For Linux distributions (e.g., deb, rpm packages).
    • Application Bundles: For macOS (.app bundles).
    • Executable Installers: For Windows (.exe installers, MSI packages).
    • Simple Executable Distribution: For simpler applications, just distributing the executable file might be sufficient.

5. Data Flow (Detailed)

Let's trace a more detailed data flow for a common user interaction: Typing text into a TextField widget.

  1. Key Press in Terminal: User presses a key (e.g., 'a') in the Terminal Emulator.
  2. Raw Input to Application: The Terminal Emulator sends the raw keyboard input (e.g., byte code representing 'a') to the running .NET application.
  3. ConsoleDriver Receives Input: The ConsoleDriver (e.g., WindowsDriver or CursesDriver depending on the platform) uses platform-specific APIs to read the raw input from the console input stream.
  4. InputManager Processing: The InputManager receives the raw input from the ConsoleDriver. It buffers input, decodes character sequences (handling multi-byte characters and escape sequences), and identifies key events (KeyDown, KeyUp, KeyPress).
  5. Focus Determination: The InputManager determines which View currently has focus. In this case, assume the TextField widget has focus.
  6. Event Dispatch to TextField: The InputManager dispatches the KeyPress event (containing information about the 'a' key) to the focused TextField widget.
  7. TextField Event Handler: The TextField widget's internal event handler for KeyPress is invoked.
  8. Text Buffer Update: The TextField's event handler updates its internal text buffer by appending the character 'a'.
  9. View Redraw Request: The TextField marks itself as needing to be redrawn because its text content has changed. This typically involves setting a "dirty" flag.
  10. Application Main Loop - Redraw Phase: In the application's main loop, during the redraw phase, the Application checks for views that are marked as "dirty".
  11. Layout (Potentially): If the text change in the TextField could affect the layout (e.g., if the TextField is auto-sizing), the LayoutManager might be involved to recalculate the layout. In this simple case, it's likely that only the TextField's internal layout needs to be adjusted.
  12. Rendering Engine - Widget Rendering: The Rendering Engine is invoked to redraw the TextField. It accesses the TextField's text buffer and its current position and size.
  13. Screen Buffer Update: The Rendering Engine writes the characters representing the updated text of the TextField into the Screen Buffer ("GG"), along with the appropriate attributes (colors, styles) from the ColorScheme.
  14. ConsoleDriver Output: The ConsoleDriver takes the updated portion of the Screen Buffer and uses platform-specific APIs to write the character data and control sequences to the console output stream.
  15. Terminal Emulator Display Update: The Terminal Emulator receives the output stream from the application and updates the terminal display, showing the typed character 'a' in the TextField.

6. Security Considerations (Preliminary)

While terminal.gui operates within the text-based terminal environment, and might seem less susceptible to typical GUI-related vulnerabilities, there are still security aspects to consider:

  • Input Validation and Sanitization: Applications using terminal.gui should still perform proper input validation and sanitization, especially for user-provided text input (e.g., in TextFields, TextViews). Although terminal output is text-based, vulnerabilities like command injection could still be possible if user input is not handled carefully and is used to construct system commands or other sensitive operations.
  • ANSI Escape Code Injection: While terminal.gui uses ANSI escape codes for rendering, applications should be cautious about directly embedding user-provided data into ANSI escape sequences. Maliciously crafted input could potentially inject escape codes that could manipulate the terminal in unintended ways (though the impact is generally limited within the terminal context).
  • Denial of Service (DoS): Excessive or malformed input could potentially lead to DoS vulnerabilities. For example, very long strings in TextFields or rapid input events might consume excessive resources. terminal.gui and applications should be designed to handle input gracefully and prevent resource exhaustion.
  • Clipboard Security: If the application uses the clipboard functionality, consider the security implications of data being copied to and pasted from the system clipboard, especially if sensitive data is involved.
  • Dependency Security: As a .NET library, terminal.gui relies on the .NET runtime and potentially other NuGet packages. Regularly updating dependencies and being aware of security advisories for .NET and related libraries is important.
  • Terminal Emulator Vulnerabilities: The security of the application also depends on the security of the underlying Terminal Emulator. Vulnerabilities in the Terminal Emulator itself could potentially be exploited, although this is outside the scope of terminal.gui's direct control. Users should be advised to use reputable and updated terminal emulators.
  • Information Disclosure: Care should be taken to avoid unintentional information disclosure through the TUI. Sensitive data should be handled securely and displayed only when necessary and in a controlled manner.

This preliminary security consideration section provides a starting point for more in-depth threat modeling. The next step would be to perform a detailed threat model to identify specific threats, vulnerabilities, and mitigation strategies based on this design document.

7. Future Considerations

  • Accessibility Enhancements: Continuously improve accessibility features to meet evolving accessibility standards and user needs.
  • Advanced Layout Capabilities: Explore and implement more sophisticated layout managers, such as constraint-based layout, to provide greater flexibility in UI design.
  • Driver Extensibility: Further enhance driver extensibility to support different output targets beyond traditional terminals (e.g., web-based terminals, embedded displays).
  • Theming and Styling System: Develop a more powerful and flexible theming and styling system, potentially using CSS-like syntax or declarative styling approaches.
  • Testing and Quality Assurance: Implement comprehensive unit and integration tests to ensure the library's robustness and reliability.
  • Community Engagement: Actively engage with the open-source community to gather feedback, encourage contributions, and foster a collaborative development environment.

This design document provides a comprehensive overview of the terminal.gui project's architecture and serves as a solid foundation for further development and security analysis. It will be used as the basis for subsequent threat modeling activities to ensure the project is secure and robust.