threat-modeling.md

Threat Model Analysis for emilk/egui

Threat: UI Spoofing via Rendering Manipulation

• Description: An attacker exploits a vulnerability in egui's text rendering or layout engine to subtly alter the appearance of UI elements. They might shift character positions in a password field, change button colors, or otherwise manipulate the intended rendering of egui components to mislead the user. This is not general XSS; it requires a bug in egui's rendering.
  • Impact: Users could be tricked into entering sensitive information into incorrect fields, clicking malicious buttons, or misinterpreting the UI, leading to credential theft, unauthorized actions, or data breaches.
  • Affected egui Component:
    • egui::Painter: Core rendering component.
    • egui::FontDefinitions, egui::FontData, egui::text::LayoutJob: Font and text layout.
    • egui::Style: Styling system vulnerabilities.
    • Widgets like egui::TextEdit, egui::Button, egui::Label (if they have rendering-specific bugs).
  • Risk Severity: High
  • Mitigation Strategies:
    • Code Review: Thorough manual review of egui::Painter and text rendering, focusing on off-by-one errors, clipping, and Unicode handling.
    • Fuzz Testing: Extensive fuzzing of text rendering and layout with diverse inputs, including unusual Unicode, large fonts, and edge-case layouts.
    • Visual Regression Testing: Automated tests to detect subtle UI rendering changes.

Threat: Input Injection via Widget Vulnerabilities

• Description: An attacker exploits a bug in an egui input widget (e.g., TextEdit, Slider, DragValue) to inject unexpected values or trigger unintended behavior within the Wasm module. This is not about bypassing application validation; it's about flaws in how the widget handles input before passing it to the application (e.g., a buffer overflow in TextEdit).
  • Impact: Manipulation of application state, bypassing input validation, triggering unexpected code paths, or potential denial-of-service.
  • Affected egui Component:
    • egui::TextEdit: Text input vulnerabilities (buffer overflows, encoding issues, sanitization).
    • egui::Slider, egui::DragValue: Numerical input vulnerabilities (overflows, range clamping).
    • egui::ComboBox, egui::RadioButton: Selection input vulnerabilities.
    • egui::widgets::text_edit::TextBuffer: Internal buffer used by TextEdit.
  • Risk Severity: High
  • Mitigation Strategies:
    • Input Validation (within egui): Each widget must perform robust validation before updating state or passing data. Includes length checks, character restrictions, and range validation.
    • Fuzz Testing: Fuzz each input widget with diverse inputs, including boundary values, invalid characters, and long strings.
    • Memory Safety (Rust): Leverage Rust's features to prevent buffer overflows. Minimize unsafe code in input handling.
    • Defensive Programming: Use assertions and defensive techniques to catch unexpected input or state inconsistencies.

Threat: Memory Corruption within egui

• Description: An attacker exploits a memory safety vulnerability (e.g., buffer overflow, use-after-free) within the egui library itself to corrupt the Wasm module's memory. This could be in unsafe Rust code, a dependency, or a rare compiler bug.
  • Impact: Arbitrary code execution within the Wasm sandbox, giving the attacker complete control of the application's behavior (though still sandboxed).
  • Affected egui Component: Potentially any component, especially those using unsafe or interacting with external libraries (font rendering, image loading).
    • egui::Painter: If it uses unsafe for optimization.
    • Components using external crates with vulnerabilities.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Minimize unsafe: Drastically reduce unsafe code in egui. Justify and review each unsafe block thoroughly.
    • Dependency Auditing: Regularly audit dependencies for known vulnerabilities (using cargo audit, cargo crev).
    • Fuzz Testing (Memory Safety): Use fuzzers designed for memory safety (AFL, libFuzzer, Honggfuzz).
    • Static Analysis: Use static analysis tools to find potential memory safety issues.
    • Compiler Updates: Keep the Rust compiler and toolchain up-to-date.