threat-modeling.md

Threat Model Analysis for ocornut/imgui

Threat: Input Buffer Overflow in InputText()

• Description: An attacker provides an excessively long string to an ImGui::InputText() field that lacks proper bounds checking within ImGui's internal handling. The attacker crafts the input to exceed the allocated buffer size, potentially overwriting adjacent memory used by ImGui. This is distinct from application-level buffer overflows.
• Impact:
  • Potential application crash (Denial of Service).
  • Possible arbitrary code execution (if the overflow overwrites critical data or function pointers within ImGui's memory space, though less likely with modern memory protections).
  • Unpredictable application behavior.
• ImGui Component Affected: ImGui::InputText(), and potentially related internal string handling functions within the ImGui library.
• Risk Severity: High (potentially Critical if code execution is possible, but more likely High due to DoS).
• Mitigation Strategies:
  • Use InputText() with Size Limits: Always use the ImGui::InputText() overload that accepts a buffer size parameter (char buf[size]). Never use an unbounded buffer. This is the primary mitigation.
  • Fuzz Testing: Specifically target InputText() with fuzzing, focusing on edge cases and boundary conditions within ImGui's parsing.
  • Stay Updated: Regularly update to the latest version of ImGui, as vulnerabilities are often patched quickly.

Threat: Denial of Service via Excessive Widget Creation

• Description: An attacker repeatedly triggers the creation of a large number of ImGui windows, widgets (buttons, sliders, etc.), or deeply nested layouts. This overwhelms ImGui's internal memory management and rendering systems. The attack vector could be through a script interacting with exposed ImGui controls, or by exploiting a vulnerability in the application logic that unintentionally creates excessive ImGui elements.
• Impact:
  • Application slowdown and unresponsiveness due to high CPU and memory usage within ImGui.
  • Application crash due to memory exhaustion caused by ImGui's internal allocations.
• ImGui Component Affected: All widget creation functions (e.g., ImGui::Begin(), ImGui::Button(), ImGui::SliderFloat(), etc.), and layout functions (e.g., ImGui::Columns(), ImGui::TreeNode()) within the ImGui library.
• Risk Severity: High
• Mitigation Strategies:
  • Limit Widget Count (Application-Level, but ImGui-Focused): Implement application-level logic to restrict the maximum number of ImGui windows, widgets, and nested elements. This is crucial for preventing ImGui-specific DoS.
  • Rate Limiting (Application-Level, ImGui-Focused): Limit the rate at which new ImGui windows or widgets can be created.
  • Resource Monitoring (ImGui-Specific): Monitor ImGui's resource usage (if possible) and trigger alerts or take corrective action if thresholds are exceeded. This might involve custom instrumentation.

Threat: Code Execution via Vulnerable Callback Function (Indirect, but High Risk due to ImGui)

• Description: The application uses an ImGui callback function (e.g., for a button click) that contains a vulnerability (e.g., a buffer overflow, format string vulnerability). An attacker triggers the callback through ImGui. While the vulnerability is in the application's code, the attack vector is through ImGui, making it relevant here.
• Impact:
  • Arbitrary code execution with the privileges of the application.
• ImGui Component Affected: Any ImGui widget that can trigger a callback (e.g., ImGui::Button(), ImGui::MenuItem()). The vulnerability is not in ImGui itself, but in the application's callback function, which is invoked by ImGui.
• Risk Severity: Critical
• Mitigation Strategies:
  • Secure Coding Practices: Apply secure coding practices to all application code, especially callback functions. Avoid common vulnerabilities like buffer overflows, format string bugs, and injection flaws.
  • Input Validation (Application-Level): Validate any data passed to the callback function, even if it originates from ImGui.
  • Code Review: Thoroughly review all callback functions for potential vulnerabilities. This is the most important mitigation.

Threat: Format String Vulnerability in Custom Text() Formatting

• Description: The application uses ImGui::Text() or ImGui::TextColored() with user-provided format strings, creating a format string vulnerability. An attacker provides a malicious format string that is then processed by ImGui.
• Impact:
  • Information disclosure (reading arbitrary memory locations).
  • Potential application crash (Denial of Service).
  • Possible arbitrary code execution (though less likely than information disclosure).
• ImGui Component Affected: ImGui::Text(), ImGui::TextUnformatted(), ImGui::TextColored(), ImGui::TextWrapped(), ImGui::LabelText(). The vulnerability is in how the application uses these functions, but the functions themselves are the attack surface.
• Risk Severity: High (potentially Critical if code execution is possible).
• Mitigation Strategies:
  • Avoid User-Provided Format Strings: Never allow users to directly control the format string passed to ImGui::Text() or related functions. This is the most crucial mitigation.
  • Use ImGui::TextUnformatted(): If you just need to display a string without formatting, use ImGui::TextUnformatted().
  • Sanitize Input (If Necessary, but Discouraged): If you must use user-provided input in a formatted string, heavily sanitize it to remove any format specifiers (e.g., %s, %d, %x). This is generally discouraged; prefer building the string programmatically.
  • Use ImGui::Text("%s", variable): Use this safe method to display variable content.