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threat-modeling.md

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Threat Model Analysis for ibireme/yytext

Threat: Buffer Overflow in YYTextParser

  • Description: An attacker crafts a specially designed rich text string with excessively long attributes, values, or text segments. This input is designed to overflow buffers within the YYTextParser component during the parsing process, potentially leading to a crash or arbitrary code execution. The attacker might use malformed nested attributes or extremely long strings within a single attribute.
  • Impact: Denial of Service (DoS) through application crash. Potential for Remote Code Execution (RCE) if the overflow can be controlled to overwrite critical memory regions.
  • Affected Component: YYTextParser (specifically, functions related to parsing attributes, text segments, and nested structures). This includes functions like those handling string copying, length calculations, and memory allocation within the parser.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Robust Input Validation: Implement strict length limits and character restrictions before passing any data to YYTextParser. Validate the structure of the input to ensure it conforms to expected formats.
    • Fuzz Testing: Perform extensive fuzz testing of YYTextParser with a wide range of malformed and oversized inputs.
    • Memory Safety: Compile YYText with memory safety features (e.g., AddressSanitizer) to detect and prevent buffer overflows.
    • Code Review: Manually review the YYTextParser code for potential buffer overflow vulnerabilities, paying close attention to string handling and memory allocation.

Threat: Denial of Service via Recursive Layout in YYTextLayout

  • Description: An attacker provides input with deeply nested or cyclical layout constraints (e.g., attachments referencing other attachments in a loop, or excessively nested text containers). This forces YYTextLayout to perform excessive calculations, potentially leading to a stack overflow or excessive CPU consumption, causing the application to become unresponsive.
  • Impact: Denial of Service (DoS) due to application unresponsiveness or crash.
  • Affected Component: YYTextLayout (specifically, functions related to calculating layout, resolving constraints, and handling nested elements). This includes functions that recursively traverse the layout tree.
  • Risk Severity: High
  • Mitigation Strategies:
    • Depth Limiting: Impose a strict limit on the nesting depth of layout elements (attachments, containers, etc.) before passing data to YYTextLayout.
    • Cycle Detection: Implement mechanisms to detect and prevent cyclical layout dependencies.
    • Resource Limits: Set resource limits (e.g., CPU time, memory usage) for the layout process to prevent it from consuming excessive resources.
    • Asynchronous Layout: Perform layout calculations in a background thread to prevent blocking the main thread and maintain application responsiveness.

Threat: Unsafe Deserialization in NSCoding Implementation (if used)

  • Description: If YYText uses NSCoding for serialization and deserialization of its data structures, and if an attacker can control the serialized data, they might be able to exploit vulnerabilities in the NSCoding implementation (or custom class implementations) to achieve arbitrary code execution. This is a common vulnerability pattern with object serialization. The attacker could provide a crafted serialized object that, when deserialized by YYText, triggers the execution of malicious code.
  • Impact: Remote Code Execution (RCE).
  • Affected Component: Any YYText classes that implement NSCoding (e.g., YYTextLayout, YYTextAttachment, custom subclasses). Specifically, the initWithCoder: methods.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Avoid NSCoding if Possible: If possible, avoid using NSCoding for untrusted data. Consider using a more secure serialization format like JSON or Protocol Buffers with strict schema validation.
    • Secure Coding Practices: If NSCoding must be used, follow secure coding practices for NSCoding. Use NSSecureCoding and validate the class type of each object during deserialization within the initWithCoder: method. Do not assume the type of any object being deserialized.
    • Input Validation: Never deserialize data from untrusted sources directly. Validate and sanitize the serialized data before attempting to deserialize it. This validation should check for structural integrity and expected data types.

Threat: Improper handling of URL schemes in YYTextView

  • Description: An attacker crafts a rich text string containing malicious URLs with custom or unexpected URL schemes. When a user interacts with these URLs (e.g., taps on them), the application, through YYTextView's handling, might be tricked into executing unintended actions or opening malicious applications. This relies on YYTextView's URL handling logic and its interaction with the system's URL scheme handling.
    • Impact: Potentially leading to phishing attacks, launching of malicious applications, or execution of arbitrary code if a custom URL scheme handler (that YYTextView invokes) is vulnerable.
    • Affected Component: YYTextView (specifically, the handling of URL interactions and delegate methods related to URL opening, such as textView:shouldInteractWithURL:inRange:interaction:).
    • Risk Severity: High
    • Mitigation Strategies:
      • URL Scheme Whitelisting: Implement a strict whitelist of allowed URL schemes within the YYTextViewDelegate. Only allow known-safe schemes (e.g., http, https, mailto). Block or sanitize any URLs with unrecognized or potentially dangerous schemes.
      • Delegate Validation: If using YYTextViewDelegate methods to handle URL interactions, carefully validate the URL before taking any action. Do not blindly open URLs without checking their safety and scheme. This validation should occur within the delegate method.
      • User Confirmation: Prompt the user for confirmation before opening any URL, especially if it uses a non-standard scheme. This provides an additional layer of defense even if validation fails.
      • Sandboxing (if applicable): If custom URL scheme handling is necessary, and those schemes are handled by other parts of the application, consider performing the handling within a sandboxed environment to limit the potential impact of exploits. This is less directly related to YYText itself, but relevant to the overall threat.