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attack-surface.md

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Attack Surface Analysis for libuv/libuv

Attack Surface: File System Access (Path Traversal & Symlink Attacks)

  • Description: Exploitation of vulnerabilities related to file system operations where libuv's APIs are used to access files or directories based on attacker-controlled paths, leading to unauthorized access or manipulation.
  • How libuv Contributes: libuv provides the core file system APIs (e.g., uv_fs_open, uv_fs_read, uv_fs_write, uv_fs_readdir, uv_fs_lstat). Misuse of these APIs, particularly with insufficient path sanitization or improper handling of symbolic links, directly enables these attacks.
  • Example: An attacker provides a path like ../../../../etc/passwd to a function that uses uv_fs_open without proper sanitization, allowing them to read the system's password file. Or, an attacker creates a symlink that points to a sensitive file, and the application, using libuv functions, follows the symlink without checking.
  • Impact: Unauthorized access to sensitive files, data modification, potential code execution (if configuration files are overwritten).
  • Risk Severity: Critical (if sensitive files are accessible) to High.
  • Mitigation Strategies:
    • Strict Path Validation: Implement rigorous validation of all user-supplied file paths before passing them to libuv functions. Use a whitelist approach, allowing access only to explicitly permitted directories and files.
    • Avoid Relative Paths: Prefer absolute paths and avoid constructing paths based on user input.
    • Symlink Handling: Use uv_fs_lstat to check for symbolic links and handle them appropriately. Consider using O_NOFOLLOW with uv_fs_open (where available) to prevent following symbolic links.
    • Least Privilege: Run the application with the minimum necessary file system permissions.

Attack Surface: Network Input Handling (Buffer Overflows)

  • Description: Vulnerabilities arising from processing network data where libuv's networking APIs are used, and incorrect buffer management in callbacks leads to buffer overflows.
  • How libuv Contributes: libuv provides the core networking APIs (e.g., uv_tcp_bind, uv_tcp_connect, uv_read_start, uv_write). The vulnerability arises from how the application uses these APIs, specifically in the uv_read_cb and uv_write_cb callbacks.
  • Example: An attacker sends a large, malformed packet to a server using libuv. The uv_read_cb callback doesn't properly check the nread parameter and copies data beyond the allocated buffer's boundaries.
  • Impact: Remote code execution (RCE), denial-of-service, data corruption.
  • Risk Severity: Critical (for RCE) to High.
  • Mitigation Strategies:
    • Robust Buffer Management: Carefully check buffer sizes in uv_read_cb and uv_write_cb. Ensure nread is within the bounds of the allocated buffer. Use appropriate buffer allocation and deallocation techniques.
    • Input Validation: Validate all incoming network data according to the expected protocol before processing it within the libuv callbacks.

Attack Surface: Process Spawning (Command Injection)

  • Description: Vulnerabilities related to executing external processes via libuv's uv_spawn function, where attacker-controlled input is used to construct the command or arguments, leading to arbitrary command execution.
  • How libuv Contributes: libuv provides the uv_spawn function. The vulnerability is a direct result of how the application uses this function, specifically the insecure construction of commands.
  • Example: An application uses uv_spawn to run a system utility. The command is constructed by concatenating a string with user input: system("my_utility " + user_input). An attacker provides input like "; rm -rf /", leading to the execution of a destructive command.
  • Impact: Arbitrary command execution, complete system compromise, data loss, privilege escalation.
  • Risk Severity: Critical.
  • Mitigation Strategies:
    • Avoid Shell Interpretation: Never construct commands directly from user input. Use the args array in uv_process_options_t to pass arguments separately, preventing shell interpretation.
    • Whitelist Commands: If possible, use a whitelist of allowed commands and arguments.
    • Input Sanitization: Rigorously sanitize and validate all user input before passing it to uv_spawn, even when using the args array.
    • Least Privilege: Run the application and spawned processes with the minimum necessary privileges.

Attack Surface: libuv Internal Bugs (Zero-Days - High Impact)

  • Description: Undiscovered vulnerabilities within the libuv library itself that could lead to high-impact exploits.
  • How libuv Contributes: This is inherent to using any third-party library, including libuv. The vulnerability exists within libuv's code.
  • Example: A zero-day vulnerability is discovered in libuv's handling of TCP connections, allowing for remote code execution.
  • Impact: Varies, but focused on high-impact scenarios like remote code execution or complete denial-of-service.
  • Risk Severity: Critical.
  • Mitigation Strategies:
    • Stay Updated: Keep libuv updated to the latest stable version, applying security patches promptly.
    • Monitor Advisories: Monitor security advisories and mailing lists related to libuv.
    • Defense in Depth: Implement multiple layers of security so that a single vulnerability in libuv doesn't lead to a complete compromise. This includes strong input validation, least privilege, and network segmentation.
    • Rapid Patching Plan: Have a well-defined process for rapidly deploying updates in response to newly discovered vulnerabilities.