attack-surface.md

Attack Surface Analysis for libuv/libuv

Attack Surface: Event Loop Saturation

• Description: An attacker floods the application with events, overwhelming the libuv event loop and causing denial of service.
• How libuv contributes: Libuv's core functionality is the event loop. Applications rely on it to process all I/O and timers. If the event loop is saturated, the application becomes unresponsive because libuv is unable to process events in a timely manner.
• Example: A malicious client rapidly opens thousands of TCP connections to a server application using libuv, exceeding the server's capacity to handle new connections and process existing ones within the event loop's processing time.
• Impact: Denial of Service (DoS), application unresponsiveness, service disruption.
• Risk Severity: High
• Mitigation Strategies:
  • Implement connection rate limiting at the application level.
  • Set maximum connection limits to prevent excessive connection attempts.
  • Use connection queues with backpressure mechanisms to manage incoming connection requests.
  • Monitor event loop latency and CPU usage to detect saturation attempts.
  • Employ load balancing and scaling to distribute load across multiple instances.

Attack Surface: File Descriptor Exhaustion

• Description: Attacker exhausts available file descriptors by rapidly opening resources (sockets, files) without proper closure, leading to application failure.
• How libuv contributes: Libuv manages file descriptors for various I/O operations like sockets, files, and pipes. Improper resource management in the application using libuv can lead to descriptor leaks, as libuv relies on the application to correctly close handles.
• Example: An attacker sends a series of requests that cause the application to open sockets using libuv but due to a bug in the application's handle closing logic, these sockets are not properly closed. Repeated attacks exhaust the system's file descriptor limit, preventing the application from accepting new connections or opening files.
• Impact: Denial of Service (DoS), application crashes, inability to handle new connections or file operations.
• Risk Severity: High
• Mitigation Strategies:
  • Implement robust resource management within the application, ensuring timely closure of all libuv handles (sockets, files, etc.).
  • Use resource limits at the OS level (e.g., ulimit on Linux) to restrict the maximum number of file descriptors an application can use as a last resort.
  • Employ connection pooling and resource reuse techniques to minimize the creation of new file descriptors.
  • Regularly audit application code for resource leaks, especially in error handling paths and asynchronous operations involving libuv handles.

Attack Surface: Memory Exhaustion (via Libuv Usage)

• Description: Improper memory management in application code interacting with libuv leads to memory leaks or excessive allocation, causing application crash or DoS.
• How libuv contributes: While libuv itself is memory-efficient, applications using it must correctly manage memory associated with handles, buffers, and callbacks. Memory leaks in callbacks or data processing related to libuv events directly impact the application's stability when using libuv's asynchronous features.
• Example: A memory leak in a callback function that processes data received from a socket using uv_read. If the callback allocates memory to process the received data but fails to free it under certain conditions (e.g., error handling paths, specific data patterns), repeated network activity can lead to memory exhaustion and application crash.
• Impact: Denial of Service (DoS), application crashes, performance degradation.
• Risk Severity: High
• Mitigation Strategies:
  • Thoroughly review and test application code, especially libuv event callbacks, for memory leaks.
  • Use memory profiling tools (e.g., Valgrind, AddressSanitizer) during development and testing to detect memory leaks and excessive memory allocation.
  • Implement resource limits and safeguards against unbounded data accumulation in buffers used with libuv operations.
  • Ensure proper cleanup of allocated memory in all libuv callbacks and during handle closure.

Attack Surface: Path Traversal via File System Operations

• Description: Unsanitized user-controlled paths used with libuv file system APIs allow attackers to access or manipulate files outside intended directories.
• How libuv contributes: Libuv provides file system APIs (uv_fs_*) that applications use to interact with the file system. If these APIs are used with untrusted input without proper validation, path traversal vulnerabilities can arise directly from the application's use of libuv's file system functionalities.
• Example: An application uses uv_fs_open with a file path provided by a user request. An attacker crafts a malicious path like ../../../../etc/passwd and sends it to the application. If the application doesn't sanitize this path before passing it to uv_fs_open, libuv will attempt to open the file at the attacker-controlled path, potentially exposing sensitive system files.
• Impact: Information Disclosure, unauthorized file access, potential data manipulation or application compromise.
• Risk Severity: High
• Mitigation Strategies:
  • Sanitize and validate all user-provided file paths before using them with libuv file system APIs.
  • Use allowlists to define permitted directories and file paths, restricting access to only necessary locations.
  • Employ path canonicalization techniques to resolve symbolic links and .. components, preventing traversal attempts.
  • Implement the principle of least privilege for file system access, ensuring the application only has the necessary permissions.

Attack Surface: Command Injection via Child Process Spawning

• Description: Unsanitized user input used in uv_spawn arguments allows attackers to execute arbitrary commands on the server.
• How libuv contributes: Libuv's uv_spawn API is used to create and manage child processes. If command arguments or the command itself are constructed using untrusted user input without proper sanitization before being passed to uv_spawn, it creates a direct pathway for command injection through libuv's process spawning functionality.
• Example: An application uses uv_spawn to execute a command based on user-provided input, such as processing a filename. An attacker injects malicious shell commands into the filename input, like ; rm -rf /. If the application directly passes this unsanitized input to uv_spawn, libuv will execute the command, leading to arbitrary command execution on the server with the application's privileges.
• Impact: Remote Code Execution (RCE), complete system compromise, data breach, and full control over the application and potentially the underlying system.
• Risk Severity: Critical
• Mitigation Strategies:
  • Avoid constructing shell commands directly from user input.
  • Strictly sanitize and validate all input used in uv_spawn arguments, including command name and arguments.
  • Use parameterized commands or safer alternatives to shell execution if possible, such as directly invoking executables without shell interpretation.
  • Apply the principle of least privilege for child process execution, limiting the permissions of spawned processes.

Attack Surface: Unsafe Handling of External Data in Callbacks

• Description: Lack of input validation and sanitization in libuv event callbacks processing external data leads to vulnerabilities like buffer overflows, format string bugs, and injection attacks.
• How libuv contributes: Libuv's asynchronous nature relies heavily on callbacks to handle events like data received on sockets or file system events. If application code within these callbacks processes external data received via libuv without proper validation, it directly exposes the application to vulnerabilities arising from unsafely handled data within the libuv event processing flow.
• Example: A buffer overflow vulnerability in a callback function that processes data received from a network socket using uv_read_cb. If the callback directly copies the received data into a fixed-size buffer without checking the data length, an attacker can send data exceeding the buffer size, leading to a buffer overflow and potentially Remote Code Execution.
• Impact: Remote Code Execution (RCE), Denial of Service (DoS), data corruption, information disclosure, depending on the specific vulnerability exploited.
• Risk Severity: Critical
• Mitigation Strategies:
  • Treat all data received through libuv callbacks as untrusted and potentially malicious.
  • Implement robust input validation and sanitization within all libuv callback functions before processing or using the data.
  • Use safe memory handling practices to prevent buffer overflows, such as using bounds-checking functions or dynamic memory allocation.
  • Employ secure coding practices to avoid injection vulnerabilities (e.g., SQL injection, command injection) when processing data received in callbacks.
  • Utilize memory-safe programming languages or libraries where appropriate to mitigate memory-related vulnerabilities.