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Threat Model Analysis for yhirose/cpp-httplib

Threat: Slowloris Attack

  • Threat: Slowloris Attack
    • Description: An attacker opens numerous connections to the server and sends HTTP requests very slowly, byte by byte, or sends incomplete requests. The attacker keeps these connections alive as long as possible, tying up server resources and preventing legitimate users from connecting. cpp-httplib's connection handling, if not properly configured, is susceptible to this.
    • Impact: Denial of Service (DoS). Legitimate users are unable to access the application. Server resources (threads, memory, file descriptors) are exhausted.
    • Affected Component: httplib::Server (overall connection handling), potentially httplib::ThreadPool if used. The core issue is how the server manages incoming connections and their associated resources.
    • Risk Severity: High
    • Mitigation Strategies:
      • Use svr.set_read_timeout(...) and svr.set_write_timeout(...) to set short timeouts for reading and writing data on connections. This is crucial for mitigating Slowloris.
      • Use svr.set_max_connections(...) to limit the maximum number of concurrent connections.
      • Consider using an event-driven, non-blocking approach (if your application design allows) to minimize the overhead of idle connections.

Threat: Large Request Body DoS

  • Threat: Large Request Body DoS
    • Description: An attacker sends a request with an extremely large body (e.g., a multi-gigabyte upload). The server, if not configured to limit body size, attempts to read the entire body into memory, leading to resource exhaustion and a potential crash.
    • Impact: Denial of Service (DoS). The server may crash or become unresponsive due to excessive memory consumption.
    • Affected Component: httplib::Request::body, and the handlers that process the request body (e.g., within your svr.Post(...) callback). The vulnerability lies in the lack of a default body size limit.
    • Risk Severity: High
    • Mitigation Strategies:
      • Mandatory: Use svr.set_payload_max_length(...) to set a strict limit on the maximum allowed size of request bodies. This is the primary defense.
      • If large uploads are expected, implement a streaming approach where the request body is processed in chunks without loading the entire body into memory at once. Use the httplib::Request object's callbacks to handle data incrementally.

Threat: Directory Traversal (when serving static files)

  • Threat: Directory Traversal (when serving static files)
    • Description: If using cpp-httplib's built-in file serving capabilities, an attacker uses ../ sequences in a URL to navigate outside the intended directory and access arbitrary files on the server. This is due to insufficient input validation within the file serving logic if not properly implemented by the developer.
    • Impact: Unauthorized access to files on the server, potentially including sensitive configuration files or source code.
    • Affected Component: httplib::Server::set_mount_point(...) and httplib::Server::set_base_dir(...), and crucially, the developer's implementation of request handlers that interact with these functions. The vulnerability is in how the developer uses these functions, not inherently in the functions themselves, but the library provides the mechanism for the vulnerability.
    • Risk Severity: High
    • Mitigation Strategies:
      • Crucially: Sanitize user-provided input used to construct file paths. Normalize paths and reject or carefully handle ../ sequences. This is the developer's responsibility.
      • Use svr.set_base_dir(...) to define a restricted base directory for file serving.
      • Avoid using user input directly in file paths. If necessary, validate it rigorously using a robust path sanitization library.

Threat: Vulnerability in cpp-httplib itself (Hypothetical)

  • Threat: Vulnerability in cpp-httplib itself (Hypothetical - but important to acknowledge)
    • Description: An unknown, hypothetical vulnerability exists within the cpp-httplib library code itself (e.g., a buffer overflow, integer overflow, use-after-free, etc.). This is a threat to any library, and is important to include.
    • Impact: Varies depending on the nature of the vulnerability, potentially ranging from DoS to remote code execution (RCE). Could be Critical.
    • Affected Component: Any part of the cpp-httplib library.
    • Risk Severity: Unknown (but potentially Critical)
    • Mitigation Strategies:
      • Keep cpp-httplib updated to the latest version. This is the most important mitigation for unknown vulnerabilities.
      • Monitor security advisories and vulnerability databases for reports related to cpp-httplib.
      • Perform regular security audits and code reviews of your application, including its interaction with cpp-httplib.
      • Consider fuzz testing cpp-httplib to proactively discover vulnerabilities.