mitigations.md

Mitigation Strategies Analysis for yhirose/cpp-httplib

Mitigation Strategy: Limit Request Size (cpp-httplib Configuration)

• Description:

  1. Determine Payload Limit: Analyze your application's needs and decide on a reasonable maximum size for HTTP request bodies. This should be large enough for legitimate use cases but small enough to prevent abuse and resource exhaustion.
  2. Use set_payload_max_length(): In your server initialization code (where you create the httplib::Server object), call the set_payload_max_length(size_t length) method. Pass the determined maximum size in bytes as the length argument. For example, to limit the payload to 10MB: server.set_payload_max_length(10 * 1024 * 1024);.
  3. Handle Automatic Rejection: cpp-httplib will automatically reject requests exceeding this limit with a 413 Payload Too Large status code. Ensure your application gracefully handles these rejections, although cpp-httplib manages the rejection process itself.
  4. Consider Header Size Limits (Custom Implementation if needed): While cpp-httplib doesn't have a dedicated function for header size limits, if you need to enforce them, you might need to implement custom logic within your request handlers to inspect the raw request data and check header sizes before cpp-httplib fully parses the request. This is a more advanced step and might not be necessary in many cases.

• Threats Mitigated:

  • Denial of Service (DoS) - Payload Based (High Severity): Prevents attackers from sending excessively large requests to overwhelm the server, consuming resources (memory, bandwidth) and leading to service disruption.
  • Buffer Overflow (Potential - Low Severity): Acts as a defense-in-depth measure against potential buffer overflows that might arise from processing extremely large inputs, although cpp-httplib is designed to be memory-safe.

• Impact:

  • DoS - Payload Based: High - Effectively mitigates payload-based DoS attacks by limiting the resource consumption from oversized requests.
  • Buffer Overflow: Low - Provides a minor layer of protection as a preventative measure.

• Currently Implemented:

  • A default payload limit of 10MB is set globally for the server in src/server_config.cpp using server.set_payload_max_length(10 * 1024 * 1024);.

• Missing Implementation:

  • No explicit header size limits are implemented using cpp-httplib features. If header-based DoS is a significant concern, custom header size checking might be considered.

Mitigation Strategy: Implement Security Headers (cpp-httplib Header Manipulation)

• Description:

  1. Identify Necessary Security Headers: Determine which security headers are relevant for your application based on its security requirements and the threats you want to mitigate. Common security headers include: Content-Security-Policy, X-Frame-Options, X-Content-Type-Options, Strict-Transport-Security, Referrer-Policy, and Permissions-Policy.
  2. Use set_header() in Route Handlers: Within each of your cpp-httplib route handlers (using Get, Post, etc.), use the response.set_header(header_name, header_value) method to add security headers to the HTTP response.
  3. Set Appropriate Header Values: Carefully configure the values of each security header according to best practices and your application's specific needs. Refer to security header documentation (e.g., OWASP recommendations) for guidance on setting secure values. For example:

     server.Get("/protected-page", [](const httplib::Request& req, httplib::Response& res) {
         res.set_header("Content-Security-Policy", "default-src 'self'");
         res.set_header("X-Frame-Options", "DENY");
         // ... rest of handler logic ...
     });

  4. Apply Headers Consistently: Ensure that security headers are applied consistently across all relevant response types and routes in your application. Consider creating helper functions or middleware to streamline header setting and avoid repetition.

• Threats Mitigated:

  • Cross-Site Scripting (XSS) (High Severity): Content-Security-Policy header significantly reduces XSS risk by controlling the sources from which the browser is allowed to load resources.
  • Clickjacking (Medium Severity): X-Frame-Options and Content-Security-Policy (with frame-ancestors directive) can prevent clickjacking attacks by controlling whether the page can be embedded in frames.
  • MIME-Sniffing Attacks (Low Severity): X-Content-Type-Options: nosniff prevents browsers from MIME-sniffing responses away from the declared content type, reducing potential for certain types of attacks.
  • Insecure HTTP Connections (Medium Severity): Strict-Transport-Security (HSTS) enforces HTTPS connections for returning visitors, reducing the risk of downgrade attacks and man-in-the-middle attacks.
  • Referer Leakage (Low to Medium Severity): Referrer-Policy controls how much referrer information is sent with requests, potentially reducing information leakage.
  • Feature Policy Abuse (Low to Medium Severity): Permissions-Policy (formerly Feature-Policy) allows controlling browser features, mitigating potential abuse of features like geolocation or microphone access.

• Impact:

  • XSS: High - CSP is a very effective mitigation for many types of XSS.
  • Clickjacking: Medium - X-Frame-Options and CSP provide good protection against clickjacking.
  • MIME-Sniffing Attacks: Low - Minor but helpful security enhancement.
  • Insecure HTTP Connections: Medium - HSTS significantly improves HTTPS enforcement for returning users.
  • Referer Leakage: Low to Medium - Reduces information leakage depending on policy and application context.
  • Feature Policy Abuse: Low to Medium - Reduces risk depending on the features controlled and application vulnerabilities.

• Currently Implemented:

  • X-Frame-Options: DENY is set globally for all responses in src/server_config.cpp using a middleware function.

• Missing Implementation:

  • Content-Security-Policy is not implemented. This is a crucial header for XSS mitigation and should be implemented.
  • X-Content-Type-Options, Strict-Transport-Security, Referrer-Policy, and Permissions-Policy are not implemented. Consider adding these based on application needs and security posture.
  • CSP is not configured, and its implementation should be carefully designed based on the application's resource loading requirements.

Mitigation Strategy: Secure Cookie Handling (cpp-httplib Cookie Management)

• Description:

  1. Use set_cookie() for Setting Cookies: When setting cookies in your cpp-httplib route handlers, use the response.set_cookie(const char* name, const char* value) method.
  2. Set HttpOnly Attribute: To prevent client-side JavaScript from accessing cookies (mitigating XSS-based cookie theft), append the ; HttpOnly attribute to the cookie value string when calling set_cookie(). Example: res.set_cookie("sessionid", "your_session_value; HttpOnly");
  3. Set Secure Attribute: To ensure cookies are only transmitted over HTTPS, append the ; Secure attribute. Example: res.set_cookie("sessionid", "your_session_value; Secure; HttpOnly"); (Important: Only set Secure if your application is running over HTTPS).
  4. Set SameSite Attribute: To mitigate Cross-Site Request Forgery (CSRF) attacks, consider setting the SameSite attribute. Common values are Strict or Lax. Append ; SameSite=Strict or ; SameSite=Lax to the cookie value string. Choose the appropriate value based on your application's CSRF protection needs. Example: res.set_cookie("sessionid", "your_session_value; Secure; HttpOnly; SameSite=Strict");
  5. Review Cookie Usage: Audit your application's cookie usage to ensure that cookies are only used when necessary and that all cookies are configured with appropriate security attributes.

• Threats Mitigated:

  • Cross-Site Scripting (XSS) - Cookie Theft (High Severity): HttpOnly attribute prevents JavaScript from accessing cookies, reducing the risk of attackers stealing session cookies or other sensitive cookie data through XSS vulnerabilities.
  • Cross-Site Request Forgery (CSRF) (Medium to High Severity): SameSite attribute provides a degree of protection against CSRF attacks by controlling when cookies are sent in cross-site requests. The effectiveness depends on the chosen SameSite value and browser compatibility.
  • Man-in-the-Middle Attacks - Cookie Exposure (Medium Severity): Secure attribute ensures cookies are only transmitted over HTTPS, preventing them from being intercepted in plaintext over insecure HTTP connections.

• Impact:

  • XSS - Cookie Theft: High - HttpOnly is a very effective mitigation for cookie theft via XSS.
  • CSRF: Medium to High - SameSite provides good CSRF protection, especially SameSite=Strict, but might require adjustments based on application functionality.
  • Man-in-the-Middle Attacks - Cookie Exposure: Medium - Secure attribute is essential for protecting cookie confidentiality over HTTPS.

• Currently Implemented:

  • Cookies are used for session management in src/session_manager.cpp.
  • HttpOnly attribute is set for session cookies in src/session_manager.cpp.

• Missing Implementation:

  • Secure attribute is not consistently set for all cookies, especially in development environments where HTTPS might not be enforced. Ensure Secure is always set in production and ideally also in secure development/staging environments.
  • SameSite attribute is not implemented for session cookies or other cookies. Consider implementing SameSite=Strict or SameSite=Lax for session cookies to enhance CSRF protection.

Mitigation Strategy: TLS/SSL Configuration (cpp-httplib HTTPS Server)

• Description:

  1. Enable HTTPS Server: Use cpp-httplib::SSLServer instead of cpp-httplib::Server to create an HTTPS server. This requires compiling cpp-httplib with SSL support (e.g., linking against OpenSSL).
  2. Provide Certificate and Private Key: When creating the SSLServer object, you need to provide the paths to your SSL certificate file and private key file. Use the constructor httplib::SSLServer(const char *cert_path, const char *private_key_path). Ensure these files are securely stored and accessible only to the server process.
  3. Configure Cipher Suites (Advanced): cpp-httplib might allow configuration of TLS cipher suites through underlying SSL library options (e.g., OpenSSL). If so, configure strong cipher suites and disable weak or outdated ones. This might involve using set_socket_options or similar mechanisms provided by cpp-httplib to pass options to the underlying SSL library.
  4. Enforce HTTPS Redirection (Application Logic): If you want to ensure all traffic is over HTTPS, implement HTTP to HTTPS redirection in your application logic. For example, if a user accesses the HTTP version of your site, redirect them to the HTTPS version. This is application-level logic and not directly a cpp-httplib feature, but crucial for HTTPS enforcement.
  5. Keep TLS/SSL Library Updated: Ensure the underlying TLS/SSL library used by cpp-httplib (e.g., OpenSSL) is kept updated to the latest version to patch known vulnerabilities. This is a general system maintenance task but critical for HTTPS security.

• Threats Mitigated:

  • Man-in-the-Middle Attacks (High Severity): HTTPS encryption protects communication between the client and server from eavesdropping and tampering by attackers in the network.
  • Data Confidentiality and Integrity (High Severity): HTTPS ensures the confidentiality and integrity of data transmitted between the client and server, protecting sensitive information like passwords, session tokens, and personal data.
  • Downgrade Attacks (Medium Severity): HSTS (implemented via security headers, see above) and proper TLS/SSL configuration help prevent downgrade attacks where attackers try to force the client to use insecure HTTP instead of HTTPS.

• Impact:

  • Man-in-the-Middle Attacks: High - HTTPS is essential for mitigating MITM attacks and ensuring secure communication.
  • Data Confidentiality and Integrity: High - HTTPS provides crucial protection for sensitive data.
  • Downgrade Attacks: Medium - TLS/SSL configuration and HSTS contribute to preventing downgrade attacks.

• Currently Implemented:

  • The application is currently configured to run only over HTTP using httplib::Server. HTTPS is not enabled.

• Missing Implementation:

  • HTTPS is not implemented. Switch to httplib::SSLServer and configure certificate and private key paths in src/server_config.cpp to enable HTTPS.
  • Cipher suite configuration is not explicitly managed. Investigate if cpp-httplib provides mechanisms to configure cipher suites and implement secure cipher suite settings.
  • HTTP to HTTPS redirection is not implemented. Add redirection logic in src/server.cpp or using middleware to redirect HTTP requests to HTTPS.

Mitigation Strategy: Connection Limits and Timeouts (cpp-httplib Socket Options)

• Description:

  1. Set Connection Timeout: Use server.set_socket_options(socket_options) with appropriate socket options to set connection timeouts. Specifically, explore options like SO_RCVTIMEO (receive timeout) and SO_SNDTIMEO (send timeout) to limit the time the server will wait for data to be received or sent on a connection. Consult your operating system's socket options documentation for available options and their usage.
  2. Set Socket Timeout (General Timeout): Consider using SO_TIMEOUT if supported by your OS and cpp-httplib's socket option handling, to set a general timeout for socket operations.
  3. Operating System Level Connection Limits (External to cpp-httplib): While cpp-httplib itself might not directly provide high-level connection limiting features, rely on operating system level mechanisms (e.g., ulimit on Linux, firewall rules, or load balancer configurations) to limit the number of concurrent connections to your server. These are external to cpp-httplib but essential for overall DoS prevention.
  4. Application Level Request Timeouts (Application Logic): Implement application-level timeouts for request processing within your route handlers. If a request takes too long to process, terminate the processing and return an error response. This prevents long-running requests from consuming resources indefinitely.

• Threats Mitigated:

  • Denial of Service (DoS) - Slowloris/Slow Read Attacks (Medium to High Severity): Connection timeouts can help mitigate slowloris and slow read attacks by closing connections that are idle or transmitting data very slowly, preventing resource exhaustion from lingering connections.
  • Resource Starvation (Medium Severity): Timeouts prevent connections and requests from hanging indefinitely, freeing up server resources and preventing resource starvation for legitimate users.

• Impact:

  • DoS - Slowloris/Slow Read Attacks: Medium to High - Connection timeouts are effective in mitigating slow connection attacks.
  • Resource Starvation: Medium - Improves resource management and prevents resource starvation from long-running operations.

• Currently Implemented:

  • No explicit connection timeouts or socket options are currently configured using cpp-httplib's set_socket_options.

• Missing Implementation:

  • Implement connection timeouts using server.set_socket_options to set appropriate socket timeout values. Research suitable timeout values for your application and operating system.
  • Application-level request timeouts are not implemented within route handlers. Consider adding logic to monitor request processing time and terminate long-running requests.
  • Operating system level connection limits are not explicitly configured as part of the application deployment. Ensure appropriate OS-level limits are in place in the deployment environment.