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Mitigation Strategies Analysis for openresty/openresty

Mitigation Strategy: 1. Input Validation and Sanitization in Lua Scripts

  • Mitigation Strategy: Input Validation and Sanitization in Lua Scripts

  • Description:

    1. Identify Lua Input Points: Pinpoint all locations within your Lua scripts where external data is processed. This includes data from ngx.req methods (URI arguments, POST arguments, headers, cookies) and any external data sources accessed by Lua.
    2. Define Lua Validation Rules: For each input point in Lua, establish validation rules based on expected data types, formats, lengths, and allowed characters. Prioritize whitelisting valid inputs.
    3. Implement Lua Validation Logic: Write Lua code to validate inputs against defined rules within your Lua scripts. Utilize Lua's string manipulation functions and libraries.
    4. Sanitize Lua Inputs: If validation succeeds, sanitize the input in Lua to prevent injection attacks. Use parameterized queries for database interactions from Lua, HTML escaping for outputting data in HTML from Lua, and careful escaping for any command execution (which should be minimized in Lua).
    5. Handle Invalid Lua Inputs: Implement error handling in Lua for invalid inputs. Return informative error responses (avoiding sensitive details), log invalid input attempts, and reject requests as needed.

  • Threats Mitigated:

    • SQL Injection (High Severity): Prevents SQL injection vulnerabilities arising from unsanitized inputs processed by Lua scripts interacting with databases.
    • Command Injection (High Severity): Reduces command injection risks if Lua scripts (insecurely) execute system commands with unsanitized inputs.
    • Lua Code Injection (High Severity): Mitigates Lua code injection if Lua scripts dynamically evaluate or execute code based on unsanitized inputs.
    • Cross-Site Scripting (XSS) (Medium Severity): Prevents XSS vulnerabilities if Lua scripts generate HTML output with unsanitized user inputs.
    • Path Traversal (Medium Severity): Reduces path traversal risks if Lua scripts handle file paths based on unsanitized user inputs.

  • Impact: Significantly reduces injection vulnerabilities within the Lua scripting layer of OpenResty applications.

  • Currently Implemented: Partially implemented. Input validation exists in Lua for user authentication forms in lua/user_auth.lua.

  • Missing Implementation: Input validation is lacking in many API endpoints handled by Lua scripts, particularly in lua/api_endpoints.lua and lua/data_processing.lua, especially for file uploads, search, and data updates.

Mitigation Strategy: 2. Secure Lua Library Management

  • Mitigation Strategy: Secure Lua Library Management

  • Description:

    1. Lua Library Inventory: Maintain a detailed inventory of all Lua libraries used in your OpenResty project, including both standard Lua libraries and third-party libraries utilized within OpenResty.
    2. Verify Lua Library Sources: For each third-party Lua library, rigorously verify its source. Use reputable sources like LuaRocks or trusted GitHub repositories. Avoid libraries from unknown or untrusted origins.
    3. Lua Library Vulnerability Scanning: Regularly scan Lua library dependencies for known vulnerabilities. Manually check security advisories or explore Lua-specific dependency scanning tools if available.
    4. Keep Lua Libraries Updated: Establish a process for regularly updating Lua libraries used in OpenResty applications to their latest versions, prioritizing security patches. Test updates in staging before production.
    5. Minimize Lua Dependencies: Limit the number of third-party Lua libraries to only those essential for your OpenResty application's functionality to reduce the attack surface.
    6. Lua Library Vendoring: For critical Lua libraries, consider vendoring them within your project to control versions and reduce reliance on external repositories during OpenResty deployments.

  • Threats Mitigated:

    • Dependency Vulnerabilities (High to Critical Severity): Prevents exploitation of vulnerabilities in outdated or compromised Lua libraries used by OpenResty applications.
    • Supply Chain Attacks (Medium to High Severity): Reduces the risk of using malicious Lua libraries from compromised or untrusted sources within the OpenResty environment.

  • Impact: Significantly reduces risks from third-party Lua code within OpenResty applications.

  • Currently Implemented: Partially implemented. A list of Lua libraries exists in docs/lua_dependencies.md, but lacks active maintenance and vulnerability auditing. Sources are generally LuaRocks/GitHub, but without formal verification.

  • Missing Implementation: Implement automated vulnerability scanning for Lua libraries (if tools exist, otherwise manual process). Establish a regular Lua library update schedule and a formal process for vetting new Lua libraries before use in OpenResty.

Mitigation Strategy: 3. Code Review and Static Analysis for Lua Scripts

  • Mitigation Strategy: Code Review and Static Analysis for Lua Scripts

  • Description:

    1. Lua Code Review Process: Implement mandatory code reviews specifically for all Lua code changes in your OpenResty project before merging. Train developers on secure Lua coding practices and OpenResty-specific security concerns.
    2. Security Focus in Lua Reviews: During Lua code reviews, prioritize security aspects: input validation, database interactions (from Lua), external command execution (from Lua), sensitive data handling in Lua, error handling in Lua, and overall Lua script logic for vulnerabilities.
    3. Static Analysis for Lua: Explore and utilize static analysis tools designed for Lua code to automatically detect potential security flaws in your OpenResty Lua scripts. Integrate static analysis into the development workflow.
    4. Address Lua Findings: Actively address security vulnerabilities identified in Lua code reviews or static analysis. Prioritize high-severity findings and track resolved issues.
    5. Regular Lua Code Review: Periodically conduct security-focused code reviews of existing Lua scripts in your OpenResty application, not just new changes.

  • Threats Mitigated:

    • Coding Errors Leading to Vulnerabilities (High to Low Severity): Code review and static analysis detect various Lua coding errors causing vulnerabilities in OpenResty applications.
    • Logic Errors and Business Logic Flaws (Medium to High Severity): Helps identify flaws in Lua application logic exploitable for malicious purposes within OpenResty.

  • Impact: Significantly reduces vulnerabilities introduced through Lua coding errors in OpenResty applications.

  • Currently Implemented: Partially implemented. Code reviews occur for major feature branches, but security is not always the primary focus in Lua code reviews.

  • Missing Implementation: Formally integrate security into the Lua code review process. Train developers on secure Lua coding. Explore and implement Lua static analysis tools. Create security-focused Lua code review guidelines and integrate static analysis.

Mitigation Strategy: 4. Principle of Least Privilege in Lua Script Execution

  • Mitigation Strategy: Principle of Least Privilege in Lua Script Execution

  • Description:

    1. Identify Lua Privilege Needs: Analyze each Lua script in your OpenResty application and determine the minimum privileges required for its function. Does it need to execute commands, access the file system, or network resources from Lua?
    2. Restrict Lua Command Execution: Minimize or eliminate the use of Lua functions like os.execute or io.popen. If necessary, rigorously sanitize inputs. Consider safer Lua alternatives.
    3. Limit Lua File System Access: If Lua scripts need file system access, restrict access to specific directories and files using file system permissions. Use chroot or containerization to isolate the Lua execution environment within OpenResty.
    4. Lua Network Access Control: If Lua scripts make network connections, restrict outbound network access to only necessary destinations using firewalls or network policies.
    5. OpenResty Worker User: Ensure OpenResty worker processes run under a dedicated, low-privilege user account, not root.

  • Threats Mitigated:

    • Privilege Escalation (High Severity): Limits the impact of Lua vulnerabilities by restricting privileges available to attackers compromising Lua scripts in OpenResty.
    • Lateral Movement (Medium Severity): Restricts attacker movement within the system if a Lua script in OpenResty is compromised.

  • Impact: Significantly reduces potential damage from exploits targeting Lua scripts in OpenResty.

  • Currently Implemented: Partially implemented. OpenResty workers run as non-root user (nginx). Lua scripts might still have broader file system access than needed.

  • Missing Implementation: Review Lua scripts and restrict file system and network access where possible. Implement stricter controls on command execution from Lua. Implement fine-grained privilege control within the Lua execution environment in OpenResty.

Mitigation Strategy: 5. Careful Handling of Data Between Nginx and Lua

  • Mitigation Strategy: Secure Data Handling Between Nginx and Lua

  • Description:

    1. Minimize Nginx-Lua Data Transfer: Pass only essential data between Nginx and Lua. Avoid unnecessary data transfer.
    2. Sanitize Nginx Variables in Lua: Treat Nginx variables accessed in Lua (headers, client IP) as untrusted input. Sanitize or validate them in Lua before security-sensitive operations within Lua scripts.
    3. Secure Shared Dictionaries: If using Nginx shared dictionaries for data sharing between Nginx and Lua, avoid storing sensitive data in plain text. Encrypt or hash sensitive data in shared dictionaries.
    4. Prevent Sensitive Data in Logs: Avoid logging sensitive data passed between Nginx and Lua in Nginx access or error logs. Configure logging to exclude sensitive information.
    5. Secure Communication Channels (if applicable): If data is exchanged between Nginx and Lua via external channels (sockets, queues), secure these channels with encryption and authentication.

  • Threats Mitigated:

    • Information Disclosure (Medium to High Severity): Improper data handling between Nginx and Lua can expose sensitive data in logs or shared data mechanisms.
    • Data Tampering (Medium Severity): Insecure data transfer between Nginx and Lua could allow interception and modification.
    • Injection Vulnerabilities (Medium Severity): Unsanitized Nginx variables in Lua can become injection vectors.

  • Impact: Reduces data leaks and manipulation risks related to Nginx-Lua interaction in OpenResty.

  • Currently Implemented: Partially implemented. Basic awareness of avoiding logging sensitive data. Shared dictionaries used for caching, but without encryption of sensitive cached data.

  • Missing Implementation: Implement systematic sanitization of Nginx variables used in Lua, especially for security-sensitive operations. Encrypt sensitive data in shared dictionaries. Establish guidelines for secure Nginx-Lua data transfer.

Mitigation Strategy: 6. Optimize Lua Scripts for Performance and Resource Usage

  • Mitigation Strategy: Lua Script Performance Optimization

  • Description:

    1. Lua Profiling: Use Lua profilers (if available in OpenResty) or performance monitoring to identify bottlenecks in Lua scripts within OpenResty.
    2. Optimize Lua Code: Optimize Lua code for efficiency: avoid unnecessary computations, use efficient data structures, minimize string operations, and leverage Lua's performance features.
    3. Lua Caching: Implement caching in Lua to reduce redundant computations and database queries. Utilize Nginx shared dictionaries for caching within OpenResty.
    4. Optimize Lua Database Queries: Optimize database queries executed from Lua scripts for efficiency and security.
    5. Asynchronous Lua Operations: Leverage OpenResty's non-blocking I/O in Lua scripts. Use asynchronous database clients and network libraries in Lua to avoid blocking operations.

  • Threats Mitigated:

    • Resource Exhaustion DoS Attacks (Medium to High Severity): Optimized Lua scripts reduce resource usage, making OpenResty applications less vulnerable to resource exhaustion DoS.
    • Slowloris and similar DoS attacks (Medium Severity): Efficient Lua scripts handle slow requests better, mitigating slow DoS attacks against OpenResty.
    • Performance Issues (Low to Medium Severity): Improves OpenResty application performance and responsiveness.

  • Impact: Reduces susceptibility to resource-based DoS attacks and improves OpenResty application performance.

  • Currently Implemented: Partially implemented. Basic caching using shared dictionaries exists. Database queries are generally optimized, but Lua script performance is not regularly profiled.

  • Missing Implementation: Implement regular Lua script profiling and optimization as part of OpenResty development. Expand caching and ensure efficient resource use in all Lua scripts.