Skip to content

Latest commit

 

History

History
173 lines (146 loc) · 17.5 KB

sec-design-deep-analysis.md

File metadata and controls

173 lines (146 loc) · 17.5 KB

Okay, let's perform a deep security analysis of wrk based on the provided security design review.

1. Objective, Scope, and Methodology

  • Objective: To conduct a thorough security analysis of the wrk HTTP benchmarking tool, focusing on its key components, identifying potential vulnerabilities, and recommending mitigation strategies. The analysis will consider the tool's design, code (inferred from documentation and general knowledge of similar tools), and intended usage. The primary goal is to identify security risks within wrk itself, not the systems it tests.
  • Scope: The analysis will cover the following key components of wrk:
    • Command Line Interface (CLI)
    • Request Generator
    • Response Processor
    • Reporter
    • Lua Engine (and interaction with user-provided Lua scripts)
    • Build and Deployment processes
    • Dependencies (LuaJIT, OpenSSL, and others inferred from the Makefile and common practice)
  • Methodology:
    1. Architecture and Component Inference: Based on the C4 diagrams and descriptions, we'll infer the likely internal architecture and data flow within wrk. Since we don't have direct access to the code, this will involve some educated assumptions based on how similar benchmarking tools are typically built.
    2. Threat Modeling: For each component, we'll identify potential threats using a combination of STRIDE (Spoofing, Tampering, Repudiation, Information Disclosure, Denial of Service, Elevation of Privilege) and consideration of the tool's specific purpose.
    3. Vulnerability Analysis: We'll analyze the potential vulnerabilities arising from the identified threats.
    4. Mitigation Recommendations: We'll propose specific, actionable mitigation strategies to address the identified vulnerabilities. These will be tailored to wrk's design and usage.

2. Security Implications of Key Components

We'll break down each component, identify threats, analyze vulnerabilities, and suggest mitigations.

  • 2.1 Command Line Interface (CLI)

    • Threats:
      • Tampering: Maliciously crafted command-line arguments could lead to unexpected behavior, crashes, or potentially code execution.
      • Information Disclosure: Poorly handled error messages might reveal information about the system running wrk.
      • Denial of Service: Invalid or excessively large arguments could cause wrk to consume excessive resources or crash.
    • Vulnerabilities:
      • Buffer Overflows: If argument parsing is not handled carefully, long arguments could overflow buffers, potentially leading to crashes or code execution (especially in C).
      • Integer Overflows: Incorrect handling of numeric arguments (threads, connections, duration) could lead to integer overflows, resulting in unexpected behavior.
      • Format String Vulnerabilities: If arguments are directly used in printf-like functions without proper sanitization, format string vulnerabilities could exist.
      • Argument Injection: If arguments are passed to shell commands without proper escaping, command injection vulnerabilities could be present.
    • Mitigation Strategies:
      • Robust Input Validation: Implement strict validation of all command-line arguments:
        • Check for expected data types (integer, string, etc.).
        • Enforce length limits.
        • Validate numeric ranges (e.g., threads must be > 0).
        • Use a dedicated argument parsing library (e.g., getopt or a more robust alternative) to handle argument parsing securely.
      • Avoid Shell Commands: Minimize the use of shell commands. If necessary, use system calls directly (e.g., execve) and never construct shell commands using user-provided input without extremely careful sanitization and escaping.
      • Safe String Handling: Use safe string handling functions (e.g., snprintf instead of sprintf) to prevent buffer overflows.
      • Limit Error Message Detail: Avoid revealing sensitive system information in error messages.

  • 2.2 Request Generator

    • Threats:
      • Tampering: Malicious Lua scripts or manipulated internal data structures could alter the generated requests, leading to unexpected behavior or attacks against the target server.
      • Denial of Service: The request generator itself could be exploited to consume excessive resources on the machine running wrk.
    • Vulnerabilities:
      • HTTP Request Smuggling: If wrk doesn't properly handle HTTP/1.1 chunked encoding or other request features, it might be vulnerable to request smuggling attacks (although this is primarily a concern for the target server, wrk should still generate valid requests).
      • Resource Exhaustion: Poorly managed threads or connections could lead to resource exhaustion on the benchmarking machine.
      • Lua Script Injection: Vulnerabilities in the Lua Engine's integration with the Request Generator could allow malicious scripts to interfere with request generation.
    • Mitigation Strategies:
      • Validate Generated Requests: Before sending requests, perform basic validation to ensure they conform to HTTP standards (e.g., valid headers, correct formatting). This helps prevent accidental request smuggling issues.
      • Resource Limits: Implement limits on the number of threads, connections, and open file descriptors to prevent resource exhaustion.
      • Secure Lua Integration: Carefully review the interaction between the Request Generator and the Lua Engine. Ensure that the Lua API exposed to scripts is minimal and well-defined, limiting the script's ability to interfere with core wrk functionality.
      • Connection Pooling and Reuse: Implement connection pooling to reduce the overhead of establishing new connections for each request.

  • 2.3 Response Processor

    • Threats:
      • Tampering: Malicious responses from the server (if compromised) could potentially exploit vulnerabilities in the Response Processor.
      • Information Disclosure: The Response Processor might inadvertently leak information about the target server or the benchmarking process.
      • Denial of Service: Malformed or excessively large responses could cause the Response Processor to crash or consume excessive resources.
    • Vulnerabilities:
      • Buffer Overflows: If response headers or bodies are not handled carefully, buffer overflows could occur.
      • Integer Overflows: Incorrect handling of response sizes or timing data could lead to integer overflows.
      • XML/JSON Parsing Vulnerabilities: If wrk parses responses (e.g., for API testing), vulnerabilities in the XML or JSON parser could be exploited.
      • Lua Script Interaction: Vulnerabilities in the Lua Engine's interaction with the Response Processor could allow malicious scripts to access or modify response data inappropriately.
    • Mitigation Strategies:
      • Robust Input Validation: Validate response headers and bodies:
        • Enforce length limits.
        • Check for expected content types (if applicable).
      • Safe String Handling: Use safe string handling functions to prevent buffer overflows.
      • Secure Parsing: If parsing XML or JSON, use a well-vetted and up-to-date parser known to be secure.
      • Secure Lua Integration: Carefully review the interaction between the Response Processor and the Lua Engine. Limit the script's access to response data and prevent it from interfering with core wrk functionality.
      • Resource Limits: Implement limits on the size of responses that wrk will process to prevent denial-of-service attacks.

  • 2.4 Reporter

    • Threats:
      • Tampering: Manipulated internal data structures could lead to incorrect or misleading results being reported.
      • Information Disclosure: Poorly formatted output or error messages could reveal information about the system running wrk.
    • Vulnerabilities:
      • Format String Vulnerabilities: If results are formatted using printf-like functions without proper sanitization, format string vulnerabilities could exist.
    • Mitigation Strategies:
      • Safe String Formatting: Use safe string formatting functions (e.g., snprintf) to prevent format string vulnerabilities.
      • Data Validation: Validate the data being reported to ensure it's within expected ranges and formats.
      • Clear and Concise Output: Design the output format to be clear, concise, and avoid revealing unnecessary information.

  • 2.5 Lua Engine (and Lua Script Interaction)

    • Threats:
      • Tampering: Malicious Lua scripts could perform unauthorized actions on the system running wrk.
      • Elevation of Privilege: A malicious script could potentially exploit vulnerabilities in the Lua Engine or its integration with wrk to gain elevated privileges.
      • Denial of Service: A malicious script could consume excessive resources or crash wrk.
      • Information Disclosure: A malicious script could access sensitive information.
    • Vulnerabilities:
      • Arbitrary Code Execution: The most significant risk is that a malicious Lua script could execute arbitrary code on the system running wrk.
      • File System Access: The script might be able to read, write, or delete files on the system.
      • Network Access: The script might be able to make network connections to arbitrary hosts.
      • System Calls: The script might be able to execute system calls.
      • Lua Sandbox Escape: Vulnerabilities in the LuaJIT implementation or wrk's Lua integration could allow a script to escape the intended sandbox and access restricted resources.
    • Mitigation Strategies:
      • Lua Sandboxing: Implement a robust Lua sandbox to restrict the capabilities of user-provided scripts. This is crucial.
        • Disable Dangerous Modules: Disable or carefully restrict access to Lua modules that provide access to the file system (io, os), network (socket), or system calls.
        • Whitelist Allowed Functions: Instead of blacklisting dangerous functions, explicitly whitelist the functions that scripts are allowed to use.
        • Resource Limits: Limit the CPU time, memory, and network bandwidth that scripts can consume.
        • Custom require Function: Implement a custom require function to prevent scripts from loading arbitrary Lua modules.
      • Input Validation: Validate the Lua script itself before executing it. This is difficult to do comprehensively, but basic checks for suspicious patterns (e.g., attempts to access io or os) can be helpful.
      • Regular LuaJIT Updates: Keep LuaJIT up-to-date to address any security vulnerabilities that are discovered.
      • Documentation: Clearly document the security risks associated with Lua scripting and advise users to only run trusted scripts.
      • Consider Alternatives: Evaluate if a different scripting language or approach (e.g., a more restricted configuration language) could provide the necessary functionality with a lower security risk.

  • 2.6 Build and Deployment Processes

    • Threats:
      • Tampering: The build process could be compromised, leading to the distribution of a malicious wrk executable.
      • Supply Chain Attacks: Compromised dependencies (LuaJIT, OpenSSL) could introduce vulnerabilities into wrk.
    • Vulnerabilities:
      • Compromised Build Server: If the build server (e.g., GitHub Actions) is compromised, an attacker could inject malicious code into the build process.
      • Outdated Dependencies: Using outdated versions of LuaJIT or OpenSSL could expose wrk to known vulnerabilities.
      • Unsigned Binaries: Distributing unsigned binaries makes it difficult for users to verify the integrity of the executable.
    • Mitigation Strategies:
      • Secure Build Environment: Ensure the build server is secure and well-maintained. Use a minimal, hardened operating system and restrict access to the server.
      • Dependency Management: Use a dependency management tool to track and audit dependencies. Regularly review and update dependencies to their latest secure versions.
      • Static Analysis: Integrate static analysis tools (e.g., linters, SAST) into the build process to identify potential vulnerabilities in the C code and Lua integration.
      • Fuzz Testing: Implement fuzz testing to identify unexpected behavior or crashes caused by malformed inputs.
      • Code Signing: Digitally sign the released binaries to ensure their authenticity and integrity. This allows users to verify that the executable has not been tampered with.
      • Reproducible Builds: Strive for reproducible builds, where the same source code always produces the same binary output. This makes it easier to verify that the build process has not been compromised.

  • 2.7 Dependencies (LuaJIT, OpenSSL)

    • Threats: Vulnerabilities in the dependencies.
    • Mitigation: Keep dependencies updated. Use specific, pinned versions.

3. Actionable Mitigation Strategies (Summary and Prioritization)

The following mitigation strategies are prioritized based on their importance and impact on wrk's security:

  • High Priority:

    • Lua Sandboxing (Component 2.5): This is the most critical mitigation. Implement a robust sandbox to restrict the capabilities of user-provided Lua scripts. This should include disabling dangerous modules, whitelisting allowed functions, and setting resource limits.
    • Robust Input Validation (Components 2.1, 2.2, 2.3): Implement strict validation of all inputs, including command-line arguments, generated requests, and received responses. Use safe string handling functions and prevent buffer/integer overflows.
    • Dependency Management (Component 2.6): Regularly review and update dependencies (LuaJIT, OpenSSL) to their latest secure versions. Use a dependency management tool to track and audit dependencies.
    • Code Signing (Component 2.6): Digitally sign the released binaries to ensure their authenticity and integrity.

  • Medium Priority:

    • Secure Build Environment (Component 2.6): Ensure the build server is secure and well-maintained.
    • Static Analysis (Component 2.6): Integrate static analysis tools into the build process.
    • Fuzz Testing (Component 2.6): Implement fuzz testing.
    • Resource Limits (Components 2.2, 2.3, 2.5): Implement limits on threads, connections, response sizes, and Lua script resource usage to prevent denial-of-service attacks.
    • Secure Lua Integration (Components 2.2, 2.3): Carefully review the interaction between the core wrk components and the Lua Engine.

  • Low Priority:

    • Documentation of Security Considerations: Add a section to the README or a separate security document that explicitly addresses security considerations.
    • Avoid Shell Commands (Component 2.1): Minimize the use of shell commands.
    • Limit Error Message Detail (Component 2.1, 2.4): Avoid revealing sensitive system information in error messages.

4. Addressing Questions and Assumptions

  • Questions:

    • Testing Strategy: The lack of detailed testing information is a concern. wrk should have comprehensive unit and integration tests, including tests specifically designed to exercise security-relevant code paths (e.g., input validation, Lua script execution).
    • Vulnerability Handling Process: A clear process for handling security vulnerabilities is essential. This should include a way for users to report vulnerabilities and a commitment to timely patching and disclosure.
    • Future Features: Any new features that involve handling user input or interacting with external systems should be carefully reviewed for security implications.
    • Supported Versions: wrk should clearly document the supported versions of LuaJIT and OpenSSL and commit to supporting only secure versions.
    • Known Limitations: Documenting any known limitations or edge cases will help users avoid unexpected behavior and potential security issues.

  • Assumptions:

    • The assumptions about business posture and security posture seem reasonable. The focus on providing a reliable and accurate benchmarking tool is paramount, and a moderate level of security is appropriate. The assumption that users are responsible for the security of their Lua scripts and target servers is valid, but wrk must still protect itself from malicious scripts.

Conclusion

wrk is a valuable tool for HTTP benchmarking, but its security relies heavily on careful coding practices and robust input validation. The most significant security risk is the execution of user-provided Lua scripts. Implementing a strong Lua sandbox is absolutely essential to mitigate this risk. Regularly updating dependencies, using secure coding practices, and integrating security testing into the build process are also crucial for maintaining wrk's security. The recommendations above provide a concrete path towards improving the security posture of wrk.