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attack-surface.md

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Attack Surface Analysis for alibaba/tengine

Attack Surface: Misconfigured Modules

  • Description: Tengine's modular architecture allows enabling/disabling features via modules. Incorrectly configured or unnecessary modules expand the attack surface specific to Tengine's implementation.
    • Tengine Contribution: Tengine's modularity is the direct contributor. The risk stems from how Tengine handles module loading, configuration parsing, and inter-module communication.
    • Example: A custom-compiled Tengine module (or a third-party module not properly vetted) contains a buffer overflow vulnerability that can be triggered by a specially crafted HTTP request. This is distinct from a general web application vulnerability because it's within Tengine's module code.
    • Impact: Information disclosure, unauthorized access to files, potential remote code execution within the Tengine process.
    • Risk Severity: High to Critical.
    • Mitigation Strategies:
      • Disable Unused Modules: Only enable essential Tengine modules. This directly reduces the Tengine-specific attack surface.
      • Strict Module Configuration Audits: Focus on Tengine-specific directives within each module's configuration. Understand the security implications of each setting.
      • Secure Custom Module Development: If building custom modules, follow rigorous secure coding practices specifically for Tengine module development. Use memory-safe languages if possible.
      • Third-Party Module Vetting: Thoroughly vet any third-party Tengine modules before deploying them. Examine the source code if available.

Attack Surface: HTTP/2 and HTTP/3 Vulnerabilities

  • Description: Exploiting vulnerabilities specific to Tengine's implementation of the HTTP/2 and HTTP/3 protocols.
    • Tengine Contribution: Tengine's specific implementation of these protocols is the attack surface. This is not a general web server issue; it's about how Tengine handles the complexities of these protocols.
    • Example: A flaw in Tengine's handling of HTTP/2 stream multiplexing allows an attacker to cause a denial-of-service by exhausting server resources dedicated to managing HTTP/2 connections. This is specific to Tengine's connection management logic.
    • Impact: Denial of service, potential Tengine process crashes.
    • Risk Severity: High.
    • Mitigation Strategies:
      • Prioritize Tengine Updates: Focus on updates specifically addressing HTTP/2 and HTTP/3 vulnerabilities in Tengine's changelog.
      • Tengine-Specific Configuration: Use Tengine's directives to limit HTTP/2 and HTTP/3 resource usage (e.g., http2_max_concurrent_streams, http3_max_concurrent_streams). These are Tengine-specific controls.
      • Disable if Unnecessary: If these protocols are not essential, disable them in Tengine's configuration to eliminate this Tengine-specific attack surface.

Attack Surface: Lua Scripting (ngx_lua) Risks (When used within Tengine)

  • Description: Vulnerabilities within Lua scripts embedded within Tengine's configuration using the ngx_lua module.
    • Tengine Contribution: The ngx_lua module, a part of Tengine, provides the mechanism for embedding and executing Lua code. The risk is directly tied to Tengine's integration with Lua.
    • Example: A Lua script within Tengine, intended to modify response headers, contains a code injection vulnerability allowing an attacker to execute arbitrary Lua code within the Tengine process.
    • Impact: Code injection within Tengine, data breaches, Tengine process compromise, denial of service.
    • Risk Severity: High to Critical.
    • Mitigation Strategies:
      • Secure Lua Coding for Tengine: Apply secure coding practices specifically within the context of Tengine's Lua environment. Understand how Lua interacts with Tengine's request processing.
      • Tengine-Specific Sandboxing (if available): Explore any Tengine-provided mechanisms for sandboxing or restricting Lua script execution.
      • Minimize Lua Usage: If possible, reduce the reliance on complex Lua scripting within Tengine to minimize this Tengine-specific attack surface.

Attack Surface: Vulnerabilities in Tengine's Codebase

  • Description: Exploiting known or unknown (zero-day) vulnerabilities in Tengine's core code or its built-in modules.
    • Tengine Contribution: This is entirely about Tengine's code. The vulnerability exists within Tengine itself.
    • Example: A buffer overflow vulnerability in Tengine's handling of HTTP request headers allows an attacker to execute arbitrary code within the Tengine worker process.
    • Impact: Complete Tengine server compromise, data breaches, denial of service.
    • Risk Severity: Critical.
    • Mitigation Strategies:
      • Immediate Tengine Updates: Prioritize applying security updates for Tengine as soon as they are released. This is the primary defense.
      • Monitor Tengine Security Advisories: Actively monitor Tengine's official security channels for vulnerability announcements.
      • Consider Tengine-Specific Hardening Guides: Look for hardening guides specifically tailored to Tengine, focusing on mitigating potential code-level vulnerabilities.