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Threat Model Analysis for alibaba/tengine

Threat: Remote Code Execution via trim_filter Module Vulnerability

  • Description: An attacker crafts a malicious HTTP request that exploits a buffer overflow or other vulnerability in the trim_filter module. The attacker might send a specially crafted request body or headers that, when processed by trim_filter, overwrites memory and allows the execution of arbitrary code.
  • Impact: Complete server compromise. The attacker gains full control of the Tengine process and potentially the underlying operating system.
  • Affected Component: trim_filter module.
  • Risk Severity: Critical.
  • Mitigation Strategies:
    • Apply security patches for trim_filter immediately upon release.
    • Disable trim_filter if it's not strictly necessary.
    • Implement strict input validation before the request reaches trim_filter (defense in depth).
    • Use a Web Application Firewall (WAF) with rules to detect and block exploit attempts targeting trim_filter.
    • Run Tengine with the least necessary privileges (not as root).

Threat: Denial of Service via concat Module Resource Exhaustion

  • Description: An attacker sends a large number of requests that utilize the concat module to combine many files. The attacker might request the concatenation of extremely large files or a very high number of small files, exhausting server resources (CPU, memory, file descriptors).
  • Impact: Service unavailability. Legitimate users are unable to access the application.
  • Affected Component: concat module.
  • Risk Severity: High.
  • Mitigation Strategies:
    • Limit the number of files that can be concatenated in a single request using the concat_max_files directive.
    • Set a reasonable size limit for concatenated files using the concat_unique and potentially custom size limiting logic.
    • Implement rate limiting to prevent an attacker from sending too many concat requests.
    • Monitor resource usage (CPU, memory, file descriptors) and set alerts for unusual spikes.

Threat: Session Hijacking via session_sticky Module Misconfiguration

  • Description: The session_sticky module is misconfigured, allowing an attacker to predict or manipulate session identifiers. For example, the cookie name or generation algorithm might be predictable, or the module might not properly handle edge cases like server restarts or failovers. While session management is often an application-level concern, Tengine's session_sticky module directly participates in this process, making misconfiguration a Tengine-specific threat.
  • Impact: An attacker can hijack legitimate user sessions, gaining unauthorized access to the application.
  • Affected Component: session_sticky module.
  • Risk Severity: High.
  • Mitigation Strategies:
    • Use a strong, randomly generated cookie name for session_sticky.
    • Ensure the session ID generation algorithm is cryptographically secure.
    • Thoroughly test the session_sticky configuration under various scenarios, including server restarts and failovers.
    • Implement additional session security measures at the application level (e.g., HSTS, secure cookies, short session timeouts) – but critically, ensure the Tengine module itself is correctly configured.

Threat: Bypass of Security Controls via Vulnerability in a Custom Security Module

  • Description: A custom Tengine security module (e.g., a module designed to implement custom WAF rules or anti-DDoS measures) contains a vulnerability. An attacker crafts a request that exploits this vulnerability to bypass the intended security controls.
  • Impact: The attacker can bypass security measures, potentially leading to SQL injection, cross-site scripting (XSS), or other attacks that the module was supposed to prevent.
  • Affected Component: Custom Tengine security module.
  • Risk Severity: High to Critical (depending on the module's purpose).
  • Mitigation Strategies:
    • Thoroughly audit and test the custom security module for vulnerabilities.
    • Follow secure coding practices when developing the module.
    • Implement robust input validation and output encoding within the module.
    • Regularly review and update the module's code.
    • Consider using a well-established WAF instead of relying solely on a custom module.

Threat: Denial of Service via HTTP/2 Rapid Reset (CVE-2023-44487) Exploitation in Tengine's HTTP/2 Implementation

  • Description: An attacker exploits the HTTP/2 Rapid Reset vulnerability (CVE-2023-44487) by sending a flood of HTTP/2 requests with RST_STREAM frames, causing Tengine to consume excessive resources. This is a vulnerability that affected many HTTP/2 implementations.
  • Impact: Denial of service. Legitimate users are unable to access the application.
  • Affected Component: Tengine's HTTP/2 implementation.
  • Risk Severity: High.
  • Mitigation Strategies:
    • Upgrade Tengine: Ensure Tengine is updated to a version that includes the patch for CVE-2023-44487. This is the most crucial step.
    • Limit Concurrent Streams: Configure http2_max_concurrent_streams to a reasonable value to limit the number of concurrent streams per connection.
    • Implement Rate Limiting: Use Tengine's or a separate component's rate limiting features to restrict the number of requests per client.
    • Monitor for Suspicious Traffic: Monitor HTTP/2 traffic for patterns indicative of Rapid Reset attacks (high volume of RST_STREAM frames).

Threat: Integer Overflow in Tengine's Core or Modules

  • Description: An attacker crafts a malicious request with specially designed integer values that, when processed by Tengine's core or a specific module, cause an integer overflow. This can lead to unexpected behavior, memory corruption, or potentially even code execution.
  • Impact: Varies depending on the location and nature of the overflow. Could range from denial of service to remote code execution.
  • Affected Component: Tengine core or any module that handles integer calculations.
  • Risk Severity: Medium to Critical (depending on the impact). Classified as at least High due to the potential for RCE.
  • Mitigation Strategies:
    • Code Audits: Regularly audit Tengine's codebase and any custom modules for potential integer overflow vulnerabilities.
    • Safe Integer Libraries: Use safe integer libraries or techniques that prevent or detect integer overflows.
    • Input Validation: Strictly validate all integer inputs to ensure they are within expected ranges.
    • Fuzz Testing: Perform fuzz testing on Tengine and its modules to identify potential integer overflow vulnerabilities.
    • Update Tengine: Keep Tengine updated to the latest version, as patches often address such vulnerabilities.