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attack-surface.md

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Attack Surface Analysis for cloudflare/pingora

Attack Surface: 1. Upstream Misconfiguration

  • Description: Incorrect configuration of upstream servers (the servers Pingora proxies to) can lead to various vulnerabilities. This is the primary attack surface specific to a reverse proxy.
    • How Pingora Contributes: Pingora's core function is to route traffic to upstreams based on configuration. This configuration is the direct attack point. Pingora's flexibility in defining upstreams increases the potential for misconfiguration.
    • Example: An administrator configures a proxy_pass rule that uses a user-supplied query parameter (?host=) to determine the upstream host, without any validation. An attacker provides ?host=internal.database.server, gaining access to an internal database.
    • Impact: * Server-Side Request Forgery (SSRF) - Critical * Open Redirects - Critical * Denial of Service (DoS) - High * Information Disclosure - High * Risk Severity: Critical (SSRF, Open Redirects), High (DoS, Information Disclosure)
    • Mitigation Strategies: * Strict Input Validation: Never trust user input to determine upstream targets. Use allow-lists (whitelists) of permitted upstream hosts and paths. Validate all inputs that influence routing. * Hardcoded Upstreams (where feasible): If the set of upstreams is static, hardcode them in the configuration. Avoid dynamic upstream selection based on user input. * Configuration Management & Validation: Use a robust configuration management system with strict validation checks before deployment. Version control and audit configurations. * Network Segmentation: Isolate Pingora and upstream servers in separate network segments to limit the blast radius of a successful attack. Use a DMZ for Pingora.

Attack Surface: 2. Custom Filter Vulnerabilities (Rust Code)

  • Description: Bugs or security flaws in custom Rust code implemented as Pingora filters, particularly involving unsafe blocks or external crate dependencies.
    • How Pingora Contributes: Pingora's extensibility through custom Rust filters directly introduces a code execution attack surface. The filter runs within the Pingora process.
    • Example: A filter designed to add a custom header contains a buffer overflow in its unsafe Rust code when handling a very long header value. An attacker sends a crafted request with an extremely long header to trigger the overflow and execute arbitrary code.
    • Impact: * Remote Code Execution (RCE) - Critical * Authentication/Authorization Bypass - High * Data Modification/Corruption - High * Risk Severity: Critical (RCE), High (Auth Bypass, Data Modification)
    • Mitigation Strategies: * Minimize unsafe Rust: Avoid unsafe code whenever possible. If unsafe is absolutely necessary, heavily scrutinize and justify it. Use safe abstractions where available. * Rigorous Code Review: Mandatory, thorough code reviews of all custom filter code, with a specific focus on security vulnerabilities. * Static Analysis: Use static analysis tools (Clippy, cargo audit, etc.) to automatically detect potential vulnerabilities. * Fuzzing: Employ fuzzing techniques to test filters with a wide range of inputs, including malformed and unexpected data, to uncover edge cases and vulnerabilities. * Dependency Auditing: Regularly audit dependencies (crates) used by filters for known vulnerabilities. Use cargo audit or similar tools. * Resource Limits: Enforce resource limits (CPU, memory) on filters to mitigate DoS risks from buggy or malicious filters.

Attack Surface: 3. Dependency Vulnerabilities (Pingora's Crates)

  • Description: Vulnerabilities in third-party Rust crates used directly by the Pingora library itself.
    • How Pingora Contributes: Pingora, as a software project, has its own dependencies. Vulnerabilities in these dependencies directly impact Pingora's security. This is distinct from vulnerabilities in crates used by custom filters.
    • Example: A crate used by Pingora for TLS handling has a known vulnerability that allows for remote code execution. An attacker exploits this vulnerability to gain control of the Pingora process, regardless of any custom filters.
    • Impact: * Remote Code Execution (RCE) - Critical * Denial of Service (DoS) - High * Information Disclosure - High * Risk Severity: Critical (RCE), High (DoS, Information Disclosure)
    • Mitigation Strategies: * Regular Updates: Keep Pingora itself updated to the latest released version. The Pingora maintainers will address vulnerabilities in its dependencies. * Dependency Scanning (of Pingora): While primarily the responsibility of the Pingora maintainers, users can use tools like cargo audit on the Pingora source code (if available) to identify potential issues before they are officially patched. This is a proactive, but less common, approach. * Monitor Pingora Releases: Pay close attention to Pingora's release notes and security advisories for information about patched vulnerabilities.

Attack Surface: 4. HTTP Request Handling Issues (Within Pingora's Core)

  • Description: Improper handling of malformed or malicious HTTP requests within Pingora's core HTTP parsing and processing logic.
    • How Pingora Contributes: Pingora's core functionality includes parsing and processing HTTP requests. Bugs in this core logic are directly attributable to Pingora.
    • Example: Pingora's HTTP/2 implementation has a vulnerability that allows for header smuggling. An attacker crafts a malicious HTTP/2 request to bypass security checks or access unauthorized resources.
    • Impact: * HTTP Request Smuggling - High * Header Injection - High * Risk Severity: High
    • Mitigation Strategies: * Rely on Pingora Updates: The primary mitigation is to keep Pingora updated to the latest version. The Pingora developers are responsible for fixing bugs in the core HTTP handling. * Report Issues: If you discover a potential vulnerability in Pingora's HTTP handling, report it responsibly to the Pingora maintainers. * WAF (as a secondary defense): A Web Application Firewall (WAF) in front of Pingora can provide an additional layer of defense against some HTTP-level attacks, but it should not be relied upon as the primary defense. The core issue lies within Pingora.