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attack-surface.md

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Attack Surface Analysis for twitter/twemproxy

Attack Surface: Configuration Injection

  • Description: Attackers exploit vulnerabilities to modify the Twemproxy configuration file (typically YAML), injecting malicious settings.
  • How Twemproxy Contributes: Twemproxy's behavior is entirely determined by its configuration file. Unauthorized modification directly controls its functionality and security.
  • Example: An attacker gains access and modifies the servers section to point to a malicious backend, enabling data theft. Or, they disable security features.
  • Impact: Complete system compromise, data breach, denial of service, data manipulation.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Strict File Permissions: Restrictive permissions (read-only for Twemproxy user, no write access for others).
    • File Integrity Monitoring: Detect unauthorized changes to the configuration file (e.g., AIDE, Tripwire).
    • Secure Configuration Management: Use tools like Ansible, Chef, or Puppet for consistent and secure configuration.
    • No User Input to Config: Never allow user input to influence the configuration file. Use secure templating.
    • Principle of Least Privilege: Run Twemproxy as a non-root user.

Attack Surface: Denial of Service (DoS) - Connection Exhaustion

  • Description: Attackers flood Twemproxy with connection requests, exceeding its limits and blocking legitimate clients.
  • How Twemproxy Contributes: Twemproxy acts as a connection multiplexer and has finite connection handling capacity.
  • Example: A botnet opens thousands of connections to Twemproxy, exhausting the client_connections limit.
  • Impact: Service unavailability for legitimate users.
  • Risk Severity: High
  • Mitigation Strategies:
    • Connection Limits: Configure a reasonable client_connections limit in Twemproxy.
    • Rate Limiting (Pre-Twemproxy): Implement rate limiting before requests reach Twemproxy (firewall, load balancer, application logic). This is essential.
    • Load Balancing: Use multiple Twemproxy instances behind a load balancer.
    • Monitoring: Monitor connection counts and alert on high numbers.

Attack Surface: Denial of Service (DoS) - Resource Exhaustion (CPU/Memory)

  • Description: Attackers send crafted requests to consume excessive CPU or memory on the Twemproxy server.
  • How Twemproxy Contributes: While lightweight, Twemproxy can still be overwhelmed by malicious or excessive requests.
  • Example: An attacker sends many pipelined requests with large keys/values, causing high memory usage. Or, they exploit a bug in Twemproxy's request parsing.
  • Impact: Service unavailability, potential server crashes.
  • Risk Severity: High
  • Mitigation Strategies:
    • Rate Limiting (Pre-Twemproxy): Essential to prevent resource exhaustion. Implement before Twemproxy.
    • Request Size Limits: If possible, limit request and pipeline sizes.
    • Resource Monitoring: Monitor Twemproxy's CPU and memory usage.
    • cgroups (Linux): Use cgroups to limit Twemproxy's resource consumption.
    • Command Filtering (with extreme caution): Restrict allowed commands at Twemproxy level if feasible, but carefully to avoid breaking application.

Attack Surface: Backend Server Exposure (Due to Twemproxy Misconfiguration)

  • Description: Attackers bypass Twemproxy or exploit its misconfigurations to directly access backend servers.
  • How Twemproxy Contributes: Twemproxy's role is to proxy, but incorrect configuration can expose the backend. This is distinct from general network misconfigurations.
  • Example: Twemproxy is configured with an incorrect listen address, making the backend servers directly accessible on a public interface. Or, Twemproxy's error messages leak backend server IP addresses.
  • Impact: Data breach, data manipulation, denial of service on backend servers.
  • Risk Severity: High
  • Mitigation Strategies:
    • Correct listen Configuration: Ensure Twemproxy listens only on the intended interface and port, and that this interface is not publicly accessible.
    • Backend Authentication: Use strong authentication between Twemproxy and backend servers (e.g., TLS with client certificates, if supported).
    • Avoid Information Leakage: Configure Twemproxy to provide generic error messages, preventing backend server detail disclosure.
    • Network Segmentation and Firewalling: While not solely Twemproxy's responsibility, these are critical in preventing direct backend access even if Twemproxy is misconfigured.

Attack Surface: Unencrypted Communication (Facilitated by Twemproxy's Default)

  • Description: Sensitive data is transmitted in plain text because Twemproxy doesn't enable encryption by default.
  • How Twemproxy Contributes: Twemproxy, by default, does not encrypt traffic. This requires explicit configuration.
  • Example: An attacker on the network captures unencrypted Redis commands and responses.
  • Impact: Data breach, credential theft.
  • Risk Severity: High
  • Mitigation Strategies:
    • TLS/SSL (Client-Twemproxy): Configure TLS/SSL for client-to-Twemproxy communication.
    • TLS/SSL (Twemproxy-Backend): Configure TLS/SSL for Twemproxy-to-backend communication (if supported by the backend).
    • Secure Tunnels (Alternative): If the backend lacks TLS support, use secure tunnels (SSH, VPN).