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attack-surface.md

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Attack Surface Analysis for square/retrofit

Attack Surface: Deserialization Vulnerabilities

  • Description: Exploitation of flaws in data deserialization processes to execute arbitrary code, cause denial of service, or gain unauthorized access.
  • Retrofit Contribution: Retrofit relies on converter libraries (like Gson, Jackson, Moshi) to deserialize server responses. Vulnerabilities in these libraries or insecure custom converters directly expose the application.
  • Example: An attacker crafts a malicious JSON response that, when deserialized by a vulnerable Gson library used with Retrofit, triggers remote code execution on the application's device.
  • Impact: Remote Code Execution (RCE), Denial of Service (DoS), Data Breach, Application Crash.
  • Risk Severity: Critical to High.
  • Mitigation Strategies:
    • Use Secure and Updated Converters: Choose well-maintained and actively updated converter libraries. Regularly update dependencies to patch known vulnerabilities.
    • Converter Security Audits: If using custom converters, conduct thorough security audits and penetration testing to identify and fix potential deserialization flaws.
    • Schema Validation: Employ schema validation techniques to ensure incoming data conforms to expected structures, limiting the attack surface for malicious payloads.

Attack Surface: Parameter Injection Vulnerabilities (HTTP Parameter Pollution, Header Injection)

  • Description: Manipulating HTTP requests by injecting malicious parameters or headers through user-controlled input that is not properly sanitized or encoded.
  • Retrofit Contribution: Retrofit's annotations like @Path, @Query, @QueryMap, @Header, and @Headers allow dynamic parameter and header injection. If developers directly use unsanitized user input with these annotations, vulnerabilities arise.
  • Example: An application uses @Query("search") String query and directly takes user input for query. An attacker inputs vulnerable_param=malicious_value&search=safe_value leading to HTTP Parameter Pollution, potentially bypassing security checks. Another example is injecting a malicious header like X-Forwarded-For: <script>alert('XSS')</script> if user input is used in @Header.
  • Impact: Bypassing security controls, Server-Side Request Forgery (SSRF), Cross-Site Scripting (XSS) if headers are reflected, Data Manipulation, Unauthorized Access.
  • Risk Severity: High.
  • Mitigation Strategies:
    • Input Validation and Sanitization: Strictly validate and sanitize all user-provided input before using it in Retrofit API calls. Use allow-lists and escape/encode input appropriately.
    • Proper Encoding: Ensure correct URL encoding of parameters, especially when using @Query and @Path.
    • Header Sanitization: Sanitize user-controlled input before setting it in headers. Avoid directly using user input to construct header values if possible.

Attack Surface: Insecure HTTP Client Configuration (OkHttp)

  • Description: Vulnerabilities arising from misconfigurations or weaknesses in the underlying HTTP client (typically OkHttp) used by Retrofit.
  • Retrofit Contribution: Retrofit uses OkHttp by default. Insecure OkHttp configurations directly translate to vulnerabilities in Retrofit-based applications.
  • Example: An application disables TLS certificate validation in OkHttp to bypass certificate pinning issues during development. This configuration is accidentally deployed to production, making the application vulnerable to Man-in-the-Middle (MITM) attacks.
  • Impact: Man-in-the-Middle (MITM) attacks, Data Interception, Data Tampering, Exposure of Sensitive Data, Compromised Communication Security.
  • Risk Severity: Critical to High.
  • Mitigation Strategies:
    • Secure TLS/SSL Configuration: Configure OkHttp to use strong TLS versions (TLS 1.2+) and secure cipher suites. Enforce certificate validation and hostname verification.
    • Regular OkHttp Updates: Keep the OkHttp dependency up-to-date to patch known vulnerabilities.
    • Review OkHttp Configuration: Regularly review and audit OkHttp configurations to ensure they adhere to security best practices.

Attack Surface: Interceptors Misuse and Vulnerabilities

  • Description: Security issues introduced by improperly implemented or vulnerable Retrofit interceptors, which modify HTTP requests and responses.
  • Retrofit Contribution: Retrofit interceptors provide a powerful mechanism to intercept and modify requests and responses. Misuse or vulnerabilities in interceptor logic directly impact the application's security.
  • Example: An interceptor designed for logging inadvertently logs sensitive authentication tokens in plain text. Another example is an interceptor that modifies request headers based on user-controlled input without proper validation, leading to header injection.
  • Impact: Exposure of Sensitive Data (logging), Request Smuggling, Response Manipulation, Bypassing Security Controls, Data Integrity Issues.
  • Risk Severity: High.
  • Mitigation Strategies:
    • Secure Logging Practices: Avoid logging sensitive data in interceptors. If logging is necessary, implement secure logging mechanisms and redact sensitive information before logging.
    • Interceptor Security Review: Thoroughly review interceptor code for potential security vulnerabilities. Ensure request and response modifications are secure and based on trusted logic.
    • Principle of Least Privilege for Interceptors: Limit the scope and functionality of interceptors to only what is necessary.