attack-surface.md

Attack Surface Analysis for spring-projects/spring-framework

Attack Surface: SpEL Injection

• Description: Exploitation of Spring Expression Language (SpEL) by injecting malicious code through user-supplied input that is incorporated into SpEL expressions.
• Spring Contribution: Spring's pervasive use of SpEL in annotations (e.g., @Value, @PreAuthorize), configuration, and integration with template engines (like Thymeleaf) creates numerous potential injection points unique to Spring. This is a core Spring feature that introduces this risk.
• Example:

  @PreAuthorize("#input == 'safeValue'") //Vulnerable if 'input' comes from user without sanitization
  public void securedMethod(String input) { ... }

  An attacker providing input as T(java.lang.Runtime).getRuntime().exec('calc') could execute arbitrary code.
• Impact: Remote Code Execution (RCE), allowing attackers to take complete control of the server.
• Risk Severity: Critical
• Mitigation Strategies:
  • Avoid User Input in SpEL: The primary mitigation is to never directly incorporate unsanitized user input into SpEL expressions.
  • Strict Whitelisting: If user input must be used, implement strict whitelisting of allowed characters and patterns. Reject any input that doesn't match the whitelist. Escaping is not sufficient.
  • Limited SpEL Context: Use a SimpleEvaluationContext (instead of StandardEvaluationContext) to restrict the available SpEL features, significantly reducing the attack surface. This limits access to reflection and system calls, a Spring-specific mitigation.
  • Template Engine Security: When using SpEL in template engines (e.g., Thymeleaf), rely on the template engine's built-in escaping mechanisms (e.g., th:text in Thymeleaf). Avoid unescaped output (th:utext) with user-provided data.

Attack Surface: Mass Assignment / Over-Posting

• Description: Attackers submit extra, unexpected fields in HTTP requests that are bound to internal object models, bypassing intended security checks or modifying sensitive data.
• Spring Contribution: Spring's data binding mechanisms (e.g., @ModelAttribute, @RequestBody) are specifically designed to automatically bind request data to objects. This core Spring feature, while convenient, is the direct cause of this vulnerability if not handled carefully.
• Example:

  // Vulnerable Controller
  @PostMapping("/updateProfile")
  public String updateProfile(@ModelAttribute User user) {
      // ... saves the user object, potentially including unintended fields ...
  }

  An attacker could submit isAdmin=true along with other profile data, potentially gaining administrative privileges.
• Impact: Privilege escalation, data corruption, bypassing security controls.
• Risk Severity: High
• Mitigation Strategies:
  • Use DTOs (Data Transfer Objects): Use DTOs that precisely define the expected input fields. This is the best practice and directly addresses the Spring data binding mechanism.
  • @InitBinder with setAllowedFields or setDisallowedFields: In controllers, use @InitBinder (a Spring-specific feature) to explicitly whitelist or blacklist fields that can be bound. This provides fine-grained control over Spring's data binding.
  • @JsonView (with Jackson): For JSON payloads, use @JsonView (often used with Spring) to control which fields are included during serialization and deserialization, mitigating the risk at the data binding level.

Attack Surface: Insecure Deserialization

• Description: Attackers exploit vulnerabilities in the deserialization process to execute arbitrary code when the application deserializes untrusted data.
• Spring Contribution: Spring provides mechanisms for deserializing data from various sources (e.g., @RequestBody with JSON, XML, or, historically, Java Serialization). Spring Boot's auto-configuration can also influence which deserialization features are enabled. The vulnerability arises from how Spring handles deserialization.
• Example: Using @RequestBody with a vulnerable Jackson configuration (e.g., default typing enabled) to deserialize untrusted JSON, or using Java Serialization with untrusted input.
• Impact: Remote Code Execution (RCE).
• Risk Severity: Critical
• Mitigation Strategies:
  • Avoid Java Serialization: If at all possible, completely avoid using Java Serialization with untrusted data.
  • Restrict Deserialized Types (JSON): When using JSON deserialization (e.g., with Jackson, commonly used with Spring), use @JsonTypeInfo with a whitelist of allowed types. Never use default typing or overly permissive type configurations. This directly controls Spring's deserialization behavior.
  • Safe Deserialization Libraries: If you must use a format prone to deserialization issues, consider using libraries specifically designed for safe deserialization.
  • Input Validation: Even with safe deserialization practices, thoroughly validate the deserialized data after deserialization.

Attack Surface: Spring Boot Actuator Misconfiguration

• Description: Exposure of sensitive information or management capabilities through Spring Boot Actuator endpoints without proper authentication and authorization.
• Spring Contribution: Spring Boot Actuator is a Spring Boot-specific feature that provides these endpoints. The vulnerability is entirely due to the presence and misconfiguration of this Spring Boot component.
• Example: Accessing /actuator/env or /actuator/heapdump without authentication, revealing environment variables (including secrets) or a heap dump (containing sensitive data).
• Impact: Information disclosure, potential for further attacks (e.g., using exposed credentials).
• Risk Severity: High (can be Critical depending on exposed information)
• Mitigation Strategies:
  • Require Authentication: Use Spring Security to require authentication for all Actuator endpoints. This leverages Spring Security to protect a Spring Boot feature.
  • Restrict Access: Implement authorization rules to limit access to specific roles or users, again using Spring Security.
  • Disable Unnecessary Endpoints: Disable any Actuator endpoints that are not absolutely necessary. Use management.endpoints.web.exposure.exclude in application.properties or application.yml (Spring Boot configuration).
  • Customize Endpoint Exposure: Fine-tune which endpoints are exposed and what information they reveal using Spring Boot configuration properties.
  • Separate Management Port: Consider running Actuator endpoints on a separate port (using management.server.port, a Spring Boot property) that is not exposed to the public internet.

Attack Surface: Misconfigured Spring Security

• Description: Incorrectly configured authorization rules, weak password hashing, or other security misconfigurations within Spring Security itself.
• Spring Contribution: This vulnerability is entirely within the scope of Spring Security, a major Spring project. The misconfiguration is of a Spring-provided security mechanism.
• Example:
  • Using permitAll() for sensitive endpoints in your Spring Security configuration.
  • Using a weak password hashing algorithm (e.g., plain text, MD5) or a low iteration count for BCrypt within Spring Security's configuration.
• Impact: Unauthorized access, data breaches, privilege escalation.
• Risk Severity: High (can be Critical depending on the misconfiguration)
• Mitigation Strategies:
  • Principle of Least Privilege: Grant only the minimum necessary permissions to each user role within Spring Security.
  • Method Security: Prefer method-level security annotations (@PreAuthorize, @PostAuthorize - Spring Security features) over URL-based configuration.
  • Strong Password Hashing: Use a strong password hashing algorithm (e.g., BCrypt or Argon2) with a high cost factor/iteration count, configured within Spring Security.
  • Session Fixation Protection: Rely on Spring Security's built-in session fixation protection (it's enabled by default).
  • Regular Audits: Regularly review and audit your Spring Security configuration.
  • Thorough Testing: Extensively test your Spring Security configuration.

Attack Surface: Query Injection (Spring Data)

• Description: Injection of malicious code into queries used by Spring Data modules (e.g., Spring Data JPA, Spring Data MongoDB).
• Spring Contribution: While Spring Data simplifies data access, the use of custom queries (e.g., @Query annotation) within Spring Data, combined with unsanitized user input, creates this Spring-specific vulnerability. The core issue is how Spring Data handles these custom queries.
• Example:

  // Vulnerable repository method (Spring Data JPA)
  @Query("SELECT u FROM User u WHERE u.username = '" + username + "'") // Vulnerable!
  User findByUsernameVulnerable(String username);

  If username is attacker-controlled, they could inject SQL.
• Impact: Data breaches, data modification, denial of service.
• Risk Severity: High
• Mitigation Strategies:
  • Parameterized Queries: Always use parameterized queries or Spring Data's query methods (which inherently use parameters). Never construct queries using string concatenation with user input. This directly addresses how Spring Data interacts with the database.
  • Input Validation: Validate user input even when using parameterized queries, as an additional layer of defense.
  • Use QueryDSL: Consider using QueryDSL (often used with Spring Data) for type-safe query construction, further reducing the risk.