mitigations.md

Mitigation Strategies Analysis for apache/solr

Mitigation Strategy: Input Validation and Sanitization for Solr Queries

• Mitigation Strategy: Input Validation and Sanitization for Solr Queries
• Description:
  1. Identify User Inputs in Solr Queries: Pinpoint all locations in your application where user-provided data is incorporated into Solr queries. This includes search parameters, filter values, and facet queries.
  2. Define Validation Rules for Solr Query Parameters: For each user input field used in Solr queries, define strict validation rules based on the expected data type, format, and allowed characters within the context of Solr Query Syntax. For example, validate date ranges are in Solr's date format, and numeric ranges are valid numbers.
  3. Implement Solr Query Sanitization: Use Solr's built-in escaping mechanisms or a sanitization library in your application code specifically designed for Solr Query Language. This involves escaping special characters that have meaning in Solr Query Language (e.g., +, -, :, (, ), *, ?, ~, ^, [, ], {, }, \, /, &&, ||) before embedding user input into queries.
  4. Utilize Solr Parameterized Queries (if client library supports): If your Solr client library supports parameterized queries, use them to separate query logic from user-provided data. This is the most effective method to prevent Solr Query Language Injection by ensuring user input is treated as data, not query commands.
  5. Regularly Review and Update Solr Query Validation: Periodically review and update validation and sanitization rules as your application's search features evolve and new query parameters are introduced in Solr interactions.
• List of Threats Mitigated:
  • Solr Query Language Injection (High Severity): Attackers can manipulate Solr queries to bypass intended search logic, access unauthorized data indexed in Solr, or potentially exploit vulnerabilities in older Solr versions.
• Impact:
  • Solr Query Language Injection: High - Effectively eliminates the risk of query injection vulnerabilities within Solr interactions if implemented correctly.
• Currently Implemented:
  • Partially implemented in the main search functionality. Server-side sanitization is applied using a custom Java utility class that escapes special characters before constructing Solr queries.
• Missing Implementation:
  • Parameterized queries are not utilized. Sanitization is not consistently applied across all features interacting with Solr, especially in administrative or less frequently used search interfaces. Validation rules are not comprehensive for all Solr query parameters.

Mitigation Strategy: Access Control and Authentication within Solr

• Mitigation Strategy: Access Control and Authentication within Solr
• Description:
  1. Enable Solr Authentication: Configure Solr's built-in security features to enable authentication for all requests to Solr. Choose a suitable authentication mechanism supported by Solr, such as Basic Authentication, Kerberos, LDAP, or PKI, based on your security infrastructure. Configure this in security.json.
  2. Implement Solr Authorization: Define granular authorization rules within Solr's security.json configuration to control access to specific Solr collections, cores, request handlers, and update functionalities. Use roles and permissions to restrict actions based on user identity.
  3. Integrate Solr Authentication with External Systems (if needed): Integrate Solr authentication with your organization's existing identity provider (e.g., LDAP, Active Directory) through Solr's authentication plugins for centralized user management and consistent access policies across systems.
  4. Restrict Access to Solr Admin UI via Solr Configuration: Within Solr's security.json, configure access control lists (ACLs) to restrict access to the Solr Admin UI to only authorized users or roles. Consider disabling the Admin UI entirely in production environments if it's not actively required for monitoring.
  5. Regularly Review Solr Access Controls: Periodically review and audit the access control configurations defined in security.json to ensure they remain aligned with security policies and user roles within the context of Solr access.
• List of Threats Mitigated:
  • Unauthorized Access to Solr Data (High Severity): Without Solr authentication and authorization, anyone with network access to Solr can potentially access and retrieve sensitive data indexed in Solr collections.
  • Unauthorized Modification of Solr Data (High Severity): Lack of Solr access control can allow unauthorized users to modify, delete, or corrupt data within Solr, impacting data integrity and application functionality.
  • Exploitation of Solr Admin UI (Medium Severity): An unprotected Solr Admin UI can be exploited to gain information about the Solr instance, potentially leading to further attacks or misconfigurations of Solr itself.
• Impact:
  • Unauthorized Access to Solr Data: High - Significantly reduces the risk of unauthorized access to sensitive data stored and managed by Solr.
  • Unauthorized Modification of Solr Data: High - Significantly reduces the risk of unauthorized data manipulation within Solr.
  • Exploitation of Solr Admin UI: Medium - Reduces the risk of attacks originating from or facilitated by the Solr Admin UI.
• Currently Implemented:
  • Basic Authentication is enabled for Solr using security.json.
• Missing Implementation:
  • Granular authorization rules within security.json are not fully implemented. All authenticated users currently have broad read access to all collections. Integration with LDAP for centralized Solr user management via Solr authentication plugins is missing. Access control to the Admin UI within security.json is not configured beyond basic authentication.

Mitigation Strategy: Disable Unnecessary Solr Request Handlers and Features

• Mitigation Strategy: Disable Unnecessary Solr Request Handlers and Features
• Description:
  1. Identify Required Solr Handlers: Analyze your application's interaction with Solr and identify the specific request handlers that are actively used for querying, updating, and other operations. Consult Solr documentation to understand the purpose of each handler defined in solrconfig.xml.
  2. Disable Unused Solr Handlers in solrconfig.xml: In your solrconfig.xml file, disable any request handlers that are not essential for your application's functionality. Specifically, review and disable handlers like VelocityResponseWriter, XsltResponseWriter, JupyterResponseWriter, and any other handlers not explicitly required. Comment out or remove their <requestHandler> definitions in solrconfig.xml.
  3. Review Default Solr Features: Examine other Solr features and components enabled by default in solrconfig.xml that might not be necessary. Disable any unused features to minimize the attack surface of the Solr instance.
  4. Regularly Audit Enabled Solr Features: Periodically review the list of enabled request handlers and features in solrconfig.xml to ensure that only necessary components are active. As application requirements change, re-evaluate the need for each enabled Solr feature.
• List of Threats Mitigated:
  • Remote Code Execution via Vulnerable Solr Handlers (High Severity - for handlers like VelocityResponseWriter, XsltResponseWriter, JupyterResponseWriter): Vulnerable request handlers, if enabled, can be exploited to achieve remote code execution on the Solr server.
  • Information Disclosure through Solr Features (Medium Severity): Unnecessary Solr handlers or features might expose sensitive information or functionalities that can be misused by attackers to gain insights into the Solr setup or indexed data.
• Impact:
  • Remote Code Execution: High - Eliminates the risk associated with known vulnerabilities in unused, but enabled, Solr request handlers.
  • Information Disclosure: Medium - Reduces the potential for information disclosure through unnecessary Solr features and handlers.
• Currently Implemented:
  • VelocityResponseWriter and XsltResponseWriter are commented out in solrconfig.xml.
• Missing Implementation:
  • JupyterResponseWriter is still enabled in solrconfig.xml. A comprehensive audit of all enabled request handlers and features in solrconfig.xml has not been performed to identify and disable other potentially unnecessary components.

Mitigation Strategy: Secure Solr Configuration Files Access

• Mitigation Strategy: Secure Solr Configuration Files Access
• Description:
  1. Restrict File System Permissions for Solr Configs: Ensure that all Solr configuration files (solr.xml, managed-schema, solrconfig.xml, security.json, etc.) located in Solr's configuration directories are readable only by the user account under which the Solr process runs and by authorized administrators. Prevent public read access at the operating system level.
  2. Prevent Web Server Access to Solr Config Directories: If Solr is accessed through a web server, configure the web server to explicitly prevent direct HTTP access to Solr's configuration directories and files. Ensure these directories are not served as static content by the web server.
  3. Version Control and Audit Solr Configuration Changes: Store Solr configuration files in a version control system (like Git) to track all changes and facilitate auditing of modifications. Implement a review and approval process for configuration changes before deploying them to Solr instances.
  4. Regular Security Audits of Solr Configurations: Periodically audit Solr configuration files for potential security misconfigurations, such as overly permissive access controls defined in security.json, insecure settings in solrconfig.xml, or unintentionally exposed sensitive information within configuration files.
• List of Threats Mitigated:
  • Information Disclosure via Solr Configuration Files (Medium Severity): Exposed Solr configuration files can reveal sensitive details about the Solr setup, including authentication configurations, internal network paths, and potentially hints about vulnerabilities or internal application logic.
  • Configuration Tampering of Solr (Medium Severity): If Solr configuration files are writable by unauthorized users (at the file system level), attackers could modify them to compromise the Solr instance's security, functionality, or data integrity.
• Impact:
  • Information Disclosure: Medium - Reduces the risk of information leakage through unauthorized access to Solr configuration files.
  • Configuration Tampering: Medium - Reduces the risk of unauthorized modifications to Solr's configuration, protecting its intended security posture.
• Currently Implemented:
  • File system permissions are set to restrict read access to Solr configuration files to the Solr user and administrators. Solr configuration files are managed in a Git repository.
• Missing Implementation:
  • Web server configuration has not been explicitly verified to prevent direct HTTP access to Solr configuration directories. Regular security audits specifically focused on Solr configuration files are not routinely performed.

Mitigation Strategy: Keep Solr and Solr Dependencies Up-to-Date

• Mitigation Strategy: Keep Solr and Solr Dependencies Up-to-Date
• Description:
  1. Establish Solr Update Process: Define a formal process for regularly checking for and applying updates to Apache Solr itself and its direct dependencies. This includes subscribing to Apache Solr security mailing lists and monitoring official release notes for security advisories and patch announcements.
  2. Regular Solr Update Schedule: Establish a schedule for applying Solr updates, ideally on a regular basis (e.g., monthly or quarterly), or more frequently when critical security vulnerabilities are disclosed for Solr or its dependencies.
  3. Test Solr Updates in Non-Production: Before deploying updates to production Solr instances, thoroughly test them in a staging or development environment that mirrors production to ensure compatibility with your application and prevent regressions or unexpected issues.
  4. Manage Solr Dependencies: Utilize dependency management tools (e.g., Maven, Gradle if building Solr from source or managing custom Solr plugins) to track and manage Solr's dependencies. Ensure these dependencies are also kept updated to their latest secure versions.
  5. Integrate Vulnerability Scanning for Solr: Integrate vulnerability scanning tools into your CI/CD pipeline to automatically identify outdated and vulnerable components within your Solr deployment, including Solr itself and its libraries.
• List of Threats Mitigated:
  • Exploitation of Known Solr Vulnerabilities (High Severity): Running outdated versions of Solr exposes the system to exploitation of publicly known security vulnerabilities that are actively targeted by attackers. This can lead to remote code execution, data breaches, or denial of service specifically targeting Solr.
• Impact:
  • Exploitation of Known Solr Vulnerabilities: High - Significantly reduces the risk of exploitation of known vulnerabilities in Solr and its dependencies by ensuring timely patching and updates.
• Currently Implemented:
  • A documented process for updating Solr exists, but it's not consistently followed for proactive security patching. Updates are often driven by feature requirements rather than security maintenance.
• Missing Implementation:
  • A regular, scheduled update cadence for Solr is not in place. Vulnerability scanning specifically targeting Solr and its dependencies is not integrated into the CI/CD pipeline. Dependency management is used for build processes but not actively leveraged for tracking and applying security updates to Solr's runtime dependencies.

Mitigation Strategy: Implement Solr Query Timeouts

• Mitigation Strategy: Implement Solr Query Timeouts
• Description:
  1. Configure timeAllowed in Solr queryResponseWriter: In your solrconfig.xml, configure the queryResponseWriter section to set the timeAllowed parameter. This parameter defines the maximum time (in milliseconds) that Solr will spend executing a single query.
  2. Set Appropriate Solr Query Timeout Values: Determine suitable timeout values for Solr queries based on the expected query performance and typical response times for your application's search operations. Start with conservative values and adjust them based on monitoring and performance testing of Solr queries.
  3. Test Application's Handling of Solr Query Timeouts: Test how your application gracefully handles Solr query timeout exceptions. Ensure the application can catch timeout errors and provide user-friendly error messages without exposing sensitive Solr or system information.
  4. Monitor Solr Query Performance and Timeouts: Implement monitoring of Solr query performance metrics, including query execution times and the frequency of query timeouts. Identify any queries that consistently approach or exceed the timeout limit and investigate potential performance bottlenecks or optimize slow queries within Solr.
• List of Threats Mitigated:
  • Denial of Service (DoS) against Solr via Resource Exhaustion (High Severity): Maliciously crafted or excessively complex Solr queries can consume significant Solr server resources (CPU, memory, I/O), potentially leading to resource exhaustion and denial of service for legitimate users of the Solr service.
• Impact:
  • Denial of Service (DoS): High - Significantly reduces the risk of DoS attacks against Solr caused by long-running or resource-intensive queries by limiting their execution time.
• Currently Implemented:
  • Query timeouts are configured in solrconfig.xml with a default timeAllowed value of 3000 milliseconds (3 seconds).
• Missing Implementation:
  • Timeout values have not been specifically tuned for different types of Solr queries or application use cases. Active monitoring of Solr query performance and timeout occurrences is not in place to identify and address potential issues or optimize timeout settings.

Mitigation Strategy: Disable Solr XML External Entity (XXE) Processing

• Mitigation Strategy: Disable Solr XML External Entity (XXE) Processing
• Description:
  1. Configure Solr XML Parsers for XXE Prevention: When using Solr features that process XML data (e.g., Data Import Handler, update requests in XML format), explicitly configure the underlying XML parsers used by Solr to disable external entity processing. This is typically done by setting parser features in Solr's configuration.
  2. Disable DOCTYPE Declarations in Solr XML Parsing: Configure Solr's XML parsers to disallow DOCTYPE declarations within XML documents being processed. DOCTYPE declarations are often used to define external entities, making them a key component of XXE attacks.
  3. Disable External Entity Resolution in Solr: Explicitly disable the resolution of external entities by Solr's XML parsers. The specific configuration method depends on the XML parser library used by Solr internally (which is often Java's built-in XML processing libraries). This might involve setting specific parser features programmatically or via configuration.
  4. Verify Solr XXE Mitigation: Thoroughly test your Solr setup to confirm that XXE processing is effectively disabled. Use security testing tools or manual testing techniques to validate that Solr is not vulnerable to XXE injection when processing XML data.
• List of Threats Mitigated:
  • XML External Entity (XXE) Injection in Solr (High Severity): XXE vulnerabilities in Solr's XML processing can allow attackers to perform server-side file inclusion, potentially reading local files on the Solr server, accessing sensitive data, or in some cases, achieving remote code execution if the underlying system is vulnerable.
• Impact:
  • XML External Entity (XXE) Injection: High - Eliminates the risk of XXE injection vulnerabilities within Solr's XML processing capabilities.
• Currently Implemented:
  • It is assumed that default XML parser configurations in recent Solr versions have mitigations against XXE vulnerabilities. However, explicit configuration within Solr to definitively disable XXE processing has not been actively implemented or verified.
• Missing Implementation:
  • Explicit configuration to disable XXE processing in the XML parsers used by Solr has not been implemented and rigorously verified. Security testing specifically to confirm XXE mitigation in Solr is lacking.