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Mitigation Strategies Analysis for apache/solr

Mitigation Strategy: Authentication and Authorization (RBAC)

Mitigation Strategy: Implement Role-Based Access Control (RBAC) with Strong Authentication within Solr.

  • Description:

    1. Choose Authentication Method: Select a Solr-supported authentication method. Prioritize Kerberos or PKI if feasible. If using Basic Authentication, always enforce HTTPS (this is external, but essential). JWT is an option if integrating with an existing identity provider.
    2. Configure Authentication Plugin: In Solr's security.json, configure the chosen authentication plugin (e.g., BasicAuthPlugin, KerberosPlugin). Provide necessary parameters (e.g., realm, keytab file for Kerberos).
    3. Define Roles: Identify distinct user roles within your application (e.g., "searcher," "indexer," "administrator," "analyst"). Document these roles clearly.
    4. Define Permissions: For each role, define specific permissions. Use Solr's authorization framework (typically Rule-Based Authorization). Permissions should specify:
      • Collection: Which Solr collections the role can access.
      • Path: Which Solr API endpoints (e.g., /select, /update, /admin/cores) the role can access.
      • Method: Which HTTP methods (GET, POST, etc.) are allowed for each path.
      • Params: (Optional) Restrict access based on specific query parameters.
    5. Assign Permissions to Roles: In security.json, create authorization rules that map roles to permissions. Use the "role" property to specify the role and the "permissions" property to list the allowed actions.
    6. Assign Users to Roles: Associate users with their appropriate roles. The mechanism for this depends on the authentication method. For Basic Authentication, you might manage users and roles directly in security.json. For Kerberos or JWT, user-role mapping might be handled by your identity provider (external, but the mapping is used by Solr).
    7. Enable Authorization: Ensure that the authorization plugin is enabled in security.json.
    8. Test Thoroughly: Test all roles and permissions to ensure they function as expected. Try to access resources with different users and roles to verify access control.
    9. Regular Review: Periodically review and update roles and permissions to reflect changes in the application or user base.

  • Threats Mitigated:

    • Unauthorized Access (Severity: Critical): Prevents unauthorized users from accessing Solr data or performing administrative actions via Solr's API.
    • Data Breaches (Severity: Critical): Limits the scope of potential data breaches by restricting access to sensitive data based on roles.
    • Privilege Escalation (Severity: High): Prevents users from gaining access to resources or performing actions beyond their authorized privileges within Solr.
    • Insider Threats (Severity: High): Reduces the risk of malicious or accidental actions by authorized users by limiting their permissions within Solr.

  • Impact:

    • Unauthorized Access: Risk reduced significantly (from Critical to Low/Negligible with proper implementation).
    • Data Breaches: Impact of a breach significantly reduced, as attackers can only access data permitted by the compromised user's role.
    • Privilege Escalation: Risk significantly reduced, as users cannot elevate their privileges beyond their assigned role.
    • Insider Threats: Impact reduced, as users are limited in the actions they can perform.

  • Currently Implemented:

    • Basic Authentication with HTTPS is implemented on the staging server (staging.example.com). (HTTPS is external, but the authentication is configured in Solr).
    • Rule-Based Authorization is partially implemented, with roles defined for "reader" and "writer" on the products collection.

  • Missing Implementation:

    • Kerberos authentication is not implemented, but is planned for the production environment.
    • Authorization is missing for the logs collection.
    • Path-based permissions are not fully implemented; only collection-level permissions are in place.
    • Regular review process for roles and permissions is not yet formalized.
    • No authorization implemented on development servers.

Mitigation Strategy: Input Validation and Parameterized Queries (within Solr Client Code)

Mitigation Strategy: Implement Strict Input Validation and Use Parameterized Queries in the code that interacts with Solr.

  • Description:

    1. Identify All Input Points: Identify all points in your application code where user-supplied data is used to construct Solr queries.
    2. Use Parameterized Queries: Never build Solr queries by directly concatenating user input with query strings. Instead, use Solr's parameterized query features through your client library:
      • Use the client library's methods for setting the q parameter.
      • Use the client library's methods for setting fq (filter query) parameters.
      • Use the client library's methods for setting other named parameters (e.g., sort, start, rows).
      • Use Solr client libraries (e.g., SolrJ for Java) which provide methods for safely constructing queries with parameters. This is crucial.
    3. Whitelist Allowed Parameters: In your application code, create a whitelist of allowed query parameters for each endpoint. Reject any requests containing unexpected parameters.
    4. Validate Input Types: For each parameter, validate that the user-supplied input conforms to the expected data type (e.g., integer, date, string with a maximum length). Use appropriate validation libraries or functions within your application code.
    5. Sanitize Input (if necessary): If you must handle potentially dangerous input (e.g., HTML), use a robust sanitization library (e.g., OWASP Java Encoder) in your application code to remove or escape malicious characters. Never rely on simple string replacements.
    6. Test Thoroughly: Test all input points with various inputs, including valid, invalid, and potentially malicious inputs. Use fuzz testing techniques to generate a wide range of inputs.

  • Threats Mitigated:

    • Solr Injection Attacks (Severity: Critical): Prevents attackers from injecting malicious code into Solr queries through your application.
    • XXE Attacks (Severity: Critical): Reduces the risk of XXE attacks by controlling how XML input is processed before it reaches Solr.
    • RCE via Velocity/RunExecutable (Severity: Critical): By controlling input before it reaches Solr, reduces the risk of exploiting vulnerabilities in these components.
    • Data Exfiltration (Severity: High): Prevents attackers from using injection attacks to extract sensitive data.

  • Impact:

    • Solr Injection Attacks: Risk significantly reduced (from Critical to Low/Negligible with proper implementation).
    • XXE/RCE Attacks: Risk significantly reduced, although other mitigations (disabling vulnerable components) are also crucial.
    • Data Exfiltration: Risk significantly reduced.

  • Currently Implemented:

    • The main search endpoint (/search) uses parameterized queries with SolrJ.
    • Basic input type validation is implemented for the q parameter (string length limit).

  • Missing Implementation:

    • Whitelisting of allowed parameters is not implemented.
    • Input validation is not implemented for all API endpoints.
    • Sanitization of HTML input is not implemented (currently, HTML input is rejected).
    • Fuzz testing is not part of the regular testing process.
    • No input validation on development servers.

Mitigation Strategy: Disable Unnecessary Solr Features

Mitigation Strategy: Disable or Secure Unnecessary Solr Features in Solr's configuration.

  • Description:

    1. Identify Unused Features: Review the Solr configuration (solrconfig.xml, security.json) and identify any features that are not required for the application. Common candidates include:
      • RemoteStreaming
      • Config API
      • Admin UI (disabling within Solr, not just blocking network access)
      • VelocityResponseWriter
      • RunExecutableListener
      • Update Request Processors (custom ones)
    2. Disable Features: For each unused feature, disable it in the configuration. This often involves setting a configuration property to false or removing the relevant configuration section. For example, in solrconfig.xml, you might remove request handlers or response writers.
    3. Secure Features (if needed): If a feature must be used, ensure it is configured securely within Solr:
      • Config API: Restrict access using authorization rules in security.json.
      • Admin UI: Disable it entirely in solrconfig.xml if possible. If not, restrict access using authorization rules in security.json.
      • VelocityResponseWriter: Use a patched Solr version and consider alternatives. If used, configure it securely.
      • RunExecutableListener: Use a patched Solr version and consider alternatives. If used, configure it securely.
      • Update Request Processors: Carefully review and audit any custom update request processors. Restrict their capabilities using Solr's security features.
    4. Test Thoroughly: After disabling or securing features, test the application thoroughly to ensure that functionality is not affected and that the security measures are effective.

  • Threats Mitigated:

    • RCE via Velocity/RunExecutable (Severity: Critical): Disabling these features eliminates the risk of exploitation through these specific components.
    • Unauthorized Configuration Changes (Severity: High): Securing the Config API prevents unauthorized modifications via the API.
    • Information Disclosure (Severity: Medium): Disabling or securing the Admin UI prevents unauthorized access to system information through the UI.
    • Exploitation of Unknown Vulnerabilities (Severity: Variable): Reducing the attack surface by disabling unused features reduces the likelihood of exploitation of unknown vulnerabilities in those features.
    • Remote Streaming Exploitation (Severity: High): Disabling remote streaming prevents potential data leaks or RCE through this feature.

  • Impact:

    • RCE: Risk eliminated for disabled features. Risk significantly reduced for secured features.
    • Unauthorized Configuration Changes: Risk significantly reduced.
    • Information Disclosure: Risk significantly reduced.
    • Exploitation of Unknown Vulnerabilities: Risk reduced.

  • Currently Implemented:

    • VelocityResponseWriter is disabled in solrconfig.xml.
    • RunExecutableListener is disabled in solrconfig.xml.
    • Admin UI access is restricted via network firewall rules on the staging server (this is external, but the ideal solution is to disable it in solrconfig.xml).

  • Missing Implementation:

    • RemoteStreaming is not explicitly disabled (should be verified in solrconfig.xml).
    • Config API is not secured with authorization rules in security.json.
    • Admin UI is not disabled in solrconfig.xml on development servers.
    • A comprehensive review of all Solr features and their security implications has not been conducted recently.

Mitigation Strategy: Solr Configuration Audits and Patching

Mitigation Strategy: Conduct Regular Security Audits of Solr's Configuration and Apply Patches Promptly to the Solr installation.

  • Description:

    1. Subscribe to Security Announcements: Subscribe to the Apache Solr security announcements mailing list to be notified of new vulnerabilities.
    2. Patching Schedule: Establish a regular patching schedule for Solr. Apply security patches as soon as possible after they are released. This involves downloading and installing the updated Solr version.
    3. Testing Patches: Before deploying patches to production, test them thoroughly in a non-production environment (staging, QA). This involves running your application against the patched Solr instance.
    4. Configuration Reviews: Regularly review Solr's configuration files (solrconfig.xml, security.json, and any other relevant configuration files) for security vulnerabilities. This is a manual process of examining the configuration for best practices and potential misconfigurations.
    5. Dependency Management: Keep all Solr dependencies (including the JVM) up-to-date. This involves updating the JVM and any libraries used by Solr.
    6. Log Review (Solr Logs): Regularly review Solr logs for suspicious activity. This involves examining the logs generated by Solr itself.

  • Threats Mitigated:

    • Exploitation of Known Vulnerabilities (Severity: Variable, depends on the vulnerability): Patching addresses known vulnerabilities in Solr itself.
    • Configuration Errors (Severity: Variable): Security audits can identify misconfigurations in Solr's configuration files that could lead to security vulnerabilities.
    • Weaknesses in Custom Code (Severity: Variable): Code reviews can identify security flaws in custom Solr components (if any are used).

  • Impact:

    • Exploitation of Known Vulnerabilities: Risk significantly reduced by timely patching.
    • Configuration Errors: Risk reduced by identifying and correcting misconfigurations.
    • Weaknesses in Custom Code: Risk reduced by identifying and fixing vulnerabilities.

  • Currently Implemented:

    • The team subscribes to the Solr security announcements mailing list.
    • Patches are applied to the staging server within one week of release.

  • Missing Implementation:

    • A formal patching schedule for production is not yet defined.
    • Regular, formal configuration reviews are not performed.
    • Dependency management is not automated.
    • Regular Solr log review is not formalized.
    • No patching or security audits on development servers.