attack-surface.md

Attack Surface Analysis for ankane/searchkick

Attack Surface: Search Query Injection

• Description: Attackers inject malicious Elasticsearch query syntax into search queries due to insufficient input sanitization, manipulating search logic or potentially executing unintended Elasticsearch operations.
• Searchkick Contribution: Searchkick's searchkick_search method directly passes user-provided search terms to Elasticsearch. Without proper sanitization before using Searchkick's search methods, the application becomes vulnerable to query injection attacks via the search interface provided by Searchkick.
• Example: A user enters a search query like "title:foo OR _source:true". If this is passed directly to searchkick_search without sanitization, an attacker could use Elasticsearch's _source:true parameter to retrieve all fields of indexed documents, potentially including sensitive data not intended for search results.
• Impact: Unauthorized access to data within Elasticsearch indices, potential bypass of intended search logic, and in vulnerable Elasticsearch configurations, potential execution of arbitrary Elasticsearch functions.
• Risk Severity: High
• Mitigation Strategies:
  • Developers:
    • Strict Input Sanitization: Thoroughly sanitize and validate all user input before it is used in searchkick_search. Implement allowlists for permitted characters and patterns in search terms.
    • Utilize Parameterized Queries/Query Builders: Employ Searchkick's or the Elasticsearch client's query builder methods to construct queries programmatically. Avoid raw string interpolation of user input into query strings.
    • Principle of Least Privilege (Elasticsearch User): Configure the Elasticsearch user credentials used by Searchkick with the minimum necessary permissions. Restrict or disable potentially dangerous Elasticsearch features like scripting if not required.

Attack Surface: Elasticsearch Access Control Weakness (Exploited via Searchkick)

• Description: Inadequate access control to the underlying Elasticsearch cluster, while not introduced by Searchkick, becomes a critical vulnerability that can be exploited through Searchkick if the application using Searchkick has access to a weakly secured Elasticsearch instance.
• Searchkick Contribution: Searchkick acts as an interface to Elasticsearch. If the Elasticsearch instance it connects to is publicly accessible or has weak authentication, Searchkick provides a pathway for attackers to potentially exploit these pre-existing Elasticsearch security weaknesses through the application. While Searchkick itself doesn't create the access control vulnerability, it relies on the security of the Elasticsearch setup and can be used to leverage any existing weaknesses.
• Example: The Elasticsearch instance used by Searchkick is exposed to the public internet without authentication. An attacker, gaining access through the application that uses Searchkick (or even directly if network access allows), can then directly interact with the Elasticsearch instance on ports 9200/9300, bypassing the application layer and Searchkick, to read, modify, or delete indexed data.
• Impact: Complete data breach, unauthorized data manipulation or deletion within Elasticsearch, denial of service against the Elasticsearch cluster.
• Risk Severity: Critical
• Mitigation Strategies:
  • Developers/System Administrators:
    • Enforce Strong Elasticsearch Authentication and Authorization: Implement robust authentication (e.g., username/password, API keys, RBAC) and authorization mechanisms within Elasticsearch itself.
    • Network Segmentation for Elasticsearch: Isolate the Elasticsearch cluster on a private network, restricting access only to authorized application servers. Use firewalls to enforce network access policies.
    • Secure Elasticsearch Configuration Best Practices: Adhere to Elasticsearch security best practices, including disabling default credentials, enabling HTTPS for communication, and regularly applying security patches to Elasticsearch.
    • Principle of Least Privilege (Searchkick User): Ensure the Elasticsearch user account used by Searchkick has the absolute minimum necessary permissions required for indexing and searching, and no more.

Attack Surface: Data Injection leading to Stored XSS (via Search Results)

• Description: Malicious data injected into indexed content, when displayed in search results without proper output encoding, results in Stored Cross-Site Scripting (XSS) vulnerabilities.
• Searchkick Contribution: Searchkick indexes data from Rails models. If these models contain user-provided content that is not sanitized before being stored and indexed, and if search results displaying this content are not properly output-encoded, Searchkick indirectly facilitates the delivery of Stored XSS payloads to users viewing search results. Searchkick makes the malicious content easily searchable and retrievable for display.
• Example: A user submits a comment containing <script>alert('XSS')</script>. This comment is stored in the database and indexed by Searchkick. When search results containing this comment are displayed on the website, and the application fails to HTML-encode the comment content before rendering it in the search results, the JavaScript code will execute in the browser of any user viewing those search results.
• Impact: Account compromise, session hijacking, redirection to malicious websites, website defacement, theft of sensitive user information.
• Risk Severity: High
• Mitigation Strategies:
  • Developers:
    • Mandatory Output Encoding of Search Results: Always and consistently HTML-encode all data retrieved from Searchkick and displayed in search results within the application's user interface. Utilize templating engine features or security libraries designed for output encoding (e.g., ERB::Util.html_escape in Ruby on Rails).
    • Proactive Input Sanitization at Model Level: Sanitize and validate user input at the model level before data is persisted and indexed by Searchkick. Employ HTML sanitization libraries (like Rails::Html::Sanitizer) to remove or escape potentially harmful HTML tags and attributes from user-provided content before indexing.
    • Implement Content Security Policy (CSP): Deploy a robust Content Security Policy to further mitigate the impact of potential XSS vulnerabilities by controlling the sources from which the browser is permitted to load resources, limiting the damage even if XSS is successfully injected.