mitigations.md

Mitigation Strategies Analysis for owncloud/core

Mitigation Strategy: Strict Input Validation and Sanitization (Core)

• Description:

  1. Identify Core Input Points: Within the core repository, pinpoint all locations where user-supplied data enters the application logic. This is crucially different from the previous, broader list, as we're focusing only on the core components. Examples within core might include:
     • Core API endpoints defined within core.
     • Internal functions within core that handle file paths, user IDs, or other data ultimately derived from user input.
     • Database query construction within core (even if abstracted).
     • Configuration settings read and processed within core.
  2. Define Core-Specific Whitelists: For each identified input point within core, define strict whitelists of allowed characters or data formats. These whitelists should be as restrictive as possible.
  3. Implement Validation in Core: Use PHP's filter_var() and custom validation functions within the core codebase to validate all inputs against the defined whitelists. Reject any invalid input before it's used in any further processing.
  4. Implement Sanitization in Core: After validation, sanitize the input within core using appropriate filter_var() sanitization filters. Prioritize validation over sanitization.
  5. Layered Validation (Within Core): If core has multiple layers of abstraction, implement validation at each layer where user-derived data is handled. Don't assume that a lower layer has already validated the input.
  6. Regular Expression Review (Core): Carefully review all regular expressions used within core for input validation to prevent ReDoS vulnerabilities.

• Threats Mitigated:

  • Path Traversal (High Severity): If core handles file paths, this prevents accessing files outside the intended directory.
  • Cross-Site Scripting (XSS) (High Severity): If core generates any HTML output, this reduces the risk (output encoding is still the primary defense, but this adds a layer).
  • Code Injection (High Severity): Prevents injection of PHP code or other executable code through input handled within core.
  • Denial of Service (DoS) (Medium Severity): Can help prevent some DoS attacks by limiting input lengths within core.
  • Server-Side Request Forgery (SSRF) (High Severity): If core makes external requests based on user input, this is critical.

• Impact: (Same as previous, but focused on the impact within core's responsibilities)

  • Path Traversal: Risk reduced from High to Low (within core).
  • XSS: Risk reduced from High to Medium (within core).
  • Code Injection: Risk reduced from High to Low (within core).
  • DoS: Risk reduced from Medium to Low (for input-related DoS within core).
  • SSRF: Risk reduced from High to Low (if applicable within core).

• Currently Implemented (Likely/Partially - Core):

  • Some level of input validation is likely present in core API handlers.
  • Database interactions within core likely use prepared statements (see below).

• Missing Implementation (Potential Areas - Core):

  • Consistent and comprehensive validation across all core input points.
  • Sufficiently strict whitelisting.
  • Layered validation within core's internal functions.
  • Thorough review of regular expressions for ReDoS.

Mitigation Strategy: Secure File Type Verification (Core)

• Description:

  1. Core File Handling: Identify all locations within the core repository where file uploads or file processing occurs. This might involve core file storage logic, or internal functions that handle file metadata.
  2. Avoid MIME Type Reliance (Core): Ensure that core code never relies solely on the MIME type provided by the client for file type determination.
  3. File Signature Analysis (Core): Implement file signature analysis (magic bytes) using PHP's finfo_file() within the core codebase to determine the true file type.
  4. Core Whitelist: Maintain a whitelist of allowed file extensions and corresponding magic byte signatures within core, or in a configuration file loaded by core.
  5. Verification in Core: The verification process (reading file bytes, comparing to the whitelist) must be implemented within the core codebase.
  6. Archive Handling (Core): If core handles archive extraction or processing, implement size limits, content scanning, and file type restrictions within core.
  7. Executable File Restrictions (Core): Implement strict restrictions on executable file types within core's file handling logic.

• Threats Mitigated:

  • File Upload Attacks (High Severity): Prevents uploading malicious files disguised as other types, if core handles file uploads.
  • Cross-Site Scripting (XSS) (High Severity): Reduces XSS risk if core handles file uploads that could contain malicious HTML.
  • Remote Code Execution (RCE) (High Severity): Prevents execution of malicious code uploaded through core's file handling.

• Impact: (Focused on core's responsibilities)

  • File Upload Attacks: Risk reduced from High to Low (within core).
  • XSS: Risk reduced from High to Medium (within core).
  • RCE: Risk reduced from High to Low (within core).

• Currently Implemented (Likely/Partially - Core):

  • May be present in core file storage logic, but might be incomplete or rely on less secure methods.

• Missing Implementation (Potential Areas - Core):

  • Consistent application across all core file handling functions.
  • Robust handling of archive files within core.
  • Primary reliance on file signature analysis (magic bytes) within core.

Mitigation Strategy: Prepared Statements and Parameterized Queries (Core)

• Description:

  1. Core Database Interactions: Identify all database interactions within the core repository.
  2. PDO Usage (Core): Ensure that core uses PHP's PDO (or a demonstrably secure equivalent) for all database access.
  3. No Concatenation (Core): Absolutely no direct concatenation of user-supplied data into SQL queries within core.
  4. Prepared Statements (Core): Use prepared statements with placeholders and bindParam()/bindValue() for every database query within core.
  5. Code Audit (Core): Thoroughly audit all core code that interacts with the database to confirm the consistent use of prepared statements.
  6. ORM Usage Review (Core): If an ORM is used within core, verify that it correctly uses prepared statements and doesn't have any known vulnerabilities that could lead to SQL injection.

• Threats Mitigated:

  • SQL Injection (Critical Severity): Completely prevents SQL injection attacks targeting database interactions managed by core.

• Impact:

  • SQL Injection: Risk reduced from Critical to Negligible (within core).

• Currently Implemented (Likely/Partially - Core):

  • ownCloud core likely uses PDO and prepared statements in most database interactions.

• Missing Implementation (Potential Areas - Core):

  • Older parts of the core codebase.
  • Any custom SQL queries that bypass the standard database abstraction layer.
  • Stored procedures used by core (need separate review).

Mitigation Strategy: Output Encoding (Context-Specific) (Core)

• Description:

  1. Identify Core Output Points: Identify all locations within the core repository where user-supplied or user-influenced data is included in output sent to the client (e.g., API responses, HTML fragments).
  2. Context-Specific Encoding (Core): Use the appropriate encoding function within core based on the output context:
     • HTML: htmlspecialchars() with appropriate flags.
     • JavaScript: A dedicated JavaScript encoding function.
     • URLs: urlencode() or a robust URL encoding library.
  3. Templating Engine (Core): If core uses a templating engine, ensure it's configured for automatic and context-aware output encoding.
  4. Double Encoding Prevention (Core): Implement checks within core to avoid double encoding.
  5. API Responses (Core): Ensure that API responses generated by core properly encode data, especially if returning JSON or XML.

• Threats Mitigated:

  • Cross-Site Scripting (XSS) (High Severity): Prevents XSS attacks if core generates any output containing user data.

• Impact:

  • XSS: Risk reduced from High to Low (within core's output generation).

• Currently Implemented (Likely/Partially - Core):

  • core likely has some output encoding, especially in API responses.

• Missing Implementation (Potential Areas - Core):

  • Consistent encoding across all core output points.
  • Correct context-specific encoding.
  • Double encoding issues.