mitigations.md

Mitigation Strategies Analysis for ffmpegwasm/ffmpeg.wasm

Mitigation Strategy: Subresource Integrity (SRI) for ffmpeg.wasm

• Description:
  1. Generate the SRI hash for the specific ffmpeg.wasm file version being used. This can be done using command-line tools or online generators.
  2. In the HTML, when loading ffmpeg.wasm via a <script> tag, add the integrity attribute with the generated hash.
  3. Include crossorigin="anonymous" if loading from a CDN to enable SRI for cross-origin requests.

     <script src="https://cdn.example.com/ffmpeg.wasm" integrity="sha384-YOUR_SRI_HASH_HERE" crossorigin="anonymous"></script>

     This ensures the browser verifies the integrity of the ffmpeg.wasm file before execution.
  • Threats Mitigated:
    • Compromised ffmpeg.wasm Delivery (High Severity) - Mitigates risks if the CDN or delivery mechanism serving ffmpeg.wasm is compromised and serves a malicious version.
    • Man-in-the-Middle Attacks on ffmpeg.wasm (Medium Severity) - Prevents execution if an attacker intercepts and modifies the ffmpeg.wasm file during transit.
  • Impact:
    • Compromised ffmpeg.wasm Delivery: High reduction - Prevents execution of a malicious ffmpeg.wasm file.
    • Man-in-the-Middle Attacks on ffmpeg.wasm: High reduction - Prevents execution of a tampered ffmpeg.wasm file.
  • Currently Implemented: Yes, implemented in the index.html file where ffmpeg.wasm is loaded from CDN, using integrity and crossorigin attributes.
  • Missing Implementation: Not applicable, SRI is implemented for initial ffmpeg.wasm loading.

Mitigation Strategy: Version Pinning of ffmpeg.wasm

• Description:
  1. Explicitly specify a fixed, tested version of ffmpeg.wasm in your project's dependencies or CDN URL. Avoid using latest or dynamic tags. Example: https://cdn.example.com/[email protected]/ffmpeg-core.js.
  2. Document the pinned version in project documentation.
  3. Establish a process to review and update to newer versions after testing and security checks in a staging environment.
  • Threats Mitigated:
    • Unexpected ffmpeg.wasm Behavior from New Versions (Medium Severity) - Prevents automatic updates to potentially buggy or incompatible ffmpeg.wasm versions.
    • Exposure to Unpatched Vulnerabilities in Older ffmpeg.wasm (Medium Severity) - While pinning prevents unexpected updates, neglecting updates can lead to using vulnerable versions.
  • Impact:
    • Unexpected ffmpeg.wasm Behavior from New Versions: High reduction - Prevents instability from automatic updates.
    • Exposure to Unpatched Vulnerabilities in Older ffmpeg.wasm: Medium reduction - Requires active version management to update eventually.
  • Currently Implemented: Yes, version 4.4.1 is pinned in the CDN URL for ffmpeg.wasm loading, documented in README.md.
  • Missing Implementation: A formal, documented, and ideally automated process for regular version review and update of ffmpeg.wasm is missing.

Mitigation Strategy: Host ffmpeg.wasm Locally

• Description:
  1. Download ffmpeg.wasm from a trusted source (official releases).
  2. Include ffmpeg.wasm in your project's static assets.
  3. Configure your server to serve it from your domain.
  4. Update the <script> tag to load ffmpeg.wasm from your domain: <script src="/static/js/ffmpeg.wasm"></script>. This reduces reliance on external CDNs for ffmpeg.wasm delivery.
  • Threats Mitigated:
    • CDN Compromise Serving Malicious ffmpeg.wasm (High Severity) - Eliminates the risk of a compromised CDN serving a malicious ffmpeg.wasm.
    • CDN Outages Affecting ffmpeg.wasm Availability (Low Severity) - Ensures ffmpeg.wasm availability independent of CDN uptime.
  • Impact:
    • CDN Compromise Serving Malicious ffmpeg.wasm: High reduction - Removes CDN as a supply chain risk for ffmpeg.wasm.
    • CDN Outages Affecting ffmpeg.wasm Availability: High reduction - Ensures local availability of ffmpeg.wasm.
  • Currently Implemented: No, currently loading ffmpeg.wasm from a public CDN.
  • Missing Implementation: Needs implementation in build process to include ffmpeg.wasm in static assets and update HTML to load it locally.

Mitigation Strategy: Strict Input File Validation Before ffmpeg.wasm Processing

• Description:
  1. Implement client-side JavaScript validation before files are processed by ffmpeg.wasm.
     • Check MIME type against a whitelist (e.g., video/mp4, audio/mpeg).
     • Check file extension against a whitelist (e.g., mp4, mp3, wav).
     • Check file size against a maximum limit.
  2. (Optional, if server-side component exists) Implement server-side re-validation of MIME type, extension, size, and potentially magic numbers.
  3. Reject invalid files and provide clear error messages to the user. This ensures only expected media types are processed by ffmpeg.wasm.
  • Threats Mitigated:
    • Malicious File Processing by ffmpeg.wasm (High Severity) - Prevents ffmpeg.wasm from processing files that are not expected media types and might contain exploits.
    • Denial of Service (DoS) via Large Files to ffmpeg.wasm (Medium Severity) - Limits processing of excessively large files by ffmpeg.wasm, preventing resource exhaustion.
  • Impact:
    • Malicious File Processing by ffmpeg.wasm: High reduction - Significantly reduces risk of processing malicious files with ffmpeg.wasm.
    • Denial of Service (DoS) via Large Files to ffmpeg.wasm: High reduction - Prevents resource exhaustion in ffmpeg.wasm processing.
  • Currently Implemented: Yes, client-side validation for MIME type, extension, and size is implemented in the file upload component before ffmpeg.wasm is used.
  • Missing Implementation: Server-side validation (even if server-side ffmpeg is not used) and magic number validation are not implemented.

Mitigation Strategy: Sanitize Filenames and Paths for ffmpeg.wasm Commands

• Description:
  1. When using user-provided filenames or constructing paths for ffmpeg.wasm commands, sanitize these inputs.
  2. If constructing command strings manually (less recommended), escape special characters. Prefer using the ffmpeg.wasm API's options objects.
  3. For file operations within ffmpeg.wasm's virtual file system, sanitize filenames to prevent path traversal. This prevents command injection and path traversal vulnerabilities when interacting with ffmpeg.wasm.
  • Threats Mitigated:
    • Command Injection in ffmpeg.wasm Operations (High Severity) - Prevents attackers from injecting malicious commands if filenames are used unsafely in ffmpeg.wasm command construction.
    • Path Traversal within ffmpeg.wasm Virtual File System (Medium Severity) - Reduces risk of accessing files outside intended areas in ffmpeg.wasm's virtual file system.
  • Impact:
    • Command Injection in ffmpeg.wasm Operations: High reduction - Prevents command injection attacks against ffmpeg.wasm.
    • Path Traversal within ffmpeg.wasm Virtual File System: Medium reduction - Reduces risk of unintended file access within ffmpeg.wasm.
  • Currently Implemented: Basic filename sanitization (replacing spaces and special chars with underscores) is implemented before using filenames in ffmpeg.wasm commands.
  • Missing Implementation: More robust sanitization using whitelists or dedicated libraries could be implemented. Current sanitization is basic.

Mitigation Strategy: Limit Allowed FFmpeg Operations (Command Whitelisting for ffmpeg.wasm)

• Description:
  1. Identify necessary ffmpeg functionalities for your application.
  2. Create a whitelist of allowed ffmpeg commands and options that your application will use with ffmpeg.wasm.
  3. Enforce this whitelist in your application code. Reject any ffmpeg.wasm operations not on the whitelist.
  4. Regularly review and update the whitelist as needed. This restricts the attack surface by limiting the ffmpeg features accessible via ffmpeg.wasm.
  • Threats Mitigated:
    • Abuse of Unintended ffmpeg Functionality via ffmpeg.wasm (Medium to High Severity) - Prevents attackers from leveraging powerful or dangerous ffmpeg features through ffmpeg.wasm that are not intended for application use.
    • Reduced Impact of Command Injection in ffmpeg.wasm (Medium Severity) - Even if command injection occurs, limiting allowed commands restricts attacker options within ffmpeg.wasm.
  • Impact:
    • Abuse of Unintended ffmpeg Functionality via ffmpeg.wasm: High reduction - Significantly limits the attack surface of ffmpeg.wasm usage.
    • Reduced Impact of Command Injection in ffmpeg.wasm: Medium reduction - Limits potential damage from command injection by restricting available commands.
  • Currently Implemented: Implicit whitelisting - only video conversion to MP4 and audio extraction to MP3 are implemented in the application's UI and code using ffmpeg.wasm.
  • Missing Implementation: A formal, configurable whitelist and enforcement mechanism for ffmpeg.wasm commands is missing. The whitelisting is currently implicit in the code.

Mitigation Strategy: Timeouts for ffmpeg.wasm Processing

• Description:
  1. Implement timeouts for all ffmpeg.wasm operations.
  2. Set reasonable maximum execution times based on expected processing durations.
  3. Use setTimeout or similar mechanisms to monitor ffmpeg.wasm command execution time.
  4. Terminate ffmpeg.wasm processes that exceed timeouts and inform the user. This prevents long-running ffmpeg.wasm processes from exhausting browser resources.
  • Threats Mitigated:
    • Denial of Service (DoS) via Resource Exhaustion by ffmpeg.wasm (Medium Severity) - Prevents excessively long ffmpeg.wasm processing from tying up browser resources and causing DoS for the user.
    • Runaway ffmpeg.wasm Processes (Low Severity) - Limits impact of unexpected hangs or infinite loops in ffmpeg.wasm.
  • Impact:
    • Denial of Service (DoS) via Resource Exhaustion by ffmpeg.wasm: High reduction - Prevents resource exhaustion from long ffmpeg.wasm processes.
    • Runaway ffmpeg.wasm Processes: High reduction - Limits impact of hung ffmpeg.wasm processes.
  • Currently Implemented: Yes, timeouts are implemented for ffmpeg.wasm operations, currently set to 60 seconds.
  • Missing Implementation: Timeout value (60 seconds) is hardcoded and should be configurable. More granular timeouts based on operation type could be considered.

Mitigation Strategy: Isolate ffmpeg.wasm in Web Workers

• Description:
  1. Move all ffmpeg.wasm code and operations into a dedicated Web Worker.
  2. Main thread communicates with the worker via message passing.
  3. File handling and ffmpeg.wasm command execution occur within the worker.
  4. Main thread handles UI updates and worker communication only. This isolates ffmpeg.wasm execution from the main browser thread.
  • Threats Mitigated:
    • Main Thread Blocking by ffmpeg.wasm (Low Severity) - Prevents resource-intensive ffmpeg.wasm operations from freezing the main UI thread.
    • Slightly Reduced XSS Impact Related to ffmpeg.wasm (Low Severity) - Isolating ffmpeg.wasm in a worker provides a minor layer of separation.
  • Impact:
    • Main Thread Blocking by ffmpeg.wasm: High reduction - Ensures a responsive UI during ffmpeg.wasm processing.
    • Slightly Reduced XSS Impact Related to ffmpeg.wasm: Low reduction - Minor isolation benefit.
  • Currently Implemented: No, ffmpeg.wasm operations are currently performed in the main thread.
  • Missing Implementation: Refactoring to move ffmpeg.wasm execution to a Web Worker is a significant missing implementation.

Mitigation Strategy: Robust Error Handling and Logging for ffmpeg.wasm

• Description:
  1. Implement comprehensive error handling for all ffmpeg.wasm operations using try...catch.
  2. Log detailed error information (messages, commands, filenames, timestamps) for debugging and security monitoring (browser console and server-side if applicable).
  3. Display user-friendly error messages without revealing sensitive details.
  4. Monitor error logs for anomalies. This aids in debugging, security monitoring, and prevents information disclosure.
  • Threats Mitigated:
    • Information Disclosure via ffmpeg.wasm Error Messages (Low Severity) - Prevents revealing sensitive technical details in error messages.
    • Operational Issues with ffmpeg.wasm (Non-security) - Improves debugging and stability of ffmpeg.wasm integration.
    • Detection of Anomalous ffmpeg.wasm Activity (Medium Severity) - Enables detection of unusual error patterns that might indicate attacks.
  • Impact:
    • Information Disclosure via ffmpeg.wasm Error Messages: High reduction - Prevents leakage of sensitive info.
    • Operational Issues with ffmpeg.wasm: High reduction - Improves maintainability and stability.
    • Detection of Anomalous ffmpeg.wasm Activity: Medium reduction - Enhances security monitoring.
  • Currently Implemented: Basic error handling with try...catch and user-friendly messages is implemented. Errors are logged to the browser console.
  • Missing Implementation: Detailed logging (command details, timestamps), server-side logging, and error log monitoring are missing.

Mitigation Strategy: Regular Security Audits and Updates for ffmpeg.wasm Integration

• Description:
  1. Conduct periodic security audits of your application's ffmpeg.wasm integration (input validation, command handling, error handling, dependencies).
  2. Stay informed about ffmpeg and ffmpeg.wasm security updates and vulnerabilities.
  3. Regularly update ffmpeg.wasm to the latest stable version after testing in staging.
  4. Document audit process, findings, and update history. This ensures ongoing security and addresses known vulnerabilities in ffmpeg.wasm.
  • Threats Mitigated:
    • Unpatched Vulnerabilities in ffmpeg.wasm (High Severity) - Ensures timely patching of known security flaws in ffmpeg.wasm.
    • Security Misconfigurations in ffmpeg.wasm Integration (Medium Severity) - Regular audits help identify and fix security weaknesses in how ffmpeg.wasm is used.
  • Impact:
    • Unpatched Vulnerabilities in ffmpeg.wasm: High reduction - Reduces exposure to known vulnerabilities.
    • Security Misconfigurations in ffmpeg.wasm Integration: Medium reduction - Improves overall security posture.
  • Currently Implemented: No formal security audit process or regular update schedule for ffmpeg.wasm is in place.
  • Missing Implementation: A formal security audit schedule, a system for tracking security advisories, a staging environment for testing updates, and documented processes are needed.