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attack-surface.md

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Attack Surface Analysis for ffmpegwasm/ffmpeg.wasm

Attack Surface: 1. Maliciously Crafted Media Files - Format String Vulnerabilities

  • Description: Exploiting vulnerabilities in FFmpeg's format parsing logic using specially crafted media files to trigger format string bugs within ffmpeg.wasm.
  • ffmpeg.wasm Contribution: ffmpeg.wasm directly uses FFmpeg's parsing libraries, inheriting any format string vulnerabilities present in the underlying C/C++ codebase. Processing user-provided media files with ffmpeg.wasm exposes this attack surface.
  • Example: A user uploads a .mp4 file with maliciously crafted metadata. When ffmpeg.wasm parses this metadata, it triggers a format string vulnerability, potentially leading to memory corruption or unexpected behavior within the WASM environment.
  • Impact: Memory corruption, potential for arbitrary code execution within the WASM sandbox (though sandbox escape is highly unlikely), denial of service.
  • Risk Severity: High
  • Mitigation Strategies:
    • Regular Updates: Keep ffmpeg.wasm updated to the latest version. Updates often include patches for format string vulnerabilities in the underlying FFmpeg.
    • Input Validation (Limited Effectiveness): While challenging for format string vulnerabilities specifically, implement general input validation to ensure files adhere to expected formats and sizes.
    • Sandboxing: Rely on the WebAssembly sandbox to limit the impact of potential code execution.

Attack Surface: 2. Maliciously Crafted Media Files - Buffer Overflow/Underflow

  • Description: Exploiting buffer overflow or underflow vulnerabilities in FFmpeg's media processing logic by providing crafted media files that cause improper memory handling within ffmpeg.wasm.
  • ffmpeg.wasm Contribution: ffmpeg.wasm's core function is media processing, making it directly susceptible to buffer overflow/underflow issues inherent in FFmpeg's decoding and processing routines.
  • Example: A user uploads a .avi file with a manipulated header that causes ffmpeg.wasm to allocate an insufficient buffer when decoding a video frame, leading to a buffer overflow when the frame data is processed.
  • Impact: Memory corruption, potential for arbitrary code execution within the WASM sandbox, denial of service, application crash.
  • Risk Severity: High
  • Mitigation Strategies:
    • Regular Updates: Keep ffmpeg.wasm updated to benefit from bug fixes and security patches in the underlying FFmpeg library that address buffer overflow/underflow vulnerabilities.
    • Resource Limits: Implement resource limits (memory, processing time) to mitigate the impact of potential DoS attacks caused by memory exhaustion from overflows.
    • Sandboxing: WebAssembly sandbox provides a layer of protection, limiting the scope of damage from memory corruption.

Attack Surface: 3. Maliciously Crafted Media Files - Integer Overflow/Underflow

  • Description: Exploiting integer overflow or underflow vulnerabilities during media file processing within ffmpeg.wasm, leading to incorrect memory allocation sizes and subsequent memory corruption.
  • ffmpeg.wasm Contribution: ffmpeg.wasm's media processing involves numerous calculations with file sizes and stream lengths. Integer overflow/underflow vulnerabilities in FFmpeg's C/C++ code are directly inherited by ffmpeg.wasm.
  • Example: A user uploads a media file with an extremely large declared stream length in its header. When ffmpeg.wasm attempts to allocate memory based on this length without proper overflow checks, an integer overflow occurs, resulting in a small memory allocation. Subsequent data processing then leads to a buffer overflow.
  • Impact: Memory corruption, potential for arbitrary code execution within the WASM sandbox, denial of service, application crash.
  • Risk Severity: High
  • Mitigation Strategies:
    • Regular Updates: Keep ffmpeg.wasm updated to benefit from fixes in the underlying FFmpeg library that address integer overflow/underflow vulnerabilities.
    • Secure Coding Practices in FFmpeg (Indirect): Rely on the security practices of the FFmpeg project itself, which actively works to mitigate these types of vulnerabilities.

Attack Surface: 4. Denial of Service (DoS) via Complex Files

  • Description: Causing a denial of service by providing excessively complex or malformed media files that consume excessive resources (CPU, memory, processing time) when processed by ffmpeg.wasm.
  • ffmpeg.wasm Contribution: ffmpeg.wasm performs resource-intensive media processing in the browser. Maliciously crafted files can exploit inefficiencies in processing certain formats or structures, leading to resource exhaustion within the client's browser or server if processing is offloaded.
  • Example: A user uploads a video file with an extremely high resolution, frame rate, or deeply nested codec structure. Processing this file with ffmpeg.wasm consumes all available CPU and memory in the browser tab, causing the application to become unresponsive or crash.
  • Impact: Denial of service, application unresponsiveness, degraded user experience, client-side or server-side crashes.
  • Risk Severity: High
  • Mitigation Strategies:
    • Resource Limits: Implement client-side or server-side resource limits on media processing. Limit file size, processing time, and potentially complexity metrics (e.g., resolution, frame rate).
    • Input Validation: Reject files that exceed predefined complexity thresholds or file size limits.
    • Throttling/Rate Limiting: Implement throttling or rate limiting on media processing requests to prevent abuse.

Attack Surface: 5. Exploiting Codec Vulnerabilities

  • Description: Targeting known vulnerabilities in specific codecs used by FFmpeg by providing media files encoded with those codecs to trigger the vulnerabilities within ffmpeg.wasm.
  • ffmpeg.wasm Contribution: ffmpeg.wasm supports a wide range of codecs, directly incorporating the codec implementations from the underlying FFmpeg library, including any vulnerabilities present in those codecs.
  • Example: A known vulnerability exists in a specific version of the H.264 decoder used by FFmpeg. An attacker uploads a video file specifically encoded to trigger this H.264 vulnerability when processed by ffmpeg.wasm.
  • Impact: Memory corruption, potential for arbitrary code execution within the WASM sandbox, denial of service, application crash.
  • Risk Severity: High
  • Mitigation Strategies:
    • Regular Updates: Keep ffmpeg.wasm updated to benefit from patches for codec vulnerabilities in the underlying FFmpeg library.
    • Codec Blacklisting (Advanced): Consider blacklisting or disabling the use of specific codecs known to have vulnerabilities if your application's functionality allows it.

Attack Surface: 6. Dependency and Supply Chain Risks - Compromised ffmpeg.wasm Package

  • Description: The risk of using a compromised ffmpeg.wasm package from a package registry (like npm) or CDN, where a malicious version could be distributed, directly impacting applications using ffmpeg.wasm.
  • ffmpeg.wasm Contribution: Applications directly depend on the ffmpeg.wasm package. If this package is compromised, the malicious code becomes part of the application's execution environment, specifically within the ffmpeg.wasm module.
  • Example: An attacker compromises the npm registry account for the ffmpeg.wasm package and uploads a malicious version containing a backdoor. Developers unknowingly install this compromised version, and their applications become vulnerable through the compromised ffmpeg.wasm library.
  • Impact: Complete application compromise, data theft, malware distribution, arbitrary code execution within the application's context.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Package Integrity Checks: Use package integrity checks (like npm audit, yarn audit, or verifying checksums) to detect known vulnerabilities and potential tampering.
    • Subresource Integrity (SRI): When loading ffmpeg.wasm from a CDN, use Subresource Integrity (SRI) to ensure the loaded file matches the expected hash and has not been tampered with.
    • Reputable Sources: Download ffmpeg.wasm from reputable sources (official npm package, official CDN) and verify the publisher.

Attack Surface: 7. Resource Exhaustion - Uncontrolled Processing

  • Description: Allowing users to initiate media processing tasks via ffmpeg.wasm without proper resource limits, leading to resource exhaustion on the client or server and causing denial of service.
  • ffmpeg.wasm Contribution: ffmpeg.wasm is the component performing the resource-intensive processing. Lack of control over its execution can lead to resource exhaustion.
  • Example: An application allows users to upload and convert videos without any limits. A user uploads a very large or complex video, causing ffmpeg.wasm to consume excessive CPU and memory, potentially crashing the user's browser or causing server overload if processing is server-side.
  • Impact: Denial of service, application unresponsiveness, degraded user experience, client-side or server-side crashes.
  • Risk Severity: High
  • Mitigation Strategies:
    • Resource Limits: Implement resource limits on media processing: file size limits, processing time limits, and complexity limits.
    • Throttling/Rate Limiting: Implement throttling or rate limiting on media processing requests.
    • Progress Indicators and User Feedback: Provide clear progress indicators to manage user expectations and prevent them from initiating excessive requests.