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Attack Surface Analysis for naptha/tesseract.js

Attack Surface: Maliciously Crafted Input Images - Image Parsing Exploits

Description: Exploiting vulnerabilities within image parsing libraries (used by browsers or WASM) when tesseract.js processes user-provided images. Specially crafted images can trigger these vulnerabilities.

tesseract.js Contribution: tesseract.js directly processes user-supplied images for OCR. It relies on underlying image decoding mechanisms, making it a vector if those mechanisms are vulnerable.

Example: A malicious actor uploads a crafted TIFF image to an application using tesseract.js. This TIFF image exploits a buffer overflow in the browser's TIFF decoding library triggered when tesseract.js attempts OCR. This could lead to arbitrary code execution within the user's browser.

Impact: Critical. Arbitrary code execution on the client-side (user's browser), potentially leading to complete compromise of the user's session, data theft, malware installation, or further attacks. In server-side Node.js scenarios, server compromise is possible.

Risk Severity: Critical

Mitigation Strategies:

  • Strict Input Validation: Implement checks to validate image file types and sizes before processing with tesseract.js. While deep image parsing validation is complex, basic checks can help.
  • Content Security Policy (CSP): Enforce a strict CSP to significantly limit the capabilities of JavaScript, mitigating the impact of potential code execution from image parsing exploits.
  • Browser and Runtime Updates: Mandate or encourage users to use up-to-date browsers and Node.js versions, as these updates frequently contain critical security patches for image handling and WASM runtimes.
  • Sandboxed Processing (Server-side Node.js): If using Node.js, isolate tesseract.js processing within a sandboxed environment (like containers or VMs) to contain potential exploits and limit server-wide impact.

Attack Surface: Algorithmic Complexity DoS via Input Images

Description: Denial of Service (DoS) attacks achieved by providing tesseract.js with images that are designed to be computationally expensive to process, overwhelming system resources.

tesseract.js Contribution: tesseract.js's core OCR functionality can be resource-intensive, especially with complex or noisy images. Attackers can exploit this to cause DoS.

Example: An attacker floods an application using tesseract.js with numerous requests, each containing very large, high-resolution images with complex backgrounds and distorted text. Processing these images simultaneously exhausts server CPU and memory, causing the application to become unresponsive and deny service to legitimate users.

Impact: High. Denial of Service (DoS), rendering the application unavailable to legitimate users. This can lead to business disruption and reputational damage.

Risk Severity: High

Mitigation Strategies:

  • Rate Limiting and Request Throttling: Implement strict rate limiting on OCR requests based on user IP or session to prevent abuse. Throttling can slow down attackers and protect resources.
  • Resource Quotas and Monitoring: Set resource limits (CPU, memory) for the application or tesseract.js processing. Implement monitoring to detect unusual resource consumption patterns that might indicate a DoS attack.
  • Asynchronous Processing and Queues: Process OCR tasks asynchronously using queues. This prevents a surge of requests from blocking the main application thread and allows for controlled processing.
  • Input Image Restrictions: Enforce reasonable limits on image size, resolution, and file types accepted for OCR processing to reduce the potential for resource exhaustion.

Attack Surface: WASM Module Vulnerabilities - Inherited from Tesseract Engine

Description: Security vulnerabilities originating from the underlying C++ Tesseract engine that persist in the compiled WebAssembly module used by tesseract.js.

tesseract.js Contribution: tesseract.js directly relies on the WASM module compiled from the C++ Tesseract codebase. Any security flaws in the upstream C++ code can potentially be present and exploitable in tesseract.js.

Example: A memory corruption vulnerability exists in a specific text rendering function within the C++ Tesseract engine. This vulnerability is not fully mitigated during WASM compilation. An attacker crafts an image that, when processed by tesseract.js, triggers this vulnerable code path in the WASM module, potentially leading to unexpected behavior or denial of service.

Impact: High. Potential for unexpected behavior, denial of service, or in less likely scenarios, memory corruption within the WASM sandbox. While full sandbox escape is improbable in browsers, unexpected behavior can still be exploited.

Risk Severity: High

Mitigation Strategies:

  • Regular tesseract.js Updates: Keep tesseract.js updated to the latest version. Updates often include security patches addressing vulnerabilities in the underlying Tesseract engine.
  • Monitor Tesseract Security Advisories: Track security advisories and vulnerability reports for the upstream Tesseract project. Apply updates to tesseract.js promptly when upstream fixes are released.
  • WASM Runtime Security Reliance: Depend on the security features of the browser or Node.js WASM runtime environment to provide a baseline level of sandboxing and isolation for the WASM module.