threat-modeling.md

Threat Model Analysis for nodejs/string_decoder

Threat: Denial of Service (DoS) through Maliciously Crafted Byte Streams

• Description: An attacker sends specially crafted byte streams specifically designed to exploit processing inefficiencies or potential vulnerabilities within the string_decoder module itself. This can involve sending extremely long or complex multi-byte sequences that force string_decoder into computationally expensive operations, leading to excessive CPU and memory consumption. The attacker aims to overwhelm the server's resources specifically through malicious input processed by string_decoder, causing service disruption.
• Impact: Application slowdown to unresponsiveness, application crashes and complete service disruption, resource exhaustion on the server making it unavailable for legitimate users.
• Affected Component: string_decoder module (core decoding algorithms and processing logic).
• Risk Severity: High
• Mitigation Strategies:
  • Implement strict input validation and sanitization, including size limits on byte streams processed by string_decoder.
  • Apply rate limiting to endpoints that handle user-provided byte streams to mitigate DoS attempts.
  • Continuously monitor application resource usage (CPU, memory) to detect and respond to potential DoS attacks in real-time.
  • Keep Node.js and its core modules, including string_decoder (updated via Node.js updates), updated to the latest stable versions to benefit from performance improvements and security patches.

Threat: Indirect Injection Vulnerabilities via Encoding Confusion

• Description: An attacker exploits subtle encoding discrepancies or leverages vulnerabilities in string_decoder's decoding process to manipulate input strings in a way that bypasses application-level input validation and sanitization. By carefully crafting byte streams, the attacker can cause string_decoder to produce decoded strings that appear benign initially but contain malicious payloads or control characters that are later interpreted as commands or code in downstream application components (like database queries or shell commands). The attacker leverages string_decoder as a tool to subtly alter input and enable injection attacks indirectly.
• Impact: Successful exploitation of injection vulnerabilities such as SQL Injection, Command Injection, or Cross-Site Scripting (XSS), leading to data breaches, unauthorized access, or malicious code execution within the application or on client browsers.
• Affected Component: string_decoder module (specifically its decoding process and potential for subtle encoding transformations), application's input validation and sanitization logic (which is bypassed due to encoding confusion), and downstream components that process the seemingly sanitized decoded string.
• Risk Severity: High
• Mitigation Strategies:
  • Perform robust input validation and sanitization after the string has been decoded by string_decoder. This ensures that validation is applied to the actual string that will be used by the application, accounting for any transformations introduced by decoding.
  • Maintain consistent encoding practices throughout the entire application stack to minimize the risk of encoding-related confusion and vulnerabilities. Explicitly define and enforce encoding standards.
  • Apply the principle of least privilege to components that process decoded strings. Limit the permissions and capabilities of these components to reduce the potential impact of successful injection attacks.
  • Implement proper output encoding (e.g., HTML entity encoding) whenever decoded strings are used in web contexts to prevent XSS vulnerabilities.