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Attack Surface Analysis for feross/safe-buffer

Attack Surface: Information Disclosure via allocUnsafe Misuse

Description: Incorrect use of Buffer.allocUnsafe() can lead to the exposure of previously used memory contents if the buffer is not fully overwritten before being used or sent to an output. This is the most significant direct risk associated with safe-buffer.

How safe-buffer Contributes: safe-buffer provides allocUnsafe, which is inherently unsafe if not used correctly. The library explicitly warns about this, but the responsibility for safe usage lies with the developer. The very existence of this function within the safe-buffer API is the direct contribution.

Example:

//Vulnerable code
const buffer = Buffer.allocUnsafe(1024);
buffer.write("Hello"); // Only a small portion is overwritten
res.send(buffer); // Potentially leaks uninitialized memory (sensitive data)

Impact: Leakage of sensitive data (e.g., previous requests, encryption keys, other process memory, secrets). This can lead to credential theft, session hijacking, or other serious security breaches.

Risk Severity: High (potentially Critical, depending on the leaked data)

Mitigation Strategies:

  • Avoid allocUnsafe: Prefer Buffer.alloc() whenever possible. allocUnsafe should only be used when absolutely necessary for performance, and with extreme caution. This is the primary and most effective mitigation.
  • Immediate Overwrite: If allocUnsafe must be used, ensure the entire buffer is immediately and completely overwritten with known, safe data before any part of it is exposed or used in a way that could leak information. Zero-fill the buffer immediately after allocation if the intended data isn't immediately available.
  • Code Reviews: Mandatory code reviews should specifically scrutinize any use of allocUnsafe to ensure proper handling and complete overwriting. This is a crucial preventative measure.
  • Linters: Use linters (e.g., ESLint) with rules to flag or warn about the use of allocUnsafe. Configure the linter to treat allocUnsafe usage as an error, requiring explicit justification and override comments.
  • Static Analysis: Consider using static analysis tools that can detect potential information leaks related to uninitialized memory.