secure-file-validator

A secure file validation library for Node.js that performs signature checking and content validation. It hardenings app from malicious file uploads by validating file types, checking file signatures, and scanning for suspicious patterns.

This library is built following industry-standard security guidelines:

• OWASP Unrestricted File Upload Prevention
• CWE-434: Unrestricted Upload of File with Dangerous Type
• NIST Security Guidelines for File Uploads

Features

• 🔒 Secure file signature validation
• 📝 Content pattern scanning for malicious code
• 🎯 Support for multiple file types (JPEG, PNG, GIF, PDF, SVG)
• ⚡ Promise-based async/await API
• 🛡️ Built-in security checks for PDF and SVG files
• 📦 Zero dependencies
• 🌟 TypeScript support
• ⚙️ Customizable file size validation

Installation

npm install secure-file-validator

Usage

Basic Usage (Default 5MB limit)

import { validateFile } from "secure-file-validator";

try {
  const result = await validateFile("path/to/your/file.pdf");

  if (result.status) {
    console.log("File is valid:", result.message);
  } else {
    console.log("File validation failed:", result.message);
  }
} catch (error) {
  console.error("Error:", error);
}

Custom File Size Limit

import { validateFile } from "secure-file-validator";

// Example: Set 10MB limit
const TEN_MB = 10 * 1024 * 1024; // 10MB in bytes

try {
  const result = await validateFile("path/to/your/file.pdf", {
    maxSizeInBytes: TEN_MB,
  });

  if (result.status) {
    console.log("File is valid:", result.message);
  } else {
    console.log("File validation failed:", result.message);
  }
} catch (error) {
  console.error("Error:", error);
}

Using Size Constants

// File size constants for convenience
const KB = 1024;
const MB = 1024 * KB;
const GB = 1024 * MB;

// Examples
const options = {
  maxSizeInBytes: 10 * MB, // 10MB
  // or
  // maxSizeInBytes: 1 * GB  // 1GB
};

const result = await validateFile("path/to/file.pdf", options);

Advanced Usage

import {
  validateFile,
  validateFileContent,
  checkFileSignature,
} from "secure-file-validator";

// Example: Custom validation pipeline with size limit
async function validateUserUpload(filePath) {
  const options = {
    maxSizeInBytes: 15 * 1024 * 1024, // 15MB limit
  };

  // First, validate the entire file
  const fileValidation = await validateFile(filePath, options);
  if (!fileValidation.status) {
    return fileValidation;
  }

  // Then, perform additional content validation if needed
  const contentValidation = await validateFileContent(filePath);
  return contentValidation;
}

Supported File Types

Category	File Type
Images	JPEG/JPG
Images	PNG
Images	GIF
Documents	PDF
Vector Graphics	SVG

API Reference

validateFile(filePath, options)

Main validation function that performs all checks.

Parameter	Type	Description	Default
filePath	string	Path to the file to validate	required
options	Object	Configuration options	{}
options.maxSizeInBytes	number	Maximum file size in bytes	5MB

Return Type	Description
Promise<Object>	Async result object
Promise<Object>.status	boolean indicating validation result
Promise<Object>.message	string containing detailed message

validateFileContent(filePath)

Performs content-specific validation.

Parameter	Type	Description	Default
filePath	string	Path to the file to validate	required

Return Type	Description
Promise<Object>	Async result object
Promise<Object>.status	boolean indicating validation result
Promise<Object>.message	string containing detailed message

checkFileSignature(buffer, signatures)

Checks file buffer against known signatures.

Parameter	Type	Description	Default
buffer	Buffer	File buffer to check	required
signatures	Array<Array<number>>	Valid signatures to check against	required

Return Type	Description
boolean	True if signature matches, false otherwise

File Size Configuration

The file size limit is configurable through the maxSizeInBytes option:

// Common file size limits
const limits = {
  small: 1 * 1024 * 1024, // 1MB
  medium: 10 * 1024 * 1024, // 10MB
  large: 100 * 1024 * 1024, // 100MB
  custom: 15.5 * 1024 * 1024, // 15.5MB
};

// Usage
const result = await validateFile("file.pdf", {
  maxSizeInBytes: limits.medium,
});

Example Results

// Successful validation
{
  status: true,
  message: "Content validation passed"
}

// Failed validation (file size)
{
  status: false,
  message: "File size exceeds limit of 5MB"
}

// Failed validation (invalid file type)
{
  status: false,
  message: "Invalid file extension"
}

// Failed validation (malicious content)
{
  status: false,
  message: "Suspicious pattern detected: /<script/i"
}

Limitations

• Only supports specified file types
• No stream processing support
• Binary file content is not deeply analyzed
• Pattern matching is done on string representation of files

Error Handling

try {
  const options = { maxSizeInBytes: 10 * 1024 * 1024 }; // 10MB
  const result = await validateFile("path/to/file.pdf", options);

  if (!result.status) {
    // Handle invalid file
    console.error("Validation failed:", result.message);
    // Take appropriate action (e.g., delete file, notify user)
  }
} catch (error) {
  // Handle system errors
  console.error("System error:", error.message);
  // Take appropriate action (e.g., log error, notify admin)
}

Contributing

Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.

FAQ

Q: How can I set a custom file size limit?
A: You can pass the limit in bytes using the options parameter:

const limit = 10 * 1024 * 1024; // 10MB
const result = await validateFile("file.pdf", { maxSizeInBytes: limit });

Q: What's the default file size limit?
A: The default limit is 5MB if no custom limit is specified.

Q: Can I set unlimited file size?
A: While technically possible by setting a very large number, it's not recommended as files are read into memory during validation.

Q: How can I handle different size limits for different file types?
A: You can create a wrapper function:

async function validateWithTypeLimit(filePath) {
  const extension = path.extname(filePath).toLowerCase();
  const limits = {
    ".pdf": 10 * 1024 * 1024, // 10MB for PDFs
    ".jpg": 5 * 1024 * 1024, // 5MB for JPGs
    ".svg": 2 * 1024 * 1024, // 2MB for SVGs
  };

  return validateFile(filePath, {
    maxSizeInBytes: limits[extension] || 5 * 1024 * 1024,
  });
}

License

This project is licensed under the MIT License

Thank you 😀