Implement Robust File Permission and Access Error Handling

[SoYan500]

Implement Robust File Permission and Access Error Handling

Description

Task

Implement robust error handling for file access and permission issues

Acceptance Criteria

• Correctly handle file not found errors
• Prevent unauthorized file access
• Sanitize and validate file paths
• Provide clear, secure error messages
• Prevent directory traversal attacks

Summary of Work

Overview

This pull request adds comprehensive error handling for file access and permission issues in the CDN file serving application, enhancing security and providing clear error feedback.

Key Changes

• Implemented FileAccessError custom error class for specific file access scenarios
• Enhanced safeReadFile function with detailed error handling for different file access scenarios
• Added path validation to prevent directory traversal attacks
• Provided granular error messages for different access failure reasons

Implementation Details

Error Handling Improvements

1. File Not Found Handling

   • Catch and transform ENOENT error to user-friendly 'File not found' message
   • Prevents information disclosure about system file structure

2. Permission Denial Handling

   • Detect and handle EACCES errors with specific 'Permission denied' message
   • Prevents unauthorized file access attempts

3. Path Validation

   • Normalize and resolve file paths to prevent directory traversal
   • Throw FileAccessError if file is outside allowed CDN directory

Error Scenarios Covered

• Attempting to access non-existent files
• Trying to read files without read permissions
• Attempting to access files outside the CDN directory

Testing Approach

• Comprehensive error scenario testing
• Validation of path normalization and resolution
• Ensuring no system-sensitive information is leaked

Security Considerations

• Uses path.normalize() and path.resolve() to sanitize file paths
• Implements strict path checking to prevent directory traversal
• Provides minimal, safe error information to clients

Performance Impact

• Minimal overhead with lightweight error handling
• Fast path validation and error detection

Changes Made

• Added comprehensive error handling in safeReadFile function
• Implemented FileAccessError for specific file access scenarios
• Enhanced path validation to prevent directory traversal
• Added granular error messages for different access failure reasons

Tests

• Verify file not found error handling
• Test permission denied scenarios
• Validate path traversal prevention
• Check error message content and specificity

Signatures

Staking Key

Hi85KVXFxw53EPtx9aU3JKWcUn9tJerXEX8vkPivdGYZ: 7UHHPTTDQsYBM5LNWZegxbrVs9pfH3Kqg5u2JrjXpYmAjEXRX8EVkjKVRgLM4qGuWyt8rytf9ir5ifBSG5sTKocvfTVi7tH7gsv1y2aaTCuKRprpRx7aLGmyKYrYnGi7aJQQdWhxdVUqbasgZavNc9CxaiaGS925pwfJKvAf83FXWqEi8wUfZrwDxXMKxYPrdtyhFUHMykras12ngwtG8q4b43pyNahwUeUjAhNX4wjhznGLdQiHfaRKViqqdtsDLnUmAaG3ZP2xduHLJDqkHhmDXoLWvojSa8XUnMHK6sTnvJnBnSDagEDTqdqLZw8bmQ8aeqwamzR5xwGzA6156mT9ghzPb2TTGj4kuJmqVFpgmgxEUsXQxepeXuZqF1bBBbVNGC396V11BcF56GcdhSUzuZaAZDSrY

Public Key

3EHUVFpx8xQCU8AdKG7vneVy5eTeeM6p8tXohn7RFoav: 73MQyVk4D8ygJoQ3oRGVERZ9gmD15LAhLdKP2Nn6SUfk9QDL5bHGaDwpchMmP7EYQXeSNbE6iEnRNZY83F2exkvX2p31cjD4pUoiyi7skd6NeKAbn8JFHXtAUKzuLsnLhguxdYSaec6hBFNDv6pfk8GA2ieG7GD371YfwgBe6QzcW7f4nCVQetUQJMbHwgPAmfbn8Lbyww3d3GGVD43KtC1RabaceeeP1qfHfrChbKqKW2JPVNzXPVrRRgGHLZXFiU17gHmVT8MqRUhQq1Jaa436DUevcRFUSpDwXc73dUiViNh3GvujfhtXsdUgCmiJBK2W5o3ZbRBkLQeh9tdaAVCpf8HaiKnntzamdi8N4Ybuw6yWVB3UHSoScdjMq5dYdCKuPgXC9VeyUZGGxcDoQQvACk3QzUgNQ