RFE: Zmodem support

[TangTing520]

The RZ SZ command is not supported

[billchurch]

Seems like you are looking for Zmodem support.

This project would probably be a way to accomplish this. I will add it to the list but no ETA when it could be achieved.

[TangTing520]

OK, thank you for your reply

[billchurch]

Zmodem Support - Future Enhancement Requirements

Thank you for this feature request! Zmodem file transfer support would be a valuable addition to WebSSH2. Here are the requirements and implementation considerations for this enhancement:

Technical Requirements

1. xterm.js Zmodem Addon Integration

• Library: Integrate xterm-addon-zmodem
• Dependencies: Add zmodem.js library for protocol handling
• Client Integration: Modify webssh2_client to load and attach the addon

2. Protocol Implementation

Client-Side (Browser):

// Detect zmodem sequences
terminal.attachCustomKeyEventHandler((event) => {
  // Detect ZRQINIT sequence (rz command)
  // Detect ZRINIT sequence (sz command)
});

// Handle file selection for upload
const fileInput = document.createElement('input');
fileInput.type = 'file';
fileInput.onchange = handleFileUpload;

// Handle file download
zmodem.on('download', (filename, data) => {
  saveAs(new Blob([data]), filename);
});

Server-Side (Node.js):

// Proxy zmodem data between SSH and WebSocket
ssh.on('data', (data) => {
  if (isZmodemSequence(data)) {
    handleZmodemTransfer(data);
  }
});

3. User Interface Components

• Upload Dialog: File picker when rz is detected
• Download Progress: Progress bar for transfers
• Cancel Button: Allow users to abort transfers
• Transfer Status: Show speed, time remaining, success/failure

4. Security Considerations

• File Size Limits: Implement configurable max file size
• File Type Restrictions: Optional whitelist/blacklist for extensions
• Rate Limiting: Prevent abuse through transfer limits
• Sandboxing: Ensure transfers don't escape designated directories
• Virus Scanning: Optional integration with AV scanning

5. Configuration Options

{
  "zmodem": {
    "enabled": true,
    "maxFileSize": 104857600,  // 100MB
    "allowedExtensions": ["*"],
    "blockedExtensions": [".exe", ".dll"],
    "uploadDirectory": "/tmp/uploads",
    "downloadDirectory": "/tmp/downloads",
    "timeout": 30000
  }
}

Implementation Steps

1. Phase 1: Basic Integration

   • Add xterm-addon-zmodem to webssh2_client
   • Implement basic rz/sz detection
   • Create minimal file transfer UI

2. Phase 2: Full Protocol Support

   • Handle all Zmodem commands (rz, sz, rb, sb)
   • Implement error recovery and resume
   • Add progress tracking

3. Phase 3: Security & Polish

   • Add security controls
   • Implement configuration options
   • Create comprehensive testing suite
   • Add documentation

Testing Requirements

• Unit tests for protocol detection
• Integration tests with real SSH servers
• Performance tests with large files
• Security tests for path traversal, size limits
• Browser compatibility testing

Documentation Needs

• User guide for file transfers
• Configuration reference
• Security best practices
• Troubleshooting guide

Alternative Approaches

For immediate file transfer needs, consider:

1. SCP/SFTP Integration: Use existing SSH file transfer protocols
2. Base64 Encoding: Simple but inefficient workaround
3. External Tools: Separate file manager interface

Estimated Effort

• Development: 2-3 weeks for full implementation
• Testing: 1 week
• Documentation: 2-3 days

This is marked as a future enhancement. Community contributions are welcome! If you're interested in implementing this, please comment below and we can provide guidance.

References

• xterm-addon-zmodem
• zmodem.js
• Zmodem Protocol Specification