SFTPServerLib 1.0.2

SFTP Server

A lightweight, enterprise-ready SFTP server built on .NET 8 using the FxSsh library. Compatible with popular SFTP clients like FileZilla, WinSCP, and OpenSSH.

Installation

dotnet add package SFTPServerLib

Features

• Full SFTP v3 Support - Upload, download, rename, delete files and directories
• User Management - Built-in user authentication with granular permissions
• Audit Logging - Track all file operations for compliance and debugging
• Connection Limits - Configure maximum concurrent connections
• Cross-Platform - Runs on Windows, macOS, and Linux
• Secure - RSA and ECDSA host key support with SHA-2 algorithms

Quick Start

Basic Usage

using SFTPServer.Services;

// Create configuration
var config = new SftpServerConfiguration
{
    ListenAddress = "127.0.0.1",
    Port = 22,
    EnableLogging = true,
    MaxConnections = 100
};

// Create user manager and configure users
var userManager = new UserManager();

// Add a user with full permissions
userManager.AddOrUpdateUser(new UserAccount("admin", "admin123", config.RootDirectory)
{
    IsEnabled = true,
    CanUpload = true,
    CanDownload = true,
    CanDelete = true,
    CanCreateDirectory = true
});

// Create and start SFTP server
var server = new SftpServer(config, userManager);
server.Start();

Console.WriteLine("Press Ctrl+C to stop the server...");
await Task.Delay(-1);

Configuration

SftpServerConfiguration Properties

* RootDirectory defaults:

• All platforms: ~/.sftp/root (user's home directory)
• Fallback: {TempPath}/sftp/root if home directory is unavailable

** AuditLogPath defaults:

• All platforms: ~/.sftp/logs/audit.log (user's home directory)
• Fallback: {TempPath}/sftp/logs/audit.log if home directory is unavailable

Note: The server automatically detects the user's home directory using environment variables (HOME on Linux/macOS, USERPROFILE on Windows) and handles permission errors gracefully.

User Management

UserAccount Properties

UserManager Methods

var userManager = new UserManager();

// Add or update a user
userManager.AddOrUpdateUser(new UserAccount("john", "password123", "/home/john"));

// Get a user
var user = userManager.GetUser("john");

// Remove a user
userManager.RemoveUser("john");

// Get all users
var allUsers = userManager.GetAllUsers();

// Check permissions
bool canUpload = userManager.HasPermission("john", SftpOperation.Write);

Tested Clients

Underlying Technology: FxSsh

This SFTP server is built on top of the FxSsh library, a lightweight SSH server implementation.

Supported Algorithms

RFC Compliance

FxSsh adheres to the following RFC documents:

• RFC4250 - Protocol Assigned Numbers
• RFC4251 - Protocol Architecture
• RFC4252 - Authentication Protocol
• RFC4253 - Transport Layer Protocol
• RFC4254 - Connection Protocol
• RFC4344 - Transport Layer Encryption Modes
• RFC5656 - Elliptic Curve Algorithm Integration
• RFC6668 - SHA-2 Data Integrity Algorithms
• RFC8332 - Use of RSA Keys with SHA-2
• draft-ietf-secsh-filexfer-02 - SSH File Transfer Protocol (SFTP v3)

License

The MIT license

Target: .NET 8