OpenSSH GUI

A cross-platform desktop application for managing SSH keys, known hosts, and authorized keys — built with Avalonia UI, ReactiveUI, and .NET 10.

The goal of this project is to give users a modern, keyboard-friendly GUI for everything that usually requires ssh-keygen or hand-editing text files. It runs on Windows, Linux, and macOS and works entirely locally — no cloud, no telemetry.

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Features

• Browse, inspect, and manage all SSH key files in your configured lookup paths
• Generate new SSH keys (RSA, ECDSA, ED25519) with configurable bit size, comment, password, and format
• Convert keys between OpenSSH and PuTTY v2/v3 formats in one click
• Change or clear the passphrase of any key file
• Rename key files safely (both private and public halves move together)
• Display SHA-256 fingerprints without ever unlocking the private key
• Open a FileInfo window per key to inspect, rename, delete, convert, or copy the password
• Edit the local known_hosts file; mark individual key entries or whole hosts for deletion
• Edit the local authorized_keys file
• Connect to a remote SSH server and edit its known_hosts and authorized_keys in the same UI
• Quick-connect from pre-configured ~/.ssh/config host blocks
• Export public or private key content to the clipboard
• Application settings: log level, theme (dark/light/system), font size, lookup paths, cache cleanup
• Full dark and light theme with a VS Code–inspired teal/amber/red colour palette

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Screenshots

Main Window

The main window lists all discovered SSH keys in a table. Each row shows:

• Lock/key icon indicating whether the key is encrypted and whether the passphrase has been provided
• Key algorithm (RSA, ECDSA, ED25519) and format (OpenSSH / PuTTY)
• SHA-256 fingerprint; password-protected keys show a Provide Password button inline
• Comment
• Action buttons: export public key, export private key, open FileInfo window

Main Window — Password Entered

Once a passphrase is provided, the fingerprint column shows the actual hash and a Forget Password button appears.

Add New SSH Key

Fields:

Field	Notes
Key filename	Directory dropdown (from lookup paths) + filename text box
Keytype	RSA / ECDSA / ED25519 — default name updates automatically
Bitsize	Populated from the cryptographic legal key sizes for the chosen type; hidden for ED25519
Password	Optional; leave blank for an unencrypted key
Comment	Defaults to user@hostname
Key Format	OpenSSH or PuTTY v2/v3

The Add button stays disabled until the filename passes validation (non-empty and not already on disk).

FileInfo Window

Shows all files associated with the key (e.g. id_ed25519 + id_ed25519.pub). From here you can:

• Change password — prompts for the new passphrase via a secure input dialog
• Rename — moves both halves, prompts for overwrite if a conflict is detected
• Delete — removes all associated files from disk
• Convert format — the SplitButton converts to the default target; the dropdown allows choosing any other available format
• Password field — shows masked passphrase with a toggle-visibility eye button and a copy-to-clipboard button

Application Settings

Section	Options
Log Level	Verbose / Debug / Information / Warning / Error / Fatal
Theme	Default (system) / Dark / Light
Cache Options	Delete log files older than N days; clear whole application cache
Font Size	Numeric up/down; reset button restores the default
Lookup Paths	Add/remove directories the key crawler searches

Connect to Server

The connection window supports:

• Preconfigured connections — populated automatically from ~/.ssh/config host blocks that carry an IdentityFile directive
• Manual entry of hostname, username, and either a password or a public key from the recognised key list
• Test connection button — attempts a connection and shows a colour-coded status badge (unknown / success / failed)
• After a successful test, the Accept button becomes active and establishes the session for the rest of the UI

Edit known_hosts

Displays every known host in a collapsible list. Each host shows its individual key entries (algorithm + fingerprint). Toggle buttons mark individual keys or entire hosts for deletion on save. A Remote tab appears when a server connection is active, allowing the same edits on the server's known_hosts.

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Architecture Overview

The project is split into four assemblies:

Assembly	Role
OpenSSH_GUI	Avalonia application shell — views, view models, DI wiring, app lifecycle
OpenSSH_GUI.Core	Domain logic — key management, SSH config crawling, server connections, backup service
OpenSSH_GUI.SshConfig	SSH ~/.ssh/config parser, serialiser, and IConfiguration provider
OpenSSH_GUI.Dialogs	Reusable modal dialogs (message box, secure password input, validated text input)

Key Components

SshKeyManager is the central service. It owns the observable collection of SshKeyFile instances and exposes async operations for generate, rename, change-password, change-format, delete, and reload. Every destructive operation backs up the affected files first and restores them on failure.

SshKeyFile is a reactive record. It uses ReactiveUI.SourceGenerators to expose observable properties for fingerprint, comment, key type, format, password state, and file metadata. The fingerprint is extracted without decrypting the private key by parsing the unencrypted public key blob directly (supports OpenSSH .pub, OpenSSH private key header, and PPK v2/v3 headers).

DirectoryCrawler is an IAsyncEnumerable-based crawler that reads ~/.ssh/config identity files first (marking them as config-provided) and then enumerates the configured lookup directories for any remaining key files.

SshConfigParser is a zero-dependency recursive-descent parser for ssh_config(5) syntax. It handles Host, Match, and Include directives, wildcard patterns, quoted values, and inline comments, and exposes the result as an IConfiguration source so the rest of the app can bind directly via IOptions<T>.

ServerConnection wraps SSH.NET's SshClient and adds OS detection, remote known_hosts/authorized_keys read/write, and environment variable resolution on both Unix and Windows remote shells.

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Installation

No installer is required. Download the self-contained binary for your platform and run it directly.

The application creates the following paths on first launch if they do not exist:

• ~/.ssh/ (mode 700 on Unix)
• /etc/ssh/ or %PROGRAMDATA%\ssh\ (mode 755 on Unix)
• ~/.ssh/known_hosts and ~/.ssh/authorized_keys
• %APPDATA%\OpenSSH_GUI\ — configuration and log files

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Configuration File

Application settings are stored as JSON at:

• Linux / macOS: ~/.config/OpenSSH_GUI/OpenSSH_GUI.json
• Windows: %APPDATA%\OpenSSH_GUI\OpenSSH_GUI.json

The file is created automatically on first run. You can also edit it by hand — changes are picked up at runtime via IOptionsMonitor.

{
  "LookupPaths": [ "/home/user/.ssh" ],
  "PreferredTheme": "Dark",
  "LogLevel": "Warning",
  "FontSize": 14,
  "LoggerConfiguration": {
    "LogFileName": "OpenSSH_GUI.log",
    "LogFilePath": "/home/user/.config/OpenSSH_GUI/log"
  }
}

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Building from Source

Requirements: .NET 10 SDK.

git clone https://github.com/frequency403/OpenSSH-GUI
cd OpenSSH-GUI
dotnet build
dotnet run --project OpenSSH_GUI

Tests:

dotnet test OpenSSH_GUI.Tests

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Security Notes

• Passphrases are handled as raw byte buffers (SshKeyFilePassword) backed by a ReactiveBufferWriter<byte>. The buffer is zeroed via CryptographicOperations.ZeroMemory when cleared or disposed.
• The secure password input dialog (SecureInputDialog) intercepts TextInputEvent at tunnel phase to avoid Avalonia's default string accumulation in the TextBox internal buffer.
• Private key files are never read unless the user explicitly provides a passphrase. Fingerprints and metadata are always extracted from the unencrypted public portions of the key file.
• All destructive file operations (rename, convert, change password) create backups before modifying any file and restore them automatically on failure.

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Known Limitations

• SSH config editing (local ~/.ssh/config and remote sshd_config) is not yet implemented (placeholder menu items exist).
• Remote server operations require the connecting user to have read/write access to ~/.ssh/known_hosts and ~/.ssh/authorized_keys on the remote machine.

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Used Libraries

Library	Purpose
Avalonia UI	Cross-platform UI framework
ReactiveUI	MVVM + reactive extensions
ReactiveUI.SourceGenerators	Source-generated reactive properties and commands
ReactiveUI.Validation	Inline form validation
SSH.NET	SSH client
SshNet.Keygen	Key generation and format conversion
SshNet.PuttyKeyFile	PuTTY key file support
Material.Icons.Avalonia	Icon set
Serilog	Structured logging
BouncyCastle	SHA-256 fingerprint computation
Microsoft.Extensions.Hosting	DI, configuration, hosted services

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Authors

• Oliver Schantz — idea and primary development — GitHub

See also the contributors list.

License

This project is licensed under the MIT License.