Merge pull request #1 from ergosteur/claude/optimistic-davinci-2i411w

Rewrite SSH handler from C# to Rust for minimal footprint

.github/workflows/build.yml

@@ -16,38 +16,14 @@ jobs:
     - name: Checkout repository
       uses: actions/checkout@v4
 
-    - name: Configure Git Line Endings
+    - name: Setup Rust
-      run: git config --global core.autocrlf input
+      uses: dtolnay/rust-toolchain@stable
-
-    - name: Setup .NET
-      uses: actions/setup-dotnet@v4
       with:
-        dotnet-version: 8.0.x
+        targets: x86_64-pc-windows-msvc
 
-    - name: Restore dependencies
+    - name: Build ssh-handler (Rust)
-      run: dotnet restore
+      working-directory: SshHandlerRs
-
+      run: cargo build --release --target x86_64-pc-windows-msvc
-    # 1. Build Framework-Dependent FIRST (The tiny one)
-    - name: Build Framework-Dependent (Requires .NET 8)
-      run: >
-        dotnet publish SshHandler/SshHandler.csproj --configuration Release 
-        --self-contained false 
-        /p:PublishSingleFile=true 
-        -o ./publish-dotnet8
-
-    # 2. Clean to prevent artifact leakage
-    - name: Clean intermediate files
-      run: dotnet clean SshHandler/SshHandler.csproj
-
-    # 3. Build Standalone SECOND (The heavy one)
-    - name: Build Standalone (Includes Runtime)
-      run: >
-        dotnet publish SshHandler/SshHandler.csproj --configuration Release 
-        --runtime win-x64 
-        --self-contained true 
-        /p:PublishSingleFile=true 
-        /p:IncludeNativeLibrariesForSelfExtract=true
-        -o ./publish-standalone
 
     - name: Ensure Unix Line Endings for Shell Script
       shell: pwsh
@@ -64,10 +40,11 @@ jobs:
       run: |
         $tag = "${{ github.ref_name }}"
         if (-not $tag -or $tag -eq "main") { $tag = "manual" }
+        # Branch names (workflow_dispatch) can contain "/", which breaks file paths.
+        $tag = $tag -replace '[\\/]', '-'
 
-        # Rename Executables
+        # Rename Rust executable
-        Move-Item ./publish-standalone/SshHandler.exe "./SshHandler-$tag-Standalone.exe"
+        Move-Item SshHandlerRs/target/x86_64-pc-windows-msvc/release/ssh-handler.exe "./ssh-handler-rs-$tag.exe"
-        Move-Item ./publish-dotnet8/SshHandler.exe "./SshHandler-$tag-dotnet8.exe"
 
         # Rename Scripts
         Copy-Item "ssh-handler.sh" "./ssh-handler-$tag.sh"
@@ -78,8 +55,7 @@ jobs:
       if: startsWith(github.ref, 'refs/tags/')
       with:
         files: |
-          SshHandler-*-Standalone.exe
+          ssh-handler-rs-*.exe
-          SshHandler-*-dotnet8.exe
           ssh-handler-*.sh
           openssh_protocol_handler-*.bat
         generate_release_notes: true

.gitignore

@@ -1,21 +1,4 @@
 # .gitignore
 
-# User-specific files
+# Rust
-*.rsuser
+/SshHandlerRs/target/
-*.suo
-*.user
-*.userosscache
-*.sln.docstates
-
-# Build results
-[Dd]ebug/
-[Dd]ebugPublic/
-[Rr]elease/
-[Rr]eleases/
-x64/
-x86/
-[Aa][Rr][Mm]/
-[Aa][Rr][Mm]64/
-bld/
-[Bb]in/
-[Oo]bj/

SshHandler.sln

@@ -1,21 +0,0 @@
-Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio Version 17
-VisualStudioVersion = 17.0.31903.59
-MinimumVisualStudioVersion = 10.0.40219.1
-Project("{50924D75-2903-46D4-86DD-02269EFDBCA9}") = "SshHandler", "SshHandler\SshHandler.csproj", "{960BAB18-309B-42D0-B67E-B4EF8E7F7490}"
-EndProject
-Global
-	GlobalSection(SolutionConfigurationPlatforms) = preSolution
-		Debug|Any CPU = Debug|Any CPU
-		Release|Any CPU = Release|Any CPU
-	EndGlobalSection
-	GlobalSection(ProjectConfigurationPlatforms) = postSolution
-		{960BAB18-309B-42D0-B67E-B4EF8E7F7490}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{960BAB18-309B-42D0-B67E-B4EF8E7F7490}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{960BAB18-309B-42D0-B67E-B4EF8E7F7490}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{960BAB18-309B-42D0-B67E-B4EF8E7F7490}.Release|Any CPU.Build.0 = Release|Any CPU
-	EndGlobalSection
-	GlobalSection(SolutionProperties) = preSolution
-		HideSolutionNode = FALSE
-	EndGlobalSection
-EndGlobal

SshHandler/Form1.Designer.cs

@@ -1,113 +0,0 @@
-partial class Form1
-{
-    /// <summary>
-    /// Required designer variable.
-    /// </summary>
-    private System.ComponentModel.IContainer components = null;
-
-    /// <summary>
-    /// Clean up any resources being used.
-    /// </summary>
-    /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
-    protected override void Dispose(bool disposing)
-    {
-        if (disposing && (components != null))
-        {
-            components.Dispose();
-        }
-        base.Dispose(disposing);
-    }
-
-    #region Windows Form Designer generated code
-
-    /// <summary>
-    /// Required method for Designer support - do not modify
-    /// the contents of this method with the code editor.
-    /// </summary>
-    private void InitializeComponent()
-    {
-        this.label1 = new System.Windows.Forms.Label();
-        this.targetTextBox = new System.Windows.Forms.TextBox();
-        this.legacyCheckBox = new System.Windows.Forms.CheckBox();
-        this.connectButton = new System.Windows.Forms.Button();
-        this.cancelButton = new System.Windows.Forms.Button();
-        this.SuspendLayout();
-        // 
-        // label1
-        // 
-        this.label1.AutoSize = true;
-        this.label1.Location = new System.Drawing.Point(12, 15);
-        this.label1.Name = "label1";
-        this.label1.Size = new System.Drawing.Size(73, 15);
-        this.label1.TabIndex = 0;
-        this.label1.Text = "Connect to:";
-        // 
-        // targetTextBox
-        // 
-        this.targetTextBox.Location = new System.Drawing.Point(15, 33);
-        this.targetTextBox.Name = "targetTextBox";
-        this.targetTextBox.Size = new System.Drawing.Size(357, 23);
-        this.targetTextBox.TabIndex = 1;
-        // 
-        // legacyCheckBox
-        // 
-        this.legacyCheckBox.AutoSize = true;
-        this.legacyCheckBox.Location = new System.Drawing.Point(15, 71);
-        this.legacyCheckBox.Name = "legacyCheckBox";
-        this.legacyCheckBox.Size = new System.Drawing.Size(206, 19);
-        this.legacyCheckBox.TabIndex = 2;
-        this.legacyCheckBox.Text = "Enable Legacy Mode (for old devices)";
-        this.legacyCheckBox.UseVisualStyleBackColor = true;
-        // 
-        // connectButton
-        // 
-        this.connectButton.Location = new System.Drawing.Point(297, 106);
-        this.connectButton.Name = "connectButton";
-        this.connectButton.Size = new System.Drawing.Size(75, 23);
-        this.connectButton.TabIndex = 3;
-        this.connectButton.Text = "Connect";
-        this.connectButton.UseVisualStyleBackColor = true;
-        this.connectButton.Click += new System.EventHandler(this.connectButton_Click);
-        // 
-        // cancelButton
-        // 
-        this.cancelButton.DialogResult = System.Windows.Forms.DialogResult.Cancel;
-        this.cancelButton.Location = new System.Drawing.Point(216, 106);
-        this.cancelButton.Name = "cancelButton";
-        this.cancelButton.Size = new System.Drawing.Size(75, 23);
-        this.cancelButton.TabIndex = 4;
-        this.cancelButton.Text = "Cancel";
-        this.cancelButton.UseVisualStyleBackColor = true;
-        this.cancelButton.Click += new System.EventHandler(this.cancelButton_Click);
-        // 
-        // Form1
-        // 
-        this.AcceptButton = this.connectButton;
-        this.AutoScaleDimensions = new System.Drawing.SizeF(7F, 15F);
-        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
-        this.CancelButton = this.cancelButton;
-        this.ClientSize = new System.Drawing.Size(384, 141);
-        this.Controls.Add(this.cancelButton);
-        this.Controls.Add(this.connectButton);
-        this.Controls.Add(this.legacyCheckBox);
-        this.Controls.Add(this.targetTextBox);
-        this.Controls.Add(this.label1);
-        this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedDialog;
-        this.MaximizeBox = false;
-        this.MinimizeBox = false;
-        this.Name = "Form1";
-        this.ShowIcon = false;
-        this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
-        this.Text = "SSH Connection";
-        this.ResumeLayout(false);
-        this.PerformLayout();
-    }
-
-    #endregion
-
-    private System.Windows.Forms.Label label1;
-    private System.Windows.Forms.TextBox targetTextBox;
-    private System.Windows.Forms.CheckBox legacyCheckBox;
-    private System.Windows.Forms.Button connectButton;
-    private System.Windows.Forms.Button cancelButton;
-}

SshHandler/Form1.cs

@@ -1,40 +0,0 @@
-using System;
-using System.Windows.Forms;
-
-public partial class Form1 : Form
-{
-    // This property will store the result for the main program
-    public string FinalSshCommand { get; private set; }
-
-    public Form1(string initialTarget)
-    {
-        InitializeComponent();
-        targetTextBox.Text = initialTarget;
-        // Select the text for easy editing
-        targetTextBox.SelectAll();
-        targetTextBox.Focus();
-    }
-
-    private void connectButton_Click(object sender, EventArgs e)
-    {
-        string target = targetTextBox.Text;
-        bool useLegacy = legacyCheckBox.Checked;
-
-        string legacyArgs = "-o KexAlgorithms=+diffie-hellman-group1-sha1,diffie-hellman-group14-sha1 " +
-                            "-o HostKeyAlgorithms=+ssh-rsa " +
-                            "-o MACs=+hmac-sha1,hmac-sha1-96";
-
-        // Build the arguments for ssh.exe
-        string arguments = $"-A -C {(useLegacy ? legacyArgs : "")} {target}";
-
-        FinalSshCommand = arguments;
-        this.DialogResult = DialogResult.OK; // Set dialog result to OK
-        this.Close(); // Close the form
-    }
-
-    private void cancelButton_Click(object sender, EventArgs e)
-    {
-        this.DialogResult = DialogResult.Cancel; // Set dialog result to Cancel
-        this.Close();
-    }
-}

SshHandler/Form1.resx

@@ -1,67 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<root>
-  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
-    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
-    <xsd:element name="root" msdata:IsDataSet="true">
-      <xsd:complexType>
-        <xsd:choice maxOccurs="unbounded">
-          <xsd:element name="metadata">
-            <xsd:complexType>
-              <xsd:sequence>
-                <xsd:element name="value" type="xsd:string" minOccurs="0" />
-              </xsd:sequence>
-              <xsd:attribute name="name" use="required" type="xsd:string" />
-              <xsd:attribute name="type" type="xsd:string" />
-              <xsd:attribute name="mimetype" type="xsd:string" />
-              <xsd:attribute ref="xml:space" />
-            </xsd:complexType>
-          </xsd:element>
-          <xsd:element name="assembly">
-            <xsd:complexType>
-              <xsd:attribute name="alias" type="xsd:string" />
-              <xsd:attribute name="name" type="xsd:string" />
-            </xsd:complexType>
-          </xsd:element>
-          <xsd:element name="data">
-            <xsd:complexType>
-              <xsd:sequence>
-                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
-                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
-              </xsd:sequence>
-              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
-              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
-              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
-              <xsd:attribute ref="xml:space" />
-            </xsd:complexType>
-          </xsd:element>
-          <xsd:element name="resheader">
-            <xsd:complexType>
-              <xsd:sequence>
-                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
-              </xsd:sequence>
-              <xsd:attribute name="name" type="xsd:string" use="required" />
-            </xsd:complexType>
-          </xsd:element>
-        </xsd:choice>
-      </xsd:complexType>
-    </xsd:element>
-  </xsd:schema>
-  <resheader name="resmimetype">
-    <value>text/microsoft-resx</value>
-  </resheader>
-  <resheader name="version">
-    <value>2.0</value>
-  </resheader>
-  <resheader name="reader">
-    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
-  </resheader>
-  <resheader name="writer">
-    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
-  </resheader>
-  <data name="$this.ClientSize" type="System.Drawing.Size, System.Drawing">
-    <value>384, 141</value>
-  </data>
-  <data name="$this.Text" xml:space="preserve">
-    <value>SSH Connection</value>
-  </data>
-</root>

SshHandler/Program.cs

@@ -1,106 +0,0 @@
-using Microsoft.Win32;
-using System;
-using System.Diagnostics;
-using System.Security.Principal;
-using System.Windows.Forms;
-
-static class Program
-{
-    private const string ProtocolName = "ssh";
-
-    [STAThread]
-    static void Main(string[] args)
-    {
-        Application.EnableVisualStyles();
-        Application.SetCompatibleTextRenderingDefault(false);
-
-        // If no arguments, run setup mode.
-        if (args.Length == 0)
-        {
-            SetupHandler();
-        }
-        // Otherwise, run handler mode.
-        else
-        {
-            HandleConnection(args[0]);
-        }
-    }
-
-    static void HandleConnection(string url)
-    {
-        string target = url.Replace("ssh://", "").TrimEnd('/');
-        if (!target.Contains("@"))
-        {
-            target = $"{Environment.UserName}@{target}";
-        }
-
-        // Show the form as a dialog
-        using (var form = new Form1(target))
-        {
-            if (form.ShowDialog() == DialogResult.OK)
-            {
-                // If user clicked "Connect", run the command
-                ProcessStartInfo psi = new ProcessStartInfo
-                {
-                    FileName = "ssh.exe",
-                    Arguments = form.FinalSshCommand,
-                    UseShellExecute = true,
-                    CreateNoWindow = false
-                };
-                Process.Start(psi);
-            }
-        }
-    }
-
-    static void SetupHandler()
-    {
-        if (!IsAdmin())
-        {
-            MessageBox.Show("Please run this application as an administrator to register the URL handler.", "Admin Privileges Required", MessageBoxButtons.OK, MessageBoxIcon.Error);
-            return;
-        }
-
-        // The path is simple and correct because it's a native app
-        string exePath = Application.ExecutablePath;
-        string commandStr = $"\"{exePath}\" \"%1\"";
-
-        var confirmResult = MessageBox.Show(
-            "This will register this application to handle all ssh:// links.\n\n" +
-            $"Command:\n{commandStr}\n\n" +
-            "Do you want to proceed?",
-            "Registry Setup",
-            MessageBoxButtons.YesNo,
-            MessageBoxIcon.Information);
-
-        if (confirmResult == DialogResult.Yes)
-        {
-            try
-            {
-                // Write the keys to HKEY_CLASSES_ROOT
-                using (RegistryKey key = Registry.ClassesRoot.CreateSubKey(ProtocolName))
-                {
-                    key.SetValue("", $"URL:{ProtocolName} Protocol");
-                    key.SetValue("URL Protocol", "");
-                }
-                using (RegistryKey key = Registry.ClassesRoot.CreateSubKey($"{ProtocolName}\\shell\\open\\command"))
-                {
-                    key.SetValue("", commandStr);
-                }
-                MessageBox.Show("Successfully registered ssh:// protocol handler!", "Success", MessageBoxButtons.OK, MessageBoxIcon.Information);
-            }
-            catch (Exception ex)
-            {
-                MessageBox.Show($"Failed to write to registry:\n{ex.Message}", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
-            }
-        }
-    }
-
-    private static bool IsAdmin()
-    {
-        using (WindowsIdentity identity = WindowsIdentity.GetCurrent())
-        {
-            WindowsPrincipal principal = new WindowsPrincipal(identity);
-            return principal.IsInRole(WindowsBuiltInRole.Administrator);
-        }
-    }
-}

SshHandler/SshHandler.csproj

@@ -1,12 +0,0 @@
-<Project Sdk="Microsoft.NET.Sdk">
-
-  <PropertyGroup>
-    <OutputType>WinExe</OutputType>
-    <TargetFramework>net8.0-windows</TargetFramework>
-    <Nullable>enable</Nullable>
-    <UseWindowsForms>true</UseWindowsForms>
-    <ImplicitUsings>enable</ImplicitUsings>
-    <ApplicationIcon>ssh_icon.ico</ApplicationIcon>
-  </PropertyGroup>
-
-</Project>

SshHandlerRs/Cargo.lock

@@ -0,0 +1,460 @@
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+# It is not intended for manual editing.
+version = 4
+
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+dependencies = [
+ "find-msvc-tools",
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+]
+
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SshHandlerRs/Cargo.toml

@@ -0,0 +1,32 @@
+[package]
+name = "ssh-handler"
+version = "0.1.0"
+edition = "2021"
+
+[[bin]]
+name = "ssh-handler"
+path = "src/main.rs"
+
+[dependencies]
+windows = { version = "0.58", features = [
+    "Win32_Foundation",
+    "Win32_System_Registry",
+    "Win32_System_LibraryLoader",
+    "Win32_UI_WindowsAndMessaging",
+    "Win32_UI_Shell",
+    "Win32_UI_Controls",
+    "Win32_UI_Input_KeyboardAndMouse",
+    "Win32_System_Threading",
+    "Win32_System_LibraryLoader",
+    "Win32_Security",
+] }
+
+[build-dependencies]
+embed-resource = "2"
+
+[profile.release]
+opt-level = "z"
+lto = true
+codegen-units = 1
+panic = "abort"
+strip = true

SshHandlerRs/README.md

@@ -0,0 +1,46 @@
+# ssh-handler (Rust)
+
+The Windows `ssh://` protocol handler, in Rust — raw Win32 (via `windows-rs`)
+instead of a managed GUI framework. This started as a rewrite of an earlier
+.NET/WinForms version (since removed) whose self-contained publish was
+~150MB and paid CLR startup cost on every single `ssh://` link click. This
+version has no runtime, no GC, no JIT — cold start is just process creation
+plus a native dialog box. Release build is ~250KB.
+
+## Building
+
+CI (`.github/workflows/build.yml`) builds natively on `windows-latest` with
+the MSVC toolchain:
+
+```sh
+cargo build --release --target x86_64-pc-windows-msvc
+```
+
+Cross-compiling from Linux also works, e.g. for local iteration:
+
+```sh
+rustup target add x86_64-pc-windows-gnu
+sudo apt install mingw-w64
+cargo build --release --target x86_64-pc-windows-gnu
+```
+
+The dialog is a native Win32 resource (`resources/ssh_handler.rc`), compiled
+via `embed-resource` in `build.rs` — no GUI toolkit dependency.
+
+## Behavior
+
+- No arguments: setup mode. Checks for admin rights, confirms with the user,
+  then registers `ssh_handler_rs` as an `ssh://` handler using the "Default
+  Programs" capability model (a dedicated ProgID with
+  `Capabilities\UrlAssociations`, plus a
+  `HKLM\SOFTWARE\RegisteredApplications` entry) — the same pattern
+  `openssh_protocol_handler.bat` uses, and the one Windows 10/11 actually
+  honors in Settings > Apps > Default Apps > "Choose default apps by link
+  type". A bare `HKCR\ssh\shell\open\command` write (what the old .NET
+  version did) gets silently ignored once a `UserChoice` already exists for
+  the protocol, which is the common case.
+- `ssh://user@host` argument: handler mode. Parses the target (defaulting the
+  username to the current Windows user if omitted), shows a small dialog to
+  confirm/edit the target and optionally enable "legacy mode" (older
+  KEX/HostKey/MAC/cipher algorithms for old SSH servers), then launches
+  `ssh.exe -A -C ... user@host` via `ShellExecuteW`.

SshHandlerRs/build.rs

@@ -0,0 +1,3 @@
+fn main() {
+    embed_resource::compile("resources/ssh_handler.rc", embed_resource::NONE);
+}

SshHandlerRs/resources/resource.h

@@ -0,0 +1,4 @@
+#define IDI_APPICON       102
+#define IDD_CONNECT       101
+#define IDC_EDIT_TARGET   1001
+#define IDC_CHECK_LEGACY  1002

SshHandlerRs/resources/ssh_handler.rc

@@ -0,0 +1,17 @@
+#include <windows.h>
+#include "resource.h"
+
+IDI_APPICON ICON "ssh_icon.ico"
+
+IDD_CONNECT DIALOGEX 0, 0, 260, 92
+STYLE DS_MODALFRAME | DS_CENTER | WS_POPUP | WS_CAPTION | WS_SYSMENU
+CAPTION "SSH Connect"
+FONT 9, "Segoe UI"
+BEGIN
+    LTEXT           "Target:", -1, 10, 13, 240, 10
+    EDITTEXT        IDC_EDIT_TARGET, 10, 25, 240, 14, ES_AUTOHSCROLL
+    CONTROL         "Legacy mode (older/insecure algorithms)", IDC_CHECK_LEGACY,
+                    "Button", BS_AUTOCHECKBOX | WS_TABSTOP, 10, 47, 240, 12
+    DEFPUSHBUTTON   "Connect", IDOK, 94, 68, 75, 16
+    PUSHBUTTON      "Cancel", IDCANCEL, 174, 68, 75, 16
+END

SshHandlerRs/src/main.rs

@@ -0,0 +1,311 @@
+#![windows_subsystem = "windows"]
+
+use windows::core::{w, PCWSTR};
+use windows::Win32::Foundation::{HWND, LPARAM, WPARAM};
+use windows::Win32::System::Registry::{
+    RegCreateKeyExW, RegSetValueExW, HKEY, HKEY_CLASSES_ROOT, HKEY_LOCAL_MACHINE, KEY_WRITE,
+    REG_OPTION_NON_VOLATILE, REG_SZ,
+};
+use windows::Win32::System::LibraryLoader::GetModuleHandleW;
+use windows::Win32::UI::Controls::IsDlgButtonChecked;
+use windows::Win32::UI::Input::KeyboardAndMouse::SetFocus;
+use windows::Win32::UI::Shell::{IsUserAnAdmin, ShellExecuteW};
+use windows::Win32::UI::WindowsAndMessaging::{
+    DialogBoxParamW, EndDialog, GetDlgItem, GetDlgItemTextW, GetWindowLongPtrW, MessageBoxW,
+    SendDlgItemMessageW, SetDlgItemTextW, SetWindowLongPtrW, GWLP_USERDATA, IDCANCEL, IDOK, IDYES,
+    MB_ICONERROR, MB_ICONINFORMATION, MB_ICONQUESTION, MB_OK, MB_YESNO, SW_SHOWNORMAL, WM_CLOSE,
+    WM_COMMAND, WM_INITDIALOG,
+};
+
+const IDD_CONNECT: u16 = 101;
+const IDC_EDIT_TARGET: i32 = 1001;
+const IDC_CHECK_LEGACY: i32 = 1002;
+const BST_CHECKED: usize = 1;
+const EM_SETSEL: u32 = 0x00B1;
+
+const LEGACY_ARGS: &str = "-o KexAlgorithms=+diffie-hellman-group1-sha1,diffie-hellman-group14-sha1 \
+-o HostKeyAlgorithms=+ssh-rsa -o MACs=+hmac-sha1,hmac-sha1-96 -o ciphers=+aes256-cbc";
+
+/// Our ProgID / capability-provider identifier under HKCR and RegisteredApplications.
+/// Distinct from the .bat's "ssh_custom_handler" so both can coexist/be told apart.
+const PROG_ID: &str = "ssh_handler_rs";
+const APP_DISPLAY_NAME: &str = "SSH Handler (Rust)";
+
+fn to_wide(s: &str) -> Vec<u16> {
+    s.encode_utf16().chain(std::iter::once(0)).collect()
+}
+
+fn message_box(text: &str, caption: &str, flags: windows::Win32::UI::WindowsAndMessaging::MESSAGEBOX_STYLE) -> windows::Win32::UI::WindowsAndMessaging::MESSAGEBOX_RESULT {
+    let text = to_wide(text);
+    let caption = to_wide(caption);
+    unsafe {
+        MessageBoxW(
+            None,
+            PCWSTR(text.as_ptr()),
+            PCWSTR(caption.as_ptr()),
+            flags,
+        )
+    }
+}
+
+fn current_exe_path() -> String {
+    std::env::current_exe()
+        .map(|p| p.display().to_string())
+        .unwrap_or_default()
+}
+
+fn current_username() -> String {
+    std::env::var("USERNAME").unwrap_or_else(|_| "user".to_string())
+}
+
+/// Data passed into / out of the connect dialog.
+struct DialogData {
+    initial_target: Vec<u16>,
+    result_target: String,
+    legacy: bool,
+    accepted: bool,
+}
+
+unsafe extern "system" fn dialog_proc(hwnd: HWND, msg: u32, wparam: WPARAM, lparam: LPARAM) -> isize {
+    match msg {
+        WM_INITDIALOG => {
+            // lparam carries the raw pointer to our DialogData (see DialogBoxParamW call).
+            SetWindowLongPtrW(hwnd, GWLP_USERDATA, lparam.0);
+            let data = &*(lparam.0 as *const DialogData);
+            let _ = SetDlgItemTextW(hwnd, IDC_EDIT_TARGET, PCWSTR(data.initial_target.as_ptr()));
+            // Select all text in the edit box and give it focus.
+            let _ = SendDlgItemMessageW(hwnd, IDC_EDIT_TARGET, EM_SETSEL, WPARAM(0), LPARAM(-1));
+            let edit_hwnd = GetDlgItem(hwnd, IDC_EDIT_TARGET).unwrap_or_default();
+            let _ = SetFocus(edit_hwnd);
+            1 // we set focus ourselves
+        }
+        WM_COMMAND => {
+            let control_id = (wparam.0 & 0xFFFF) as i32;
+            if control_id == IDOK.0 {
+                let ptr = GetWindowLongPtrW(hwnd, GWLP_USERDATA) as *mut DialogData;
+                if !ptr.is_null() {
+                    let data = &mut *ptr;
+                    let mut buf = [0u16; 512];
+                    let len = GetDlgItemTextW(hwnd, IDC_EDIT_TARGET, &mut buf);
+                    data.result_target = String::from_utf16_lossy(&buf[..len as usize]);
+                    data.legacy =
+                        IsDlgButtonChecked(hwnd, IDC_CHECK_LEGACY) as usize == BST_CHECKED;
+                    data.accepted = true;
+                }
+                let _ = EndDialog(hwnd, IDOK.0 as isize);
+                return 1;
+            } else if control_id == IDCANCEL.0 {
+                let ptr = GetWindowLongPtrW(hwnd, GWLP_USERDATA) as *mut DialogData;
+                if !ptr.is_null() {
+                    (&mut *ptr).accepted = false;
+                }
+                let _ = EndDialog(hwnd, IDCANCEL.0 as isize);
+                return 1;
+            }
+            0
+        }
+        WM_CLOSE => {
+            let ptr = GetWindowLongPtrW(hwnd, GWLP_USERDATA) as *mut DialogData;
+            if !ptr.is_null() {
+                (&mut *ptr).accepted = false;
+            }
+            let _ = EndDialog(hwnd, IDCANCEL.0 as isize);
+            1
+        }
+        _ => 0,
+    }
+}
+
+fn show_connect_dialog(initial_target: &str) -> Option<(String, bool)> {
+    let mut data = Box::new(DialogData {
+        initial_target: to_wide(initial_target),
+        result_target: String::new(),
+        legacy: false,
+        accepted: false,
+    });
+    let data_ptr = data.as_mut() as *mut DialogData;
+
+    unsafe {
+        let hinstance: windows::Win32::Foundation::HINSTANCE =
+            GetModuleHandleW(None).unwrap_or_default().into();
+        DialogBoxParamW(
+            hinstance,
+            windows::core::PCWSTR(IDD_CONNECT as *const u16),
+            None,
+            Some(dialog_proc),
+            LPARAM(data_ptr as isize),
+        );
+    }
+
+    if data.accepted {
+        Some((data.result_target.clone(), data.legacy))
+    } else {
+        None
+    }
+}
+
+fn is_admin() -> bool {
+    unsafe { IsUserAnAdmin().as_bool() }
+}
+
+fn setup_handler() {
+    if !is_admin() {
+        message_box(
+            "Please run this application as an administrator to register the URL handler.",
+            "Admin Privileges Required",
+            MB_OK | MB_ICONERROR,
+        );
+        return;
+    }
+
+    let exe_path = current_exe_path();
+    let command_str = format!("\"{exe_path}\" \"%1\"");
+
+    let prompt = format!(
+        "This will register this application ({APP_DISPLAY_NAME}) as a candidate handler for ssh:// links.\n\n\
+        Command:\n{command_str}\n\n\
+        After this, you may need to open Settings > Apps > Default Apps > \"Choose default apps by link type\", \
+        find \"ssh\", and select {APP_DISPLAY_NAME} explicitly — Windows does not let an installer silently \
+        override an existing default protocol handler.\n\n\
+        Do you want to proceed?"
+    );
+    let result = message_box(&prompt, "Registry Setup", MB_YESNO | MB_ICONQUESTION);
+    if result != IDYES {
+        return;
+    }
+
+    match register_protocol(&exe_path, &command_str) {
+        Ok(()) => {
+            message_box(
+                &format!(
+                    "Registered {APP_DISPLAY_NAME} as an ssh:// handler.\n\n\
+                    If ssh:// links don't launch it, open Settings > Apps > Default Apps > \
+                    \"Choose default apps by link type\", find \"ssh\", and pick it there."
+                ),
+                "Success",
+                MB_OK | MB_ICONINFORMATION,
+            );
+        }
+        Err(e) => {
+            message_box(
+                &format!("Failed to write to registry:\n{e:?}"),
+                "Error",
+                MB_OK | MB_ICONERROR,
+            );
+        }
+    }
+}
+
+/// Sets a REG_SZ value. `value_name = None` targets the key's default (unnamed) value.
+fn reg_set_sz(hkey: HKEY, value_name: Option<&str>, data: &str) -> windows::core::Result<()> {
+    let name_wide = value_name.map(to_wide);
+    let name_ptr = match &name_wide {
+        Some(w) => PCWSTR(w.as_ptr()),
+        None => PCWSTR::null(),
+    };
+    let data_wide = to_wide(data);
+    let bytes = unsafe {
+        std::slice::from_raw_parts(data_wide.as_ptr() as *const u8, data_wide.len() * 2)
+    };
+    unsafe { RegSetValueExW(hkey, name_ptr, 0, REG_SZ, Some(bytes)) }.ok()
+}
+
+fn reg_create_key(root: HKEY, subkey: &str) -> windows::core::Result<HKEY> {
+    let subkey_wide = to_wide(subkey);
+    let mut key = HKEY::default();
+    unsafe {
+        RegCreateKeyExW(
+            root,
+            PCWSTR(subkey_wide.as_ptr()),
+            0,
+            None,
+            REG_OPTION_NON_VOLATILE,
+            KEY_WRITE,
+            None,
+            &mut key,
+            None,
+        )
+    }
+    .ok()?;
+    Ok(key)
+}
+
+/// Registers via the "Default Programs" capability model (RegisteredApplications +
+/// a distinct ProgID with Capabilities\UrlAssociations), the same pattern
+/// `openssh_protocol_handler.bat` uses — this is what actually shows up in and gets
+/// honored by Windows' "Choose default apps by link type" UI. A bare
+/// HKCR\ssh\shell\open\command write is ignored once a UserChoice already exists for
+/// the protocol, which is the common case on Windows 10/11.
+fn register_protocol(exe_path: &str, command_str: &str) -> windows::core::Result<()> {
+    // Declare "ssh" as a URL protocol scheme (legacy marker some apps still check for).
+    let ssh_key = reg_create_key(HKEY_CLASSES_ROOT, "ssh")?;
+    reg_set_sz(ssh_key, None, "URL:ssh Protocol")?;
+    reg_set_sz(ssh_key, Some("URL Protocol"), "")?;
+
+    // Our ProgID: the actual open command plus Default-Apps display metadata.
+    let cmd_key = reg_create_key(HKEY_CLASSES_ROOT, &format!("{PROG_ID}\\shell\\open\\command"))?;
+    reg_set_sz(cmd_key, None, command_str)?;
+
+    let app_key = reg_create_key(HKEY_CLASSES_ROOT, &format!("{PROG_ID}\\Application"))?;
+    reg_set_sz(app_key, Some("ApplicationIcon"), &format!("\"{exe_path}\",0"))?;
+    reg_set_sz(app_key, Some("ApplicationName"), APP_DISPLAY_NAME)?;
+    reg_set_sz(
+        app_key,
+        Some("ApplicationDescription"),
+        "Handles ssh:// links via Windows OpenSSH",
+    )?;
+
+    let caps_key = reg_create_key(
+        HKEY_CLASSES_ROOT,
+        &format!("{PROG_ID}\\Capabilities\\UrlAssociations"),
+    )?;
+    reg_set_sz(caps_key, Some("ssh"), PROG_ID)?;
+
+    // Tell Windows' Default Apps UI this app exists as a capability provider.
+    let registered_key = reg_create_key(HKEY_LOCAL_MACHINE, "SOFTWARE\\RegisteredApplications")?;
+    reg_set_sz(
+        registered_key,
+        Some(APP_DISPLAY_NAME),
+        &format!("Software\\Classes\\{PROG_ID}\\Capabilities"),
+    )?;
+
+    Ok(())
+}
+
+fn handle_connection(url: &str) {
+    let mut target = url.trim_start_matches("ssh://").trim_end_matches('/').to_string();
+    if !target.contains('@') {
+        target = format!("{}@{}", current_username(), target);
+    }
+
+    let Some((final_target, legacy)) = show_connect_dialog(&target) else {
+        return;
+    };
+
+    let legacy_args = if legacy { LEGACY_ARGS } else { "" };
+    let arguments = format!("-A -C {legacy_args} {final_target}");
+
+    let ssh_exe = w!("ssh.exe");
+    let args_wide = to_wide(&arguments);
+    let verb = w!("open");
+
+    unsafe {
+        ShellExecuteW(
+            None,
+            verb,
+            ssh_exe,
+            PCWSTR(args_wide.as_ptr()),
+            None,
+            SW_SHOWNORMAL,
+        );
+    }
+}
+
+fn main() {
+    let args: Vec<String> = std::env::args().skip(1).collect();
+    if args.is_empty() {
+        setup_handler();
+    } else {
+        handle_connection(&args[0]);
+    }
+}