Start the tray when the install finishes

The MSI's exit dialog starts it from the unelevated UI process, so it runs
as the signed-in user.

core/Cargo.lock

@@ -261,6 +261,15 @@ dependencies = [
  "hybrid-array",
 ]
 
+[[package]]
+name = "block2"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdeb9d870516001442e364c5220d3574d2da8dc765554b4a617230d33fa58ef5"
+dependencies = [
+ "objc2",
+]
+
 [[package]]
 name = "borsh"
 version = "1.8.1"
@@ -669,6 +678,16 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "dispatch2"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e0e367e4e7da84520dedcac1901e4da967309406d1e51017ae1abfb97adbd38"
+dependencies = [
+ "bitflags 2.13.2",
+ "objc2",
+]
+
 [[package]]
 name = "displaydoc"
 version = "0.2.7"
@@ -680,6 +699,12 @@ dependencies = [
  "syn 3.0.6",
 ]
 
+[[package]]
+name = "dpi"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d8b14ccef22fc6f5a8f4d7d768562a182c04ce9a3b3157b91390b52ddfdf1a76"
+
 [[package]]
 name = "either"
 version = "1.18.0"
@@ -751,6 +776,15 @@ dependencies = [
  "getrandom 0.4.3",
 ]
 
+[[package]]
+name = "fdeflate"
+version = "0.3.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e6853b52649d4ac5c0bd02320cddc5ba956bdb407c4b75a2c6b75bf51500f8c"
+dependencies = [
+ "simd-adler32",
+]
+
 [[package]]
 name = "find-msvc-tools"
 version = "0.1.13"
@@ -771,7 +805,7 @@ checksum = "6e634e2e0ebac1ee034020da1ca582e17ffe4e0f5e985823721e168928136dcb"
 dependencies = [
  "crc32fast",
  "libz-sys",
- "miniz_oxide",
+ "miniz_oxide 0.9.1",
  "zlib-rs",
 ]
 
@@ -1452,6 +1486,16 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "keyboard-types"
+version = "0.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0fbe853b403ae61a04233030ae8a79d94975281ed9770a1f9e246732b534b28d"
+dependencies = [
+ "bitflags 2.13.2",
+ "serde",
+]
+
 [[package]]
 name = "konst"
 version = "0.2.20"
@@ -1595,6 +1639,16 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "68354c5c6bd36d73ff3feceb05efa59b6acb7626617f4962be322a825e61f79a"
 
+[[package]]
+name = "miniz_oxide"
+version = "0.8.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fa76a2c86f704bdb222d66965fb3d63269ce38518b83cb0575fca855ebb6316"
+dependencies = [
+ "adler2",
+ "simd-adler32",
+]
+
 [[package]]
 name = "miniz_oxide"
 version = "0.9.1"
@@ -1636,6 +1690,24 @@ dependencies = [
  "uuid",
 ]
 
+[[package]]
+name = "muda"
+version = "0.21.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4340e89c178916e62879c5c36b7f699019369be413e496178a6983ce91b8bc03"
+dependencies = [
+ "crossbeam-channel",
+ "dpi",
+ "keyboard-types",
+ "objc2",
+ "objc2-app-kit",
+ "objc2-core-foundation",
+ "objc2-foundation",
+ "png",
+ "thiserror",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "multer"
 version = "3.1.0"
@@ -1742,6 +1814,66 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "objc2"
+version = "0.6.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "08849bbd4767dfae9457696856ae1c84fe4e0281bbe4a7abff2d0e06fb7981f8"
+dependencies = [
+ "objc2-encode",
+]
+
+[[package]]
+name = "objc2-app-kit"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d49e936b501e5c5bf01fda3a9452ff86dc3ea98ad5f283e1455153142d97518c"
+dependencies = [
+ "bitflags 2.13.2",
+ "objc2",
+ "objc2-core-foundation",
+ "objc2-foundation",
+]
+
+[[package]]
+name = "objc2-core-foundation"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2a180dd8642fa45cdb7dd721cd4c11b1cadd4929ce112ebd8b9f5803cc79d536"
+dependencies = [
+ "bitflags 2.13.2",
+ "dispatch2",
+ "objc2",
+]
+
+[[package]]
+name = "objc2-core-graphics"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e022c9d066895efa1345f8e33e584b9f958da2fd4cd116792e15e07e4720a807"
+dependencies = [
+ "bitflags 2.13.2",
+ "objc2-core-foundation",
+]
+
+[[package]]
+name = "objc2-encode"
+version = "4.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ef25abbcd74fb2609453eb695bd2f860d389e457f67dc17cafc8b8cbc89d0c33"
+
+[[package]]
+name = "objc2-foundation"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e3e0adef53c21f888deb4fa59fc59f7eb17404926ee8a6f59f5df0fd7f9f3272"
+dependencies = [
+ "bitflags 2.13.2",
+ "block2",
+ "objc2",
+ "objc2-core-foundation",
+]
+
 [[package]]
 name = "oid-registry"
 version = "0.8.1"
@@ -1864,6 +1996,19 @@ version = "0.3.34"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f6b464fbc74e149a392436b17d523f769e057cb6877f6a5c4618bc6f11800548"
 
+[[package]]
+name = "png"
+version = "0.18.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "60769b8b31b2a9f263dae2776c37b1b28ae246943cf719eb6946a1db05128a61"
+dependencies = [
+ "bitflags 2.13.2",
+ "crc32fast",
+ "fdeflate",
+ "flate2",
+ "miniz_oxide 0.8.9",
+]
+
 [[package]]
 name = "portable-atomic"
 version = "1.15.0"
@@ -3230,7 +3375,9 @@ dependencies = [
  "clap",
  "core-foundation 0.10.1",
  "directories",
+ "muda",
  "percent-encoding",
+ "png",
  "rama",
  "rand",
  "rcgen",
@@ -3246,6 +3393,7 @@ dependencies = [
  "tracing",
  "tracing-appender",
  "tracing-subscriber",
+ "tray-icon",
  "which",
  "windows",
  "windows-registry",
@@ -3652,6 +3800,25 @@ dependencies = [
  "tracing-serde",
 ]
 
+[[package]]
+name = "tray-icon"
+version = "0.26.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4f5cc5858ecf9574ddd8f0032a2ff7ffd6f7724d2b81e48b9374984b3fd6ddc9"
+dependencies = [
+ "crossbeam-channel",
+ "muda",
+ "objc2",
+ "objc2-app-kit",
+ "objc2-core-foundation",
+ "objc2-core-graphics",
+ "objc2-foundation",
+ "once_cell",
+ "png",
+ "thiserror",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "try-lock"
 version = "0.2.5"

core/Cargo.toml

@@ -3,6 +3,7 @@ name = "strix-firewall"
 version = "0.1.0"
 edition = "2021"
 license = "Apache-2.0"
+authors = ["Strix"]
 description = "Screens package downloads for known malware before they reach your machine"
 repository = "https://github.com/usestrix/firewall"
 homepage = "https://github.com/usestrix/firewall"
@@ -10,14 +11,20 @@ homepage = "https://github.com/usestrix/firewall"
 # as an integration test; new tests/*.rs need an explicit [[test]] entry.
 autotests = false
 
-# Only Windows ships the service.
+# Only Windows ships the service and tray.
 [package.metadata.dist.binaries]
-x86_64-pc-windows-msvc = ["firewall", "firewall-service"]
+x86_64-pc-windows-msvc = ["firewall", "firewall-service", "firewall-tray"]
 aarch64-apple-darwin = ["firewall"]
 x86_64-apple-darwin = ["firewall"]
 aarch64-unknown-linux-gnu = ["firewall"]
 x86_64-unknown-linux-gnu = ["firewall"]
 
+[package.metadata.wix]
+upgrade-guid = "D944C2F6-BF55-4B21-A60E-1BBDB1A66293"
+path-guid = "033B1050-23D0-4F5A-A0D3-F4757B4B67E0"
+license = false
+eula = false
+
 [lib]
 name = "firewall"
 # The macOS extension links a staticlib, built on demand:
@@ -32,6 +39,10 @@ path = "src/main.rs"
 name = "firewall-service"
 path = "src/bin/firewall-service.rs"
 
+[[bin]]
+name = "firewall-tray"
+path = "src/bin/firewall-tray.rs"
+
 [[bin]]
 name = "firewall-uninstall"
 path = "src/bin/firewall-uninstall.rs"
@@ -100,19 +111,14 @@ security-framework = "3.7.0"
 security-framework-sys = "2.17.0"
 
 [target.'cfg(windows)'.dependencies]
+muda = { version = "0.21.2", default-features = false }
+png = "0.18.1"
 rama = { version = "0.4.0", features = ["dns-hickory"] }
 schannel = "0.1.29"
 tokio = { version = "1.53.1", features = ["net"] }
 tracing-appender = "0.2.5"
-windows = { version = "0.62", features = [
-    "Win32_Foundation",
-    "Win32_Security",
-    "Win32_Security_Authorization",
-    "Win32_Security_Cryptography",
-    "Win32_System_Com",
-    "Win32_System_Environment",
-    "Win32_UI_Shell",
-] }
+tray-icon = { version = "0.26.1", default-features = false }
+windows = { version = "0.62", features = ["Win32_Foundation", "Win32_Security", "Win32_Security_Authorization", "Win32_Security_Cryptography", "Win32_System_Com", "Win32_System_Environment", "Win32_System_Threading", "Win32_UI_Shell", "Win32_UI_WindowsAndMessaging"] }
 windows-registry = "0.6.1"
 windows-service = "0.8.0"
 

core/src/bin/firewall-service.rs

@@ -2,14 +2,25 @@
 
 #[cfg(windows)]
 fn main() {
-    if let Err(e) = firewall::os::windows::run_service() {
-        tracing::error!("could not run the service: {e}");
-        firewall::telemetry::error("service");
-        firewall::telemetry::flush();
-        std::process::exit(1)
+    // Run by the MSI as it removes the firewall.
+    if std::env::args().nth(1).as_deref() == Some("uninstall") {
+        firewall::init_logging("info");
+        if let Err(e) = firewall::os::windows::uninstall() {
+            fail("uninstall", &format!("could not uninstall: {e}"))
+        }
+    } else if let Err(e) = firewall::os::windows::run_service() {
+        fail("service", &format!("could not run the service: {e}"))
     }
 }
 
+#[cfg(windows)]
+fn fail(kind: &'static str, message: &str) -> ! {
+    tracing::error!("{message}");
+    firewall::telemetry::error(kind);
+    firewall::telemetry::flush();
+    std::process::exit(1)
+}
+
 /// The service is Windows-only.
 #[cfg(not(windows))]
 fn main() {}

core/src/bin/firewall-tray.rs

@@ -0,0 +1,11 @@
+//! The notification-area icon, started at sign-in. A GUI app, so no console opens with it.
+#![windows_subsystem = "windows"]
+
+#[cfg(windows)]
+fn main() -> Result<(), rama::error::BoxError> {
+    firewall::os::windows::run_tray()
+}
+
+/// The tray is Windows-only.
+#[cfg(not(windows))]
+fn main() {}

core/src/os/windows/ca.rs

@@ -7,9 +7,11 @@ use schannel::cert_context::CertContext;
 use schannel::cert_store::{CertAdd, CertStore};
 use std::io;
 use std::path::Path;
+use std::time::{SystemTime, UNIX_EPOCH};
 use tracing::warn;
 use windows::Win32::Security::Authorization::{GetNamedSecurityInfoW, SE_FILE_OBJECT};
 use windows::Win32::Security::*;
+use windows_registry::Type;
 
 /// SYSTEM and admins write, users only read, so no one else can plant a CA for node.
 const DATA_DIR_ACL: &str = concat!(
@@ -20,6 +22,9 @@ const DATA_DIR_ACL: &str = concat!(
     "(A;OICI;FRFX;;;BU)", // allow Users read and execute only
 );
 
+/// 1970 in FILETIME, which counts 100 ns from 1601.
+const FILETIME_UNIX_EPOCH: u128 = 116_444_736_000_000_000;
+
 /// Trusted machine-wide so restarts keep it; replaced if the hosts change.
 pub fn load_or_create_ca(
     hosts: &[&str],
@@ -34,6 +39,16 @@ pub fn load_or_create_ca(
             LOCAL_MACHINE
                 .create(REGISTRY_KEY)?
                 .set_string("ca", ca.to_blob(hosts))?;
+            // Windows discards CRLs it cached before now, in case an old CA's is cached at our URL.
+            let now = SystemTime::now().duration_since(UNIX_EPOCH)?.as_nanos() / 100
+                + FILETIME_UNIX_EPOCH;
+            let chain = r"SOFTWARE\Microsoft\Cryptography\OID\EncodingType 0\CertDllCreateCertificateChainEngine\Config";
+            let resync = (now as u64).to_le_bytes();
+            LOCAL_MACHINE.create(chain)?.set_bytes(
+                "ChainCacheResyncFiletime",
+                Type::Bytes,
+                &resync,
+            )?;
             ca
         }
     };

core/src/os/windows/mod.rs

@@ -4,9 +4,13 @@
 mod ca;
 mod service;
 mod tpm;
+mod tray;
+mod uninstall;
 
 pub use service::run as run_service;
 pub use tpm::CaKey;
+pub use tray::run as run_tray;
+pub use uninstall::uninstall;
 
 use rama::error::BoxError;
 use std::net::Ipv4Addr;

core/src/os/windows/tpm.rs

@@ -27,6 +27,13 @@ impl CaKey {
         }
     }
 
+    pub(super) fn delete_machine_key() -> Result<(), BoxError> {
+        if let Some(key) = open_key(KEY_NAME, NCRYPT_MACHINE_KEY_FLAG)? {
+            key.delete_from_tpm()?;
+        }
+        Ok(())
+    }
+
     /// A per-user key under a random name, which needs no elevation; `delete_from_tpm` it after.
     pub fn create_test_key() -> WinResult<Self> {
         let name = format!("Strix Firewall test {:016x}", rand::random::<u64>());

core/src/os/windows/tray.rs

@@ -0,0 +1,195 @@
+//! The notification-area icon, started at sign-in as the menu bar app is on macOS.
+
+use super::*;
+use muda::{Menu, MenuEvent, MenuItem, PredefinedMenuItem};
+use std::io::Cursor;
+use tray_icon::{Icon, MouseButtonState, TrayIcon, TrayIconBuilder, TrayIconEvent};
+use windows::core::{w, PCWSTR};
+use windows::Win32::Foundation::*;
+use windows::Win32::System::Threading::CreateMutexW;
+use windows::Win32::UI::Shell::*;
+use windows::Win32::UI::WindowsAndMessaging::*;
+use windows_registry::CURRENT_USER;
+use windows_service::service::{Service, ServiceAccess, ServiceState};
+use windows_service::service_manager::{ServiceManager, ServiceManagerAccess};
+
+const MENU_PAUSE: &str = "pause";
+const MENU_LOG: &str = "log";
+const MENU_QUIT: &str = "quit";
+const LOGO: &[u8] = include_bytes!("tray.png");
+
+/// Runs until Quit, once per session.
+pub fn run() -> Result<(), BoxError> {
+    // Held until we exit.
+    let _mutex = unsafe { CreateMutexW(None, false, w!(r"Local\StrixFirewallTray"))? };
+    if unsafe { GetLastError() } == ERROR_ALREADY_EXISTS {
+        return Ok(());
+    }
+    let status = MenuItem::new("", false, None);
+    let pause = MenuItem::with_id(MENU_PAUSE, "", false, None);
+    let menu = Menu::with_items(&[
+        &status,
+        &PredefinedMenuItem::separator(),
+        &pause,
+        &MenuItem::with_id(MENU_LOG, "Open logs", true, None),
+        &PredefinedMenuItem::separator(),
+        &MenuItem::with_id(MENU_QUIT, "Quit", true, None),
+    ])?;
+    let (logo, logo_size) = logo_mask()?;
+    let icon = TrayIconBuilder::new().with_menu(Box::new(menu)).build()?;
+    let window = HWND(icon.window_handle());
+    let mut tray = Tray {
+        icon,
+        logo,
+        logo_size,
+        drawn: None,
+        status,
+        pause,
+        state: None,
+    };
+    tray.update();
+    unsafe { SetTimer(None, 0, 2000, None) };
+    let mut message = MSG::default();
+    while unsafe { GetMessageW(&mut message, None, 0, 0) }.0 > 0 {
+        unsafe { DispatchMessageW(&message) };
+        // WM_CLOSE, as the MSI sends, destroys the icon's window.
+        if !unsafe { IsWindow(Some(window)) }.as_bool() {
+            break;
+        }
+        // Ours, not the icon window's own hover timer.
+        if message.message == WM_TIMER && message.hwnd.is_invalid() {
+            tray.update();
+        }
+        while let Ok(event) = TrayIconEvent::receiver().try_recv() {
+            // The menu opens on release, so this keeps it current.
+            if let TrayIconEvent::Click {
+                button_state: MouseButtonState::Down,
+                ..
+            } = event
+            {
+                tray.update();
+            }
+        }
+        while let Ok(event) = MenuEvent::receiver().try_recv() {
+            if event.id == MENU_QUIT {
+                return Ok(());
+            }
+            tray.on_menu(event.id.as_ref());
+        }
+    }
+    Ok(())
+}
+
+struct Tray {
+    icon: TrayIcon,
+    /// The logo's alpha channel; it is square.
+    logo: Vec<u8>,
+    logo_size: u32,
+    /// Whether the taskbar was light and the service screening when the icon was last set.
+    drawn: Option<(bool, bool)>,
+    status: MenuItem,
+    pause: MenuItem,
+    /// As the menu last showed it.
+    state: Option<ServiceState>,
+}
+
+impl Tray {
+    fn update(&mut self) {
+        self.state = service_state();
+        let screening = self.state == Some(ServiceState::Running);
+        let light = light_taskbar();
+        if self.drawn != Some((light, screening)) {
+            let rgba = logo_rgba(&self.logo, light, screening);
+            if let Ok(icon) = Icon::from_rgba(rgba, self.logo_size, self.logo_size) {
+                let _ = self.icon.set_icon(Some(icon));
+            }
+            self.drawn = Some((light, screening));
+        }
+        let text = status_text(self.state);
+        let tip = format!("Strix Firewall: {text}");
+        let _ = self.icon.set_tooltip(Some(tip));
+        self.status.set_text(text);
+        let pause = if screening { "Pause" } else { "Resume" };
+        self.pause.set_text(pause);
+        self.pause.set_enabled(self.state.is_some());
+    }
+
+    fn on_menu(&self, id: &str) {
+        let state = self.state;
+        let screening = state == Some(ServiceState::Running);
+        let action: fn() -> Result<(), BoxError> = match id {
+            MENU_PAUSE if screening => || Ok(open_service()?.pause().map(drop)?),
+            MENU_PAUSE if state == Some(ServiceState::Paused) => {
+                || Ok(open_service()?.resume().map(drop)?)
+            }
+            MENU_PAUSE => || Ok(open_service()?.start::<&str>(&[])?),
+            MENU_LOG => {
+                let log = HSTRING::from(data_dir().as_path());
+                let none = PCWSTR::null();
+                unsafe { ShellExecuteW(None, w!("open"), &log, none, none, SW_SHOWNORMAL) };
+                return;
+            }
+            _ => return,
+        };
+        if let Err(error) = action() {
+            let text = HSTRING::from(error.to_string());
+            unsafe { MessageBoxW(None, &text, w!("Strix Firewall"), MB_ICONERROR) };
+        }
+    }
+}
+
+/// `None` when the service is not installed.
+fn service_state() -> Option<ServiceState> {
+    let manager =
+        ServiceManager::local_computer(None::<&str>, ServiceManagerAccess::CONNECT).ok()?;
+    let service = manager
+        .open_service(SERVICE_NAME, ServiceAccess::QUERY_STATUS)
+        .ok()?;
+    Some(service.query_status().ok()?.current_state)
+}
+
+fn light_taskbar() -> bool {
+    let personalize = r"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize";
+    let Ok(key) = CURRENT_USER.open(personalize) else {
+        return false;
+    };
+    key.get_u32("SystemUsesLightTheme").is_ok_and(|light| light == 1)
+}
+
+fn status_text(state: Option<ServiceState>) -> &'static str {
+    match state {
+        Some(ServiceState::Running) => "Screening downloads",
+        Some(ServiceState::Paused) => "Paused",
+        _ => "Not running",
+    }
+}
+
+fn open_service() -> Result<Service, BoxError> {
+    let manager = ServiceManager::local_computer(None::<&str>, ServiceManagerAccess::CONNECT)?;
+    let access = ServiceAccess::START | ServiceAccess::PAUSE_CONTINUE;
+    Ok(manager.open_service(SERVICE_NAME, access)?)
+}
+
+/// The alpha channel of the RGBA logo, and its width.
+fn logo_mask() -> Result<(Vec<u8>, u32), BoxError> {
+    let mut reader = png::Decoder::new(Cursor::new(LOGO)).read_info()?;
+    let mut rgba = vec![0; reader.output_buffer_size().ok_or("logo too large")?];
+    let info = reader.next_frame(&mut rgba)?;
+    let mut alpha = Vec::with_capacity(rgba.len() / 4);
+    for pixel in rgba.chunks(4) {
+        alpha.push(pixel[3]);
+    }
+    Ok((alpha, info.width))
+}
+
+/// White on a dark taskbar and black on a light one, as macOS draws a template image; dimmed
+/// when not screening.
+fn logo_rgba(mask: &[u8], light: bool, screening: bool) -> Vec<u8> {
+    let shade = if light { 0 } else { 255 };
+    let mut rgba = Vec::with_capacity(mask.len() * 4);
+    for &alpha in mask {
+        let alpha = if screening { alpha } else { alpha / 2 };
+        rgba.extend([shade, shade, shade, alpha]);
+    }
+    rgba
+}

core/src/os/windows/uninstall.rs

@@ -0,0 +1,41 @@
+use super::ca::remove_our_cas_except;
+use super::tpm::CaKey;
+use super::*;
+use std::io::ErrorKind;
+use std::path::Path;
+use tracing::info;
+
+/// Run by the MSI after it deletes the service, which would restore the hosts entries. Does
+/// nothing for what is already gone.
+pub fn uninstall() -> Result<(), BoxError> {
+    write_hosts_entries(&[])?;
+    remove_our_cas_except(None)?;
+    none_if_missing(LOCAL_MACHINE.remove_tree(REGISTRY_KEY))?;
+    CaKey::delete_machine_key()?;
+    let entries = match std::fs::read_dir(data_dir()) {
+        Err(error) if error.kind() == ErrorKind::NotFound => Vec::new(),
+        entries => entries?.collect::<Result<Vec<_>, _>>()?,
+    };
+    for path in entries.into_iter().map(|entry| entry.path()) {
+        // The admin's config stays for a reinstall, as on macOS.
+        if path != config_file() {
+            remove_path(&path)?;
+        }
+    }
+    // Fails while the config is in it.
+    let _ = std::fs::remove_dir(data_dir());
+    info!("removed the CA, its key and the data folder");
+    Ok(())
+}
+
+/// A file or a folder, if it is there.
+fn remove_path(path: &Path) -> std::io::Result<()> {
+    let removed = match path.is_dir() {
+        true => std::fs::remove_dir_all(path),
+        false => std::fs::remove_file(path),
+    };
+    match removed {
+        Err(error) if error.kind() == ErrorKind::NotFound => Ok(()),
+        removed => removed,
+    }
+}

core/wix/main.wxs

@@ -0,0 +1,193 @@
+<?xml version='1.0' encoding='windows-1252'?>
+<!--
+  Copyright (C) 2017 Christopher R. Field.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+-->
+
+<?if $(sys.BUILDARCH) = x64 or $(sys.BUILDARCH) = arm64 ?>
+    <?define PlatformProgramFilesFolder = "ProgramFiles64Folder" ?>
+<?else ?>
+    <?define PlatformProgramFilesFolder = "ProgramFilesFolder" ?>
+<?endif ?>
+
+<Wix xmlns='http://schemas.microsoft.com/wix/2006/wi' xmlns:util='http://schemas.microsoft.com/wix/UtilExtension'>
+
+    <Product
+        Id='*'
+        Name='strix-firewall'
+        UpgradeCode='D944C2F6-BF55-4B21-A60E-1BBDB1A66293'
+        Manufacturer='Strix'
+        Language='1033'
+        Codepage='1252'
+        Version='$(var.Version)'>
+
+        <Package Id='*'
+            Keywords='Installer'
+            Description='Screens package downloads for known malware before they reach your machine'
+            Manufacturer='Strix'
+            InstallerVersion='500'
+            Languages='1033'
+            Compressed='yes'
+            InstallScope='perMachine'
+            SummaryCodepage='1252'
+            />
+
+        <MajorUpgrade
+            Schedule='afterInstallInitialize'
+            DowngradeErrorMessage='A newer version of [ProductName] is already installed. Setup will now exit.'/>
+
+        <Media Id='1' Cabinet='media1.cab' EmbedCab='yes' DiskPrompt='CD-ROM #1'/>
+        <Property Id='DiskPrompt' Value='strix-firewall Installation'/>
+
+        <Directory Id='TARGETDIR' Name='SourceDir'>
+            <Directory Id='$(var.PlatformProgramFilesFolder)' Name='PFiles'>
+                <Directory Id='APPLICATIONFOLDER' Name='Strix Firewall'>
+                    <Component Id='Path' Guid='033B1050-23D0-4F5A-A0D3-F4757B4B67E0' KeyPath='yes'>
+                        <Environment
+                            Id='PATH'
+                            Name='PATH'
+                            Value='[APPLICATIONFOLDER]'
+                            Permanent='no'
+                            Part='last'
+                            Action='set'
+                            System='yes'/>
+                    </Component>
+                    <Component Id='binary0' Guid='*'>
+                        <File
+                            Id='exe0'
+                            Name='firewall.exe'
+                            DiskId='1'
+                            Source='$(var.CargoTargetBinDir)\firewall.exe'
+                            KeyPath='yes'/>
+                    </Component>
+                    <Component Id='binary1' Guid='*'>
+                        <File
+                            Id='exe1'
+                            Name='firewall-service.exe'
+                            DiskId='1'
+                            Source='$(var.CargoTargetBinDir)\firewall-service.exe'
+                            KeyPath='yes'/>
+                        <ServiceInstall
+                            Name='StrixFirewall'
+                            DisplayName='Strix Firewall'
+                            Description='Screens package downloads for known malware'
+                            Type='ownProcess'
+                            Start='auto'
+                            ErrorControl='normal'
+                            Vital='yes'>
+                            <!-- The default, except that interactive users (IU) may also start (RP), stop (WP) and pause (DT) it, as the tray does. -->
+                            <PermissionEx Sddl='D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)(A;;CCLCSWRPWPDTLOCRRC;;;IU)(A;;CCLCSWLOCRRC;;;SU)'/>
+                        </ServiceInstall>
+                        <!-- Waits, so a service that cannot start fails the install. -->
+                        <ServiceControl Id='StrixFirewall' Name='StrixFirewall' Start='install' Stop='both' Remove='uninstall' Wait='yes'/>
+                        <!-- For clients that read no trust store. SSL_CERT_FILE would replace OpenSSL's bundle. -->
+                        <Environment Id='NODE_EXTRA_CA_CERTS' Name='NODE_EXTRA_CA_CERTS' Value='[CommonAppDataFolder]Strix Firewall\ca.pem' Action='set' System='yes'/>
+                        <Environment Id='UV_SYSTEM_CERTS' Name='UV_SYSTEM_CERTS' Value='1' Action='set' System='yes'/>
+                    </Component>
+                    <Component Id='binary2' Guid='*'>
+                        <File
+                            Id='exe2'
+                            Name='firewall-tray.exe'
+                            DiskId='1'
+                            Source='$(var.CargoTargetBinDir)\firewall-tray.exe'
+                            KeyPath='yes'/>
+                        <RegistryValue
+                            Root='HKLM'
+                            Key='SOFTWARE\Microsoft\Windows\CurrentVersion\Run'
+                            Name='Strix Firewall'
+                            Type='string'
+                            Value='"[#exe2]"'/>
+                    </Component>
+                </Directory>
+            </Directory>
+        </Directory>
+
+        <Feature
+            Id='Binaries'
+            Title='Application'
+            Description='Installs the firewall and its service.'
+            Level='1'
+            ConfigurableDirectory='APPLICATIONFOLDER'
+            AllowAdvertise='no'
+            Display='expand'
+            Absent='disallow'>
+            <ComponentRef Id='binary0'/>
+            <ComponentRef Id='binary1'/>
+            <ComponentRef Id='binary2'/>
+
+            <Feature
+                Id='Environment'
+                Title='PATH Environment Variable'
+                Description='Add the install location of the [ProductName] executable to the PATH system environment variable. This allows the [ProductName] executable to be called from any location.'
+                Level='1'
+                Absent='allow'>
+                <ComponentRef Id='Path'/>
+            </Feature>
+        </Feature>
+
+        <!-- Removing the app must not leave the hosts file pointing at a service that is gone. -->
+        <CustomAction
+            Id='UninstallFirewall'
+            FileKey='exe1'
+            ExeCommand='uninstall'
+            Execute='deferred'
+            Impersonate='no'
+            Return='check'/>
+        <!--
+          Registry hosts lead nowhere while the service is down, so bring it back, also when it fails to
+          start. Through sc.exe, as MsiServiceConfigFailureActions cannot restart a service.
+        -->
+        <CustomAction
+            Id='SetFailureActions'
+            Directory='APPLICATIONFOLDER'
+            ExeCommand='"[System64Folder]sc.exe" failure StrixFirewall reset= 3600 actions= restart/5000/restart/5000/restart/5000'
+            Execute='deferred'
+            Impersonate='no'
+            Return='check'/>
+        <CustomAction
+            Id='SetFailureFlag'
+            Directory='APPLICATIONFOLDER'
+            ExeCommand='"[System64Folder]sc.exe" failureflag StrixFirewall 1'
+            Execute='deferred'
+            Impersonate='no'
+            Return='check'/>
+        <!-- From the exit dialog, which runs as the signed-in user rather than elevated. -->
+        <CustomAction
+            Id='StartTray'
+            Directory='APPLICATIONFOLDER'
+            ExeCommand='"[#exe2]"'
+            Return='asyncNoWait'/>
+        <!-- Before its file is replaced or removed. Trays WM_CLOSE does not reach, as in other sessions, are terminated. -->
+        <util:CloseApplication Id='CloseTray' Target='firewall-tray.exe' CloseMessage='yes' RebootPrompt='no' TerminateProcess='0'/>
+        <InstallExecuteSequence>
+            <!-- An upgrade removes the old version too, but should keep screening. -->
+            <Custom Action='UninstallFirewall' After='DeleteServices'>REMOVE~="ALL" AND NOT UPGRADINGPRODUCTCODE</Custom>
+            <Custom Action='SetFailureActions' After='InstallServices'>NOT REMOVE~="ALL"</Custom>
+            <Custom Action='SetFailureFlag' After='SetFailureActions'>NOT REMOVE~="ALL"</Custom>
+            <!-- The default, before InstallFiles, is after RemoveFiles, which would find the tray still running. -->
+            <Custom Action='WixCloseApplications' Before='RemoveFiles'/>
+        </InstallExecuteSequence>
+
+        <SetProperty Id='ARPINSTALLLOCATION' Value='[APPLICATIONFOLDER]' After='CostFinalize'/>
+        <Property Id='ARPHELPLINK' Value='https://github.com/usestrix/firewall'/>
+
+        <UI>
+            <UIRef Id='WixUI_FeatureTree'/>
+            <Publish Dialog='WelcomeDlg' Control='Next' Event='NewDialog' Value='CustomizeDlg' Order='99'>1</Publish>
+            <Publish Dialog='CustomizeDlg' Control='Back' Event='NewDialog' Value='WelcomeDlg' Order='99'>1</Publish>
+            <Publish Dialog='ExitDialog' Control='Finish' Event='DoAction' Value='StartTray' Order='1'>NOT Installed</Publish>
+        </UI>
+    </Product>
+
+</Wix>

dist-workspace.toml

@@ -4,7 +4,9 @@ members = ["cargo:core"]
 [dist]
 cargo-dist-version = "0.32.0"
 ci = "github"
-installers = ["shell", "powershell", "homebrew"]
+installers = ["shell", "powershell", "homebrew", "msi"]
+# core/wix/main.wxs is edited to install the service.
+allow-dirty = ["msi"]
 tap = "usestrix/homebrew-tap"
 publish-jobs = ["homebrew", "./publish-crates"]
 targets = ["aarch64-apple-darwin", "x86_64-apple-darwin", "aarch64-unknown-linux-gnu", "x86_64-unknown-linux-gnu", "x86_64-pc-windows-msvc"]