fix: WebView permissions only for the app's own origin (#22)

Linux (WebKitGTK) allowed every permission request of every kind; Windows
(WebView2) auto-allowed mic/camera/notifications without checking who asked.

Now (src-tauri/src/webview_permissions.rs, unit-tested):
- Linux: microphone/camera/screen, device labels, notifications and location
  are granted when the page in the window is the app
  (http://localhost:44548; debug builds also the bundled/dev page).
  Everything else is denied (WebKitGTK has no prompt of its own). WebKitGTK
  doesn't say which frame asked; frames are gated earlier by the Permissions
  Policy (cinny gives microphone/camera only to the same-origin call frame).
- Windows: the same grants (minus location, which keeps WebView2's prompt),
  checked against the origin of the frame that asked (args.Uri()). Other
  origins are denied mic/camera/notifications/location; other kinds keep
  WebView2's default handling.
- Denials are logged ("webview: denied …").

Tested on Linux with a release build under Xvfb + PulseAudio (no WebDriver:
WebKit's automation mode bypasses the handler), before/after:
- app page: mic, device labels, location allowed (unchanged)
- same-origin call frame: mic allowed (unchanged)
- cross-origin frame without allow=: blocked before the handler (unchanged)
- foreign top-level page: mic, device labels, location now denied (were
  allowed)
Real cinny build: boots, logs in, no denials. Windows code type-checked
(x86_64-pc-windows-gnu).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src-tauri/src/gpu_workarounds.rs

@@ -1,17 +1,22 @@
 //! WebKitGTK workarounds for NVIDIA's proprietary driver on Linux.
 //!
-//! On NVIDIA + Wayland (reported on CachyOS/KDE, driver 615, webkit2gtk 2.52)
-//! the app never shows a window: GDK dies with "Error 71 (Protocol error)
-//! dispatching to Wayland display", and under XWayland WebKit's DMA-BUF
-//! renderer then fails with "Failed to create GBM buffer … Invalid argument".
-//! `WEBKIT_DISABLE_DMABUF_RENDERER=1 GDK_BACKEND=x11` makes it run normally.
+//! Diagnosed on CachyOS/KDE Wayland, RTX 3070, driver 615.71.09, webkit2gtk
+//! 2.52.6 (reported 2026-09-27, WAYLAND_DEBUG trace in the PR):
+//! - Native Wayland: the compositor kills the connection with
+//!   `wp_linux_drm_syncobj_surface_v1 … "explicit sync is used, but no acquire
+//!   point is set"` (GDK: "Error 71 (Protocol error)"), i.e. an explicit-sync
+//!   bug between WebKit and the driver, not a buffer-format problem.
+//!   `__NV_DISABLE_EXPLICIT_SYNC=1` fixes it and keeps WebKit's GPU (DMA-BUF)
+//!   renderer, so that is the default on native Wayland.
+//! - X11 / XWayland: the DMA-BUF renderer can't allocate or import buffers
+//!   ("Failed to create GBM buffer … Invalid argument", "Failed to import
+//!   DMABuf"), so there it is disabled (`WEBKIT_DISABLE_DMABUF_RENDERER=1`,
+//!   shared-memory frames). We never force X11 any more.
 //!
-//! So, before GTK/WebKit initialise, and only when the NVIDIA driver is loaded:
-//! - `WEBKIT_DISABLE_DMABUF_RENDERER=1`;
-//! - on a Wayland session with XWayland available, `GDK_BACKEND=x11`.
-//!
-//! Anything the user already set wins, and `LOTUS_NO_GPU_WORKAROUNDS=1`
-//! disables all of it (e.g. once a newer driver/WebKit fixes this).
+//! Opt-ins / opt-outs (anything the user already set always wins):
+//! - `LOTUS_GPU_SAFE_MODE=1`: last resort, shared-memory rendering on Wayland
+//!   too (slower, especially at high resolutions).
+//! - `LOTUS_NO_GPU_WORKAROUNDS=1`: change nothing.
 
 /// Environment variables to set: pure, for tests.
 pub(crate) fn decide(
@@ -22,15 +27,30 @@ pub(crate) fn decide(
     if !nvidia || set("LOTUS_NO_GPU_WORKAROUNDS") {
         return Vec::new();
     }
-    let mut out = Vec::new();
-    if !set("WEBKIT_DISABLE_DMABUF_RENDERER") {
-        out.push(("WEBKIT_DISABLE_DMABUF_RENDERER", "1"));
-    }
-    let wayland = set("WAYLAND_DISPLAY")
+    let wayland_session = set("WAYLAND_DISPLAY")
         || get("XDG_SESSION_TYPE").is_some_and(|v| v.eq_ignore_ascii_case("wayland"));
-    // Only fall back to X11 when there is an X server (XWayland) to talk to.
-    if wayland && set("DISPLAY") && !set("GDK_BACKEND") {
-        out.push(("GDK_BACKEND", "x11"));
+    // GTK uses Wayland unless GDK_BACKEND says otherwise (it may list
+    // several, e.g. "wayland,x11": the first one wins).
+    let native_wayland = wayland_session
+        && get("GDK_BACKEND").map_or(true, |v| {
+            v.is_empty()
+                || v.trim_start().to_ascii_lowercase().starts_with("wayland")
+                || v.trim() == "*"
+        });
+
+    let mut out = Vec::new();
+    let mut want = |k: &'static str, v: &'static str| {
+        if !set(k) {
+            out.push((k, v));
+        }
+    };
+    if native_wayland {
+        want("__NV_DISABLE_EXPLICIT_SYNC", "1");
+        if set("LOTUS_GPU_SAFE_MODE") {
+            want("WEBKIT_DISABLE_DMABUF_RENDERER", "1");
+        }
+    } else {
+        want("WEBKIT_DISABLE_DMABUF_RENDERER", "1");
     }
     out
 }
@@ -44,9 +64,20 @@ fn nvidia_driver_loaded() -> bool {
 /// Call first thing in `main`, before anything starts GTK or spawns threads.
 pub fn apply() {
     #[cfg(target_os = "linux")]
-    for (key, value) in decide(nvidia_driver_loaded(), |k| std::env::var(k).ok()) {
-        eprintln!("gpu-workarounds: NVIDIA driver detected, setting {key}={value} (LOTUS_NO_GPU_WORKAROUNDS=1 to disable)");
-        std::env::set_var(key, value);
+    {
+        let changes = decide(nvidia_driver_loaded(), |k| std::env::var(k).ok());
+        if changes.is_empty() {
+            return;
+        }
+        let list: Vec<String> = changes.iter().map(|(k, v)| format!("{k}={v}")).collect();
+        eprintln!(
+            "gpu-workarounds: NVIDIA driver detected, setting {} \
+             (LOTUS_GPU_SAFE_MODE=1 for shared-memory rendering, LOTUS_NO_GPU_WORKAROUNDS=1 to disable)",
+            list.join(" ")
+        );
+        for (key, value) in changes {
+            std::env::set_var(key, value);
+        }
     }
 }
 
@@ -71,51 +102,70 @@ mod tests {
     }
 
     #[test]
-    fn nvidia_wayland_gets_both() {
+    fn nvidia_wayland_keeps_gpu_renderer_and_disables_explicit_sync() {
         assert_eq!(
             run(true, WAYLAND),
-            vec![
-                ("WEBKIT_DISABLE_DMABUF_RENDERER", "1"),
-                ("GDK_BACKEND", "x11")
-            ]
+            vec![("__NV_DISABLE_EXPLICIT_SYNC", "1")]
         );
     }
 
     #[test]
-    fn nvidia_x11_session_only_disables_dmabuf() {
-        assert_eq!(
-            run(true, &[("DISPLAY", ":0")]),
-            vec![("WEBKIT_DISABLE_DMABUF_RENDERER", "1")]
-        );
-    }
-
-    #[test]
-    fn wayland_without_xwayland_keeps_wayland() {
-        assert_eq!(
-            run(true, &[("WAYLAND_DISPLAY", "wayland-0")]),
-            vec![("WEBKIT_DISABLE_DMABUF_RENDERER", "1")]
-        );
+    fn never_forces_x11() {
+        for env in [
+            WAYLAND,
+            &[("DISPLAY", ":0")][..],
+            &[("WAYLAND_DISPLAY", "w")][..],
+        ] {
+            assert!(run(true, env).iter().all(|(k, _)| *k != "GDK_BACKEND"));
+        }
     }
 
     #[test]
     fn xdg_session_type_counts_as_wayland() {
         assert_eq!(
-            run(true, &[("XDG_SESSION_TYPE", "wayland"), ("DISPLAY", ":1")]),
+            run(true, &[("XDG_SESSION_TYPE", "wayland")]),
+            vec![("__NV_DISABLE_EXPLICIT_SYNC", "1")]
+        );
+    }
+
+    #[test]
+    fn nvidia_x11_session_disables_dmabuf_renderer() {
+        assert_eq!(
+            run(true, &[("DISPLAY", ":0"), ("XDG_SESSION_TYPE", "x11")]),
+            vec![("WEBKIT_DISABLE_DMABUF_RENDERER", "1")]
+        );
+    }
+
+    #[test]
+    fn user_forced_x11_on_wayland_counts_as_x11() {
+        let mut env = WAYLAND.to_vec();
+        env.push(("GDK_BACKEND", "x11"));
+        assert_eq!(
+            run(true, &env),
+            vec![("WEBKIT_DISABLE_DMABUF_RENDERER", "1")]
+        );
+        let mut env = WAYLAND.to_vec();
+        env.push(("GDK_BACKEND", "wayland,x11"));
+        assert_eq!(run(true, &env), vec![("__NV_DISABLE_EXPLICIT_SYNC", "1")]);
+    }
+
+    #[test]
+    fn safe_mode_adds_shared_memory_rendering_on_wayland() {
+        let mut env = WAYLAND.to_vec();
+        env.push(("LOTUS_GPU_SAFE_MODE", "1"));
+        assert_eq!(
+            run(true, &env),
             vec![
-                ("WEBKIT_DISABLE_DMABUF_RENDERER", "1"),
-                ("GDK_BACKEND", "x11")
+                ("__NV_DISABLE_EXPLICIT_SYNC", "1"),
+                ("WEBKIT_DISABLE_DMABUF_RENDERER", "1")
             ]
         );
     }
 
     #[test]
     fn user_settings_win() {
-        let env = [
-            ("WAYLAND_DISPLAY", "wayland-0"),
-            ("DISPLAY", ":0"),
-            ("WEBKIT_DISABLE_DMABUF_RENDERER", "0"),
-            ("GDK_BACKEND", "wayland"),
-        ];
+        let mut env = WAYLAND.to_vec();
+        env.push(("__NV_DISABLE_EXPLICIT_SYNC", "0"));
         assert!(run(true, &env).is_empty());
     }
 

src-tauri/src/lib.rs

@@ -13,6 +13,8 @@ use tauri_plugin_opener::OpenerExt;
 
 pub mod gpu_workarounds;
 mod native;
+#[cfg(any(target_os = "linux", target_os = "windows", test))]
+mod webview_permissions;
 
 /// Bring the main window to the foreground from the tray / a hidden /
 /// minimized state. Shared by the tray, single-instance, and deep-link paths.
@@ -1221,41 +1223,76 @@ pub fn run() {
                 let _ = window_vibrancy::apply_mica(&window, Some(true));
             }
 
-            // Auto-grant camera, microphone, and notification permissions in WebView2.
-            #[cfg(target_os = "windows")]
-            window.with_webview(|webview| {
-                use webview2_com::{
-                    Microsoft::Web::WebView2::Win32::{
-                        COREWEBVIEW2_PERMISSION_KIND,
-                        COREWEBVIEW2_PERMISSION_KIND_CAMERA,
-                        COREWEBVIEW2_PERMISSION_KIND_MICROPHONE,
-                        COREWEBVIEW2_PERMISSION_KIND_NOTIFICATIONS,
-                        COREWEBVIEW2_PERMISSION_STATE_ALLOW,
-                    },
-                    PermissionRequestedEventHandler,
-                };
+            // cinny-desktop #22: the app's own page gets the microphone, camera
+            // and notifications without a prompt; other origins (room widgets,
+            // link-preview embeds) are refused them. See webview_permissions.
+            #[cfg(any(target_os = "linux", target_os = "windows"))]
+            let app_origins = webview_permissions::AppOrigins::new(
+                port,
+                app.config().build.dev_url.as_ref(),
+            );
 
-                let controller = webview.controller();
-                if let Ok(core) = unsafe { controller.CoreWebView2() } {
-                    let handler = PermissionRequestedEventHandler::create(Box::new(
-                        |_sender, args| {
-                            if let Some(args) = args {
-                                let mut kind = COREWEBVIEW2_PERMISSION_KIND(0);
-                                unsafe { args.PermissionKind(&mut kind) }?;
-                                if kind == COREWEBVIEW2_PERMISSION_KIND_MICROPHONE
-                                    || kind == COREWEBVIEW2_PERMISSION_KIND_CAMERA
-                                    || kind == COREWEBVIEW2_PERMISSION_KIND_NOTIFICATIONS
-                                {
-                                    unsafe {
-                                        args.SetState(COREWEBVIEW2_PERMISSION_STATE_ALLOW)
-                                    }?;
-                                }
-                            }
-                            Ok(())
+            #[cfg(target_os = "windows")]
+            window.with_webview({
+                let app_origins = app_origins.clone();
+                move |webview| {
+                    use webview2_com::{
+                        Microsoft::Web::WebView2::Win32::{
+                            COREWEBVIEW2_PERMISSION_KIND,
+                            COREWEBVIEW2_PERMISSION_KIND_CAMERA,
+                            COREWEBVIEW2_PERMISSION_KIND_GEOLOCATION,
+                            COREWEBVIEW2_PERMISSION_KIND_MICROPHONE,
+                            COREWEBVIEW2_PERMISSION_KIND_NOTIFICATIONS,
+                            COREWEBVIEW2_PERMISSION_STATE_ALLOW,
+                            COREWEBVIEW2_PERMISSION_STATE_DENY,
                         },
-                    ));
-                    let mut token = Default::default();
-                    let _ = unsafe { core.add_PermissionRequested(&handler, &mut token) };
+                        PermissionRequestedEventHandler,
+                    };
+                    use webview_permissions::{decide, Decision, Kind, WINDOWS_GRANTS};
+
+                    let controller = webview.controller();
+                    if let Ok(core) = unsafe { controller.CoreWebView2() } {
+                        let handler = PermissionRequestedEventHandler::create(Box::new(
+                            move |_sender, args| {
+                                if let Some(args) = args {
+                                    let mut raw = COREWEBVIEW2_PERMISSION_KIND(0);
+                                    unsafe { args.PermissionKind(&mut raw) }?;
+                                    let kind = if raw == COREWEBVIEW2_PERMISSION_KIND_MICROPHONE
+                                        || raw == COREWEBVIEW2_PERMISSION_KIND_CAMERA
+                                    {
+                                        Kind::Media
+                                    } else if raw == COREWEBVIEW2_PERMISSION_KIND_NOTIFICATIONS {
+                                        Kind::Notifications
+                                    } else if raw == COREWEBVIEW2_PERMISSION_KIND_GEOLOCATION {
+                                        Kind::Geolocation
+                                    } else {
+                                        Kind::Other
+                                    };
+                                    // The origin of the frame that asked.
+                                    let mut uri = windows::core::PWSTR::null();
+                                    unsafe { args.Uri(&mut uri) }?;
+                                    let uri = webview2_com::take_pwstr(uri);
+                                    match decide(kind, &uri, &app_origins, WINDOWS_GRANTS) {
+                                        Decision::Allow => unsafe {
+                                            args.SetState(COREWEBVIEW2_PERMISSION_STATE_ALLOW)
+                                        }?,
+                                        Decision::Deny => {
+                                            eprintln!(
+                                                "webview: denied {kind:?} permission to {uri}"
+                                            );
+                                            unsafe {
+                                                args.SetState(COREWEBVIEW2_PERMISSION_STATE_DENY)
+                                            }?
+                                        }
+                                        Decision::Default => {}
+                                    }
+                                }
+                                Ok(())
+                            },
+                        ));
+                        let mut token = Default::default();
+                        let _ = unsafe { core.add_PermissionRequested(&handler, &mut token) };
+                    }
                 }
             })?;
 
@@ -1263,19 +1300,48 @@ pub fn run() {
             // default (unlike WebView2/WKWebView), which leaves
             // `navigator.mediaDevices` undefined and makes Element Call
             // report "browser does not support WebRTC". Turn them on and
-            // auto-grant the resulting camera/mic permission prompt, mirroring
-            // the WebView2 handling above.
+            // answer the permission requests, mirroring the WebView2 handling
+            // above. WebKitGTK doesn't say which frame asked, so the origin
+            // checked is the page in the window (see webview_permissions).
             #[cfg(target_os = "linux")]
-            window.with_webview(|webview| {
-                use webkit2gtk::{PermissionRequestExt, SettingsExt, WebViewExt};
+            window.with_webview(move |webview| {
+                use webkit2gtk::glib::prelude::ObjectExt;
+                use webkit2gtk::{
+                    DeviceInfoPermissionRequest, GeolocationPermissionRequest,
+                    NotificationPermissionRequest, PermissionRequestExt, SettingsExt,
+                    UserMediaPermissionRequest, WebViewExt,
+                };
+                use webview_permissions::{decide, Decision, Kind, LINUX_GRANTS};
 
                 let wv = webview.inner();
                 if let Some(settings) = WebViewExt::settings(&wv) {
                     settings.set_enable_media_stream(true);
                     settings.set_enable_webrtc(true);
                 }
-                wv.connect_permission_request(|_webview, request| {
-                    request.allow();
+                wv.connect_permission_request(move |wv, request| {
+                    let kind = if request.is::<UserMediaPermissionRequest>() {
+                        Kind::Media
+                    } else if request.is::<DeviceInfoPermissionRequest>() {
+                        Kind::DeviceInfo
+                    } else if request.is::<NotificationPermissionRequest>() {
+                        Kind::Notifications
+                    } else if request.is::<GeolocationPermissionRequest>() {
+                        Kind::Geolocation
+                    } else {
+                        Kind::Other
+                    };
+                    let uri = wv.uri().map(|u| u.to_string()).unwrap_or_default();
+                    match decide(kind, &uri, &app_origins, LINUX_GRANTS) {
+                        Decision::Allow => request.allow(),
+                        // No prompt of our own: anything not granted is denied.
+                        Decision::Deny | Decision::Default => {
+                            eprintln!(
+                                "webview: denied {} to {uri}",
+                                request.type_().name()
+                            );
+                            request.deny();
+                        }
+                    }
                     true
                 });
             })?;

src-tauri/src/webview_permissions.rs

@@ -0,0 +1,221 @@
+//! Which WebView permission requests the app grants (cinny-desktop #22).
+//!
+//! The web client asks for the microphone/camera/screen (calls, voice
+//! messages), the device list (audio-output picker), notifications and the
+//! location (location sharing). Those are granted without a prompt, but only
+//! to the app's own origin. Everything else is left alone (Windows: WebView2's
+//! own prompt) or denied (Linux: WebKitGTK has no prompt of its own).
+//!
+//! What "the requesting origin" means differs per engine:
+//! - WebView2 reports the origin of the frame that asked (`args.Uri()`), so a
+//!   room widget or link-preview embed is refused here.
+//! - WebKitGTK doesn't say which frame asked; the check is on the page loaded
+//!   in the window. Frames are gated before the request gets this far by the
+//!   Permissions Policy: cinny only puts `microphone; camera` in the `allow=`
+//!   of the call frame (same origin on desktop), and cross-origin frames get
+//!   neither location nor notifications.
+
+use tauri::Url;
+
+/// A permission request, reduced to what the policy cares about.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(crate) enum Kind {
+    /// Microphone, camera or screen capture (getUserMedia/getDisplayMedia).
+    Media,
+    /// Device labels/ids from enumerateDevices (WebKitGTK only).
+    #[cfg_attr(not(target_os = "linux"), allow(dead_code))]
+    DeviceInfo,
+    Notifications,
+    Geolocation,
+    /// Anything else: clipboard read, storage access, pointer lock, DRM, …
+    Other,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(crate) enum Decision {
+    Allow,
+    Deny,
+    /// Let the engine decide (WebView2 prompts; WebKitGTK denies).
+    Default,
+}
+
+/// What the Linux (WebKitGTK) handler grants to the app.
+#[cfg_attr(not(target_os = "linux"), allow(dead_code))]
+pub(crate) const LINUX_GRANTS: &[Kind] = &[
+    Kind::Media,
+    Kind::DeviceInfo,
+    Kind::Notifications,
+    Kind::Geolocation,
+];
+/// What the Windows (WebView2) handler grants to the app. Location keeps
+/// WebView2's own prompt, as before.
+#[cfg_attr(not(target_os = "windows"), allow(dead_code))]
+pub(crate) const WINDOWS_GRANTS: &[Kind] = &[Kind::Media, Kind::Notifications];
+
+/// The decision for a request of `kind` from `uri`.
+pub(crate) fn decide(kind: Kind, uri: &str, app: &AppOrigins, grants: &[Kind]) -> Decision {
+    if kind == Kind::Other {
+        return Decision::Default;
+    }
+    if !app.contains(uri) {
+        return Decision::Deny;
+    }
+    if grants.contains(&kind) {
+        Decision::Allow
+    } else {
+        Decision::Default
+    }
+}
+
+/// scheme, host, port (explicit or the scheme's default).
+type Origin = (String, String, Option<u16>);
+
+fn origin_of(uri: &str) -> Option<Origin> {
+    let url = Url::parse(uri).ok()?;
+    let host = url.host_str()?.to_ascii_lowercase();
+    Some((url.scheme().to_owned(), host, url.port_or_known_default()))
+}
+
+/// The origins the app's own page is served from.
+#[derive(Clone, Debug)]
+pub(crate) struct AppOrigins(Vec<Origin>);
+
+impl AppOrigins {
+    /// Release builds load `http://localhost:{port}` (tauri-plugin-localhost).
+    /// Debug builds load the bundled page (`tauri://localhost`, or
+    /// `http://tauri.localhost` on Windows) or, under `tauri dev`, `dev_url`.
+    pub(crate) fn new(port: u16, dev_url: Option<&Url>) -> Self {
+        let mut uris = vec![format!("http://localhost:{port}/")];
+        if cfg!(debug_assertions) {
+            uris.push("tauri://localhost/".into());
+            uris.push("http://tauri.localhost/".into());
+            if let Some(dev) = dev_url {
+                uris.push(dev.to_string());
+            }
+        }
+        Self(uris.iter().filter_map(|u| origin_of(u)).collect())
+    }
+
+    pub(crate) fn contains(&self, uri: &str) -> bool {
+        origin_of(uri).is_some_and(|o| self.0.contains(&o))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn app() -> AppOrigins {
+        AppOrigins::new(44548, None)
+    }
+
+    #[test]
+    fn app_origin_matches_only_the_app() {
+        let app = app();
+        assert!(app.contains("http://localhost:44548/"));
+        assert!(app.contains("http://localhost:44548/#/home/!room:server"));
+        assert!(app.contains("http://LOCALHOST:44548/public/element-call/index.html"));
+        for other in [
+            "http://localhost:44549/",
+            "https://localhost:44548/",
+            "http://127.0.0.1:44548/",
+            "http://localhost/",
+            "http://localhost.evil.example:44548/",
+            "http://evil.example/?http://localhost:44548/",
+            "https://www.youtube-nocookie.com/embed/x",
+            "https://chat.lotusguild.org/",
+            "about:blank",
+            "data:text/html,hi",
+            "null",
+            "",
+        ] {
+            assert!(!app.contains(other), "{other}");
+        }
+    }
+
+    #[test]
+    fn debug_builds_also_accept_the_bundled_and_dev_pages() {
+        let dev = Url::parse("http://localhost:8080").unwrap();
+        let app = AppOrigins::new(44548, Some(&dev));
+        assert_eq!(
+            app.contains("tauri://localhost/index.html"),
+            cfg!(debug_assertions)
+        );
+        assert_eq!(
+            app.contains("http://tauri.localhost/"),
+            cfg!(debug_assertions)
+        );
+        assert_eq!(
+            app.contains("http://localhost:8080/"),
+            cfg!(debug_assertions)
+        );
+        assert!(app.contains("http://localhost:44548/"));
+        assert!(!app.contains("tauri://evil/"));
+    }
+
+    #[test]
+    fn app_gets_its_grants_without_a_prompt() {
+        let app = app();
+        let uri = "http://localhost:44548/";
+        for kind in [
+            Kind::Media,
+            Kind::DeviceInfo,
+            Kind::Notifications,
+            Kind::Geolocation,
+        ] {
+            assert_eq!(
+                decide(kind, uri, &app, LINUX_GRANTS),
+                Decision::Allow,
+                "{kind:?}"
+            );
+        }
+        assert_eq!(
+            decide(Kind::Media, uri, &app, WINDOWS_GRANTS),
+            Decision::Allow
+        );
+        assert_eq!(
+            decide(Kind::Notifications, uri, &app, WINDOWS_GRANTS),
+            Decision::Allow
+        );
+        // Location on Windows keeps WebView2's prompt.
+        assert_eq!(
+            decide(Kind::Geolocation, uri, &app, WINDOWS_GRANTS),
+            Decision::Default
+        );
+    }
+
+    #[test]
+    fn other_origins_are_refused() {
+        let app = app();
+        for uri in [
+            "https://widget.example/",
+            "https://www.youtube-nocookie.com/embed/x",
+            "",
+        ] {
+            for kind in [
+                Kind::Media,
+                Kind::DeviceInfo,
+                Kind::Notifications,
+                Kind::Geolocation,
+            ] {
+                assert_eq!(decide(kind, uri, &app, LINUX_GRANTS), Decision::Deny);
+                assert_eq!(decide(kind, uri, &app, WINDOWS_GRANTS), Decision::Deny);
+            }
+        }
+    }
+
+    #[test]
+    fn other_kinds_are_left_to_the_engine() {
+        let app = app();
+        for uri in ["http://localhost:44548/", "https://widget.example/"] {
+            assert_eq!(
+                decide(Kind::Other, uri, &app, LINUX_GRANTS),
+                Decision::Default
+            );
+            assert_eq!(
+                decide(Kind::Other, uri, &app, WINDOWS_GRANTS),
+                Decision::Default
+            );
+        }
+    }
+}