Added a session cookie for the app window

runtime/src/app_access.rs

@@ -0,0 +1,104 @@
+use log::{error, info};
+use once_cell::sync::Lazy;
+use tauri::webview::Cookie;
+use tauri::{Url, WebviewWindow};
+use crate::api_token::{generate_api_token, APIToken};
+
+/// The token which the app window presents to the .NET server as the value of its session cookie.
+/// Every start makes a new one.
+pub static UI_ACCESS_TOKEN: Lazy<APIToken> = Lazy::new(generate_api_token);
+
+/// The name of the session cookie. The .NET server expects the same name.
+pub const SESSION_COOKIE_NAME: &str = "ai_studio_session";
+
+/// The environment variable which carries the token to the .NET server.
+pub const DOTNET_ENV_UI_TOKEN: &str = "AI_STUDIO_UI_TOKEN";
+
+/// The host of the app. The .NET server listens on this address only, and the session cookie
+/// belongs to it.
+pub const APP_HOST: &str = "127.0.0.1";
+
+/// Builds the session cookie of the app window.
+///
+/// The cookie is for the app host alone and lives as long as the window: it has no expiry date,
+/// scripts cannot read it, and the window never sends it with a request which another site
+/// started. We parse it from text because the `cookie` crate, whose builder would need its
+/// `SameSite` type, is no direct dependency of ours.
+pub fn session_cookie() -> Cookie<'static> {
+    let token = UI_ACCESS_TOKEN.to_hex_text();
+    Cookie::parse(format!("{SESSION_COOKIE_NAME}={token}; Domain={APP_HOST}; Path=/; HttpOnly; SameSite=Strict"))
+        .expect("The session cookie consists of fixed attributes and a hexadecimal token, which always parse.")
+}
+
+/// Puts the session cookie into the cookie store of the given window, before the window opens
+/// the app at the given URL.
+///
+/// Setting the cookie does not wait for the webview, and WebView2 even adds it in the background.
+/// Reading the cookies back waits until the webview has handled everything sent before, so the
+/// cookie is in place once this function returns. That reading is also the only way to learn
+/// whether setting the cookie worked.
+///
+/// Blocks until the main thread has answered, so never call it on a worker of the async runtime.
+/// The log never shows the value of the cookie.
+pub fn hand_over_session_cookie(window: &WebviewWindow, app_url: &Url) {
+    if let Err(error) = window.set_cookie(session_cookie()) {
+        error!(Source = "App access"; "Failed to hand the session cookie to the app window: {error}");
+        return;
+    }
+
+    match window.cookies_for_url(app_url.clone()) {
+        Ok(cookies) if cookies.iter().any(|cookie| cookie.name() == SESSION_COOKIE_NAME) => {
+            info!(Source = "App access"; "The app window got its session cookie.");
+        },
+
+        Ok(_) => {
+            error!(Source = "App access"; "The app window lacks its session cookie after it was set.");
+        },
+
+        Err(error) => {
+            error!(Source = "App access"; "Failed to check the session cookie of the app window: {error}");
+        },
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn the_session_cookie_carries_the_token() {
+        let cookie = session_cookie();
+
+        assert_eq!(cookie.name(), SESSION_COOKIE_NAME);
+        assert_eq!(cookie.value(), UI_ACCESS_TOKEN.to_hex_text());
+    }
+
+    #[test]
+    fn the_session_cookie_belongs_to_the_app_host_alone() {
+        let cookie = session_cookie();
+
+        assert_eq!(cookie.domain(), Some(APP_HOST));
+        assert_eq!(cookie.path(), Some("/"));
+    }
+
+    #[test]
+    fn the_session_cookie_is_hidden_from_scripts_and_other_sites() {
+        let cookie = session_cookie();
+
+        assert_eq!(cookie.http_only(), Some(true));
+        assert!(cookie.same_site().is_some_and(|same_site| same_site.is_strict()));
+    }
+
+    #[test]
+    fn the_session_cookie_lives_only_as_long_as_the_window() {
+        let cookie = session_cookie();
+
+        assert!(cookie.expires().is_none());
+        assert!(cookie.max_age().is_none());
+    }
+
+    #[test]
+    fn the_ui_token_differs_from_the_api_token() {
+        assert!(!UI_ACCESS_TOKEN.validate(&APIToken::from_hex_text(crate::runtime_api_token::API_TOKEN.to_hex_text())));
+    }
+}

runtime/src/app_window.rs

@@ -21,6 +21,7 @@ use tauri_plugin_updater::{UpdaterExt, Update};
 use tauri_plugin_opener::OpenerExt;
 use tokio::sync::broadcast;
 use tokio::time;
+use crate::app_access::hand_over_session_cookie;
 use crate::clipboard::shutdown_clipboard;
 use crate::data_restore::apply_pending_restore;
 use crate::dotnet::{cleanup_dotnet_server, start_dotnet_server, stop_dotnet_server};
@@ -677,7 +678,8 @@ pub fn send_event(event: Event) {
     }
 }
 
-/// Changes the location of the main window to the given URL.
+/// Changes the location of the main window to the given URL. The window gets its session cookie
+/// first, so that the .NET server lets it in.
 pub async fn change_location_to(url: tauri::Url) {
     // Try to get the main window. If it is not available yet, wait for it:
     let mut main_window_ready = false;
@@ -707,14 +709,24 @@ pub async fn change_location_to(url: tauri::Url) {
     //
     // The window navigates by itself instead of through a script of the page it shows. That page
     // comes from Tauri, which is another site than the app, so the app would count as opened by
-    // another site. We take the window out of the lock first: navigating needs the main thread,
+    // another site, and the window would withhold the session cookie. We take the window out of
-    // which may wait for this lock meanwhile.
+    // the lock first: the cookie and the navigation need the main thread, which may wait for this
+    // lock meanwhile.
+    //
+    // Handing over the cookie waits for the main thread. This function serves a request of the
+    // runtime API, so the waiting happens outside the async runtime, see runtime/AGENTS.md.
     //
     let main_window = main_window_spawn_clone.lock().unwrap().clone().unwrap();
-    let location_change_result = main_window.navigate(url.clone());
+    let navigation = tokio::task::spawn_blocking(move || {
-    match location_change_result {
+        hand_over_session_cookie(&main_window, &url);
-        Ok(_) => info!("The app location was changed to {url}."),
+        match main_window.navigate(url.clone()) {
-        Err(e) => error!("Failed to change the app location to {url}: {e}."),
+            Ok(_) => info!("The app location was changed to {url}."),
+            Err(e) => error!("Failed to change the app location to {url}: {e}."),
+        }
+    });
+
+    if let Err(error) = navigation.await {
+        error!("Failed to open the app in the main window: {error}");
     }
 }
 

runtime/src/dotnet.rs

@@ -9,6 +9,7 @@ use tauri::{Manager, Url};
 use tauri_plugin_shell::process::{CommandChild, CommandEvent, TerminatedPayload};
 use tauri_plugin_shell::ShellExt;
 use crate::runtime_api_token::API_TOKEN;
+use crate::app_access::{APP_HOST, DOTNET_ENV_UI_TOKEN, UI_ACCESS_TOKEN};
 use crate::app_window::change_location_to;
 use crate::runtime_certificate::CERTIFICATE_FINGERPRINT;
 use crate::encryption::ENCRYPTION;
@@ -177,46 +178,43 @@ fn dotnet_bundle_extraction_directory<R: tauri::Runtime>(app_handle: &tauri::App
 /// but also remove that code from any production build.
 #[cfg(debug_assertions)]
 pub fn create_startup_env_file() {
-
-    // Get the secret password & salt and convert it to a base64 string:
-    let secret_password = BASE64_STANDARD.encode(ENCRYPTION.secret_password);
-    let secret_key_salt = BASE64_STANDARD.encode(ENCRYPTION.secret_key_salt);
-    let api_port = *API_SERVER_PORT;
-
     warn!(Source = "Bootloader .NET"; "Development environment detected; create the startup env file at '../startup.env'.");
     let env_file_path = std::path::PathBuf::from("..").join("startup.env");
     let mut env_file = std::fs::File::create(env_file_path).unwrap();
-    let mut env_file_lines = vec![
+    let env_file_lines: Vec<String> = ipc_environment()
-        format!("AI_STUDIO_SECRET_PASSWORD={secret_password}"),
+        .into_iter()
-        format!("AI_STUDIO_SECRET_KEY_SALT={secret_key_salt}"),
+        .map(|(key, value)| format!("{key}={value}"))
-        format!("AI_STUDIO_CERTIFICATE_FINGERPRINT={}", CERTIFICATE_FINGERPRINT.get().unwrap()),
+        .collect();
-        format!("AI_STUDIO_API_PORT={api_port}"),
-        format!("AI_STUDIO_API_TOKEN={}", API_TOKEN.to_hex_text()),
-    ];
-    for (key, value) in external_http_custom_root_certificate_policy_environment() {
-        env_file_lines.push(format!("{key}={value}"));
-    }
 
     std::io::Write::write_all(&mut env_file, env_file_lines.join("\n").as_bytes()).unwrap();
     info!(Source = "Bootloader .NET"; "The startup env file was created successfully.");
 }
 
-/// Starts the .NET server in a separate process.
+/// Returns the environment which the .NET server needs to talk to this runtime and to let only
-pub fn start_dotnet_server<R: tauri::Runtime>(app_handle: tauri::AppHandle<R>) {
+/// the app window in. The sidecar gets it, and so does the startup env file in the development
+/// environment, so neither of them can miss a variable.
+fn ipc_environment() -> Vec<(String, String)> {
 
     // Get the secret password & salt and convert it to a base64 string:
     let secret_password = BASE64_STANDARD.encode(ENCRYPTION.secret_password);
     let secret_key_salt = BASE64_STANDARD.encode(ENCRYPTION.secret_key_salt);
     let api_port = *API_SERVER_PORT;
 
-    let mut dotnet_server_environment: HashMap<String, String> = HashMap::from_iter([
+    let mut environment = vec![
         (String::from("AI_STUDIO_SECRET_PASSWORD"), secret_password),
         (String::from("AI_STUDIO_SECRET_KEY_SALT"), secret_key_salt),
         (String::from("AI_STUDIO_CERTIFICATE_FINGERPRINT"), CERTIFICATE_FINGERPRINT.get().unwrap().to_string()),
         (String::from("AI_STUDIO_API_PORT"), format!("{api_port}")),
         (String::from("AI_STUDIO_API_TOKEN"), API_TOKEN.to_hex_text().to_string()),
-    ]);
+        (String::from(DOTNET_ENV_UI_TOKEN), UI_ACCESS_TOKEN.to_hex_text().to_string()),
-    dotnet_server_environment.extend(external_http_custom_root_certificate_policy_environment());
+    ];
+    environment.extend(external_http_custom_root_certificate_policy_environment());
+    environment
+}
+
+/// Starts the .NET server in a separate process.
+pub fn start_dotnet_server<R: tauri::Runtime>(app_handle: tauri::AppHandle<R>) {
+    let mut dotnet_server_environment: HashMap<String, String> = HashMap::from_iter(ipc_environment());
     if let Some(extraction_directory) = dotnet_bundle_extraction_directory(&app_handle) {
         dotnet_server_environment.insert(String::from(DOTNET_ENV_BUNDLE_EXTRACT_BASE_DIR), extraction_directory);
     }
@@ -319,7 +317,7 @@ pub async fn dotnet_ready() {
 /// address only, so the window goes there directly instead of resolving `localhost`, which may
 /// answer with the IPv6 loopback address first.
 fn app_address(port: u16) -> String {
-    format!("http://127.0.0.1:{port}/")
+    format!("http://{APP_HOST}:{port}/")
 }
 
 /// Stops the .NET server process.
@@ -364,4 +362,26 @@ mod tests {
         let url = Url::parse(app_address(61153).as_str()).unwrap();
         assert!(is_local_http_url(&url));
     }
+
+    #[test]
+    fn the_ipc_environment_carries_every_variable_the_dotnet_server_needs() {
+        // Only the start of the app generates the certificate this fingerprint belongs to:
+        let _ = CERTIFICATE_FINGERPRINT.set(String::from("test-fingerprint"));
+
+        let environment = ipc_environment();
+        let keys: Vec<&str> = environment.iter().map(|(key, _)| key.as_str()).collect();
+        for expected in [
+            "AI_STUDIO_SECRET_PASSWORD",
+            "AI_STUDIO_SECRET_KEY_SALT",
+            "AI_STUDIO_CERTIFICATE_FINGERPRINT",
+            "AI_STUDIO_API_PORT",
+            "AI_STUDIO_API_TOKEN",
+            DOTNET_ENV_UI_TOKEN,
+        ] {
+            assert!(keys.contains(&expected), "The environment lacks {expected}.");
+        }
+
+        let ui_token = environment.iter().find(|(key, _)| key == DOTNET_ENV_UI_TOKEN).map(|(_, value)| value.as_str());
+        assert_eq!(ui_token, Some(UI_ACCESS_TOKEN.to_hex_text()));
+    }
 }

runtime/src/lib.rs

@@ -4,6 +4,7 @@ pub mod environment;
 pub mod dotnet;
 pub mod network;
 pub mod api_token;
+pub mod app_access;
 pub mod app_window;
 pub mod secret;
 pub mod clipboard;