Multi-user servers: email and invite codes at sign-up and sign-in

Create account takes an email and an invite or setup code (none with open
sign-up), joins servers that already have accounts, and Settings shows the
account email (admins manage people from the web vault).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src-tauri/src/main.rs

@@ -154,17 +154,18 @@ fn state(app: State<'_, App>) -> AppState {
 
 // Argon2id takes ~0.5 s, so these run as async commands off the main thread.
 
-/// "Create a new account": a new vault here, registered with a fresh server using its setup code.
+/// "Create a new account": a new vault here, registered with the server using its setup code or an invite.
 #[tauri::command]
 async fn create_account(
     app: State<'_, App>,
     server_url: String,
     pins: String,
     setup_code: String,
+    email: String,
     master_password: String,
 ) -> CmdResult<String> {
     let master_password = Zeroizing::new(master_password);
-    let sk = app.sync.create_account(&server_url, sync::parse_pins(&pins), &setup_code, master_password).await;
+    let sk = app.sync.create_account(&server_url, sync::parse_pins(&pins), &setup_code, &email, master_password).await;
     app.activity.touch();
     sk.map(|s| s.to_string())
 }
@@ -378,8 +379,8 @@ async fn server_setup_open(app: State<'_, App>) -> CmdResult<bool> {
 }
 
 #[tauri::command]
-async fn register_server(app: State<'_, App>, setup_code: String) -> CmdResult<()> {
-    app.sync.register(&setup_code).await
+async fn register_server(app: State<'_, App>, setup_code: String, email: String) -> CmdResult<()> {
+    app.sync.register(&setup_code, &email).await
 }
 
 #[tauri::command]

src-tauri/src/sync.rs

@@ -139,8 +139,22 @@ fn now_secs() -> u64 {
 }
 
 /// User-facing text for a core error.
+/// Deliberately loose ([email protected]); the server normalises and checks it again.
+fn looks_like_email(s: &str) -> bool {
+    match s.split_once('@') {
+        Some((user, domain)) => {
+            !user.is_empty() && !domain.contains('@') && domain.contains('.') && !s.contains(char::is_whitespace)
+        }
+        None => false,
+    }
+}
+
 pub fn describe(e: &CoreError) -> String {
     match e {
+        CoreError::Server { status: 409, .. } => {
+            "An account with this email already exists on the server. Sign in to it instead, or use another email."
+                .into()
+        }
         CoreError::Network { msg } => format!("Can't reach the server: {msg}"),
         CoreError::PinMismatch => {
             "The server's certificate doesn't match the pinned keys. Someone may be intercepting \
@@ -344,33 +358,43 @@ impl SyncService {
         Ok(())
     }
 
-    /// "Create a new account": creates the vault here and registers it with a fresh server using the setup code
-    /// (`KV_SETUP_CODE`). Returns the Secret Key for the Emergency Kit.
+    /// "Create a new account": creates the vault here and registers it with the server, using its setup code
+    /// (`KV_SETUP_CODE`, first account), an admin's invite, or nothing with open sign-up. Returns the Secret Key
+    /// for the Emergency Kit.
     pub async fn create_account(
         &self,
         server_url: &str,
         pins: Vec<String>,
         setup_code: &str,
+        email: &str,
         master_password: Zeroizing<String>,
     ) -> Result<Zeroizing<String>, String> {
         if self.core.has_account() {
             return Err("This computer already has a vault.".into());
         }
-        if setup_code.trim().is_empty() {
-            return Err("Enter the server's setup code.".into());
+        let email = email.trim();
+        if !looks_like_email(email) {
+            return Err("Enter your email address. You sign in with it on new devices.".into());
         }
+        let code = setup_code.trim();
         self.configure(server_url, pins)?;
         let info = self.core.server_info().await.map_err(|e| describe(&e))?;
-        if !info.setup_open {
+        if !info.setup_open && !info.multi_user {
             return Err(
                 "This server already has an account. Choose “Use my phone” or “Paste setup code” instead.".into()
             );
         }
+        if code.is_empty() && info.setup_open {
+            return Err("Enter the server's setup code (KV_SETUP_CODE in its .env).".into());
+        }
+        if code.is_empty() && !info.open_signup {
+            return Err("Enter the invite code your server's admin sent you.".into());
+        }
         let sk = Zeroizing::new(self.core.create_account(master_password.to_string()).map_err(|e| describe(&e))?);
         self.remember_secret_key(&sk);
-        if let Err(e) = self.core.register_account(setup_code.trim().to_string()).await {
+        if let Err(e) = self.core.register_account(code.to_string(), Some(email.to_string())).await {
             return Err(format!(
-                "Your vault was created on this computer, but the server refused it: {}. Check the setup code in \
+                "Your vault was created on this computer, but the server refused it: {}. Check the code in \
                  Settings → Sync and try again.",
                 describe(&e)
             ));
@@ -379,9 +403,17 @@ impl SyncService {
         Ok(sk)
     }
 
-    /// For a vault created before sync was set up: registers it with a fresh server.
-    pub async fn register(&self, setup_code: &str) -> Result<(), String> {
-        self.core.register_account(setup_code.trim().to_string()).await.map_err(|e| describe(&e))?;
+    /// For a vault created before sync was set up: registers it with the server (setup code, invite, or nothing
+    /// with open sign-up).
+    pub async fn register(&self, setup_code: &str, email: &str) -> Result<(), String> {
+        let email = email.trim();
+        if !looks_like_email(email) {
+            return Err("Enter your email address. You sign in with it on new devices.".into());
+        }
+        self.core
+            .register_account(setup_code.trim().to_string(), Some(email.to_string()))
+            .await
+            .map_err(|e| describe(&e))?;
         self.sync_now().await.map(|_| ())
     }
 
@@ -678,7 +710,7 @@ mod tests {
         let phone_key: Arc<dyn kv_ffi::DeviceSigner> =
             Arc::new(DeviceKey::load_or_create_file(phone_dir.path()).unwrap());
         phone.set_device_signer(phone_key, "phone".into(), PlatformDto::Ios).unwrap();
-        phone.register_account(SETUP_TOKEN.into()).await.unwrap();
+        phone.register_account(SETUP_TOKEN.into(), Some("[email protected]".into())).await.unwrap();
         server.state().require_approval = true;
 
         let dir = tempfile::tempdir().unwrap();

src-tauri/tests/live_sync.rs

@@ -73,7 +73,8 @@ async fn create_join_approve_and_sync() {
 
     // A: "Create a new account".
     let a = instance(da.path());
-    let sk = a.create_account(&server, vec![], &code, Zeroizing::new(PASSWORD.into())).await.unwrap();
+    let sk =
+        a.create_account(&server, vec![], &code, "[email protected]", Zeroizing::new(PASSWORD.into())).await.unwrap();
     assert!(sk.starts_with("K1"));
     assert!(a.status().logged_in);
     assert!(a.status().last_sync_at.is_some(), "first sync after registration: {:?}", a.status().last_error);

src/main.ts

@@ -349,6 +349,7 @@ function finishSetup(body: HTMLElement, view: SetupView) {
 
 function createPanel(body: HTMLElement, status: SyncStatus) {
   const url = serverInput(status);
+  const email = input({ type: "email", autocomplete: "email", spellcheck: false });
   const code = input({ spellcheck: false });
   const pins = input({ placeholder: "base64, comma-separated", spellcheck: false }, true);
   const pw = input({ type: "password", autocomplete: "new-password" });
@@ -366,7 +367,7 @@ function createPanel(body: HTMLElement, status: SyncStatus) {
     btn.disabled = true;
     btn.textContent = "Creating…";
     try {
-      const secretKey = await invoke<string>("create_account", { serverUrl: url.value, pins: pins.value, setupCode: code.value, masterPassword: pw.value });
+      const secretKey = await invoke<string>("create_account", { serverUrl: url.value, pins: pins.value, setupCode: code.value, email: email.value, masterPassword: pw.value });
       pw.value = pw2.value = "";
       await showSecretKey(secretKey);
     } catch (e) {
@@ -380,9 +381,10 @@ function createPanel(body: HTMLElement, status: SyncStatus) {
     }
   };
   body.append(
-    p("kv-muted", "For the first device on a new server. You'll get a Secret Key: keep it with your Emergency Kit."),
+    p("kv-muted", "A new account on your Kestrove server. You'll get a Secret Key: keep it with your Emergency Kit."),
     field("Your Kestrove server", url),
-    field("Setup code", code, "KV_SETUP_CODE in your server's .env."),
+    field("Email", email, "You sign in with it on new devices."),
+    field("Invite or setup code", code, "The invite from your server's admin, or KV_SETUP_CODE from its .env for the first account. Empty with open sign-up."),
     h("details", "", h("summary", "kv-small", "Certificate pins (advanced)"), field("SPKI pins", pins)),
     field("Master password", pw, "10 or more characters."),
     field("Repeat master password", pw2),
@@ -737,6 +739,7 @@ function renderSyncSettings(box: HTMLElement, s: SyncStatus, reload: () => Promi
   // A vault from before sync (or whose registration failed): connect it.
   const url = input({ type: "url", placeholder: "https://kestrove.example.com", value: s.server_url ?? "" });
   const pins = input({ value: s.pins.join(", ") }, true);
+  const email = input({ type: "email", autocomplete: "email", spellcheck: false });
   const code = input({});
   const err = errBox();
   const btn = button("Connect", "primary");
@@ -745,9 +748,10 @@ function renderSyncSettings(box: HTMLElement, s: SyncStatus, reload: () => Promi
     err.replaceChildren();
     try {
       await invoke("configure_server", { serverUrl: url.value, pins: pins.value });
-      if (await invoke<boolean>("server_setup_open")) {
-        if (!code.value.trim()) throw new Error("This server has no account yet: enter its setup code to register this vault.");
-        await invoke("register_server", { setupCode: code.value });
+      const setupOpen = await invoke<boolean>("server_setup_open");
+      if (setupOpen && !code.value.trim()) throw new Error("This server has no account yet: enter its setup code to register this vault.");
+      if (setupOpen || email.value.trim()) {
+        await invoke("register_server", { setupCode: code.value, email: email.value });
       } else {
         await invoke("sync_now");
       }
@@ -758,7 +762,8 @@ function renderSyncSettings(box: HTMLElement, s: SyncStatus, reload: () => Promi
     }
   };
   box.append(h("div", "kv-card pad stack", field("Your Kestrove server", url), field("SPKI pins", pins, "Optional."),
-    field("Setup code", code, "Only for a new server."), err, h("div", "actions", btn)));
+    field("Email", email, "To register this vault as a new account."),
+    field("Invite or setup code", code, "An admin's invite, or the setup code of a new server."), err, h("div", "actions", btn)));
 }
 
 async function renderDevices(box: HTMLElement) {