fix(signer): Amber-compatible handshake — bunker:// URIs, deferred identity, ack wait

- parse_connect_uri accepts bunker:// as well as nostrconnect://
- URI authority key is no longer treated as identity (Amber mints a
  per-connection comms key); real identity learned via get_public_key
  after the connect ack, then persisted (profile row + secret re-key)
- connect ack awaited in a spawned handshake task with a 120s human
  approval window; session stays Connecting (all signing fails closed)
  until identity is verified
- absent perms= no longer locally denies signing; enforcement is
  delegated to the signer's approval UI
- send_rpc honours its timeout parameter

src/signer/nip46_client.rs

@@ -34,6 +34,9 @@ const MAX_PENDING_APPROVALS: usize = 20;
 /// How long an outbound NIP-46 request (e.g. our own `sign_event`) may wait
 /// for the remote signer's response before it is abandoned.
 const REQUEST_TIMEOUT: Duration = Duration::from_secs(30);
+/// The connect handshake can involve a human approving the app on the
+/// signer's screen, so it gets a far longer leash than ordinary RPCs.
+const HANDSHAKE_TIMEOUT: Duration = Duration::from_secs(120);
 
 /// Internal state for a pending approval.
 struct PendingApprovalInner {
@@ -74,6 +77,12 @@ struct Nip46Inner {
     remote_pending: HashMap<String, PendingRemoteRequest>,
     keys: Option<Keys>,
     active_npub: Option<String>,
+    /// The remote signer's REAL identity key, learned from the
+    /// `get_public_key` RPC after the connect handshake completes. The
+    /// pubkey in the connect URI may be a per-connection communication key
+    /// (Amber's `bunker://` flow mints one per app) and must never be used
+    /// as an identity. `None` until the handshake resolves it.
+    identity: Option<PublicKey>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
@@ -99,6 +108,7 @@ impl Nip46ClientSigner {
                 remote_pending: HashMap::new(),
                 keys: None,
                 active_npub: None,
+                identity: None,
             })),
             app,
         }
@@ -132,10 +142,22 @@ impl Nip46ClientSigner {
         }
     }
 
-    /// Parse a nostrconnect:// URI.
+    /// Parse a `nostrconnect://` or `bunker://` URI.
+    ///
+    /// Both carry the same wire shape (authority = the signer's public key,
+    /// `relay=` params, optional `secret=`). `nostrconnect://` is the
+    /// client-initiated flow (we generated the URI); `bunker://` is the
+    /// signer-initiated flow (Amber and self-hosted bunkers show one of
+    /// these). NOTE: with `bunker://` the authority key may be a
+    /// per-connection communication key (Amber mints one per app), NOT the
+    /// user's identity — identity is learned later via `get_public_key`.
     fn parse_connect_uri(raw: &str) -> Result<ConnectUri, AppError> {
-        let rest = raw.trim().strip_prefix("nostrconnect://").ok_or_else(|| {
+        let rest = raw
-            AppError::config("Paste the nostrconnect:// link from your Nostr app.")
+            .trim()
+            .strip_prefix("nostrconnect://")
+            .or_else(|| raw.trim().strip_prefix("bunker://"))
+            .ok_or_else(|| {
+                AppError::config("Paste the bunker:// or nostrconnect:// link from your Nostr app.")
             })?;
 
         let (authority, query) = match rest.split_once('?') {
@@ -262,8 +284,13 @@ impl Nip46ClientSigner {
         // Persist the connection AND its secret in the vault. The secret is
         // encrypted under the vault key (when a password is set) and keyed by
         // the connection's opaque VaultRef — never stored inline on the
-        // connection, never logged. Evaluates to the remote identity's npub.
+        // connection, never logged.
-        let remote_npub = {
+        //
+        // No profile is created yet: the URI key may be a per-connection
+        // communication key (Amber's bunker:// flow mints one per app), NOT
+        // the user's identity. The profile row is created by the handshake
+        // once `get_public_key` reveals the real identity.
+        {
             let mut app = self.app.lock().await;
             // Remove any existing connection for the same signer from the
             // same profile (reconnect replaces the old connection).
@@ -287,19 +314,8 @@ impl Nip46ClientSigner {
                 crate::vault::delete_connection_secret(&mut app.vault, &vault_ref);
             }
             app.vault.nip46_connections.push(connection.clone());
-            // The remote identity gets its own profile row so publishing has
-            // a selection: marked Nip46Client with no local secret, so every
-            // signing path for it routes through this connection and key
-            // export refuses it. If the peer key collides with an existing
-            // local (embedded) profile the connect fails closed.
-            let remote_npub = PublicKey::from_hex(&connection.signer_pubkey)
-                .map_err(|e| AppError::internal(format!("Invalid signer public key: {e}")))?
-                .to_bech32()
-                .map_err(|e| AppError::internal(format!("Could not encode npub: {e}")))?;
-            profiles::store_remote_profile(&mut app.vault, &remote_npub, connection.label.clone())?;
             app.save_vault()?;
-            remote_npub
+        }
-        };
 
         // Update state to connecting
         {
@@ -313,9 +329,10 @@ impl Nip46ClientSigner {
             inner.connection = Some(connection.clone());
             inner.conversation_key = Some(conversation);
             inner.keys = Some(keys.clone());
-            // The signing identity is the remote signer's key, and the vault
+            // Identity is unknown until the handshake's `get_public_key`
-            // now holds a matching Nip46Client profile row (active).
+            // resolves it; nothing may sign before then.
-            inner.active_npub = Some(remote_npub);
+            inner.identity = None;
+            inner.active_npub = None;
             inner.pending.clear();
         }
 
@@ -504,6 +521,21 @@ impl Nip46ClientSigner {
         &self,
         method: &str,
         params: Vec<String>,
+    ) -> Result<String, SigningError> {
+        self.send_rpc(method, params, REQUEST_TIMEOUT, true).await
+    }
+
+    /// Send an encrypted NIP-46 RPC and await its response.
+    ///
+    /// `require_connected` gates on the session phase: ordinary RPCs need a
+    /// fully established session, while the handshake itself runs while the
+    /// phase is still `Connecting`.
+    async fn send_rpc(
+        &self,
+        method: &str,
+        params: Vec<String>,
+        timeout: Duration,
+        require_connected: bool,
     ) -> Result<String, SigningError> {
         let id = uuid::Uuid::new_v4().to_string();
         let (sender, receiver) = oneshot::channel();
@@ -529,7 +561,7 @@ impl Nip46ClientSigner {
                     SigningError::ConnectionExpired
                 });
             }
-            if !matches!(inner.phase, Nip46Phase::Connected) {
+            if require_connected && !matches!(inner.phase, Nip46Phase::Connected) {
                 return Err(SigningError::NotConnected);
             }
             if inner.remote_pending.len() >= MAX_PENDING_APPROVALS {
@@ -555,7 +587,7 @@ impl Nip46ClientSigner {
             return Err(SigningError::Network { detail });
         }
 
-        match tokio::time::timeout(REQUEST_TIMEOUT, receiver).await {
+        match tokio::time::timeout(timeout, receiver).await {
             Ok(Ok(result)) => result.map_err(|detail| SigningError::Internal { detail }),
             Ok(Err(_)) => {
                 // The waiter was dropped (disconnect/fail) while awaiting.
@@ -625,25 +657,46 @@ impl Nip46ClientSigner {
             .await
             .map_err(|e| format!("Could not subscribe: {e}"))?;
 
-        // Send connect request
+        // The connect handshake runs as its own task: it publishes `connect`
-        self.send_connect(&client, &keys, &conversation, &uri)
+        // and then must AWAIT the signer's ack — which can wait on a human
-            .await?;
+        // approving us in Amber — followed by `get_public_key` to learn the
-
+        // REAL signing identity. Responses only arrive through the demux
-        // Mark as connected
+        // loop below, so the handshake must not block it. The session stays
-        self.inner.lock().await.phase = Nip46Phase::Connected;
+        // `Connecting` (and every signing path fails closed) until the
+        // handshake resolves the identity.
+        {
+            let handshake = self.clone();
+            let peer = uri.peer;
+            let expected_secret = uri.secret.clone();
+            tokio::spawn(async move {
+                if let Err(e) = handshake.clone().run_handshake(peer, expected_secret).await {
+                    handshake.fail(e);
+                }
+            });
+        }
 
         // Handle incoming requests
         loop {
-            let incoming = match notifications.next().await {
+            let incoming =
-                Some(nostr_sdk::client::ClientNotification::Event {
+                match tokio::time::timeout(Duration::from_secs(2), notifications.next()).await {
+                    Ok(Some(nostr_sdk::client::ClientNotification::Event {
                         subscription_id,
                         event,
                         ..
-                }) if subscription_id == *subscription.id() => event,
+                    })) if subscription_id == *subscription.id() => event,
-                Some(nostr_sdk::client::ClientNotification::Shutdown) | None => {
+                    Ok(Some(nostr_sdk::client::ClientNotification::Shutdown)) | Ok(None) => {
                         return Err("Connection closed".to_string());
                     }
-                Some(_) => continue,
+                    Ok(Some(_)) => continue,
+                    Err(_elapsed) => {
+                        // Idle tick: if the handshake task failed, the session is
+                        // dead — exit so teardown runs instead of listening on a
+                        // connection that can never sign.
+                        if matches!(self.inner.lock().await.phase, Nip46Phase::Error(_)) {
+                            return Err("Connect handshake failed".to_string());
+                        }
+                        continue;
+                    }
                 };
 
             let event = *incoming;
@@ -932,31 +985,44 @@ impl Nip46ClientSigner {
         }
     }
 
-    async fn send_connect(
+    /// The connect handshake, run as its own task alongside the demux loop.
-        &self,
+    ///
-        client: &Client,
+    /// 1. Send `connect` (our client pubkey + the URI secret, resolved
-        keys: &Keys,
+    ///    on-demand from the vault — never from memory).
-        conversation: &ConversationKey,
+    /// 2. Await the signer's ack. This is where a human approving us in
-        uri: &ConnectUri,
+    ///    Amber happens, so the wait is long (HANDSHAKE_TIMEOUT).
+    /// 3. Call `get_public_key` to learn the REAL signing identity. The
+    ///    pubkey in the connect URI may be a per-connection communication
+    ///    key (Amber mints one per app); trusting it would publish under a
+    ///    throwaway key.
+    /// 4. Persist the identity: create/refresh the secretless
+    ///    `Nip46Client` profile row, re-key the vault secret store under
+    ///    it, and only then flip the phase to `Connected`.
+    ///
+    /// Until step 4 completes the session is `Connecting`, so every signing
+    /// path fails closed — nothing can publish under an unverified key.
+    async fn run_handshake(
+        self,
+        peer: PublicKey,
+        expected_secret: Option<String>,
     ) -> Result<(), String> {
-        // Resolve the nostrconnect secret ON-DEMAND from the vault — the single
+        // Resolve the connect secret ON-DEMAND from the vault — the single
-        // source of truth — rather than reading an in-memory copy. The
+        // source of truth. Fail-closed: if the vault cannot produce the
-        // connection carries no secret; it is keyed by its VaultRef and fetched
+        // secret the connect is refused rather than sent incomplete.
-        // fresh here. Fail-closed: if the vault cannot produce the secret
+        // (Also snapshot the connection label for the profile row below.)
-        // (e.g. it is encrypted and currently locked) the connect is refused
+        let (secret, label, connect_ref) = {
-        // instead of being sent without it.
-        let secret = {
             let connection = {
                 let inner = self.inner.lock().await;
                 inner.connection.clone()
             }
             .ok_or("No active NIP-46 connection to resolve the secret for")?;
+            let label = connection.label.clone();
             let vault_ref = crate::signer::VaultRef::from_connection(&connection);
             let app = self.app.lock().await;
             // Copy the key out before the immutable borrow of the vault so the
             // two are never borrowed at once.
             let vault_key = app.vault_key().copied();
-            match crate::vault::resolve_connection_secret(
+            let secret = match crate::vault::resolve_connection_secret(
                 &app.vault,
                 vault_key.as_ref(),
                 &vault_ref,
@@ -968,21 +1034,89 @@ impl Nip46ClientSigner {
                         "Could not resolve the connection secret from the vault: {e}"
                     ))
                 }
-            }
+            };
+            (secret, label, vault_ref)
         };
 
-        let mut params = vec![keys.public_key().to_hex()];
+        let mut params = vec![{
+            let inner = self.inner.lock().await;
+            inner
+                .keys
+                .as_ref()
+                .ok_or("No session keys")?
+                .public_key()
+                .to_hex()
+        }];
         if let Some(secret) = &secret {
             params.push(secret.clone());
         }
-        let payload = json!({
+
-            "id": uuid::Uuid::new_v4().to_string(),
+        // Await the ack (may wait on a human approving in Amber).
-            "method": "connect",
+        let ack = self
-            "params": params,
+            .send_rpc("connect", params, HANDSHAKE_TIMEOUT, false)
-        })
-        .to_string();
-        self.publish_payload(client, keys, conversation, &uri.peer, &payload)
             .await
+            .map_err(|e| format!("The signer refused the connection: {e}"))?;
+
+        // Anti-spoofing: per NIP-46, a signer answering a nostrconnect://
+        // (secret-carrying) handshake must echo the secret back. A mismatch
+        // means something other than the intended signer answered.
+        if let Some(expected) = &expected_secret {
+            let trimmed = ack.trim();
+            if trimmed != expected.as_str() {
+                return Err(
+                    "The signer did not echo the connection secret; refusing the connection."
+                        .to_string(),
+                );
+            }
+        }
+
+        // Learn the REAL signing identity from the signer itself.
+        let identity = self
+            .send_rpc("get_public_key", vec![], REQUEST_TIMEOUT, false)
+            .await
+            .map_err(|e| format!("The signer would not reveal its public key: {e}"))?;
+        let identity = PublicKey::from_hex(identity.trim())
+            .map_err(|e| format!("The signer returned an unreadable public key: {e}"))?;
+        let identity_npub = identity
+            .to_bech32()
+            .map_err(|e| format!("Could not encode identity npub: {e}"))?;
+
+        // Persist: profile row for the identity, connection + secret store
+        // re-keyed under it. Refuses (fails the handshake) if the identity
+        // collides with a local profile.
+        {
+            let mut app = self.app.lock().await;
+            profiles::store_remote_profile(&mut app.vault, &identity_npub, label)
+                .map_err(|e| e.message().to_string())?;
+            // Re-key the stored secret under the identity npub so the
+            // connection row, VaultRef, and secret store all agree.
+            if let Some(s) = &secret {
+                let new_ref =
+                    crate::signer::VaultRef::new(Some(identity_npub.clone()), peer.to_hex());
+                let vault_key = app.vault_key().copied();
+                crate::vault::store_connection_secret(
+                    &mut app.vault,
+                    vault_key.as_ref(),
+                    &new_ref,
+                    s,
+                )
+                .map_err(|e| e.message().to_string())?;
+                crate::vault::delete_connection_secret(&mut app.vault, &connect_ref);
+            }
+            if let Some(conn) = app.vault.nip46_connections.iter_mut().find(|c| {
+                c.signer_pubkey == peer.to_hex() && c.profile_npub != Some(identity_npub.clone())
+            }) {
+                conn.profile_npub = Some(identity_npub.clone());
+            }
+            app.save_vault().map_err(|e| e.message().to_string())?;
+        }
+
+        // Identity verified: adopt it and open the session for signing.
+        let mut inner = self.inner.lock().await;
+        inner.identity = Some(identity);
+        inner.active_npub = Some(identity_npub);
+        inner.phase = Nip46Phase::Connected;
+        Ok(())
     }
 
     async fn publish_payload(
@@ -1021,13 +1155,10 @@ impl Clone for Nip46ClientSigner {
 impl Signer for Nip46ClientSigner {
     async fn get_public_key(&self) -> Result<PublicKey, SigningError> {
         let inner = self.inner.lock().await;
-        let connection = inner
+        // The identity learned from the signer during the handshake — NOT
-            .connection
+        // the URI key, which for bunker:// flows is a per-connection comms
-            .as_ref()
+        // key. Until the handshake resolves it the session is not usable.
-            .ok_or(SigningError::NotConnected)?;
+        inner.identity.clone().ok_or(SigningError::NotConnected)
-        PublicKey::from_hex(&connection.signer_pubkey).map_err(|e| SigningError::Internal {
-            detail: format!("Invalid signer public key: {e}"),
-        })
     }
 
     async fn sign_event(&self, event: UnsignedEvent) -> Result<Event, SigningError> {
@@ -1120,31 +1251,40 @@ impl Signer for Nip46ClientSigner {
             .and_then(|c| c.permissions.clone())
     }
 
+    // NOTE on the `None` arms below: when the connect URI declared no
+    // `perms=`, there is no local grant list to enforce — enforcement lives
+    // on the signer itself (Amber shows an approval screen per request).
+    // Sending the request and letting the signer decide is the NIP-46 flow;
+    // refusing locally would make bunker:// connections (which carry no
+    // perms) unusable. When perms WERE declared, the local list is enforced
+    // as an additional guard.
     fn can_sign_event(&self, kind: u16) -> bool {
         match self.permissions() {
             Some(ref perms) => perms.is_sign_event_kind_allowed(kind),
-            None => false,
+            None => true,
         }
     }
 
     fn can_encrypt(&self) -> bool {
         match self.permissions() {
             Some(ref perms) => perms.is_encrypt_allowed(),
-            None => false,
+            None => true,
         }
     }
 
     fn can_decrypt(&self) -> bool {
         match self.permissions() {
             Some(ref perms) => perms.is_decrypt_allowed(),
-            None => false,
+            None => true,
         }
     }
 
     fn can_get_public_key(&self) -> bool {
+        // `get_public_key` is part of the connect handshake for every
+        // signer; with no declared perms the signer still answers it.
         match self.permissions() {
             Some(ref perms) => perms.is_get_public_key_allowed(),
-            None => false,
+            None => true,
         }
     }