feat(wasm): secure device API (private keys never cross to JS)

- register_device() generates signing + deploy keypairs via core device
  module, stores them in DEVICE_STATE (once_cell Lazy<Mutex>), and
  returns only public keys to JS
- sign_for_git() signs data using the internal signing key
- get_device_info() returns name and public keys; returns null if not
  registered
- clear_device() zeroes and drops device state (logout / re-registration)
- Removed generate_device_keypair() which exposed raw private key bytes

Fixes audit I5: private key material no longer crosses the WASM boundary.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/relicario-wasm/Cargo.toml

@@ -19,6 +19,7 @@ ed25519-dalek = { version = "2", features = ["rand_core"] }
 base64 = "0.22"
 hex = "0.4"
 rand = "0.8"
+once_cell = "1"
 
 [dev-dependencies]
 wasm-bindgen-test = "0.3"

crates/relicario-wasm/src/device.rs

@@ -0,0 +1,71 @@
+//! WASM device key management -- private keys never cross to JS.
+
+use std::sync::Mutex;
+
+use once_cell::sync::Lazy;
+use zeroize::Zeroizing;
+
+use relicario_core::device as core_device;
+
+/// In-memory device key storage (private keys held in WASM linear memory).
+static DEVICE_STATE: Lazy<Mutex<Option<DeviceState>>> = Lazy::new(|| Mutex::new(None));
+
+struct DeviceState {
+    name: String,
+    signing_private: Zeroizing<String>,
+    signing_public: String,
+    /// Deploy key stored for future SSH git operations; not yet used for signing.
+    #[allow(dead_code)]
+    deploy_private: Zeroizing<String>,
+    deploy_public: String,
+}
+
+/// Register a new device, storing the keypairs internally and returning
+/// only the public keys. Private keys never leave WASM memory.
+pub fn register_device(name: &str) -> Result<(String, String), String> {
+    let (signing_priv, signing_pub) =
+        core_device::generate_keypair().map_err(|e| e.to_string())?;
+    let (deploy_priv, deploy_pub) =
+        core_device::generate_keypair().map_err(|e| e.to_string())?;
+
+    let state = DeviceState {
+        name: name.to_string(),
+        signing_private: signing_priv,
+        signing_public: signing_pub.clone(),
+        deploy_private: deploy_priv,
+        deploy_public: deploy_pub.clone(),
+    };
+
+    *DEVICE_STATE.lock().unwrap() = Some(state);
+
+    Ok((signing_pub, deploy_pub))
+}
+
+/// Sign `data` using the registered device's signing key.
+/// Returns a base64-encoded signature.
+pub fn sign_for_git(data: &[u8]) -> Result<String, String> {
+    let guard = DEVICE_STATE.lock().unwrap();
+    let state = guard
+        .as_ref()
+        .ok_or_else(|| "no device registered".to_string())?;
+
+    core_device::sign(&state.signing_private, data).map_err(|e| e.to_string())
+}
+
+/// Return current device info: (name, signing_public_key, deploy_public_key).
+/// Returns None if no device has been registered in this session.
+pub fn get_device_info() -> Option<(String, String, String)> {
+    let guard = DEVICE_STATE.lock().unwrap();
+    guard.as_ref().map(|s| {
+        (
+            s.name.clone(),
+            s.signing_public.clone(),
+            s.deploy_public.clone(),
+        )
+    })
+}
+
+/// Clear device state (call on logout or before re-registration).
+pub fn clear_device() {
+    *DEVICE_STATE.lock().unwrap() = None;
+}

crates/relicario-wasm/src/lib.rs

@@ -5,6 +5,7 @@
 //! looked up per call via a u32 handle. JS cannot read key bytes.
 
 mod session;
+mod device;
 
 use wasm_bindgen::prelude::*;
 
@@ -206,26 +207,53 @@ pub fn rate_passphrase(p: &str) -> Result<JsValue, JsError> {
     }))
 }
 
-use ed25519_dalek::SigningKey;
-use base64::Engine;
-
-/// Generate an ed25519 keypair for device registration.
-/// Returns JSON: { "public_key_hex": "...", "private_key_base64": "..." }
+/// Register a new device, generating ed25519 keypairs for signing and deploy.
+/// Returns JSON: { "signing_public_key": "ssh-ed25519 ...", "deploy_public_key": "ssh-ed25519 ..." }
+/// Private keys are kept internal to WASM and never cross to JS.
 #[wasm_bindgen]
-pub fn generate_device_keypair() -> Result<JsValue, JsError> {
-    let mut rng = rand::thread_rng();
-    let signing_key = SigningKey::generate(&mut rng);
-    let verifying_key = signing_key.verifying_key();
-
-    let public_hex = hex::encode(verifying_key.as_bytes());
-    let private_b64 = base64::engine::general_purpose::STANDARD.encode(signing_key.as_bytes());
+pub fn register_device(name: &str) -> Result<JsValue, JsError> {
+    let (signing_pub, deploy_pub) =
+        device::register_device(name).map_err(|e| JsError::new(&e))?;
 
     js_value_for(&serde_json::json!({
-        "public_key_hex": public_hex,
-        "private_key_base64": private_b64,
+        "signing_public_key": signing_pub,
+        "deploy_public_key": deploy_pub,
     }))
 }
 
+/// Sign `data` using the registered device's signing key.
+/// Returns JSON: { "signature": "<base64>" }
+/// Errors if no device has been registered via register_device().
+#[wasm_bindgen]
+pub fn sign_for_git(data: &[u8]) -> Result<JsValue, JsError> {
+    let signature = device::sign_for_git(data).map_err(|e| JsError::new(&e))?;
+
+    js_value_for(&serde_json::json!({
+        "signature": signature,
+    }))
+}
+
+/// Get the current device's name and public keys.
+/// Returns JSON: { "name": "...", "signing_public_key": "...", "deploy_public_key": "..." }
+/// Returns null if no device is registered in this session.
+#[wasm_bindgen]
+pub fn get_device_info() -> Result<JsValue, JsError> {
+    match device::get_device_info() {
+        Some((name, signing_pub, deploy_pub)) => js_value_for(&serde_json::json!({
+            "name": name,
+            "signing_public_key": signing_pub,
+            "deploy_public_key": deploy_pub,
+        })),
+        None => Ok(JsValue::NULL),
+    }
+}
+
+/// Clear the in-memory device state (call on logout or before re-registration).
+#[wasm_bindgen]
+pub fn clear_device() {
+    device::clear_device();
+}
+
 /// Extract field history from a decrypted item JSON.
 /// Returns JSON array of { field_id, field_name, current_value, entries: [{ value, changed_at }] }
 #[wasm_bindgen]
@@ -307,6 +335,8 @@ pub fn totp_compute(
 
 // ── Backup container bridge ─────────────────────────────────────────────────
 
+use base64::Engine;
+
 use relicario_core::backup::{
     pack_backup as core_pack_backup,
     unpack_backup as core_unpack_backup,