fix: cross-browser sync import corrupting local encryption + v2.0.9

Root cause: when importing an encrypted sync code from another device,
_decryptFromSync was replacing the local encryption config (salt) with
the source device's salt. This caused:
1. Local key cache derived from wrong salt
2. Local data (encrypted with local salt) became unreadable
3. _applyData tried to write with the wrong key

Fixed with a complete refactor of cross-device decryption:
- authenticateForSync() derives a TEMPORARY key using the source salt
- Temporary key stored separately as 'tempSyncKey' in IndexedDB
- Local encryption config and cached key are NEVER modified
- After decryption, _applyData writes via _writeSecure using the
  LOCAL key (which uses the local salt)
- _handleDecryptedMeta extracted for code reuse

Also:
- Options.js auth handler detects pending sync import and routes to
  authenticateForSync instead of regular authenticate
- After auth success, automatically retries the import
- README updated: imported passwords are protected (dots in UI,
  vault password to reveal, AES-256 encrypted at rest)
- Bumped to v2.0.9

https://claude.ai/code/session_01SWSwDfMVij53bCTNSCLMwn

README.md

@@ -89,7 +89,7 @@ Import your existing data from password managers and browser autofill to pre-pop
 | Plain CSV (2 columns) | Real → substitute pairs |
 | Plain text (1 per line) | Auto-categorized values needing substitutes |
 
-Passwords are imported as exact-match mappings (e.g. `MyS3cret!` → `[REDACTED-PASSWORD-1]`) so they get caught in any context — not just `password=value` patterns.
+Passwords are imported as exact-match mappings (e.g. `MyS3cret!` → `[REDACTED-PASSWORD-1]`) so they get caught in any context — not just `password=value` patterns. Imported passwords are protected: they're shown as dots in the UI and require your vault encryption password to reveal. When at-rest encryption is enabled, imported passwords are AES-256 encrypted in storage like all other sensitive data.
 
 Go to **Options** → **Transfer Data** → **Import CSV / Password Export**.
 

manifest.firefox.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "Silent Send",
-  "version": "2.0.7",
+  "version": "2.0.9",
   "description": "Intercepts personal info and substitutes it with user-defined replacements before sending to AI services.",
   "browser_specific_settings": {
     "gecko": {

manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "Silent Send",
-  "version": "2.0.7",
+  "version": "2.0.9",
   "description": "Intercepts personal info and substitutes it with user-defined replacements before sending to AI services.",
   "permissions": [
     "storage",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "silent-send",
-  "version": "2.0.7",
+  "version": "2.0.9",
   "private": true,
   "license": "BSL-1.1",
   "description": "Browser extension that substitutes personal data before sending to AI services",

src/lib/sync.js

@@ -460,47 +460,100 @@ const SilentSendSync = {
   async _decryptFromSync(data) {
     if (!data?._ssEncrypted) return { data, decrypted: false };
 
-    // Always use the sync envelope's salt/verificationBlob for decryption,
+    // Decrypt using the SOURCE device's salt (embedded in the sync envelope).
-    // not the local config. Different devices have different salts, so the
+    // We derive a TEMPORARY key — never modify the local config or cached key,
-    // local key won't decrypt data encrypted with another device's salt.
+    // because the local data is encrypted with the LOCAL salt.
-    let config = await this._getSyncEncryption();
+    const sourceSalt = data._encConfig?.salt;
-
+    const sourceVerification = data._encConfig?.verificationBlob;
-    if (data._encConfig) {
-      // Use the source's salt for this decryption, but don't overwrite
-      // the local config permanently yet — only if decryption succeeds
-      config = {
-        ...(config || {}),
-        enabled: true,
-        salt: data._encConfig.salt,
-        verificationBlob: data._encConfig.verificationBlob,
-      };
-    }
-
-    if (!config?.enabled) {
-      return { data: null, decrypted: false, needsAuth: true };
-    }
-
-    // Try to get a key using the sync envelope's salt
-    // First check if we have a cached key that matches
-    let keyInfo = await SilentSendCrypto.getCachedKey();
-
-    // If the cached key's salt doesn't match the sync data's salt,
-    // we need to re-derive from the password
-    if (keyInfo && data._encConfig && keyInfo.salt !== data._encConfig.salt) {
-      keyInfo = null; // force re-auth with the correct salt
-    }
-
-    if (!keyInfo) {
-      // Need the user to enter the password — save the sync salt temporarily
-      // so authenticate() uses it to derive the correct key
-      if (data._encConfig) {
-        await this._saveSyncEncryption(config);
-      }
-      return { data: null, decrypted: false, needsAuth: true };
-    }
 
+    if (!sourceSalt) {
+      // No embedded config — try local key (same-device sync like browser.storage.sync)
+      const keyInfo = await SilentSendCrypto.getCachedKey();
+      if (!keyInfo) return { data: null, decrypted: false, needsAuth: true };
+      try {
         const decrypted = await SilentSendCrypto.decryptWithKey(data.payload, keyInfo.key);
+        return this._handleDecryptedMeta(decrypted);
+      } catch {
+        return { data: null, decrypted: false, needsAuth: true };
+      }
+    }
 
+    // Cross-device: need to derive a temporary key from the source salt.
+    // Check if we have a stored password-derived key for this source salt.
+    const tempKeyStore = await this._getTempSyncKey(sourceSalt);
+    if (tempKeyStore) {
+      try {
+        const decrypted = await SilentSendCrypto.decryptWithKey(data.payload, tempKeyStore.key);
+        return this._handleDecryptedMeta(decrypted);
+      } catch { /* wrong key, fall through to prompt */ }
+    }
+
+    // Need the user's password to derive a key with the source salt.
+    // Store the source salt temporarily so the auth prompt can use it.
+    this._pendingSyncSalt = sourceSalt;
+    this._pendingSyncVerification = sourceVerification;
+    return { data: null, decrypted: false, needsAuth: true, syncSalt: sourceSalt };
+  },
+
+  /**
+   * Authenticate specifically for a cross-device sync import.
+   * Derives a temporary key with the source device's salt.
+   * Does NOT modify the local encryption config or cached key.
+   */
+  async authenticateForSync(password) {
+    const salt = this._pendingSyncSalt;
+    const verification = this._pendingSyncVerification;
+    if (!salt) return { success: false, reason: 'No pending sync import.' };
+
+    // Derive key with the source salt
+    const { key } = await SilentSendCrypto.deriveAndReturnKey(password, salt);
+
+    // Verify password against the source's verification blob
+    if (verification) {
+      try {
+        await SilentSendCrypto.decryptWithKey(verification, key);
+      } catch {
+        return { success: false, reason: 'Wrong password.' };
+      }
+    }
+
+    // Store this temporary key for the source salt (NOT in the main cache)
+    await this._storeTempSyncKey(salt, key);
+    this._pendingSyncSalt = null;
+    this._pendingSyncVerification = null;
+
+    return { success: true };
+  },
+
+  async _storeTempSyncKey(salt, key) {
+    try {
+      const db = await SilentSendCrypto._openCacheDB();
+      await new Promise((resolve, reject) => {
+        const tx = db.transaction('keys', 'readwrite');
+        tx.objectStore('keys').put({ key, salt, storedAt: Date.now() }, 'tempSyncKey');
+        tx.oncomplete = resolve;
+        tx.onerror = () => reject(tx.error);
+      });
+    } catch { /* non-fatal */ }
+  },
+
+  async _getTempSyncKey(salt) {
+    try {
+      const db = await SilentSendCrypto._openCacheDB();
+      return new Promise((resolve) => {
+        const tx = db.transaction('keys', 'readonly');
+        const req = tx.objectStore('keys').get('tempSyncKey');
+        req.onsuccess = () => {
+          const entry = req.result;
+          if (entry?.key && entry.salt === salt) resolve(entry);
+          else resolve(null);
+        };
+        req.onerror = () => resolve(null);
+      });
+    } catch { return null; }
+  },
+
+  async _handleDecryptedMeta(decrypted) {
     // Restore full encryption config from inner metadata
     if (decrypted._encMeta) {
       const fullConfig = await this._getSyncEncryption();

src/options/options.html

@@ -591,7 +591,7 @@
     </section>
 
     <footer>
-      <p>Silent Send v2.0.7</p>
+      <p>Silent Send v2.0.9</p>
     </footer>
   </div>
 

src/options/options.js

@@ -1016,24 +1016,29 @@ async function initSyncEncryptionUI() {
       return;
     }
 
-    // Check if this is re-verification (key exists) or first-device (needs full auth)
-    const cached = await SilentSendCrypto.getCachedKey();
     let result;
+
+    // If there's a pending sync import, use authenticateForSync
+    // (derives a temporary key with the source salt, doesn't touch local config)
+    if (window.__ssPendingSyncImport) {
+      result = await SilentSendSync.authenticateForSync(password);
+    } else {
+      // Normal auth: check if re-verification or first-device
+      const cached = await SilentSendCrypto.getCachedKey();
       if (cached) {
-      // Re-verification — password alone is enough
         result = await SilentSendSync.reverifyWithPassword(password);
       } else {
-      // First device — full auth with password + TOTP if configured
         result = await SilentSendSync.authenticate(password, totpCode || undefined);
       }
+    }
 
     if (result.success) {
       $('#syncAuthPrompt').style.display = 'none';
       $('#syncAuthPassword').value = '';
       $('#syncAuthTOTPForPassword').value = '';
-      setSyncEncStatus(cached ? 'Re-verified with password.' : 'Authenticated. Sync data unlocked.', 'ok');
+      setSyncEncStatus('Authenticated.', 'ok');
 
-      // If there's a pending sync import, retry it now that auth succeeded
+      // If there's a pending sync import, retry it now
       if (window.__ssPendingSyncImport) {
         const retry = window.__ssPendingSyncImport;
         window.__ssPendingSyncImport = null;