05/22 Enhance codes and fix bugs 2

app/static/js/recover.js

@@ -103,9 +103,10 @@ const Recover = (() => {
 
   /**
    * Derive an AES-256-GCM key from the recovery code using PBKDF2.
-   * Salt is fixed to 'passkeeper-recovery' — the recovery code itself is the secret.
+   * `salt` should be the user's email (per-user uniqueness).
+   * Falls back to the legacy fixed salt for backward compatibility.
    */
-  async function deriveRecoveryKey(recoveryCode) {
+  async function deriveRecoveryKey(recoveryCode, salt = "passkeeper-recovery") {
     const baseKey = await subtle.importKey(
       "raw",
       strToBytes(recoveryCode),
@@ -116,7 +117,7 @@ const Recover = (() => {
     return subtle.deriveKey(
       {
         name: "PBKDF2",
-        salt: strToBytes("passkeeper-recovery"),
+        salt: strToBytes(salt),
         iterations: 200_000,
         hash: "SHA-256",
       },
@@ -216,15 +217,26 @@ const Recover = (() => {
       }
       const data = await res.json();
 
-      // Attempt to decrypt enc_key_salt using the recovery code
-      const recoveryKey = await deriveRecoveryKey(rawCode);
+      // Attempt to decrypt enc_key_salt using the recovery code.
+      // Try email-as-salt first (new format), fall back to the legacy fixed salt
+      // so that recovery codes generated before this fix still work.
       let decryptedEncKeySalt;
       try {
-        decryptedEncKeySalt = await decryptEncKeySalt(
-          recoveryKey,
-          data.recovery_enc_salt,
-          data.recovery_iv,
-        );
+        const keyWithEmail = await deriveRecoveryKey(rawCode, email);
+        try {
+          decryptedEncKeySalt = await decryptEncKeySalt(
+            keyWithEmail,
+            data.recovery_enc_salt,
+            data.recovery_iv,
+          );
+        } catch {
+          const keyLegacy = await deriveRecoveryKey(rawCode);
+          decryptedEncKeySalt = await decryptEncKeySalt(
+            keyLegacy,
+            data.recovery_enc_salt,
+            data.recovery_iv,
+          );
+        }
       } catch {
         showError(
           "recover-error-1",