backups: add backup multiple targets

src/hush.js

@@ -152,10 +152,25 @@ function decryptFilePath(filePath, encryption) {
     return { result: decryptedParts.join('/') };
 }
 
+// this function is used in migrations - 20200512172301-settings-backup-encryption.js
+function generateEncryptionKeysSync(password) {
+    assert.strictEqual(typeof password, 'string');
+
+    const aesKeys = crypto.scryptSync(password, Buffer.from('CLOUDRONSCRYPTSALT', 'utf8'), 128);
+    return {
+        dataKey: aesKeys.subarray(0, 32).toString('hex'),
+        dataHmacKey: aesKeys.subarray(32, 64).toString('hex'),
+        filenameKey: aesKeys.subarray(64, 96).toString('hex'),
+        filenameHmacKey: aesKeys.subarray(96).toString('hex')
+    };
+}
+
 exports = module.exports = {
     EncryptStream,
     DecryptStream,
 
     encryptFilePath,
     decryptFilePath,
+
+    generateEncryptionKeysSync,
 };