accounts/keystore: double-check keystore file after creation (#17348)

accounts/keystore/key.go

@@ -179,26 +179,34 @@ func storeNewKey(ks keyStore, rand io.Reader, auth string) (*Key, accounts.Accou
 	return key, a, err
 }
 
-func writeKeyFile(file string, content []byte) error {
+func writeTemporaryKeyFile(file string, content []byte) (string, error) {
 	// Create the keystore directory with appropriate permissions
 	// in case it is not present yet.
 	const dirPerm = 0700
 	if err := os.MkdirAll(filepath.Dir(file), dirPerm); err != nil {
-		return err
+		return "", err
 	}
 	// Atomic write: create a temporary hidden file first
 	// then move it into place. TempFile assigns mode 0600.
 	f, err := ioutil.TempFile(filepath.Dir(file), "."+filepath.Base(file)+".tmp")
 	if err != nil {
-		return err
+		return "", err
 	}
 	if _, err := f.Write(content); err != nil {
 		f.Close()
 		os.Remove(f.Name())
-		return err
+		return "", err
 	}
 	f.Close()
-	return os.Rename(f.Name(), file)
+	return f.Name(), nil
+}
+
+func writeKeyFile(file string, content []byte) error {
+	name, err := writeTemporaryKeyFile(file, content)
+	if err != nil {
+		return err
+	}
+	return os.Rename(name, file)
 }
 
 // keyFileName implements the naming convention for keyfiles: