From 6e3abdfd140de5f6666f74026607a521f119e087 Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Wed, 23 Aug 2017 11:30:09 -0700
Subject: [PATCH] macaroons: ensure all bytes read from db are copied before
 returning
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This commit is a precautionary commit put in place in order to ensure
that the logic of macaroon retrieval doesn’t run into a bug triggered
by returning a reference into bolt’s active memory map. This can arise
if one returns a pointer directly read from the database. We seek to
avoid this by instead ensuring all byte slices are fully copied before
returning.
---
 macaroons/store.go | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/macaroons/store.go b/macaroons/store.go
index d381854b1..232e0d6ce 100644
--- a/macaroons/store.go
+++ b/macaroons/store.go
@@ -52,11 +52,14 @@ func NewRootKeyStorage(db *bolt.DB) (*RootKeyStorage, error) {
 func (r *RootKeyStorage) Get(id string) ([]byte, error) {
 	var rootKey []byte
 	err := r.View(func(tx *bolt.Tx) error {
-		rootKey = tx.Bucket(rootKeyBucketName).Get([]byte(id))
-		if len(rootKey) == 0 {
+		dbKey := tx.Bucket(rootKeyBucketName).Get([]byte(id))
+		if len(dbKey) == 0 {
 			return fmt.Errorf("root key with id %s doesn't exist",
 				id)
 		}
+
+		rootKey = make([]byte, len(dbKey))
+		copy(rootKey[:], dbKey)
 		return nil
 	})
 	if err != nil {
@@ -127,21 +130,23 @@ func (s *Storage) Put(location string, item string) error {
 
 // Get implements the Get method for the bakery.Storage interface.
 func (s *Storage) Get(location string) (string, error) {
-	var item string
+	var item []byte
 	err := s.View(func(tx *bolt.Tx) error {
 		itemBytes := tx.Bucket(macaroonBucketName).Get([]byte(location))
 		if len(itemBytes) == 0 {
 			return fmt.Errorf("couldn't get item for location %s",
 				location)
 		}
-		item = string(itemBytes)
+
+		item = make([]byte, len(itemBytes))
+		copy(item, itemBytes)
 		return nil
 	})
 	if err != nil {
 		return "", err
 	}
 
-	return item, nil
+	return string(item), nil
 }
 
 // Del implements the Del method for the bakery.Storage interface.