wallet2: fix `store_to()` and `change_password()`

Resolves #8932 and:
2. Not storing cache when new path is different from old in `store_to()` and
3. Detecting same path when new path contains entire string of old path in `store_to()` and
4. Changing your password / decrypting your keys (in this method or others) and providing a bad original password and getting no error and
5. Changing your password and storing to a new file

2 files changed, 90 insertions, 34 deletions

diff --git a/src/wallet/wallet2.cpp b/src/wallet/wallet2.cpp
index 42e2f1d41..875360c5c 100644
--- a/src/wallet/wallet2.cpp
+++ b/src/wallet/wallet2.cpp
@@ -1003,6 +1003,24 @@ uint64_t num_priv_multisig_keys_post_setup(uint64_t threshold, uint64_t total)
   return n_multisig_keys;
 }
 
+/**
+ * @brief Derives the chacha key to encrypt wallet cache files given the chacha key to encrypt the wallet keys files
+ *
+ * @param keys_data_key the chacha key that encrypts wallet keys files
+ * @return crypto::chacha_key the chacha key that encrypts the wallet cache files
+ */
+crypto::chacha_key derive_cache_key(const crypto::chacha_key& keys_data_key)
+{
+  static_assert(HASH_SIZE == sizeof(crypto::chacha_key), "Mismatched sizes of hash and chacha key");
+
+  crypto::chacha_key cache_key;
+  epee::mlocked<tools::scrubbed_arr<char, HASH_SIZE+1>> cache_key_data;
+  memcpy(cache_key_data.data(), &keys_data_key, HASH_SIZE);
+  cache_key_data[HASH_SIZE] = config::HASH_KEY_WALLET_CACHE;
+  cn_fast_hash(cache_key_data.data(), HASH_SIZE+1, (crypto::hash&) cache_key);
+
+  return cache_key;
+}
   //-----------------------------------------------------------------
 } //namespace
 
@@ -4406,6 +4424,10 @@ boost::optional<wallet2::keys_file_data> wallet2::get_keys_file_data(const epee:
   crypto::chacha_key key;
   crypto::generate_chacha_key(password.data(), password.size(), key, m_kdf_rounds);
 
+  // We use m_cache_key as a deterministic test to see if given key corresponds to original password
+  const crypto::chacha_key cache_key = derive_cache_key(key);
+  THROW_WALLET_EXCEPTION_IF(cache_key != m_cache_key, error::invalid_password);
+
   if (m_ask_password == AskPasswordToDecrypt && !m_unattended && !m_watch_only)
   {
     account.encrypt_viewkey(key);
@@ -4630,11 +4652,8 @@ void wallet2::setup_keys(const epee::wipeable_string &password)
     m_account.decrypt_viewkey(key);
   }
 
-  static_assert(HASH_SIZE == sizeof(crypto::chacha_key), "Mismatched sizes of hash and chacha key");
-  epee::mlocked<tools::scrubbed_arr<char, HASH_SIZE+1>> cache_key_data;
-  memcpy(cache_key_data.data(), &key, HASH_SIZE);
-  cache_key_data[HASH_SIZE] = config::HASH_KEY_WALLET_CACHE;
-  cn_fast_hash(cache_key_data.data(), HASH_SIZE+1, (crypto::hash&)m_cache_key);
+  m_cache_key = derive_cache_key(key);
+
   get_ringdb_key();
 }
 //----------------------------------------------------------------------------------------------------
@@ -4643,9 +4662,8 @@ void wallet2::change_password(const std::string &filename, const epee::wipeable_
   if (m_ask_password == AskPasswordToDecrypt && !m_unattended && !m_watch_only)
     decrypt_keys(original_password);
   setup_keys(new_password);
-  rewrite(filename, new_password);
   if (!filename.empty())
-    store();
+    store_to(filename, new_password, true); // force rewrite keys file to possible new location
 }
 //----------------------------------------------------------------------------------------------------
 /*!
@@ -5151,6 +5169,10 @@ void wallet2::encrypt_keys(const crypto::chacha_key &key)
 
 void wallet2::decrypt_keys(const crypto::chacha_key &key)
 {
+  // We use m_cache_key as a deterministic test to see if given key corresponds to original password
+  const crypto::chacha_key cache_key = derive_cache_key(key);
+  THROW_WALLET_EXCEPTION_IF(cache_key != m_cache_key, error::invalid_password);
+
   m_account.encrypt_viewkey(key);
   m_account.decrypt_keys(key);
 }
@@ -6311,22 +6333,32 @@ void wallet2::store()
     store_to("", epee::wipeable_string());
 }
 //----------------------------------------------------------------------------------------------------
-void wallet2::store_to(const std::string &path, const epee::wipeable_string &password)
+void wallet2::store_to(const std::string &path, const epee::wipeable_string &password, bool force_rewrite_keys)
 {
   trim_hashchain();
 
+  const bool had_old_wallet_files = !m_wallet_file.empty();
+  THROW_WALLET_EXCEPTION_IF(!had_old_wallet_files && path.empty(), error::wallet_internal_error,
+    "Cannot resave wallet to current file since wallet was not loaded from file to begin with");
+
   // if file is the same, we do:
-  // 1. save wallet to the *.new file
-  // 2. remove old wallet file
-  // 3. rename *.new to wallet_name
+  // 1. overwrite the keys file iff force_rewrite_keys is specified
+  // 2. save cache to the *.new file
+  // 3. rename *.new to wallet_name, replacing old cache file
+  // else we do:
+  // 1. prepare new file names with "path" variable
+  // 2. store new keys files
+  // 3. remove old keys file
+  // 4. store new cache file
+  // 5. remove old cache file
 
   // handle if we want just store wallet state to current files (ex store() replacement);
-  bool same_file = true;
-  if (!path.empty())
+  bool same_file = had_old_wallet_files && path.empty();
+  if (had_old_wallet_files && !path.empty())
   {
-    std::string canonical_path = boost::filesystem::canonical(m_wallet_file).string();
-    size_t pos = canonical_path.find(path);
-    same_file = pos != std::string::npos;
+    const std::string canonical_old_path = boost::filesystem::canonical(m_wallet_file).string();
+    const std::string canonical_new_path = boost::filesystem::weakly_canonical(path).string();
+    same_file = canonical_old_path == canonical_new_path;
   }
 
 
@@ -6347,7 +6379,7 @@ void wallet2::store_to(const std::string &path, const epee::wipeable_string &pas
   }
 
   // get wallet cache data
-  boost::optional<wallet2::cache_file_data> cache_file_data = get_cache_file_data(password);
+  boost::optional<wallet2::cache_file_data> cache_file_data = get_cache_file_data();
   THROW_WALLET_EXCEPTION_IF(cache_file_data == boost::none, error::wallet_internal_error, "failed to generate wallet cache data");
 
   const std::string new_file = same_file ? m_wallet_file + ".new" : path;
@@ -6356,12 +6388,20 @@ void wallet2::store_to(const std::string &path, const epee::wipeable_string &pas
   const std::string old_address_file = m_wallet_file + ".address.txt";
   const std::string old_mms_file = m_mms_file;
 
-  // save keys to the new file
-  // if we here, main wallet file is saved and we only need to save keys and address files
-  if (!same_file) {
+  if (!same_file)
+  {
     prepare_file_names(path);
+  }
+
+  if (!same_file || force_rewrite_keys)
+  {
     bool r = store_keys(m_keys_file, password, false);
     THROW_WALLET_EXCEPTION_IF(!r, error::file_save_error, m_keys_file);
+  }
+
+  if (!same_file && had_old_wallet_files)
+  {
+    bool r = false;
     if (boost::filesystem::exists(old_address_file))
     {
       // save address to the new file
@@ -6374,11 +6414,6 @@ void wallet2::store_to(const std::string &path, const epee::wipeable_string &pas
         LOG_ERROR("error removing file: " << old_address_file);
       }
     }
-    // remove old wallet file
-    r = boost::filesystem::remove(old_file);
-    if (!r) {
-      LOG_ERROR("error removing file: " << old_file);
-    }
     // remove old keys file
     r = boost::filesystem::remove(old_keys_file);
     if (!r) {
@@ -6392,8 +6427,9 @@ void wallet2::store_to(const std::string &path, const epee::wipeable_string &pas
         LOG_ERROR("error removing file: " << old_mms_file);
       }
     }
-  } else {
-    // save to new file
+  }
+
+  // Save cache to new file. If storing to the same file, the temp path has the ".new" extension
 #ifdef WIN32
     // On Windows avoid using std::ofstream which does not work with UTF-8 filenames
     // The price to pay is temporary higher memory consumption for string stream + binary archive
@@ -6413,10 +6449,20 @@ void wallet2::store_to(const std::string &path, const epee::wipeable_string &pas
     THROW_WALLET_EXCEPTION_IF(!success || !ostr.good(), error::file_save_error, new_file);
 #endif
 
+  if (same_file)
+  {
     // here we have "*.new" file, we need to rename it to be without ".new"
     std::error_code e = tools::replace_file(new_file, m_wallet_file);
     THROW_WALLET_EXCEPTION_IF(e, error::file_save_error, m_wallet_file, e);
   }
+  else if (!same_file && had_old_wallet_files)
+  {
+    // remove old wallet file
+    bool r = boost::filesystem::remove(old_file);
+    if (!r) {
+      LOG_ERROR("error removing file: " << old_file);
+    }
+  }
   
   if (m_message_store.get_active())
   {
@@ -6426,7 +6472,7 @@ void wallet2::store_to(const std::string &path, const epee::wipeable_string &pas
   }
 }
 //----------------------------------------------------------------------------------------------------
-boost::optional<wallet2::cache_file_data> wallet2::get_cache_file_data(const epee::wipeable_string &passwords)
+boost::optional<wallet2::cache_file_data> wallet2::get_cache_file_data()
 {
   trim_hashchain();
   try
diff --git a/src/wallet/wallet2.h b/src/wallet/wallet2.h
index baeffe096..3790f7121 100644
--- a/src/wallet/wallet2.h
+++ b/src/wallet/wallet2.h
@@ -940,22 +940,32 @@ private:
     /*!
      * \brief store_to  Stores wallet to another file(s), deleting old ones
      * \param path      Path to the wallet file (keys and address filenames will be generated based on this filename)
-     * \param password  Password to protect new wallet (TODO: probably better save the password in the wallet object?)
+     * \param password  Password that currently locks the wallet
+     * \param force_rewrite_keys if true, always rewrite keys file
+     *
+     * Leave both "path" and "password" blank to restore the cache file to the current position in the disk
+     * (which is the same as calling `store()`). If you want to store the wallet with a new password,
+     * use the method `change_password()`.
+     *
+     * Normally the keys file is not overwritten when storing, except when force_rewrite_keys is true
+     * or when `path` is a new wallet file.
+     *
+     * \throw error::invalid_password If storing keys file and old password is incorrect
      */
-    void store_to(const std::string &path, const epee::wipeable_string &password);
+    void store_to(const std::string &path, const epee::wipeable_string &password, bool force_rewrite_keys = false);
     /*!
      * \brief get_keys_file_data  Get wallet keys data which can be stored to a wallet file.
-     * \param password            Password of the encrypted wallet buffer (TODO: probably better save the password in the wallet object?)
+     * \param password            Password that currently locks the wallet
      * \param watch_only          true to include only view key, false to include both spend and view keys
      * \return                    Encrypted wallet keys data which can be stored to a wallet file
+     * \throw                     error::invalid_password if password does not match current wallet
      */
     boost::optional<wallet2::keys_file_data> get_keys_file_data(const epee::wipeable_string& password, bool watch_only);
     /*!
      * \brief get_cache_file_data   Get wallet cache data which can be stored to a wallet file.
-     * \param password              Password to protect the wallet cache data (TODO: probably better save the password in the wallet object?)
-     * \return                      Encrypted wallet cache data which can be stored to a wallet file
+     * \return                      Encrypted wallet cache data which can be stored to a wallet file (using current password)
      */
-    boost::optional<wallet2::cache_file_data> get_cache_file_data(const epee::wipeable_string& password);
+    boost::optional<wallet2::cache_file_data> get_cache_file_data();
 
     std::string path() const;