Merge pull request #8619

e71c8bf wallet: background sync with just the view key (j-berman)

src/cryptonote_basic/account.cpp

@@ -152,6 +152,17 @@ DISABLE_VS_WARNINGS(4244 4345)
     m_keys.m_multisig_keys.clear();
   }
   //-----------------------------------------------------------------
+  void account_base::set_spend_key(const crypto::secret_key& spend_secret_key)
+  {
+    // make sure derived spend public key matches saved public spend key
+    crypto::public_key spend_public_key;
+    crypto::secret_key_to_public_key(spend_secret_key, spend_public_key);
+    CHECK_AND_ASSERT_THROW_MES(m_keys.m_account_address.m_spend_public_key == spend_public_key,
+        "Unexpected derived public spend key");
+
+    m_keys.m_spend_secret_key = spend_secret_key;
+  }
+  //-----------------------------------------------------------------
   crypto::secret_key account_base::generate(const crypto::secret_key& recovery_key, bool recover, bool two_random)
   {
     crypto::secret_key first = generate_keys(m_keys.m_account_address.m_spend_public_key, m_keys.m_spend_secret_key, recovery_key, recover);

src/cryptonote_basic/account.h

@@ -95,6 +95,7 @@ namespace cryptonote
     bool store(const std::string& file_path);
 
     void forget_spend_key();
+    void set_spend_key(const crypto::secret_key& spend_secret_key);
     const std::vector<crypto::secret_key> &get_multisig_keys() const { return m_keys.m_multisig_keys; }
 
     void encrypt_keys(const crypto::chacha_key &key) { m_keys.encrypt(key); }

src/cryptonote_config.h

@@ -241,6 +241,8 @@ namespace config
   const unsigned char HASH_KEY_ENCRYPTED_PAYMENT_ID = 0x8d;
   const unsigned char HASH_KEY_WALLET = 0x8c;
   const unsigned char HASH_KEY_WALLET_CACHE = 0x8d;
+  const unsigned char HASH_KEY_BACKGROUND_CACHE = 0x8e;
+  const unsigned char HASH_KEY_BACKGROUND_KEYS_FILE = 0x8f;
   const unsigned char HASH_KEY_RPC_PAYMENT_NONCE = 0x58;
   const unsigned char HASH_KEY_MEMORY = 'k';
   const unsigned char HASH_KEY_MULTISIG[] = {'M', 'u', 'l', 't' , 'i', 's', 'i', 'g', 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };

src/simplewallet/simplewallet.cpp

@@ -148,6 +148,17 @@ typedef cryptonote::simple_wallet sw;
     } \
   } while(0)
 
+#define CHECK_IF_BACKGROUND_SYNCING(msg) \
+  do \
+  { \
+    if (m_wallet->is_background_wallet() || m_wallet->is_background_syncing()) \
+    { \
+      std::string type = m_wallet->is_background_wallet() ? "background wallet" : "background syncing wallet"; \
+      fail_msg_writer() << boost::format(tr("%s %s")) % type % msg; \
+      return false; \
+    } \
+  } while (0)
+
 static std::string get_human_readable_timespan(std::chrono::seconds seconds);
 static std::string get_human_readable_timespan(uint64_t seconds);
 
@@ -314,7 +325,7 @@ namespace
     auto pwd_container = tools::password_container::prompt(verify, prompt);
     if (!pwd_container)
     {
-      tools::fail_msg_writer() << sw::tr("failed to read wallet password");
+      tools::fail_msg_writer() << sw::tr("failed to read password");
     }
     return pwd_container;
   }
@@ -324,6 +335,11 @@ namespace
     return password_prompter(verify ? sw::tr("Enter a new password for the wallet") : sw::tr("Wallet password"), verify);
   }
 
+  boost::optional<tools::password_container> background_sync_cache_password_prompter(bool verify)
+  {
+    return password_prompter(verify ? sw::tr("Enter a custom password for the background sync cache") : sw::tr("Background sync cache password"), verify);
+  }
+
   inline std::string interpret_rpc_response(bool ok, const std::string& status)
   {
     std::string err;
@@ -441,6 +457,41 @@ namespace
     return "invalid";
   }
 
+  const struct
+  {
+    const char *name;
+    tools::wallet2::BackgroundSyncType background_sync_type;
+  } background_sync_type_names[] =
+  {
+    { "off", tools::wallet2::BackgroundSyncOff },
+    { "reuse-wallet-password", tools::wallet2::BackgroundSyncReusePassword },
+    { "custom-background-password", tools::wallet2::BackgroundSyncCustomPassword },
+  };
+
+  bool parse_background_sync_type(const std::string &s, tools::wallet2::BackgroundSyncType &background_sync_type)
+  {
+    for (size_t n = 0; n < sizeof(background_sync_type_names) / sizeof(background_sync_type_names[0]); ++n)
+    {
+      if (s == background_sync_type_names[n].name)
+      {
+        background_sync_type = background_sync_type_names[n].background_sync_type;
+        return true;
+      }
+    }
+    fail_msg_writer() << cryptonote::simple_wallet::tr("failed to parse background sync type");
+    return false;
+  }
+
+  std::string get_background_sync_type_name(tools::wallet2::BackgroundSyncType type)
+  {
+    for (size_t n = 0; n < sizeof(background_sync_type_names) / sizeof(background_sync_type_names[0]); ++n)
+    {
+      if (type == background_sync_type_names[n].background_sync_type)
+        return background_sync_type_names[n].name;
+    }
+    return "invalid";
+  }
+
   std::string get_version_string(uint32_t version)
   {
     return boost::lexical_cast<std::string>(version >> 16) + "." + boost::lexical_cast<std::string>(version & 0xffff);
@@ -793,6 +844,7 @@ bool simple_wallet::spendkey(const std::vector<std::string> &args/* = std::vecto
     fail_msg_writer() << tr("wallet is watch-only and has no spend key");
     return true;
   }
+  CHECK_IF_BACKGROUND_SYNCING("has no spend key");
   // don't log
   PAUSE_READLINE();
   if (m_wallet->key_on_device()) {
@@ -823,6 +875,7 @@ bool simple_wallet::print_seed(bool encrypted)
     fail_msg_writer() << tr("wallet is watch-only and has no seed");
     return true;
   }
+  CHECK_IF_BACKGROUND_SYNCING("has no seed");
 
   const multisig::multisig_account_status ms_status{m_wallet->get_multisig_status()};
   if (ms_status.multisig_is_active)
@@ -900,6 +953,7 @@ bool simple_wallet::seed_set_language(const std::vector<std::string> &args/* = s
     fail_msg_writer() << tr("wallet is watch-only and has no seed");
     return true;
   }
+  CHECK_IF_BACKGROUND_SYNCING("has no seed");
 
   epee::wipeable_string password;
   {
@@ -1046,6 +1100,7 @@ bool simple_wallet::prepare_multisig_main(const std::vector<std::string> &args,
     fail_msg_writer() << tr("wallet is watch-only and cannot be made multisig");
     return false;
   }
+  CHECK_IF_BACKGROUND_SYNCING("cannot be made multisig");
 
   if(m_wallet->get_num_transfer_details())
   {
@@ -2105,6 +2160,7 @@ bool simple_wallet::save_known_rings(const std::vector<std::string> &args)
 
 bool simple_wallet::freeze_thaw(const std::vector<std::string> &args, bool freeze)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot freeze/thaw");
   if (args.empty())
   {
     fail_msg_writer() << boost::format(tr("usage: %s <key_image>|<pubkey>")) % (freeze ? "freeze" : "thaw");
@@ -2144,6 +2200,7 @@ bool simple_wallet::thaw(const std::vector<std::string> &args)
 
 bool simple_wallet::frozen(const std::vector<std::string> &args)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot see frozen key images");
   if (args.empty())
   {
     size_t ntd = m_wallet->get_num_transfer_details();
@@ -2794,6 +2851,57 @@ bool simple_wallet::set_track_uses(const std::vector<std::string> &args/* = std:
   return true;
 }
 
+bool simple_wallet::setup_background_sync(const std::vector<std::string> &args/* = std::vector<std::string>()*/)
+{
+  if (m_wallet->get_multisig_status().multisig_is_active)
+  {
+    fail_msg_writer() << tr("background sync not implemented for multisig wallet");
+    return true;
+  }
+  if (m_wallet->watch_only())
+  {
+    fail_msg_writer() << tr("background sync not implemented for watch only wallet");
+    return true;
+  }
+  if (m_wallet->key_on_device())
+  {
+    fail_msg_writer() << tr("command not supported by HW wallet");
+    return true;
+  }
+
+  tools::wallet2::BackgroundSyncType background_sync_type;
+  if (!parse_background_sync_type(args[1], background_sync_type))
+  {
+    fail_msg_writer() << tr("invalid option");
+    return true;
+  }
+
+  const auto pwd_container = get_and_verify_password();
+  if (!pwd_container)
+    return true;
+
+  try
+  {
+    boost::optional<epee::wipeable_string> background_cache_password = boost::none;
+    if (background_sync_type == tools::wallet2::BackgroundSyncCustomPassword)
+    {
+      const auto background_pwd_container = background_sync_cache_password_prompter(true);
+      if (!background_pwd_container)
+        return true;
+      background_cache_password = background_pwd_container->password();
+    }
+
+    LOCK_IDLE_SCOPE();
+    m_wallet->setup_background_sync(background_sync_type, pwd_container->password(), background_cache_password);
+  }
+  catch (const std::exception &e)
+  {
+    fail_msg_writer() << tr("Error setting background sync type: ") << e.what();
+  }
+
+  return true;
+}
+
 bool simple_wallet::set_show_wallet_name_when_locked(const std::vector<std::string> &args/* = std::vector<std::string>()*/)
 {
   const auto pwd_container = get_and_verify_password();
@@ -3026,6 +3134,7 @@ bool simple_wallet::apropos(const std::vector<std::string> &args)
 
 bool simple_wallet::scan_tx(const std::vector<std::string> &args)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot scan tx");
   if (args.empty())
   {
     PRINT_USAGE(USAGE_SCAN_TX);
@@ -3243,6 +3352,8 @@ simple_wallet::simple_wallet()
                                   "  Ignore outputs of amount below this threshold when spending.\n "
                                   "track-uses <1|0>\n "
                                   "  Whether to keep track of owned outputs uses.\n "
+                                  "background-sync <off|reuse-wallet-password|custom-background-password>\n "
+                                  "  Set this to enable scanning in the background with just the view key while the wallet is locked.\n "
                                   "setup-background-mining <1|0>\n "
                                   "  Whether to enable background mining. Set this to support the network and to get a chance to receive new monero.\n "
                                   "device-name <device_name[:device_spec]>\n "
@@ -3645,6 +3756,7 @@ bool simple_wallet::set_variable(const std::vector<std::string> &args)
     success_msg_writer() << "ignore-outputs-above = " << cryptonote::print_money(m_wallet->ignore_outputs_above());
     success_msg_writer() << "ignore-outputs-below = " << cryptonote::print_money(m_wallet->ignore_outputs_below());
     success_msg_writer() << "track-uses = " << m_wallet->track_uses();
+    success_msg_writer() << "background-sync = " << get_background_sync_type_name(m_wallet->background_sync_type());
     success_msg_writer() << "setup-background-mining = " << setup_background_mining_string;
     success_msg_writer() << "device-name = " << m_wallet->device_name();
     success_msg_writer() << "export-format = " << (m_wallet->export_format() == tools::wallet2::ExportFormat::Ascii ? "ascii" : "binary");
@@ -3660,6 +3772,7 @@ bool simple_wallet::set_variable(const std::vector<std::string> &args)
   }
   else
   {
+    CHECK_IF_BACKGROUND_SYNCING("cannot change wallet settings");
 
 #define CHECK_SIMPLE_VARIABLE(name, f, help) do \
   if (args[0] == name) { \
@@ -3713,6 +3826,7 @@ bool simple_wallet::set_variable(const std::vector<std::string> &args)
     CHECK_SIMPLE_VARIABLE("ignore-outputs-above", set_ignore_outputs_above, tr("amount"));
     CHECK_SIMPLE_VARIABLE("ignore-outputs-below", set_ignore_outputs_below, tr("amount"));
     CHECK_SIMPLE_VARIABLE("track-uses", set_track_uses, tr("0 or 1"));
+    CHECK_SIMPLE_VARIABLE("background-sync", setup_background_sync, tr("off (default); reuse-wallet-password (reuse the wallet password to encrypt the background cache); custom-background-password (use a custom background password to encrypt the background cache)"));
     CHECK_SIMPLE_VARIABLE("show-wallet-name-when-locked", set_show_wallet_name_when_locked, tr("1 or 0"));
     CHECK_SIMPLE_VARIABLE("inactivity-lock-timeout", set_inactivity_lock_timeout, tr("unsigned integer (seconds, 0 to disable)"));
     CHECK_SIMPLE_VARIABLE("setup-background-mining", set_setup_background_mining, tr("1/yes or 0/no"));
@@ -4653,7 +4767,10 @@ std::string simple_wallet::get_mnemonic_language()
 //----------------------------------------------------------------------------------------------------
 boost::optional<tools::password_container> simple_wallet::get_and_verify_password() const
 {
-  auto pwd_container = default_password_prompter(m_wallet_file.empty());
+  const bool verify = m_wallet_file.empty();
+  auto pwd_container = (m_wallet->is_background_wallet() && m_wallet->background_sync_type() == tools::wallet2::BackgroundSyncCustomPassword)
+    ? background_sync_cache_password_prompter(verify)
+    : default_password_prompter(verify);
   if (!pwd_container)
     return boost::none;
 
@@ -4956,6 +5073,8 @@ boost::optional<epee::wipeable_string> simple_wallet::open_wallet(const boost::p
       prefix = tr("Opened watch-only wallet");
     else if (ms_status.multisig_is_active)
       prefix = (boost::format(tr("Opened %u/%u multisig wallet%s")) % ms_status.threshold % ms_status.total % (ms_status.is_ready ? "" : " (not yet finalized)")).str();
+    else if (m_wallet->is_background_wallet())
+      prefix = tr("Opened background wallet");
     else
       prefix = tr("Opened wallet");
     message_writer(console_color_white, true) <<
@@ -5163,6 +5282,10 @@ void simple_wallet::stop_background_mining()
 //----------------------------------------------------------------------------------------------------
 void simple_wallet::check_background_mining(const epee::wipeable_string &password)
 {
+  // Background mining can be toggled from the main wallet
+  if (m_wallet->is_background_wallet() || m_wallet->is_background_syncing())
+    return;
+
   tools::wallet2::BackgroundMiningSetupType setup = m_wallet->setup_background_mining();
   if (setup == tools::wallet2::BackgroundMiningNo)
   {
@@ -5978,6 +6101,7 @@ bool simple_wallet::show_blockchain_height(const std::vector<std::string>& args)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::rescan_spent(const std::vector<std::string> &args)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot rescan spent");
   if (!m_wallet->is_trusted_daemon())
   {
     fail_msg_writer() << tr("this command requires a trusted daemon. Enable with --trusted-daemon");
@@ -6233,10 +6357,27 @@ void simple_wallet::check_for_inactivity_lock(bool user)
           "                ||     ||" << std::endl <<
           "" << std::endl;
     }
+
+    bool started_background_sync = false;
+    if (!m_wallet->is_background_wallet() &&
+        m_wallet->background_sync_type() != tools::wallet2::BackgroundSyncOff)
+    {
+      LOCK_IDLE_SCOPE();
+      m_wallet->start_background_sync();
+      started_background_sync = true;
+    }
+
     while (1)
     {
       const char *inactivity_msg = user ? "" : tr("Locked due to inactivity.");
-      tools::msg_writer() << inactivity_msg << (inactivity_msg[0] ? " " : "") << tr("The wallet password is required to unlock the console.");
+      tools::msg_writer() << inactivity_msg << (inactivity_msg[0] ? " " : "") << (
+        (m_wallet->is_background_wallet() && m_wallet->background_sync_type() == tools::wallet2::BackgroundSyncCustomPassword)
+            ? tr("The background password is required to unlock the console.")
+            : tr("The wallet password is required to unlock the console.")
+      );
+
+      if (m_wallet->is_background_syncing())
+        tools::msg_writer() << tr("\nSyncing in the background while locked...") << std::endl;
 
       const bool show_wallet_name = m_wallet->show_wallet_name_when_locked();
       if (show_wallet_name)
@@ -6249,8 +6390,16 @@ void simple_wallet::check_for_inactivity_lock(bool user)
       }
       try
       {
-        if (get_and_verify_password())
+        const auto pwd_container = get_and_verify_password();
+        if (pwd_container)
+        {
+          if (started_background_sync)
+          {
+            LOCK_IDLE_SCOPE();
+            m_wallet->stop_background_sync(pwd_container->password());
+          }
           break;
+        }
       }
       catch (...) { /* do nothing, just let the loop loop */ }
     }
@@ -6277,6 +6426,7 @@ bool simple_wallet::on_command(bool (simple_wallet::*cmd)(const std::vector<std:
 bool simple_wallet::transfer_main(const std::vector<std::string> &args_, bool called_by_mms)
 {
 //  "transfer [index=<N1>[,<N2>,...]] [<priority>] [<ring_size>] <address> <amount> [<payment_id>]"
+  CHECK_IF_BACKGROUND_SYNCING("cannot transfer");
   if (!try_connect_to_daemon())
     return false;
 
@@ -6690,6 +6840,7 @@ bool simple_wallet::transfer_main(const std::vector<std::string> &args_, bool ca
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::transfer(const std::vector<std::string> &args_)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot transfer");
   if (args_.size() < 1)
   {
     PRINT_USAGE(USAGE_TRANSFER);
@@ -6702,6 +6853,7 @@ bool simple_wallet::transfer(const std::vector<std::string> &args_)
 
 bool simple_wallet::sweep_unmixable(const std::vector<std::string> &args_)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot sweep");
   if (!try_connect_to_daemon())
     return true;
 
@@ -6809,6 +6961,7 @@ bool simple_wallet::sweep_unmixable(const std::vector<std::string> &args_)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::sweep_main(uint32_t account, uint64_t below, const std::vector<std::string> &args_)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot sweep");
   auto print_usage = [this, account, below]()
   {
     if (below)
@@ -7090,6 +7243,7 @@ bool simple_wallet::sweep_main(uint32_t account, uint64_t below, const std::vect
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::sweep_single(const std::vector<std::string> &args_)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot sweep");
   if (!try_connect_to_daemon())
     return true;
 
@@ -7328,12 +7482,14 @@ bool simple_wallet::sweep_single(const std::vector<std::string> &args_)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::sweep_all(const std::vector<std::string> &args_)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot sweep");
   sweep_main(m_current_subaddress_account, 0, args_);
   return true;
 }
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::sweep_account(const std::vector<std::string> &args_)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot sweep");
   auto local_args = args_;
   if (local_args.empty())
   {
@@ -7354,6 +7510,7 @@ bool simple_wallet::sweep_account(const std::vector<std::string> &args_)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::sweep_below(const std::vector<std::string> &args_)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot sweep");
   uint64_t below = 0;
   if (args_.size() < 1)
   {
@@ -7372,6 +7529,7 @@ bool simple_wallet::sweep_below(const std::vector<std::string> &args_)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::donate(const std::vector<std::string> &args_)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot donate");
   std::vector<std::string> local_args = args_;
   if(local_args.empty() || local_args.size() > 5)
   {
@@ -7433,6 +7591,7 @@ bool simple_wallet::donate(const std::vector<std::string> &args_)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::accept_loaded_tx(const std::function<size_t()> get_num_txes, const std::function<const tools::wallet2::tx_construction_data&(size_t)> &get_tx, const std::string &extra_message)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot load tx");
   // gather info to ask the user
   uint64_t amount = 0, amount_to_dests = 0, change = 0;
   size_t min_ring_size = ~0;
@@ -7613,6 +7772,7 @@ bool simple_wallet::sign_transfer(const std::vector<std::string> &args_)
      fail_msg_writer() << tr("This is a watch only wallet");
      return true;
   }
+  CHECK_IF_BACKGROUND_SYNCING("cannot sign transfer");
 
   bool export_raw = false;
   std::string unsigned_filename = "unsigned_monero_tx";
@@ -7720,6 +7880,8 @@ std::string get_tx_key_stream(crypto::secret_key tx_key, std::vector<crypto::sec
 
 bool simple_wallet::get_tx_key(const std::vector<std::string> &args_)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot get tx key");
+
   std::vector<std::string> local_args = args_;
 
   if (m_wallet->key_on_device() && m_wallet->get_account().get_device().get_type() != hw::device::TREZOR)
@@ -7760,6 +7922,8 @@ bool simple_wallet::get_tx_key(const std::vector<std::string> &args_)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::set_tx_key(const std::vector<std::string> &args_)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot set tx key");
+
   std::vector<std::string> local_args = args_;
 
   if(local_args.size() != 2 && local_args.size() != 3) {
@@ -7836,6 +8000,8 @@ bool simple_wallet::set_tx_key(const std::vector<std::string> &args_)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::get_tx_proof(const std::vector<std::string> &args)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot get tx proof");
+
   if (args.size() != 2 && args.size() != 3)
   {
     PRINT_USAGE(USAGE_GET_TX_PROOF);
@@ -8042,6 +8208,7 @@ bool simple_wallet::check_tx_proof(const std::vector<std::string> &args)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::get_spend_proof(const std::vector<std::string> &args)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot get spend proof");
   if (m_wallet->key_on_device())
   {
     fail_msg_writer() << tr("command not supported by HW wallet");
@@ -8126,6 +8293,7 @@ bool simple_wallet::check_spend_proof(const std::vector<std::string> &args)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::get_reserve_proof(const std::vector<std::string> &args)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot get reserve proof");
   if (m_wallet->key_on_device())
   {
     fail_msg_writer() << tr("command not supported by HW wallet");
@@ -8812,6 +8980,8 @@ bool simple_wallet::unspent_outputs(const std::vector<std::string> &args_)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::rescan_blockchain(const std::vector<std::string> &args_)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot rescan");
+
   uint64_t start_height = 0;
   ResetType reset_type = ResetSoft;
 
@@ -9036,6 +9206,7 @@ bool simple_wallet::account(const std::vector<std::string> &args/* = std::vector
   if (command == "new")
   {
     // create a new account and switch to it
+    CHECK_IF_BACKGROUND_SYNCING("cannot create new account");
     std::string label = boost::join(local_args, " ");
     if (label.empty())
       label = tr("(Untitled account)");
@@ -9066,6 +9237,7 @@ bool simple_wallet::account(const std::vector<std::string> &args/* = std::vector
   else if (command == "label" && local_args.size() >= 1)
   {
     // set label of the specified account
+    CHECK_IF_BACKGROUND_SYNCING("cannot modify account");
     uint32_t index_major;
     if (!epee::string_tools::get_xtype_from_string(index_major, local_args[0]))
     {
@@ -9087,6 +9259,7 @@ bool simple_wallet::account(const std::vector<std::string> &args/* = std::vector
   }
   else if (command == "tag" && local_args.size() >= 2)
   {
+    CHECK_IF_BACKGROUND_SYNCING("cannot modify account");
     const std::string tag = local_args[0];
     std::set<uint32_t> account_indices;
     for (size_t i = 1; i < local_args.size(); ++i)
@@ -9111,6 +9284,7 @@ bool simple_wallet::account(const std::vector<std::string> &args/* = std::vector
   }
   else if (command == "untag" && local_args.size() >= 1)
   {
+    CHECK_IF_BACKGROUND_SYNCING("cannot modify account");
     std::set<uint32_t> account_indices;
     for (size_t i = 0; i < local_args.size(); ++i)
     {
@@ -9134,6 +9308,7 @@ bool simple_wallet::account(const std::vector<std::string> &args/* = std::vector
   }
   else if (command == "tag_description" && local_args.size() >= 1)
   {
+    CHECK_IF_BACKGROUND_SYNCING("cannot modify account");
     const std::string tag = local_args[0];
     std::string description;
     if (local_args.size() > 1)
@@ -9251,6 +9426,7 @@ bool simple_wallet::print_address(const std::vector<std::string> &args/* = std::
   }
   else if (local_args[0] == "new")
   {
+    CHECK_IF_BACKGROUND_SYNCING("cannot add address");
     local_args.erase(local_args.begin());
     std::string label;
     if (local_args.size() > 0)
@@ -9263,6 +9439,7 @@ bool simple_wallet::print_address(const std::vector<std::string> &args/* = std::
   }
   else if (local_args[0] == "mnew")
   {
+    CHECK_IF_BACKGROUND_SYNCING("cannot add addresses");
     local_args.erase(local_args.begin());
     if (local_args.size() != 1)
     {
@@ -9288,6 +9465,7 @@ bool simple_wallet::print_address(const std::vector<std::string> &args/* = std::
   }
   else if (local_args[0] == "one-off")
   {
+    CHECK_IF_BACKGROUND_SYNCING("cannot add address");
     local_args.erase(local_args.begin());
     std::string label;
     if (local_args.size() != 2)
@@ -9306,6 +9484,7 @@ bool simple_wallet::print_address(const std::vector<std::string> &args/* = std::
   }
   else if (local_args.size() >= 2 && local_args[0] == "label")
   {
+    CHECK_IF_BACKGROUND_SYNCING("cannot modify address");
     if (!epee::string_tools::get_xtype_from_string(index, local_args[1]))
     {
       fail_msg_writer() << tr("failed to parse index: ") << local_args[1];
@@ -9452,6 +9631,8 @@ bool simple_wallet::print_integrated_address(const std::vector<std::string> &arg
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::address_book(const std::vector<std::string> &args/* = std::vector<std::string>()*/)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot get address book");
+
   if (args.size() == 0)
   {
   }
@@ -9512,6 +9693,8 @@ bool simple_wallet::address_book(const std::vector<std::string> &args/* = std::v
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::set_tx_note(const std::vector<std::string> &args)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot set tx note");
+
   if (args.size() == 0)
   {
     PRINT_USAGE(USAGE_SET_TX_NOTE);
@@ -9540,6 +9723,8 @@ bool simple_wallet::set_tx_note(const std::vector<std::string> &args)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::get_tx_note(const std::vector<std::string> &args)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot get tx note");
+
   if (args.size() != 1)
   {
     PRINT_USAGE(USAGE_GET_TX_NOTE);
@@ -9565,6 +9750,8 @@ bool simple_wallet::get_tx_note(const std::vector<std::string> &args)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::set_description(const std::vector<std::string> &args)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot set description");
+
   // 0 arguments allowed, for setting the description to empty string
 
   std::string description = "";
@@ -9581,6 +9768,8 @@ bool simple_wallet::set_description(const std::vector<std::string> &args)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::get_description(const std::vector<std::string> &args)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot get description");
+
   if (args.size() != 0)
   {
     PRINT_USAGE(USAGE_GET_DESCRIPTION);
@@ -9639,6 +9828,8 @@ bool simple_wallet::wallet_info(const std::vector<std::string> &args)
     type = tr("Watch only");
   else if (ms_status.multisig_is_active)
     type = (boost::format(tr("%u/%u multisig%s")) % ms_status.threshold % ms_status.total % (ms_status.is_ready ? "" : " (not yet finalized)")).str();
+  else if (m_wallet->is_background_wallet())
+    type = tr("Background wallet");
   else
     type = tr("Normal");
   message_writer() << tr("Type: ") << type;
@@ -9650,6 +9841,7 @@ bool simple_wallet::wallet_info(const std::vector<std::string> &args)
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::sign(const std::vector<std::string> &args)
 {
+  CHECK_IF_BACKGROUND_SYNCING("cannot sign");
   if (m_wallet->key_on_device())
   {
     fail_msg_writer() << tr("command not supported by HW wallet");
@@ -9757,6 +9949,7 @@ bool simple_wallet::export_key_images(const std::vector<std::string> &args_)
     fail_msg_writer() << tr("command not supported by HW wallet");
     return true;
   }
+  CHECK_IF_BACKGROUND_SYNCING("cannot export key images");
   auto args = args_;
 
   if (m_wallet->watch_only())
@@ -9810,6 +10003,7 @@ bool simple_wallet::import_key_images(const std::vector<std::string> &args)
     fail_msg_writer() << tr("command not supported by HW wallet");
     return true;
   }
+  CHECK_IF_BACKGROUND_SYNCING("cannot import key images");
   if (!m_wallet->is_trusted_daemon())
   {
     fail_msg_writer() << tr("this command requires a trusted daemon. Enable with --trusted-daemon");
@@ -9918,6 +10112,7 @@ bool simple_wallet::export_outputs(const std::vector<std::string> &args_)
     fail_msg_writer() << tr("command not supported by HW wallet");
     return true;
   }
+  CHECK_IF_BACKGROUND_SYNCING("cannot export outputs");
   auto args = args_;
 
   bool all = false;
@@ -9967,6 +10162,7 @@ bool simple_wallet::import_outputs(const std::vector<std::string> &args)
     fail_msg_writer() << tr("command not supported by HW wallet");
     return true;
   }
+  CHECK_IF_BACKGROUND_SYNCING("cannot import outputs");
   if (args.size() != 1)
   {
     PRINT_USAGE(USAGE_IMPORT_OUTPUTS);

src/simplewallet/simplewallet.h

@@ -147,6 +147,7 @@ namespace cryptonote
     bool set_ignore_outputs_above(const std::vector<std::string> &args = std::vector<std::string>());
     bool set_ignore_outputs_below(const std::vector<std::string> &args = std::vector<std::string>());
     bool set_track_uses(const std::vector<std::string> &args = std::vector<std::string>());
+    bool setup_background_sync(const std::vector<std::string> &args = std::vector<std::string>());
     bool set_show_wallet_name_when_locked(const std::vector<std::string> &args = std::vector<std::string>());
     bool set_inactivity_lock_timeout(const std::vector<std::string> &args = std::vector<std::string>());
     bool set_setup_background_mining(const std::vector<std::string> &args = std::vector<std::string>());

src/wallet/api/wallet.cpp

@@ -58,6 +58,40 @@ using namespace cryptonote;
 #undef MONERO_DEFAULT_LOG_CATEGORY
 #define MONERO_DEFAULT_LOG_CATEGORY "WalletAPI"
 
+#define LOCK_REFRESH() \
+    bool refresh_enabled = m_refreshEnabled; \
+    m_refreshEnabled = false; \
+    m_wallet->stop(); \
+    m_refreshCV.notify_one(); \
+    boost::mutex::scoped_lock lock(m_refreshMutex); \
+    boost::mutex::scoped_lock lock2(m_refreshMutex2); \
+    epee::misc_utils::auto_scope_leave_caller scope_exit_handler = epee::misc_utils::create_scope_leave_handler([&](){ \
+        /* m_refreshMutex's still locked here */ \
+        if (refresh_enabled) \
+            startRefresh(); \
+    })
+
+#define PRE_VALIDATE_BACKGROUND_SYNC() \
+  do \
+  { \
+    clearStatus(); \
+    if (m_wallet->key_on_device()) \
+    { \
+        setStatusError(tr("HW wallet cannot use background sync")); \
+        return false; \
+    } \
+    if (m_wallet->watch_only()) \
+    { \
+        setStatusError(tr("View only wallet cannot use background sync")); \
+        return false; \
+    } \
+    if (m_wallet->get_multisig_status().multisig_is_active) \
+    { \
+        setStatusError(tr("Multisig wallet cannot use background sync")); \
+        return false; \
+    } \
+  } while (0)
+
 namespace Monero {
 
 namespace {
@@ -766,6 +800,8 @@ bool WalletImpl::close(bool store)
 
 std::string WalletImpl::seed(const std::string& seed_offset) const
 {
+    if (checkBackgroundSync("cannot get seed"))
+        return std::string();
     epee::wipeable_string seed;
     if (m_wallet)
         m_wallet->get_seed(seed, seed_offset);
@@ -779,6 +815,8 @@ std::string WalletImpl::getSeedLanguage() const
 
 void WalletImpl::setSeedLanguage(const std::string &arg)
 {
+    if (checkBackgroundSync("cannot set seed language"))
+        return;
     m_wallet->set_seed_language(arg);
 }
 
@@ -802,6 +840,8 @@ void WalletImpl::statusWithErrorString(int& status, std::string& errorString) co
 
 bool WalletImpl::setPassword(const std::string &password)
 {
+    if (checkBackgroundSync("cannot change password"))
+        return false;
     clearStatus();
     try {
         m_wallet->change_password(m_wallet->get_wallet_file(), m_password, password);
@@ -931,6 +971,8 @@ bool WalletImpl::init(const std::string &daemon_address, uint64_t upper_transact
 
 void WalletImpl::setRefreshFromBlockHeight(uint64_t refresh_from_block_height)
 {
+    if (checkBackgroundSync("cannot change refresh height"))
+        return;
     m_wallet->set_refresh_from_block_height(refresh_from_block_height);
 }
 
@@ -1039,6 +1081,8 @@ void WalletImpl::refreshAsync()
 
 bool WalletImpl::rescanBlockchain()
 {
+    if (checkBackgroundSync("cannot rescan blockchain"))
+        return false;
     clearStatus();
     m_refreshShouldRescan = true;
     doRefresh();
@@ -1047,6 +1091,8 @@ bool WalletImpl::rescanBlockchain()
 
 void WalletImpl::rescanBlockchainAsync()
 {
+    if (checkBackgroundSync("cannot rescan blockchain"))
+        return;
     m_refreshShouldRescan = true;
     refreshAsync();
 }
@@ -1070,7 +1116,7 @@ int WalletImpl::autoRefreshInterval() const
 UnsignedTransaction *WalletImpl::loadUnsignedTx(const std::string &unsigned_filename) {
   clearStatus();
   UnsignedTransactionImpl * transaction = new UnsignedTransactionImpl(*this);
-  if (!m_wallet->load_unsigned_tx(unsigned_filename, transaction->m_unsigned_tx_set)){
+  if (checkBackgroundSync("cannot load tx") || !m_wallet->load_unsigned_tx(unsigned_filename, transaction->m_unsigned_tx_set)){
     setStatusError(tr("Failed to load unsigned transactions"));
     transaction->m_status = UnsignedTransaction::Status::Status_Error;
     transaction->m_errorString = errorString();
@@ -1090,6 +1136,8 @@ UnsignedTransaction *WalletImpl::loadUnsignedTx(const std::string &unsigned_file
 
 bool WalletImpl::submitTransaction(const string &fileName) {
   clearStatus();
+  if (checkBackgroundSync("cannot submit tx"))
+    return false;
   std::unique_ptr<PendingTransactionImpl> transaction(new PendingTransactionImpl(*this));
 
   bool r = m_wallet->load_tx(fileName, transaction->m_pending_tx);
@@ -1113,6 +1161,8 @@ bool WalletImpl::exportKeyImages(const string &filename, bool all)
     setStatusError(tr("Wallet is view only"));
     return false;
   }
+  if (checkBackgroundSync("cannot export key images"))
+    return false;
   
   try
   {
@@ -1133,6 +1183,8 @@ bool WalletImpl::exportKeyImages(const string &filename, bool all)
 
 bool WalletImpl::importKeyImages(const string &filename)
 {
+  if (checkBackgroundSync("cannot import key images"))
+    return false;
   if (!trustedDaemon()) {
     setStatusError(tr("Key images can only be imported with a trusted daemon"));
     return false;
@@ -1156,6 +1208,8 @@ bool WalletImpl::importKeyImages(const string &filename)
 
 bool WalletImpl::exportOutputs(const string &filename, bool all)
 {
+    if (checkBackgroundSync("cannot export outputs"))
+        return false;
     if (m_wallet->key_on_device())
     {
         setStatusError(string(tr("Not supported on HW wallets.")) + filename);
@@ -1186,6 +1240,8 @@ bool WalletImpl::exportOutputs(const string &filename, bool all)
 
 bool WalletImpl::importOutputs(const string &filename)
 {
+    if (checkBackgroundSync("cannot import outputs"))
+        return false;
     if (m_wallet->key_on_device())
     {
         setStatusError(string(tr("Not supported on HW wallets.")) + filename);
@@ -1218,6 +1274,8 @@ bool WalletImpl::importOutputs(const string &filename)
 
 bool WalletImpl::scanTransactions(const std::vector<std::string> &txids)
 {
+    if (checkBackgroundSync("cannot scan transactions"))
+        return false;
     if (txids.empty())
     {
         setStatusError(string(tr("Failed to scan transactions: no transaction ids provided.")));
@@ -1256,8 +1314,86 @@ bool WalletImpl::scanTransactions(const std::vector<std::string> &txids)
     return true;
 }
 
+bool WalletImpl::setupBackgroundSync(const Wallet::BackgroundSyncType background_sync_type, const std::string &wallet_password, const optional<std::string> &background_cache_password)
+{
+    try
+    {
+        PRE_VALIDATE_BACKGROUND_SYNC();
+
+        tools::wallet2::BackgroundSyncType bgs_type;
+        switch (background_sync_type)
+        {
+            case Wallet::BackgroundSync_Off: bgs_type = tools::wallet2::BackgroundSyncOff; break;
+            case Wallet::BackgroundSync_ReusePassword: bgs_type = tools::wallet2::BackgroundSyncReusePassword; break;
+            case Wallet::BackgroundSync_CustomPassword: bgs_type = tools::wallet2::BackgroundSyncCustomPassword; break;
+            default: setStatusError(tr("Unknown background sync type")); return false;
+        }
+
+        boost::optional<epee::wipeable_string> bgc_password = background_cache_password
+            ? boost::optional<epee::wipeable_string>(*background_cache_password)
+            : boost::none;
+
+        LOCK_REFRESH();
+        m_wallet->setup_background_sync(bgs_type, wallet_password, bgc_password);
+    }
+    catch (const std::exception &e)
+    {
+        LOG_ERROR("Failed to setup background sync: " << e.what());
+        setStatusError(string(tr("Failed to setup background sync: ")) + e.what());
+        return false;
+    }
+    return true;
+}
+
+Wallet::BackgroundSyncType WalletImpl::getBackgroundSyncType() const
+{
+    switch (m_wallet->background_sync_type())
+    {
+        case tools::wallet2::BackgroundSyncOff: return Wallet::BackgroundSync_Off;
+        case tools::wallet2::BackgroundSyncReusePassword: return Wallet::BackgroundSync_ReusePassword;
+        case tools::wallet2::BackgroundSyncCustomPassword: return Wallet::BackgroundSync_CustomPassword;
+        default: setStatusError(tr("Unknown background sync type")); return Wallet::BackgroundSync_Off;
+    }
+}
+
+bool WalletImpl::startBackgroundSync()
+{
+    try
+    {
+        PRE_VALIDATE_BACKGROUND_SYNC();
+        LOCK_REFRESH();
+        m_wallet->start_background_sync();
+    }
+    catch (const std::exception &e)
+    {
+        LOG_ERROR("Failed to start background sync: " << e.what());
+        setStatusError(string(tr("Failed to start background sync: ")) + e.what());
+        return false;
+    }
+    return true;
+}
+
+bool WalletImpl::stopBackgroundSync(const std::string &wallet_password)
+{
+    try
+    {
+        PRE_VALIDATE_BACKGROUND_SYNC();
+        LOCK_REFRESH();
+        m_wallet->stop_background_sync(epee::wipeable_string(wallet_password));
+    }
+    catch (const std::exception &e)
+    {
+        LOG_ERROR("Failed to stop background sync: " << e.what());
+        setStatusError(string(tr("Failed to stop background sync: ")) + e.what());
+        return false;
+    }
+    return true;
+}
+
 void WalletImpl::addSubaddressAccount(const std::string& label)
 {
+    if (checkBackgroundSync("cannot add account"))
+        return;
     m_wallet->add_subaddress_account(label);
 }
 size_t WalletImpl::numSubaddressAccounts() const
@@ -1270,10 +1406,14 @@ size_t WalletImpl::numSubaddresses(uint32_t accountIndex) const
 }
 void WalletImpl::addSubaddress(uint32_t accountIndex, const std::string& label)
 {
+    if (checkBackgroundSync("cannot add subbaddress"))
+        return;
     m_wallet->add_subaddress(accountIndex, label);
 }
 std::string WalletImpl::getSubaddressLabel(uint32_t accountIndex, uint32_t addressIndex) const
 {
+    if (checkBackgroundSync("cannot get subbaddress label"))
+        return "";
     try
     {
         return m_wallet->get_subaddress_label({accountIndex, addressIndex});
@@ -1287,6 +1427,8 @@ std::string WalletImpl::getSubaddressLabel(uint32_t accountIndex, uint32_t addre
 }
 void WalletImpl::setSubaddressLabel(uint32_t accountIndex, uint32_t addressIndex, const std::string &label)
 {
+    if (checkBackgroundSync("cannot set subbaddress label"))
+        return;
     try
     {
         return m_wallet->set_subaddress_label({accountIndex, addressIndex}, label);
@@ -1300,6 +1442,9 @@ void WalletImpl::setSubaddressLabel(uint32_t accountIndex, uint32_t addressIndex
 
 MultisigState WalletImpl::multisig() const {
     MultisigState state;
+    if (checkBackgroundSync("cannot use multisig"))
+        return state;
+
     const multisig::multisig_account_status ms_status{m_wallet->get_multisig_status()};
 
     state.isMultisig = ms_status.multisig_is_active;
@@ -1312,6 +1457,8 @@ MultisigState WalletImpl::multisig() const {
 }
 
 string WalletImpl::getMultisigInfo() const {
+    if (checkBackgroundSync("cannot use multisig"))
+        return string();
     try {
         clearStatus();
         return m_wallet->get_multisig_first_kex_msg();
@@ -1324,6 +1471,8 @@ string WalletImpl::getMultisigInfo() const {
 }
 
 string WalletImpl::makeMultisig(const vector<string>& info, const uint32_t threshold) {
+    if (checkBackgroundSync("cannot make multisig"))
+        return string();
     try {
         clearStatus();
 
@@ -1479,6 +1628,9 @@ PendingTransaction *WalletImpl::createTransactionMultDest(const std::vector<stri
     PendingTransactionImpl * transaction = new PendingTransactionImpl(*this);
 
     do {
+        if (checkBackgroundSync("cannot create transactions"))
+            break;
+
         std::vector<uint8_t> extra;
         std::string extra_nonce;
         vector<cryptonote::tx_destination_entry> dsts;
@@ -1645,6 +1797,9 @@ PendingTransaction *WalletImpl::createSweepUnmixableTransaction()
     PendingTransactionImpl * transaction = new PendingTransactionImpl(*this);
 
     do {
+        if (checkBackgroundSync("cannot sweep"))
+            break;
+
         try {
             transaction->m_pending_tx = m_wallet->create_unmixable_sweep_transactions();
             pendingTxPostProcess(transaction);
@@ -1778,11 +1933,15 @@ uint32_t WalletImpl::defaultMixin() const
 
 void WalletImpl::setDefaultMixin(uint32_t arg)
 {
+    if (checkBackgroundSync("cannot set default mixin"))
+        return;
     m_wallet->default_mixin(arg);
 }
 
 bool WalletImpl::setCacheAttribute(const std::string &key, const std::string &val)
 {
+    if (checkBackgroundSync("cannot set cache attribute"))
+        return false;
     m_wallet->set_attribute(key, val);
     return true;
 }
@@ -1796,6 +1955,8 @@ std::string WalletImpl::getCacheAttribute(const std::string &key) const
 
 bool WalletImpl::setUserNote(const std::string &txid, const std::string &note)
 {
+    if (checkBackgroundSync("cannot set user note"))
+        return false;
     cryptonote::blobdata txid_data;
     if(!epee::string_tools::parse_hexstr_to_binbuff(txid, txid_data) || txid_data.size() != sizeof(crypto::hash))
       return false;
@@ -1807,6 +1968,8 @@ bool WalletImpl::setUserNote(const std::string &txid, const std::string &note)
 
 std::string WalletImpl::getUserNote(const std::string &txid) const
 {
+    if (checkBackgroundSync("cannot get user note"))
+        return "";
     cryptonote::blobdata txid_data;
     if(!epee::string_tools::parse_hexstr_to_binbuff(txid, txid_data) || txid_data.size() != sizeof(crypto::hash))
       return "";
@@ -1817,6 +1980,9 @@ std::string WalletImpl::getUserNote(const std::string &txid) const
 
 std::string WalletImpl::getTxKey(const std::string &txid_str) const
 {
+    if (checkBackgroundSync("cannot get tx key"))
+        return "";
+
     crypto::hash txid;
     if(!epee::string_tools::hex_to_pod(txid_str, txid))
     {
@@ -1901,6 +2067,9 @@ bool WalletImpl::checkTxKey(const std::string &txid_str, std::string tx_key_str,
 
 std::string WalletImpl::getTxProof(const std::string &txid_str, const std::string &address_str, const std::string &message) const
 {
+    if (checkBackgroundSync("cannot get tx proof"))
+        return "";
+
     crypto::hash txid;
     if (!epee::string_tools::hex_to_pod(txid_str, txid))
     {
@@ -1957,6 +2126,9 @@ bool WalletImpl::checkTxProof(const std::string &txid_str, const std::string &ad
 }
 
 std::string WalletImpl::getSpendProof(const std::string &txid_str, const std::string &message) const {
+    if (checkBackgroundSync("cannot get spend proof"))
+        return "";
+
     crypto::hash txid;
     if(!epee::string_tools::hex_to_pod(txid_str, txid))
     {
@@ -1999,6 +2171,9 @@ bool WalletImpl::checkSpendProof(const std::string &txid_str, const std::string
 }
 
 std::string WalletImpl::getReserveProof(bool all, uint32_t account_index, uint64_t amount, const std::string &message) const {
+    if (checkBackgroundSync("cannot get reserve proof"))
+        return "";
+
     try
     {
         clearStatus();
@@ -2045,6 +2220,9 @@ bool WalletImpl::checkReserveProof(const std::string &address, const std::string
 
 std::string WalletImpl::signMessage(const std::string &message, const std::string &address)
 {
+    if (checkBackgroundSync("cannot sign message"))
+        return "";
+
     if (address.empty()) {
         return m_wallet->sign(message, tools::wallet2::sign_with_spend_key);
     }
@@ -2171,6 +2349,16 @@ bool WalletImpl::isDeterministic() const
     return m_wallet->is_deterministic();
 }
 
+bool WalletImpl::isBackgroundSyncing() const
+{
+    return m_wallet->is_background_syncing();
+}
+
+bool WalletImpl::isBackgroundWallet() const
+{
+    return m_wallet->is_background_wallet();
+}
+
 void WalletImpl::clearStatus() const
 {
     boost::lock_guard<boost::mutex> l(m_statusMutex);
@@ -2239,9 +2427,7 @@ void WalletImpl::doRefresh()
             if(rescan)
                 m_wallet->rescan_blockchain(false);
             m_wallet->refresh(trustedDaemon());
-            if (!m_synchronized) {
+            m_synchronized = m_wallet->is_synced();
-                m_synchronized = true;
-            }
             // assuming if we have empty history, it wasn't initialized yet
             // for further history changes client need to update history in
             // "on_money_received" and "on_money_sent" callbacks
@@ -2344,6 +2530,24 @@ bool WalletImpl::doInit(const string &daemon_address, const std::string &proxy_a
     return true;
 }
 
+bool WalletImpl::checkBackgroundSync(const std::string &message) const
+{
+    clearStatus();
+    if (m_wallet->is_background_wallet())
+    {
+        LOG_ERROR("Background wallets " + message);
+        setStatusError(tr("Background wallets ") + message);
+        return true;
+    }
+    if (m_wallet->is_background_syncing())
+    {
+        LOG_ERROR(message + " while background syncing");
+        setStatusError(message + tr(" while background syncing. Stop background syncing first."));
+        return true;
+    }
+    return false;
+}
+
 bool WalletImpl::parse_uri(const std::string &uri, std::string &address, std::string &payment_id, uint64_t &amount, std::string &tx_description, std::string &recipient_name, std::vector<std::string> &unknown_parameters, std::string &error)
 {
     return m_wallet->parse_uri(uri, address, payment_id, amount, tx_description, recipient_name, unknown_parameters, error);
@@ -2362,6 +2566,8 @@ std::string WalletImpl::getDefaultDataDir() const
 bool WalletImpl::rescanSpent()
 {
   clearStatus();
+  if (checkBackgroundSync("cannot rescan spent"))
+    return false;
   if (!trustedDaemon()) {
     setStatusError(tr("Rescan spent can only be used with a trusted daemon"));
     return false;

src/wallet/api/wallet.h

@@ -173,6 +173,13 @@ public:
     bool importOutputs(const std::string &filename) override;
     bool scanTransactions(const std::vector<std::string> &txids) override;
 
+    bool setupBackgroundSync(const BackgroundSyncType background_sync_type, const std::string &wallet_password, const optional<std::string> &background_cache_password = optional<std::string>()) override;
+    BackgroundSyncType getBackgroundSyncType() const override;
+    bool startBackgroundSync() override;
+    bool stopBackgroundSync(const std::string &wallet_password) override;
+    bool isBackgroundSyncing() const override;
+    bool isBackgroundWallet() const override;
+
     virtual void disposeTransaction(PendingTransaction * t) override;
     virtual uint64_t estimateTransactionFee(const std::vector<std::pair<std::string, uint64_t>> &destinations,
                                             PendingTransaction::Priority priority) const override;
@@ -239,6 +246,7 @@ private:
     bool isNewWallet() const;
     void pendingTxPostProcess(PendingTransactionImpl * pending);
     bool doInit(const std::string &daemon_address, const std::string &proxy_address, uint64_t upper_transaction_size_limit = 0, bool ssl = false);
+    bool checkBackgroundSync(const std::string &message) const;
 
 private:
     friend class PendingTransactionImpl;
@@ -254,6 +262,10 @@ private:
     mutable boost::mutex m_statusMutex;
     mutable int m_status;
     mutable std::string m_errorString;
+    // TODO: harden password handling in the wallet API, see relevant discussion
+    // https://github.com/monero-project/monero-gui/issues/1537
+    // https://github.com/feather-wallet/feather/issues/72#issuecomment-1405602142
+    // https://github.com/monero-project/monero/pull/8619#issuecomment-1632951461
     std::string m_password;
     std::unique_ptr<TransactionHistoryImpl> m_history;
     std::unique_ptr<Wallet2CallbackImpl> m_wallet2Callback;

src/wallet/api/wallet2_api.h

@@ -446,6 +446,12 @@ struct Wallet
         ConnectionStatus_WrongVersion
     };
 
+    enum BackgroundSyncType {
+        BackgroundSync_Off = 0,
+        BackgroundSync_ReusePassword = 1,
+        BackgroundSync_CustomPassword = 2
+    };
+
     virtual ~Wallet() = 0;
     virtual std::string seed(const std::string& seed_offset = "") const = 0;
     virtual std::string getSeedLanguage() const = 0;
@@ -946,6 +952,42 @@ struct Wallet
      */
     virtual bool scanTransactions(const std::vector<std::string> &txids) = 0;
 
+    /*!
+     * \brief setupBackgroundSync       - setup background sync mode with just a view key
+     * \param background_sync_type      - the mode the wallet background syncs in
+     * \param wallet_password
+     * \param background_cache_password - custom password to encrypt background cache, only needed for custom password background sync type
+     * \return                          - true on success
+     */
+    virtual bool setupBackgroundSync(const BackgroundSyncType background_sync_type, const std::string &wallet_password, const optional<std::string> &background_cache_password) = 0;
+
+    /*!
+     * \brief getBackgroundSyncType     - get mode the wallet background syncs in
+     * \return                          - the type, or off if type is unknown
+     */
+    virtual BackgroundSyncType getBackgroundSyncType() const = 0;
+
+    /**
+     * @brief startBackgroundSync - sync the chain in the background with just view key
+     */
+    virtual bool startBackgroundSync() = 0;
+
+    /**
+     * @brief stopBackgroundSync  - bring back spend key and process background synced txs
+     * \param wallet_password
+     */
+    virtual bool stopBackgroundSync(const std::string &wallet_password) = 0;
+
+    /**
+     * @brief isBackgroundSyncing - returns true if the wallet is background syncing
+     */
+    virtual bool isBackgroundSyncing() const = 0;
+
+    /**
+     * @brief isBackgroundWallet - returns true if the wallet is a background wallet
+     */
+    virtual bool isBackgroundWallet() const = 0;
+
     virtual TransactionHistory * history() = 0;
     virtual AddressBook * addressBook() = 0;
     virtual Subaddress * subaddress() = 0;

src/wallet/wallet2.h

@@ -250,6 +250,20 @@ private:
       BackgroundMiningNo = 2,
     };
 
+    enum BackgroundSyncType {
+      BackgroundSyncOff = 0,
+      BackgroundSyncReusePassword = 1,
+      BackgroundSyncCustomPassword = 2,
+    };
+
+    static BackgroundSyncType background_sync_type_from_str(const std::string &background_sync_type_str)
+    {
+      if (background_sync_type_str == "off") return BackgroundSyncOff;
+      if (background_sync_type_str == "reuse-wallet-password") return BackgroundSyncReusePassword;
+      if (background_sync_type_str == "custom-background-password") return BackgroundSyncCustomPassword;
+      throw std::logic_error("Unknown background sync type");
+    };
+
     enum ExportFormat {
       Binary = 0,
       Ascii,
@@ -276,7 +290,12 @@ private:
     //! Just parses variables.
     static std::unique_ptr<wallet2> make_dummy(const boost::program_options::variables_map& vm, bool unattended, const std::function<boost::optional<password_container>(const char *, bool)> &password_prompter);
 
-    static bool verify_password(const std::string& keys_file_name, const epee::wipeable_string& password, bool no_spend_key, hw::device &hwdev, uint64_t kdf_rounds);
+    static bool verify_password(const std::string& keys_file_name, const epee::wipeable_string& password, bool no_spend_key, hw::device &hwdev, uint64_t kdf_rounds)
+    {
+      crypto::secret_key spend_key = crypto::null_skey;
+      return verify_password(keys_file_name, password, no_spend_key, hwdev, kdf_rounds, spend_key);
+    };
+    static bool verify_password(const std::string& keys_file_name, const epee::wipeable_string& password, bool no_spend_key, hw::device &hwdev, uint64_t kdf_rounds, crypto::secret_key &spend_key_out);
     static bool query_device(hw::device::device_type& device_type, const std::string& keys_file_name, const epee::wipeable_string& password, uint64_t kdf_rounds = 1);
 
     wallet2(cryptonote::network_type nettype = cryptonote::MAINNET, uint64_t kdf_rounds = 1, bool unattended = false, std::unique_ptr<epee::net_utils::http::http_client_factory> http_client_factory = std::unique_ptr<epee::net_utils::http::http_client_factory>(new net::http::client_factory()));
@@ -786,6 +805,54 @@ private:
       END_SERIALIZE()
     };
 
+    struct background_synced_tx_t
+    {
+      uint64_t index_in_background_sync_data;
+      cryptonote::transaction tx;
+      std::vector<uint64_t> output_indices;
+      uint64_t height;
+      uint64_t block_timestamp;
+      bool double_spend_seen;
+
+      BEGIN_SERIALIZE_OBJECT()
+        VERSION_FIELD(0)
+        VARINT_FIELD(index_in_background_sync_data)
+
+        // prune tx; don't need to keep signature data
+        if (!tx.serialize_base(ar))
+          return false;
+
+        FIELD(output_indices)
+        VARINT_FIELD(height)
+        VARINT_FIELD(block_timestamp)
+        FIELD(double_spend_seen)
+      END_SERIALIZE()
+    };
+
+    struct background_sync_data_t
+    {
+      bool first_refresh_done = false;
+      uint64_t start_height = 0;
+      std::unordered_map<crypto::hash, background_synced_tx_t> txs;
+
+      // Relevant wallet settings
+      uint64_t wallet_refresh_from_block_height;
+      size_t subaddress_lookahead_major;
+      size_t subaddress_lookahead_minor;
+      RefreshType wallet_refresh_type;
+
+      BEGIN_SERIALIZE_OBJECT()
+        VERSION_FIELD(0)
+        FIELD(first_refresh_done)
+        FIELD(start_height)
+        FIELD(txs)
+        FIELD(wallet_refresh_from_block_height)
+        VARINT_FIELD(subaddress_lookahead_major)
+        VARINT_FIELD(subaddress_lookahead_minor)
+        VARINT_FIELD(wallet_refresh_type)
+      END_SERIALIZE()
+    };
+
     typedef std::tuple<uint64_t, crypto::public_key, rct::key> get_outs_entry;
 
     struct parsed_block
@@ -998,7 +1065,8 @@ private:
     /*!
      * \brief verifies given password is correct for default wallet keys file
      */
-    bool verify_password(const epee::wipeable_string& password);
+    bool verify_password(const epee::wipeable_string& password) {crypto::secret_key key = crypto::null_skey; return verify_password(password, key);};
+    bool verify_password(const epee::wipeable_string& password, crypto::secret_key &spend_key_out);
     cryptonote::account_base& get_account(){return m_account;}
     const cryptonote::account_base& get_account()const{return m_account;}
 
@@ -1085,6 +1153,7 @@ private:
 
     cryptonote::network_type nettype() const { return m_nettype; }
     bool watch_only() const { return m_watch_only; }
+    bool is_background_wallet() const { return m_is_background_wallet; }
     multisig::multisig_account_status get_multisig_status() const;
     bool has_multisig_partial_key_images() const;
     bool has_unknown_key_images() const;
@@ -1294,11 +1363,17 @@ private:
         return;
       }
       a & m_has_ever_refreshed_from_node;
+      if(ver < 31)
+      {
+        m_background_sync_data = background_sync_data_t{};
+        return;
+      }
+      a & m_background_sync_data;
     }
 
     BEGIN_SERIALIZE_OBJECT()
       MAGIC_FIELD("monero wallet cache")
-      VERSION_FIELD(1)
+      VERSION_FIELD(2)
       FIELD(m_blockchain)
       FIELD(m_transfers)
       FIELD(m_account_public_address)
@@ -1331,6 +1406,12 @@ private:
         return true;
       }
       FIELD(m_has_ever_refreshed_from_node)
+      if (version < 2)
+      {
+        m_background_sync_data = background_sync_data_t{};
+        return true;
+      }
+      FIELD(m_background_sync_data)
     END_SERIALIZE()
 
     /*!
@@ -1346,6 +1427,8 @@ private:
      * \return                Whether path is valid format
      */
     static bool wallet_valid_path_format(const std::string& file_path);
+    static std::string make_background_wallet_file_name(const std::string &wallet_file);
+    static std::string make_background_keys_file_name(const std::string &wallet_file);
     static bool parse_long_payment_id(const std::string& payment_id_str, crypto::hash& payment_id);
     static bool parse_short_payment_id(const std::string& payment_id_str, crypto::hash8& payment_id);
     static bool parse_payment_id(const std::string& payment_id_str, crypto::hash& payment_id);
@@ -1392,6 +1475,9 @@ private:
     void ignore_outputs_below(uint64_t value) { m_ignore_outputs_below = value; }
     bool track_uses() const { return m_track_uses; }
     void track_uses(bool value) { m_track_uses = value; }
+    BackgroundSyncType background_sync_type() const { return m_background_sync_type; }
+    void setup_background_sync(BackgroundSyncType background_sync_type, const epee::wipeable_string &wallet_password, const boost::optional<epee::wipeable_string> &background_cache_password);
+    bool is_background_syncing() const { return m_background_syncing; }
     bool show_wallet_name_when_locked() const { return m_show_wallet_name_when_locked; }
     void show_wallet_name_when_locked(bool value) { m_show_wallet_name_when_locked = value; }
     BackgroundMiningSetupType setup_background_mining() const { return m_setup_background_mining; }
@@ -1666,6 +1752,9 @@ private:
     uint64_t get_bytes_sent() const;
     uint64_t get_bytes_received() const;
 
+    void start_background_sync();
+    void stop_background_sync(const epee::wipeable_string &wallet_password, const crypto::secret_key &spend_secret_key = crypto::null_skey);
+
     // MMS -------------------------------------------------------------------------------------------------
     mms::message_store& get_message_store() { return m_message_store; };
     const mms::message_store& get_message_store() const { return m_message_store; };
@@ -1698,6 +1787,9 @@ private:
      * \return                Whether it was successful.
      */
     bool store_keys(const std::string& keys_file_name, const epee::wipeable_string& password, bool watch_only = false);
+    bool store_keys(const std::string& keys_file_name, const crypto::chacha_key& key, bool watch_only = false, bool background_keys_file = false);
+    boost::optional<wallet2::keys_file_data> get_keys_file_data(const crypto::chacha_key& key, bool watch_only = false, bool background_keys_file = false);
+    bool store_keys_file_data(const std::string& keys_file_name, wallet2::keys_file_data &keys_file_data, bool background_keys_file = false);
     /*!
      * \brief Load wallet keys information from wallet file.
      * \param keys_file_name Name of wallet file
@@ -1711,6 +1803,7 @@ private:
      */
     bool load_keys_buf(const std::string& keys_buf, const epee::wipeable_string& password);
     bool load_keys_buf(const std::string& keys_buf, const epee::wipeable_string& password, boost::optional<crypto::chacha_key>& keys_to_encrypt);
+    void load_wallet_cache(const bool use_fs, const std::string& cache_buf = "");
     void process_new_transaction(const crypto::hash &txid, const cryptonote::transaction& tx, const std::vector<uint64_t> &o_indices, uint64_t height, uint8_t block_version, uint64_t ts, bool miner_tx, bool pool, bool double_spend_seen, const tx_cache_data &tx_cache_data, std::map<std::pair<uint64_t, uint64_t>, size_t> *output_tracker_cache = NULL, bool ignore_callbacks = false);
     bool should_skip_block(const cryptonote::block &b, uint64_t height) const;
     void process_new_blockchain_entry(const cryptonote::block& b, const cryptonote::block_complete_entry& bche, const parsed_block &parsed_block, const crypto::hash& bl_id, uint64_t height, const std::vector<tx_cache_data> &tx_cache_data, size_t tx_cache_data_offset, std::map<std::pair<uint64_t, uint64_t>, size_t> *output_tracker_cache = NULL);
@@ -1719,6 +1812,15 @@ private:
     void get_short_chain_history(std::list<crypto::hash>& ids, uint64_t granularity = 1) const;
     bool clear();
     void clear_soft(bool keep_key_images=false);
+    /*
+     * clear_user_data clears data created by the user, which is mostly data
+     * that a view key cannot identify on chain. This function was initially
+     * added to ensure that a "background" wallet (a wallet that syncs with just
+     * a view key hot in memory) does not have any sensitive data loaded that it
+     * does not need in order to sync. Future devs should take care to ensure
+     * that this function deletes data that is not useful for background syncing
+     */
+    void clear_user_data();
     void pull_blocks(bool first, bool try_incremental, uint64_t start_height, uint64_t& blocks_start_height, const std::list<crypto::hash> &short_chain_history, std::vector<cryptonote::block_complete_entry> &blocks, std::vector<cryptonote::COMMAND_RPC_GET_BLOCKS_FAST::block_output_indices> &o_indices, uint64_t &current_height, std::vector<std::tuple<cryptonote::transaction, crypto::hash, bool>>& process_pool_txs);
     void pull_hashes(uint64_t start_height, uint64_t& blocks_start_height, const std::list<crypto::hash> &short_chain_history, std::vector<crypto::hash> &hashes);
     void fast_refresh(uint64_t stop_height, uint64_t &blocks_start_height, std::list<crypto::hash> &short_chain_history, bool force = false);
@@ -1770,10 +1872,23 @@ private:
     bool get_ring(const crypto::chacha_key &key, const crypto::key_image &key_image, std::vector<uint64_t> &outs);
     crypto::chacha_key get_ringdb_key();
     void setup_keys(const epee::wipeable_string &password);
+    const crypto::chacha_key get_cache_key();
+    void verify_password_with_cached_key(const epee::wipeable_string &password);
+    void verify_password_with_cached_key(const crypto::chacha_key &key);
     size_t get_transfer_details(const crypto::key_image &ki) const;
     tx_entry_data get_tx_entries(const std::unordered_set<crypto::hash> &txids);
     void sort_scan_tx_entries(std::vector<process_tx_entry_t> &unsorted_tx_entries);
     void process_scan_txs(const tx_entry_data &txs_to_scan, const tx_entry_data &txs_to_reprocess, const std::unordered_set<crypto::hash> &tx_hashes_to_reprocess, detached_blockchain_data &dbd);
+    void write_background_sync_wallet(const epee::wipeable_string &wallet_password, const epee::wipeable_string &background_cache_password);
+    void process_background_cache_on_open();
+    void process_background_cache(const background_sync_data_t &background_sync_data, const hashchain &background_chain, uint64_t last_block_reward);
+    void reset_background_sync_data(background_sync_data_t &background_sync_data);
+    void store_background_cache(const crypto::chacha_key &custom_background_key, const bool do_reset_background_sync_data = true);
+    void store_background_keys(const crypto::chacha_key &custom_background_key);
+
+    bool lock_background_keys_file(const std::string &background_keys_file);
+    bool unlock_background_keys_file();
+    bool is_background_keys_file_locked() const;
 
     void register_devices();
     hw::device& lookup_device(const std::string & device_descriptor);
@@ -1885,6 +2000,8 @@ private:
     uint64_t m_ignore_outputs_above;
     uint64_t m_ignore_outputs_below;
     bool m_track_uses;
+    bool m_is_background_wallet;
+    BackgroundSyncType m_background_sync_type;
     bool m_show_wallet_name_when_locked;
     uint32_t m_inactivity_lock_timeout;
     BackgroundMiningSetupType m_setup_background_mining;
@@ -1912,6 +2029,7 @@ private:
 
     uint64_t m_last_block_reward;
     std::unique_ptr<tools::file_locker> m_keys_file_locker;
+    std::unique_ptr<tools::file_locker> m_background_keys_file_locker;
     
     mms::message_store m_message_store;
     bool m_original_keys_available;
@@ -1919,6 +2037,7 @@ private:
     crypto::secret_key m_original_view_secret_key;
 
     crypto::chacha_key m_cache_key;
+    boost::optional<crypto::chacha_key> m_custom_background_key = boost::none;
     std::shared_ptr<wallet_keys_unlocker> m_encrypt_keys_after_refresh;
 
     bool m_unattended;
@@ -1934,9 +2053,13 @@ private:
 
     static boost::mutex default_daemon_address_lock;
     static std::string default_daemon_address;
+
+    bool m_background_syncing;
+    bool m_processing_background_cache;
+    background_sync_data_t m_background_sync_data;
   };
 }
-BOOST_CLASS_VERSION(tools::wallet2, 30)
+BOOST_CLASS_VERSION(tools::wallet2, 31)
 BOOST_CLASS_VERSION(tools::wallet2::transfer_details, 12)
 BOOST_CLASS_VERSION(tools::wallet2::multisig_info, 1)
 BOOST_CLASS_VERSION(tools::wallet2::multisig_info::LR, 0)
@@ -1952,6 +2075,8 @@ BOOST_CLASS_VERSION(tools::wallet2::signed_tx_set, 1)
 BOOST_CLASS_VERSION(tools::wallet2::tx_construction_data, 4)
 BOOST_CLASS_VERSION(tools::wallet2::pending_tx, 3)
 BOOST_CLASS_VERSION(tools::wallet2::multisig_sig, 1)
+BOOST_CLASS_VERSION(tools::wallet2::background_synced_tx_t, 0)
+BOOST_CLASS_VERSION(tools::wallet2::background_sync_data_t, 0)
 
 namespace boost
 {
@@ -2450,6 +2575,29 @@ namespace boost
         return;
       a & x.multisig_sigs;
     }
+
+    template <class Archive>
+    inline void serialize(Archive& a, tools::wallet2::background_synced_tx_t &x, const boost::serialization::version_type ver)
+    {
+      a & x.index_in_background_sync_data;
+      a & x.tx;
+      a & x.output_indices;
+      a & x.height;
+      a & x.block_timestamp;
+      a & x.double_spend_seen;
+    }
+
+    template <class Archive>
+    inline void serialize(Archive& a, tools::wallet2::background_sync_data_t &x, const boost::serialization::version_type ver)
+    {
+      a & x.first_refresh_done;
+      a & x.start_height;
+      a & x.txs;
+      a & x.wallet_refresh_from_block_height;
+      a & x.subaddress_lookahead_major;
+      a & x.subaddress_lookahead_minor;
+      a & x.wallet_refresh_type;
+    }
   }
 }
 

src/wallet/wallet_errors.h

@@ -63,6 +63,7 @@ namespace tools
     //       invalid_password
     //       invalid_priority
     //       invalid_multisig_seed
+    //       invalid_spend_key
     //       refresh_error *
     //         acc_outs_lookup_error
     //         block_parse_error
@@ -97,6 +98,9 @@ namespace tools
     //       wallet_files_doesnt_correspond
     //       scan_tx_error *
     //         wont_reprocess_recent_txs_via_untrusted_daemon
+    //       background_sync_error *
+    //         background_wallet_already_open
+    //         background_custom_password_same_as_wallet_password
     //
     // * - class with protected ctor
 
@@ -304,6 +308,16 @@ namespace tools
       std::string to_string() const { return wallet_logic_error::to_string(); }
     };
 
+    struct invalid_spend_key : public wallet_logic_error
+    {
+      explicit invalid_spend_key(std::string&& loc)
+        : wallet_logic_error(std::move(loc), "invalid spend key")
+      {
+      }
+
+      std::string to_string() const { return wallet_logic_error::to_string(); }
+    };
+
     //----------------------------------------------------------------------------------------------------
     struct invalid_pregenerated_random : public wallet_logic_error
     {
@@ -948,6 +962,31 @@ namespace tools
       }
     };
     //----------------------------------------------------------------------------------------------------
+    struct background_sync_error : public wallet_logic_error
+    {
+    protected:
+      explicit background_sync_error(std::string&& loc, const std::string& message)
+        : wallet_logic_error(std::move(loc), message)
+      {
+      }
+    };
+    //----------------------------------------------------------------------------------------------------
+    struct background_wallet_already_open : public background_sync_error
+    {
+      explicit background_wallet_already_open(std::string&& loc, const std::string& background_wallet_file)
+        : background_sync_error(std::move(loc), "background wallet " + background_wallet_file + " is already opened by another wallet program")
+      {
+      }
+    };
+    //----------------------------------------------------------------------------------------------------
+    struct background_custom_password_same_as_wallet_password : public background_sync_error
+    {
+      explicit background_custom_password_same_as_wallet_password(std::string&& loc)
+        : background_sync_error(std::move(loc), "custom background password must be different than wallet password")
+      {
+      }
+    };
+    //----------------------------------------------------------------------------------------------------
 
 #if !defined(_MSC_VER)
 

src/wallet/wallet_rpc_server.cpp

@@ -73,6 +73,54 @@ using namespace epee;
     } \
   } while(0)
 
+#define CHECK_IF_BACKGROUND_SYNCING() \
+  do \
+  { \
+    if (!m_wallet) { return not_open(er); } \
+    if (m_wallet->is_background_wallet()) \
+    { \
+      er.code = WALLET_RPC_ERROR_CODE_IS_BACKGROUND_WALLET; \
+      er.message = "This command is disabled for background wallets."; \
+      return false; \
+    } \
+    if (m_wallet->is_background_syncing()) \
+    { \
+      er.code = WALLET_RPC_ERROR_CODE_IS_BACKGROUND_SYNCING; \
+      er.message = "This command is disabled while background syncing. Stop background syncing to use this command."; \
+      return false; \
+    } \
+  } while(0)
+
+#define PRE_VALIDATE_BACKGROUND_SYNC() \
+  do \
+  { \
+    if (!m_wallet) { return not_open(er); } \
+    if (m_restricted) \
+    { \
+      er.code = WALLET_RPC_ERROR_CODE_DENIED; \
+      er.message = "Command unavailable in restricted mode."; \
+      return false; \
+    } \
+    if (m_wallet->key_on_device()) \
+    { \
+      er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR; \
+      er.message = "Command not supported by HW wallet"; \
+      return false; \
+    } \
+    if (m_wallet->get_multisig_status().multisig_is_active) \
+    { \
+      er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR; \
+      er.message = "Multisig wallet cannot enable background sync"; \
+      return false; \
+    } \
+    if (m_wallet->watch_only()) \
+    { \
+      er.code = WALLET_RPC_ERROR_CODE_WATCH_ONLY; \
+      er.message = "Watch-only wallet cannot enable background sync"; \
+      return false; \
+    } \
+  } while (0)
+
 namespace
 {
   const command_line::arg_descriptor<std::string, true> arg_rpc_bind_port = {"rpc-bind-port", "Sets bind port for server"};
@@ -291,6 +339,9 @@ namespace tools
   {
     if (!m_wallet)
       return;
+    // Background mining can be toggled from the main wallet
+    if (m_wallet->is_background_wallet() || m_wallet->is_background_syncing())
+      return;
 
     tools::wallet2::BackgroundMiningSetupType setup = m_wallet->setup_background_mining();
     if (setup == tools::wallet2::BackgroundMiningNo)
@@ -581,6 +632,7 @@ namespace tools
   bool wallet_rpc_server::on_create_address(const wallet_rpc::COMMAND_RPC_CREATE_ADDRESS::request& req, wallet_rpc::COMMAND_RPC_CREATE_ADDRESS::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       if (req.count < 1 || req.count > 65536) {
@@ -618,6 +670,7 @@ namespace tools
   bool wallet_rpc_server::on_label_address(const wallet_rpc::COMMAND_RPC_LABEL_ADDRESS::request& req, wallet_rpc::COMMAND_RPC_LABEL_ADDRESS::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       m_wallet->set_subaddress_label(req.index, req.label);
@@ -680,6 +733,7 @@ namespace tools
   bool wallet_rpc_server::on_create_account(const wallet_rpc::COMMAND_RPC_CREATE_ACCOUNT::request& req, wallet_rpc::COMMAND_RPC_CREATE_ACCOUNT::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       m_wallet->add_subaddress_account(req.label);
@@ -697,6 +751,7 @@ namespace tools
   bool wallet_rpc_server::on_label_account(const wallet_rpc::COMMAND_RPC_LABEL_ACCOUNT::request& req, wallet_rpc::COMMAND_RPC_LABEL_ACCOUNT::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       m_wallet->set_subaddress_label({req.account_index, 0}, req.label);
@@ -712,6 +767,7 @@ namespace tools
   bool wallet_rpc_server::on_get_account_tags(const wallet_rpc::COMMAND_RPC_GET_ACCOUNT_TAGS::request& req, wallet_rpc::COMMAND_RPC_GET_ACCOUNT_TAGS::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     const std::pair<std::map<std::string, std::string>, std::vector<std::string>> account_tags = m_wallet->get_account_tags();
     for (const std::pair<const std::string, std::string>& p : account_tags.first)
     {
@@ -731,6 +787,7 @@ namespace tools
   bool wallet_rpc_server::on_tag_accounts(const wallet_rpc::COMMAND_RPC_TAG_ACCOUNTS::request& req, wallet_rpc::COMMAND_RPC_TAG_ACCOUNTS::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       m_wallet->set_account_tag(req.accounts, req.tag);
@@ -746,6 +803,7 @@ namespace tools
   bool wallet_rpc_server::on_untag_accounts(const wallet_rpc::COMMAND_RPC_UNTAG_ACCOUNTS::request& req, wallet_rpc::COMMAND_RPC_UNTAG_ACCOUNTS::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       m_wallet->set_account_tag(req.accounts, "");
@@ -761,6 +819,7 @@ namespace tools
   bool wallet_rpc_server::on_set_account_tag_description(const wallet_rpc::COMMAND_RPC_SET_ACCOUNT_TAG_DESCRIPTION::request& req, wallet_rpc::COMMAND_RPC_SET_ACCOUNT_TAG_DESCRIPTION::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       m_wallet->set_account_tag_description(req.tag, req.description);
@@ -791,6 +850,7 @@ namespace tools
   bool wallet_rpc_server::on_freeze(const wallet_rpc::COMMAND_RPC_FREEZE::request& req, wallet_rpc::COMMAND_RPC_FREEZE::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       if (req.key_image.empty())
@@ -819,6 +879,7 @@ namespace tools
   bool wallet_rpc_server::on_thaw(const wallet_rpc::COMMAND_RPC_THAW::request& req, wallet_rpc::COMMAND_RPC_THAW::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       if (req.key_image.empty())
@@ -847,6 +908,7 @@ namespace tools
   bool wallet_rpc_server::on_frozen(const wallet_rpc::COMMAND_RPC_FROZEN::request& req, wallet_rpc::COMMAND_RPC_FROZEN::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       if (req.key_image.empty())
@@ -874,6 +936,8 @@ namespace tools
   //------------------------------------------------------------------------------------------------------------------------------
   bool wallet_rpc_server::validate_transfer(const std::list<wallet_rpc::transfer_destination>& destinations, const std::string& payment_id, std::vector<cryptonote::tx_destination_entry>& dsts, std::vector<uint8_t>& extra, bool at_least_one_destination, epee::json_rpc::error& er)
   {
+    CHECK_IF_BACKGROUND_SYNCING();
+
     crypto::hash8 integrated_payment_id = crypto::null_hash8;
     std::string extra_nonce;
     for (auto it = destinations.begin(); it != destinations.end(); it++)
@@ -1203,6 +1267,7 @@ namespace tools
     }
 
     CHECK_MULTISIG_ENABLED();
+    CHECK_IF_BACKGROUND_SYNCING();
 
     cryptonote::blobdata blob;
     if (!epee::string_tools::parse_hexstr_to_binbuff(req.unsigned_txset, blob))
@@ -1284,6 +1349,7 @@ namespace tools
       er.message = "command not supported by watch-only wallet";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
     if(req.unsigned_txset.empty() && req.multisig_txset.empty())
     {
       er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR;
@@ -1553,6 +1619,7 @@ namespace tools
     }
 
     CHECK_MULTISIG_ENABLED();
+    CHECK_IF_BACKGROUND_SYNCING();
 
     try
     {
@@ -2115,6 +2182,7 @@ namespace tools
             er.message = "The wallet is watch-only. Cannot retrieve seed.";
             return false;
           }
+          CHECK_IF_BACKGROUND_SYNCING();
           if (!m_wallet->is_deterministic())
           {
             er.code = WALLET_RPC_ERROR_CODE_NON_DETERMINISTIC;
@@ -2143,6 +2211,7 @@ namespace tools
             er.message = "The wallet is watch-only. Cannot retrieve spend key.";
             return false;
           }
+          CHECK_IF_BACKGROUND_SYNCING();
           epee::wipeable_string key = epee::to_hex::wipeable_string(m_wallet->get_account().get_keys().m_spend_secret_key);
           res.key = std::string(key.data(), key.size());
       }
@@ -2164,6 +2233,7 @@ namespace tools
       er.message = "Command unavailable in restricted mode.";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
 
     try
     {
@@ -2177,6 +2247,79 @@ namespace tools
     return true;
   }
   //------------------------------------------------------------------------------------------------------------------------------
+  bool wallet_rpc_server::on_setup_background_sync(const wallet_rpc::COMMAND_RPC_SETUP_BACKGROUND_SYNC::request& req, wallet_rpc::COMMAND_RPC_SETUP_BACKGROUND_SYNC::response& res, epee::json_rpc::error& er, const connection_context *ctx)
+  {
+    try
+    {
+      PRE_VALIDATE_BACKGROUND_SYNC();
+      const tools::wallet2::BackgroundSyncType background_sync_type = tools::wallet2::background_sync_type_from_str(req.background_sync_type);
+      boost::optional<epee::wipeable_string> background_cache_password = boost::none;
+      if (background_sync_type == tools::wallet2::BackgroundSyncCustomPassword)
+        background_cache_password = boost::optional<epee::wipeable_string>(req.background_cache_password);
+      m_wallet->setup_background_sync(background_sync_type, req.wallet_password, background_cache_password);
+    }
+    catch (...)
+    {
+      handle_rpc_exception(std::current_exception(), er, WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR);
+      return false;
+    }
+    return true;
+  }
+  //------------------------------------------------------------------------------------------------------------------------------
+  bool wallet_rpc_server::on_start_background_sync(const wallet_rpc::COMMAND_RPC_START_BACKGROUND_SYNC::request& req, wallet_rpc::COMMAND_RPC_START_BACKGROUND_SYNC::response& res, epee::json_rpc::error& er, const connection_context *ctx)
+  {
+    try
+    {
+      PRE_VALIDATE_BACKGROUND_SYNC();
+      m_wallet->start_background_sync();
+    }
+    catch (...)
+    {
+      handle_rpc_exception(std::current_exception(), er, WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR);
+      return false;
+    }
+    return true;
+  }
+  //------------------------------------------------------------------------------------------------------------------------------
+  bool wallet_rpc_server::on_stop_background_sync(const wallet_rpc::COMMAND_RPC_STOP_BACKGROUND_SYNC::request& req, wallet_rpc::COMMAND_RPC_STOP_BACKGROUND_SYNC::response& res, epee::json_rpc::error& er, const connection_context *ctx)
+  {
+    try
+    {
+      PRE_VALIDATE_BACKGROUND_SYNC();
+      crypto::secret_key spend_secret_key = crypto::null_skey;
+
+      // Load the spend key from seed if seed is provided
+      if (!req.seed.empty())
+      {
+        crypto::secret_key recovery_key;
+        std::string language;
+
+        if (!crypto::ElectrumWords::words_to_bytes(req.seed, recovery_key, language))
+        {
+          er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR;
+          er.message = "Electrum-style word list failed verification";
+          return false;
+        }
+
+        if (!req.seed_offset.empty())
+          recovery_key = cryptonote::decrypt_key(recovery_key, req.seed_offset);
+
+        // generate spend key
+        cryptonote::account_base account;
+        account.generate(recovery_key, true, false);
+        spend_secret_key = account.get_keys().m_spend_secret_key;
+      }
+
+      m_wallet->stop_background_sync(req.wallet_password, spend_secret_key);
+    }
+    catch (...)
+    {
+      handle_rpc_exception(std::current_exception(), er, WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR);
+      return false;
+    }
+    return true;
+  }
+  //------------------------------------------------------------------------------------------------------------------------------
   bool wallet_rpc_server::on_sign(const wallet_rpc::COMMAND_RPC_SIGN::request& req, wallet_rpc::COMMAND_RPC_SIGN::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
@@ -2186,6 +2329,7 @@ namespace tools
       er.message = "Command unavailable in restricted mode.";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
 
     tools::wallet2::message_signature_type_t signature_type = tools::wallet2::sign_with_spend_key;
     if (req.signature_type == "spend" || req.signature_type == "")
@@ -2278,6 +2422,7 @@ namespace tools
       er.message = "Command unavailable in restricted mode.";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
 
     if (req.txids.size() != req.notes.size())
     {
@@ -2350,6 +2495,7 @@ namespace tools
       er.message = "Command unavailable in restricted mode.";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
 
     m_wallet->set_attribute(req.key, req.value);
 
@@ -2377,6 +2523,7 @@ namespace tools
   bool wallet_rpc_server::on_get_tx_key(const wallet_rpc::COMMAND_RPC_GET_TX_KEY::request& req, wallet_rpc::COMMAND_RPC_GET_TX_KEY::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
 
     crypto::hash txid;
     if (!epee::string_tools::hex_to_pod(req.txid, txid))
@@ -2468,6 +2615,7 @@ namespace tools
   bool wallet_rpc_server::on_get_tx_proof(const wallet_rpc::COMMAND_RPC_GET_TX_PROOF::request& req, wallet_rpc::COMMAND_RPC_GET_TX_PROOF::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
 
     crypto::hash txid;
     if (!epee::string_tools::hex_to_pod(req.txid, txid))
@@ -2584,6 +2732,7 @@ namespace tools
   bool wallet_rpc_server::on_get_reserve_proof(const wallet_rpc::COMMAND_RPC_GET_RESERVE_PROOF::request& req, wallet_rpc::COMMAND_RPC_GET_RESERVE_PROOF::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
 
     boost::optional<std::pair<uint32_t, uint64_t>> account_minreserve;
     if (!req.all)
@@ -2826,6 +2975,7 @@ namespace tools
       er.message = "command not supported by HW wallet";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
 
     try
     {
@@ -2855,6 +3005,7 @@ namespace tools
       er.message = "command not supported by HW wallet";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
 
     cryptonote::blobdata blob;
     if (!epee::string_tools::parse_hexstr_to_binbuff(req.outputs_data_hex, blob))
@@ -2880,6 +3031,7 @@ namespace tools
   bool wallet_rpc_server::on_export_key_images(const wallet_rpc::COMMAND_RPC_EXPORT_KEY_IMAGES::request& req, wallet_rpc::COMMAND_RPC_EXPORT_KEY_IMAGES::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       std::pair<uint64_t, std::vector<std::pair<crypto::key_image, crypto::signature>>> ski = m_wallet->export_key_images(req.all);
@@ -2916,6 +3068,7 @@ namespace tools
       er.message = "This command requires a trusted daemon.";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       std::vector<std::pair<crypto::key_image, crypto::signature>> ski;
@@ -2984,6 +3137,7 @@ namespace tools
   bool wallet_rpc_server::on_get_address_book(const wallet_rpc::COMMAND_RPC_GET_ADDRESS_BOOK_ENTRY::request& req, wallet_rpc::COMMAND_RPC_GET_ADDRESS_BOOK_ENTRY::response& res, epee::json_rpc::error& er, const connection_context *ctx)
   {
     if (!m_wallet) return not_open(er);
+    CHECK_IF_BACKGROUND_SYNCING();
     const auto ab = m_wallet->get_address_book();
     if (req.entries.empty())
     {
@@ -3029,6 +3183,7 @@ namespace tools
       er.message = "Command unavailable in restricted mode.";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
 
     cryptonote::address_parse_info info;
     er.message = "";
@@ -3071,6 +3226,7 @@ namespace tools
       er.message = "Command unavailable in restricted mode.";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
 
     const auto ab = m_wallet->get_address_book();
     if (req.index >= ab.size())
@@ -3133,6 +3289,7 @@ namespace tools
       er.message = "Command unavailable in restricted mode.";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
 
     const auto ab = m_wallet->get_address_book();
     if (req.index >= ab.size())
@@ -3203,6 +3360,7 @@ namespace tools
           er.message = "Command unavailable in restricted mode.";
           return false;
       }
+      CHECK_IF_BACKGROUND_SYNCING();
 
       std::unordered_set<crypto::hash> txids;
       std::list<std::string>::const_iterator i = req.txids.begin();
@@ -3242,6 +3400,7 @@ namespace tools
       er.message = "Command unavailable in restricted mode.";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
     try
     {
       m_wallet->rescan_spent();
@@ -3506,6 +3665,7 @@ namespace tools
       er.message = "Command unavailable in restricted mode.";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
     if (m_wallet->verify_password(req.old_password))
     {
       try
@@ -4039,6 +4199,7 @@ namespace tools
       er.message = "wallet is watch-only and cannot be made multisig";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
 
     res.multisig_info = m_wallet->get_multisig_first_kex_msg();
     return true;
@@ -4066,6 +4227,7 @@ namespace tools
       er.message = "wallet is watch-only and cannot be made multisig";
       return false;
     }
+    CHECK_IF_BACKGROUND_SYNCING();
 
     try
     {

src/wallet/wallet_rpc_server.h

@@ -160,6 +160,9 @@ namespace tools
         MAP_JON_RPC_WE("set_log_categories", on_set_log_categories, wallet_rpc::COMMAND_RPC_SET_LOG_CATEGORIES)
         MAP_JON_RPC_WE("estimate_tx_size_and_weight", on_estimate_tx_size_and_weight, wallet_rpc::COMMAND_RPC_ESTIMATE_TX_SIZE_AND_WEIGHT)
         MAP_JON_RPC_WE("get_version",        on_get_version,        wallet_rpc::COMMAND_RPC_GET_VERSION)
+        MAP_JON_RPC_WE("setup_background_sync", on_setup_background_sync, wallet_rpc::COMMAND_RPC_SETUP_BACKGROUND_SYNC)
+        MAP_JON_RPC_WE("start_background_sync", on_start_background_sync, wallet_rpc::COMMAND_RPC_START_BACKGROUND_SYNC)
+        MAP_JON_RPC_WE("stop_background_sync", on_stop_background_sync, wallet_rpc::COMMAND_RPC_STOP_BACKGROUND_SYNC)
       END_JSON_RPC_MAP()
     END_URI_MAP2()
 
@@ -252,6 +255,9 @@ namespace tools
       bool on_set_log_categories(const wallet_rpc::COMMAND_RPC_SET_LOG_CATEGORIES::request& req, wallet_rpc::COMMAND_RPC_SET_LOG_CATEGORIES::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
       bool on_estimate_tx_size_and_weight(const wallet_rpc::COMMAND_RPC_ESTIMATE_TX_SIZE_AND_WEIGHT::request& req, wallet_rpc::COMMAND_RPC_ESTIMATE_TX_SIZE_AND_WEIGHT::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
       bool on_get_version(const wallet_rpc::COMMAND_RPC_GET_VERSION::request& req, wallet_rpc::COMMAND_RPC_GET_VERSION::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
+      bool on_setup_background_sync(const wallet_rpc::COMMAND_RPC_SETUP_BACKGROUND_SYNC::request& req, wallet_rpc::COMMAND_RPC_SETUP_BACKGROUND_SYNC::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
+      bool on_start_background_sync(const wallet_rpc::COMMAND_RPC_START_BACKGROUND_SYNC::request& req, wallet_rpc::COMMAND_RPC_START_BACKGROUND_SYNC::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
+      bool on_stop_background_sync(const wallet_rpc::COMMAND_RPC_STOP_BACKGROUND_SYNC::request& req, wallet_rpc::COMMAND_RPC_STOP_BACKGROUND_SYNC::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);
 
       //json rpc v2
       bool on_query_key(const wallet_rpc::COMMAND_RPC_QUERY_KEY::request& req, wallet_rpc::COMMAND_RPC_QUERY_KEY::response& res, epee::json_rpc::error& er, const connection_context *ctx = NULL);

src/wallet/wallet_rpc_server_commands_defs.h

@@ -2729,5 +2729,69 @@ namespace wallet_rpc
     typedef epee::misc_utils::struct_init<response_t> response;
   };
 
+  struct COMMAND_RPC_SETUP_BACKGROUND_SYNC
+  {
+    struct request_t
+    {
+      std::string background_sync_type;
+      std::string wallet_password;
+      std::string background_cache_password;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(background_sync_type)
+        KV_SERIALIZE(wallet_password)
+        KV_SERIALIZE_OPT(background_cache_password, (std::string)"")
+      END_KV_SERIALIZE_MAP()
+    };
+    typedef epee::misc_utils::struct_init<request_t> request;
+
+    struct response_t
+    {
+      BEGIN_KV_SERIALIZE_MAP()
+      END_KV_SERIALIZE_MAP()
+    };
+    typedef epee::misc_utils::struct_init<response_t> response;
+  };
+
+  struct COMMAND_RPC_START_BACKGROUND_SYNC
+  {
+    struct request_t
+    {
+      BEGIN_KV_SERIALIZE_MAP()
+      END_KV_SERIALIZE_MAP()
+    };
+    typedef epee::misc_utils::struct_init<request_t> request;
+
+    struct response_t
+    {
+      BEGIN_KV_SERIALIZE_MAP()
+      END_KV_SERIALIZE_MAP()
+    };
+    typedef epee::misc_utils::struct_init<response_t> response;
+  };
+
+  struct COMMAND_RPC_STOP_BACKGROUND_SYNC
+  {
+    struct request_t
+    {
+      std::string wallet_password;
+      std::string seed;
+      std::string seed_offset;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(wallet_password)
+        KV_SERIALIZE_OPT(seed, (std::string)"")
+        KV_SERIALIZE_OPT(seed_offset, (std::string)"")
+      END_KV_SERIALIZE_MAP()
+    };
+    typedef epee::misc_utils::struct_init<request_t> request;
+
+    struct response_t
+    {
+      BEGIN_KV_SERIALIZE_MAP()
+      END_KV_SERIALIZE_MAP()
+    };
+    typedef epee::misc_utils::struct_init<response_t> response;
+  };
 }
 }

src/wallet/wallet_rpc_server_error_codes.h

@@ -81,3 +81,5 @@
 #define WALLET_RPC_ERROR_CODE_DISABLED               -48
 #define WALLET_RPC_ERROR_CODE_PROXY_ALREADY_DEFINED  -49
 #define WALLET_RPC_ERROR_CODE_NONZERO_UNLOCK_TIME    -50
+#define WALLET_RPC_ERROR_CODE_IS_BACKGROUND_WALLET   -51
+#define WALLET_RPC_ERROR_CODE_IS_BACKGROUND_SYNCING  -52

tests/functional_tests/transfer.py

@@ -30,6 +30,7 @@
 
 from __future__ import print_function
 import json
+import util_resources
 import pprint
 from deepdiff import DeepDiff
 pp = pprint.PrettyPrinter(indent=2)
@@ -46,6 +47,17 @@ seeds = [
     'dilute gutter certain antics pamphlet macro enjoy left slid guarded bogeys upload nineteen bomb jubilee enhanced irritate turnip eggs swung jukebox loudly reduce sedan slid',
 ]
 
+def diff_transfers(actual_transfers, expected_transfers, ignore_order = True):
+    # The payments containers aren't ordered; re-scanning can lead to diff orders
+    diff = DeepDiff(actual_transfers, expected_transfers, ignore_order = ignore_order)
+    if diff != {}:
+        pp.pprint(diff)
+    assert diff == {}
+
+def diff_incoming_transfers(actual_transfers, expected_transfers):
+    # wallet2 m_transfers container is ordered and order should be the same across rescans
+    diff_transfers(actual_transfers, expected_transfers, ignore_order = False)
+
 class TransferTest():
     def run_test(self):
         self.reset()
@@ -64,6 +76,8 @@ class TransferTest():
         self.check_multiple_submissions()
         self.check_scan_tx()
         self.check_subtract_fee_from_outputs()
+        self.check_background_sync()
+        self.check_background_sync_reorg_recovery()
 
     def reset(self):
         print('Resetting blockchain')
@@ -875,12 +889,6 @@ class TransferTest():
 
         print('Testing scan_tx')
 
-        def diff_transfers(actual_transfers, expected_transfers):
-            diff = DeepDiff(actual_transfers, expected_transfers)
-            if diff != {}:
-                pp.pprint(diff)
-            assert diff == {}
-
         # set up sender_wallet
         sender_wallet = self.wallet[0]
         try: sender_wallet.close_wallet()
@@ -1162,5 +1170,385 @@ class TransferTest():
         except AssertionError:
             pass
 
+    def check_background_sync(self):
+        daemon = Daemon()
+
+        print('Testing background sync')
+
+        # Some helper functions
+        def stop_with_wrong_inputs(wallet, wallet_password, seed = ''):
+            invalid = False
+            try: wallet.stop_background_sync(wallet_password = wallet_password, seed = seed)
+            except: invalid = True
+            assert invalid
+
+        def open_with_wrong_password(wallet, filename, password):
+            invalid_password = False
+            try: wallet.open_wallet(filename, password = password)
+            except: invalid_password = True
+            assert invalid_password
+
+        def restore_wallet(wallet, seed, filename = '', password = ''):
+            wallet.close_wallet()
+            if filename != '':
+                util_resources.remove_wallet_files(filename)
+            wallet.restore_deterministic_wallet(seed = seed, filename = filename, password = password)
+            wallet.auto_refresh(enable = False)
+            assert wallet.get_transfers() == {}
+
+        def assert_correct_transfers(wallet, expected_transfers, expected_inc_transfers, expected_balance):
+            diff_transfers(wallet.get_transfers(), expected_transfers)
+            diff_incoming_transfers(wallet.incoming_transfers(transfer_type = 'all'), expected_inc_transfers)
+            assert wallet.get_balance().balance == expected_balance
+
+        # Set up sender_wallet. Prepare to sweep single output to receiver.
+        # We're testing a sweep because it makes sure background sync can
+        # properly pick up txs which do not have a change output back to sender.
+        sender_wallet = self.wallet[0]
+        try: sender_wallet.close_wallet()
+        except: pass
+        sender_wallet.restore_deterministic_wallet(seed = seeds[0])
+        sender_wallet.auto_refresh(enable = False)
+        sender_wallet.refresh()
+        res = sender_wallet.incoming_transfers(transfer_type = 'available')
+        unlocked = [x for x in res.transfers if x.unlocked and x.amount > 0]
+        assert len(unlocked) > 0
+        ki = unlocked[0].key_image
+        amount = unlocked[0].amount
+        spent_txid = unlocked[0].tx_hash
+        sender_wallet.refresh()
+        res = sender_wallet.get_transfers()
+        out_len = 0 if 'out' not in res else len(res.out)
+        sender_starting_balance = sender_wallet.get_balance().balance
+
+        # Background sync type options
+        reuse_password = sender_wallet.background_sync_options.reuse_password
+        custom_password = sender_wallet.background_sync_options.custom_password
+
+        # set up receiver_wallet
+        receiver_wallet = self.wallet[1]
+        try: receiver_wallet.close_wallet()
+        except: pass
+        receiver_wallet.restore_deterministic_wallet(seed = seeds[1])
+        receiver_wallet.auto_refresh(enable = False)
+        receiver_wallet.refresh()
+        res = receiver_wallet.get_transfers()
+        in_len = 0 if 'in' not in res else len(res['in'])
+        receiver_starting_balance = receiver_wallet.get_balance().balance
+
+        # transfer from sender_wallet to receiver_wallet
+        dst = '44Kbx4sJ7JDRDV5aAhLJzQCjDz2ViLRduE3ijDZu3osWKBjMGkV1XPk4pfDUMqt1Aiezvephdqm6YD19GKFD9ZcXVUTp6BW'
+        res = sender_wallet.sweep_single(dst, key_image = ki)
+        assert len(res.tx_hash) == 32*2
+        txid = res.tx_hash
+        assert res.fee > 0
+        fee = res.fee
+        assert res.amount == amount - fee
+
+        expected_sender_balance = sender_starting_balance - amount
+        expected_receiver_balance = receiver_starting_balance + (amount - fee)
+
+        print('Checking background sync on outgoing wallet')
+        sender_wallet.setup_background_sync(background_sync_type = reuse_password)
+        sender_wallet.start_background_sync()
+        # Mine block to an uninvolved wallet
+        daemon.generateblocks('46r4nYSevkfBUMhuykdK3gQ98XDqDTYW1hNLaXNvjpsJaSbNtdXh1sKMsdVgqkaihChAzEy29zEDPMR3NHQvGoZCLGwTerK', 1)
+        # sender should still be able to scan the transfer normally because we
+        # spent an output that had a known key image
+        sender_wallet.refresh()
+        transfers = sender_wallet.get_transfers()
+        assert 'pending' not in transfers or len(transfers.pending) == 0
+        assert 'pool' not in transfers or len (transfers.pool) == 0
+        assert len(transfers.out) == out_len + 1
+        tx = [x for x in transfers.out if x.txid == txid]
+        assert len(tx) == 1
+        tx = tx[0]
+        assert tx.amount == amount - fee
+        assert tx.fee == fee
+        assert len(tx.destinations) == 1
+        assert tx.destinations[0].amount == amount - fee
+        assert tx.destinations[0].address == dst
+        incoming_transfers = sender_wallet.incoming_transfers(transfer_type = 'all')
+        assert len([x for x in incoming_transfers.transfers if x.tx_hash == spent_txid and x.key_image == ki and x.spent]) == 1
+        assert sender_wallet.get_balance().balance == expected_sender_balance
+
+        # Restore and check background syncing outgoing wallet
+        restore_wallet(sender_wallet, seeds[0])
+        sender_wallet.setup_background_sync(background_sync_type = reuse_password)
+        sender_wallet.start_background_sync()
+        sender_wallet.refresh()
+        for i, out_tx in enumerate(transfers.out):
+            if 'destinations' in out_tx:
+                del transfers.out[i]['destinations'] # destinations are not expected after wallet restore
+        # sender's balance should be higher because can't detect spends while
+        # background sync enabled, only receives
+        background_bal = sender_wallet.get_balance().balance
+        assert background_bal > expected_sender_balance
+        background_transfers = sender_wallet.get_transfers()
+        assert 'out' not in background_transfers or len(background_transfers.out) == 0
+        assert 'in' in background_transfers and len(background_transfers['in']) > 0
+        background_incoming_transfers = sender_wallet.incoming_transfers(transfer_type = 'all')
+        assert len(background_incoming_transfers) == len(incoming_transfers)
+        assert len([x for x in background_incoming_transfers.transfers if x.spent or x.key_image != '']) == 0
+        assert len([x for x in background_incoming_transfers.transfers if x.tx_hash == spent_txid]) == 1
+
+        # Try to stop background sync with the wrong seed
+        stop_with_wrong_inputs(sender_wallet, wallet_password = '', seed = seeds[1])
+
+        # Stop background sync and check transfers update correctly
+        sender_wallet.stop_background_sync(wallet_password = '', seed = seeds[0])
+        assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
+
+        # Check stopping a wallet with wallet files saved to disk
+        for background_sync_type in [reuse_password, custom_password]:
+            restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
+            background_cache_password = None if background_sync_type == reuse_password else 'background_password'
+            sender_wallet.setup_background_sync(background_sync_type = background_sync_type, wallet_password = 'test_password', background_cache_password = background_cache_password)
+            sender_wallet.start_background_sync()
+            sender_wallet.refresh()
+            assert_correct_transfers(sender_wallet, background_transfers, background_incoming_transfers, background_bal)
+            stop_with_wrong_inputs(sender_wallet, 'wrong_password')
+            sender_wallet.stop_background_sync(wallet_password = 'test_password')
+            assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
+
+        # Close wallet while background syncing, then reopen
+        for background_sync_type in [reuse_password, custom_password]:
+            restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
+            background_cache_password = None if background_sync_type == reuse_password else 'background_password'
+            sender_wallet.setup_background_sync(background_sync_type = background_sync_type, wallet_password = 'test_password', background_cache_password = background_cache_password)
+            sender_wallet.start_background_sync()
+            sender_wallet.refresh()
+            assert_correct_transfers(sender_wallet, background_transfers, background_incoming_transfers, background_bal)
+            sender_wallet.close_wallet()
+            open_with_wrong_password(sender_wallet, 'test1', 'wrong_password')
+            sender_wallet.open_wallet('test1', password = 'test_password')
+            # It should reopen with spend key loaded and correctly scan all transfers
+            assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
+
+        # Close wallet while syncing normally, then reopen
+        for background_sync_type in [reuse_password, custom_password]:
+            restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
+            background_cache_password = None if background_sync_type == reuse_password else 'background_password'
+            sender_wallet.setup_background_sync(background_sync_type = background_sync_type, wallet_password = 'test_password', background_cache_password = background_cache_password)
+            sender_wallet.refresh()
+            assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
+            sender_wallet.close_wallet()
+            open_with_wrong_password(sender_wallet, 'test1', 'wrong_password')
+            sender_wallet.open_wallet('test1', password = 'test_password')
+            assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
+
+        # Create background cache using custom password, then use it to sync, then reopen main wallet
+        for background_cache_password in ['background_password', '']:
+            restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
+            assert not util_resources.file_exists('test1.background')
+            assert not util_resources.file_exists('test1.background.keys')
+            sender_wallet.setup_background_sync(background_sync_type = custom_password, wallet_password = 'test_password', background_cache_password = background_cache_password)
+            assert util_resources.file_exists('test1.background')
+            assert util_resources.file_exists('test1.background.keys')
+            sender_wallet.close_wallet()
+            open_with_wrong_password(sender_wallet, 'test1.background', 'test_password')
+            sender_wallet.open_wallet('test1.background', password = background_cache_password)
+            sender_wallet.refresh()
+            assert_correct_transfers(sender_wallet, background_transfers, background_incoming_transfers, background_bal)
+            sender_wallet.close_wallet()
+            sender_wallet.open_wallet('test1', password = 'test_password')
+            assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
+
+        # Check that main wallet keeps background cache encrypted with custom password in sync
+        restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
+        sender_wallet.setup_background_sync(background_sync_type = background_sync_type, wallet_password = 'test_password', background_cache_password = 'background_password')
+        sender_wallet.refresh()
+        assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
+        sender_wallet.close_wallet()
+        sender_wallet.open_wallet('test1.background', password = 'background_password')
+        assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
+
+        # Try using wallet password as custom background password
+        restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
+        assert not util_resources.file_exists('test1.background')
+        assert not util_resources.file_exists('test1.background.keys')
+        same_password = False
+        try: sender_wallet.setup_background_sync(background_sync_type = custom_password, wallet_password = 'test_password', background_cache_password = 'test_password')
+        except: same_password = True
+        assert same_password
+        assert not util_resources.file_exists('test1.background')
+        assert not util_resources.file_exists('test1.background.keys')
+
+        # Turn off background sync
+        for background_sync_type in [reuse_password, custom_password]:
+            restore_wallet(sender_wallet, seeds[0], 'test1', 'test_password')
+            background_cache_password = None if background_sync_type == reuse_password else 'background_password'
+            sender_wallet.setup_background_sync(background_sync_type = background_sync_type, wallet_password = 'test_password', background_cache_password = background_cache_password)
+            if background_sync_type == custom_password:
+                assert util_resources.file_exists('test1.background')
+                assert util_resources.file_exists('test1.background.keys')
+                sender_wallet.close_wallet()
+                assert util_resources.file_exists('test1.background')
+                assert util_resources.file_exists('test1.background.keys')
+            else:
+                assert not util_resources.file_exists('test1.background')
+                assert not util_resources.file_exists('test1.background.keys')
+                sender_wallet.close_wallet()
+                assert not util_resources.file_exists('test1.background')
+                assert not util_resources.file_exists('test1.background.keys')
+            sender_wallet.open_wallet('test1', password = 'test_password')
+            sender_wallet.setup_background_sync(background_sync_type = sender_wallet.background_sync_options.off, wallet_password = 'test_password')
+            assert not util_resources.file_exists('test1.background')
+            assert not util_resources.file_exists('test1.background.keys')
+            sender_wallet.close_wallet()
+            assert not util_resources.file_exists('test1.background')
+            assert not util_resources.file_exists('test1.background.keys')
+            sender_wallet.open_wallet('test1', password = 'test_password')
+
+        # Sanity check against outgoing wallet restored at height 0
+        sender_wallet.close_wallet()
+        sender_wallet.restore_deterministic_wallet(seed = seeds[0], restore_height = 0)
+        sender_wallet.refresh()
+        assert_correct_transfers(sender_wallet, transfers, incoming_transfers, expected_sender_balance)
+
+        print('Checking background sync on incoming wallet')
+        receiver_wallet.setup_background_sync(background_sync_type = reuse_password)
+        receiver_wallet.start_background_sync()
+        receiver_wallet.refresh()
+        transfers = receiver_wallet.get_transfers()
+        assert 'pending' not in transfers or len(transfers.pending) == 0
+        assert 'pool' not in transfers or len (transfers.pool) == 0
+        assert len(transfers['in']) == in_len + 1
+        tx = [x for x in transfers['in'] if x.txid == txid]
+        assert len(tx) == 1
+        tx = tx[0]
+        assert tx.amount == amount - fee
+        assert tx.fee == fee
+        incoming_transfers = receiver_wallet.incoming_transfers(transfer_type = 'all')
+        assert len([x for x in incoming_transfers.transfers if x.tx_hash == txid and x.key_image == '' and not x.spent]) == 1
+        assert receiver_wallet.get_balance().balance == expected_receiver_balance
+
+        # Restore and check background syncing incoming wallet
+        restore_wallet(receiver_wallet, seeds[1])
+        receiver_wallet.setup_background_sync(background_sync_type = reuse_password)
+        receiver_wallet.start_background_sync()
+        receiver_wallet.refresh()
+        if 'out' in transfers:
+            for i, out_tx in enumerate(transfers.out):
+                if 'destinations' in out_tx:
+                    del transfers.out[i]['destinations'] # destinations are not expected after wallet restore
+        background_bal = receiver_wallet.get_balance().balance
+        assert background_bal >= expected_receiver_balance
+        background_transfers = receiver_wallet.get_transfers()
+        assert 'out' not in background_transfers or len(background_transfers.out) == 0
+        assert 'in' in background_transfers and len(background_transfers['in']) > 0
+        background_incoming_transfers = receiver_wallet.incoming_transfers(transfer_type = 'all')
+        assert len(background_incoming_transfers) == len(incoming_transfers)
+        assert len([x for x in background_incoming_transfers.transfers if x.spent or x.key_image != '']) == 0
+        assert len([x for x in background_incoming_transfers.transfers if x.tx_hash == txid]) == 1
+
+        # Stop background sync and check transfers update correctly
+        receiver_wallet.stop_background_sync(wallet_password = '', seed = seeds[1])
+        diff_transfers(receiver_wallet.get_transfers(), transfers)
+        incoming_transfers = receiver_wallet.incoming_transfers(transfer_type = 'all')
+        assert len(background_incoming_transfers) == len(incoming_transfers)
+        assert len([x for x in incoming_transfers.transfers if x.tx_hash == txid and x.key_image != '' and not x.spent]) == 1
+        assert receiver_wallet.get_balance().balance == expected_receiver_balance
+
+        # Check a fresh incoming wallet with wallet files saved to disk and encrypted with password
+        restore_wallet(receiver_wallet, seeds[1], 'test2', 'test_password')
+        receiver_wallet.setup_background_sync(background_sync_type = reuse_password, wallet_password = 'test_password')
+        receiver_wallet.start_background_sync()
+        receiver_wallet.refresh()
+        assert_correct_transfers(receiver_wallet, background_transfers, background_incoming_transfers, background_bal)
+        stop_with_wrong_inputs(receiver_wallet, 'wrong_password')
+        receiver_wallet.stop_background_sync(wallet_password = 'test_password')
+        assert_correct_transfers(receiver_wallet, transfers, incoming_transfers, expected_receiver_balance)
+
+        # Close receiver's wallet while background sync is enabled then reopen
+        restore_wallet(receiver_wallet, seeds[1], 'test2', 'test_password')
+        receiver_wallet.setup_background_sync(background_sync_type = reuse_password, wallet_password = 'test_password')
+        receiver_wallet.start_background_sync()
+        receiver_wallet.refresh()
+        diff_transfers(receiver_wallet.get_transfers(), background_transfers)
+        diff_incoming_transfers(receiver_wallet.incoming_transfers(transfer_type = 'all'), background_incoming_transfers)
+        assert receiver_wallet.get_balance().balance == background_bal
+        receiver_wallet.close_wallet()
+        receiver_wallet.open_wallet('test2', password = 'test_password')
+        # It should reopen with spend key loaded and correctly scan all transfers
+        assert_correct_transfers(receiver_wallet, transfers, incoming_transfers, expected_receiver_balance)
+
+        # Sanity check against incoming wallet restored at height 0
+        receiver_wallet.close_wallet()
+        receiver_wallet.restore_deterministic_wallet(seed = seeds[1], restore_height = 0)
+        receiver_wallet.refresh()
+        assert_correct_transfers(receiver_wallet, transfers, incoming_transfers, expected_receiver_balance)
+
+        # Clean up
+        util_resources.remove_wallet_files('test1')
+        util_resources.remove_wallet_files('test2')
+        for i in range(2):
+            self.wallet[i].close_wallet()
+            self.wallet[i].restore_deterministic_wallet(seed = seeds[i])
+
+    def check_background_sync_reorg_recovery(self):
+        daemon = Daemon()
+
+        print('Testing background sync reorg recovery')
+
+        # Disconnect daemon from peers
+        daemon.out_peers(0)
+
+        # Background sync type options
+        sender_wallet = self.wallet[0]
+        reuse_password = sender_wallet.background_sync_options.reuse_password
+        custom_password = sender_wallet.background_sync_options.custom_password
+
+        for background_sync_type in [reuse_password, custom_password]:
+            # Set up wallet saved to disk
+            sender_wallet.close_wallet()
+            util_resources.remove_wallet_files('test1')
+            sender_wallet.restore_deterministic_wallet(seed = seeds[0], filename = 'test1', password = '')
+            sender_wallet.auto_refresh(enable = False)
+            sender_wallet.refresh()
+            sender_starting_balance = sender_wallet.get_balance().balance
+
+            # Send tx and mine a block
+            amount = 1000000000000
+            assert sender_starting_balance > amount
+            dst = {'address': '44Kbx4sJ7JDRDV5aAhLJzQCjDz2ViLRduE3ijDZu3osWKBjMGkV1XPk4pfDUMqt1Aiezvephdqm6YD19GKFD9ZcXVUTp6BW', 'amount': amount}
+            res = sender_wallet.transfer([dst])
+            assert len(res.tx_hash) == 32*2
+            txid = res.tx_hash
+
+            daemon.generateblocks('46r4nYSevkfBUMhuykdK3gQ98XDqDTYW1hNLaXNvjpsJaSbNtdXh1sKMsdVgqkaihChAzEy29zEDPMR3NHQvGoZCLGwTerK', 1)
+
+            # Make sure the wallet can see the tx
+            sender_wallet.refresh()
+            transfers = sender_wallet.get_transfers()
+            assert 'pool' not in transfers or len (transfers.pool) == 0
+            tx = [x for x in transfers.out if x.txid == txid]
+            assert len(tx) == 1
+            tx = tx[0]
+            assert sender_wallet.get_balance().balance < (sender_starting_balance - amount)
+
+            # Pop the block while background syncing
+            background_cache_password = None if background_sync_type == reuse_password else 'background_password'
+            sender_wallet.setup_background_sync(background_sync_type = background_sync_type, wallet_password = '', background_cache_password = background_cache_password)
+            sender_wallet.start_background_sync()
+            daemon.pop_blocks(1)
+            daemon.flush_txpool()
+
+            daemon.generateblocks('46r4nYSevkfBUMhuykdK3gQ98XDqDTYW1hNLaXNvjpsJaSbNtdXh1sKMsdVgqkaihChAzEy29zEDPMR3NHQvGoZCLGwTerK', 1)
+
+            # Make sure the wallet can no longer see the tx
+            sender_wallet.refresh()
+            sender_wallet.stop_background_sync(wallet_password = '', seed = seeds[0])
+            transfers = sender_wallet.get_transfers()
+            no_tx = [x for x in transfers.out if x.txid == txid]
+            assert len(no_tx) == 0
+            assert sender_wallet.get_balance().balance == sender_starting_balance
+
+        # Clean up
+        daemon.out_peers(12)
+        util_resources.remove_wallet_files('test1')
+        self.wallet[0].close_wallet()
+        self.wallet[0].restore_deterministic_wallet(seed = seeds[0])
+
 if __name__ == '__main__':
     TransferTest().run_test()

tests/functional_tests/util_resources.py

@@ -37,6 +37,8 @@
 from __future__ import print_function
 import subprocess
 import psutil
+import os
+import errno
 
 def available_ram_gb():
     ram_bytes = psutil.virtual_memory().available
@@ -51,3 +53,26 @@ def get_time_pi_seconds(cores, app_dir='.'):
     miliseconds = int(decoded)
 
     return miliseconds / 1000.0
+
+def remove_file(name):
+    WALLET_DIRECTORY = os.environ['WALLET_DIRECTORY']
+    assert WALLET_DIRECTORY != ''
+    try:
+        os.unlink(WALLET_DIRECTORY + '/' + name)
+    except OSError as e:
+        if e.errno != errno.ENOENT:
+            raise
+
+def get_file_path(name):
+    WALLET_DIRECTORY = os.environ['WALLET_DIRECTORY']
+    assert WALLET_DIRECTORY != ''
+    return WALLET_DIRECTORY + '/' + name
+
+def remove_wallet_files(name):
+    for suffix in ['', '.keys', '.background', '.background.keys', '.address.txt']:
+        remove_file(name + suffix)
+
+def file_exists(name):
+    WALLET_DIRECTORY = os.environ['WALLET_DIRECTORY']
+    assert WALLET_DIRECTORY != ''
+    return os.path.isfile(WALLET_DIRECTORY + '/' + name)

tests/functional_tests/wallet.py

@@ -34,8 +34,7 @@
 
 from __future__ import print_function
 import sys
-import os
+import util_resources
-import errno
 
 from framework.wallet import Wallet
 from framework.daemon import Daemon
@@ -54,24 +53,6 @@ class WalletTest():
       self.change_password()
       self.store()
 
-    def remove_file(self, name):
-        WALLET_DIRECTORY = os.environ['WALLET_DIRECTORY']
-        assert WALLET_DIRECTORY != ''
-        try:
-            os.unlink(WALLET_DIRECTORY + '/' + name)
-        except OSError as e:
-            if e.errno != errno.ENOENT:
-                raise
-
-    def remove_wallet_files(self, name):
-        for suffix in ['', '.keys']:
-            self.remove_file(name + suffix)
-
-    def file_exists(self, name):
-        WALLET_DIRECTORY = os.environ['WALLET_DIRECTORY']
-        assert WALLET_DIRECTORY != ''
-        return os.path.isfile(WALLET_DIRECTORY + '/' + name)
-
     def reset(self):
         print('Resetting blockchain')
         daemon = Daemon()
@@ -333,7 +314,7 @@ class WalletTest():
         try: wallet.close_wallet()
         except: pass
 
-        self.remove_wallet_files('test1')
+        util_resources.remove_wallet_files('test1')
 
         seed = 'velvet lymph giddy number token physics poetry unquoted nibs useful sabotage limits benches lifestyle eden nitrogen anvil fewest avoid batch vials washing fences goat unquoted'
         res = wallet.restore_deterministic_wallet(seed = seed, filename = 'test1')
@@ -359,7 +340,7 @@ class WalletTest():
 
         wallet.close_wallet()
 
-        self.remove_wallet_files('test1')
+        util_resources.remove_wallet_files('test1')
 
     def store(self):
         print('Testing store')
@@ -369,22 +350,26 @@ class WalletTest():
         try: wallet.close_wallet()
         except: pass
 
-        self.remove_wallet_files('test1')
+        util_resources.remove_wallet_files('test1')
 
         seed = 'velvet lymph giddy number token physics poetry unquoted nibs useful sabotage limits benches lifestyle eden nitrogen anvil fewest avoid batch vials washing fences goat unquoted'
         res = wallet.restore_deterministic_wallet(seed = seed, filename = 'test1')
         assert res.address == '42ey1afDFnn4886T7196doS9GPMzexD9gXpsZJDwVjeRVdFCSoHnv7KPbBeGpzJBzHRCAs9UxqeoyFQMYbqSWYTfJJQAWDm'
         assert res.seed == seed
 
-        self.remove_file('test1')
+        util_resources.remove_file('test1')
-        assert self.file_exists('test1.keys')
+        assert util_resources.file_exists('test1.keys')
-        assert not self.file_exists('test1')
+        assert not util_resources.file_exists('test1')
         wallet.store()
-        assert self.file_exists('test1.keys')
+        assert util_resources.file_exists('test1.keys')
-        assert self.file_exists('test1')
+        assert util_resources.file_exists('test1')
 
         wallet.close_wallet()
-        self.remove_wallet_files('test1')
+
+        wallet.open_wallet(filename = 'test1', password = '')
+        wallet.close_wallet()
+
+        util_resources.remove_wallet_files('test1')
 
 
 if __name__ == '__main__':

tests/unit_tests/wipeable_string.cpp

@@ -211,3 +211,15 @@ TEST(wipeable_string, to_hex)
   ASSERT_TRUE(epee::to_hex::wipeable_string(epee::span<const uint8_t>((const uint8_t*)"", 0)) == epee::wipeable_string(""));
   ASSERT_TRUE(epee::to_hex::wipeable_string(epee::span<const uint8_t>((const uint8_t*)"abc", 3)) == epee::wipeable_string("616263"));
 }
+
+TEST(wipeable_string, to_string)
+{
+  // Converting a wipeable_string to a string defeats the purpose of wipeable_string,
+  // but nice to know this works
+  std::string str;
+  {
+    epee::wipeable_string wipeable_str("foo");
+    str = std::string(wipeable_str.data(), wipeable_str.size());
+  }
+  ASSERT_TRUE(str == std::string("foo"));
+}

utils/python-rpc/framework/wallet.py

@@ -1153,3 +1153,45 @@ class Wallet(object):
             'id': '0'
         }
         return self.rpc.send_json_rpc_request(frozen)
+
+    class BackgroundSyncOptions(object):
+        def __init__(self):
+            self.off = 'off'
+            self.reuse_password = 'reuse-wallet-password'
+            self.custom_password = 'custom-background-password'
+    background_sync_options = BackgroundSyncOptions()
+
+    def setup_background_sync(self, background_sync_type = background_sync_options.off, wallet_password = '', background_cache_password = ''):
+        setup_background_sync = {
+            'method': 'setup_background_sync',
+            'jsonrpc': '2.0',
+            'params' : {
+                'background_sync_type': background_sync_type,
+                'wallet_password': wallet_password,
+                'background_cache_password': background_cache_password,
+            },
+            'id': '0'
+        }
+        return self.rpc.send_json_rpc_request(setup_background_sync)
+
+    def start_background_sync(self):
+        start_background_sync = {
+            'method': 'start_background_sync',
+            'jsonrpc': '2.0',
+            'params' : {},
+            'id': '0'
+        }
+        return self.rpc.send_json_rpc_request(start_background_sync)
+
+    def stop_background_sync(self, wallet_password = '', seed = '', seed_offset = ''):
+        stop_background_sync = {
+            'method': 'stop_background_sync',
+            'jsonrpc': '2.0',
+            'params' : {
+                'wallet_password': wallet_password,
+                'seed': seed,
+                'seed_offset': seed_offset,
+            },
+            'id': '0'
+        }
+        return self.rpc.send_json_rpc_request(stop_background_sync)