wallet: add watch only wallet support

The new save_watch_only saves a copy of the keys file without the
spend key. It can then be given away to be used as a normal keys
file, but with no spend ability.

src/simplewallet/simplewallet.cpp

@@ -299,6 +299,7 @@ simple_wallet::simple_wallet()
   m_cmd_binder.set_handler("set_log", boost::bind(&simple_wallet::set_log, this, _1), "set_log <level> - Change current log detalization level, <level> is a number 0-4");
   m_cmd_binder.set_handler("address", boost::bind(&simple_wallet::print_address, this, _1), "Show current wallet public address");
   m_cmd_binder.set_handler("save", boost::bind(&simple_wallet::save, this, _1), "Save wallet synchronized data");
+  m_cmd_binder.set_handler("save_watch_only", boost::bind(&simple_wallet::save_watch_only, this, _1), "Save watch only keys file");
   m_cmd_binder.set_handler("viewkey", boost::bind(&simple_wallet::viewkey, this, _1), "Get viewkey");
   m_cmd_binder.set_handler("spendkey", boost::bind(&simple_wallet::spendkey, this, _1), "Get spendkey");
   m_cmd_binder.set_handler("seed", boost::bind(&simple_wallet::seed, this, _1), "Get deterministic seed");
@@ -680,7 +681,8 @@ bool simple_wallet::open_wallet(const string &wallet_file, const std::string& pa
   try
   {
     m_wallet->load(m_wallet_file, password);
-    message_writer(epee::log_space::console_color_white, true) << "Opened wallet: "
+    std::string wallet_type = m_wallet->watch_only() ? "watch-only wallet" : "wallet";
+    message_writer(epee::log_space::console_color_white, true) << "Opened " << wallet_type << ": "
       << m_wallet->get_account().get_public_address_str(m_wallet->testnet());
     // If the wallet file is deprecated, we should ask for mnemonic language again and store
     // everything in the new format.
@@ -760,6 +762,30 @@ bool simple_wallet::save(const std::vector<std::string> &args)
 
   return true;
 }
+//----------------------------------------------------------------------------------------------------
+bool simple_wallet::save_watch_only(const std::vector<std::string> &args/* = std::vector<std::string>()*/)
+{
+  bool success = false;
+  tools::password_container pwd_container;
+  success = pwd_container.read_password();
+  if (!success)
+  {
+    fail_msg_writer() << "failed to read wallet password";
+    return true;
+  }
+
+  /* verify password before using so user doesn't accidentally set a new password for rewritten wallet */
+  success = m_wallet->verify_password(pwd_container.password());
+  if (!success)
+  {
+    fail_msg_writer() << "invalid password";
+    return true;
+  }
+
+  m_wallet->write_watch_only_wallet(m_wallet_file, pwd_container.password());
+  return true;
+}
+
 //----------------------------------------------------------------------------------------------------
 bool simple_wallet::start_mining(const std::vector<std::string>& args)
 {
@@ -1104,6 +1130,12 @@ bool simple_wallet::transfer(const std::vector<std::string> &args_)
      return true;
   }
 
+  if(m_wallet->watch_only())
+  {
+     fail_msg_writer() << "This is a watch only wallet";
+     return true;
+  }
+
   std::vector<uint8_t> extra;
   if (1 == local_args.size() % 2)
   {
@@ -1316,6 +1348,12 @@ bool simple_wallet::sweep_dust(const std::vector<std::string> &args_)
   if (!try_connect_to_daemon())
     return true;
 
+  if(m_wallet->watch_only())
+  {
+     fail_msg_writer() << "This is a watch only wallet";
+     return true;
+  }
+
   try
   {
     uint64_t total_dust = m_wallet->unlocked_dust_balance(tools::tx_dust_policy(::config::DEFAULT_DUST_THRESHOLD));

src/simplewallet/simplewallet.h

@@ -109,6 +109,7 @@ namespace cryptonote
     );
     bool print_address(const std::vector<std::string> &args = std::vector<std::string>());
     bool save(const std::vector<std::string> &args);
+    bool save_watch_only(const std::vector<std::string> &args);
     bool set_variable(const std::vector<std::string> &args);
     bool set_log(const std::vector<std::string> &args);
 

src/wallet/wallet2.cpp

@@ -472,12 +472,17 @@ bool wallet2::clear()
  * \brief Stores wallet information to wallet file.
  * \param  keys_file_name Name of wallet file
  * \param  password       Password of wallet file
+ * \param  watch_only     true to save only view key, false to save both spend and view keys
  * \return                Whether it was successful.
  */
-bool wallet2::store_keys(const std::string& keys_file_name, const std::string& password)
+bool wallet2::store_keys(const std::string& keys_file_name, const std::string& password, bool watch_only)
 {
   std::string account_data;
-  bool r = epee::serialization::store_t_to_binary(m_account, account_data);
+  cryptonote::account_base account = m_account;
+
+  if (watch_only)
+    account.forget_spend_key();
+  bool r = epee::serialization::store_t_to_binary(account, account_data);
   CHECK_AND_ASSERT_MES(r, false, "failed to serialize wallet keys");
   wallet2::keys_file_data keys_file_data = boost::value_initialized<wallet2::keys_file_data>();
 
@@ -493,6 +498,10 @@ bool wallet2::store_keys(const std::string& keys_file_name, const std::string& p
     json.AddMember("seed_language", value, json.GetAllocator());
   }
 
+  rapidjson::Value value2(rapidjson::kNumberType);
+  value2.SetInt(watch_only ? 1 :0); // WTF ? JSON has different true and false types, and not boolean ??
+  json.AddMember("watch_only", value2, json.GetAllocator());
+
   // Serialize the JSON object
   rapidjson::StringBuffer buffer;
   rapidjson::Writer<rapidjson::StringBuffer> writer(buffer);
@@ -552,6 +561,7 @@ void wallet2::load_keys(const std::string& keys_file_name, const std::string& pa
   if (json.Parse(account_data.c_str(), keys_file_data.account_data.size()).HasParseError())
   {
     is_old_file_format = true;
+    m_watch_only = false;
   }
   else
   {
@@ -562,12 +572,21 @@ void wallet2::load_keys(const std::string& keys_file_name, const std::string& pa
       set_seed_language(std::string(json["seed_language"].GetString(), json["seed_language"].GetString() +
         json["seed_language"].GetStringLength()));
     }
+    if (json.HasMember("watch_only"))
+    {
+      m_watch_only = json["watch_only"].GetInt() != 0;
+    }
+    else
+    {
+      m_watch_only = false;
+    }
   }
 
   const cryptonote::account_keys& keys = m_account.get_keys();
   r = epee::serialization::load_t_from_binary(m_account, account_data);
   r = r && verify_keys(keys.m_view_secret_key,  keys.m_account_address.m_view_public_key);
-  r = r && verify_keys(keys.m_spend_secret_key, keys.m_account_address.m_spend_public_key);
+  if(!m_watch_only)
+    r = r && verify_keys(keys.m_spend_secret_key, keys.m_account_address.m_spend_public_key);
   THROW_WALLET_EXCEPTION_IF(!r, error::invalid_password);
 }
 
@@ -642,7 +661,7 @@ crypto::secret_key wallet2::generate(const std::string& wallet_, const std::stri
 
   m_account_public_address = m_account.get_keys().m_account_address;
 
-  bool r = store_keys(m_keys_file, password);
+  bool r = store_keys(m_keys_file, password, false);
   THROW_WALLET_EXCEPTION_IF(!r, error::file_save_error, m_keys_file);
 
   r = file_io_utils::save_string_to_file(m_wallet_file + ".address.txt", m_account.get_public_address_str(m_testnet));
@@ -666,9 +685,24 @@ void wallet2::rewrite(const std::string& wallet_name, const std::string& passwor
   prepare_file_names(wallet_name);
   boost::system::error_code ignored_ec;
   THROW_WALLET_EXCEPTION_IF(!boost::filesystem::exists(m_keys_file, ignored_ec), error::file_not_found, m_keys_file);
-  bool r = store_keys(m_keys_file, password);
+  bool r = store_keys(m_keys_file, password, false);
   THROW_WALLET_EXCEPTION_IF(!r, error::file_save_error, m_keys_file);
 }
+/*!
+ * \brief Rewrites to the wallet file for wallet upgrade (doesn't generate key, assumes it's already there)
+ * \param wallet_name Name of wallet file (should exist)
+ * \param password    Password for wallet file
+ */
+void wallet2::write_watch_only_wallet(const std::string& wallet_name, const std::string& password)
+{
+  prepare_file_names(wallet_name);
+  boost::system::error_code ignored_ec;
+  std::string filename = m_keys_file + "-watchonly";
+  bool watch_only_keys_file_exists = boost::filesystem::exists(filename, ignored_ec);
+  THROW_WALLET_EXCEPTION_IF(watch_only_keys_file_exists, error::file_save_error, filename);
+  bool r = store_keys(filename, password, true);
+  THROW_WALLET_EXCEPTION_IF(!r, error::file_save_error, filename);
+}
 //----------------------------------------------------------------------------------------------------
 void wallet2::wallet_exists(const std::string& file_path, bool& keys_file_exists, bool& wallet_file_exists)
 {

src/wallet/wallet2.h

@@ -151,6 +151,7 @@ namespace tools
      * \param password    Password for wallet file
      */
     void rewrite(const std::string& wallet_name, const std::string& password);
+    void write_watch_only_wallet(const std::string& wallet_name, const std::string& password);
     void load(const std::string& wallet, const std::string& password);
     void store();
 
@@ -198,6 +199,7 @@ namespace tools
 
     bool testnet() const { return m_testnet; }
     bool restricted() const { return m_restricted; }
+    bool watch_only() const { return m_watch_only; }
 
     uint64_t balance() const;
     uint64_t unlocked_balance() const;
@@ -260,9 +262,10 @@ namespace tools
      * \brief  Stores wallet information to wallet file.
      * \param  keys_file_name Name of wallet file
      * \param  password       Password of wallet file
+     * \param  watch_only     true to save only view key, false to save both spend and view keys
      * \return                Whether it was successful.
      */
-    bool store_keys(const std::string& keys_file_name, const std::string& password);
+    bool store_keys(const std::string& keys_file_name, const std::string& password, bool watch_only = false);
     /*!
      * \brief Load wallet information from wallet file.
      * \param keys_file_name Name of wallet file
@@ -306,6 +309,7 @@ namespace tools
     bool m_restricted;
     std::string seed_language; /*!< Language of the mnemonics (seed). */
     bool is_old_file_format; /*!< Whether the wallet file is of an old file format */
+    bool m_watch_only; /*!< no spend key */
   };
 }
 BOOST_CLASS_VERSION(tools::wallet2, 7)