wallet: cold wallet transaction signing

This change adds the ability to create a new unsigned transaction
from a watch only wallet, and save it to a file. This file can
then be moved to another computer/VM where a cold wallet may load
it, sign it, and save it. That cold wallet does not need to have
a blockchain nor daemon. The signed transaction file can then be
moved back to the watch only wallet, which can load it and send
it to the daemon.

Two new simplewallet commands to use it:
sign_transfer (on the cold wallet)
submit_transfer (on the watch only wallet)

The transfer command used on a watch only wallet now writes an
unsigned transaction set in a file called 'unsigned_monero_tx'
instead of submitting the tx to the daemon as a normal wallet does.
The signed tx file is called 'signed_monero_tx'.

2 files changed, 273 insertions, 26 deletions

diff --git a/src/simplewallet/simplewallet.cpp b/src/simplewallet/simplewallet.cpp
index 7260ecf8a..d3938362e 100644
--- a/src/simplewallet/simplewallet.cpp
+++ b/src/simplewallet/simplewallet.cpp
@@ -389,11 +389,6 @@ bool simple_wallet::seed_set_language(const std::vector<std::string> &args/* = s
 bool simple_wallet::set_always_confirm_transfers(const std::vector<std::string> &args/* = std::vector<std::string>()*/)
 {
   bool success = false;
-  if (m_wallet->watch_only())
-  {
-    fail_msg_writer() << tr("wallet is watch-only and cannot transfer");
-    return true;
-  }
   tools::password_container pwd_container(m_wallet_file.empty());
   success = pwd_container.read_password();
   if (!success)
@@ -654,6 +649,8 @@ simple_wallet::simple_wallet()
   m_cmd_binder.set_handler("transfer", boost::bind(&simple_wallet::transfer_new, this, _1), tr("Same as transfer_original, but using a new transaction building algorithm"));
   m_cmd_binder.set_handler("sweep_unmixable", boost::bind(&simple_wallet::sweep_unmixable, this, _1), tr("Send all unmixable outputs to yourself with mixin 0"));
   m_cmd_binder.set_handler("sweep_all", boost::bind(&simple_wallet::sweep_all, this, _1), tr("Send all unlocked balance an address"));
+  m_cmd_binder.set_handler("sign_transfer", boost::bind(&simple_wallet::sign_transfer, this, _1), tr("Sign a transaction from a file"));
+  m_cmd_binder.set_handler("submit_transfer", boost::bind(&simple_wallet::submit_transfer, this, _1), tr("Submit a signed transaction from a file"));
   m_cmd_binder.set_handler("set_log", boost::bind(&simple_wallet::set_log, this, _1), tr("set_log <level> - Change current log detail level, <0-4>"));
   m_cmd_binder.set_handler("address", boost::bind(&simple_wallet::print_address, this, _1), tr("Show current wallet public address"));
   m_cmd_binder.set_handler("integrated_address", boost::bind(&simple_wallet::print_integrated_address, this, _1), tr("integrated_address [PID] - Encode a payment ID into an integrated address for the current wallet public address (no argument uses a random payment ID), or decode an integrated address to standard address and payment ID"));
@@ -2313,12 +2310,6 @@ bool simple_wallet::transfer_main(int transfer_type, const std::vector<std::stri
      return true;
   }
 
-  if(m_wallet->watch_only())
-  {
-     fail_msg_writer() << tr("this is a watch only wallet");
-     return true;
-  }
-
   std::vector<uint8_t> extra;
   bool payment_id_seen = false;
   if (1 == local_args.size() % 2)
@@ -2455,7 +2446,19 @@ bool simple_wallet::transfer_main(int transfer_type, const std::vector<std::stri
     }
 
     // actually commit the transactions
-    while (!ptx_vector.empty())
+    if (m_wallet->watch_only())
+    {
+      bool r = m_wallet->save_tx(ptx_vector, "unsigned_monero_tx");
+      if (!r)
+      {
+        fail_msg_writer() << tr("Failed to write transaction(s) to file");
+      }
+      else
+      {
+        success_msg_writer(true) << tr("Unsigned transaction(s) successfully written to file: ") << "unsigned_monero_tx";
+      }
+    }
+    else while (!ptx_vector.empty())
     {
       auto & ptx = ptx_vector.back();
       m_wallet->commit_tx(ptx);
@@ -2562,12 +2565,6 @@ bool simple_wallet::sweep_unmixable(const std::vector<std::string> &args_)
   if (!try_connect_to_daemon())
     return true;
 
-  if(m_wallet->watch_only())
-  {
-     fail_msg_writer() << tr("this is a watch only wallet");
-     return true;
-  }
-
   LOCK_IDLE_SCOPE();
   try
   {
@@ -2617,7 +2614,19 @@ bool simple_wallet::sweep_unmixable(const std::vector<std::string> &args_)
     }
 
     // actually commit the transactions
-    while (!ptx_vector.empty())
+    if (m_wallet->watch_only())
+    {
+      bool r = m_wallet->save_tx(ptx_vector, "unsigned_monero_tx");
+      if (!r)
+      {
+        fail_msg_writer() << tr("Failed to write transaction(s) to file");
+      }
+      else
+      {
+        success_msg_writer(true) << tr("Unsigned transaction(s) successfully written to file: ") << "unsigned_monero_tx";
+      }
+    }
+    else while (!ptx_vector.empty())
     {
       auto & ptx = ptx_vector.back();
       m_wallet->commit_tx(ptx);
@@ -2714,12 +2723,6 @@ bool simple_wallet::sweep_all(const std::vector<std::string> &args_)
   if (!try_connect_to_daemon())
     return true;
 
-  if(m_wallet->watch_only())
-  {
-     fail_msg_writer() << tr("this is a watch only wallet");
-     return true;
-  }
-
   std::vector<std::string> local_args = args_;
 
   size_t fake_outs_count;
@@ -2849,7 +2852,19 @@ bool simple_wallet::sweep_all(const std::vector<std::string> &args_)
     }
 
     // actually commit the transactions
-    while (!ptx_vector.empty())
+    if (m_wallet->watch_only())
+    {
+      bool r = m_wallet->save_tx(ptx_vector, "unsigned_monero_tx");
+      if (!r)
+      {
+        fail_msg_writer() << tr("Failed to write transaction(s) to file");
+      }
+      else
+      {
+        success_msg_writer(true) << tr("Unsigned transaction(s) successfully written to file: ") << "unsigned_monero_tx";
+      }
+    }
+    else while (!ptx_vector.empty())
     {
       auto & ptx = ptx_vector.back();
       m_wallet->commit_tx(ptx);
@@ -2941,6 +2956,235 @@ bool simple_wallet::sweep_all(const std::vector<std::string> &args_)
   return true;
 }
 //----------------------------------------------------------------------------------------------------
+bool simple_wallet::accept_loaded_tx(const tools::wallet2::unsigned_tx_set &txs)
+{
+  // gather info to ask the user
+  uint64_t amount = 0, amount_to_dests = 0, change = 0;
+  size_t min_mixin = ~0;
+  std::unordered_map<std::string, uint64_t> dests;
+  const std::string wallet_address = m_wallet->get_account().get_public_address_str(m_wallet->testnet());
+  for (size_t n = 0; n < txs.txes.size(); ++n)
+  {
+    const tools::wallet2::tx_construction_data &cd = txs.txes[n];
+    for (size_t s = 0; s < cd.sources.size(); ++s)
+    {
+      amount += cd.sources[s].amount;
+      size_t mixin = cd.sources[s].outputs.size() - 1;
+      if (mixin < min_mixin)
+        min_mixin = mixin;
+    }
+    for (size_t d = 0; d < cd.destinations.size(); ++d)
+    {
+      const tx_destination_entry &entry = cd.destinations[d];
+      std::string address = get_account_address_as_str(m_wallet->testnet(), entry.addr);
+      std::unordered_map<std::string,uint64_t>::iterator i = dests.find(address);
+      if (i == dests.end())
+        dests.insert(std::make_pair(address, entry.amount));
+      else
+        i->second += entry.amount;
+      amount_to_dests += entry.amount;
+    }
+    if (cd.change_dts.amount > 0)
+    {
+      dests.insert(std::make_pair(get_account_address_as_str(m_wallet->testnet(), cd.change_dts.addr), cd.change_dts.amount));
+      amount_to_dests += cd.change_dts.amount;
+      change += cd.change_dts.amount;
+    }
+  }
+  std::string dest_string;
+  for (std::unordered_map<std::string, uint64_t>::const_iterator i = dests.begin(); i != dests.end(); )
+  {
+    dest_string += (boost::format(tr("sending %s to %s")) % print_money(i->second) % i->first).str();
+    ++i;
+    if (i != dests.end())
+      dest_string += ", ";
+  }
+  if (dest_string.empty())
+    dest_string = tr("with no destinations");
+
+  uint64_t fee = amount - amount_to_dests;
+  std::string prompt_str = (boost::format(tr("Loaded %lu transactions, for %s, fee %s, change %s, %s, with min mixin %lu (full details in log file). Is this okay? (Y/Yes/N/No)")) % (unsigned long)txs.txes.size() % print_money(amount) % print_money(fee) % print_money(change) % dest_string % (unsigned long)min_mixin).str();
+  std::string accepted = command_line::input_line(prompt_str);
+  return is_it_true(accepted);
+}
+//----------------------------------------------------------------------------------------------------
+bool simple_wallet::sign_transfer(const std::vector<std::string> &args_)
+{
+  if(m_wallet->watch_only())
+  {
+     fail_msg_writer() << tr("This is a watch only wallet");
+     return true;
+  }
+
+  try
+  {
+    bool r = m_wallet->sign_tx("unsigned_monero_tx", "signed_monero_tx", [&](const tools::wallet2::unsigned_tx_set &tx){ return accept_loaded_tx(tx); });
+    if (!r)
+    {
+      fail_msg_writer() << tr("Failed to sign transaction");
+      return true;
+    }
+  }
+  catch (const std::exception &e)
+  {
+    fail_msg_writer() << tr("Failed to sign transaction: ") << e.what();
+    return true;
+  }
+
+  success_msg_writer(true) << tr("Transaction successfully signed to file: ") << "signed_monero_tx";
+  return true;
+}
+//----------------------------------------------------------------------------------------------------
+bool simple_wallet::submit_transfer(const std::vector<std::string> &args_)
+{
+  if (!try_connect_to_daemon())
+    return true;
+
+  try
+  {
+    std::vector<tools::wallet2::pending_tx> ptx_vector;
+    bool r = m_wallet->load_tx("signed_monero_tx", ptx_vector);
+    if (!r)
+    {
+      fail_msg_writer() << tr("Failed to load transaction from file");
+      return true;
+    }
+
+    // if more than one tx necessary, prompt user to confirm
+    if (m_wallet->always_confirm_transfers())
+    {
+        uint64_t total_fee = 0;
+        uint64_t dust_not_in_fee = 0;
+        uint64_t dust_in_fee = 0;
+        for (size_t n = 0; n < ptx_vector.size(); ++n)
+        {
+          total_fee += ptx_vector[n].fee;
+
+          if (ptx_vector[n].dust_added_to_fee)
+            dust_in_fee += ptx_vector[n].dust;
+          else
+            dust_not_in_fee += ptx_vector[n].dust;
+        }
+
+        std::stringstream prompt;
+        if (ptx_vector.size() > 1)
+        {
+          prompt << boost::format(tr("Your transaction needs to be split into %llu transactions.  "
+            "This will result in a transaction fee being applied to each transaction, for a total fee of %s")) %
+            ((unsigned long long)ptx_vector.size()) % print_money(total_fee);
+        }
+        else
+        {
+          prompt << boost::format(tr("The transaction fee is %s")) %
+            print_money(total_fee);
+        }
+        if (dust_in_fee != 0) prompt << boost::format(tr(", of which %s is dust from change")) % print_money(dust_in_fee);
+        if (dust_not_in_fee != 0)  prompt << tr(".") << ENDL << boost::format(tr("A total of %s from dust change will be sent to dust address"))
+                                                   % print_money(dust_not_in_fee);
+        prompt << tr(".") << ENDL << tr("Is this okay?  (Y/Yes/N/No)");
+
+        std::string accepted = command_line::input_line(prompt.str());
+        if (std::cin.eof())
+          return true;
+        if (accepted != "Y" && accepted != "y" && accepted != "Yes" && accepted != "yes")
+        {
+          fail_msg_writer() << tr("transaction cancelled.");
+
+          // would like to return false, because no tx made, but everything else returns true
+          // and I don't know what returning false might adversely affect.  *sigh*
+          return true;
+        }
+    }
+
+    // actually commit the transactions
+    while (!ptx_vector.empty())
+    {
+      auto & ptx = ptx_vector.back();
+      m_wallet->commit_tx(ptx);
+      success_msg_writer(true) << tr("Money successfully sent, transaction: ") << get_transaction_hash(ptx.tx);
+
+      // if no exception, remove element from vector
+      ptx_vector.pop_back();
+    }
+  }
+  catch (const tools::error::daemon_busy&)
+  {
+    fail_msg_writer() << tr("daemon is busy. Please try later");
+  }
+  catch (const tools::error::no_connection_to_daemon&)
+  {
+    fail_msg_writer() << tr("no connection to daemon. Please, make sure daemon is running.");
+  }
+  catch (const tools::error::wallet_rpc_error& e)
+  {
+    LOG_ERROR("Unknown RPC error: " << e.to_string());
+    fail_msg_writer() << tr("RPC error: ") << e.what();
+  }
+  catch (const tools::error::get_random_outs_error&)
+  {
+    fail_msg_writer() << tr("failed to get random outputs to mix");
+  }
+  catch (const tools::error::not_enough_money& e)
+  {
+    fail_msg_writer() << boost::format(tr("not enough money to transfer, available only %s, transaction amount %s = %s + %s (fee)")) %
+      print_money(e.available()) %
+      print_money(e.tx_amount() + e.fee()) %
+      print_money(e.tx_amount()) %
+      print_money(e.fee());
+  }
+  catch (const tools::error::not_enough_outs_to_mix& e)
+  {
+    auto writer = fail_msg_writer();
+    writer << tr("not enough outputs for specified mixin_count") << " = " << e.mixin_count() << ":";
+    for (std::pair<uint64_t, uint64_t> outs_for_amount : e.scanty_outs())
+    {
+      writer << "\n" << tr("output amount") << " = " << print_money(outs_for_amount.first) << ", " << tr("found outputs to mix") << " = " << outs_for_amount.second;
+    }
+  }
+  catch (const tools::error::tx_not_constructed&)
+  {
+    fail_msg_writer() << tr("transaction was not constructed");
+  }
+  catch (const tools::error::tx_rejected& e)
+  {
+    fail_msg_writer() << (boost::format(tr("transaction %s was rejected by daemon with status: ")) % get_transaction_hash(e.tx())) << e.status();
+  }
+  catch (const tools::error::tx_sum_overflow& e)
+  {
+    fail_msg_writer() << e.what();
+  }
+  catch (const tools::error::zero_destination&)
+  {
+    fail_msg_writer() << tr("one of destinations is zero");
+  }
+  catch (const tools::error::tx_too_big& e)
+  {
+    fail_msg_writer() << tr("Failed to find a suitable way to split transactions");
+  }
+  catch (const tools::error::transfer_error& e)
+  {
+    LOG_ERROR("unknown transfer error: " << e.to_string());
+    fail_msg_writer() << tr("unknown transfer error: ") << e.what();
+  }
+  catch (const tools::error::wallet_internal_error& e)
+  {
+    LOG_ERROR("internal error: " << e.to_string());
+    fail_msg_writer() << tr("internal error: ") << e.what();
+  }
+  catch (const std::exception& e)
+  {
+    LOG_ERROR("unexpected error: " << e.what());
+    fail_msg_writer() << tr("unexpected error: ") << e.what();
+  }
+  catch (...)
+  {
+    LOG_ERROR("Unknown error");
+    fail_msg_writer() << tr("unknown error");
+  }
+
+  return true;
+}
+//----------------------------------------------------------------------------------------------------
 bool simple_wallet::get_tx_key(const std::vector<std::string> &args_)
 {
   std::vector<std::string> local_args = args_;
diff --git a/src/simplewallet/simplewallet.h b/src/simplewallet/simplewallet.h
index 6eb18ed9a..61e956ce9 100644
--- a/src/simplewallet/simplewallet.h
+++ b/src/simplewallet/simplewallet.h
@@ -125,6 +125,8 @@ namespace cryptonote
     bool transfer_new(const std::vector<std::string> &args);
     bool sweep_all(const std::vector<std::string> &args);
     bool sweep_unmixable(const std::vector<std::string> &args);
+    bool sign_transfer(const std::vector<std::string> &args);
+    bool submit_transfer(const std::vector<std::string> &args);
     std::vector<std::vector<cryptonote::tx_destination_entry>> split_amounts(
         std::vector<cryptonote::tx_destination_entry> dsts, size_t num_splits
     );
@@ -152,6 +154,7 @@ namespace cryptonote
     uint64_t get_daemon_blockchain_height(std::string& err);
     bool try_connect_to_daemon(bool silent = false);
     bool ask_wallet_create_if_needed();
+    bool accept_loaded_tx(const tools::wallet2::unsigned_tx_set &txs);
     bool get_address_from_str(const std::string &str, cryptonote::account_public_address &address, bool &has_payment_id, crypto::hash8 &payment_id);
 
     /*!