wallet: include a suggested number of confirmations based on amount

This is based on how much an attacking miner stands to lose in block
rewardy by mining a private chain which double spends a payment.
This is not foolproof, since mining is based on luck, and breaks
down as the attacking miner nears 50% of the network hash rate,
and the estimation is based on a constant block reward.

src/simplewallet/simplewallet.cpp

@@ -7408,8 +7408,12 @@ bool simple_wallet::show_transfer(const std::vector<std::string> &args)
       if (pd.m_unlock_time < CRYPTONOTE_MAX_BLOCK_NUMBER)
       {
         uint64_t bh = std::max(pd.m_unlock_time, pd.m_block_height + CRYPTONOTE_DEFAULT_TX_SPENDABLE_AGE);
+        uint64_t last_block_reward = m_wallet->get_last_block_reward();
+        uint64_t suggested_threshold = last_block_reward ? (pd.m_amount + last_block_reward - 1) / last_block_reward : 0;
         if (bh >= last_block_height)
           success_msg_writer() << "Locked: " << (bh - last_block_height) << " blocks to unlock";
+        else if (suggested_threshold > 0)
+          success_msg_writer() << std::to_string(last_block_height - bh) << " confirmations (" << suggested_threshold << " suggested threshold)";
         else
           success_msg_writer() << std::to_string(last_block_height - bh) << " confirmations";
       }

src/wallet/wallet2.cpp

@@ -686,7 +686,8 @@ wallet2::wallet2(network_type nettype, bool restricted):
   m_light_wallet_unlocked_balance(0),
   m_key_on_device(false),
   m_ring_history_saved(false),
-  m_ringdb()
+  m_ringdb(),
+  m_last_block_reward(0)
 {
 }
 
@@ -1672,6 +1673,7 @@ void wallet2::process_new_blockchain_entry(const cryptonote::block& b, const cry
       process_new_transaction(b.tx_hashes[idx], parsed_block.txes[idx], parsed_block.o_indices.indices[idx+1].indices, height, b.timestamp, false, false, false, tx_cache_data[tx_cache_data_offset++]);
     }
     TIME_MEASURE_FINISH(txs_handle_time);
+    m_last_block_reward = cryptonote::get_outs_money_amount(b.miner_tx);
     LOG_PRINT_L2("Processed block: " << bl_id << ", height " << height << ", " <<  miner_tx_handle_time + txs_handle_time << "(" << miner_tx_handle_time << "/" << txs_handle_time <<")ms");
   }else
   {
@@ -3166,6 +3168,7 @@ void wallet2::generate(const std::string& wallet_, const epee::wipeable_string&
   cryptonote::block b;
   generate_genesis(b);
   m_blockchain.push_back(get_block_hash(b));
+  m_last_block_reward = cryptonote::get_outs_money_amount(b.miner_tx);
   add_subaddress_account(tr("Primary account"));
 
   if (!wallet_.empty())
@@ -3224,6 +3227,7 @@ crypto::secret_key wallet2::generate(const std::string& wallet_, const epee::wip
   cryptonote::block b;
   generate_genesis(b);
   m_blockchain.push_back(get_block_hash(b));
+  m_last_block_reward = cryptonote::get_outs_money_amount(b.miner_tx);
   add_subaddress_account(tr("Primary account"));
 
   if (!wallet_.empty())
@@ -3319,6 +3323,7 @@ void wallet2::generate(const std::string& wallet_, const epee::wipeable_string&
   cryptonote::block b;
   generate_genesis(b);
   m_blockchain.push_back(get_block_hash(b));
+  m_last_block_reward = cryptonote::get_outs_money_amount(b.miner_tx);
   add_subaddress_account(tr("Primary account"));
 
   if (!wallet_.empty())
@@ -3371,6 +3376,7 @@ void wallet2::generate(const std::string& wallet_, const epee::wipeable_string&
   cryptonote::block b;
   generate_genesis(b);
   m_blockchain.push_back(get_block_hash(b));
+  m_last_block_reward = cryptonote::get_outs_money_amount(b.miner_tx);
   add_subaddress_account(tr("Primary account"));
 
   if (!wallet_.empty())
@@ -3417,6 +3423,7 @@ void wallet2::restore(const std::string& wallet_, const epee::wipeable_string& p
     m_subaddress_lookahead_major = 5;
     m_subaddress_lookahead_minor = 20;
   }
+  m_last_block_reward = cryptonote::get_outs_money_amount(b.miner_tx);
   add_subaddress_account(tr("Primary account"));
   if (!wallet_.empty()) {
     store();
@@ -3513,6 +3520,7 @@ std::string wallet2::make_multisig(const epee::wipeable_string &password,
   cryptonote::block b;
   generate_genesis(b);
   m_blockchain.push_back(get_block_hash(b));
+  m_last_block_reward = cryptonote::get_outs_money_amount(b.miner_tx);
   add_subaddress_account(tr("Primary account"));
 
   if (!m_wallet_file.empty())
@@ -4015,6 +4023,7 @@ void wallet2::load(const std::string& wallet_, const epee::wipeable_string& pass
   if (m_blockchain.empty())
   {
     m_blockchain.push_back(genesis_hash);
+    m_last_block_reward = cryptonote::get_outs_money_amount(genesis.miner_tx);
   }
   else
   {
@@ -4404,6 +4413,7 @@ void wallet2::rescan_blockchain(bool refresh)
   generate_genesis(genesis);
   crypto::hash genesis_hash = get_block_hash(genesis);
   m_blockchain.push_back(genesis_hash);
+  m_last_block_reward = cryptonote::get_outs_money_amount(genesis.miner_tx);
   add_subaddress_account(tr("Primary account"));
 
   if (refresh)
@@ -10006,6 +10016,7 @@ void wallet2::import_blockchain(const std::tuple<size_t, crypto::hash, std::vect
   generate_genesis(genesis);
   crypto::hash genesis_hash = get_block_hash(genesis);
   check_genesis(genesis_hash);
+  m_last_block_reward = cryptonote::get_outs_money_amount(genesis.miner_tx);
 }
 //----------------------------------------------------------------------------------------------------
 std::vector<tools::wallet2::transfer_details> wallet2::export_outputs() const

src/wallet/wallet2.h

@@ -762,6 +762,9 @@ namespace tools
     void rescan_blockchain(bool refresh = true);
     bool is_transfer_unlocked(const transfer_details& td) const;
     bool is_transfer_unlocked(uint64_t unlock_time, uint64_t block_height) const;
+
+    uint64_t get_last_block_reward() const { return m_last_block_reward; }
+
     template <class t_archive>
     inline void serialize(t_archive &a, const unsigned int ver)
     {
@@ -863,6 +866,9 @@ namespace tools
       if(ver < 24)
         return;
       a & m_ring_history_saved;
+      if(ver < 25)
+        return;
+      a & m_last_block_reward;
     }
 
     /*!
@@ -1298,9 +1304,11 @@ namespace tools
     bool m_ring_history_saved;
     std::unique_ptr<ringdb> m_ringdb;
     boost::optional<crypto::chacha_key> m_ringdb_key;
+
+    uint64_t m_last_block_reward;
   };
 }
-BOOST_CLASS_VERSION(tools::wallet2, 24)
+BOOST_CLASS_VERSION(tools::wallet2, 25)
 BOOST_CLASS_VERSION(tools::wallet2::transfer_details, 9)
 BOOST_CLASS_VERSION(tools::wallet2::multisig_info, 1)
 BOOST_CLASS_VERSION(tools::wallet2::multisig_info::LR, 0)

src/wallet/wallet_rpc_server.cpp

@@ -74,6 +74,21 @@ namespace
     }
     return pwd_container;
   }
+  //------------------------------------------------------------------------------------------------------------------------------
+  void set_confirmations(tools::wallet_rpc::transfer_entry &entry, uint64_t blockchain_height, uint64_t block_reward)
+  {
+    if (entry.height >= blockchain_height)
+    {
+      entry.confirmations = 0;
+      entry.suggested_confirmations_threshold = 0;
+      return;
+    }
+    entry.confirmations = blockchain_height - entry.height;
+    if (block_reward == 0)
+      entry.suggested_confirmations_threshold = 0;
+    else
+      entry.suggested_confirmations_threshold = (entry.amount + block_reward - 1) / block_reward;
+  }
 }
 
 namespace tools
@@ -258,6 +273,7 @@ namespace tools
     entry.type = "in";
     entry.subaddr_index = pd.m_subaddr_index;
     entry.address = m_wallet->get_subaddress_as_str(pd.m_subaddr_index);
+    set_confirmations(entry, m_wallet->get_blockchain_current_height(), m_wallet->get_last_block_reward());
   }
   //------------------------------------------------------------------------------------------------------------------------------
   void wallet_rpc_server::fill_transfer_entry(tools::wallet_rpc::transfer_entry &entry, const crypto::hash &txid, const tools::wallet2::confirmed_transfer_details &pd)
@@ -284,6 +300,7 @@ namespace tools
     entry.type = "out";
     entry.subaddr_index = { pd.m_subaddr_account, 0 };
     entry.address = m_wallet->get_subaddress_as_str({pd.m_subaddr_account, 0});
+    set_confirmations(entry, m_wallet->get_blockchain_current_height(), m_wallet->get_last_block_reward());
   }
   //------------------------------------------------------------------------------------------------------------------------------
   void wallet_rpc_server::fill_transfer_entry(tools::wallet_rpc::transfer_entry &entry, const crypto::hash &txid, const tools::wallet2::unconfirmed_transfer_details &pd)
@@ -303,6 +320,7 @@ namespace tools
     entry.type = is_failed ? "failed" : "pending";
     entry.subaddr_index = { pd.m_subaddr_account, 0 };
     entry.address = m_wallet->get_subaddress_as_str({pd.m_subaddr_account, 0});
+    set_confirmations(entry, m_wallet->get_blockchain_current_height(), m_wallet->get_last_block_reward());
   }
   //------------------------------------------------------------------------------------------------------------------------------
   void wallet_rpc_server::fill_transfer_entry(tools::wallet_rpc::transfer_entry &entry, const crypto::hash &payment_id, const tools::wallet2::pool_payment_details &ppd)
@@ -322,6 +340,7 @@ namespace tools
     entry.type = "pool";
     entry.subaddr_index = pd.m_subaddr_index;
     entry.address = m_wallet->get_subaddress_as_str(pd.m_subaddr_index);
+    set_confirmations(entry, m_wallet->get_blockchain_current_height(), m_wallet->get_last_block_reward());
   }
   //------------------------------------------------------------------------------------------------------------------------------
   bool wallet_rpc_server::on_getbalance(const wallet_rpc::COMMAND_RPC_GET_BALANCE::request& req, wallet_rpc::COMMAND_RPC_GET_BALANCE::response& res, epee::json_rpc::error& er)

src/wallet/wallet_rpc_server_commands_defs.h

@@ -47,7 +47,7 @@
 // advance which version they will stop working with
 // Don't go over 32767 for any of these
 #define WALLET_RPC_VERSION_MAJOR 1
-#define WALLET_RPC_VERSION_MINOR 0
+#define WALLET_RPC_VERSION_MINOR 1
 #define MAKE_WALLET_RPC_VERSION(major,minor) (((major)<<16)|(minor))
 #define WALLET_RPC_VERSION MAKE_WALLET_RPC_VERSION(WALLET_RPC_VERSION_MAJOR, WALLET_RPC_VERSION_MINOR)
 namespace tools
@@ -1194,6 +1194,8 @@ namespace wallet_rpc
     cryptonote::subaddress_index subaddr_index;
     std::string address;
     bool double_spend_seen;
+    uint64_t confirmations;
+    uint64_t suggested_confirmation_threshold;
 
     BEGIN_KV_SERIALIZE_MAP()
       KV_SERIALIZE(txid);
@@ -1209,6 +1211,8 @@ namespace wallet_rpc
       KV_SERIALIZE(subaddr_index);
       KV_SERIALIZE(address);
       KV_SERIALIZE(double_spend_seen)
+      KV_SERIALIZE_OPT(confirmations, 0)
+      KV_SERIALIZE_OPT(suggested_confirmation_threshold, 0)
     END_KV_SERIALIZE_MAP()
   };