simplewallet: allow setting tx keys when sending to a subaddress

The tx key derivation is different then

src/simplewallet/simplewallet.cpp

@@ -208,7 +208,7 @@ namespace
   const char* USAGE_ADDRESS_BOOK("address_book [(add (<address>|<integrated address>) [<description possibly with whitespaces>])|(delete <index>)]");
   const char* USAGE_SET_VARIABLE("set <option> [<value>]");
   const char* USAGE_GET_TX_KEY("get_tx_key <txid>");
-  const char* USAGE_SET_TX_KEY("set_tx_key <txid> <tx_key>");
+  const char* USAGE_SET_TX_KEY("set_tx_key <txid> <tx_key> [<subaddress>]");
   const char* USAGE_CHECK_TX_KEY("check_tx_key <txid> <txkey> <address>");
   const char* USAGE_GET_TX_PROOF("get_tx_proof <txid> <address> [<message>]");
   const char* USAGE_CHECK_TX_PROOF("check_tx_proof <txid> <address> <signature_file> [<message>]");
@@ -7884,11 +7884,27 @@ bool simple_wallet::set_tx_key(const std::vector<std::string> &args_)
 {
   std::vector<std::string> local_args = args_;
 
-  if(local_args.size() != 2) {
+  if(local_args.size() != 2 && local_args.size() != 3) {
     PRINT_USAGE(USAGE_SET_TX_KEY);
     return true;
   }
 
+  boost::optional<cryptonote::account_public_address> single_destination_subaddress;
+  if (local_args.size() > 1)
+  {
+    cryptonote::address_parse_info info;
+    if (cryptonote::get_account_address_from_str_or_url(info, m_wallet->nettype(), local_args.back(), oa_prompter))
+    {
+      if (!info.is_subaddress)
+      {
+        fail_msg_writer() << tr("Last argument is an address, but not a subaddress");
+        return true;
+      }
+      single_destination_subaddress = info.address;
+      local_args.pop_back();
+    }
+  }
+
   crypto::hash txid;
   if (!epee::string_tools::hex_to_pod(local_args[0], txid))
   {
@@ -7928,12 +7944,14 @@ bool simple_wallet::set_tx_key(const std::vector<std::string> &args_)
 
   try
   {
-    m_wallet->set_tx_key(txid, tx_key, additional_tx_keys);
+    m_wallet->set_tx_key(txid, tx_key, additional_tx_keys, single_destination_subaddress);
     success_msg_writer() << tr("Tx key successfully stored.");
   }
   catch (const std::exception &e)
   {
     fail_msg_writer() << tr("Failed to store tx key: ") << e.what();
+    if (!single_destination_subaddress)
+      fail_msg_writer() << tr("It could be because the transfer was to a subaddress. If this is the case, pass the subaddress last");
   }
   return true;
 }

src/wallet/wallet2.cpp

@@ -10915,7 +10915,7 @@ bool wallet2::get_tx_key(const crypto::hash &txid, crypto::secret_key &tx_key, s
   return true;
 }
 //----------------------------------------------------------------------------------------------------
-void wallet2::set_tx_key(const crypto::hash &txid, const crypto::secret_key &tx_key, const std::vector<crypto::secret_key> &additional_tx_keys)
+void wallet2::set_tx_key(const crypto::hash &txid, const crypto::secret_key &tx_key, const std::vector<crypto::secret_key> &additional_tx_keys, const boost::optional<cryptonote::account_public_address> &single_destination_subaddress)
 {
   // fetch tx from daemon and check if secret keys agree with corresponding public keys
   COMMAND_RPC_GET_TRANSACTIONS::request req = AUTO_VAL_INIT(req);
@@ -10956,6 +10956,16 @@ void wallet2::set_tx_key(const crypto::hash &txid, const crypto::secret_key &tx_
       found = true;
       break;
     }
+    // when sent to a single subaddress, the derivation is different
+    if (single_destination_subaddress)
+    {
+      calculated_pub_key = rct::rct2pk(rct::scalarmultKey(rct::pk2rct(single_destination_subaddress->m_spend_public_key), rct::sk2rct(tx_key)));
+      if (calculated_pub_key == pub_key_field.pub_key)
+      {
+        found = true;
+        break;
+      }
+    }
   }
   THROW_WALLET_EXCEPTION_IF(!found, error::wallet_internal_error, "Given tx secret key doesn't agree with the tx public key in the blockchain");
   tx_extra_additional_pub_keys additional_tx_pub_keys;

src/wallet/wallet2.h

@@ -1106,7 +1106,7 @@ private:
     void credits_target(uint64_t threshold) { m_credits_target = threshold; }
 
     bool get_tx_key_cached(const crypto::hash &txid, crypto::secret_key &tx_key, std::vector<crypto::secret_key> &additional_tx_keys) const;
-    void set_tx_key(const crypto::hash &txid, const crypto::secret_key &tx_key, const std::vector<crypto::secret_key> &additional_tx_keys);
+    void set_tx_key(const crypto::hash &txid, const crypto::secret_key &tx_key, const std::vector<crypto::secret_key> &additional_tx_keys, const boost::optional<cryptonote::account_public_address> &single_destination_subaddress = boost::none);
     bool get_tx_key(const crypto::hash &txid, crypto::secret_key &tx_key, std::vector<crypto::secret_key> &additional_tx_keys);
     void check_tx_key(const crypto::hash &txid, const crypto::secret_key &tx_key, const std::vector<crypto::secret_key> &additional_tx_keys, const cryptonote::account_public_address &address, uint64_t &received, bool &in_pool, uint64_t &confirmations);
     void check_tx_key_helper(const crypto::hash &txid, const crypto::key_derivation &derivation, const std::vector<crypto::key_derivation> &additional_derivations, const cryptonote::account_public_address &address, uint64_t &received, bool &in_pool, uint64_t &confirmations);