wallet: new {ex,im}port_key_images commands and RPC calls

They are used to export a signed set of key images from a wallet
with a private spend key, so an auditor with the matching view key
may see which of those are spent, and which are not.

src/simplewallet/simplewallet.cpp

@@ -662,6 +662,8 @@ simple_wallet::simple_wallet()
   m_cmd_binder.set_handler("status", boost::bind(&simple_wallet::status, this, _1), tr("Show wallet status information"));
   m_cmd_binder.set_handler("sign", boost::bind(&simple_wallet::sign, this, _1), tr("Sign the contents of a file"));
   m_cmd_binder.set_handler("verify", boost::bind(&simple_wallet::verify, this, _1), tr("Verify a signature on the contents of a file"));
+  m_cmd_binder.set_handler("export_key_images", boost::bind(&simple_wallet::export_key_images, this, _1), tr("Export a signed set of key images"));
+  m_cmd_binder.set_handler("import_key_images", boost::bind(&simple_wallet::import_key_images, this, _1), tr("Import signed key images list and verify their spent status"));
   m_cmd_binder.set_handler("help", boost::bind(&simple_wallet::help, this, _1), tr("Show this help"));
 }
 //----------------------------------------------------------------------------------------------------
@@ -3480,6 +3482,111 @@ bool simple_wallet::verify(const std::vector<std::string> &args)
   return true;
 }
 //----------------------------------------------------------------------------------------------------
+bool simple_wallet::export_key_images(const std::vector<std::string> &args)
+{
+  if (args.size() != 1)
+  {
+    fail_msg_writer() << tr("usage: export_key_images <filename>");
+    return true;
+  }
+  if (m_wallet->watch_only())
+  {
+    fail_msg_writer() << tr("wallet is watch-only and cannot export key images");
+    return true;
+  }
+  std::string filename = args[0];
+
+  try
+  {
+    std::vector<std::pair<crypto::key_image, crypto::signature>> ski = m_wallet->export_key_images();
+    std::string data;
+    for (const auto &i: ski)
+    {
+      data += epee::string_tools::pod_to_hex(i.first);
+      data += epee::string_tools::pod_to_hex(i.second);
+    }
+    bool r = epee::file_io_utils::save_string_to_file(filename, data);
+    if (!r)
+    {
+      fail_msg_writer() << tr("failed to save file ") << filename;
+      return true;
+    }
+  }
+  catch (std::exception &e)
+  {
+    LOG_ERROR("Error exporting key images: " << e.what());
+    fail_msg_writer() << "Error exporting key images: " << e.what();
+    return true;
+  }
+
+  success_msg_writer() << tr("Signed key images exported to ") << filename;
+  return true;
+}
+//----------------------------------------------------------------------------------------------------
+bool simple_wallet::import_key_images(const std::vector<std::string> &args)
+{
+  if (args.size() != 1)
+  {
+    fail_msg_writer() << tr("usage: import_key_images <filename>");
+    return true;
+  }
+  std::string filename = args[0];
+
+  std::string data;
+  bool r = epee::file_io_utils::load_file_to_string(filename, data);
+  if (!r)
+  {
+    fail_msg_writer() << tr("failed to read file ") << filename;
+    return true;
+  }
+
+  const size_t record_size = sizeof(crypto::key_image)*2 + sizeof(crypto::signature)*2;
+  if (data.size() % record_size)
+  {
+    fail_msg_writer() << "Bad data size from file " << filename;
+    return true;
+  }
+  size_t nki = data.size() / record_size;
+
+  std::vector<std::pair<crypto::key_image, crypto::signature>> ski;
+  ski.reserve(nki);
+  for (size_t n = 0; n < nki; ++n)
+  {
+    cryptonote::blobdata bd;
+
+    if(!epee::string_tools::parse_hexstr_to_binbuff(std::string(&data[n * record_size], sizeof(crypto::key_image)*2), bd))
+    {
+      fail_msg_writer() << tr("failed to parse key image");
+      return false;
+    }
+    crypto::key_image key_image = *reinterpret_cast<const crypto::key_image*>(bd.data());
+
+    if(!epee::string_tools::parse_hexstr_to_binbuff(std::string(&data[n * record_size + sizeof(crypto::key_image)*2], sizeof(crypto::signature)*2), bd))
+    {
+      fail_msg_writer() << tr("failed to parse signature");
+      return false;
+    }
+    crypto::signature signature = *reinterpret_cast<const crypto::signature*>(bd.data());
+
+    ski.push_back(std::make_pair(key_image, signature));
+  }
+
+  try
+  {
+    uint64_t spent = 0, unspent = 0;
+    uint64_t height = m_wallet->import_key_images(ski, spent, unspent);
+    success_msg_writer() << "Signed key images imported to height " << height << ", "
+        << print_money(spent) << " spent, " << print_money(unspent) << " unspent";
+  }
+  catch (const std::exception &e)
+  {
+    fail_msg_writer() << "Failed to import key images: " << e.what();
+    return true;
+  }
+
+  return true;
+}
+//----------------------------------------------------------------------------------------------------
 bool simple_wallet::process_command(const std::vector<std::string> &args)
 {
   return m_cmd_binder.process_command_vec(args);

src/simplewallet/simplewallet.h

@@ -145,6 +145,8 @@ namespace cryptonote
     bool set_default_fee_multiplier(const std::vector<std::string> &args);
     bool sign(const std::vector<std::string> &args);
     bool verify(const std::vector<std::string> &args);
+    bool export_key_images(const std::vector<std::string> &args);
+    bool import_key_images(const std::vector<std::string> &args);
 
     uint64_t get_daemon_blockchain_height(std::string& err);
     bool try_connect_to_daemon(bool silent = false);

src/wallet/wallet2.cpp

@@ -3286,7 +3286,123 @@ bool wallet2::verify(const std::string &data, const cryptonote::account_public_a
   memcpy(&s, decoded.data(), sizeof(s));
   return crypto::check_signature(hash, address.m_spend_public_key, s);
 }
+//----------------------------------------------------------------------------------------------------
+std::vector<std::pair<crypto::key_image, crypto::signature>> wallet2::export_key_images() const
+{
+  std::vector<std::pair<crypto::key_image, crypto::signature>> ski;
+
+  ski.reserve(m_transfers.size());
+  for (size_t n = 0; n < m_transfers.size(); ++n)
+  {
+    const transfer_details &td = m_transfers[n];
+
+    crypto::hash hash;
+    crypto::cn_fast_hash(&td.m_key_image, sizeof(td.m_key_image), hash);
+
+    // get ephemeral public key
+    const cryptonote::tx_out &out = td.m_tx.vout[td.m_internal_output_index];
+    THROW_WALLET_EXCEPTION_IF(out.target.type() != typeid(txout_to_key), error::wallet_internal_error,
+        "Output is not txout_to_key");
+    const cryptonote::txout_to_key &o = boost::get<const cryptonote::txout_to_key>(out.target);
+    const crypto::public_key pkey = o.key;
+
+    // get tx pub key
+    std::vector<tx_extra_field> tx_extra_fields;
+    if(!parse_tx_extra(td.m_tx.extra, tx_extra_fields))
+    {
+      // Extra may only be partially parsed, it's OK if tx_extra_fields contains public key
+    }
+    tx_extra_pub_key pub_key_field;
+    THROW_WALLET_EXCEPTION_IF(!find_tx_extra_field_by_type(tx_extra_fields, pub_key_field), error::wallet_internal_error,
+        "Public key wasn't found in the transaction extra");
+    crypto::public_key tx_pub_key = pub_key_field.pub_key;
+
+    // generate ephemeral secret key
+    crypto::key_image ki;
+    cryptonote::keypair in_ephemeral;
+    cryptonote::generate_key_image_helper(m_account.get_keys(), tx_pub_key, td.m_internal_output_index, in_ephemeral, ki);
+    THROW_WALLET_EXCEPTION_IF(ki != td.m_key_image,
+        error::wallet_internal_error, "key_image generated not matched with cached key image");
+    THROW_WALLET_EXCEPTION_IF(in_ephemeral.pub != pkey,
+        error::wallet_internal_error, "key_image generated ephemeral public key not matched with output_key");
 
+    // sign the key image with the output secret key
+    crypto::signature signature;
+    std::vector<const crypto::public_key*> key_ptrs;
+    key_ptrs.push_back(&pkey);
+
+    crypto::generate_ring_signature((const crypto::hash&)td.m_key_image, td.m_key_image, key_ptrs, in_ephemeral.sec, 0, &signature);
+
+    ski.push_back(std::make_pair(td.m_key_image, signature));
+  }
+  return ski;
+}
+//----------------------------------------------------------------------------------------------------
+uint64_t wallet2::import_key_images(const std::vector<std::pair<crypto::key_image, crypto::signature>> &signed_key_images, uint64_t &spent, uint64_t &unspent)
+{
+  COMMAND_RPC_IS_KEY_IMAGE_SPENT::request req = AUTO_VAL_INIT(req);
+  COMMAND_RPC_IS_KEY_IMAGE_SPENT::response daemon_resp = AUTO_VAL_INIT(daemon_resp);
+
+  THROW_WALLET_EXCEPTION_IF(signed_key_images.size() > m_transfers.size(), error::wallet_internal_error,
+      "The blockchain is out of date compared to the signed key images");
+
+  if (signed_key_images.empty())
+  {
+    spent = 0;
+    unspent = 0;
+    return 0;
+  }
+
+  for (size_t n = 0; n < signed_key_images.size(); ++n)
+  {
+    const transfer_details &td = m_transfers[n];
+    const crypto::key_image &key_image = signed_key_images[n].first;
+    const crypto::signature &signature = signed_key_images[n].second;
+
+    // get ephemeral public key
+    const cryptonote::tx_out &out = td.m_tx.vout[td.m_internal_output_index];
+    THROW_WALLET_EXCEPTION_IF(out.target.type() != typeid(txout_to_key), error::wallet_internal_error,
+      "Non txout_to_key output found");
+    const cryptonote::txout_to_key &o = boost::get<cryptonote::txout_to_key>(out.target);
+    const crypto::public_key pkey = o.key;
+
+    std::vector<const crypto::public_key*> pkeys;
+    pkeys.push_back(&pkey);
+    THROW_WALLET_EXCEPTION_IF(!crypto::check_ring_signature((const crypto::hash&)key_image, key_image, pkeys, &signature),
+        error::wallet_internal_error, "Signature check failed: key image " + epee::string_tools::pod_to_hex(key_image)
+        + ", signature " + epee::string_tools::pod_to_hex(signature) + ", pubkey " + epee::string_tools::pod_to_hex(*pkeys[0]));
+
+    req.key_images.push_back(epee::string_tools::pod_to_hex(key_image));
+  }
+
+  m_daemon_rpc_mutex.lock();
+  bool r = epee::net_utils::invoke_http_json_remote_command2(m_daemon_address + "/is_key_image_spent", req, daemon_resp, m_http_client, 200000);
+  m_daemon_rpc_mutex.unlock();
+  THROW_WALLET_EXCEPTION_IF(!r, error::no_connection_to_daemon, "is_key_image_spent");
+  THROW_WALLET_EXCEPTION_IF(daemon_resp.status == CORE_RPC_STATUS_BUSY, error::daemon_busy, "is_key_image_spent");
+  THROW_WALLET_EXCEPTION_IF(daemon_resp.status != CORE_RPC_STATUS_OK, error::is_key_image_spent_error, daemon_resp.status);
+  THROW_WALLET_EXCEPTION_IF(daemon_resp.spent_status.size() != signed_key_images.size(), error::wallet_internal_error,
+    "daemon returned wrong response for is_key_image_spent, wrong amounts count = " +
+    std::to_string(daemon_resp.spent_status.size()) + ", expected " +  std::to_string(signed_key_images.size()));
+
+  spent = 0;
+  unspent = 0;
+  for (size_t n = 0; n < daemon_resp.spent_status.size(); ++n)
+  {
+    transfer_details &td = m_transfers[n];
+    uint64_t amount = td.m_tx.vout[td.m_internal_output_index].amount;
+    td.m_spent = daemon_resp.spent_status[n] != COMMAND_RPC_IS_KEY_IMAGE_SPENT::UNSPENT;
+    if (td.m_spent)
+      spent += amount;
+    else
+      unspent += amount;
+    LOG_PRINT_L2("Transfer " << n << ": " << print_money(amount) << " (" << td.m_global_output_index << "): "
+        << (td.m_spent ? "spent" : "unspent") << " (key image " << req.key_images[n] << ")");
+  }
+  LOG_PRINT_L1("Total: " << print_money(spent) << " spent, " << print_money(unspent) << " unspent");
+
+  return m_transfers[signed_key_images.size() - 1].m_block_height;
+}
 //----------------------------------------------------------------------------------------------------
 void wallet2::generate_genesis(cryptonote::block& b) {
   if (m_testnet)

src/wallet/wallet2.h

@@ -394,8 +394,10 @@ namespace tools
     std::string sign(const std::string &data) const;
     bool verify(const std::string &data, const cryptonote::account_public_address &address, const std::string &signature) const;
 
-    void update_pool_state();
+    std::vector<std::pair<crypto::key_image, crypto::signature>> export_key_images() const;
+    uint64_t import_key_images(const std::vector<std::pair<crypto::key_image, crypto::signature>> &signed_key_images, uint64_t &spent, uint64_t &unspent);
 
+    void update_pool_state();
   private:
     /*!
      * \brief  Stores wallet information to wallet file.

src/wallet/wallet_rpc_server.cpp

@@ -995,5 +995,71 @@ namespace tools
     return true;
   }
   //------------------------------------------------------------------------------------------------------------------------------
+  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)
+  {
+    try
+    {
+      std::vector<std::pair<crypto::key_image, crypto::signature>> ski = m_wallet.export_key_images();
+      res.signed_key_images.resize(ski.size());
+      for (size_t n = 0; n < ski.size(); ++n)
+      {
+         res.signed_key_images[n].key_image = epee::string_tools::pod_to_hex(ski[n].first);
+         res.signed_key_images[n].signature = epee::string_tools::pod_to_hex(ski[n].second);
+      }
+    }
+
+    catch (...)
+    {
+      er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR;
+      er.message = "Failed";
+      return false;
+    }
+
+    return true;
+  }
+  //------------------------------------------------------------------------------------------------------------------------------
+  bool wallet_rpc_server::on_import_key_images(const wallet_rpc::COMMAND_RPC_IMPORT_KEY_IMAGES::request& req, wallet_rpc::COMMAND_RPC_IMPORT_KEY_IMAGES::response& res, epee::json_rpc::error& er)
+  {
+    try
+    {
+      std::vector<std::pair<crypto::key_image, crypto::signature>> ski;
+      ski.resize(req.signed_key_images.size());
+      for (size_t n = 0; n < ski.size(); ++n)
+      {
+        cryptonote::blobdata bd;
+
+        if(!epee::string_tools::parse_hexstr_to_binbuff(req.signed_key_images[n].key_image, bd))
+        {
+          er.code = WALLET_RPC_ERROR_CODE_WRONG_KEY_IMAGE;
+          er.message = "failed to parse key image";
+          return false;
+        }
+        ski[n].first = *reinterpret_cast<const crypto::key_image*>(bd.data());
+
+        if(!epee::string_tools::parse_hexstr_to_binbuff(req.signed_key_images[n].signature, bd))
+        {
+          er.code = WALLET_RPC_ERROR_CODE_WRONG_SIGNATURE;
+          er.message = "failed to parse signature";
+          return false;
+        }
+        ski[n].second = *reinterpret_cast<const crypto::signature*>(bd.data());
+      }
+      uint64_t spent = 0, unspent = 0;
+      uint64_t height = m_wallet.import_key_images(ski, spent, unspent);
+      res.spent = spent;
+      res.unspent = unspent;
+      res.height = height;
+    }
+
+    catch (...)
+    {
+      er.code = WALLET_RPC_ERROR_CODE_UNKNOWN_ERROR;
+      er.message = "Failed";
+      return false;
+    }
+
+    return true;
+  }
+  //------------------------------------------------------------------------------------------------------------------------------
 }
 

src/wallet/wallet_rpc_server.h

@@ -82,6 +82,8 @@ namespace tools
         MAP_JON_RPC_WE("get_transfers",      on_get_transfers,      wallet_rpc::COMMAND_RPC_GET_TRANSFERS)
         MAP_JON_RPC_WE("sign",               on_sign,               wallet_rpc::COMMAND_RPC_SIGN)
         MAP_JON_RPC_WE("verify",             on_verify,             wallet_rpc::COMMAND_RPC_VERIFY)
+        MAP_JON_RPC_WE("export_key_images",  on_export_key_images,  wallet_rpc::COMMAND_RPC_EXPORT_KEY_IMAGES)
+        MAP_JON_RPC_WE("import_key_images",  on_import_key_images,  wallet_rpc::COMMAND_RPC_IMPORT_KEY_IMAGES)
       END_JSON_RPC_MAP()
     END_URI_MAP2()
 
@@ -107,6 +109,8 @@ namespace tools
       bool on_get_transfers(const wallet_rpc::COMMAND_RPC_GET_TRANSFERS::request& req, wallet_rpc::COMMAND_RPC_GET_TRANSFERS::response& res, epee::json_rpc::error& er);
       bool on_sign(const wallet_rpc::COMMAND_RPC_SIGN::request& req, wallet_rpc::COMMAND_RPC_SIGN::response& res, epee::json_rpc::error& er);
       bool on_verify(const wallet_rpc::COMMAND_RPC_VERIFY::request& req, wallet_rpc::COMMAND_RPC_VERIFY::response& res, epee::json_rpc::error& er);
+      bool 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);
+      bool on_import_key_images(const wallet_rpc::COMMAND_RPC_IMPORT_KEY_IMAGES::request& req, wallet_rpc::COMMAND_RPC_IMPORT_KEY_IMAGES::response& res, epee::json_rpc::error& er);
 
       bool handle_command_line(const boost::program_options::variables_map& vm);