Reserve proof

1 files changed, 245 insertions, 0 deletions

diff --git a/src/wallet/wallet2.cpp b/src/wallet/wallet2.cpp
index 2af41f588..963783002 100644
--- a/src/wallet/wallet2.cpp
+++ b/src/wallet/wallet2.cpp
@@ -7947,6 +7947,251 @@ bool wallet2::check_tx_proof(const crypto::hash &txid, const cryptonote::account
   return false;
 }
 
+std::string wallet2::get_reserve_proof(const boost::optional<std::pair<uint32_t, uint64_t>> &account_minreserve, const std::string &message)
+{
+  THROW_WALLET_EXCEPTION_IF(m_watch_only || m_multisig, error::wallet_internal_error, "Reserve proof can only be generated by a full wallet");
+  THROW_WALLET_EXCEPTION_IF(balance_all() == 0, error::wallet_internal_error, "Zero balance");
+  THROW_WALLET_EXCEPTION_IF(account_minreserve && balance(account_minreserve->first) < account_minreserve->second, error::wallet_internal_error,
+    "Not enough balance in this account for the requested minimum reserve amount");
+
+  // determine which outputs to include in the proof
+  std::vector<size_t> selected_transfers;
+  for (size_t i = 0; i < m_transfers.size(); ++i)
+  {
+    const transfer_details &td = m_transfers[i];
+    if (!td.m_spent && (!account_minreserve || account_minreserve->first == td.m_subaddr_index.major))
+      selected_transfers.push_back(i);
+  }
+
+  if (account_minreserve)
+  {
+    // minimize the number of outputs included in the proof, by only picking the N largest outputs that can cover the requested min reserve amount
+    std::sort(selected_transfers.begin(), selected_transfers.end(), [&](const size_t a, const size_t b)
+      { return m_transfers[a].amount() > m_transfers[b].amount(); });
+    while (selected_transfers.size() >= 2 && m_transfers[selected_transfers[1]].amount() >= account_minreserve->second)
+      selected_transfers.erase(selected_transfers.begin());
+    size_t sz = 0;
+    uint64_t total = 0;
+    while (total < account_minreserve->second)
+    {
+      total += m_transfers[selected_transfers[sz]].amount();
+      ++sz;
+    }
+    selected_transfers.resize(sz);
+  }
+
+  // compute signature prefix hash
+  std::string prefix_data = message;
+  prefix_data.append((const char*)&m_account.get_keys().m_account_address, sizeof(cryptonote::account_public_address));
+  for (size_t i = 0; i < selected_transfers.size(); ++i)
+  {
+    prefix_data.append((const char*)&m_transfers[selected_transfers[i]].m_key_image, sizeof(crypto::key_image));
+  }
+  crypto::hash prefix_hash;
+  crypto::cn_fast_hash(prefix_data.data(), prefix_data.size(), prefix_hash);
+
+  // generate proof entries
+  std::vector<reserve_proof_entry> proofs(selected_transfers.size());
+  std::unordered_set<cryptonote::subaddress_index> subaddr_indices = { {0,0} };
+  for (size_t i = 0; i < selected_transfers.size(); ++i)
+  {
+    const transfer_details &td = m_transfers[selected_transfers[i]];
+    reserve_proof_entry& proof = proofs[i];
+    proof.txid = td.m_txid;
+    proof.index_in_tx = td.m_internal_output_index;
+    proof.key_image = td.m_key_image;
+    subaddr_indices.insert(td.m_subaddr_index);
+
+    // get tx pub key 
+    const crypto::public_key tx_pub_key = get_tx_pub_key_from_extra(td.m_tx, td.m_pk_index);
+    THROW_WALLET_EXCEPTION_IF(tx_pub_key == crypto::null_pkey, error::wallet_internal_error, "The tx public key isn't found");
+    const std::vector<crypto::public_key> additional_tx_pub_keys = get_additional_tx_pub_keys_from_extra(td.m_tx);
+
+    // determine which tx pub key was used for deriving the output key
+    const crypto::public_key *tx_pub_key_used = &tx_pub_key;
+    for (int i = 0; i < 2; ++i)
+    {
+      proof.shared_secret = rct::rct2pk(rct::scalarmultKey(rct::pk2rct(*tx_pub_key_used), rct::sk2rct(m_account.get_keys().m_view_secret_key)));
+      crypto::key_derivation derivation;
+      THROW_WALLET_EXCEPTION_IF(!crypto::generate_key_derivation(proof.shared_secret, rct::rct2sk(rct::I), derivation),
+        error::wallet_internal_error, "Failed to generate key derivation");
+      crypto::public_key subaddress_spendkey;
+      THROW_WALLET_EXCEPTION_IF(!derive_subaddress_public_key(td.get_public_key(), derivation, proof.index_in_tx, subaddress_spendkey),
+        error::wallet_internal_error, "Failed to derive subaddress public key");
+      if (m_subaddresses.count(subaddress_spendkey) == 1)
+        break;
+      THROW_WALLET_EXCEPTION_IF(additional_tx_pub_keys.empty(), error::wallet_internal_error,
+        "Normal tx pub key doesn't derive the expected output, while the additional tx pub keys are empty");
+      THROW_WALLET_EXCEPTION_IF(i == 1, error::wallet_internal_error,
+        "Neither normal tx pub key nor additional tx pub key derive the expected output key");
+      tx_pub_key_used = &additional_tx_pub_keys[proof.index_in_tx];
+    }
+
+    // generate signature for shared secret
+    crypto::generate_tx_proof(prefix_hash, m_account.get_keys().m_account_address.m_view_public_key, *tx_pub_key_used, boost::none, proof.shared_secret, m_account.get_keys().m_view_secret_key, proof.shared_secret_sig);
+
+    // derive ephemeral secret key
+    crypto::key_image ki;
+    cryptonote::keypair ephemeral;
+    const bool r = cryptonote::generate_key_image_helper(m_account.get_keys(), m_subaddresses, td.get_public_key(), tx_pub_key,  additional_tx_pub_keys, td.m_internal_output_index, ephemeral, ki);
+    THROW_WALLET_EXCEPTION_IF(!r, error::wallet_internal_error, "Failed to generate key image");
+    THROW_WALLET_EXCEPTION_IF(ephemeral.pub != td.get_public_key(), error::wallet_internal_error, "Derived public key doesn't agree with the stored one");
+
+    // generate signature for key image
+    const std::vector<const crypto::public_key*> pubs = { &ephemeral.pub };
+    crypto::generate_ring_signature(prefix_hash, td.m_key_image, &pubs[0], 1, ephemeral.sec, 0, &proof.key_image_sig);
+  }
+
+  // collect all subaddress spend keys that received those outputs and generate their signatures
+  std::unordered_map<crypto::public_key, crypto::signature> subaddr_spendkeys;
+  for (const cryptonote::subaddress_index &index : subaddr_indices)
+  {
+    crypto::secret_key subaddr_spend_skey = m_account.get_keys().m_spend_secret_key;
+    if (!index.is_zero())
+    {
+      crypto::secret_key m = cryptonote::get_subaddress_secret_key(m_account.get_keys().m_view_secret_key, index);
+      crypto::secret_key tmp = subaddr_spend_skey;
+      sc_add((unsigned char*)&subaddr_spend_skey, (unsigned char*)&m, (unsigned char*)&tmp);
+    }
+    crypto::public_key subaddr_spend_pkey;
+    secret_key_to_public_key(subaddr_spend_skey, subaddr_spend_pkey);
+    crypto::generate_signature(prefix_hash, subaddr_spend_pkey, subaddr_spend_skey, subaddr_spendkeys[subaddr_spend_pkey]);
+  }
+
+  // serialize & encode
+  std::ostringstream oss;
+  boost::archive::portable_binary_oarchive ar(oss);
+  ar << proofs << subaddr_spendkeys;
+  return "ReserveProofV1" + tools::base58::encode(oss.str());
+}
+
+bool wallet2::check_reserve_proof(const cryptonote::account_public_address &address, const std::string &message, const std::string &sig_str, uint64_t &total, uint64_t &spent)
+{
+  uint32_t rpc_version;
+  THROW_WALLET_EXCEPTION_IF(!check_connection(&rpc_version), error::wallet_internal_error, "Failed to connect to daemon: " + get_daemon_address());
+  THROW_WALLET_EXCEPTION_IF(rpc_version < MAKE_CORE_RPC_VERSION(1, 0), error::wallet_internal_error, "Daemon RPC version is too old");
+
+  static constexpr char header[] = "ReserveProofV1";
+  THROW_WALLET_EXCEPTION_IF(!boost::string_ref{sig_str}.starts_with(header), error::wallet_internal_error,
+    "Signature header check error");
+
+  std::string sig_decoded;
+  THROW_WALLET_EXCEPTION_IF(!tools::base58::decode(sig_str.substr(std::strlen(header)), sig_decoded), error::wallet_internal_error,
+    "Signature decoding error");
+
+  std::istringstream iss(sig_decoded);
+  boost::archive::portable_binary_iarchive ar(iss);
+  std::vector<reserve_proof_entry> proofs;
+  std::unordered_map<crypto::public_key, crypto::signature> subaddr_spendkeys;
+  ar >> proofs >> subaddr_spendkeys;
+
+  THROW_WALLET_EXCEPTION_IF(subaddr_spendkeys.count(address.m_spend_public_key) == 0, error::wallet_internal_error,
+    "The given address isn't found in the proof");
+
+  // compute signature prefix hash
+  std::string prefix_data = message;
+  prefix_data.append((const char*)&address, sizeof(cryptonote::account_public_address));
+  for (size_t i = 0; i < proofs.size(); ++i)
+  {
+    prefix_data.append((const char*)&proofs[i].key_image, sizeof(crypto::key_image));
+  }
+  crypto::hash prefix_hash;
+  crypto::cn_fast_hash(prefix_data.data(), prefix_data.size(), prefix_hash);
+
+  // fetch txes from daemon
+  COMMAND_RPC_GET_TRANSACTIONS::request gettx_req;
+  COMMAND_RPC_GET_TRANSACTIONS::response gettx_res;
+  for (size_t i = 0; i < proofs.size(); ++i)
+    gettx_req.txs_hashes.push_back(epee::string_tools::pod_to_hex(proofs[i].txid));
+  m_daemon_rpc_mutex.lock();
+  bool ok = net_utils::invoke_http_json("/gettransactions", gettx_req, gettx_res, m_http_client);
+  m_daemon_rpc_mutex.unlock();
+  THROW_WALLET_EXCEPTION_IF(!ok || gettx_res.txs.size() != proofs.size(),
+    error::wallet_internal_error, "Failed to get transaction from daemon");
+
+  // check spent status
+  COMMAND_RPC_IS_KEY_IMAGE_SPENT::request kispent_req;
+  COMMAND_RPC_IS_KEY_IMAGE_SPENT::response kispent_res;
+  for (size_t i = 0; i < proofs.size(); ++i)
+    kispent_req.key_images.push_back(epee::string_tools::pod_to_hex(proofs[i].key_image));
+  m_daemon_rpc_mutex.lock();
+  ok = epee::net_utils::invoke_http_json("/is_key_image_spent", kispent_req, kispent_res, m_http_client, rpc_timeout);
+  m_daemon_rpc_mutex.unlock();
+  THROW_WALLET_EXCEPTION_IF(!ok || kispent_res.spent_status.size() != proofs.size(),
+    error::wallet_internal_error, "Failed to get key image spent status from daemon");
+
+  total = spent = 0;
+  for (size_t i = 0; i < proofs.size(); ++i)
+  {
+    const reserve_proof_entry& proof = proofs[i];
+    THROW_WALLET_EXCEPTION_IF(gettx_res.txs[i].in_pool, error::wallet_internal_error, "Tx is unconfirmed");
+
+    cryptonote::blobdata tx_data;
+    ok = string_tools::parse_hexstr_to_binbuff(gettx_res.txs[i].as_hex, tx_data);
+    THROW_WALLET_EXCEPTION_IF(!ok, error::wallet_internal_error, "Failed to parse transaction from daemon");
+
+    crypto::hash tx_hash, tx_prefix_hash;
+    cryptonote::transaction tx;
+    THROW_WALLET_EXCEPTION_IF(!cryptonote::parse_and_validate_tx_from_blob(tx_data, tx, tx_hash, tx_prefix_hash), error::wallet_internal_error,
+      "Failed to validate transaction from daemon");
+    THROW_WALLET_EXCEPTION_IF(tx_hash != proof.txid, error::wallet_internal_error, "Failed to get the right transaction from daemon");
+
+    THROW_WALLET_EXCEPTION_IF(proof.index_in_tx >= tx.vout.size(), error::wallet_internal_error, "index_in_tx is out of bound");
+
+    const cryptonote::txout_to_key* const out_key = boost::get<cryptonote::txout_to_key>(std::addressof(tx.vout[proof.index_in_tx].target));
+    THROW_WALLET_EXCEPTION_IF(!out_key, error::wallet_internal_error, "Output key wasn't found")
+
+    // get tx pub key
+    const crypto::public_key tx_pub_key = get_tx_pub_key_from_extra(tx);
+    THROW_WALLET_EXCEPTION_IF(tx_pub_key == crypto::null_pkey, error::wallet_internal_error, "The tx public key isn't found");
+    const std::vector<crypto::public_key> additional_tx_pub_keys = get_additional_tx_pub_keys_from_extra(tx);
+
+    // check singature for shared secret
+    ok = crypto::check_tx_proof(prefix_hash, address.m_view_public_key, tx_pub_key, boost::none, proof.shared_secret, proof.shared_secret_sig);
+    if (!ok && additional_tx_pub_keys.size() == tx.vout.size())
+      ok = crypto::check_tx_proof(prefix_hash, address.m_view_public_key, additional_tx_pub_keys[proof.index_in_tx], boost::none, proof.shared_secret, proof.shared_secret_sig);
+    if (!ok)
+      return false;
+
+    // check signature for key image
+    const std::vector<const crypto::public_key*> pubs = { &out_key->key };
+    ok = crypto::check_ring_signature(prefix_hash, proof.key_image, &pubs[0], 1, &proof.key_image_sig);
+    if (!ok)
+      return false;
+
+    // check if the address really received the fund
+    crypto::key_derivation derivation;
+    THROW_WALLET_EXCEPTION_IF(!crypto::generate_key_derivation(proof.shared_secret, rct::rct2sk(rct::I), derivation), error::wallet_internal_error, "Failed to generate key derivation");
+    crypto::public_key subaddr_spendkey;
+    crypto::derive_subaddress_public_key(out_key->key, derivation, proof.index_in_tx, subaddr_spendkey);
+    THROW_WALLET_EXCEPTION_IF(subaddr_spendkeys.count(subaddr_spendkey) == 0, error::wallet_internal_error,
+      "The address doesn't seem to have received the fund");
+
+    // check amount
+    uint64_t amount = tx.vout[proof.index_in_tx].amount;
+    if (amount == 0)
+    {
+      // decode rct
+      crypto::secret_key shared_secret;
+      crypto::derivation_to_scalar(derivation, proof.index_in_tx, shared_secret);
+      rct::ecdhTuple ecdh_info = tx.rct_signatures.ecdhInfo[proof.index_in_tx];
+      rct::ecdhDecode(ecdh_info, rct::sk2rct(shared_secret));
+      amount = rct::h2d(ecdh_info.amount);
+    }
+    total += amount;
+    if (kispent_res.spent_status[i])
+      spent += amount;
+  }
+
+  // check signatures for all subaddress spend keys
+  for (const auto &i : subaddr_spendkeys)
+  {
+    if (!crypto::check_signature(prefix_hash, i.first, i.second))
+      return false;
+  }
+  return true;
+}
+
 std::string wallet2::get_wallet_file() const
 {
   return m_wallet_file;