wallet: new import_outputs/export_outputs commands

The intended use is to export outputs from a hot wallet, which
can scan incoming transfers from the network, and import them
in the cold wallet, which can't. The cold wallet can then compute
key images for those outputs, which can then be exported with
export_key_images, etc.

2 files changed, 52 insertions, 1 deletions

diff --git a/src/wallet/wallet2.cpp b/src/wallet/wallet2.cpp
index a02c2e4e5..ba8c65540 100644
--- a/src/wallet/wallet2.cpp
+++ b/src/wallet/wallet2.cpp
@@ -4243,7 +4243,11 @@ std::vector<std::pair<crypto::key_image, crypto::signature>> wallet2::export_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,
+
+    bool zero_key_image = true;
+    for (size_t i = 0; i < sizeof(td.m_key_image); ++i)
+      zero_key_image &= (td.m_key_image.data[i] == 0);
+    THROW_WALLET_EXCEPTION_IF(!zero_key_image && 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");
@@ -4330,6 +4334,50 @@ uint64_t wallet2::import_key_images(const std::vector<std::pair<crypto::key_imag
   return m_transfers[signed_key_images.size() - 1].m_block_height;
 }
 //----------------------------------------------------------------------------------------------------
+std::vector<tools::wallet2::transfer_details> wallet2::export_outputs() const
+{
+  std::vector<tools::wallet2::transfer_details> outs;
+
+  outs.reserve(m_transfers.size());
+  for (size_t n = 0; n < m_transfers.size(); ++n)
+  {
+    const transfer_details &td = m_transfers[n];
+
+    outs.push_back(td);
+  }
+
+  return outs;
+}
+//----------------------------------------------------------------------------------------------------
+size_t wallet2::import_outputs(const std::vector<tools::wallet2::transfer_details> &outputs)
+{
+  m_transfers.clear();
+  m_transfers.reserve(outputs.size());
+  for (size_t i = 0; i < outputs.size(); ++i)
+  {
+    transfer_details td = outputs[i];
+
+    // the hot wallet wouldn't have known about key images (except if we already exported them)
+    cryptonote::keypair in_ephemeral;
+    std::vector<tx_extra_field> tx_extra_fields;
+    tx_extra_pub_key pub_key_field;
+
+    THROW_WALLET_EXCEPTION_IF(td.m_tx.vout.empty(), error::wallet_internal_error, "tx with no outputs at index " + i);
+    THROW_WALLET_EXCEPTION_IF(!parse_tx_extra(td.m_tx.extra, tx_extra_fields), error::wallet_internal_error,
+        "Transaction extra has unsupported format at index " + i);
+    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 at index " + i);
+
+    cryptonote::generate_key_image_helper(m_account.get_keys(), pub_key_field.pub_key, td.m_internal_output_index, in_ephemeral, td.m_key_image);
+    THROW_WALLET_EXCEPTION_IF(in_ephemeral.pub != boost::get<cryptonote::txout_to_key>(td.m_tx.vout[td.m_internal_output_index].target).key,
+        error::wallet_internal_error, "key_image generated ephemeral public key not matched with output_key at index " + i);
+
+    m_transfers.push_back(td);
+  }
+
+  return m_transfers.size();
+}
+//----------------------------------------------------------------------------------------------------
 void wallet2::generate_genesis(cryptonote::block& b) {
   if (m_testnet)
   {
diff --git a/src/wallet/wallet2.h b/src/wallet/wallet2.h
index 39a2a37f1..8afe35aca 100644
--- a/src/wallet/wallet2.h
+++ b/src/wallet/wallet2.h
@@ -473,6 +473,9 @@ 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;
 
+    std::vector<tools::wallet2::transfer_details> export_outputs() const;
+    size_t import_outputs(const std::vector<tools::wallet2::transfer_details> &outputs);
+
     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);