blockchain: reinstate double spending checks in check_tx_inputs

This fixes some double spending tests.
This may or may not be unneeded in normal (non test) circumstances,
to be determined later. Keeping these for now may be slower, but safer.

1 files changed, 7 insertions, 3 deletions

diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp
index 86efc8821..e3ce66073 100644
--- a/src/cryptonote_core/blockchain.cpp
+++ b/src/cryptonote_core/blockchain.cpp
@@ -2008,9 +2008,7 @@ bool Blockchain::have_tx_keyimges_as_spent(const transaction &tx) const
   return false;
 }
 //------------------------------------------------------------------
-// This function validates transaction inputs and their keys.  Previously
-// it also performed double spend checking, but that has been moved to its
-// own function.
+// This function validates transaction inputs and their keys.
 bool Blockchain::check_tx_inputs(const transaction& tx, uint64_t* pmax_used_block_height)
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
@@ -2112,6 +2110,12 @@ bool Blockchain::check_tx_inputs(const transaction& tx, uint64_t* pmax_used_bloc
     // make sure tx output has key offset(s) (is signed to be used)
     CHECK_AND_ASSERT_MES(in_to_key.key_offsets.size(), false, "empty in_to_key.key_offsets in transaction with id " << get_transaction_hash(tx));
 
+    if(have_tx_keyimg_as_spent(in_to_key.k_image))
+    {
+      LOG_PRINT_L1("Key image already spent in blockchain: " << epee::string_tools::pod_to_hex(in_to_key.k_image));
+      return false;
+    }
+
     // basically, make sure number of inputs == number of signatures
     CHECK_AND_ASSERT_MES(sig_index < tx.signatures.size(), false, "wrong transaction: not signature entry for input with index= " << sig_index);