Review comments

src/cryptonote_core/blockchain.cpp

@@ -3499,12 +3499,10 @@ bool Blockchain::have_tx_keyimges_as_spent(const transaction &tx) const
   LOG_PRINT_L3("Blockchain::" << __func__);
   for (const txin_v& in: tx.vin)
   {
-    if (in.type() != typeid(txin_to_key))
-      continue;
-    const auto &tokey_in = boost::get<txin_to_key>(in);
-    if(have_tx_keyimg_as_spent(tokey_in.k_image))
+    CHECKED_GET_SPECIFIC_VARIANT(in, const txin_to_key, in_to_key, true);
+    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(tokey_in.k_image));
+      LOG_PRINT_L1("Key image already spent in blockchain: " << epee::string_tools::pod_to_hex(in_to_key));
       return true;
     }
   }

src/cryptonote_core/tx_pool.cpp

@@ -234,6 +234,26 @@ namespace cryptonote
       return false;
     }
 
+    if (!check_inputs_types_supported(tx))
+    {
+      // TODO: do more cheap semantics checks earlier. This is here so the have_tx_keyimges_as_spent below can only fail when expected.
+      MERROR("Unsupported input types for tx id= " << id);
+      tvc.m_verifivation_failed = true;
+      tvc.m_invalid_input = true;
+      return false;
+    }
+
+    if (version && version > HF_VERSION_FCMP_PLUS_PLUS)
+    {
+      // TODO: do more cheap semantics checks earlier. This is here to protect overloading have_tx_keyimges_as_spent with many DB reads.
+      if (tx.vin.empty() || tx.vin.size() > FCMP_PLUS_PLUS_MAX_INPUTS)
+      {
+        tvc.m_verifivation_failed = true;
+        tvc.m_invalid_input = true;
+        return false;
+      }
+    }
+
     // if the transaction came from a block popped from the chain,
     // don't check if we have its key images as spent.
     // TODO: Investigate why not?