consensus: from v12, enforce >= 2 outputs

src/cryptonote_basic/verification_context.h

@@ -48,6 +48,7 @@ namespace cryptonote
     bool m_overspend;
     bool m_fee_too_low;
     bool m_not_rct;
+    bool m_too_few_outputs;
   };
 
   struct block_verification_context

src/cryptonote_config.h

@@ -147,6 +147,7 @@
 #define HF_VERSION_PER_BYTE_FEE                 8
 #define HF_VERSION_SMALLER_BP                   10
 #define HF_VERSION_LONG_TERM_BLOCK_WEIGHT       10
+#define HF_VERSION_MIN_2_OUTPUTS                12
 
 #define PER_KB_FEE_QUANTIZATION_DECIMALS        8
 

src/cryptonote_core/blockchain.cpp

@@ -2800,6 +2800,19 @@ bool Blockchain::check_tx_inputs(transaction& tx, tx_verification_context &tvc,
 
   const uint8_t hf_version = m_hardfork->get_current_version();
 
+  if (hf_version >= HF_VERSION_MIN_2_OUTPUTS)
+  {
+    if (tx.version >= 2)
+    {
+      if (tx.vout.size() < 2)
+      {
+        MERROR_VER("Tx " << get_transaction_hash(tx) << " has fewer than two outputs");
+        tvc.m_too_few_outputs = true;
+        return false;
+      }
+    }
+  }
+
   // from hard fork 2, we require mixin at least 2 unless one output cannot mix with 2 others
   // if one output cannot mix with 2 others, we accept at most 1 output that can mix
   if (hf_version >= 2)

src/rpc/core_rpc_server.cpp

@@ -875,6 +875,8 @@ namespace cryptonote
         add_reason(reason, "fee too low");
       if ((res.not_rct = tvc.m_not_rct))
         add_reason(reason, "tx is not ringct");
+      if ((res.too_few_outputs = tvc.m_too_few_outputs))
+        add_reason(reason, "too few outputs");
       const std::string punctuation = reason.empty() ? "" : ": ";
       if (tvc.m_verifivation_failed)
       {

src/rpc/core_rpc_server_commands_defs.h

@@ -609,6 +609,7 @@ namespace cryptonote
       bool overspend;
       bool fee_too_low;
       bool not_rct;
+      bool too_few_outputs;
       bool sanity_check_failed;
       bool untrusted;
 
@@ -624,6 +625,7 @@ namespace cryptonote
         KV_SERIALIZE(overspend)
         KV_SERIALIZE(fee_too_low)
         KV_SERIALIZE(not_rct)
+        KV_SERIALIZE(too_few_outputs)
         KV_SERIALIZE(sanity_check_failed)
         KV_SERIALIZE(untrusted)
       END_KV_SERIALIZE_MAP()

src/rpc/daemon_handler.cpp

@@ -343,6 +343,11 @@ namespace rpc
         if (!res.error_details.empty()) res.error_details += " and ";
         res.error_details = "tx is not ringct";
       }
+      if (tvc.m_too_few_outputs)
+      {
+        if (!res.error_details.empty()) res.error_details += " and ";
+        res.error_details = "too few outputs";
+      }
       if (res.error_details.empty())
       {
         res.error_details = "an unknown issue was found with the transaction";

src/wallet/wallet2.cpp

@@ -213,6 +213,8 @@ namespace
         add_reason(reason, "invalid input");
       if (res.invalid_output)
         add_reason(reason, "invalid output");
+      if (res.too_few_outputs)
+        add_reason(reason, "too few outputs");
       if (res.too_big)
         add_reason(reason, "too big");
       if (res.overspend)

tests/functional_tests/transfer.py

@@ -564,6 +564,7 @@ class TransferTest():
         assert res.overspend == False
         assert res.fee_too_low == False
         assert res.not_rct == False
+        assert res.too_few_outputs == False
 
         res = daemon.get_transactions([txes[0][0]])
         assert len(res.txs) >= 1