Prevent coinbases from being spent to transparent outputs.

src/main.cpp

@@ -1629,7 +1629,12 @@ bool NonContextualCheckInputs(const CTransaction& tx, CValidationState &state, c
             assert(coins);
 
             if (coins->IsCoinBase()) {
-                
+                // Ensure that coinbases cannot be spent to transparent outputs
+                if (!tx.vout.empty()) {
+                    return state.Invalid(
+                        error("CheckInputs(): tried to spend coinbase with transparent outputs"),
+                        REJECT_INVALID, "bad-txns-coinbase-spend-has-transparent-outputs");
+                }
             }
 
             // Check for negative or overflow input values

src/test/coins_tests.cpp

@@ -6,6 +6,9 @@
 #include "random.h"
 #include "uint256.h"
 #include "test/test_bitcoin.h"
+#include "consensus/validation.h"
+#include "main.h"
+#include "undo.h"
 
 #include <vector>
 #include <map>
@@ -475,4 +478,48 @@ BOOST_AUTO_TEST_CASE(coins_cache_simulation_test)
     BOOST_CHECK(missed_an_entry);
 }
 
+BOOST_AUTO_TEST_CASE(coins_coinbase_spends)
+{
+    CCoinsViewTest base;
+    CCoinsViewCacheTest cache(&base);
+
+    // Create coinbase transaction
+    CMutableTransaction mtx;
+    mtx.vin.resize(1);
+    mtx.vin[0].scriptSig = CScript() << OP_1;
+    mtx.vin[0].nSequence = 0;
+    mtx.vout.resize(1);
+    mtx.vout[0].nValue = 500;
+    mtx.vout[0].scriptPubKey = CScript() << OP_1;
+
+    CTransaction tx(mtx);
+
+    BOOST_CHECK(tx.IsCoinBase());
+
+    CValidationState state;
+    UpdateCoins(tx, state, cache, 100);
+
+    // Create coinbase spend
+    CMutableTransaction mtx2;
+    mtx2.vin.resize(1);
+    mtx2.vin[0].prevout = COutPoint(tx.GetHash(), 0);
+    mtx2.vin[0].scriptSig = CScript() << OP_1;
+    mtx2.vin[0].nSequence = 0;
+
+    {
+        CTransaction tx2(mtx2);
+        BOOST_CHECK(NonContextualCheckInputs(tx2, state, cache, false, SCRIPT_VERIFY_NONE, false, NULL));
+    }
+
+    mtx2.vout.resize(1);
+    mtx2.vout[0].nValue = 500;
+    mtx2.vout[0].scriptPubKey = CScript() << OP_1;
+
+    {
+        CTransaction tx2(mtx2);
+        BOOST_CHECK(!NonContextualCheckInputs(tx2, state, cache, false, SCRIPT_VERIFY_NONE, false, NULL));
+        BOOST_CHECK(state.GetRejectReason() == "bad-txns-coinbase-spend-has-transparent-outputs");
+    }
+}
+
 BOOST_AUTO_TEST_SUITE_END()