Merge #14249: [0.16] Fix crash bug with duplicate inputs within a transaction

9bd08fd465 [qa] backport: Test for duplicate inputs within a transaction (Suhas Daftuar)
d1dee20547 Fix crash bug with duplicate inputs within a transaction (Suhas Daftuar)

Pull request description:

  This is a backport of #14247 to 0.16.

Tree-SHA512: f11b2b0f2d8089bbac7542f78a0f14fc15c693604cb1168ef5ea71852a206da7eb53b6e420376ed1380583961176ba2d283e409e19d783c7a68c3407933a89b0

src/validation.cpp

@@ -3032,7 +3032,7 @@ bool CheckBlock(const CBlock& block, CValidationState& state, const Consensus::P
 
     // Check transactions
     for (const auto& tx : block.vtx)
-        if (!CheckTransaction(*tx, state, false))
+        if (!CheckTransaction(*tx, state, true))
             return state.Invalid(false, state.GetRejectCode(), state.GetRejectReason(),
                                  strprintf("Transaction check failed (tx hash %s) %s", tx->GetHash().ToString(), state.GetDebugMessage()));
 

test/functional/p2p_invalid_block.py

@@ -95,7 +95,18 @@ class InvalidBlockRequestTest(ComparisonTestFramework):
         assert(block2_orig.vtx != block2.vtx)
 
         self.tip = block2.sha256
-        yield TestInstance([[block2, RejectResult(16, b'bad-txns-duplicate')], [block2_orig, True]])
+        yield TestInstance([[block2, RejectResult(16, b'bad-txns-duplicate')]])
+
+        # Check transactions for duplicate inputs
+        self.log.info("Test duplicate input block.")
+
+        block2_dup = copy.deepcopy(block2_orig)
+        block2_dup.vtx[2].vin.append(block2_dup.vtx[2].vin[0])
+        block2_dup.vtx[2].rehash()
+        block2_dup.hashMerkleRoot = block2_dup.calc_merkle_root()
+        block2_dup.rehash()
+        block2_dup.solve()
+        yield TestInstance([[block2_dup, RejectResult(16, b'bad-txns-inputs-duplicate')], [block2_orig, True]])
         height += 1
 
         '''