Merge pull request dogecoin#3725 from patricklodder/bugfix/auxpow-che…

…ck-order

Check auxpow PoW before the auxpow itself.

src/auxpow.cpp

@@ -101,6 +101,10 @@ CAuxPow::check(const uint256& hashAuxBlock, int nChainId,
           != parentBlock.hashMerkleRoot)
         return error("Aux POW merkle root incorrect");
 
+    // Check that there is at least one input.
+    if (tx->vin.empty())
+        return error("Aux POW coinbase has no inputs");
+
     const CScript script = tx->vin[0].scriptSig;
 
     // Check that the same work is not submitted twice to our chain.

src/dogecoin.cpp

@@ -115,11 +115,12 @@ bool CheckAuxPowProofOfWork(const CBlockHeader& block, const Consensus::Params&
     if (!block.IsAuxpow())
         return error("%s : auxpow on block with non-auxpow version", __func__);
 
-    if (!block.auxpow->check(block.GetHash(), block.GetChainId(), params))
-        return error("%s : AUX POW is not valid", __func__);
     if (!CheckProofOfWork(block.auxpow->getParentBlockPoWHash(), block.nBits, params))
         return error("%s : AUX proof of work failed", __func__);
 
+    if (!block.auxpow->check(block.GetHash(), block.GetChainId(), params))
+        return error("%s : AUX POW is not valid", __func__);
+
     return true;
 }
 

src/test/auxpow_tests.cpp

@@ -203,6 +203,15 @@ BOOST_AUTO_TEST_CASE(check_auxpow)
     builder.setCoinbase(scr);
     BOOST_CHECK(builder.get().check(hashAux, ourChainId, params));
 
+    /* An auxpow without any inputs in the parent coinbase tx should be
+     handled gracefully (and be considered invalid).  */
+    CMutableTransaction mtx(*builder.parentBlock.vtx[0]);
+    mtx.vin.clear();
+    builder.parentBlock.vtx.clear();
+    builder.parentBlock.vtx.push_back (MakeTransactionRef(std::move (mtx)));
+    builder.parentBlock.hashMerkleRoot = BlockMerkleRoot(builder.parentBlock);
+    BOOST_CHECK(!builder.get().check(hashAux, ourChainId, params));
+
     /* Check that the auxpow is invalid if we change either the aux block's
      hash or the chain ID.  */
     uint256 modifiedAux(hashAux);