Merge #753: getnewblockhex: Take data push for arbitrary data in block coinbase c…

6d9639b21 getnewblockhex: Take data push for arbitrary data in block coinbase commitment (Gregory Sanders)

Pull request description:

  …ommitment

  Useful for non-consensus proof of publication of data.

Tree-SHA512: 8967238c97b5188db50f99d7a8d8a1b26712a6b4c02812880502b5eb9572f7ca6a509a2020cb9661b2931f7d2b06f0580baa8652516b529b2386e92e73767a73

src/miner.cpp

@@ -102,7 +102,7 @@ void BlockAssembler::resetBlock()
 Optional<int64_t> BlockAssembler::m_last_block_num_txs{nullopt};
 Optional<int64_t> BlockAssembler::m_last_block_weight{nullopt};
 
-std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn, int min_tx_age, DynaFedParamEntry* proposed_entry)
+std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn, int min_tx_age, DynaFedParamEntry* proposed_entry, CScript const* commit_script)
 {
     assert(min_tx_age >= 0);
     int64_t nTimeStart = GetTimeMicros();
@@ -195,6 +195,10 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
         }
     }
     coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
+    // Non-consensus commitment output before finishing coinbase transaction
+    if (commit_script) {
+        coinbaseTx.vout.insert(coinbaseTx.vout.begin(), CTxOut(policyAsset, 0, *commit_script));
+    }
     pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
     pblocktemplate->vchCoinbaseCommitment = GenerateCoinbaseCommitment(*pblock, pindexPrev, chainparams.GetConsensus());
     pblocktemplate->vTxFees[0] = -nFees;

src/miner.h

@@ -159,7 +159,7 @@ public:
     BlockAssembler(const CChainParams& params, const Options& options);
 
     /** Construct a new block template with coinbase to scriptPubKeyIn. min_tx_age is in seconds */
-    std::unique_ptr<CBlockTemplate> CreateNewBlock(const CScript& scriptPubKeyIn, int min_tx_age=0, DynaFedParamEntry* = nullptr);
+    std::unique_ptr<CBlockTemplate> CreateNewBlock(const CScript& scriptPubKeyIn, int min_tx_age=0, DynaFedParamEntry* = nullptr, CScript const* commit_script = nullptr);
 
     static Optional<int64_t> m_last_block_num_txs;
     static Optional<int64_t> m_last_block_weight;

src/rpc/mining.cpp

@@ -999,7 +999,7 @@ static UniValue estimaterawfee(const JSONRPCRequest& request)
 
 UniValue getnewblockhex(const JSONRPCRequest& request)
 {
-    if (request.fHelp || request.params.size() > 2)
+    if (request.fHelp || request.params.size() > 3)
         throw std::runtime_error(
             RPCHelpMan{"getnewblockhex",
                 "\nGets hex representation of a proposed, unmined new block\n",
@@ -1017,6 +1017,7 @@ UniValue getnewblockhex(const JSONRPCRequest& request)
                             },
                         },
                         "proposed_parameters"},
+                        {"commit_data", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "Data in hex to be committed to in an additional coinbase output."},
                 },
                 RPCResult{
                     "blockhex      (hex) The block hex\n"
@@ -1071,9 +1072,17 @@ UniValue getnewblockhex(const JSONRPCRequest& request)
         proposed.m_serialize_type = 2;
     }
 
+    // Any commitment required for non-consensus reasons.
+    // This will be placed in the first coinbase output.
+    CScript data_commitment;
+    if (!request.params[2].isNull()) {
+        std::vector<unsigned char> data_bytes = ParseHex(request.params[2].get_str());
+        data_commitment = CScript() << OP_RETURN << data_bytes;
+    }
+
     CScript feeDestinationScript = Params().GetConsensus().mandatory_coinbase_destination;
     if (feeDestinationScript == CScript()) feeDestinationScript = CScript() << OP_TRUE;
-    std::unique_ptr<CBlockTemplate> pblocktemplate(BlockAssembler(Params()).CreateNewBlock(feeDestinationScript, required_wait, &proposed));
+    std::unique_ptr<CBlockTemplate> pblocktemplate(BlockAssembler(Params()).CreateNewBlock(feeDestinationScript, required_wait, &proposed, data_commitment.empty() ? nullptr : &data_commitment));
     if (!pblocktemplate.get()) {
         throw JSONRPCError(RPC_INTERNAL_ERROR, "Wallet keypool empty");
     }
@@ -1474,7 +1483,7 @@ static const CRPCCommand commands[] =
     { "mining",             "getblocktemplate",       &getblocktemplate,       {"template_request"} },
     { "generating",         "combineblocksigs",       &combineblocksigs,       {"blockhex","signatures"} },
     { "mining",             "submitheader",           &submitheader,           {"hexdata"} },
-    { "generating",         "getnewblockhex",         &getnewblockhex,         {"min_tx_age", "proposed_parameters"} },
+    { "generating",         "getnewblockhex",         &getnewblockhex,         {"min_tx_age", "proposed_parameters", "commit_data"} },
     { "generating",         "getcompactsketch",       &getcompactsketch,       {"block_hex"} },
     { "generating",         "consumecompactsketch",   &consumecompactsketch,   {"sketch"} },
     { "generating",         "consumegetblocktxn",     &consumegetblocktxn,     {"full_block", "block_tx_req"} },

test/functional/feature_blocksign.py

@@ -10,6 +10,13 @@ from test_framework import (
     address,
     key,
 )
+from test_framework.messages import (
+    FromHex,
+    CBlock,
+)
+from test_framework.script import (
+    CScript
+)
 
 # Generate wallet import format from private key.
 def wif(pk):
@@ -115,6 +122,14 @@ class BlockSignTest(BitcoinTestFramework):
                 miner.sendtoaddress(miner_next.getnewaddress(), int(miner.getbalance()['bitcoin']/10), "", "", True)
         # miner makes a block
         block = miner.getnewblockhex()
+        block_struct = FromHex(CBlock(), block)
+
+        # make another block with the commitment field filled out
+        dummy_block = miner.getnewblockhex(commit_data="deadbeef")
+        dummy_struct = FromHex(CBlock(), dummy_block)
+        assert_equal(len(dummy_struct.vtx[0].vout), len(block_struct.vtx[0].vout) + 1)
+        # OP_RETURN deadbeef
+        assert_equal(CScript(dummy_struct.vtx[0].vout[0].scriptPubKey).hex(), '6a04deadbeef')
 
         # All nodes get compact blocks, first node may get complete
         # block in 0.5 RTT even with transactions thanks to p2p connection