Merge #430: [0.17] Mandatory coinbase feature

0d20b55 add mandatory coinbase functional test (Gregory Sanders)
edb0532 add consensus.mandatory_coinbase_destination (Gregory Sanders)

Pull request description:

  Includes functional test

Tree-SHA512: e7fdf4584c5a61516778dff272c0f4c9964fee515b705c4fd3ade842954bcc7426bdaf5273a64e4b2472fedc940ead7552c0ec80b4608aac381f91a8f2356d95

src/chainparams.cpp

@@ -420,6 +420,11 @@ class CCustomParams : public CRegTestParams {
         consensus.nMinimumChainWork = uint256S(args.GetArg("-con_nminimumchainwork", "0x0"));
         consensus.defaultAssumeValid = uint256S(args.GetArg("-con_defaultassumevalid", "0x00"));
 
+        // All non-zero coinbase outputs must go to this scriptPubKey
+        std::vector<unsigned char> man_bytes = ParseHex(gArgs.GetArg("-con_mandatorycoinbase", ""));
+        consensus.mandatory_coinbase_destination = CScript(man_bytes.begin(), man_bytes.end()); // Blank script allows any coinbase destination
+
+
         nPruneAfterHeight = (uint64_t)args.GetArg("-npruneafterheight", nPruneAfterHeight);
         fDefaultConsistencyChecks = args.GetBoolArg("-fdefaultconsistencychecks", fDefaultConsistencyChecks);
         fMineBlocksOnDemand = args.GetBoolArg("-fmineblocksondemand", fMineBlocksOnDemand);

src/chainparamsbase.cpp

@@ -22,6 +22,7 @@ void SetupChainParamsBaseOptions()
                                    "This is intended for regression testing tools and app development.", true, OptionsCategory::CHAINPARAMS);
     gArgs.AddArg("-testnet", "Use the test chain", false, OptionsCategory::CHAINPARAMS);
     gArgs.AddArg("-vbparams=deployment:start:end", "Use given start/end times for specified version bits deployment (regtest or custom only)", true, OptionsCategory::CHAINPARAMS);
+    gArgs.AddArg("-con_mandatorycoinbase", "All non-zero valued coinbase outputs must go to this scriptPubKey, if set.", false, OptionsCategory::CHAINPARAMS);
     gArgs.AddArg("-seednode=<ip>", "Use specified node as seed node. This option can be specified multiple times to connect to multiple nodes. (custom only)", true, OptionsCategory::CHAINPARAMS);
 }
 

src/consensus/params.h

@@ -11,6 +11,8 @@
 #include <map>
 #include <string>
 
+#include <script/script.h> // mandatory_coinbase_destination
+
 namespace Consensus {
 
 enum DeploymentPos
@@ -75,6 +77,9 @@ struct Params {
     int64_t DifficultyAdjustmentInterval() const { return nPowTargetTimespan / nPowTargetSpacing; }
     uint256 nMinimumChainWork;
     uint256 defaultAssumeValid;
+
+    // Elements-specific chainparams
+    CScript mandatory_coinbase_destination;
 };
 } // namespace Consensus
 

src/validation.cpp

@@ -1850,6 +1850,17 @@ bool CChainState::ConnectBlock(const CBlock& block, CValidationState& state, CBl
 
     nBlocksTotal++;
 
+    // Check that all non-zero coinbase outputs pay to the required destination
+    const CScript& mandatory_coinbase_destination = chainparams.GetConsensus().mandatory_coinbase_destination;
+    if (mandatory_coinbase_destination != CScript()) {
+        for (auto& txout : block.vtx[0]->vout) {
+            if (txout.scriptPubKey != mandatory_coinbase_destination && txout.nValue != 0) {
+                return state.DoS(100, error("ConnectBlock(): Coinbase outputs didnt match required scriptPubKey"),
+                                 REJECT_INVALID, "bad-coinbase-txos");
+            }
+        }
+    }
+
     bool fScriptChecks = true;
     if (!hashAssumeValid.IsNull()) {
         // We've been configured with the hash of a block which has been externally verified to have a valid history.

test/functional/mandatory_coinbase.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+# Copyright (c) 2014-2018 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test mandatory coinbase feature"""
+
+from binascii import b2a_hex
+
+from test_framework.blocktools import create_coinbase
+from test_framework.messages import CBlock
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_equal, assert_raises_rpc_error
+
+mandatory_privkey = "cNaQCDwmmh4dS9LzCgVtyy1e1xjCJ21GUDHe9K98nzb689JvinGV"
+mandatory_address = "n3NkSZqoPMCQN5FENxUBw4qVATbytH6FDK"
+mandatory_pubkey = "02fcba7ecf41bc7e1be4ee122d9d22e3333671eb0a3a87b5cdf099d59874e1940f"
+mandatory_script = "76a914efc58b838b3153174bf3d1677b7213353a4dccfd88ac"
+
+def b2x(b):
+    return b2a_hex(b).decode('ascii')
+
+def assert_template(node, block, expect, rehash=True):
+    if rehash:
+        block.hashMerkleRoot = block.calc_merkle_root()
+    rsp = node.getblocktemplate({'data': b2x(block.serialize()), 'mode': 'proposal'})
+    assert_equal(rsp, expect)
+
+class MandatoryCoinbaseTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 2
+        self.setup_clean_chain = True
+        # Non-zero coinbase outputs *must* match this. Not setting it means anything is allowed
+        self.extra_args = [["-con_mandatorycoinbase="+mandatory_script], []]
+
+    def run_test(self):
+        node0 = self.nodes[0]
+        node1 = self.nodes[1]
+
+        node0.importprivkey(mandatory_privkey)
+
+        self.log.info("generatetoaddress: Making blocks of various kinds, checking for rejection")
+
+        # Create valid blocks to get out of IBD and get some funds (subsidy goes to permitted addr)
+        node0.generatetoaddress(101, mandatory_address)
+
+        # Generating for another address will not work
+        assert_raises_rpc_error(-1, "CreateNewBlock: TestBlockValidity failed: bad-coinbase-txos", node0.generatetoaddress, 1, node0.getnewaddress())
+
+        # Have non-mandatory node make a template
+        self.sync_all()
+        tmpl = node1.getblocktemplate()
+
+        # We make a block with OP_TRUE coinbase output that will fail on node0
+        coinbase_tx = create_coinbase(height=int(tmpl["height"]) + 1)
+        # sequence numbers must not be max for nLockTime to have effect
+        coinbase_tx.vin[0].nSequence = 2 ** 32 - 2
+        coinbase_tx.rehash()
+
+        block = CBlock()
+        block.nVersion = tmpl["version"]
+        block.hashPrevBlock = int(tmpl["previousblockhash"], 16)
+        block.nTime = tmpl["curtime"]
+        block.nBits = int(tmpl["bits"], 16)
+        block.nNonce = 0
+        block.vtx = [coinbase_tx]
+
+        self.log.info("getblocktemplate: Test block on both nodes")
+        assert_equal(node0.submitblock(b2x(block.serialize())), 'invalid')
+        assert_template(node1, block, None)
+
+        self.log.info("getblocktemplate: Test non-subsidy block on both nodes")
+        # Without block reward anything goes, this allows commitment outputs like segwit
+        coinbase_tx.vout[0].nValue = 0
+        coinbase_tx.rehash()
+        block.vtx = [coinbase_tx]
+        assert_template(node0, block, None)
+        assert_template(node1, block, None)
+
+if __name__ == '__main__':
+    MandatoryCoinbaseTest().main()