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// Copyright (c) 2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <chainparams.h>
#include <consensus/consensus.h>
#include <consensus/merkle.h>
#include <kernel/coinstats.h>
#include <node/miner.h>
#include <script/interpreter.h>
#include <streams.h>
#include <test/fuzz/FuzzedDataProvider.h>
#include <test/fuzz/fuzz.h>
#include <test/fuzz/util.h>
#include <test/util/mining.h>
#include <test/util/setup_common.h>
#include <util/chaintype.h>
#include <validation.h>
FUZZ_TARGET(utxo_total_supply)
{
/** The testing setup that creates a chainman only (no chainstate) */
ChainTestingSetup test_setup{
ChainType::REGTEST,
{
.extra_args = {"-testactivationheight=bip34@2"},
},
};
// Create chainstate
test_setup.LoadVerifyActivateChainstate();
auto& node{test_setup.m_node};
auto& chainman{*Assert(test_setup.m_node.chainman)};
FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
const auto ActiveHeight = [&]() {
LOCK(chainman.GetMutex());
return chainman.ActiveHeight();
};
const auto PrepareNextBlock = [&]() {
// Use OP_FALSE to avoid BIP30 check from hitting early
auto block = PrepareBlock(node, CScript{} << OP_FALSE);
// Replace OP_FALSE with OP_TRUE
{
CMutableTransaction tx{*block->vtx.back()};
tx.vout.at(0).scriptPubKey = CScript{} << OP_TRUE;
block->vtx.back() = MakeTransactionRef(tx);
}
return block;
};
/** The block template this fuzzer is working on */
auto current_block = PrepareNextBlock();
/** Append-only set of tx outpoints, entries are not removed when spent */
std::vector<std::pair<COutPoint, CTxOut>> txos;
/** The utxo stats at the chain tip */
kernel::CCoinsStats utxo_stats;
/** The total amount of coins in the utxo set */
CAmount circulation{0};
// Store the tx out in the txo map
const auto StoreLastTxo = [&]() {
// get last tx
const CTransaction& tx = *current_block->vtx.back();
// get last out
const uint32_t i = tx.vout.size() - 1;
// store it
txos.emplace_back(COutPoint{tx.GetHash(), i}, tx.vout.at(i));
if (current_block->vtx.size() == 1 && tx.vout.at(i).scriptPubKey[0] == OP_RETURN) {
// also store coinbase
const uint32_t i = tx.vout.size() - 2;
txos.emplace_back(COutPoint{tx.GetHash(), i}, tx.vout.at(i));
}
};
const auto AppendRandomTxo = [&](CMutableTransaction& tx) {
const auto& txo = txos.at(fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, txos.size() - 1));
tx.vin.emplace_back(txo.first);
tx.vout.emplace_back(txo.second.nValue, txo.second.scriptPubKey); // "Forward" coin with no fee
};
const auto UpdateUtxoStats = [&]() {
LOCK(chainman.GetMutex());
chainman.ActiveChainstate().ForceFlushStateToDisk();
utxo_stats = std::move(
*Assert(kernel::ComputeUTXOStats(kernel::CoinStatsHashType::NONE, &chainman.ActiveChainstate().CoinsDB(), chainman.m_blockman, {})));
// Check that miner can't print more money than they are allowed to
assert(circulation == utxo_stats.total_amount);
};
// Update internal state to chain tip
StoreLastTxo();
UpdateUtxoStats();
assert(ActiveHeight() == 0);
// Get at which height we duplicate the coinbase
// Assuming that the fuzzer will mine relatively short chains (less than 200 blocks), we want the duplicate coinbase to be not too high.
// Up to 300 seems reasonable.
int64_t duplicate_coinbase_height = fuzzed_data_provider.ConsumeIntegralInRange(0, 300);
// Always pad with OP_0 at the end to avoid bad-cb-length error
const CScript duplicate_coinbase_script = CScript() << duplicate_coinbase_height << OP_0;
// Mine the first block with this duplicate
current_block = PrepareNextBlock();
StoreLastTxo();
{
// Create duplicate (CScript should match exact format as in CreateNewBlock)
CMutableTransaction tx{*current_block->vtx.front()};
tx.vin.at(0).scriptSig = duplicate_coinbase_script;
// Mine block and create next block template
current_block->vtx.front() = MakeTransactionRef(tx);
}
current_block->hashMerkleRoot = BlockMerkleRoot(*current_block);
assert(!MineBlock(node, current_block).IsNull());
circulation += GetBlockSubsidy(ActiveHeight(), Params().GetConsensus());
assert(ActiveHeight() == 1);
UpdateUtxoStats();
current_block = PrepareNextBlock();
StoreLastTxo();
// Limit to avoid timeout, but enough to cover duplicate_coinbase_height
// and CVE-2018-17144.
LIMITED_WHILE(fuzzed_data_provider.remaining_bytes(), 2'00)
{
CallOneOf(
fuzzed_data_provider,
[&] {
// Append an input-output pair to the last tx in the current block
CMutableTransaction tx{*current_block->vtx.back()};
AppendRandomTxo(tx);
current_block->vtx.back() = MakeTransactionRef(tx);
StoreLastTxo();
},
[&] {
// Append a tx to the list of txs in the current block
CMutableTransaction tx{};
AppendRandomTxo(tx);
current_block->vtx.push_back(MakeTransactionRef(tx));
StoreLastTxo();
},
[&] {
// Append the current block to the active chain
node::RegenerateCommitments(*current_block, chainman);
const bool was_valid = !MineBlock(node, current_block).IsNull();
const auto prev_utxo_stats = utxo_stats;
if (was_valid) {
if (duplicate_coinbase_height == ActiveHeight()) {
// we mined the duplicate coinbase
assert(current_block->vtx.at(0)->vin.at(0).scriptSig == duplicate_coinbase_script);
}
circulation += GetBlockSubsidy(ActiveHeight(), Params().GetConsensus());
}
UpdateUtxoStats();
if (!was_valid) {
// utxo stats must not change
assert(prev_utxo_stats.hashSerialized == utxo_stats.hashSerialized);
}
current_block = PrepareNextBlock();
StoreLastTxo();
});
}
}
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