1// Copyright (c) The Bitcoin Core developers
2// Distributed under the MIT software license, see the accompanying
3// file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5#include <index/txospenderindex.h>
6
7#include <common/args.h>
8#include <crypto/siphash.h>
9#include <dbwrapper.h>
10#include <flatfile.h>
11#include <index/base.h>
12#include <index/disktxpos.h>
13#include <interfaces/chain.h>
14#include <logging.h>
15#include <node/blockstorage.h>
16#include <primitives/block.h>
17#include <primitives/transaction.h>
18#include <random.h>
19#include <serialize.h>
20#include <streams.h>
21#include <tinyformat.h>
22#include <uint256.h>
23#include <util/fs.h>
24#include <validation.h>
25
26#include <cstddef>
27#include <cstdio>
28#include <exception>
29#include <ios>
30#include <span>
31#include <string>
32#include <utility>
33#include <vector>
34
35/* The database is used to find the spending transaction of a given utxo.
36 * For every input of every transaction it stores a key that is a pair(siphash(input outpoint), transaction location on disk) and a zero-byte value.
37 * To find the spending transaction of an outpoint, we perform a range query on siphash(outpoint), and for each returned key load the transaction
38 * and return it if it does spend the provided outpoint.
39 */
40
41// LevelDB key prefix. We only have one key for now but it will make it easier to add others if needed.
42constexpr uint8_t DB_TXOSPENDERINDEX{'s'};
43
44std::unique_ptr<TxoSpenderIndex> g_txospenderindex;
45
46struct DBKey {
47    uint64_t hash;
48    CDiskTxPos pos;
49
50    explicit DBKey(const uint64_t& hash_in, const CDiskTxPos& pos_in) : hash(hash_in), pos(pos_in) {}
51
52    SERIALIZE_METHODS(DBKey, obj)
53    {
54        uint8_t prefix{DB_TXOSPENDERINDEX};
55        READWRITE(prefix);
56        if (prefix != DB_TXOSPENDERINDEX) {
57            throw std::ios_base::failure("Invalid format for spender index DB key");
58        }
59        READWRITE(obj.hash);
60        READWRITE(obj.pos);
61    }
62};
63
64TxoSpenderIndex::TxoSpenderIndex(std::unique_ptr<interfaces::Chain> chain, size_t n_cache_size, bool f_memory, bool f_wipe)
65    : BaseIndex(std::move(chain), "txospenderindex", "txospenderidx"), m_db{std::make_unique<DB>(gArgs.GetDataDirNet() / "indexes" / "txospenderindex" / "db", n_cache_size, f_memory, f_wipe, /*f_obfuscate=*/false, /*f_bloom=*/false)}
66{
67    if (!m_db->Read("siphash_key", m_siphash_key)) {
68        FastRandomContext rng(false);
69        m_siphash_key = {rng.rand64(), rng.rand64()};
70        m_db->Write("siphash_key", m_siphash_key, /*fSync=*/ true);
71    }
72}
73
74interfaces::Chain::NotifyOptions TxoSpenderIndex::CustomOptions()
75{
76    interfaces::Chain::NotifyOptions options;
77    options.disconnect_data = true;
78    return options;
79}
80
81static uint64_t CreateKeyPrefix(std::pair<uint64_t, uint64_t> siphash_key, const COutPoint& vout)
82{
83    return PresaltedSipHasher(siphash_key.first, siphash_key.second)(vout.hash.ToUint256(), vout.n);
84}
85
86static DBKey CreateKey(std::pair<uint64_t, uint64_t> siphash_key, const COutPoint& vout, const CDiskTxPos& pos)
87{
88    return DBKey(CreateKeyPrefix(siphash_key, vout), pos);
89}
90
91void TxoSpenderIndex::WriteSpenderInfos(const std::vector<std::pair<COutPoint, CDiskTxPos>>& items)
92{
93    CDBBatch batch(*m_db);
94    for (const auto& [outpoint, pos] : items) {
95        DBKey key(CreateKey(m_siphash_key, outpoint, pos));
96        // The key encodes the spent outpoint hash and disk position. The value is only a marker.
97        // Older entries may contain serialized empty strings; FindSpender() reads only keys.
98        batch.Write(key, std::span<const std::byte>{});
99    }
100    m_db->WriteBatch(batch);
101}
102
103
104void TxoSpenderIndex::EraseSpenderInfos(const std::vector<std::pair<COutPoint, CDiskTxPos>>& items)
105{
106    CDBBatch batch(*m_db);
107    for (const auto& [outpoint, pos] : items) {
108        batch.Erase(CreateKey(m_siphash_key, outpoint, pos));
109    }
110    m_db->WriteBatch(batch);
111}
112
113static std::vector<std::pair<COutPoint, CDiskTxPos>> BuildSpenderPositions(const interfaces::BlockInfo& block)
114{
115    std::vector<std::pair<COutPoint, CDiskTxPos>> items;
116    items.reserve(block.data->vtx.size());
117
118    CDiskTxPos pos({block.file_number, block.data_pos}, GetSizeOfCompactSize(block.data->vtx.size()));
119    for (const auto& tx : block.data->vtx) {
120        if (!tx->IsCoinBase()) {
121            for (const auto& input : tx->vin) {
122                items.emplace_back(input.prevout, pos);
123            }
124        }
125        pos.nTxOffset += ::GetSerializeSize(TX_WITH_WITNESS(*tx));
126    }
127
128    return items;
129}
130
131
132bool TxoSpenderIndex::CustomAppend(const interfaces::BlockInfo& block)
133{
134    WriteSpenderInfos(BuildSpenderPositions(block));
135    return true;
136}
137
138bool TxoSpenderIndex::CustomRemove(const interfaces::BlockInfo& block)
139{
140    EraseSpenderInfos(BuildSpenderPositions(block));
141    return true;
142}
143
144util::Expected<TxoSpender, std::string> TxoSpenderIndex::ReadTransaction(const CDiskTxPos& tx_pos) const
145{
146    AutoFile file{m_chainstate->m_blockman.OpenBlockFile(tx_pos, /*fReadOnly=*/true)};
147    if (file.IsNull()) {
148        return util::Unexpected("cannot open block");
149    }
150    CBlockHeader header;
151    TxoSpender spender;
152    try {
153        file >> header;
154        file.seek(tx_pos.nTxOffset, SEEK_CUR);
155        file >> TX_WITH_WITNESS(spender.tx);
156        spender.block_hash = header.GetHash();
157        return spender;
158    } catch (const std::exception& e) {
159        return util::Unexpected(e.what());
160    }
161}
162
163util::Expected<std::optional<TxoSpender>, std::string> TxoSpenderIndex::FindSpender(const COutPoint& txo) const
164{
165    const uint64_t prefix{CreateKeyPrefix(m_siphash_key, txo)};
166    std::unique_ptr<CDBIterator> it(m_db->NewIterator());
167    DBKey key(prefix, CDiskTxPos());
168
169    // find all keys that start with the outpoint hash, load the transaction at the location specified in the key
170    // and return it if it does spend the provided outpoint
171    for (it->Seek(std::pair{DB_TXOSPENDERINDEX, prefix}); it->Valid() && it->GetKey(key) && key.hash == prefix; it->Next()) {
172        if (const auto spender{ReadTransaction(key.pos)}) {
173            for (const auto& input : spender->tx->vin) {
174                if (input.prevout == txo) {
175                    return std::optional{*spender};
176                }
177            }
178        } else {
179            LogError("Deserialize or I/O error - %s", spender.error());
180            return util::Unexpected{strprintf("IO error finding spending tx for outpoint %s:%d.", txo.hash.GetHex(), txo.n)};
181        }
182    }
183    return util::Expected<std::optional<TxoSpender>, std::string>(std::nullopt);
184}
185
186BaseIndex::DB& TxoSpenderIndex::GetDB() const { return *m_db; }
187