Branch data Line data Source code
1 : : // Copyright (c) 2019-2021 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 <signet.h>
6 : :
7 : : #include <array>
8 : : #include <cstdint>
9 : : #include <vector>
10 : :
11 : : #include <common/system.h>
12 : : #include <consensus/merkle.h>
13 : : #include <consensus/params.h>
14 : : #include <consensus/validation.h>
15 : : #include <core_io.h>
16 : : #include <hash.h>
17 : : #include <logging.h>
18 : : #include <primitives/block.h>
19 : : #include <primitives/transaction.h>
20 : : #include <script/interpreter.h>
21 : : #include <span.h>
22 : : #include <streams.h>
23 : : #include <uint256.h>
24 : : #include <util/strencodings.h>
25 : :
26 : : static constexpr uint8_t SIGNET_HEADER[4] = {0xec, 0xc7, 0xda, 0xa2};
27 : :
28 : : static constexpr unsigned int BLOCK_SCRIPT_VERIFY_FLAGS = SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_DERSIG | SCRIPT_VERIFY_NULLDUMMY;
29 : :
30 : 0 : static bool FetchAndClearCommitmentSection(const Span<const uint8_t> header, CScript& witness_commitment, std::vector<uint8_t>& result)
31 : : {
32 : 0 : CScript replacement;
33 : 0 : bool found_header = false;
34 : 0 : result.clear();
35 : :
36 : : opcodetype opcode;
37 [ # # ][ # # ]: 0 : CScript::const_iterator pc = witness_commitment.begin();
38 : 0 : std::vector<uint8_t> pushdata;
39 [ # # ][ # # ]: 0 : while (witness_commitment.GetOp(pc, opcode, pushdata)) {
40 [ # # ]: 0 : if (pushdata.size() > 0) {
41 [ # # ][ # # ]: 0 : if (!found_header && pushdata.size() > (size_t)header.size() && Span{pushdata}.first(header.size()) == header) {
[ # # ][ # # ]
42 : : // pushdata only counts if it has the header _and_ some data
43 [ # # ]: 0 : result.insert(result.end(), pushdata.begin() + header.size(), pushdata.end());
44 [ # # ]: 0 : pushdata.erase(pushdata.begin() + header.size(), pushdata.end());
45 : 0 : found_header = true;
46 : 0 : }
47 [ # # ]: 0 : replacement << pushdata;
48 : 0 : } else {
49 [ # # ]: 0 : replacement << opcode;
50 : : }
51 : : }
52 : :
53 [ # # ][ # # ]: 0 : if (found_header) witness_commitment = replacement;
54 : 0 : return found_header;
55 : 0 : }
56 : :
57 : 0 : static uint256 ComputeModifiedMerkleRoot(const CMutableTransaction& cb, const CBlock& block)
58 : : {
59 : 0 : std::vector<uint256> leaves;
60 [ # # ]: 0 : leaves.resize(block.vtx.size());
61 [ # # ][ # # ]: 0 : leaves[0] = cb.GetHash();
62 [ # # ]: 0 : for (size_t s = 1; s < block.vtx.size(); ++s) {
63 [ # # ][ # # ]: 0 : leaves[s] = block.vtx[s]->GetHash();
64 : 0 : }
65 [ # # ]: 0 : return ComputeMerkleRoot(std::move(leaves));
66 : 0 : }
67 : :
68 : 0 : std::optional<SignetTxs> SignetTxs::Create(const CBlock& block, const CScript& challenge)
69 : : {
70 : 0 : CMutableTransaction tx_to_spend;
71 : 0 : tx_to_spend.nVersion = 0;
72 : 0 : tx_to_spend.nLockTime = 0;
73 [ # # ][ # # ]: 0 : tx_to_spend.vin.emplace_back(COutPoint(), CScript(OP_0), 0);
[ # # ]
74 [ # # ]: 0 : tx_to_spend.vout.emplace_back(0, challenge);
75 : :
76 [ # # ]: 0 : CMutableTransaction tx_spending;
77 : 0 : tx_spending.nVersion = 0;
78 : 0 : tx_spending.nLockTime = 0;
79 [ # # ][ # # ]: 0 : tx_spending.vin.emplace_back(COutPoint(), CScript(), 0);
[ # # ]
80 [ # # ][ # # ]: 0 : tx_spending.vout.emplace_back(0, CScript(OP_RETURN));
81 : :
82 : : // can't fill any other fields before extracting signet
83 : : // responses from block coinbase tx
84 : :
85 : : // find and delete signet signature
86 [ # # ]: 0 : if (block.vtx.empty()) return std::nullopt; // no coinbase tx in block; invalid
87 [ # # ][ # # ]: 0 : CMutableTransaction modified_cb(*block.vtx.at(0));
88 : :
89 [ # # ]: 0 : const int cidx = GetWitnessCommitmentIndex(block);
90 [ # # ]: 0 : if (cidx == NO_WITNESS_COMMITMENT) {
91 : 0 : return std::nullopt; // require a witness commitment
92 : : }
93 : :
94 [ # # ]: 0 : CScript& witness_commitment = modified_cb.vout.at(cidx).scriptPubKey;
95 : :
96 : 0 : std::vector<uint8_t> signet_solution;
97 [ # # ][ # # ]: 0 : if (!FetchAndClearCommitmentSection(SIGNET_HEADER, witness_commitment, signet_solution)) {
98 : : // no signet solution -- allow this to support OP_TRUE as trivial block challenge
99 : 0 : } else {
100 : : try {
101 [ # # ][ # # ]: 0 : SpanReader v{signet_solution};
102 [ # # ]: 0 : v >> tx_spending.vin[0].scriptSig;
103 [ # # ]: 0 : v >> tx_spending.vin[0].scriptWitness.stack;
104 [ # # ][ # # ]: 0 : if (!v.empty()) return std::nullopt; // extraneous data encountered
105 [ # # ]: 0 : } catch (const std::exception&) {
106 : 0 : return std::nullopt; // parsing error
107 [ # # ]: 0 : }
108 : : }
109 [ # # ]: 0 : uint256 signet_merkle = ComputeModifiedMerkleRoot(modified_cb, block);
110 : :
111 : 0 : std::vector<uint8_t> block_data;
112 [ # # ]: 0 : VectorWriter writer{block_data, 0};
113 [ # # ]: 0 : writer << block.nVersion;
114 [ # # ]: 0 : writer << block.hashPrevBlock;
115 [ # # ]: 0 : writer << signet_merkle;
116 [ # # ]: 0 : writer << block.nTime;
117 [ # # ]: 0 : tx_to_spend.vin[0].scriptSig << block_data;
118 [ # # ][ # # ]: 0 : tx_spending.vin[0].prevout = COutPoint(tx_to_spend.GetHash(), 0);
119 : :
120 [ # # ][ # # ]: 0 : return SignetTxs{tx_to_spend, tx_spending};
121 : 0 : }
122 : :
123 : : // Signet block solution checker
124 : 0 : bool CheckSignetBlockSolution(const CBlock& block, const Consensus::Params& consensusParams)
125 : : {
126 [ # # ]: 0 : if (block.GetHash() == consensusParams.hashGenesisBlock) {
127 : : // genesis block solution is always valid
128 : 0 : return true;
129 : : }
130 : :
131 : 0 : const CScript challenge(consensusParams.signet_challenge.begin(), consensusParams.signet_challenge.end());
132 [ # # ]: 0 : const std::optional<SignetTxs> signet_txs = SignetTxs::Create(block, challenge);
133 : :
134 [ # # ]: 0 : if (!signet_txs) {
135 [ # # ][ # # ]: 0 : LogPrint(BCLog::VALIDATION, "CheckSignetBlockSolution: Errors in block (block solution parse failure)\n");
[ # # ][ # # ]
[ # # ]
136 : 0 : return false;
137 : : }
138 : :
139 : 0 : const CScript& scriptSig = signet_txs->m_to_sign.vin[0].scriptSig;
140 : 0 : const CScriptWitness& witness = signet_txs->m_to_sign.vin[0].scriptWitness;
141 : :
142 [ # # ]: 0 : PrecomputedTransactionData txdata;
143 [ # # ][ # # ]: 0 : txdata.Init(signet_txs->m_to_sign, {signet_txs->m_to_spend.vout[0]});
[ # # ]
144 [ # # ]: 0 : TransactionSignatureChecker sigcheck(&signet_txs->m_to_sign, /* nInIn= */ 0, /* amountIn= */ signet_txs->m_to_spend.vout[0].nValue, txdata, MissingDataBehavior::ASSERT_FAIL);
145 : :
146 [ # # ][ # # ]: 0 : if (!VerifyScript(scriptSig, signet_txs->m_to_spend.vout[0].scriptPubKey, &witness, BLOCK_SCRIPT_VERIFY_FLAGS, sigcheck)) {
147 [ # # ][ # # ]: 0 : LogPrint(BCLog::VALIDATION, "CheckSignetBlockSolution: Errors in block (block solution invalid)\n");
[ # # ][ # # ]
[ # # ]
148 : 0 : return false;
149 : : }
150 : 0 : return true;
151 : 0 : }
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