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1 : : // Copyright (c) 2009-2010 Satoshi Nakamoto
2 : : // Copyright (c) 2009-2022 The Bitcoin Core developers
3 : : // Distributed under the MIT software license, see the accompanying
4 : : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
5 : :
6 : : #ifndef BITCOIN_SCRIPT_INTERPRETER_H
7 : : #define BITCOIN_SCRIPT_INTERPRETER_H
8 : :
9 : : #include <consensus/amount.h>
10 : : #include <hash.h>
11 : : #include <primitives/transaction.h>
12 : : #include <script/script_error.h> // IWYU pragma: export
13 : : #include <span.h>
14 : : #include <uint256.h>
15 : :
16 : : #include <cstddef>
17 : : #include <cstdint>
18 : : #include <optional>
19 : : #include <vector>
20 : :
21 : : class CPubKey;
22 : : class CScript;
23 : : class CScriptNum;
24 : : class XOnlyPubKey;
25 : : struct CScriptWitness;
26 : :
27 : : /** Signature hash types/flags */
28 : : enum
29 : : {
30 : : SIGHASH_ALL = 1,
31 : : SIGHASH_NONE = 2,
32 : : SIGHASH_SINGLE = 3,
33 : : SIGHASH_ANYONECANPAY = 0x80,
34 : :
35 : : SIGHASH_DEFAULT = 0, //!< Taproot only; implied when sighash byte is missing, and equivalent to SIGHASH_ALL
36 : : SIGHASH_OUTPUT_MASK = 3,
37 : : SIGHASH_INPUT_MASK = 0x80,
38 : : };
39 : :
40 : : /** Script verification flags.
41 : : *
42 : : * All flags are intended to be soft forks: the set of acceptable scripts under
43 : : * flags (A | B) is a subset of the acceptable scripts under flag (A).
44 : : */
45 : : enum : uint32_t {
46 : : SCRIPT_VERIFY_NONE = 0,
47 : :
48 : : // Evaluate P2SH subscripts (BIP16).
49 : : SCRIPT_VERIFY_P2SH = (1U << 0),
50 : :
51 : : // Passing a non-strict-DER signature or one with undefined hashtype to a checksig operation causes script failure.
52 : : // Evaluating a pubkey that is not (0x04 + 64 bytes) or (0x02 or 0x03 + 32 bytes) by checksig causes script failure.
53 : : // (not used or intended as a consensus rule).
54 : : SCRIPT_VERIFY_STRICTENC = (1U << 1),
55 : :
56 : : // Passing a non-strict-DER signature to a checksig operation causes script failure (BIP62 rule 1)
57 : : SCRIPT_VERIFY_DERSIG = (1U << 2),
58 : :
59 : : // Passing a non-strict-DER signature or one with S > order/2 to a checksig operation causes script failure
60 : : // (BIP62 rule 5).
61 : : SCRIPT_VERIFY_LOW_S = (1U << 3),
62 : :
63 : : // verify dummy stack item consumed by CHECKMULTISIG is of zero-length (BIP62 rule 7).
64 : : SCRIPT_VERIFY_NULLDUMMY = (1U << 4),
65 : :
66 : : // Using a non-push operator in the scriptSig causes script failure (BIP62 rule 2).
67 : : SCRIPT_VERIFY_SIGPUSHONLY = (1U << 5),
68 : :
69 : : // Require minimal encodings for all push operations (OP_0... OP_16, OP_1NEGATE where possible, direct
70 : : // pushes up to 75 bytes, OP_PUSHDATA up to 255 bytes, OP_PUSHDATA2 for anything larger). Evaluating
71 : : // any other push causes the script to fail (BIP62 rule 3).
72 : : // In addition, whenever a stack element is interpreted as a number, it must be of minimal length (BIP62 rule 4).
73 : : SCRIPT_VERIFY_MINIMALDATA = (1U << 6),
74 : :
75 : : // Discourage use of NOPs reserved for upgrades (NOP1-10)
76 : : //
77 : : // Provided so that nodes can avoid accepting or mining transactions
78 : : // containing executed NOP's whose meaning may change after a soft-fork,
79 : : // thus rendering the script invalid; with this flag set executing
80 : : // discouraged NOPs fails the script. This verification flag will never be
81 : : // a mandatory flag applied to scripts in a block. NOPs that are not
82 : : // executed, e.g. within an unexecuted IF ENDIF block, are *not* rejected.
83 : : // NOPs that have associated forks to give them new meaning (CLTV, CSV)
84 : : // are not subject to this rule.
85 : : SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS = (1U << 7),
86 : :
87 : : // Require that only a single stack element remains after evaluation. This changes the success criterion from
88 : : // "At least one stack element must remain, and when interpreted as a boolean, it must be true" to
89 : : // "Exactly one stack element must remain, and when interpreted as a boolean, it must be true".
90 : : // (BIP62 rule 6)
91 : : // Note: CLEANSTACK should never be used without P2SH or WITNESS.
92 : : // Note: WITNESS_V0 and TAPSCRIPT script execution have behavior similar to CLEANSTACK as part of their
93 : : // consensus rules. It is automatic there and does not need this flag.
94 : : SCRIPT_VERIFY_CLEANSTACK = (1U << 8),
95 : :
96 : : // Verify CHECKLOCKTIMEVERIFY
97 : : //
98 : : // See BIP65 for details.
99 : : SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY = (1U << 9),
100 : :
101 : : // support CHECKSEQUENCEVERIFY opcode
102 : : //
103 : : // See BIP112 for details
104 : : SCRIPT_VERIFY_CHECKSEQUENCEVERIFY = (1U << 10),
105 : :
106 : : // Support segregated witness
107 : : //
108 : : SCRIPT_VERIFY_WITNESS = (1U << 11),
109 : :
110 : : // Making v1-v16 witness program non-standard
111 : : //
112 : : SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM = (1U << 12),
113 : :
114 : : // Segwit script only: Require the argument of OP_IF/NOTIF to be exactly 0x01 or empty vector
115 : : //
116 : : // Note: TAPSCRIPT script execution has behavior similar to MINIMALIF as part of its consensus
117 : : // rules. It is automatic there and does not depend on this flag.
118 : : SCRIPT_VERIFY_MINIMALIF = (1U << 13),
119 : :
120 : : // Signature(s) must be empty vector if a CHECK(MULTI)SIG operation failed
121 : : //
122 : : SCRIPT_VERIFY_NULLFAIL = (1U << 14),
123 : :
124 : : // Public keys in segregated witness scripts must be compressed
125 : : //
126 : : SCRIPT_VERIFY_WITNESS_PUBKEYTYPE = (1U << 15),
127 : :
128 : : // Making OP_CODESEPARATOR and FindAndDelete fail any non-segwit scripts
129 : : //
130 : : SCRIPT_VERIFY_CONST_SCRIPTCODE = (1U << 16),
131 : :
132 : : // Taproot/Tapscript validation (BIPs 341 & 342)
133 : : //
134 : : SCRIPT_VERIFY_TAPROOT = (1U << 17),
135 : :
136 : : // Making unknown Taproot leaf versions non-standard
137 : : //
138 : : SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_TAPROOT_VERSION = (1U << 18),
139 : :
140 : : // Making unknown OP_SUCCESS non-standard
141 : : SCRIPT_VERIFY_DISCOURAGE_OP_SUCCESS = (1U << 19),
142 : :
143 : : // Making unknown public key versions (in BIP 342 scripts) non-standard
144 : : SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_PUBKEYTYPE = (1U << 20),
145 : :
146 : : // Constants to point to the highest flag in use. Add new flags above this line.
147 : : //
148 : : SCRIPT_VERIFY_END_MARKER
149 : : };
150 : :
151 : : bool CheckSignatureEncoding(const std::vector<unsigned char> &vchSig, unsigned int flags, ScriptError* serror);
152 : :
153 : 0 : struct PrecomputedTransactionData
154 : : {
155 : : // BIP341 precomputed data.
156 : : // These are single-SHA256, see https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#cite_note-16.
157 : : uint256 m_prevouts_single_hash;
158 : : uint256 m_sequences_single_hash;
159 : : uint256 m_outputs_single_hash;
160 : : uint256 m_spent_amounts_single_hash;
161 : : uint256 m_spent_scripts_single_hash;
162 : : //! Whether the 5 fields above are initialized.
163 : 0 : bool m_bip341_taproot_ready = false;
164 : :
165 : : // BIP143 precomputed data (double-SHA256).
166 : : uint256 hashPrevouts, hashSequence, hashOutputs;
167 : : //! Whether the 3 fields above are initialized.
168 : 0 : bool m_bip143_segwit_ready = false;
169 : :
170 : : std::vector<CTxOut> m_spent_outputs;
171 : : //! Whether m_spent_outputs is initialized.
172 : 0 : bool m_spent_outputs_ready = false;
173 : :
174 : 0 : PrecomputedTransactionData() = default;
175 : :
176 : : /** Initialize this PrecomputedTransactionData with transaction data.
177 : : *
178 : : * @param[in] tx The transaction for which data is being precomputed.
179 : : * @param[in] spent_outputs The CTxOuts being spent, one for each tx.vin, in order.
180 : : * @param[in] force Whether to precompute data for all optional features,
181 : : * regardless of what is in the inputs (used at signing
182 : : * time, when the inputs aren't filled in yet). */
183 : : template <class T>
184 : : void Init(const T& tx, std::vector<CTxOut>&& spent_outputs, bool force = false);
185 : :
186 : : template <class T>
187 : : explicit PrecomputedTransactionData(const T& tx);
188 : : };
189 : :
190 : : enum class SigVersion
191 : : {
192 : : BASE = 0, //!< Bare scripts and BIP16 P2SH-wrapped redeemscripts
193 : : WITNESS_V0 = 1, //!< Witness v0 (P2WPKH and P2WSH); see BIP 141
194 : : TAPROOT = 2, //!< Witness v1 with 32-byte program, not BIP16 P2SH-wrapped, key path spending; see BIP 341
195 : : TAPSCRIPT = 3, //!< Witness v1 with 32-byte program, not BIP16 P2SH-wrapped, script path spending, leaf version 0xc0; see BIP 342
196 : : };
197 : :
198 : 0 : struct ScriptExecutionData
199 : : {
200 : : //! Whether m_tapleaf_hash is initialized.
201 : 0 : bool m_tapleaf_hash_init = false;
202 : : //! The tapleaf hash.
203 : : uint256 m_tapleaf_hash;
204 : :
205 : : //! Whether m_codeseparator_pos is initialized.
206 : 0 : bool m_codeseparator_pos_init = false;
207 : : //! Opcode position of the last executed OP_CODESEPARATOR (or 0xFFFFFFFF if none executed).
208 : : uint32_t m_codeseparator_pos;
209 : :
210 : : //! Whether m_annex_present and (when needed) m_annex_hash are initialized.
211 : 0 : bool m_annex_init = false;
212 : : //! Whether an annex is present.
213 : : bool m_annex_present;
214 : : //! Hash of the annex data.
215 : : uint256 m_annex_hash;
216 : :
217 : : //! Whether m_validation_weight_left is initialized.
218 : 0 : bool m_validation_weight_left_init = false;
219 : : //! How much validation weight is left (decremented for every successful non-empty signature check).
220 : : int64_t m_validation_weight_left;
221 : :
222 : : //! The hash of the corresponding output
223 : : std::optional<uint256> m_output_hash;
224 : : };
225 : :
226 : : /** Signature hash sizes */
227 : : static constexpr size_t WITNESS_V0_SCRIPTHASH_SIZE = 32;
228 : : static constexpr size_t WITNESS_V0_KEYHASH_SIZE = 20;
229 : : static constexpr size_t WITNESS_V1_TAPROOT_SIZE = 32;
230 : :
231 : : static constexpr uint8_t TAPROOT_LEAF_MASK = 0xfe;
232 : : static constexpr uint8_t TAPROOT_LEAF_TAPSCRIPT = 0xc0;
233 : : static constexpr size_t TAPROOT_CONTROL_BASE_SIZE = 33;
234 : : static constexpr size_t TAPROOT_CONTROL_NODE_SIZE = 32;
235 : : static constexpr size_t TAPROOT_CONTROL_MAX_NODE_COUNT = 128;
236 : : static constexpr size_t TAPROOT_CONTROL_MAX_SIZE = TAPROOT_CONTROL_BASE_SIZE + TAPROOT_CONTROL_NODE_SIZE * TAPROOT_CONTROL_MAX_NODE_COUNT;
237 : :
238 : : extern const HashWriter HASHER_TAPSIGHASH; //!< Hasher with tag "TapSighash" pre-fed to it.
239 : : extern const HashWriter HASHER_TAPLEAF; //!< Hasher with tag "TapLeaf" pre-fed to it.
240 : : extern const HashWriter HASHER_TAPBRANCH; //!< Hasher with tag "TapBranch" pre-fed to it.
241 : :
242 : : template <class T>
243 : : uint256 SignatureHash(const CScript& scriptCode, const T& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const PrecomputedTransactionData* cache = nullptr);
244 : :
245 : 0 : class BaseSignatureChecker
246 : : {
247 : : public:
248 : 0 : virtual bool CheckECDSASignature(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const
249 : : {
250 : 0 : return false;
251 : : }
252 : :
253 : 0 : virtual bool CheckSchnorrSignature(Span<const unsigned char> sig, Span<const unsigned char> pubkey, SigVersion sigversion, ScriptExecutionData& execdata, ScriptError* serror = nullptr) const
254 : : {
255 : 0 : return false;
256 : : }
257 : :
258 : 0 : virtual bool CheckLockTime(const CScriptNum& nLockTime) const
259 : : {
260 : 0 : return false;
261 : : }
262 : :
263 : 0 : virtual bool CheckSequence(const CScriptNum& nSequence) const
264 : : {
265 : 0 : return false;
266 : : }
267 : :
268 : 4 : virtual ~BaseSignatureChecker() {}
269 : : };
270 : :
271 : : /** Enum to specify what *TransactionSignatureChecker's behavior should be
272 : : * when dealing with missing transaction data.
273 : : */
274 : : enum class MissingDataBehavior
275 : : {
276 : : ASSERT_FAIL, //!< Abort execution through assertion failure (for consensus code)
277 : : FAIL, //!< Just act as if the signature was invalid
278 : : };
279 : :
280 : : template<typename T>
281 : : bool SignatureHashSchnorr(uint256& hash_out, ScriptExecutionData& execdata, const T& tx_to, uint32_t in_pos, uint8_t hash_type, SigVersion sigversion, const PrecomputedTransactionData& cache, MissingDataBehavior mdb);
282 : :
283 : : template <class T>
284 : 0 : class GenericTransactionSignatureChecker : public BaseSignatureChecker
285 : : {
286 : : private:
287 : : const T* txTo;
288 : : const MissingDataBehavior m_mdb;
289 : : unsigned int nIn;
290 : : const CAmount amount;
291 : : const PrecomputedTransactionData* txdata;
292 : :
293 : : protected:
294 : : virtual bool VerifyECDSASignature(const std::vector<unsigned char>& vchSig, const CPubKey& vchPubKey, const uint256& sighash) const;
295 : : virtual bool VerifySchnorrSignature(Span<const unsigned char> sig, const XOnlyPubKey& pubkey, const uint256& sighash) const;
296 : :
297 : : public:
298 : 0 : GenericTransactionSignatureChecker(const T* txToIn, unsigned int nInIn, const CAmount& amountIn, MissingDataBehavior mdb) : txTo(txToIn), m_mdb(mdb), nIn(nInIn), amount(amountIn), txdata(nullptr) {}
299 : 0 : GenericTransactionSignatureChecker(const T* txToIn, unsigned int nInIn, const CAmount& amountIn, const PrecomputedTransactionData& txdataIn, MissingDataBehavior mdb) : txTo(txToIn), m_mdb(mdb), nIn(nInIn), amount(amountIn), txdata(&txdataIn) {}
300 : : bool CheckECDSASignature(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const override;
301 : : bool CheckSchnorrSignature(Span<const unsigned char> sig, Span<const unsigned char> pubkey, SigVersion sigversion, ScriptExecutionData& execdata, ScriptError* serror = nullptr) const override;
302 : : bool CheckLockTime(const CScriptNum& nLockTime) const override;
303 : : bool CheckSequence(const CScriptNum& nSequence) const override;
304 : : };
305 : :
306 : : using TransactionSignatureChecker = GenericTransactionSignatureChecker<CTransaction>;
307 : : using MutableTransactionSignatureChecker = GenericTransactionSignatureChecker<CMutableTransaction>;
308 : :
309 : 0 : class DeferringSignatureChecker : public BaseSignatureChecker
310 : : {
311 : : protected:
312 : : const BaseSignatureChecker& m_checker;
313 : :
314 : : public:
315 : 0 : DeferringSignatureChecker(const BaseSignatureChecker& checker) : m_checker(checker) {}
316 : :
317 : 0 : bool CheckECDSASignature(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const override
318 : : {
319 : 0 : return m_checker.CheckECDSASignature(scriptSig, vchPubKey, scriptCode, sigversion);
320 : : }
321 : :
322 : 0 : bool CheckSchnorrSignature(Span<const unsigned char> sig, Span<const unsigned char> pubkey, SigVersion sigversion, ScriptExecutionData& execdata, ScriptError* serror = nullptr) const override
323 : : {
324 : 0 : return m_checker.CheckSchnorrSignature(sig, pubkey, sigversion, execdata, serror);
325 : : }
326 : :
327 : 0 : bool CheckLockTime(const CScriptNum& nLockTime) const override
328 : : {
329 : 0 : return m_checker.CheckLockTime(nLockTime);
330 : : }
331 : 0 : bool CheckSequence(const CScriptNum& nSequence) const override
332 : : {
333 : 0 : return m_checker.CheckSequence(nSequence);
334 : : }
335 : : };
336 : :
337 : : /** Compute the BIP341 tapleaf hash from leaf version & script. */
338 : : uint256 ComputeTapleafHash(uint8_t leaf_version, Span<const unsigned char> script);
339 : : /** Compute the BIP341 tapbranch hash from two branches.
340 : : * Spans must be 32 bytes each. */
341 : : uint256 ComputeTapbranchHash(Span<const unsigned char> a, Span<const unsigned char> b);
342 : : /** Compute the BIP341 taproot script tree Merkle root from control block and leaf hash.
343 : : * Requires control block to have valid length (33 + k*32, with k in {0,1,..,128}). */
344 : : uint256 ComputeTaprootMerkleRoot(Span<const unsigned char> control, const uint256& tapleaf_hash);
345 : :
346 : : bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptExecutionData& execdata, ScriptError* error = nullptr);
347 : : bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptError* error = nullptr);
348 : : bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CScriptWitness* witness, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror = nullptr);
349 : :
350 : : size_t CountWitnessSigOps(const CScript& scriptSig, const CScript& scriptPubKey, const CScriptWitness* witness, unsigned int flags);
351 : :
352 : : int FindAndDelete(CScript& script, const CScript& b);
353 : :
354 : : #endif // BITCOIN_SCRIPT_INTERPRETER_H
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