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1 : : // Copyright (c) 2009-2010 Satoshi Nakamoto
2 : : // Copyright (c) 2009-present 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 <script/verify_flags.h> // IWYU pragma: export
14 : : #include <span.h>
15 : : #include <uint256.h>
16 : :
17 : : #include <cstddef>
18 : : #include <cstdint>
19 : : #include <optional>
20 : : #include <vector>
21 : :
22 : : class CPubKey;
23 : : class CScript;
24 : : class CScriptNum;
25 : : class XOnlyPubKey;
26 : : struct CScriptWitness;
27 : :
28 : : /** Signature hash types/flags */
29 : : enum
30 : : {
31 : : SIGHASH_ALL = 1,
32 : : SIGHASH_NONE = 2,
33 : : SIGHASH_SINGLE = 3,
34 : : SIGHASH_ANYONECANPAY = 0x80,
35 : :
36 : : SIGHASH_DEFAULT = 0, //!< Taproot only; implied when sighash byte is missing, and equivalent to SIGHASH_ALL
37 : : SIGHASH_OUTPUT_MASK = 3,
38 : : SIGHASH_INPUT_MASK = 0x80,
39 : : };
40 : :
41 : : /** Script verification flags.
42 : : *
43 : : * All flags are intended to be soft forks: the set of acceptable scripts under
44 : : * flags (A | B) is a subset of the acceptable scripts under flag (A).
45 : : */
46 : :
47 : : static constexpr script_verify_flags SCRIPT_VERIFY_NONE{0};
48 : :
49 : : enum class script_verify_flag_name : uint8_t {
50 : : // Evaluate P2SH subscripts (BIP16).
51 : : SCRIPT_VERIFY_P2SH,
52 : :
53 : : // Passing a non-strict-DER signature or one with undefined hashtype to a checksig operation causes script failure.
54 : : // Evaluating a pubkey that is not (0x04 + 64 bytes) or (0x02 or 0x03 + 32 bytes) by checksig causes script failure.
55 : : // (not used or intended as a consensus rule).
56 : : SCRIPT_VERIFY_STRICTENC,
57 : :
58 : : // Passing a non-strict-DER signature to a checksig operation causes script failure (BIP62 rule 1)
59 : : SCRIPT_VERIFY_DERSIG,
60 : :
61 : : // Passing a non-strict-DER signature or one with S > order/2 to a checksig operation causes script failure
62 : : // (BIP62 rule 5).
63 : : SCRIPT_VERIFY_LOW_S,
64 : :
65 : : // verify dummy stack item consumed by CHECKMULTISIG is of zero-length (BIP62 rule 7).
66 : : SCRIPT_VERIFY_NULLDUMMY,
67 : :
68 : : // Using a non-push operator in the scriptSig causes script failure (BIP62 rule 2).
69 : : SCRIPT_VERIFY_SIGPUSHONLY,
70 : :
71 : : // Require minimal encodings for all push operations (OP_0... OP_16, OP_1NEGATE where possible, direct
72 : : // pushes up to 75 bytes, OP_PUSHDATA up to 255 bytes, OP_PUSHDATA2 for anything larger). Evaluating
73 : : // any other push causes the script to fail (BIP62 rule 3).
74 : : // In addition, whenever a stack element is interpreted as a number, it must be of minimal length (BIP62 rule 4).
75 : : SCRIPT_VERIFY_MINIMALDATA,
76 : :
77 : : // Discourage use of NOPs reserved for upgrades (NOP1-10)
78 : : //
79 : : // Provided so that nodes can avoid accepting or mining transactions
80 : : // containing executed NOP's whose meaning may change after a soft-fork,
81 : : // thus rendering the script invalid; with this flag set executing
82 : : // discouraged NOPs fails the script. This verification flag will never be
83 : : // a mandatory flag applied to scripts in a block. NOPs that are not
84 : : // executed, e.g. within an unexecuted IF ENDIF block, are *not* rejected.
85 : : // NOPs that have associated forks to give them new meaning (CLTV, CSV)
86 : : // are not subject to this rule.
87 : : SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS,
88 : :
89 : : // Require that only a single stack element remains after evaluation. This changes the success criterion from
90 : : // "At least one stack element must remain, and when interpreted as a boolean, it must be true" to
91 : : // "Exactly one stack element must remain, and when interpreted as a boolean, it must be true".
92 : : // (BIP62 rule 6)
93 : : // Note: CLEANSTACK should never be used without P2SH or WITNESS.
94 : : // Note: WITNESS_V0 and TAPSCRIPT script execution have behavior similar to CLEANSTACK as part of their
95 : : // consensus rules. It is automatic there and does not need this flag.
96 : : SCRIPT_VERIFY_CLEANSTACK,
97 : :
98 : : // Verify CHECKLOCKTIMEVERIFY
99 : : //
100 : : // See BIP65 for details.
101 : : SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY,
102 : :
103 : : // support CHECKSEQUENCEVERIFY opcode
104 : : //
105 : : // See BIP112 for details
106 : : SCRIPT_VERIFY_CHECKSEQUENCEVERIFY,
107 : :
108 : : // Support segregated witness
109 : : //
110 : : SCRIPT_VERIFY_WITNESS,
111 : :
112 : : // Making v1-v16 witness program non-standard
113 : : //
114 : : SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM,
115 : :
116 : : // Segwit script only: Require the argument of OP_IF/NOTIF to be exactly 0x01 or empty vector
117 : : //
118 : : // Note: TAPSCRIPT script execution has behavior similar to MINIMALIF as part of its consensus
119 : : // rules. It is automatic there and does not depend on this flag.
120 : : SCRIPT_VERIFY_MINIMALIF,
121 : :
122 : : // Signature(s) must be empty vector if a CHECK(MULTI)SIG operation failed
123 : : //
124 : : SCRIPT_VERIFY_NULLFAIL,
125 : :
126 : : // Public keys in segregated witness scripts must be compressed
127 : : //
128 : : SCRIPT_VERIFY_WITNESS_PUBKEYTYPE,
129 : :
130 : : // Making OP_CODESEPARATOR and FindAndDelete fail any non-segwit scripts
131 : : //
132 : : SCRIPT_VERIFY_CONST_SCRIPTCODE,
133 : :
134 : : // Taproot/Tapscript validation (BIPs 341 & 342)
135 : : //
136 : : SCRIPT_VERIFY_TAPROOT,
137 : :
138 : : // Making unknown Taproot leaf versions non-standard
139 : : //
140 : : SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_TAPROOT_VERSION,
141 : :
142 : : // Making unknown OP_SUCCESS non-standard
143 : : SCRIPT_VERIFY_DISCOURAGE_OP_SUCCESS,
144 : :
145 : : // Making unknown public key versions (in BIP 342 scripts) non-standard
146 : : SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_PUBKEYTYPE,
147 : :
148 : : // Constants to point to the highest flag in use. Add new flags above this line.
149 : : //
150 : : SCRIPT_VERIFY_END_MARKER
151 : : };
152 : : using enum script_verify_flag_name;
153 : :
154 : : static constexpr int MAX_SCRIPT_VERIFY_FLAGS_BITS = static_cast<int>(SCRIPT_VERIFY_END_MARKER);
155 : :
156 : : // assert there is still a spare bit
157 : : static_assert(0 < MAX_SCRIPT_VERIFY_FLAGS_BITS && MAX_SCRIPT_VERIFY_FLAGS_BITS <= 63);
158 : :
159 : : static constexpr script_verify_flags::value_type MAX_SCRIPT_VERIFY_FLAGS = ((script_verify_flags::value_type{1} << MAX_SCRIPT_VERIFY_FLAGS_BITS) - 1);
160 : :
161 : : bool CheckSignatureEncoding(const std::vector<unsigned char> &vchSig, script_verify_flags flags, ScriptError* serror);
162 : :
163 [ # # ]: 304606 : struct PrecomputedTransactionData
164 : : {
165 : : // BIP341 precomputed data.
166 : : // These are single-SHA256, see https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#cite_note-16.
167 : : uint256 m_prevouts_single_hash;
168 : : uint256 m_sequences_single_hash;
169 : : uint256 m_outputs_single_hash;
170 : : uint256 m_spent_amounts_single_hash;
171 : : uint256 m_spent_scripts_single_hash;
172 : : //! Whether the 5 fields above are initialized.
173 : : bool m_bip341_taproot_ready = false;
174 : :
175 : : // BIP143 precomputed data (double-SHA256).
176 : : uint256 hashPrevouts, hashSequence, hashOutputs;
177 : : //! Whether the 3 fields above are initialized.
178 : : bool m_bip143_segwit_ready = false;
179 : :
180 : : std::vector<CTxOut> m_spent_outputs;
181 : : //! Whether m_spent_outputs is initialized.
182 : : bool m_spent_outputs_ready = false;
183 : :
184 : 1927163 : PrecomputedTransactionData() = default;
185 : :
186 : : /** Initialize this PrecomputedTransactionData with transaction data.
187 : : *
188 : : * @param[in] tx The transaction for which data is being precomputed.
189 : : * @param[in] spent_outputs The CTxOuts being spent, one for each tx.vin, in order.
190 : : * @param[in] force Whether to precompute data for all optional features,
191 : : * regardless of what is in the inputs (used at signing
192 : : * time, when the inputs aren't filled in yet). */
193 : : template <class T>
194 : : void Init(const T& tx, std::vector<CTxOut>&& spent_outputs, bool force = false);
195 : :
196 : : template <class T>
197 : : explicit PrecomputedTransactionData(const T& tx);
198 : : };
199 : :
200 : : enum class SigVersion
201 : : {
202 : : BASE = 0, //!< Bare scripts and BIP16 P2SH-wrapped redeemscripts
203 : : WITNESS_V0 = 1, //!< Witness v0 (P2WPKH and P2WSH); see BIP 141
204 : : TAPROOT = 2, //!< Witness v1 with 32-byte program, not BIP16 P2SH-wrapped, key path spending; see BIP 341
205 : : TAPSCRIPT = 3, //!< Witness v1 with 32-byte program, not BIP16 P2SH-wrapped, script path spending, leaf version 0xc0; see BIP 342
206 : : };
207 : :
208 [ + + ]: 2943995 : struct ScriptExecutionData
209 : : {
210 : : //! Whether m_tapleaf_hash is initialized.
211 : : bool m_tapleaf_hash_init = false;
212 : : //! The tapleaf hash.
213 : : uint256 m_tapleaf_hash;
214 : :
215 : : //! Whether m_codeseparator_pos is initialized.
216 : : bool m_codeseparator_pos_init = false;
217 : : //! Opcode position of the last executed OP_CODESEPARATOR (or 0xFFFFFFFF if none executed).
218 : : uint32_t m_codeseparator_pos;
219 : :
220 : : //! Whether m_annex_present and (when needed) m_annex_hash are initialized.
221 : : bool m_annex_init = false;
222 : : //! Whether an annex is present.
223 : : bool m_annex_present;
224 : : //! Hash of the annex data.
225 : : uint256 m_annex_hash;
226 : :
227 : : //! Whether m_validation_weight_left is initialized.
228 : : bool m_validation_weight_left_init = false;
229 : : //! How much validation weight is left (decremented for every successful non-empty signature check).
230 : : int64_t m_validation_weight_left;
231 : :
232 : : //! The hash of the corresponding output
233 : : std::optional<uint256> m_output_hash;
234 : : };
235 : :
236 : : /** Signature hash sizes */
237 : : static constexpr size_t WITNESS_V0_SCRIPTHASH_SIZE = 32;
238 : : static constexpr size_t WITNESS_V0_KEYHASH_SIZE = 20;
239 : : static constexpr size_t WITNESS_V1_TAPROOT_SIZE = 32;
240 : :
241 : : static constexpr uint8_t TAPROOT_LEAF_MASK = 0xfe;
242 : : static constexpr uint8_t TAPROOT_LEAF_TAPSCRIPT = 0xc0;
243 : : static constexpr size_t TAPROOT_CONTROL_BASE_SIZE = 33;
244 : : static constexpr size_t TAPROOT_CONTROL_NODE_SIZE = 32;
245 : : static constexpr size_t TAPROOT_CONTROL_MAX_NODE_COUNT = 128;
246 : : static constexpr size_t TAPROOT_CONTROL_MAX_SIZE = TAPROOT_CONTROL_BASE_SIZE + TAPROOT_CONTROL_NODE_SIZE * TAPROOT_CONTROL_MAX_NODE_COUNT;
247 : :
248 : : extern const HashWriter HASHER_TAPSIGHASH; //!< Hasher with tag "TapSighash" pre-fed to it.
249 : : extern const HashWriter HASHER_TAPLEAF; //!< Hasher with tag "TapLeaf" pre-fed to it.
250 : : extern const HashWriter HASHER_TAPBRANCH; //!< Hasher with tag "TapBranch" pre-fed to it.
251 : :
252 : : /** Data structure to cache SHA256 midstates for the ECDSA sighash calculations
253 : : * (bare, P2SH, P2WPKH, P2WSH). */
254 [ + + - - ]: 1207270 : class SigHashCache
255 : : {
256 : : /** For each sighash mode (ALL, SINGLE, NONE, ALL|ANYONE, SINGLE|ANYONE, NONE|ANYONE),
257 : : * optionally store a scriptCode which the hash is for, plus a midstate for the SHA256
258 : : * computation just before adding the hash_type itself. */
259 : : std::optional<std::pair<CScript, HashWriter>> m_cache_entries[6];
260 : :
261 : : /** Given a hash_type, find which of the 6 cache entries is to be used. */
262 : : int CacheIndex(int32_t hash_type) const noexcept;
263 : :
264 : : public:
265 : : /** Load into writer the SHA256 midstate if found in this cache. */
266 : : [[nodiscard]] bool Load(int32_t hash_type, const CScript& script_code, HashWriter& writer) const noexcept;
267 : : /** Store into this cache object the provided SHA256 midstate. */
268 : : void Store(int32_t hash_type, const CScript& script_code, const HashWriter& writer) noexcept;
269 : : };
270 : :
271 : : template <class T>
272 : : uint256 SignatureHash(const CScript& scriptCode, const T& txTo, unsigned int nIn, int32_t nHashType, const CAmount& amount, SigVersion sigversion, const PrecomputedTransactionData* cache = nullptr, SigHashCache* sighash_cache = nullptr);
273 : :
274 [ + - + - ]: 1209027 : class BaseSignatureChecker
275 : : {
276 : : public:
277 : 9875 : virtual bool CheckECDSASignature(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const
278 : : {
279 : 9875 : return false;
280 : : }
281 : :
282 : 0 : virtual bool CheckSchnorrSignature(std::span<const unsigned char> sig, std::span<const unsigned char> pubkey, SigVersion sigversion, ScriptExecutionData& execdata, ScriptError* serror = nullptr) const
283 : : {
284 : 0 : return false;
285 : : }
286 : :
287 : 17 : virtual bool CheckLockTime(const CScriptNum& nLockTime) const
288 : : {
289 : 17 : return false;
290 : : }
291 : :
292 : 33 : virtual bool CheckSequence(const CScriptNum& nSequence) const
293 : : {
294 : 33 : return false;
295 : : }
296 : :
297 [ + - ]: 824894 : virtual ~BaseSignatureChecker() = default;
[ + + + + ]
298 : : };
299 : :
300 : : /** Enum to specify what *TransactionSignatureChecker's behavior should be
301 : : * when dealing with missing transaction data.
302 : : */
303 : : enum class MissingDataBehavior
304 : : {
305 : : ASSERT_FAIL, //!< Abort execution through assertion failure (for consensus code)
306 : : FAIL, //!< Just act as if the signature was invalid
307 : : };
308 : :
309 : : template<typename T>
310 : : 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);
311 : :
312 : : template <class T>
313 [ + + ]: 1204841 : class GenericTransactionSignatureChecker : public BaseSignatureChecker
314 : : {
315 : : private:
316 : : const T* txTo;
317 : : const MissingDataBehavior m_mdb;
318 : : unsigned int nIn;
319 : : const CAmount amount;
320 : : const PrecomputedTransactionData* txdata;
321 : : mutable SigHashCache m_sighash_cache;
322 : :
323 : : protected:
324 : : virtual bool VerifyECDSASignature(const std::vector<unsigned char>& vchSig, const CPubKey& vchPubKey, const uint256& sighash) const;
325 : : virtual bool VerifySchnorrSignature(std::span<const unsigned char> sig, const XOnlyPubKey& pubkey, const uint256& sighash) const;
326 : :
327 : : public:
328 [ + - ]: 202133 : GenericTransactionSignatureChecker(const T* txToIn, unsigned int nInIn, const CAmount& amountIn, MissingDataBehavior mdb) : txTo(txToIn), m_mdb(mdb), nIn(nInIn), amount(amountIn), txdata(nullptr) {}
329 [ + - ]: 999992 : 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) {}
330 : : bool CheckECDSASignature(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const override;
331 : : bool CheckSchnorrSignature(std::span<const unsigned char> sig, std::span<const unsigned char> pubkey, SigVersion sigversion, ScriptExecutionData& execdata, ScriptError* serror = nullptr) const override;
332 : : bool CheckLockTime(const CScriptNum& nLockTime) const override;
333 : : bool CheckSequence(const CScriptNum& nSequence) const override;
334 : : };
335 : :
336 : : using TransactionSignatureChecker = GenericTransactionSignatureChecker<CTransaction>;
337 : : using MutableTransactionSignatureChecker = GenericTransactionSignatureChecker<CMutableTransaction>;
338 : :
339 : 199451 : class DeferringSignatureChecker : public BaseSignatureChecker
340 : : {
341 : : protected:
342 : : const BaseSignatureChecker& m_checker;
343 : :
344 : : public:
345 [ + - ]: 199451 : DeferringSignatureChecker(const BaseSignatureChecker& checker) : m_checker(checker) {}
346 : :
347 : 0 : bool CheckECDSASignature(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const override
348 : : {
349 : 0 : return m_checker.CheckECDSASignature(scriptSig, vchPubKey, scriptCode, sigversion);
350 : : }
351 : :
352 : 1100 : bool CheckSchnorrSignature(std::span<const unsigned char> sig, std::span<const unsigned char> pubkey, SigVersion sigversion, ScriptExecutionData& execdata, ScriptError* serror = nullptr) const override
353 : : {
354 : 1100 : return m_checker.CheckSchnorrSignature(sig, pubkey, sigversion, execdata, serror);
355 : : }
356 : :
357 : 14799 : bool CheckLockTime(const CScriptNum& nLockTime) const override
358 : : {
359 : 14799 : return m_checker.CheckLockTime(nLockTime);
360 : : }
361 : 14224 : bool CheckSequence(const CScriptNum& nSequence) const override
362 : : {
363 : 14224 : return m_checker.CheckSequence(nSequence);
364 : : }
365 : : };
366 : :
367 : : /** Compute the BIP341 tapleaf hash from leaf version & script. */
368 : : uint256 ComputeTapleafHash(uint8_t leaf_version, std::span<const unsigned char> script);
369 : : /** Compute the BIP341 tapbranch hash from two branches.
370 : : * Spans must be 32 bytes each. */
371 : : uint256 ComputeTapbranchHash(std::span<const unsigned char> a, std::span<const unsigned char> b);
372 : : /** Compute the BIP341 taproot script tree Merkle root from control block and leaf hash.
373 : : * Requires control block to have valid length (33 + k*32, with k in {0,1,..,128}). */
374 : : uint256 ComputeTaprootMerkleRoot(std::span<const unsigned char> control, const uint256& tapleaf_hash);
375 : :
376 : : bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, script_verify_flags flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptExecutionData& execdata, ScriptError* error = nullptr);
377 : : bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, script_verify_flags flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptError* error = nullptr);
378 : : bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CScriptWitness* witness, script_verify_flags flags, const BaseSignatureChecker& checker, ScriptError* serror = nullptr);
379 : :
380 : : size_t CountWitnessSigOps(const CScript& scriptSig, const CScript& scriptPubKey, const CScriptWitness* witness, script_verify_flags flags);
381 : :
382 : : int FindAndDelete(CScript& script, const CScript& b);
383 : :
384 : : const std::map<std::string, script_verify_flag_name>& ScriptFlagNamesToEnum();
385 : :
386 : : std::vector<std::string> GetScriptFlagNames(script_verify_flags flags);
387 : :
388 : : #endif // BITCOIN_SCRIPT_INTERPRETER_H
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