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Merge bitcoin/bitcoin#33891: kernel: Expose reusable PrecomputedTransactionData in script validation

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44e006d438 [kernel] Expose reusable PrecomputedTransactionData in script valid (Josh Doman)

Pull request description:

  This PR exposes a reusable `PrecomputedTransactionData` object in script validation using libkernel.

  Currently, libkernel computes `PrecomputedTransactionData` each time `btck_script_pubkey_verify` is called, exposing clients to quadratic hashing when validating a transaction with multiple inputs. By externalizing `PrecomputedTransactionData` and making it reusable, libkernel can eliminate this attack vector.

  I discussed this problem in [this issue](https://github.com/TheCharlatan/rust-bitcoinkernel/issues/46). The design of this PR is inspired by @sedited's comments.

  The PR introduces three new APIs for managing the `btck_PrecomputedTransactionData` object:
  ```c
  /**
   * @brief Create precomputed transaction data for script verification.
   *
   * @param[in] tx_to             Non-null.
   * @param[in] spent_outputs     Nullable for non-taproot verification. Points to an array of
   *                              outputs spent by the transaction.
   * @param[in] spent_outputs_len Length of the spent_outputs array.
   * @return                      The precomputed data, or null on error.
   */
  btck_PrecomputedTransactionData* btck_precomputed_transaction_data_create(
      const btck_Transaction* tx_to,
      const btck_TransactionOutput** spent_outputs, size_t spent_outputs_len) BITCOINKERNEL_ARG_NONNULL(1);

  /**
   * @brief Copy precomputed transaction data.
   *
   * @param[in] precomputed_txdata  Non-null.
   * @return                      The copied precomputed transaction data.
   */
  btck_PrecomputedTransactionData* btck_precomputed_transaction_data_copy(
      const btck_PrecomputedTransactionData* precomputed_txdata) BITCOINKERNEL_ARG_NONNULL(1);

  /**
   * Destroy the precomputed transaction data.
   */
  void btck_precomputed_transaction_data_destroy(btck_PrecomputedTransactionData* precomputed_txdata);
  ```

  The PR also modifies `btck_script_pubkey_verify` so that it accepts `precomputed_txdata` instead of `spent_outputs`:
  ```c
  /**
   * @brief Verify if the input at input_index of tx_to spends the script pubkey
   * under the constraints specified by flags. If the
   * `btck_ScriptVerificationFlags_WITNESS` flag is set in the flags bitfield, the
   * amount parameter is used. If the taproot flag is set, the precomputed data
   * must contain the spent outputs.
   *
   * @param[in] script_pubkey      Non-null, script pubkey to be spent.
   * @param[in] amount             Amount of the script pubkey's associated output. May be zero if
   *                               the witness flag is not set.
   * @param[in] tx_to              Non-null, transaction spending the script_pubkey.
   * @param[in] precomputed_txdata Nullable if the taproot flag is not set. Otherwise, precomputed data
   *                               for tx_to with the spent outputs must be provided.
   * @param[in] input_index        Index of the input in tx_to spending the script_pubkey.
   * @param[in] flags              Bitfield of btck_ScriptVerificationFlags controlling validation constraints.
   * @param[out] status            Nullable, will be set to an error code if the operation fails, or OK otherwise.
   * @return                       1 if the script is valid, 0 otherwise.
   */
  int btck_script_pubkey_verify(
      const btck_ScriptPubkey* script_pubkey,
      int64_t amount,
      const btck_Transaction* tx_to,
      const btck_PrecomputedTransactionData* precomputed_txdata,
      unsigned int input_index,
      btck_ScriptVerificationFlags flags,
      btck_ScriptVerifyStatus* status) BITCOINKERNEL_ARG_NONNULL(1, 3);
  ```

  As before, an error is thrown if the taproot flag is set and `spent_outputs` is not provided in `precomputed_txdata` (or `precomputed_txdata` is null). For simple single-input non-taproot verification, `precomputed_txdata` may be null, and the kernel will construct the precomputed data on-the-fly.

  Both the C++ wrapper and the test suite are updated with the new API. Tests cover both `precomputed_txdata` reuse and nullability.

  Appreciate feedback on this concept / approach!

ACKs for top commit:
  sedited:
    Re-ACK 44e006d438
  stringintech:
    ACK 44e006d

Tree-SHA512: 1ed435173e6ff4ec82bc603194cf182c685cb79f167439a442b9b179a32f6c189c358f04d4cb56d153fab04e3424a11b73c31680e42b87b8a6efcc3ccefc366c
This commit is contained in:
merge-script
2025-12-27 16:20:43 +00:00
parent e703360577 44e006d438
commit eb0594e23f
4 changed files with 220 additions and 73 deletions
Download Patch File Download Diff File Expand all files Collapse all files

130
src/test/kernel/test_kernel.cpp
View File

@@ -218,7 +218,7 @@ public:
void run_verify_test(
const ScriptPubkey& spent_script_pubkey,
const Transaction& spending_tx,
std::span<TransactionOutput> spent_outputs,
const PrecomputedTransactionData* precomputed_txdata,
int64_t amount,
unsigned int input_index,
bool taproot)
@@ -229,7 +229,7 @@ void run_verify_test(
BOOST_CHECK(spent_script_pubkey.Verify(
amount,
spending_tx,
spent_outputs,
precomputed_txdata,
input_index,
ScriptVerificationFlags::ALL,
status));
@@ -238,7 +238,7 @@ void run_verify_test(
BOOST_CHECK(!spent_script_pubkey.Verify(
amount,
spending_tx,
spent_outputs,
precomputed_txdata,
input_index,
ScriptVerificationFlags::ALL,
status));
@@ -248,7 +248,7 @@ void run_verify_test(
BOOST_CHECK(spent_script_pubkey.Verify(
amount,
spending_tx,
spent_outputs,
precomputed_txdata,
input_index,
VERIFY_ALL_PRE_TAPROOT,
status));
@@ -257,7 +257,7 @@ void run_verify_test(
BOOST_CHECK(spent_script_pubkey.Verify(
0,
spending_tx,
spent_outputs,
precomputed_txdata,
input_index,
VERIFY_ALL_PRE_SEGWIT,
status));
@@ -499,37 +499,114 @@ BOOST_AUTO_TEST_CASE(btck_transaction_input)
CheckHandle(point_0, point_1);
}
BOOST_AUTO_TEST_CASE(btck_precomputed_txdata) {
auto tx_data{hex_string_to_byte_vec("02000000013f7cebd65c27431a90bba7f796914fe8cc2ddfc3f2cbd6f7e5f2fc854534da95000000006b483045022100de1ac3bcdfb0332207c4a91f3832bd2c2915840165f876ab47c5f8996b971c3602201c6c053d750fadde599e6f5c4e1963df0f01fc0d97815e8157e3d59fe09ca30d012103699b464d1d8bc9e47d4fb1cdaa89a1c5783d68363c4dbc4b524ed3d857148617feffffff02836d3c01000000001976a914fc25d6d5c94003bf5b0c7b640a248e2c637fcfb088ac7ada8202000000001976a914fbed3d9b11183209a57999d54d59f67c019e756c88ac6acb0700")};
auto tx{Transaction{tx_data}};
auto tx_data_2{hex_string_to_byte_vec("02000000000101904f4ee5c87d20090b642f116e458cd6693292ad9ece23e72f15fb6c05b956210500000000fdffffff02e2010000000000002251200839a723933b56560487ec4d67dda58f09bae518ffa7e148313c5696ac837d9f10060000000000002251205826bcdae7abfb1c468204170eab00d887b61ab143464a4a09e1450bdc59a3340140f26e7af574e647355830772946356c27e7bbc773c5293688890f58983499581be84de40be7311a14e6d6422605df086620e75adae84ff06b75ce5894de5e994a00000000")};
auto tx2{Transaction{tx_data_2}};
auto precomputed_txdata{PrecomputedTransactionData{
/*tx_to=*/tx,
/*spent_outputs=*/{},
}};
auto precomputed_txdata_2{PrecomputedTransactionData{
/*tx_to=*/tx2,
/*spent_outputs=*/{},
}};
CheckHandle(precomputed_txdata, precomputed_txdata_2);
}
BOOST_AUTO_TEST_CASE(btck_script_verify_tests)
{
// Legacy transaction aca326a724eda9a461c10a876534ecd5ae7b27f10f26c3862fb996f80ea2d45d
auto legacy_spent_script_pubkey{ScriptPubkey{hex_string_to_byte_vec("76a9144bfbaf6afb76cc5771bc6404810d1cc041a6933988ac")}};
auto legacy_spending_tx{Transaction{hex_string_to_byte_vec("02000000013f7cebd65c27431a90bba7f796914fe8cc2ddfc3f2cbd6f7e5f2fc854534da95000000006b483045022100de1ac3bcdfb0332207c4a91f3832bd2c2915840165f876ab47c5f8996b971c3602201c6c053d750fadde599e6f5c4e1963df0f01fc0d97815e8157e3d59fe09ca30d012103699b464d1d8bc9e47d4fb1cdaa89a1c5783d68363c4dbc4b524ed3d857148617feffffff02836d3c01000000001976a914fc25d6d5c94003bf5b0c7b640a248e2c637fcfb088ac7ada8202000000001976a914fbed3d9b11183209a57999d54d59f67c019e756c88ac6acb0700")}};
run_verify_test(
/*spent_script_pubkey*/ ScriptPubkey{hex_string_to_byte_vec("76a9144bfbaf6afb76cc5771bc6404810d1cc041a6933988ac")},
/*spending_tx*/ Transaction{hex_string_to_byte_vec("02000000013f7cebd65c27431a90bba7f796914fe8cc2ddfc3f2cbd6f7e5f2fc854534da95000000006b483045022100de1ac3bcdfb0332207c4a91f3832bd2c2915840165f876ab47c5f8996b971c3602201c6c053d750fadde599e6f5c4e1963df0f01fc0d97815e8157e3d59fe09ca30d012103699b464d1d8bc9e47d4fb1cdaa89a1c5783d68363c4dbc4b524ed3d857148617feffffff02836d3c01000000001976a914fc25d6d5c94003bf5b0c7b640a248e2c637fcfb088ac7ada8202000000001976a914fbed3d9b11183209a57999d54d59f67c019e756c88ac6acb0700")},
/*spent_outputs*/ {},
/*amount*/ 0,
/*input_index*/ 0,
/*is_taproot*/ false);
/*spent_script_pubkey=*/legacy_spent_script_pubkey,
/*spending_tx=*/legacy_spending_tx,
/*precomputed_txdata=*/nullptr,
/*amount=*/0,
/*input_index=*/0,
/*taproot=*/false);
// Legacy transaction aca326a724eda9a461c10a876534ecd5ae7b27f10f26c3862fb996f80ea2d45d with precomputed_txdata
auto legacy_precomputed_txdata{PrecomputedTransactionData{
/*tx_to=*/legacy_spending_tx,
/*spent_outputs=*/{},
}};
run_verify_test(
/*spent_script_pubkey=*/legacy_spent_script_pubkey,
/*spending_tx=*/legacy_spending_tx,
/*precomputed_txdata=*/&legacy_precomputed_txdata,
/*amount=*/0,
/*input_index=*/0,
/*taproot=*/false);
// Segwit transaction 1a3e89644985fbbb41e0dcfe176739813542b5937003c46a07de1e3ee7a4a7f3
auto segwit_spent_script_pubkey{ScriptPubkey{hex_string_to_byte_vec("0020701a8d401c84fb13e6baf169d59684e17abd9fa216c8cc5b9fc63d622ff8c58d")}};
auto segwit_spending_tx{Transaction{hex_string_to_byte_vec("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")}};
run_verify_test(
/*spent_script_pubkey*/ ScriptPubkey{hex_string_to_byte_vec("0020701a8d401c84fb13e6baf169d59684e17abd9fa216c8cc5b9fc63d622ff8c58d")},
/*spending_tx*/ Transaction{hex_string_to_byte_vec("010000000001011f97548fbbe7a0db7588a66e18d803d0089315aa7d4cc28360b6ec50ef36718a0100000000ffffffff02df1776000000000017a9146c002a686959067f4866b8fb493ad7970290ab728757d29f0000000000220020701a8d401c84fb13e6baf169d59684e17abd9fa216c8cc5b9fc63d622ff8c58d04004730440220565d170eed95ff95027a69b313758450ba84a01224e1f7f130dda46e94d13f8602207bdd20e307f062594022f12ed5017bbf4a055a06aea91c10110a0e3bb23117fc014730440220647d2dc5b15f60bc37dc42618a370b2a1490293f9e5c8464f53ec4fe1dfe067302203598773895b4b16d37485cbe21b337f4e4b650739880098c592553add7dd4355016952210375e00eb72e29da82b89367947f29ef34afb75e8654f6ea368e0acdfd92976b7c2103a1b26313f430c4b15bb1fdce663207659d8cac749a0e53d70eff01874496feff2103c96d495bfdd5ba4145e3e046fee45e84a8a48ad05bd8dbb395c011a32cf9f88053ae00000000")},
/*spent_outputs*/ {},
/*amount*/ 18393430,
/*input_index*/ 0,
/*is_taproot*/ false);
/*spent_script_pubkey=*/segwit_spent_script_pubkey,
/*spending_tx=*/segwit_spending_tx,
/*precomputed_txdata=*/nullptr,
/*amount=*/18393430,
/*input_index=*/0,
/*taproot=*/false);
// Segwit transaction 1a3e89644985fbbb41e0dcfe176739813542b5937003c46a07de1e3ee7a4a7f3 with precomputed_txdata
auto segwit_precomputed_txdata{PrecomputedTransactionData{
/*tx_to=*/segwit_spending_tx,
/*spent_outputs=*/{},
}};
run_verify_test(
/*spent_script_pubkey=*/segwit_spent_script_pubkey,
/*spending_tx=*/segwit_spending_tx,
/*precomputed_txdata=*/&segwit_precomputed_txdata,
/*amount=*/18393430,
/*input_index=*/0,
/*taproot=*/false);
// Taproot transaction 33e794d097969002ee05d336686fc03c9e15a597c1b9827669460fac98799036
auto taproot_spent_script_pubkey{ScriptPubkey{hex_string_to_byte_vec("5120339ce7e165e67d93adb3fef88a6d4beed33f01fa876f05a225242b82a631abc0")}};
std::vector<TransactionOutput> spent_outputs;
spent_outputs.emplace_back(taproot_spent_script_pubkey, 88480);
auto taproot_spending_tx{Transaction{hex_string_to_byte_vec("01000000000101d1f1c1f8cdf6759167b90f52c9ad358a369f95284e841d7a2536cef31c0549580100000000fdffffff020000000000000000316a2f49206c696b65205363686e6f7272207369677320616e6420492063616e6e6f74206c69652e204062697462756734329e06010000000000225120a37c3903c8d0db6512e2b40b0dffa05e5a3ab73603ce8c9c4b7771e5412328f90140a60c383f71bac0ec919b1d7dbc3eb72dd56e7aa99583615564f9f99b8ae4e837b758773a5b2e4c51348854c8389f008e05029db7f464a5ff2e01d5e6e626174affd30a00")}};
std::vector<TransactionOutput> taproot_spent_outputs;
taproot_spent_outputs.emplace_back(taproot_spent_script_pubkey, 88480);
auto taproot_precomputed_txdata{PrecomputedTransactionData{
/*tx_to=*/taproot_spending_tx,
/*spent_outputs=*/taproot_spent_outputs,
}};
run_verify_test(
/*spent_script_pubkey*/ taproot_spent_script_pubkey,
/*spending_tx*/ Transaction{hex_string_to_byte_vec("01000000000101d1f1c1f8cdf6759167b90f52c9ad358a369f95284e841d7a2536cef31c0549580100000000fdffffff020000000000000000316a2f49206c696b65205363686e6f7272207369677320616e6420492063616e6e6f74206c69652e204062697462756734329e06010000000000225120a37c3903c8d0db6512e2b40b0dffa05e5a3ab73603ce8c9c4b7771e5412328f90140a60c383f71bac0ec919b1d7dbc3eb72dd56e7aa99583615564f9f99b8ae4e837b758773a5b2e4c51348854c8389f008e05029db7f464a5ff2e01d5e6e626174affd30a00")},
/*spent_outputs*/ spent_outputs,
/*amount*/ 88480,
/*input_index*/ 0,
/*is_taproot*/ true);
/*spent_script_pubkey=*/taproot_spent_script_pubkey,
/*spending_tx=*/taproot_spending_tx,
/*precomputed_txdata=*/&taproot_precomputed_txdata,
/*amount=*/88480,
/*input_index=*/0,
/*taproot=*/true);
// Two-input taproot transaction e8e8320f40c31ed511570e9cdf1d241f8ec9a5cc392e6105240ac8dbea2098de
auto taproot2_spent_script_pubkey0{ScriptPubkey{hex_string_to_byte_vec("5120b7da80f57e36930b0515eb09293e25858d13e6b91fee6184943f5a584cb4248e")}};
auto taproot2_spent_script_pubkey1{ScriptPubkey{hex_string_to_byte_vec("5120ab78e077d062e7b8acd7063668b4db5355a1b5d5fd2a46a8e98e62e5e63fab77")}};
auto taproot2_spending_tx{Transaction{hex_string_to_byte_vec("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")}};
std::vector<TransactionOutput> taproot2_spent_outputs;
taproot2_spent_outputs.emplace_back(taproot2_spent_script_pubkey0, 546);
taproot2_spent_outputs.emplace_back(taproot2_spent_script_pubkey1, 135125);
auto taproot2_precomputed_txdata{PrecomputedTransactionData{
/*tx_to=*/taproot2_spending_tx,
/*spent_outputs=*/taproot2_spent_outputs,
}};
run_verify_test(
/*spent_script_pubkey=*/taproot2_spent_script_pubkey0,
/*spending_tx=*/taproot2_spending_tx,
/*precomputed_txdata=*/&taproot2_precomputed_txdata,
/*amount=*/546,
/*input_index=*/0,
/*taproot=*/true);
run_verify_test(
/*spent_script_pubkey=*/taproot2_spent_script_pubkey1,
/*spending_tx=*/taproot2_spending_tx,
/*precomputed_txdata=*/&taproot2_precomputed_txdata,
/*amount=*/135125,
/*input_index=*/1,
/*taproot=*/true);
}
BOOST_AUTO_TEST_CASE(logging_tests)
@@ -954,8 +1031,9 @@ BOOST_AUTO_TEST_CASE(btck_chainman_regtest_tests)
}
BOOST_CHECK(inputs.size() == spent_outputs.size());
ScriptVerifyStatus status = ScriptVerifyStatus::OK;
const PrecomputedTransactionData precomputed_txdata{transaction, spent_outputs};
for (size_t i{0}; i < inputs.size(); ++i) {
BOOST_CHECK(spent_outputs[i].GetScriptPubkey().Verify(spent_outputs[i].Amount(), transaction, spent_outputs, i, ScriptVerificationFlags::ALL, status));
BOOST_CHECK(spent_outputs[i].GetScriptPubkey().Verify(spent_outputs[i].Amount(), transaction, &precomputed_txdata, i, ScriptVerificationFlags::ALL, status));
}
}
}