Merge bitcoin/bitcoin#28539: lib: add taproot support to libconsensus

ff8e2fc2e2416f6f3b84cdb40db8ac168596b579 fuzz: add coverage for `bitcoinconsensus_verify_script_with_spent_outputs` (brunoerg)
c5f2a757d736f14d27ac5256a9df887cd2f174f1 docs: add release notes for #28539 (brunoerg)
de54882348502d860cf1e504100aa8fb1e52aa88 docs: add docs for additional libconsensus functions (Jake Rawsthorne)
70106e0689546fee497814c63a6a4747e0937b36 docs: link to rust-bitcoinconsensus (Jake Rawsthorne)
fb0db07e414fec3318b3af683167ebef9c82fc84 lib: add Taproot support to libconsensus (Jake Rawsthorne)

Pull request description:

  Grabbed from #21158. Closes #21133.

ACKs for top commit:
  achow101:
    ACK ff8e2fc2e2416f6f3b84cdb40db8ac168596b579
  theStack:
    ACK ff8e2fc2e2416f6f3b84cdb40db8ac168596b579
  darosior:
    re-ACK ff8e2fc2e2416f6f3b84cdb40db8ac168596b579

Tree-SHA512: bf6f500c7e8c9ff6884137c2cd9b4522c586e52848dd639b774b94d998b0516b877498d24f3a6cc7425aedf81d18b0d30c1ccf19e2d527fdfdfa3955ca49b6e7

4 files changed, 141 insertions, 4 deletions

diff --git a/src/script/bitcoinconsensus.cpp b/src/script/bitcoinconsensus.cpp
index 4fab481b39..71005cfb6e 100644
--- a/src/script/bitcoinconsensus.cpp
+++ b/src/script/bitcoinconsensus.cpp
@@ -72,14 +72,34 @@ static bool verify_flags(unsigned int flags)
 
 static int verify_script(const unsigned char *scriptPubKey, unsigned int scriptPubKeyLen, CAmount amount,
                                     const unsigned char *txTo        , unsigned int txToLen,
+                                    const UTXO *spentOutputs, unsigned int spentOutputsLen,
                                     unsigned int nIn, unsigned int flags, bitcoinconsensus_error* err)
 {
     if (!verify_flags(flags)) {
         return set_error(err, bitcoinconsensus_ERR_INVALID_FLAGS);
     }
+
+    if (flags & bitcoinconsensus_SCRIPT_FLAGS_VERIFY_TAPROOT && spentOutputs == nullptr) {
+        return set_error(err, bitcoinconsensus_ERR_SPENT_OUTPUTS_REQUIRED);
+    }
+
     try {
         TxInputStream stream(PROTOCOL_VERSION, txTo, txToLen);
         CTransaction tx(deserialize, stream);
+
+        std::vector<CTxOut> spent_outputs;
+        if (spentOutputs != nullptr) {
+            if (spentOutputsLen != tx.vin.size()) {
+                return set_error(err, bitcoinconsensus_ERR_SPENT_OUTPUTS_MISMATCH);
+            }
+            for (size_t i = 0; i < spentOutputsLen; i++) {
+                CScript spk = CScript(spentOutputs[i].scriptPubKey, spentOutputs[i].scriptPubKey + spentOutputs[i].scriptPubKeySize);
+                const CAmount& value = spentOutputs[i].value;
+                CTxOut tx_out = CTxOut(value, spk);
+                spent_outputs.push_back(tx_out);
+            }
+        }
+
         if (nIn >= tx.vin.size())
             return set_error(err, bitcoinconsensus_ERR_TX_INDEX);
         if (GetSerializeSize(tx, PROTOCOL_VERSION) != txToLen)
@@ -89,18 +109,34 @@ static int verify_script(const unsigned char *scriptPubKey, unsigned int scriptP
         set_error(err, bitcoinconsensus_ERR_OK);
 
         PrecomputedTransactionData txdata(tx);
+
+        if (spentOutputs != nullptr && flags & bitcoinconsensus_SCRIPT_FLAGS_VERIFY_TAPROOT) {
+            txdata.Init(tx, std::move(spent_outputs));
+        }
+
         return VerifyScript(tx.vin[nIn].scriptSig, CScript(scriptPubKey, scriptPubKey + scriptPubKeyLen), &tx.vin[nIn].scriptWitness, flags, TransactionSignatureChecker(&tx, nIn, amount, txdata, MissingDataBehavior::FAIL), nullptr);
     } catch (const std::exception&) {
         return set_error(err, bitcoinconsensus_ERR_TX_DESERIALIZE); // Error deserializing
     }
 }
 
+int bitcoinconsensus_verify_script_with_spent_outputs(const unsigned char *scriptPubKey, unsigned int scriptPubKeyLen, int64_t amount,
+                                    const unsigned char *txTo        , unsigned int txToLen,
+                                    const UTXO *spentOutputs, unsigned int spentOutputsLen,
+                                    unsigned int nIn, unsigned int flags, bitcoinconsensus_error* err)
+{
+    CAmount am(amount);
+    return ::verify_script(scriptPubKey, scriptPubKeyLen, am, txTo, txToLen, spentOutputs, spentOutputsLen, nIn, flags, err);
+}
+
 int bitcoinconsensus_verify_script_with_amount(const unsigned char *scriptPubKey, unsigned int scriptPubKeyLen, int64_t amount,
                                     const unsigned char *txTo        , unsigned int txToLen,
                                     unsigned int nIn, unsigned int flags, bitcoinconsensus_error* err)
 {
     CAmount am(amount);
-    return ::verify_script(scriptPubKey, scriptPubKeyLen, am, txTo, txToLen, nIn, flags, err);
+    UTXO *spentOutputs = nullptr;
+    unsigned int spentOutputsLen = 0;
+    return ::verify_script(scriptPubKey, scriptPubKeyLen, am, txTo, txToLen, spentOutputs, spentOutputsLen, nIn, flags, err);
 }
 
 
@@ -113,7 +149,9 @@ int bitcoinconsensus_verify_script(const unsigned char *scriptPubKey, unsigned i
     }
 
     CAmount am(0);
-    return ::verify_script(scriptPubKey, scriptPubKeyLen, am, txTo, txToLen, nIn, flags, err);
+    UTXO *spentOutputs = nullptr;
+    unsigned int spentOutputsLen = 0;
+    return ::verify_script(scriptPubKey, scriptPubKeyLen, am, txTo, txToLen, spentOutputs, spentOutputsLen, nIn, flags, err);
 }
 
 unsigned int bitcoinconsensus_version()
diff --git a/src/script/bitcoinconsensus.h b/src/script/bitcoinconsensus.h
index f2f2ff8686..a202b5ba06 100644
--- a/src/script/bitcoinconsensus.h
+++ b/src/script/bitcoinconsensus.h
@@ -31,7 +31,7 @@
 extern "C" {
 #endif
 
-#define BITCOINCONSENSUS_API_VER 1
+#define BITCOINCONSENSUS_API_VER 2
 
 typedef enum bitcoinconsensus_error_t
 {
@@ -41,6 +41,8 @@ typedef enum bitcoinconsensus_error_t
     bitcoinconsensus_ERR_TX_DESERIALIZE,
     bitcoinconsensus_ERR_AMOUNT_REQUIRED,
     bitcoinconsensus_ERR_INVALID_FLAGS,
+    bitcoinconsensus_ERR_SPENT_OUTPUTS_REQUIRED,
+    bitcoinconsensus_ERR_SPENT_OUTPUTS_MISMATCH
 } bitcoinconsensus_error;
 
 /** Script verification flags */
@@ -53,11 +55,19 @@ enum
     bitcoinconsensus_SCRIPT_FLAGS_VERIFY_CHECKLOCKTIMEVERIFY = (1U << 9), // enable CHECKLOCKTIMEVERIFY (BIP65)
     bitcoinconsensus_SCRIPT_FLAGS_VERIFY_CHECKSEQUENCEVERIFY = (1U << 10), // enable CHECKSEQUENCEVERIFY (BIP112)
     bitcoinconsensus_SCRIPT_FLAGS_VERIFY_WITNESS             = (1U << 11), // enable WITNESS (BIP141)
+    bitcoinconsensus_SCRIPT_FLAGS_VERIFY_TAPROOT             = (1U << 17), // enable TAPROOT (BIPs 341 & 342)
     bitcoinconsensus_SCRIPT_FLAGS_VERIFY_ALL                 = bitcoinconsensus_SCRIPT_FLAGS_VERIFY_P2SH | bitcoinconsensus_SCRIPT_FLAGS_VERIFY_DERSIG |
                                                                bitcoinconsensus_SCRIPT_FLAGS_VERIFY_NULLDUMMY | bitcoinconsensus_SCRIPT_FLAGS_VERIFY_CHECKLOCKTIMEVERIFY |
-                                                               bitcoinconsensus_SCRIPT_FLAGS_VERIFY_CHECKSEQUENCEVERIFY | bitcoinconsensus_SCRIPT_FLAGS_VERIFY_WITNESS
+                                                               bitcoinconsensus_SCRIPT_FLAGS_VERIFY_CHECKSEQUENCEVERIFY | bitcoinconsensus_SCRIPT_FLAGS_VERIFY_WITNESS |
+                                                               bitcoinconsensus_SCRIPT_FLAGS_VERIFY_TAPROOT
 };
 
+typedef struct {
+    const unsigned char *scriptPubKey;
+    unsigned int scriptPubKeySize;
+    int64_t value;
+} UTXO;
+
 /// Returns 1 if the input nIn of the serialized transaction pointed to by
 /// txTo correctly spends the scriptPubKey pointed to by scriptPubKey under
 /// the additional constraints specified by flags.
@@ -70,6 +80,11 @@ EXPORT_SYMBOL int bitcoinconsensus_verify_script_with_amount(const unsigned char
                                     const unsigned char *txTo        , unsigned int txToLen,
                                     unsigned int nIn, unsigned int flags, bitcoinconsensus_error* err);
 
+EXPORT_SYMBOL int bitcoinconsensus_verify_script_with_spent_outputs(const unsigned char *scriptPubKey, unsigned int scriptPubKeyLen, int64_t amount,
+                                    const unsigned char *txTo        , unsigned int txToLen,
+                                    const UTXO *spentOutputs, unsigned int spentOutputsLen,
+                                    unsigned int nIn, unsigned int flags, bitcoinconsensus_error* err);
+
 EXPORT_SYMBOL unsigned int bitcoinconsensus_version();
 
 #ifdef __cplusplus
diff --git a/src/test/fuzz/script_bitcoin_consensus.cpp b/src/test/fuzz/script_bitcoin_consensus.cpp
index fcd66b234e..846389863d 100644
--- a/src/test/fuzz/script_bitcoin_consensus.cpp
+++ b/src/test/fuzz/script_bitcoin_consensus.cpp
@@ -28,4 +28,23 @@ FUZZ_TARGET(script_bitcoin_consensus)
     }
     (void)bitcoinconsensus_verify_script(random_bytes_1.data(), random_bytes_1.size(), random_bytes_2.data(), random_bytes_2.size(), n_in, flags, err_p);
     (void)bitcoinconsensus_verify_script_with_amount(random_bytes_1.data(), random_bytes_1.size(), money, random_bytes_2.data(), random_bytes_2.size(), n_in, flags, err_p);
+
+    std::vector<UTXO> spent_outputs;
+    std::vector<std::vector<unsigned char>> spent_spks;
+    if (n_in <= 24386) {
+        spent_outputs.reserve(n_in);
+        spent_spks.reserve(n_in);
+        for (size_t i = 0; i < n_in; ++i) {
+            spent_spks.push_back(ConsumeRandomLengthByteVector(fuzzed_data_provider));
+            const CAmount value{ConsumeMoney(fuzzed_data_provider)};
+            const auto spk_size{static_cast<unsigned>(spent_spks.back().size())};
+            spent_outputs.push_back({.scriptPubKey = spent_spks.back().data(), .scriptPubKeySize = spk_size, .value = value});
+        }
+    }
+
+    const auto spent_outs_size{static_cast<unsigned>(spent_outputs.size())};
+
+    (void)bitcoinconsensus_verify_script_with_spent_outputs(
+            random_bytes_1.data(), random_bytes_1.size(), money, random_bytes_2.data(), random_bytes_2.size(),
+            spent_outputs.data(), spent_outs_size, n_in, flags, err_p);
 }
diff --git a/src/test/script_tests.cpp b/src/test/script_tests.cpp
index 94656b229e..624d0b2c12 100644
--- a/src/test/script_tests.cpp
+++ b/src/test/script_tests.cpp
@@ -1637,6 +1637,37 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_invalid_flags)
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_INVALID_FLAGS);
 }
 
+/* Test bitcoinconsensus_verify_script returns spent outputs required err */
+BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_spent_outputs_required_err)
+{
+    unsigned int libconsensus_flags{bitcoinconsensus_SCRIPT_FLAGS_VERIFY_TAPROOT};
+    const int nIn{0};
+
+    CScript scriptPubKey;
+    CScript scriptSig;
+    CScriptWitness wit;
+
+    scriptPubKey << OP_EQUAL;
+    CTransaction creditTx{BuildCreditingTransaction(scriptPubKey, 1)};
+    CTransaction spendTx{BuildSpendingTransaction(scriptSig, wit, creditTx)};
+
+    CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
+    stream << spendTx;
+
+    bitcoinconsensus_error err;
+    int result{bitcoinconsensus_verify_script_with_spent_outputs(scriptPubKey.data(), scriptPubKey.size(), creditTx.vout[0].nValue, UCharCast(stream.data()), stream.size(), nullptr, 0, nIn, libconsensus_flags, &err)};
+    BOOST_CHECK_EQUAL(result, 0);
+    BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_SPENT_OUTPUTS_REQUIRED);
+
+    result = bitcoinconsensus_verify_script_with_amount(scriptPubKey.data(), scriptPubKey.size(), creditTx.vout[0].nValue, UCharCast(stream.data()), stream.size(), nIn, libconsensus_flags, &err);
+    BOOST_CHECK_EQUAL(result, 0);
+    BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_SPENT_OUTPUTS_REQUIRED);
+
+    result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), UCharCast(stream.data()), stream.size(), nIn, libconsensus_flags, &err);
+    BOOST_CHECK_EQUAL(result, 0);
+    BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_SPENT_OUTPUTS_REQUIRED);
+}
+
 #endif // defined(HAVE_CONSENSUS_LIB)
 
 static std::vector<unsigned int> AllConsensusFlags()
@@ -1685,12 +1716,29 @@ static void AssetTest(const UniValue& test)
         PrecomputedTransactionData txdata;
         txdata.Init(tx, std::vector<CTxOut>(prevouts));
         CachingTransactionSignatureChecker txcheck(&tx, idx, prevouts[idx].nValue, true, txdata);
+
+#if defined(HAVE_CONSENSUS_LIB)
+        CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
+        stream << tx;
+        std::vector<UTXO> utxos;
+        utxos.resize(prevouts.size());
+        for (size_t i = 0; i < prevouts.size(); i++) {
+            utxos[i].scriptPubKey = prevouts[i].scriptPubKey.data();
+            utxos[i].scriptPubKeySize = prevouts[i].scriptPubKey.size();
+            utxos[i].value = prevouts[i].nValue;
+        }
+#endif
+
         for (const auto flags : ALL_CONSENSUS_FLAGS) {
             // "final": true tests are valid for all flags. Others are only valid with flags that are
             // a subset of test_flags.
             if (fin || ((flags & test_flags) == flags)) {
                 bool ret = VerifyScript(tx.vin[idx].scriptSig, prevouts[idx].scriptPubKey, &tx.vin[idx].scriptWitness, flags, txcheck, nullptr);
                 BOOST_CHECK(ret);
+#if defined(HAVE_CONSENSUS_LIB)
+                int lib_ret = bitcoinconsensus_verify_script_with_spent_outputs(prevouts[idx].scriptPubKey.data(), prevouts[idx].scriptPubKey.size(), prevouts[idx].nValue, UCharCast(stream.data()), stream.size(), utxos.data(), utxos.size(), idx, flags, nullptr);
+                BOOST_CHECK(lib_ret == 1);
+#endif
             }
         }
     }
@@ -1702,11 +1750,28 @@ static void AssetTest(const UniValue& test)
         PrecomputedTransactionData txdata;
         txdata.Init(tx, std::vector<CTxOut>(prevouts));
         CachingTransactionSignatureChecker txcheck(&tx, idx, prevouts[idx].nValue, true, txdata);
+
+#if defined(HAVE_CONSENSUS_LIB)
+        CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
+        stream << tx;
+        std::vector<UTXO> utxos;
+        utxos.resize(prevouts.size());
+        for (size_t i = 0; i < prevouts.size(); i++) {
+            utxos[i].scriptPubKey = prevouts[i].scriptPubKey.data();
+            utxos[i].scriptPubKeySize = prevouts[i].scriptPubKey.size();
+            utxos[i].value = prevouts[i].nValue;
+        }
+#endif
+
         for (const auto flags : ALL_CONSENSUS_FLAGS) {
             // If a test is supposed to fail with test_flags, it should also fail with any superset thereof.
             if ((flags & test_flags) == test_flags) {
                 bool ret = VerifyScript(tx.vin[idx].scriptSig, prevouts[idx].scriptPubKey, &tx.vin[idx].scriptWitness, flags, txcheck, nullptr);
                 BOOST_CHECK(!ret);
+#if defined(HAVE_CONSENSUS_LIB)
+                int lib_ret = bitcoinconsensus_verify_script_with_spent_outputs(prevouts[idx].scriptPubKey.data(), prevouts[idx].scriptPubKey.size(), prevouts[idx].nValue, UCharCast(stream.data()), stream.size(), utxos.data(), utxos.size(), idx, flags, nullptr);
+                BOOST_CHECK(lib_ret == 0);
+#endif
             }
         }
     }