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

2 files changed, 57 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