Add zcash_script V5 functions

Co-authored-by: Jack Grigg <jack@z.cash>

src/script/zcash_script.cpp

@@ -127,6 +127,39 @@ void* zcash_script_new_precomputed_tx(
     }
 }
 
+void* zcash_script_new_precomputed_tx_v5(
+    const unsigned char* txTo,
+    unsigned int txToLen,
+    const unsigned char* allPrevOutputs,
+    unsigned int allPrevOutputsLen,
+    zcash_script_error* err)
+{
+    try {
+        TxInputStream stream(SER_NETWORK, PROTOCOL_VERSION, txTo, txToLen);
+        CTransaction tx;
+        stream >> tx;
+        if (GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION) != txToLen) {
+            set_error(err, zcash_script_ERR_TX_SIZE_MISMATCH);
+            return nullptr;
+        }
+
+        try {
+            auto preTx = new PrecomputedTransaction(tx, allPrevOutputs, allPrevOutputsLen);
+            // Deserializing the tx did not error.
+            set_error(err, zcash_script_ERR_OK);
+            return preTx;
+        } catch (const std::exception&) {
+            // We had some error when parsing allPrevOutputs inside the
+            // PrecomputedTransactionData constructor.
+            set_error(err, zcash_script_ERR_ALL_PREV_OUTPUTS_DESERIALIZE);
+            return nullptr;
+        }
+    } catch (const std::exception&) {
+        set_error(err, zcash_script_ERR_TX_DESERIALIZE); // Error deserializing
+        return nullptr;
+    }
+}
+
 void zcash_script_free_precomputed_tx(void* pre_preTx)
 {
     PrecomputedTransaction* preTx = static_cast<PrecomputedTransaction*>(pre_preTx);
@@ -196,6 +229,53 @@ int zcash_script_verify(
     }
 }
 
+int zcash_script_verify_v5(
+    const unsigned char* txTo,
+    unsigned int txToLen,
+    const unsigned char* allPrevOutputs,
+    unsigned int allPrevOutputsLen,
+    unsigned int nIn,
+    unsigned int flags,
+    uint32_t consensusBranchId,
+    zcash_script_error* err)
+{
+    try {
+        TxInputStream stream(SER_NETWORK, PROTOCOL_VERSION, txTo, txToLen);
+        CTransaction tx;
+        stream >> tx;
+        if (nIn >= tx.vin.size())
+            return set_error(err, zcash_script_ERR_TX_INDEX);
+        if (GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION) != txToLen)
+            return set_error(err, zcash_script_ERR_TX_SIZE_MISMATCH);
+
+        // TODO: we can swap this second deserialization for an FFI call by
+        // fetching this through PrecomputedTransactionData. Simplicity for now.
+        CDataStream sAllPrevOutputs(
+            reinterpret_cast<const char*>(allPrevOutputs),
+            reinterpret_cast<const char*>(allPrevOutputs + allPrevOutputsLen),
+            SER_NETWORK,
+            PROTOCOL_VERSION);
+        std::vector<CTxOut> prevOutputs;
+        sAllPrevOutputs >> prevOutputs;
+        if (!(tx.IsCoinBase() ? prevOutputs.empty() : tx.vin.size() == prevOutputs.size())) {
+            return set_error(err, zcash_script_ERR_ALL_PREV_OUTPUTS_SIZE_MISMATCH);
+        }
+
+        // Regardless of the verification result, the tx did not error.
+        set_error(err, zcash_script_ERR_OK);
+        PrecomputedTransactionData txdata(tx, allPrevOutputs, allPrevOutputsLen);
+        return VerifyScript(
+            tx.vin[nIn].scriptSig,
+            prevOutputs[nIn].scriptPubKey,
+            flags,
+            TransactionSignatureChecker(&tx, txdata, nIn, prevOutputs[nIn].nValue),
+            consensusBranchId,
+            NULL);
+    } catch (const std::exception&) {
+        return set_error(err, zcash_script_ERR_TX_DESERIALIZE); // Error deserializing
+    }
+}
+
 unsigned int zcash_script_legacy_sigop_count_precomputed(
     const void* pre_preTx,
     zcash_script_error* err)

src/script/zcash_script.h

@@ -33,7 +33,7 @@
 extern "C" {
 #endif
 
-#define ZCASH_SCRIPT_API_VER 2
+#define ZCASH_SCRIPT_API_VER 3
 
 typedef enum zcash_script_error_t
 {
@@ -43,6 +43,8 @@ typedef enum zcash_script_error_t
     zcash_script_ERR_TX_DESERIALIZE,
     // Defined since API version 3.
     zcash_script_ERR_TX_VERSION,
+    zcash_script_ERR_ALL_PREV_OUTPUTS_SIZE_MISMATCH,
+    zcash_script_ERR_ALL_PREV_OUTPUTS_DESERIALIZE,
 } zcash_script_error;
 
 /** Script verification flags */
@@ -70,6 +72,27 @@ void* zcash_script_new_precomputed_tx(
     unsigned int txToLen,
     zcash_script_error* err);
 
+/// Deserializes the given transaction and precomputes values to improve
+/// script verification performance. Must be used for V5 transactions;
+/// may also be used for previous versions.
+///
+/// allPrevOutputs must point to the encoding of the vector of all outputs
+/// from previous transactions that are spent by the inputs of the given transaction.
+/// The outputs must be encoded as specified by Bitcoin. The full encoding will thus
+/// consist of a CompactSize prefix containing the number of outputs, followed by
+/// the concatenated outputs, each of them encoded as (value, CompactSize, pk_script).
+///
+/// Returns a pointer to the precomputed transaction. Free this with
+/// zcash_script_free_precomputed_tx once you are done.
+///
+/// If not NULL, err will contain an error/success code for the operation.
+void* zcash_script_new_precomputed_tx_v5(
+    const unsigned char* txTo,
+    unsigned int txToLen,
+    const unsigned char* allPrevOutputs,
+    unsigned int allPrevOutputsLen,
+    zcash_script_error* err);
+
 /// Frees a precomputed transaction previously created with
 /// zcash_script_new_precomputed_tx.
 void zcash_script_free_precomputed_tx(void* preTx);
@@ -108,6 +131,30 @@ EXPORT_SYMBOL int zcash_script_verify(
     uint32_t consensusBranchId,
     zcash_script_error* err);
 
+/// Returns 1 if the input nIn of the serialized transaction pointed to by
+/// txTo correctly spends the matching output in allPrevOutputs under
+/// the additional constraints specified by flags. Must be used for V5 transactions;
+/// may also be used for previous versions.
+///
+/// allPrevOutputs must point to the encoding of the vector of all outputs
+/// from previous transactions that are spent by the inputs of the given transaction.
+/// The outputs must be encoded as specified by Bitcoin. The full encoding will thus
+/// consist of a CompactSize prefix containing the number of outputs, followed by
+/// the concatenated outputs, each of them encoded as (value, CompactSize, pk_script).
+///
+/// If not NULL, err will contain an error/success code for the operation.
+/// Note that script verification failure is indicated by err being set to
+/// zcash_script_ERR_OK and a return value of 0.
+EXPORT_SYMBOL int zcash_script_verify_v5(
+    const unsigned char* txTo,
+    unsigned int txToLen,
+    const unsigned char* allPrevOutputs,
+    unsigned int allPrevOutputsLen,
+    unsigned int nIn,
+    unsigned int flags,
+    uint32_t consensusBranchId,
+    zcash_script_error* err);
+
 /// Returns the number of transparent signature operations in the
 /// transparent inputs and outputs of the precomputed transaction
 /// pointed to by preTx.