Construct and use PrecomputedTransactionData in PSBT signing

10 files changed, 50 insertions, 21 deletions

diff --git a/src/node/psbt.cpp b/src/node/psbt.cpp
index c189018268..b013b6d579 100644
--- a/src/node/psbt.cpp
+++ b/src/node/psbt.cpp
@@ -23,6 +23,8 @@ PSBTAnalysis AnalyzePSBT(PartiallySignedTransaction psbtx)
 
     result.inputs.resize(psbtx.tx->vin.size());
 
+    const PrecomputedTransactionData txdata = PrecomputePSBTData(psbtx);
+
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
         PSBTInput& input = psbtx.inputs[i];
         PSBTInputAnalysis& input_analysis = result.inputs[i];
@@ -61,7 +63,7 @@ PSBTAnalysis AnalyzePSBT(PartiallySignedTransaction psbtx)
 
             // Figure out what is missing
             SignatureData outdata;
-            bool complete = SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, 1, &outdata);
+            bool complete = SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, 1, &outdata);
 
             // Things are missing
             if (!complete) {
@@ -121,7 +123,7 @@ PSBTAnalysis AnalyzePSBT(PartiallySignedTransaction psbtx)
             PSBTInput& input = psbtx.inputs[i];
             Coin newcoin;
 
-            if (!SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, 1, nullptr, true) || !psbtx.GetInputUTXO(newcoin.out, i)) {
+            if (!SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, nullptr, 1) || !psbtx.GetInputUTXO(newcoin.out, i)) {
                 success = false;
                 break;
             } else {
diff --git a/src/psbt.cpp b/src/psbt.cpp
index a849b2ea53..9894749fab 100644
--- a/src/psbt.cpp
+++ b/src/psbt.cpp
@@ -227,7 +227,24 @@ void UpdatePSBTOutput(const SigningProvider& provider, PartiallySignedTransactio
     psbt_out.FromSignatureData(sigdata);
 }
 
-bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, int sighash, SignatureData* out_sigdata, bool use_dummy)
+PrecomputedTransactionData PrecomputePSBTData(const PartiallySignedTransaction& psbt)
+{
+    const CMutableTransaction& tx = *psbt.tx;
+    bool have_all_spent_outputs = true;
+    std::vector<CTxOut> utxos(tx.vin.size());
+    for (size_t idx = 0; idx < tx.vin.size(); ++idx) {
+        if (!psbt.GetInputUTXO(utxos[idx], idx)) have_all_spent_outputs = false;
+    }
+    PrecomputedTransactionData txdata;
+    if (have_all_spent_outputs) {
+        txdata.Init(tx, std::move(utxos), true);
+    } else {
+        txdata.Init(tx, {}, true);
+    }
+    return txdata;
+}
+
+bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, const PrecomputedTransactionData* txdata, int sighash, SignatureData* out_sigdata)
 {
     PSBTInput& input = psbt.inputs.at(index);
     const CMutableTransaction& tx = *psbt.tx;
@@ -267,10 +284,10 @@ bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction&
 
     sigdata.witness = false;
     bool sig_complete;
-    if (use_dummy) {
+    if (txdata == nullptr) {
         sig_complete = ProduceSignature(provider, DUMMY_SIGNATURE_CREATOR, utxo.scriptPubKey, sigdata);
     } else {
-        MutableTransactionSignatureCreator creator(&tx, index, utxo.nValue, sighash);
+        MutableTransactionSignatureCreator creator(&tx, index, utxo.nValue, txdata, sighash);
         sig_complete = ProduceSignature(provider, creator, utxo.scriptPubKey, sigdata);
     }
     // Verify that a witness signature was produced in case one was required.
@@ -302,8 +319,9 @@ bool FinalizePSBT(PartiallySignedTransaction& psbtx)
     //   PartiallySignedTransaction did not understand them), this will combine them into a final
     //   script.
     bool complete = true;
+    const PrecomputedTransactionData txdata = PrecomputePSBTData(psbtx);
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
-        complete &= SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, SIGHASH_ALL);
+        complete &= SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, SIGHASH_ALL);
     }
 
     return complete;
diff --git a/src/psbt.h b/src/psbt.h
index 96ae39fdb8..f6b82b43de 100644
--- a/src/psbt.h
+++ b/src/psbt.h
@@ -567,11 +567,18 @@ enum class PSBTRole {
 
 std::string PSBTRoleName(PSBTRole role);
 
+/** Compute a PrecomputedTransactionData object from a psbt. */
+PrecomputedTransactionData PrecomputePSBTData(const PartiallySignedTransaction& psbt);
+
 /** Checks whether a PSBTInput is already signed. */
 bool PSBTInputSigned(const PSBTInput& input);
 
-/** Signs a PSBTInput, verifying that all provided data matches what is being signed. */
-bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, int sighash = SIGHASH_ALL, SignatureData* out_sigdata = nullptr, bool use_dummy = false);
+/** Signs a PSBTInput, verifying that all provided data matches what is being signed.
+ *
+ * txdata should be the output of PrecomputePSBTData (which can be shared across
+ * multiple SignPSBTInput calls). If it is nullptr, a dummy signature will be created.
+ **/
+bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, const PrecomputedTransactionData* txdata, int sighash = SIGHASH_ALL, SignatureData* out_sigdata = nullptr);
 
 /** Counts the unsigned inputs of a PSBT. */
 size_t CountPSBTUnsignedInputs(const PartiallySignedTransaction& psbt);
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 414c6637a5..2fa033aee3 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -1655,6 +1655,7 @@ static RPCHelpMan utxoupdatepsbt()
     }
 
     // Fill the inputs
+    const PrecomputedTransactionData txdata = PrecomputePSBTData(psbtx);
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
         PSBTInput& input = psbtx.inputs.at(i);
 
@@ -1671,7 +1672,7 @@ static RPCHelpMan utxoupdatepsbt()
         // Update script/keypath information using descriptor data.
         // Note that SignPSBTInput does a lot more than just constructing ECDSA signatures
         // we don't actually care about those here, in fact.
-        SignPSBTInput(public_provider, psbtx, i, /* sighash_type */ 1);
+        SignPSBTInput(public_provider, psbtx, i, &txdata, /* sighash_type */ 1);
     }
 
     // Update script/keypath information using descriptor data.
diff --git a/src/wallet/external_signer_scriptpubkeyman.cpp b/src/wallet/external_signer_scriptpubkeyman.cpp
index fe2c810afa..03bb5d8b2c 100644
--- a/src/wallet/external_signer_scriptpubkeyman.cpp
+++ b/src/wallet/external_signer_scriptpubkeyman.cpp
@@ -62,10 +62,10 @@ bool ExternalSignerScriptPubKeyMan::DisplayAddress(const CScript scriptPubKey, c
 }
 
 // If sign is true, transaction must previously have been filled
-TransactionError ExternalSignerScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbt, int sighash_type, bool sign, bool bip32derivs, int* n_signed) const
+TransactionError ExternalSignerScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type, bool sign, bool bip32derivs, int* n_signed) const
 {
     if (!sign) {
-        return DescriptorScriptPubKeyMan::FillPSBT(psbt, sighash_type, false, bip32derivs, n_signed);
+        return DescriptorScriptPubKeyMan::FillPSBT(psbt, txdata, sighash_type, false, bip32derivs, n_signed);
     }
 
     // Already complete if every input is now signed
diff --git a/src/wallet/external_signer_scriptpubkeyman.h b/src/wallet/external_signer_scriptpubkeyman.h
index 1786958912..166b81d886 100644
--- a/src/wallet/external_signer_scriptpubkeyman.h
+++ b/src/wallet/external_signer_scriptpubkeyman.h
@@ -29,7 +29,7 @@ class ExternalSignerScriptPubKeyMan : public DescriptorScriptPubKeyMan
 
   bool DisplayAddress(const CScript scriptPubKey, const ExternalSigner &signer) const;
 
-  TransactionError FillPSBT(PartiallySignedTransaction& psbt, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr) const override;
+  TransactionError FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr) const override;
 };
 #endif
 
diff --git a/src/wallet/scriptpubkeyman.cpp b/src/wallet/scriptpubkeyman.cpp
index 2eb9ca5c6d..c8669f4b03 100644
--- a/src/wallet/scriptpubkeyman.cpp
+++ b/src/wallet/scriptpubkeyman.cpp
@@ -597,7 +597,7 @@ SigningResult LegacyScriptPubKeyMan::SignMessage(const std::string& message, con
     return SigningResult::SIGNING_FAILED;
 }
 
-TransactionError LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, int sighash_type, bool sign, bool bip32derivs, int* n_signed) const
+TransactionError LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, const PrecomputedTransactionData& txdata, int sighash_type, bool sign, bool bip32derivs, int* n_signed) const
 {
     if (n_signed) {
         *n_signed = 0;
@@ -626,7 +626,7 @@ TransactionError LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psb
         }
         SignatureData sigdata;
         input.FillSignatureData(sigdata);
-        SignPSBTInput(HidingSigningProvider(this, !sign, !bip32derivs), psbtx, i, sighash_type);
+        SignPSBTInput(HidingSigningProvider(this, !sign, !bip32derivs), psbtx, i, &txdata, sighash_type);
 
         bool signed_one = PSBTInputSigned(input);
         if (n_signed && (signed_one || !sign)) {
@@ -2083,7 +2083,7 @@ SigningResult DescriptorScriptPubKeyMan::SignMessage(const std::string& message,
     return SigningResult::OK;
 }
 
-TransactionError DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, int sighash_type, bool sign, bool bip32derivs, int* n_signed) const
+TransactionError DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, const PrecomputedTransactionData& txdata, int sighash_type, bool sign, bool bip32derivs, int* n_signed) const
 {
     if (n_signed) {
         *n_signed = 0;
@@ -2133,7 +2133,7 @@ TransactionError DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction&
             }
         }
 
-        SignPSBTInput(HidingSigningProvider(keys.get(), !sign, !bip32derivs), psbtx, i, sighash_type);
+        SignPSBTInput(HidingSigningProvider(keys.get(), !sign, !bip32derivs), psbtx, i, &txdata, sighash_type);
 
         bool signed_one = PSBTInputSigned(input);
         if (n_signed && (signed_one || !sign)) {
diff --git a/src/wallet/scriptpubkeyman.h b/src/wallet/scriptpubkeyman.h
index b8e34fbac3..3c4603608c 100644
--- a/src/wallet/scriptpubkeyman.h
+++ b/src/wallet/scriptpubkeyman.h
@@ -235,7 +235,7 @@ public:
     /** Sign a message with the given script */
     virtual SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const { return SigningResult::SIGNING_FAILED; };
     /** Adds script and derivation path information to a PSBT, and optionally signs it. */
-    virtual TransactionError FillPSBT(PartiallySignedTransaction& psbt, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr) const { return TransactionError::INVALID_PSBT; }
+    virtual TransactionError FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr) const { return TransactionError::INVALID_PSBT; }
 
     virtual uint256 GetID() const { return uint256(); }
 
@@ -394,7 +394,7 @@ public:
 
     bool SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, std::string>& input_errors) const override;
     SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const override;
-    TransactionError FillPSBT(PartiallySignedTransaction& psbt, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr) const override;
+    TransactionError FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr) const override;
 
     uint256 GetID() const override;
 
@@ -605,7 +605,7 @@ public:
 
     bool SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, std::string>& input_errors) const override;
     SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const override;
-    TransactionError FillPSBT(PartiallySignedTransaction& psbt, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr) const override;
+    TransactionError FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr) const override;
 
     uint256 GetID() const override;
 
diff --git a/src/wallet/test/psbt_wallet_tests.cpp b/src/wallet/test/psbt_wallet_tests.cpp
index ce7e661b67..1cefa386b7 100644
--- a/src/wallet/test/psbt_wallet_tests.cpp
+++ b/src/wallet/test/psbt_wallet_tests.cpp
@@ -71,7 +71,7 @@ BOOST_AUTO_TEST_CASE(psbt_updater_test)
 
     // Try to sign the mutated input
     SignatureData sigdata;
-    BOOST_CHECK(spk_man->FillPSBT(psbtx, SIGHASH_ALL, true, true) != TransactionError::OK);
+    BOOST_CHECK(spk_man->FillPSBT(psbtx, PrecomputePSBTData(psbtx), SIGHASH_ALL, true, true) != TransactionError::OK);
 }
 
 BOOST_AUTO_TEST_CASE(parse_hd_keypath)
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 4b6630de3c..ac96e8fcaf 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1830,6 +1830,7 @@ TransactionError CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bool& comp
     if (n_signed) {
         *n_signed = 0;
     }
+    const PrecomputedTransactionData txdata = PrecomputePSBTData(psbtx);
     LOCK(cs_wallet);
     // Get all of the previous transactions
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
@@ -1856,7 +1857,7 @@ TransactionError CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bool& comp
     // Fill in information from ScriptPubKeyMans
     for (ScriptPubKeyMan* spk_man : GetAllScriptPubKeyMans()) {
         int n_signed_this_spkm = 0;
-        TransactionError res = spk_man->FillPSBT(psbtx, sighash_type, sign, bip32derivs, &n_signed_this_spkm);
+        TransactionError res = spk_man->FillPSBT(psbtx, txdata, sighash_type, sign, bip32derivs, &n_signed_this_spkm);
         if (res != TransactionError::OK) {
             return res;
         }