psbt: Check sighash types in SignPSBTInput and take sighash as optional

src/node/psbt.cpp

@@ -64,7 +64,7 @@ PSBTAnalysis AnalyzePSBT(PartiallySignedTransaction psbtx)
 
             // Figure out what is missing
             SignatureData outdata;
-            bool complete = SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, 1, &outdata) == PSBTError::OK;
+            bool complete = SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, std::nullopt, &outdata) == PSBTError::OK;
 
             // Things are missing
             if (!complete) {
@@ -124,7 +124,7 @@ PSBTAnalysis AnalyzePSBT(PartiallySignedTransaction psbtx)
             PSBTInput& input = psbtx.inputs[i];
             Coin newcoin;
 
-            if (SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, nullptr, 1) != PSBTError::OK || !psbtx.GetInputUTXO(newcoin.out, i)) {
+            if (SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, nullptr, std::nullopt) != PSBTError::OK || !psbtx.GetInputUTXO(newcoin.out, i)) {
                 success = false;
                 break;
             } else {

src/psbt.cpp

@@ -375,7 +375,7 @@ PrecomputedTransactionData PrecomputePSBTData(const PartiallySignedTransaction&
     return txdata;
 }
 
-PSBTError SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, const PrecomputedTransactionData* txdata, int sighash,  SignatureData* out_sigdata, bool finalize)
+PSBTError SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, const PrecomputedTransactionData* txdata, std::optional<int> sighash,  SignatureData* out_sigdata, bool finalize)
 {
     PSBTInput& input = psbt.inputs.at(index);
     const CMutableTransaction& tx = *psbt.tx;
@@ -413,12 +413,25 @@ PSBTError SignPSBTInput(const SigningProvider& provider, PartiallySignedTransact
         return PSBTError::MISSING_INPUTS;
     }
 
+    // Get the sighash type
+    // If both the field and the paramter are provided, they must match
+    // If only the psbt field is provided, refuse to sign. For user safety, the desired sighash must
+    // be provided if the PSBT wants something other than DEFAULT
+    // If only the paramter is provider, use it and add it to the PSBT if it is other than SIGHASH_DEFAULT
+    // for all input types, and not SIGHASH_ALL for non-taproot input types.
+    // If neither are provided, use SIGHASH_DEFAULT
+    if (!sighash) sighash = utxo.scriptPubKey.IsPayToTaproot() ? SIGHASH_DEFAULT : SIGHASH_ALL;
+    if (input.sighash_type && input.sighash_type != sighash) {
+        return PSBTError::SIGHASH_MISMATCH;
+    }
+    Assert(sighash.has_value());
+
     sigdata.witness = false;
     bool sig_complete;
     if (txdata == nullptr) {
         sig_complete = ProduceSignature(provider, DUMMY_SIGNATURE_CREATOR, utxo.scriptPubKey, sigdata);
     } else {
-        MutableTransactionSignatureCreator creator(tx, index, utxo.nValue, txdata, 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.
@@ -489,7 +502,7 @@ bool FinalizePSBT(PartiallySignedTransaction& psbtx)
     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, &txdata, SIGHASH_ALL, nullptr, true) == PSBTError::OK);
+        complete &= (SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, std::nullopt, nullptr, true) == PSBTError::OK);
     }
 
     return complete;

src/psbt.h

@@ -1239,7 +1239,7 @@ bool PSBTInputSignedAndVerified(const PartiallySignedTransaction psbt, unsigned
  * 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.
  **/
-PSBTError SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, const PrecomputedTransactionData* txdata, int sighash = SIGHASH_ALL, SignatureData* out_sigdata = nullptr, bool finalize = true);
+PSBTError SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, const PrecomputedTransactionData* txdata, std::optional<int> sighash = std::nullopt, SignatureData* out_sigdata = nullptr, bool finalize = true);
 
 /**  Reduces the size of the PSBT by dropping unnecessary `non_witness_utxos` (i.e. complete previous transactions) from a psbt when all inputs are segwit v1. */
 void RemoveUnnecessaryTransactions(PartiallySignedTransaction& psbtx, const int& sighash_type);

src/rpc/rawtransaction.cpp

@@ -163,7 +163,7 @@ static std::vector<RPCArg> CreateTxDoc()
 
 // Update PSBT with information from the mempool, the UTXO set, the txindex, and the provided descriptors.
 // Optionally, sign the inputs that we can using information from the descriptors.
-PartiallySignedTransaction ProcessPSBT(const std::string& psbt_string, const std::any& context, const HidingSigningProvider& provider, int sighash_type, bool finalize)
+PartiallySignedTransaction ProcessPSBT(const std::string& psbt_string, const std::any& context, const HidingSigningProvider& provider, std::optional<int> sighash_type, bool finalize)
 {
     // Unserialize the transactions
     PartiallySignedTransaction psbtx;
@@ -1690,7 +1690,7 @@ static RPCHelpMan utxoupdatepsbt()
         request.params[0].get_str(),
         request.context,
         HidingSigningProvider(&provider, /*hide_secret=*/true, /*hide_origin=*/false),
-        /*sighash_type=*/SIGHASH_ALL,
+        /*sighash_type=*/std::nullopt,
         /*finalize=*/false);
 
     DataStream ssTx{};
@@ -1957,7 +1957,7 @@ RPCHelpMan descriptorprocesspsbt()
         EvalDescriptorStringOrObject(descs[i], provider, /*expand_priv=*/true);
     }
 
-    int sighash_type = ParseSighashString(request.params[2]);
+    std::optional<int> sighash_type = ParseSighashString(request.params[2]);
     bool bip32derivs = request.params[3].isNull() ? true : request.params[3].get_bool();
     bool finalize = request.params[4].isNull() ? true : request.params[4].get_bool();
 

src/rpc/rawtransaction_util.cpp

@@ -304,12 +304,15 @@ void ParsePrevouts(const UniValue& prevTxsUnival, FlatSigningProvider* keystore,
 
 void SignTransaction(CMutableTransaction& mtx, const SigningProvider* keystore, const std::map<COutPoint, Coin>& coins, const UniValue& hashType, UniValue& result)
 {
-    int nHashType = ParseSighashString(hashType);
+    std::optional<int> nHashType = ParseSighashString(hashType);
+    if (!nHashType) {
+        nHashType = SIGHASH_DEFAULT;
+    }
 
     // Script verification errors
     std::map<int, bilingual_str> input_errors;
 
-    bool complete = SignTransaction(mtx, keystore, coins, nHashType, input_errors);
+    bool complete = SignTransaction(mtx, keystore, coins, *nHashType, input_errors);
     SignTransactionResultToJSON(mtx, complete, coins, input_errors, result);
 }
 

src/rpc/util.cpp

@@ -376,10 +376,10 @@ UniValue DescribeAddress(const CTxDestination& dest)
  *
  * @pre The sighash argument should be string or null.
 */
-int ParseSighashString(const UniValue& sighash)
+std::optional<int> ParseSighashString(const UniValue& sighash)
 {
     if (sighash.isNull()) {
-        return SIGHASH_DEFAULT;
+        return std::nullopt;
     }
     const auto result{SighashFromStr(sighash.get_str())};
     if (!result) {

src/rpc/util.h

@@ -138,7 +138,7 @@ CTxDestination AddAndGetMultisigDestination(const int required, const std::vecto
 UniValue DescribeAddress(const CTxDestination& dest);
 
 /** Parse a sighash string representation and raise an RPC error if it is invalid. */
-int ParseSighashString(const UniValue& sighash);
+std::optional<int> ParseSighashString(const UniValue& sighash);
 
 //! Parse a confirm target option and raise an RPC error if it is invalid.
 unsigned int ParseConfirmTarget(const UniValue& value, unsigned int max_target);

src/wallet/rpc/spend.cpp

@@ -951,12 +951,15 @@ RPCHelpMan signrawtransactionwithwallet()
     // Parse the prevtxs array
     ParsePrevouts(request.params[1], nullptr, coins);
 
-    int nHashType = ParseSighashString(request.params[2]);
+    std::optional<int> nHashType = ParseSighashString(request.params[2]);
+    if (!nHashType) {
+        nHashType = SIGHASH_DEFAULT;
+    }
 
     // Script verification errors
     std::map<int, bilingual_str> input_errors;
 
-    bool complete = pwallet->SignTransaction(mtx, coins, nHashType, input_errors);
+    bool complete = pwallet->SignTransaction(mtx, coins, *nHashType, input_errors);
     UniValue result(UniValue::VOBJ);
     SignTransactionResultToJSON(mtx, complete, coins, input_errors, result);
     return result;
@@ -1621,7 +1624,7 @@ RPCHelpMan walletprocesspsbt()
     }
 
     // Get the sighash type
-    int nHashType = ParseSighashString(request.params[2]);
+    std::optional<int> nHashType = ParseSighashString(request.params[2]);
 
     // Fill transaction with our data and also sign
     bool sign = request.params[1].isNull() ? true : request.params[1].get_bool();

src/wallet/scriptpubkeyman.cpp

@@ -637,7 +637,6 @@ std::optional<PSBTError> LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransact
     if (n_signed) {
         *n_signed = 0;
     }
-    if (!sighash_type) sighash_type = SIGHASH_DEFAULT;
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
         const CTxIn& txin = psbtx.tx->vin[i];
         PSBTInput& input = psbtx.inputs.at(i);
@@ -660,7 +659,7 @@ std::optional<PSBTError> LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransact
             // There's no UTXO so we can just skip this now
             continue;
         }
-        PSBTError res = SignPSBTInput(HidingSigningProvider(this, !sign, !bip32derivs), psbtx, i, &txdata, *sighash_type, nullptr, finalize);
+        PSBTError res = SignPSBTInput(HidingSigningProvider(this, !sign, !bip32derivs), psbtx, i, &txdata, sighash_type, nullptr, finalize);
         if (res != PSBTError::OK && res != PSBTError::INCOMPLETE) {
             return res;
         }
@@ -2538,7 +2537,6 @@ std::optional<PSBTError> DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTran
     if (n_signed) {
         *n_signed = 0;
     }
-    if (!sighash_type) sighash_type = SIGHASH_DEFAULT;
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
         const CTxIn& txin = psbtx.tx->vin[i];
         PSBTInput& input = psbtx.inputs.at(i);
@@ -2609,7 +2607,7 @@ std::optional<PSBTError> DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTran
             }
         }
 
-        PSBTError res = SignPSBTInput(HidingSigningProvider(keys.get(), /*hide_secret=*/!sign, /*hide_origin=*/!bip32derivs), psbtx, i, &txdata, *sighash_type, nullptr, finalize);
+        PSBTError res = SignPSBTInput(HidingSigningProvider(keys.get(), /*hide_secret=*/!sign, /*hide_origin=*/!bip32derivs), psbtx, i, &txdata, sighash_type, nullptr, finalize);
         if (res != PSBTError::OK && res != PSBTError::INCOMPLETE) {
             return res;
         }

src/wallet/wallet.cpp

@@ -2196,7 +2196,6 @@ std::optional<PSBTError> CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bo
     if (n_signed) {
         *n_signed = 0;
     }
-    if (!sighash_type) sighash_type = SIGHASH_DEFAULT;
     LOCK(cs_wallet);
     // Get all of the previous transactions
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {