psbt: Actually use SIGHASH_DEFAULT

Make the behavior align with the help text by actually using
SIGHASH_DEFAULT as the default sighash for signing PSBTs.

src/core_read.cpp

@@ -248,7 +248,7 @@ std::vector<unsigned char> ParseHexUV(const UniValue& v, const std::string& strN
 
 int ParseSighashString(const UniValue& sighash)
 {
-    int hash_type = SIGHASH_ALL;
+    int hash_type = SIGHASH_DEFAULT;
     if (!sighash.isNull()) {
         static std::map<std::string, int> map_sighash_values = {
             {std::string("DEFAULT"), int(SIGHASH_DEFAULT)},

src/wallet/scriptpubkeyman.h

@@ -236,7 +236,7 @@ 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, const PrecomputedTransactionData& txdata, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const { return TransactionError::INVALID_PSBT; }
+    virtual TransactionError FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = SIGHASH_DEFAULT, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const { return TransactionError::INVALID_PSBT; }
 
     virtual uint256 GetID() const { return uint256(); }
 
@@ -400,7 +400,7 @@ public:
 
     bool SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, bilingual_str>& input_errors) const override;
     SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) 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, bool finalize = true) const override;
+    TransactionError FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = SIGHASH_DEFAULT, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
 
     uint256 GetID() const override;
 
@@ -609,7 +609,7 @@ public:
 
     bool SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, bilingual_str>& input_errors) const override;
     SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) 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, bool finalize = true) const override;
+    TransactionError FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = SIGHASH_DEFAULT, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
 
     uint256 GetID() const override;
 

src/wallet/wallet.h

@@ -561,7 +561,7 @@ public:
      */
     TransactionError FillPSBT(PartiallySignedTransaction& psbtx,
                   bool& complete,
-                  int sighash_type = 1 /* SIGHASH_ALL */,
+                  int sighash_type = SIGHASH_DEFAULT,
                   bool sign = true,
                   bool bip32derivs = true,
                   size_t* n_signed = nullptr,

test/functional/rpc_psbt.py

@@ -457,7 +457,7 @@ class PSBTTest(BitcoinTestFramework):
             wrpc = self.nodes[2].get_wallet_rpc("wallet{}".format(i))
             for key in signer['privkeys']:
                 wrpc.importprivkey(key)
-            signed_tx = wrpc.walletprocesspsbt(signer['psbt'])['psbt']
+            signed_tx = wrpc.walletprocesspsbt(signer['psbt'], True, "ALL")['psbt']
             assert_equal(signed_tx, signer['result'])
 
         # Combiner test