From 522934703a7c23e39c064a04fd09586dbb146f12 Mon Sep 17 00:00:00 2001
From: Kittywhiskers Van Gogh <63189531+kittywhiskers@users.noreply.github.com>
Date: Tue, 29 Jan 2019 21:32:38 -0800
Subject: [PATCH] merge #14978: Factor out PSBT utilities from RPCs for use in
 GUI code; related refactoring

---
 src/Makefile.am                       |   4 +
 src/core_io.h                         |   6 +-
 src/core_read.cpp                     |  17 +-
 src/node/transaction.cpp              |  60 ++-
 src/node/transaction.h                |  33 +-
 src/psbt.cpp                          | 240 ++++++++++++
 src/psbt.h                            | 506 ++++++++++++++++++++++++++
 src/rpc/rawtransaction.cpp            |  56 +--
 src/rpc/util.cpp                      |  29 ++
 src/rpc/util.h                        |   5 +
 src/script/sign.cpp                   | 177 ---------
 src/script/sign.h                     | 480 ------------------------
 src/wallet/psbtwallet.cpp             |  50 +++
 src/wallet/psbtwallet.h               |  36 ++
 src/wallet/rpcwallet.cpp              |  59 +--
 src/wallet/rpcwallet.h                |   1 -
 src/wallet/test/psbt_wallet_tests.cpp |   5 +-
 test/functional/rpc_psbt.py           |   3 +
 18 files changed, 1016 insertions(+), 751 deletions(-)
 create mode 100644 src/psbt.cpp
 create mode 100644 src/psbt.h
 create mode 100644 src/wallet/psbtwallet.cpp
 create mode 100644 src/wallet/psbtwallet.h

diff --git a/src/Makefile.am b/src/Makefile.am
index c356a985d3e91..b97e05c15a463 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -227,6 +227,7 @@ BITCOIN_CORE_H = \
   policy/policy.h \
   pow.h \
   protocol.h \
+  psbt.h \
   random.h \
   reverse_iterator.h \
   reverselock.h \
@@ -291,6 +292,7 @@ BITCOIN_CORE_H = \
   wallet/crypter.h \
   wallet/db.h \
   wallet/fees.h \
+  wallet/psbtwallet.h \
   wallet/rpcwallet.h \
   wallet/wallet.h \
   wallet/walletdb.h \
@@ -431,6 +433,7 @@ libdash_wallet_a_SOURCES = \
   wallet/db.cpp \
   wallet/fees.cpp \
   wallet/init.cpp \
+  wallet/psbtwallet.cpp \
   wallet/rpcdump.cpp \
   wallet/rpcwallet.cpp \
   wallet/wallet.cpp \
@@ -577,6 +580,7 @@ libdash_common_a_SOURCES = \
   netbase.cpp \
   net_permissions.cpp \
   policy/feerate.cpp \
+  psbt.cpp \
   protocol.cpp \
   saltedhasher.cpp \
   scheduler.cpp \
diff --git a/src/core_io.h b/src/core_io.h
index 863b0b98c4f11..82a4cfe4fda14 100644
--- a/src/core_io.h
+++ b/src/core_io.h
@@ -28,9 +28,13 @@ std::string ScriptToAsmStr(const CScript& script, const bool fAttemptSighashDeco
 [[nodiscard]] bool DecodeHexBlk(CBlock&, const std::string& strHexBlk);
 uint256 ParseHashStr(const std::string&, const std::string& strName);
 std::vector<unsigned char> ParseHexUV(const UniValue& v, const std::string& strName);
-bool DecodePSBT(PartiallySignedTransaction& psbt, const std::string& base64_tx, std::string& error);
 int ParseSighashString(const UniValue& sighash);
 
+//! Decode a base64ed PSBT into a PartiallySignedTransaction
+[[nodiscard]] bool DecodeBase64PSBT(PartiallySignedTransaction& decoded_psbt, const std::string& base64_psbt, std::string& error);
+//! Decode a raw (binary blob) PSBT into a PartiallySignedTransaction
+[[nodiscard]] bool DecodeRawPSBT(PartiallySignedTransaction& decoded_psbt, const std::string& raw_psbt, std::string& error);
+
 // core_write.cpp
 UniValue ValueFromAmount(const CAmount& amount);
 std::string FormatScript(const CScript& script);
diff --git a/src/core_read.cpp b/src/core_read.cpp
index a98e9e046a3df..68d28d8654019 100644
--- a/src/core_read.cpp
+++ b/src/core_read.cpp
@@ -4,6 +4,7 @@
 
 #include <core_io.h>
 
+#include <psbt.h>
 #include <primitives/block.h>
 #include <primitives/transaction.h>
 #include <script/script.h>
@@ -125,10 +126,20 @@ bool DecodeHexBlk(CBlock& block, const std::string& strHexBlk)
     return true;
 }
 
-bool DecodePSBT(PartiallySignedTransaction& psbt, const std::string& base64_tx, std::string& error)
+bool DecodeBase64PSBT(PartiallySignedTransaction& psbt, const std::string& base64_tx, std::string& error)
 {
-    std::vector<unsigned char> tx_data = DecodeBase64(base64_tx.c_str());
-    CDataStream ss_data(tx_data, SER_NETWORK, PROTOCOL_VERSION);
+    bool invalid;
+    std::string tx_data = DecodeBase64(base64_tx, &invalid);
+    if (invalid) {
+        error = "invalid base64";
+        return false;
+    }
+    return DecodeRawPSBT(psbt, tx_data, error);
+}
+
+bool DecodeRawPSBT(PartiallySignedTransaction& psbt, const std::string& tx_data, std::string& error)
+{
+    CDataStream ss_data(tx_data.data(), tx_data.data() + tx_data.size(), SER_NETWORK, PROTOCOL_VERSION);
     try {
         ss_data >> psbt;
         if (!ss_data.empty()) {
diff --git a/src/node/transaction.cpp b/src/node/transaction.cpp
index 3e6ae02e19c37..6f6d3ac4b119e 100644
--- a/src/node/transaction.cpp
+++ b/src/node/transaction.cpp
@@ -5,7 +5,6 @@
 
 #include <consensus/validation.h>
 #include <net.h>
-#include <rpc/server.h>
 #include <txmempool.h>
 #include <validation.h>
 #include <validationinterface.h>
@@ -14,9 +13,38 @@
 
 #include <future>
 
-uint256 BroadcastTransaction(const CTransactionRef tx, const bool allowhighfees) {
+const char* TransactionErrorString(const TransactionError err)
+{
+    switch (err) {
+        case TransactionError::OK:
+            return "No error";
+        case TransactionError::MISSING_INPUTS:
+            return "Missing inputs";
+        case TransactionError::ALREADY_IN_CHAIN:
+            return "Transaction already in block chain";
+        case TransactionError::P2P_DISABLED:
+            return "Peer-to-peer functionality missing or disabled";
+        case TransactionError::MEMPOOL_REJECTED:
+            return "Transaction rejected by AcceptToMemoryPool";
+        case TransactionError::MEMPOOL_ERROR:
+            return "AcceptToMemoryPool failed";
+        case TransactionError::INVALID_PSBT:
+            return "PSBT is not sane";
+        case TransactionError::PSBT_MISMATCH:
+            return "PSBTs not compatible (different transactions)";
+        case TransactionError::SIGHASH_MISMATCH:
+            return "Specified sighash value does not match existing value";
+
+        case TransactionError::UNKNOWN_ERROR:
+        default: break;
+    }
+    return "Unknown error";
+}
+
+bool BroadcastTransaction(const CTransactionRef tx, uint256& hashTx, TransactionError& error, std::string& err_string, const bool allowhighfees, const bool bypass_limits)
+{
     std::promise<void> promise;
-    const uint256& hashTx = tx->GetHash();
+    hashTx = tx->GetHash();
 
     CAmount nMaxRawTxFee = maxTxFee;
     if (allowhighfees)
@@ -36,14 +64,19 @@ uint256 BroadcastTransaction(const CTransactionRef tx, const bool allowhighfees)
         CValidationState state;
         bool fMissingInputs;
         if (!AcceptToMemoryPool(mempool, state, std::move(tx), &fMissingInputs,
-                                false /* plTxnReplaced */, false /* bypass_limits */, nMaxRawTxFee)) {
+                                bypass_limits, nMaxRawTxFee)) {
             if (state.IsInvalid()) {
-                throw JSONRPCError(RPC_TRANSACTION_REJECTED, FormatStateMessage(state));
+                err_string = FormatStateMessage(state);
+                error = TransactionError::MEMPOOL_REJECTED;
+                return false;
             } else {
                 if (fMissingInputs) {
-                    throw JSONRPCError(RPC_TRANSACTION_ERROR, "Missing inputs");
+                    error = TransactionError::MISSING_INPUTS;
+                    return false;
                 }
-                throw JSONRPCError(RPC_TRANSACTION_ERROR, FormatStateMessage(state));
+                err_string = FormatStateMessage(state);
+                error = TransactionError::MEMPOOL_ERROR;
+                return false;
             }
         } else {
             // If wallet is enabled, ensure that the wallet has been made aware
@@ -56,7 +89,8 @@ uint256 BroadcastTransaction(const CTransactionRef tx, const bool allowhighfees)
             });
         }
     } else if (fHaveChain) {
-        throw JSONRPCError(RPC_TRANSACTION_ALREADY_IN_CHAIN, "transaction already in block chain");
+        error = TransactionError::ALREADY_IN_CHAIN;
+        return false;
     } else {
         // Make sure we don't block forever if re-sending
         // a transaction already in mempool.
@@ -67,10 +101,12 @@ uint256 BroadcastTransaction(const CTransactionRef tx, const bool allowhighfees)
 
     promise.get_future().wait();
 
-    if(!g_connman)
-        throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
+    if(!g_connman) {
+        error = TransactionError::P2P_DISABLED;
+        return false;
+    }
 
     g_connman->RelayTransaction(*tx);
 
-    return hashTx;
-}
+    return true;
+    }
diff --git a/src/node/transaction.h b/src/node/transaction.h
index 1916c6db267e8..3534c709a4cf5 100644
--- a/src/node/transaction.h
+++ b/src/node/transaction.h
@@ -8,7 +8,36 @@
 #include <primitives/transaction.h>
 #include <uint256.h>
 
-/** Broadcast a transaction */
-uint256 BroadcastTransaction(CTransactionRef tx, bool allowhighfees = false);
+enum class TransactionError {
+    OK = 0,
+    UNKNOWN_ERROR,
+
+    MISSING_INPUTS,
+    ALREADY_IN_CHAIN,
+    P2P_DISABLED,
+    MEMPOOL_REJECTED,
+    MEMPOOL_ERROR,
+    INVALID_PSBT,
+    PSBT_MISMATCH,
+    SIGHASH_MISMATCH,
+
+    ERROR_COUNT
+};
+
+#define TRANSACTION_ERR_LAST TransactionError::ERROR_COUNT
+
+const char* TransactionErrorString(const TransactionError error);
+
+/**
+ * Broadcast a transaction
+ *
+ * @param[in]  tx the transaction to broadcast
+ * @param[out] &txid the txid of the transaction, if successfully broadcast
+ * @param[out] &error reference to UniValue to fill with error info on failure
+ * @param[out] &err_string reference to std::string to fill with error string if available
+ * @param[in]  allowhighfees whether to allow fees exceeding maxTxFee
+ * return true on success, false on error (and fills in `error`)
+ */
+bool BroadcastTransaction(const CTransactionRef tx, uint256& txid, TransactionError& error, std::string& err_string, const bool allowhighfees = false, const bool bypass_limits = false);
 
 #endif // BITCOIN_NODE_TRANSACTION_H
diff --git a/src/psbt.cpp b/src/psbt.cpp
new file mode 100644
index 0000000000000..9e5906305e4ca
--- /dev/null
+++ b/src/psbt.cpp
@@ -0,0 +1,240 @@
+// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <psbt.h>
+#include <util/strencodings.h>
+
+bool PartiallySignedTransaction::IsNull() const
+{
+    return !tx && inputs.empty() && outputs.empty() && unknown.empty();
+}
+
+bool PartiallySignedTransaction::Merge(const PartiallySignedTransaction& psbt)
+{
+    // Prohibited to merge two PSBTs over different transactions
+    if (tx->GetHash() != psbt.tx->GetHash()) {
+        return false;
+    }
+
+    for (unsigned int i = 0; i < inputs.size(); ++i) {
+        inputs[i].Merge(psbt.inputs[i]);
+    }
+    for (unsigned int i = 0; i < outputs.size(); ++i) {
+        outputs[i].Merge(psbt.outputs[i]);
+    }
+    unknown.insert(psbt.unknown.begin(), psbt.unknown.end());
+
+    return true;
+}
+
+bool PartiallySignedTransaction::IsSane() const
+{
+    for (PSBTInput input : inputs) {
+        if (!input.IsSane()) return false;
+    }
+    return true;
+}
+
+bool PartiallySignedTransaction::AddInput(const CTxIn& txin, PSBTInput& psbtin)
+{
+    if (std::find(tx->vin.begin(), tx->vin.end(), txin) != tx->vin.end()) {
+        return false;
+    }
+    tx->vin.push_back(txin);
+    psbtin.partial_sigs.clear();
+    psbtin.final_script_sig.clear();
+    inputs.push_back(psbtin);
+    return true;
+}
+
+bool PartiallySignedTransaction::AddOutput(const CTxOut& txout, const PSBTOutput& psbtout)
+{
+    tx->vout.push_back(txout);
+    outputs.push_back(psbtout);
+    return true;
+}
+
+bool PartiallySignedTransaction::GetInputUTXO(CTxOut& utxo, int input_index) const
+{
+    PSBTInput input = inputs[input_index];
+    int prevout_index = tx->vin[input_index].prevout.n;
+    if (input.non_witness_utxo) {
+        utxo = input.non_witness_utxo->vout[prevout_index];
+    } else {
+        return false;
+    }
+    return true;
+}
+
+bool PSBTInput::IsNull() const
+{
+    return !non_witness_utxo && partial_sigs.empty() && unknown.empty() && hd_keypaths.empty() && redeem_script.empty();
+}
+
+void PSBTInput::FillSignatureData(SignatureData& sigdata) const
+{
+    if (!final_script_sig.empty()) {
+        sigdata.scriptSig = final_script_sig;
+        sigdata.complete = true;
+    }
+    if (sigdata.complete) {
+        return;
+    }
+
+    sigdata.signatures.insert(partial_sigs.begin(), partial_sigs.end());
+    if (!redeem_script.empty()) {
+        sigdata.redeem_script = redeem_script;
+    }
+    for (const auto& key_pair : hd_keypaths) {
+        sigdata.misc_pubkeys.emplace(key_pair.first.GetID(), key_pair);
+    }
+}
+
+void PSBTInput::FromSignatureData(const SignatureData& sigdata)
+{
+    if (sigdata.complete) {
+        partial_sigs.clear();
+        hd_keypaths.clear();
+        redeem_script.clear();
+
+        if (!sigdata.scriptSig.empty()) {
+            final_script_sig = sigdata.scriptSig;
+        }
+        return;
+    }
+
+    partial_sigs.insert(sigdata.signatures.begin(), sigdata.signatures.end());
+    if (redeem_script.empty() && !sigdata.redeem_script.empty()) {
+        redeem_script = sigdata.redeem_script;
+    }
+    for (const auto& entry : sigdata.misc_pubkeys) {
+        hd_keypaths.emplace(entry.second);
+    }
+}
+
+void PSBTInput::Merge(const PSBTInput& input)
+{
+    if (!non_witness_utxo && input.non_witness_utxo) non_witness_utxo = input.non_witness_utxo;
+
+    partial_sigs.insert(input.partial_sigs.begin(), input.partial_sigs.end());
+    hd_keypaths.insert(input.hd_keypaths.begin(), input.hd_keypaths.end());
+    unknown.insert(input.unknown.begin(), input.unknown.end());
+
+    if (redeem_script.empty() && !input.redeem_script.empty()) redeem_script = input.redeem_script;
+    if (final_script_sig.empty() && !input.final_script_sig.empty()) final_script_sig = input.final_script_sig;
+}
+
+bool PSBTInput::IsSane() const
+{
+    return true;
+}
+
+void PSBTOutput::FillSignatureData(SignatureData& sigdata) const
+{
+    if (!redeem_script.empty()) {
+        sigdata.redeem_script = redeem_script;
+    }
+    for (const auto& key_pair : hd_keypaths) {
+        sigdata.misc_pubkeys.emplace(key_pair.first.GetID(), key_pair);
+    }
+}
+
+void PSBTOutput::FromSignatureData(const SignatureData& sigdata)
+{
+    if (redeem_script.empty() && !sigdata.redeem_script.empty()) {
+        redeem_script = sigdata.redeem_script;
+    }
+    for (const auto& entry : sigdata.misc_pubkeys) {
+        hd_keypaths.emplace(entry.second);
+    }
+}
+
+bool PSBTOutput::IsNull() const
+{
+    return redeem_script.empty() && hd_keypaths.empty() && unknown.empty();
+}
+
+void PSBTOutput::Merge(const PSBTOutput& output)
+{
+    hd_keypaths.insert(output.hd_keypaths.begin(), output.hd_keypaths.end());
+    unknown.insert(output.unknown.begin(), output.unknown.end());
+
+    if (redeem_script.empty() && !output.redeem_script.empty()) redeem_script = output.redeem_script;
+}
+
+bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& tx, PSBTInput& input, int index, int sighash)
+{
+    // if this input has a final scriptsig, don't do anything with it
+    if (!input.final_script_sig.empty()) {
+        return true;
+    }
+
+    // Fill SignatureData with input info
+    SignatureData sigdata;
+    input.FillSignatureData(sigdata);
+
+    // Get UTXO
+    CTxOut utxo;
+    if (input.non_witness_utxo) {
+        // If we're taking our information from a non-witness UTXO, verify that it matches the prevout.
+        if (input.non_witness_utxo->GetHash() != tx.vin[index].prevout.hash) return false;
+        utxo = input.non_witness_utxo->vout[tx.vin[index].prevout.n];
+    } else {
+        return false;
+    }
+
+    MutableTransactionSignatureCreator creator(&tx, index, utxo.nValue, sighash);
+    bool sig_complete = ProduceSignature(provider, creator, utxo.scriptPubKey, sigdata);
+    input.FromSignatureData(sigdata);
+    return sig_complete;
+}
+
+bool FinalizePSBT(PartiallySignedTransaction& psbtx)
+{
+    // Finalize input signatures -- in case we have partial signatures that add up to a complete
+    //   signature, but have not combined them yet (e.g. because the combiner that created this
+    //   PartiallySignedTransaction did not understand them), this will combine them into a final
+    //   script.
+    bool complete = true;
+    for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
+        PSBTInput& input = psbtx.inputs.at(i);
+        complete &= SignPSBTInput(DUMMY_SIGNING_PROVIDER, *psbtx.tx, input, i, 1);
+    }
+
+    return complete;
+}
+
+bool FinalizeAndExtractPSBT(PartiallySignedTransaction& psbtx, CMutableTransaction& result)
+{
+    // It's not safe to extract a PSBT that isn't finalized, and there's no easy way to check
+    //   whether a PSBT is finalized without finalizing it, so we just do this.
+    if (!FinalizePSBT(psbtx)) {
+        return false;
+    }
+
+    result = *psbtx.tx;
+    for (unsigned int i = 0; i < result.vin.size(); ++i) {
+        result.vin[i].scriptSig = psbtx.inputs[i].final_script_sig;
+    }
+    return true;
+}
+
+bool CombinePSBTs(PartiallySignedTransaction& out, TransactionError& error, const std::vector<PartiallySignedTransaction>& psbtxs)
+{
+    out = psbtxs[0]; // Copy the first one
+
+    // Merge
+    for (auto it = std::next(psbtxs.begin()); it != psbtxs.end(); ++it) {
+        if (!out.Merge(*it)) {
+            error = TransactionError::PSBT_MISMATCH;
+            return false;
+        }
+    }
+    if (!out.IsSane()) {
+        error = TransactionError::INVALID_PSBT;
+        return false;
+    }
+
+    return true;
+}
diff --git a/src/psbt.h b/src/psbt.h
new file mode 100644
index 0000000000000..2d05cb132eafa
--- /dev/null
+++ b/src/psbt.h
@@ -0,0 +1,506 @@
+// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_PSBT_H
+#define BITCOIN_PSBT_H
+
+#include <attributes.h>
+#include <node/transaction.h>
+#include <primitives/transaction.h>
+#include <pubkey.h>
+#include <script/sign.h>
+
+// Magic bytes
+static constexpr uint8_t PSBT_MAGIC_BYTES[5] = {'p', 's', 'b', 't', 0xff};
+
+// Global types
+static constexpr uint8_t PSBT_GLOBAL_UNSIGNED_TX = 0x00;
+
+// Input types
+static constexpr uint8_t PSBT_IN_NON_WITNESS_UTXO = 0x00;
+static constexpr uint8_t PSBT_IN_PARTIAL_SIG = 0x02;
+static constexpr uint8_t PSBT_IN_SIGHASH = 0x03;
+static constexpr uint8_t PSBT_IN_REDEEMSCRIPT = 0x04;
+static constexpr uint8_t PSBT_IN_BIP32_DERIVATION = 0x06;
+static constexpr uint8_t PSBT_IN_SCRIPTSIG = 0x07;
+
+// Output types
+static constexpr uint8_t PSBT_OUT_REDEEMSCRIPT = 0x00;
+static constexpr uint8_t PSBT_OUT_BIP32_DERIVATION = 0x02;
+
+// The separator is 0x00. Reading this in means that the unserializer can interpret it
+// as a 0 length key which indicates that this is the separator. The separator has no value.
+static constexpr uint8_t PSBT_SEPARATOR = 0x00;
+
+/** A structure for PSBTs which contain per-input information */
+struct PSBTInput
+{
+    CTransactionRef non_witness_utxo;
+    CScript redeem_script;
+    CScript final_script_sig;
+    std::map<CPubKey, KeyOriginInfo> hd_keypaths;
+    std::map<CKeyID, SigPair> partial_sigs;
+    std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
+    int sighash_type = 0;
+
+    bool IsNull() const;
+    void FillSignatureData(SignatureData& sigdata) const;
+    void FromSignatureData(const SignatureData& sigdata);
+    void Merge(const PSBTInput& input);
+    bool IsSane() const;
+    PSBTInput() {}
+
+    template <typename Stream>
+    inline void Serialize(Stream& s) const {
+        // Write the utxo
+        if (non_witness_utxo) {
+            SerializeToVector(s, PSBT_IN_NON_WITNESS_UTXO);
+            SerializeToVector(s, non_witness_utxo);
+        }
+
+        if (final_script_sig.empty()) {
+            // Write any partial signatures
+            for (auto sig_pair : partial_sigs) {
+                SerializeToVector(s, PSBT_IN_PARTIAL_SIG, MakeSpan(sig_pair.second.first));
+                s << sig_pair.second.second;
+            }
+
+            // Write the sighash type
+            if (sighash_type > 0) {
+                SerializeToVector(s, PSBT_IN_SIGHASH);
+                SerializeToVector(s, sighash_type);
+            }
+
+            // Write the redeem script
+            if (!redeem_script.empty()) {
+                SerializeToVector(s, PSBT_IN_REDEEMSCRIPT);
+                s << redeem_script;
+            }
+
+            // Write any hd keypaths
+            SerializeHDKeypaths(s, hd_keypaths, PSBT_IN_BIP32_DERIVATION);
+        }
+
+        // Write script sig
+        if (!final_script_sig.empty()) {
+            SerializeToVector(s, PSBT_IN_SCRIPTSIG);
+            s << final_script_sig;
+        }
+
+        // Write unknown things
+        for (auto& entry : unknown) {
+            s << entry.first;
+            s << entry.second;
+        }
+
+        s << PSBT_SEPARATOR;
+    }
+
+
+    template <typename Stream>
+    inline void Unserialize(Stream& s) {
+        // Read loop
+        bool found_sep = false;
+        while(!s.empty()) {
+            // Read
+            std::vector<unsigned char> key;
+            s >> key;
+
+            // the key is empty if that was actually a separator byte
+            // This is a special case for key lengths 0 as those are not allowed (except for separator)
+            if (key.empty()) {
+                found_sep = true;
+                break;
+            }
+
+            // First byte of key is the type
+            unsigned char type = key[0];
+
+            // Do stuff based on type
+            switch(type) {
+                case PSBT_IN_NON_WITNESS_UTXO:
+                    if (non_witness_utxo) {
+                        throw std::ios_base::failure("Duplicate Key, input non-witness utxo already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Non-witness utxo key is more than one byte type");
+                    }
+                    UnserializeFromVector(s, non_witness_utxo);
+                    break;
+                case PSBT_IN_PARTIAL_SIG:
+                {
+                    // Make sure that the key is the size of pubkey + 1
+                    if (key.size() != CPubKey::PUBLIC_KEY_SIZE + 1 && key.size() != CPubKey::COMPRESSED_PUBLIC_KEY_SIZE + 1) {
+                        throw std::ios_base::failure("Size of key was not the expected size for the type partial signature pubkey");
+                    }
+                    // Read in the pubkey from key
+                    CPubKey pubkey(key.begin() + 1, key.end());
+                    if (!pubkey.IsFullyValid()) {
+                       throw std::ios_base::failure("Invalid pubkey");
+                    }
+                    if (partial_sigs.count(pubkey.GetID()) > 0) {
+                        throw std::ios_base::failure("Duplicate Key, input partial signature for pubkey already provided");
+                    }
+
+                    // Read in the signature from value
+                    std::vector<unsigned char> sig;
+                    s >> sig;
+
+                    // Add to list
+                    partial_sigs.emplace(pubkey.GetID(), SigPair(pubkey, std::move(sig)));
+                    break;
+                }
+                case PSBT_IN_SIGHASH:
+                    if (sighash_type > 0) {
+                        throw std::ios_base::failure("Duplicate Key, input sighash type already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Sighash type key is more than one byte type");
+                    }
+                    UnserializeFromVector(s, sighash_type);
+                    break;
+                case PSBT_IN_REDEEMSCRIPT:
+                {
+                    if (!redeem_script.empty()) {
+                        throw std::ios_base::failure("Duplicate Key, input redeemScript already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Input redeemScript key is more than one byte type");
+                    }
+                    s >> redeem_script;
+                    break;
+                }
+                case PSBT_IN_BIP32_DERIVATION:
+                {
+                    DeserializeHDKeypaths(s, key, hd_keypaths);
+                    break;
+                }
+                case PSBT_IN_SCRIPTSIG:
+                {
+                    if (!final_script_sig.empty()) {
+                        throw std::ios_base::failure("Duplicate Key, input final scriptSig already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Final scriptSig key is more than one byte type");
+                    }
+                    s >> final_script_sig;
+                    break;
+                }
+                // Unknown stuff
+                default:
+                    if (unknown.count(key) > 0) {
+                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
+                    }
+                    // Read in the value
+                    std::vector<unsigned char> val_bytes;
+                    s >> val_bytes;
+                    unknown.emplace(std::move(key), std::move(val_bytes));
+                    break;
+            }
+        }
+
+        if (!found_sep) {
+            throw std::ios_base::failure("Separator is missing at the end of an input map");
+        }
+    }
+
+    template <typename Stream>
+    PSBTInput(deserialize_type, Stream& s) {
+        Unserialize(s);
+    }
+};
+
+/** A structure for PSBTs which contains per output information */
+struct PSBTOutput
+{
+    CScript redeem_script;
+    std::map<CPubKey, KeyOriginInfo> hd_keypaths;
+    std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
+
+    bool IsNull() const;
+    void FillSignatureData(SignatureData& sigdata) const;
+    void FromSignatureData(const SignatureData& sigdata);
+    void Merge(const PSBTOutput& output);
+    bool IsSane() const;
+    PSBTOutput() {}
+
+    template <typename Stream>
+    inline void Serialize(Stream& s) const {
+        // Write the redeem script
+        if (!redeem_script.empty()) {
+            SerializeToVector(s, PSBT_OUT_REDEEMSCRIPT);
+            s << redeem_script;
+        }
+
+        // Write any hd keypaths
+        SerializeHDKeypaths(s, hd_keypaths, PSBT_OUT_BIP32_DERIVATION);
+
+        // Write unknown things
+        for (auto& entry : unknown) {
+            s << entry.first;
+            s << entry.second;
+        }
+
+        s << PSBT_SEPARATOR;
+    }
+
+
+    template <typename Stream>
+    inline void Unserialize(Stream& s) {
+        // Read loop
+        bool found_sep = false;
+        while(!s.empty()) {
+            // Read
+            std::vector<unsigned char> key;
+            s >> key;
+
+            // the key is empty if that was actually a separator byte
+            // This is a special case for key lengths 0 as those are not allowed (except for separator)
+            if (key.empty()) {
+                found_sep = true;
+                break;
+            }
+
+            // First byte of key is the type
+            unsigned char type = key[0];
+
+            // Do stuff based on type
+            switch(type) {
+                case PSBT_OUT_REDEEMSCRIPT:
+                {
+                    if (!redeem_script.empty()) {
+                        throw std::ios_base::failure("Duplicate Key, output redeemScript already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Output redeemScript key is more than one byte type");
+                    }
+                    s >> redeem_script;
+                    break;
+                }
+                case PSBT_OUT_BIP32_DERIVATION:
+                {
+                    DeserializeHDKeypaths(s, key, hd_keypaths);
+                    break;
+                }
+                // Unknown stuff
+                default: {
+                    if (unknown.count(key) > 0) {
+                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
+                    }
+                    // Read in the value
+                    std::vector<unsigned char> val_bytes;
+                    s >> val_bytes;
+                    unknown.emplace(std::move(key), std::move(val_bytes));
+                    break;
+                }
+            }
+        }
+
+        if (!found_sep) {
+            throw std::ios_base::failure("Separator is missing at the end of an output map");
+        }
+    }
+
+    template <typename Stream>
+    PSBTOutput(deserialize_type, Stream& s) {
+        Unserialize(s);
+    }
+};
+
+/** A version of CTransaction with the PSBT format*/
+struct PartiallySignedTransaction
+{
+    boost::optional<CMutableTransaction> tx;
+    std::vector<PSBTInput> inputs;
+    std::vector<PSBTOutput> outputs;
+    std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
+
+    bool IsNull() const;
+
+    /** Merge psbt into this. The two psbts must have the same underlying CTransaction (i.e. the
+      * same actual Bitcoin transaction.) Returns true if the merge succeeded, false otherwise. */
+    [[nodiscard]] bool Merge(const PartiallySignedTransaction& psbt);
+    bool IsSane() const;
+    bool AddInput(const CTxIn& txin, PSBTInput& psbtin);
+    bool AddOutput(const CTxOut& txout, const PSBTOutput& psbtout);
+    PartiallySignedTransaction() {}
+    PartiallySignedTransaction(const PartiallySignedTransaction& psbt_in) : tx(psbt_in.tx), inputs(psbt_in.inputs), outputs(psbt_in.outputs), unknown(psbt_in.unknown) {}
+
+    /**
+     * Finds the UTXO for a given input index
+     *
+     * @param[out] utxo The UTXO of the input if found
+     * @param[in] input_index Index of the input to retrieve the UTXO of
+     * @return Whether the UTXO for the specified input was found
+     */
+    bool GetInputUTXO(CTxOut& utxo, int input_index) const;
+
+    template <typename Stream>
+    inline void Serialize(Stream& s) const {
+
+        // magic bytes
+        s << PSBT_MAGIC_BYTES;
+
+        // unsigned tx flag
+        SerializeToVector(s, PSBT_GLOBAL_UNSIGNED_TX);
+
+        // Write serialized tx to a stream
+        SerializeToVector(s, *tx);
+
+        // Write the unknown things
+        for (auto& entry : unknown) {
+            s << entry.first;
+            s << entry.second;
+        }
+
+        // Separator
+        s << PSBT_SEPARATOR;
+
+        // Write inputs
+        for (const PSBTInput& input : inputs) {
+            s << input;
+        }
+        // Write outputs
+        for (const PSBTOutput& output : outputs) {
+            s << output;
+        }
+    }
+
+
+    template <typename Stream>
+    inline void Unserialize(Stream& s) {
+        // Read the magic bytes
+        uint8_t magic[5];
+        s >> magic;
+        if (!std::equal(magic, magic + 5, PSBT_MAGIC_BYTES)) {
+            throw std::ios_base::failure("Invalid PSBT magic bytes");
+        }
+
+        // Read global data
+        bool found_sep = false;
+        while(!s.empty()) {
+            // Read
+            std::vector<unsigned char> key;
+            s >> key;
+
+            // the key is empty if that was actually a separator byte
+            // This is a special case for key lengths 0 as those are not allowed (except for separator)
+            if (key.empty()) {
+                found_sep = true;
+                break;
+            }
+
+            // First byte of key is the type
+            unsigned char type = key[0];
+
+            // Do stuff based on type
+            switch(type) {
+                case PSBT_GLOBAL_UNSIGNED_TX:
+                {
+                    if (tx) {
+                        throw std::ios_base::failure("Duplicate Key, unsigned tx already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Global unsigned tx key is more than one byte type");
+                    }
+                    CMutableTransaction mtx;
+                    UnserializeFromVector(s, mtx);
+                    tx = std::move(mtx);
+                    // Make sure that all scriptSigs are empty
+                    for (const CTxIn& txin : tx->vin) {
+                        if (!txin.scriptSig.empty()) {
+                            throw std::ios_base::failure("Unsigned tx does not have empty scriptSigs.");
+                        }
+                    }
+                    break;
+                }
+                // Unknown stuff
+                default: {
+                    if (unknown.count(key) > 0) {
+                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
+                    }
+                    // Read in the value
+                    std::vector<unsigned char> val_bytes;
+                    s >> val_bytes;
+                    unknown.emplace(std::move(key), std::move(val_bytes));
+                }
+            }
+        }
+
+        if (!found_sep) {
+            throw std::ios_base::failure("Separator is missing at the end of the global map");
+        }
+
+        // Make sure that we got an unsigned tx
+        if (!tx) {
+            throw std::ios_base::failure("No unsigned transcation was provided");
+        }
+
+        // Read input data
+        unsigned int i = 0;
+        while (!s.empty() && i < tx->vin.size()) {
+            PSBTInput input;
+            s >> input;
+            inputs.push_back(input);
+
+            // Make sure the non-witness utxo matches the outpoint
+            if (input.non_witness_utxo && input.non_witness_utxo->GetHash() != tx->vin[i].prevout.hash) {
+                throw std::ios_base::failure("Non-witness UTXO does not match outpoint hash");
+            }
+            ++i;
+        }
+        // Make sure that the number of inputs matches the number of inputs in the transaction
+        if (inputs.size() != tx->vin.size()) {
+            throw std::ios_base::failure("Inputs provided does not match the number of inputs in transaction.");
+        }
+
+        // Read output data
+        i = 0;
+        while (!s.empty() && i < tx->vout.size()) {
+            PSBTOutput output;
+            s >> output;
+            outputs.push_back(output);
+            ++i;
+        }
+        // Make sure that the number of outputs matches the number of outputs in the transaction
+        if (outputs.size() != tx->vout.size()) {
+            throw std::ios_base::failure("Outputs provided does not match the number of outputs in transaction.");
+        }
+        // Sanity check
+        if (!IsSane()) {
+            throw std::ios_base::failure("PSBT is not sane.");
+        }
+    }
+
+    template <typename Stream>
+    PartiallySignedTransaction(deserialize_type, Stream& s) {
+        Unserialize(s);
+    }
+};
+
+/** Signs a PSBTInput, verifying that all provided data matches what is being signed. */
+bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& tx, PSBTInput& input, int index, int sighash = SIGHASH_ALL);
+
+/**
+ * Finalizes a PSBT if possible, combining partial signatures.
+ *
+ * @param[in,out] &psbtx reference to PartiallySignedTransaction to finalize
+ * return True if the PSBT is now complete, false otherwise
+ */
+bool FinalizePSBT(PartiallySignedTransaction& psbtx);
+
+/**
+ * Finalizes a PSBT if possible, and extracts it to a CMutableTransaction if it could be finalized.
+ *
+ * @param[in]  &psbtx reference to PartiallySignedTransaction
+ * @param[out] result CMutableTransaction representing the complete transaction, if successful
+ * @return True if we successfully extracted the transaction, false otherwise
+ */
+bool FinalizeAndExtractPSBT(PartiallySignedTransaction& psbtx, CMutableTransaction& result);
+
+/**
+ * Combines PSBTs with the same underlying transaction, resulting in a single PSBT with all partial signatures from each input.
+ *
+ * @param[out] &out   the combined PSBT, if successful
+ * @param[out] &error reference to TransactionError to fill with error info on failure
+ * @param[in]  psbtxs the PSBTs to combine
+ * @return True if we successfully combined the transactions, false if they were not compatible
+ */
+bool CombinePSBTs(PartiallySignedTransaction& out, TransactionError& error, const std::vector<PartiallySignedTransaction>& psbtxs);
+
+#endif // BITCOIN_PSBT_H
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 627758b613c0b..c9fcf75473b26 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -19,6 +19,8 @@
 #include <node/transaction.h>
 #include <policy/policy.h>
 #include <primitives/transaction.h>
+#include <psbt.h>
+#include <rpc/util.h>
 #include <rpc/rawtransaction.h>
 #include <rpc/server.h>
 #include <script/script.h>
@@ -1103,7 +1105,16 @@ UniValue sendrawtransaction(const JSONRPCRequest& request)
     CTransactionRef tx(MakeTransactionRef(std::move(mtx)));
     bool allowhighfees = false;
     if (!request.params[1].isNull()) allowhighfees = request.params[1].get_bool();
-    return BroadcastTransaction(tx, allowhighfees).GetHex();
+    bool bypass_limits = false;
+    if (!request.params[3].isNull()) bypass_limits = request.params[3].get_bool();
+    uint256 txid;
+    TransactionError err;
+    std::string err_string;
+    if (!BroadcastTransaction(tx, txid, err, err_string, allowhighfees, bypass_limits)) {
+        throw JSONRPCTransactionError(err, err_string);
+    }
+
+    return txid.GetHex();
 }
 
 static UniValue testmempoolaccept(const JSONRPCRequest& request)
@@ -1291,7 +1302,7 @@ UniValue decodepsbt(const JSONRPCRequest& request)
     // Unserialize the transactions
     PartiallySignedTransaction psbtx;
     std::string error;
-    if (!DecodePSBT(psbtx, request.params[0].get_str(), error)) {
+    if (!DecodeBase64PSBT(psbtx, request.params[0].get_str(), error)) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("TX decode failed %s", error));
     }
 
@@ -1458,23 +1469,16 @@ UniValue combinepsbt(const JSONRPCRequest& request)
     for (unsigned int i = 0; i < txs.size(); ++i) {
         PartiallySignedTransaction psbtx;
         std::string error;
-        if (!DecodePSBT(psbtx, txs[i].get_str(), error)) {
+        if (!DecodeBase64PSBT(psbtx, txs[i].get_str(), error)) {
             throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("TX decode failed %s", error));
         }
         psbtxs.push_back(psbtx);
     }
 
-    PartiallySignedTransaction merged_psbt(psbtxs[0]); // Copy the first one
-
-    // Merge
-    for (auto it = std::next(psbtxs.begin()); it != psbtxs.end(); ++it) {
-        if (*it != merged_psbt) {
-            throw JSONRPCError(RPC_INVALID_PARAMETER, "PSBTs do not refer to the same transactions.");
-        }
-        merged_psbt.Merge(*it);
-    }
-    if (!merged_psbt.IsSane()) {
-        throw JSONRPCError(RPC_INVALID_PARAMETER, "Merged PSBT is inconsistent");
+    PartiallySignedTransaction merged_psbt;
+    TransactionError error;
+    if (!CombinePSBTs(merged_psbt, error, psbtxs)) {
+        throw JSONRPCTransactionError(error);
     }
 
     UniValue result(UniValue::VOBJ);
@@ -1514,31 +1518,27 @@ UniValue finalizepsbt(const JSONRPCRequest& request)
     // Unserialize the transactions
     PartiallySignedTransaction psbtx;
     std::string error;
-    if (!DecodePSBT(psbtx, request.params[0].get_str(), error)) {
+    if (!DecodeBase64PSBT(psbtx, request.params[0].get_str(), error)) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("TX decode failed %s", error));
     }
 
-    // Get all of the previous transactions
-    bool complete = true;
-    for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
-        PSBTInput& input = psbtx.inputs.at(i);
+    bool extract = request.params[1].isNull() || (!request.params[1].isNull() && request.params[1].get_bool());
 
-        complete &= SignPSBTInput(DUMMY_SIGNING_PROVIDER, *psbtx.tx, input, i, 1);
-    }
+    CMutableTransaction mtx;
+    bool complete = FinalizeAndExtractPSBT(psbtx, mtx);
 
     UniValue result(UniValue::VOBJ);
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
-    bool extract = request.params[1].isNull() || (!request.params[1].isNull() && request.params[1].get_bool());
+    std::string result_str;
+
     if (complete && extract) {
-        CMutableTransaction mtx(*psbtx.tx);
-        for (unsigned int i = 0; i < mtx.vin.size(); ++i) {
-            mtx.vin[i].scriptSig = psbtx.inputs[i].final_script_sig;
-        }
         ssTx << mtx;
-        result.pushKV("hex", HexStr(ssTx));
+        result_str = HexStr(ssTx.str());
+        result.pushKV("hex", result_str);
     } else {
         ssTx << psbtx;
-        result.pushKV("psbt", EncodeBase64(ssTx.str()));
+        result_str = EncodeBase64(ssTx.str());
+        result.pushKV("psbt", result_str);
     }
     result.pushKV("complete", complete);
 
diff --git a/src/rpc/util.cpp b/src/rpc/util.cpp
index 02e251d408ade..2c904b3ba50bf 100644
--- a/src/rpc/util.cpp
+++ b/src/rpc/util.cpp
@@ -92,3 +92,32 @@ UniValue DescribeAddress(const CTxDestination& dest)
 {
     return boost::apply_visitor(DescribeAddressVisitor(), dest);
 }
+
+RPCErrorCode RPCErrorFromTransactionError(TransactionError terr)
+{
+    switch (terr) {
+        case TransactionError::MEMPOOL_REJECTED:
+            return RPC_TRANSACTION_REJECTED;
+        case TransactionError::ALREADY_IN_CHAIN:
+            return RPC_TRANSACTION_ALREADY_IN_CHAIN;
+        case TransactionError::P2P_DISABLED:
+            return RPC_CLIENT_P2P_DISABLED;
+        case TransactionError::INVALID_PSBT:
+        case TransactionError::PSBT_MISMATCH:
+            return RPC_INVALID_PARAMETER;
+        case TransactionError::SIGHASH_MISMATCH:
+            return RPC_DESERIALIZATION_ERROR;
+        default: break;
+    }
+    return RPC_TRANSACTION_ERROR;
+}
+
+UniValue JSONRPCTransactionError(TransactionError terr, const std::string& err_string)
+{
+    if (err_string.length() > 0) {
+        return JSONRPCError(RPCErrorFromTransactionError(terr), err_string);
+    } else {
+        return JSONRPCError(RPCErrorFromTransactionError(terr), TransactionErrorString(terr));
+    }
+}
+
diff --git a/src/rpc/util.h b/src/rpc/util.h
index 6432d69d345c6..81901eebafe0d 100644
--- a/src/rpc/util.h
+++ b/src/rpc/util.h
@@ -5,10 +5,12 @@
 #ifndef BITCOIN_RPC_UTIL_H
 #define BITCOIN_RPC_UTIL_H
 
+#include <node/transaction.h>
 #include <pubkey.h>
 #include <script/standard.h>
 #include <univalue.h>
 #include <util/strencodings.h>
+#include <rpc/protocol.h>
 
 #include <boost/variant/static_visitor.hpp>
 
@@ -25,4 +27,7 @@ CScript CreateMultisigRedeemscript(const int required, const std::vector<CPubKey
 
 UniValue DescribeAddress(const CTxDestination& dest);
 
+RPCErrorCode RPCErrorFromTransactionError(TransactionError terr);
+UniValue JSONRPCTransactionError(TransactionError terr, const std::string& err_string = "");
+
 #endif // BITCOIN_RPC_UTIL_H
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index ccc93eb0332a6..3b74d1568001b 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -205,33 +205,6 @@ bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreato
     return sigdata.complete;
 }
 
-bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& tx, PSBTInput& input, int index, int sighash)
-{
-    // if this input has a final scriptsig, don't do anything with it
-    if (!input.final_script_sig.empty()) {
-        return true;
-    }
-
-    // Fill SignatureData with input info
-    SignatureData sigdata;
-    input.FillSignatureData(sigdata);
-
-    // Get UTXO
-    CTxOut utxo;
-    if (input.non_witness_utxo) {
-        // If we're taking our information from a non-witness UTXO, verify that it matches the prevout.
-        if (input.non_witness_utxo->GetHash() != tx.vin[index].prevout.hash) return false;
-        utxo = input.non_witness_utxo->vout[tx.vin[index].prevout.n];
-    } else {
-        return false;
-    }
-
-    MutableTransactionSignatureCreator creator(&tx, index, utxo.nValue, sighash);
-    bool sig_complete = ProduceSignature(provider, creator, utxo.scriptPubKey, sigdata);
-    input.FromSignatureData(sigdata);
-    return sig_complete;
-}
-
 class SignatureExtractorChecker final : public BaseSignatureChecker
 {
 private:
@@ -433,156 +406,6 @@ bool IsSolvable(const SigningProvider& provider, const CScript& script)
     return false;
 }
 
-bool PartiallySignedTransaction::IsNull() const
-{
-    return !tx && inputs.empty() && outputs.empty() && unknown.empty();
-}
-
-void PartiallySignedTransaction::Merge(const PartiallySignedTransaction& psbt)
-{
-    for (unsigned int i = 0; i < inputs.size(); ++i) {
-        inputs[i].Merge(psbt.inputs[i]);
-    }
-    for (unsigned int i = 0; i < outputs.size(); ++i) {
-        outputs[i].Merge(psbt.outputs[i]);
-    }
-    unknown.insert(psbt.unknown.begin(), psbt.unknown.end());
-}
-
-bool PartiallySignedTransaction::IsSane() const
-{
-    for (PSBTInput input : inputs) {
-        if (!input.IsSane()) return false;
-    }
-    return true;
-}
-
-bool PartiallySignedTransaction::AddInput(const CTxIn& txin, PSBTInput& psbtin)
-{
-    if (std::find(tx->vin.begin(), tx->vin.end(), txin) != tx->vin.end()) {
-        return false;
-    }
-    tx->vin.push_back(txin);
-    psbtin.partial_sigs.clear();
-    psbtin.final_script_sig.clear();
-    inputs.push_back(psbtin);
-    return true;
-}
-
-bool PartiallySignedTransaction::AddOutput(const CTxOut& txout, const PSBTOutput& psbtout)
-{
-    tx->vout.push_back(txout);
-    outputs.push_back(psbtout);
-    return true;
-}
-
-bool PartiallySignedTransaction::GetInputUTXO(CTxOut& utxo, int input_index) const
-{
-    PSBTInput input = inputs[input_index];
-    int prevout_index = tx->vin[input_index].prevout.n;
-    if (input.non_witness_utxo) {
-        utxo = input.non_witness_utxo->vout[prevout_index];
-    } else {
-        return false;
-    }
-    return true;
-}
-
-bool PSBTInput::IsNull() const
-{
-    return !non_witness_utxo && partial_sigs.empty() && unknown.empty() && hd_keypaths.empty() && redeem_script.empty();
-}
-
-void PSBTInput::FillSignatureData(SignatureData& sigdata) const
-{
-    if (!final_script_sig.empty()) {
-        sigdata.scriptSig = final_script_sig;
-        sigdata.complete = true;
-    }
-    if (sigdata.complete) {
-        return;
-    }
-
-    sigdata.signatures.insert(partial_sigs.begin(), partial_sigs.end());
-    if (!redeem_script.empty()) {
-        sigdata.redeem_script = redeem_script;
-    }
-    for (const auto& key_pair : hd_keypaths) {
-        sigdata.misc_pubkeys.emplace(key_pair.first.GetID(), key_pair);
-    }
-}
-
-void PSBTInput::FromSignatureData(const SignatureData& sigdata)
-{
-    if (sigdata.complete) {
-        partial_sigs.clear();
-        hd_keypaths.clear();
-        redeem_script.clear();
-
-        if (!sigdata.scriptSig.empty()) {
-            final_script_sig = sigdata.scriptSig;
-        }
-        return;
-    }
-
-    partial_sigs.insert(sigdata.signatures.begin(), sigdata.signatures.end());
-    if (redeem_script.empty() && !sigdata.redeem_script.empty()) {
-        redeem_script = sigdata.redeem_script;
-    }
-    for (const auto& entry : sigdata.misc_pubkeys) {
-        hd_keypaths.emplace(entry.second);
-    }
-}
-
-void PSBTInput::Merge(const PSBTInput& input)
-{
-    if (!non_witness_utxo && input.non_witness_utxo) non_witness_utxo = input.non_witness_utxo;
-
-    partial_sigs.insert(input.partial_sigs.begin(), input.partial_sigs.end());
-    hd_keypaths.insert(input.hd_keypaths.begin(), input.hd_keypaths.end());
-    unknown.insert(input.unknown.begin(), input.unknown.end());
-
-    if (redeem_script.empty() && !input.redeem_script.empty()) redeem_script = input.redeem_script;
-    if (final_script_sig.empty() && !input.final_script_sig.empty()) final_script_sig = input.final_script_sig;
-}
-
-bool PSBTInput::IsSane() const
-{
-    return true;
-}
-
-void PSBTOutput::FillSignatureData(SignatureData& sigdata) const
-{
-    if (!redeem_script.empty()) {
-        sigdata.redeem_script = redeem_script;
-    }
-    for (const auto& key_pair : hd_keypaths) {
-        sigdata.misc_pubkeys.emplace(key_pair.first.GetID(), key_pair);
-    }
-}
-
-void PSBTOutput::FromSignatureData(const SignatureData& sigdata)
-{
-    if (redeem_script.empty() && !sigdata.redeem_script.empty()) {
-        redeem_script = sigdata.redeem_script;
-    }
-    for (const auto& entry : sigdata.misc_pubkeys) {
-        hd_keypaths.emplace(entry.second);
-    }
-}
-
-bool PSBTOutput::IsNull() const
-{
-    return redeem_script.empty() && hd_keypaths.empty() && unknown.empty();
-}
-
-void PSBTOutput::Merge(const PSBTOutput& output)
-{
-    hd_keypaths.insert(output.hd_keypaths.begin(), output.hd_keypaths.end());
-    unknown.insert(output.unknown.begin(), output.unknown.end());
-
-    if (redeem_script.empty() && !output.redeem_script.empty()) redeem_script = output.redeem_script;
-}
 
 bool HidingSigningProvider::GetCScript(const CScriptID& scriptid, CScript& script) const
 {
diff --git a/src/script/sign.h b/src/script/sign.h
index 873af5dd0c70f..af7574ad6fea8 100644
--- a/src/script/sign.h
+++ b/src/script/sign.h
@@ -116,28 +116,6 @@ struct SignatureData {
     void MergeSignatureData(SignatureData sigdata);
 };
 
-// Magic bytes
-static constexpr uint8_t PSBT_MAGIC_BYTES[5] = {'p', 's', 'b', 't', 0xff};
-
-// Global types
-static constexpr uint8_t PSBT_GLOBAL_UNSIGNED_TX = 0x00;
-
-// Input types
-static constexpr uint8_t PSBT_IN_NON_WITNESS_UTXO = 0x00;
-static constexpr uint8_t PSBT_IN_PARTIAL_SIG = 0x02;
-static constexpr uint8_t PSBT_IN_SIGHASH = 0x03;
-static constexpr uint8_t PSBT_IN_REDEEMSCRIPT = 0x04;
-static constexpr uint8_t PSBT_IN_BIP32_DERIVATION = 0x06;
-static constexpr uint8_t PSBT_IN_SCRIPTSIG = 0x07;
-
-// Output types
-static constexpr uint8_t PSBT_OUT_REDEEMSCRIPT = 0x00;
-static constexpr uint8_t PSBT_OUT_BIP32_DERIVATION = 0x02;
-
-// The separator is 0x00. Reading this in means that the unserializer can interpret it
-// as a 0 length key which indicates that this is the separator. The separator has no value.
-static constexpr uint8_t PSBT_SEPARATOR = 0x00;
-
 // Takes a stream and multiple arguments and serializes them into a vector and then into the stream
 // The resulting output into the stream has the total serialized length of all of the objects followed by all objects concatenated with each other.
 template<typename Stream, typename... X>
@@ -211,461 +189,6 @@ void SerializeHDKeypaths(Stream& s, const std::map<CPubKey, KeyOriginInfo>& hd_k
     }
 }
 
-/** A structure for PSBTs which contain per-input information */
-struct PSBTInput
-{
-    CTransactionRef non_witness_utxo;
-    CScript redeem_script;
-    CScript final_script_sig;
-    std::map<CPubKey, KeyOriginInfo> hd_keypaths;
-    std::map<CKeyID, SigPair> partial_sigs;
-    std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
-    int sighash_type = 0;
-
-    bool IsNull() const;
-    void FillSignatureData(SignatureData& sigdata) const;
-    void FromSignatureData(const SignatureData& sigdata);
-    void Merge(const PSBTInput& input);
-    bool IsSane() const;
-    PSBTInput() {}
-
-    template <typename Stream>
-    inline void Serialize(Stream& s) const {
-        // Write the utxo
-        if (non_witness_utxo) {
-            SerializeToVector(s, PSBT_IN_NON_WITNESS_UTXO);
-            OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion());
-            SerializeToVector(os, non_witness_utxo);
-        }
-
-        if (final_script_sig.empty()) {
-            // Write any partial signatures
-            for (auto sig_pair : partial_sigs) {
-                SerializeToVector(s, PSBT_IN_PARTIAL_SIG, MakeSpan(sig_pair.second.first));
-                s << sig_pair.second.second;
-            }
-
-            // Write the sighash type
-            if (sighash_type > 0) {
-                SerializeToVector(s, PSBT_IN_SIGHASH);
-                SerializeToVector(s, sighash_type);
-            }
-
-            // Write the redeem script
-            if (!redeem_script.empty()) {
-                SerializeToVector(s, PSBT_IN_REDEEMSCRIPT);
-                s << redeem_script;
-            }
-
-            // Write any hd keypaths
-            SerializeHDKeypaths(s, hd_keypaths, PSBT_IN_BIP32_DERIVATION);
-        }
-
-        // Write script sig
-        if (!final_script_sig.empty()) {
-            SerializeToVector(s, PSBT_IN_SCRIPTSIG);
-            s << final_script_sig;
-        }
-
-        // Write unknown things
-        for (auto& entry : unknown) {
-            s << entry.first;
-            s << entry.second;
-        }
-
-        s << PSBT_SEPARATOR;
-    }
-
-
-    template <typename Stream>
-    inline void Unserialize(Stream& s) {
-        // Read loop
-        bool found_sep = false;
-        while(!s.empty()) {
-            // Read
-            std::vector<unsigned char> key;
-            s >> key;
-
-            // the key is empty if that was actually a separator byte
-            // This is a special case for key lengths 0 as those are not allowed (except for separator)
-            if (key.empty()) {
-                found_sep = true;
-                break;
-            }
-
-            // First byte of key is the type
-            unsigned char type = key[0];
-
-            // Do stuff based on type
-            switch(type) {
-                case PSBT_IN_NON_WITNESS_UTXO:
-                {
-                    if (non_witness_utxo) {
-                        throw std::ios_base::failure("Duplicate Key, input non-witness utxo already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Non-witness utxo key is more than one byte type");
-                    }
-                    // Set the stream to unserialize with witness since this is always a valid network transaction
-                    OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion());
-                    UnserializeFromVector(os, non_witness_utxo);
-                    break;
-                }
-                case PSBT_IN_PARTIAL_SIG:
-                {
-                    // Make sure that the key is the size of pubkey + 1
-                    if (key.size() != CPubKey::PUBLIC_KEY_SIZE + 1 && key.size() != CPubKey::COMPRESSED_PUBLIC_KEY_SIZE + 1) {
-                        throw std::ios_base::failure("Size of key was not the expected size for the type partial signature pubkey");
-                    }
-                    // Read in the pubkey from key
-                    CPubKey pubkey(key.begin() + 1, key.end());
-                    if (!pubkey.IsFullyValid()) {
-                       throw std::ios_base::failure("Invalid pubkey");
-                    }
-                    if (partial_sigs.count(pubkey.GetID()) > 0) {
-                        throw std::ios_base::failure("Duplicate Key, input partial signature for pubkey already provided");
-                    }
-
-                    // Read in the signature from value
-                    std::vector<unsigned char> sig;
-                    s >> sig;
-
-                    // Add to list
-                    partial_sigs.emplace(pubkey.GetID(), SigPair(pubkey, std::move(sig)));
-                    break;
-                }
-                case PSBT_IN_SIGHASH:
-                    if (sighash_type > 0) {
-                        throw std::ios_base::failure("Duplicate Key, input sighash type already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Sighash type key is more than one byte type");
-                    }
-                    UnserializeFromVector(s, sighash_type);
-                    break;
-                case PSBT_IN_REDEEMSCRIPT:
-                {
-                    if (!redeem_script.empty()) {
-                        throw std::ios_base::failure("Duplicate Key, input redeemScript already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Input redeemScript key is more than one byte type");
-                    }
-                    s >> redeem_script;
-                    break;
-                }
-                case PSBT_IN_BIP32_DERIVATION:
-                {
-                    DeserializeHDKeypaths(s, key, hd_keypaths);
-                    break;
-                }
-                case PSBT_IN_SCRIPTSIG:
-                {
-                    if (!final_script_sig.empty()) {
-                        throw std::ios_base::failure("Duplicate Key, input final scriptSig already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Final scriptSig key is more than one byte type");
-                    }
-                    s >> final_script_sig;
-                    break;
-                }
-                // Unknown stuff
-                default:
-                    if (unknown.count(key) > 0) {
-                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
-                    }
-                    // Read in the value
-                    std::vector<unsigned char> val_bytes;
-                    s >> val_bytes;
-                    unknown.emplace(std::move(key), std::move(val_bytes));
-                    break;
-            }
-        }
-
-        if (!found_sep) {
-            throw std::ios_base::failure("Separator is missing at the end of an input map");
-        }
-    }
-
-    template <typename Stream>
-    PSBTInput(deserialize_type, Stream& s) {
-        Unserialize(s);
-    }
-};
-
-/** A structure for PSBTs which contains per output information */
-struct PSBTOutput
-{
-    CScript redeem_script;
-    std::map<CPubKey, KeyOriginInfo> hd_keypaths;
-    std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
-
-    bool IsNull() const;
-    void FillSignatureData(SignatureData& sigdata) const;
-    void FromSignatureData(const SignatureData& sigdata);
-    void Merge(const PSBTOutput& output);
-    bool IsSane() const;
-    PSBTOutput() {}
-
-    template <typename Stream>
-    inline void Serialize(Stream& s) const {
-        // Write the redeem script
-        if (!redeem_script.empty()) {
-            SerializeToVector(s, PSBT_OUT_REDEEMSCRIPT);
-            s << redeem_script;
-        }
-
-        // Write any hd keypaths
-        SerializeHDKeypaths(s, hd_keypaths, PSBT_OUT_BIP32_DERIVATION);
-
-        // Write unknown things
-        for (auto& entry : unknown) {
-            s << entry.first;
-            s << entry.second;
-        }
-
-        s << PSBT_SEPARATOR;
-    }
-
-
-    template <typename Stream>
-    inline void Unserialize(Stream& s) {
-        // Read loop
-        bool found_sep = false;
-        while(!s.empty()) {
-            // Read
-            std::vector<unsigned char> key;
-            s >> key;
-
-            // the key is empty if that was actually a separator byte
-            // This is a special case for key lengths 0 as those are not allowed (except for separator)
-            if (key.empty()) {
-                found_sep = true;
-                break;
-            }
-
-            // First byte of key is the type
-            unsigned char type = key[0];
-
-            // Do stuff based on type
-            switch(type) {
-                case PSBT_OUT_REDEEMSCRIPT:
-                {
-                    if (!redeem_script.empty()) {
-                        throw std::ios_base::failure("Duplicate Key, output redeemScript already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Output redeemScript key is more than one byte type");
-                    }
-                    s >> redeem_script;
-                    break;
-                }
-                case PSBT_OUT_BIP32_DERIVATION:
-                {
-                    DeserializeHDKeypaths(s, key, hd_keypaths);
-                    break;
-                }
-                // Unknown stuff
-                default: {
-                    if (unknown.count(key) > 0) {
-                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
-                    }
-                    // Read in the value
-                    std::vector<unsigned char> val_bytes;
-                    s >> val_bytes;
-                    unknown.emplace(std::move(key), std::move(val_bytes));
-                    break;
-                }
-            }
-        }
-
-        if (!found_sep) {
-            throw std::ios_base::failure("Separator is missing at the end of an output map");
-        }
-    }
-
-    template <typename Stream>
-    PSBTOutput(deserialize_type, Stream& s) {
-        Unserialize(s);
-    }
-};
-
-/** A version of CTransaction with the PSBT format*/
-struct PartiallySignedTransaction
-{
-    boost::optional<CMutableTransaction> tx;
-    std::vector<PSBTInput> inputs;
-    std::vector<PSBTOutput> outputs;
-    std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
-
-    bool IsNull() const;
-    void Merge(const PartiallySignedTransaction& psbt);
-    bool IsSane() const;
-    bool AddInput(const CTxIn& txin, PSBTInput& psbtin);
-    bool AddOutput(const CTxOut& txout, const PSBTOutput& psbtout);
-    PartiallySignedTransaction() {}
-    PartiallySignedTransaction(const PartiallySignedTransaction& psbt_in) : tx(psbt_in.tx), inputs(psbt_in.inputs), outputs(psbt_in.outputs), unknown(psbt_in.unknown) {}
-
-    // Only checks if they refer to the same transaction
-    friend bool operator==(const PartiallySignedTransaction& a, const PartiallySignedTransaction &b)
-    {
-        return a.tx->GetHash() == b.tx->GetHash();
-    }
-    friend bool operator!=(const PartiallySignedTransaction& a, const PartiallySignedTransaction &b)
-    {
-        return !(a == b);
-    }
-
-    /**
-     * Finds the UTXO for a given input index
-     *
-     * @param[out] utxo The UTXO of the input if found
-     * @param[in] input_index Index of the input to retrieve the UTXO of
-     * @return Whether the UTXO for the specified input was found
-     */
-    bool GetInputUTXO(CTxOut& utxo, int input_index) const;
-
-    template <typename Stream>
-    inline void Serialize(Stream& s) const {
-
-        // magic bytes
-        s << PSBT_MAGIC_BYTES;
-
-        // unsigned tx flag
-        SerializeToVector(s, PSBT_GLOBAL_UNSIGNED_TX);
-
-        // Write serialized tx to a stream
-        OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion());
-        SerializeToVector(os, *tx);
-
-        // Write the unknown things
-        for (auto& entry : unknown) {
-            s << entry.first;
-            s << entry.second;
-        }
-
-        // Separator
-        s << PSBT_SEPARATOR;
-
-        // Write inputs
-        for (const PSBTInput& input : inputs) {
-            s << input;
-        }
-        // Write outputs
-        for (const PSBTOutput& output : outputs) {
-            s << output;
-        }
-    }
-
-
-    template <typename Stream>
-    inline void Unserialize(Stream& s) {
-        // Read the magic bytes
-        uint8_t magic[5];
-        s >> magic;
-        if (!std::equal(magic, magic + 5, PSBT_MAGIC_BYTES)) {
-            throw std::ios_base::failure("Invalid PSBT magic bytes");
-        }
-
-        // Read global data
-        bool found_sep = false;
-        while(!s.empty()) {
-            // Read
-            std::vector<unsigned char> key;
-            s >> key;
-
-            // the key is empty if that was actually a separator byte
-            // This is a special case for key lengths 0 as those are not allowed (except for separator)
-            if (key.empty()) {
-                found_sep = true;
-                break;
-            }
-
-            // First byte of key is the type
-            unsigned char type = key[0];
-
-            // Do stuff based on type
-            switch(type) {
-                case PSBT_GLOBAL_UNSIGNED_TX:
-                {
-                    if (tx) {
-                        throw std::ios_base::failure("Duplicate Key, unsigned tx already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Global unsigned tx key is more than one byte type");
-                    }
-                    CMutableTransaction mtx;
-                    // Set the stream to serialize with non-witness since this should always be non-witness
-                    OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion());
-                    UnserializeFromVector(os, mtx);
-                    tx = std::move(mtx);
-                    // Make sure that all scriptSigs are empty
-                    for (const CTxIn& txin : tx->vin) {
-                        if (!txin.scriptSig.empty()) {
-                            throw std::ios_base::failure("Unsigned tx does not have empty scriptSigs.");
-                        }
-                    }
-                    break;
-                }
-                // Unknown stuff
-                default: {
-                    if (unknown.count(key) > 0) {
-                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
-                    }
-                    // Read in the value
-                    std::vector<unsigned char> val_bytes;
-                    s >> val_bytes;
-                    unknown.emplace(std::move(key), std::move(val_bytes));
-                }
-            }
-        }
-
-        if (!found_sep) {
-            throw std::ios_base::failure("Separator is missing at the end of the global map");
-        }
-
-        // Make sure that we got an unsigned tx
-        if (!tx) {
-            throw std::ios_base::failure("No unsigned transcation was provided");
-        }
-
-        // Read input data
-        unsigned int i = 0;
-        while (!s.empty() && i < tx->vin.size()) {
-            PSBTInput input;
-            s >> input;
-            inputs.push_back(input);
-
-            // Make sure the non-witness utxo matches the outpoint
-            if (input.non_witness_utxo && input.non_witness_utxo->GetHash() != tx->vin[i].prevout.hash) {
-                throw std::ios_base::failure("Non-witness UTXO does not match outpoint hash");
-            }
-            ++i;
-        }
-        // Make sure that the number of inputs matches the number of inputs in the transaction
-        if (inputs.size() != tx->vin.size()) {
-            throw std::ios_base::failure("Inputs provided does not match the number of inputs in transaction.");
-        }
-
-        // Read output data
-        i = 0;
-        while (!s.empty() && i < tx->vout.size()) {
-            PSBTOutput output;
-            s >> output;
-            outputs.push_back(output);
-            ++i;
-        }
-        // Make sure that the number of outputs matches the number of outputs in the transaction
-        if (outputs.size() != tx->vout.size()) {
-            throw std::ios_base::failure("Outputs provided does not match the number of outputs in transaction.");
-        }
-        // Sanity check
-        if (!IsSane()) {
-            throw std::ios_base::failure("PSBT is not sane.");
-        }
-    }
-
-    template <typename Stream>
-    PartiallySignedTransaction(deserialize_type, Stream& s) {
-        Unserialize(s);
-    }
-};
-
 /** Produce a script signature using a generic signature creator. */
 bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreator& creator, const CScript& scriptPubKey, SignatureData& sigdata);
 
@@ -673,9 +196,6 @@ bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreato
 bool SignSignature(const SigningProvider &provider, const CScript& fromPubKey, CMutableTransaction& txTo, unsigned int nIn, const CAmount& amount, int nHashType);
 bool SignSignature(const SigningProvider &provider, const CTransaction& txFrom, CMutableTransaction& txTo, unsigned int nIn, int nHashType);
 
-/** Signs a PSBTInput, verifying that all provided data matches what is being signed. */
-bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& tx, PSBTInput& input, int index, int sighash = SIGHASH_ALL);
-
 /** Extract signature data from a transaction input, and insert it. */
 SignatureData DataFromTransaction(const CMutableTransaction& tx, unsigned int nIn, const CTxOut& txout);
 void UpdateInput(CTxIn& input, const SignatureData& data);
diff --git a/src/wallet/psbtwallet.cpp b/src/wallet/psbtwallet.cpp
new file mode 100644
index 0000000000000..97c58feca3822
--- /dev/null
+++ b/src/wallet/psbtwallet.cpp
@@ -0,0 +1,50 @@
+// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <wallet/psbtwallet.h>
+
+bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, TransactionError& error, bool& complete, int sighash_type, bool sign, bool bip32derivs)
+{
+    LOCK(pwallet->cs_wallet);
+    // Get all of the previous transactions
+    complete = true;
+    for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
+        const CTxIn& txin = psbtx.tx->vin[i];
+        PSBTInput& input = psbtx.inputs.at(i);
+
+        const uint256& txhash = txin.prevout.hash;
+        const auto it = pwallet->mapWallet.find(txhash);
+        if (it != pwallet->mapWallet.end()) {
+            const CWalletTx& wtx = it->second;
+            // We only need the non_witness_utxo, which is a superset of the witness_utxo.
+            //   The signing code will switch to the smaller witness_utxo if this is ok.
+            input.non_witness_utxo = wtx.tx;
+        }
+
+        // Get the Sighash type
+        if (sign && input.sighash_type > 0 && input.sighash_type != sighash_type) {
+            error = TransactionError::SIGHASH_MISMATCH;
+            return false;
+        }
+
+        complete &= SignPSBTInput(HidingSigningProvider(pwallet, !sign, !bip32derivs), *psbtx.tx, input, i, sighash_type);
+    }
+
+    // Fill in the bip32 keypaths and redeemscripts for the outputs so that hardware wallets can identify change
+    for (unsigned int i = 0; i < psbtx.tx->vout.size(); ++i) {
+        const CTxOut& out = psbtx.tx->vout.at(i);
+        PSBTOutput& psbt_out = psbtx.outputs.at(i);
+
+        // Fill a SignatureData with output info
+        SignatureData sigdata;
+        psbt_out.FillSignatureData(sigdata);
+
+        MutableTransactionSignatureCreator creator(psbtx.tx.get_ptr(), 0, out.nValue, 1);
+        ProduceSignature(HidingSigningProvider(pwallet, true, !bip32derivs), creator, out.scriptPubKey, sigdata);
+        psbt_out.FromSignatureData(sigdata);
+    }
+
+    return true;
+}
+
diff --git a/src/wallet/psbtwallet.h b/src/wallet/psbtwallet.h
new file mode 100644
index 0000000000000..b679f5c6ba6c2
--- /dev/null
+++ b/src/wallet/psbtwallet.h
@@ -0,0 +1,36 @@
+// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_WALLET_PSBTWALLET_H
+#define BITCOIN_WALLET_PSBTWALLET_H
+
+#include <node/transaction.h>
+#include <psbt.h>
+#include <primitives/transaction.h>
+#include <wallet/wallet.h>
+
+/**
+ * Fills out a PSBT with information from the wallet. Fills in UTXOs if we have
+ * them. Tries to sign if sign=true. Sets `complete` if the PSBT is now complete
+ * (i.e. has all required signatures or signature-parts, and is ready to
+ * finalize.) Sets `error` and returns false if something goes wrong.
+ *
+ * @param[in]  pwallet pointer to a wallet
+ * @param[in]  &psbtx reference to PartiallySignedTransaction to fill in
+ * @param[out] &error reference to UniValue to fill with error info on failure
+ * @param[out] &complete indicates whether the PSBT is now complete
+ * @param[in]  sighash_type the sighash type to use when signing (if PSBT does not specify)
+ * @param[in]  sign whether to sign or not
+ * @param[in]  bip32derivs whether to fill in bip32 derivation information if available
+ * return true on success, false on error (and fills in `error`)
+ */
+bool FillPSBT(const CWallet* pwallet,
+              PartiallySignedTransaction& psbtx,
+              TransactionError& error,
+              bool& complete,
+              int sighash_type = 1 /* SIGHASH_ALL */,
+              bool sign = true,
+              bool bip32derivs = false);
+
+#endif // BITCOIN_WALLET_PSBTWALLET_H
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 337e491937ea1..ac1899b460110 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -11,6 +11,7 @@
 #include <httpserver.h>
 #include <keepass.h>
 #include <net.h>
+#include <node/transaction.h>
 #include <policy/feerate.h>
 #include <policy/fees.h>
 #include <rpc/mining.h>
@@ -26,6 +27,7 @@
 #include <util/validation.h>
 #include <validation.h>
 #include <wallet/coincontrol.h>
+#include <wallet/psbtwallet.h>
 #include <wallet/rpcwallet.h>
 #include <wallet/wallet.h>
 #include <wallet/walletdb.h>
@@ -4394,49 +4396,6 @@ void AddKeypathToMap(const CWallet* pwallet, const CKeyID& keyID, std::map<CPubK
     hd_keypaths.emplace(vchPubKey, std::move(info));
 }
 
-bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, const CTransaction* txConst, int sighash_type, bool sign, bool bip32derivs)
-{
-    LOCK(pwallet->cs_wallet);
-    // Get all of the previous transactions
-    bool complete = true;
-    for (unsigned int i = 0; i < txConst->vin.size(); ++i) {
-        const CTxIn& txin = txConst->vin[i];
-        PSBTInput& input = psbtx.inputs.at(i);
-
-        // If we don't know about this input, skip it and let someone else deal with it
-        const uint256& txhash = txin.prevout.hash;
-        const auto it = pwallet->mapWallet.find(txhash);
-        if (it != pwallet->mapWallet.end()) {
-            const CWalletTx& wtx = it->second;
-            CTxOut utxo = wtx.tx->vout[txin.prevout.n];
-            // Update both UTXOs from the wallet.
-            input.non_witness_utxo = wtx.tx;
-        }
-
-        // Get the Sighash type
-        if (sign && input.sighash_type > 0 && input.sighash_type != sighash_type) {
-            throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Specified Sighash and sighash in PSBT do not match.");
-        }
-
-        complete &= SignPSBTInput(HidingSigningProvider(pwallet, !sign, !bip32derivs), *psbtx.tx, input, i, sighash_type);
-    }
-
-    // Fill in the bip32 keypaths and redeemscripts for the outputs so that hardware wallets can identify change
-    for (unsigned int i = 0; i < txConst->vout.size(); ++i) {
-        const CTxOut& out = txConst->vout.at(i);
-        PSBTOutput& psbt_out = psbtx.outputs.at(i);
-
-        // Fill a SignatureData with output info
-        SignatureData sigdata;
-        psbt_out.FillSignatureData(sigdata);
-
-        MutableTransactionSignatureCreator creator(psbtx.tx.get_ptr(), 0, out.nValue, 1);
-        ProduceSignature(HidingSigningProvider(pwallet, true, !bip32derivs), creator, out.scriptPubKey, sigdata);
-        psbt_out.FromSignatureData(sigdata);
-    }
-    return complete;
-}
-
 UniValue walletprocesspsbt(const JSONRPCRequest& request)
 {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
@@ -4481,7 +4440,7 @@ UniValue walletprocesspsbt(const JSONRPCRequest& request)
     // Unserialize the transaction
     PartiallySignedTransaction psbtx;
     std::string error;
-    if (!DecodePSBT(psbtx, request.params[0].get_str(), error)) {
+    if (!DecodeBase64PSBT(psbtx, request.params[0].get_str(), error)) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("TX decode failed %s", error));
     }
 
@@ -4495,7 +4454,11 @@ UniValue walletprocesspsbt(const JSONRPCRequest& request)
     // Fill transaction with our data and also sign
     bool sign = request.params[1].isNull() ? true : request.params[1].get_bool();
     bool bip32derivs = request.params[3].isNull() ? false : request.params[3].get_bool();
-    bool complete = FillPSBT(pwallet, psbtx, &txConst, nHashType, sign, bip32derivs);
+    bool complete = true;
+    TransactionError err;
+    if (!FillPSBT(pwallet, psbtx, err, complete, nHashType, sign, bip32derivs)) {
+        throw JSONRPCTransactionError(err);
+    }
 
     UniValue result(UniValue::VOBJ);
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
@@ -4603,7 +4566,11 @@ UniValue walletcreatefundedpsbt(const JSONRPCRequest& request)
 
     // Fill transaction with out data but don't sign
     bool bip32derivs = request.params[4].isNull() ? false : request.params[4].get_bool();
-    FillPSBT(pwallet, psbtx, &txConst, 1, false, bip32derivs);
+    bool complete = true;
+    TransactionError err;
+    if (!FillPSBT(pwallet, psbtx, err, complete, 1, false, bip32derivs)) {
+        throw JSONRPCTransactionError(err);
+    }
 
     // Serialize the PSBT
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
diff --git a/src/wallet/rpcwallet.h b/src/wallet/rpcwallet.h
index 5843687bdf1a2..8da57d0fe87ad 100644
--- a/src/wallet/rpcwallet.h
+++ b/src/wallet/rpcwallet.h
@@ -30,5 +30,4 @@ bool EnsureWalletIsAvailable(CWallet *, bool avoidException);
 
 UniValue getaddressinfo(const JSONRPCRequest& request);
 UniValue signrawtransactionwithwallet(const JSONRPCRequest& request);
-bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, const CTransaction* txConst, int sighash_type = 1, bool sign = true, bool bip32derivs = false);
 #endif //BITCOIN_WALLET_RPCWALLET_H
diff --git a/src/wallet/test/psbt_wallet_tests.cpp b/src/wallet/test/psbt_wallet_tests.cpp
index 916dacb53a402..7ffbe6be3b528 100644
--- a/src/wallet/test/psbt_wallet_tests.cpp
+++ b/src/wallet/test/psbt_wallet_tests.cpp
@@ -5,6 +5,7 @@
 #include <key_io.h>
 #include <script/sign.h>
 #include <util/strencodings.h>
+#include <wallet/psbtwallet.h>
 #include <wallet/rpcwallet.h>
 #include <wallet/wallet.h>
 #include <univalue.h>
@@ -58,7 +59,9 @@ BOOST_AUTO_TEST_CASE(psbt_updater_test)
     const CTransaction txConst(*psbtx.tx);
 
     // Fill transaction with our data
-    FillPSBT(&m_wallet, psbtx, &txConst, 1, false, true);
+    TransactionError err;
+    bool complete = true;
+    FillPSBT(&m_wallet, psbtx, err, complete, false, true);
 
     // Get the final tx
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
diff --git a/test/functional/rpc_psbt.py b/test/functional/rpc_psbt.py
index a51db72216240..9e8fe110ae3a5 100755
--- a/test/functional/rpc_psbt.py
+++ b/test/functional/rpc_psbt.py
@@ -183,5 +183,8 @@ def run_test(self):
         psbt = self.nodes[1].walletcreatefundedpsbt([], [{p2pkh : 1}], 0, {"includeWatching" : True}, True)
         self.nodes[0].decodepsbt(psbt['psbt'])
 
+        # Test decoding error: invalid base64
+        assert_raises_rpc_error(-22, "TX decode failed invalid base64", self.nodes[0].decodepsbt, ";definitely not base64;")
+
 if __name__ == '__main__':
     PSBTTest().main()