Create wallet RPCs for PSBT

walletprocesspsbt takes a PSBT format transaction, updates the
PSBT with any inputs related to this wallet, signs, and finalizes
the transaction. There is also an option to not sign and just
update.

walletcreatefundedpsbt creates a PSBT from user provided data
in the same form as createrawtransaction. It also funds the transaction
and takes an options argument in the same form as fundrawtransaction.
The resulting PSBT is blank with no input or output data filled
in.

2 files changed, 331 insertions, 0 deletions

diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 7cd9f4cfd3..6d2499ee8a 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -4390,6 +4390,332 @@ UniValue sethdseed(const JSONRPCRequest& request)
     return NullUniValue;
 }
 
+bool ParseHDKeypath(std::string keypath_str, std::vector<uint32_t>& keypath)
+{
+    std::stringstream ss(keypath_str);
+    std::string item;
+    bool first = true;
+    while (std::getline(ss, item, '/')) {
+        if (item.compare("m") == 0) {
+            if (first) {
+                first = false;
+                continue;
+            }
+            return false;
+        }
+        // Finds whether it is hardened
+        uint32_t path = 0;
+        size_t pos = item.find("'");
+        if (pos != std::string::npos) {
+            // The hardened tick can only be in the last index of the string
+            if (pos != item.size() - 1) {
+                return false;
+            }
+            path |= 0x80000000;
+            item = item.substr(0, item.size() - 1); // Drop the last character which is the hardened tick
+        }
+
+        // Ensure this is only numbers
+        if (item.find_first_not_of( "0123456789" ) != std::string::npos) {
+            return false;
+        }
+        uint32_t number;
+        ParseUInt32(item, &number);
+        path |= number;
+
+        keypath.push_back(path);
+        first = false;
+    }
+    return true;
+}
+
+void AddKeypathToMap(const CWallet* pwallet, const CKeyID& keyID, std::map<CPubKey, std::vector<uint32_t>>& hd_keypaths)
+{
+    CPubKey vchPubKey;
+    if (!pwallet->GetPubKey(keyID, vchPubKey)) {
+        return;
+    }
+    CKeyMetadata meta;
+    auto it = pwallet->mapKeyMetadata.find(keyID);
+    if (it != pwallet->mapKeyMetadata.end()) {
+        meta = it->second;
+    }
+    std::vector<uint32_t> keypath;
+    if (!meta.hdKeypath.empty()) {
+        if (!ParseHDKeypath(meta.hdKeypath, keypath)) {
+            throw JSONRPCError(RPC_INTERNAL_ERROR, "Internal keypath is broken");
+        }
+        // Get the proper master key id
+        CKey key;
+        pwallet->GetKey(meta.hd_seed_id, key);
+        CExtKey masterKey;
+        masterKey.SetSeed(key.begin(), key.size());
+        // Add to map
+        keypath.insert(keypath.begin(), ReadLE32(masterKey.key.GetPubKey().GetID().begin()));
+    } else { // Single pubkeys get the master fingerprint of themselves
+        keypath.insert(keypath.begin(), ReadLE32(vchPubKey.GetID().begin()));
+    }
+    hd_keypaths.emplace(vchPubKey, keypath);
+}
+
+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];
+            input.non_witness_utxo = wtx.tx;
+            input.witness_utxo = utxo;
+        }
+
+        // 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.");
+        }
+
+        SignatureData sigdata;
+        if (sign) {
+            complete &= SignPSBTInput(*pwallet, *psbtx.tx, input, sigdata, i, sighash_type);
+        } else {
+            complete &= SignPSBTInput(PublicOnlySigningProvider(pwallet), *psbtx.tx, input, sigdata, i, sighash_type);
+        }
+
+        // Drop the unnecessary UTXO
+        if (sigdata.witness) {
+            input.non_witness_utxo = nullptr;
+        } else {
+            input.witness_utxo.SetNull();
+        }
+
+        // Get public key paths
+        if (bip32derivs) {
+            for (const auto& pubkey_it : sigdata.misc_pubkeys) {
+                AddKeypathToMap(pwallet, pubkey_it.first, input.hd_keypaths);
+            }
+        }
+    }
+
+    // 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);
+
+        // Dummy tx so we can use ProduceSignature to get stuff out
+        CMutableTransaction dummy_tx;
+        dummy_tx.vin.push_back(CTxIn());
+        dummy_tx.vout.push_back(CTxOut());
+
+        // Fill a SignatureData with output info
+        SignatureData sigdata;
+        psbt_out.FillSignatureData(sigdata);
+
+        MutableTransactionSignatureCreator creator(psbtx.tx.get_ptr(), 0, out.nValue, 1);
+        ProduceSignature(*pwallet, creator, out.scriptPubKey, sigdata);
+        psbt_out.FromSignatureData(sigdata);
+
+        // Get public key paths
+        if (bip32derivs) {
+            for (const auto& pubkey_it : sigdata.misc_pubkeys) {
+                AddKeypathToMap(pwallet, pubkey_it.first, psbt_out.hd_keypaths);
+            }
+        }
+    }
+    return complete;
+}
+
+UniValue walletprocesspsbt(const JSONRPCRequest& request)
+{
+    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
+    CWallet* const pwallet = wallet.get();
+
+    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
+        return NullUniValue;
+    }
+
+    if (request.fHelp || request.params.size() < 1 || request.params.size() > 4)
+        throw std::runtime_error(
+            "walletprocesspsbt \"psbt\" ( sign \"sighashtype\" bip32derivs )\n"
+            "\nUpdate a PSBT with input information from our wallet and then sign inputs\n"
+            "that we can sign for.\n"
+            + HelpRequiringPassphrase(pwallet) + "\n"
+
+            "\nArguments:\n"
+            "1. \"psbt\"                      (string, required) The transaction base64 string\n"
+            "2. sign                          (boolean, optional, default=true) Also sign the transaction when updating\n"
+            "3. \"sighashtype\"            (string, optional, default=ALL) The signature hash type to sign with if not specified by the PSBT. Must be one of\n"
+            "       \"ALL\"\n"
+            "       \"NONE\"\n"
+            "       \"SINGLE\"\n"
+            "       \"ALL|ANYONECANPAY\"\n"
+            "       \"NONE|ANYONECANPAY\"\n"
+            "       \"SINGLE|ANYONECANPAY\"\n"
+            "4. bip32derivs                    (boolean, optiona, default=false) If true, includes the BIP 32 derivation paths for public keys if we know them\n"
+
+            "\nResult:\n"
+            "{\n"
+            "  \"psbt\" : \"value\",          (string) The base64-encoded partially signed transaction\n"
+            "  \"complete\" : true|false,   (boolean) If the transaction has a complete set of signatures\n"
+            "  ]\n"
+            "}\n"
+
+            "\nExamples:\n"
+            + HelpExampleCli("walletprocesspsbt", "\"psbt\"")
+        );
+
+    RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VBOOL, UniValue::VSTR});
+
+    // Unserialize the transaction
+    PartiallySignedTransaction psbtx;
+    std::string error;
+    if (!DecodePSBT(psbtx, request.params[0].get_str(), error)) {
+        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("TX decode failed %s", error));
+    }
+
+    // Get the sighash type
+    int nHashType = ParseSighashString(request.params[2]);
+
+    // Use CTransaction for the constant parts of the
+    // transaction to avoid rehashing.
+    const CTransaction txConst(*psbtx.tx);
+
+    // 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);
+
+    UniValue result(UniValue::VOBJ);
+    CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
+    ssTx << psbtx;
+    result.push_back(Pair("psbt", EncodeBase64((unsigned char*)ssTx.data(), ssTx.size())));
+    result.push_back(Pair("complete", complete));
+
+    return result;
+}
+
+UniValue walletcreatefundedpsbt(const JSONRPCRequest& request)
+{
+    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
+    CWallet* const pwallet = wallet.get();
+
+    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
+        return NullUniValue;
+    }
+
+    if (request.fHelp || request.params.size() < 2 || request.params.size() > 6)
+        throw std::runtime_error(
+                            "walletcreatefundedpsbt [{\"txid\":\"id\",\"vout\":n},...] [{\"address\":amount},{\"data\":\"hex\"},...] ( locktime ) ( replaceable ) ( options bip32derivs )\n"
+                            "\nCreates and funds a transaction in the Partially Signed Transaction format. Inputs will be added if supplied inputs are not enough\n"
+                            "Implements the Creator and Updater roles.\n"
+                            "\nArguments:\n"
+                            "1. \"inputs\"                (array, required) A json array of json objects\n"
+                            "     [\n"
+                            "       {\n"
+                            "         \"txid\":\"id\",      (string, required) The transaction id\n"
+                            "         \"vout\":n,         (numeric, required) The output number\n"
+                            "         \"sequence\":n      (numeric, optional) The sequence number\n"
+                            "       } \n"
+                            "       ,...\n"
+                            "     ]\n"
+                            "2. \"outputs\"               (array, required) a json array with outputs (key-value pairs)\n"
+                            "   [\n"
+                            "    {\n"
+                            "      \"address\": x.xxx,    (obj, optional) A key-value pair. The key (string) is the bitcoin address, the value (float or string) is the amount in " + CURRENCY_UNIT + "\n"
+                            "    },\n"
+                            "    {\n"
+                            "      \"data\": \"hex\"        (obj, optional) A key-value pair. The key must be \"data\", the value is hex encoded data\n"
+                            "    }\n"
+                            "    ,...                     More key-value pairs of the above form. For compatibility reasons, a dictionary, which holds the key-value pairs directly, is also\n"
+                            "                             accepted as second parameter.\n"
+                            "   ]\n"
+                            "3. locktime                  (numeric, optional, default=0) Raw locktime. Non-0 value also locktime-activates inputs\n"
+                            "4. replaceable               (boolean, optional, default=false) Marks this transaction as BIP125 replaceable.\n"
+                            "                             Allows this transaction to be replaced by a transaction with higher fees. If provided, it is an error if explicit sequence numbers are incompatible.\n"
+                            "5. options                 (object, optional)\n"
+                            "   {\n"
+                            "     \"changeAddress\"          (string, optional, default pool address) The bitcoin address to receive the change\n"
+                            "     \"changePosition\"         (numeric, optional, default random) The index of the change output\n"
+                            "     \"change_type\"            (string, optional) The output type to use. Only valid if changeAddress is not specified. Options are \"legacy\", \"p2sh-segwit\", and \"bech32\". Default is set by -changetype.\n"
+                            "     \"includeWatching\"        (boolean, optional, default false) Also select inputs which are watch only\n"
+                            "     \"lockUnspents\"           (boolean, optional, default false) Lock selected unspent outputs\n"
+                            "     \"feeRate\"                (numeric, optional, default not set: makes wallet determine the fee) Set a specific fee rate in " + CURRENCY_UNIT + "/kB\n"
+                            "     \"subtractFeeFromOutputs\" (array, optional) A json array of integers.\n"
+                            "                              The fee will be equally deducted from the amount of each specified output.\n"
+                            "                              The outputs are specified by their zero-based index, before any change output is added.\n"
+                            "                              Those recipients will receive less bitcoins than you enter in their corresponding amount field.\n"
+                            "                              If no outputs are specified here, the sender pays the fee.\n"
+                            "                                  [vout_index,...]\n"
+                            "     \"replaceable\"            (boolean, optional) Marks this transaction as BIP125 replaceable.\n"
+                            "                              Allows this transaction to be replaced by a transaction with higher fees\n"
+                            "     \"conf_target\"            (numeric, optional) Confirmation target (in blocks)\n"
+                            "     \"estimate_mode\"          (string, optional, default=UNSET) The fee estimate mode, must be one of:\n"
+                            "         \"UNSET\"\n"
+                            "         \"ECONOMICAL\"\n"
+                            "         \"CONSERVATIVE\"\n"
+                            "   }\n"
+                            "6. bip32derivs                    (boolean, optiona, default=false) If true, includes the BIP 32 derivation paths for public keys if we know them\n"
+                            "\nResult:\n"
+                            "{\n"
+                            "  \"psbt\": \"value\",        (string)  The resulting raw transaction (base64-encoded string)\n"
+                            "  \"fee\":       n,         (numeric) Fee in " + CURRENCY_UNIT + " the resulting transaction pays\n"
+                            "  \"changepos\": n          (numeric) The position of the added change output, or -1\n"
+                            "}\n"
+                            "\nExamples:\n"
+                            "\nCreate a transaction with no inputs\n"
+                            + HelpExampleCli("walletcreatefundedpsbt", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" \"[{\\\"data\\\":\\\"00010203\\\"}]\"")
+                            );
+
+    RPCTypeCheck(request.params, {
+        UniValue::VARR,
+        UniValueType(), // ARR or OBJ, checked later
+        UniValue::VNUM,
+        UniValue::VBOOL,
+        UniValue::VOBJ
+        }, true
+    );
+
+    CAmount fee;
+    int change_position;
+    CMutableTransaction rawTx = ConstructTransaction(request.params[0], request.params[1], request.params[2], request.params[3]);
+    FundTransaction(pwallet, rawTx, fee, change_position, request.params[4]);
+
+    // Make a blank psbt
+    PartiallySignedTransaction psbtx;
+    psbtx.tx = rawTx;
+    for (unsigned int i = 0; i < rawTx.vin.size(); ++i) {
+        psbtx.inputs.push_back(PSBTInput());
+    }
+    for (unsigned int i = 0; i < rawTx.vout.size(); ++i) {
+        psbtx.outputs.push_back(PSBTOutput());
+    }
+
+    // Use CTransaction for the constant parts of the
+    // transaction to avoid rehashing.
+    const CTransaction txConst(*psbtx.tx);
+
+    // Fill transaction with out data but don't sign
+    bool bip32derivs = request.params[5].isNull() ? false : request.params[5].get_bool();
+    FillPSBT(pwallet, psbtx, &txConst, 1, false, bip32derivs);
+
+    // Serialize the PSBT
+    CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
+    ssTx << psbtx;
+
+    UniValue result(UniValue::VOBJ);
+    result.pushKV("psbt", EncodeBase64((unsigned char*)ssTx.data(), ssTx.size()));
+    result.pushKV("fee", ValueFromAmount(fee));
+    result.pushKV("changepos", change_position);
+    return result;
+}
+
 extern UniValue abortrescan(const JSONRPCRequest& request); // in rpcdump.cpp
 extern UniValue dumpprivkey(const JSONRPCRequest& request); // in rpcdump.cpp
 extern UniValue importprivkey(const JSONRPCRequest& request);
@@ -4406,6 +4732,8 @@ static const CRPCCommand commands[] =
 { //  category              name                                actor (function)                argNames
     //  --------------------- ------------------------          -----------------------         ----------
     { "rawtransactions",    "fundrawtransaction",               &fundrawtransaction,            {"hexstring","options","iswitness"} },
+    { "wallet",             "walletprocesspsbt",                &walletprocesspsbt,             {"psbt","sign","sighashtype","bip32derivs"} },
+    { "wallet",             "walletcreatefundedpsbt",           &walletcreatefundedpsbt,        {"inputs","outputs","locktime","replaceable","options","bip32derivs"} },
     { "hidden",             "resendwallettransactions",         &resendwallettransactions,      {} },
     { "wallet",             "abandontransaction",               &abandontransaction,            {"txid"} },
     { "wallet",             "abortrescan",                      &abortrescan,                   {} },
diff --git a/src/wallet/rpcwallet.h b/src/wallet/rpcwallet.h
index b841f3e424..64556b5824 100644
--- a/src/wallet/rpcwallet.h
+++ b/src/wallet/rpcwallet.h
@@ -11,6 +11,8 @@ class CRPCTable;
 class CWallet;
 class JSONRPCRequest;
 class UniValue;
+struct PartiallySignedTransaction;
+class CTransaction;
 
 void RegisterWalletRPCCommands(CRPCTable &t);
 
@@ -28,4 +30,5 @@ 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