Split DecodePSBT into Base64 and Raw versions

Split up DecodePSBT, which both decodes base64 and then deserializes a
PartiallySignedTransaction, into two functions: DecodeBase64PSBT, which retains
the old behavior, and DecodeRawPSBT, which only performs the deserialization.

Add a test for base64 decoding failure.

Author: gwillen

src/core_io.h

@@ -37,7 +37,11 @@ bool DecodeHexBlockHeader(CBlockHeader&, const std::string& hex_header);
  */
 bool ParseHashStr(const std::string& strHex, uint256& result);
 std::vector<unsigned char> ParseHexUV(const UniValue& v, const std::string& strName);
-NODISCARD bool DecodePSBT(PartiallySignedTransaction& psbt, const std::string& base64_tx, std::string& error);
+
+//! 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);
 int ParseSighashString(const UniValue& sighash);
 
 // core_write.cpp

src/core_read.cpp

@@ -176,10 +176,20 @@ 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()) {

src/rpc/rawtransaction.cpp

@@ -1323,7 +1323,7 @@ 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));
     }
 
@@ -1524,7 +1524,7 @@ 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);
@@ -1581,7 +1581,7 @@ 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));
     }
 

src/wallet/rpcwallet.cpp

@@ -4046,7 +4046,7 @@ 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));
     }
 

test/functional/rpc_psbt.py

@@ -293,5 +293,8 @@ 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()