Merge #13960: Fix PSBT deserialization of 0-input transactions

bd19cc78cfc455cf06e120adb0d12c2f96ba8fca Serialize non-witness utxo as a non-witness tx but always deserialize as witness (Andrew Chow)
43811e63380d803e037de69dc0567aae590fa109 Fix PSBT deserialization of 0-input transactions (Andrew Chow)

Pull request description:

  0-input transactions can be ambiguously deserialized as being witness transactions. Since the unsigned transaction is never serialized as a witness transaction as it has no witnesses, we should always deserialize it as a non-witness transaction and set the serialization flags as such.

  When a transaction is serliazed for the non-witness-utxo, it is always a valid network transaction and thus it should be always be deserialized as a witness transaction and the deserialzation flags are set as such.

  Fixes #13958

Tree-SHA512: 1937b3cb2618534478d4f533541fb9efce3cb5badb5d1964bfe19400f4aacc6c8ecedaf1f20d26b20baf94f81fd07dfb15b3b08089ecbd63aeecbc18c7c48086

2 files changed, 13 insertions, 4 deletions

diff --git a/src/script/sign.h b/src/script/sign.h
index 24cddda51b..80fda617e9 100644
--- a/src/script/sign.h
+++ b/src/script/sign.h
@@ -223,7 +223,8 @@ struct PSBTInput
         // If there is a non-witness utxo, then don't add the witness one.
         if (non_witness_utxo) {
             SerializeToVector(s, PSBT_IN_NON_WITNESS_UTXO);
-            SerializeToVector(s, non_witness_utxo);
+            OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion() | SERIALIZE_TRANSACTION_NO_WITNESS);
+            SerializeToVector(os, non_witness_utxo);
         } else if (!witness_utxo.IsNull()) {
             SerializeToVector(s, PSBT_IN_WITNESS_UTXO);
             SerializeToVector(s, witness_utxo);
@@ -297,13 +298,17 @@ struct PSBTInput
             // 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);
+                    // Set the stream to unserialize with witness since this is always a valid network transaction
+                    OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion() & ~SERIALIZE_TRANSACTION_NO_WITNESS);
+                    UnserializeFromVector(os, non_witness_utxo);
                     break;
+                }
                 case PSBT_IN_WITNESS_UTXO:
                     if (!witness_utxo.IsNull()) {
                         throw std::ios_base::failure("Duplicate Key, input witness utxo already provided");
@@ -547,7 +552,8 @@ struct PartiallySignedTransaction
         SerializeToVector(s, PSBT_GLOBAL_UNSIGNED_TX);
 
         // Write serialized tx to a stream
-        SerializeToVector(s, *tx);
+        OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion() | SERIALIZE_TRANSACTION_NO_WITNESS);
+        SerializeToVector(os, *tx);
 
         // Write the unknown things
         for (auto& entry : unknown) {
@@ -601,7 +607,9 @@ struct PartiallySignedTransaction
                         throw std::ios_base::failure("Global unsigned tx key is more than one byte type");
                     }
                     CMutableTransaction mtx;
-                    UnserializeFromVector(s, mtx);
+                    // Set the stream to serialize with non-witness since this should always be non-witness
+                    OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion() | SERIALIZE_TRANSACTION_NO_WITNESS);
+                    UnserializeFromVector(os, mtx);
                     tx = std::move(mtx);
                     // Make sure that all scriptSigs and scriptWitnesses are empty
                     for (const CTxIn& txin : tx->vin) {
diff --git a/src/streams.h b/src/streams.h
index 2dcca6646d..096ebfc9c2 100644
--- a/src/streams.h
+++ b/src/streams.h
@@ -61,6 +61,7 @@ public:
 
     int GetVersion() const { return nVersion; }
     int GetType() const { return nType; }
+    size_t size() const { return stream->size(); }
 };
 
 template<typename S>