psbt: add MuSig2 fields

Co-authored-by: Salvatore Ingala <[email protected]>

Author: Sjors

hwilib/psbt.py

@@ -103,6 +103,9 @@ class PartiallySignedInput:
     PSBT_IN_TAP_BIP32_DERIVATION = 0x16
     PSBT_IN_TAP_INTERNAL_KEY = 0x17
     PSBT_IN_TAP_MERKLE_ROOT = 0x18
+    PSBT_IN_MUSIG2_PARTICIPANT_PUBKEYS = 0x1a
+    PSBT_IN_MUSIG2_PUB_NONCE = 0x1b
+    PSBT_IN_MUSIG2_PARTIAL_SIG = 0x1c
 
     def __init__(self, version: int) -> None:
         self.non_witness_utxo: Optional[CTransaction] = None
@@ -125,6 +128,9 @@ def __init__(self, version: int) -> None:
         self.tap_bip32_paths: Dict[bytes, Tuple[Set[bytes], KeyOriginInfo]] = {}
         self.tap_internal_key = b""
         self.tap_merkle_root = b""
+        self.musig2_participant_pubkeys: Dict[bytes, List[bytes]] = {}
+        self.musig2_pub_nonces: Dict[Tuple[bytes, bytes, Optional[bytes]], bytes] = {}
+        self.musig2_partial_sigs: Dict[Tuple[bytes, bytes, Optional[bytes]], bytes] = {}
         self.unknown: Dict[bytes, bytes] = {}
 
         self.version: int = version
@@ -153,6 +159,9 @@ def set_null(self) -> None:
         self.sequence = None
         self.time_locktime = None
         self.height_locktime = None
+        self.musig2_participant_pubkeys.clear()
+        self.musig2_pub_nonces.clear()
+        self.musig2_partial_sigs.clear()
         self.unknown.clear()
 
     def deserialize(self, f: Readable) -> None:
@@ -335,22 +344,51 @@ def deserialize(self, f: Readable) -> None:
                 for i in range(0, num_hashes):
                     leaf_hashes.add(vs.read(32))
                 self.tap_bip32_paths[xonly] = (leaf_hashes, KeyOriginInfo.deserialize(vs.read()))
-            elif key_type == PartiallySignedInput.PSBT_IN_TAP_INTERNAL_KEY:
+            elif key_type == PartiallySignedInput.PSBT_IN_MUSIG2_PARTICIPANT_PUBKEYS:
                 if key in key_lookup:
-                    raise PSBTSerializationError("Duplicate key, input Taproot internal key already provided")
-                elif len(key) != 1:
-                    raise PSBTSerializationError("Input Taproot internal key key is more than one byte type")
-                self.tap_internal_key = deser_string(f)
-                if len(self.tap_internal_key) != 32:
-                    raise PSBTSerializationError("Input Taproot internal key is not 32 bytes")
-            elif key_type == PartiallySignedInput.PSBT_IN_TAP_MERKLE_ROOT:
+                    raise PSBTSerializationError("Duplicate key, input Musig2 participant pubkeys already provided")
+                elif len(key) != 1 + 33:
+                    raise PSBTSerializationError("Input Musig2 aggregate compressed pubkey is not 33 bytes")
+
+                pubkeys_cat = deser_string(f)
+                if len(pubkeys_cat) == 0:
+                    raise PSBTSerializationError("The list of compressed pubkeys for Musig2 cannot be empty")
+                if (len(pubkeys_cat) % 33) != 0:
+                    raise PSBTSerializationError("The compressed pubkeys for Musig2 must be exactly 33 bytes long")
+                pubkeys = []
+                for i in range(0, len(pubkeys_cat), 33):
+                    pubkeys.append(pubkeys_cat[i: i + 33])
+
+                self.musig2_participant_pubkeys[key[1:]] = pubkeys
+            elif key_type == PartiallySignedInput.PSBT_IN_MUSIG2_PUB_NONCE:
                 if key in key_lookup:
-                    raise PSBTSerializationError("Duplicate key, input Taproot merkle root already provided")
-                elif len(key) != 1:
-                    raise PSBTSerializationError("Input Taproot merkle root key is more than one byte type")
-                self.tap_merkle_root = deser_string(f)
-                if len(self.tap_merkle_root) != 32:
-                    raise PSBTSerializationError("Input Taproot merkle root is not 32 bytes")
+                    raise PSBTSerializationError("Duplicate key, Musig2 public nonce already provided")
+                elif len(key) not in [1 + 33 + 33, 1 + 33 + 33 + 32]:
+                    raise PSBTSerializationError("Invalid key length for Musig2 public nonce")
+
+                providing_pubkey = key[1:1+33]
+                aggregate_pubkey = key[1+33:1+33+33]
+                tapleaf_hash = None if len(key) == 1 + 33 + 33 else key[1+33+33:]
+
+                public_nonces = deser_string(f)
+                if len(public_nonces) != 66:
+                    raise PSBTSerializationError("The length of the public nonces in Musig2 must be exactly 66 bytes")
+
+                self.musig2_pub_nonces[(providing_pubkey, aggregate_pubkey, tapleaf_hash)] = public_nonces
+            elif key_type == PartiallySignedInput.PSBT_IN_MUSIG2_PARTIAL_SIG:
+                if key in key_lookup:
+                    raise PSBTSerializationError("Duplicate key, Musig2 partial signature already provided")
+                elif len(key) not in [1 + 33 + 33, 1 + 33 + 33 + 32]:
+                    raise PSBTSerializationError("Invalid key length for Musig2 partial signature")
+
+                providing_pubkey = key[1:1+33]
+                aggregate_pubkey = key[1+33:1+33+33]
+                tapleaf_hash = None if len(key) == 1 + 33 + 33 else key[1+33+33:]
+
+                partial_sig = deser_string(f)
+                if len(partial_sig) != 32:
+                    raise PSBTSerializationError("The length of the partial signature in Musig2 must be exactly 32 bytes")
+                self.musig2_partial_sigs[(providing_pubkey, aggregate_pubkey, tapleaf_hash)] = partial_sig
             else:
                 if key in self.unknown:
                     raise PSBTSerializationError("Duplicate key, key for unknown value already provided")
@@ -441,6 +479,20 @@ def serialize(self) -> bytes:
             witstack = self.final_script_witness.serialize()
             r += ser_string(witstack)
 
+        for pk, pubkeys in self.musig2_participant_pubkeys.items():
+            r += ser_string(ser_compact_size(PartiallySignedInput.PSBT_IN_MUSIG2_PARTICIPANT_PUBKEYS) + pk)
+            r += ser_string(b''.join(pubkeys))
+
+        for (pk, aggpk, hash), pubnonce in self.musig2_pub_nonces.items():
+            key_value = pk + aggpk + (hash or b'')
+            r += ser_string(ser_compact_size(PartiallySignedInput.PSBT_IN_MUSIG2_PUB_NONCE) + key_value)
+            r += ser_string(pubnonce)
+
+        for (pk, aggpk, hash), partial_sig in self.musig2_partial_sigs.items():
+            key_value = pk + aggpk + (hash or b'')
+            r += ser_string(ser_compact_size(PartiallySignedInput.PSBT_IN_MUSIG2_PARTIAL_SIG) + key_value)
+            r += ser_string(partial_sig)
+
         if self.version >= 2:
             if len(self.prev_txid) != 0:
                 r += ser_string(ser_compact_size(PartiallySignedInput.PSBT_IN_PREVIOUS_TXID))
@@ -483,6 +535,7 @@ class PartiallySignedOutput:
     PSBT_OUT_TAP_INTERNAL_KEY = 0x05
     PSBT_OUT_TAP_TREE = 0x06
     PSBT_OUT_TAP_BIP32_DERIVATION = 0x07
+    PSBT_OUT_MUSIG2_PARTICIPANT_PUBKEYS = 0x08
 
     def __init__(self, version: int) -> None:
         self.redeem_script = b""
@@ -493,6 +546,7 @@ def __init__(self, version: int) -> None:
         self.tap_internal_key = b""
         self.tap_tree = b""
         self.tap_bip32_paths: Dict[bytes, Tuple[Set[bytes], KeyOriginInfo]] = {}
+        self.musig2_participant_pubkeys: Dict[bytes, List[bytes]] = {}
         self.unknown: Dict[bytes, bytes] = {}
 
         self.version: int = version
@@ -509,6 +563,7 @@ def set_null(self) -> None:
         self.tap_bip32_paths.clear()
         self.amount = None
         self.script = b""
+        self.musig2_participant_pubkeys = {}
         self.unknown.clear()
 
     def deserialize(self, f: Readable) -> None:
@@ -589,6 +644,22 @@ def deserialize(self, f: Readable) -> None:
                 for i in range(0, num_hashes):
                     leaf_hashes.add(vs.read(32))
                 self.tap_bip32_paths[xonly] = (leaf_hashes, KeyOriginInfo.deserialize(vs.read()))
+            elif key_type == PartiallySignedOutput.PSBT_OUT_MUSIG2_PARTICIPANT_PUBKEYS:
+                if key in key_lookup:
+                    raise PSBTSerializationError("Duplicate key, output Musig2 participant pubkeys already provided")
+                elif len(key) != 1 + 33:
+                    raise PSBTSerializationError("Output Musig2 aggregate compressed pubkey is not 33 bytes")
+
+                pubkeys_cat = deser_string(f)
+                if len(pubkeys_cat) == 0:
+                    raise PSBTSerializationError("The list of compressed pubkeys for Musig2 cannot be empty")
+                if (len(pubkeys_cat) % 33) != 0:
+                    raise PSBTSerializationError("The compressed pubkeys for Musig2 must be exactly 33 bytes long")
+                pubkeys = []
+                for i in range(0, len(pubkeys_cat), 33):
+                    pubkeys.append(pubkeys_cat[i: i + 33])
+
+                self.musig2_participant_pubkeys[key[1:]] = pubkeys
             else:
                 if key in self.unknown:
                     raise PSBTSerializationError("Duplicate key, key for unknown value already provided")
@@ -646,6 +717,11 @@ def serialize(self) -> bytes:
             value += origin.serialize()
             r += ser_string(value)
 
+        for pk, pubkeys in self.musig2_participant_pubkeys.items():
+            r += ser_string(ser_compact_size(
+                PartiallySignedOutput.PSBT_OUT_MUSIG2_PARTICIPANT_PUBKEYS) + pk)
+            r += ser_string(b''.join(pubkeys))
+
         for key, value in sorted(self.unknown.items()):
             r += ser_string(key)
             r += ser_string(value)