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psbt: add MuSig2 fields #784

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psbt: add MuSig2 fields #784

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92 changes: 92 additions & 0 deletions hwilib/psbt.py
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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
Expand Down Expand Up @@ -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:
Expand Down Expand Up @@ -351,6 +360,51 @@ def deserialize(self, f: Readable) -> None:
self.tap_merkle_root = deser_string(f)
if len(self.tap_merkle_root) != 32:
raise PSBTSerializationError("Input Taproot merkle root is not 32 bytes")
elif key_type == PartiallySignedInput.PSBT_IN_MUSIG2_PARTICIPANT_PUBKEYS:
if key in key_lookup:
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, 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")
Expand Down Expand Up @@ -441,6 +495,20 @@ 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))
Expand Down Expand Up @@ -483,6 +551,7 @@ 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""
Expand All @@ -493,6 +562,7 @@ 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
Expand All @@ -509,6 +579,7 @@ 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:
Expand Down Expand Up @@ -589,6 +660,22 @@ 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")
Expand Down Expand Up @@ -646,6 +733,11 @@ 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)
Expand Down
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