signing/multisig: minor refactoring

src/apps/wallet/sign_tx/multisig.py

@@ -8,22 +8,42 @@ from apps.wallet.sign_tx.writers import *
 from apps.common.hash_writer import *
 
 
+class MultisigFingerprint:
+    def __init__(self):
+        self.fingerprint = None  # multisig fingerprint bytes
+        self.mismatch = False  # flag if multisig input fingerprints are equal
+
+    def add(self, multisig: MultisigRedeemScriptType):
+        fp = multisig_fingerprint(multisig)
+        assert fp is not None
+        if self.fingerprint is None:
+            self.fingerprint = fp
+        elif self.fingerprint != fp:
+            self.mismatch = True
+
+    def matches(self, multisig: MultisigRedeemScriptType):
+        fp = multisig_fingerprint(multisig)
+        assert fp is not None
+        if self.mismatch is False and self.fingerprint == fp:
+            return True
+        else:
+            return False
+
+
 def multisig_fingerprint(multisig: MultisigRedeemScriptType) -> bytes:
     pubkeys = multisig.pubkeys
     m = multisig.m
     n = len(pubkeys)
 
-    if n < 1 or n > 15:
+    if n < 1 or n > 15 or m < 1 or m > 15:
-        return None
+        raise SigningError(FailureType.DataError,
-    if m < 1 or m > 15:
+                           'Invalid multisig parameters')
-        return None
 
     for hd in pubkeys:
         d = hd.node
-        if len(d.public_key) != 33:
+        if len(d.public_key) != 33 or len(d.chain_code) != 32:
-            return None
+            raise SigningError(FailureType.DataError,
-        if len(d.chain_code) != 32:
+                               'Invalid multisig parameters')
-            return None
 
     # casting to bytes(), sorting on bytearray() is not supported in MicroPython
     pubkeys = sorted(pubkeys, key=lambda hd: bytes(hd.node.public_key))

src/apps/wallet/sign_tx/signing.py

@@ -51,7 +51,9 @@ async def check_tx_fee(tx: SignTx, root):
     # are the same as in Phase 2.  it is thus not required to fully hash the
     # tx, as the SignTx info is streamed only once
     h_first = HashWriter(sha256)  # not a real tx hash
-    bip143 = Bip143()
+
+    bip143 = Bip143()  # bip143 transaction hashing
+    multifp = MultisigFingerprint()  # control fp of multisig inputs
     weight = TxWeightCalculator(tx.inputs_count, tx.outputs_count)
 
     txo_bin = TxOutputBinType()
@@ -64,8 +66,6 @@ async def check_tx_fee(tx: SignTx, root):
     change_out = 0  # change output amount
     wallet_path = []  # common prefix of input paths
     segwit = {}  # dict of booleans stating if input is segwit
-    multisig_fp = bytes()  # multisig fingerprint
-    multisig_fp_mismatch = False  # flag if multisig input fingerprints are equal
 
     for i in range(tx.inputs_count):
         # STAGE_REQUEST_1_INPUT
@@ -77,11 +77,7 @@ async def check_tx_fee(tx: SignTx, root):
         bip143.add_sequence(txi)
 
         if txi.multisig:
-            fp = multisig_fingerprint(txi.multisig)
+            multifp.add(txi.multisig)
-            if not len(multisig_fp):
-                multisig_fp = fp
-            elif multisig_fp != fp:
-                multisig_fp_mismatch = True
 
         if coin.force_bip143:
             is_bip143 = (txi.script_type == InputScriptType.SPENDADDRESS)
@@ -95,7 +91,8 @@ async def check_tx_fee(tx: SignTx, root):
             segwit_in += txi.amount
             total_in += txi.amount
 
-        elif txi.script_type in [InputScriptType.SPENDWITNESS, InputScriptType.SPENDP2SHWITNESS]:
+        elif txi.script_type in (InputScriptType.SPENDWITNESS,
+                                 InputScriptType.SPENDP2SHWITNESS):
             if not coin.segwit:
                 raise SigningError(FailureType.DataError,
                                    'Segwit not enabled on this coin')
@@ -106,7 +103,8 @@ async def check_tx_fee(tx: SignTx, root):
             segwit_in += txi.amount
             total_in += txi.amount
 
-        elif txi.script_type in [InputScriptType.SPENDADDRESS, InputScriptType.SPENDMULTISIG]:
+        elif txi.script_type in (InputScriptType.SPENDADDRESS,
+                                 InputScriptType.SPENDMULTISIG):
             segwit[i] = False
             total_in += await get_prevtx_output_value(
                 tx_req, txi.prev_hash, txi.prev_index)
@@ -121,7 +119,7 @@ async def check_tx_fee(tx: SignTx, root):
         txo_bin.amount = txo.amount
         txo_bin.script_pubkey = output_derive_script(txo, coin, root)
         weight.add_output(txo_bin.script_pubkey)
-        if (change_out == 0) and is_change(txo, wallet_path, segwit_in, multisig_fp, multisig_fp_mismatch):
+        if (change_out == 0) and is_change(txo, wallet_path, segwit_in, multifp):
             change_out = txo.amount
         elif not await confirm_output(txo, coin):
             raise SigningError(FailureType.ActionCancelled,
@@ -248,8 +246,9 @@ async def sign_tx(tx: SignTx, root):
                     # for the signing process the script_sig is equal
                     # to the previous tx's scriptPubKey (P2PKH) or a redeem script (P2SH)
                     if txi_sign.script_type == InputScriptType.SPENDMULTISIG:
-                        txi_sign.script_sig = script_multisig(multisig_get_pubkeys(txi_sign.multisig),
+                        txi_sign.script_sig = script_multisig(
-                                                              txi_sign.multisig.m)
+                            multisig_get_pubkeys(txi_sign.multisig),
+                            txi_sign.multisig.m)
                     elif txi_sign.script_type == InputScriptType.SPENDADDRESS:
                         txi_sign.script_sig = output_script_p2pkh(
                             ecdsa_hash_pubkey(key_sign_pub))
@@ -554,8 +553,8 @@ def ecdsa_sign(node, digest: bytes) -> bytes:
     return sigder
 
 
-def is_change(txo: TxOutputType, wallet_path, segwit_in: int, multisig_fp: bytes, multisig_fp_mismatch: bool) -> bool:
+def is_change(txo: TxOutputType, wallet_path, segwit_in: int, multifp: MultisigFingerprint) -> bool:
     if txo.multisig:
-        if multisig_fp_mismatch or (multisig_fp != multisig_fingerprint(txo.multisig)):
+        if not multifp.matches(txo.multisig):
             return False
     return output_is_change(txo, wallet_path, segwit_in)