core/sign_tx: Reuse get_prevtx_output_value() in Decred.

core/src/apps/wallet/sign_tx/decred.py

@@ -4,11 +4,12 @@ from micropython import const
 from trezor.crypto.hashlib import blake256
 from trezor.messages import FailureType, InputScriptType
 from trezor.messages.SignTx import SignTx
+from trezor.messages.TransactionType import TransactionType
 from trezor.messages.TxInputType import TxInputType
 from trezor.messages.TxOutputBinType import TxOutputBinType
 from trezor.messages.TxOutputType import TxOutputType
 from trezor.messages.TxRequestSerializedType import TxRequestSerializedType
-from trezor.utils import HashWriter
+from trezor.utils import HashWriter, ensure
 
 from apps.common import coininfo, seed
 from apps.wallet.sign_tx import addresses, helpers, multisig, progress, scripts, writers
@@ -20,6 +21,9 @@ DECRED_SERIALIZE_WITNESS_SIGNING = const(3 << 16)
 
 DECRED_SIGHASHALL = const(1)
 
+if False:
+    from typing import Union
+
 
 class DecredPrefixHasher:
     """
@@ -57,15 +61,19 @@ class Decred(Bitcoin):
     def initialize(
         self, tx: SignTx, keychain: seed.Keychain, coin: coininfo.CoinInfo
     ) -> None:
+        ensure(coin.decred)
         super().initialize(tx, keychain, coin)
 
         # This is required because the last serialized output obtained in
-        # `check_fee` will only be sent to the client in `sign_tx`
+        # phase 1 will only be sent to the client in phase 2
         self.last_output_bytes = None  # type: bytearray
 
     def init_hash143(self) -> None:
         self.hash143 = DecredPrefixHasher(self.tx)  # pseudo BIP-0143 prefix hashing
 
+    def create_hash_writer(self) -> HashWriter:
+        return HashWriter(blake256())
+
     async def phase1(self) -> None:
         await super().phase1()
         self.hash143.add_locktime_expiry(self.tx)
@@ -75,7 +83,7 @@ class Decred(Bitcoin):
         w_txi = writers.empty_bytearray(8 if i == 0 else 0 + 9 + len(txi.prev_hash))
         if i == 0:  # serializing first input => prepend headers
             self.write_sign_tx_header(w_txi, False)
-        writers.write_tx_input_decred(w_txi, txi)
+        self.write_tx_input(w_txi, txi)
         self.tx_req.serialized = TxRequestSerializedType(None, None, w_txi)
 
     async def phase1_confirm_output(
@@ -127,7 +135,7 @@ class Decred(Bitcoin):
             else:
                 raise SigningError("Unsupported input script type")
 
-            h_witness = HashWriter(blake256())
+            h_witness = self.create_hash_writer()
             writers.write_uint32(
                 h_witness, self.tx.version | DECRED_SERIALIZE_WITNESS_SIGNING
             )
@@ -143,7 +151,7 @@ class Decred(Bitcoin):
                 h_witness, double=self.coin.sign_hash_double, reverse=False
             )
 
-            h_sign = HashWriter(blake256())
+            h_sign = self.create_hash_writer()
             writers.write_uint32(h_sign, DECRED_SIGHASHALL)
             writers.write_bytes_fixed(h_sign, prefix_hash, writers.TX_HASH_SIZE)
             writers.write_bytes_fixed(h_sign, witness_hash, writers.TX_HASH_SIZE)
@@ -175,36 +183,7 @@ class Decred(Bitcoin):
 
         await helpers.request_tx_finish(self.tx_req)
 
-    async def get_prevtx_output_value(self, prev_hash: bytes, prev_index: int) -> int:
+    def check_prevtx_output(self, txo_bin: TxOutputBinType) -> None:
-        total_out = 0  # sum of output amounts
-
-        # STAGE_REQUEST_2_PREV_META
-        tx = await helpers.request_tx_meta(self.tx_req, self.coin, prev_hash)
-
-        if tx.outputs_cnt <= prev_index:
-            raise SigningError(
-                FailureType.ProcessError, "Not enough outputs in previous transaction."
-            )
-
-        txh = HashWriter(blake256())
-        writers.write_uint32(txh, tx.version | DECRED_SERIALIZE_NO_WITNESS)
-        writers.write_varint(txh, tx.inputs_cnt)
-
-        for i in range(tx.inputs_cnt):
-            # STAGE_REQUEST_2_PREV_INPUT
-            txi = await helpers.request_tx_input(self.tx_req, i, self.coin, prev_hash)
-            writers.write_tx_input_decred(txh, txi)
-
-        writers.write_varint(txh, tx.outputs_cnt)
-
-        for o in range(tx.outputs_cnt):
-            # STAGE_REQUEST_2_PREV_OUTPUT
-            txo_bin = await helpers.request_tx_output(
-                self.tx_req, o, self.coin, prev_hash
-            )
-            writers.write_tx_output(txh, txo_bin)
-            if o == prev_index:
-                total_out += txo_bin.amount
         if (
             txo_bin.decred_script_version is not None
             and txo_bin.decred_script_version != 0
@@ -214,15 +193,20 @@ class Decred(Bitcoin):
                 "Cannot use utxo that has script_version != 0",
             )
 
-        writers.write_uint32(txh, tx.lock_time)
+    def write_tx_input(self, w: writers.Writer, i: TxInputType) -> None:
-        writers.write_uint32(txh, tx.expiry)
+        writers.write_tx_input_decred(w, i)
 
-        if (
+    def write_sign_tx_header(self, w: writers.Writer, has_segwit: bool) -> None:
-            writers.get_tx_hash(txh, double=self.coin.sign_hash_double, reverse=True)
+        writers.write_uint32(w, self.tx.version)  # nVersion
-            != prev_hash
+        writers.write_varint(w, self.tx.inputs_count)
-        ):
-            raise SigningError(
-                FailureType.ProcessError, "Encountered invalid prev_hash"
-            )
 
-        return total_out
+    def write_tx_header(
+        self, w: writers.Writer, tx: Union[SignTx, TransactionType], has_segwit: bool
+    ) -> None:
+        writers.write_uint32(w, tx.version | DECRED_SERIALIZE_NO_WITNESS)
+
+    async def write_prev_tx_footer(
+        self, w: writers.Writer, tx: TransactionType, prev_hash: bytes
+    ) -> None:
+        writers.write_uint32(w, tx.lock_time)
+        writers.write_uint32(w, tx.expiry)

core/src/apps/wallet/sign_tx/signing.py

@@ -98,13 +98,16 @@ class Bitcoin:
         # h_first is used to make sure the inputs and outputs streamed in Phase 1
         # are the same as in Phase 2 when signing legacy inputs.  it is thus not required to fully hash the
         # tx, as the SignTx info is streamed only once
-        self.h_first = utils.HashWriter(sha256())  # not a real tx hash
+        self.h_first = self.create_hash_writer()  # not a real tx hash
 
         self.init_hash143()
 
     def init_hash143(self) -> None:
         self.hash143 = segwit_bip143.Bip143()  # BIP-0143 transaction hashing
 
+    def create_hash_writer(self) -> utils.HashWriter:
+        return utils.HashWriter(sha256())
+
     async def phase1(self) -> None:
         weight = tx_weight.TxWeightCalculator(
             self.tx.inputs_count, self.tx.outputs_count
@@ -267,7 +270,7 @@ class Bitcoin:
         )
         if i_sign == 0:  # serializing first input => prepend headers
             self.write_sign_tx_header(w_txi, True)
-        writers.write_tx_input(w_txi, txi_sign)
+        self.write_tx_input(w_txi, txi_sign)
         self.tx_req.serialized = TxRequestSerializedType(serialized_tx=w_txi)
 
     async def phase2_sign_segwit_input(self, i: int) -> Tuple[bytearray, bytes]:
@@ -308,9 +311,9 @@ class Bitcoin:
 
     async def phase2_sign_nonsegwit_input(self, i_sign: int) -> None:
         # hash of what we are signing with this input
-        h_sign = utils.HashWriter(sha256())
+        h_sign = self.create_hash_writer()
         # same as h_first, checked before signing the digest
-        h_second = utils.HashWriter(sha256())
+        h_second = self.create_hash_writer()
 
         self.write_sign_tx_header(h_sign, has_segwit=False)
 
@@ -341,7 +344,7 @@ class Bitcoin:
                     )
             else:
                 txi.script_sig = bytes()
-            writers.write_tx_input(h_sign, txi)
+            self.write_tx_input(h_sign, txi)
 
         writers.write_varint(h_sign, self.tx.outputs_count)
 
@@ -382,7 +385,7 @@ class Bitcoin:
         )
         if i_sign == 0:  # serializing first input => prepend headers
             self.write_sign_tx_header(w_txi_sign, True in self.segwit.values())
-        writers.write_tx_input(w_txi_sign, txi_sign)
+        self.write_tx_input(w_txi_sign, txi_sign)
         self.tx_req.serialized = TxRequestSerializedType(i_sign, signature, w_txi_sign)
 
     async def phase2_serialize_output(self, i: int) -> bytearray:
@@ -410,7 +413,7 @@ class Bitcoin:
                 FailureType.ProcessError, "Not enough outputs in previous transaction."
             )
 
-        txh = utils.HashWriter(sha256())
+        txh = self.create_hash_writer()
 
         # TODO set has_segwit correctly
         self.write_tx_header(txh, tx, has_segwit=False)
@@ -419,7 +422,7 @@ class Bitcoin:
         for i in range(tx.inputs_cnt):
             # STAGE_REQUEST_2_PREV_INPUT
             txi = await helpers.request_tx_input(self.tx_req, i, self.coin, prev_hash)
-            writers.write_tx_input(txh, txi)
+            self.write_tx_input(txh, txi)
 
         writers.write_varint(txh, tx.outputs_cnt)
 
@@ -431,6 +434,7 @@ class Bitcoin:
             writers.write_tx_output(txh, txo_bin)
             if o == prev_index:
                 amount_out = txo_bin.amount
+                self.check_prevtx_output(txo_bin)
 
         await self.write_prev_tx_footer(txh, tx, prev_hash)
 
@@ -444,6 +448,9 @@ class Bitcoin:
 
         return amount_out
 
+    def check_prevtx_output(self, txo_bin: TxOutputBinType) -> None:
+        pass
+
     # TX Helpers
     # ===
 
@@ -451,6 +458,9 @@ class Bitcoin:
         SIGHASH_ALL = const(0x01)
         return SIGHASH_ALL
 
+    def write_tx_input(self, w: writers.Writer, i: TxInputType) -> None:
+        writers.write_tx_input(w, i)
+
     def write_sign_tx_header(self, w: writers.Writer, has_segwit: bool) -> None:
         self.write_tx_header(w, self.tx, has_segwit)
         writers.write_varint(w, self.tx.inputs_count)
@@ -551,7 +561,7 @@ class Bitcoin:
             if i.multisig:
                 # p2wsh in p2sh
                 pubkeys = multisig.multisig_get_pubkeys(i.multisig)
-                witness_script_hasher = utils.HashWriter(sha256())
+                witness_script_hasher = self.create_hash_writer()
                 scripts.write_output_script_multisig(
                     witness_script_hasher, pubkeys, i.multisig.m
                 )