wallet: add layout_sign_tx

It's now possible to sign transactions through myTREZOR.

src/apps/wallet/__init__.py

@@ -1,7 +1,7 @@
 from trezor.wire import register_type, protobuf_handler
 from trezor.utils import unimport
 from trezor.messages.wire_types import \
-    GetPublicKey, GetAddress, SignMessage
+    GetPublicKey, GetAddress, SignTx, SignMessage
 
 
 @unimport
@@ -16,6 +16,12 @@ def dispatch_GetAddress(*args, **kwargs):
     return layout_get_address(*args, **kwargs)
 
 
+@unimport
+def dispatch_SignTx(*args, **kwargs):
+    from .layout_sign_tx import layout_sign_tx
+    return layout_sign_tx(*args, **kwargs)
+
+
 @unimport
 def dispatch_SignMessage(*args, **kwargs):
     from .layout_sign_message import layout_sign_message
@@ -25,4 +31,5 @@ def dispatch_SignMessage(*args, **kwargs):
 def boot():
     register_type(GetPublicKey, protobuf_handler, dispatch_GetPublicKey)
     register_type(GetAddress, protobuf_handler, dispatch_GetAddress)
+    register_type(SignTx, protobuf_handler, dispatch_SignTx)
     register_type(SignMessage, protobuf_handler, dispatch_SignMessage)

src/apps/wallet/layout_sign_tx.py

@@ -0,0 +1,41 @@
+from trezor.utils import unimport
+from trezor import wire
+
+
+async def confirm_output(output):
+    return True
+
+
+async def confirm_total(total_out, fee):
+    return True
+
+
+@unimport
+async def layout_sign_tx(message, session_id):
+    from ..common.seed import get_root_node
+    from ..common import signtx
+
+    from trezor.messages import RequestType
+    from trezor.messages.TxRequest import TxRequest
+    from trezor.messages.wire_types import TxAck
+
+    root = await get_root_node(session_id)
+
+    signer = signtx.sign_tx(message, root)
+    res = None
+    while True:
+        try:
+            req = signer.send(res)
+        except signtx.SigningError as e:
+            raise wire.FailureError(*e.args)
+        if isinstance(req, TxRequest):
+            if req.request_type == RequestType.TXFINISHED:
+                break
+            res = await wire.reply_message(session_id, req, TxAck)
+        elif isinstance(req, signtx.UiConfirmOutput):
+            res = await confirm_output(req.output)
+        elif isinstance(req, signtx.UiConfirmTotal):
+            res = await confirm_total(req.total_out, req.fee)
+        else:
+            raise ValueError('Invalid signing instruction')
+    return req