mirror of
https://github.com/trezor/trezor-firmware.git
synced 2024-11-24 00:18:26 +00:00
133 lines
4.1 KiB
Python
133 lines
4.1 KiB
Python
import struct
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from . import mapping
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class NotImplementedException(Exception):
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pass
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class ConnectionError(Exception):
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pass
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class Transport(object):
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def __init__(self, device, *args, **kwargs):
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self.device = device
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self.session_depth = 0
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self._open()
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def _open(self):
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raise NotImplementedException("Not implemented")
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def _close(self):
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raise NotImplementedException("Not implemented")
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def _write(self, msg, protobuf_msg):
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raise NotImplementedException("Not implemented")
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def _read(self):
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raise NotImplementedException("Not implemented")
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def _session_begin(self):
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pass
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def _session_end(self):
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pass
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def ready_to_read(self):
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"""
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Returns True if there is data to be read from the transport. Otherwise, False.
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"""
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raise NotImplementedException("Not implemented")
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def session_begin(self):
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"""
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Apply a lock to the device in order to preform synchronous multistep "conversations" with the device. For example, before entering the transaction signing workflow, one begins a session. After the transaction is complete, the session may be ended.
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"""
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if self.session_depth == 0:
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self._session_begin()
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self.session_depth += 1
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def session_end(self):
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"""
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End a session. Se session_begin for an in depth description of TREZOR sessions.
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"""
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self.session_depth -= 1
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self.session_depth = max(0, self.session_depth)
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if self.session_depth == 0:
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self._session_end()
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def close(self):
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"""
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Close the connection to the physical device or file descriptor represented by the Transport.
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"""
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self._close()
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def write(self, msg):
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"""
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Write mesage to tansport. msg should be a member of a valid `protobuf class <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_ with a SerializeToString() method.
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"""
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ser = msg.SerializeToString()
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header = struct.pack(">HL", mapping.get_type(msg), len(ser))
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self._write(b"##" + header + ser, msg)
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def read(self):
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"""
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If there is data available to be read from the transport, reads the data and tries to parse it as a protobuf message. If the parsing succeeds, return a protobuf object.
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Otherwise, returns None.
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"""
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if not self.ready_to_read():
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return None
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data = self._read()
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if data is None:
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return None
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return self._parse_message(data)
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def read_blocking(self):
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"""
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Same as read, except blocks untill data is available to be read.
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"""
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while True:
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data = self._read()
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if data != None:
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break
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return self._parse_message(data)
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def _parse_message(self, data):
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(msg_type, data) = data
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if msg_type == 'protobuf':
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return data
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else:
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inst = mapping.get_class(msg_type)()
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inst.ParseFromString(data)
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return inst
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def _read_headers(self, read_f):
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# Try to read headers until some sane value are detected
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is_ok = False
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while not is_ok:
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# Align cursor to the beginning of the header ("##")
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c = read_f.read(1)
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i = 0
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while c != b"#":
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i += 1
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if i >= 64:
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# timeout
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raise Exception("Timed out while waiting for the magic character")
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c = read_f.read(1)
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if read_f.read(1) != b"#":
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# Second character must be # to be valid header
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raise Exception("Second magic character is broken")
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# Now we're most likely on the beginning of the header
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try:
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headerlen = struct.calcsize(">HL")
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(msg_type, datalen) = struct.unpack(">HL", read_f.read(headerlen))
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break
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except:
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raise Exception("Cannot parse header length")
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return (msg_type, datalen)
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