trezor-firmware/python/src/trezorlib/transport/__init__.py

# This file is part of the Trezor project.
#
# Copyright (C) 2012-2022 SatoshiLabs and contributors
#
# This library is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License version 3
# as published by the Free Software Foundation.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the License along with this library.
# If not, see <https://www.gnu.org/licenses/lgpl-3.0.html>.

import logging
from typing import (
    TYPE_CHECKING,
    Iterable,
    List,
    Optional,
    Sequence,
    Tuple,
    Type,
    TypeVar,
)

from ..exceptions import TrezorException

if TYPE_CHECKING:
    from ..models import TrezorModel

    T = TypeVar("T", bound="Transport")

LOG = logging.getLogger(__name__)

UDEV_RULES_STR = """
Do you have udev rules installed?
https://github.com/trezor/trezor-common/blob/master/udev/51-trezor.rules
""".strip()


MessagePayload = Tuple[int, bytes]


class TransportException(TrezorException):
    pass


class DeviceIsBusy(TransportException):
    pass


class Transport:
    """Raw connection to a Trezor device.

    Transport subclass represents a kind of communication link: Trezor Bridge, WebUSB
    or USB-HID connection, or UDP socket of listening emulator(s).
    It can also enumerate devices available over this communication link, and return
    them as instances.

    Transport instance is a thing that:
    - can be identified and requested by a string URI-like path
    - can open and close sessions, which enclose related operations
    - can read and write protobuf messages

    You need to implement a new Transport subclass if you invent a new way to connect
    a Trezor device to a computer.
    """

    PATH_PREFIX: str
    ENABLED = False

    def __str__(self) -> str:
        return self.get_path()

    def get_path(self) -> str:
        raise NotImplementedError

    def begin_session(self) -> None:
        raise NotImplementedError

    def end_session(self) -> None:
        raise NotImplementedError

    def read(self) -> MessagePayload:
        raise NotImplementedError

    def write(self, message_type: int, message_data: bytes) -> None:
        raise NotImplementedError

    def find_debug(self: "T") -> "T":
        raise NotImplementedError

    @classmethod
    def enumerate(
        cls: Type["T"], models: Optional[Iterable["TrezorModel"]] = None
    ) -> Iterable["T"]:
        raise NotImplementedError

    @classmethod
    def find_by_path(cls: Type["T"], path: str, prefix_search: bool = False) -> "T":
        for device in cls.enumerate():
            if (
                path is None
                or device.get_path() == path
                or (prefix_search and device.get_path().startswith(path))
            ):
                return device

        raise TransportException(f"{cls.PATH_PREFIX} device not found: {path}")


def all_transports() -> Iterable[Type["Transport"]]:
    from .bridge import BridgeTransport
    from .hid import HidTransport
    from .udp import UdpTransport
    from .webusb import WebUsbTransport

    transports: Tuple[Type["Transport"], ...] = (
        BridgeTransport,
        HidTransport,
        UdpTransport,
        WebUsbTransport,
    )
    return set(t for t in transports if t.ENABLED)


def enumerate_devices(
    models: Optional[Iterable["TrezorModel"]] = None,
) -> Sequence["Transport"]:
    devices: List["Transport"] = []
    for transport in all_transports():
        name = transport.__name__
        try:
            found = list(transport.enumerate(models))
            LOG.info(f"Enumerating {name}: found {len(found)} devices")
            devices.extend(found)
        except NotImplementedError:
            LOG.error(f"{name} does not implement device enumeration")
        except Exception as e:
            excname = e.__class__.__name__
            LOG.error(f"Failed to enumerate {name}. {excname}: {e}")
    return devices


def get_transport(
    path: Optional[str] = None, prefix_search: bool = False
) -> "Transport":
    if path is None:
        try:
            return next(iter(enumerate_devices()))
        except StopIteration:
            raise TransportException("No Trezor device found") from None

    # Find whether B is prefix of A (transport name is part of the path)
    # or A is prefix of B (path is a prefix, or a name, of transport).
    # This naively expects that no two transports have a common prefix.
    def match_prefix(a: str, b: str) -> bool:
        return a.startswith(b) or b.startswith(a)

    LOG.info(
        "looking for device by {}: {}".format(
            "prefix" if prefix_search else "full path", path
        )
    )
    transports = [t for t in all_transports() if match_prefix(path, t.PATH_PREFIX)]
    if transports:
        return transports[0].find_by_path(path, prefix_search=prefix_search)

    raise TransportException(f"Could not find device by path: {path}")