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# Copyright 2016-2018 Yubico AB
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from typing import Optional
import usb.core
import usb.util
from ..exceptions import YubiHsmConnectionError
from . import YhsmBackend
YUBIHSM_VID = 0x1050
YUBIHSM_PID = 0x0030
class UsbBackend(YhsmBackend):
"""A backend for communicating with a YubiHSM directly over USB."""
def __init__(self, serial: Optional[int] = None, timeout: Optional[int] = None):
"""Construct a UsbBackend, connected to a YubiHSM via USB.
:param serial: (optional) The serial number of the YubiHSM to connect to.
:param timeout: (optional) A read/write timeout in seconds.
"""
err = None
for device in usb.core.find(
find_all=True, idVendor=YUBIHSM_VID, idProduct=YUBIHSM_PID
): # type: ignore
try:
cfg = device.get_active_configuration() # type: ignore
except usb.core.USBError:
cfg = None
if cfg is None or cfg.bConfigurationValue != 0x01: # type: ignore
try:
device.set_configuration(0x01) # type: ignore
except usb.core.USBError as e:
err = YubiHsmConnectionError(e)
continue
if serial is None or int(device.serial_number) == serial: # type: ignore
break
usb.util.dispose_resources(device)
else:
raise err or YubiHsmConnectionError("No YubiHSM found.")
# Flush any data waiting to be read
try:
device.read(0x81, 0xFFFF, 10) # type: ignore
except usb.core.USBError:
pass # Errors here are expected, and ignored
self._device = device
# pyusb expects milliseconds or None if no timeout
self.timeout = None if timeout is None else timeout * 1000
def transceive(self, msg):
try:
sent = self._device.write(0x01, msg, self.timeout) # type: ignore
if sent != len(msg):
raise YubiHsmConnectionError("Error sending data over USB.")
if sent % 64 == 0:
if self._device.write(0x01, b"", self.timeout) != 0: # type: ignore
raise YubiHsmConnectionError("Error sending data over USB.")
return bytes(bytearray(self._device.read(0x81, 0xFFFF, self.timeout))) # type: ignore
except usb.core.USBError as e:
raise YubiHsmConnectionError(e)
def close(self):
usb.util.dispose_resources(self._device)
def __repr__(self):
v_int = self._device.bcdDevice # type: ignore
version = "{}.{}.{}".format((v_int >> 8) & 0xF, (v_int >> 4) & 0xF, v_int & 0xF)
return (
"{0.__class__.__name__}(version={1}, serial={0._device.serial_number})"
).format(self, version)
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