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- # Copyright 2016 Google Inc. All Rights Reserved.
- #
- # 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.
- """This module implements the low level device API.
- This module exposes a low level SecurityKey class,
- representing the physical security key device.
- """
- import logging
- from pyu2f import apdu
- from pyu2f import errors
- class SecurityKey(object):
- """Low level api for talking to a security key.
- This class implements the low level api specified in FIDO
- U2F for talking to a security key.
- """
- def __init__(self, transport):
- self.transport = transport
- self.use_legacy_format = False
- self.logger = logging.getLogger('pyu2f.hardware')
- def CmdRegister(self, challenge_param, app_param):
- """Register security key.
- Ask the security key to register with a particular origin & client.
- Args:
- challenge_param: Arbitrary 32 byte challenge string.
- app_param: Arbitrary 32 byte applciation parameter.
- Returns:
- A binary structure containing the key handle, attestation, and a
- signature over that by the attestation key. The precise format
- is dictated by the FIDO U2F specs.
- Raises:
- TUPRequiredError: A Test of User Precense is required to proceed.
- ApduError: Something went wrong on the device.
- """
- self.logger.debug('CmdRegister')
- if len(challenge_param) != 32 or len(app_param) != 32:
- raise errors.InvalidRequestError()
- body = bytearray(challenge_param + app_param)
- response = self.InternalSendApdu(apdu.CommandApdu(
- 0,
- apdu.CMD_REGISTER,
- 0x03, # Per the U2F reference code tests
- 0x00,
- body))
- response.CheckSuccessOrRaise()
- return response.body
- def CmdAuthenticate(self,
- challenge_param,
- app_param,
- key_handle,
- check_only=False):
- """Attempt to obtain an authentication signature.
- Ask the security key to sign a challenge for a particular key handle
- in order to authenticate the user.
- Args:
- challenge_param: SHA-256 hash of client_data object as a bytes
- object.
- app_param: SHA-256 hash of the app id as a bytes object.
- key_handle: The key handle to use to issue the signature as a bytes
- object.
- check_only: If true, only check if key_handle is valid.
- Returns:
- A binary structure containing the key handle, attestation, and a
- signature over that by the attestation key. The precise format
- is dictated by the FIDO U2F specs.
- Raises:
- TUPRequiredError: If check_only is False, a Test of User Precense
- is required to proceed. If check_only is True, this means
- the key_handle is valid.
- InvalidKeyHandleError: The key_handle is not valid for this device.
- ApduError: Something else went wrong on the device.
- """
- self.logger.debug('CmdAuthenticate')
- if len(challenge_param) != 32 or len(app_param) != 32:
- raise errors.InvalidRequestError()
- control = 0x07 if check_only else 0x03
- body = bytearray(challenge_param + app_param +
- bytearray([len(key_handle)]) + key_handle)
- response = self.InternalSendApdu(apdu.CommandApdu(
- 0, apdu.CMD_AUTH, control, 0x00, body))
- response.CheckSuccessOrRaise()
- return response.body
- def CmdVersion(self):
- """Obtain the version of the device and test transport format.
- Obtains the version of the device and determines whether to use ISO
- 7816-4 or the U2f variant. This function should be called at least once
- before CmdAuthenticate or CmdRegister to make sure the object is using the
- proper transport for the device.
- Returns:
- The version of the U2F protocol in use.
- """
- self.logger.debug('CmdVersion')
- response = self.InternalSendApdu(apdu.CommandApdu(
- 0, apdu.CMD_VERSION, 0x00, 0x00))
- if not response.IsSuccess():
- raise errors.ApduError(response.sw1, response.sw2)
- return response.body
- def CmdBlink(self, time):
- self.logger.debug('CmdBlink')
- self.transport.SendBlink(time)
- def CmdWink(self):
- self.logger.debug('CmdWink')
- self.transport.SendWink()
- def CmdPing(self, data):
- self.logger.debug('CmdPing')
- return self.transport.SendPing(data)
- def InternalSendApdu(self, apdu_to_send):
- """Send an APDU to the device.
- Sends an APDU to the device, possibly falling back to the legacy
- encoding format that is not ISO7816-4 compatible.
- Args:
- apdu_to_send: The CommandApdu object to send
- Returns:
- The ResponseApdu object constructed out of the devices reply.
- """
- response = None
- if not self.use_legacy_format:
- response = apdu.ResponseApdu(self.transport.SendMsgBytes(
- apdu_to_send.ToByteArray()))
- if response.sw1 == 0x67 and response.sw2 == 0x00:
- # If we failed using the standard format, retry with the
- # legacy format.
- self.use_legacy_format = True
- return self.InternalSendApdu(apdu_to_send)
- else:
- response = apdu.ResponseApdu(self.transport.SendMsgBytes(
- apdu_to_send.ToLegacyU2FByteArray()))
- return response
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