171 lines
5.6 KiB
Python
171 lines
5.6 KiB
Python
# Copyright 2016 Google Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""This module implements the low level device API.
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This module exposes a low level SecurityKey class,
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representing the physical security key device.
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"""
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import logging
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from pyu2f import apdu
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from pyu2f import errors
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class SecurityKey(object):
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"""Low level api for talking to a security key.
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This class implements the low level api specified in FIDO
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U2F for talking to a security key.
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"""
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def __init__(self, transport):
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self.transport = transport
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self.use_legacy_format = False
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self.logger = logging.getLogger('pyu2f.hardware')
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def CmdRegister(self, challenge_param, app_param):
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"""Register security key.
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Ask the security key to register with a particular origin & client.
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Args:
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challenge_param: Arbitrary 32 byte challenge string.
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app_param: Arbitrary 32 byte applciation parameter.
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Returns:
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A binary structure containing the key handle, attestation, and a
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signature over that by the attestation key. The precise format
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is dictated by the FIDO U2F specs.
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Raises:
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TUPRequiredError: A Test of User Precense is required to proceed.
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ApduError: Something went wrong on the device.
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"""
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self.logger.debug('CmdRegister')
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if len(challenge_param) != 32 or len(app_param) != 32:
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raise errors.InvalidRequestError()
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body = bytearray(challenge_param + app_param)
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response = self.InternalSendApdu(apdu.CommandApdu(
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0,
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apdu.CMD_REGISTER,
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0x03, # Per the U2F reference code tests
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0x00,
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body))
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response.CheckSuccessOrRaise()
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return response.body
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def CmdAuthenticate(self,
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challenge_param,
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app_param,
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key_handle,
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check_only=False):
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"""Attempt to obtain an authentication signature.
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Ask the security key to sign a challenge for a particular key handle
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in order to authenticate the user.
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Args:
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challenge_param: SHA-256 hash of client_data object as a bytes
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object.
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app_param: SHA-256 hash of the app id as a bytes object.
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key_handle: The key handle to use to issue the signature as a bytes
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object.
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check_only: If true, only check if key_handle is valid.
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Returns:
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A binary structure containing the key handle, attestation, and a
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signature over that by the attestation key. The precise format
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is dictated by the FIDO U2F specs.
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Raises:
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TUPRequiredError: If check_only is False, a Test of User Precense
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is required to proceed. If check_only is True, this means
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the key_handle is valid.
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InvalidKeyHandleError: The key_handle is not valid for this device.
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ApduError: Something else went wrong on the device.
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"""
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self.logger.debug('CmdAuthenticate')
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if len(challenge_param) != 32 or len(app_param) != 32:
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raise errors.InvalidRequestError()
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control = 0x07 if check_only else 0x03
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body = bytearray(challenge_param + app_param +
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bytearray([len(key_handle)]) + key_handle)
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response = self.InternalSendApdu(apdu.CommandApdu(
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0, apdu.CMD_AUTH, control, 0x00, body))
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response.CheckSuccessOrRaise()
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return response.body
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def CmdVersion(self):
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"""Obtain the version of the device and test transport format.
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Obtains the version of the device and determines whether to use ISO
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7816-4 or the U2f variant. This function should be called at least once
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before CmdAuthenticate or CmdRegister to make sure the object is using the
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proper transport for the device.
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Returns:
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The version of the U2F protocol in use.
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"""
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self.logger.debug('CmdVersion')
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response = self.InternalSendApdu(apdu.CommandApdu(
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0, apdu.CMD_VERSION, 0x00, 0x00))
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if not response.IsSuccess():
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raise errors.ApduError(response.sw1, response.sw2)
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return response.body
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def CmdBlink(self, time):
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self.logger.debug('CmdBlink')
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self.transport.SendBlink(time)
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def CmdWink(self):
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self.logger.debug('CmdWink')
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self.transport.SendWink()
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def CmdPing(self, data):
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self.logger.debug('CmdPing')
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return self.transport.SendPing(data)
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def InternalSendApdu(self, apdu_to_send):
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"""Send an APDU to the device.
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Sends an APDU to the device, possibly falling back to the legacy
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encoding format that is not ISO7816-4 compatible.
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Args:
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apdu_to_send: The CommandApdu object to send
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Returns:
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The ResponseApdu object constructed out of the devices reply.
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"""
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response = None
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if not self.use_legacy_format:
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response = apdu.ResponseApdu(self.transport.SendMsgBytes(
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apdu_to_send.ToByteArray()))
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if response.sw1 == 0x67 and response.sw2 == 0x00:
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# If we failed using the standard format, retry with the
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# legacy format.
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self.use_legacy_format = True
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return self.InternalSendApdu(apdu_to_send)
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else:
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response = apdu.ResponseApdu(self.transport.SendMsgBytes(
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apdu_to_send.ToLegacyU2FByteArray()))
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return response
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