223 lines
6.2 KiB
Python
223 lines
6.2 KiB
Python
#!/usr/bin/env python
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import string
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from random import choice
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import base64
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from hashlib import sha1
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import hmac
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import requests
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class YubicoWS(object):
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register_ws = 'https://upgrade.yubico.com/getapikey/?format=json'
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api_ws = None
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_protocol = 'https'
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_servers = [
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'api.yubico.com',
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'api2.yubico.com',
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'api3.yubico.com',
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'api4.yubico.com',
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'api5.yubico.com',
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]
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_server = None
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_api_ws = '%s://%s/wsapi/2.0/'
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_errors = {
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'BAD_OTP': 'The OTP is invalid format.',
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'REPLAYED_OTP': 'The OTP has already been seen by the service.',
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'BAD_SIGNATURE': 'The HMAC signature verification failed.',
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'MISSING_PARAMETER': 'The request lacks a parameter.',
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'NO_SUCH_CLIENT': 'The request id does not exist.',
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'OPERATION_NOT_ALLOWED': 'The request id is not allowed '
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'to verify OTPs.',
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'BACKEND_ERROR': 'Unexpected error in our server. Please contact '
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'us if you see this error.',
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# 2.0
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'NOT_ENOUGH_ANSWERS': 'Server could not get requested number of syncs '
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'during before timeout',
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'REPLAYED_REQUEST': 'Server has seen the OTP/Nonce combination before',
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}
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def __init__(self, **kwargs):
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self._protocol = kwargs.get('protocol', self._protocol)
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self._server = kwargs.get('server', None)
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self.select_server()
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def select_server(self):
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"Select server if provided, otherwise uses one from the list"
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if self._server and self._server in self._servers:
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self.api_ws = self._api_ws % (self._protocol, self._server)
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else:
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self.api_ws = self._api_ws % (
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self._protocol,
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choice(self._servers)
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)
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def register_api_key(self, email, otp):
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"Registers an API Key with the servers"
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data = {
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'email': email,
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'otp': str.lower(otp)
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}
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response = requests.post(self.register_ws, data)
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ws_response = response.json()
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if not ws_response['status']:
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raise YubicoWSError(ws_response['error'])
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return ws_response
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def verify(self, yubikey_id, otp, key=None):
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"Verifies the provided OTP with the server"
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endpoint = 'verify'
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url = self.api_ws + endpoint
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# Check otp format
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if not (len(otp) > 32 and len(otp) < 48):
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raise OTPIncorrectFormat()
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nonce = self.generate_nonce()
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data = {
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'id': str(yubikey_id),
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'otp': str.lower(otp),
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'nonce': nonce
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}
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# Use API key for signing the message if key is provided
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if key:
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data['h'] = self.sign(data, key)
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response = requests.get(url, params=data)
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ws_response = self.parse_ws_response(response.text)
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if ws_response['status'] == 'OK':
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# Check if response is valid
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if not (ws_response['nonce'] == data['nonce']
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and ws_response['otp'] == otp):
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raise YubicoWSInvalidResponse()
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if key:
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signature = self.sign(ws_response, key)
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if ws_response['h'] != signature:
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raise YubicoWSResponseBadSignature(
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"The signature sent by the server is invalid"
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)
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else:
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raise YubicoWSError(self._errors[ws_response['status']])
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return ws_response
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def sign(self, data, key):
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"Signs the message with the provided key"
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# Sort k=v dict
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params = []
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for k in sorted(data.keys()):
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if k != 'h': # Just in case
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key_value = "%s=%s" % (k, data[k])
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params.append(key_value)
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# Join as urlparams
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parameters = '&'.join(params)
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# hmac-sha1
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hashed_string = hmac.new(
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base64.b64decode(key),
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parameters,
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sha1
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).digest()
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# base64 encode
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signature = base64.b64encode(hashed_string)
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return signature
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def parse_ws_response(self, text):
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"Parses the API key=value response into a dict"
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data = {}
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for line in text.split():
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key, value = line.split('=', 1)
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data[key.strip()] = value.strip()
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return data
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def generate_nonce(self):
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"Generates a random string"
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chars = string.ascii_lowercase + string.digits
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return ''.join(choice(chars) for x in range(40))
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class Yubikey(object):
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id = None
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key = None
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prefix = None
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_last_result = False
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def __init__(self, yubikey_id=None, key=None, **kwargs):
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self.ws = YubicoWS(**kwargs)
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if yubikey_id:
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self.id = yubikey_id
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if key:
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self.key = key
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def register(self, email, otp):
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"Registers this yubikey"
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result = False
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if not self.id:
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credentials = self.ws.register_api_key(email, otp)
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if credentials['status']:
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self.id = credentials['id']
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self.key = credentials['key']
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result = True
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return result
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def verify(self, otp):
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"Verify an OTP to check if its valid"
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result = False
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if self.id:
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self.get_prefix(otp)
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try:
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self.ws.verify(self.id, otp, key=self.key)
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result = True
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except (YubicoWSResponseBadSignature, YubicoWSError):
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result = False
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self._last_result = result
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return result
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def get_prefix(self, otp):
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"Get prefix from an OTP if present"
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if len(otp) > 32:
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self.prefix = str.lower(otp[:-32])
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class YubicoWSError(Exception):
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def __init__(self, message=None):
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self.msg = "Web Service responded with an error: %s" % message
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def __str__(self):
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return repr(self.msg)
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class YubicoWSInvalidResponse(Exception):
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msg = 'Response from the server is invalid'
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class WSResponseError(Exception):
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def __str__(self):
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return repr(self.msg)
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class OTPIncorrectFormat(Exception):
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pass
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class YubicoWSResponseBadSignature(Exception):
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pass
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