Merge pull request #2 from RenWal/feature/pbkdf2-login

Support PBKDF2 login on FritzOS 7.25

src/FritzboxInterface.py

@@ -2,7 +2,8 @@
 """
  FritzboxInterface - A munin plugin for Linux to monitor AVM Fritzbox
  Copyright (C) 2015 Christian Stade-Schuldt
- Copyright (C) 2019 Rene Walendy
+ Copyright (C) 2021 Rene Walendy
+ Copyright (c) 2021 Oliver Edelmann
  Author: Christian Stade-Schuldt, Rene Walendy
  Like Munin, this plugin is licensed under the GNU GPL v2 license
  http://www.opensource.org/licenses/GPL-2.0
@@ -69,6 +70,32 @@ def postPageWithLogin(self, page: str, data={}) -> str:
 
  return jsonData
 
+ # Code from https://avm.de/fileadmin/user_upload/Global/Service/Schnittstellen/AVM_Technical_Note_-_Session_ID_deutsch_2021-05-03.pdf
+ def __calculate_pbkdf2_response(self, challenge) -> str:
+ """ Calculate the response for a given challenge via PBKDF2 """
+ challenge_parts = challenge.split("$")
+ # Extract all necessary values encoded into the challenge
+ iter1 = int(challenge_parts[1])
+ salt1 = bytes.fromhex(challenge_parts[2])
+ iter2 = int(challenge_parts[3])
+ salt2 = bytes.fromhex(challenge_parts[4])
+ # Hash twice, once with static salt...
+ # Once with dynamic salt.
+ hash1 = hashlib.pbkdf2_hmac("sha256", self.config.password.encode(), salt1, iter1)
+ hash2 = hashlib.pbkdf2_hmac("sha256", hash1, salt2, iter2)
+ return f"{challenge_parts[4]}${hash2.hex()}"
+
+ # Code from https://avm.de/fileadmin/user_upload/Global/Service/Schnittstellen/AVM_Technical_Note_-_Session_ID_deutsch_2021-05-03.pdf
+ def __calculate_md5_response(self, challenge) -> str:
+ """ Calculate the response for a challenge using legacy MD5 """
+ response = challenge + "-" + self.config.password
+ # the legacy response needs utf_16_le encoding
+ response = response.encode("utf_16_le")
+ md5_sum = hashlib.md5()
+ md5_sum.update(response)
+ response = challenge + "-" + md5_sum.hexdigest()
+ return response
+
  def __getSessionId(self) -> str:
  """Obtains the session id after login into the Fritzbox.
  See https://avm.de/fileadmin/user_upload/Global/Service/Schnittstellen/AVM_Technical_Note_-_Session_ID.pdf
@@ -79,7 +106,7 @@ def __getSessionId(self) -> str:
 
  headers = {"Accept": "application/xml", "Content-Type": "text/plain"}
 
- url = '{}/login_sid.lua'.format(self.__baseUri)
+ url = '{}/login_sid.lua?version=2'.format(self.__baseUri)
  try:
  r = requests.get(url, headers=headers, verify=self.config.certificateFile)
  r.raise_for_status()
@@ -92,10 +119,10 @@ def __getSessionId(self) -> str:
  session_id = root.xpath('//SessionInfo/SID/text()')[0]
  if session_id == "0000000000000000":
  challenge = root.xpath('//SessionInfo/Challenge/text()')[0]
- challenge_bf = ('{}-{}'.format(challenge, self.config.password)).encode('utf-16le')
- m = hashlib.md5()
- m.update(challenge_bf)
- response_bf = '{}-{}'.format(challenge, m.hexdigest().lower())
+ if challenge.startswith("2$"): # we received a PBKDF2 challenge
+  response_bf = self.__calculate_pbkdf2_response(challenge)
+ else: # or fall back to MD5
+  response_bf = self.__calculate_md5_response(challenge)
  params['response'] = response_bf
  else:
  return session_id