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ttt/pywidevine/L3/cdm/cdm.py

363 lines
15 KiB

import base64
import os
import time
import binascii
from google.protobuf.message import DecodeError
from google.protobuf import text_format
from pywidevine.L3.cdm.formats import wv_proto2_pb2 as wv_proto2
from pywidevine.L3.cdm.session import Session
from pywidevine.L3.cdm.key import Key
from Cryptodome.Random import get_random_bytes
from Cryptodome.Random import random
from Cryptodome.Cipher import PKCS1_OAEP, AES
from Cryptodome.Hash import CMAC, SHA256, HMAC, SHA1
from Cryptodome.PublicKey import RSA
from Cryptodome.Signature import pss
from Cryptodome.Util import Padding
import logging
class Cdm:
def __init__(self):
self.logger = logging.getLogger(__name__)
self.sessions = {}
def open_session(self, init_data_b64, device, raw_init_data = None, offline=False):
self.logger.debug("open_session(init_data_b64={}, device={}".format(init_data_b64, device))
self.logger.info("opening new cdm session")
if device.session_id_type == 'android':
# format: 16 random hexdigits, 2 digit counter, 14 0s
rand_ascii = ''.join(random.choice('ABCDEF0123456789') for _ in range(16))
counter = '01' # this resets regularly so its fine to use 01
rest = '00000000000000'
session_id = rand_ascii + counter + rest
session_id = session_id.encode('ascii')
elif device.session_id_type == 'chrome':
rand_bytes = get_random_bytes(16)
session_id = rand_bytes
else:
# other formats NYI
self.logger.error("device type is unusable")
return 1
if raw_init_data and isinstance(raw_init_data, (bytes, bytearray)):
# used for NF key exchange, where they don't provide a valid PSSH
init_data = raw_init_data
self.raw_pssh = True
else:
init_data = self._parse_init_data(init_data_b64)
self.raw_pssh = False
if init_data:
new_session = Session(session_id, init_data, device, offline)
else:
self.logger.error("unable to parse init data")
return 1
self.sessions[session_id] = new_session
self.logger.info("session opened and init data parsed successfully")
return session_id
def _parse_init_data(self, init_data_b64):
parsed_init_data = wv_proto2.WidevineCencHeader()
try:
self.logger.debug("trying to parse init_data directly")
parsed_init_data.ParseFromString(base64.b64decode(init_data_b64)[32:])
except DecodeError:
self.logger.debug("unable to parse as-is, trying with removed pssh box header")
try:
id_bytes = parsed_init_data.ParseFromString(base64.b64decode(init_data_b64)[32:])
except DecodeError:
self.logger.error("unable to parse, unsupported init data format")
return None
self.logger.debug("init_data:")
for line in text_format.MessageToString(parsed_init_data).splitlines():
self.logger.debug(line)
return parsed_init_data
def close_session(self, session_id):
self.logger.debug("close_session(session_id={})".format(session_id))
self.logger.info("closing cdm session")
if session_id in self.sessions:
self.sessions.pop(session_id)
self.logger.info("cdm session closed")
return 0
else:
self.logger.info("session {} not found".format(session_id))
return 1
def set_service_certificate(self, session_id, cert_b64):
self.logger.debug("set_service_certificate(session_id={}, cert={})".format(session_id, cert_b64))
self.logger.info("setting service certificate")
if session_id not in self.sessions:
self.logger.error("session id doesn't exist")
return 1
session = self.sessions[session_id]
message = wv_proto2.SignedMessage()
try:
message.ParseFromString(base64.b64decode(cert_b64))
except DecodeError:
self.logger.error("failed to parse cert as SignedMessage")
service_certificate = wv_proto2.SignedDeviceCertificate()
if message.Type:
self.logger.debug("service cert provided as signedmessage")
try:
service_certificate.ParseFromString(message.Msg)
except DecodeError:
self.logger.error("failed to parse service certificate")
return 1
else:
self.logger.debug("service cert provided as signeddevicecertificate")
try:
service_certificate.ParseFromString(base64.b64decode(cert_b64))
except DecodeError:
self.logger.error("failed to parse service certificate")
return 1
self.logger.debug("service certificate:")
for line in text_format.MessageToString(service_certificate).splitlines():
self.logger.debug(line)
session.service_certificate = service_certificate
session.privacy_mode = True
return 0
def get_license_request(self, session_id):
self.logger.debug("get_license_request(session_id={})".format(session_id))
self.logger.info("getting license request")
if session_id not in self.sessions:
self.logger.error("session ID does not exist")
return 1
session = self.sessions[session_id]
# raw pssh will be treated as bytes and not parsed
if self.raw_pssh:
license_request = wv_proto2.SignedLicenseRequestRaw()
else:
license_request = wv_proto2.SignedLicenseRequest()
client_id = wv_proto2.ClientIdentification()
if not os.path.exists(session.device_config.device_client_id_blob_filename):
self.logger.error("no client ID blob available for this device")
return 1
with open(session.device_config.device_client_id_blob_filename, "rb") as f:
try:
cid_bytes = client_id.ParseFromString(f.read())
except DecodeError:
self.logger.error("client id failed to parse as protobuf")
return 1
self.logger.debug("building license request")
if not self.raw_pssh:
license_request.Type = wv_proto2.SignedLicenseRequest.MessageType.Value('LICENSE_REQUEST')
license_request.Msg.ContentId.CencId.Pssh.CopyFrom(session.init_data)
else:
license_request.Type = wv_proto2.SignedLicenseRequestRaw.MessageType.Value('LICENSE_REQUEST')
license_request.Msg.ContentId.CencId.Pssh = session.init_data # bytes
if session.offline:
license_type = wv_proto2.LicenseType.Value('OFFLINE')
else:
license_type = wv_proto2.LicenseType.Value('DEFAULT')
license_request.Msg.ContentId.CencId.LicenseType = license_type
license_request.Msg.ContentId.CencId.RequestId = session_id
license_request.Msg.Type = wv_proto2.LicenseRequest.RequestType.Value('NEW')
license_request.Msg.RequestTime = int(time.time())
license_request.Msg.ProtocolVersion = wv_proto2.ProtocolVersion.Value('CURRENT')
if session.device_config.send_key_control_nonce:
license_request.Msg.KeyControlNonce = random.randrange(1, 2**31)
if session.privacy_mode:
if session.device_config.vmp:
self.logger.debug("vmp required, adding to client_id")
self.logger.debug("reading vmp hashes")
vmp_hashes = wv_proto2.FileHashes()
with open(session.device_config.device_vmp_blob_filename, "rb") as f:
try:
vmp_bytes = vmp_hashes.ParseFromString(f.read())
except DecodeError:
self.logger.error("vmp hashes failed to parse as protobuf")
return 1
client_id._FileHashes.CopyFrom(vmp_hashes)
self.logger.debug("privacy mode & service certificate loaded, encrypting client id")
self.logger.debug("unencrypted client id:")
for line in text_format.MessageToString(client_id).splitlines():
self.logger.debug(line)
cid_aes_key = get_random_bytes(16)
cid_iv = get_random_bytes(16)
cid_cipher = AES.new(cid_aes_key, AES.MODE_CBC, cid_iv)
encrypted_client_id = cid_cipher.encrypt(Padding.pad(client_id.SerializeToString(), 16))
service_public_key = RSA.importKey(session.service_certificate._DeviceCertificate.PublicKey)
service_cipher = PKCS1_OAEP.new(service_public_key)
encrypted_cid_key = service_cipher.encrypt(cid_aes_key)
encrypted_client_id_proto = wv_proto2.EncryptedClientIdentification()
encrypted_client_id_proto.ServiceId = session.service_certificate._DeviceCertificate.ServiceId
encrypted_client_id_proto.ServiceCertificateSerialNumber = session.service_certificate._DeviceCertificate.SerialNumber
encrypted_client_id_proto.EncryptedClientId = encrypted_client_id
encrypted_client_id_proto.EncryptedClientIdIv = cid_iv
encrypted_client_id_proto.EncryptedPrivacyKey = encrypted_cid_key
license_request.Msg.EncryptedClientId.CopyFrom(encrypted_client_id_proto)
else:
license_request.Msg.ClientId.CopyFrom(client_id)
if session.device_config.private_key_available:
key = RSA.importKey(open(session.device_config.device_private_key_filename).read())
session.device_key = key
else:
self.logger.error("need device private key, other methods unimplemented")
return 1
self.logger.debug("signing license request")
hash = SHA1.new(license_request.Msg.SerializeToString())
signature = pss.new(key).sign(hash)
license_request.Signature = signature
session.license_request = license_request
self.logger.debug("license request:")
for line in text_format.MessageToString(session.license_request).splitlines():
self.logger.debug(line)
self.logger.info("license request created")
self.logger.debug("license request b64: {}".format(base64.b64encode(license_request.SerializeToString())))
return license_request.SerializeToString()
def provide_license(self, session_id, license_b64):
self.logger.debug("provide_license(session_id={}, license_b64={})".format(session_id, license_b64))
self.logger.info("decrypting provided license")
if session_id not in self.sessions:
self.logger.error("session does not exist")
return 1
session = self.sessions[session_id]
if not session.license_request:
self.logger.error("generate a license request first!")
return 1
license = wv_proto2.SignedLicense()
try:
license.ParseFromString(base64.b64decode(license_b64))
except DecodeError:
self.logger.error("unable to parse license - check protobufs")
return 1
session.license = license
self.logger.debug("license:")
for line in text_format.MessageToString(license).splitlines():
self.logger.debug(line)
self.logger.debug("deriving keys from session key")
oaep_cipher = PKCS1_OAEP.new(session.device_key)
session.session_key = oaep_cipher.decrypt(license.SessionKey)
lic_req_msg = session.license_request.Msg.SerializeToString()
enc_key_base = b"ENCRYPTION\000" + lic_req_msg + b"\0\0\0\x80"
auth_key_base = b"AUTHENTICATION\0" + lic_req_msg + b"\0\0\2\0"
enc_key = b"\x01" + enc_key_base
auth_key_1 = b"\x01" + auth_key_base
auth_key_2 = b"\x02" + auth_key_base
auth_key_3 = b"\x03" + auth_key_base
auth_key_4 = b"\x04" + auth_key_base
cmac_obj = CMAC.new(session.session_key, ciphermod=AES)
cmac_obj.update(enc_key)
enc_cmac_key = cmac_obj.digest()
cmac_obj = CMAC.new(session.session_key, ciphermod=AES)
cmac_obj.update(auth_key_1)
auth_cmac_key_1 = cmac_obj.digest()
cmac_obj = CMAC.new(session.session_key, ciphermod=AES)
cmac_obj.update(auth_key_2)
auth_cmac_key_2 = cmac_obj.digest()
cmac_obj = CMAC.new(session.session_key, ciphermod=AES)
cmac_obj.update(auth_key_3)
auth_cmac_key_3 = cmac_obj.digest()
cmac_obj = CMAC.new(session.session_key, ciphermod=AES)
cmac_obj.update(auth_key_4)
auth_cmac_key_4 = cmac_obj.digest()
auth_cmac_combined_1 = auth_cmac_key_1 + auth_cmac_key_2
auth_cmac_combined_2 = auth_cmac_key_3 + auth_cmac_key_4
session.derived_keys['enc'] = enc_cmac_key
session.derived_keys['auth_1'] = auth_cmac_combined_1
session.derived_keys['auth_2'] = auth_cmac_combined_2
self.logger.debug('verifying license signature')
lic_hmac = HMAC.new(session.derived_keys['auth_1'], digestmod=SHA256)
lic_hmac.update(license.Msg.SerializeToString())
self.logger.debug("calculated sig: {} actual sig: {}".format(lic_hmac.hexdigest(), binascii.hexlify(license.Signature)))
if lic_hmac.digest() != license.Signature:
self.logger.info("license signature doesn't match - writing bin so they can be debugged")
with open("original_lic.bin", "wb") as f:
f.write(base64.b64decode(license_b64))
with open("parsed_lic.bin", "wb") as f:
f.write(license.SerializeToString())
self.logger.info("continuing anyway")
self.logger.debug("key count: {}".format(len(license.Msg.Key)))
for key in license.Msg.Key:
if key.Id:
key_id = key.Id
else:
key_id = wv_proto2.License.KeyContainer.KeyType.Name(key.Type).encode('utf-8')
encrypted_key = key.Key
iv = key.Iv
type = wv_proto2.License.KeyContainer.KeyType.Name(key.Type)
cipher = AES.new(session.derived_keys['enc'], AES.MODE_CBC, iv=iv)
decrypted_key = cipher.decrypt(encrypted_key)
if type == "OPERATOR_SESSION":
permissions = []
perms = key._OperatorSessionKeyPermissions
for (descriptor, value) in perms.ListFields():
if value == 1:
permissions.append(descriptor.name)
print(permissions)
else:
permissions = []
session.keys.append(Key(key_id, type, Padding.unpad(decrypted_key, 16), permissions))
self.logger.info("decrypted all keys")
return 0
def get_keys(self, session_id):
if session_id in self.sessions:
return self.sessions[session_id].keys
else:
self.logger.error("session not found")
return 1