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PSSH: Parse PlayReadyObjects efficiently, parse multiple records 

The previous method was overall fine, but assumed only one PlayReadyHeader was in the PlayReadyObject. It also incorrectly assumed the start data to be garbage data when it's actually the header for the PlayReadyObject.
This commit is contained in:
rlaphoenix 2022-12-26 23:33:10 +00:00
parent 3a910bd03a
commit 61097ce6de
1 changed files with 40 additions and 20 deletions
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48
pywidevine/pssh.py
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@ -3,6 +3,7 @@ from __future__ import annotations
import base64
import binascii
import string
from io import BytesIO
from typing import Union, Optional
from uuid import UUID
@ -214,8 +215,8 @@ class PSSH:
Get all Key IDs from within the Box or Init Data, wherever possible.
Supports:
- Version 1 Boxes
- Widevine Headers
- Version 1 PSSH Boxes
- WidevineCencHeaders
- PlayReadyHeaders (4.0.0.0->4.3.0.0)
"""
if self.version == 1 and self.__key_ids:
@ -236,24 +237,43 @@ class PSSH:
]
if self.system_id == PSSH.SystemId.PlayReady:
xml_string = self.init_data.decode("utf-16-le")
# some of these init data has garbage(?) in front of it
xml_string = xml_string[xml_string.index("<"):]
xml = load_xml(xml_string)
header_version = xml.attrib["version"]
if header_version == "4.0.0.0":
key_ids = xml.xpath("DATA/KID/text()")
elif header_version == "4.1.0.0":
key_ids = xml.xpath("DATA/PROTECTINFO/KID/@VALUE")
elif header_version in ("4.2.0.0", "4.3.0.0"):
key_ids = xml.xpath("DATA/PROTECTINFO/KIDS/KID/@VALUE")
# Assuming init data is a PRO (PlayReadyObject)
# https://learn.microsoft.com/en-us/playready/specifications/playready-header-specification
pro_data = BytesIO(self.init_data)
pro_length = int.from_bytes(pro_data.read(4), "little")
if pro_length != len(self.init_data):
raise ValueError("The PlayReadyObject seems to be corrupt (too big or small, or missing data).")
pro_record_count = int.from_bytes(pro_data.read(2), "little")
for _ in range(pro_record_count):
prr_type = int.from_bytes(pro_data.read(2), "little")
prr_length = int.from_bytes(pro_data.read(2), "little")
prr_value = pro_data.read(prr_length)
if prr_type != 0x01:
# No PlayReady Header, skip and hope for something else
# TODO: Add support for Embedded License Stores (0x03)
continue
prr_header = load_xml(prr_value.decode("utf-16-le"))
prr_header_version = prr_header.attrib["version"]
if prr_header_version == "4.0.0.0":
key_ids = prr_header.xpath("DATA/KID/text()")
elif prr_header_version == "4.1.0.0":
key_ids = prr_header.xpath("DATA/PROTECTINFO/KID/@VALUE")
elif prr_header_version in ("4.2.0.0", "4.3.0.0"):
# TODO: Retain the Encryption Scheme information in v4.3.0.0
# This is because some Key IDs can be AES-CTR while some are AES-CBC.
# Conversion to WidevineCencHeader could use this information.
key_ids = prr_header.xpath("DATA/PROTECTINFO/KIDS/KID/@VALUE")
else:
raise ValueError(f"Unsupported PlayReady header version {header_version}")
raise ValueError(f"Unsupported PlayReadyHeader version {prr_header_version}")
return [
UUID(bytes=base64.b64decode(key_id))
for key_id in key_ids
]
raise ValueError("Unsupported PlayReadyObject, no PlayReadyHeader within the object.")
raise ValueError(f"This PSSH is not supported by key_ids() property, {self.dumps()}")
def dump(self) -> bytes: