From fc47bbb4369a22b08402f6af6157d9b2fc89836d Mon Sep 17 00:00:00 2001 From: rlaphoenix Date: Fri, 5 Aug 2022 05:32:41 +0100 Subject: [PATCH] PSSH: Merge get_as_box into the Constructor Also improves the code of it overall including documentation. The _box class instance variable has been removed and the raw box is no longer kept. --- pywidevine/cdm.py | 2 +- pywidevine/pssh.py | 134 +++++++++++++++++++++++----------------- pywidevine/remotecdm.py | 2 +- 3 files changed, 78 insertions(+), 60 deletions(-) diff --git a/pywidevine/cdm.py b/pywidevine/cdm.py index 56b93ed..faacb1d 100644 --- a/pywidevine/cdm.py +++ b/pywidevine/cdm.py @@ -268,7 +268,7 @@ class Cdm: if not init_data: raise InvalidInitData("The init_data must not be empty.") try: - init_data = PSSH.get_as_box(init_data).init_data + init_data = PSSH(init_data).init_data except (ValueError, binascii.Error, DecodeError) as e: raise InvalidInitData(str(e)) diff --git a/pywidevine/pssh.py b/pywidevine/pssh.py index 5dc9a08..ee1977d 100644 --- a/pywidevine/pssh.py +++ b/pywidevine/pssh.py @@ -21,8 +21,82 @@ class PSSH: Widevine = UUID(bytes=b"\xed\xef\x8b\xa9\x79\xd6\x4a\xce\xa3\xc8\x27\xdc\xd5\x1d\x21\xed") PlayReady = UUID(bytes=b"\x9a\x04\xf0\x79\x98\x40\x42\x86\xab\x92\xe6\x5b\xe0\x88\x5f\x95") - def __init__(self, box: Container): - self._box = box + def __init__(self, data: Union[Container, str, bytes], strict: bool = False): + """ + Load a PSSH box or Widevine Cenc Header data as a new v0 PSSH box. + + [Strict mode (strict=True)] + + Supports the following forms of input data in either Base64 or Bytes form: + - Full PSSH mp4 boxes (as defined by pymp4 Box). + - Full Widevine Cenc Headers (as defined by WidevinePsshData proto). + + [Lenient mode (strict=False, default)] + + If the data is not supported in Strict mode, and is assumed not to be corrupt or + parsed incorrectly, the License Server likely accepts a custom init_data value + during a License Request call. This is uncommon behavior but not out of realm of + possibilities. For example, Netflix does this with it's MSL WidevineExchange + scheme. + + Lenient mode will craft a new v0 PSSH box with the init_data field set to + the provided data as-is. The data will first be base64 decoded. This behavior + may not work in your scenario and if that's the case please manually craft + your own PSSH box with the init_data field to be used in License Requests. + + Raises: + ValueError: If the data is empty. + TypeError: If the data is an unexpected type. + binascii.Error: If the data could not be decoded as Base64 if provided as a + string. + DecodeError: If the data could not be parsed as a PSSH mp4 box nor a Widevine + Cenc Header and strict mode is enabled. + """ + if not data: + raise ValueError("Data must not be empty.") + + if isinstance(data, Container): + box = data + else: + if isinstance(data, str): + try: + data = base64.b64decode(data) + except (binascii.Error, binascii.Incomplete) as e: + raise binascii.Error(f"Could not decode data as Base64, {e}") + + if not isinstance(data, bytes): + raise TypeError(f"Expected data to be a {Container}, bytes, or base64, not {data!r}") + + try: + box = Box.parse(data) + except (IOError, construct.ConstructError): # not a box + try: + cenc_header = WidevinePsshData() + cenc_header.ParseFromString(data) + cenc_header = cenc_header.SerializeToString() + if cenc_header != data: # not actually a WidevinePsshData + raise DecodeError() + except DecodeError: # not a widevine cenc header + if strict: + raise DecodeError(f"Could not parse data as a {Container} nor a {WidevinePsshData}.") + # Data is not a Widevine Cenc Header, it's something custom. + # The license server likely has something custom to parse it. + # See doc-string about Lenient mode for more information. + cenc_header = data + + box = Box.parse(Box.build(dict( + type=b"pssh", + version=0, + flags=0, + system_ID=PSSH.SystemId.Widevine, + init_data=cenc_header + ))) + + self.version = box.version + self.flags = box.flags + self.system_id = box.system_ID + self.key_ids = box.key_IDs + self.init_data = box.init_data @staticmethod def from_playready_pssh(box: Container) -> Container: @@ -78,62 +152,6 @@ class PSSH: ))) return box - - @staticmethod - def get_as_box(data: Union[Container, bytes, str], strict: bool = False) -> Container: - """ - Get possibly arbitrary data as a parsed PSSH mp4 box. - - Parameters: - data: PSSH mp4 box, Widevine Cenc Header (init data), or arbitrary data to - parse or craft into a PSSH mp4 box. - strict: Do not return a PSSH box for arbitrary data. Require the data to be - at least a PSSH mp4 box, or a Widevine Cenc Header. - - Raises: - ValueError: If the data is empty, or an unexpected type. - binascii.Error: If the data could not be decoded as Base64 if provided - as a string. - DecodeError: If the data could not be parsed as a PSSH mp4 box - nor a Widevine Cenc Header while strict=True. - """ - if not data: - raise ValueError("Data must not be empty.") - - if isinstance(data, Container): - return data - - if isinstance(data, str): - try: - data = base64.b64decode(data) - except (binascii.Error, binascii.Incomplete) as e: - raise binascii.Error(f"Could not decode data as Base64, {e}") - - if isinstance(data, bytes): - try: - data = Box.parse(data) - except (IOError, construct.ConstructError): - if strict: - try: - cenc_header = WidevinePsshData() - if cenc_header.MergeFromString(data) < len(data): - raise DecodeError() - except DecodeError: - raise DecodeError(f"Could not parse data as a PSSH mp4 box nor a Widevine Cenc Header.") - else: - data = cenc_header.SerializeToString() - data = Box.parse(Box.build(dict( - type=b"pssh", - version=0, - flags=0, - system_ID=PSSH.SystemId.Widevine, - init_data=data - ))) - else: - raise ValueError(f"Data is an unexpected type, expected bytes got {data!r}.") - - return data - @staticmethod def get_key_ids(box: Container) -> list[UUID]: """ diff --git a/pywidevine/remotecdm.py b/pywidevine/remotecdm.py index bda74fb..3842902 100644 --- a/pywidevine/remotecdm.py +++ b/pywidevine/remotecdm.py @@ -164,7 +164,7 @@ class RemoteCdm(Cdm): if not init_data: raise InvalidInitData("The init_data must not be empty.") try: - init_data = PSSH.get_as_box(init_data).init_data + init_data = PSSH(init_data).init_data except (ValueError, binascii.Error, DecodeError) as e: raise InvalidInitData(str(e))