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PSSH: Implement Widevine to PlayReady conversion

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The XML creation is a bit dodgy because I despise XML. If you like lxml, feel free to make a pull request.
This commit is contained in:
rlaphoenix 2022-12-27 00:24:15 +00:00
parent 2648d1c669
commit c9f55c6e6b
1 changed files with 66 additions and 0 deletions
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66
pywidevine/pssh.py
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@ -326,6 +326,72 @@ class PSSH:
self.init_data = cenc_header.SerializeToString()
self.system_id = PSSH.SystemId.Widevine
def widevine_to_playready(
self,
la_url: Optional[str] = None,
lui_url: Optional[str] = None,
ds_id: Optional[bytes] = None,
decryptor_setup: Optional[str] = None,
custom_data: Optional[str] = None
) -> None:
"""
Convert Widevine PSSH data to PlayReady v4.3.0.0 PSSH data.
Note that it is impossible to create the CHECKSUM values for AES-CTR Key IDs
as you must encrypt the Key ID with the Content Encryption Key using AES-ECB.
This may cause software incompatibilities.
Parameters:
la_url: Contains the URL for the license acquisition Web service.
Only absolute URLs are allowed.
lui_url: Contains the URL for the license acquisition Web service.
Only absolute URLs are allowed.
ds_id: Service ID for the domain service.
decryptor_setup: This tag may only contain the value "ONDEMAND". It
indicates to an application that it should not expect the full
license chain for the content to be available for acquisition, or
already present on the client machine, prior to setting up the
media graph. If this tag is not set then it indicates that an
application can enforce the license to be acquired, or already
present on the client machine, prior to setting up the media graph.
custom_data: The content author can add custom XML inside this
element. Microsoft code does not act on any data contained inside
this element. The Syntax of this params XML is not validated.
"""
if self.system_id != PSSH.SystemId.Widevine:
raise ValueError(f"This is not a Widevine PSSH, {self.system_id}")
key_ids_xml = ""
for key_id in self.key_ids:
# Note that it's impossible to create the CHECKSUM value without the Key for the KID
key_ids_xml += f"""
<KID ALGID="AESCTR" VALUE="{base64.b64encode(key_id.bytes).decode()}"></KID>
"""
prr_value = f"""
<WRMHEADER xmlns="http://schemas.microsoft.com/DRM/2007/03/PlayReadyHeader" version="4.3.0.0">
<DATA>
<PROTECTINFO>
<KIDS>{key_ids_xml}</KIDS>
</PROTECTINFO>
{f'<LA_URL>%s</LA_URL>' % la_url if la_url else ''}
{f'<LUI_URL>%s</LUI_URL>' % lui_url if lui_url else ''}
{f'<DS_ID>%s</DS_ID>' % base64.b64encode(ds_id).decode() if ds_id else ''}
{f'<DECRYPTORSETUP>%s</DECRYPTORSETUP>' % decryptor_setup if decryptor_setup else ''}
{f'<CUSTOMATTRIBUTES xmlns="">%s</CUSTOMATTRIBUTES>' % custom_data if custom_data else ''}
</DATA>
</WRMHEADER>
""".encode("utf-16-le")
prr_length = len(prr_value).to_bytes(2, "little")
prr_type = (1).to_bytes(2, "little") # Has PlayReadyHeader
pro_record_count = (1).to_bytes(2, "little")
pro = pro_record_count + prr_type + prr_length + prr_value
pro = (len(pro) + 4).to_bytes(4, "little") + pro
self.init_data = pro
self.system_id = PSSH.SystemId.PlayReady
def set_key_ids(self, key_ids: list[UUID]) -> None:
"""Overwrite all Key IDs with the specified Key IDs."""
if self.system_id != PSSH.SystemId.Widevine: