Add Widevine Key Class

pywidevine/key.py

@@ -0,0 +1,63 @@
+from __future__ import annotations
+
+import base64
+from typing import Optional, Union
+from uuid import UUID
+
+from Crypto.Cipher import AES
+from Crypto.Util import Padding
+
+from pywidevine.license_protocol_pb2 import License
+
+
+class Key:
+    def __init__(self, type_: str, kid: UUID, key: bytes, permissions: Optional[list[str]] = None):
+        self.type = type_
+        self.kid = kid
+        self.key = key
+        self.permissions = permissions or []
+
+    def __repr__(self) -> str:
+        return "{name}({items})".format(
+            name=self.__class__.__name__,
+            items=", ".join([f"{k}={repr(v)}" for k, v in self.__dict__.items()])
+        )
+
+    @classmethod
+    def from_key_container(cls, key: License.KeyContainer, enc_key: bytes) -> Key:
+        """Load Key from a KeyContainer object."""
+        permissions = []
+        if key.type == License.KeyContainer.KeyType.OPERATOR_SESSION:
+            for descriptor, value in key.operator_session_key_permissions.ListFields():
+                if value == 1:
+                    permissions.append(descriptor.name)
+
+        return Key(
+            type_=License.KeyContainer.KeyType.Name(key.type),
+            kid=cls.kid_to_uuid(key.id),
+            key=Padding.unpad(
+                AES.new(enc_key, AES.MODE_CBC, iv=key.iv).decrypt(key.key),
+                16
+            ),
+            permissions=permissions
+        )
+
+    @staticmethod
+    def kid_to_uuid(kid: Union[str, bytes]) -> UUID:
+        """
+        Convert a Key ID from a string or bytes to a UUID object.
+        At first this may seem very simple but some types of Key IDs
+        may not be 16 bytes and some may be decimal vs. hex.
+        """
+        if isinstance(kid, str):
+            kid = base64.b64decode(kid)
+        if not kid:
+            kid = b"\x00" * 16
+
+        if kid.decode(errors="replace").isdigit():
+            return UUID(int=int(kid.decode()))
+
+        if len(kid) < 16:
+            kid += b"\x00" * (16 - len(kid))
+
+        return UUID(bytes=kid)