Initial commit

librespot/audio/decrypt.py

@@ -0,0 +1,45 @@
+from __future__ import annotations
+from Cryptodome.Cipher import AES
+from Cryptodome.Util import Counter
+from librespot.audio.storage import ChannelManager
+from librespot.structure import AudioDecrypt
+import io
+import time
+
+
+class AesAudioDecrypt(AudioDecrypt):
+    audio_aes_iv = b'r\xe0g\xfb\xdd\xcb\xcfw\xeb\xe8\xbcd?c\r\x93'
+    cipher = None
+    decrypt_count = 0
+    decrypt_total_time = 0
+    iv_int = int.from_bytes(audio_aes_iv, "big")
+    iv_diff = 0x100
+    key: bytes
+
+    def __init__(self, key: bytes):
+        self.key = key
+
+    def decrypt_chunk(self, chunk_index: int, buffer: bytes):
+        new_buffer = io.BytesIO()
+        iv = self.iv_int + int(ChannelManager.chunk_size * chunk_index / 16)
+        start = time.time_ns()
+        for i in range(0, len(buffer), 4096):
+            cipher = AES.new(key=self.key,
+                             mode=AES.MODE_CTR,
+                             counter=Counter.new(128, initial_value=iv))
+            count = min(4096, len(buffer) - i)
+            decrypted_buffer = cipher.decrypt(buffer[i:i + count])
+            new_buffer.write(decrypted_buffer)
+            if count != len(decrypted_buffer):
+                raise RuntimeError(
+                    "Couldn't process all data, actual: {}, expected: {}".
+                    format(len(decrypted_buffer), count))
+            iv += self.iv_diff
+        self.decrypt_total_time += time.time_ns() - start
+        self.decrypt_count += 1
+        new_buffer.seek(0)
+        return new_buffer.read()
+
+    def decrypt_time_ms(self):
+        return 0 if self.decrypt_count == 0 else int(
+            (self.decrypt_total_time / self.decrypt_count) / 1000000)