update

tidal_dl_ng/helper/decryption.py

@@ -0,0 +1,63 @@
+import base64
+import pathlib
+
+from Crypto.Cipher import AES
+from Crypto.Util import Counter
+
+
+def decrypt_security_token(security_token: str) -> (str, str):
+    """
+    The `decrypt_security_token` function decrypts a security token into a key and nonce pair using AES
+    encryption.
+
+    Args:
+      security_token (str): The `security_token` parameter in the `decrypt_security_token` function is a
+    string that represents an encrypted security token. This function decrypts the security token into a
+    key and nonce pair using AES encryption. security_token should match the securityToken value from the web response.
+
+    Returns:
+      The `decrypt_security_token` function returns a tuple containing the key and nonce extracted from
+    the decrypted security token.
+    """
+
+    # Do not change this
+    master_key = "UIlTTEMmmLfGowo/UC60x2H45W6MdGgTRfo/umg4754="
+
+    # Decode the base64 strings to ascii strings
+    master_key = base64.b64decode(master_key)
+    security_token = base64.b64decode(security_token)
+
+    # Get the IV from the first 16 bytes of the securityToken
+    iv = security_token[:16]
+    encrypted_st = security_token[16:]
+
+    # Initialize decryptor
+    decryptor = AES.new(master_key, AES.MODE_CBC, iv)
+
+    # Decrypt the security token
+    decrypted_st = decryptor.decrypt(encrypted_st)
+
+    # Get the audio stream decryption key and nonce from the decrypted security token
+    key = decrypted_st[:16]
+    nonce = decrypted_st[16:24]
+
+    return key, nonce
+
+
+def decrypt_file(path_file_encrypted: pathlib.Path, path_file_destination: pathlib.Path, key: str, nonce: str) -> None:
+    """
+    Decrypts an encrypted MQA file given the file, key and nonce.
+    TODO: Is it really only necessary for MQA of for all other formats, too?
+    """
+
+    # Initialize counter and file decryptor
+    counter = Counter.new(64, prefix=nonce, initial_value=0)
+    decryptor = AES.new(key, AES.MODE_CTR, counter=counter)
+
+    # Open and decrypt
+    with path_file_encrypted.open("rb") as f_src:
+        audio_decrypted = decryptor.decrypt(f_src.read())
+
+        # Replace with decrypted file
+        with path_file_destination.open("wb") as f_dst:
+            f_dst.write(audio_decrypted)