Add some helper scripts

scripts/build_proto.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+
+if [ ! -e "setup.py" ]; then
+    >&2 echo "Run this script from pyatv root directory (where setup.py is)!"
+    exit 1
+fi
+
+protoc --proto_path=. --python_out=. pyatv/protobuf/*.proto

scripts/chacha20_decrypt.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+#
+# Simple helper script that tries to decrypt CHACHA20 encrypted data with
+# specified keys and some nounces. Just update constans below and run
+# the script:
+#
+# $ ./bruteforce.py
+# ...
+# Data decrypted!
+#  - Nounce : 000000000000000000000000
+#  - Key    : 7f0a54c5b15ccafc4927582c11d3394a55c95e489e72d12222a91b06f34c6094
+#  - Data   : 080b200082012d0a2b6b4d5254656c65766973696f6e52656d6f74654e6f77506c6179696e67417274776f726b4368616e676564
+#
+
+import sys
+import binascii
+from cryptography.hazmat.primitives.ciphers.aead import ChaCha20Poly1305
+
+
+# Example data
+DATA = "E8E786E4E673A38808063FEFDAF79D66B99C0745DA45C704DE51D4855FAE752F3B92ECA29E1DF5EF6B48C72BE4E87FC660BF5CE57D768365E60397E7C97D16AB233441B9"
+KEYS = ["70743888c9eda99d1a24c5a94a26f85a0fec26f4cba16f919e5c23f892ecfbab",
+        "7f0a54c5b15ccafc4927582c11d3394a55c95e489e72d12222a91b06f34c6094"]
+
+
+def decrypt(data, nounce, key):
+  data = binascii.unhexlify(data.replace(' ', ''))
+  inputKey = binascii.unhexlify(key.replace(' ', ''))
+  inputNonce = b'\x00\x00\x00\x00' + nounce.to_bytes(length=8, byteorder='little')
+  chacha = ChaCha20Poly1305(inputKey)
+  try:
+    print('Trying key {0} with nounce {1}'.format(inputKey, inputNonce))
+    decryptedData = chacha.decrypt(inputNonce, data, None)
+    print('Data decrypted!\n - Nounce : {0}\n - Key    : {1}\n - Data   : {2}'.format(
+        binascii.hexlify(inputNonce).decode(),
+        binascii.hexlify(inputKey).decode(),
+        binascii.hexlify(decryptedData).decode()))
+    sys.exit(0)
+  except Exception as ex:
+    pass
+
+
+if __name__ == '__main__':
+  for key in KEYS:
+    for nounce in range(128):
+      decrypt(DATA, nounce, key)