diff options
| -rw-r--r-- | slixmpp/plugins/xep_0454/__init__.py | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/slixmpp/plugins/xep_0454/__init__.py b/slixmpp/plugins/xep_0454/__init__.py index 9e9c3b02..09d41221 100644 --- a/slixmpp/plugins/xep_0454/__init__.py +++ b/slixmpp/plugins/xep_0454/__init__.py @@ -73,6 +73,46 @@ class XEP_0454(BasePlugin): return (payload, fragment) @classmethod + def decrypt(cls, input_file: IO[bytes], fragment: str) -> bytes: + """ + Decrypts file-like. + + :param input_file: Binary file stream on the file, containing the + tag (16 bytes) at the end. + :param fragment: 88 hex chars string composed of iv (24 chars) + + key (64 chars). + """ + + assert len(fragment) == 88 + aes_gcm_iv = bytes.fromhex(fragment[:24]) + aes_gcm_key = bytes.fromhex(fragment[24:]) + + # Find 16 bytes tag + input_file.seek(-16, SEEK_END) + tag = input_file.read() + + aes_gcm = Cipher( + algorithms.AES(aes_gcm_key), + modes.GCM(aes_gcm_iv, tag), + ).decryptor() + + size = input_file.seek(0, SEEK_END) + input_file.seek(0) + + count = size - 16 + plain = b'' + while count >= 0: + buf = input_file.read(4096) + count -= len(buf) + if count <= 0: + buf += input_file.read() + buf = buf[:-16] + plain += aes_gcm.update(buf) + plain += aes_gcm.finalize() + + return plain + + @classmethod def format_url(cls, url: str, fragment: str) -> str: """Helper to format a HTTPS URL to an AESGCM URI""" if not url.startswith('https://') or url.find('#') != -1: |