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+# -*- coding: utf-8 -*-
+# libolm python bindings
+# Copyright © 2015-2017 OpenMarket Ltd
+# Copyright © 2018 Damir Jelić <poljar@termina.org.uk>
+"""libolm Group session module.
+
+This module contains the group session part of the Olm library. It contains two
+classes for creating inbound and outbound group sessions.
+
+Examples:
+ >>> outbound = OutboundGroupSession()
+ >>> InboundGroupSession(outbound.session_key)
+"""
+
+# pylint: disable=redefined-builtin,unused-import
+from builtins import bytes, super
+from typing import AnyStr, Optional, Tuple, Type
+
+from future.utils import bytes_to_native_str
+
+# pylint: disable=no-name-in-module
+from _libolm import ffi, lib # type: ignore
+
+from ._compat import URANDOM, to_bytes
+from ._finalize import track_for_finalization
+
+
+def _clear_inbound_group_session(session):
+ # type: (ffi.cdata) -> None
+ lib.olm_clear_inbound_group_session(session)
+
+
+def _clear_outbound_group_session(session):
+ # type: (ffi.cdata) -> None
+ lib.olm_clear_outbound_group_session(session)
+
+
+class OlmGroupSessionError(Exception):
+ """libolm Group session error exception."""
+
+
+class InboundGroupSession(object):
+ """Inbound group session for encrypted multiuser communication."""
+
+ def __new__(
+ cls, # type: Type[InboundGroupSession]
+ session_key=None # type: Optional[str]
+ ):
+ # type: (...) -> InboundGroupSession
+ obj = super().__new__(cls)
+ obj._buf = ffi.new("char[]", lib.olm_inbound_group_session_size())
+ obj._session = lib.olm_inbound_group_session(obj._buf)
+ track_for_finalization(obj, obj._session, _clear_inbound_group_session)
+ return obj
+
+ def __init__(self, session_key):
+ # type: (AnyStr) -> None
+ """Create a new inbound group session.
+ Start a new inbound group session, from a key exported from
+ an outbound group session.
+
+ Raises OlmGroupSessionError on failure. The error message of the
+ exception will be "OLM_INVALID_BASE64" if the session key is not valid
+ base64 and "OLM_BAD_SESSION_KEY" if the session key is invalid.
+ """
+ if False: # pragma: no cover
+ self._session = self._session # type: ffi.cdata
+
+ byte_session_key = to_bytes(session_key)
+
+ key_buffer = ffi.new("char[]", byte_session_key)
+ ret = lib.olm_init_inbound_group_session(
+ self._session, key_buffer, len(byte_session_key)
+ )
+ self._check_error(ret)
+
+ def pickle(self, passphrase=""):
+ # type: (Optional[str]) -> bytes
+ """Store an inbound group session.
+
+ Stores a group session as a base64 string. Encrypts the session using
+ the supplied passphrase. Returns a byte object containing the base64
+ encoded string of the pickled session.
+
+ Args:
+ passphrase(str, optional): The passphrase to be used to encrypt
+ the session.
+ """
+ byte_passphrase = bytes(passphrase, "utf-8") if passphrase else b""
+
+ passphrase_buffer = ffi.new("char[]", byte_passphrase)
+ pickle_length = lib.olm_pickle_inbound_group_session_length(
+ self._session)
+ pickle_buffer = ffi.new("char[]", pickle_length)
+
+ ret = lib.olm_pickle_inbound_group_session(
+ self._session, passphrase_buffer, len(byte_passphrase),
+ pickle_buffer, pickle_length
+ )
+
+ self._check_error(ret)
+
+ return ffi.unpack(pickle_buffer, pickle_length)
+
+ @classmethod
+ def from_pickle(cls, pickle, passphrase=""):
+ # type: (bytes, Optional[str]) -> InboundGroupSession
+ """Load a previously stored inbound group session.
+
+ Loads an inbound group session from a pickled base64 string and returns
+ an InboundGroupSession object. Decrypts the session using the supplied
+ passphrase. Raises OlmSessionError on failure. If the passphrase
+ doesn't match the one used to encrypt the session then the error
+ message for the exception will be "BAD_ACCOUNT_KEY". If the base64
+ couldn't be decoded then the error message will be "INVALID_BASE64".
+
+ Args:
+ pickle(bytes): Base64 encoded byte string containing the pickled
+ session
+ passphrase(str, optional): The passphrase used to encrypt the
+ session
+ """
+ if not pickle:
+ raise ValueError("Pickle can't be empty")
+
+ byte_passphrase = bytes(passphrase, "utf-8") if passphrase else b""
+ passphrase_buffer = ffi.new("char[]", byte_passphrase)
+ pickle_buffer = ffi.new("char[]", pickle)
+
+ obj = cls.__new__(cls)
+
+ ret = lib.olm_unpickle_inbound_group_session(
+ obj._session,
+ passphrase_buffer,
+ len(byte_passphrase),
+ pickle_buffer,
+ len(pickle)
+ )
+ obj._check_error(ret)
+
+ return obj
+
+ def _check_error(self, ret):
+ # type: (int) -> None
+ if ret != lib.olm_error():
+ return
+
+ last_error = bytes_to_native_str(ffi.string(
+ lib.olm_inbound_group_session_last_error(self._session)))
+
+ raise OlmGroupSessionError(last_error)
+
+ def decrypt(self, ciphertext):
+ # type: (AnyStr) -> Tuple[str, int]
+ """Decrypt a message
+
+ Returns a tuple of the decrypted plain-text and the message index of
+ the decrypted message or raises OlmGroupSessionError on failure.
+ On failure the error message of the exception will be:
+
+ * OLM_INVALID_BASE64 if the message is not valid base64
+ * OLM_BAD_MESSAGE_VERSION if the message was encrypted with an
+ unsupported version of the protocol
+ * OLM_BAD_MESSAGE_FORMAT if the message headers could not be
+ decoded
+ * OLM_BAD_MESSAGE_MAC if the message could not be verified
+ * OLM_UNKNOWN_MESSAGE_INDEX if we do not have a session key
+ corresponding to the message's index (i.e., it was sent before
+ the session key was shared with us)
+
+ Args:
+ ciphertext(str): Base64 encoded ciphertext containing the encrypted
+ message
+ """
+ if not ciphertext:
+ raise ValueError("Ciphertext can't be empty.")
+
+ byte_ciphertext = to_bytes(ciphertext)
+
+ ciphertext_buffer = ffi.new("char[]", byte_ciphertext)
+
+ max_plaintext_length = lib.olm_group_decrypt_max_plaintext_length(
+ self._session, ciphertext_buffer, len(byte_ciphertext)
+ )
+ plaintext_buffer = ffi.new("char[]", max_plaintext_length)
+ ciphertext_buffer = ffi.new("char[]", byte_ciphertext)
+
+ message_index = ffi.new("uint32_t*")
+ plaintext_length = lib.olm_group_decrypt(
+ self._session, ciphertext_buffer, len(byte_ciphertext),
+ plaintext_buffer, max_plaintext_length,
+ message_index
+ )
+
+ self._check_error(plaintext_length)
+
+ return bytes_to_native_str(ffi.unpack(
+ plaintext_buffer,
+ plaintext_length
+ )), message_index[0]
+
+ @property
+ def id(self):
+ # type: () -> str
+ """str: A base64 encoded identifier for this session."""
+ id_length = lib.olm_inbound_group_session_id_length(self._session)
+ id_buffer = ffi.new("char[]", id_length)
+ ret = lib.olm_inbound_group_session_id(
+ self._session,
+ id_buffer,
+ id_length
+ )
+ self._check_error(ret)
+ return bytes_to_native_str(ffi.unpack(id_buffer, id_length))
+
+ @property
+ def first_known_index(self):
+ # type: () -> int
+ """int: The first message index we know how to decrypt."""
+ return lib.olm_inbound_group_session_first_known_index(self._session)
+
+ def export_session(self, message_index):
+ # type: (int) -> str
+ """Export an inbound group session
+
+ Export the base64-encoded ratchet key for this session, at the given
+ index, in a format which can be used by import_session().
+
+ Raises OlmGroupSessionError on failure. The error message for the
+ exception will be:
+
+ * OLM_UNKNOWN_MESSAGE_INDEX if we do not have a session key
+ corresponding to the given index (ie, it was sent before the
+ session key was shared with us)
+
+ Args:
+ message_index(int): The message index at which the session should
+ be exported.
+ """
+
+ export_length = lib.olm_export_inbound_group_session_length(
+ self._session)
+
+ export_buffer = ffi.new("char[]", export_length)
+ ret = lib.olm_export_inbound_group_session(
+ self._session,
+ export_buffer,
+ export_length,
+ message_index
+ )
+ self._check_error(ret)
+ return bytes_to_native_str(ffi.unpack(export_buffer, export_length))
+
+ @classmethod
+ def import_session(cls, session_key):
+ # type: (AnyStr) -> InboundGroupSession
+ """Create an InboundGroupSession from an exported session key.
+
+ Creates an InboundGroupSession with an previously exported session key,
+ raises OlmGroupSessionError on failure. The error message for the
+ exception will be:
+
+ * OLM_INVALID_BASE64 if the session_key is not valid base64
+ * OLM_BAD_SESSION_KEY if the session_key is invalid
+
+ Args:
+ session_key(str): The exported session key with which the inbound
+ group session will be created
+ """
+ obj = cls.__new__(cls)
+
+ byte_session_key = to_bytes(session_key)
+
+ key_buffer = ffi.new("char[]", byte_session_key)
+ ret = lib.olm_import_inbound_group_session(
+ obj._session,
+ key_buffer,
+ len(byte_session_key)
+ )
+ obj._check_error(ret)
+
+ return obj
+
+
+class OutboundGroupSession(object):
+ """Outbound group session for encrypted multiuser communication."""
+
+ def __new__(cls):
+ # type: (Type[OutboundGroupSession]) -> OutboundGroupSession
+ obj = super().__new__(cls)
+ obj._buf = ffi.new("char[]", lib.olm_outbound_group_session_size())
+ obj._session = lib.olm_outbound_group_session(obj._buf)
+ track_for_finalization(
+ obj,
+ obj._session,
+ _clear_outbound_group_session
+ )
+ return obj
+
+ def __init__(self):
+ # type: () -> None
+ """Create a new outbound group session.
+
+ Start a new outbound group session. Raises OlmGroupSessionError on
+ failure. If there weren't enough random bytes for the session creation
+ the error message for the exception will be NOT_ENOUGH_RANDOM.
+ """
+ if False: # pragma: no cover
+ self._session = self._session # type: ffi.cdata
+
+ random_length = lib.olm_init_outbound_group_session_random_length(
+ self._session
+ )
+ random = URANDOM(random_length)
+ random_buffer = ffi.new("char[]", random)
+
+ ret = lib.olm_init_outbound_group_session(
+ self._session, random_buffer, random_length
+ )
+ self._check_error(ret)
+
+ def _check_error(self, ret):
+ # type: (int) -> None
+ if ret != lib.olm_error():
+ return
+
+ last_error = bytes_to_native_str(ffi.string(
+ lib.olm_outbound_group_session_last_error(self._session)
+ ))
+
+ raise OlmGroupSessionError(last_error)
+
+ def pickle(self, passphrase=""):
+ # type: (Optional[str]) -> bytes
+ """Store an outbound group session.
+
+ Stores a group session as a base64 string. Encrypts the session using
+ the supplied passphrase. Returns a byte object containing the base64
+ encoded string of the pickled session.
+
+ Args:
+ passphrase(str, optional): The passphrase to be used to encrypt
+ the session.
+ """
+ byte_passphrase = bytes(passphrase, "utf-8") if passphrase else b""
+ passphrase_buffer = ffi.new("char[]", byte_passphrase)
+ pickle_length = lib.olm_pickle_outbound_group_session_length(
+ self._session)
+ pickle_buffer = ffi.new("char[]", pickle_length)
+
+ ret = lib.olm_pickle_outbound_group_session(
+ self._session, passphrase_buffer, len(byte_passphrase),
+ pickle_buffer, pickle_length
+ )
+ self._check_error(ret)
+ return ffi.unpack(pickle_buffer, pickle_length)
+
+ @classmethod
+ def from_pickle(cls, pickle, passphrase=""):
+ # type: (bytes, Optional[str]) -> OutboundGroupSession
+ """Load a previously stored outbound group session.
+
+ Loads an outbound group session from a pickled base64 string and
+ returns an OutboundGroupSession object. Decrypts the session using the
+ supplied passphrase. Raises OlmSessionError on failure. If the
+ passphrase doesn't match the one used to encrypt the session then the
+ error message for the exception will be "BAD_ACCOUNT_KEY". If the
+ base64 couldn't be decoded then the error message will be
+ "INVALID_BASE64".
+
+ Args:
+ pickle(bytes): Base64 encoded byte string containing the pickled
+ session
+ passphrase(str, optional): The passphrase used to encrypt the
+ """
+ if not pickle:
+ raise ValueError("Pickle can't be empty")
+
+ byte_passphrase = bytes(passphrase, "utf-8") if passphrase else b""
+ passphrase_buffer = ffi.new("char[]", byte_passphrase)
+ pickle_buffer = ffi.new("char[]", pickle)
+
+ obj = cls.__new__(cls)
+
+ ret = lib.olm_unpickle_outbound_group_session(
+ obj._session,
+ passphrase_buffer,
+ len(byte_passphrase),
+ pickle_buffer,
+ len(pickle)
+ )
+ obj._check_error(ret)
+
+ return obj
+
+ def encrypt(self, plaintext):
+ # type: (AnyStr) -> str
+ """Encrypt a message.
+
+ Returns the encrypted ciphertext.
+
+ Args:
+ plaintext(str): A string that will be encrypted using the group
+ session.
+ """
+ byte_plaintext = to_bytes(plaintext)
+ message_length = lib.olm_group_encrypt_message_length(
+ self._session, len(byte_plaintext)
+ )
+
+ message_buffer = ffi.new("char[]", message_length)
+
+ plaintext_buffer = ffi.new("char[]", byte_plaintext)
+
+ ret = lib.olm_group_encrypt(
+ self._session,
+ plaintext_buffer, len(byte_plaintext),
+ message_buffer, message_length,
+ )
+ self._check_error(ret)
+ return bytes_to_native_str(ffi.unpack(message_buffer, message_length))
+
+ @property
+ def id(self):
+ # type: () -> str
+ """str: A base64 encoded identifier for this session."""
+ id_length = lib.olm_outbound_group_session_id_length(self._session)
+ id_buffer = ffi.new("char[]", id_length)
+
+ ret = lib.olm_outbound_group_session_id(
+ self._session,
+ id_buffer,
+ id_length
+ )
+ self._check_error(ret)
+
+ return bytes_to_native_str(ffi.unpack(id_buffer, id_length))
+
+ @property
+ def message_index(self):
+ # type: () -> int
+ """int: The current message index of the session.
+
+ Each message is encrypted with an increasing index. This is the index
+ for the next message.
+ """
+ return lib.olm_outbound_group_session_message_index(self._session)
+
+ @property
+ def session_key(self):
+ # type: () -> str
+ """The base64-encoded current ratchet key for this session.
+
+ Each message is encrypted with a different ratchet key. This function
+ returns the ratchet key that will be used for the next message.
+ """
+ key_length = lib.olm_outbound_group_session_key_length(self._session)
+ key_buffer = ffi.new("char[]", key_length)
+
+ ret = lib.olm_outbound_group_session_key(
+ self._session,
+ key_buffer,
+ key_length
+ )
+ self._check_error(ret)
+
+ return bytes_to_native_str(ffi.unpack(key_buffer, key_length))