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authorHubert Chathi <hubert@uhoreg.ca>2018-10-16 00:31:56 -0400
committerHubert Chathi <hubert@uhoreg.ca>2018-10-16 00:31:56 -0400
commit5ef6a844d6fd3d58d1eb85dcd188ac6b6baa3fbe (patch)
tree267b23b74f57cc1d017dea8b844e318201fb5db9 /python/olm/group_session.py
parent357d4ff4795d89d623663b3996ddd2dfd4990971 (diff)
overwrite buffers that may contain sensitive data
also reduce the amount of memory copying that we do
Diffstat (limited to 'python/olm/group_session.py')
-rw-r--r--python/olm/group_session.py165
1 files changed, 103 insertions, 62 deletions
diff --git a/python/olm/group_session.py b/python/olm/group_session.py
index bbb5e56..814ce27 100644
--- a/python/olm/group_session.py
+++ b/python/olm/group_session.py
@@ -33,7 +33,7 @@ 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 ._compat import URANDOM, to_bytearray, to_bytes
from ._finalize import track_for_finalization
@@ -78,12 +78,17 @@ class InboundGroupSession(object):
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)
- )
+ byte_session_key = to_bytearray(session_key)
+
+ try:
+ ret = lib.olm_init_inbound_group_session(
+ self._session,
+ ffi.from_buffer(byte_session_key), len(byte_session_key)
+ )
+ finally:
+ if byte_session_key is not session_key:
+ for i in range(0, len(byte_session_key)):
+ byte_session_key[i] = 0
self._check_error(ret)
def pickle(self, passphrase=""):
@@ -98,19 +103,23 @@ class InboundGroupSession(object):
passphrase(str, optional): The passphrase to be used to encrypt
the session.
"""
- byte_passphrase = bytes(passphrase, "utf-8") if passphrase else b""
+ byte_passphrase = bytearray(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)
+ try:
+ ret = lib.olm_pickle_inbound_group_session(
+ self._session,
+ ffi.from_buffer(byte_passphrase), len(byte_passphrase),
+ pickle_buffer, pickle_length
+ )
+ self._check_error(ret)
+ finally:
+ # clear out copies of the passphrase
+ for i in range(0, len(byte_passphrase)):
+ byte_passphrase[i] = 0
return ffi.unpack(pickle_buffer, pickle_length)
@@ -135,20 +144,25 @@ class InboundGroupSession(object):
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)
+ byte_passphrase = bytearray(passphrase, "utf-8") if passphrase else b""
+ # copy because unpickle will destroy the buffer
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)
+ try:
+ ret = lib.olm_unpickle_inbound_group_session(
+ obj._session,
+ ffi.from_buffer(byte_passphrase),
+ len(byte_passphrase),
+ pickle_buffer,
+ len(pickle)
+ )
+ obj._check_error(ret)
+ finally:
+ # clear out copies of the passphrase
+ for i in range(0, len(byte_passphrase)):
+ byte_passphrase[i] = 0
return obj
@@ -189,12 +203,15 @@ class InboundGroupSession(object):
byte_ciphertext = to_bytes(ciphertext)
+ # copy because max_plaintext_length will destroy the buffer
ciphertext_buffer = ffi.new("char[]", byte_ciphertext)
max_plaintext_length = lib.olm_group_decrypt_max_plaintext_length(
self._session, ciphertext_buffer, len(byte_ciphertext)
)
+ self._check_error(max_plaintext_length)
plaintext_buffer = ffi.new("char[]", max_plaintext_length)
+ # copy because max_plaintext_length will destroy the buffer
ciphertext_buffer = ffi.new("char[]", byte_ciphertext)
message_index = ffi.new("uint32_t*")
@@ -206,10 +223,15 @@ class InboundGroupSession(object):
self._check_error(plaintext_length)
- return bytes_to_native_str(ffi.unpack(
+ plaintext = bytes_to_native_str(ffi.unpack(
plaintext_buffer,
plaintext_length
- )), message_index[0]
+ ))
+
+ # clear out copies of the plaintext
+ lib.memset(plaintext_buffer, 0, max_plaintext_length)
+
+ return plaintext, message_index[0]
@property
def id(self):
@@ -281,15 +303,19 @@ class InboundGroupSession(object):
"""
obj = cls.__new__(cls)
- byte_session_key = to_bytes(session_key)
+ byte_session_key = to_bytearray(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)
+ try:
+ ret = lib.olm_import_inbound_group_session(
+ obj._session,
+ ffi.from_buffer(byte_session_key),
+ len(byte_session_key)
+ )
+ obj._check_error(ret)
+ finally:
+ if byte_session_key is not session_key:
+ for i in range(0, len(byte_session_key)):
+ byte_session_key[i] = 0
return obj
@@ -323,10 +349,9 @@ class OutboundGroupSession(object):
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._session, ffi.from_buffer(random), random_length
)
self._check_error(ret)
@@ -353,17 +378,23 @@ class OutboundGroupSession(object):
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)
+ byte_passphrase = bytearray(passphrase, "utf-8") if passphrase else b""
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)
+ try:
+ ret = lib.olm_pickle_outbound_group_session(
+ self._session,
+ ffi.from_buffer(byte_passphrase), len(byte_passphrase),
+ pickle_buffer, pickle_length
+ )
+ self._check_error(ret)
+ finally:
+ # clear out copies of the passphrase
+ for i in range(0, len(byte_passphrase)):
+ byte_passphrase[i] = 0
+
return ffi.unpack(pickle_buffer, pickle_length)
@classmethod
@@ -387,20 +418,25 @@ class OutboundGroupSession(object):
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)
+ byte_passphrase = bytearray(passphrase, "utf-8") if passphrase else b""
+ # copy because unpickle will destroy the buffer
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)
+ try:
+ ret = lib.olm_unpickle_outbound_group_session(
+ obj._session,
+ ffi.from_buffer(byte_passphrase),
+ len(byte_passphrase),
+ pickle_buffer,
+ len(pickle)
+ )
+ obj._check_error(ret)
+ finally:
+ # clear out copies of the passphrase
+ for i in range(0, len(byte_passphrase)):
+ byte_passphrase[i] = 0
return obj
@@ -414,21 +450,26 @@ class OutboundGroupSession(object):
plaintext(str): A string that will be encrypted using the group
session.
"""
- byte_plaintext = to_bytes(plaintext)
+ byte_plaintext = to_bytearray(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)
+ try:
+ ret = lib.olm_group_encrypt(
+ self._session,
+ ffi.from_buffer(byte_plaintext), len(byte_plaintext),
+ message_buffer, message_length,
+ )
+ self._check_error(ret)
+ finally:
+ # clear out copies of plaintext
+ if byte_plaintext is not plaintext:
+ for i in range(0, len(byte_plaintext)):
+ byte_plaintext[i] = 0
- 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