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overwrite buffers that may contain sensitive data

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also reduce the amount of memory copying that we do
This commit is contained in:
Hubert Chathi 2018-10-16 00:31:56 -04:00
parent 357d4ff479
commit 5ef6a844d6
6 changed files with 235 additions and 127 deletions
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2
python/Makefile
View file

@ -3,6 +3,8 @@ all: olm-python2 olm-python3
include/olm/olm.h: ../include/olm/olm.h ../include/olm/inbound_group_session.h ../include/olm/outbound_group_session.h
mkdir -p include/olm
$(CPP) -I dummy -I ../include ../include/olm/olm.h -o include/olm/olm.h
# add memset to the header so that we can use it to clear buffers
echo 'void *memset(void *s, int c, size_t n);' >> include/olm/olm.h
olm-python2: include/olm/olm.h
DEVELOP=$(DEVELOP) python2 setup.py build

10
python/olm/_compat.py
View file

@ -26,6 +26,16 @@ except ImportError: # pragma: no cover
URANDOM = urandom # type: ignore
def to_bytearray(string):
# type: (AnyStr) -> bytes
if isinstance(string, bytes):
return bytearray(string)
elif isinstance(string, str):
return bytearray(string, "utf-8")
raise TypeError("Invalid type {}".format(type(string)))
def to_bytes(string):
# type: (AnyStr) -> bytes
if isinstance(string, bytes):

62
python/olm/account.py
View file

@ -37,7 +37,7 @@ 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
from ._finalize import track_for_finalization
# This is imported only for type checking purposes
@ -82,12 +82,12 @@ class Account(object):
random_length = lib.olm_create_account_random_length(self._account)
random = URANDOM(random_length)
random_buffer = ffi.new("char[]", random)
self._check_error(
lib.olm_create_account(self._account, random_buffer,
lib.olm_create_account(self._account, ffi.from_buffer(random),
random_length))
def _check_error(self, ret):
# type: (int) -> None
if ret != lib.olm_error():
@ -111,15 +111,23 @@ class Account(object):
passphrase(str, optional): The passphrase to be used to encrypt
the account.
"""
byte_key = bytes(passphrase, "utf-8") if passphrase else b""
key_buffer = ffi.new("char[]", byte_key)
byte_key = bytearray(passphrase, "utf-8") if passphrase else b""
pickle_length = lib.olm_pickle_account_length(self._account)
pickle_buffer = ffi.new("char[]", pickle_length)
self._check_error(
lib.olm_pickle_account(self._account, key_buffer, len(byte_key),
pickle_buffer, pickle_length))
try:
self._check_error(
lib.olm_pickle_account(self._account,
ffi.from_buffer(byte_key),
len(byte_key),
pickle_buffer,
pickle_length))
finally:
# zero out copies of the passphrase
for i in range(0, len(byte_key)):
byte_key[i] = 0
return ffi.unpack(pickle_buffer, pickle_length)
@classmethod
@ -143,15 +151,22 @@ class Account(object):
if not pickle:
raise ValueError("Pickle can't be empty")
byte_key = bytes(passphrase, "utf-8") if passphrase else b""
key_buffer = ffi.new("char[]", byte_key)
byte_key = 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_account(obj._account, key_buffer, len(byte_key),
pickle_buffer, len(pickle))
obj._check_error(ret)
try:
ret = lib.olm_unpickle_account(obj._account,
ffi.from_buffer(byte_key),
len(byte_key),
pickle_buffer,
len(pickle))
obj._check_error(ret)
finally:
for i in range(0, len(byte_key)):
byte_key[i] = 0
return obj
@ -178,14 +193,21 @@ class Account(object):
Args:
message(str): The message to sign.
"""
bytes_message = to_bytes(message)
bytes_message = to_bytearray(message)
out_length = lib.olm_account_signature_length(self._account)
message_buffer = ffi.new("char[]", bytes_message)
out_buffer = ffi.new("char[]", out_length)
self._check_error(
lib.olm_account_sign(self._account, message_buffer,
len(bytes_message), out_buffer, out_length))
try:
self._check_error(
lib.olm_account_sign(self._account,
ffi.from_buffer(bytes_message),
len(bytes_message), out_buffer,
out_length))
finally:
# clear out copies of the message, which may be plaintext
if bytes_message is not message:
for i in range(0, len(bytes_message)):
bytes_message[i] = 0
return bytes_to_native_str(ffi.unpack(out_buffer, out_length))
@ -214,10 +236,10 @@ class Account(object):
random_length = lib.olm_account_generate_one_time_keys_random_length(
self._account, count)
random = URANDOM(random_length)
random_buffer = ffi.new("char[]", random)
self._check_error(
lib.olm_account_generate_one_time_keys(
self._account, count, random_buffer, random_length))
self._account, count, ffi.from_buffer(random), random_length))
@property
def one_time_keys(self):

163
python/olm/group_session.py
View file

@ -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)
byte_session_key = to_bytearray(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)
)
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

106
python/olm/session.py
View file

@ -40,7 +40,7 @@ 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
# This is imported only for type checking purposes
@ -164,15 +164,22 @@ class Session(object):
passphrase(str, optional): The passphrase to be used to encrypt
the session.
"""
byte_key = bytes(passphrase, "utf-8") if passphrase else b""
key_buffer = ffi.new("char[]", byte_key)
byte_key = bytearray(passphrase, "utf-8") if passphrase else b""
pickle_length = lib.olm_pickle_session_length(self._session)
pickle_buffer = ffi.new("char[]", pickle_length)
self._check_error(
lib.olm_pickle_session(self._session, key_buffer, len(byte_key),
pickle_buffer, pickle_length))
try:
self._check_error(
lib.olm_pickle_session(self._session,
ffi.from_buffer(byte_key),
len(byte_key),
pickle_buffer, pickle_length))
finally:
# clear out copies of the passphrase
for i in range(0, len(byte_key)):
byte_key[i] = 0
return ffi.unpack(pickle_buffer, pickle_length)
@classmethod
@ -196,16 +203,23 @@ class Session(object):
if not pickle:
raise ValueError("Pickle can't be empty")
byte_key = bytes(passphrase, "utf-8") if passphrase else b""
key_buffer = ffi.new("char[]", byte_key)
byte_key = bytearray(passphrase, "utf-8") if passphrase else b""
# copy because unpickle will destroy the buffer
pickle_buffer = ffi.new("char[]", pickle)
session = cls.__new__(cls)
ret = lib.olm_unpickle_session(session._session, key_buffer,
len(byte_key), pickle_buffer,
len(pickle))
session._check_error(ret)
try:
ret = lib.olm_unpickle_session(session._session,
ffi.from_buffer(byte_key),
len(byte_key),
pickle_buffer,
len(pickle))
session._check_error(ret)
finally:
# clear out copies of the passphrase
for i in range(0, len(byte_key)):
byte_key[i] = 0
return session
@ -217,29 +231,32 @@ class Session(object):
Args:
plaintext(str): The plaintext message that will be encrypted.
"""
byte_plaintext = to_bytes(plaintext)
byte_plaintext = to_bytearray(plaintext)
r_length = lib.olm_encrypt_random_length(self._session)
random = URANDOM(r_length)
random_buffer = ffi.new("char[]", random)
message_type = lib.olm_encrypt_message_type(self._session)
try:
message_type = lib.olm_encrypt_message_type(self._session)
self._check_error(message_type)
self._check_error(message_type)
ciphertext_length = lib.olm_encrypt_message_length(
self._session, len(plaintext)
)
ciphertext_buffer = ffi.new("char[]", ciphertext_length)
ciphertext_length = lib.olm_encrypt_message_length(
self._session, len(byte_plaintext)
)
ciphertext_buffer = ffi.new("char[]", ciphertext_length)
plaintext_buffer = ffi.new("char[]", byte_plaintext)
self._check_error(lib.olm_encrypt(
self._session,
plaintext_buffer, len(byte_plaintext),
random_buffer, r_length,
ciphertext_buffer, ciphertext_length,
))
self._check_error(lib.olm_encrypt(
self._session,
ffi.from_buffer(byte_plaintext), len(byte_plaintext),
ffi.from_buffer(random), r_length,
ciphertext_buffer, ciphertext_length,
))
finally:
# clear out copies of plaintext
if byte_plaintext is not plaintext:
for i in range(0, len(byte_plaintext)):
byte_plaintext[i] = 0
if message_type == lib.OLM_MESSAGE_TYPE_PRE_KEY:
return OlmPreKeyMessage(
@ -274,22 +291,34 @@ class Session(object):
raise ValueError("Ciphertext can't be empty")
byte_ciphertext = to_bytes(message.ciphertext)
# make a copy the ciphertext buffer, because
# olm_decrypt_max_plaintext_length wants to destroy something
ciphertext_buffer = ffi.new("char[]", byte_ciphertext)
max_plaintext_length = lib.olm_decrypt_max_plaintext_length(
self._session, message.message_type, ciphertext_buffer,
len(byte_ciphertext)
)
self._check_error(max_plaintext_length)
plaintext_buffer = ffi.new("char[]", max_plaintext_length)
# make a copy the ciphertext buffer, because
# olm_decrypt_max_plaintext_length wants to destroy something
ciphertext_buffer = ffi.new("char[]", byte_ciphertext)
plaintext_length = lib.olm_decrypt(
self._session, message.message_type, ciphertext_buffer,
len(byte_ciphertext), plaintext_buffer, max_plaintext_length
self._session, message.message_type,
ciphertext_buffer, len(byte_ciphertext),
plaintext_buffer, max_plaintext_length
)
self._check_error(plaintext_length)
return bytes_to_native_str(
plaintext = bytes_to_native_str(
ffi.unpack(plaintext_buffer, plaintext_length))
# clear out copies of the plaintext
lib.memset(plaintext_buffer, 0, max_plaintext_length)
return plaintext
@property
def id(self):
# type: () -> str
@ -331,16 +360,16 @@ class Session(object):
ret = None
byte_ciphertext = to_bytes(message.ciphertext)
# make a copy, because olm_matches_inbound_session(_from) will distroy
# it
message_buffer = ffi.new("char[]", byte_ciphertext)
if identity_key:
byte_id_key = to_bytes(identity_key)
identity_key_buffer = ffi.new("char[]", byte_id_key)
ret = lib.olm_matches_inbound_session_from(
self._session,
identity_key_buffer, len(byte_id_key),
ffi.from_buffer(byte_id_key), len(byte_id_key),
message_buffer, len(byte_ciphertext)
)
@ -447,14 +476,11 @@ class OutboundSession(Session):
self._session)
random = URANDOM(session_random_length)
random_buffer = ffi.new("char[]", random)
identity_key_buffer = ffi.new("char[]", byte_id_key)
one_time_key_buffer = ffi.new("char[]", byte_one_time)
self._check_error(lib.olm_create_outbound_session(
self._session,
account._account,
identity_key_buffer, len(byte_id_key),
one_time_key_buffer, len(byte_one_time),
random_buffer, session_random_length
ffi.from_buffer(byte_id_key), len(byte_id_key),
ffi.from_buffer(byte_one_time), len(byte_one_time),
ffi.from_buffer(random), session_random_length
))

19
python/olm/utility.py
View file

@ -36,7 +36,7 @@ from typing import AnyStr, Type
# pylint: disable=no-name-in-module
from _libolm import ffi, lib # type: ignore
from ._compat import to_bytes
from ._compat import to_bytearray, to_bytes
from ._finalize import track_for_finalization
@ -80,13 +80,20 @@ class _Utility(object):
cls._allocate()
byte_key = to_bytes(key)
byte_message = to_bytes(message)
byte_message = to_bytearray(message)
byte_signature = to_bytes(signature)
cls._check_error(
lib.olm_ed25519_verify(cls._utility, byte_key, len(byte_key),
byte_message, len(byte_message),
byte_signature, len(byte_signature)))
try:
cls._check_error(
lib.olm_ed25519_verify(cls._utility, byte_key, len(byte_key),
ffi.from_buffer(byte_message),
len(byte_message),
byte_signature, len(byte_signature)))
finally:
# clear out copies of the message, which may be a plaintext
if byte_message is not message:
for i in range(0, len(byte_message)):
byte_message[i] = 0
def ed25519_verify(key, message, signature):