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Use new Secure Message API in PyThemis #401

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merged 3 commits into from
Mar 4, 2019
Merged

Use new Secure Message API in PyThemis #401

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6374ac8
Use new Secure Message API in PyThemis
ilammy Mar 1, 2019
3e9c004
Improve key kind verification and tests
ilammy Mar 1, 2019
fcd400c
Early key kind checks for sign/verify mode
ilammy Mar 1, 2019
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90 changes: 68 additions & 22 deletions src/wrappers/themis/python/pythemis/smessage.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
import warnings
from ctypes import cdll, create_string_buffer, c_int, string_at, byref
from ctypes.util import find_library
from enum import IntEnum

from .exception import ThemisError, THEMIS_CODES

Expand All @@ -24,82 +25,127 @@

class SMessage(object):
def __init__(self, private_key, peer_public_key):
if not (private_key and peer_public_key):
if not private_key:
raise ThemisError(THEMIS_CODES.FAIL,
"Secure Message failed creating")
"Secure Message: missing private key")
if not peer_public_key:
raise ThemisError(THEMIS_CODES.FAIL,
"Secure Message: missing public key")
if not _private_key(private_key):
raise ThemisError(THEMIS_CODES.FAIL,
"Secure Message: invalid private key")
if not _public_key(peer_public_key):
raise ThemisError(THEMIS_CODES.FAIL,
"Secure Message: invalid public key")
self.private_key = private_key
self.peer_public_key = peer_public_key

def wrap(self, message):
encrypted_message_length = c_int(0)
res = themis.themis_secure_message_wrap(
res = themis.themis_secure_message_encrypt(
self.private_key, len(self.private_key),
self.peer_public_key, len(self.peer_public_key),
message, len(message), None, byref(encrypted_message_length))
if res != THEMIS_CODES.BUFFER_TOO_SMALL:
raise ThemisError(res, "Secure Message failed encrypting")
raise ThemisError(res, "Secure Message failed to encrypt")
encrypted_message = create_string_buffer(encrypted_message_length.value)
res = themis.themis_secure_message_wrap(
res = themis.themis_secure_message_encrypt(
self.private_key, len(self.private_key),
self.peer_public_key, len(self.peer_public_key),
message, len(message), encrypted_message,
byref(encrypted_message_length))
if res != THEMIS_CODES.SUCCESS:
raise ThemisError(res, "Secure Message failed encrypting")
raise ThemisError(res, "Secure Message failed to encrypt")

return string_at(encrypted_message, encrypted_message_length.value)

def unwrap(self, message):
plain_message_length = c_int(0)
res = themis.themis_secure_message_unwrap(
res = themis.themis_secure_message_decrypt(
self.private_key, len(self.private_key),
self.peer_public_key, len(self.peer_public_key),
message, len(message), None, byref(plain_message_length))
if res != THEMIS_CODES.BUFFER_TOO_SMALL:
raise ThemisError(res, "Secure Message failed decrypting")
raise ThemisError(res, "Secure Message failed to decrypt")
plain_message = create_string_buffer(plain_message_length.value)
res = themis.themis_secure_message_unwrap(
res = themis.themis_secure_message_decrypt(
self.private_key, len(self.private_key),
self.peer_public_key, len(self.peer_public_key),
message, len(message), plain_message, byref(plain_message_length))
if res != THEMIS_CODES.SUCCESS:
raise ThemisError(res, "Secure Message failed decrypting")
raise ThemisError(res, "Secure Message failed to decrypt")
return string_at(plain_message, plain_message_length.value)


def ssign(private_key, message):
if not private_key:
raise ThemisError(THEMIS_CODES.FAIL,
"Secure Message: missing private key")
if not _private_key(private_key):
raise ThemisError(THEMIS_CODES.FAIL,
"Secure Message: invalid private key")
encrypted_message_length = c_int(0)
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can you add private_key length check and error message here as well? I think it would be nice addition to this PR

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Yeah, it makes sense to check keys for sign/verify mode as well. I'll add the checks.

res = themis.themis_secure_message_wrap(
private_key, len(private_key), None, 0, message, len(message),
res = themis.themis_secure_message_sign(
private_key, len(private_key), message, len(message),
None, byref(encrypted_message_length))
if res != THEMIS_CODES.BUFFER_TOO_SMALL:
raise ThemisError(res, "Secure Message failed singing")
raise ThemisError(res, "Secure Message failed to sign")
encrypted_message = create_string_buffer(encrypted_message_length.value)
res = themis.themis_secure_message_wrap(
private_key, len(private_key), None, 0, message, len(message),
res = themis.themis_secure_message_sign(
private_key, len(private_key), message, len(message),
encrypted_message, byref(encrypted_message_length))
if res != THEMIS_CODES.SUCCESS:
raise ThemisError(res, "Secure Message failed singing")
raise ThemisError(res, "Secure Message failed to sign")
return string_at(encrypted_message, encrypted_message_length.value)


def sverify(public_key, message):
if not public_key:
raise ThemisError(THEMIS_CODES.FAIL,
"Secure Message: missing public key")
if not _public_key(public_key):
raise ThemisError(THEMIS_CODES.FAIL,
"Secure Message: invalid public key")
plain_message_length = c_int(0)
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similar check

res = themis.themis_secure_message_unwrap(
None, 0, public_key, len(public_key), message, len(message),
res = themis.themis_secure_message_verify(
public_key, len(public_key), message, len(message),
None, byref(plain_message_length))
if res != THEMIS_CODES.BUFFER_TOO_SMALL:
raise ThemisError(res, "Secure Message failed verifying")
raise ThemisError(res, "Secure Message failed to verify")
plain_message = create_string_buffer(plain_message_length.value)
res = themis.themis_secure_message_unwrap(
None, 0, public_key, len(public_key), message, len(message),
res = themis.themis_secure_message_verify(
public_key, len(public_key), message, len(message),
plain_message, byref(plain_message_length))
if res != THEMIS_CODES.SUCCESS:
raise ThemisError(res, "Secure Message failed verifying")
raise ThemisError(res, "Secure Message failed to verify")

return string_at(plain_message, plain_message_length.value)


class THEMIS_KEY(IntEnum):
INVALID = 0
RSA_PRIVATE = 1
RSA_PUBLIC = 2
EC_PRIVATE = 3
EC_PUBLIC = 4


def _public_key(key):
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👍

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better to make this function public to allow use it for apps

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and better to rename to something like validate_public_key because _public_key looks like getter function

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Mmm... I'm not against it but I think there's a better way.

These two functions are effectively internal helpers which implement a particular check specifically for Secure Message needs. However, the user may have different needs that that. I think that for general use it would be better to export C functions themis_is_valid_asym_key and themis_get_asym_key_kind which provide a bit more information about the keys. Then the user could implement their of is_valid_public_key function the way they want.

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will be great. but not only is_valid_public_key, I think is_valid_private_key will be useful for users too.

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I think it's a good idea overall, but let's do it later if you don't mind: #409

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sure

res = themis.themis_is_valid_asym_key(key, len(key))
if res != THEMIS_CODES.SUCCESS:
return False
kind = themis.themis_get_asym_key_kind(key, len(key))
return kind in [THEMIS_KEY.RSA_PUBLIC, THEMIS_KEY.EC_PUBLIC]


def _private_key(key):
res = themis.themis_is_valid_asym_key(key, len(key))
if res != THEMIS_CODES.SUCCESS:
return False
kind = themis.themis_get_asym_key_kind(key, len(key))
return kind in [THEMIS_KEY.RSA_PRIVATE, THEMIS_KEY.EC_PRIVATE]


class smessage(SMessage):
def __init__(self, *args, **kwargs):
warnings.warn("smessage is deprecated in favor of SMessage.")
Expand Down
11 changes: 10 additions & 1 deletion tests/pythemis/test_smessage.py
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,9 @@ def encrypt_decrypt(self, private, public):
with self.assertRaises(ThemisError):
smessage.SMessage(private, "")

with self.assertRaises(ThemisError):
smessage.SMessage(public, private)

encryptor = smessage.SMessage(private, public)
with self.assertRaises(ThemisError):
encryptor.wrap("")
Expand All @@ -57,16 +60,22 @@ def sign_verify(self, private, public):
with self.assertRaises(ThemisError):
smessage.ssign("", "")

with self.assertRaises(TypeError):
with self.assertRaises(ThemisError):
smessage.ssign(None, self.message)

with self.assertRaises(ThemisError):
smessage.ssign(private, "")

with self.assertRaises(ThemisError):
smessage.ssign(public, "message")

encrypted_message = smessage.ssign(private, self.message)
with self.assertRaises(ThemisError):
smessage.sverify(public, "")

with self.assertRaises(ThemisError):
smessage.sverify(private, encrypted_message)

with self.assertRaises(ThemisError):
smessage.sverify(public, b"".join([b"11", encrypted_message]))

Expand Down