diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/leap/common/crypto.py | 114 | ||||
| -rw-r--r-- | src/leap/common/tests/test_crypto.py | 80 |
2 files changed, 194 insertions, 0 deletions
diff --git a/src/leap/common/crypto.py b/src/leap/common/crypto.py new file mode 100644 index 0000000..f49933b --- /dev/null +++ b/src/leap/common/crypto.py @@ -0,0 +1,114 @@ +# -*- coding: utf-8 -*- +# crypto.py +# Copyright (C) 2013 LEAP +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. + + +from Crypto.Cipher import AES +from Crypto.Random import random +from Crypto.Util import Counter +from leap.common.check import leap_assert, leap_assert_type + + +# +# encryption methods +# + +class EncryptionMethods(object): + """ + Representation of encryption methods that can be used. + """ + + AES_256_CTR = 'aes-256-ctr' + + +class UnknownEncryptionMethod(Exception): + """ + Raised when trying to encrypt/decrypt with unknown method. + """ + pass + + +# +# encrypt/decrypt functions +# + +# In the future, we might want to implement other encryption schemes and +# possibly factor out the actual encryption/decryption routines of the +# following functions to specific classes, while not changing the API. + +def encrypt_sym(data, key, method=EncryptionMethods.AES_256_CTR): + """ + Encrypt C{data} with C{key}, using C{method} encryption method. + + @param data: The data to be encrypted. + @type data: str + @param key: The key used to encrypt C{data} (must be 256 bits long). + @type key: str + @param method: The encryption method to use. + @type method: str + + @return: A tuple with the initial value and the encrypted data. + @rtype: (long, str) + """ + leap_assert_type(key, str) + + # AES-256 in CTR mode + if method == EncryptionMethods.AES_256_CTR: + leap_assert( + len(key) == 32, # 32 x 8 = 256 bits. + 'Wrong key size: %s bits (must be 256 bits long).' % (len(key)*8)) + iv = random.getrandbits(256) + ctr = Counter.new(128, initial_value=iv) + cipher = AES.new(key=key, mode=AES.MODE_CTR, counter=ctr) + return iv, cipher.encrypt(data) + + # raise if method is unknown + raise UnknownEncryptionMethod('Unkwnown method: %s' % method) + + +def decrypt_sym(data, key, method=EncryptionMethods.AES_256_CTR, **kwargs): + """ + Decrypt C{data} with C{key} using C{method} encryption method. + + @param data: The data to be decrypted with prepended IV. + @type data: str + @param key: The key used to decrypt C{data} (must be 256 bits long). + @type key: str + @param method: The encryption method to use. + @type method: str + @param kwargs: Other parameters specific to each encryption method. + @type kwargs: long + + @return: The decrypted data. + @rtype: str + """ + leap_assert_type(key, str) + + # AES-256 in CTR mode + if method == EncryptionMethods.AES_256_CTR: + # assert params + leap_assert( + len(key) == 32, # 32 x 8 = 256 bits. + 'Wrong key size: %s (must be 256 bits long).' % len(key)) + leap_assert( + 'iv' in kwargs, + 'AES-256-CTR needs an initial value given as.') + ctr = Counter.new(128, initial_value=kwargs['iv']) + cipher = AES.new(key, AES.MODE_CTR, counter=ctr) + return cipher.decrypt(data) + + # raise if method is unknown + raise UnknownEncryptionMethod('Unkwnown method: %s' % method) diff --git a/src/leap/common/tests/test_crypto.py b/src/leap/common/tests/test_crypto.py new file mode 100644 index 0000000..b704c05 --- /dev/null +++ b/src/leap/common/tests/test_crypto.py @@ -0,0 +1,80 @@ +## -*- coding: utf-8 -*- +# test_crypto.py +# Copyright (C) 2013 LEAP +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. + + +""" +Tests for the crypto submodule. +""" + + +from leap.common.testing.basetest import BaseLeapTest +from leap.common import crypto +from Crypto import Random + + +class CryptoTestCase(BaseLeapTest): + + def setUp(self): + pass + + def tearDown(self): + pass + + def test_encrypt_decrypt_sym(self): + # generate 256-bit key + key = Random.new().read(32) + iv, cyphertext = crypto.encrypt_sym( + 'data', key, + method=crypto.EncryptionMethods.AES_256_CTR) + self.assertTrue(cyphertext is not None) + self.assertTrue(cyphertext != '') + self.assertTrue(cyphertext != 'data') + plaintext = crypto.decrypt_sym( + cyphertext, key, iv=iv, + method=crypto.EncryptionMethods.AES_256_CTR) + self.assertEqual('data', plaintext) + + def test_decrypt_with_wrong_iv_fails(self): + key = Random.new().read(32) + iv, cyphertext = crypto.encrypt_sym( + 'data', key, + method=crypto.EncryptionMethods.AES_256_CTR) + self.assertTrue(cyphertext is not None) + self.assertTrue(cyphertext != '') + self.assertTrue(cyphertext != 'data') + iv += 1 + plaintext = crypto.decrypt_sym( + cyphertext, key, iv=iv, + method=crypto.EncryptionMethods.AES_256_CTR) + self.assertNotEqual('data', plaintext) + + def test_decrypt_with_wrong_key_fails(self): + key = Random.new().read(32) + iv, cyphertext = crypto.encrypt_sym( + 'data', key, + method=crypto.EncryptionMethods.AES_256_CTR) + self.assertTrue(cyphertext is not None) + self.assertTrue(cyphertext != '') + self.assertTrue(cyphertext != 'data') + wrongkey = Random.new().read(32) # 256-bits key + # ensure keys are different in case we are extremely lucky + while wrongkey == key: + wrongkey = Random.new().read(32) + plaintext = crypto.decrypt_sym( + cyphertext, wrongkey, iv=iv, + method=crypto.EncryptionMethods.AES_256_CTR) + self.assertNotEqual('data', plaintext) |