diff options
Diffstat (limited to 'client')
| -rw-r--r-- | client/src/leap/soledad/client/_crypto.py | 200 | ||||
| -rw-r--r-- | client/src/leap/soledad/client/secrets.py | 2 |
2 files changed, 67 insertions, 135 deletions
diff --git a/client/src/leap/soledad/client/_crypto.py b/client/src/leap/soledad/client/_crypto.py index b1c6b059..d9211322 100644 --- a/client/src/leap/soledad/client/_crypto.py +++ b/client/src/leap/soledad/client/_crypto.py @@ -36,6 +36,7 @@ from twisted.internet import defer from twisted.internet import interfaces from twisted.web.client import FileBodyProducer +from cryptography.exceptions import InvalidTag from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes from cryptography.hazmat.backends.multibackend import MultiBackend from cryptography.hazmat.backends.openssl.backend \ @@ -44,7 +45,7 @@ from cryptography.hazmat.backends.openssl.backend \ from zope.interface import implements -MAC_KEY_LENGTH = 64 +SECRET_LENGTH = 64 CRYPTO_BACKEND = MultiBackend([OpenSSLBackend()]) @@ -53,7 +54,7 @@ BLOB_SIGNATURE_MAGIC = '\x13\x37' ENC_SCHEME = namedtuple('SCHEME', 'symkey')(1) -ENC_METHOD = namedtuple('METHOD', 'aes_256_ctr')(1) +ENC_METHOD = namedtuple('METHOD', 'aes_256_gcm')(1) DocInfo = namedtuple('DocInfo', 'doc_id rev') @@ -95,8 +96,7 @@ class SoledadCrypto(object): raw = blob.getvalue() return '{"raw": "' + raw + '"}' - content = BytesIO() - content.write(str(doc.get_json())) + content = BytesIO(str(doc.get_json())) info = DocInfo(doc.doc_id, doc.rev) del doc encryptor = BlobEncryptor(info, content, secret=self.secret) @@ -125,7 +125,7 @@ class SoledadCrypto(object): def encrypt_sym(data, key): """ - Encrypt data using AES-256 cipher in CTR mode. + Encrypt data using AES-256 cipher in GCM mode. :param data: The data to be encrypted. :type data: str @@ -138,13 +138,15 @@ def encrypt_sym(data, key): """ encryptor = AESWriter(key) encryptor.write(data) - ciphertext = encryptor.end() - return base64.b64encode(encryptor.iv), ciphertext + _, ciphertext = encryptor.end() + iv = base64.b64encode(encryptor.iv) + tag = base64.b64encode(encryptor.tag) + return iv, tag, ciphertext -def decrypt_sym(data, key, iv): +def decrypt_sym(data, key, iv, tag): """ - Decrypt data using AES-256 cipher in CTR mode. + Decrypt data using AES-256 cipher in GCM mode. :param data: The data to be decrypted. :type data: str @@ -158,51 +160,43 @@ def decrypt_sym(data, key, iv): :rtype: str """ _iv = base64.b64decode(str(iv)) - decryptor = AESWriter(key, _iv, encrypt=False) + tag = base64.b64decode(str(tag)) + decryptor = AESWriter(key, _iv, tag=tag) decryptor.write(data) - plaintext = decryptor.end() + _, plaintext = decryptor.end() return plaintext class BlobEncryptor(object): """ Produces encrypted data from the cleartext data associated with a given - SoledadDocument using AES-256 cipher in CTR mode, together with a - HMAC-SHA512 Message Authentication Code. + SoledadDocument using AES-256 cipher in GCM mode. The production happens using a Twisted's FileBodyProducer, which uses a Cooperator to schedule calls and can be paused/resumed. Each call takes at most 65536 bytes from the input. Both the production input and output are file descriptors, so they can be applied to a stream of data. """ - def __init__(self, doc_info, content_fd, result=None, secret=None): + def __init__(self, doc_info, content_fd, secret=None): if not secret: raise EncryptionDecryptionError('no secret given') self.doc_id = doc_info.doc_id self.rev = doc_info.rev - - content_fd.seek(0) - self._producer = FileBodyProducer(content_fd, readSize=2**16) self._content_fd = content_fd - - self._preamble = BytesIO() - self.result = result or BytesIO() + self._producer = FileBodyProducer(content_fd, readSize=2**16) sym_key = _get_sym_key_for_doc(doc_info.doc_id, secret) - mac_key = _get_mac_key_for_doc(doc_info.doc_id, secret) - - self._aes_fd = BytesIO() - _aes = AESWriter(sym_key, _buffer=self._aes_fd) - self._iv = _aes.iv - self._hmac_writer = HMACWriter(mac_key) - self._write_preamble() - - self._crypter = VerifiedAESWriter(_aes, self._hmac_writer) + self._aes = AESWriter(sym_key) + self._aes.authenticate(self._make_preamble()) @property def iv(self): - return self._iv + return self._aes.iv + + @property + def tag(self): + return self._aes.tag def encrypt(self): """ @@ -212,39 +206,31 @@ class BlobEncryptor(object): callback will be invoked with the resulting ciphertext. :rtype: twisted.internet.defer.Deferred """ - d = self._producer.startProducing(self._crypter) + d = self._producer.startProducing(self._aes) d.addCallback(lambda _: self._end_crypto_stream()) return d - def _write_preamble(self): - - def write(data): - self._preamble.write(data) - self._hmac_writer.write(data) - + def _make_preamble(self): current_time = int(time.time()) - write(PACMAN.pack( + return PACMAN.pack( BLOB_SIGNATURE_MAGIC, ENC_SCHEME.symkey, - ENC_METHOD.aes_256_ctr, + ENC_METHOD.aes_256_gcm, current_time, self.iv, str(self.doc_id), - str(self.rev))) + str(self.rev)) def _end_crypto_stream(self): - encrypted, content_hmac = self._crypter.end() - - preamble = self._preamble.getvalue() - - self.result.write( + preamble, encrypted = self._aes.end() + result = BytesIO() + result.write( base64.urlsafe_b64encode(preamble)) - self.result.write(' ') - self.result.write( - base64.urlsafe_b64encode(encrypted + content_hmac)) - self.result.seek(0) - return defer.succeed(self.result) + result.write(' ') + result.write( + base64.urlsafe_b64encode(encrypted + self.tag)) + return defer.succeed(result) class BlobDecryptor(object): @@ -252,7 +238,7 @@ class BlobDecryptor(object): Decrypts an encrypted blob associated with a given Document. Will raise an exception if the blob doesn't have the expected structure, or - if the HMAC doesn't verify. + if the GCM tag doesn't verify. """ def __init__(self, doc_info, ciphertext_fd, result=None, @@ -264,16 +250,11 @@ class BlobDecryptor(object): self.rev = doc_info.rev ciphertext_fd, preamble, iv = self._consume_preamble(ciphertext_fd) - mac_key = _get_mac_key_for_doc(doc_info.doc_id, secret) - self._current_hmac = BytesIO() - _hmac_writer = HMACWriter(mac_key, self._current_hmac) - _hmac_writer.write(preamble) self.result = result or BytesIO() sym_key = _get_sym_key_for_doc(doc_info.doc_id, secret) - _aes = AESWriter(sym_key, iv, self.result, - encrypt=False) - self._decrypter = VerifiedAESWriter(_aes, _hmac_writer, encrypt=False) + self._aes = AESWriter(sym_key, iv, self.result, tag=self.tag) + self._aes.authenticate(preamble) self._producer = FileBodyProducer(ciphertext_fd, readSize=2**16) @@ -281,7 +262,7 @@ class BlobDecryptor(object): ciphertext_fd.seek(0) try: preamble, ciphertext = _split(ciphertext_fd.getvalue()) - self.doc_hmac, ciphertext = ciphertext[-64:], ciphertext[:-64] + self.tag, ciphertext = ciphertext[-16:], ciphertext[:-16] except (TypeError, binascii.Error): raise InvalidBlob ciphertext_fd.close() @@ -300,7 +281,7 @@ class BlobDecryptor(object): # TODO check timestamp if sch != ENC_SCHEME.symkey: raise InvalidBlob('invalid scheme') - if meth != ENC_METHOD.aes_256_ctr: + if meth != ENC_METHOD.aes_256_gcm: raise InvalidBlob('invalid encryption scheme') if rev != self.rev: raise InvalidBlob('invalid revision') @@ -308,14 +289,11 @@ class BlobDecryptor(object): raise InvalidBlob('invalid revision') return BytesIO(ciphertext), preamble, iv - def _check_hmac(self): - if self._current_hmac.getvalue() != self.doc_hmac: - raise InvalidBlob('HMAC could not be verifed') - def _end_stream(self): - self._decrypter.end() - self._check_hmac() - return self.result.getvalue() + try: + return self._aes.end()[1] + except InvalidTag: + raise InvalidBlob('Invalid Tag. Blob authentication failed.') def decrypt(self): """ @@ -325,83 +303,41 @@ class BlobDecryptor(object): callback will be invoked with the resulting ciphertext. :rtype: twisted.internet.defer.Deferred """ - d = self._producer.startProducing(self._decrypter) + d = self._producer.startProducing(self._aes) d.addCallback(lambda _: self._end_stream()) return d -class GenericWriter(object): - """ - A Twisted's Consumer implementation that can perform one opearation at the - written data and another at the end of the stream. - """ - implements(interfaces.IConsumer) - - def __init__(self, process, close, result=None): - self.result = result or BytesIO() - self.process, self.close = process, close - - def write(self, data): - out = self.process(data) - if out: - self.result.write(out) - return out - - def end(self): - self.result.write(self.close()) - return self.result.getvalue() - - -class HMACWriter(GenericWriter): - """ - A Twisted's Consumer implementation that takes an input file descriptor and - produces a HMAC-SHA512 Message Authentication Code. - """ - implements(interfaces.IConsumer) - hashtype = 'sha512' - - def __init__(self, key, result=None): - hmac_obj = hmac.new(key, '', getattr(hashlib, self.hashtype)) - GenericWriter.__init__(self, hmac_obj.update, hmac_obj.digest, result) - - -class AESWriter(GenericWriter): +class AESWriter(object): """ A Twisted's Consumer implementation that takes an input file descriptor and - applies AES-256 cipher in CTR mode. + applies AES-256 cipher in GCM mode. """ implements(interfaces.IConsumer) - def __init__(self, key, iv=None, _buffer=None, encrypt=True): + def __init__(self, key, iv=None, _buffer=None, tag=None): if len(key) != 32: raise EncryptionDecryptionError('key is not 256 bits') self.iv = iv or os.urandom(16) - cipher = _get_aes_ctr_cipher(key, self.iv) - cipher = cipher.encryptor() if encrypt else cipher.decryptor() - GenericWriter.__init__(self, cipher.update, cipher.finalize, _buffer) - + self.buffer = _buffer or BytesIO() + cipher = _get_aes_gcm_cipher(key, self.iv, tag) + cipher = cipher.decryptor() if tag else cipher.encryptor() + self.cipher, self.aead = cipher, '' -class VerifiedAESWriter(object): - """ - A Twisted's Consumer implementation that flows data into two writers. - Here we can combine AESEncryptor and HMACWriter. - It directs the resulting ciphertext into HMAC-SHA512 processing if - pipe=True or writes the ciphertext to both (fan out, which is the case when - decrypting). - """ - implements(interfaces.IConsumer) + def authenticate(self, data): + self.aead += data + self.cipher.authenticate_additional_data(data) - def __init__(self, aes_writer, hmac_writer, encrypt=True): - self.encrypt = encrypt - self.aes_writer = aes_writer - self.hmac_writer = hmac_writer + @property + def tag(self): + return self.cipher.tag def write(self, data): - enc_chunk = self.aes_writer.write(data) - self.hmac_writer.write(enc_chunk if self.encrypt else data) + self.buffer.write(self.cipher.update(data)) def end(self): - return self.aes_writer.end(), self.hmac_writer.end() + self.buffer.write(self.cipher.finalize()) + return self.aead, self.buffer.getvalue() def is_symmetrically_encrypted(content): @@ -425,18 +361,14 @@ def _hmac_sha256(key, data): return hmac.new(key, data, hashlib.sha256).digest() -def _get_mac_key_for_doc(doc_id, secret): - key = secret[:MAC_KEY_LENGTH] - return _hmac_sha256(key, doc_id) - - def _get_sym_key_for_doc(doc_id, secret): - key = secret[MAC_KEY_LENGTH:] + key = secret[SECRET_LENGTH:] return _hmac_sha256(key, doc_id) -def _get_aes_ctr_cipher(key, iv): - return Cipher(algorithms.AES(key), modes.CTR(iv), backend=CRYPTO_BACKEND) +def _get_aes_gcm_cipher(key, iv, tag): + mode = modes.GCM(iv, tag) + return Cipher(algorithms.AES(key), mode, backend=CRYPTO_BACKEND) def _split(base64_raw_payload): diff --git a/client/src/leap/soledad/client/secrets.py b/client/src/leap/soledad/client/secrets.py index 21c4f291..1eb6f31d 100644 --- a/client/src/leap/soledad/client/secrets.py +++ b/client/src/leap/soledad/client/secrets.py @@ -34,7 +34,7 @@ from leap.soledad.common import soledad_assert_type from leap.soledad.common import document from leap.soledad.common.log import getLogger from leap.soledad.client import events -from leap.soledad.client._crypto import encrypt_sym, decrypt_sym +from leap.soledad.client.crypto import encrypt_sym, decrypt_sym logger = getLogger(__name__) |