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-rw-r--r--client/src/leap/soledad/client/_crypto.py83
1 files changed, 61 insertions, 22 deletions
diff --git a/client/src/leap/soledad/client/_crypto.py b/client/src/leap/soledad/client/_crypto.py
index a235e246..163c9e4e 100644
--- a/client/src/leap/soledad/client/_crypto.py
+++ b/client/src/leap/soledad/client/_crypto.py
@@ -39,9 +39,6 @@ from twisted.internet import interfaces
from twisted.logger import Logger
from twisted.web.client import FileBodyProducer
-from cryptography.exceptions import InvalidSignature
-from cryptography.hazmat.primitives import hashes
-from cryptography.hazmat.primitives.hmac import HMAC
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends.multibackend import MultiBackend
from cryptography.hazmat.backends.openssl.backend \
@@ -133,8 +130,7 @@ class SoledadCrypto(object):
del doc
ciphertext.write(str(payload))
decryptor = BlobDecryptor(info, ciphertext, secret=self.secret)
- buf = decryptor.decrypt()
- return buf.getvalue()
+ return decryptor.decrypt()
def encrypt_sym(data, key):
@@ -291,29 +287,45 @@ class BlobDecryptor(object):
def __init__(self, doc_info, ciphertext_fd, result=None,
secret=None):
+ if not secret:
+ raise EncryptionDecryptionError('no secret given')
+ ciphertext_fd.seek(0)
+
self.doc_id = doc_info.doc_id
self.rev = doc_info.rev
- self.ciphertext = ciphertext_fd
-
self.sym_key = _get_sym_key_for_doc(doc_info.doc_id, secret)
self.mac_key = _get_mac_key_for_doc(doc_info.doc_id, secret)
+ self._read_preamble(ciphertext_fd)
+
+ self._producer = FileBodyProducer(self.ciphertext, readSize=2**16)
+ self._content_fd = self.ciphertext
+
self.result = result or BytesIO()
- def decrypt(self):
+ self._aes_fd = BytesIO()
+ self._aes = AESDecryptor(self.sym_key, self.iv, self.result)
+ self._hmac = HMACWriter(self.mac_key)
+ self._hmac.write(self.preamble)
+
+ self._decrypter = VerifiedDecrypter(self._aes, self._hmac)
+
+ def _read_preamble(self, ciphertext):
try:
- preamble, ciphertext = _split(self.ciphertext.getvalue())
- hmac, ciphertext = ciphertext[-64:], ciphertext[:-64]
+ self.preamble, ciphertext = _split(ciphertext.getvalue())
+ self.doc_hmac, self.ciphertext = ciphertext[-64:], ciphertext[:-64]
except (TypeError, binascii.Error):
raise InvalidBlob
- self.ciphertext.close()
- if len(preamble) != PACMAN.size:
+ self.ciphertext = BytesIO(self.ciphertext)
+
+ if len(self.preamble) != PACMAN.size:
raise InvalidBlob
try:
- unpacked_data = PACMAN.unpack(preamble)
+ unpacked_data = PACMAN.unpack(self.preamble)
pad, ts, sch, meth, iv, doc_id, rev = unpacked_data
+ self.iv = iv
except struct.error:
raise InvalidBlob
if pad != '\x80':
@@ -329,18 +341,28 @@ class BlobDecryptor(object):
if rev != self.rev:
raise InvalidBlob('invalid revision')
- h = HMAC(self.mac_key, hashes.SHA512(), backend=crypto_backend)
- h.update(preamble)
- h.update(ciphertext)
- try:
- h.verify(hmac)
- except InvalidSignature:
+ def _check_hmac(self):
+ if self._hmac._hmac.digest() != self.doc_hmac:
raise InvalidBlob('HMAC could not be verifed')
- decryptor = _get_aes_ctr_cipher(self.sym_key, iv).decryptor()
+ def decrypt(self):
+ """
+ Starts producing encrypted data from the cleartext data.
+
+ :return: A deferred which will be fired when encryption ends and whose
+ callback will be invoked with the resulting ciphertext.
+ :rtype: twisted.internet.defer.Deferred
+ """
+ d = self._producer.startProducing(self._decrypter)
+ d.addCallback(lambda _: self._check_hmac())
+ d.addCallback(lambda _: self.result.getvalue())
+ return d
- # TODO pass chunks, streaming, instead
- # Use AESDecryptor below
+ def decrypt_whole(self):
+ ciphertext = self.ciphertext.getvalue()
+ self.hmac_obj.update(ciphertext)
+ self._check_hmac()
+ decryptor = _get_aes_ctr_cipher(self.sym_key, self.iv).decryptor()
self.result.write(decryptor.update(ciphertext))
self.result.write(decryptor.finalize())
@@ -412,6 +434,23 @@ class VerifiedEncrypter(object):
self.hmac.write(enc_chunk)
+class VerifiedDecrypter(object):
+ """
+ A Twisted's Consumer implementation combining AESDecryptor and HMACWriter.
+ It directs the resulting ciphertext into HMAC-SHA512 processing, then
+ decrypt.
+ """
+ implements(interfaces.IConsumer)
+
+ def __init__(self, decrypter, hmac):
+ self.decrypter = decrypter
+ self.hmac = hmac
+
+ def write(self, enc_chunk):
+ self.hmac.write(enc_chunk)
+ self.decrypter.write(enc_chunk)
+
+
class AESDecryptor(object):
"""
A Twisted's Consumer implementation that consumes data encrypted with