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import binascii
import hashlib
import hmac
import os
from cStringIO import StringIO
from twisted.persisted import dirdbm
from twisted.internet import defer
from twisted.internet import interfaces
from twisted.internet import reactor
from twisted.web import client
from twisted.web.client import FileBodyProducer
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends.multibackend import MultiBackend
from cryptography.hazmat.backends.openssl.backend \
import Backend as OpenSSLBackend
from zope.interface import implements
from leap.common.config import get_path_prefix
from leap.soledad.client.secrets import SoledadSecrets
MAC_KEY_LENGTH = 64
crypto_backend = MultiBackend([OpenSSLBackend()])
class AESWriter(object):
implements(interfaces.IConsumer)
def __init__(self, key, fd, iv=None):
if iv is None:
iv = os.urandom(16)
cipher = _get_aes_ctr_cipher(key, iv)
self.encryptor = cipher.encryptor()
self.fd = fd
self.done = False
self.deferred = defer.Deferred()
def write(self, data):
encrypted = self.encryptor.update(data)
self.fd.write(encrypted)
return encrypted
def end(self):
if not self.done:
self.encryptor.finalize()
self.fd.seek(0)
self.deferred.callback(self.fd)
self.done = True
class HMACWriter(object):
implements(interfaces.IConsumer)
def __init__(self, key):
self.done = False
self.deferred = defer.Deferred()
self.digest = ''
self._hmac = hmac.new(key, '', hashlib.sha256)
def write(self, data):
self._hmac.update(data)
def end(self):
if not self.done:
self.digest = self._hmac.digest()
self.deferred.callback(self.digest)
self.done = True
class EncryptAndHMAC(object):
implements(interfaces.IConsumer)
def __init__(self, crypter, hmac):
self.crypter = crypter
self.hmac = hmac
def write(self, data):
enc_chunk = self.crypter.write(data)
self.hmac.write(enc_chunk)
class NewDocCryptoStreamer(object):
staging_path = os.path.join(get_path_prefix(), 'leap', 'soledad', 'staging')
staged_template = """
{"_enc_scheme": "symkey",
"_enc_method": "aes-256-ctr",
"_mac_method": "hmac",
"_mac_hash": "sha256",
"_encoding": "ENCODING",
"_enc_json": "ENC",
"_enc_iv": "IV",
"_mac": "MAC"}"""
def __init__(self, content_fd, doc_id, rev, secret=None):
self._content_fd = content_fd
self._contentFileProducer = FileBodyProducer(
content_fd, readSize=2**8)
self.doc_id = doc_id
self.rev = rev
self._encrypted_fd = StringIO()
self.iv = os.urandom(16)
sym_key = _get_sym_key_for_doc(doc_id, secret)
mac_key = _get_mac_key_for_doc(doc_id, secret)
crypter = AESWriter(sym_key, self._encrypted_fd, self.iv)
hmac = HMACWriter(mac_key)
self.crypter_consumer = crypter
self.hmac_consumer = hmac
self._prime_hmac()
self.encrypt_and_mac_consumer = EncryptAndHMAC(crypter, hmac)
def encrypt_stream(self):
d = self._contentFileProducer.startProducing(
self.encrypt_and_mac_consumer)
d.addCallback(self.end_crypto_stream)
d.addCallback(self.persist_encrypted_doc)
return d
def end_crypto_stream(self, ignored):
self.crypter_consumer.end()
self._post_hmac()
self.hmac_consumer.end()
return defer.succeed('ok')
def persist_encrypted_doc(self, ignored, encoding='hex'):
# TODO to avoid blocking on io, this can use a
# version of dbm that chunks the writes to the
# disk fd by using the same FileBodyProducer strategy
# that we're using here, long live to the Cooperator.
# this will benefit
# TODO -- transition to hex: needs migration FIXME
if encoding == 'b64':
encode = binascii.b2a_base64
elif encoding == 'hex':
encode = binascii.b2a_hex
else:
raise RuntimeError('Unknown encoding: %s' % encoding)
db = dirdbm.DirDBM(self.staging_path)
key = '{doc_id}@{rev}'.format(
doc_id=self.doc_id, rev=self.rev)
value = self.staged_template.replace(
'ENCODING', encoding).replace(
'ENC', encode(self._encrypted_fd.read())).replace(
'IV', binascii.b2a_base64(self.iv)).replace(
'MAC', encode(self.hmac_consumer.digest))
db[key] = value
self._content_fd.close()
self._encrypted_fd.close()
def _prime_hmac(self):
pre = '{doc_id}{rev}'.format(
doc_id=self.doc_id, rev=self.rev)
self.hmac_consumer.write(pre)
def _post_hmac(self):
# FIXME -- original impl passed b64 encoded iv
post = '{enc_scheme}{enc_method}{enc_iv}'.format(
enc_scheme='symkey',
enc_method='aes-256-ctr',
enc_iv=binascii.b2a_base64(self.iv))
self.hmac_consumer.write(post)
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:]
return _hmac_sha256(key, doc_id)
def _get_aes_ctr_cipher(key, iv):
return Cipher(algorithms.AES(key), modes.CTR(iv), backend=crypto_backend)
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