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authorKali Kaneko <kali@leap.se>2016-09-14 01:50:52 -0400
committerVictor Shyba <victor1984@riseup.net>2016-11-18 15:55:52 -0300
commitf95dd49dd67dd752ba52825b27cbea7c4f44ef24 (patch)
tree3453f30e9788a229d3200dd3021160bb1dd6f7bf
parentec6ccbdeab1cba6534cb22ed247041b6da821884 (diff)
[feature] streaming crypto implementation
-rw-r--r--client/src/leap/soledad/client/_crypto.py200
1 files changed, 200 insertions, 0 deletions
diff --git a/client/src/leap/soledad/client/_crypto.py b/client/src/leap/soledad/client/_crypto.py
new file mode 100644
index 00000000..e4093a9e
--- /dev/null
+++ b/client/src/leap/soledad/client/_crypto.py
@@ -0,0 +1,200 @@
+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)